Materials for use in a 3D printer and methods for printing an object with a 3D printer

Abstract

Materials for use in a 3D printer, including: several metal particles with an average cross-sectional length of less than or equal to 100 nm; and a stabilizing material comprising an organoamine, carboxylic acid, thiol and derivatives thereof, xanthogenic acid, polyethylene glycols, polyvinylpyridine, polyvinylpyrrolidone or a combination thereof; the metal particles and the stabilizing material agglomerate to form particles with an average cross-sectional length of about 1 µm to about 250 µm.

Description

General state of the art

[0001] 3D printing is used to create complex 3D objects directly from a computer-aided digital design. 3D printing technology can generally be divided into three categories: (1) stereolithography (“SLA”), (2) fused deposition modeling (“FDM”), and (3) powder bed technology, which involves a laser beam and / or an electric beam. SLA selectively solidifies photosensitive (UV-curable) polymers using a laser (e.g., laser sintering) or another light source, while FDM selectively deposits thermoplastically molten polymer through a heated nozzle. However, both SLA and FDM are limited to plastics and are not used to create metal objects.

[0002] Powder bed fusion technology can be used to create metallic objects with micrometer-sized powders, employing laser sintering. The metal powders used in laser sintering can be potentially explosive. To reduce the risk of powder ignition, printers using powder bed fusion technology are often housed in a nitrogen-sealed chamber, making them unsuitable for home use. Furthermore, the objects produced are often porous internally, making them weaker than objects manufactured using conventional methods. Therefore, an improved 3D printing process and an improved metal material are needed for its use.

[0003] DE 10 2009 015 470 A1 relates to a process for the production of metal nanoparticles in which metal ions are reduced in the presence of a polymeric stabilizer to form metal nanoparticles.

[0004] US 2006 / 0 073 667 A1 relates to a process for the production of stabilized silver nanoparticles and to silver nanoparticles obtained therefrom. The process comprises the step of reacting a silver compound with a reducing agent comprising a hydrazine compound, in the presence of a thermally removable stabilizer in a reaction mixture comprising the silver compound, the reducing agent, the stabilizer, and an optional solvent, to form a variety of silver-containing nanoparticles with molecules of the stabilizer on the surface of the silver-containing nanoparticles.

[0005] CA 2 677 894 A1 relates to a nanoparticle composite comprising a nanoparticle with a mean diameter in the range of 1 to 100 nm, wherein the nanoparticle is substantially enclosed with a plurality of stabilizing polyelectrolyte units. (3) further discloses a method for producing such stabilized composite nanoparticles, comprising the following steps: providing a solution comprising a nanoparticle and a plurality of polyelectrolyte stabilizing units; adding a collapsible agent to the solution to collapse the plurality of polyelectrolyte stabilizing units around the nanoparticle to form a composite nanoparticle; and modifying the plurality of polyelectrolyte stabilizing units in the solution to change their transport properties.

[0006] US 2010 / 0 226 811 A1 discloses a process comprising the following steps: (a) forming a structure comprising non-coalesced silver-containing nanoparticles; (b) heating the non-coalesced silver-containing nanoparticles to form coalesced silver-containing nanoparticles; and (c) subjecting the non-coalesced silver-containing nanoparticles or the coalesced silver-containing nanoparticles or both to plasma treatment, wherein the feature has a low electrical conductivity before step (c), but the electrical conductivity of the feature is increased by at least approximately 100 times after steps (b) and (c), wherein step (c) is performed during one or more of the steps before heating, during heating, or after heating. Brief description

[0007] The following is a simplified summary to provide a basic understanding of some aspects of one or more embodiments of the teachings presented here. This summary is not a comprehensive overview and is not intended to identify key or main elements of the teachings presented here, nor to outline the scope of the disclosure. Rather, its main purpose is to present one or more concepts in a simplified manner as a prelude to the detailed description presented later.

