Monday, 4 February 2013

Process of Creating Diamonds Through Man

James Hannay's first attempt to create diamonds nearly proved a disaster when the iron tubes in which he had sealed his material exploded under the intense heat and pressure that was generated in the experiment., in 1880. He sealed a mixture of hydrocarbons, bone oil and lithium into thick
Nearly two centuries ago the French physicist Lavoisier showed that diamond was nothing more than crystallized carbon, and from that point on attempts at making artificial diamonds became a popular pursuit for scientists and for confidence tricksters.

Some of the earliest experiments were carried out by two Frenchmen, Cagniard de Latour and Gannal, who presented their findings to the Academy of Sciences in 1828. De Latour submitted ten tubes containing a number of light brown crystals, brilliant, transparent and hard. Under examination, they proved impervious to the most intense heat but were easily scratched, which led the academicians to conclude that the "diamonds" were merely silicates.

Gannal's gems caused more of a stir. His method was appealing in its simplicity. He introduced carbon disulphide and water into a matrix together with pieces of phosphorus, which soon dissolved in the disulphide. The idea was that the phosphorus would gradually absorb the sulphur in the disulphide of carbon, and that the carbon, thus reduced to its elementary state, would crystallize. 

Diamond RingAfter some months a conglomeration of tiny crystals appeared. They were capable of scratching steel, but they themselves could not be scratched. They were clear and shone with a brilliant luster, and an eminent Parisian jeweler pronounced them to be diamonds. They may well have been, but subsequent tests showed that if they were, they were not produced in the way Gannal described. The probability is that they were introduced into the matrix at some point during the process.

A few years later another French physicist, named Despretz, is believed to have had more success. His first attempt by the application of the most intense heat to carbon had come to nothing even though he is reported to have "united and arrayed all the Bunsen burners that he could procure in Paris and so obtained a current of the most prodigious intensity." Such violent means having failed, Despretz substituted weak and intermittent currents of induction which he maintained through his apparatus for several months. 

Black layers of carbon were deposited on platinum wires, and under microscopic examination these were found to contain crystals of octahedral shape. When tested, the black powder was able to polish a ruby, but the crystals were too tiny to be submitted to more conclusive testing. Despretz's method bears a marked similarity to one reported in the Journal de Physique of Genoa in 1812 in which the current from a strong Galvanic battery was passed through a mass of charcoal. A substance was produced which "appeared to have the greatest resemblance to diamonds."

 Ring Diamond
The experiments described were some of the better-known ones carried out for the most part by reputable scientists in a spirit of genuine scientific enquiry, but there were many others which were dubious in both method and intention. One such experiment was described in scathing terms in The Gentleman's Magazine of August 1868:

There are no longer alchemists who believe in the transmutation of metals, the base into the precious; but those still exist who hold it possible to make diamonds from worthless material. One of this class has proposed a solution of the famous problem to the French Academy, and the august body has smiled upon, not at, the project. M. Caliste Saix is the happy discoverer who has found the way to cheat Nature out of her riches, and with praiseworthy disinterestedness he has given his method freely to the world. 

The process consists in passing a stream of chlorine gas over fused cast iron: a perchloride of the metal is formed and volatilizes leaving the carbon in the metal intact. According to the author, the carbon must, under the circumstances, crystallize and appear as diamonds. 60 grams [2 ounces] weight of jewels is to come from 1 kilogram [2.2 pounds] of iron; the raw material costing 20 francs and the precious product realizing 75,000 francs. The process is creating some stir in France, but we cannot hear that any diamonds have actually been made.

Heart Shaped Man Created DiamondA better-known experiment was that carried out by a young Scots chemist, James Hannay wrought-iron tubes and placed them into a large reverbatory furnace. The idea was that the high pressure and intense heat would cause the carbon to recrystallize as diamond. It was a dangerous experiment which nearly cost him his life when most of the tubes exploded, wrecking the furnace and the laboratory. However, the surviving tubes were found to contain a mass of solid material covering their walls, which when scraped yielded a number of tiny crystals. 

