WO2007117603A2

WO2007117603A2 - Nanofilm compositions and methods of manufacture and use thereof

Info

Publication number: WO2007117603A2
Application number: PCT/US2007/008585
Authority: WO
Inventors: David E. Reisner; Cynthia Kuper; Xinqing Ma; T. Danny Xiao
Original assignee: Versamat Llc
Priority date: 2006-04-07
Filing date: 2007-04-06
Publication date: 2007-10-18
Also published as: WO2007117603A3

Abstract

The invention encompasses compositions comprising a nanofilm, for example, a nanofilm of titanium nitride on a article of jewelry, that can improve, for example, engineered thickness and color to match the original color of a jewel while providing significantly improved durability such as scratch resistance and anti-fading of color and engineered thickness and color to create more colors for the jewels for customer satisfaction to provide significantly improved durability such as scratch resistance.

Description

NANOFILM COMPOSITIONS AND METHODS OF MANUFACTURE AND USE THEREOF

I. FIELD OF THE INVENTION

[0001] The invention encompasses compositions comprising a nanofilm, for example, a nanofilm of titanium nitride on a article of jewelry, that can improve, for example, engineered thickness and color to match the original color of a jewel while providing significantly improved durability such as scratch resistance and anti-fading of color and engineered thickness and color to create more colors for the jewels for customer satisfaction to provide significantly improved durability such as scratch resistance. In particular, the invention encompasses, a TiN film that can be engineered to match a gold color exactly, or since its color is so close to the gold, or a nanofilm that will be transparent, while providing superior scratch and corrosion resistance. The nanofilm for jewelry will improve the existing products by enhancing surface properties such as brightness and self-clean function.

II. BACKGROUND OF THE INVENTION

[0002] To date, there is not any literature available in which a thin layer of nanofilm can be used for jewelry to improve scratch resistance while providing the same appearance of gold and enhancing the color of the jewelry and provide scratch resistance simultaneously. TiN has been used to increase the hardness and scratch resistance of tools such as coating a layer of TiN on top of WC/Co machine tools, or coating TiN on top of tool steels (e.g., drill bits). TiN has also been used in the household or other decorations to give gold appearance. In a related prior art, Thomas Klein, et al, in a patent (DE 4320072), described a process for coating ceramic surface using a liquid solution process followed by heat treatment to make more colorful ceramic surfaces. The process comprises treating the surfaces with an aqueous gold salt solution (Au concentration 0.1-10 wt.%), evaporating the water, and thermally decomposing the Au salts at 300-1400°. The Au salt is AuCU or HAuCL4, and the penetration is approx. 0.502 mm, thus permitting machining of the surfaces. In a related technology, the coating of amorphous angstrom layers of transparent TiN has also been described in an US patent (us patent 6270831) using sputtering techniques. This film, since is amorphous in natures, has limitations compared to a functional nanostructured or nanocrystalline TiN films.

[0003] In today's technology, since gold is soft, alloy elements are added to it in order to increase its scratch resistance. However, this process depreciates the value of the gold. A nanofilm coated gold not only retains the same value of the gold but also provides required durability of the jeweliy. This ceramic πanofilm can later on be removed by etching or light polishing if necessary.

[0004] Physical vapor deposition of TiN, today, is a commercialized technology for coating tools, and decorative components, and those are hard and thick coatings/or films. To date, there is no related art that teaches of coating nanostructured TiN transparent films for jewelry applications. m. SUMMARY OF THE INVENTION

[0005] The invention encompasses jewelry compositions comprising a jewelry substrate and a nanofϊlm coating. Particularly, the invention encompasses jewelry compositions, wherein the jewelry substrate is comprised of precious metal, or an alloy thereof and the nanofϊlm coating layer is titanium nitride or an alloy of titanium nitride.

[0006] In another embodiment, the invention encompasses methods for producing a nanofilm coated jewelry composition comprising coating a jewelry substrate with a deposited layer of titanium nitride or an alloy thereof comprising depositing said layer using physical vapor deposition ("PVD"), chemical vapor deposition ("CVD"), sol-gel, or thermal spray.

IV. DETAILED DESCRIPTION OF THE INVENTION

A. ^■> Overview

[0007] The invention encompasses jewelry compositions comprising a jewelry substrate and a nanofilm coating.

