Method for providing nanocrystalline diamond coatings on gemstones and other substrates

Abstract

A method to apply nano-crystalline diamond onto a selected substrate, including preparing Nanodiamond slurry of Nanodiamond particles dispersed in a medium. The medium may include a liquid or a sol-gel. The selected substrate is immersed in the Nanodiamond slurry for a predetermined period of time. Then the substrate is removed from the slurry. The substrate is then dried with a flow of inert gas. The substrate is left coated with a coating of the nanodiamond particles that are highly adherently held by van der Waals forces.

Claims

1. A method to apply nano-crystalline diamond onto a selected substrate, comprising preparing a nanodiamond slurry of nanodiamond particles dispersed in a medium; immersing the selected substrate in the nanodiamond slurry for a predetermined period of time; removing the substrate from the slurry; and drying the substrate and nanodiamond slurry that is adherent to the substrate with a flow of inert gas whereby the substrate is left coated with a coating of the nanodiamond particles that are adherently held by van der Waals forces; and selecting the medium in which the nanodiamond particles are dispersed to be a chemically functionalized carrier medium that includes a volatile component and an inorganic oxide, the volatile component being selected to evaporate at ambient room temperature or at elevated temperature and atmospheric pressure to leave behind the inorganic oxide.

2. The method as claimed in claim 1, further comprising performing sonication of the selected substrate during or after immersion in the slurry.

3. The method as claimed in claim 2, further comprising predetermining a duration of the sonication via experimentation for the selected substrate.

4. The method as claimed in claim 1, further comprising rinsing the substrate with solvent prior to drying the substrate with a flow on inert gas.

5. The method as claimed in claim 1, further comprising: placing the selected substrate under vacuum in an ion assisted plasma deposition system; and depositing an optically transparent film of diamond like carbon over the coating of the nanodiamond particles.

6. The method as claimed in claim 1, further comprising: placing the selected substrate under vacuum in an ion assisted plasma deposition system; and depositing an oxide or nitride layer over the coating of the nanodiamond particles.

7. The method as claimed in claim 1, further comprising selecting the medium to be a liquid.

8. The method as claimed in claim 1, further comprising selecting the medium to be a sol-gel medium.

9. The method as claimed in claim 8, further comprising selecting the sol-gel medium to include an organic component that is volatile at below 200 C to facilitate curing by volatilization.

10. The method as claimed in claim 1, further comprising: selecting the selected substrate to have fractures that are open to a substrate surface; and precleaning the substrate with one or more cleaning agents.

11. The method as claimed in claim 10, further comprising selecting the one or more cleaning agents from a group consisting of alcohols, acetone, sulfuric acid, hydrogen peroxide, water and a combination of the foregoing.

12. The method as claimed in claim 10, further comprising: cleaning the substrate with caustics or acids; and rinsing the substrate between cleaning the substrate with the strong caustics or acids.

13. The method as claimed in claim 10, further comprising laser drilling, to facilitate access to the fractures.

14. The method as claimed in claim 1, further comprising placing the selected substrate immersed in the slurry into a pressure chamber that can be maintained at above fifty atmospheres pressure and pressurizing the pressure chamber to above fifty atmospheres pressure.

15. The method as claimed in claim 14, further comprising: removing the selected substrate from the slurry and the pressure chamber; immersing the selected substrate in a solvent; sonicating the selected substrate in the solvent; removing the selected substrate from the solvent; and drying the selected substrate in the flow of the inert gas following removal of the selected substrate from the solvent.

16. The method as claimed in claim 1, further comprising: applying a layer of chemical vapor deposition diamond over the coating of the nanodiamond particles using the coating of nanodiamond particles as a seed layer.

17. The method as claimed in claim 16, further comprising: placing the substrate with coating of the nanodiamond particles in a chamber of a chemical vapor deposition system: evacuating the chamber to below 20 mTorr; and flowing reaction gases into the chamber including methane diluted with hydrogen.

18. The method as claimed in claim 17, further comprising: using cooling systems to maintain a temperature of the gemstone below 750 C.