Hannay promptly dispatched the crystals to the British Museum where the keeper of minerals was confident enough to pronounce them to be diamonds. But unlike those of his French predecessors, Hannay's synthetic "diamonds" still exist, and in 1943 two crystallographers subjected them to exhaustive testing. Their conclusion was that of the twelve crystals, eleven were diamonds and one was not. Doubts must remain about the apparent success of Hannay's experiments, if only because of the positive assertion of today's scientists that his iron tubes could never have contained the pressure necessary for converting the materials used into diamond.

Twelve years later Henri Moissan, a French physicist of note, carried out a series of experiments based on his view of how diamonds had come to be found in meteorites. He argued that if a mixture of carbon and iron was superheated and then cooled abruptly by being plunged into water, a rigid crust would be formed and extremely high pressure produced at the center. This combination of intense heat and very high pressure would be enough to crystallize the carbon. 

DiamondsA number of crystals duly appeared as a result of this process and in his report to the Academy of Sciences, Moissan claimed that they were indeed diamonds. Again doubts have been cast on the success of these experiments both because later attempts to reproduce them have failed to create any-thing but silicon carbide or alumina, and because Moissan's widow is said to have brought allegations of fraud against one of her husband's assistants, claiming that he introduced diamonds into the mixture so that the experiments would appear to be a success.

But it was another Frenchman, Henry Lemoine, who in 1905 really shook the diamond world. Reputedly an engineer once employed by Moissan, he approached Sir Julius Wernher, partner of Alfred Beit and a director of De Beers, with the claim that he could manufacture large, flawless synthetic diamonds by a new and secret process. Sir Julius was a hard-headed businessman but his concern for the future of the diamond industry was so great that he was prepared to treat Lemoine's claim seriously. Lemoine arranged a demonstration in the basement of a Paris warehouse and duly produced from his electric furnace, twenty-five diamonds of good size and excellent color. Sir Julius and Alfred Beit were impressed enough to advance Lemoine £64,000 to build a factory to continue his experiments at Argeles, a town in the Pyrenees. They also obtained an option on the secret formula which had been deposited under seal in a London bank.

Man Made DiamondFor three years Lemoine continued his experiments, occasionally sending samples of his work to Sir Julius in London and regularly making demands for further cash advances. Two things soon began to shake Sir Julius's confidence in his protégé. One was a report that Lemoine's factory at Argeles had blossomed into a flourishing utility company supplying electricity to the neighboring villages. The other was that the "synthetic diamonds" bore a remarkable resemblance to the very distinctive crystals from De Beers' own Jagersfontein mine. 

Another demonstration was demanded, this time in the presence of Francis Oates, an expert from Kimberley. Lemoine had no choice but to comply and placed a handful of carbon in his electric furnace which he claimed was capable of producing a heat of 3,000,000°F. When the furnace was opened to, Lemoine's great astonishment, not one but two fine white diamonds lay in the ashes. Oates was less surprised. Suspecting a ruse and that the furnace was not capable of producing such heat, he had cleverly slipped a diamond into the retort. Lemoine was arrested and charged with fraud.

Beautiful DiamondThe trial became something of a cause célèbre in Paris and the press made the most of the accusations and counteraccusations, especially those aimed by Lemoine at Sir Julius Wernher. One was that Sir Julius had conspired with him to sell the secret formula to De Beers for $25 million at the same time that he was making a killing on the side through stock market dealings. However, the press's championing of Lemoine was severely strained by his apparent reluctance either to rout his accusers by releasing his formula or by proving to the court that he could in fact make diamonds. At last he agreed to carry out a demonstration of his secret manufacturing process, but postponed the date time and time again. 