[0008] In one embodiment, the invention encompasses jewelry compositions, wherein the jewelry substrate is comprised of precious metal, or an alloy thereof.

[0009] In another embodiment, the invention encompasses jewelry compositions, wherein the precious metal is gold, silver, platinum, or stainless steel, or an alloy thereof. In another embodiment, the invention encompasses jewelry compositions, wherein the precious metal is gold. In another embodiment, the invention encompasses jewelry compositions, wherein the precious metal is silver. In another embodiment, the invention encompasses jewelry compositions, wherein the precious metal is platinum. In another embodiment, the invention encompasses jewelry compositions, wherein the precious metal is stainless steel. [0010] In another embodiment, the invention encompasses jewelry compositions, wherein the nanofilm coating is titanium nitride. In another embodiment, the invention encompasses jewelry compositions, wherein the nanofilm coating is an alloy of titanium nitride. In another embodiment, the invention encompasses jewelry compositions, wherein the nanofilm coating provides corrosion resistance. In another embodiment, the invention encompasses jewelry compositions, wherein the nanofilm coating provides scratch resistance. In another embodiment, the invention encompasses jewelry compositions, wherein the nanofilm coating provides a desired color to the jewelry composition. In an illustrative embodiment, the jewelry substrate is gold and the nanofilm coating is titanium nitride. In another illustrative embodiment, the jewelry substrate is gold and the nanofilm coating is an alloy of titanium nitride. In another illustrative embodiment, the jewelry substrate is silver and the nanofilm coating is titanium nitride. In another illustrative embodiment, the jewelry substrate is silver and the nanofilm coating is an alloy of titanium nitride. In another illustrative embodiment, the jewelry substrate is platinum and the nanofilm coating is titanium nitride. In another illustrative embodiment, the jewelry substrate is platinum and the nanofilm coating is an alloy of titanium nitride. In another illustrative embodiment, the jewelry substrate is stainless steel and the nanofilm coating is titanium nitride. In another illustrative embodiment, the jewelry substrate is stainless steel and the nanofilm coating is an alloy of titanium nitride. [0011] In another embodiment, the invention encompasses a method for producing a nanofilm coated jewelry composition comprising coating a jewelry substrate with a deposited layer of titanium nitride or an alloy thereof. In another embodiment, the deposited layer is deposited by CVD. In another embodiment, the deposited layer is deposited by sol-gel. In another embodiment, the deposited layer is deposited by PVD. In another embodiment, the deposited layer is deposited by thermal spray. In another embodiment, the deposited layer is deposited by plasma assisted CVD. In another embodiment, the deposited layer is deposited by plasma assisted PVD. Another embodiment, comprises a post coating treatment. Another embodiment comprises polishing.

B. Compositions of the Invention

[0012] The present invention encompasses compositions, preferably jewelry compositions comprising a jewelry substrate and a nanofilm coating, as well as, any particular materials that can benefit from the coating in their normal use. The jewelry compositions include those which can benefit from a wear resistant coating, corrosion resistance, scratch resistance, or a desired color.

[0013] As used herein, and unless otherwise indicated, the term "nanofilm" refers to a nanostructured film having a physical structure, with size of the structure (here defined as particle size) being 1-300 nanometers, or being smaller than the wavelength of the visible light. When the structure is smaller than the wavelength of the visible light, the structure will then be transparent. The nanostructυred film (or each individual particle) can be either amorphous or crystalline. This physical dimension can be observed by a high resolution transmission electron microscophy. When particles are being crystalline, this physical dimension can be measured using transmission electron microscopy combined with micro-micro diffraction patterns, or by x-ray analysis, where the dimension, d, of the grain can be derived using a Scherrer equation from x-ray peak broadening:

where λ is the wavelength of the X-ray beam (λ = 0.154 nm for Cu Kccj radiation), θ is the diffraction angle for the peak, W and W₀ are the XRD linewidths for the nanostructured and micrometer sized material of the same composition, respectively. Amorphous material is defined as matters does not posses long-range order of repeated atomic or lattice structure. Crystalline material is defined as matters possess long range order of repeated order of repeated atomic or lattice structure.

[0014] Preferably, the nanofilm coating is a ceramic coating. In the preferred embodiment, the ceramic coating is composed of titanium nitride (TiN), which is applied over the substrate by any appropriate method, such as those discussed herein.

