Silver nanowires and noble metal-coated silver nanowire-conductive polymer composites that exhibit percolation conduction at low dosages

Abstract

A composite material is described in which noble metal-coated silver nanowires are loaded into a polymer. The composite material has a resistivity of about 100 Ω·cm or less, or from about 100 Ω·cm to about 1×10, depending on the amount of noble metal-coated silver nanowires loaded into the polymer. 11 The composite material can have a resistivity of Ω·cm. The noble metal coated silver nanowires can be platinum coated silver nanowires. Metal particulate matter, such as silver flakes or silver particles, can be added to the composite material to achieve desired properties. Composite precursor compositions and methods for preparing the composite material are described.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to co-pending U.S. Provisional Patent Application No. 63 / 414,143, filed October 7, 2022, to Virkar et al., entitled "Silver Nanowire And Noble-Metal Coated Silver Nanowire Conductive Polymer Composites With Low Loading Percolation Conduction," which is incorporated herein by reference.

[0002] The present invention relates to composite materials having precious metal coated silver nanowires loaded in a polymer, which can achieve relatively low resistivity values. The present invention further relates to composite precursor compositions having relatively low loadings of precious metal coated silver nanowires in the composition, which can be cured to form a composite, and methods of forming the composite precursor compositions. [Background technology]

[0003] There has been considerable interest in developing silver nanowires to form transparent conductive films. The one-dimensional nature of metal nanowires allows for the formation of a conductive network at low metal loadings. Higher particle loadings can generally be used to form conductive composites, especially when transparency is not an issue. The establishment of a conductive network presents additional challenges in thicker structures with three-dimensional configurations. Conductive composites are typically formed using silver particles or carbon conductors to provide mechanical strength and electrical conductivity, for example, as an antistatic material or other similar uses. Summary of the Invention [Means for solving the problem]

[0004] In a first aspect, the present invention relates to a composite material comprising precious metal-coated silver nanowires and a polymer matrix combined to form the composite material. The composite material can have a resistivity of about 100 Ω·cm or less, or about 1 Ω·cm or less. The composite material can include about 0.01 wt.% to about 40 wt.%, or about 0.1 wt.% to about 20 wt.% of the precious metal-coated silver nanowires. In some embodiments, the precious metal-coated silver nanowires can include platinum-coated silver nanowires. In some embodiments, the composite material can include at least about 90 wt.% of the polymer matrix. For example, additional metal particulates can be added to the composite material in an amount equal to or less than the approximate weight of the precious metal-coated silver nanowires. The composite material can be configured as a Peterson resistor when the composite material is in contact with two bus bars of opposite polarity, thereby applying a voltage, so that current flows between the bus bars.

[0005] In another aspect, the present invention provides a method for manufacturing a piezoelectric ceramic substrate having a dielectric constant of about 100 Ω·cm to about 1×10 11 The present invention relates to a composite material comprising noble metal-coated silver nanowires and a polymer matrix combined to form a composite material having a resistivity of Ω·cm. The composite material can include no more than about 10.0 wt.%, in some embodiments no more than about 2.0 wt.%, or no more than about 0.1 wt.% of the noble metal-coated silver nanowires. In some embodiments, the noble metal-coated silver nanowires can include platinum-coated silver nanowires. In some embodiments, the composite material can include at least about 90 wt.% of the polymer matrix. Another metal particulate material can be added to the composite material in an amount equal to or less than approximately the weight of the noble metal-coated silver nanowires.

[0006] In another aspect, the present invention relates to a composite precursor composition that can be used to form a composite material. In some embodiments, the composite precursor composition can be cured to form a composite material having a resistivity of about 100 Ω·cm or less, or about 1 Ω·cm or less. The composite precursor composition includes precious metal-coated silver nanowires, which can be about 0.01 wt % to about 40 wt %, or about 0.1 wt % to about 20 wt %, of the solids content of the composite precursor composition. In some embodiments, the precious metal-coated silver nanowires can include platinum-coated silver nanowires. The composite precursor composition also includes a polymer precursor composition, which can be a monomer, an oligomer, a solid polymer dissolved in a solvent, or a combination thereof. The solids content of the composite precursor composition can include at least about 90 wt % of the polymer precursor composition. Another metal particulate material can be added to the composite precursor composition in an amount equal to or less than approximately the weight of the precious metal-coated silver nanowires. The composite precursor composition can be cured to form a solid material by heating, exposure to radiation, chemical treatment, exposure to water or oxygen, or a combination thereof.

[0007] In another aspect, the present invention provides a method for manufacturing a piezoelectric ceramic substrate having a dielectric constant of about 100 Ω·cm to about 1×10 11The present invention relates to a composite precursor composition that can be used to form a composite material having a resistivity of Ω·cm. The composite precursor composition includes noble metal-coated silver nanowires, which may be about 2.0 wt. % or less, or about 0.1 wt. % or less, of the solids content of the composite precursor composition. In some embodiments, the noble metal-coated silver nanowires may include platinum-coated silver nanowires. The composite precursor composition also includes a polymer precursor composition, which may be a monomer, an oligomer, a solid polymer dissolved in a solvent, or a combination thereof. The solids content of the composite precursor composition may include at least about 90 wt. % of the polymer precursor composition. Another metal particulate material can be added to the composite precursor composition in an amount equal to or less than approximately the weight of the noble metal-coated silver nanowires. The composite precursor composition can be cured to form a solid material by heating, exposure to radiation, chemical treatment, exposure to water or oxygen, or a combination thereof.

[0008] In another aspect, the present invention relates to a method for forming a composite precursor composition, comprising blending a dispersion of precious metal coated nanowires with a polymer precursor composition to form a well-mixed blend. This method can be used to form the composite precursor compositions described above. In some embodiments, the composite precursor composition can be cured to form a composite material having a resistivity of about 100 Ω·cm or less, or about 1 Ω·cm or less. In some embodiments, the composite precursor composition can be cured to form a composite material having a resistivity of about 100 Ω·cm to about 1×10 11 Composite materials with resistivities of Ω·cm can be formed. [Brief explanation of the drawings]

[0009] [Figure 1A] This is an image obtained for ActiveGrid® Ink GEN5 silver nanowires after heating at 200° C. for approximately 16 hours. [Figure 1B] This is an image obtained for ActiveGrid® Ink GEN7 silver nanowires after heating at 200° C. for approximately 16 hours. [Figure 1C] This is an image obtained for ActiveGrid® Ink GEN8 silver nanowires after heating at 200° C. for approximately 16 hours. [Figure 1D] This is an image obtained for platinum-coated GEN5 silver nanowires after heating at 200° C. for approximately 16 hours. DETAILED DESCRIPTION OF THE INVENTION

