High-temperature Cu ink-based conductor with oxidation and corrosion resistance

[0001] This application is a National Phase entry of International Application No. PCT/US2022/030905, filed May 25, 2022, which claims priority to U.S. Provisional Application No. 63/193,025, filed May 25, 2021, the disclosures of which are incorporated herein by reference.

[0002] This invention was made with government support under grant no. W911NF-20-2-0016 awarded by the U.S. Army Research Laboratory and under agreement no. FA8650-20-2-5506 awarded by the U.S. Air Force Research Laboratory. The government has certain rights in the invention.

[0003] Advanced electronics are undergoing a paradigm shift to increase its printability, portability, miniaturization, and versatility in different environments. Simultaneously, electrical conducting materials, like metals, must complement the shift towards reliable, highly resistant, and high performance conductors under extreme environments such as high temperatures and in reactive atmospheres. Achieving such disparate functionalities will require rational design and manufacturing of the conductor material and its hierarchical structures. However, traditional metal conductors are energetically expensive to produce and are susceptible to extreme environments, creating a challenge for next-generation flexible electronics applications. Printable electronics, on the other hand, allows miniaturizing of electronic devices to be increasingly versatile and portable. However, the difficulties lie in the nanoscaled materials used, where the higher surface-to-volume ratios lead to lower melting points and greater susceptibility to oxidation and corrosion, relative to their bulk counterparts. In addition, the two most common types of conductors have diametrically opposite properties: Higher melting point with lower conductivities (e.g., tungsten and nickel) and lower melting points with higher conductivities (e.g., silver and gold). One promising metal conductor is copper, an ubiquitous electrically conductive material used in electronics, with high conductivities and a melting point higher than most other highly conductive metals, and is significantly more abundant and inexpensive. Nonetheless, a rudimentary issue with bulk copper materials is their high susceptibility to oxidation under ambient conditions. Despite the tremendous success of energetically expensive fabrication of copper conductors through electroplating or alloying, printable copper conductors with the controlled feature dimensions have been highly sought after. As such, there is a need for developing a new printable conductive material with amplified electric performance and stability.

[0004] Copper has attracted immense interest in advanced electronics attributed to its abundance, high electrical and thermal characteristics. However, the ease of oxidation when subjected to heat and humidity drastically limit its material reliability under extreme environments, which require continuous operation at elevated temperatures and in reactive atmospheres. Described herein is the hybridization strategies for achieving a thermally stable (upwards of 1300° C.), anti-oxidation and -corrosion printed conductor by utilizing two-dimensional single-crystalline copper (111) nanoplates as the building block, with the capability of being additively manufactured on flexible ceramics. Anti-oxidative copper nanostructures with a low sheet resistance of 4 mΩ/sq/mil were prepared by means of surface coordinated formate ligands that inculcates high oxidation and corrosion resistance on a molecular level, enabling continuous operation under atmospheric conditions up to 350° C. In addition, a rapid in-situ copper-graphene conversion led to a hybridized conductor, which displays stability at elevated temperatures up to 1300° C., substantially exceeding the melting point of bulk copper (1084° C.) with high ampacity. Further mechanistic studies revealed a clear indication of in-situ graphene conversion via X-ray photoelectron spectroscopy and high temperature stability from copper and graphene interfaces, as well as preferential stacking of copper nanoplates. These improved characteristics of copper at high temperatures are distinctly suited for the emerging high temperature electronics with the recent surge of portable, flexible, miniaturized and versatile smart electronics.

[0005] The present disclosure provides compositions, composite structures, and uses thereof.

[0006] 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.

[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.

[0010] 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.

[0043] 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.

[0044] All ranges provided herein include all values that fall within the ranges to the tenth decimal place, unless indicated otherwise.

[0045] Copper has attracted immense interest in advanced electronics attributed to its abundance, high electrical and thermal characteristics. However, the ease of oxidation when subjected to heat and humidity drastically limit its material reliability under extreme environments, which require continuous operation at elevated temperatures and in reactive atmospheres. Described herein is the hybridization strategies for achieving a thermally stable (upwards of 1300° C.), anti-oxidation and -corrosion printed conductor by utilizing two-dimensional single-crystalline copper (111) nanoplates as the building block, with the capability of being additively manufactured on flexible ceramics. Anti-oxidative copper nanostructures with a low sheet resistance of 4 mΩ/sq/mil were prepared by means of surface coordinated formate ligands that inculcates high oxidation and corrosion resistance on a molecular level, enabling continuous operation under atmospheric conditions up to 350° C. In addition, a rapid in-situ copper-graphene conversion led to a hybridized conductor, which displays stability at elevated temperatures up to 1300° C., substantially exceeding the melting point of bulk copper (1084° C.) with high ampacity. Further mechanistic studies revealed a clear indication of in-situ graphene conversion via X-ray photoelectron spectroscopy and high temperature stability from copper and graphene interfaces, as well as preferential stacking of copper nanoplates. These improved characteristics of copper at high temperatures are distinctly suited for the emerging high temperature electronics with the recent surge of portable, flexible, miniaturized and versatile smart electronics.

