Conductivity enhanced metal-nanocarbon hybrids and method for preparation

Abstract

A method of enhancing the conductivity of metal-nanomaterial hybrids includes subjecting a cathode substrate to an electrolyte solution including a nanomaterial and metal ions. The cathode substrate is spaced from a metal anode in the electrolyte solution. A pulsed waveform is applied across the cathode and anode to electrodeposit metal ions from the electrolyte solution onto the cathode substrate as a coating and to electrophoretically embed the nanomaterial in the electrolyte solution into the coating on the cathode substrate.

Description

RELATED APPLICATIONS

[0001] This application claims benefit of and priority to U.S. Provisional Application Ser. No. 63 / 777,764 filed Mar. 26, 2025, under 35 U.S.C. §§ 119, 120, 363, 365, and 37 C.F.R. § 1.55 and § 1.78, which is incorporated herein by this reference.GOVERNMENT RIGHTS

[0002] This invention was made with U.S. Government support under Contract No. DE-SC0021676 awarded by the Department of Energy, and Contract No. 80NSSC21C0179 awarded by NASA. The Government has certain rights in the subject invention.FIELD OF THE INVENTION

[0003] The present invention relates to conductivity enhanced materials and fabrication methods, and their applications in thermal straps, electronic devices, and the like.BACKGROUND OF THE INVENTION

[0004] There are numerous applications that require new materials that enhance thermal and electrical conductivity with reduced mass. There are numerous power consuming applications, wherein a very high-quality conductor is required. Such a conductor can conduct either heat and / or electricity or in numerous applications both.

[0005] Metals are a well-established conductor because they behave according to the Wiedemann-Franz law.

[0006] One notable example of high conduction that is not a metal is diamond, which is the hardest form of carbon. Diamonds are known to be the best thermal conductor, yet they do not conduct electricity. Silver is an excellent conductor of electricity. However, the supply of silver is constrained, and therefore the price is higher. Aluminum is often used as a conductor on long range transmission lines due to its low weight despite it being less conductive than copper or silver. Copper is a mainstay for standard wiring as it offers reasonably good conductivity for standard applications and supply is more available. However, there exists a desire for improved materials for demanding applications such as semiconductors, and the like. Superconductors do exist but typically function at cryogenic conditions making them impractical for widespread applications. Past work has established that copper and carbon can be combined to improve the conductivity of the resulting material. Issues exist with both the processes utilized and the viability of the produced article as it is difficult to properly combine the two materials to achieve a useful and / or durable result. It is an intent of this invention to describe a flexible set of electrochemical processes that can be utilized to tailor the attributes of a produced conductor to provide desirable conduction properties for a given application in a form that can be reliable, repeatable and functional. These conductors can be applied directly on a substrate for use or applied onto a donor substrate and removed for further processing and or use in any given application. In addition, the coating may be applied to the surface of an existing conductor to enhance overall conductivity and / or corrosion resistance. For example, nickel plated wire is often utilized for high temperature applications.

[0007] Graphene-metal hybrid materials can be synthesized through approaches such as chemical vapor deposition (CVD), electrical conversion process, powder metallurgy, electrodeposition, etc. Graphene has been directly grown on the surface of copper foil via CVD. However, the high synthesis temperature (>several hundred Celsius) limits its large-scale synthesis and industrial applications. In addition, graphene materials grown on the surface of copper foil are not only easily scratched during mechanical operation, but often delaminates in operational environments due to different thermal expansion for graphene and copper during thermal cycling. Metal-carbon materials have been produced using an electrical conversion process by applying electrical current into carbon materials infused molten metals. The molten metal formed carbon materials have shown higher thermal and electrical conductivity and higher strength compared to conventional metals. However, challenges are high variability in carbon distribution in the metal matrix, high concentrations of micropores, and thermal stability of carbon materials in molten metal carbon formed materials. These challenges may result in the variability in property measurements and inconsistent conversion yields of molten metal formed materials. Due to the agglomeration of graphene, powder metallurgy remains the challenge on the interface creation between graphene and metal matrix. Metal-carbon composites have been synthesized via electrochemical deposition.

[0008] Prior attempts demonstrate the potential performance enhancement given by creating composite material out of carbon and metals include U.S. Pat. Nos. 8,349,759 B2; 8,541,335 B2; 8,541,336 B2; 8,546,292 B2; 8,551,905 B2; 8,647,534 B2; 9,273,380 B2, all incorporated herein by this reference. However, in the prior art, the fabrication of these materials requires high temperatures and melting of the material to create the composite that they have coined as covetic.

[0009] Japanese Patent Application JP2020108622 discloses an approach for laminating Cu with Ag paste for improved conductive properties. This laminate formation requires a polymer adhesive and curing. U.S. Patent Application US20230022914A1 discloses an approach for laminating metal and nanocarbons with ultrasonic vibration. This laminate formation requires an ultrasonic vibration. Patent Application WO2001049795A1 is directed to a resin and an anodic electrocoat. U.S. Patent Application 20150322588A1 discloses an approach for functionally grading a composite metal / (glass, ceramic or polymer) coating using a pulse electro-codeposition process. U.S. Patent Application 20210380832A1 discloses a method to print conductive inks consisting of a binder and a metal powder. All of these references are incorporated herein by this reference.

[0010] Trace printing by electrodeposition through a pipet using a pulse electrodeposition process is highlighted in the following papers: Daryadel, S., Behroozfar, A., Minary-Jolandan, M., Toward Control of Microstructure in Microscale Additive Manufacturing of Cu Using Localized Electrodeposition, Adv. Eng. Mater, 2018, 1800946; Ali, B., et al., Additive Printing of Pure Nanocrystalline Nickel Thin Films Using Room Environment Electroplating, Nanotechnology, 2019; and Behroozfar, A., Microscale 3D Printing of Nanotwinned Copper. Adv. Matls, 2018. 30(4): 1705107. All of these references are also incorporated herein by this reference.

[0011] U.S. Pat. Nos. 9,395,718; 8,790,742; and 7,972,650 disclose trace printing of metallic polymer traces using an x,y,z print controller. These print formations require solvent extraction and metal curing. U.S. Pat. No. 11,008,664 B2 discloses a method to 3D print Cu with graphene using a plating electrolyte with additives and a separate reservoir of graphene. This work uses a single electrolyte containing graphene and no additives. Additionally, it shows that pulse can control the physical properties of the material deposited. All of these references are also incorporated herein by this reference.BRIEF SUMMARY OF THE INVENTION

[0012] Aside from the preferred embodiments disclosed herein, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details set forth in the following description or illustrated in the drawings. Moreover, the claims are not to be read restrictively unless there is clear and convincing evidence manifesting in certain exclusion, restriction, or disclaimer.

[0013] The present invention relates to an efficient, scalable and manufacturing-ready approach for production of conductivity enhanced metal (Cu, Ag, Ni, etc.)-nanocarbon (graphene, carbon nanotubes, etc.) hybrids, such as hybrid graphene-Cu foils / traces / coatings, and their government and commercial applications in thermal straps, electronic devices, and space landing systems.

[0014] The problem of producing low-cost high performance materials with enhanced conductivity and strength properties for electric and thermal applications is solved, in one example, by the development of pulsed reverse electrolytic co-deposition technology combining electrodeposition and electrophoretic deposition processes, for scalable production of composite metal coatings consisting of nanomaterials such as graphene, carbon nanotubes and the like distributed in a metal matrix such as Cu, Ag, Ni and the like wherein said composite metal coating exhibits enhanced electrical conductivity, and or thermal conductivity, and or mechanical strength.

[0015] The feasibility of the invention has been demonstrated. The hybrid and layered graphene-Cu hybrid foils have been fabricated pulsed electrodeposition at a sub-alpha scale (4″×4″) and printing of traces with less the 1 mm width through a direct print nozzle. The existence of graphene contents in graphene-Cu hybrid foils has been identified via Raman spectrometry. The hybrid and layered Cu-Graphene foils exhibited more than 50% and 5% of thermal conductivity enhancement compared to commercial Cu foils, respectively. The hybrid and layered Cu-Graphene foils with post thermal reduction treatment exhibit more than 90% and 100% conductivity enhancement compared to commercial Cu foils. In addition, the hybrid Cu-Graphene foils exhibit 50% sheet resistance reduction compared to commercial Cu foils. Direct printing of Cu-Graphene using meniscus-confined co-deposition on gold wafers demonstrated a 20% conductivity enhancement compared to Cu prints. Additionally, Cu-Graphene direct printing onto a 3D printed Ag polymer trace showed a 20% and 30% decrease in temperature rise during an applied current across the trace compared to the bare Ag and Cu-coated silver trace, respectively; note, the decrease in temperature rise correlates directly with an enhancement of thermal conductivity by Cu-Graphene. Results showed the direct print application of Cu-Graphene leads to solderable pads that enable pick and place circuit board fabrication.

[0016] Electrochemical approaches are particularly practical because they are cost-effective processes with simple equipment for large-scale manufacturing. The carbon materials are dispersed in the electrodeposition solution, which results in the carbon material being uniformly distributed in the metal matrix.

[0017] To address the need for the government and commercial applications in thermal straps, electronic devices, and space landing systems, an efficient, scalable, and manufacturing-ready approach for production of conductivity enhanced graphene-Cu hybrid foils / coatings has been developed. These high-performance foils can be used to fabricate thermal straps to reduce cooldown time of advanced conduction cooling for SRF systems. The fabrication approach detailed herein is a specific instance of a general method to produce electrodepositable metals (Cu, Ag, Ni, etc.)-nanocarbon (graphene, carbon nanotubes, etc.) hybrids.

[0018] Table 1 compares commercially procured annealed Cu foils at thicknesses of 10 and 25 microns directly to produced copper graphene foils prepared as a composite or in layers and with / without annealing. The data presented is a head-to-head experimental result and does not represent the theoretical numbers associated with Cu but the measured numbers within an identical experimental set. It would be desirable to be able to select attributes of interest such as low mass, low cost, high availability, high conductivity, etc. and produce a tailored article comprised of low cost highly available materials, that exhibit the more desirable attributes of conduction. It is an intent of this invention to describe a flexible set of process that can be utilized to tailor the attributes of a produced conductor to provide desirable conduction properties for a given application.TABLE 1Density, Sheet Resistance, and Thermal Conductivity Comparisonbetween commercial annealed Cu foils and the producedCopper Graphene foils with and without annealing.Sheet ResistanceThermal ConductivityMassmΩ / cm2 (10 μmw / m · K (25 μmMetal Type(g / cm3)thicknessthickness)Copper8.965164Copper8.962.5263graphene foilCopper8.96Data not available312graphene foilannealed

[0019] In various embodiments, conductivity enhanced hybrid graphene-Cu materials have been fabricated via two approaches: electro-codeposition with a pulsed electric field with simultaneously deposited Cu and graphene materials formed a composite hybrid graphene-Cu foils in a single tank and electro-codeposition with a pulsed electric field in which we simultaneously deposit Cu and graphene materials formed a composite hybrid graphene-Cu trace. This is accomplished by using a 3D printer and a confined meniscus.

[0020] In another embodiment, pulsed electric field operation is used to control the amount a graphene incorporation and thus dynamically control the physical properties of the material.

[0021] In another embodiment, pulse electric field operation is used to control the foil / coating size / thickness to match the dimensions of the practical applications.

[0022] In another embodiment, pulse electric field operation is used to directly apply the high conductivity material to a conductive wire reducing its skin resistance to match the dimensions of the specific high frequency application. The required skin thickness is governed by a well-known equation which is frequency dependency and also dependent on the resistance. For high frequency applications, a low resistance hybrid material would be ideal and physical coating dimensions would be quite thin, for example in the micron range.

[0023] In another embodiment, the hybrid Cu-Graphene foils exhibit more than 50% conductivity enhancement compared to commercial Cu foils. In another embodiment, the hybrid Cu-Graphene foils with post thermal reduction treatment exhibit more than 90% conductivity enhancement compared to commercial Cu foils. In another embodiment, the hybrid Cu-Graphene foils exhibit more than 50% increase in strain strength. In another embodiment, the hybrid Cu-Graphene foils exhibit ~50% sheet resistance reduction compared to commercial Cu foils. In another embodiment, the hybrid Cu-Graphene traces exhibit a 20% increase in conductivity compared to Cu print onto gold wafers using meniscus-confined electro-codeposition. In another embodiment, the hybrid Cu-Graphene traces exhibited a 20% and 30% decrease in temperature rise during an applied current compared to a bare Ag and Cu-coated Ag trace, respectively.

[0024] These new materials could be used in combination with cryocoolers for X-Ray equipment or superconducting radio frequency technology; they could be used for thermal transport on satellites; semi-conductor backplanes; or high conductivity traces for direct printed circuits. The incorporation of nano-carbons into electrodeposited metallics offers the possibility to change physical properties of the materials through the local organization of the carbon in the grain boundaries of the amorphous deposit. The addition of an anneal post deposition allows for crystal formation of the carbon / metal deposit.

[0025] One such nano-carbon material, graphene, is a two-dimensional (2D) material with excellent physical and chemical properties, such as thermal and electronic conductivity, high mechanical strength and large specific surface area. Graphene and its derivatives have shown great potential in applications ranging from thermal management, energy storage, corrosion, to sensors. Conjugated systems of composite materials may have collective properties that are drastically different than a simple combination of individual components. The intrinsic physiochemical properties of graphene and a metal (copper) matrix, combined with advanced fabrication techniques, could tailor graphene-copper hybrid properties and make the hybrid as ideal thermal strap materials for conduction cooling of superconducting radiofrequency (SRF) systems.

