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MEI Online: Commodities: Non-Metallic Ores: Diamond: Latest News: March 30th 2005

 
 

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:: Synthetic Diamonds: Threat or Opportunity?

For many years now diamonds have been manufactured in production plants, not wrested from the earth ­ production reportedly now runs at more than 100 t/y, but hitherto these have been industrial diamonds, used for abrasives, in drillbits, and so on. Indeed, the De Beers group company Element Six (previously De Beers Industrial Diamonds) is the world’s leading supplier of manufactured industrial diamond materials and superabrasives.

Other leading manufacturers of industrial diamonds include Sumitomo Electric and Diamond Innovations. However, the last few years have seen the perfection of technologies which allow the manufacture of gem-quality diamonds, and two US companies are currently doing so. Are these a threat to the traditional, naturally-formed, mined gem diamonds? “We are very supportive of the existing mine diamond industry and we have no intention of dis-rupting that industry," assures Bruce Likly, spokesman for Apollo Diamonds, one of the two US com-panies now manufacturing large and gem-quality diamonds. “Apollo believes that the gemstone diamond market will support the existing mine-diamond industry and the new industry, with the manufactured component ramping up slowly over time," he explains.

Apollo Diamonds is based in Boston, Massa-chusetts, while the other manufacturer, Gemesis, is located in Sarasota, Florida; they employ entirely different technologies. Both Gemesis and Apollo make it clear to clients and in their advertising and information campaigns that their diamonds are manufactured products, not naturally-occurring stones. Since the first of these manufactured gem diamonds entered the US market in 2003, journalists from major media organisations and leading journals have been having fun confounding leading diamantiers in Europe and North America with the products of these companies. Thus, US magazines Wired and Newsweek fooled respected diamantiers in Antwerp and New York respectively by presenting them with synthetic gem diamonds without revealing their provenance. Wired’s Joshua Davis was told by his ‘victim’ that the yellow diamond he presented for examination was a very rare stone, worth at least $10 000 and maybe $15 000 ­ actually, it was made for less than $100. In New York’s diamond district, one diamantier offered to buy the synthetic diamond brought to him by Newsweek reporter Michael Hastings, thinking it was natural, while another confessed that he could not distinguish synthetics from naturals.

The reason for these errors and uncertainties is, of course, quite simple ­ the synthetics are not fakes, they are not copies; they are real diamonds. It is just that they are produced differently ­ and the paradox is that, although the synthetic diamonds are cheaper than the natural ones, they are, at the moment, actually rarer. Because they are produced differently to natural diamonds, there are differences between synthetics and naturals that can be detected, but only with high-technology devices ­ devices that De Beers has spent considerable time and money to develop and perfect. For example, synthetics lack the natural flaws and inclusions found in mine diamonds, there can be differences in the nitrogen content and they react differently to hard ultraviolet light. But such equipment is not a practical proposition for most diamond dealers and a real fear for the future is that, as synthetic-diamond manufacturing technology gets cheaper and smaller, it could open the way for the unscrupulous to make synthetics and pass them off as naturals, damaging the market for all the legitimate players.

Diamonds are carbon, and diamond is one of the three allotropes ­ that is, natural structural forms of the element ­ of carbon, the other two being graphite (most familiar as the ‘lead’ in pencils) and the fullerenes (discovered as recently as 1990 but not relevant to this story). While graphite is the most thermodynamically stable allotrope of carbon, diamond is only slightly less stable thermodynamically and is much less reactive, has a more rigid structure and, of course, is much harder ­ the hardest known natural substance. To clarify, in graphite, each carbon atom is bonded to another three carbon atoms, forming layers of carbon with layers of free electrons sandwiched in between; the result is that, while each carbon layer is strong, they can easily slide over each other. This makes graphite soft and fragile. In contrast, in diamond, each carbon atom is bonded to another four carbon atoms in a three-dimensional structure, giving a very rigid and very strong structure because none of its component atoms can move ­ there are no free electrons. As is well known, natural diamonds were formed more than 150 km below the earth’s surface, insituations in which the abundant carbon, in graphiteform, was subject to temperatures greater than1 200 C and pressures greater than 50 kilobars, over time periods that could run into millions of years. Later ­ and it can be millions of years later ­ they are brought to, or near, the surface by upwellings or eruptions of magma, which subsequently cool, forming kimberlite.