[0046] The present disclosure provides compositions, composite structures, and uses thereof.

[0047] 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.

[0048] In various examples, the conductive slurry composition comprises copper nanoplates. In various examples, the conductive slurry composition does not comprise copper nanowires. The copper nanoplates may further comprise one or more layers of graphene or a graphene-material or a formate layer.

[0049] Various amounts of copper nanoplates are used. In various examples, the copper nanoplates 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 nanoplates, such as functionalize with graphene or formate.

[0050] 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).

[0051] 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 μm, including all 0.1 nm values and ranges therebetween. In various examples, the copper nanoplates have a thickness of 10 to 100 nm, including all 0.1 values and ranges therebetween (e.g., 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).

[0052] The copper nanoplates may comprise copper or a copper alloy. In various examples, the copper alloy is chosen from a copper gold alloy, a copper silver alloy, a copper zinc alloy, a copper aluminum alloy, a copper nickel alloy, and a copper platinum alloy.

[0053] In various examples, the copper nanoplates further comprise 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.

[0054] 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 C₁ to C₆ alcohol (e.g., ethanol), diethylene glycol butyl ether, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, diethylene glycol monobutyl ether acetate, dibasic ester mixture, Terpineol, or a combination thereof.

[0055] 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.

[0056] 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.

[0057] The conductive slurry may further comprise (hydroxypropyl)methyl cellulose (HPMC). The concentration of the HPMC may be 0.1 to 10 weight percent, relative to the total weight of the conductive ink, including all 0.01 weight percent values and ranges therebetween.

[0058] In various examples, the copper nanoplates are functionalized with graphene or a graphene material. In various other examples, the copper nanoplates are surface functionalized with one or more formate groups.

[0059] Various ratios of copper nanoplates weight to the graphene material and/or graphene-precursor material can be used. In various examples, the ratio of the nanoplate weight to the graphene material and/or graphene-precursor material weight is 95:5 to 99.9:0.1, including all 0.1 ratio values and ranges therebetween.

[0060] 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.

[0061] 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 graphene-material precursor may be an organic small molecule. Non-limiting examples of graphene-material precursors include dopamine, aniline, and the like, and combinations thereof.

[0062] In various embodiments, the conductive slurry is a conductive ink.

[0063] The nanoplates may either be functionalized with graphene/graphene materials or formate groups. In various embodiments, a nanoplate is functionalized with both graphene/graphene materials and formate groups.

[0064] The nanoplates 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.

[0065] In an aspect, the present disclosure provides a method of making a conductive slurry composition of the present disclosure.

[0066] 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.

[0067] Various copper salts may be used 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.

[0068] 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).

[0069] 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.

[0070] 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).

[0071] 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).

[0072] 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.

[0073] 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 HDA; the iodide salt is provided as 90 mg of NaI; and 900 mL water.

[0074] In an aspect, the present disclosure provides a method for printing a conductive ink.

[0075] 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.

[0076] 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-C₈ alkylcarboxlic acid, such as, for example, acetic acid, and the like).

[0077] 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 C₆-C₁₅ alkylcarboxlic acid, such as, for example, dodecanoic acid, and the like).

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] The steps of the method described in the various embodiments and examples disclosed herein are sufficient to carry out the methods of the present invention. Thus, in an embodiment, the method consists essentially of a combination of the steps of the methods disclosed herein. In another embodiment, the method consists of such steps.

[0083] The following Statements are examples of the present disclosure and are not intended to be limiting in any way.

[0084] Statement 1. A conductive slurry composition comprising a slurry of copper nanoplates in water. In various examples, the composition comprises less than 10 wt. % copper nanowires.

[0085] Statement 2. A conductive slurry composition according to Statement 1, wherein the copper nanoplates have a longest linear dimension (e.g., length) of 100 nm to 10 μm, including all 0.1 nm values and ranges therebetween.

[0086] Statement 3. A conductive slurry composition according to Statement 1 or Statement 2, wherein the copper nanoplates have a thickness of 1 to 20 nm, including all 0.1 nm values and ranges therebetween or a thickness of 10 to 100 nm, including all 0.1 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, 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).

