WO2005005687A1

WO2005005687A1 - Method of coating nanosturctures with metal using metal salts

Info

Publication number: WO2005005687A1
Application number: PCT/US2004/017440
Authority: WO
Inventors: Christopher H. Cooper; William K. Cooper; Alan G. Cummings
Original assignee: Seldon Technologies, Llc
Priority date: 2003-07-02
Filing date: 2004-07-02
Publication date: 2005-01-20

Abstract

Disclosed herein is a method of making a metal or metalloid coated nanostructured material comprising: dissolving a metal or metalloid containing salt in a liquid medium to form a solution; contacting the nanostructured material with the solution for a time sufficient to form an intermediate coating on the nanostructured material; and subjecting the intermediate coated nanostructured material to at least one process to decompose the salt, thereby leaving a metal or metalloid coating on the nanostructured material. Also disclosed is a metal or metalloid coated nanostructured material made by this method.

Description

METHOD OF COATING NANOSTRUCTURES WITH METAL USING METAL SALTS [001] This application claims the benefit of domestic priority to U.S. Provisional Patent Application No. 60/484,125, filed July 2, 2003, which is herein incorporated by reference in its entirety. [002] Disclosed herein is a method of coating nanostructured materials with metals or metalloids through a metal or metalloid salt process. i Also disclosed herein are coated nanostructured materials made by such a process, as well as products containing such coated nanostructured materials. [003] Nanostructured material have shown extraordinary promise due to their high conductivities, very small size, high surface areas, and other features that make them useful in a number of fields. For example, in the electronics sector they are particularly beneficial for their small size and high conductivities. [004] One type of nanostructured material, carbon nanotubes, have garnered a lot of interest and support for a myriad of properties such as extremely high conductance and strength. The nanostructured materials can be further tailored and improved to exhibit an even broader range of properties by coating them with various materials, including metals, polymers and ceramics. [005] To date, most coatings for nanostructures have been created using deposition methods such as physical or chemical vapor deposition techniques. Such techniques common to the art include CVD, MOCVD, and various sputtering techniques. In addition to being very costly and complex, these methods have limitations, including the inability to produce large quantities of material in a single batch and uniform layer thicknesses. A novel method that would allow large quantities of nanostructures to be coated at a lower overall cost than current methods would allow for larger use of these materials. SUMMARY OF INVENTION [006] The present disclosure solves the aforementioned problems as it relates to coating nanostructured materials with metals or metalloids. "Nanostructured" refers to a structure on a nano-scale (e.g., one billionth of a meter), such as on the atomic or molecular level. "Nanostructured material" is a material comprising at least one nanstructure. Examples of such nanostructured materials include, but are not limited to nanotubes, such as carbon nanotubes, nanowires, diamond, buckyballs, fullerene compounds, and biological moieties. [007] One aspect disclosed herein relates to a method of making a metal or metalloid coated nanostructured material comprising dissolving a metal or metalloid containing salt in a liquid medium to form a solution; [008] contacting the nanostructured material with the solution for a time sufficient to form an intermediate coating on the nanostructured material; and [009] subjecting the intermediate coated nanostructured material to at least one process to decompose the salt, thereby leaving a metal or metalloid coating on the nanostructured material. [010] Metalloids generally refer to those elements located along the line between the metals and nonmetals in the periodic table, and include boron, silicon, germanium, arsenic, antimony, and tellurium. Polonium is also often considered a metalloid. Non-limiting examples of nitride metalloids are cubic boron nitride (cBN) and Si₃N₄. An example of a carbide metalloid is B C. An example of a bimetalloid compound is SiB₆. BRIEF DESCRIPTION OF DRAWING [011] Fig. 1 is a representation showing how metals may concentrate at the intersection point of two