Sintered superhard materials.

Diamond or cubic boron nitride particles can be sintered into strong masses at high temperatures and very high pressures at which these crystalline forms are stable. Most of the desirable physical properties of the sintered masses, such as hardness and thermal conductivity, approach those of large single crystals; their resistance to wear and catastrophic splitting is superior. The sintered masses are produced on a commercial scale and are increasingly used as cutting tools on hard or abrasive materials, as wire-drawing dies, in rock drills, and in special high-pressure apparatus.

Hexagonal diamonds in meteorites: implications.

A new polymorph of carbon, hexagonal diamond, has been discovered in the Canyon Diablo and Goalpara meteorites. This phase had been synthesized recently under specific high-pressure conditions in the laboratory. Our results: provide strong evidence that diamonds found in these meteorites were produced by intense shock pressures acting on crystalline graphite inclusions present within the meteorite before impact, rather than by disintegration of larger, statically grown diamonds, as some theories propose.

Materials and techniques for pressure calibration by resistance-jump transitions up to 500 kilobars.

The resistance jump of alpha-->epsilon transitions for Fe-V alloys up to 20-wt. % V is observed by static compression. It is used along with alpha-->epsilon transitions for Fe-Co alloys and some other transitions as the basis for pressure calibration up to 500 kilobar.