It should be noted that the diamonds were not formed in the kimberlites; they merely transported them into the reach, knowledge and desire of humanity. In 2003, De Beers had just over 55% of the global market share for gem diamonds, Russia’s Alrosa had just over 10%, rising Israeli star Lev Leviev had 9%, BHP Billiton 6,5%, Rio Tinto almost 6%, with the rest of the market split between smaller players. So, how are synthetic gem diamonds made? It was in 1954, after four years of trial and error and study, that scientists working for the giant US General Electric Corporation (GE) discovered how to manufacture diamonds. Using a specially-built machine called a Belt press, the GE scientists subjected graphite, in the presence of an iron compound called troilite, to temperatures of almost 1 600 C, and pressures 70 000 times greater than on the earth’s surface. In this process the liquid troilite acted as a solvent on the graphite, dissolving the carbon which then, as the temperature and pressure reached their peak, crystallised as diamonds. The resulting diamonds were small and far from gem quality, but this breakthrough led to today’s industrial diamond-manufacturing industry. But it took decades to get from manufacturing industrial-quality diamonds to manufacturing gem-quality stones. But now it has been done ­ in fact, two completely separate technologies have been developed that produce gem-quality diamonds.

One of these technologies, today used by Gemesis, was developed in Russia. This process uses high-temperature, high-pressure crystal-growth chambers, each reportedly about the size of a washing machine. A tiny ‘seed’ of natural diamond is placed in a chamber, bathed in a molten solution of graphite and a proprietary metal-based catalyst at a temperature of about 1 500 C and a pressure 58 000 times greater that that experienced at the earth’s surface. The result is the precipitation of the carbon onto the diamond seed crystal; with this method ittakes a little less than three-and-a-half days to produce a 2,8-carat yellow diamond. Such a diamond can then be cut and polished to give a stone of more than 1,5-carats.

Apollo Diamonds uses an entirely different technology, called chemical vapour deposition (CVD). The CVD technology has also taken decades to develop to the point that it can produce single-crystal gem-quality diamonds. It should be noted that CVD is also used to produce polycrystalline industrial diamonds, as well as crystalline forms of silicon, gallium arsenide and other materials for use as semi-conductors. Apollo uses its own, modified and patented, version of CVD to achieve this. In CVD processes, the key to creating a diamond is not graphite but hydrogen. Hydrogen gas and methane flow through a chamber which contains a diamond seed crystal ­ “we don’t grow a diamond out of nothing," as Likly phrases it ­ and the hydrogen is split into atomic hydrogen by the action of a hot filament or a microwave-generated plasma. This atomic hydrogen then reacts with the methane to produce methyl radical and hydrogen gas; the methyl radical then deposits on to the diamond seed, forming new diamond carbon-carbon bonds. It should be noted that, at its surface, a diamond’s carbon lattice has ‘dangling bonds’ that can, potentially, cross-link to reorganise the surface into carbon’s more stable allotrope of graphite. By capping these dangling bonds with hydrogen, graphite formation is prevented, and reactive surface sites for the attachment of carbon radicals are created. The result is that a diamond is grown, in the form of a ‘plate’, about the size of a shirt button, but thicker, which can then be cut and polished into a gemstone. A low-pressure system, CVD is cheaper than the alternative high-pressure technology. “The company is already manufacturing andselling single-crystal diamonds, but they are in the preproduction manufacturing build-out phase, and the diamonds produced to date have gone primarilyto the optics and electronics industries," reports Likly. “Gemstones should be available by the end of this year," he adds.