nanostructures. DETAILED DESCRIPTION OF THE INVENTION [012] The present disclosure describes the coating of nanostructure materials with metals or metalloids through a metal salt process. In this process, the metal salt is coated over the nanostructure, using a process, such as liquid phase chemistry. [013] As stated, the present invention relates to a method of making a metal or metalloid coated nanostructured material comprising dissolving a metal or metalloid containing salt in a liquid medium to form a solution. The liquid medium may comprise water, organic solvents, acids, or bases. Non- limiting examples of the organic solvents include alcohols, such as ethanol, isopropanol, methanol, and xylene. [014] After the solution is formed, it is brought into contact with the nanostructured material for a time sufficient to form an intermediate coating on the nanostructured material. The time of this coating step varies depending on the amount and thickness of coating to be deposited. For example, the time to form an intermediate coating on the nanostructured material may range from a few seconds (for the deposition of a low concentration of metal) to a few minutes (for a denser concentration of metal) to hours and even days for a. thick metal coating. According to different aspects of the invention, the time to form an intermediate layer is less than 48 hours, such as greater than 1 second to 12 hours or even greater than 1 second to 1 hour. [015] In one embodiment, a reaction may be induced, such as by thermal processing, to achieve thermodynamic effects, and form the resulting intermediate coating. In its simplest form, merely drying the coated nanostructured may be used to drive off the salt and to form a metal layer. [016] The intermediate coated nanostructured material is then subjected to at least one process to decompose the salt, thereby leaving a metal or metalloid coating on the nanostructured material. As used herein "decompose," "decomposition" or any version thereof means to separate the metal salt into constituent parts or elements, leaving the metal component on the surface of the carbon nanotube and driving off the salt component. For example, by using an appropriate temperature known to one skilled in the art, i an intermediate layer of NaCl, which was deposited via an aqueous solution, can be decomposed to leave Na on the surface of the carbon nanotube while driving off gaseous CI. [017] In one embodiment, the metal or metalloid comprises at least one material chosen from gold, platinum, titanium, rhodium, indium, copper, iron, palladium, gallium, germanium, tin, lead, tungsten, niobium, molybdenum, silver, nickel, cobalt, potassium, sodium, mixtures thereof, and alloys thereof. [018] "Chosen from" or "selected from" as used herein refers to selection of individual components or the combination of two (or more) components. [019] The above-mentioned metals or metalloids may be complexed with at least one anion chosen from chlorides, bromides, nitrates, chlorates, chlorites, sulfates, and sulfites. Gold chloride, tin chloride and silver nitrate represent non-limiting examples of such complexed metals. [020] The above-described method may further includes at least one process for decomposing the salt. For example, such a process may comprise a thermal treatment process at or below the decomposition temperature of the intermediate coating. One skilled in the art would readily be able to determine the decomposition temperature for the particular metal salt of interest. [021] As shown in Fig. 1 , during deposition of the metal and subsequent annealing, metals may concentrate at the intersection point of two nanostructures. Therefore, in one embodiment, the metal coating can be used to glue or bond two or more nanostructures together. These nanostructures may either be the same type of material or two different nanostructured compounds. [022] Non-limiting examples of how such nanostructured material are made can be found in co-pending U.S. Patent Application No. 10/794,056, entitled "Purification of Fluids with Nanomaterials," filed March 8, 2004, which is herein incorporated by reference. [023] The method described herein may also include a process for fusing all of the elements of the nanostructured material, including the metal coating layer, together, after the salt anion is removed. For example, one process may include heating the metal or metalloid coated nanostructured material to a temperature sufficient to fuse together at