EP4608921A2 - Ultrahigh temperature, flexible, printed copper electronics - Google Patents

Abstract

Provided are conductive slurry compositions that may be used as a printable ink. The conductive slurry composition has a conductive filler, which may be a copper nanoplates, copper silver alloy nanoparticle, and/or silver-coated alloy nanoparticle. The conductive slurries may be used to manufacture flexible electronics. Also provided are methods of making the compositions and flexible electronics formed from said compositions.

Description

Attorney Docket No.: 011520.01804

ULTRAHIGH TEMPERATURE, FLEXIBLE, PRINTED COPPER ELECTRONICS

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application Number 63/381,524, filed on October 28, 2022, the disclosure of which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0002] This invention was made with government support under contract no.

W91 INF-20-2-0016 awarded by the U.S. Army Research Lab. The government has certain rights in the invention.

BACKGROUND OF THE DISCLOSURE

[0003] Flexible hybrid electronics (FHEs) are advancing at a rapid pace, which are critical for creating functional and long-lasting devices. Usability under extreme conditions like high temperatures and reactive environments, however, provides a different set of challenges as most flexible electronics operate up to moderate temperatures and use substrates such as polymers. Various considerations must be addressed for flexible electronics to be applicable under extreme conditions. There are three distinct but important aspects of high-temperature FHE device that must be improved upon for more efficient use: The conductor (the metal of choice), advanced substrate material (flexible thin ceramics), and system passivation with thermal management (further thermal and reactive protection from environment). The metal used as the conductor should ideally have high conductivity, high resistance to environmental conditions, and be reliable over a long period of time. Precious metals, such as gold, platinum, and silver, show great promise due to their inherent physicochemical properties; however, the low abundance and high cost of these metals proves to be a limiting factor, necessitating the need for other materials. Copper, on the contrary, is highly abundant, has high conductivity, and relatively high melting point.

However, bulk copper is known to have high susceptibility to oxidation in ambient conditions. Additionally, printable FHEs typically utilize nanoscale materials, which exacerbates the problems with oxidation and corrosion, relative to its bulk counterparts.

BRIEF SUMMARY OF THE DISCLOSURE

[0004] The present disclosure provides compositions, composite structures, and uses thereof. [0005] In an aspect, the present disclosure provides compositions. In various examples, the composition is made by a method of the present disclosure. Non-limiting examples of compositions are provided herein. A composition may be referred to as a conductive slurry or a conductive slurry composition. The conductive slurry may be a conductive ink, printable conductive ink, or a conductive ink composition.

[0006] In various examples, the conductive slurry composition comprises copper nanoplates or nanoparticles. In various examples, the conductive slurry composition does not comprise copper nanowires. The nanoplates may be copper or copper/silver core/shell nanoplates. The copper nanoplates may further comprise one or more layers of graphene or a graphene-material or a formate layer. In various other embodiments, the conductive slurry composition comprises copper nanoparticles (e.g., copper silver alloy nanoparticles or silver coated copper nanoparticles). As used throughout, the term “conductive filler” may be used to refer to nanoplates or nanoparticles. The conductive filler may be copper or a copper silver alloy.

[0007] In an aspect, the present disclosure provides a method of making a conductive slurry composition of the present disclosure.

[0008] In an aspect, the present disclosure provides a method for printing a conductive ink.

[0009] In an aspect, an object (e.g., conductor) may be printed (e.g., 3D printed) from a conductive slurry composition of the present disclosure. The printed object may be passivated with, for example, formate groups, which may be desirable for the printed (e.g., solid) object.

BRIEF DESCRIPTION OF THE FIGURES

[0010] For a fuller understanding of the nature and objects of the disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying figures.

[0011] Figure 1 shows (a) printable ink with two major components: (i) the Cu-based building blocks or conductive fillers and (ii) the additives used in hybridizing with the building blocks for high temperature stability, (b) The final device with an AI2O3 layer coating (top) and the (ceramic or aerogel) substrate, (c) Depiction of how the conductors made for testing and in-situ measurements.

[0012] Figure 2 shows (a) a brief schematic depicting a Cu seed and the resulting variety of nanostructures possible. The listed precursors are used in the following samples. (b) A representative SEM images of the Cu nanoplates that were printed and sintered. The inset shows the sizing curves for the control (typical), CuBr, and ascorbic acid variations, (c) The corresponding conductivity (left y-axis, black) and sheet resistance (right y-axis, red) for each sample synthesized. The pre-sintered conductors and post-sintered conductors are shown, light and darker colors, respectively. The sample are , from left to right, the typical concentration (control), CuCl, CuBr, increased HDA concentration, increased CuCh concentration, decreased Nal concentration, ascorbic acid, and HC1 addition, (d) SEM image showing a mixture of Cu NPLs and NWs as a result of decreasing the concentration of Nal in the synthesis precursor and (e) the corresponding conductivity (pre and post-sinter) of conductors printed from synthesized nanostructures at various Nal concentrations. The scale bars represent 10 pm.

[0013] Figure 3 shows (a) oxidation resistance of several copper-based conductors (Cu NPLs, black; Cu/Ag core/ shell NPLs, red; Cu/Ag 9: 1, brown) at 160 °C for 98 hours. The ratios determine the Cu: Ag molar ratios, (b) Powder XRD patterns of the conductors (Cu NPL, Cu/Ag NPL, and CuAg 9:1 NPs) before (darker line) and after (lighter line) the accelerated oxidation test. Guidelines for copper (red dashed line) and silver (red dashed line) peaks are shown. A zoomed in graph of 2 theta values at 35 to 40 are provided for clarity for the copper oxide peak at approximately 2 theta of 36.5 (blue dashed line).

[0014] Figure 4 shows (a) a schematic of Cu interfaced with graphene (both red and blue representing carbons) or BN (blue representing boron and red representing nitrogen), (b) The RT curve comparison between Cu-BN (dashed lines) and Cu-G (solid line), (c) The stability-over-time curves at 400 °C comparison between Cu-G (black) and CuAg-G (blue), (d) The SEM images of Cu-G conductor before (top) and after (bottom) the stability-overtime heating measurement. The scale bars represent 10 pm.

[0015] Figure 5 shows (a) an image of the setup for the hydrogen torch testing. The RT curves of the Cu-G conductor during the torch test of the (b) front (c shows the measured resistance of the conductor (1000 nm layer thickness) post-torching) and (d) back at ALD thickness of 25 (black), 50 (red), 75 (blue), 100 (green) and 1000 (purple) nm AI2O3 layers. [0016] Figure 6 shows SEM images of (a) control, (b) CuCl, (c) CuBr, (d) increased HDA (1.5x), (e) increased CuCh (L5x), (f) decreased Nal (0.5x), (g) ascorbic acid, and (f) addition of HC1. The variations in synthesis are replacing the copper precursor (b and c), increasing/decreasing the amount of material (d-f), replacing the reducing agent (g), and adding additional precursor (h). The scale bar (white rectangle) represents 10 pm). [0017] Figure 7 shows overlaid sizing curves of NPLs for the different variation of precursors used: CuCl (red), increased HDA concentration (orange), concentration (pink), decreased Nal concentration (green), and HC1 addition (cyan).

[0018] Figure 8 shows a picture of the printed conductors of each variation in the synthetic procedure (starting from top left to bottom right). All the conductors have already been sintered. There is a clear difference between the good (shiny and copper colored) and bad (dull and black) conductors.

[0019] Figure 9 shows images of synthetic solution containing increased CuCh concentrations: 2x CuCh (5.1), 2.5x CuCh (5.2), and 3x CuCh (5.3).

