| 摘要 |
Broadly, the present invention is directed to a diamond product comprising a core of diamond containing at least about 1 wt-% <1><3>C and an epitaxial diamond coating on said core containing at least 1 wt-% less <1><3>C than is contained is said diamond core. The diamond core will have a lattice parameter that is smaller that the lattice parameter of the diamond coating. When the coating is forced to grow epitaxially so that it must have the same lattice constant as the diamond core, the coating will be placed under compression. Since <1><3>C diamond has the smallest lattice parameter known and the lattice parameter of diamond is a function of isotopic composition, the diamond core should contain more <1><3>C than is contained in the coating in order for the coating to be placed under compression. Accordingly, the diamond core can be composed of natural or synthetic diamond having a natural isotopic composition and the coating can be <1><2>C or <1><3>C. Alternatively, the core can be <1><3>C and the coating <1><2>C. When mixtures of isotopes comprise the core and/or coating, their composition should vary by at least 1 wt-% <1><3>C with the higher incidence of <1><3>C isotope being located in the core. |