[0008] The present invention provides a material for use in a 3D printer, comprising several metal particles with an average cross-sectional length of less than or equal to 100 nm; and a stabilizing material comprising an organoamine, carboxylic acid, thiol and derivatives thereof, xanthogenic acid, polyethylene glycols, polyvinylpyridine, polyvinylpyrrolidone or a combination thereof, wherein the metal particles and the stabilizing material agglomerate to form particles having an average cross-sectional length of about 1 µm to about 250 µm.

[0009] A method for printing an object with a 3D printer is also provided, comprising loading several stabilized particles into a dispensing bed of the 3D printer, wherein the stabilized particles comprise: several metal particles with an average cross-sectional length of less than or equal to 100 nm; and a stabilizing material comprising an amine, organoamine, carboxylic acid, thiol and derivatives thereof, xanthogenic acid, polyethylene glycols, polyvinylpyridine, polyvinylpyrrolidone, or a combination thereof, wherein the metal particles and the stabilizing material agglomerate to form particles having an average cross-sectional length of about 1 µm to about 250 µm. A portion of the stabilized particles can be transferred from the dispensing bed to a build bed of the 3D printer.The stabilized particles in the build bed can be sintered at a temperature of approximately 200 °C or less to form the printed object. Brief description of the drawings

[0010] The accompanying drawings, which are included in and form part of the specification, represent embodiments of the teachings presented here and, together with the description, serve to explain the principles of the disclosure. They show: Fig. 1 An illustrative system for printing metallic 3D objects according to one or more disclosed embodiments. Detailed description

[0011] The following section provides detailed reference to embodiments of the present teachings, examples of which are shown in the attached drawings. Wherever possible, the same reference numbers are used in all drawings to designate the same, identical, or similar parts.

[0012] As used herein, and unless expressly stated otherwise, the term "printer" includes any device that performs a printing output function for any purpose, such as a digital copier, bookbinding machine, fax machine, multifunction device, electrostatographic device, 3D printer capable of producing 3D objects, etc. It will be understood that the structures depicted in the figures may include additional features not shown for the sake of simplicity, and that depicted structures may be omitted or modified.

[0013] Multiple metallic particles can be used by a 3D printer to create a metallic object. The metallic particles can be any metal or metal alloy, such as silver, gold, aluminum, platinum, palladium, copper, cobalt, chromium, indium, titanium, zirconium, nickel, an alloy thereof, or a combination thereof. The metallic particles have an average cross-sectional length (e.g., diameter) that is less than or equal to approximately 100 nm, less than or equal to approximately 50 nm, or less than or equal to approximately 20 nm. Particles of this size can also be referred to as nanoparticles. The metallic nanoparticles can be in powder form. Furthermore, the metallic nanoparticles can be a silver-nanoparticle composite or a metal-nanoparticle composite, such as Au-Ag, Ag-Cu, Ag-Ni, Au-Cu, Au-Ni, Au-Ag-Cu, and Au-Ag-Pd.The various components of the composite materials can be present in quantities ranging from, for example, approximately 0.01 to approximately 99.9 wt.%, in particular from approximately 10 to approximately 90 wt.%.

[0014] Heat diffusion can be difficult to control at higher temperatures, as this can initiate the sintering of unwanted powder components, resulting in inconsistencies on the printed object. However, metallic particles of the size described above (i.e., nanoparticles) can have melting and / or sintering temperatures of less than or equal to approximately 200 °C, less than or equal to approximately 150 °C, less than or equal to approximately 125 °C, or less than or equal to approximately 100 °C. By reducing the melting and / or sintering temperature to the range described above, the amount of heat diffusion generated during the printing process can also be reduced. This can reduce inconsistency and improve printing precision.

[0015] Compared to "micrometer-sized particles" or "microparticles" (e.g., particles with an average cross-sectional length of about 1 µm to about 999 µm), metallic nanoparticles can exhibit improved absorption due to their surface plasmon absorption in the UV and visible ranges. For example, silver nanoparticles exhibit strong absorption at about 410 to 420 nm. See, e.g., (J. of Microelectronics and Electronic Packaging, 2013, 10, 49-53). This absorption can enable the use of a low-current laser (and a low-temperature laser—e.g., a blue laser). In some embodiments, the particle size (e.g., average cross-sectional length) of the nanoparticles can be smaller than the wavelength of the sintering light source (laser, xenon lamp, electron beam, etc.).