[0010] Composites have been formed using noble metal-coated silver nanowires, particularly platinum-coated nanowires, in a polymer matrix, which surprisingly provide a number of desirable properties. Described herein are polymer composites based on noble metal-coated silver nanowires that reach the electron percolation threshold and provide good conductivity at low metal loadings. Surprisingly, it has been found that nanowires coated with noble metals, particularly platinum, can have significantly improved electrical conductivity at comparable metal loadings compared to uncoated nanowires. The underlying mechanism for the improved electrical conductivity of platinum-coated nanowires is unclear and may be related to the nanowire surface and specific interactions with organic components in the composite, but the applicant does not wish to be limited by theory. Thus, reasonable electrical conductivity can be achieved at surprisingly low metal loadings, which can result in composite mechanical properties that are substantially similar to those of the polymer matrix itself. Noble metal-coated silver nanowires have the additional advantage of being more stable to heat treatment, even at relatively low (noble metal) coating levels. These unexpected advantages suggest potentially expanded utility for precious metal-coated silver nanowires in a range of applications where the use of uncoated silver nanowires or other silver particulate materials, such as silver flakes or silver particles, may be less desirable or impractical. Furthermore, the precious metal coating can provide improved chemical resistance to oxidation and corrosion. These filled polymer composites provide desirable materials for reinforced conductive adhesives and polymer composites where low to moderate electrical conductivity is desired but the properties of high metal loading composites are not suitable. Conductive composites can also be effective in transferring or dissipating heat.

[0011] In the structures described herein, the materials form three-dimensional structures. In other words, structures with significant thickness are formed from the materials. Depending on the polymer, the resulting composite can be transparent or opaque, because low metal loadings may not qualitatively change the properties of the polymer. As described further below, silver nanowires have found important use in forming thin, transparent conductive films. To form highly transparent films, the metal nanowires are sparse, so they do not cover most of the surface. For highly transparent films, the polymer binder essentially provides uniform coating and processing stability, so that even with a high volume percentage of nanowires, which is typically in the nanometer range in terms of thickness, the coating maintains excellent optical properties. Highly transparent conductive films, with a conductive layer transmittance of at least about 90%, generally have a polymer overcoat to stabilize the structure after conductive film processing is complete. In thicker films, metal nanowires are dispersed in a thicker polymer layer, so the volume percent of metal can be lower, possibly much lower, than in sparsely transparent films, but the total amount of metal can be comparable or even greater in the area of ​​material on the surface, depending on the thickness. In these three-dimensional systems, the factors driving the percolation threshold to achieve lower values ​​of electrical resistance appear to be different from the nearly two-dimensional structure of highly transparent films. In this context, percolation refers to the establishment of adequate electrical conduction pathways, including discrete conductive elements forming a structure. In some embodiments, it may be desirable to use lower dosages to achieve lower values ​​of resistivity while still achieving the stability of the noble metal coating. Intermediate systems with lower transmittance values, between 70% and 80%, are described in U.S. Patent No. 10,487,222 to de Zeeuw et al., entitled "Conductive Transparent Coating for Rigid and Flexible Substrates," incorporated herein by reference. The conductive coating in the '222 patent has greater than 60% by weight of metal particles.

[0012] Polymers with relatively high metal particle loadings can be used to make electrically conductive adhesives of polymer films and fillers. Electrically conductive adhesives with high metal particulate loadings, generally greater than 75 weight percent, are shown in U.S. Patent No. 9,589,693 to Dreezen et al., entitled "Electrically Conductive Adhesives," incorporated herein by reference. Generally, for a composite or adhesive to be electrically conductive using silver or carbon particles, the loadings are much higher, >30 weight percent. Metal loadings are also useful for improving thermal conductivity. Table 1 compares the general characteristics of different conductive fillers.

[0013] [Table 1]

[0014] High-optical-quality transparent conductive coatings have been successfully formed from silver nanowires, possessing desirable mechanical properties, such as stretchability and stability against repeated folding and unfolding, while maintaining electrical conductivity. Regarding transparent coatings, the use of nanowires to form transparent conductive coatings can have important applications in devices with displays and touch sensors. Higher metal loadings have been shown to decrease electrical resistance, while simultaneously decreasing visible light transmittance. In some embodiments, metal-based transparent electrically conductive elements, e.g., coatings, include a sparse metal conductive layer. The conductive layer is generally sparse, providing the desired amount of optical transparency within the conductive structure, rather than around it, so that the metal coating has many small but significant gaps on the conductive element layer. For example, a transparent electrically conductive coating can include metal nanowires deposited along the layer, where sufficient contact for electron percolation can be achieved to form a suitable conductive path. The one-dimensional morphology of the nanowires favors the formation of a sparse metal conductive layer. In embodiments of the transparent conductive layer, the transparent electrically conductive coating can include a fused metal nanostructured network, which has been found to exhibit desirable electrical, optical, and mechanical properties. In the fused structure, unlike the corresponding non-fused structure, electrons can be conducted through the network rather than hopping between individual nanowires (percolation). Unless otherwise specified, conductivity as referred to herein means electrical conductivity.

[0015] Applicant's application of the fusion process can be controlled to selectively deposit metal at the junctions between metal nanowires or to form a fused mass for nanoparticulate yet low-conductivity structures. When forming a fused metal nanostructured network, the fusion process can be controlled to deposit a desired amount of silver that bonds to the junctions. The system can be balanced to obtain a thermodynamic driving force for melting that occurs primarily at the junctions between adjacent metal nanowires, the constituent elements of which form the fused metal nanostructured network. One solution for forming a fused metal nanostructured layer is further described in U.S. Patent No. 9,183,968 B1 to Li et al., entitled "Metal Nanowire Inks for the Formation of Transparent Conductive Films with Fused Networks," (hereinafter the '968 patent), which is incorporated herein by reference. The process described herein does not involve melting the nanowires.

[0016] The synthesis of thin silver nanowires is described in U.S. Pat. No. 10,714,230 B2 to Hu et al. (hereinafter the '230 patent), entitled "Thin and Uniform Silver Nanowires, Methods of Synthesis and Transparent Conductive Films Formed from the Nanowires," which is incorporated herein by reference. High-quality silver nanowire products with small, uniform diameters and high purity are desirable for some display applications, while lower-grade silver nanowires may be sufficient for less optically demanding applications. For opaque composites such as those described herein, nanowires with somewhat larger diameters, which are less expensive to produce, can achieve the desired results, although thinner nanowires can provide a more dispersed system in the composite and may be desirable from a processing standpoint, depending on length, stiffness, and other factors.

[0017] Applicant has previously described the synthesis of noble metal coated silver nanowires suitable for large-scale production. See U.S. Pat. No. 9,530,534 to Hu et al. (hereinafter the '534 patent), entitled "Transparent Conductive Film," which is incorporated herein by reference. Noble metal coated nanowires have been shown to have improved stability in transparent conductive films under accelerated abrasion conditions using heat and humidity, as shown, for example, in Figures 16 and 17 of the '534 patent.