[0020] Figure 10 shows SEM images of nanostructures synthesized at various concentrations (rows) and times (columns). The various ascorbic acid concentrations tested are lx (top row), 3x (middle row), and 6x (bottom row). The various synthesis times tested are 6 (left column), 9 (middle column), and 12 (right column) hrs. The scale bars represent 10 pm.

[0021] Figure 11 shows conductivity measurements of sintered prints at various synthesis time (x-axis) and concentrations (lx, left in each series; 3x, middle in each series; 6x, right in each series).

[0022] Figure 12 shows SEM images of nanostructures with less Nal concentrations are shown: (a) 0.135 mM Nal, (b) 0.081 mM Nal, and (c) 0.027 mM Nal. The inset (with black border) is a zoomed in image. The inset (with border in (c)) is a imaged that has been zoomed in significantly to better identify the nanostructures. The white scale bar represents 10 pm), while the scale bar represents 1 pm. The inset represents the size curve and average size of the Cu NPLs.

[0023] Figure 13 shows SEM image of Cu/Ag (a) NPLs and (b) 9: 1 alloyed NPs.

EDS linescans were measured along the yellow line. The intensities correspond to copper (red) and silver (cyan).

[0024] Figure 14 shows SEM image and EDS of Cu/Ag (a and b) 1 : 1 alloyed NPs, (c and d) 3 : 1 alloyed NPs, and (e and f) 6: 1 alloyed NPs. EDS linescans were measured along the yellow line. The intensities correspond to copper (red) and silver (cyan).

[0025] Figure 15 shows oxidation resistance of the other CuAg alloy (CuAg NP 1 : 1; CuAg NP 3: 1; CuAg 6: 1) at 160 °C for 98 hours.

[0026] Figure 16 shows powder XRD patterns of the conductors (CuAg 1 : 1, CuAg 3: 1, and CuAg 6: 1) before (darker line) and after (lighter line) the accelerated oxidation test in. A zoomed in graph at 35 to 40 2 theta values are provided for clarity for the copper oxide peak at approximately 36.5 2 theta.

[0027] Figure 17 shows an RT curve of Cu/Ag-BN (red, dashed line), Cu/Ag-G (solid line), CuAg-BN (dashed line), and CuAg-G (solid line).

[0028] Figure 18 shows stability-over-time curves at 400 °C of Cu/Ag-BN (dashed line), Cu/Ag-G (solid line), CuAg-BN (dashed line), and CuAg-G (solid line) over 8 hours. [0029] Figure 19 shows Cu NPL conductors coated with (a) 25 nm, (b) 50 nm, (c) 75 nm, and (d) 100 nm AI2O3 thin coating. For each conductor, an image before (top) and after (bottom) the front torch test was performed.

[0030] Figure 20 shows measured resistances of the conductors (a, 25 nm; b, 50 nm; c, 75 nm; d, 100 nm) post-torch test. The measurement was from end to end (through the point of impact).

[0031] Figure 21 shows measured resistances of the conductors (a, 25 nm; b, 50 nm; c, 75 nm; d, 100 nm) post-torch test. The measurement was on undamaged part of the conductor.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0032] Although claimed subject matter will be described in terms of certain embodiments, other embodiments, including embodiments that do not provide all of the benefits and features set forth herein, are also within the scope of this disclosure. Various structural, logical, process step, and electronic changes may be made without departing from the scope of the disclosure.

[0033] All ranges provided herein include all values that fall within the ranges to the tenth decimal place, unless indicated otherwise.

[0034] The present disclosure provides compositions, composite structures, and uses thereof.

[0035] In an aspect, the present disclosure provides compositions. In various examples, the composition is made by a method of the present disclosure. Non-limiting examples of compositions are provided herein. A composition may be referred to as a conductive slurry or a conductive slurry composition. The conductive slurry may be a conductive ink, printable conductive ink, or a conductive ink composition.

[0036] In various examples, the conductive slurry composition comprises copper nanoplates or nanoparticles. In various examples, the conductive slurry composition does not comprise copper nanowires. The nanoplates may be copper or copper/silver core/shell nanoplates. The copper nanoplates may further comprise one or more layers of graphene or a graphene-material or a formate layer. In various other embodiments, the conductive slurry composition comprises copper nanoparticles (e.g., copper silver alloy nanoparticles or silver coated copper nanoparticles). As used throughout, the term “conductive filler” may be used to refer to nanoplates or nanoparticles. The conductive filler may be copper or a copper silver alloy.

[0037] Various amounts of conductive filler are used. In various examples, the conductive filler are present at 10 to 30 wt.% in the conductive slurry composition (based on the total weight of the conductive slurry composition including water), including all 0.1 wt.% values and ranges therebetween. This weight percent further includes any functionalization on the conductive filler, such as functionalize with graphene or formate. In various examples, the concentration of the conductive filler is 25 wt.%. In various other examples, when the conductive filler is a silver coated copper nanoparticles (copper/ silver core/shell) may be 30 to 70 wt.%, including all 0.1 wt.% values and ranges therebetween.

[0038] In various examples, the majority of the copper in the conductive slurry composition has a nanoplates morphology. In various examples, less 10 wt.% of the copper has a nanowire morphology (e.g., less than 10 wt.%, less than 9 wt.%, less than 8 wt.%, less than 7 wt.%, less than 6 wt.%, less than 5 wt.%, less than 4 wt.%, less than 3 wt.%, less than 2 wt.%, less than 1 wt.%, or no detectable amount of nanowires).

[0039] In various examples, the majority of the copper in the conductive slurry composition has a nanoparticle morphology. In various examples, less 10 wt.% of the copper has a nanowire morphology (e.g., less than 10 wt.%, less than 9 wt.%, less than 8 wt.%, less than 7 wt.%, less than 6 wt.%, less than 5 wt.%, less than 4 wt.%, less than 3 wt.%, less than 2 wt.%, less than 1 wt.%, or no detectable amount of nanowires). In various embodiments, at least a portion of the copper has a nanoparticle morphology and at least a portion of the nanoparticles are at least partially or completely coated with silver. The silver coating may be uniformly or non-uniformly coated on the nanoparticles.

[0040] The copper nanoplates of the conductive slurry composition may have a variety of lengths and thicknesses. For example, the copper nanoplates may have a longest linear dimension (e.g., a length) of 100 nm to 10 pm, including all 0.1 nm values and ranges therebetween. In various examples, the copper nanoplates have a thickness of 1 to 100 nm, including all 0.1 values and ranges therebetween (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68,69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100 nm). In various embodiments, the dimensions are roughly uniform or uniform across the length of an axis of a nanoplate (e.g., the thickness is 15 nm across the entire length of a nanoplates).

[0041] The copper nanoparticles of the conductive slurry composition may have a variety of lengths. For example, the copper nanoparticles may have a longest linear dimension (e.g., a length) of 1 to 100 nm, including all 0.1 values and ranges therebetween (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,

52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68,69, 70, 71, 72, 73, 74, 75, 76,

77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100 nm). In various other embodiments, when the nanoparticles are silver coated nanoparticles, they may have a longest linear dimension of 5 to 15 microns, including all integer nm values and ranges therebetween.

[0042] In various examples, the conductive filler further comprises iodide. The iodide may adsorb onto the { 111 } facets. Without intending to be bound by any particular theory, it is considered the adsorption of the iodide forces growth parallel to the basal plane, which in turn results in plate formation rather than wire formation.

[0043] Various liquids, which may be referred to as dispersants or solvents, can be used to form a slurry of copper nanoplates. In various examples, the liquid is water, an organic liquid, such as, for example, a Ci to Ce alcohol (e.g., ethanol), diethylene glycol butyl ether, 2-ethoxyethyl acetate, ethylene glycol, 2-butoxyethyl acetate, diethylene glycol monobutyl ether acetate, dibasic ester mixture, terpineol, or a combination thereof.