[0087] Statement 4. A conductive slurry composition according to any one of the preceding Statements, wherein the copper nanoplates comprise copper or a copper alloy.

[0088] Statement 5. A conductive slurry composition according to Statement 4, wherein the copper alloy is a copper gold alloy, a copper silver alloy, a copper zinc alloy, a copper aluminum alloy, a copper nickel alloy, or a copper platinum alloy.

[0089] Statement 6. A conductive slurry composition according to any one of the preceding Statements, wherein the copper nanoplates further comprise iodide.

[0090] Statement 7. A conductive slurry composition according to any one of the preceding Statements, further comprising (hydroxypropyl)methyl cellulose (HPMC) (e.g., the concentration of HPMC is 0.1 to 10 weight percent, relative to the total weight of the conductive ink).

[0091] Statement 8. A conductive slurry composition according to any one of the preceding Statements, wherein the copper nanoplates are functionalized with graphene or a graphene material.

[0092] Statement 9. A conductive slurry composition according to any one of Statements 1-7, wherein the copper nanoplates are surface functionalized with one or more formate groups.

[0093] Statement 10. A conductive slurry composition according to any one of the preceding Statements, wherein the conductive slurry composition is a conductive ink (e.g., conductive ink composition).

[0094] Statement 11. A method of making a conductive slurry composition, comprising: contacting a copper salt (e.g., a copper(II) salt, or a copper (I) salt, such as, for example, copper(II) chloride or copper(II) bromide, cuprous (I) chloride), an aliphatic amine, D-glucose (or ascorbic acid), an iodide salt (e.g., sodium iodide, potassium iodide), and water to form a reaction mixture; and heating the reaction mixture to form a conductive slurry composition according to any one of Statements 1-10.

[0095] Statement 12. A method according to Statement 11, wherein the aliphatic amine has from 10 to 20 carbon atoms.

[0096] Statement 13. A method according to Statement 12, wherein the aliphatic amine is hexadecylamine (HDA).

[0097] Statement 14. A method according to any one of Statements 11-13, further comprising mixing HPMC with water (e.g., deionized water); and adding the HPMC-water mixture to the conductive ink composition.

[0098] Statement 15. A method according to any one of Statements 11-14, wherein the reaction mixture is heated for a period of time ranging from 5-48 hours, including all integer second values and ranges therebetween (e.g., 6, 9, 9.5, 10, 11, 12, and 18).

[0099] Statement 16. A method according to any one of Statements 11-15, wherein the reaction mixture is heated to a temperature from 60° C. to 140° C.

[0100] Statement 17. A method according to any one of Statements 11-16, wherein the temperature is at least 100° C.

[0101] Statement 18. A method according to any one of Statements 11-15, wherein the reaction mixture is heated to a temperature of 100° C. or less.

[0102] Statement 19. A method according to Statement 18, wherein a mixture comprising one or more formate salts (e.g., a mixture comprising ethylene glycol, water, and one or more formate salts, such as, for example, sodium formate and copper formate) is added to the conductive slurry composition and subsequently heated at 100-150° C., including all ° C. values and ranges therebetween.

[0103] Statement 20. A method according to any one of Statement 11-19, wherein the components are provided in the following amounts or in amounts based on ratios of the following amounts: 2.4 g copper(II) chloride; 3.9 g D-glucose; 14.55 g HDA; 90 mg NaI; and 900 mL water.

[0104] Statement 21. A method according to Statement 20, wherein the mixture comprising one or more formate salts comprises; 50 mL ethylene glycol and 4 mL of a solution comprising: 30 g sodium formate and 15 mg copper formate dissolved in 150 ml of water.

[0105] Statement 22. A method of printing a conductive ink, comprising: extruding a conductive ink composition according to Statement 10, and washing the extruded ink with an acid (e.g., an organic acid) to remove residual aliphatic amine.

[0106] Statement 23. A conductor printed using a conductive slurry composition according to any one of Statements 1-10.

[0107] The following examples are presented to illustrate the present disclosure. They are not intended to be limiting in any matter.

[0108] This example provides a description the controlled growth and hybridization strategies of 2D single-crystalline copper (111)-rich nanoplates (Cu NPLs) as a building block for the development of high temperature stability, anti-oxidation and anti-corrosion conductor materials.