[0026] Featured is a method of enhancing the conductivity of metal-nanomaterial hybrids wherein a cathode substrate is subject to an electrolyte solution including a nanomaterial and metal ions. The cathode substrate is spaced from a metal anode in the electrolyte solution. A pulsed waveform is applied across the cathode and anode to electrodeposit metal ions from the electrolyte solution onto the cathode substrate as a coating and to electrophoretically embed the nanomaterial in the electrolyte solution into the coating on the cathode substrate. The pulsed waveform is preferably configured to produce a cathodic pulse which electrodeposits the metal ions onto the cathode substrate and which electrophoretically embeds the nanomaterial into the coating followed by an anodic pulse which improves deposition uniformity.

[0027] In some embodiments, the cathode substrate is stainless steel, the metal ions are copper, and the nanomaterial is graphene in sheet form and the concentration of the nanomaterial in the electrolyte solution is between 2.5 to 25 mg / L.

[0028] The method may further include heating the coating to further improve its thermal and electrical conductivity. The preferred coating exhibits a 20-50% decrease in electrical resistivity compared to the electrical resistivity of a metal sheet material made of the metal ions, a 30% or greater increase in thermal conductivity compared to the thermal conductivity of a metal sheet material made of the metal ions, and a 50% or greater increase in thermal conductivity compared to the thermal conductivity of a metal sheet material made of the metal ions.

[0029] In one version, the cathode substrate is placed in the electrolyte solution. In another version, the electrolyte solution is pumped through a nozzle to the cathode substrate and the cathode substrate is moved relative to the nozzle and / or the nozzle moves relative to the cathode substrate.

[0030] The coating may be removed from the cathode substrate. The nanomaterial can be graphene, nanocarbon, and / or borophene. In one example, the graphene is reduced graphene oxide. The metal ions can be nickel, silver, copper, and / or other plateable metal ion.

[0031] Usually, the pulsed waveform is repeated a plurality of times. The anode is preferably metal to replenish the metal ions in the electrolyte solution. The anode metal can be nickel, silver, copper, and / or other plateable metal material.

[0032] Also featured is a method of enhancing the conductivity of metal-nanomaterial hybrids comprising placing a cathode substrate in a container including an electrolyte solution with a nanomaterial and metal ions, the cathode substrate spaced from a metal anode also in the electrolyte solution, electrodepositing metal ions from the electrolyte solution onto the cathode substrate forming a coating on the cathode substrate in said container, and electrophoretically embedding the nanomaterial in the electrolyte solution into said coating on the cathode substrate in said container. A pulsed waveform can be applied across the cathode substrate and metal anode and is configured to produce a cathodic pulse which electrodeposits the metal ions onto the cathode substrate and which electrophoretically embeds the nanomaterial into the coating followed by an anodic pulse which improves deposition uniformity.

[0033] Also featured is a method of enhancing the conductivity of metal-nanomaterial hybrids comprising placing a metal anode in a nozzle with an electrolyte solution including a nanomaterial and metal ions, directing the nozzle at a cathode substrate, providing relative movement between the cathode substrate and the nozzle, and applying a pulsed waveform across the cathode substrate and anode to electrodeposit metal ions from the electrolyte solution onto the cathode substrate as a coating and electrophoretically embedding the nanomaterial in the electrolyte solution into the coating on the cathode substrate. Preferably, the pulsed waveform is configured to produce a cathodic pulse which electrodeposits the metal ions onto the cathode substrate and which electrophoretically embeds the nanomaterial into the coating followed by an anodic pulse which improves deposition uniformity.

[0034] The subject invention, however, in other embodiments, need not achieve all these objectives and the claims hereof should not be limited to structures or methods capable of achieving these objectives.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0035] Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:

[0036] FIG. 1 is a schematic view of an as-plated hybrid coating on a substrate;

[0037] FIG. 2 is a schematic view of an as-plated hybrid coating peeled off from the substrate;

[0038] FIG. 3 contains photographs of hybrid graphene-Cu Cu foil formed and peeled from a stainless steel substrate;

[0039] FIG. 4 is a schematic representation of an electrolytic codeposition apparatus;

[0040] FIG. 5 is a schematic representation of the direct print setup for electrolytic-codeposition;

[0041] FIG. 6 is a schematic of electro-codeposition approach for fabricating hybrid graphene-Cu foils;

[0042] FIG. 7 is a representation of a duplex pulsating boundary layer;

[0043] FIGS. 8A-8B are representations of a macroprofile and a microprofile boundary layer under direct current and pulse current conditions;

[0044] FIG. 9 is a summary of guiding principles for the impact of pulse parameters on deposit distribution;

[0045] FIG. 10 depicts an exemplary process flow chart for the application of a hybrid coating application and annealing process;

[0046] FIG. 11 is a comparison of Stress-Strain Curves of Cu foil and graphene-Cu hybrid foil;

[0047] FIG. 12 describes the effect of nanocarbon concentration on sheet resistance;

[0048] FIG. 13 is a comparison of sheet resistance of hybrid graphene-Cu foil with commercial Cu foil and electrodeposited Cu foils;

[0049] FIG. 14 is the comparison of thermal conductivity of hybrid graphene-Cu foil with commercial Cu foil and electrodeposited Cu foils;

[0050] FIG. 15 is the comparison of thermal conductivity of hybrid and layered graphene-Cu foils with and without post thermal reduction treatment and commercial Cu foil;

[0051] FIGS. 16A and 16B are images of Cu (FIG. 16A) and Cu-Graphene (FIG. 16B) on Au;

[0052] FIG. 17 are line scans of a typical thick (Left) and thin (Right) Cu-Graphene traces on Au;

[0053] FIG. 18 shows copper (green) and hybrid (blue; Cu / Graphene) printing on a gold wafer at 5- and 3-minute print duration;

[0054] FIG. 19A describes material layers and FIG. 19B describes a circuit with hybrid (Cu / Gr), copper, and silver regions;

[0055] FIG. 20A shows an IR temperature response at 0.5 A and FIG. 20B shows a temperature response at 1.0 A; and

[0056] FIG. 21 illustrates Raman spectra of a hybrid graphene-Cu foil.DETAILED DESCRIPTION OF THE INVENTION

[0057] Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer.

[0058] The intrinsic physiochemical, thermal, and mechanical properties of nanocarbon (graphene, carbon nanotube, etc.) and metal (Cu, Ag, Ni, etc.) matrix are used, combined with pulsed electrodeposition techniques for hybrid material fabrication. These fabricated hybrid materials / coatings can be used for thermal straps, semiconductor backplanes, thermal transport on satellites, or high conductivity traces for direct printed circuits. Other 2D nanomaterials with similar properties (such as Borophene) are suitable as well.

[0059] In electro-codeposition the concentration of the carbon materials in the metal deposit must be controlled to achieve the targeted conductivity enhancement. The addition of an annealing (heating) step allows for the crystallinity of the metallic deposit to improve leading to a further enhancement in the conductive and physical properties of the materials. The electro-codeposition method can be utilized to deposit these composite materials for various form factors including in the production of foils, additive coating (on a substrate), or in the form of circuit board traces.

[0060] FIG. 1 shows an as-plated hybrid coating 100, prepared by electro-codeposition, which comprises of the metal 110 and nanocarbon 120. The substrate 200 may be any conductive material, such as steel, Au, Cu, Ag polymer ink, or etc. The metal 100 may be any metal that can be electrodeposited (Cu, Ag, Ni, etc.). The nanocarbon 120 (graphene, carbon nanotubes, and carbon nanobundles, etc.) can be suspended in the electrodeposition electrolyte. In some cases, the hybrid graphene-Cu coatings can be peeled from the substrate 200 to create a free-standing hybrid graphene-copper foils or plates 100, FIG. 2. In some cases, the free-standing hybrid foil is then subsequently annealed. In an instance where the coating is to be peeled, the substrate surface ideally has a chromium passivating layer. If the coating is intended to remain on the substrate, then the surface should be free of an oxide scale in order to maintain adhesion. By performing an annealing operation (high temperature<than the melting point and in a reducing environment), constituents from the hybrid coating system 100 can diffuse causing the grain size of the metal to increase leading to an enhancement of the hybrid material properties. The annealing operation does not melt or deform the prepared hybrid material. FIG. 3 illustrates the hybrid material 100 peeled of substrate 200.

[0061] FIG. 4 is a schematic representation of an electrolytic codeposition apparatus 600. Included is a controllable power supply 620 with an anode lead 640 and a cathode lead 660 capable of delivering a direct current (DC), pulse current (PC) or pulse reverse current (PRC) to an electrolytic cell 700. The electrolytic cell includes a cell container 710 with an anode 720, a cathode 740, and an electro codeposition electrolyte solution 730 with one or more metal elements 741 dissolved in the electrolyte and suspended nanocarbon materials 743 also in the electrolyte.

[0062] A method of enhancing the conductivity of metal-nanomaterial hybrids, features subjecting cathode substrate 740 to an electrolyte solution 730 including a nanomaterial 743 and metal ions 741. The cathode substrate 740 is spaced from a metal anode 720 in the electrolyte solution. Anode 720 can be sacrificial to replenish the metal ions 741 in the electrolyte.

[0063] A pulsed waveform is applied across the cathode 740 and anode 720 to electrodeposit metal ions 741 from the electrolyte solution 730 onto the cathode substrate 740 as a coating and electrophoretically embedding the nanomaterial 743 in the electrolyte solution into the coating 745 on the cathode substrate. The pulsed waveform is configured to produce a cathodic pulse which electrodeposits the metal ions onto the cathode substrate and which electrophoretically embeds the nanomaterial into the coating followed by an anodic pulse which improves deposition uniformity. In the example of FIG. 4, the cathode substrate 740 is placed in the electrolyte solution 730.

[0064] Cathode substrate 740 can be stainless steel, the metal ions 741 may be copper, and the carbon nanomaterial 743 can be graphene in sheet form. The nanomaterial can be graphene, nanocarbon, and / or borophene. The graphene is preferably reduced graphene oxide.

[0065] Preferably, the concentration of the nanomaterial in the electrolyte solution is between 2.5 to 25 mg / L. The metal ions 741 can be nickel, silver, copper, and / or other plateable metal ions.

[0066] Preferably, the pulsed waveform is repeated a plurality of times.

[0067] FIG. 5 is a schematic representation of a direct print electrolytic codeposition apparatus 800. Included is a power supply 820 with an anode lead 840 and a cathode lead 860 capable of delivering a direct current (DC), pulse current (PC) or pulse reverse current (PRC) to an electrolytic solution 930 in nozzle 910. The electrolytic droplet 940 is formed at the end of a nozzle capillary 910. The anode 840 is inside the capillary and the cathode is the print substrate 740. The codeposition electrolytic solution 930 includes one or more metal elements 741 dissolved in the electrolyte solution along with suspended nanocarbon materials 743. In this example, the electrolyte solution 930 is pumped through nozzle 910 to the cathode substrate 740 and the cathode substrate 740 is moved relative to the nozzle 910 and / or the nozzle 910 moves relative to the cathode substrate 740.

[0068] In either case, electrolytic codeposition may be practiced using direct current, pulse current or pulse reverse current. In direct current codeposition processes, the current is applied to the electrolytic cell and generally held constant for a period of time, after which the deposit is formed on the oppositely charged electrode substrate. In pulse current / pulse reverse current electrolytic codeposition, the current is interrupted and or reversed in predetermined ways. By properly selecting the pulse current / pulse reverse current waveform parameters, the codeposit thickness, uniformity of codeposition, localization of codeposition, and properties are tuned for the specific application. Numerous embodiments of pulse current / pulse reverse current deposition are described by the common assignee of the instant invention in U.S. Pat. Nos. 6,080,504; 6,203,684; 6,210,555; 6,303,014; 6,309,528; 6,319,384; 6,524,461; 6,551,484; 6,652,727; 6,750,144; 6,827,833; 6,863,793; 6,878,259; 8,603,315; 10,100,423; 10,684,522; and 11,411,258 which are all incorporated herein by this reference.

[0069] FIG. 6 represents a generalized pulse current / pulse reverse current waveform. The generalized waveform parameters are characterized by a cathodic pulse followed by an off-time and followed by an anodic pulse and followed by an off-time. One skilled in the art recognizes that one or both off-times may be eliminated and that the either the cathodic pulse or the anodic pulse may be eliminated. The waveform parameters are: 1) anodic pulse current density, ianodic, 2) anodic on-time, ton, anodic, 3) cathodic pulse current density, icathodic, 4) cathodic on-time, ton, cathodic, 5) cathodic off-time, toff, cathodic and 6) anodic off-time, toff, anodic. The sum of the anodic and cathodic on-times and the off-time is the pulse period, T. The inverse of the pulse period is the frequency, f, of the pulse. The anodic, γa, and cathodic,γc, duty cycles are the ratios of the respective on-times to the pulse period. The average current density (iaver) or net deposition rate is given by:i aver=ic⁢γc-ia⁢γa(1)

[0070] Just as there are infinite combinations of height, width, and length to obtain a given volume, in pulse processing there are unlimited combinations of peak voltages / current densities, duty cycles, and frequencies to obtain a given deposition rate in electrolytic deposition processes. These parameters provide the potential for much greater process / product control compared to conventional DC deposition processes.