least two nanotubes, wherein the metal may act as a solder joint between the nanotubes. This temperature is typically the annealing temperature of the deposited nano- metal. For example, this temperature is typically that at which there is ion mobility, and in some case surface diffusion. In one embodiment, the temperature may range from 200°C to 600°C, such as 250°C to 350°C and 300°C. [024] As used herein the term "fused," "fusion," or any version of the word "fuse" is defined as the bonding of nanotubes at their point or points of contact. For example, such bonding can be Carbon-Carbon chemical bonding including sp³ hybridization or chemical bonding of carbon to other atoms. [025] Non-limiting examples of how such fused nanostructured material are made can be found in co-pending U.S. Patent Application No. 10/859,346, entitled "Fused Nanostructured Material," filed June 3, 2004, which is herein incorporated by reference. [026] The nanbstructured material to be coated may comprise various nanotubes, including carbon nanotubes. When used, the carbon nanotubes may be single-walled, multi-walled, nanoscrolled or combinations thereof. [027] In addition, the carbon nanotubes may take a variety of known morphologies, such as those chosen from nanohorns, cylinders, nanospirals, dendrites, spider nanotube structures, Y-junction nanotubes, nanorods, and bamboo morphology. [028] The above described nanotube shapes are more particularly defined in M.S. Dresselhaus.G. Dresselhaus, and P. Avouris, eds. Carbon Nanotubes: Synthesis, Structure, Properties, and Applications, Topics in Applied Physics. Vol. 80. 2000, Springer-Verlag; and "A Chemical Route to Carbon Nanoscrolls, Lisa M. Viculis, Julia J. Mack, and Richard B. Kaner; Science 28 February 2003; 299, both of which are herein incorporated by reference. [029] The nanostructured material may comprise nanorods, such as metallic or metalloid oxide nanorods. Unlike nanotubes, nanorods are typically filled and have a multi-layer, graphite-type structure, aligned either parallel, perpendicular, or at an angle to the axis. Non-limiting examples of metallic oxides or metalloid oxides that may form the nanorods include, copper oxide, magnesium oxide, silicon oxide, gold oxide, silver oxide, titanium oxide, and ferric oxide. [030] In another embodiment, the nanostructured material comprises metal or metalloid nanowires. Nanowires differ from nanorods in that they have a larger length to width aspect ratio and a degree in flexibility not exhibited by nanorods. Non-limiting examples of metals or metalloids that may form the nanowires include gold, platinum, titanium, rhodium, indium, I copper, iron, palladium, gallium, germanium, tin, lead, tungsten, niobium, molybdenum, silver, nickel, cobalt, potassium, sodium, mixtures and alloys thereof. [031 ] In yet another embodiment, the nanostructured material comprises nano-wires or nano-threads of diamond, plastic, metal, ceramics, including glass. [032] The nanostructure material may comprise a three dimensional structure of one or more of the previously defined materials, such as one or more of the following: nanotubes, nanowires, nanorods, buckyballs (and/or diamond and fullerene compounds), and biological moieties. In one embodiment, the three-dimensional structure comprises a combination of carbon nanotubes, nanowires, and nanorods. [033] In addition, the three-dimensional structure may optionally comprise at least one support material chosen from polymers, ceramics, and metals. The polymers, ceramics, and metals used as support material may be in any useful form, including fibers, beads, particles, wires, sheets, foils, and combinations thereof. [034] Typical polymers that may be used as a support material include single or multi-component polymers. The single or multi-component polymers may be chosen from nylon, polyurethane, acrylic, methacrylic, polycarbonate, epoxy, silicone rubbers, natural rubbers, synthetic rubbers, vulcanized rubbers, polystyrene, aramid, polyethylene, ultra-high-molecular weight polyethylene, high-density polyethylene (HDPE), low-density polyethylene (LDPE), poly(p-fenyl-2, 6-benzobisoxazol), polypropylene, polychloroprene, polyimide, polyamide, polyacrylonitrile, polyhydroaminoester, polyester (polyethylene terephthalate), polybutylene terephthalate, poly-paraphylene terephtalamide, polyester ester ketene, viton fluoroelastomer, polytetrafluoroethylene, and polyvinylchloride. [035] Typical ceramics that may be used as a support material