[0016] Furthermore, metallic nanoparticles are less prone to scattering and / or reflecting the laser beam than larger microparticles. Light scattering and / or reflection can result in a feature size larger than the laser beam, thus leading to lower resolution in the resulting object. Metallic nanoparticles can enable 3D printing at resolutions of less than or equal to approximately 25 µm, less than or equal to approximately 10 µm, or less than or equal to approximately 5 µm. This can facilitate the fabrication of metallic objects with smooth surfaces (e.g., low surface roughness).

[0017] A stabilizing material (or stabilizer) is added to the metallic nanoparticles to form a stabilized nanoparticle matrix (e.g., in powder form). The stabilizing material comprises an amine (e.g., organoamine), carboxylic acid, thiol and derivatives thereof, -OC(S)SH (xanthogenic acid), polyethylene glycols, polyvinylpyridine, polyvinylpyrrolidone, and other organic surfactants, or a combination thereof. The metallic nanoparticles with the stabilizing material, or at least partially thereof, can be in the form of multiple particles having an average cross-sectional length (e.g., diameter) of less than or equal to approximately 100 nm, less than or equal to approximately 50 nm, or less than or equal to approximately 20 nm. In some embodiments, at least a portion of the stabilizing material can adhere to the surface of the metallic nanoparticles.In other words, the metallic nanoparticles can be isolated from one another by the stabilizing material and form a discontinuous phase. In embodiments, the stabilizing material can be an organic stabilizer. The term "organic" in "organic stabilizer" refers, for example, to the presence of carbon atom(s); however, the organic stabilizer can also contain one or more non-metallic heteroatoms, such as nitrogen, oxygen, halogen, and the like. The organic stabilizer can be an organoamine stabilizer, such as the one described in US 7,270,694 B2. Examples of organoamines include alkylamines, such as...Butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, hexadecylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, diaminopentane, diaminohexane, diaminoheptane, diaminooctane, diaminononane, diaminodecane, diaminooctanedipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, methylpropylamine, ethylpropylamine, propylbutylamine, ethylbutylamine, ethylpentylamine, propylpentylamine, butylpentylamine, tributylamine, trihexylamine, and the like, or mixtures thereof. Examples of other organic stabilizers may include, for example, thiol and its derivatives, -OC(S)SH (xanthogenic acid), polyethylene glycols, polyvinylpyridine, polyvinylpyrrolidone, and other organic surfactants. The organic stabilizer can be selected from the group consisting of a thiol, such as butanethiol, pentanethiol, hexanethiol, heptanethiol, octanethiol, decanthiol, dodecanethiol; and a dithiol, such as...1,2-Ethanedithiol, 1,3-propanedithiol, and 1,4-butanedithiol; or a mixture of a thiol and a dithiol. The organic stabilizer can be selected from the group consisting of a xanthic acid such as O-methylxanthate, O-ethylxanthate, O-propylxanthic acid, O-butylxanthic acid, O-pentylxanthic acid, O-hexylxanthic acid, O-heptylxanthic acid, O-octylxanthic acid, O-nonylxanthic acid, O-decylxanthic acid, O-undecylxanthic acid, and O-dodecylxanthic acid. Organic stabilizers containing a pyridine derivative (e.g., dodecylpyridine) and / or organophosphine capable of stabilizing metal nanoparticles can also be used.

[0018] Other examples of stabilized silver nanoparticles may include: carboxylic acid-organoamine complex stabilized silver nanoparticles described in US 2009 / 0148600 A1; the carboxylic acid-stabilizer silver nanoparticles described in US 2007 / 0099357 A1; and heat-removable stabilizers and UV-degradable stabilizers, such as those described in US 2009 / 0181183 A1.

