INDUSTRIAL DIAMONDS | EN

Polycrystalline
Annually the market for polycrystalline diamonds accounts for over 100 million dollars. Polycrystalline diamonds are available in various forms according to their use: rectangular, square, triangle or cylindrical. The Polycrystalline diamond has no cleavage planes as natural diamonds and is therefore less “fragile”. It will not splinter as easily as natural diamonds. Natural diamonds also have the tendency to polish when subjected to friction, which is not the case for polycrystalline diamonds, which continually expose new crystals.
 
Polycrystalline diamonds for industrial use are designed to offer longer working life and superior performance. In addition to this a high thermic stability of up to 1200° is achieved. They are to replace the natural monocrystaline diamonds for dressing (rectifying) aluminium oxide and carbon silicon wheels. Synthetic polycrystalline diamonds are dense and omnidirectional linked by a G.E process under high pressure and temperature, which gives them a great mechanical and uniform résistance in all directions.
 
On February 6th 2003, Japanese scientists announced that they had manufactured, on the basis of graphite, the world's hardest synthetic polycrystalline diamonds. The team lead by geologist Tetsuo Irifune of Uhime University had heated graphite to a temperature of 1.800 and 2.000 C° for a period of several minutes (the usual temperature used is 1.500 to 1.800 C°). Furthermore, they applied a pressure in access of the 70 Gigapascale, which is usually used. Through this process they obtained polycrystalline diamonds of 1 to 2 millimetres. According to these scientists this new process produces synthetics that are twice as resistant as conventional diamonds at 140.000 on the scale of Rosiwal (carburandum being 1000). Professor Irifune's diamonds would have strength of 280.000, which is enormous!
 
The applications are seemingly endless: drilling tools for rocks, metal saws and, perhaps, a revolution in the diamond cutting industry.
 
Synthetic Diamond Film
A further advancement has been made in the technical evolution and applications of industrial diamonds. Thanks to this new revolutionary process, a diamond film can be deposited on any surface, on spectacle lenses, watch glasses, electronic components, optical windows for X-rays and infra-red or engine parts thereby assuring higher performance. These techniques are already currently being applied in drilling bits, sawing and cutting tools.
 
It will also be used as semi-conductor or as film on silicone semi-conductors. Thanks to its excellent thermal properties, diamond could make 'chips' much faster and smaller in volume. It is already used in the manufacture of loudspeakers, tools, lenses, and optical disks in lasers and in semi-conductors and represents a budget of 200 million dollars per year for just these few applications.
 
That process is known as Chemical Vapour Deposition (CVD), which consists of heating methane gas, composed of 1 atom carbon and 4 hydrogen, at a much lower pressure than applied conventionally. A mixture of hydrogen and methane is injected in a quartz tube and exposed to micron waves under which the molecules disintegrate and creating plasma or a vapour of ionized atoms. The carbon atoms settle and crystallize as a diamond film on the required object.
 
In the precious stones industry we can foresee a diamond film deposit on delicate stones such as emeralds and others in order to augment their résistance to wear; opals would benefit by not only increasing their résistance to wear but also help them to retain their moisture which causes them to crack. American researchers have succeeded in depositing an ultra thin film using the same microwaves that are used in the kitchen. Generally, these films can be easily detected with a microscope, the colour is metallic or brownish and “graining” an unusual exterior look. Colour shift is visible. Despite all these properties they are not as hard as natural diamonds. Diamond film is also used on flexible bases as on conveyor belts, flexible discs and polishing turrets etc. A system has been perfected to internally scour pipes such as heating pipes, gas pipes etc. It is also possible to deposit a film of micrograins containing diamonds of different sizes on polyester tissue by an electrolyte method using De Beers’s abrasives. One of the main problems is that of sticking the diamond film on metal as on carbon tungsten, cobalt and on ceramics. The manufacturers jealously guard me secret of this technique.
 