(0015] Advantageously, the nanofilm coating of the present invention can be applied in relatively thin layers to substrates, typically on the order of nanometers. [0016] While the preferred embodiment uses TiN as the ceramic coating, there are other ceramics from the family of ceramics known as transition metal nitrides, which might be used in the present invention. These nanofilm coating materials include titanium nitride, among others. These materials are classified in terms of properties of hardness, corrosion resistance, color and high spectral reflectance (smoothness). What is important to the preferred embodiment of the invention is that the material selected for the nanofilm coating have the desirable characteristics of TiN. It should also be realized that TiN can be used alone or in combination with other materials having desirable characteristics. These other materials might also include other conductive (transitional metal nitrides) or non-conductive ceramics. [0017J Titanium nitride is a ceramic whose crystalline form is well known for its advantageous properties of hardness, wear resistance, inertness, diffusion resistance, corrosion resistance and thermal stability in such applications where a low friction interface is needed to protect moving parts from wear.

[0018] As TiN can be applied at thicknesses in the nanometer or even angstrom level, the jewelry substrate coated part's dimensions are not materially affected. Furthermore, TiN exhibits a very high load carrying capacity and toughness. TiN also has excellent adhesion qualities so that it does not spall, even under plastic deformation of the surface. The high toughness and excellent adhesion properties are due to a metallurgical bonding between some substrates and the TiN coating. In particular, the TiN coating bonds well with other metals such as steel and stainless steel.

[0019] The nanofilm coating of the invention advantageously has high hardness and low friction coefficients. TiN will not wear off or wear away quickly from repeated use to leave a substrate exposed. Consequently, the compositions of the present invention have a longer useful lifespan.

10020] Nanostructured Ceramic and nitride-coatings for the application onto metal and mineralogical substrates such that the coatings consist of grains having the dimensions of from about 10 to about 3000 angstoms and exhibit X-ray diffraction such that when placed in an x-ray diffractometer a spectra is obtained. (And an amorphous coating will have no spectra).

These coatings may have long range, bulk, order and thus be polycrystalline. They may have neither short range nor long range order but still consists of grains or particles having

10-3000A dimensions comprising Ihe bulk coating and be nanostructured.

[0021] The nanostructured coating may have a thickness as to be optically transparent, typically about lnm to about l.OOOnm. These coatings may be comprised of ceramics and nitrides and not have a nanostructure but have a thickness of about 1 nm up to 1 ,000nm and be amorphous.

[0022] The coatings may be applied by painting on a substrate such the nanoparticulate ceramic or nitride is mixed with a polymer matrix and in liquid form until otherwise treated.

This method would yield a thick amorphous or crystalline coating ( for example 10 microns to about lmm)

[0023] The coatings, independent of their thickness and method of deposition, will be hard.

Hardness is a property measured in the simplest of ways using a Moh's or Vicker's hardness scale. The fundamental of the Moh's scale is the scratch test. The theory behind the scratch test is that a material softer than another can not scratch that material. In order to impose a surface defect, such as scratch the "scratching material" must be harder than the substrate on which it is impingent. The relative hardness is then related by the Moh's scale Talc is assigned a Moh's hardness of 1, being the softest material and diamond a hardness of 10, being the hardest material. All other materials fall somewhere in between. In this manner through the creation of hard coatings we create scratch proof compounds, otherwise not seen.

[0024] Gold is a soft material compared to most minerals. After being coated with a nanostructured hard coating the coated gold materials will be impervious to scratches from other materials as these ceramics and nitrides at film thickness levels of about 1 - 1 OOOnm have a Moh's hardness of X. producing precious metals commonly used in jewelry, such as gold, silver and platinum with scratch resistance benefits the industry by preserving the value of the precious metal. Due to the hard protective coatings these metals no longer need to undergo polishing, a technique that removes a surface layer of the metal to restore the original luster and pristine condition. Continuous polish diminishes the weight of the metal over time, thus reducing its value.

[0025] When examining the potential applications of the nanofϊlm coating of the present invention, jewelry has the potential benefits of improved wear, scratch resistance, corrosion resistance, application of desired color, and combinations thereof.