Ironically enough, De Beers is also capable of manufacturing large diamonds, although to date it has done so largely as a means of developing technologies and techniques to distinguish synthetic diamonds from natural ones, although the group has reportedly also supplied such synthetic diamonds to the electronics industry to act as heat sinks. But are synthetic gem diamonds a threat to natural diamonds and to the diamond-mining companies in terms of sales and market penetration? This question can be phrased differently: are synthetics acceptable to women, at whom all gem diamonds are targeted, directly or (via malepurchasers) indirectly? A reporter for US journal National Jeweller did a quick, unscientific survey of female friends and colleagues and found that most would buy syntheticsfor themselves but would strongly object if their boyfriends or husbands gave them synthetics as gifts. Inspired by this, this journalist did a similar survey of some of the women working at Creamer Media. The results were pretty much the same ­ of the 15 women (the majority journalists) asked, ten said they would buy synthetic diamonds for themselves, one was uncertain, and four said they wouldn’t. But when it came to getting synthetic diamonds as gifts from their boyfriends or husbands, only five said this would be acceptable and ten affirmed it would not be.

So, there is clearly a niche, and an important one, for synthetics, but there is also a large market that currently remains reserved for naturals. But there is a point that needs to be highlighted ­ these synthetic gem diamonds are entering the global market at precisely the time when there appears to be a shortage of natural rough stones, reportedly caused by De Beers selling down its stockpile to finance its transformation into a privately-held company, coupled with the lack of sizeable new diamond-mines coming into production. Thus, there seems to be a gap opening in the market, a gap that is likely to endure for a few years, just at the moment the gem-diamond manufacturers need it.

The only question is: could they ramp production up sufficiently to meet the demand? And, if they can and do, will they actually help the mine-diamond producers by providing people with affordable diamonds, and so avoid them switching to other precious and semi-precious stones? But gemstone production is only one part of the synthetic diamonds story, and it may be the least important part. “Apollo is working on three distinct market segments at the moment ­ gemstones; optics and electronics; and nanotechnology," reports Likly. Diamond has many interesting properties other than its hardness ­ it is also the least compressibleand stiffest known material, it is the best heat conductor and cools faster, has extremely low thermal expansion, a low coefficient of friction, is chemically inert, and resistant to radiation. Normally, diamond is an excellent electrical insulator but, if it contains the right kind and quantity of trace materials, or dopants as they are called, it is an excellent semiconductor. But natural diamonds are too expensive, too uncertain in terms of their dopants, and their form is usually inconvenient, to make exploitation of their remarkable properties technically and financially practicable. But with synthetic diamonds, all this changes. As they are manufactured, specific dopants can be introduced into the diamond’s carbon lattice, to ensure specific properties. Thus, replace some of the carbon atoms in the diamond lattice with boron, and the result is a semiconducting diamond. Further, the CVD process allows diamondto be produced in the form of a wafer, not a stone.

Both Element Six and Apollo, using their own CVD technologies, can produce diamond wafers, with Apollo reporting that it can produce these wafers in squares ranging from 3 mm x 3 mm to 10 mm x 10 mm, with 25 mm x 25 mm becoming available soon; thicknesses range from 250 micrometres to 4 mm. To cite one very important application, such wafers can be used to conduct heat away from micro-processors and nanotechnology machines muchfaster than any other material; how to get rid of the heat generated by the activities of these minutedevices is one of the biggest problems facing electronics and nanotechnology today. Manufactured diamonds in wafer form seem to be the answer. And, although semiconductors made from diamond will never replace those made from silicon ­ the latter is too cheap and plentiful ­ they could very well displace them in specialised, high-power, high-temperature applications. In optics, the transparency of diamond and itsresistance to chemical attack, makes it a desirablematerial for optical windows for instruments employ-ed in extreme environments ­ again, only synthetics can meet the need.

Today’s diamond manufacturing technologies have opened entirely new markets for the beautiful allotrope of carbon, and created an entirely new future for it. Perhaps synthetic-diamond manufacturing technology may be too important to waste on something as frivilous as gemstones. It is clear that synthetic diamonds do not pose a threat to De Beers, or to any of the other major diamond-miners, as companies, because they allhave the financial resources to move into gemstone manufacturing themselves, if they need to, and De Beers has its own very considerable diamond-manufacturing technologies. But, in the long run, do synthetics threaten the creation of new mines? The disparity between the capital investment for a major new diamond mine and that for a gem-diamond manufacturing facility is enormous ­ will a mine really be worth the money? There are many questions; only time will give the answers.

 

 

   

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