[0018] Desirable methods for forming metal coatings on silver nanowires can include modifications of galvanic displacement or direct deposition of the coating metal. In controlled galvanic displacement, ions of gold, platinum, or another noble metal, typically provided as a metal ion complex in solution, oxidize the silver in the wires at elevated temperatures while being reduced to elemental noble metal. In direct deposition, a reaction solution is formed using a dispersion of silver nanowires, and a coating solution containing noble metal ions is gradually added to the reaction solution. This reaction solution is maintained under reducing conditions. Hydrazine is a convenient reducing agent because its by-products are nitrogen and water, although other reducing agents can also be used. The coating process can be appropriately controlled to obtain a uniform coating. In addition to the optional use of strongly coordinating ligands and / or polymeric capping agents, controlling the reaction can involve gradually adding a metal ion complex of the coating metal as the metal ion source solution to the reaction solution. The reaction can be conveniently carried out in an aqueous solution, optionally with some alcohol or other cosolvent. A coordinating ligand can be included in the solution containing the metal ions. These metal ions are PtCl6 -2The noble metal coating can be provided in a suitable complex, such as a complex. As used herein, noble metal refers to a metal having a higher standard reduction potential than silver, and therefore includes gold, platinum, iridium, rhodium, palladium, and osmium, with gold and platinum being of particular interest. The thickness of the noble metal coating can generally be adjusted during the deposition process. To achieve the remarkable electrical conductivity results and stability against various degradation forms observed herein, the noble metal coating can be very thin, such as a single layer or a few atomic layers thick.

[0019] Generally, metal nanowires desirably have an average diameter of about 500 nm or less, in some embodiments about 100 nm or less, in further embodiments about 50 nm or less, and in other embodiments about 30 nm or less. With respect to average length, longer nanowires are expected to provide better electrical conductivity within the network. Generally, metal nanowires can have an average length of at least 1 micron, in further embodiments at least 2.5 microns, and in other embodiments, from about 5 microns to about 100 microns, although future synthetic techniques may enable the production of longer nanowires. Nanowire dimensions can be reasonably controlled by adjusting synthesis parameters. Silver nanowires can be sonicated, if desired, to fragment the nanowires into shorter lengths, which can be done before applying a noble metal coating to avoid damaging the coating. Aspect ratios can be defined as the ratio of average length divided by average diameter, and in some embodiments, nanowires can have an aspect ratio of at least about 25, in further embodiments from about 50 to about 5,000, and in further embodiments from about 100 to about 2,000. A person of ordinary skill in the art will recognize that additional ranges of nanowire sizes within the explicit ranges above are contemplated and are within the present disclosure. The application of a noble metal coating does not qualitatively alter the aforementioned nanowire size ranges.

[0020] Direct deposition methods allow for the deposition of larger amounts of precious metal, resulting in smoother coatings and more stable silver metal cores than can be achieved using galvanic exchange. Generally, the precious metal coating can be about 55% by weight or less, and in further embodiments, about 0.03% to about 40% by weight, and in further embodiments, about 0.9% to about 25% by weight, based on the amount of silver. The amount of metal coated, as a fraction of the total nanowires coated, generally ranges from about 0.02 atomic percent (at.%) to about 35 at.%, and in further embodiments, from about 0.1 at.% to about 25 at.%, and in further embodiments, from about 0.5 at.% to about 20 at.%. Assuming the coating is uniform and has bulk material density, the thickness of the coating can be estimated from the weight of the coating and the average parameters of the initial nanowires. A person of ordinary skill in the art will recognize that additional ranges of coating amounts within the explicit ranges above are contemplated and are within the scope of the present disclosure.

[0021] The electrically conductive composites described herein provide another set of materials for use in devices that utilize electrically conductive polymer-type materials. Because the composites can exhibit good electrical conductivity with relatively low metal loadings, the composites can have properties substantially similar to unfilled polymers. Because the composites can be formed with a wide range of polymers, the composites can also achieve a corresponding wide range of mechanical properties. This freedom in composite composition design allows for the formation of a wide range of desirable composite compositions.

[0022] Although precious metal coated silver nanowires can provide significantly reduced electrical resistance at low to moderate usage levels, in embodiments where low electrical conductivity is desired, it may be desirable for the coating to provide resistance to corrosion and other degradation pathways. In these embodiments, the concentration of precious metal coated silver nanowires can be reduced, nanowire morphologies with lower conductivity can be used, and / or the polymer matrix can be selected to favor higher electrical resistance, either due to its inherent insulating properties and / or its ability to interact with the metal nanowires. These materials can be used for electrostatic discharge, grounding, or another suitable purpose.

[0023] The composite material is suitable for forming resistive heaters. The amount of metal can be adjusted to balance the amount of current used for a particular heating level. Platinum-coated nanowires can take advantage of their higher heat resistance, allowing heaters to achieve higher temperatures without damaging them. At lower usage levels, precious metal-coated silver nanowires do not significantly alter the polymer properties of the composite, allowing transparent polymers to be used to form transparent heating elements. For heating elements, electrical resistance does not need to be too low. The conductive composite is suitable for a wide range of other applications, such as those involving electrically conductive adhesives.

[0024] Composite and precursor compositions The precursor composition is a depositable material that can be cured to yield an electrically conductive composite of precious metal-coated silver nanowires loaded in a polymer matrix. Curing broadly refers to the process by which the precursor composition is converted into a solid mass of conductive composite. Curing can refer to the crosslinking reaction, polymerization, and / or solvent removal of the polymer. After curing, the product is an electrically conductive composite material that, in some embodiments, has significant electrical conductivity with relatively low metal loading. The polymer can be formed using a wide range of suitable polymers that may or may not crosslink after curing. For example, suitable processing aids can be included in the precursor composition to facilitate the deposition and / or curing process.

[0025] The precursor composition may be a liquid / ink or paste that can be appropriately deposited for the appropriate application. A curing process converts the precursor composition into a solid mass. The precursor composition has the general characteristic of being depositable as a coating, a dispensable composition, a printed structure, an extrudable material, a spreadable paste, etc., and the rheology of the composition can be selected depending on the deposition method. The precursor composition generally comprises platinum-coated nanowires and an organic component, which optionally has a volatile component. The organic component can include a monomer, an oligomer, a polymer, a dissolved polymer binder, a volatile solvent, a combination thereof, etc.

[0026] The choice of polymer is generally determined by the use of the composite. The choice of polymer is generally not limited, provided that it can be dispersed to form a relatively uniform composite. Examples are described based on both hydrophilic and hydrophobic polymers. The use of silver nanowire-filled composites to form adhesives is described in U.S. Patent Application Publication No. 2016 / 0177146A to Mun et al., entitled "Adhesive Film and Display Member Including the Same" (hereinafter the '146 Application), which is incorporated herein by reference. The '146 Application describes the use of polyacrylates, polymethacrylates, or copolymers thereof with each other or with other monomers. Other suitable thermoplastic polymers include, for example, polyamides, polyesters, polyethers, polyacetals, block polyester ether copolymers, acrylonitrile butadiene styrene copolymers, polyacrylates, polybutylene terephthalate, polyolefins such as polyethylene and / or polypropylene (co)polymers, polyimides, polyarylene oxides, polyalkylene oxides, polystyrenes, polyethersulfones, polyurethanes, epoxies, and mixtures, copolymers, or blends thereof. The formation of silver nanowire composites for non-adhesive coatings is described in Cortes et al., "High-performance thermoplastic composites poly(ether ketone ketone) / silver nanowires: Morphological, mechanical, and electrical properties," Journal of Non-Crystalline Solids, 2014, vol. 391, pp. 106-111, which is incorporated herein by reference.

