Abstract: The improved diamond composite (10) exhibits increased oxidation resistance at elevated temperatures, as well as anti-reflective properties. The composite (10) includes a diamond (12), the surfaces (14) of which are protected by an adherent coating (16) consisting essentially of a layer (18) of hafnium carbide adhering and chemically bonded to the diamond (12), a layer (20) of hafnium oxy-carbide adhering and chemically bonded to the hafnium carbide layer (18) and an oxidation-resistant layer (22) of hafnium oxide adhering and chemically bonded to the hafnium oxy-carbide layer (20). Preferably, the coating (16) is sufficiently thin so that it or at least the hafnium oxide layer (22) thereof has about one-quarterwavelength thickness.

Abstract: The improved diamond composite (10) exhibits increased oxidation resistance at elevated temperatures, as well as anti-reflective properties. The composite (10) includes a diamond (12), the surfaces (14) of which are protected by an adherent coating (16) consisting essentially of a layer (18) of hafnium carbide adhering and chemically bonded to the diamond (12), a layer (20) of hafnium oxy-carbide adhering and chemically bonded to the hafnium carbide layer (18) and an oxidation-resistant layer (22) of hafnium oxide adhering and chemically bonded to the hafnium oxy-carbide layer (20). Preferably, the coating (16) is sufficiently thin so that it or at least the hafnium oxide layer (22) thereof has about one-quarterwavelength thickness. The method of forming the composite (10) employs sputtering hafnium metal in an argon atmosphere, preferably at about 100.degree.