# US 10,370,252 B1 · Methods of altering the color of a diamond by irradiation and high-pressure/high-temperature processing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,370,252 B1 - Document ID: US10370252B1 - Status: Granted - Kind: B1 - Application number: 14/517,729 - Filed: 2014-10-17 - Granted: 2019-08-06 - Earliest claimed: 2011-04-26 - Assignees: US Synthetic Corporation - Applicants: US Synthetic Corporation - Inventors: Louis McConkie Pope, II - Web page: https://patentgrep.com/patent/US10370252B1 ## CPC - C23C 16/402: {Silicon dioxide} - C30B 29/04: Diamond - C30B 33/02: Heat treatment (C30B33/04, C30B33/06 take precedence) - C30B 33/04: using electric or magnetic fields or particle radiation - B01J 3/062: {characterised by the composition of the materials to be processed} - B01J 2203/062: Diamond - B01J 2203/0655: Diamond - B01J 2203/0695: Colour change - C23C 16/505: using radio frequency discharges - C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) - C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS ## Abstract Embodiments of methods of altering the color of diamonds are disclosed. In an embodiment, a method for altering the color of diamonds includes identifying and selecting a diamond having a suitable nitrogen content, HPHT processing the selected diamond under diamond-stable conditions to alter the color of the selected diamond from a first color to a second color, irradiating the HPHT-processed diamond with an electron source having an energy between about 1 MeV and about 20 MeV so as to alter the color of the selected diamond from the second color to a third color, and annealing the irradiated diamond either under partial vacuum conditions, or under HPHT diamond-stable conditions so as to alter the color from the third color to a fourth color (e.g., pink, red, or purple, depending on the nitrogen content of the selected diamond). ## Claims ### Claim 1 A method of altering a color of a natural diamond, the method comprising: subjecting the natural diamond to a high-pressure/high-temperature (“HPHT”) process under diamond-stable conditions effective to alter the natural diamond from a first color to a second color that is different than the first color; irradiating the natural diamond with electrons having an energy effective to alter the natural diamond from the second color to a third color that is different than the first color and the second color; and annealing the natural diamond at a temperature of 950° C. or less effective to alter the natural diamond from the third color to a fourth color that is different than the first, second, and third colors and that is pink or purple. ### Claim 2 (depends on 1) The method of claim 1, further comprising, prior to subjecting the natural diamond to the HPHT process, identifying a nitrogen content of the natural diamond. ### Claim 3 (depends on 2) The method of claim 2 wherein the nitrogen content is no more than about 200 ppm. ### Claim 4 (depends on 2) The method of claim 2 wherein the nitrogen content is no more than about 50 ppm. ### Claim 5 (depends on 2) The method of claim 2 wherein the nitrogen content is no more than about 25 ppm. ### Claim 6 (depends on 2) The method of claim 2 wherein identifying a nitrogen content of the natural diamond includes identifying the nitrogen content via infrared spectroscopy. ### Claim 7 (depends on 1) The method of claim 1 wherein subjecting the natural diamond to an HPHT process under diamond-stable conditions effective to alter the natural diamond from the first color to a second color that is different than the first color includes subjecting the natural diamond to a temperature of at least about 1000° C. and a pressure of at least about 4 GPa. ### Claim 8 (depends on 7) The method of claim 7 wherein the temperature is between about 1800° C. and about 2500° C., and wherein the pressure is between about 5 GPa and about 10 GPa. ### Claim 9 (depends on 1) The method of claim 1 wherein the pressure is between about 5 GPa and about 8 GPa. ### Claim 10 (depends on 1) The method of claim 1 wherein the energy of the electrons is between about 1 MeV and about 20 MeV. ### Claim 11 (depends on 10) The method of claim 10 wherein the energy of the electrons is between about 2 MeV and about 5 MeV. ### Claim 12 (depends on 1) The method of claim 1 wherein annealing the natural diamond at a temperature of less than 950° C. effective to alter the natural diamond from the third color to a fourth color that is different than the first, second, and third colors includes annealing the natural diamond under partial vacuum and with the temperature at about 900° C. ### Claim 13 (depends on 1) The method of claim 1 wherein annealing the natural diamond at a temperature of less than 950° C. effective to alter the natural diamond from the third color to a fourth color that is different than the first, second, and third colors includes annealing the natural diamond at about 100 kPa and with the temperature between about 850° C. and about 950° C. ### Claim 14 (depends on 1) The method of claim 1, further comprising pre-irradiating the natural diamond prior to subjecting the natural diamond to the HPHT process. ### Claim 15 (depends on 1) The method of claim 1 wherein the first color is brown, the second color is yellow, and the third color is blue-green. ### Claim 16 (depends on 1) The method of claim 1 wherein the natural diamond is type IaB. ### Claim 17 A method of altering a color of a natural diamond, the method comprising: subjecting the natural diamond to a high-pressure/high-temperature process under diamond-stable conditions effective to alter the natural diamond from a first color that is brown to a second color that is yellow; irradiating the natural diamond with electrons having an energy effective to alter the natural diamond from the second color to a third, blue-green color that is different than the first color and the second color; and annealing the natural diamond under diamond-stable conditions including a pressure of at least 4 GPa and a temperature of at least about 1000° C. effective to alter the color of the natural diamond from the third, blue-green color to a fourth color that is pink or purple. ### Claim 18 A method of altering a color of a type IaB natural diamond, the method comprising: subjecting the type IaB natural diamond to a high-pressure/high-temperature process under diamond-stable conditions effective to alter the type IaB natural diamond from a first color to a second color that is yellow; irradiating the type IaB natural diamond with electrons having an energy effective to alter the type IaB diamond from the second color to a third color that is different than the first color and the second color; and annealing the type IaB natural diamond at about 100 kPa and at a temperature between about 850° C. and about 950° C. under conditions effective to alter the type IaB natural diamond from the third color to a fourth color that is pink or purple. ### Claim 19 (depends on 18) The method of claim 18 wherein annealing the type IaB natural diamond includes annealing the natural diamond at a temperature of about 900° C. ### Claim 20 (depends on 1) The method of claim 1 further comprising pre-irradiating the natural diamond prior to subjecting the natural diamond to the HPHT process, wherein pre-irradiating the natural diamond includes pre-irradiating the natural diamond at a different energy level than an energy level used for irradiating the natural diamond with electrons.