[0071] Mass transport in pulse current / pulse reverse current electrolytic and electrophoretic deposition processes is a combination of steady state and non-steady state diffusion processes. The mass transfer limited current density (il) is related to the reactant concentration gradient (Cb-Cs) and to the diffusion layer thickness (δ) by the following equation:il=- nFD⁢(δ⁢C / δ⁢x)x=0=- nFD [(Cb-Cs) / δ](2)where n, F, and D are the number of equivalents, Faraday's constant, and diffusivity of the reacting species, respectively. In DC electrolysis, δ is a time-invariant quantity for a given electrode geometry and hydrodynamic condition. In pulse / pulse reverse electrolysis, however, δ varies from zero at the beginning of the pulse to its steady state value when the Nernst diffusion layer is fully established. The corresponding mass transport limiting current density would then be equal to an infinite value at t=0 and decreases to a steady state value of the DC limiting current density. The advantage of pulse / pulse reverse electrolysis is that the current can be interrupted before δ has a chance to reach steady state. This allows the reacting ions to diffuse back to the electrode surface and replenish the surface concentration to its original value before the next current interruption. Therefore, the concentration of reacting species in the vicinity of the electrode pulsates with the frequency of the modulation.FIG. 7 illustrates a duplex diffusion layer including a pulsating layer, δp, and a stationary layer, as during pulse electrolysis. Since the thickness of the pulsating diffusion layer is determined by the waveform parameters, this layer may be thought of as an electrodynamic diffusion layer. By assuming a linear concentration gradient across the pulsating diffusion layer and conducting a mass balance, the pulsating diffusion layer thickness (δp) as:δp=(2⁢D⁢ton)1 / 2(3)where ton is the pulse on time. When the pulse on time is equal to the transition time, the concentration of reacting species at the interface drops to zero at the end of the pulse. An expression for the transition time, τ, is:τ=((n⁢F )2⁢Cb2⁢D) / 2⁢ic2(4)More exact solutions are given by integrating Fick's diffusion equation:δp=2⁢((D⁢ton) / π)1 / 2(5)τ=π⁡((n⁢F )2⁢Cb2⁢D) / 4⁢ic2(6)The same equation for the pulsating diffusion layer is also relevant to pulse-reverse deposition. The key points in the development of pulse current / pulse reverse current deposition processes are: (1) the electrodynamic diffusion layer thickness is proportional to the pulse on time and (2) transition time is inversely proportional to the current.In electrolytic codeposition of nanocarbon process, the amount of deposit and concentration of the nanocarbons distributed is determined by the current distribution. The current distribution is controlled by primary (geometrical), secondary (kinetic) or tertiary (mass transport) effects. The addition of secondary or tertiary effects tends to make the current distribution more uniform, as compared to primary effects alone. If the applied waveform is designed such that the pulse on-time is much longer than the transition time, the tertiary current distribution will play an important role in the deposition. With the addition of tertiary control, the concept of macro- and micro-profiles influence the current distribution.FIG. 8A illustrates a macroprofile wherein the roughness of the surface is large compared with the thickness of the diffusion layer, and the diffusion layer tends to follow the surface contour. Under mass transport or diffusion control, a macroprofile results in a uniform current distribution and tends to follow the surface contour producing a conformal deposit during deposition. FIG. 8B illustrates a microprofile wherein the roughness of the surface is small compared with the thickness of the diffusion layer. Under mass transport control, a microprofile results in a non-uniform current distribution and a non-conformal deposition of material, beneficial for creating a more uniform coating surface devoid of pores. By applying the appropriate waveform, one skilled in the art can effectively focus or defocus the current distribution to create non-uniform or uniform deposition respectively.

[0077] FIG. 9 summarizes four pulse current waveform types, independent of cathodic pulse or anodic pulse, to influence the current distribution and hence the deposition distribution in an electrolytic codeposition process or layered electrodeposition / electrophoretic deposition processes. In some embodiments of the instant invention, a direct current is employed to codeposit a hybrid or layered coating system. In other cases, a pulse reverse current is employed to codeposit a hybrid or layered coating system. In other cases, a pulse reverse current is employed to codeposit a hybrid or layered coating system. In some embodiments, a codeposit a hybrid or layered coating system is uniformly deposited across a surface. In other embodiments, a codeposit or a layered hybrid coating system is locally deposited across a surface. By properly selecting the pulse current / pulse reverse current waveform parameters, the codeposit thickness, uniformity of codeposition, localization of codeposition, and properties are tuned for the desired conductivity enhancement.

[0078] FIG. 10 presents an embodiment of the process steps in the graphene-Cu hybrid coating electro-codeposition method of the instant invention. FIG. 10 shows the general process utilized in preparation of the working examples provided. The process can include a substrate pre-treatment step 1201 to clean / degrease the surface of the substrate 1200 freeing it from any oils or particulates, this is commonly done with a solvent like acetone or isopropanol. This step is often followed by a water rinse 1220 before the graphene-Cu hybrid coating 1210 is applied to the surface. Thus, a properly prepared substrate 1200 attributes include: clean, conductive, resistant to acid, water break free surface for the deposition of the graphene-Cu hybrid deposit. The coated component is often then rinsed 1220 and air dried 1230. The coated component is peeled off from the substrate to form free-standing graphene-copper hybrid foils 1240. Finally, the graphene-copper hybrid foils are thermally reduced 1250 by applying a temperature (300° C.-400° C.) and a flow of mixed gases (5% H2 with 95% Ar).

[0079] FIG. 12 illustrates the influence on resistance by varying the amount of nanocarbon in the electrolytic cell. The range of 2.5 to 25 mg / L produced lower resistance, while the preferred range of 5 to 15 mg / L provided the highest performance gains.

[0080] The following examples illustrate various embodiments.Baseline for Evaluation

[0081] Commercial copper foils were purchased for a baseline evaluation. These commercial foils are annealed copper foils obtained from McMaster-Carr. The thickness of commercial Cu foils is around 25 μm.Working Example I (without Graphene Contents and Using DC)

[0082] Pure copper foils were prepared through direct current electrodeposition. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. A solid copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. Prior to the application of the electrodeposited Cu coating, the stainless-steel substrate was cleaned and rinsed with soap and DI water. The pure Cu plating electrolyte consisted of 45 g / L copper sulfate pentahydrate (CuSO4·5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), and 350 ppm polyethylene glycol (PEG).

[0083] The pure copper was electrodeposited using a direct current condition at a current density of 50 mA / cm2 for 26 min. This operation was completed at approximately 25° C. After application of the pure copper coating on stainless steel substrates, the Cu coatings were air dried and peeled directly from the substrate surface as Cu foils for post characterization.Working Example II (without Graphene Contents and Using PC)

[0084] Pure copper foils were prepared through pulse current electrodeposition. The pure copper foils were prepared to be used as a baseline for evaluation of the invention. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. The substrates were first cleaned / degreased with a solvent like acetone or isopropanol, then rinsed with DI water. A copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. The pure Cu plating electrolyte consisted of 45 g / L copper sulfate pentahydrate (CuSO4 5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), and 350 ppm polyethylene glycol (PEG).

[0085] The pure copper was also electrodeposited using a pulse waveform with a cathodic current of 50 mA / cm2 for 0.5 ms followed by an open circuit time off of 1.5 ms; then repeat consistently for 105 min. This operation was completed at approximately 25° C. After application of the pure copper coating on stainless steel substrates, the Cu coatings were air dried and peeled directly from the substrate surface as Cu foils for post characterization.Working Example III (with Graphene Contents and Using DC)

[0086] The hybrid Graphene-Cu foils were prepared through direct current electro-codeposition. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. A copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. Prior to the application of the electrodeposited Cu coating, the stainless-steel substrate cleaned and rinsed with soap and DI water. The pure Graphene-Cu electrolyte consisted of 90 g / L copper sulfate pentahydrate (CuSO4 5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), 350 ppm polyethylene glycol (PEG), Cetyltrimethyl Ammonium Bromide (CTAB) 5 mg / L, polyvinylpyrrolidone (PVP) 5 mg / L, and reduced graphene oxide (RGO) 5 mg / L.

[0087] The hybrid Graphene-Cu foils were electro-codeposited using a direct current condition at a current density of 20 mA / cm2 for 60 min. This operation was completed at approximately 25° C. After the application of the hybrid Graphene-Cu on stainless steel substrates, the hybrid Graphene-Cu coatings were air dried and peeled directly from the substrate surface as hybrid Graphene-Cu foils for post characterization.Working Example IV (with Graphene Contents and Using Pc)

[0088] The hybrid Graphene-Cu foils were prepared through pulse current electro-codeposition. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. A copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. Prior to the application of the electrodeposited Cu coating, the stainless-steel substrate was cleaned and rinsed with soap and DI water. The pure Cu plating electrolyte consisted of 90 g / L copper sulfate pentahydrate (CuSO4 5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), 350 ppm polyethylene glycol (PEG), Cetyltrimethyl Ammonium Bromide (CTAB) 5 mg / L, polyvinylpyrrolidone (PVP) 5 mg / L, and reduced graphene oxide (RGO) 5 mg / L.

[0089] The synthesis process of hybrid graphene-copper foils and traces by pulse / pulse-reverse electro-codeposition process are demonstrated in FIG. 6. During the electro-codeposition process, the stainless-steel substrate and the counter electrode (Cu plate) will be fixed relative to one another and connected to a pulsed power source. Cu anode is a sacrificial counter electrode to maintain the Cu concentration constant during the fabrication process. Reduced graphene oxide (RGO) nanosheets are used as graphene contents. Cetyltrimethyl Ammonium Bromide (CTAB) and polyvinylpyrrolidone (PVP) as dispersants for dispersing RGO nanosheets in Cu plating bath. CTAB also provide the positive charges for RGO sheets. With the positive charges, both RGO sheets and Cu are deposited on the substrate under cathodic current. Under anodic current the hybrid coating is preferentially removed from areas exposed to higher current densities, to improve deposit uniformity. With alternate electrical fields under pulse current reverse process, RGO sheets were distributed and embedded in the copper matrix to form hybrid graphene-copper. The optimization of the mass transport in pulse / pulse reverse process provides the opportunities to control the foil / coating thickness and uniformity (the amounts of hybrid graphene-Cu). The hybrid graphene-Cu foils / traces / coatings were formed on stainless steel substrates using the FARADAYIC® Electro-Codeposition process, then peeled off from the substrates as free-standing hybrid graphene-copper foils.

[0090] The hybrid Graphene-Cu foils were electro-codeposited using a pulse waveform with a cathodic current of 20 mA / cm2 for 0.5 ms followed by an open circuit time off of 1.5 ms; then repeat consistently for 240 min. This operation was completed at approximately 25° C. After the application of the hybrid Graphene-Cu on stainless steel substrates, the hybrid Graphene-Cu coatings were air dried and peeled directly from the substrate surface as hybrid Graphene-Cu foils for post characterization.Working Example V (Analysis)

[0091] Comparing the thermal and electrical conductivity of hybrid and layered Cu-Graphene foil samples prepared above (EXAMPLE VI and V) versus a commercial Cu foil (baseline) and electrodeposited Cu foil (EXAMPLE I) samples were measured and shown in FIG. 13 and FIG. 14. The thermal conductivity of hybrid and layered Cu-Graphene foils fabricated as shown above are more than 50% and 5% higher than the thermal conductivity of commercial Cu foil, respectively.Working Example VI

[0092] The post thermal reduction treatments were carried out on hybrid graphene-Cu foils. The hybrid graphene-Cu foils were prepared through pulse current electro-codeposition as demonstrated in WORKING EXAMPLE V. The hybrid graphene-Cu foils were placed a tube furnace with vacuum capacity. The tube furnace system was first evacuated for 20 min and then backfilled with mixed gases of 5% H2 with 95% Ar at a flow rate of 0.3 L / min. Second, the tube furnace was heated to 400° C. in 30 min. Third, the hybrid graphene-Cu foils were thermal reduced for 2 hours. Finally, the furnace was opened and cooled down to room temperature for post characterization.Working Example VII

[0093] FIG. 11 shows the improved mechanical strain as compared to standard Cu foil. Comparing the thermal and electrical conductivity of hybrid and layered Cu-Graphene foil samples post anneal versus a commercial Cu foil and electrodeposited Cu foil were measured. The results are shown in FIGS. 13-15. As shown, the post thermal reduction treatment led to a significant improvement in thermal conductivity. The hybrid foils with post thermal reduction treatment exhibit more than 90% and 100% conductivity enhancement compared to commercial Cu foils.

