Graphite diamonds made from

Carbon is something we encounter every day. Graphite, which is pure carbon, is the lead in pencils. Diamonds are carbon and so is charcoal. Some hard coals are up to 98% carbon. Carbon is also present in all living things. Forests, for example, are made almost entirely of carbon-containing compounds. Carbon and carbon compounds are widely used as raw materials in industrial products. Many plastics, detergents, foods, and medicines are made from carbon-containing compounds. 

Traditionally, synthetic diamonds are made from graphite. Since the 1950s, scientists have known how to use pressure and heat to manufacture synthetic diamonds. Gradually, the quality of the synthetic gems has improved. Today, it is difficult to tell a good synthetic diamond from a natural stone. According to the American Museum of Natural History, currently about 80 tons of synthetic diamonds are manufactured each year. 

Boron-doped diamond electrodes — Electrode material made from synthetic diamond (- diamond electrode) for example via vapor deposition techniques. In an atmosphere of methane (as a carbon source) and hydrogen (as etchant) at ca. 600 °C diamond seeds tend to grow whereas graphitic carbon deposits are etched... 

Single pulse, shock tube decomposition of acetic acid in argon involves the same pair of homogeneous, molecular first-order reactions as thermolysis (19). Platinum on graphite catalyzes the decomposition at 500-800 K at low pressures (20). Ketene, methane, carbon oxides, and a variety of minor products are obtained. Photochemical decomposition yields methane and carbon dioxide and a number of free radicals, which have complicated pathways (21). Electron impact and gamma rays appear to generate these same products (22). Electron cyclotron resonance plasma made from acetic acid deposits a diamond [7782-40-3] film on suitable surfaces (23). The film, having a polycrystalline structure, is a useful electrical insulator (24) and widespread industrial exploitation of diamond films appears to be on the horizon (25). 

The value of AH is an approximate measure of the stability of a substance relative to the elements from which it is made. The standard enthalpies of formation of graphite, diamond, water, ethyne (acetylene, C2H2), ammonia and sodium chloride are shown in Fig. 13.6. The reference states of elements define an energy baseline or sea level . Compounds such as ethyne, for which AHf is positive, and which therefore possess a greater enthalpy than their constituent elements, appear above sea level and are called endothermic compounds. Compounds such as water, ammonia and sodium chloride, for which AHf is negative and which therefore possess a lower enthalpy than their constituent elements, appear below sea level and are called exothermic compounds. 

Carbon is found as three allotropes, or structural forms diamond, graphite, and fullerenes. Even though they are made from the same atom, these three allotropes have wildly different properties and applications because of the different bonding arrangements within each one. 

Diamond has a higher density than graphite (Pgraphite = 2.25 diamond = 3.51 gcm ), and this allows artificial diamonds to be made from graphite at high pressures (see Box 14.5). There are two structural modifications of graphite. 

Carbon fibers have been known since their development by Thomas Edison in 1870 and have been under continuous development for the past 60 years (Hearle, 2001 Peebles, 1995). The current interest in carbon fibers stems from their excellent mechanical properties and thermal stabiUty. Carbon can be found in nature in many forms. Diamond, graphite, and ash are all made from pure carbon atoms with different atomic arrangements. Diamonds are made from covalent 3D bonds between carbon atoms. Graphite and carbon fibers are made from sheets of covalent-bonded carbon atoms. These sheets are connected to each other via a weak secondary bond. 

Diamonds are now commercially made from graphite. The development of the process for this was greatly aided by prior knowledge of the energy and entropy changes in the oxidation of two forms of carbon, diamond and graphite, to CO2. The following sketch shows how AU and AS were estimated even before diamond synthesis was accomplished (see Box 2). 

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