19. The method as claimed in claim 17, further comprising: applying the layer of chemical vapor deposition diamond to a thickness of 10 to 12 microns to achieve a black colored coating.

20. The method as claimed in claim 1, further comprising: depositing a sub-20 nm layer of titanium, titanium oxide, graphite or silicon carbide over the substrate.

21. A method to apply nano-crystalline diamond onto a selected substrate, comprising preparing a nanodiamond slurry of nanodiamond particles dispersed in a medium; immersing the selected substrate in the nanodiamond slurry for a predetermined period of time; removing the substrate from the slurry; and drying the substrate and nanodiamond slurry that is adherent to the substrate with a flow of inert gas whereby the substrate is left coated with a coating of the nanodiamond particles that are adherently held by van der Waals forces; applying a layer of chemical vapor deposition diamond over the coating of the nanodiamond particles using the coating of nanodiamond particles as a seed layer; placing the substrate with coating of the nanodiamond particles in a chamber of a chemical vapor deposition system: evacuating the chamber to below 20 mTorr; flowing reaction gases into the chamber including methane diluted with hydrogen; selecting the substrate to be a gemstone having a table side and a pavilion side; loading the gemstone onto a flat holder table side down such that the pavilion side of the gemstone is exposed; applying the layer of chemical vapor deposition diamond to a thickness of less than 100 nanometers to the exposed pavilion side; removing the gemstone from the flat holder; reloading the gemstone onto another fixture table side up such that the table side of the gemstone is exposed; and applying the layer of chemical vapor deposition diamond to a thickness of less than 100 nanometers to the exposed table side.

22. The method as claimed in claim 21, further comprising selecting the medium to be a chemically functionalized carrier medium.

23. The method as claimed in claim 22, further comprising selecting the chemically functionalized carrier medium to include a volatile component and an inorganic oxide, the volatile component being selected to evaporate at ambient room temperature or at elevated temperature and atmospheric pressure to leave behind the inorganic oxide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of a faceted gem being immersed in a nanodiamond slurry in accordance with the present invention;

(2) FIG. 2 is a micrograph view of gemstone pavilion facets which have been coated with a nanodiamond slurry;

(3) FIG. 3 is a high resolution transmission electron micrograph of nanodiamond clusters in accordance with the invention;

(4) FIG. 4 is a lattice image of a nanodiamond particle in accordance with the invention;

(5) FIG. 5 is a graph of XPS data on nanodiamond;

(6) FIG. 6 is a schematic view of a plasma ion-assisted deposition system used for depositing an optically transparent high quality DLC on various substrates layer of oxides, nitrides, oxynitrides of various transition metals or a combination thereof;

(7) FIG. 7 is a scanning electron microscope image of nanodiamond coating on a gem surface;

(8) FIG. 8 is a high magnification scanning electron microscope image of a gem surface coated with nanodiamond film;

(9) FIG. 9 is a transmission electron microscope cross sectional view of a nanodiamond coating on a gem surface;

(10) FIG. 10 is a high resolution image of nanodiamond particles with a lattice spacing consistent with diamond coating on a gem surface; and

(11) FIG. 11 is a schematic view of a diamond that has been filled with nanocrystalline diamond particles in accordance with the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(12) The procedure outlined below provides the step-by-step method to produce the nano-crystalline diamond coating according to one embodiment of the invention:

(13) 1. Commercially obtained nanodiamond powders are used to prepare a slurry in a solvent media such as dimethyl sulfoxide (DMSO), ethanol or preparation of functionalized nanodiamond with improved solubility in polar organic solvents such as alcohols or tetrahydrofuran (THF). Functionalized nanodiamonds are prepared by its reactions with alkylithium reagents, diamines and amino acids. [Functionalization of Nanoscale Diamond Powder: Fluoro-, Alkyl-, Amino-, and Amino Acid-Nanodiamond Derivatives, Yu Liu, Zhenning Gu, John L. Margrave, and Valery N. Khabashesku* Chem. Mater., 2004, 16 (20), pp 3924-393. The choice of nanodiamond powder is based upon the size of nanodiamond particle desired in the nanodiamond coating and varies from 5-20 nm sized powders to several 100 nm sized powders. In one embodiment of the invention, powders containing nanodiamond less than 100 nm in size are used for the nanodiamond coating.