[0044] A conductive slurry composition can comprise various amounts of liquids. In various examples, a dispersion comprises 10 to 70 wt. % of a liquid based on the total weight of the composition, including all wt. % values and ranges therebetween (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 228, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68,69, or 70 wt. %). It is desirable to use an amount of liquid that forms a dispersion or slurry. In various embodiments, the liquid is water.

[0045] The conductive slurry composition may further comprise one or more additive. Without intending to be bound by any particular theory, it is considered that the additive improves the flowability and/or viscosity of the slurry, which may be used as an ink, for example, an ink for printing. Non-limiting examples of additives include water-soluble primary amines (e.g., alkylamines, such as, for example, C10-C20 alkyl amines (hexadecylamines)). An additive or additives may be present in a dispersion at 1 to 10 wt.% based on the total weight of the conductive slurry composition.

[0046] The conductive slurry may further comprise (hydroxypropyl)methyl cellulose (HPMC). The concentration of the HPMC may be 0.1 to 30 weight percent, relative to the total weight of the conductive ink, including all 0.01 weight percent values and ranges therebetween. In various embodiments, the concentration of the HPMC is 25 wt.%. In various other embodiments, the concentration of HPMC is 0.1 to to 10 weight percent, including all 0.01 weight percent values and ranges therebetween.

[0047] In various examples, the conductive filler is functionalized with graphene or a graphene material or boron nitride. In various other examples, the conductive filler is surface functionalized with one or more formate groups.

[0048] Various ratios of conductive filler weight to the graphene material and/or graphene-precursor material can be used. In various examples, the ratio of the conductive filler weight to the graphene material and/or graphene-precursor material and/or boron nitride weight is 90: 10 to 99.9:0.1, including all 0.1 ratio values and ranges therebetween. In various examples, the weight percent of the graphene-precursor (e.g., dopamine) is 0.1 to 1.0 wt.%, including all 0.01 wt.% values and ranges therebetween (e.g., 0.3 wt.%), which is a ratio of 99.7:0.3. In various examples, the weight percent of boron nitride is 1 to 10 wt.%, including all 0.1 values and ranges therebetween (e.g., 8 wt.%), which is a ratio of 92:8.

[0049] Various graphene materials may be used. Combinations of graphene materials may be used. Non-limiting examples of graphene materials include graphene, reduced graphene oxide, and combinations thereof. The graphene materials may be exfoliated sheets. Non-limiting examples of exfoliated sheet graphene materials include exfoliated graphene sheets, exfoliated reduced graphene sheets, exfoliated graphene oxide sheets, and combinations thereof. Suitable graphene materials are known in the art and are commercially available or can be made by processes known in the art.

[0050] Graphene-material precursors react or decompose (e.g., thermally react or thermally decompose) to form a graphene material. Various graphene material precursors may be used. Combinations of graphene material precursors may be used. A graphenematerial precursor may be an organic small molecule. Non-limiting examples of graphenematerial precursors include dopamine, aniline, and the like, and combinations thereof.

[0051] In various embodiments, the conductive slurry is a conductive ink. [0052] The conductive filler may either be functionalized with graphene/graphene materials or formate groups. In various embodiments, the conductive filler is functionalized with both graphene/graphene materials and formate groups. In various examples, copper or copper silver nanoplates are functionalized with graphene or a graphene material. In various examples, copper or copper silver nanoplates are functionalized with formate groups. In various examples, copper or copper silver nanoplates are functionalized with graphene/graphene material and formate groups. In various other examples, the conductive filler is functionalized/hybridized with boron nitride. In various examples, the copper or copper silver nanoplates are functionalized with boron nitride. In various examples, the copper or copper silver nanoparticles are functionalized with boron nitride.

[0053] The conductive filler (e.g., nanoplates or nanoparticles) may have one or more desirable properties. Non-limiting examples of desirable properties include an electrical conductivity, thermal conductivity, heat dissipation, breakdown current, mechanical properties (e.g., Young’s modulus), and the like, and combinations thereof. In various examples, the nanoplates exhibit an electrical conductivity of 1 MS/m to 35 MS/m.

[0054] In various embodiments, the composition comprises silver coated copper nanoparticles. The silver coated copper nanoparticles may have a particle size (e.g., longest linear dimension) of 5 to 15 microns, including all integer nm values and ranges therebetween.

[0055] A composition of the present disclosure may comprise silver coated copper nanoparticles in a concentration of 10 to 30 weight percent (wt%) silver, including all 0.1 wt% ranges and values therebetween. In various embodiments, the weight percent is rrelative to the total weight of the nanoparticle. The sintering/curing process used to prepared the formulations can be carried out in a heat press or oven/fumace or by means of photonic, microwave or reactive sintering.

[0056] In various embodiments, the silver coated copper nanoparticle loading is 30- 40 wt%, including all 0.1 wt% values and ranges therebetween. The composition may further comprise water, where the concentration is 35-45 wt%, including all 0.1 wt% values and ranges therebetween. The composition may further comprise hydroxypropyl methylcellulose (HPMC), where the concentration is 0.1-10 wt%, including all 0.01 wt% values and ranges therebetween. The composition may further comprise an alcohol, such as, for example, ethanol. For example, when the alcohol is ethanol, the concentration is 12.5-17.5 wt%, including all 0.01 ranges and values therebetween. The composition may further comprise a polyol (i.e., glycol), such as, for example, ethylene glycol. The concentration of the polyol (e.g., ethylene glycol) may be 7.5-12.5 wt% ethylene glycol, including all 0.01 wt% values and ranges therebetween. The composition may further comprise graphene and/or boron nitride at a concentration of 0 to 1 wt%, including all 0.01 wt% values and ranges therebetween. In various examples, a composition is 32.5 weight percent silver coated copper nanoparticles, 42.5 weight percent water, 0.9 weight percent hydroxypropyl methylcellulose (HPMC), 14.5 weight percent alcohol (e.g., ethanol), 9.6 weight percent polyol (e.g., ethylene glycol).

[0057] A composition comprising silver coated copper nanoparticle at a loading of a 30-40 wt% may have desirable features. For example, such a composition may have a lowest achievable sheet resistance of 30 milliohms/square/1 mil obtained using the four-point probe method. In various other examples, such a composition may have a lowest achievable sheet resistance of 20 milliohms/square/2 mil obtained using the four-point probe method. In various examples, such a composition may have a maximum conductivity of 2.8 MS/m. [0058] In various embodiments, the silver coated copper nanoparticle loading is 40- 50 wt%, including all 0.1 wt% values and ranges therebetween. The composition may further comprise water, where the concentration is 30-40 wt%, including all 0.1 wt% values and ranges therebetween. The composition may further comprise hydroxypropyl methylcellulose (HPMC), where the concentration is 0.1-10 wt%, including all 0.01 wt% values and ranges therebetween. The composition may further comprise an alcohol, such as, for example, ethanol. For example, when the alcohol is ethanol, the concentration is 8-13 wt%, including all 0.01 ranges and values therebetween. The composition may further comprise a polyol (i.e., glycol), such as, for example, ethylene glycol. The concentration of the polyol (e.g., ethylene glycol) may be 5-10 wt% ethylene glycol, including all 0.01 wt% values and ranges therebetween. The composition may further comprise graphene and/or boron nitride at a concentration of 0 to 1 wt%, including all 0.01 wt% values and ranges therebetween. In various examples, 46.2 weight percent silver coated copper nanoparticles, 33.9 weight percent water, 0.8 weight percent hydroxypropyl methylcellulose (HPMC), 11.3 weight percent alcohol (e.g., ethanol), 7.8 weight percent polyol (e.g., ethylene glycol).