[0027] In some embodiments, the polymer precursor of the precursor composition can function as a non-volatile solvent. Generally, the precursor composition can include up to about 40 wt. % of an optional volatile solvent. Correspondingly, the precursor composition can include about 60 wt. % to 100 wt. % of a non-volatile organic component as part of the organic portion of the precursor composition. A suitable solvent should be compatible with dissolving the components of the polymer precursor and dispersing the precious metal-coated nanowires. Some monomers or oligomers may be suitable as non-volatile solvents. Volatile solvents can have low or high boiling points. Low-boiling solvents, such as ethanol or isopropanol, can require less energy for final solvent removal than high-boiling solvents, such as ethylene glycol or another polyol. The amount of volatile solvent can be selected based on the properties of the polymer precursor, for example, to achieve solubility for the polymer precursor and to accommodate the desired processing method, e.g., to adjust viscosity or other related properties. The noble metal coated silver nanowires can be compatible with a wide range of polymers, and because the noble metal coated nanowires are generally present in a relatively small volume percent, the precursor composition can generally be processed after formation in the same manner as unfilled polymers, as is generally known in the art.

[0028] The amount of metal nanowires or precious metal-coated silver nanowires used can be determined by various parameters, such as the desired electrical conductivity, mechanical properties, cost, and processability. At a sufficient level of use, the metal nanowires pass through a so-called percolation threshold, where a rapid increase in conductivity and a corresponding decrease in resistance occur. After a series of rapid increases in conductivity, the increase in conductivity with increasing use may exhibit a relatively smaller slope. It may or may not be desirable for the metal nanowire use to exceed the percolation threshold. Generally, for embodiments of interest herein, the metal use in the polymer composite may be about 40 wt % or less, in some embodiments, about 0.001 weight percent (wt %) to about 30 wt %, in further embodiments, about 0.01 wt % to about 20 wt %, in some embodiments, about 0.0025 wt % to about 15 wt %, and in other embodiments, about 0.1 wt % to about 10 wt %. It should be recognized that the upper and lower limits of these ranges can be interchangeable, such as about 0.01 wt % to about 10 wt %. If the conductive precursor composition has a volatile component or releases other volatile by-products during curing, the precursor composition will have a correspondingly lower metal nanowire concentration than the metal nanowire concentration in the cured composite, based on the magnitude of the corresponding organic contribution. Equivalent loadings, in terms of volume percent (based on the density of the nanowires and resin / polymer system), can also be obtained. Generally, the metal loading in the polymer composite can be about 10% by volume or less, in some embodiments about 0.0001 volume percent (vol%) to about 10% by volume, in further embodiments about 0.001% to about 5% by volume, and in other embodiments about 0.01% to about 2% by volume. As discussed below, for some applications, it is desirable for the conductive composite to have higher resistivity values. For these embodiments, the noble metal-coated silver nanowires can be present in the composite at a concentration of about 10% by weight or less, in some embodiments about 2% by weight or less, in other embodiments about 0.1% by weight or less, in further embodiments about 0.025% by weight or less, and in other embodiments about 0.01% by weight or less, resulting in a concentration of about 1×10 11Resistivity values ​​of Ω·cm or less can be achieved. A person of ordinary skill in the art will recognize that additional ranges of nanowire loadings within the explicit ranges above are contemplated and are within the present disclosure.

[0029] Metal nanowires, including precious metal-coated silver nanowires, should generally be kept wet to avoid forming nanowires that cannot be redispersed. Due to their relative fragility, ultrasonic treatment generally cannot be used to disperse aggregated metal nanowires because it can fragment the nanowires; therefore, metal nanowires are generally processed from a dispersed state to form a well-blended material. As previously mentioned, ultrasonic treatment can be selectively used to form shorter nanowires through fragmentation. A typical process involves introducing dispersed metal nanowires at a dilute concentration. Applicants have recently discovered processing methods for forming metal nanowire dispersions with much higher concentrations, depending on the dimensions of the metal nanowires. See co-pending U.S. Provisional Patent Application No. 63 / 459,495 (hereinafter the '495 application) to Virkar et al., entitled "High Loadings of Silver Nanowires: Dispersions and Conductive Pastes; And Corresponding Methods," incorporated herein by reference. The use of more concentrated dispersions of precious metal-coated nanowires allows for some processing latitude, while the use of less concentrated nanowire dispersions may be adequate for forming equivalent composites with adequate solvent removal at a convenient processing time. However, in general, the dispersion of precious metal-coated silver nanowires is blended with the organic components and thoroughly mixed to form the precursor composition. Depending on the scale of processing, industrial mixers of appropriate sizes are commercially available.

[0030] The results presented herein are based on the loading of metal nanowires into a polymer matrix. Other metal, carbon-based, or other filler materials and particles (non-wire) can be added along with the noble metal-coated silver nanowires to increase conductivity (electrical and / or thermal) and possibly impart desired mechanical properties to the final composite. In some embodiments, the composite is substantially free of other conductive metal particulate matter and / or other carbon-based conductive particulate matter, although some amount of metal particulate matter contaminants will generally be present along with the metal nanowires. The other particulate matter may be other metal particles, such as metal nanoparticles other than metal nanowires, or carbon particles, such as graphite particles, carbon black, graphene sheets, fullerenes, carbon nanotubes, carbon nanofibers, etc. Suitable conductive additives include, for example, silver nanoparticles and / or silver flakes. The amount of the additional electrically conductive additive is not particularly limited, but generally, on a weight percent basis, is about 5 times or less than the nanowires, in other embodiments about 2 times or less, in further embodiments about or less than the weight percent of the metal nanowires, and in some embodiments about 0.5 times or less than the weight percent of the nanowires. A person of ordinary skill in the art will recognize that additional ranges of added conductive particles within the explicit ranges above are contemplated and are within the present disclosure.

[0031] As previously mentioned, the precursor composition can include additional components or additives, which can be referred to as processing aids, with the understanding that the precursor composition can broadly cover a wide range of compositions spanning a corresponding wide range of functionality. In some embodiments, the precursor composition can generally include up to about 10 wt. % of processing aids, such as crosslinkers, viscosity modifiers, plasticizers, curing agents (copolymer components), surfactants, etc. Crosslinkers can be thermal or UV initiators, crosslinking reactants, etc. The selection of processing aids is generally influenced by the choice of polymer and corresponding deposition method used.