(14) 2. A mixture of Nanodiamond slurry with methanol (or ethanol or IPA) as diluents is prepared.

(15) 3. The substrate intended for nano-crystalline diamond coating is immersed in the mixture (FIG. 1).

(16) 4. Sonication is performed in a regular sonic bath for a duration that is optimized via experimentation for various substrates. In the case of sonication of faceted gems in the nanodiamond slurry the sonication time is typically 10-30 minutes. The duration of the sonication is derived experimentally by performing the sonication of the object to be coated with nanodiamond for various durations and examining the objects using analytical techniques such as electron microscopy. A sonic bath is a piece of industrial or laboratory equipment that includes a container, or bath, used for cleaning, or mixing things inserted into the bath, by application of ultrasonic vibrations through the liquid in the bath. There are several commercially available ultrasonic bath systems which vary in their ability to apply ultrasonic energy by ultrasound frequency (15-400 kHz).

(17) 5. Remove the substrate from the mixture and quickly rinse with solvent to avoid formation of big agglomerates.

(18) 6. After rinsing with solvent the treated substrate is dried with nitrogen flow or the flow of another inert gas. The resulting coating consists of highly adherent Nanodiamond particles that are held in place by van der Waal's forces. FIG. 2 depicts micrographs of nanocrystalline diamond particles using high resolution transmission electron microscopy (HRTEM). FIG. 5 depicts X-ray photoelectron spectroscopy (XPS) data of nanodiamond material.

(19) 7. The nano-crystalline diamond coated substrate is placed under vacuum in an ion-assisted plasma deposition system such as that depicted in FIG. 6.

(20) 8. A thin optically transparent film of DLC is deposited on the nano-crystalline diamond coated substrate to further stabilize the highly adherent layer. The deposition parameters are chosen so as to allow an optimum thickness of DLC film containing high percentage of sp3 bonds and optical transparency to be deposited. Optimum thickness in one example embodiment is about thirty nanometers. Alternatively, the nanocrystalline diamond coated substrate may be stabilized with deposition of an oxide or nitride of various metallic or non-metallic species using the ion-assisted plasma deposition system depicted in FIG. 4. Oxides, Nitrides and/or Oxy-nitrides may be chosen from any of the series of transition metals and may be selected from a group of metals including but not limited to Zinc, Titanium, Titanium-Aluminum, Silicon, Yttrium, Silver, Platinum, Gold, Zirconium or Tantalum. These coatings may be used in conjunction with the deposition of a DLC coating or used without the DLC coating.

(21) Diamond-like-carbon (DLC) coatings are formed when ionized and decomposed carbon or hydrocarbon species land on the surface of a substrate with energy typically 10-300 eV. DLC films may possess exceptional mechanical, optical, electrical, chemical and tribological properties and can be deposited at low substrate temperature (<200 C.). DLC film properties include high hardness, high optical band gap and high electrical resistivity. They generally are inert and demonstrate low friction and wear coefficients.

(22) Such films are generally amorphous (i.e have no dominant crystalline lattice structure) and consist of a mixture of sp2 (trigonal structuringgraphite) & sp3 (tetrahedral structuringdiamond) phases. The sp3/sp2 ratio of the DLC film is controlled by the conditions of the deposition including but not limited to the chamber pressure, gas flow rate, and voltage.

(23) In another example embodiment to create nanocrystalline diamond coating on a gem or other media the following procedure can be followed:

(24) 1. A Nanodiamond slurry is prepared by dispersing nanodiamond particles in a solgel media. The composition of the solgel media is optimized according to the substrate to be coated. In an example embodiment of the invention solgels in oxides of Zinc, Titanium, Silicon, or Aluminum is used to create a composite film of nanodiamond particles.

(25) 2. The substrate intended for nanocrystalline diamond coating is immersed in the Nanodiamond solgel for a duration that is optimized by experimentation for various substrates according to the desired density of the composite film, adhesion to the substrate material, and desired appearance.