[0059] A composition comprising silver coated copper nanoparticle at a loading of a 40-50 wt% may have desirable features. For example, such a composition may have a lowest achievable sheet resistance of 15 milliohms/square/1 mil obtained using the four-point probe method. In various other examples, such a composition may have a lowest achievable sheet resistance of 10 milliohms/square/2 mil obtained using the four-point probe method. In various other examples, such a composition may have a maximum conductivity of 4.1 MS/m. [0060] In various embodiments, the silver coated copper nanoparticle loading is 50- 60 wt%, including all 0.1 wt% values and ranges therebetween. The composition may further comprise water, where the concentration is 25-35 wt%, including all 0.1 wt% values and ranges therebetween. The composition may further comprise hydroxypropyl methylcellulose (HPMC), where the concentration is 0.1-10 wt%, including all 0.01 wt% values and ranges therebetween. The composition may further comprise an alcohol, such as, for example, ethanol. For example, when the alcohol is ethanol, the concentration is 7-12 wt%, including all 0.01 ranges and values therebetween. The composition may further comprise a polyol (i.e., glycol), such as, for example, ethylene glycol. The concentration of the polyol (e.g., ethylene glycol) may be 4-9 wt% ethylene glycol, including all 0.01 wt% values and ranges therebetween. The composition may further comprise graphene and/or boron nitride at a concentration of 0 to 1 wt%, including all 0.01 wt% values and ranges therebetween. In various examples, 54.8 weight percent silver coated copper nanoparticles, 28.4 weight percent water, 0.6 weight percent hydroxypropyl methylcellulose (HPMC), 9.7 weight percent alcohol (e.g., ethanol), 6.5 weight percent polyol (e.g., ethylene glycol).

[0061] A composition comprising silver coated copper nanoparticle at a loading of a 50-60 wt% may have desirable features. For example, such a composition may have a lowest achievable sheet resistance of 9 milliohms/square/1 mil be obtained using the four-point probe method. In various other examples, such a composition may have a lowest achievable sheet resistance of 1 milliohms/square/2 mil obtained using the four-point probe method. In various other examples, such a composition may have a maximum conductivity of 30 MS/m. [0062] In various embodiments, the silver coated copper nanoparticle loading is 60- 70 wt%, including all 0.1 wt% values and ranges therebetween. The composition may further comprise water, where the concentration is 20-30 wt%, including all 0.1 wt% values and ranges therebetween. The composition may further comprise hydroxypropyl methylcellulose (HPMC), where the concentration is 0.1-10 wt%, including all 0.01 wt% values and ranges therebetween. The composition may further comprise an alcohol, such as, for example, ethanol. For example, when the alcohol is ethanol, the concentration is 7-12 wt%, including all 0.01 ranges and values therebetween. The composition may further comprise a polyol (i.e., a glycol), such as, for example, ethylene glycol. The concentration of the polyol (e.g., ethylene glycol) may be 4-9 wt% ethylene glycol, including all 0.01 wt% values and ranges therebetween. The composition may further comprise graphene and/or boron nitride at a concentration of 0 to 1 wt%, including all 0.01 wt% values and ranges therebetween. In various examples, 62.2 weight percent silver coated copper nanoparticles, 23.8 weight percent water, 0.5 weight percent hydroxypropyl methylcellulose (HPMC), 8.1 weight percent alcohol (e.g., ethanol), 5.4 weight percent polyol (e.g., ethylene glycol).

[0063] A composition comprising silver coated copper nanoparticle at a loading of a 60-70 wt% may have desirable features. For example, such a composition may have a lowest achievable sheet resistance of 5 milliohms/square/1 mil be obtained using the four-point probe method. In various other examples, such a composition may have a lowest achievable sheet resistance of 0.66 milliohms/square/2 mil obtained using the four-point probe method. In various other examples, such a composition may have a maximum conductivity of 46 MS/m.

[0064] In an aspect, the present disclosure provides a method of making a conductive slurry composition of the present disclosure.

[0065] In various embodiments, the method comprises contacting a copper salt, an aliphatic amine, D-glucose or ascorbic acid, an iodide salt, and water to form a reaction mixture; and heating the reaction mixture to form a conductive slurry composition of the present disclosure.

[0066] In various embodiments, the method for preparing a copper nanoplates comprises contacting a copper precursor (e.g., CuCh, CuCl, or CuBr), a reducing agent (e.g., glucose or ascorbic acid), a surfactant (e.g., HD A), sodium iodide, and water. In various embodiments, an acid (e.g., HC1) may also be added .

[0067] In various embodiments, the method for preparing copper silver nanoplates comprises contacting copper nanoplates with a formic acid solution and washing with an alcohol (e.g., ethanol) followed by centrifugation. The plates are then washed with a polyvinylpyrrolidone (PVP)/diethylhydroxylamine (DEHA) solution in water. The ratio of nanoplates may be dispersed in water at a ratio of nanoplates to PVP to ascorbic acid at a molar ratio of 1 : 2 : 5.5. A silver salt (e.g., silver nitrate) is then added to the dispersion. [0068] In various embodiments, the method for preparing copper silver nanoparticles comprises mixing CuCh, AgNCh, ascorbic acid, HD A, sodium iodide, and water and mixed via blender. The resulting mixture is heated (e.g., heated to 100 °C) for 12 hours. The nanoparticles may be collected via centrifugation and then washed with an alcohol (e.g., ethanol).

[0069] Various copper salts may be used as copper precursors in the method. For example, the copper salt may be a copper (I) or a copper (II) salt. For example, a copper (I) salt may be cuprous (I) chloride. For example, a copper (II) salt may be copper(II) chloride or copper(II) bromide. In various examples, the copper salt may be a combination of various copper salts described herein.

[0070] Various aliphatic amines may be used in the method. For example, the aliphatic amine may have 10 to 20 carbon atoms and may be linear or branched and/or have various degrees of unsaturation. In various embodiments, the aliphatic amine is hexadecylamine (HDA).

[0071] In various embodiments, one or more additives may be added during the method. In various examples, the method may further comprise mixing HPMC with water into the reaction mixture.

[0072] The reaction mixture may be heated for various lengths of time and at various temperatures. For example, the reaction mixture is heated for a period of time ranging from 5-48 hours, including all second values and ranges therebetween (e.g., (e.g., 6, 9, 9.5, 10, 11, 12, 13, 18, 19, 20, 25, 30, 35, 40, 45, or 48 hours). In various examples, the reaction mixture is maintained at a constant temperature for the full period of time. In various embodiments, the reaction mixture is at a temperature of 60 °C to 140 °C, including all 0.1 values and ranges therebetween (e.g., the temperature is at least 100 °C or is heated to a temperature of 100 °C or less).

[0073] In various embodiments, the method further comprises functionalizing the copper nanoplates with formate groups. Functionalization may be achieved by adding a mixture comprising one or more formate salts to the conductive slurry composition and heating the mixture of the conductive slurry composition and the formate salt mixture to a temperature of 100 to 150 °C, including all 0.1 °C values and ranges therebetween. The formate salts may be sodium formate, copper formate, or a combination thereof. The mixture comprising one or more formate salts may ethylene glycol (e.g., 50 mL of ethylene glycol) and a solution comprising sodium formate (e.g., 30 g of sodium formate) and copper formate (e.g., 15 mg copper formate) in water (e.g., 150 mL of water).