[0026] The nanofilm coatings of the present invention provides many unique advantages over the prior art. For example, the TiN coating does not significantly wear off, thereby providing improved reliability and durability. Advantageously, the TiN coating can also be repeatedly cleaned so that the device, which is coated can be reused many times. Furthermore, many different sterilization techniques can be used without damaging the TiN coating. [0027] While the invention teaches that the substrate can be gold, silver, platinum or stainless steel, other materials can also be used. These other materials might also be conductive metals such as titanium, but can also include non-conductive materials such as plastics.

C. Methods of Synthesis of the Nanofilm Coatings

1. Chemical Vapor Deposition

[0028] In one embodiment, the nanofilm is applied onto an article of jewelry using chemical vapor deposition ("CVD"). According to the present invention, titanium nitride films are deposited on jewelry substrates or other substrates using a chemical vapor deposition reaction. In this reaction, titanium tetrachloride (TiCl₄) is reacted with ammonia gas in a diluent to form titanium nitride on the surface of the substrate. For purposes of the present invention, the substrate will include precious metals, for example, gold, platinum, silver and gemstones. The method which is generally used to deposit a TiN film which may be from 5-500 run thick. The reaction temperature in the present invention will be less than 550⁰C, generally about 500⁰C to about 350⁰C and preferably about 450⁰C.

J0029] In an illustrative embodiment, suitable reactor for use in the present invention is a perpendicular flow reactor, where the flow of reactant gases are pumped from above the substrate directly down upon the substrate perpendicular to the plane of the substrate, or a laminar flow reactor where the gas passes parallel to the plane of the substrate. [0030] With either type of reactor, the reaction rate will vary depending upon the reaction temperature. When the reaction temperature is very high the deposition rate is dependent upon the ability of the reactants to reach the surface of the substrate. This is also referred to as the mass transfer area.

[0031] The reaction itself employs three gases: titanium tetrachloride, ammonia and a diluent. The diluent will be an inert gas such as helium, argon, hydrogen or nitrogen. Generally, equimolar portions of titanium tetrachloride and ammonia are used in the present invention and generally a 10-fold excess of diluent. The total gas flow rate should be from 1 slm to about 50 slm and the inlet gas temperature should be about 150⁰C.

[0032] The preferred reactor for the present invention is a rotating disk reactor. The rotating disk reactor has a rotating susceptor, which supports a patterned wafer substrate. The susceptor and thus the substrate are rotated in a clockwise direction by means of a motor, which drives shaft affixed to susceptor or support. Susceptor is further provided with a temperature controlling device to heat the wafer to the desired temperature. The reaction chamber is provided with an exhaust port through which the reaction gas by-products and unreacted starting materials are exhausted. The chamber itself is pressure controlled to maintain a constant and desired reaction pressure. Generally this will be from 1 to 100 Torr. [0033] The reacting gases themselves are fed to a reservoir near the top of the reaction chamber where they are mixed. The mixed reactant gases flow downwardly through a shower head dispenser toward the wafer, which is being rotated on the susceptor.

[0034] As discussed, the invention utilizes a reaction between a metal-bearing compound like titanium tetrachloride and a reducing gas like ammonia. Each of the metal-bearing compound and the reducing gas are contained in a hot inert carrier gas, and reacted in immediate proximity to a hotter glass surface. When the temperature of the glass surface is above 400⁰C Preferably at temperatures of about 600⁰C. or above deposition rates are fastest and quality is optimum. Of course, many jewelry substrates will soften and have practical procesing limit of about 700 ⁰C. A preferred combination of reactants, titanium tetrachloride and ammonia, react rapidly to form a strongly adherent film whose composition is primarily titanium nitride, TiN, with some chlorine also included in the film. The deposition atmosphere should be kept free of oxygen and water vapor, or the deposited film will consist primarily of titanium oxide, rather than the desired titanium nitride. Very small amounts of oxygen and moisture seem to be tolerated where an excess of ammonia is used. While titanium dioxide does increase the reflection from the glass surface, it does not absorb light nearly as much as titanium nitride does. [0035] The films are smooth and mirror-like, and free of haze. Thin films, e.g. those of about 200 angstroms, are silvery in reflected color, while thicker films are golden, pale blue, gray, black, reddish or brown in color as the thickness builds towards 0.1 microns. The transmitted colors are neutral, gray, light yellow, pale green, pale blue or brown. [0036] The mechanical properties of the films are good. Abrasion and scratch-resistance are comparable or better than commercially available coatings. The chemical resistance of the films is excellent, and they resist water, soaps, bases and acids, except for hydrofluoric acid, which etches both the films and the glass.