(26) 3. The substrate is removed from the Nanodiamond solgel and dried with nitrogen flow or the flow of another inert gas. The composition of the Solgel media is optimized to achieve curing via volatilization of the organic component via a low temperature (<150 C) or room temperature cure.

(27) 4. The resulting coating consists of a matrix of Nanodiamond particles dispersed in the solgel media that adheres to the substrate.

(28) The solgel based nano-crystalline diamond slurry as described above can be used on objects such as jewelry eyewear or other decorative objects to provide protection from oxidation, corrosion and/or abrasion and additionally, in some cases, can be used to impart color to the object or to provide the coated object with the ability to block UV radiation.

(29) The procedure outlined below provides a step-by-step method to produce the nanocrystalline diamond coating according to another embodiment of the invention:

(30) 1. Prepare a mixture of Nanodiamond slurry with, for example, methanol (or ethanol or isopropyl alcohol) as diluent. The nanodiamond slurry consists of nanodiamond particle such as DND particles dispersed in water based or solvent based media. Solvent based media may include other organic solvents. It is helpful if the slurry is prepared so that the nanodiamond particles remain in suspension for the duration of the procedure.

(31) 2. Immerse the substrate intended for nanocrystalline diamond coating into the nanodiamond slurry mixture (FIG. 1).

(32) 3. Perform sonication in a regular sonic bath for a duration that can be optimized via experimentation for various substrates. Sonication may be accomplished by placing a vessel containing the substrate and nanodiamond slurry contained in a vessel into a water bath in an ultrasound unit.

(33) 4. Remove the substrate from the mixture and quickly rinse with solvent to avoid formation of big agglomerates. Acetone and isopropanol can be used in sequence for this purpose.

(34) 5. After rinsing with solvent dry with a flow of inert gas such as nitrogen. The drying can also be accomplished with another inert gas such as argon. The resulting coating consists of highly adherent nanodiamond particles that are held in place by van der Waal's forces. FIGS. 2 depicts micrographs of the nanocrystalline diamond particles using high resolution transmission electron microscopy (HRTEM). FIG. 5 shows X-ray photoelectron spectroscopy (XPS) data of DND material.

(35) 6. The nano-crystalline diamond coated substrate is placed under vacuum in an ion-assisted plasma deposition system (FIG. 6). An example appropriate ion-assisted plasma deposition system is described in a U.S. Published Patent Application 2006/0182883 the contents of which are incorporated by reference herein.

(36) 7. A thin optically transparent film of, for example DLC or zinc oxide is deposited on the nano-crystalline diamond coated substrate to further stabilize the highly adherent layer. The deposition parameters are chosen so as to allow an optimum thickness of DLC film containing high percentage of sp3 bonds and optical transparency to be deposited. A high percentage of sp3 bonds in this context may be about seventy percent but may vary depending on the application. Generally, a higher concentration of sp3 bonds leads to a harder coating but a higher percentage of sp3 bonds may interfere with optical transparency or clarity. Alternatively, the nanocrystalline diamond coated substrate may be stabilized with deposition of an oxide, nitride or various metallic or non-metallic species using the ion-assisted plasma deposition system shown in FIG. 6. Example Oxides include but are not limited to e.g. SiO.sub.2, TiO.sub.2, Al.sub.2O.sub.3, V.sub.2O.sub.3, Fe.sub.2O.sub.3, Cr.sub.2O.sub.3, NiO, Ta.sub.2O.sub.5. Example Nitrides include but are not limited to e.g., TiN.sub.x, ZrN, TaN. Examples of other coating species include but are not limited to TiZrN, TiCN, TiC.sub.xN.sub.y, ZrC.sub.xN.sub.y, Au, Ag and Cu.

(37) Procedure to create nano-crystalline diamond coating on a gem or other media in another embodiment of the invention:

(38) 1. The Nanodiamond slurry is prepared by dispersing DND particles in a sol-gel media. The composition of the sol-gel media is optimized according to the substrate to be coated.