[0094] The sheet resistance of hybrid graphene-copper hybrid foils was evaluated using a four-point probe system. As shown, the hybrid Cu-Graphene foils exhibit ~50% sheet resistance reduction compared to commercial Cu foils.Baseline for Evaluation (Au Substrate)

[0095] Commercial gold-coated silicon wafers were purchased for a baseline evaluation. The gold wafers were purchased from LGA Thin Films. The silicon wafer backing has a 10 nm chromium adhesion layer with a 100 nm gold layer on top for electrodeposition of copper or copper-graphene onto the gold substrate.Working Example VIII (Pure Cu Trace Printing on Au Substrate)

[0096] A plastic nozzle 910, FIG. 5 with a diameter of ~1 mm was backfilled with a copper plating electrolyte (95 g / L copper sulfate, 52 g / L sulfuric acid, 6.5 mM hydrochloric acid, 350 ppm polyethylene glycol, 5 mg / L polyvinylpyrrolidone, and 5 mg / L cetrimonium bromide). A copper wire was inserted into the nozzle and acted as the anode. The nozzle, controlled by an x, y, z stage was placed 300 μm above the gold cathode substrate. A meniscus was formed onto the gold wafer by pushing solution through the nozzle via a positive displacement pump set to operate at 0.6 mL / Hr. A 500 Hz pulse current at a 25% duty cycle (0.5 ms on, 1.5 ms off, 2 ms total time) was applied while simultaneously moving the nozzle in the x or y direction via the 3D printing x, y, x positioner at a speed of 1.6 mm / s. Printing of the copper material occurred only where the electrolyte, confined within the meniscus, wetted the gold substrate. The printing of the Cu onto the Au substrate is shown in FIG. 16. The printed copper line was tested using a variety of methods to determine material properties.Working Example IX (Hybrid Cu-Graphene Printing on Au Substrate)

[0097] A plastic nozzle with a diameter of ~1 mm was backfilled with a copper plating electrolyte (95 g / L copper sulfate, 52 g / L sulfuric acid, 6.5 mM hydrochloric acid, 350 ppm polyethylene glycol, 5 mg / L polyvinylpyrrolidone, 5 mg / L cetrimonium bromide, and 5 mg / L reduced graphene oxide). A copper wire was inserted into the nozzle and acted as the anode. The nozzle, controlled by an x, y, z stage was placed 300 μm above the gold cathode substrate. A meniscus was formed onto the gold wafer by pushing solution through the nozzle via a positive displacement pump set to operate at 0.6 mL / Hr. A 500 Hz pulse current at a 25% duty cycle (0.5 ms on, 1.5 ms off, 2 ms total time) was applied while simultaneously moving the nozzle in the x or y direction via the 3D printing x, y, x positioner at a speed of 1.6 mm / s. Printing of the copper-graphene material occurred only where the electrolyte, confined within the meniscus, wetted the gold substrate. The printed copper-graphene line was tested using a variety of methods to determine material properties.Working Example X (Analysis of Print Traces on Gold Substrate)

[0098] Copper or copper-graphene traces on gold were then tested to measure their conductivity. First, optical profilometry was used to characterize the dimensions of the copper trace. The dimensions of the line varied based on the total deposition time, but a typical trace had a length of 6 mm, width of 3 mm, and a height of 500 nm, as shown in FIG. 17. The copper traces were analyzed using a commercially available four-point probe to measure the sheet resistance of the line. The conductivity of the line is calculated using software based on the dimensions of the trace. Raman spectrometry was used to confirm graphene composition in the hybrid foils. Both hybrid and layered graphene-Cu hybrid foils were examined by Raman spectroscopy using the inVia Reflex Micro-Raman system manufactured by Renishaw PLC with samples being assessed at 514 nm excitation. As shown in FIG. 18, both Raman spectra exhibited two peaks: the D band at ~1350 cm−1; the G band at 1600 cm−1. The D band is attributed to defects in the graphene, and G band is associated with the tangential vibrations of sp2 bonded carbon atoms. These two featured bands indicate the existence of graphene in both hybrid and layered graphene-Cu foils.

[0099] The conductivity of the copper and copper-graphene trace is provided in FIG. 18. The copper-graphene traces showed a 20% increase in conductivity compared to the copper traces.Baseline for Evaluation (Ag Seed Trace)

[0100] A conductive silver ink was printed onto a polyimide insulator backing. The thickness of the silver trace ranged between 10-30 μm while the dimensions of the trace (width, length, and shape) were variable depending the desired characteristics of the trace, as shown in FIG. 19 (line 3). The silver trace acted as the substrate for electrodeposition of copper or copper-graphene onto the silver. The method for trace printing of conductive materials is highlighted in U.S. Pat. Nos. 9,395,718; 8,790,742; and 7,972,650 all incorporated herein by this reference.Working Example XI (Pure Cu Trace Printing on Ag Seed Trace)

[0101] A plastic nozzle with a diameter of ~1 mm was backfilled with a copper plating electrolyte (95 g / L copper sulfate, 52 g / L sulfuric acid, 6.5 mM hydrochloric acid, 350 ppm polyethylene glycol, 5 mg / L polyvinylpyrrolidone, and 5 mg / L cetrimonium bromide). A copper wire was inserted into the nozzle and acted as the anode. The nozzle, controlled by an x, y, z stage was placed 300 μm above the gold cathode substrate. A meniscus was formed onto the gold wafer by pushing solution through the nozzle via a positive displacement pump set to operate at 0.6 mL / Hr. A 500 Hz pulse current at a 25% duty cycle (0.5 ms on, 1.5 ms off, 2 ms total time) was applied while simultaneously moving the nozzle in the x or y direction via the 3D printing x, y, x positioner at a speed of 1.6 mm / s. Printing of the copper material occurred only where the electrolyte, confined within the meniscus, wetted the gold substrate. The printing of the Cu onto the Au substrate is shown in FIG. 19 (line 2). The printed copper line was tested using a variety of methods to determine material properties.Working Example XII (Hybrid Cu-Graphene Printing on Ag Seed Trace)

[0102] A plastic nozzle with a diameter of ~1 mm was backfilled with a copper plating electrolyte (95 g / L copper sulfate, 52 g / L sulfuric acid, 6.5 mM hydrochloric acid, 350 ppm polyethylene glycol, 5 mg / L polyvinylpyrrolidone, 5 mg / L cetrimonium bromide, and 5 mg / L reduced graphene oxide). A copper wire was inserted into the nozzle and acted as the anode. The nozzle, controlled by an x, y, z stage was placed 300 μm above the gold cathode substrate. A meniscus was formed onto the gold wafer by pushing solution through the nozzle via a positive displacement pump set to operate at 0.6 mL / Hr. A 500 Hz pulse current at a 25% duty cycle (0.5 ms on, 1.5 ms off, 2 ms total time) was applied while simultaneously moving the nozzle in the x or y direction via the 3D printing x, y, x positioner at a speed of 1.6 mm / s. Printing of the copper-graphene material occurred only where the electrolyte, confined within the meniscus, wetted the gold substrate. The printing of the Cu onto the Au substrate is shown in FIG. 19 (line 1). The printed copper-graphene line was tested using a variety of methods to determine material properties.Working Example XIII (Analysis of Print Trace on Ag Seed Trace)

[0103] Copper or copper-graphene traces on gold were then tested to measure their conductivity. First, optical profilometry was used to characterize the dimensions of the copper trace. The dimensions of the line varied based on the total deposition time, but a typical trace had a length of 6 mm, width of 2-3 mm, and a height of 0.5-10 μm depending on the deposition time; an example optical profilometry trace is provided in FIG. 17. The copper traces were analyzed using a commercially available four-point probe to measure the sheet resistance of the line. The conductivity of the line is calculated using software based on the dimensions of the trace. The conductivity of the copper and copper-graphene trace is provided in FIG. 18. The copper-graphene traces showed a 20% increase in conductivity compared to the copper traces.

[0104] The copper or copper-graphene prints on the silver paste were used to test the thermal properties of the material. A silver trace was printed onto a polyimide backing. The resulting trace was divided into three regions in which (1) copper-graphene electrodeposited onto the silver, (2) copper electrodeposited onto the silver trace, and a bare silver layer (FIG. 19A); all deposition conditions were identical to those described for printing on gold wafers. A 1A current is applied across three different sections of a simple resistive circuit (1) copper-graphene, (2) copper, and (3) bare silver (FIG. 19B).

[0105] FIG. 20A shows a qualitative IR image in which the temperature rise of the bare silver is greater than the copper and copper-graphene section of the trace. Note, the silver material used as the baseline substrate is a commercial polymer silver paste that is far less conductive than true bulk silver. To quantify the temperature differences, in house software is used to determine the average temperature across each section of the trace. FIG. 20B shows the average temperature of the three sections during the 1A current across each material. The copper-graphene showed a roughly 30% and 20% decrease in temperature rise during the heating of the circuit compared to silver and copper, respectively.

[0106] Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments. Other embodiments will occur to those skilled in the art and are within the following claims.

[0107] In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and / or there are many other reasons the applicant cannot be expected to describe certain insubstantial substitutes for any claim element amended.

Examples

working example i (

Working Example I (without Graphene Contents and Using DC)

[0082]Pure copper foils were prepared through direct current electrodeposition. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. A solid copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. Prior to the application of the electrodeposited Cu coating, the stainless-steel substrate was cleaned and rinsed with soap and DI water. The pure Cu plating electrolyte consisted of 45 g / L copper sulfate pentahydrate (CuSO4·5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), and 350 ppm polyethylene glycol (PEG).

[0083]The pure copper was electrodeposited using a direct current condition at a current density of 50 mA / cm2 for 26 min. This operation was completed at approximately 25° C. After application of the pure copper coating on ...

working example ii (

Working Example II (without Graphene Contents and Using PC)

[0084]Pure copper foils were prepared through pulse current electrodeposition. The pure copper foils were prepared to be used as a baseline for evaluation of the invention. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. The substrates were first cleaned / degreased with a solvent like acetone or isopropanol, then rinsed with DI water. A copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. The pure Cu plating electrolyte consisted of 45 g / L copper sulfate pentahydrate (CuSO4 5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), and 350 ppm polyethylene glycol (PEG).

[0085]The pure copper was also electrodeposited using a pulse waveform with a cathodic current of 50 mA / cm2 for 0.5 ms followed by an open circuit time off of...

working example iii (

Working Example III (with Graphene Contents and Using DC)

[0086]The hybrid Graphene-Cu foils were prepared through direct current electro-codeposition. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. A copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. Prior to the application of the electrodeposited Cu coating, the stainless-steel substrate cleaned and rinsed with soap and DI water. The pure Graphene-Cu electrolyte consisted of 90 g / L copper sulfate pentahydrate (CuSO4 5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), 350 ppm polyethylene glycol (PEG), Cetyltrimethyl Ammonium Bromide (CTAB) 5 mg / L, polyvinylpyrrolidone (PVP) 5 mg / L, and reduced graphene oxide (RGO) 5 mg / L.

[0087]The hybrid Graphene-Cu foils were electro-codeposited using a direct current condition at a cu...

RELATED APPLICATIONS

[0001] This application claims benefit of and priority to U.S. Provisional Application Ser. No. 63 / 777,764 filed Mar. 26, 2025, under 35 U.S.C. §§ 119, 120, 363, 365, and 37 C.F.R. § 1.55 and § 1.78, which is incorporated herein by this reference.GOVERNMENT RIGHTS

[0002] This invention was made with U.S. Government support under Contract No. DE-SC0021676 awarded by the Department of Energy, and Contract No. 80NSSC21C0179 awarded by NASA. The Government has certain rights in the subject invention.FIELD OF THE INVENTION

[0003] The present invention relates to conductivity enhanced materials and fabrication methods, and their applications in thermal straps, electronic devices, and the like.BACKGROUND OF THE INVENTION

[0004] There are numerous applications that require new materials that enhance thermal and electrical conductivity with reduced mass. There are numerous power consuming applications, wherein a very high-quality conductor is required. Such a conductor can conduct either heat and / or electricity or in numerous applications both.

[0005] Metals are a well-established conductor because they behave according to the Wiedemann-Franz law.

[0006] One notable example of high conduction that is not a metal is diamond, which is the hardest form of carbon. Diamonds are known to be the best thermal conductor, yet they do not conduct electricity. Silver is an excellent conductor of electricity. However, the supply of silver is constrained, and therefore the price is higher. Aluminum is often used as a conductor on long range transmission lines due to its low weight despite it being less conductive than copper or silver. Copper is a mainstay for standard wiring as it offers reasonably good conductivity for standard applications and supply is more available. However, there exists a desire for improved materials for demanding applications such as semiconductors, and the like. Superconductors do exist but typically function at cryogenic conditions making them impractical for widespread applications. Past work has established that copper and carbon can be combined to improve the conductivity of the resulting material. Issues exist with both the processes utilized and the viability of the produced article as it is difficult to properly combine the two materials to achieve a useful and / or durable result. It is an intent of this invention to describe a flexible set of electrochemical processes that can be utilized to tailor the attributes of a produced conductor to provide desirable conduction properties for a given application in a form that can be reliable, repeatable and functional. These conductors can be applied directly on a substrate for use or applied onto a donor substrate and removed for further processing and or use in any given application. In addition, the coating may be applied to the surface of an existing conductor to enhance overall conductivity and / or corrosion resistance. For example, nickel plated wire is often utilized for high temperature applications.

[0007] Graphene-metal hybrid materials can be synthesized through approaches such as chemical vapor deposition (CVD), electrical conversion process, powder metallurgy, electrodeposition, etc. Graphene has been directly grown on the surface of copper foil via CVD. However, the high synthesis temperature (>several hundred Celsius) limits its large-scale synthesis and industrial applications. In addition, graphene materials grown on the surface of copper foil are not only easily scratched during mechanical operation, but often delaminates in operational environments due to different thermal expansion for graphene and copper during thermal cycling. Metal-carbon materials have been produced using an electrical conversion process by applying electrical current into carbon materials infused molten metals. The molten metal formed carbon materials have shown higher thermal and electrical conductivity and higher strength compared to conventional metals. However, challenges are high variability in carbon distribution in the metal matrix, high concentrations of micropores, and thermal stability of carbon materials in molten metal carbon formed materials. These challenges may result in the variability in property measurements and inconsistent conversion yields of molten metal formed materials. Due to the agglomeration of graphene, powder metallurgy remains the challenge on the interface creation between graphene and metal matrix. Metal-carbon composites have been synthesized via electrochemical deposition.