[0019] The stabilizing material can coat the metallic nanoparticles to reduce or eliminate the possibility of them igniting and exploding when heated by the laser. For example, the stabilizing material can form a non-conductive organic shell that at least partially envelops the metallic nanoparticles and acts as a buffer. The explosion of the metallic nanoparticles can be prevented using the K st -explosion value can be evaluated. In some embodiments, the K stThe value must be less than 100 bar*m / sec, less than 50 bar*m / sec, or less than 25 bar*m / sec. K st This represents the size-normalized maximum rate of pressure rise for a constant-volume explosion, as measured by standard instruments using standard test procedures. This is an explosibility parameter.

[0020] The metallic nanoparticles can be present in the stabilized nanoparticle matrix in an amount of approximately 65 wt.% to approximately 75 wt.%, approximately 75 wt.% to approximately 85 wt.%, approximately 85 wt.% to approximately 95 wt.% or more, and the stabilizing material can be present in the stabilized nanoparticle matrix in an amount of approximately 5 wt.% to approximately 15 wt.%, approximately 15 wt.% to approximately 25 wt.%, approximately 25 wt.% to approximately 35 wt.% or more. The metallic nanoparticles can be present in the stabilized nanoparticle matrix in an amount of approximately 20 vol% to approximately 30 vol%, approximately 30 vol% to approximately 40 vol%, approximately 40 vol% to approximately 50 vol%, approximately 50 vol% to approximately 60 vol% or more, and the stabilizing material can be present in the stabilized nanoparticle matrix in an amount of approximately 40 vol% to approximately 50 vol%, approximately 50 vol% to approximately 60 vol%, approximately 60 vol% to approximately 70 vol% or more.In one embodiment, the metallic nanoparticles can be present in the stabilized nanoparticle matrix in an amount of about 20 vol% to about 49 vol%, and the stabilizing material can be present in the stabilized nanoparticle matrix in an amount of about 51 vol% to about 80 vol%.

[0021] The metallic nanoparticles and / or the stabilized nanoparticle matrix (i.e., the metallic nanoparticles plus the stabilizing material) can be loaded into the 3D printer in at least three different ways. In the first method, the metallic nanoparticles and / or the stabilized nanoparticle matrix agglomerate to form particles with an average cross-sectional length (e.g., diameter) of approximately 1 µm to approximately 250 µm, approximately 5 µm to approximately 250 µm, or approximately 100 µm to approximately 250 µm. In other words, the metallic nanoparticles in the 3D printer can be micrometer-sized particles. Each microparticle can contain multiple nanoparticles.

[0022] In the second form, the metallic nanoparticles and / or the stabilized nanoparticle matrix can be dispersed in one or more liquid solvents to form a paste. The solvents can be or include hydrocarbons, alcohols, esters, ketones, ethers, or a combination thereof. An example of a hydrocarbon is an aliphatic hydrocarbon such as decalin, bicyclohexyl, dodecane, tetradecane, isopar, and the like; an aromatic hydrocarbon such as xylene, trimethylbenzene, ethylbenzene, propylbenzene, butylbenzene, pentylbenzene, methylethylbenzene, tetrahydronaphthalene, and the like. An example of an alcohol is terpineol, ethylene glycol, ethanol, butanol, carbitol, and the like. An example of an ester is propylene glycol monoethyl ether acetate (PGMEA) or DPGMEA. The paste can prevent the metallic nanoparticles from forming dust clouds during the manufacturing process.Furthermore, diluting the matrix with the solvent can further reduce the risk of the nanoparticles igniting or exploding when heated by the laser. Additionally, the paste can be applied more evenly in a single layer on the build platform (described below), which can result in greater uniformity of the printed object.

[0023] In the third form, the metallic nanoparticles can be dispersed in a polymer matrix to form micrometer-sized particles (e.g., powder). The polymer matrix can be or include polyester, polycarbonate, polystyrene, acrylate polymer, polyvinylpyridine, polyvinylpyrrolidone, or a combination thereof. The micrometer-sized particles can be formed by dispersing the metallic nanoparticles in a solvent (e.g., one or more of the solvents disclosed above), drying the metallic nanoparticles, and breaking up the resulting solid to form the micrometer powder.