(39) 2. Immerse the substrate intended for nano-crystalline diamond coating in the Nanodiamond sol-gel for a duration that is optimized by experimentation for various substrates.

(40) 3. Remove substrate from Nanodiamond sol-gel and dry with nitrogen flow or a flow of another inert gas. The composition of the sol-gel media is optimized to achieve curing via volatilization of the organic component via a low temperature or room temperature cure. This can be done by the use of organic solvents that are volatile at room temperature.

(41) 4. The resulting coating consists of a matrix of Nanodiamond particles dispersed in the sol-gel media that adheres to the substrate.

(42) The sol-gel based nanocrystalline diamond slurry as described above can be used on objects such as jewelry eyewear, watches or other decorative objects to provide protection from oxidation, corrosion and/or abrasion and, additionally in some cases, be use to impart color to the object or provide the coated object with the ability to block UV radiation.

(43) Example procedure for fracture filling of diamonds with Nanodiamond in another embodiment of the invention:

(44) 1. The Nanodiamond slurry is prepared by dispersing DND particles in a chemically functionalized carrier media. The carrier media has a volatile component which easily evaporates at room temperature or elevated temperature and atmospheric pressure leaving behind an inorganic compound of oxide origin. The carrier media can be chemically functionalized in that components of the media may be chemically reactive in the formation of the fracture filling or in that portions of the media remain as part of the coating or filling.

(45) 2. Pre-clean the diamond (containing fractures that are open to the surface) with solvents including alcohol, acetone, sulfuric acid, hydrogen peroxide, and/or water, to remove surface oils, hydrocarbons and other common surface impurities therefrom.

(46) 3. Ensure that the fractures in the diamond are open to the surface by performing laser drilling if necessary. Laser drilling may be accomplished by the use of commercially available diamond laser drilling techniques.

(47) 4. Perform cleaning in strong caustics and acids with rinses in between. This assists in the removal of any oxides or glassy structures, and/or metallic traces in the diamond. The caustics or acids may include, for example, sodium hydroxide, hydrofluoric acid, nitric acid, sulfuric acid, hydrochloric acid as well as other inorganic acids and alkalis.

(48) 5. The cleaned diamond is immersed in the Chemically Functionalized Nanodiamond slurry placed in a pressure chamber maintained above 50 atmospheres. In some applications it may be beneficial to utilize centrifugal force to facilitate filling of the fractures.

(49) 6. The diamond is removed from pressure chamber after a duration optimized according to the characteristics of the fractures being filled. The required duration may be affected by the depth, width, volume or shape of the fracture to be filled.

(50) 7. The diamond is sonicated in a solvent and dried in a nitrogen flow or the flow of another inert gas (FIG. 5).

(51) In another embodiment of the invention, the following procedure is used.

(52) 1. The Nanodiamond slurry is prepared by dispersing nanodiamond particles in an appropriate carrier media such as DMSO which is further diluted using other volatile organics such as methanol, ethanol or THF. The carrier media is volatile in nature and easily evaporates at elevated temperature and atmospheric pressure leaving behind the nanodiamond particles.

(53) 2. Pre-clean the diamond (containing fractures that are open to the surface) with solvents including alcohol, acetone, sulfuric acid, hydrogen peroxide, and/or water, to remove surface oils, hydrocarbons and other common surface impurities.

(54) 3. Ensure that the fractures in the diamond are open to the surface by performing laser drilling, if necessary.

(55) 4. Perform cleaning in strong caustics and acids with rinses in between. This ensures removal of any oxides or glassy structures, and/or metallic traces in the diamond.

(56) 5. The cleaned diamond is immersed in the container of Nanodiamond slurry and placed in a pressure chamber maintained above 50 atmospheres. Unlike conventional fracture filling treatments using proprietary formulations of molten glass the diamond does not need to be exposed to elevated temperature.

(57) 6. The diamond is removed from pressure chamber after a time period optimized according to the characteristics of the fractures being filled. The fractures that have very little depth into the diamond will fill up with the nanodiamond slurry in a shorter duration (1-4 hrs) and diamonds having fractures that extend deep into the body of the stone may need to remain in the pressure vessel to promote the filling of the fractures for durations greater than 8 hours.