2. Plasma Enhanced Chemical Vapor Deposition

[0037] According to another embodiment of the invention, a titanium nitride nanofilm is formed on a jewelry substrate by plasma-enhanced chemical vapor deposition of titanium nitride formed by reacting titanium tetrachloride, ammonia and a diluent gas. [0038] The apparatus includes an RF showerhead/electrode biased by an RF feedline assembly. Plasma and reactant gases are pumped through a cylinder assembly to a substrate on susceptor. Apparatus includes a housing having a housing cover and includes an RF supply assembly, a heat pipe assembly with cooling jacket and associated fluid supply lines and a gas distributor cover with a sealing assembly. A cylinder made of an insulating material such as quartz surrounds the RF feed line assembly 24.

[0039] Cylinder is preferably formulated out of a high quality quartz such as Quartz T08-E, available from Hereaus Amersil. Quartz cylinder is supported by a showerhead/electrode, made of a conductive metal such as Nickel-200. An annular bore is formed within housing cover to receive an upper end of cylinder. 0-rings at the interface between stepped bore and cylinder form a seal at the interface. At the lower end of cylinder, an annular notch in cylinder receives a peripheral edge of the showerhead/electrode. The notch of cylinder rests upon the peripheral edge of showerhead/electrode. Showerhead/electrode includes a stem attached to RF line tubing, such as by a weld at, to form a unitary RF line. RF line is fπctionally held and supported at its top end by collar. The RF line, in turn, supports showerhead/electrode above susceptor. Showerhead/electrode, in turn, supports the cylinder within the cylinder assembly by abutting against cylinder at notch and holding it in bore. The interface between showerhead/electrode peripheral edge and cylinder notch is sealed by a compressed O-ring which is compressed between shelf 48 and a similar corresponding annular notch formed in peripheral edge of the showerhead/electrode. A plurality of gas halos or rings introduce reactant gases into cylinder. [0040] Generally, the substrate is spaced from about 0.25 to 3 inches from the showerhead/electrode. The distance should be such that active ions strike the substrate. [0041] In general, reaction gases are introduced through rings. These gases pass through cylinder and a plasma is generated as the gases pass through the showerhead/electrode. The plasma will strike the substrate.

[0042] This Apparatus can be used to deposit titanium nitride over a variety of different jewelry substrates.

[0043] In depositing the titanium nitride film, a plasma of reactant gases is created using apparatus at showerhead. The reactant gases include titanium tetrachloride, ammonia and a diluent. Although diluents such as hydrogen, helium and argon can be employed, nitrogen is preferred. These are combined together and introduced into cylinder. [0044] Cylinder is maintained at a pressure from about 0.5 to about 20 torr with about 5 ton- being preferred. The substrate is maintained at a temperature of about 400⁰C to about 500⁰C. with about 450⁰C. being preferred. The substrate is generally heated by providing heat from the support 30. The support itself is preferably rotated at about 100 rpm or more simply to provide for more even distribution. However, the substrate need not be rotated at all. [0045] The concentration of the gases is controlled by flow rate. Generally, the titanium tetrachloride will be introduced at a flow rate of about 1 to about 40 seem, with about 10 seem being preferred. The partial pressure of the TiCU must be sufficiently low to form TiN. If the TiC14 partial pressure becomes too high, a black powder is formed which is not TiN. When the total pressure is 5 torr, the partial pressure of TiC14 should be less than 0.02 torr, preferably 0.01 torrto O.OOl torr. At the lower pressures (i.e., 0.0001 torr), the reaction rate is significantly reduced and the step coverage can be unacceptable. As the total pressure increases from 5 torr, the partial pressure of TiCL_t can be increased accordingly. For TiN to be useful, the film on the substrate should be adherent and continuous. Films of this nature are gold in color. The black powder that forms is nonadherent (it can be wiped off readily). Therefore, the upper limits of the partial pressure of TiCU is that partial pressure at which a black powder begins to form on the substrate. This, of course, can vary depending on the total pressure. Generally, the molar ratio of ammonia to TiCU will be from 2: 1 (ammonia to TiCU) up to 100: 1. At this higher rate, the reaction rate will be very low. Preferably, the ratio will be about 10:1. [0046] Generally the ratio of diluent to ammonia will range from about 10:1 up to about 10,000: 1. This ratio, however, does not significantly affect the deposition. 3. Physical Vapor Deposition