[0074] In various embodiments, the method further comprises functionalizing the copper nanoplates with graphene or a graphene material. The functionalization may be achieved by blending the copper nanoplates with graphene or graphene derivatives or the graphene is prepared in situ via conversion from dopamine. For example, functionalization may be achieved by dispersing graphene or a graphene material into the slurry and sonicating the mixture of the slurry and graphene or a graphene material. [0075] In various examples, the method comprises using the following: the copper salt is provided as 2.4 g of copper(II) chloride; 3.9 g D-glucose; the aliphatic amine is 14.55 g of HD A; the iodide salt is provided as 90 mg of Nal; and 900 mL water.

[0076] In an aspect, the present disclosure provides a method for printing a conductive ink.

[0077] The method may comprise extruding a conductive ink composition and washing the extruded ink with an acid to remove residual aliphatic amine. The acid may be an organic acid or an organic acid solvent.

[0078] Various aqueous organic acid solutions can be used. An aqueous organic acid solution comprises water and one or more organic acid. Non-limiting examples of organic acids include alkylcarboxylic acids (e.g., C1-C5 alkylcarboxlic acid, such as, for example, acetic acid, and the like).

[0079] Various organic solvent acid solutions can be used. An organic solvent acid solution comprises one or more alcohol and one or more organic acid. Non-limiting examples of alcohols include C1-C5 alcohols (e.g., ethanol, and the like, and combinations thereof). Non-limiting examples of organic acids include alkylcarboxylic acids (e.g., a Ce-Cis alkylcarboxlic acid, such as, for example, dodecanoic acid, and the like).

[0080] In an aspect, an object (e.g., conductor) may be printed (e.g., 3D printed) from a conductive slurry composition of the present disclosure. The printed object may be passivated with, for example, formate groups, which may be desirable for the printed (e.g., solid) object.

[0081] In various examples, an article of manufacture is printed from the conductive slurry of the present disclosure. The article of manufacture may comprise one or more component, which may be a passive component or components (e.g., conductor(s), wire(s), and the like, and combinations thereof) and/or an active component or components (e.g., antennas, relays, switch leads, RF shields, and the like, and combinations thereof), comprising the nanoplates of the present disclosure. The nanoplates may be useful for producing electrodes.

[0082] The article of manufacture may be an electrical device. Non-limiting examples of electrical devices include electrical motors, electrical generators, transformers, switching regulators, converters, inverters, charging circuits, discharge circuits, PCL control devices, transmission and distribution units (which may be high-voltage transmission or distribution units), circuit breakers, and the like. Additional non-limiting examples include consumer electronic devices (e.g., computer, cellular phone, and the like), home appliance devices (e.g., television, washers, dryers, and the like), solar cells, sensor devices (e.g., wireless sensor devices), control devices, amplifiers, attenuators, Internet of Things (IOT) devices, audio devices, RFID devices, illuminating devices, and the like.

[0083] An electrical device or electronic devices may comprise one or more component that comprises one or more nanocomposite. Non-limiting examples of components include antennas, contacts, conductors, relays, switch leads, RF shields, and the like.

[0084] The electronic device may be flexible. For example, the conductive slurry composition may be used to print a conductor onto a substrate. The substrate may have various thicknesses. For example, the substrate may have a thickness of 10 nm to 1000 nm, including all 0.1 nm values and ranges therebetween.

[0085] The substrate may be a metal oxide or an aerogel composite. For example, the substrate may comprise AI2O3. In various examples, the substrate is AI2O3. In various examples, the aerogel composite comprises AI2O3.

[0086] In various embodiments, the flexible electronic has a metal oxide layer disposed thereon. The metal oxide layer may be disposed via atomic layer deposition. The metal oxide may be AI2O3. The metal oxide layer may be 25-100 nm thick, including all 0.1 nm values and ranges therebetween.

[0087] The flexible electronic may have one or more desirable features. For example, the flexible electronic may have a desirable thermal stability. For example, the flexible electronic may be thermally stable at 400 °C, 500 °C, 600 °C, 700 °C, 800 °C, 900 °C, 1000 °C, or over 1000 °C.

[0088] The following Statements provide various embodiments of the present disclosure.

Statement 1. A conductive slurry composition comprising a slurry of copper silver nanoplates in water or copper silver nanoparticles in water, and the conductive slurry composition comprises less than 10 wt.% copper nanowires.

Statement 2. A conductive slurry composition according to Statement 1, wherein the copper silver nanoparticles are silver-coated copper nanoparticles.

Statement 3. A conductive slurry composition according to Statement 2, wherein the silver- coated copper nanoparticles are 10 to 30 weight percenter silver, relative to the total weight of an individual silver-coated copper nanoparticle. Statement 4. A conductive slurry composition according to Statements 2 or 3, wherein the concentration of the silver-coated copper nanoparticles is 30 to 70 weight percent, relative to the total weight of the conductive slurry.

Statement 5. A conductive slurry composition according to any one of Statements 1 to 4, further comprising a graphene material or boron nitride.

Statement 6. A conductive slurry composition according to any one of Statements 1 or 5, wherein the copper silver nanoplates further comprise iodide.

Statement 7. A conductive slurry composition according to any one of the preceding Statements, further comprising (hydroxypropyl)methyl cellulose (HPMC) and the concentration of HPMC is 0.1 to 10 weight percent, relative to the total weight of the conductive ink.

Statement 8. A conductive slurry composition according to any one of the preceding Statements, wherein the conductive slurry composition is a conductive ink.

Statement 9. A flexible electronic comprising a conductor formed from a conductive slurry composition according to any one of the preceding Statements disposed on a substrate.

Statement 10. A flexible electronic according to Statement 9, wherein the substrate comprises AI2O3.

Statement 11. A flexible electronic according to Statement 10, wherein the substrate is AI2O3.

Statement 12. A flexible electronic according to Statement 9 or Statement 10, wherein the substrate is a AI2O3 aerogel composite.

Statement 13. A flexible electronic according to any one of Statements 9-12, wherein the substrate has a thickness of 25 to 1,000 nm, including every 0.1 nm value and range therebetween.

Statement 14. A flexible electronic according to any one of Statements 9-13, wherein the conductor has a metal oxide layer disposed thereon.

Statement 15. A flexible electronic according to Statement 14, wherein the metal oxide layer is AI2O3.

Statement 16. A flexible electronic according to Statement 14 or Statement 15, wherein the metal oxide layer is deposited via atomic layer deposition. [0089] The following example is presented to illustrate the present disclosure. It is not intended to be limiting in any matter.

EXAMPLE 1

[0090] This example provides a description of printed electronics of the present disclosure.

[0091] Advanced high-temperature materials, metals and ceramics, have been widely sought after for printed flexible electronics under extreme conditions. However, the thermal stability and electronic performance of these materials generally diminishes under extreme environments. Additionally, printable electronics typically utilize nanoscale materials which further exacerbate the problems with oxidation and corrosion at those extreme conditions. Described herein is the thermal and electronic stability of printed copper-flexible ceramic electronics by means of integral hybridization and passivation strategies. High electric conductivity (5.6 MS/m) and thermal stability above 400 °C are achieved in the printed graphene-passivated copper platelet features, while thermal management and stability above 1,000 °C of printed electronics can be achieved by using either ultrathin alumina or flexible alumina aerogel sheets. The findings shown here provide a pathway towards printed, extreme electronic applications for harsh service conditions.