[0032] Generally, any processing method that results in a good blend of polymer and nanowires can be suitable. Metal nanowires are generally kept dispersed in the processing liquid to avoid agglomeration. Metal nanowires are dispersed in polar solvents such as alcohol or water, but, without intending to be limited by theory, dispersion in other solvents may be possible depending on the properties of surfactants, dispersants, and other ingredients. Solution processing is generally a convenient method if a suitable solvent for the polymer or polymer precursor and nanowire dispersion is available. In general, for nanowire suspensions, suitable solvents include, for example, water, alcohols, ketones, esters, ethers (e.g., glycol ethers), aromatic compounds, alkanes, and mixtures thereof. Specific solvents include, for example, water, ethanol, isopropyl alcohol, isobutyl alcohol, tertiary butyl alcohol, ethylene glycol, triethylene glycol, methyl ethyl ketone, glycol ethers, butyl carbitol (diethylene glycol butyl ether), methyl isobutyl ketone, toluene, hexane, ethyl acetate, butyl acetate, ethyl lactate, PGMEA (2-methoxy-1-methylethyl acetate), mixtures thereof, etc. Additionally, a mixture of solvent, polymer, or monomer with nanowires can be made, and the solvent can be removed to form a nanowire-resin system that can be further processed.

[0033] To form a conductive composite composition, the precursor composition (nanowire-polymer precursor blend) can be deposited and then cured to form the conductive composite. Various coating methods, such as slot coating, can be suitable. Spray coating, using a larger orifice nozzle to accommodate the length of the nanowires, can be suitable. The paste precursor composition can be positioned and spread as appropriate for application, such as by extrusion. The concentration of volatile solvents and other processing aids can be appropriately adjusted to achieve the target conductive composite composition while facilitating deposition. Lower boiling temperature solvents can be used if at least some solvent evaporation during deposition is desired, and higher boiling temperature solvents can be used if most of the solvent removal occurs during curing.

[0034] Curing can be achieved by various means, including, but not limited to, heat, radiation, chemicals, exposure to ambient water or oxygen, or a combination thereof. Various commercially available polymers crosslink in response to ultraviolet (UV) radiation. UV radiation can be used correspondingly during the curing step. The solvent can also be removed after the deposition step (e.g., using heat, reduced pressure, and / or blown air). The appropriate temperature can depend on the polymer and is typically below 250°C. The heating time can be determined by whether the polymer is thermally crosslinked and how much solvent removal occurs. In some embodiments, the polymer matrix is ​​formed by a binder polymer that is dissolved with a solvent during deposition, which forms a solid polymer matrix after solvent removal. The polymer concentration can be selected to achieve the desired metal nanowire loading. In another embodiment, the polymer (e.g., a thermoplastic polymer) can be processed as a melt, and the metal nanowires can be blended with the molten polymer. The solvent associated with the noble metal-coated silver nanowire dispersion can evaporate during blending with the melt. The temperature of the metal should be below the temperature at which the metal nanowires are damaged. The blended polymer melt can be extruded, cast, or molded and cooled to form the resulting composite.

[0035] Conductive composite compositions, properties, and uses After curing, a conductive composite composition is formed at the location of precursor deposition. The overall organic composition of the conductive composite may change based on the reduction of volatile components of the precursor and any reactions that occur during curing. For example, the polymerization and / or curing reactions may involve the evolution of gaseous or volatile by-products based on the specific chemistry. The precious metal-coated silver nanowires become embedded in a solid polymer matrix after curing. The properties of the resulting composite are determined by the composite composition.

[0036] Under appropriate curing conditions, the precious metal-coated silver nanowires generally do not undergo significant changes during curing, although interactions with various polymer components, such as dispersants, may or may not result in changes. The mechanical properties of the composite can be affected to varying degrees by the metal loading. At low metal loadings, the mechanical properties are dominated by the polymer matrix. At higher loadings within the ranges set forth herein, the mechanical properties change to reflect the presence of the metal, which occurs through the interaction between the polymer and the metal. At higher metal loadings, the thermal conductivity of the composite should be much more influenced than by the polymer matrix alone.

[0037] The weight and volume percentage ranges for the precious metal-coated silver nanowires in the conductive composite composition are described above. The remaining weight and volume of the composite can be organic and, optionally, inorganic, to modify other properties. For example, inorganic particles such as silica, alumina, or carbon fiber can be added to increase the mechanical strength of the composite. Other inorganic or organic compositions can be added to modify color. Generally, additives that improve other properties can comprise up to about 10% by volume, and in some specific embodiments, other additives can be used. The polymer matrix comprises the remainder of the composite structure. The polymer matrix can include one or more chemically crosslinked polymers, or an uncrosslinked polymer binder with intertwined polymer chains that effectively form reversible physical crosslinks that are stable unless the polymer is dissolved or melted.

[0038] As shown in the examples below, precious metal-coated silver nanowires exhibit remarkable conductivity at low concentrations. While silver nanowires themselves can provide very good electrical conductivity, at low concentrations, precious metal-coated silver nanowires exhibit conductivity several orders of magnitude greater than the corresponding silver nanowire-filled systems. Because bulk conductivity is essentially equivalent, this dramatic increase in conductivity at lower concentrations offers numerous options for material design for low- and medium-conductivity applications. Because conductive fillers can be incorporated at low concentrations, the mechanical properties of the composite can closely approximate those of the unfilled polymer matrix, such as adhesion, cohesion, mechanical strength, elongation, and modulus. Because a wide range of polymer matrix materials is suitable, conductive composite compositions can achieve desirable electrical conductivity characteristics over a wide range of mechanical properties.

[0039] Resistivity, sometimes called volume resistivity, is equal to R·A / L, where R is the resistance in ohms, A is the area of ​​the conductive material, and L is the length of electrical conduction along the conductive element. If A and L are in centimeters, then resistivity ρ has units of ohms·cm. The bulk resistivity of silver is 1.59×10 -6 Ω·cm, and for platinum it is approximately 1.09×10 -5 Ω·cm. Because the bulk resistivity of platinum is greater than that of silver, for most electrically conductive metals, the effect of the noble metal coating is not related to the bulk resistivity properties. As the metal loading increases, the high conductivity, low resistivity of the noble metal coated silver nanowires decreases and eventually becomes irrelevant, or conversely decreases compared to the silver nanowires when the atomic percent of the noble metal coating is large, at lower nanowire loadings. The resistivity of the composite with the noble metal coated silver nanowires is at least about 100 times lower, in further embodiments at least about 1000 times lower, and in further embodiments at least about 1×10, relative to the resistivity of the silver nanowire-filled composite. 4In some embodiments, at least about 1×10 5 and in another embodiment at least about 1×10 6 The composites can have resistivity values ​​that are 1 / 2 of the resistivity of the composite with silver nanowires divided by the resistivity of the composite filled with noble metal-coated silver nanowires. At even larger ratios, electrical properties become difficult to measure, and the final boundary cannot be accurately determined. As suggested above, these examples are consistent in that the decrease in electrical resistance of the noble metal-coated silver nanowires relative to the electrical resistance of the silver nanowires becomes more pronounced as the metal loading decreases.