[0008] Prior attempts demonstrate the potential performance enhancement given by creating composite material out of carbon and metals include U.S. Pat. Nos. 8,349,759 B2; 8,541,335 B2; 8,541,336 B2; 8,546,292 B2; 8,551,905 B2; 8,647,534 B2; 9,273,380 B2, all incorporated herein by this reference. However, in the prior art, the fabrication of these materials requires high temperatures and melting of the material to create the composite that they have coined as covetic.

[0009] Japanese Patent Application JP2020108622 discloses an approach for laminating Cu with Ag paste for improved conductive properties. This laminate formation requires a polymer adhesive and curing. U.S. Patent Application US20230022914A1 discloses an approach for laminating metal and nanocarbons with ultrasonic vibration. This laminate formation requires an ultrasonic vibration. Patent Application WO2001049795A1 is directed to a resin and an anodic electrocoat. U.S. Patent Application 20150322588A1 discloses an approach for functionally grading a composite metal / (glass, ceramic or polymer) coating using a pulse electro-codeposition process. U.S. Patent Application 20210380832A1 discloses a method to print conductive inks consisting of a binder and a metal powder. All of these references are incorporated herein by this reference.

[0010] Trace printing by electrodeposition through a pipet using a pulse electrodeposition process is highlighted in the following papers: Daryadel, S., Behroozfar, A., Minary-Jolandan, M., Toward Control of Microstructure in Microscale Additive Manufacturing of Cu Using Localized Electrodeposition, Adv. Eng. Mater, 2018, 1800946; Ali, B., et al., Additive Printing of Pure Nanocrystalline Nickel Thin Films Using Room Environment Electroplating, Nanotechnology, 2019; and Behroozfar, A., Microscale 3D Printing of Nanotwinned Copper. Adv. Matls, 2018. 30(4): 1705107. All of these references are also incorporated herein by this reference.

[0011] U.S. Pat. Nos. 9,395,718; 8,790,742; and 7,972,650 disclose trace printing of metallic polymer traces using an x,y,z print controller. These print formations require solvent extraction and metal curing. U.S. Pat. No. 11,008,664 B2 discloses a method to 3D print Cu with graphene using a plating electrolyte with additives and a separate reservoir of graphene. This work uses a single electrolyte containing graphene and no additives. Additionally, it shows that pulse can control the physical properties of the material deposited. All of these references are also incorporated herein by this reference.BRIEF SUMMARY OF THE INVENTION

[0012] Aside from the preferred embodiments disclosed herein, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details set forth in the following description or illustrated in the drawings. Moreover, the claims are not to be read restrictively unless there is clear and convincing evidence manifesting in certain exclusion, restriction, or disclaimer.

[0013] The present invention relates to an efficient, scalable and manufacturing-ready approach for production of conductivity enhanced metal (Cu, Ag, Ni, etc.)-nanocarbon (graphene, carbon nanotubes, etc.) hybrids, such as hybrid graphene-Cu foils / traces / coatings, and their government and commercial applications in thermal straps, electronic devices, and space landing systems.

[0014] The problem of producing low-cost high performance materials with enhanced conductivity and strength properties for electric and thermal applications is solved, in one example, by the development of pulsed reverse electrolytic co-deposition technology combining electrodeposition and electrophoretic deposition processes, for scalable production of composite metal coatings consisting of nanomaterials such as graphene, carbon nanotubes and the like distributed in a metal matrix such as Cu, Ag, Ni and the like wherein said composite metal coating exhibits enhanced electrical conductivity, and or thermal conductivity, and or mechanical strength.

[0015] The feasibility of the invention has been demonstrated. The hybrid and layered graphene-Cu hybrid foils have been fabricated pulsed electrodeposition at a sub-alpha scale (4″×4″) and printing of traces with less the 1 mm width through a direct print nozzle. The existence of graphene contents in graphene-Cu hybrid foils has been identified via Raman spectrometry. The hybrid and layered Cu-Graphene foils exhibited more than 50% and 5% of thermal conductivity enhancement compared to commercial Cu foils, respectively. The hybrid and layered Cu-Graphene foils with post thermal reduction treatment exhibit more than 90% and 100% conductivity enhancement compared to commercial Cu foils. In addition, the hybrid Cu-Graphene foils exhibit 50% sheet resistance reduction compared to commercial Cu foils. Direct printing of Cu-Graphene using meniscus-confined co-deposition on gold wafers demonstrated a 20% conductivity enhancement compared to Cu prints. Additionally, Cu-Graphene direct printing onto a 3D printed Ag polymer trace showed a 20% and 30% decrease in temperature rise during an applied current across the trace compared to the bare Ag and Cu-coated silver trace, respectively; note, the decrease in temperature rise correlates directly with an enhancement of thermal conductivity by Cu-Graphene. Results showed the direct print application of Cu-Graphene leads to solderable pads that enable pick and place circuit board fabrication.

[0016] Electrochemical approaches are particularly practical because they are cost-effective processes with simple equipment for large-scale manufacturing. The carbon materials are dispersed in the electrodeposition solution, which results in the carbon material being uniformly distributed in the metal matrix.

[0017] To address the need for the government and commercial applications in thermal straps, electronic devices, and space landing systems, an efficient, scalable, and manufacturing-ready approach for production of conductivity enhanced graphene-Cu hybrid foils / coatings has been developed. These high-performance foils can be used to fabricate thermal straps to reduce cooldown time of advanced conduction cooling for SRF systems. The fabrication approach detailed herein is a specific instance of a general method to produce electrodepositable metals (Cu, Ag, Ni, etc.)-nanocarbon (graphene, carbon nanotubes, etc.) hybrids.

[0018] Table 1 compares commercially procured annealed Cu foils at thicknesses of 10 and 25 microns directly to produced copper graphene foils prepared as a composite or in layers and with / without annealing. The data presented is a head-to-head experimental result and does not represent the theoretical numbers associated with Cu but the measured numbers within an identical experimental set. It would be desirable to be able to select attributes of interest such as low mass, low cost, high availability, high conductivity, etc. and produce a tailored article comprised of low cost highly available materials, that exhibit the more desirable attributes of conduction. It is an intent of this invention to describe a flexible set of process that can be utilized to tailor the attributes of a produced conductor to provide desirable conduction properties for a given application.TABLE 1Density, Sheet Resistance, and Thermal Conductivity Comparisonbetween commercial annealed Cu foils and the producedCopper Graphene foils with and without annealing.Sheet ResistanceThermal ConductivityMassmΩ / cm2 (10 μmw / m · K (25 μmMetal Type(g / cm3)thicknessthickness)Copper8.965164Copper8.962.5263graphene foilCopper8.96Data not available312graphene foilannealed

[0019] In various embodiments, conductivity enhanced hybrid graphene-Cu materials have been fabricated via two approaches: electro-codeposition with a pulsed electric field with simultaneously deposited Cu and graphene materials formed a composite hybrid graphene-Cu foils in a single tank and electro-codeposition with a pulsed electric field in which we simultaneously deposit Cu and graphene materials formed a composite hybrid graphene-Cu trace. This is accomplished by using a 3D printer and a confined meniscus.

[0020] In another embodiment, pulsed electric field operation is used to control the amount a graphene incorporation and thus dynamically control the physical properties of the material.

[0021] In another embodiment, pulse electric field operation is used to control the foil / coating size / thickness to match the dimensions of the practical applications.

[0022] In another embodiment, pulse electric field operation is used to directly apply the high conductivity material to a conductive wire reducing its skin resistance to match the dimensions of the specific high frequency application. The required skin thickness is governed by a well-known equation which is frequency dependency and also dependent on the resistance. For high frequency applications, a low resistance hybrid material would be ideal and physical coating dimensions would be quite thin, for example in the micron range.

[0023] In another embodiment, the hybrid Cu-Graphene foils exhibit more than 50% conductivity enhancement compared to commercial Cu foils. In another embodiment, the hybrid Cu-Graphene foils with post thermal reduction treatment exhibit more than 90% conductivity enhancement compared to commercial Cu foils. In another embodiment, the hybrid Cu-Graphene foils exhibit more than 50% increase in strain strength. In another embodiment, the hybrid Cu-Graphene foils exhibit ~50% sheet resistance reduction compared to commercial Cu foils. In another embodiment, the hybrid Cu-Graphene traces exhibit a 20% increase in conductivity compared to Cu print onto gold wafers using meniscus-confined electro-codeposition. In another embodiment, the hybrid Cu-Graphene traces exhibited a 20% and 30% decrease in temperature rise during an applied current compared to a bare Ag and Cu-coated Ag trace, respectively.

[0024] These new materials could be used in combination with cryocoolers for X-Ray equipment or superconducting radio frequency technology; they could be used for thermal transport on satellites; semi-conductor backplanes; or high conductivity traces for direct printed circuits. The incorporation of nano-carbons into electrodeposited metallics offers the possibility to change physical properties of the materials through the local organization of the carbon in the grain boundaries of the amorphous deposit. The addition of an anneal post deposition allows for crystal formation of the carbon / metal deposit.

[0025] One such nano-carbon material, graphene, is a two-dimensional (2D) material with excellent physical and chemical properties, such as thermal and electronic conductivity, high mechanical strength and large specific surface area. Graphene and its derivatives have shown great potential in applications ranging from thermal management, energy storage, corrosion, to sensors. Conjugated systems of composite materials may have collective properties that are drastically different than a simple combination of individual components. The intrinsic physiochemical properties of graphene and a metal (copper) matrix, combined with advanced fabrication techniques, could tailor graphene-copper hybrid properties and make the hybrid as ideal thermal strap materials for conduction cooling of superconducting radiofrequency (SRF) systems.

[0026] Featured is a method of enhancing the conductivity of metal-nanomaterial hybrids wherein a cathode substrate is subject to an electrolyte solution including a nanomaterial and metal ions. The cathode substrate is spaced from a metal anode in the electrolyte solution. A pulsed waveform is applied across the cathode and anode to electrodeposit metal ions from the electrolyte solution onto the cathode substrate as a coating and to electrophoretically embed the nanomaterial in the electrolyte solution into the coating on the cathode substrate. The pulsed waveform is preferably configured to produce a cathodic pulse which electrodeposits the metal ions onto the cathode substrate and which electrophoretically embeds the nanomaterial into the coating followed by an anodic pulse which improves deposition uniformity.

[0027] In some embodiments, the cathode substrate is stainless steel, the metal ions are copper, and the nanomaterial is graphene in sheet form and the concentration of the nanomaterial in the electrolyte solution is between 2.5 to 25 mg / L.

[0028] The method may further include heating the coating to further improve its thermal and electrical conductivity. The preferred coating exhibits a 20-50% decrease in electrical resistivity compared to the electrical resistivity of a metal sheet material made of the metal ions, a 30% or greater increase in thermal conductivity compared to the thermal conductivity of a metal sheet material made of the metal ions, and a 50% or greater increase in thermal conductivity compared to the thermal conductivity of a metal sheet material made of the metal ions.

[0029] In one version, the cathode substrate is placed in the electrolyte solution. In another version, the electrolyte solution is pumped through a nozzle to the cathode substrate and the cathode substrate is moved relative to the nozzle and / or the nozzle moves relative to the cathode substrate.

[0030] The coating may be removed from the cathode substrate. The nanomaterial can be graphene, nanocarbon, and / or borophene. In one example, the graphene is reduced graphene oxide. The metal ions can be nickel, silver, copper, and / or other plateable metal ion.

[0031] Usually, the pulsed waveform is repeated a plurality of times. The anode is preferably metal to replenish the metal ions in the electrolyte solution. The anode metal can be nickel, silver, copper, and / or other plateable metal material.

[0032] Also featured is a method of enhancing the conductivity of metal-nanomaterial hybrids comprising placing a cathode substrate in a container including an electrolyte solution with a nanomaterial and metal ions, the cathode substrate spaced from a metal anode also in the electrolyte solution, electrodepositing metal ions from the electrolyte solution onto the cathode substrate forming a coating on the cathode substrate in said container, and electrophoretically embedding the nanomaterial in the electrolyte solution into said coating on the cathode substrate in said container. A pulsed waveform can be applied across the cathode substrate and metal anode and is configured to produce a cathodic pulse which electrodeposits the metal ions onto the cathode substrate and which electrophoretically embeds the nanomaterial into the coating followed by an anodic pulse which improves deposition uniformity.

[0033] Also featured is a method of enhancing the conductivity of metal-nanomaterial hybrids comprising placing a metal anode in a nozzle with an electrolyte solution including a nanomaterial and metal ions, directing the nozzle at a cathode substrate, providing relative movement between the cathode substrate and the nozzle, and applying a pulsed waveform across the cathode substrate and anode to electrodeposit metal ions from the electrolyte solution onto the cathode substrate as a coating and electrophoretically embedding the nanomaterial in the electrolyte solution into the coating on the cathode substrate. Preferably, the pulsed waveform is configured to produce a cathodic pulse which electrodeposits the metal ions onto the cathode substrate and which electrophoretically embeds the nanomaterial into the coating followed by an anodic pulse which improves deposition uniformity.