[0109] Described are three strategies to achieve greater stability and electric performance of copper. The first strategy involves utilizing surface passivation towards stability at moderate temperatures. The surface passivation is achieved through surface reconstruction utilizing a short ligand to prohibit adsorbates such as O₂ from oxidizing or corroding the surface. A short carbon chained ligand is generally preferred as longer chained ligands are insulating, but also limits the printed conductor to moderate temperatures (˜300° C.) which are suitable with flexible plastics like Kapton®. The second strategy involves utilizing graphene for high temperature applications towards greater stability and enhanced current carrying capabilities (ampacity). High electric conductivity and high thermal conductivities require different properties: the former requires free electrons due to weak bonding within the system, with the latter requiring a system with strong bonds. Ampacity is dependent on electromigration, and while a non-thermal process, in most metals will result in melting as temperature increases due to joule-heating severely hindering the current carrying capabilities for practical applications. Graphene, on the other hand, are known to sustain high ampacities with high chemical and thermal stability. The integration of two dissimilar materials (graphene and Cu) can result in a high temperature conductive material that can be employed for advanced electronics with thermal management. In addition, graphene, has shown to improve oxidation-resistant performance of composite materials at high temperatures and also suppresses the copper diffusion pathways at high temperatures, thus an enhancement in its current carrying capacity. Thirdly, the nanomaterial's dimensionality (particle, sheets, wires, etc.) can affect and determine its properties. Two-dimensional (2D) materials display strong in-plane chemical bonding, along with weak out-of-plane van der Waals interactions, along with substantial planar topology (>100 nm) and very low thicknesses. The planarity of 2D copper nanostructures allows surface coordination/reconstruction, preferential layering, and larger contact area resulting in lower contact resistance. Thus utilizing the 2D architecture with the aforementioned strategies shows promise for greater thermal and oxidation stability.

[0110] Described herein is the controlled growth and hybridization strategies of 2D single-crystalline copper (111) nanoplates (Cu NPLs) as a building block for the development of high temperature stability, anti-oxidation and anti-corrosion conductor materials, with the capability of additive manufacturing onto flexible alumina ceramics (FIG. 1a). The surface coordination of formate on printed Cu conductors (Cu-FA) has the potential to introduce high oxidation and corrosion resistance without influencing its electrical conductivity (a sheet resistance of 4 mΩ/sq/mil), in addition to the increased working temperature by 100° C. compared to untreated Cu conductors. Also utilized was an in-situ copper-graphene (Cu-G) conversion, with the resulting conductors demonstrating stability at high temperatures, surviving up to 1300° C. (FIG. 1c). This improved stability and conductivity at elevated temperatures are a result from the electronic hybridization between copper and graphene interfaces, which is supported by molecular dynamic simulations and in-situ spectroscopies. Lastly, further characterizations were made to determine the purity of the Cu NPLs in addition to their stacking orientation. The demonstrated additive manufacturing process for developing conductive Cu patterns is promising for electronics applications where specific geometric patterning is required.

[0111] FIG. 1a illustrates the schematic of the fabrication process utilized for printing the Cu ink (The illustration of FIG. 1a depicts the example of in-situ conversion of dopamine to graphene in the Cu-G conductor). Also utilized was a direct-writing, extrusion printing method, for deposition of Cu-ink patterns onto various substrates, including flexible Yttria-stabilized zirconia (YSZ) substrate. Alumina Ribbon Ceramic substrate, and polymer Kapton® substrates. Multiple printing passes allow for closely-packed, dense patterns, with desirable thicknesses. After printing, the pattern was dried under ambient conditions, and was subsequently sintered allowing further densification and decomposition of the additives. FIG. 1b shows the printed pattern on an alumina ceramic plate substrate. The electrical conductivities of various Cu-based conductors. (presented here from commercial sources) and their respective operating temperatures are shown in an Ashby plot (FIG. 1c). The Cu hybridized conductors described herein were observed to have not only higher operating temperatures than most of the printable inks, but also have higher electrical conductivities. Cu-G in inert atmosphere was shown to have the highest operation temperature, even above the melting point of bulk copper. It should be noted that the only printable inks with higher electrical conductivities are comprised of noble metals.