[0040] At higher metal loadings, the bulk metal conductivity is the limit of achievable electrical conductivity, and generally, the conductivity can be moderately lower than the bulk conductivity value. As loading decreases, the resistivity of composites with noble metal-coated silver nanowires decreases much slower than the conductivity of composites with silver nanowires with decreasing loading. This difference is particularly pronounced at loadings below about 10 wt. %. This can be seen from the parameters described in the previous paragraph, including the ratio of the two resistivities. For example, at loadings below 10 2 ~10 -3 For resistivity values ​​of this order, much lower dosages can be used when using noble metal coated silver nanowires with proper processing and polymer selection.

[0041] For heater applications, the heat generated can be expressed in terms of surface power density, which is P d =V 2 It can be evaluated as P / (R A), where V is the voltage, R is the resistance, and A is the area of ​​the heater. If V is in volts and R is in ohms, then P dis in units of watts divided by the area of ​​A. Applicants have previously described the formation of transparent heaters using noble metal coated silver nanowires based on thin fused metal nanostructured networks. See co-pending provisional patent application Ser. No. 63 / 441,656 to Chen et al., entitled "Stable Thin Film Heaters Based on Noble Metal Coated Silver Nanowires and Applications Thereof," which is incorporated herein by reference. As previously shown, noble metal coated silver nanowires have a power rating of approximately 0.5 W / cm. 2 (2000W / m 2 ), and in some embodiments, greater than about 0.6 W / cm 2 and in some embodiments at least about 1 W / cm 2 The composite materials described herein can achieve similar resistance x area values ​​for equivalent surface power densities in stable, thicker structures. These heating elements can be used in transparent or opaque heaters. These structures can provide an alternative to thin, transparent heaters that use fused metal nanostructure networks, each of which can offer advantages in different situations.

[0042] In some embodiments, for certain applications, particularly for electrostatic discharge, anti-static, or grounding purposes, it is desirable to have a lower conductivity, with a suitable resistivity being about 10 2 ~10 11 Ω cm, whereas 10 2 Values ​​below Ω·cm are sometimes considered conductive. Depending on the specific use of the material, the resistivity can be selected accordingly. Thus, for some applications, the resistivity may be between 100 and 10 8 Ω·cm, while in other applications the desired resistivity may be about 10 6 ~about 10 11The resistivity may be in the range of Ω·cm. Those skilled in the art will recognize that additional ranges within these stated resistivity ranges are contemplated and are within the scope of the present disclosure. The concentration of the noble metal-coated silver nanowires can be reduced to reach the desired resistivity range. Furthermore, other characteristics of the composite can be selected to contribute to the composite's low conductivity. For example, an electrically insulating adhesive can be used for the polymer matrix. For example, electrically insulating epoxies, silicones, polyurethanes, polysulfides, and cyanoacrylates are available from Masterbond® and DuPont. Because the slope of resistivity as a function of nanowire concentration is smaller over a wider concentration range, the composite composition can be used to efficiently target larger values ​​of resistance within the target range. The specific amount used will depend on the polymer and, optionally, the presence of any additives.

[0043] Experiments were conducted to form polymer composites using silver nanowires with and without platinum coating. Results are presented in the Examples. These results demonstrate the high electrical conductivity and thermal stability of silver nanowires with platinum coating. [Example]

[0044] General Materials and Methods The silver nanowires (Ag NWs) used in the following examples are available as components in ActiveGrid® Ink from C3Nano, Inc., the applicant. The ActiveGrid® Ink included GEN5 silver nanowires with an average diameter of approximately 20-22 nm, GEN7 silver nanowires with an average diameter of approximately 18 nm, and GEN8 ActiveGrid® Ink, which has silver nanowires with an average diameter of <16 nm. The preparation of these nanowires is described in the above-referenced '230 patent. Platinum-coated silver nanowires (Ag@Pt NWs) were prepared using platinum-coated GEN5 silver nanowires using the direct deposition method described in U.S. Pat. No. 9,530,534 B2 to Hu et al. and U.S. Pat. No. 10,714,230 B2 to Hu et al. The platinum coating can comprise approximately one or a few monolayers of platinum on the silver nanowires.

[0045] The good dilute dispersion of nanowires was blended with either a monomer or a polymer to form a composite. In some examples, the nanowires were blended with ethoxylated (20 mol%) trimethylolpropane triacrylate monomer (AM1). A blend of three UV photoinitiators (PIs) was used to initiate the polymerization of AM1; this PI blend is referred to as MP8. In some examples, the nanowires were blended with a polymer, such as polylactic acid (PLA). When blending nanowires with a polymer, the polymer was dissolved in an appropriate solvent and mixed with the nanowire dispersion, and the solvent was removed by heat and / or under reduced pressure. For nanowires blended in PLA, for example, chloroform was used as the polymer solvent. Nanowires can be dispersed in alcohol or aqueous alcohol for processing.

[0046] Composites containing nanowires blended with monomer and photoinitiator were prepared by wetting a glass slide with the blend and then placing a second glass slide on top so that a wet film formed between the two slides. These samples were subjected to a 1.8 J / cm per pass. 2 The nanowire-PLA composites were exposed to UV light by three passes through a Fusion UV System delivering an energy density of 1000 uV. After the composites were cured, they could be removed from the glass slides. For nanowire-PLA composites, thin films were formed by placing nanowire-PLA-solvent in a flat-bottom glass container and removing the solvent by evaporation under ambient conditions. The films could be peeled from the glass surface for evaluation.

[0047] The composites were evaluated by measuring resistance using a two-point probe method with silver conductor paste (DuPont™ PE828) as trace electrodes to form electrical connections; the silver paste was approximately 1-3 cm long, with channel lengths of approximately 0.2-1.0 cm wide. Copper foil tape (3M™ Copper Foil Shielding Tape 1182) was also attached to the surface of the samples to guide the silver paste and facilitate template formation. The samples were then heated at 80°C for 40 minutes to cure the paste. The resistance of each composite was measured using an electronic multimeter equipped with a pair of probes.

[0048] Example 1 - Thermal Behavior The thermal behavior of Ag nanowires and Ag@Pt nanowires was investigated. A dilute solution of the nanowires was prepared and dropped onto a glass slide. The samples were heated and images were taken at 1-hour intervals using 1000x magnification and exposure settings of 150-160 ms. Results for the sample heated at 150 °C are summarized in Table 2. Results for the sample heated at 200 °C are summarized in Table 3. Figures 1A-1C show images of GEN5, GEN7, and GEN8 silver nanowires, respectively, obtained after approximately 16 hours of heating at 200 °C, while Figure 1D shows an image obtained with platinum-coated GEN5 silver nanowires. Although the term "melting" is used in Table 3, some combination of melting, fragmentation, and oxidation was observed.

