Diamond production

Ref 4. Diamond production is 107,771,000 carats (21.6 t). Fuel products such as natural gas, peat, petroleum, etc, are not included. ... 

G. Lenzen, The History of Diamond Production and the Diamond Trade, Praeger Pubhshers, Berlin, Germany, 1966, pp. 192 1—230. 

The bulk of synthetic industrial diamond production consists of the smaller crystal sizes up to 0.7-mm particle size (25 mesh). This size range has wide utihty in industry, and a significant fraction of the world s need for diamond abrasive grit is now met by synthetic production yielding thousands of kilograms per year. Because the raw materials are plentiful, synthetic production could, if necessary, supply the world demand for diamond abrasive. Development work continues in order to improve size and utility of the manufactured product and to realize the full potential of diamonds at minimum cost. An appreciable increase in performance has been obtained by coating the diamonds with a thin layer of nickel or copper, before incorporating them into wheels. The thin layer of metal apparendy improves adhesion and heat transfer. 

A reactive gas-phase H atom is required to initiate the growth via reaction 1, which creates a reactive surface site, C (s). This site is either passivated by reaction 2, or the mechanism proceeds in the growth direction via reaction 3 in which a carbon from the gas is incorporated onto the surface. In a hydrogen-rich environment, reactions 5 and 6 lead to growth of the desired diamond product, Diamond(b). However, if the environment is carbon-rich, reaction 8 leads to undesired incorporation of the Defect(b) species, essentially buried hydrogen in the lattice. 

The mining of natural raw diamonds currently accounts for 29% of diamond production quantitywise, but this small quantity accounts for 92% of the value of raw diamonds (see Table 5.7-1). 

In principle, there are two procedures that differ in the kind of starting material used. In the first process, the explosive is detonated mixed with a graphitic substance. Two things happen simultaneously then Firstly, a direct conversion of the already existing elemental carbon, and secondly, a condensation of carbon from the explosive. Together they result in the formation of a polycrystalline diamond product with particle dimensions almost idenhcal to those of the starting material. Hence, an at least partially martensitic process can be assumed for the mechanism of formation. The yield is about 17% relative to the carbon employed or, relative... 

Figure 5.13 Scheme of the diamond production by shock synthesis according to the DuPont method. 

By February 15, 1955, diamonds had been produced in about 100 separate runs in the General Electric Research Laboratory. On this date a press conference was held and the fact that diamonds had finally been made by man was announced to the world. However, details concerning the synthesis were not released. On October 22, 1957, the company announced that diamond production had successfully been carried through the pilot plant stage—more than 100,000 carats (carat = 0.200 g) having been produced up to that time. Thus, less than three years following the successful conclusion of a 100-plus years search for a method to convert ordinary black carbon into diamond, man-made diamonds became a commercial product. Details of apparatus and methods of synthesis were finally released in the fall of 1959. 

NWT Diamond Industry www.iti.gov.nt.ca/diamond/production.htm for details on the Diavikmine. 

Market for Diamond Products. Table 1.4 gives an estimate of the market for the various categories of diamond. 

Tabie 1.4. Estimated World Market for Diamond Products in 1991... 

NATURAL AND HIGH-PRESSURE SYNTHETIC DIAMOND PRODUCTION... 

Interest in these molecules stems from not only their relationship to diamond and their potential to act as seed crystals in industrial diamond production, but also from their stability and inertness. Thus, they provide biologically compatible scaffolds for new drugs, cosmetics, and pol3meric materials. 

FIGURE 4.11 Diamond-graphite equilibrium, showing the calculated equilibrium curve and (shaded) the region of commercial diamond production. (From Wentorf, R. H. J. Diamond synthetic. In Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 4, ed. 3. Grayson, M., ed. 1978, New York Wiley. Reprinted by permission of John Wiley and Sons.)... 

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