include boron carbide, boron nitride, boron oxide, boron phosphate, beryllium oxide, spinel, garnet, lanthanum fluoride, calcium fluoride, silicon carbide, carbon and its allotropes, silicon oxide, glass, quartz, aluminum oxide, aluminum nitride, zirconium oxide, zirconium carbide, zirconium boride, zirconium nitrite, hafnium boride, thorium oxide, yttrium oxide, magnesium oxide, phosphorus oxide, cordierite, mullite, silicon nitride, ferrite, sapphire, steatite, titanium carbide, titanium nitride, titanium boride, and combinations thereof. [036] Typical metals that may be used as a support material include aluminum, boron, copper, cobalt, gold, platinum, silicon, steel, titanium, rhodium, indium, iron, palladium, germanium, tin, lead, tungsten, niobium, molybdenum, nickel, silver, zirconium, yttrium, and alloys thereof. [037] In one non-limiting embodiment, the nanostructure material comprises a three dimensional structure of one or more carbon nanotubes, nanowires, nanorods, that are fused by irradiative, electrical, chemical, thermal, or mechanical processing, either independently or in conjunction with one another. [038] For example, thermal processing of the three dimensional structure may be carried out in an oven at a temperature below the melting point of the support material, if present. [039] Examples of typical irradiative processing includes E-beam irradiation, Ultra Violet radiation, X-ray, Plasma, or other ionizing radiation. [040] Examples of typical chemical processing includes treating the carbon nanotubes with at least one chemical chosen from acids, bases, carboxyls, peroxides, and amines for a time sufficient to facilitate fusion of the carbon nanotubes with one another. Alternatively, chemical processing may comprise photochemical bonding for a time sufficient to obtain chemical cross inking. [041] As used herein, "cross linking" means that a chemical bond is formed between two or more nanotubes within the carbon nanotube nanostructured material. [042] According to one aspect of the disclosure, there is provided a method of making a metal coated carbon nanotube mesh comprising: [043] dissolving a metal salt in an aqueous solution; [044] contacting the carbon nanotube mesh with the aqueous solution for a time sufficient to form an intermediate coating of metal salt on the carbon nanotube mesh; and [045] heating the coated carbon nanotube mesh to a temperature up to 300°C for a time sufficient to substantially remove the salt from the metal salt, thereby leaving a metal coating on the carbon nanotube mesh. [046] In this embodiment, the metal salt is typically chosen from a chloride, bromide, nitrate, chlorate, chlorite, sulfate, and sulfite of gold, platinum, titanium, rhodium, indium, copper, iron, palladium, gallium, germanium, tin, lead, tungsten, niobium, molybdenum, silver, nickel, cobalt, potassium, and sodium, and mixtures thereof. [047] Particle size is determined by a number distribution, e.g., by the number of particles having a particular size. The method is typically measured by microscopic techniques, such as by a calibrated optical microscope, by calibrated polystyrene beads and by calibrated scanning force microscope or scanning electron microscope or scanning tunneling microscope and scanning electron microscope. Methods of measuring particles of the sizes described herein are taught in Walter C. McCrone's et al., The Particle Atlas, (An encyclopedia of techniques for small particle identification), Vol. I, Principles and Techniques, Ed. Two (Ann Arbor Science Pub.), which is herein incorporated by reference. [048] In one non-limiting example, a carbon nanotube mesh can be coated with gold using an aqueous solution of gold chloride. In this example, as the gold chloride condenses on the carbon nanotube mesh, the intermediate layer is formed. The whole structure can then be inserted into an oven at a temperature just below the temperature that gold chloride decomposes (e.g., such as 300° C) to remove the chloride and leaving a gold coating over the carbon nanotube mesh. [049] Tin coated carbon nanotube mesh and silver coated carbon nanomesh can be fabricated using a similar process. For example, a tin chloride aqueous solution and a silver nitrate aqueous solution, respectively, can be used to make the coated nanomesh. [050] Also disclosed herein are coated nanostructured materials made by any one or any combination of the above-described processes. [051] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention.

