Diamonds a forever

Chemtic diagrams: heterogenous (Credit: Anand Singh Rawat)EVER since the first synthetic diamond
process - the high-pressure catalytic
- was perfected by General Electric i
and De Beers in South Africa, the mat
found many applications in industry.

The remarkable mechanical prop
diamond make it ideal for many pt
Synthetic diamonds are extensively
grinding and cutting tools and in m
turing wear-resistant surfaces and evi
speaker diaphragms. In the late 1(ft
approach called the chemical vapour
tion method was developed. This rn
chief drawback is that the growth r
exceedingly slow. For a good quality d
deposit, the best growth rate at optin
ditions is roughly one micrometre p
This shortcoming has affected the eco
use 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 Partridge
coHeagues has led to the discovery
Ki2l deposition on many closely
ints, if allowed to grow (side-can increase the effective growth
ifold. They have used a small
rr tungsten spiral upon which the
diamond is deposited. The effective growth
rate is increased by the number of turns of
the spiral. They have also done detailed
calculations to show that a closely spaced grid
can be coated simultaneously with a continuous, though not very smooth, sheet of
diamond.

The increased growth rates for diamond deposition could bring down the
costs substantially and make it economical
for various other applications. These
include diamond-reinforced, high strength
composites for high technology uses. The
coming years will defenitely mean large-
scale incorporation of chemically deposited diamonds for diverse applications.