(58) 7. The diamond is sonicated in a solvent and dried in a nitrogen flow (FIG. 5).

(59) 8. In another embodiment of the invention centrifugal force is used for the filling of the fractures using the hydrostatic force generated and the rotational speed of the system is optimized according to the fill length of the fractures.

(60) An example procedure for filling of fractures and fissures in emerald with sol gel media containing a dispersion of nanodiamond particles is presented below. Emerald has a mineral composition Al2Be3[Si6O18] which comes from a class of aluminosilicates. Unlike the use of foreign materials such as oils or polymers, the filling of fractures in emeralds by materials that have the same or similar composition as the emerald should enable a superior quality filling that will not have the disadvantages of conventional fillings. A sol gel media containing an inorganic component from the class of aluminosilicates close in composition to the emerald mineral, and mixed with a chemically functionalized nanodiamond slurry containing a volatile organic component is chosen.

(61) 1. The Nanodiamond Emerald Sol Gel slurry is prepared by dispersing nanodiamond particles in an appropriate carrier media such as DMSO which is further diluted using other volatile organic liquids such as methanol, ethanol or THF and further mixing it with an aluminosilcate sol gel (commercial formulations with composition close to emerald mineral).

(62) 2. Pre-clean the emerald (containing fractures that are open to the surface) with solvents including alcohol, acetone to remove surface oils, hydrocarbons and other common surface impurities.

(63) 3. Ensure that the fractures in the emerald are open to the surface by performing mechanical drilling or laser drilling, if necessary, and perform cleaning using solvents.

(64) 4. The cleaned emerald is immersed in a container containing the Nanodiamond Emerald sol gel slurry and placed in a pressure chamber maintained above 50 atmospheres.

(65) 5. The emerald is removed from pressure chamber after a duration optimized according to the characteristics of the fractures being filled. The fractures that have very little depth into the emerald will fill up with the nanodiamond emerald solgel slurry in a shorter duration (1-4 hrs) and emeralds having fractures that extend deep into the body of the stone will need to remain in the pressure vessel to promote the filling of the fractures for durations greater than 8 hours.

(66) 6. The emerald is sonicated in a solvent and dried in a nitrogen flow or flow of other inert gas (FIG. 5).

(67) 7. In another embodiment of the invention a centrifugal force is used for the filling of the fractures using the hydrostatic force generated and the rotational speed of the system is optimized according to the fill length of the fractures.

(68) In accordance with the invention a sol gel liquid of a composition that is the same or similar to the emerald mineral is mixed with a nanodiamond slurry and when the pressure filling technique of centrifugal or pressure chamber is applied, the slurry moves into the fractures and fissures aided by the movement of the nanodiamond particles. IN this embodiment of the invention, the nanodiamond particles serve the purpose of improving transport properties of the liquid and also help in immobilizing the cured sol after the organic component is volatilized. It is known that nanoparticles dispersed composite materials are strong and adhere well when applied as a coating material.

(69) Fluid filling of microchannels can be done in various methods including but not limited to mechanical pressure (such as the pressure chamber described above), electrical force (electrohydrodynamic flow, electrophoretic flow and electroosmotic flow [1]), surface tension, centrifugal force etc [2]. Ref 1: Fuhr, G.; Schnelle, T.; Wagner, B., Travelling wave-driven microfabricated electrohydrodynamic pumps for liquids, Journal of Micromechanics and Microengineering, 4 (1994): 217-26). Ref 2: Microfluidics of Complex Fluids, Kai Kang, Ph. D. Dissertation, Ohio State University, 2003.

(70) The resulting fracture filled diamond and/or fracture containing nanocrystalline diamond with or without other carrier or solgel media, provide several advantages over existing methods:

(71) 1. The refractive index of the diamond filling is the same as the diamond or nearly so if any carrier media or solgel media is used. This should make the filled area undetectable or nearly so.