[0112] The dimension/shape control of copper nanostructures is a fundamental component in the development of printable conductive ink material, due to material size limitations that govern different printing techniques. By utilizing the wet-chemistry synthesis, scalable controlled growth of 2D single-crystalline Cu NPLs was demonstrated through the reduction of copper chloride by glucose and subsequent adsorption of iodide on the Cu (111) plane (FIGS. 6 and 7). The scanning and transmission electron microscopy (SEM and TEM) images of as-synthesized Cu NPLs are shown in FIGS. 1d and 1e, revealing the 2D architecture of as-synthesized ultrathin Cu NPLs. The selected area electron diffraction (SAED) pattern (FIG. 1e, inset) for the Cu NPLs in FIG. 1e suggests its single-crystalline nature. In addition, the hexagonal diffraction pattern is an indication that the basal plane is the Cu {111} facet. The size distribution of synthesized Cu NPLs can be controlled by manipulating the nucleation and growth by means of tuning the reaction conditions (FIG. 6b-d). By increasing the glucose to Cu²⁺ ratios (FIG. 6b), the average size of Cu NPLs can be reduced from approximately 5 μm to 3 μm as a result of increased nucleation formation. Furthermore, by increasing the reaction time (FIG. 6c), the average size of Cu NPLs can be increased from approximately 4 μm to 10 μm through the prolonged growth. In addition, the reaction temperature is an important parameter in the size control of Cu NPLs (FIG. 6d), diminishing the approximate size from 9 μm to 5 μm as the reaction temperature goes on increasing from 80° C. to 120° C. This increment in the reaction temperature results in significant increase of nucleated Cu seeds, which decreases the overall amount of Cu material for growth, thus resulting in smaller dimensions of Cu NPLs. The trends observed here can be described with the LaMer model, where increasing glucose to Cu²⁺ ratio and reaction temperature results in an increased nucleation rate, resulting in more seeds and less material for seed growth, thus leading to the formation of smaller Cu NPLs. Increasing reaction time to extend the growth period, a.k.a. Ostwald ripening, allows the Cu NPLs to grow larger. Additionally, the increase in average sizes correlates to a larger size distribution of Cu NPLs.

[0113] The observations above described the controlled synthesis of printable Cu material feedstocks for the development of aqueous based ink material to be printed for evaluation of its electrical conductivity (FIG. 2a). FIG. 2b shows the relationship between the sheet resistance and Cu loading concentrations of the printed features, where the increase of Cu concentration (wt. %) and the number of printing passes increases the thickness of the printed feature. Furthermore, the increase in thickness also correlates with the decrease in its sheet resistance. Ideally, a low sheet resistance could be achieved at higher Cu feedstock, however, the Cu ink's printability becomes increasingly difficult at feedstock concentrations above 6 wt. %. Additionally, on a linear scale (FIG. 9a) the decrease in sheet resistance becomes minor once the thickness reaches above 50 μm. Therefore, 6 wt. % Cu feedstock is selected for the following studies. In addition, the inset of FIG. 2b describes the electrical conductivity dependence on the hydroxypropyl methylcellulose (HPMC) additive concentration for printed Cu NPL features, for tuning viscosity and printability. The electrical conductivity increases from 1×10³ S/m to 8×10³ S/m, an 8-fold increase, by increasing HPMC solution content from 2 wt % to 50 wt % in the copper ink. The increased conductivity is a result of an improved adhesion and dispersibility of Cu in the preparation of the printable ink materials. The electrical conductivity improved most significantly from 10 to 20 wt. % HPMC in the printable Cu materials (from 2×10³ S/m to 6×10³ S/m), while any further increase in HPMC above 20 wt. % shows minor increments in the conductivity. Therefore, 20 wt % HPMC is selected for further studies. To further increase its conductivity (or decrease the sheet resistance), a sintering treatment for the printed Cu NPL patterns is believed crucial. Sintering resulted in the improvement on the conductivity/lower sheet resistance through the decomposition of non-conductive organics while annealing the Cu nanostructures for increased contact and density. By varying the sintering temperature (FIG. 2c) from 200 to 600° C. a clear trend is observed indicating an increased conductivity from 1.5×10⁶ S/m to 4.2×10⁶ S/m. In addition, the most significant increase of electrical conductivity occurs at the sintering temperature from 250 to 300° C. The boiling point of one of the additives, hexadecylamine (HDA), is around 330° C. (FIG. 8), which suggested that the increase conductivity at 300° C. is correlated to the removal of HDA in the printed Cu NPL features. The trend for sheet resistance of printed Cu NPL features is similar, a decrease from lower to higher sintering temperatures. However, there is no significant difference in sheet resistance when sintering from 300 to 600° C. and thus 300° C. is chosen as the sintering temperature. When investigating the effects of sintering time from 1 to 60 minutes (FIG. 2d) at 300° C. no trend is observed and that electrical conductivities varied from 3×10⁶ S/m to 3.5×10⁶ S/m. In addition, the stability of the printed copper features in ambient conditions (FIG. 2e) is measured over a duration of 42 days. The printed Cu patterns show little to no change in its conductivity over that timespan demonstrating high stability in ambient conditions.