[052] Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method of making a metal or metalloid coated nanostructured material comprising: dissolving a metal or metalloid containing salt in a liquid medium to form a solution; contacting the nanostructured material with the solution for a time sufficient to form an intermediate coating on the nanostructured material; and subjecting the intermediate coated nanostructured material to at least one process to decompose the salt component of the intermediate layer, thereby leaving a metal or metalloid coating on the nanostructured material.

2. The method of claim 1 , where the metal or metalloid comprises at least material chosen from a lanthanide metal, and an actinide metal, hafnium, zirconium, gold, platinum, titanium, rhodium, indium, copper, iron, palladium, gallium, germanium, tin, lead, tungsten, niobium, molybdenum, silver, nickel, cobalt, potassium, sodium, mixtures thereof, and alloys thereof.

3. The method of claim 2, where the metal or metalloid comprises at least one anion chosen from chlorides, bromides, nitrates, chlorates, chlorites, sulfates, and sulfites.

4. The method of claim 1 , wherein the at least one process to decompose the salt comprises a thermal treatment process at or below the decomposition temperature of the intermediate coating.

5. The method of claim 1 , further comprising heating the metal or metalloid coated nanostructured material to a temperature ranging from 200°C to 500°C.

6. The method of claim 5, further comprising heating the metal or metalloid coated nanostructured material to a temperature ranging from 250° to 350°C.

7. The method of claim 1 , wherein the nanostructured material comprises carbon nanotubes.

8. The method of claim 7, wherein the carbon nanotubes are single-walled, multi-walled, nanoscrolled or combinations thereof.

9. The method of claim 8, wherein the carbon nanotubes have a morphology chosen from nanohorns, cylinders, nanospirals, dendrites, spider nanotube structures, Y-junction nanotubes, nanorods, and bamboo morphology.

10. The method of claim 1 , wherein the nanostructured material comprises metallic oxide nanorods.

11. The method of claim 10, wherein the metallic oxide comprises at least one chosen from copper oxide, magnesium oxide, silicon oxide, gold oxide, silver oxide, titanium oxide, and ferric oxide.

12. The method of claim 1 , wherein the nanostructured material comprises metal or metalloid nanowires.

13. The method of claim 12, wherein the metal or metalloid nanowires comprise a lanthanide metal an actinide metal, hafnium, zirconium, gold, platinum, titanium, rhodium, indium, copper, iron, palladium, gallium, germanium, tin, lead, tungsten, niobium, molybdenum, silver, nickel, cobalt, potassium, sodium, mixtures thereof, and alloys thereof.

14. The method of claim 1 , wherein the nanostructure material comprises nanowires and nanothreads of diamond, plastic, metal, glass, and mixtures thereof.

15. The method of claim 1 , wherein the nanostructure material comprises a three dimensional structure of one or more carbon nanotubes, nanowires, nanorods.

16. The method of claim 15, wherein the three-dimensional structure further comprises at least one support material chosen from polymers, ceramics, and metals.

17. The method of claim 6, wherein the polymers are chosen from single or multi-component polymers.

18. The method of claim 17, wherein the single or multi-component polymers are chosen from nylon, polyurethane, acrylic, methacrylic, polycarbonate, epoxy, silicone rubbers, natural rubbers, synthetic rubbers, vulcanized rubbers, polystyrene, aramid, polyethylene, ultra-high-molecular weight polyethylene, high-density polyethylene (HDPE), low-density polyethylene (LDPE), poly(p-fenyl-2, 6-benzobisoxazol), polypropylene, polychloroprene, polyimide, polyamide, polyacrylonitrile, polyhydroaminoester, polyester (polyethylene terephthalate), polybutylene terephthalate, poly- paraphylene terephtalamide, polyester ester ketene, viton fluoroelastomer, polytetrafluoroethylene, and polyvinylchloride.