(72) 2. The fracture filled emerald contains the material of same or similar composition as the emerald mineral along with the dispersed nanodiamond particles. This renders the filled fractures undetectable or nearly so, additionally provides superior mechanical and thermal stability to the gem rendering it the ability to be set in jewelry employing various methods such as wax setting which typically is not done for emeralds. Emeralds by themselves can withstand elevated temperatures encountered in some jewelry setting operations such as wax setting, but the fillings such as oils, resins and polymers used to fill fissures and cracks cannot withstand elevated temperatures and thus emerald is always hand set very carefully. The method disclosed in this invention wherein the emerald is filled with a material of the same or similar composition as the mineral itself and further stabilized by the dispersion of nanodiamond particles provides new abilities for this gem to withstand environments of jewelry setting as well as end user handling that typically cannot be done by emeralds that are filled using conventional foreign materials. This process allows the emerald to be healed of its fractures and fissures rather than just filled.

(73) 3. The fillings in diamond or emerald cannot be removed by exposure to acids or caustics or solvents unlike conventional glass fillings for diamonds that can be attacked by acids and caustics as well as conventional fillings for emeralds which can be removed by solvents or steam.

(74) 4. The nanocrystalline diamond filling consists of the agglomerates of the sub-5 nm diamond particles integrated in the carrier matrix and do not have a tendency to migrate once the volatile component of the carrier media has been removed.

(75) A diamond that is to undergo fracture filling using nano-crystalline diamond particles as the filler material, should be inspected to verify if the fractures to be filled reach the surface. If the fractures or other flaws such as inclusions are present in the interior of the stone with no path to the surface then the diamond may undergo the laser drilling process to create an opening or nanotubule to the fracture or inclusion. The laser drilling technique is described in the prior art and is a commercially available process.

(76) The combustibility of diamond has allowed the development of laser drilling techniques which, on a microscopic scale, are able to selectively target and either remove or significantly reduce the visibility of crystal or iron oxide-stained fracture inclusions. Diamonds have been laser-drilled since at least the mid-1980s.

(77) Laser drilling involves the use of an infrared laser (wavelength about 1060 nm) to bore very fine holes (less than 0.2 millimeters or 0.005 inches in diameter) into a diamond to create a route of access to an inclusion. Because diamond is transparent to the wavelength of the laser beam, a coating of amorphous carbon or other energy-absorbent substance is applied to the surface of the diamond to initiate the drilling process. The laser then burns a narrow tube to the inclusion. Once the included crystal has been reached by the drill, the diamond is immersed in sulfuric acid to dissolve the crystal or iron oxide staining. This process is not effective for inclusions which are diamonds themselves, as diamond is not soluble in sulfuric acid).

(78) Several inclusions can be thus removed from the same diamond, and under microscopic inspection the fine bore holes are readily detectable. They are whitish and more or less straight, but may change direction slightly, and are often described as having a wrinkled appearance. In reflected light, the surface-reaching holes can be seen as dark circles breaching the diamond's facets. The diamond material removed during the drilling process is destroyed, and is often replaced with glass infilling, using the fracture filling techniques known in the prior art such as the Yehuda Treatment or the Koss process (Ref: Fracture Filling of Diamonds, Janina Skawinska A. G. (C.I.G.), Winnipeg, Man).

(79) If the flaw is an inclusion then after laser drilling procedure the diamonds are deep boiled using acids (sulfuric, nitric, hydrofluoric acids) to remove the impurities or foreign substances that make up the inclusion.

(80) The diamond containing the flaw (fracture or void from which inclusions have been removed) is then cleaned using Acetone and IPA solvent cleaning procedures in a sonic bath and thereafter placed into fixtures or specially designed vessels that contain the nanocrystalline diamond filler media. The nanocrystalline diamond filler media includes nanocrystalline diamond particle clusters suspended in various media including but not limited to distilled water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, methanol, etc. In one embodiment of the invention, the diamond submerged in the nanocrystalline diamond media containing vessel is placed inside a pressure vessel capable of applying pressures up to 50 atmospheres.

(81) The resulting fracture filled diamond, containing nanocrystalline diamond, provides several advantages over the product of existing methods.