[0114] Copper nanostructures' lower resistance to oxidation and corrosion are due to its high surface-to-volume ratio, compared to bulk. Improving its anti-oxidation and anti-corrosion is vital in prolonging the lifetime and electrical performance of printed Cu NPL features. Further described is a surface hybridization strategy where formates (FA) were introduced onto the printed single-crystalline Cu (111) NPLs (FIG. 3a). The surface passivation occurs with FA binding to neighboring copper atoms at the surface. Through this Cu-FA hybridization, the enhancement in oxidation resistance of Cu conductors was demonstrated. FIG. 3b compares the oxidation resistance between Cu NPL and Cu-FA under ambient conditions at increased temperatures. Both conductors survive oxidation at 200° C. however Cu conductor started oxidizing significantly at 250° C. The Cu-FA conductor, on the other hand, oxidized at 350° C. an increased working temperature of about 100° C. compatible with the maximum working temperature of flexible polymer substrates, like Kapton®. The increased oxidation resistance of Cu-FA can be attributed to the surface formate layer preventing oxygen from oxidizing the Cu surface. At 350° C. however, the surface formate layer decomposes, exposing and subsequently allowing oxygen on the conductor surface. In addition to the enhanced oxidation resistance, the Cu-FA hybridization also enhances the corrosion resistance. The SEM images (FIG. 3c) are shown of Cu (top) and Cu-FA (bottom) after prolonged base treatment, in which a pronounced corrosion and surface reconstruction can be observed on the Cu conductor. On the other hand. Cu-FA conductors retain their distinct shapes with little to no visible damage of the printed structure. The insets for each SEM image (FIG. 3c) correspond to the image after the base treatment. The measured resistances under base corrosion measurement (FIG. 3d) of Cu and Cu-FA reveal the anti-corrosion nature for Cu-FA with no significant resistance change. Cu-FA shows an increasing trend for the first 100 minutes, however, the resistance plateaus and remained steady. Cu, however, showed a steady increase in resistance overtime. These observations suggested the enhanced anti-oxidation and anti-corrosion performance of surface hybridized Cu conductor through the formate passivation.

[0115] In addition to the enhanced resistance to oxidative and corrosive environments, an in-situ direct conversion of molecular dopamine and hybridization strategy of Cu-graphene conductors focusing on extreme environments such as high temperatures, where the temperatures greatly exceed 1084° C. (bulk copper's melting point), was introduced. The in-situ Cu-G direct conversion is achieved through dopamine coating during the Cu ink preparation, which when carbonized at elevated temperatures, serve as a potential graphene source. This can be attributed to the presence of hydroxyl (—OH) and amine (—NH₂) groups forming an uniform coating on the Cu nanoplate surface, which in turn attributed to their strong adhesion due to non-covalent bonds (hydrogen bonding or %π-π% stacking), resulting in the enhancement of electrical conductivity due to metallic and covalent bond formation between the graphene and copper (111) nanoplates. When this nanoplate-polydopamine (PDA) mixture is sintered at a temperature of 800° C. where in-situ conversion of PDA happens, leading to the formation of Cu (111)-G conductor with high conductivity (4.3×10⁶ S/m). The in-situ conversion approach is indicative of a better overall performance and reliability, which can be attributed to a high-quality interface between the Cu (111) surface and the in-situ polymerized graphene (the graphene formation is confirmed by Raman spectroscopy shown in FIG. 12a, and the following spectroscopy studies). A model depicting how the graphene layer preferentially adsorbs onto the Cu {111} facet (FIG. 4a), effectively passivating and hybridizing the Cu conductor. The adjoined images (FIG. 4a, inset) show the printed Cu-G feature before (top) and after (bottom) sintering, showing no sign of melting after sintering up to 1400° C. significantly above bulk copper's melting point.

[0116] A SEM and energy-dispersive X-ray spectroscopy image (FIG. 4b) shows the printed Cu-G feature after sintering, revealing the uniform distribution of Cu and C elements. X-ray diffraction (XRD) is used (FIG. S7b) to characterize the Cu-G conductors after heating up to 1400° C. The three peaks observed at 20 values at 43.3°, 50.5°, and 74.1° are characteristic for Cu (FCC), corresponding to {111}. {200} and {220} planes, respectively. The intense peak related to the Cu {111} lattice plane suggests that the Cu (111) are maintained, further suggesting that the printed Cu-G conductors have survived after sintering at 1400° C. FIG. 4c shows the ampacity measurements between pure Cu NPLs and Cu-G conductors. Varying dopamine concentrations reveals an increase in ampacity from pure Cu NPLs to 0.64 wt. % G followed by a decrease in ampacity at 0.96 and 1.28 wt. % G, suggesting that 0.64 wt. % G is the optimal concentration. Cu-G (0.64 wt. %), when compared to pure Cu NPLs, shows an increase of approximately 20-fold (approximately from 0.5×10⁴ to 10×10⁴ A·cm⁻²) in current-carrying capacity, which assists in concluding that electric and thermal conductivity of Cu-G conductor is remarkably higher compared to Cu NPLs, which further accentuates the role of graphene on high temperature stability and thus reliability. In addition, high-temperature conductivity studies (FIG. 4d) are performed comparing the printed Cu NPLs and Cu-G features sintered under an inert atmosphere up to 1400° C. whereas printed Cu NPLs failed around 950° C. Both of the enhanced performances observed can be attributed to graphene's role in suppressing Cu diffusion and its high thermal conductivity, and hybridizing Cu and graphene at interface during in-situ conversion. These observations demonstrates graphene's ability to significantly suppresses Cu diffusion through preferential lattice matching, while its high thermal conductivity and hybridization reduces the likelihood of the Cu melting.

