Diamond: structure, 4 synthetic

Faceted, polycrystalline structure Synthetic diamond Blocky... 

Faceted, single crystalline structure Synthetic diamond Cubocta... 

Apart from naturally occurring diamond there is by now a variety of artificial carbon materials that feature diamond structure as well. These include the synthetic diamond generated by high pressure and temperature, but also films, polycrystalline materials resembling the carbonados (Section 1.3.2) and the so-called... 

Diamond density is about 3.52 g/cm depending on pureness. Synthetic diamonds expose metal inclusions of used catalysts. All crystal defects such as substituted atoms and atoms between lattice sites or lattice vacancies are imperfections of diamond structure and enable micro-spUntering (O Donovan 1976). Small grits are often tougher than large diamonds because they have fewer and smaller defects and inclusions (Field 1979). 

The linking pattern of two zeolites is shown in Fig. 16.24. They have the /I-cage as one of their building blocks, that is, a truncated octahedron, a polyhedron with 24 vertices and 14 faces. In the synthetic zeolite A (Linde A) the /3-cages form a cubic primitive lattice, and are joined by cubes. j3-Cages distributed in the same manner as the atoms in diamond and linked by hexagonal prisms make up the structure of faujasite (zeolite X). 

Kandelbauer A, Erlacher A, Cavaco-Paulo A, Guebitz GM (2004) Laccase catalyzed decolorization of the synthetic dye Diamond Black PV 200 and some structurally related derivatives. Biocatal Biotransformation 22 331-339... 

Natural diamond Natural graphite Synthetic diamond alloyed with iron, 23 248 in amorphous silica, 22 385 antimony impregnated, 3 53 atomic structure of, 22 232 biologically active, 17 803 as a blast furnace refractory,... 

Synthetic camphor, 24 540 Synthetic compounds, as plant growth regulators, 13 39-56 Synthetic crude oil, 13 640 Synthetic cyclic molecules, 24 35 Synthetic diamond, 3 530-543 catalyzed synthesis, 3 531-535 crystal growth, 3 535 crystal morphology, 3 534-535 crystal structure, 3 537-538 direct graphite-to-diamond process, 3 535-538... 

Cubic Phase of Boron Nitride c-BN. The cubic phase of boron nitride (c-BN) is one of the hardest materials, second only to diamond and with similar crystal structure. It is the first example of a new material theoretically predicted and then synthesized in laboratory. From automated synthesis a microcrystalline phase of cubic boron nitride is recovered at ambient conditions in a metastable state, providing the basic material for a wide range of cutting and grinding applications. Synthetic polycrystalline diamonds and nitrides are principally used as abrasives but in spite of the greater hardness of diamond, its employment as a superabrasive is limited by a relatively low chemical and thermal stability. Cubic boron nitride, on the contrary, has only half the hardness of diamond but an extremely high thermal stability and inertness. 

Diamonds are another allotrope whose crystal structure is similar to graphite. Natural diamonds were formed under higher pressure and extreme temperatures. Synthetic diamonds have been artificially produced since 1955. 

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 adamantane structure is unique as it combines three annullated cyclohexane subunits in a nearly spherical overall shape and, as such, it can be regarded as a section of the diamond crystal lattice578. Due to this property, adamantane and other diamondoid molecules are popular as model compounds for synthetic and spectroscopic purposes579 780. 

The cubic form resembles diamond in its crystal structure and is almost as hard. The theoretical density is 3.48 g/mL. It is colodess and a good electrical insulator when pure traces of impurities add color and make it semiconducting, eg, a few ppm of Be make it blue and />-type whereas small amounts of S, Si, or CN favor yellow, -type crystals. It is possible to makep—n junctions by growing -type material on j -type seed crystals (12). If this is done carefully in an alkaline-earth nitride bath using a temperature difference technique, as with large diamond crystals (see Diamond, SYNTHETIC), the resulting diodes are several mm in size and emit blue light when forward-biased (13,14). 

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