(82) 1. The refractive index of the diamond filling is the same as the diamond.

(83) 2. The filling cannot be removed by exposure to heat or acids since neither affect the nanocrystalline diamond particles unlike in the case of the glass-like fillings.

(84) The nanocrystalline diamond filling consists of the agglomerates of the sub-5 nm diamond particles integrated in the carrier matrix and do not have a tendency to migrate once the volatile component of the carrier media has been removed.

(85) The sol-gel process is a versatile solution process for making ceramic and glass materials. In general, the sol-gel process involves the transition of a system from a liquid sol (mostly colloidal) into a solid gel phase. Applying the sol-gel process, it is possible to fabricate ceramic or glass materials in a wide variety of forms: ultra-fine or spherical shaped powders, thin film coatings, ceramic fibers, microporous inorganic membranes, monolithic ceramics and glasses, or extremely porous aerogel materials.

(86) The starting materials used in the preparation of the sol are usually inorganic metal salts or metal organic compounds such as metal alkoxides. In a typical sol-gel process, the precursor is subjected to a series of hydrolysis and polymerization reactions to form a colloidal suspension, or a sol. Further processing of the sol enables one to make ceramic materials in different forms. Thin films can be produced on a piece of substrate by spin-coating or dip-coating. When the sol is cast into a mold, a wet gel will form. With further drying and heat-treatment, the gel is converted into dense ceramic or glass articles. If the liquid in a wet gel is removed under a supercritical condition, a highly porous and extremely low density material called aerogel is obtained. As the viscosity of a sol is adjusted into a proper viscosity range, ceramic fibers can be drawn from the sol. Ultra-fine and uniform ceramic powders are formed by precipitation, spray pyrolysis, or emulsion techniques.

(87) FIGS. 5, 6 7 and 8 provide the data to illustrate the microscopic analysis of a nanodiamond film deposited on a cubic zirconia gem surface using the procedures described in the invention.

(88) The procedure outlined below provides a method in accordance with another embodiment of the invention to produce a nanocrystalline or polycrystalline diamond conformal growth all over a faceted or unfaceted gem material that is capable of withstanding elevated temperature required for diamond deposition using techniques such as hot filament CVD.

(89) 1. The gem material such as a faceted cubic zirconia is pre-cleaned with solvents including acetone and isopropyl alcohol (IPA) to remove surface contamination, dirt and oils. Place the cubic zirconia in a system as described by FIG. 6 and deposit a thin seed layer of a materials such as titanium, graphite or silicon carbide (thickness sub-20 nm). This is done to promote the adhesion of the CVD diamond film that is to be grown over the gemstone surface.

(90) 2. Load the gem material such as the faceted cubic zirconia or other decorative object onto a flat holder by placing the gemstone table-side down such that the pavilion side of the gem is exposed.

(91) 3. Load the holder into a commercially available diamond CVD system.

(92) 4. The chamber of the diamond deposition system is evacuated to below 20 mTorr and the reaction gases comprising of methane (CH4) diluted with hydrogen (H2) are flowed into the system. The diamond deposition while using cooling systems to control the temperature of the holder containing the gemstones to below 750 C.

(93) 5. The thickness of the diamond film grown on the exposed surface of the gemstone is controlled by the reaction chemistry and duration of the run so that resulting thickness is in the sub-100 nm range. The chemistry of the film is controlled by the sequence of hydrogen etching to remove the non-diamond components of the film.

(94) 6. The gemstone is removed from the system after the deposition cycle and then reloaded onto another fixture that allows the stone to be placed with the table side exposed.

(95) 7. The process of diamond deposition is again run in the diamond CVD system.

(96) The invention in one embodiment includes depositing a thick layer of hot filament CVD diamond on a material such as titanium or silicon carbide or molybdenum or tantalum to create a black diamond watch dial. The procedure in this embodiment is similar to how the gemstone is coated in the CVD chamber except that the thickness is optimized to be 10-12 microns in order to achieve a black color.

(97) The present invention may be embodied in other specific forms without departing from the spirit of the essential attributes thereof; therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.