[0117] To understand the effects of graphene incorporation in copper on their bonding behavior of alloy systems, we performed molecular dynamic simulations for a pristine copper system including 6 atomic layers along [001] direction and a copper-graphene-copper heterogenous structure with temperatures at 800 K (FIG. 14). 1200 K (FIG. S10). 1600K (sintered. FIG. 5a: unsintered. FIG. 13), and 2000 K (FIG. 16). Large atomic displacements of copper atoms were observed away from their equilibrium positions in pristine 6-layer copper slab appear at around 1200 K and are enhanced when the temperature is increased up to 2000 K. On the other hand, copper atoms in the copper-graphene-copper heterogeneous structure exhibit much less deviations from their equilibrium positions. The results provide a strong evidence that the incorporation of graphene is able to enhance the bonding stability of the whole structure at higher temperature, and hence increase the melting point of the system.

[0118] X-ray photoelectron spectroscopy (XPS) can be utilized in determining present elements and their chemical environments of printed Cu-G conductors (FIG. 17). The Cu 2p XPS spectrum (FIG. 18) contains one peak corresponding to pure Cu metal at 933 eV in both sintered and unsintered prints. The Cu 2p FWHM of the unsintered film is 1.86 eV after sintering this peak decreased to 0.95 eV, indicating the bonding became more ordered after sintering. Additionally, there was no evidence of oxides, shown through the lack of any satellite peaks around binding energy range of 940-950 eV. These observations clearly indicate that the Cu sample, unsintered and sintered Cu-G, are of highly pure Cu metal. The C 1s XPS spectrum corresponds either the graphene (sintered, FIG. 5b) or for polydopamine (unsintered, FIG. 19). For the unsintered sample the C Is spectrum is deconvolved into three peaks around 284.80, 285.89, and 288.04 eV which corresponded to C—C, C—O, and C═O functional groups, respectively. The sintered Cu-G sample (FIG. 5b), on the other hand, once deconvolved clearly indicates six different chemical environments around 284.87, 286.21, 288.51, 287.42, 289.54, and 291.27 eV corresponding to sp² and sp³ carbons, C—O, C—NH_x, C—O, COO, and O—COO functional groups, respectively (binding energies shown in supporting information FIG. 19). The binding energy for similar functional groups have shifted slightly, further indicating changes in the chemical environment. Additionally, polydopamine has a ratio of 1:3 of C═O:C—O functional groups: the C 1s XPS peaks gives a ratio of 1:3.3, indicating that polydopamine is present. To further support the in-situ conversion of dopamine to graphene. N 1s XPS spectrum (FIG. 20) was investigated. The unsintered sample showed one peak at 399.61 eV which corresponds to pyridinic/pyrollic N. Once sintered, an additional peak appeared at 401.00 eV corresponding to graphitic N, indicating the successful formation of nitrogen-doped graphene of printed Cu-G conductor. The XPS data have clearly shown that printed Cu conductors are purely metallic, before and after sintering, as well as confirming the presence and conversion of polydopamine to nitrogen-doped graphene. In addition to interpreting the X-ray diffraction pattern of Cu-G conductors (FIG. 12), crystal tilt orientation teased out information regarding how the Cu NPLs are stacked. Mapping the crystal tilt (FIG. 5c) for the (111) plane (43.3°) in both sintered and unsintered prints, there is a relatively broad spectrum with the peak intensity at 270°, corresponding to the sample normal. The anisotropy in the Debye ring indicates the preferential orientation of the Cu NPLs, where the narrower peaks suggested that the alignment between the Cu NPLs is increased. The corresponding FWHM for the sintered and unsintered prints are 4° and ˜10°, respectively, suggesting that once sintered the Cu NPLs are oriented in roughly the same direction and preferentially stacked on top of one another.