[0047] Another embodiment of the invention encompasses coating a jewelry substrate with a nanofilm using physical vapor deposition. In this embodiment a jewelry substrate is placed within a chamber, evacuated and then filled with an inert gas, such as argon. The inert gas is partially ionized and excited in the plasma as previously described. The substrate is then cleaned by heating and ion-etching. The substrate may be heated by any suitable means known in the art, such as electron bombardment. In electron bombardment, a positive potential is placed on the substrate within the chamber to attract electrons from the gaseous plasma. Under a vacuum of approximately 10^'3 torr, the substrate is heated by the electrons striking the substrate surface thereby removing various oxides from the substrate surface. In depositing crystalline films, the substrates are preferably heated to at least a temperature of approximately 400 ⁰C. It should be noted that although there is also a charge buildup during electron bombardment, the electron current density between the substrate and plasma is high enough to overcome this buildup and thus allow surface heating by electron bombardment. The substrate is then subjected to ion-etching wherein the polarity of the substrate is reversed to a negative potential to attract heavy argon ions typically used for ion-etching from the-gaseous plasma to the substrate to further remove surface contaminants such as grease, dust and the like. Applicants have found, depending upon temperature, surface area of the insert to be cleaned, and degree of contamination, a ceramic substrate may be cleaned in a vacuum after a period ranging from approximately four hours to six hours. For example, the higher the heating temperature the shorter the period of cleaning required to achieve a substrate substantially free of contaminants.

[0048] A layer of titanium nitride is deposited upon the first layer. The layer of titanium nitride is deposited by introducing nitrogen gas into the vacuum chamber to react with the titanium present to form titanium nitride, or ablation of a TiN target to generate TiN vapor species followed by deposition. The negative bias of the titanium coated substrate causes a resultant glow discharge to increase the kinetic energy of the depositing titanium nitride material thereby resulting in the deposition of a coating of titanium nitride of variable thickness. As a result of the present invention, excellent coating adhesion and dense coating structures may be obtained for a ceramic substrate.

4. Sol-Gel

[0049] Another embodiment of the invention encompasses coating a jewelry substrate with a nanofilm using sol-gel process. In this embodiment, a sol-gel coating for a jewelry substrate is provided. The term "sol-gel" is a contraction of the terms "solution" and "gelation" and refers to materials undergoing a series of reactions, including hydrolyzation and condensation. Typically, a metal, such as a metal alkoxide or metal salt, hydrolyzes to form a metal hydroxide. The metal hydroxides then condense in solution to form a hybrid organic/inorganic polymer. Under certain conditions, these polymers condense to form colloidal particles or a network gel. The ratio of inorganic to organic in the polymer matrix of the sol-gel coating may be controlled to maximize performance for a particular application. For instance, increasing the amount of organic groups may improve the durability and flexibility of a sol-gel coating. Conversely, increasing the organic fraction in tile coating may also make the coating more susceptible to degradation and yellowing, particularly in a space environment. The photovoltaic effect of a typical sol-gel coated solar cell may be impaired if the transparency of the coating is adversely affected by degradation and yellowing. In a space and terrestrial environments, a balance between the processability of the coating and tie amount of resistance to the damage of the environment should be met.

[0050] Typically, a sol-gel coating is deposited on the exterior surfaces of the jewelry substrate such as the collector surfaces. For example, a sol-gel coating may be deposited on the radiator surface of the jewelry substrate. The formulation of the sol-gel coating is such that it adheres to the exterior surface of the jewelry substrate. The sol-gel coating may range from about 1 to about 10.0 Angstroms thick. A sol-gel coatings in accordance with the present invention have greater than 90% transmittance over the wavelength range of about 350 nanometers (hereafter "nm") to about 1600 run, which converts to wavelength values of about 0.35 μm to about 1.6 μm, respectively.