[0092] Described herein are strategies towards greater oxidation and thermal stability of printed electronics comprised of copper-based conductor and flexible ceramic substrates. The first strategy was to optimize conductor composition, which revolves around reconstructing the copper on the atomic scale through alloying or the structural surface coating on an atomic level. Copper-silver (CuAg) alloys typically provide the corrosion resistance or higher thermal stability. The Cu/Ag (core/shell) structure, on the other hand, requires Ag to be coated on the surface, providing a passivating layer to protect the copper from oxidation and corrosion. In addition, the hybridization choice is also important to dictate electronic conductivity, while hybridizing the copper with two-dimensional additives (like graphene and boron nitride) provides the properties of both components (Copper’s electrical conductivity and graphene’s thermal conductivity). It is also known that hybridized structures show superior oxidation and temperature stability, with little-to-no adverse effect on the copper. A unique benefit of reconstructing the surface, as opposed to alloying, is the ability to preserve the nanostructure. Improving the conductor composition is important; however, it is only one aspect of the device. Precise selection of the substrate based on application is equally important. The second strategy utilize advanced substrates that are flexible and temperature stable. Ultrathin flexible alumina ribbon ceramics provide remarkable thermal management due to its low thermal mass and high thermal conductivity. Flexible ceramic aerogels, on the other hand, provide superinsulation at higher temperatures. They have an added benefit of an ultralow thermal conductivity which hampers heat penetration, protecting the conductor from extreme temperatures. Lastly, the conductor can be passivated with the third strategy, which focuses on utilizing robust oxide layers to overcoat the conductor. This layer should be resistant to extreme temperatures while preventing the conductor from oxidizing. Depositing aluminum oxide (AI2O3) using atomic layer deposition at a low temperature allows for scalability while also allowing for long durability of the conductor under extreme conditions. In conjunction, the advanced flexible ceramic substrate prevented high temperatures from penetrating through to the conductor while the ALD coating protected the conductor from oxygen in the atmosphere and high temperatures.

[0093] In this example, all three aforementioned strategies are examined in conjunction to create a conductor device with superior oxidation stability at extreme temperatures. Focused on first was the nanostructured Cu through alloying with Ag (CuAg nanoparticles: NPs) and surface passivation with Ag (Cu/Ag core/shell nanoplates: NPLs) towards improved oxidation stability at elevated temperatures (Figure la-i). Further on, additives were later included, in-situ converted graphene (G) or boron nitride (BN), to form hybridized Cu-based conductors (Figure la-ii) for extreme conditions. Lastly, the hybridized conductors were coated with a thin layer of AI2O3 (Figure lb) as a protective barrier of the conductor to evaluate its thermal-electric stability (Figure 1c).

[0094] To develop high-temperature hybridized Cu conductors, a geometry and dimension study of printable Cu nanostructure feedstocks was performd. The controlled growth of copper nanostructures plays an important role in its structure and electric performance of printed conductors, on which the geometry and dimension of nanostructured copper can be controlled by the concentration and type of copper precursors and reducing agents (Figure 2a). Representative scanning electron microscope (SEM) images of each sample made are shown in Figure 6. A collection of these images was used to create a sizing curve for each (Figure 2b inset and Figure 7). The average size and standard deviation for each sizing curve is shown in Table 1, in which nanostructured Cu synthesized with CuBr or ascorbic acid had an average size of 8.78 pm or 0.85 pm, respectively (The control sample had an average size of 3.39 pm). Figure 2b shows a representative SEM image of a printed Cu conductor. The nanostructured geometry is distinguishable but melted together after sintering. The corresponding electrical conductivity measurements of as-synthesized Cu NPLs from different reaction conditions are shown in Figure 2c, with the optimum electric conductivity of 5.6 MS/m (Images of the conductors are shown in Figure 8). The concentration effects of CuCh, ascorbic acid, and Nal on the as-synthesized Cu NPLs and its electric performances are shown (Figure 9-11 for CuCh and ascorbic acid; Figure 12 and 2d- e for Nal). There was no strong correlation between the dimension of Cu NPLs and the conductivity of the printed conductors. In addition, both Cu nanowires and nanoplates were present suggesting the concentration of I’ is insufficient to fully transform all seeds to Cu NPLs, resulting in the growth of Cu nanowires (NWs). Figure 2e shows the Nal concentration effect on electric performance of printed Cu conductors as a result of the Cu nanostructure control during the synthesis. An increase in electrical conductivity of printed Cu conductors was observed as the concentration of Nal is decreased (from 1.9 MS/m to 6.4MS/m). There was a sudden decrease in conductivity of 1.6 MS/m once the concentration of Nal was 0.027 mM, while a decrease of Nal concentrations on as-synthesized Cu nanostructures was be observed in the SEM images (Figure 12). The average lateral dimension of Cu NPLs increase (3.83 pm to 5.89 pm) when initially decreasing Nal concentration (from 0.135 mM to 0.081 mM). However, there was a decrease in size (average lateral dimension of 0.72 pm) at 0.027 mM Nal. Figure 12 insets show the sizing curves and the average size of Cu NPLs for each concentration. This observation in size correlated to the changes in its electrical conductivity, suggesting that the Cu NPLs are essential in forming a percolating network and that the larger size NPLs can result in higher conductivities.

[0095] Table 1. Average size and standard deviation values based on the sizing curves from Figure 6.

[0096] Copper’s low oxidation resistance is exacerbated on the nanoscale due to higher surface-to-volume ratio. One method to improve the resistance is to alloy or coat the

Cu nanomaterials with a more oxidative resistant material, such as silver. Figure 13 show the SEM images and energy-dispersive X-ray spectroscopy (EDS) scan line of Cu/Ag NPLs and CuAg NPs (molar ratio of 9: 1), respectively (SEM images of the other alloys are provided in Figure 14). The line scan of the NPLs show that Cu (red) is the main element in the middle with more Ag (cyan) present at the edges, supporting its core/shell nanostructure. On the other hand, the line scan of the NPs shows both Cu and Ag present consistently throughout, supporting its alloy composition. This observation is consistent for the rest of the alloy NPs made (Figure 14b, 14d and 14f). The oxidation stability of printed conductors of Cu/Ag NPLs and CuAg NPs were evaluated against Cu NPLs (control) at an elevated temperature (160 °C) for 98 hrs (Figure 3a) (the rest shown in Figure 15). The Cu NPLs displayed the greatest decrease in electrical conductivity, dropping more than half the value at the end of the 98 hrs (2.8 MS/m to 1.2MS/m). The Cu/Ag NPLs degraded at a slower rate ending with a conductivity around 75% (2.2 MS/m to 1.5 MS/m) by the end. The CuAg alloy NPs showed high oxidation stability over the 98 hours of heating, losing less than 10% of its original conductivity (17 MS/m to 16 MS/m). Incorporating silver has shown to be effective in improving its stability towards oxidation. However, incorporating silver into the nanostructure, like in the case of an alloy, showed a much more significant improvement. The powder XRD diffractograms before and after the oxidation stability test are shown for Cu NPLs, Cu/Ag NPLs, and CuAg NPs in Figure 3b (The pXRD for the rest of the CuAg alloys are shown in Figure 15). Here, the extent of oxidation was determined for each conductor, based on how prominent an oxide peak is. For Cu NPL’s diffractogram, one dominant 29 peak was observed at 43.3 corresponding to the (111) plane. The Cu/Ag NPLs have the Cu (111) peak as in addition to the Ag (111) peak at 29 of 38.1. These match up well with what is expected, as the (111) plane is most dominant facet for the NPLs. The CuAg NPs were observed to have more 29 peaks: Cu (111) at 43.3, Cu (299) at 59.4, Cu (229) at 74.1, Ag (111) at 38.1, and Ag (299) at 44.3, which was expected from the formation of NPs. When comparing diffractograms before (darker color) and after (lighter color) the oxidation stability test, only one new 29 peak at 36.4 arises, corresponding to Cu(I) oxide. However, this peak is not intense (Figure 3b, zoomed) when compared to the peak for Cu (111). The powder XRD for other alloys are shown in Figure 16. This would suggest that a small portion of the conductor has oxidized during the test. Further, this suggests that a small amount of oxidation occurs during heating but results in a noticeable decrease in the conductivity.