[0049] [Table 2]

[0050] [Table 3]

[0051] Example 2 - AgNW and Ag@Pt NW Composites Formulated with Hydrophilic Triacrylate Monomer AM1 Formulations containing GEN5 silver nanowires and platinum-coated GEN5 silver nanowires were prepared by mixing 0.2 g or 0.35 g of each nanowire with 10 g of triacrylate monomer AM1 and 20 mg of photoinitiator blend MP8. After UV curing, the top glass slide was removed and the composite structure was detached from the bottom glass slide. The resulting composites were reddish-brown in color, with the composites made with platinum-coated nanowires being darker in color than the composites made with uncoated nanowires. The thickness of the composite structures ranged from approximately 110 to approximately 120 microns. The resistivity of each composite was measured, and the results are shown in Table 4.

[0052] The results, shown in Table 4, indicate that platinum-coated silver nanowires are much more conductive than uncoated silver nanowires. For composites made with 2.0 wt% NW loading, resistances of less than 10 Ω can be achieved using platinum-coated nanowires, as opposed to megaΩ (MΩ) for uncoated silver nanowires.

[0053] [Table 4]

[0054] Example 3 - PLA-blended AgNW and Ag@Pt NW composites Composites C1, C2, X1, and X2 containing GEN5 silver nanowires and platinum-coated GEN5 silver nanowires were prepared by mixing 10 g of PLA with 0.2 g of each nanowire, as shown in Table 5. The weight percentage of nanowires in the composites was approximately 2 wt%. These composites were cut into various sizes and their thicknesses were measured. For each sample, resistance was measured at an initial time (R0) and then at daily intervals (R1, R2, and R3) for up to three days. The samples were maintained at 85°C and 85% relative humidity. Therefore, this example also tests the stability of the composites under accelerated wear test conditions. Commercially available heat- and humidity-controlled testing equipment includes, for example, an ESPEC Model BTL-433 Environmental Chamber (ESPEC Corp. North America, Inc. Hudsonville, MI, USA) or a Thermotron SM-3.5-3800 Benchtop Environmental Chamber (Thermotron Inc., Holland, MI, USA). The results are shown in Table 5.

[0055] The PLA / Ag samples C1 and C2 exhibit very high resistance, while the PLA / Ag@Pt samples (X1 and X2) show high conductivity at nanowire loadings of approximately 2 wt%. It can also be noted that the conductivity of the PLA / Ag@Pt NW composite film samples increased upon treatment at 85 °C and 85% relative humidity. Presumably, the percolating network undergoes some polymer reorganization under high humidity and temperature conditions, improving interwire contact.

[0056] [Table 5]

[0057] Composites M1, M2, N1, and N2 containing GEN5 silver nanowires and platinum-coated GEN5 silver nanowires were prepared by mixing 0.2 g of each nanowire with 10 g of PLA, as shown in Table 6. The weight percentage of nanowires in the composites was approximately 2 wt%. These composites were cut into various sizes and their thicknesses were measured. The resistance was measured at an initial time (R0) and after one day (R1). The samples were maintained at 150°C under dry conditions. The results are shown in Table 6. These results indicate that the composite films are stable to high-temperature treatment.

[0058] [Table 6]

[0059] Example 4 - AgNW and Ag@Pt NW Composites Blended with AM1 and PLA Composites containing GEN5 silver nanowires and platinum-coated GEN5 silver nanowires were made by mixing the nanowires with AM1 or PLA, as shown in Table 7. Composites made with AM1 were UV cured as described above. The resistivity of each coating was measured, and the results are shown in Table 7.

[0060] [Table 7]

[0061] Example 5 - Ag@Pt NW composites formulated with AM1 Composite 5a was prepared by mixing Ag@Pt NW and AM1 at a normalized loading of 1.5x. Composite 5a was used to form a coating with a thickness of approximately 200 microns. The resistivity was measured and the results are shown in Table 8.

[0062] [Table 8]

[0063] Example 6 - Effect of Ag paste and Cu tape on conductivity Composites 6 and 7a-7c were prepared by mixing GEN5 silver nanowires and platinum-coated GEN5 silver nanowires with AM1, as shown in Table 9. The composite coatings were prepared as described above and maintained at °C and % relative humidity. For each sample, the resistance was measured at an initial time (R0) and then at daily intervals (R1 and R2) for up to two days. The coatings were then configured using copper foil tape and / or silver paste to form electrical connections. The resistance of each configuration was measured, and the results are shown in Table 9.

[0064] [Table 9]

[0065] Example 7 - Applied Voltage Heating Coatings of Composite 7c were prepared and constructed using either copper foil tape alone or a combination of silver paste and copper foil tape to form an electrical connection. The coatings were heated at an amperage setting of 2 over a voltage range of 1 V to 4 V. No temperature change was observed for the coating constructed using copper foil tape alone. A temperature change of approximately 10°C was observed for the coating constructed using a combination of silver paste and copper foil tape. The initial resistance (at 1 V) was approximately 14.5 Ω, and the final resistance (at 4 V) was approximately 17.7 Ω.

[0066] The foregoing embodiments are intended to be illustrative and not limiting. Additional embodiments are within the scope of the claims. Moreover, while the present invention has been described with reference to specific embodiments, those skilled in the art will recognize that changes in form and detail are possible without departing from the spirit and scope of the present invention. The incorporation by reference of any of the above documents is limited to include no subject matter contrary to the disclosure explicitly set forth herein. To the extent that a particular structure, composition, and / or process is described herein with components, elements, components, or other moieties, it should be understood that the disclosure extends to specific embodiments, embodiments that include the particular components, elements, components, other moieties, or combinations thereof, as well as embodiments that consist essentially of such particular components, components, or other moieties, or combinations thereof, which may include additional features that do not alter the basic nature of the subject matter, as suggested in the discussion, unless otherwise indicated. As used herein, the use of the term "about," unless otherwise specified, is based on the understanding of one of ordinary skill in the art in the particular circumstances, which may include measurement error and / or precision of reporting, as understood by one of ordinary skill in the art in the context of the particular parameters.

Claims

1. 1. A composite material comprising: noble metal coated silver nanowires and a polymer matrix combined to form a composite material, the composite having a thickness of about 1×10 １１ A composite material having a resistivity of Ω·cm or less.

2. 10. The composite material of claim 1, having a resistivity of less than or equal to about 100 ohm-cm.

3. 3. The composite material of claim 2, comprising about 0.01% to about 40% by weight of the noble metal coated silver nanowires.

4. 3. The composite material of claim 2, comprising about 0.1% to about 20% by weight of the noble metal coated silver nanowires.

5. 5. The composite material of claim 4, having a resistivity of about 1 ohm-cm or less.

6. 6. The composite material of any one of claims 2 to 5, wherein the noble metal coated silver nanowires comprise platinum coated silver nanowires, and the composite material comprises about 0.5% to about 10% by weight of the platinum coated silver nanowires.

