Environment Diamond

C60 has not yet been detected in primitive meteorites, a finding that could demonstrate its existence in the early solar nebular or as a component of presolar dust. However, other allotropes of carbon, diamond and graphite, have been isolated from numerous chondritic samples. Studies of the isotopic composition and trace element content and these forms of carbon suggest that they condensed in circumstellar environments. Diamond may also have been produced in the early solar nebula and meteorite parent bodies by both low-temperature-low-pressure processes and shock events. Evidence for the occurrence of another carbon allotrope, with sp hybridized bonding, commonly known as carbyne, is presented. 

Because of the importance of semiconductors in our everyday lives, it is important to draw attention to the structural similarities that exist within this group of materials. The majority of semiconductors exhibit either a diamond (Fig. 6.20) or zinc blende (Fig. 6.19) structure type, with the wurtzite structure (Fig. 6.21) being less common. In each of these prototype structures, atoms are in tetrahedral environments. Diamond-type stmetures are adopted by Si and Ge, and the addition of dopants (see Section 6.9)... 

Hydrogen-driven CVD processes are not necessarily the only type. In a nitrogen environment, diamonds are also formed (21). Supposition that diamond can be synthesized only under conditions of its thermodynamic stability is an old concept that has passed away. The diamond-graphite borderline, known as Berman-Simon extrapolation, is not an exclusion to growth of diamond at lower pressures. 

Knoop developed an accepted method of measuring abrasive hardness using a diamond indenter of pyramidal shape and forcing it into the material to be evaluated with a fixed, often 100-g, load. The depth of penetration is then determined from the length and width of the indentation produced. Unlike WoodeU s method, Knoop values are static and primarily measure resistance to plastic flow and surface deformation. Variables such as load, temperature, and environment, which affect determination of hardness by the Knoop procedure, have been examined in detail (9). 

J.m/h. Because the diamond growth takes place under atmospheric conditions, expensive vacuum chambers and associated equipment are not needed. The flame provides its own environment for diamond growth and the quaUty of the film is dependent on such process variables as the gas flow rates, gas flow ratios, substrate temperature and its distribution, purity of the gases, distance from the flame to the substrate, etc. 

Optical. Besides the gem quaHties dependent on optical properties, diamond is very useful as a light-transmitting window for lasers and for simple windows for monitoring chemical processes in corrosive and otherwise hostile environments. 

Research. A significant impact on research at high pressure has come about with the use of gem quaHty diamonds as Bridgman-type anvils in a smaU compact high pressure device (40—42). With this type of apparatus, pressures greater than those at the center of the earth (360 GPa = 3.6 Mbars) have been reached, and phase transformations of many materials have been studied. Because of the x-ray transparency of diamond, it is possible to determine the stmcture of the phases under pressure. Because of the strenuous environment, crystals selected for this appHcation have to be of very high quaHty. 

Diamond, G. L. et al., 1988, A Portable Computing System for Use in Toxic Gas Emergencies, Ontario Ministry of the Environment, ARB-150-87, ISBN 0-7729-3448-7, revised. 

With such properties, it could be the ideal material for many semiconductor applications, such as high-power and high-frequency transistors and cold cathodes, or in the harsh environment found in internal-combustion and jet engines. With the advent of CVD diamond, it is now possible to take advantage of these properties. 

CVD diamond films can be used for electrochemical applications, especially in harsh or corrosive environments. Conducting diamond electrodes, made by adding boron to CVD diamond films, are very inert compared to other electrode materials (such as platinum). Such diamond electrodes may find applications in analysis of contaminants, such as nitrates, in water supplies, and even in the removal of those contaminants. 

Diamond ML, Mackay D, Cornett RJ, et al. 1990. A model of the exchange of inorganic chemicals between water and sediments. Environ Sci Technol 24(5) 713-722. 

Macdonald RW, Barrie LA, Bidleman TF, Diamond ML, Gregor DJ, Semkin RG, Strachan WMJ, Li YF, Wania F, Alaee M, Alexeeva LB, Backus SM, Bailey R, Bewers JM, Gobeil C, Halsall CJ, Hamer T, Hoff JT, Jantunen LMM, Lockhart WL, Mackay D, Muir DCG, Pudykiewicz J, Reimer KJ, Smith JN, Stem GA, Schroeder WH, Wagemann R, Yunker MB (2000) Sci Total Environ 254 93... 

Diamond, S.A., M.C. Newman, M. Mulvey, RM. Dixon, and D. Martinson. 1989. Allozyme genotype and time to death of mosquitofish, Gamhusia affinis (Baird and Girard), during acute exposure to inorganic mercury. Environ. Toxicol. Chem. 8 613-622. 

Diamond, J.M., D.G. Mackler, M. Colhns, and D. Gruber. 1990. Derivation of a freshwater silver criteria for the New River, Virginia, using representative species. Environ. Toxicol. Chem. 9 1425-1434. 

Baird, W.M., R.A. Chemerys, L. Diamond, T.H. Meedel, and J.R. Whittaker. 1982. Metabolism of benzo[a]pyrene by Ciona intestinalis. Pages 191-200 in N.L. Richards and B.L. Jackson (eds.) Symposium Carcinogenic Polynuclear Aromatic Hydrocarbons in the Marine Environment. U.S. Environ. Protection Agency Rep. 600/9-82-013. 

Ankley, G.T., J.E. Tietge, D.L. DeFoe, K.M. Jensen, G.W. Holcombe, E.L. Durhan, and S.A. Diamond. 1998. Effects of ultraviolet light and methoprene on survival and development of Rana pipiens. Environ. Toxicol. Chem. 17 2530-2542. 

These specific, and other broader, concerns in corporate compliance with TSCA s requirements were discussed by Diamond Shamrock Corporation s D. Harlow. He described how corporate structures and procedures, including those for research and development, for companies of all sizes, have been impacted by TSCA. These impacts are generally positive in that they reflect greatly increased awareness, resources and responsiveness to questions of chemicals effects on health and environment. These benefits are seen to be in balance with their costs, expressed in the increased costs of products and services. 

Diamond, L. and O Donnell, M., Pulmonary mechanics in normal rats, ]. Appl. Physiol. Resp., Environ., Exercise Physiol., 43, 942-948,1977. 

Hamer, T. Shoeib, M. Diamond, M. Stern, G. Rosenberg, B. 2004, Using passive air samplers to assess urban-mral trends for persistent organic pollutants. 1. Organochlorine pesticides. Environ. Sci. Technol. 38 4474 483. 

Abdallah MAE, Harrad S, Ibarra C, Diamond M, MelmymukL, Robson M, Covaci A (2008) Hexabromocyclododecanes in indoor dust from Canada, the United Kingdom, and the United States. Environ Sci Technol 42 459 64... 

Harrad S, de Wit CA, Abdallah MAE, Bergh C, Bjorklund JA, Covad A, Damerud PO, de Boer J, Diamond M, Huber S, Leonards P, Mandalakis M, Oestman C, Haug LS, Thomsen C, Webster TF (2010) Indoor contamination with hexabromocyclododecanes, polybrominated diphenyl ethers, and perfluoroalkyl compounds an important exposure pathway for people Environ Sci Technol 44 3221-3231... 

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