Industrial diamond applications

Other Industrial Applications. High pressures are used industrially for many other specialized appHcations. Apart from mechanical uses in which hydrauhc pressure is used to supply power or to generate Hquid jets for mining minerals or cutting metal sheets and fabrics, most of these other operations are batch processes. Eor example, metallurgical appHcations include isostatic compaction, hot isostatic compaction (HIP), and the hydrostatic extmsion of metals. Other appHcations such as the hydrothermal synthesis of quartz (see Silica, synthetic quartz crystals), or the synthesis of industrial diamonds involve changing the phase of a substance under pressure. In the case of the synthesis of diamonds, conditions of 6 GPa (870,000 psi) and 1500°C are used (see Carbon, diamond, synthetic). 

Over the last few decades, the use of radiation sources for industrial applications has been widespread. The areas of radiation applications are as follows (i) Wires and cables (ii) heat shrinkable tubes and films (iii) polymeric foam (iv) coating on wooden panels (v) coating on thin film-video/audio tapes (vi) printing and lithography (vii) degradation of polymers (viii) irradiation of diamonds (ix) vulcanization of mbber and rubber latex (x) grain irradiation. 

An alternative to the measurement of the dimensions of the indentation by means of a microscope is the direct reading method, of which the Rockwell method is an example. The Rockwell hardness is based on indentation into the sample under the action of two consecutively applied loads - a minor load (initial) and a standardised major load (final). In order to eliminate zero error and possible surface effects due to roughness or scale, the initial or minor load is first applied and produce an initial indentation. The Rockwell hardness is based on the increment in the indentation depth produced by the major load over that produced by the minor load. Rockwell hardness scales are divided into a number of groups, each one of these corresponding to a specified penetrator and a specified value of the major load. The different combinations are designated by different subscripts used to express the Rockwell hardness number. Thus, when the test is performed with 150 kg load and a diamond cone indentor, the resulting hardness number is called the Rockwell C (Rc) hardness. If the applied load is 100 kg and the indentor used is a 1.58 mm diameter hardened steel ball, a Rockwell B (RB) hardness number is obtained. The facts that the dial has several scales and that different indentation tools can be filled, enable Rockwell machine to be used equally well for hard and soft materials and for small and thin specimens. Rockwell hardness number is dimensionless. The test is easy to carry out and rapidly accomplished. As a result it is used widely in industrial applications, particularly in quality situations. 

With the technical development achieved in the last 30 years, pressure has become a common variable in several chemical and biochemical laboratories. In addition to temperature, concentration, pH, solvent, ionic strength, etc., it helps provide a better understanding of structures and reactions in chemical, biochemical, catalytic-mechanistic studies and industrial applications. Two of the first industrial examples of the effect of pressure on reactions are the Haber process for the synthesis of ammonia and the conversion of carbon to diamond. The production of NH3 and synthetic diamonds illustrate completely different fields of use of high pressures the first application concerns reactions involving pressurized gases and the second deals with the effect of very high hydrostatic pressure on chemical reactions. High pressure analytical techniques have been developed for the majority of the physicochemical methods (spectroscopies e. g. NMR, IR, UV-visible and electrochemistry, flow methods, etc.). 

The high elastic modulus, compressive strength, and wear resistance of cemented carbides make them ideal candidates for use in boring bars, long shafts, and plungers, where reduction in deflection, chatter, and vibration are concerns. Metal, ceramic, and carbide powder-compacting dies and punches are generally made of 6 wt % and 11 wt % Co alloys, respectively. Another application area for carbides is the synthetic diamond industry where carbides are used for dies and pistons (see Carbon). 

Smith N. S., 1965, Industrial Application of the Diamond, Hutchinson and Co., London. 

When a single crystal diamond (synthetic or natural) is the substrate, epitaxial growth occurs the growing diamond replicates the substrate crystal lattice and turns to single crystal film. The film thickness usually comes to a few microns however, films of 1 mm in thickness were reported. The diamond-coated area would achieve 10 cm in diameter by order for industrial applications, much larger areas (e.g. 40 by 60 cm) are covered. Samples destined for the electrochemical measurements used to have dimensions ca. 1 by 1 cm. 

Werner Haenni, Philippe Rychen, Matthyas Fryda and Christos Comninellis, Industrial Applications of Diamond Electrodes... 

Haenni, W., Rychen, P., Fryda, M. and ComnineUis, Ch. (2004) Industrial applications of diamond electrodes. Semiconduct. Semimet. 77, 149-196. 

Haenni W., Rychen P., FrydaM. and Comninellis C. Industrial applications of diamond electrodes, in C. E. Nebel and J. Ristein, Editors, Semiconductors and Semimetals, vol. 77 (Thin-film Diamond II), p. 149, (2004). 

One method involves the microwave-induced removal of hydrogen from methane (CH, swamp gas) in a very sparse gas phase so that carbon atoms, stripped of most of their hydrogen, can settle out on the substrate and start building diamond crystals. In the past, the diamonds formed in this process were tiny and only suitable for industrial applications, but lately gem-quality crystals have been grown. The artificial diamond is virtually indistinguishable from the natural diamond because they are both just a crystalline form of carbon. 

In addition to their importance in jewelry, diamonds also have important industrial applications such as in diamond-impregnated cutting tools and as abrasives. The world use of diamonds is about 261 (26 Mg) per year, of which about 161 is synthetic. The synthetic diamond industry is a 1 billion/year business. 

Reports on man-made diamond obtained by HPHT synthesis were first published in 1955 by General Electric [4]. Usually, metals able to dissolve carbon under HPHT conditions are used as catalysts and increase growth rates. Diamond crystals of several millimeters in size can be obtained in this way, but usually small grains for abrasives are produced. Direct conversion of graphite to diamond without catalyst in HPHT apparatus is possible, but uneconomical for industrial application. Direct transformation can be done by the detonation method and produces nanosized powders of diamond and diamond-like carbon [5]. 

The commercial availability of synthetic diamond offered two advantages. First, there was potentially unlimited availability of industrial diamond compared to the limited volumes of suitable natural material and, second, it offered the opportunity of engineering material to have specific properties suited to particular industrial applications. 

This combination of properties can be traced to the same structural characteristics of diamond that give rise to its high hardness. It is therefore reasonable to expect that other ultrahard materials would also exhibit such a suite of properties. This would make them also desirable for a number of industrial applications. 

Industrial applications of diamond have developed over the years as a result of developments by tool makers, machinery manufacturers and the advert of new materials. In addition, new diamond (and cBN) products have evolved, either as a result of technological advances in synthesis or in response to the requirements of a new application, and it is this multi-partnership relationship within the industry which has resulted in the dramatic growth and diversification since the early 1960s. 

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