Diamonds a forever

EVER since the first synthetic diamondprocess - the high-pressure catalytic- was perfected by General Electric iand De Beers in South Africa, the matfound many applications in industry.

The remarkable mechanical propdiamond make it ideal for many ptSynthetic diamonds are extensivelygrinding and cutting tools and in mturing wear-resistant surfaces and evispeaker diaphragms. In the late 1(ftapproach called the chemical vapourtion method was developed. This rnchief drawback is that the growth rexceedingly slow. For a good quality ddeposit, the best growth rate at optinditions is roughly one micrometre pThis shortcoming has affected the ecouse of diamonds.A recent study by P G Partridge,Internal of Medical Science, has rised id an increase in the growth rates of D& by the chemical vapour deposi i6chmique. The technique involves @p a plasma by microwaves and a awbon charge in hydrogen gas, and pmg the diamond on a substrate a usuafly tungsten (Nature, Vol 377, 21, 1995).

r11w insight provided by PartridgecoHeagues has led to the discoveryKi2l deposition on many closelyints, if allowed to grow (side-can increase the effective growthifold. They have used a smallrr tungsten spiral upon which thediamond is deposited. The effective growthrate is increased by the number of turns ofthe spiral. They have also done detailed calculations to show that a closely spaced gridcan be coated simultaneously with a continuous, though not very smooth, sheet ofdiamond.

The increased growth rates for diamond deposition could bring down thecosts substantially and make it economicalfor various other applications. Theseinclude diamond-reinforced, high strengthcomposites for high technology uses. Thecoming years will defenitely mean large-scale incorporation of chemically deposited diamonds for diverse applications.