[0034] The subject invention, however, in other embodiments, need not achieve all these objectives and the claims hereof should not be limited to structures or methods capable of achieving these objectives.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0035] Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:

[0036] FIG. 1 is a schematic view of an as-plated hybrid coating on a substrate;

[0037] FIG. 2 is a schematic view of an as-plated hybrid coating peeled off from the substrate;

[0038] FIG. 3 contains photographs of hybrid graphene-Cu Cu foil formed and peeled from a stainless steel substrate;

[0039] FIG. 4 is a schematic representation of an electrolytic codeposition apparatus;

[0040] FIG. 5 is a schematic representation of the direct print setup for electrolytic-codeposition;

[0041] FIG. 6 is a schematic of electro-codeposition approach for fabricating hybrid graphene-Cu foils;

[0042] FIG. 7 is a representation of a duplex pulsating boundary layer;

[0043] FIGS. 8A-8B are representations of a macroprofile and a microprofile boundary layer under direct current and pulse current conditions;

[0044] FIG. 9 is a summary of guiding principles for the impact of pulse parameters on deposit distribution;

[0045] FIG. 10 depicts an exemplary process flow chart for the application of a hybrid coating application and annealing process;

[0046] FIG. 11 is a comparison of Stress-Strain Curves of Cu foil and graphene-Cu hybrid foil;

[0047] FIG. 12 describes the effect of nanocarbon concentration on sheet resistance;

[0048] FIG. 13 is a comparison of sheet resistance of hybrid graphene-Cu foil with commercial Cu foil and electrodeposited Cu foils;

[0049] FIG. 14 is the comparison of thermal conductivity of hybrid graphene-Cu foil with commercial Cu foil and electrodeposited Cu foils;

[0050] FIG. 15 is the comparison of thermal conductivity of hybrid and layered graphene-Cu foils with and without post thermal reduction treatment and commercial Cu foil;

[0051] FIGS. 16A and 16B are images of Cu (FIG. 16A) and Cu-Graphene (FIG. 16B) on Au;

[0052] FIG. 17 are line scans of a typical thick (Left) and thin (Right) Cu-Graphene traces on Au;

[0053] FIG. 18 shows copper (green) and hybrid (blue; Cu / Graphene) printing on a gold wafer at 5- and 3-minute print duration;

[0054] FIG. 19A describes material layers and FIG. 19B describes a circuit with hybrid (Cu / Gr), copper, and silver regions;

[0055] FIG. 20A shows an IR temperature response at 0.5 A and FIG. 20B shows a temperature response at 1.0 A; and

[0056] FIG. 21 illustrates Raman spectra of a hybrid graphene-Cu foil.DETAILED DESCRIPTION OF THE INVENTION

[0057] Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer.

[0058] The intrinsic physiochemical, thermal, and mechanical properties of nanocarbon (graphene, carbon nanotube, etc.) and metal (Cu, Ag, Ni, etc.) matrix are used, combined with pulsed electrodeposition techniques for hybrid material fabrication. These fabricated hybrid materials / coatings can be used for thermal straps, semiconductor backplanes, thermal transport on satellites, or high conductivity traces for direct printed circuits. Other 2D nanomaterials with similar properties (such as Borophene) are suitable as well.

[0059] In electro-codeposition the concentration of the carbon materials in the metal deposit must be controlled to achieve the targeted conductivity enhancement. The addition of an annealing (heating) step allows for the crystallinity of the metallic deposit to improve leading to a further enhancement in the conductive and physical properties of the materials. The electro-codeposition method can be utilized to deposit these composite materials for various form factors including in the production of foils, additive coating (on a substrate), or in the form of circuit board traces.

[0060] FIG. 1 shows an as-plated hybrid coating 100, prepared by electro-codeposition, which comprises of the metal 110 and nanocarbon 120. The substrate 200 may be any conductive material, such as steel, Au, Cu, Ag polymer ink, or etc. The metal 100 may be any metal that can be electrodeposited (Cu, Ag, Ni, etc.). The nanocarbon 120 (graphene, carbon nanotubes, and carbon nanobundles, etc.) can be suspended in the electrodeposition electrolyte. In some cases, the hybrid graphene-Cu coatings can be peeled from the substrate 200 to create a free-standing hybrid graphene-copper foils or plates 100, FIG. 2. In some cases, the free-standing hybrid foil is then subsequently annealed. In an instance where the coating is to be peeled, the substrate surface ideally has a chromium passivating layer. If the coating is intended to remain on the substrate, then the surface should be free of an oxide scale in order to maintain adhesion. By performing an annealing operation (high temperature<than the melting point and in a reducing environment), constituents from the hybrid coating system 100 can diffuse causing the grain size of the metal to increase leading to an enhancement of the hybrid material properties. The annealing operation does not melt or deform the prepared hybrid material. FIG. 3 illustrates the hybrid material 100 peeled of substrate 200.

[0061] FIG. 4 is a schematic representation of an electrolytic codeposition apparatus 600. Included is a controllable power supply 620 with an anode lead 640 and a cathode lead 660 capable of delivering a direct current (DC), pulse current (PC) or pulse reverse current (PRC) to an electrolytic cell 700. The electrolytic cell includes a cell container 710 with an anode 720, a cathode 740, and an electro codeposition electrolyte solution 730 with one or more metal elements 741 dissolved in the electrolyte and suspended nanocarbon materials 743 also in the electrolyte.

[0062] A method of enhancing the conductivity of metal-nanomaterial hybrids, features subjecting cathode substrate 740 to an electrolyte solution 730 including a nanomaterial 743 and metal ions 741. The cathode substrate 740 is spaced from a metal anode 720 in the electrolyte solution. Anode 720 can be sacrificial to replenish the metal ions 741 in the electrolyte.

[0063] A pulsed waveform is applied across the cathode 740 and anode 720 to electrodeposit metal ions 741 from the electrolyte solution 730 onto the cathode substrate 740 as a coating and electrophoretically embedding the nanomaterial 743 in the electrolyte solution into the coating 745 on the cathode substrate. The pulsed waveform is configured to produce a cathodic pulse which electrodeposits the metal ions onto the cathode substrate and which electrophoretically embeds the nanomaterial into the coating followed by an anodic pulse which improves deposition uniformity. In the example of FIG. 4, the cathode substrate 740 is placed in the electrolyte solution 730.

[0064] Cathode substrate 740 can be stainless steel, the metal ions 741 may be copper, and the carbon nanomaterial 743 can be graphene in sheet form. The nanomaterial can be graphene, nanocarbon, and / or borophene. The graphene is preferably reduced graphene oxide.

[0065] Preferably, the concentration of the nanomaterial in the electrolyte solution is between 2.5 to 25 mg / L. The metal ions 741 can be nickel, silver, copper, and / or other plateable metal ions.

[0066] Preferably, the pulsed waveform is repeated a plurality of times.

[0067] FIG. 5 is a schematic representation of a direct print electrolytic codeposition apparatus 800. Included is a power supply 820 with an anode lead 840 and a cathode lead 860 capable of delivering a direct current (DC), pulse current (PC) or pulse reverse current (PRC) to an electrolytic solution 930 in nozzle 910. The electrolytic droplet 940 is formed at the end of a nozzle capillary 910. The anode 840 is inside the capillary and the cathode is the print substrate 740. The codeposition electrolytic solution 930 includes one or more metal elements 741 dissolved in the electrolyte solution along with suspended nanocarbon materials 743. In this example, the electrolyte solution 930 is pumped through nozzle 910 to the cathode substrate 740 and the cathode substrate 740 is moved relative to the nozzle 910 and / or the nozzle 910 moves relative to the cathode substrate 740.

[0068] In either case, electrolytic codeposition may be practiced using direct current, pulse current or pulse reverse current. In direct current codeposition processes, the current is applied to the electrolytic cell and generally held constant for a period of time, after which the deposit is formed on the oppositely charged electrode substrate. In pulse current / pulse reverse current electrolytic codeposition, the current is interrupted and or reversed in predetermined ways. By properly selecting the pulse current / pulse reverse current waveform parameters, the codeposit thickness, uniformity of codeposition, localization of codeposition, and properties are tuned for the specific application. Numerous embodiments of pulse current / pulse reverse current deposition are described by the common assignee of the instant invention in U.S. Pat. Nos. 6,080,504; 6,203,684; 6,210,555; 6,303,014; 6,309,528; 6,319,384; 6,524,461; 6,551,484; 6,652,727; 6,750,144; 6,827,833; 6,863,793; 6,878,259; 8,603,315; 10,100,423; 10,684,522; and 11,411,258 which are all incorporated herein by this reference.

[0069] FIG. 6 represents a generalized pulse current / pulse reverse current waveform. The generalized waveform parameters are characterized by a cathodic pulse followed by an off-time and followed by an anodic pulse and followed by an off-time. One skilled in the art recognizes that one or both off-times may be eliminated and that the either the cathodic pulse or the anodic pulse may be eliminated. The waveform parameters are: 1) anodic pulse current density, ianodic, 2) anodic on-time, ton, anodic, 3) cathodic pulse current density, icathodic, 4) cathodic on-time, ton, cathodic, 5) cathodic off-time, toff, cathodic and 6) anodic off-time, toff, anodic. The sum of the anodic and cathodic on-times and the off-time is the pulse period, T. The inverse of the pulse period is the frequency, f, of the pulse. The anodic, γa, and cathodic,γc, duty cycles are the ratios of the respective on-times to the pulse period. The average current density (iaver) or net deposition rate is given by:i aver=ic⁢γc-ia⁢γa(1)

[0070] Just as there are infinite combinations of height, width, and length to obtain a given volume, in pulse processing there are unlimited combinations of peak voltages / current densities, duty cycles, and frequencies to obtain a given deposition rate in electrolytic deposition processes. These parameters provide the potential for much greater process / product control compared to conventional DC deposition processes.

[0071] Mass transport in pulse current / pulse reverse current electrolytic and electrophoretic deposition processes is a combination of steady state and non-steady state diffusion processes. The mass transfer limited current density (il) is related to the reactant concentration gradient (Cb-Cs) and to the diffusion layer thickness (δ) by the following equation:il=- nFD⁢(δ⁢C / δ⁢x)x=0=- nFD [(Cb-Cs) / δ](2)where n, F, and D are the number of equivalents, Faraday's constant, and diffusivity of the reacting species, respectively. In DC electrolysis, δ is a time-invariant quantity for a given electrode geometry and hydrodynamic condition. In pulse / pulse reverse electrolysis, however, δ varies from zero at the beginning of the pulse to its steady state value when the Nernst diffusion layer is fully established. The corresponding mass transport limiting current density would then be equal to an infinite value at t=0 and decreases to a steady state value of the DC limiting current density. The advantage of pulse / pulse reverse electrolysis is that the current can be interrupted before δ has a chance to reach steady state. This allows the reacting ions to diffuse back to the electrode surface and replenish the surface concentration to its original value before the next current interruption. Therefore, the concentration of reacting species in the vicinity of the electrode pulsates with the frequency of the modulation.FIG. 7 illustrates a duplex diffusion layer including a pulsating layer, δp, and a stationary layer, as during pulse electrolysis. Since the thickness of the pulsating diffusion layer is determined by the waveform parameters, this layer may be thought of as an electrodynamic diffusion layer. By assuming a linear concentration gradient across the pulsating diffusion layer and conducting a mass balance, the pulsating diffusion layer thickness (δp) as:δp=(2⁢D⁢ton)1 / 2(3)where ton is the pulse on time. When the pulse on time is equal to the transition time, the concentration of reacting species at the interface drops to zero at the end of the pulse. An expression for the transition time, τ, is:τ=((n⁢F )2⁢Cb2⁢D) / 2⁢ic2(4)More exact solutions are given by integrating Fick's diffusion equation:δp=2⁢((D⁢ton) / π)1 / 2(5)τ=π⁡((n⁢F )2⁢Cb2⁢D) / 4⁢ic2(6)The same equation for the pulsating diffusion layer is also relevant to pulse-reverse deposition. The key points in the development of pulse current / pulse reverse current deposition processes are: (1) the electrodynamic diffusion layer thickness is proportional to the pulse on time and (2) transition time is inversely proportional to the current.In electrolytic codeposition of nanocarbon process, the amount of deposit and concentration of the nanocarbons distributed is determined by the current distribution. The current distribution is controlled by primary (geometrical), secondary (kinetic) or tertiary (mass transport) effects. The addition of secondary or tertiary effects tends to make the current distribution more uniform, as compared to primary effects alone. If the applied waveform is designed such that the pulse on-time is much longer than the transition time, the tertiary current distribution will play an important role in the deposition. With the addition of tertiary control, the concept of macro- and micro-profiles influence the current distribution.FIG. 8A illustrates a macroprofile wherein the roughness of the surface is large compared with the thickness of the diffusion layer, and the diffusion layer tends to follow the surface contour. Under mass transport or diffusion control, a macroprofile results in a uniform current distribution and tends to follow the surface contour producing a conformal deposit during deposition. FIG. 8B illustrates a microprofile wherein the roughness of the surface is small compared with the thickness of the diffusion layer. Under mass transport control, a microprofile results in a non-uniform current distribution and a non-conformal deposition of material, beneficial for creating a more uniform coating surface devoid of pores. By applying the appropriate waveform, one skilled in the art can effectively focus or defocus the current distribution to create non-uniform or uniform deposition respectively.