[0051] The sol-gel coatings of the present invention are homogeneous mixtures of a solvent, an organosilane, alkoxide, and a catalyst which are processed to form a coating suitable for application on a solar cell. The term "homogeneous" as used herein refers to a form which has a uniform or similar structure throughout and is given the ordinary meaning know to persons skilled in the art. The sol-gel coatings may be deposited on a surface of a solar cell, such as a collector surface. The surface of the solar cell to which the sol-gel coating is applied is typically comprised of a semi-conductive material. The term "semi-conductive" as used herein refers to those materials which may become electrically conductive when supplied with energy, such as heat or light, but which may function as an insulator at low temperatures, and is given the ordinary meaning known to persons skilled in the art. However, the coating may be applied to other substrates which include metallic alloys, such as aluminum, 2024, 2219 and 6061, titanium alloys, such as Ti-6A1-4V and composite substrates, such as graphite-epoxy, graphite-cyanate ester.

[0052] In another embodiment, the sol-gel coating of the present invention includes a surfactant, which may enhance the wettability of the coating and improve adhesion of the coating to the surfaces of the solar cells. Often, an aqueous sol-gel solution may wet a surface unevenly and sag which results in thickness variations on the substrate. Including surfactant in the composition of the sot-gel provides a more evenly deposited sol-gel coating.

[0053] In a further embodiment, the sol-gel coating may include indium tin oxide (ITO). The

(ITO) can dissipate static charge that can build up in the protective coating. Often, protective coatings are grounded to prevent discharge that could damage the solar cells. The addition of

ITO to dope the coatings is useful in maintaining the sol-gel coatings and preserving the solar cells.

[0054] In an additional embodiment, the sol-gel coating is comprised of cerium, usually in a water-soluble form. The addition of cerium may absorb a portion of the ultraviolet radiation which can be harmful to the solar cell and/or the sol-gel coating. Suitable forms of cerium include cerium oxide, cerium acetate, cerium acetylacetonate, cerium 2-ethylhexonate, cerium hydroxide, cerium nitrate, cerium oxalate, cerium stearate, and cerium trifluoroacetylacetonate and mixtures thereof Other suitable forms of cerium will be known to one skilled in the art and may be included in the sol-gel composition.

5. Thermal Spray

[0055] Another embodiment of the invention encompasses coating a jewelry substrate with a nanofϊlm using thermal spray. The electric arc spray process is used to apply such coatings and high purity nitrogen is substituted for air as a propelling gas. A titanium wire is melted and the titanium is nitrided with minimum oxidation between the arc spraying device and the substrate to deposit a titanium nitride coating. The arc spray process can be used without an atmosphere chamber or a furnace or subsequent nitriding of the coating. A particularly effective coating is achieved if the titanium wire is nitrided prior to being used in the electric arc spray device. [0056] The nitrogen used as the propelling (atomizing) gas during the electric arc thermal spray process reacts with droplets of molten titanium detached from the tip of the titanium feed wire to produce the titanium nitrogen compound in flight. As the molten droplets land on the surface of the article being coated they solidify thus forming a hard titanium nitride base coating that protects against wear and corrosion. [0057J Electric arc spraying of a titanium coating utilizing nitrogen as a propelling gas is inexpensive. Furthermore, arc spraying takes minutes rather than hours, leaves no toxic byproducts, and requires a minimal capital investment.

[0058] The arc spray system includes an arc gun, a constant voltage power source, a control console and a wire feed device represented by wire spools. The arc spray gun includes two sets of feed rollers to move separate wires through the gun to the nozzle end where due to electrical current of different polarities (e.g., as shown in the drawing) an arc is struck between the wires. As the wires melt due to the influence of the electrical arc, compressed nitrogen gas is introduced into the arc on as shown by the arrow. The nitrogen gas exists the nozzle, where it causes the molten metal to be broken up into a stream of droplets. The compressed gas, in addition to atomizing the metal and sustaining electric arc, propels the atomized metal (spray stream) toward a substrate such as a conventional Hammermill screen. During aerial traverse of the atomized titanium, reaction with nitrogen forms a titanium nitride compound. [0059] The substrate can be mounted vertically or horizontally and either it or the arc gun can be oscillated to provide a uniform coating over the length of the electrode. [0060] Wire feeders can also include a pair of rollers to help feed the wire from the spools to the gun. The feed rolls in the gun and the wire feeds can either push, pull, or use a combination of both techniques to move the wire through the arc gun.