19. The method of claim 16, wherein the ceramics are chosen from at least one of the following: boron carbide, boron nitride, boron oxide, boron phosphate, beryllium oxide, spinel, garnet, lanthanum fluoride, calcium fluoride, silicon carbide, carbon and its allotropes, silicon oxide, glass, quartz, aluminum oxide, aluminum nitride, zirconium oxide, zirconium carbide, zirconium boride, zirconium nitrite, hafnium boride, thorium oxide, yttrium oxide, magnesium oxide, phosphorus oxide, cordierite, mullite, silicon nitride, ferrite, sapphire, steatite, titanium carbide, titanium nitride, titanium boride, and combinations thereof.

20. The method of claim 16, wherein the metals are chosen from at least one of the following: aluminum, boron, copper, cobalt, gold, platinum, silicon, steel, titanium, rhodium, indium, iron, palladium, germanium, tin, lead, tungsten, niobium, molybdenum, nickel, silver, zirconium, yttrium, and alloys thereof.

21. The method of claim 1 , wherein the liquid medium comprises water, organic solvents, acids, or bases.

22. The method of claim 21 , wherein the organic solvents comprise ethanol, isopropanol, methanol, orxylene.

23. The method of claim 1 , wherein the nanostructure material is further treated by at least one process chosen from irradiative, electrical, chemical, thermal, or mechanical processing, either independently or in conjunction with one another, either prior to or after coating.

24. The method of claim 23, wherein the irradiative processing comprises E-beam irradiation, Ultra Violet radiation, X-ray, Plasma, or other ionizing radiation.

25. The method of claim 23, wherein the chemical processing comprises treating the carbon nanotubes with at least one chemical chosen from acids, bases, carboxyls, peroxides, and amines.

26. The method of claim 25, wherein said acids include phosphoric acid, nitric acid, and sulfuric acid.

27. The method of claim 23, wherein the chemical processing comprises photochemical bonding for a time sufficient to obtain chemical cross linking of.

28. A method of making a metal coated carbon nanotube mesh comprising: dissolving a metal salt in an aqueous solution; contacting the carbon nanotube mesh with the aqueous solution for a time sufficient to form an intermediate coating of metal salt on the carbon nanotube mesh; and heating the coated carbon nanotube mesh to a temperature up to 300°C for a time sufficient to substantially remove the salt from the metal salt, thereby leaving a metal coating on the carbon nanotube mesh.

29. The method of claim 28, wherein the metal salt is chosen from a chloride, bromide, nitrate, chlorate, chlorite, sulfate, and sulfite of gold, platinum, titanium, rhodium, indium, copper, iron, palladium, gallium, germanium, tin, lead, tungsten, niobium, molybdenum, silver, nickel, cobalt, potassium, and sodium, and mixtures thereof.

30. The method of claim 1 , wherein the time sufficient to form an intermediate coating ranges is less than 48 hours.

31. The method of claim 30, wherein the time sufficient to form an intermediate coating ranges from greater than 1 second to 12 hours.

32. The method of claim 30, wherein the time sufficient to form an intermediate coating ranges from greater than 1 second to 1 hour.

33. A metal or metalloid coated nanostructured material made by a method comprising: dissolving a metal or metalloid containing salt in a liquid medium to form a solution; contacting the nanostructured material with the solution for a time sufficient to form an intermediate coating on the nanostructured material; and subjecting the intermediate coated nanostructured material to at least one process to decompose the salt, thereby leaving a metal or metalloid coating on the nanostructured material.

34. The metal or metalloid coated nanostructured material of claim 33, wherein the metal salt is chosen from a chloride, bromide, nitrate, chlorate, chlorite, sulfate, and sulfite of gold, platinum, titanium, rhodium, indium, copper, iron, palladium, gallium, germanium, tin, lead, tungsten, niobium, molybdenum, silver, nickel, cobalt, potassium, and sodium, and mixtures thereof.