7. 7. The composite material of claim 2, wherein the noble metal coated silver nanowires have an average diameter of 100 nm or less.

8. 8. The composite material of claim 7, wherein the noble metal coated silver nanowires comprise no more than about 2.5% by volume of the composite material.

9. The composite material of any one of claims 2 to 8, wherein the polymer matrix comprises at least about 90% by weight of the composite material.

10. 10. The composite material of any one of claims 2 to 9, wherein the composite material further comprises another metal particulate matter in an amount equal to or less than about the weight of the noble metal coated silver nanowires.

11. 11. A heater comprising two busbars of opposite polarity and a composite material according to any one of claims 2 to 10, wherein the composite material is in contact with the busbars, whereby when a voltage is applied, a current flows between the busbars.

12. Approx. 100Ω・cm ~ Approx. 1×10 １１ 10. The composite material of claim 1 having a resistivity of Ω cm.

13. 13. The composite material of claim 12, wherein the concentration of the noble metal coated silver nanowires is less than or equal to about 10.0 wt.%.

14. 13. The composite material of claim 12, wherein the concentration of the noble metal coated silver nanowires is less than or equal to about 2.0 wt.%.

15. 13. The composite material of claim 12, wherein the concentration of the noble metal coated silver nanowires is about 0.1 wt% or less.

16. 16. The composite of any one of claims 12-15, wherein the noble metal coated silver nanowires comprise platinum coated silver nanowires, and the composite comprises no more than about 2.0 wt% of the platinum coated nanowires.

17. 17. The composite material of any one of claims 12 to 16, wherein the noble metal coated silver nanowires have an average diameter of 100 nm or less.

18. 18. The composite material of any one of claims 12 to 17, wherein the noble metal coated silver nanowires comprise no more than about 2.5% by volume of the composite material.

19. The composite material of any one of claims 12 to 18, wherein the polymer matrix comprises at least about 90% by weight of the composite material.

20. 20. The composite material of any one of claims 12 to 19, wherein the composite material comprises another metal particulate matter in an amount equal to or less than about the weight of the precious metal coated silver nanowires.

21. 1. A composite precursor composition comprising: precious metal coated silver nanowires; and a polymer precursor composition, wherein the polymer precursor composition is a monomer, an oligomer, a solid polymer dissolved in a solvent, or a combination thereof, and wherein the solids content of the composite precursor composition comprises about 0.01 wt % to about 40 wt % of the precious metal coated silver nanowires.

22. 22. The composite precursor composition of claim 21, wherein the solids content of the composite precursor composition comprises about 0.1 wt % to about 20 wt % of the noble metal-coated silver nanowires.

23. 23. The composite precursor composition of claim 21 or claim 22, wherein the noble metal coated silver nanowires comprise platinum coated silver nanowires, and the solids content of the composite precursor composition comprises about 0.5 wt % to about 10 wt % of the platinum coated nanowires.

24. 24. The composite precursor composition of any one of claims 21 to 23, wherein the noble metal coated silver nanowires have an average diameter of 100 nm or less.

25. 25. The composite precursor composition of any one of claims 21 to 24, wherein the solids content of the composite precursor composition comprises at least about 90% by weight of the polymer precursor composition.

26. The composite precursor composition of any one of claims 21 to 25, further comprising a volatile solvent.

27. 27. The composite precursor composition of any one of claims 21 to 26, wherein the composite precursor composition is capable of curing to form a composite material having a resistivity of about 100 Ω-cm or less.

28. 28. The composite precursor composition of any one of claims 21 to 27, wherein the composite precursor composition is capable of curing to form a composite material having a resistivity of about 1 Ω-cm or less.

29. 29. The composite precursor composition of any one of claims 21 to 28, wherein the composite precursor composition further comprises another metal particulate material in an amount equal to or less than about the weight of the noble metal-coated silver nanowires.

30. 30. The composite precursor composition of any one of claims 21 to 29, wherein the composite precursor composition can be cured to form a solid material by heating, exposure to radiation, chemical treatment, exposure to water or oxygen, or a combination thereof.

31. 31. The composite precursor composition of any one of claims 21 to 30, wherein the solids content of the composite precursor composition comprises no more than about 2.0 wt% of the noble metal-coated silver nanowires.

32. 32. The composite precursor composition of any one of claims 21 to 31, wherein the solids content of the composite precursor composition comprises no more than about 0.1 wt% of the noble metal-coated silver nanowires.

33. 33. The composite precursor composition of any one of claims 21 to 32, wherein the noble metal coated silver nanowires comprise platinum coated silver nanowires.

34. 34. The composite precursor composition of any one of claims 21 to 33, wherein the noble metal coated silver nanowires have an average diameter of 100 nm or less.

35. 35. The composite precursor composition of any one of claims 21 to 34, wherein the solids content of the composite precursor composition comprises at least about 90% by weight of the polymer precursor composition.

36. 36. The composite precursor composition of any one of claims 21 to 35, wherein the composite material comprises another metal particulate matter in an amount equal to or less than about the weight of the noble metal coated silver nanowires.

37. The composite precursor composition is cured to have a resistivity of about 100 Ω cm to about 1×10 １１ 37. The composite precursor composition of any one of claims 21 to 36, capable of forming a composite material having a resistivity of Ω-cm.

38. 38. The composite precursor composition of any one of claims 21 to 37, wherein the composite precursor composition can be cured to form a solid material by heating, exposure to radiation, chemical treatment, exposure to water or oxygen, or a combination thereof.

39. 1. A method for forming a composite precursor composition, the method comprising blending a dispersion of precious metal coated nanowires with a polymer precursor composition to form a well-mixed blend, wherein the polymer precursor composition is a monomer, an oligomer, a polymer dissolved in a solvent, or a combination thereof, and wherein the solids content of the composite precursor composition comprises from about 0.01 wt % to about 40 wt % precious metal coated silver nanowires.

40. 40. The method of claim 39, wherein the intimately mixed blend includes a volatile solvent, and the method further comprises removing at least a portion of the volatile solvent to obtain a desired solids content of the composite precursor composition.

41. 41. The method of claim 39 or claim 40, wherein the composite precursor composition is capable of curing to form a composite material having a resistivity of about 100 Ω-cm or less.

42. 41. The method of claim 39 or claim 40, wherein the composite precursor composition is capable of curing to form a composite material having a resistivity of about 1 Ω-cm or less.

43. 43. The method of any one of claims 39-42, wherein the solids content of the composite precursor composition comprises no more than about 2.0 wt% of noble metal-coated silver nanowires.

44. The composite precursor composition is cured to have a resistivity of about 100 Ω cm to about 1×10 １１ 44. The method of any one of claims 39 to 43, capable of forming a composite material having a resistivity of Ω cm.

45. The method of claim 39, wherein the composite precursor composition is a composite precursor composition according to any one of claims 21 to 38.

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