[0061] A conventional titanium nitride coating placed on the substrate by the thermal arc spray process using titanium wire and nitrogen gas produces coatings of enhanced wear resistance, if the as-received titanium wire was pretreated to increase the nitrogen content the resultant coating was harder and the life of the parts in service was, in many instances, increased. [0062] The titanium wire pre-treatment was developed when it was realized that N2 -sprayed Ti_xN coatings were both nitrogen (N) deficient and prone to in-flight oxidation. There were two additional reasons for wire pretreatment: (1) as-supplied Ti- wires are difficult to feed through arc-spray gun conduits, and a nitride coating on the wires was discovered to lower the wire feed-friction, (2) post-deposition nitrogen annealing of arc-sprayed Ti_xN may not always be possible; some substrates may be sensitive to elevated temperatures and/or an excessively large mismatch may exist between thermal expansion coefficients of the Ti_xN coating and substrate that will damage the coating, (e.g. Ti_xN -coating on st. steel-substrate). [0100) The present invention is not to be limited in scope by the specific embodiments disclosed in the examples which are intended as illustrations of a few aspects of the invention and any embodiments that are functionally equivalent are within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art and are intended to fall within the scope of the appended claims.

[0101] All cited patents, patent applications and publications referred to in this application are herein incorporated by reference in their entirety.

Claims

CLAIMSWhat is claimed is:

1. A jewelry composition comprising a jewelry substrate and a nanofilm coating.

2. The jewelry composition of claim 1 , wherein said jewelry substrate is comprised of precious metal, or an alloy thereof.

3. The jewelry composition of claim 2, wherein said precious metal is gold, silver, platinum, or stainless steel, or an alloy thereof.

4. The jewelry composition of claim 2, wherein said precious metal is gold.

5. The jewelry composition of claim 2, wherein said precious metal is silver.

6. The jewelry composition of claim 2, wherein said precious metal is platinum.

7. The jewelry composition of claim 2, wherein said precious metal is stainless steel.

8. The jewelry composition of claim 1 , wherein the nanofilm coating is titanium nitride.

9. The jewelry composition of claim 1, wherein the nanofilm coating is an alloy of titanium nitride.

10. The jewelry composition of claim 1 , wherein said nanofilm coating provides corrosion resistance.

11. The jewelry composition of claim 1, wherein said nanofilm coating provides scratch resistance.

12. The jewelry composition of claim 1, wherein said nanofilm coating provides a desired color to the jewelry composition.

13. The jewelry composition of claim 1 , wherein the jewelry substrate is gold and the nanofilm coating is titanium nitride.

14. The jewelry composition of claim 1 , wherein the jewelry substrate is gold and the nanofilm coating is an alloy of titanium nitride.

15. The jewelry composition of claim 1 , wherein the jewelry substrate is silver and the nanofilm coating is titanium nitride.

16. The jewelry composition of claim 1 , wherein the jewelry substrate is silver and the nanofilm coating is an alloy of titanium nitride.

17. The jewelry composition of claim 1 , wherein the jewelry substrate is platinum and the nanofilm coating is titanium nitride.

18. The jewelry composition of claim 1, wherein the jewelry substrate is platinum and the nanofilm coating is an alloy of titanium nitride.

19. The jewelry composition of claim 1, wherein the jewelry substrate is stainless steel and the nanofilm coating is titanium nitride.

20. The jewelry composition of claim 1, wherein the jewelry substrate is stainless steel and the nanofilm coating is an alloy of titanium nitride.

21. A method of producing a nanofilm coated jewelry composition comprising coating a jewelry substrate with a deposited layer of titanium nitride or an alloy thereof.

22. The method of claim 21, wherein said deposited layer is deposited by chemical vapor deposition ("CVD").

23. The method of claim 21, wherein said deposited layer is deposited by sol-gel.

24. The method of claim 21 , wherein said deposited layer is deposited by physical vapor deposition ("PVD").

25. The method of claim 21, wherein said deposited layer is deposited by thermal spray.

26. The method of claim 21, wherein said deposited layer is deposited by plasma assisted CVD.

27. The method of claim 21, wherein said deposited layer is deposited by plasma assisted PVD.

28. The method of claim 21, further comprising a post coating treatment.

29. The method of claim 21, further comprising polishing.