[0097] To further improve the oxidation stability of copper, two-dimensional additives like graphene (G) or boron nitride (BN) were introduced, which can provide higher stability towards oxidation at higher temperatures. This is achieved through hybridization, where the graphene (or boron nitride) interfaces onto the copper facet, protecting it from oxygen in the atmosphere (Figure 4a, schematic). Resistance-temperature curves (RT) were collected in ambient atmosphere to evaluate at what temperature the hybridized conductor fails (Figure 4b). The Cu-BN hybrid conductor had thermal stability up until 400 °C, where the resistance started to increase rapidly (the resistance threshold of 10 Q). The Cu-G hybrid conductor, on the other hand, showed thermal stability around 460 °C where the resistance started to increase above 10 . Comparing both hybridized conductors, it suggests that the in- situ converted graphene provided a greater protection, seen by the operation temperature window increase of 60 °C. The hybridized interface between Cu and graphene is responsible for its improved protection (Figure 17). Here the graphene was converted, in-situ, from dopamine, whereas boron nitride nanosheets were exfoliated and incorporated in the ink. The nature of the in-situ conversion resulted in a more favorable interaction between the Cu NPLs and graphene whilst covering the NPLs. The boron nitride, on the other hand, was physically incorporated and possibly resulted in some aggregation of the nanosheets. The RT curve, however, only estimates the maximum temperature before its failure. To test the stability under continuous heating conditions, hybridized Cu-G and CuAg-G conductors were evaluated at 400 °C over a duration of eight hours, shown in Figure 4c (Other conductors shown in Figure 18). The CuAg-G conductor proved stable for approximately 1 hr, before the resistance started increasing, until the failure of the conductor at the 4-hour mark. On the other hand, the Cu-G conductor proved to be stable throughout the eight-hour heating period, with an increase of resistance from 0.7 to 2.2 Q by the end. This would suggest that (1) the hybridization of Cu NPLs is more effective than that of CuAg NPs; and (2) the shape of the nanostructure matters (NPL > NPs) for hybridization with graphene. It should be noted that graphene is typically grown on top of the copper (111) facet, supporting the superior interfacing of graphene on Cu NPLs. The SEM images of Cu-G before (top) and after (bottom) thermal stability testing at 400 °C are shown in Figure 4d. Before the test, the plates are somewhat melted together, but the shapes are visible and clear. After, however, the nanostructures are indescribable and fully melted together. The long exposure at 400 °C resulted in minimal degradation, but significantly changed the morphology on the microscale of the conductor.

[0098] Although the printed conductor is an essential component in flexible electronics, a suitable substrate is just as critical in proper design. Cu-G conductors were printed onto an ultrathin flexible alumina sheets with high thermal conductivity of 30 W/m*K, and flexible alumina aerogel nanocomposite sheet which is stable at high temperatures, thermal insulation with thermal conductivity of 0.03 W/m*K, and lightweight (Figure 5a). With the use of ultrathin alumina sheet substrates, a thin layer of AI2O3 with various thicknesses was coated onto the printed Cu-G conductor (at the same thickness of 10 pm) to protect it from oxidation. Figure 5a shows the setup for the hydrogen torch test. The AI2O3 coating (front) and the aerogel nanocomposite substrate (back) were evaluated for determining their respective stability against higher temperatures. The front side tests the effectiveness of AI2O3 thin layer at protecting the conductor from extreme temperatures and preventing oxidation (Figure 5b). The final reading represents either the last point before the conductor started to fail or once the temperature reached over 1,000 °C, whichever happens first. Starting from an ultrathin AI2O3 coating, its 25 nm thickness (black trace) showed thermal stability until 563 °C where the resistance changed from 6.3 to 7.1 . The 50 nm thickness (red trace) coated Cu-G conductor was stable up to 729 °C with a resistance change from 4.2 to 4.8 . The 75 nm thickness coated Cu-G conductor was stable to around 714 °C, with a change in resistance from 4.6 to 5.6 . The 100 nm thickness coated Cu-G conductor was shown to be stable up to 913 °C and a resistance from 3.9 to 5.0 , while the 1,000 nm thickness coated Cu-G has shown to be stable up to 1031 °C with an increase in resistance from 3.2 to 4.6 . Figure 5c shows the resistance (of 1.9 ) after the torch test for 1000 nm thickness coated Cu-G conductors. This shows that the printed Cu-G conductor could survive above 1,000 °C. The trend supports that thicker AI2O3 coating promoted better thermal stability of printed Cu-G conductor at higher temperatures. In comparison, the role of flexible superinsulation alumina aerogel substrates was examined to prevent the heat from penetrating the printed Cu-G conductor through the back-side testing (Figure 5d). Here, the back of the aerogel substrate was torched for a two-minute period. The temperature recorded on the other side ranged from 130 - 180 °C by the end of the two minutes. The conductors themselves showed a subtle change to resistance (no more than 0.4 change) throughout the test.

Additionally, there were no signs of damage from the conductor and substrate, demonstrating the good thermal insulation property and stability of the alumina-fiber aerogel composite. [0099] Described herein is the controlled growth of printable copper nanostructured materials for high-temperature flexible hybrid electronics. By utilizing advanced copperceramic platform, three hybridization and passivation strategies to improve thermal stability of printed copper conductor for high temperatures were demonstrated. By using an ultrathin flexible thermal conductive ceramic substrate, it is indispensable to employ a thin ALD layer coating to protect the printed Cu conductor from oxidation at high temperatures (over 1,000 °C), while a flexible ceramic aerogel substrate could prevent the heat penetration into the printed Cu conductor due to its superinsulation characteristics. The findings shown here provide a pathway towards the applications of copper materials for high-temperature electronics.

[0100] Increasing CuCh concentration. When increasing the CuCh concentration further, there were adverse effects on the synthesis. Figure 9 shows the synthesis solution after hydrothermal treatment for increasingly higher (2x, 2.5x, and 3x) Cu concentrations. The result was a lot of unusable solids which failed to form into NPLs. This result was reasonable, however, due to the lack of reducing agent present in the solution.

[0101] Varying ascorbic acid concentration and synthesis time. The SEM images of Cu nanostructures by increasing ascorbic acid concentration and varying synthesis time are shown (Figure 10). There is a decrease in size of Cu nanostructures as an increase of ascorbic acid concentration, whereas no trend in size is observed when the synthesis time is varied. When comparing the electrical conductivities of the conductors (Figure 11), the higher concentration of ascorbic acid resulted in higher values (greater than 7MS/m) with the highest conductivity observed from the synthesis with 3x increased ascorbic acid for 9 hrs (9.8MS/m). However, a clear discrepancy is shown between the NPL sizes is revealed. Previous size of NPLs synthesized with ascorbic acid resulted in average size below 1 pm, but the sizes in Figure 10c clearly show NPLs much bigger than 5 pm. While synthetically similar, the difference was the length of time the precursor was mixing prior. It is well known that ascorbic acid can reduce copper, and the longer mixing time allowed for the nucleation of many seeds, which results in smaller overall size.