[0024] Fig.Figure 1 is an illustrative 3D printer 100 for printing metallic 3D objects according to one or more disclosed embodiments. The printer 100 can have a dispensing bed 110 defined by one or more side walls 112 and a dispensing piston 116. The stabilized metallic nanoparticles (e.g., the matrix) 102 can be loaded into the dispensing bed 110 in powder and / or paste form. After loading, the upper surface 104 of the stabilized metallic nanoparticles 102 can be on the same plane as or below the upper surface 114 of the side wall 112. The dispensing piston 116 can then move upward in the direction of arrow 118 until the upper surface 104 of the stabilized nanoparticles 102 is on the same plane as or above the upper surface 114 of the side wall 112.

[0025] A transfer element (e.g., a roller) 120 can then transfer a portion 106 of the stabilized metallic nanoparticles 102 above the upper surface 114 of the side wall 112 from the delivery bed 110 into a production bed 130 (e.g., in the direction of arrow 122). The production bed 130 can be defined by one or more side walls 132 and a production flask 136. The transferred portion 106 of the stabilized nanoparticles 102 can form a first layer in the production bed 130, which has a thickness of approximately 10 µm to approximately 50 µm, approximately 50 µm to approximately 100 µm, approximately 100 µm to approximately 250 µm, or more.

[0026] A scanning system 140 can scan the stabilized metallic nanoparticles 102 in the first layer, and a laser 142 can then sinter the first layer in response to the scan results. The laser 142 can be a continuous wave laser or a pulsed laser. If the laser 142 is a pulsed laser, the pulse length and intervals can be adjusted for appropriate sintering. For example, when using the metallic nanoparticle paste in the printing process, the pulses can have a relatively long interval (e.g., from about 100 ms to about 5 s) to allow time for the solvent to at least partially evaporate. Sintering can take place at a temperature of less than or equal to about 200 °C, less than or equal to about 150 °C, less than or equal to about 125 °C, or less than or equal to about 100 °C.

[0027] Once the first layer has been sintered in the build bed 130, the feed piston 116 can move upwards in the direction of arrow 118 until the upper surface 104 of the stabilized nanoparticles 102 is on the same plane as or above the upper surface 114 of the side wall 112 of the delivery bed 110. The build bolt 136 can then move downwards. The transfer element 120 can then transfer another portion of the stabilized nanoparticles 102, located above the upper surface 114 of the side wall 112, from the delivery bed 110 to the build bed 130 to form a second layer that lies on and / or above the first layer. The laser 142 can then sinter the second layer. This process can be repeated until the desired 3D object has been produced. Example

[0028] The following example is provided for illustrative purposes and is not intended to be restrictive. 88.91 g of dodecylamine were mixed in a solvent consisting of 30 mL decalin and 6 mL methanol. The mixture was heated to 40 °C in a reaction flask under an argon atmosphere until the dodecylamine dissolved. The mixture was then cooled to 30 °C, and 6.54 g of a reducing agent (phenylhydrazine) were added while stirring. 20 g of silver acetate were then added gradually to the mixture over a period of 2 hours at a temperature between 30 °C and 35 °C. This resulted in a color change of the mixture from clear to dark brown, indicating the formation of silver nanoparticles.

[0029] The mixture was then heated to 40 °C and stirred for one hour. The mixture was then precipitated by adding 100 mL of methanol while stirring, and the mixture was collected by filtration. The collected solid was transferred to a glass beaker and stirred into 50 mL of methanol. This product was collected by filtration and dried in a vacuum oven at room temperature (e.g., 20 °C) for 24 hours, yielding 13.11 g of dark blue silver nanoparticles. The silver content was 87.6 wt%, as measured by the Ash technique. Assuming a density of 10 g / mL for the silver nanoparticles and 1.0 g / mL for the dodecylamine, the silver content in the stabilized silver nanoparticles was estimated to be approximately 41 vol%.