[0077] FIG. 9 summarizes four pulse current waveform types, independent of cathodic pulse or anodic pulse, to influence the current distribution and hence the deposition distribution in an electrolytic codeposition process or layered electrodeposition / electrophoretic deposition processes. In some embodiments of the instant invention, a direct current is employed to codeposit a hybrid or layered coating system. In other cases, a pulse reverse current is employed to codeposit a hybrid or layered coating system. In other cases, a pulse reverse current is employed to codeposit a hybrid or layered coating system. In some embodiments, a codeposit a hybrid or layered coating system is uniformly deposited across a surface. In other embodiments, a codeposit or a layered hybrid coating system is locally deposited across a surface. By properly selecting the pulse current / pulse reverse current waveform parameters, the codeposit thickness, uniformity of codeposition, localization of codeposition, and properties are tuned for the desired conductivity enhancement.

[0078] FIG. 10 presents an embodiment of the process steps in the graphene-Cu hybrid coating electro-codeposition method of the instant invention. FIG. 10 shows the general process utilized in preparation of the working examples provided. The process can include a substrate pre-treatment step 1201 to clean / degrease the surface of the substrate 1200 freeing it from any oils or particulates, this is commonly done with a solvent like acetone or isopropanol. This step is often followed by a water rinse 1220 before the graphene-Cu hybrid coating 1210 is applied to the surface. Thus, a properly prepared substrate 1200 attributes include: clean, conductive, resistant to acid, water break free surface for the deposition of the graphene-Cu hybrid deposit. The coated component is often then rinsed 1220 and air dried 1230. The coated component is peeled off from the substrate to form free-standing graphene-copper hybrid foils 1240. Finally, the graphene-copper hybrid foils are thermally reduced 1250 by applying a temperature (300° C.-400° C.) and a flow of mixed gases (5% H2 with 95% Ar).

[0079] FIG. 12 illustrates the influence on resistance by varying the amount of nanocarbon in the electrolytic cell. The range of 2.5 to 25 mg / L produced lower resistance, while the preferred range of 5 to 15 mg / L provided the highest performance gains.

[0080] The following examples illustrate various embodiments.Baseline for Evaluation

[0081] Commercial copper foils were purchased for a baseline evaluation. These commercial foils are annealed copper foils obtained from McMaster-Carr. The thickness of commercial Cu foils is around 25 μm.Working Example I (without Graphene Contents and Using DC)

[0082] Pure copper foils were prepared through direct current electrodeposition. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. A solid copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. Prior to the application of the electrodeposited Cu coating, the stainless-steel substrate was cleaned and rinsed with soap and DI water. The pure Cu plating electrolyte consisted of 45 g / L copper sulfate pentahydrate (CuSO4·5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), and 350 ppm polyethylene glycol (PEG).

[0083] The pure copper was electrodeposited using a direct current condition at a current density of 50 mA / cm2 for 26 min. This operation was completed at approximately 25° C. After application of the pure copper coating on stainless steel substrates, the Cu coatings were air dried and peeled directly from the substrate surface as Cu foils for post characterization.Working Example II (without Graphene Contents and Using PC)

[0084] Pure copper foils were prepared through pulse current electrodeposition. The pure copper foils were prepared to be used as a baseline for evaluation of the invention. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. The substrates were first cleaned / degreased with a solvent like acetone or isopropanol, then rinsed with DI water. A copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. The pure Cu plating electrolyte consisted of 45 g / L copper sulfate pentahydrate (CuSO4 5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), and 350 ppm polyethylene glycol (PEG).

[0085] The pure copper was also electrodeposited using a pulse waveform with a cathodic current of 50 mA / cm2 for 0.5 ms followed by an open circuit time off of 1.5 ms; then repeat consistently for 105 min. This operation was completed at approximately 25° C. After application of the pure copper coating on stainless steel substrates, the Cu coatings were air dried and peeled directly from the substrate surface as Cu foils for post characterization.Working Example III (with Graphene Contents and Using DC)

[0086] The hybrid Graphene-Cu foils were prepared through direct current electro-codeposition. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. A copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. Prior to the application of the electrodeposited Cu coating, the stainless-steel substrate cleaned and rinsed with soap and DI water. The pure Graphene-Cu electrolyte consisted of 90 g / L copper sulfate pentahydrate (CuSO4 5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), 350 ppm polyethylene glycol (PEG), Cetyltrimethyl Ammonium Bromide (CTAB) 5 mg / L, polyvinylpyrrolidone (PVP) 5 mg / L, and reduced graphene oxide (RGO) 5 mg / L.

[0087] The hybrid Graphene-Cu foils were electro-codeposited using a direct current condition at a current density of 20 mA / cm2 for 60 min. This operation was completed at approximately 25° C. After the application of the hybrid Graphene-Cu on stainless steel substrates, the hybrid Graphene-Cu coatings were air dried and peeled directly from the substrate surface as hybrid Graphene-Cu foils for post characterization.Working Example IV (with Graphene Contents and Using Pc)

[0088] The hybrid Graphene-Cu foils were prepared through pulse current electro-codeposition. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. A copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. Prior to the application of the electrodeposited Cu coating, the stainless-steel substrate was cleaned and rinsed with soap and DI water. The pure Cu plating electrolyte consisted of 90 g / L copper sulfate pentahydrate (CuSO4 5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), 350 ppm polyethylene glycol (PEG), Cetyltrimethyl Ammonium Bromide (CTAB) 5 mg / L, polyvinylpyrrolidone (PVP) 5 mg / L, and reduced graphene oxide (RGO) 5 mg / L.

[0089] The synthesis process of hybrid graphene-copper foils and traces by pulse / pulse-reverse electro-codeposition process are demonstrated in FIG. 6. During the electro-codeposition process, the stainless-steel substrate and the counter electrode (Cu plate) will be fixed relative to one another and connected to a pulsed power source. Cu anode is a sacrificial counter electrode to maintain the Cu concentration constant during the fabrication process. Reduced graphene oxide (RGO) nanosheets are used as graphene contents. Cetyltrimethyl Ammonium Bromide (CTAB) and polyvinylpyrrolidone (PVP) as dispersants for dispersing RGO nanosheets in Cu plating bath. CTAB also provide the positive charges for RGO sheets. With the positive charges, both RGO sheets and Cu are deposited on the substrate under cathodic current. Under anodic current the hybrid coating is preferentially removed from areas exposed to higher current densities, to improve deposit uniformity. With alternate electrical fields under pulse current reverse process, RGO sheets were distributed and embedded in the copper matrix to form hybrid graphene-copper. The optimization of the mass transport in pulse / pulse reverse process provides the opportunities to control the foil / coating thickness and uniformity (the amounts of hybrid graphene-Cu). The hybrid graphene-Cu foils / traces / coatings were formed on stainless steel substrates using the FARADAYIC® Electro-Codeposition process, then peeled off from the substrates as free-standing hybrid graphene-copper foils.

[0090] The hybrid Graphene-Cu foils were electro-codeposited using a pulse waveform with a cathodic current of 20 mA / cm2 for 0.5 ms followed by an open circuit time off of 1.5 ms; then repeat consistently for 240 min. This operation was completed at approximately 25° C. After the application of the hybrid Graphene-Cu on stainless steel substrates, the hybrid Graphene-Cu coatings were air dried and peeled directly from the substrate surface as hybrid Graphene-Cu foils for post characterization.Working Example V (Analysis)

[0091] Comparing the thermal and electrical conductivity of hybrid and layered Cu-Graphene foil samples prepared above (EXAMPLE VI and V) versus a commercial Cu foil (baseline) and electrodeposited Cu foil (EXAMPLE I) samples were measured and shown in FIG. 13 and FIG. 14. The thermal conductivity of hybrid and layered Cu-Graphene foils fabricated as shown above are more than 50% and 5% higher than the thermal conductivity of commercial Cu foil, respectively.Working Example VI

[0092] The post thermal reduction treatments were carried out on hybrid graphene-Cu foils. The hybrid graphene-Cu foils were prepared through pulse current electro-codeposition as demonstrated in WORKING EXAMPLE V. The hybrid graphene-Cu foils were placed a tube furnace with vacuum capacity. The tube furnace system was first evacuated for 20 min and then backfilled with mixed gases of 5% H2 with 95% Ar at a flow rate of 0.3 L / min. Second, the tube furnace was heated to 400° C. in 30 min. Third, the hybrid graphene-Cu foils were thermal reduced for 2 hours. Finally, the furnace was opened and cooled down to room temperature for post characterization.Working Example VII

[0093] FIG. 11 shows the improved mechanical strain as compared to standard Cu foil. Comparing the thermal and electrical conductivity of hybrid and layered Cu-Graphene foil samples post anneal versus a commercial Cu foil and electrodeposited Cu foil were measured. The results are shown in FIGS. 13-15. As shown, the post thermal reduction treatment led to a significant improvement in thermal conductivity. The hybrid foils with post thermal reduction treatment exhibit more than 90% and 100% conductivity enhancement compared to commercial Cu foils.

[0094] The sheet resistance of hybrid graphene-copper hybrid foils was evaluated using a four-point probe system. As shown, the hybrid Cu-Graphene foils exhibit ~50% sheet resistance reduction compared to commercial Cu foils.Baseline for Evaluation (Au Substrate)

[0095] Commercial gold-coated silicon wafers were purchased for a baseline evaluation. The gold wafers were purchased from LGA Thin Films. The silicon wafer backing has a 10 nm chromium adhesion layer with a 100 nm gold layer on top for electrodeposition of copper or copper-graphene onto the gold substrate.Working Example VIII (Pure Cu Trace Printing on Au Substrate)

[0096] A plastic nozzle 910, FIG. 5 with a diameter of ~1 mm was backfilled with a copper plating electrolyte (95 g / L copper sulfate, 52 g / L sulfuric acid, 6.5 mM hydrochloric acid, 350 ppm polyethylene glycol, 5 mg / L polyvinylpyrrolidone, and 5 mg / L cetrimonium bromide). A copper wire was inserted into the nozzle and acted as the anode. The nozzle, controlled by an x, y, z stage was placed 300 μm above the gold cathode substrate. A meniscus was formed onto the gold wafer by pushing solution through the nozzle via a positive displacement pump set to operate at 0.6 mL / Hr. A 500 Hz pulse current at a 25% duty cycle (0.5 ms on, 1.5 ms off, 2 ms total time) was applied while simultaneously moving the nozzle in the x or y direction via the 3D printing x, y, x positioner at a speed of 1.6 mm / s. Printing of the copper material occurred only where the electrolyte, confined within the meniscus, wetted the gold substrate. The printing of the Cu onto the Au substrate is shown in FIG. 16. The printed copper line was tested using a variety of methods to determine material properties.Working Example IX (Hybrid Cu-Graphene Printing on Au Substrate)

[0097] A plastic nozzle with a diameter of ~1 mm was backfilled with a copper plating electrolyte (95 g / L copper sulfate, 52 g / L sulfuric acid, 6.5 mM hydrochloric acid, 350 ppm polyethylene glycol, 5 mg / L polyvinylpyrrolidone, 5 mg / L cetrimonium bromide, and 5 mg / L reduced graphene oxide). A copper wire was inserted into the nozzle and acted as the anode. The nozzle, controlled by an x, y, z stage was placed 300 μm above the gold cathode substrate. A meniscus was formed onto the gold wafer by pushing solution through the nozzle via a positive displacement pump set to operate at 0.6 mL / Hr. A 500 Hz pulse current at a 25% duty cycle (0.5 ms on, 1.5 ms off, 2 ms total time) was applied while simultaneously moving the nozzle in the x or y direction via the 3D printing x, y, x positioner at a speed of 1.6 mm / s. Printing of the copper-graphene material occurred only where the electrolyte, confined within the meniscus, wetted the gold substrate. The printed copper-graphene line was tested using a variety of methods to determine material properties.Working Example X (Analysis of Print Traces on Gold Substrate)

[0098] Copper or copper-graphene traces on gold were then tested to measure their conductivity. First, optical profilometry was used to characterize the dimensions of the copper trace. The dimensions of the line varied based on the total deposition time, but a typical trace had a length of 6 mm, width of 3 mm, and a height of 500 nm, as shown in FIG. 17. The copper traces were analyzed using a commercially available four-point probe to measure the sheet resistance of the line. The conductivity of the line is calculated using software based on the dimensions of the trace. Raman spectrometry was used to confirm graphene composition in the hybrid foils. Both hybrid and layered graphene-Cu hybrid foils were examined by Raman spectroscopy using the inVia Reflex Micro-Raman system manufactured by Renishaw PLC with samples being assessed at 514 nm excitation. As shown in FIG. 18, both Raman spectra exhibited two peaks: the D band at ~1350 cm−1; the G band at 1600 cm−1. The D band is attributed to defects in the graphene, and G band is associated with the tangential vibrations of sp2 bonded carbon atoms. These two featured bands indicate the existence of graphene in both hybrid and layered graphene-Cu foils.