The court began to lose patience and finally ordered him to perform on June 18, 1908. This time Lemoine failed to appear, and it was learned that he had fled the country. The envelope containing the secret formula was opened and the contents read out to an incredulous court. All one had to do to make diamonds, according to Lemoine, was to place powdered carbon and sugar in a crucible, place it in an electric furnace, heat it to 1,600° and then apply pressure to the cover of the crucible, whereupon "diamonds should be found therein." The judge sentenced Lemoine in his absence to twenty years' imprisonment.

It was not until 1953 that scientists under the aegis of the Swedish company ASEA carried out the first repeatable synthesis and succeeded in making tiny industrial-type diamond crystals. They were less than a millimeter in size but there was no doubt that they were diamonds. Pressures of between 80,000 and 90,000 atmospheres were used at temperatures up to 2,760°C. The principle was not all that different from that of James Hannay, but both temperatures and pressures I were very much higher and the mixture of iron carbide and graphite with tantalum as a metal catalyst was a little more precise. ASEA continues to produce industrial diamonds in partnership with De Beers Consolidated Mines Limited.

Known as SDA 100, this synthetic diamond grit is a new De Beers saw diamond abrasive designed for the toughest sawing operations. It consists of extremely strong, single crystals of cubooctahedral type with sharp well-defined edges, smooth faces and a block-like shape. The crystals are relatively clear and free from inclusions and flaws, qualities which make SDA 100 exceptionally tough and long lasting.Almost simultaneously in the United States, scientists of the General Electric Company were working along the same lines and in 1955 produced their first synthetic diamonds. Their process involved a high-pressure apparatus known as the belt, a ring of tungsten carbide with a hole in the center shaped to form a cylinder flared at each end. To make diamond, carbon and a metal catalyst are placed in the hole in the belt, and two bullet-shaped pistons are driven into opposite ends of the hole at the same time as pressure is being applied by an hydraulic press and a current of electricity is passed through the center. Again, the result was very fine crystals weighing less than one-thousandth part of a carat and measuring less than a millimeter in length. In fact, they were little more than industrial diamond grit.

Making large, clear synthetic diamonds of gem quality was quite another matter. This was first achieved by General Electric scientists in 1970. They used the belt apparatus in conjunction with a special chamber containing synthetic diamond crystals which "feed" diamond seed crystals placed at either end of the chamber. Given stability of temperature and pressure, the seed crystals grow at about two to three milligrams an hour. This means that it takes almost exactly a week to produce a one-carat synthetic gem diamond. It is also possible to create the type of diamond required in the way of electrical properties, hardness and internal structure, for example, by introducing additional elements into the chamber and varying both the temperature and the pressure.

It should be stressed that General Electric did not set out deliberately to manufacture artificial gem diamonds to compete with the natural product. Better-quality synthetic diamonds were simply the result of ever-improving methods of synthesis. The first artificial diamonds of any size were made by General Electric in 1961 but they had a number of structural defects that rendered them unsuitable for industrial use. To manufacture diamonds large enough and structurally sound enough to enable them to be used in drilling bits, cutting tools and dies was the prime object of the exercise; gem-quality synthetics were an incidental, if inevitable spin-off.

Man Created DiamondsNevertheless, the announcement by General Electric of their success in creating gem diamonds caused a considerable stir in a diamond world that had already endured more than its fair share of slumps caused by overproduction from new sources. The prospect of factory-made gems flooding the market was a very real and frightening one for many diamond men who had lived through the 1920s and '30s. General Electric was at pains to allay such fears by pointing out that it was announcing a scientific achievement and not a product. De Beers issued a statement congratulating General Electric on an historic scientific breakthrough, secure in the knowledge that costs of production for artificial gems must remain prohibitive for the foresee-able future.

But cost is not the only factor which rules out synthetic diamond as serious competition for the natural stone. There are marked differences between the two products and so long as this distinction remains there will always exist a preference for the "real thing." This has certainly been the case in the past with synthetic rubies, sapphires and emeralds where the increased demand that arose from the marketing of synthetics served to emphasize the rarity and value of the natural product.

Writer – George G. Blakey
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