[0030] The silver nanoparticle powder was used in a K st -subjected to measurement. The K stThe value was approximately 20 bar*m / sec, indicating that the powder was not explosive. This can be attributed to the high volume fraction of stabilizers in the silver nanoparticle powder. In other embodiments, the K st -Value less than 50 bar*m / sec.

[0031] The silver nanoparticles were formulated as thin lines in inkjet printing ink on a polyethylene terephthalate (PET) substrate. A portion of the printed lines were heat-sintered in an oven at 130 °C for 10 minutes, while the remaining lines were subjected to pulsed light fusion with varying pulse durations from 100 µs to 50 ms. It was found that the printed lines could be sintered using pulsed light to achieve the same conductivity as those produced by heat sintering. The pulsed light source could include a laser, a xenon lamp, a mercury lamp, or a combination thereof.

[0032] A portion of the silver nanoparticles was dispersed as a paste in terpineol. The paste was loaded into the build bed. A paint knife was used to apply a uniform layer (approximately 200 µm) of the silver paste to the build bed. An argon laser (488 nm) was used to sinter the silver nanoparticles into pure conductive silver at the desired location. The silver nanoparticles exhibited a surface plasmon absorption of approximately 420 nm to 440 nm. After sintering the first layer of silver nanoparticles, the feed piston was raised approximately 200 µm, and a second layer of the silver paste was transferred to the build bed using a scoop. The second layer was approximately 200 µm thick. This second layer of paste was then used to further build the 3D object using a laser.

[0033] Notwithstanding the fact that the numerical ranges and parameters representing a broad scope of the teachings presented here are approximations, the numerical values ​​presented in the specific examples are given as precisely as possible. However, each numerical value inherently contains certain errors that necessarily result from the standard deviation of the associated test measurements. Furthermore, all ranges disclosed herein are to be understood as encompassing every single range and all subranges included therein. For example, a range of "less than 10" may include every single subrange between (and including) the minimum value of zero and the maximum value of 10, i.e., every single subrange with a minimum value equal to or greater than or equal to zero and a maximum value equal to or less than or equal to 10, e.g., 1 to 5.

Claims

[1] Material for use in a 3D printer, comprising: several metal particles with an average cross-sectional length of less than or equal to 100 nm; and a stabilizing material comprising an organoamine, carboxylic acid, thiol and derivatives thereof, xanthogenic acid, polyethylene glycols, polyvinylpyridine, polyvinylpyrrolidone or a combination thereof; the metal particles and the stabilizing material agglomerate to form particles with an average cross-sectional length of about 1 µm to about 250 µm. [2] Material according to claim 1, wherein the average cross-sectional length of the metal particles is less than or equal to about 20 nm. [3] Material according to claim 2, wherein the metal particles comprise gold, silver, aluminium, platinum, palladium, copper, cobalt, chromium, indium, titanium, zirconium, nickel, an alloy thereof or a combination thereof. [4] Material according to claim 1, further comprising a solvent comprising a hydrocarbon, an alcohol, a ketone, an ester, an ether or a combination thereof. [5] Material according to claim 1, wherein the metal particles are in a discontinuous phase. [6] Method for printing an object using a 3D printer, comprising: Loading multiple stabilized particles into a delivery bed of the 3D printer, wherein the stabilized particles include: several metal particles with an average cross-sectional length of less than or equal to 100 nm; and a stabilizing material comprising an amine, organoamine, carboxylic acid, thiol and derivatives thereof, xanthogenic acid, polyethylene glycols, polyvinylpyridine, polyvinylpyrrolidone or a combination thereof; the metal particles and the stabilizing material agglomerate to form particles with an average cross-sectional length of about 1 µm to about 250 µm; Transferring a portion of the stabilized particles from the dispensing bed to a build bed of the 3D printer; and Sintering of the stabilized particles in the build bed at a temperature less than or equal to approximately 200 °C to form the printed object.

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