[0102] Synthesis of Cu NPLs. The synthetic precursor was made up of a copper precursor (CuCh, CuCl, or CuBr), a reducing agent (glucose or ascorbic acid (AA)), a surfactant/ligand (HD A), sodium iodide, and DI H2O. The addition of HC1 in the precursor was also added in one variation. A typical synthesis consists of copper chloride dihydrate (CuCh«2H₂O, 2.4 g; 14.1 mmol; 15.7 mM), D-glucose (CeHnOe, 3.9 g; 21.6 mmol; 24 mM), hexadecylamine (HD A, 14.55 g; 60.2 mmol; 66.9 mM), and sodium iodide (Nal, 90 mg; 0.6 mmol; 0.54 mM) and were added to 900 mL of DI water. This solution was mixed (Via blender or mechanically stirred for 12 hrs) to obtain a uniform emulsion. 600 mL of the above solution was heated in an autoclavable glass bottle for 12 hrs at 100 °C, unless specified.

[0103] The Cu NPL solids are collected via centrifugation at 5000 rpm for 5 minutes. The solids obtained from centrifugation were redispersed in DI H2O, and filtered with a 180 pm membrane to remove any material left bigger than said membrane. Finally, the Cu NPLs will be centrifuged to collect the solids and further cleaned with the addition of DI H2O and ethanol at a 1 : 1 ratio and then the ink feedstock was collected via centrifugation.

[0104] Preparation of Cu/Ag core/shell NPLs. To prepare the Cu NPLs for electroless plating, Cu NPL semisolids were first treated in formic acid solution for a minute and washed via ethanol and centrifugation. The solid was then washed with a PVP/DEHA solution in DI H2O (5 wt. % PVP and 1 wt.% DEHA) twice, before being dispersed for the plating. Typically, Cu NPLs (4.5 mg/mL), PVP (4 wt. %), AA (IM) are dispersed in DI H2O at a molar ratio of 1 : 2 : 5.5. Once thoroughly mixed, AgNOs (0.025M) was added slowly (1 : 0.14 Cu : Ag molar ratio). Once all AgNOs has been added, it was allowed to stir for 10 minutes, before the NPLs are collected via centrifugation. The NPLs are further cleaned with ethanol.

[0105] Synthesis of one-pot Cu/Ag NPs. The synthetic precursor is similar to the synthesis of Cu NPLs, except with the addition of Ag. In brief, CuCh, AgNO2, AA, HD A, Nal, and DI H2O were added together and mixed via blender. This resulting solution was then heated at 100 °C for 12 hours to form Cu/Ag NPs. The NPs were collected via centrifugation at 5000 rpm for 5 minutes, before being redispersed, filtered, and further washed with ethanol.

[0106] Copper(/Ag)-(graphene/BN) ink preparation. After obtaining the ink feedstock, hydroxypropyl methylcellulose (HPMC) solution (2 wt. % in DI H2O), DI H2O and Cu semisolid feedstock was mixed together to make a conductive ink. The total ink weight consists of the conductive filler (25 wt. %), HPMC solution (20 wt. %), and additional water (55 wt. %). This mixture was then mixed in the Thinky Mixer (ARE-310) to achieve a homogenous ink. If Cu(/Ag)-G/BN ink were being prepared, dopamine (0.3 wt. % of the ink) or 4 wt. % BN solution (8 wt. % of the ink) would be added and mixed.

[0107] Direct writing through Voltera V-One was utilized for printing the conductive inks. The ink is printed via extrusion method where the conductive ink is forced out through the nozzle onto the substrate. The substrates used are plastics (Kapton®) and flexible Ribbon Ceramic (Alumina Ribbon Ceramic). After printing, the conductor was kept under ambient conditions, allowing the water to evaporate. Following this, the prints were sintered at 300 °C (800 °C for copper-graphene) under forming gas (95% Ar and 5% H2). This process promotes contact and removal of residual organics on the surface (in addition, 800 °C promotes the in- situ conversion of polydopamine to graphene).

[0108] Atomic Layer Deposition. An Atomic Layer Deposition (ALD) setup was utilized for depositing ultra-thin AI2O3 films. The coating procedure was performed using sequential exposures of Trimethylaluminum (TMA) and H2O separated by a purge of Nitrogen with a flow rate of 20 standard cubic centimeters per minute (seem). The procedure for AI2O3 consisted of 0.015 s pulse of TMA, followed by 8s of waiting time, a subsequent 0.015 s pulse of H2O and an additional 8s holding time. The number of cycles was repeated based on the desired level of thickness. As a consequence, 25, 50, 75 and 100 nm thick AI2O3 coatings were deposited on copper ink printed on Alumina Ribbon Ceramic using 236, 472, 708 and 944 cycles, respectively. The deposition was performed at 200°C. The growth rate for AI2O3 during this procedure was 1.06 A/cycle.

[0109] Hydrogen Torch Test. For the hydrogen torch test, the copper printed on Alumina Ribbon Ceramic was glued onto an alumina aerogel sample using Ultra-Temp 516 ceramic glue. This assembly was mounted on a ring stand by means of a burette clamp. The resistance and temperature were monitored using a Keithley 2450 Sourcemeter and a K-type thermocouple, respectively. Once the testing setup was complete, Nikon DSLR5500 DX was utilized for capturing the impact of the flame on the samples coated with different ALD thicknesses. Fotric 225 Pro Thermal Camera was utilized for capturing the heat signatures emanating from the sample during the test. Initially, the torch was further away and was gradually brought closer to the sample, leading to an incremental temperature rise. When evaluating the aerogel, it was conducted for a duration of two minutes. When testing the ALD coating, it was performed until the conductor failed.

EXAMPLE 2

[0110] This example provides a description of an ink of the present disclosure.

[0111] Table 2 : Silver coated copper nanoparticle ink formulations and their associated properties.

[0112] Various formulations were made based on the parameters described in Table 2.

[0113] Although the present disclosure has been described with respect to one or more particular embodiments and/or examples, it will be understood that other embodiments and/or examples of the present disclosure may be made without departing from the scope of the present disclosure.

Claims

Claims:

1. A conductive slurry composition comprising a slurry of copper silver nanoplates in water or copper silver nanoparticles in water, and the conductive slurry composition comprises less than 10 wt.% copper nanowires.

2. The conductive slurry composition according to claim 1, wherein the copper silver nanoparticles are silver-coated copper nanoparticles.

3. The conductive slurry composition according to claim 2, wherein the silver-coated copper nanoparticles are 10 to 30 weight percenter silver, relative to the total weight of an individual silver-coated copper nanoparticle.

4. The conductive slurry composition according to claim 2, wherein the concentration of the silver-coated copper nanoparticles is 30 to 70 weight percent, relative to the total weight of the conductive slurry.

5. The conductive slurry composition according to claim 1, further comprising a graphene material or boron nitride.

6. The conductive slurry composition according claim 1, wherein the copper silver nanoplates further comprise iodide.

7. The conductive slurry composition according to claim 1, further comprising (hydroxypropyl)methyl cellulose (HPMC) and the concentration of HPMC is 0.1 to 10 weight percent, relative to the total weight of the conductive slurry composition.

8. The conductive slurry composition according to claim 1, wherein the conductive slurry composition is a conductive ink.

9. A flexible electronic comprising a conductor formed from a conductive slurry composition according to claim 1 disposed on a substrate.

10. The flexible electronic according to claim 9, wherein the substrate comprises AI2O3.

11. The flexible electronic according to claim 9, wherein the substrate is AI2O3.

12. The flexible electronic according to claim 9, wherein the substrate is a AI2O3 aerogel composite.

13. The flexible electronic according to claim 9, wherein the substrate has a thickness of 25 to 1,000 nm.

14. The flexible electronic according to claim 9, wherein the conductor has a metal oxide layer disposed thereon.

15. The flexible electronic according to claim 14, wherein the metal oxide layer is AI2O3.

16. The flexible electronic according to claim 14, wherein the metal oxide layer is deposited via atomic layer deposition.