[0099] The conductivity of the copper and copper-graphene trace is provided in FIG. 18. The copper-graphene traces showed a 20% increase in conductivity compared to the copper traces.Baseline for Evaluation (Ag Seed Trace)

[0100] A conductive silver ink was printed onto a polyimide insulator backing. The thickness of the silver trace ranged between 10-30 μm while the dimensions of the trace (width, length, and shape) were variable depending the desired characteristics of the trace, as shown in FIG. 19 (line 3). The silver trace acted as the substrate for electrodeposition of copper or copper-graphene onto the silver. The method for trace printing of conductive materials is highlighted in U.S. Pat. Nos. 9,395,718; 8,790,742; and 7,972,650 all incorporated herein by this reference.Working Example XI (Pure Cu Trace Printing on Ag Seed Trace)

[0101] A plastic nozzle with a diameter of ~1 mm was backfilled with a copper plating electrolyte (95 g / L copper sulfate, 52 g / L sulfuric acid, 6.5 mM hydrochloric acid, 350 ppm polyethylene glycol, 5 mg / L polyvinylpyrrolidone, and 5 mg / L cetrimonium bromide). A copper wire was inserted into the nozzle and acted as the anode. The nozzle, controlled by an x, y, z stage was placed 300 μm above the gold cathode substrate. A meniscus was formed onto the gold wafer by pushing solution through the nozzle via a positive displacement pump set to operate at 0.6 mL / Hr. A 500 Hz pulse current at a 25% duty cycle (0.5 ms on, 1.5 ms off, 2 ms total time) was applied while simultaneously moving the nozzle in the x or y direction via the 3D printing x, y, x positioner at a speed of 1.6 mm / s. Printing of the copper material occurred only where the electrolyte, confined within the meniscus, wetted the gold substrate. The printing of the Cu onto the Au substrate is shown in FIG. 19 (line 2). The printed copper line was tested using a variety of methods to determine material properties.Working Example XII (Hybrid Cu-Graphene Printing on Ag Seed Trace)

[0102] A plastic nozzle with a diameter of ~1 mm was backfilled with a copper plating electrolyte (95 g / L copper sulfate, 52 g / L sulfuric acid, 6.5 mM hydrochloric acid, 350 ppm polyethylene glycol, 5 mg / L polyvinylpyrrolidone, 5 mg / L cetrimonium bromide, and 5 mg / L reduced graphene oxide). A copper wire was inserted into the nozzle and acted as the anode. The nozzle, controlled by an x, y, z stage was placed 300 μm above the gold cathode substrate. A meniscus was formed onto the gold wafer by pushing solution through the nozzle via a positive displacement pump set to operate at 0.6 mL / Hr. A 500 Hz pulse current at a 25% duty cycle (0.5 ms on, 1.5 ms off, 2 ms total time) was applied while simultaneously moving the nozzle in the x or y direction via the 3D printing x, y, x positioner at a speed of 1.6 mm / s. Printing of the copper-graphene material occurred only where the electrolyte, confined within the meniscus, wetted the gold substrate. The printing of the Cu onto the Au substrate is shown in FIG. 19 (line 1). The printed copper-graphene line was tested using a variety of methods to determine material properties.Working Example XIII (Analysis of Print Trace on Ag Seed Trace)

[0103] Copper or copper-graphene traces on gold were then tested to measure their conductivity. First, optical profilometry was used to characterize the dimensions of the copper trace. The dimensions of the line varied based on the total deposition time, but a typical trace had a length of 6 mm, width of 2-3 mm, and a height of 0.5-10 μm depending on the deposition time; an example optical profilometry trace is provided in FIG. 17. The copper traces were analyzed using a commercially available four-point probe to measure the sheet resistance of the line. The conductivity of the line is calculated using software based on the dimensions of the trace. The conductivity of the copper and copper-graphene trace is provided in FIG. 18. The copper-graphene traces showed a 20% increase in conductivity compared to the copper traces.

[0104] The copper or copper-graphene prints on the silver paste were used to test the thermal properties of the material. A silver trace was printed onto a polyimide backing. The resulting trace was divided into three regions in which (1) copper-graphene electrodeposited onto the silver, (2) copper electrodeposited onto the silver trace, and a bare silver layer (FIG. 19A); all deposition conditions were identical to those described for printing on gold wafers. A 1A current is applied across three different sections of a simple resistive circuit (1) copper-graphene, (2) copper, and (3) bare silver (FIG. 19B).

[0105] FIG. 20A shows a qualitative IR image in which the temperature rise of the bare silver is greater than the copper and copper-graphene section of the trace. Note, the silver material used as the baseline substrate is a commercial polymer silver paste that is far less conductive than true bulk silver. To quantify the temperature differences, in house software is used to determine the average temperature across each section of the trace. FIG. 20B shows the average temperature of the three sections during the 1A current across each material. The copper-graphene showed a roughly 30% and 20% decrease in temperature rise during the heating of the circuit compared to silver and copper, respectively.

[0106] Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments. Other embodiments will occur to those skilled in the art and are within the following claims.

[0107] In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and / or there are many other reasons the applicant cannot be expected to describe certain insubstantial substitutes for any claim element amended.

Examples

working example i (

Working Example I (without Graphene Contents and Using DC)

[0082]Pure copper foils were prepared through direct current electrodeposition. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. A solid copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. Prior to the application of the electrodeposited Cu coating, the stainless-steel substrate was cleaned and rinsed with soap and DI water. The pure Cu plating electrolyte consisted of 45 g / L copper sulfate pentahydrate (CuSO4·5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), and 350 ppm polyethylene glycol (PEG).

[0083]The pure copper was electrodeposited using a direct current condition at a current density of 50 mA / cm2 for 26 min. This operation was completed at approximately 25° C. After application of the pure copper coating on ...

working example ii (

Working Example II (without Graphene Contents and Using PC)

[0084]Pure copper foils were prepared through pulse current electrodeposition. The pure copper foils were prepared to be used as a baseline for evaluation of the invention. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. The substrates were first cleaned / degreased with a solvent like acetone or isopropanol, then rinsed with DI water. A copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. The pure Cu plating electrolyte consisted of 45 g / L copper sulfate pentahydrate (CuSO4 5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), and 350 ppm polyethylene glycol (PEG).

[0085]The pure copper was also electrodeposited using a pulse waveform with a cathodic current of 50 mA / cm2 for 0.5 ms followed by an open circuit time off of...

working example iii (

Working Example III (with Graphene Contents and Using DC)

[0086]The hybrid Graphene-Cu foils were prepared through direct current electro-codeposition. Stainless steel 304 was used as a substrate, because after deposition the foils can be peeled directly from the substrate surface. A copper bar wrapped in a porous plastic bag was used as the anode to maintain the constant copper concentration in electrolyte solution during the electrodeposition. Prior to the application of the electrodeposited Cu coating, the stainless-steel substrate cleaned and rinsed with soap and DI water. The pure Graphene-Cu electrolyte consisted of 90 g / L copper sulfate pentahydrate (CuSO4 5H2O), 52 g / L sulfuric acid (H2SO4), 6.5 mM hydrochloric acid (HCl), 350 ppm polyethylene glycol (PEG), Cetyltrimethyl Ammonium Bromide (CTAB) 5 mg / L, polyvinylpyrrolidone (PVP) 5 mg / L, and reduced graphene oxide (RGO) 5 mg / L.

[0087]The hybrid Graphene-Cu foils were electro-codeposited using a direct current condition at a cu...

Claims

1. A method of enhancing the conductivity of metal-nanomaterial hybrids, the method comprising:subjecting a cathode substrate to an electrolyte solution including a nanomaterial and metal ions, the cathode substrate spaced from a metal anode in the electrolyte solution;applying a pulsed waveform across the cathode and anode to electrodeposit metal ions from the electrolyte solution onto the cathode substrate as a coating and electrophoretically embedding the nanomaterial in the electrolyte solution into the coating on the cathode substrate; andthe pulsed waveform configured to produce a cathodic pulse which electrodeposits the metal ions onto the cathode substrate and which electrophoretically embeds the nanomaterial into the coating followed by an anodic pulse which improves deposition uniformity.

2. The method of claim 1 in which the cathode substrate is stainless steel, the metal ions are copper, and the nanomaterial is graphene in sheet form.

3. The method of claim 1 in which the concentration of the nanomaterial in the electrolyte solution is between 2.5 to 25 mg / L.

4. The method of claim 1 further including heating the coating to further improve its thermal and electrical conductivity.

5. The method of claim 4 in which the coating exhibits a 20-50% decrease in electrical resistivity compared to the electrical resistivity of a metal sheet material made of the metal ions.

6. The method of claim 4 in which the coating exhibits a 30% or greater increase in thermal conductivity compared to the thermal conductivity of a metal sheet material made of the metal ions.

7. The method of claim 4 in which the coating exhibits a 50% or greater increase in thermal conductivity compared to the thermal conductivity of a metal sheet material made of the metal ions.

8. The method of claim 1 in which the cathode substrate is placed in the electrolyte solution.

9. The method of claim 1 in which the electrolyte solution is pumped through a nozzle to the cathode substrate and the cathode substrate is moved relative to the nozzle and / or the nozzle moves relative to the cathode substrate.

10. The method of claim 1 in which the coating is removed from the cathode substrate.

11. The method of claim 1 in which the nanomaterial is graphene, nanocarbon, and / or borophene.

12. The method of claim 11 in which the graphene is reduced graphene oxide.

13. The method of claim 1 in which the metal ions are nickel, silver, copper, and / or other plateable metal ion.

14. The method of claim 1 in which the pulsed waveform is repeated a plurality of times.

15. The method of claim 1 in which the anode is metal to replenish the metal ions in the electrolyte solution.

16. The method of claim 1 in which the anode metal is nickel, silver, copper, and / or other plateable metal material.

17. A method of enhancing the conductivity of metal-nanomaterial hybrids, the method comprising:placing a cathode substrate in a container including an electrolyte solution with a nanomaterial and metal ions, the cathode substrate spaced from a metal anode also in the electrolyte solution;electrodepositing metal ions from the electrolyte solution onto the cathode substrate forming a coating on the cathode substrate in said container; andelectrophoretically embedding the nanomaterial in the electrolyte solution into said coating on the cathode substrate in said container.

18. The method of claim 17 in which a pulsed waveform applied across the cathode substrate and metal anode is configured to produce a cathodic pulse which electrodeposits the metal ions onto the cathode substrate and which electrophoretically embeds the nanomaterial into the coating followed by an anodic pulse which improves deposition uniformity.

19. The method of claim 17 in which the cathode substrate is stainless steel, the metal ions are copper, and the nanomaterial is graphene in sheet form.

20. The method of claim 17 in which the concentration of the nanomaterial in the electrolyte solution is between 2.5 to 25 mg / L.

21. The method of claim 17 further including heating the coating to further improve its thermal and electrical conductivity.

22. The method of claim 17 in which the coating exhibits a 20-50% decrease in electrical resistivity compared to the electrical resistivity of a metal sheet material made of the metal ions.

23. The method of claim 17 in which the coating exhibits a 30% or greater increase in thermal conductivity compared to the thermal conductivity of a metal sheet material made of the metal ions.

24. The method of claim 17 in which the coating exhibits a 50% or greater increase in thermal conductivity compared to the thermal conductivity of a metal sheet material made of the metal ions.

25. The method of claim 17 in which the coating is removed from the cathode substrate.

26. The method of claim 17 in which the nanomaterial is graphene, nanocarbon, and / or borophene.

27. The method of claim 26 in which the graphene is reduced graphene oxide.

28. The method of claim 17 in which the metal ions are nickel, silver, copper, and / or other plateable metal ion.

29. The method of claim 18 in which the pulsed waveform is repeated a plurality of times.

30. The method of claim 17 in which the anode is metal to replenish the metal ions in the electrolyte solution.

31. The method of claim 30 in which the anode metal is nickel, silver, copper, and / or other plateable metal material.

32. A method of enhancing the conductivity of metal-nanomaterial hybrids, the method comprising:placing a metal anode in a nozzle with an electrolyte solution including a nanomaterial and metal ions;directing the nozzle at a cathode substrate;providing relative movement between the cathode substrate and the nozzle; andapplying a pulsed waveform across the cathode substrate and anode to electrodeposit metal ions from the electrolyte solution onto the cathode substrate as a coating and electrophoretically embedding the nanomaterial in the electrolyte solution into the coating on the cathode substrate.

33. The method of claim 32 in which the pulsed waveform is configured to produce a cathodic pulse which electrodeposits the metal ions onto the cathode substrate and which electrophoretically embeds the nanomaterial into the coating followed by an anodic pulse which improves deposition uniformity.

34. The method of claim 32 in which the cathode substrate is stainless steel, the metal ions are copper, and the nanomaterial is graphene in sheet form.

35. The method of claim 32 in which the concentration of the nanomaterial in the electrolyte solution is between 2.5 to 25 mg / L.

36. The method of claim 32 further including heating the coating to further improve its thermal and electrical conductivity.

37. The method of claim 32 in which the coating exhibits a 20-50% decrease in electrical resistivity compared to the electrical resistivity of a metal sheet material made of the metal ions.

38. The method of claim 32 in which the coating exhibits a 30% or greater increase in thermal conductivity compared to the thermal conductivity of a metal sheet material made of the metal ions.

39. The method of claim 32 in which the coating exhibits a 50% or greater increase in thermal conductivity compared to the thermal conductivity of a metal sheet material made of the metal ions.

40. The method of claim 32 in which the coating is removed from the cathode substrate.

41. The method of claim 32 in which the nanomaterial is graphene, nanocarbon, and / or borophene.

42. The method of claim 41 in which the graphene is reduced graphene oxide.

43. The method of claim 32 in which the metal ions are nickel, silver, copper, and / or other plateable metal ion.

44. The method of claim 32 in which the pulsed waveform is repeated a plurality of times.

45. The method of claim 32 in which the anode is metal to replenish the metal ions in the electrolyte solution.

46. The method of claim 45 in which the anode metal is nickel, silver, copper, and / or other plateable metal material.

Images