Synthetic Diamonds
We know that diamonds have been the principal pillar of the technical revolution of the 20th Century. It is a fact that we cannot imagine drilling, sawing, tooling, polishing and honing without the use of diamonds.
 
In heavy industry as well as in precision applications such as electronics, the conquest of space etc., diamonds have become indispensable.
 
The quality of natural diamonds used for industrial purposes is mainly based on the lower qualifies; low colour, imperfect crystallization and multiple inclusions; in other words the rejections on the diamond production. The superior qualities, which are found in much smaller quantities, are used for jewellery qualities. This has no bearing on the fact that for certain industrial applications perfectly formed and pure diamonds have to be used.
 
Industrial diamonds are consumed, which means that they are used up at various stages of their working life so that, actually, millions of carats are used. Production of synthetic industrial diamonds is an eightfold of the natural production. The industrial diamond sector expanded after the Second World War resulting in shortages.
 
As early as 1880 researchers like Hanny and later in 1893 Moissan experimented at making diamonds. In Antwerp, Peiren almost succeeded in making diamonds but he was caught-up by the Swedish who in 1952 met with success followed by De Beers in 1955, General Electric, Russia and later China. They produced small abrasive crystals for industrial use and developed larger sizes for use in saws for granite, marble, precious stones, drill bits, metal and rock drilling.
 
It was only in 1970 that General Electric announced that they had the technology to create pure transparent crystals of about one carat. It was a publicity stunt as the production costs was much higher compared to natural diamond. However, in 1985, with much consternation, the powerful Japanese group Sumitomo announced that they had created "gem diamonds on an industrial base". What was once a revelation of the century was soon reduced to practical proportions.
 
True that the diamond created by Sumitomo was until then the largest synthetic diamond produced with least natural characteristics but, the colour was yellow, brown and olive. Furthermore the price was in me same proportion as to natural diamonds.
 
Above all it is the growing demand of the electronic industry that is the cause of his latest development. Average production was stones from 0.11 to 0.37 carat rough with 2 parallel faces. The largest stones could go up to 2 carats. It is worthwhile noting, that one stone of 0.10 ct. will yield, at best, 2 stones 0.03 ct., and that a stone of 2 ct., will yield, normally, 2 stones of 0.50 ct.
 
These stones meet with the specifications of the industry; high thermal concluctibility and almost pure. Sumitomo synthetic diamonds are, at present, the most perfect imitation of natural diamonds but are easily detectable by the gemmologist and will only be used for industry and not for jewellery.
 
Another well-known manufacturer of synthetic stones made a sensational announcement in the autumn of 1993. Chatham claimed to be able to produce synthetic diamonds of 2 ct., polished in desirable colours, white, pink, blue etc., at a tenth of the price of natural diamonds. The only effect this thunderbolt had on the Antwerp diamantaires was one of sentiment and they were right. Only a few months later it was announced that the problem was more difficult than foreseen. Colours were yellow and cutting was to take place in Russia and Thailand but there were problems in this field with contracts and that the price would be higher.
 
But today there are synthetic diamonds coming from HPHT technology available on the market, CVD diamonds are treated with HPHT and irradiated. All colours are made. Brownish and yellowish diamonds are turning in white. We already have more than 100 years of experience with precious stones (rubies, sapphire and emeralds).
 
How much Lenix Verneuil, Gilson, Chattham, Inamori, Cachan and other synthetics has been sold compared to the natural stones? Would the consumer offering a diamond or a ruby to his wife prefer a natural stone perhaps of a lesser quality due to budgetary reasons rather than a better synthetic? If synthetic diamonds were to become available in quantity it would in first instance be competition for cubic zirconium or moissanite. A fancy jewellery article in the first place, but the consumer must be warned and be in a position to buy diamond jewellery from the traditional jeweller. The jeweller must confide in his supplier. The gemmologist sees the difference and there are instruments to detect synthetic diamonds.
 
The only problem is that that the most important laboratories such as HRD, IGI and GIA gives certificates for “treated diamonds” and this will bring confusing for the consumer.