[0119] Described are single-crystalline Cu (111) nanoplates as the building block for the development of anti-oxidation Cu conductors with high conductivity and stability under extreme environments. Further described are two hybridization strategies for printed Cu conductors: one involving formate passivation to show anti-oxidation and anti-corrosion and the other with in-situ conversion of dopamine to graphene displaying a remarkable stability at high temperatures (1400° C.), exceeding the melting point of bulk copper (1084° C.). The printed Cu conductors display a high electric conductivity of 4× 10⁶ S/m (which is 10× lower than bulk copper) and the sheet resistance of 4 mΩ/sq/mil, which can be printed onto a variety of flexible substructures, including high temperature Kapton®; plastics and flexible Ribbon Ceramics substrates. The Cu-G conductor displays an approximate 20-fold increase in the current carrying capacity when directly compared with Cu conductor. Further demonstrated is the surface formate passivation and in-situ graphene formation, are compatible with the batch-based printable electronics manufacturing. Also investigated was the role of graphene in regards to improving the stability at high temperatures through computational modeling and in-situ spectroscopy studies. The findings shown here represent a new conductor material building block, and promising strategies to address materials reliability issues for printed electronics at high temperatures. These observations depict that the hybridized copper conductors described here feature anti-oxidation and anti-corrosion properties and stability at elevated temperatures. It is considered that the materials may be suitable for printed miniaturized electronics applications. Moreover, the ease of manufacturing and scalability reckons them desirable candidates for advanced electronics.

[0120] Synthesis of Cu NPLs. The precursor was made by adding copper chloride dihydrate (CuCl₂·2H₂O, 2.4 g), D-glucose (C₆H₁₂O₆, 3.9 g), hexadecylamine (HDA. 14.55 g), and sodium iodide (NaI, 90 mg) were added to 900 mL of DI water and mechanically stirred for 12 hours (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. In the precursor. HDA acted as a coordinating ligand to CuCl₂ and forms Cu²⁺-HDA complex. When the precursor was heated up. Cu²⁺ is gradually reduced to Cu⁰ by glucose, forming Cu seeds in the solution. When the Cu seeds grow, iodides preferentially adsorb onto the {111} facets, effectively forcing growth parallel to the basal plane.

[0121] 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 μm 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.

[0122] Copper (graphene) ink preparation. After obtaining the ink feedstock, hydroxypropyl methylcellulose (HPMC) solution (2 wt. % in DI H₂O), DI H₂O and Cu semisolid feedstock was added together to make a conductive ink. The concentrations of HPMC solution (2-20 wt. %) and Cu NPLs (0.9, 6, 8.3, and 20 wt. %) are varied, with water comprising the remaining portion of the ink. This mixture was then mixed in the Thinky Mixer (ARE-310) to achieve a homogenous ink. If copper-graphene ink (FIG. 1a scheme) was being prepared, dopamine would be added after the homogenous ink was first mixed. Varying amounts of dopamine were added and again mixed to achieve a homogenous ink mixture.

[0123] 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 (PET and Kapton®) and flexible Ribbon Ceramic (YSZ for Cu and Cu-FA and Alumina Ribbon Ceramic for Cu-G). 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).

[0124] Post-sintering formate treatment. FIG. 3a illustrates the post-sintering treatment with formate. For the formate treatment, a solution containing 50 mL of ethylene glycol and 4 mL of formate solution (30 g sodium formate and 15 mg of copper formate dissolved in 150 mL DI H₂O) was first added in an autoclavable glass bottle. The sintered Cu NPL prints were then submerged into the solution before heat treatment in a 120° C. oven for 12 hours. The resulting print was then cleaned by submerging in ethanol and water to clean off excess ethylene glycol and salt, respectively, before being dried gently with air.

[0125] Computational methods. First-principles calculations are performed by VASP code with the plane-wave implementation of the PBE generalized gradient functional. The non-local correlation functional vdW-DF is included for the long-range van der Waals interaction. The atomic structures are optimized until the forces are less than 0.01 eV/A. and the self-consistent energies are converged to 105 eV. The vacuum thickness is set to 15 Å to prevent from interactions between periodic images. The plane-wave cutoff energy is set to 400 eV. Ab initio Born-Oppenheimer molecular dynamic simulations are performed with Nose-Hoover dynamics (Nose Q=2, smearing=0.04). The NVT ensemble is used in the simulations. The simulations run for up to 10 ps with a time step of 1.0 fs.

[0126] This example provides a description of the compositions of the present disclosure.

[0127] FIGS. 21-31 provide various features of the present disclosure.

[0128] 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.