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Diamond chemical properties

Another example of epitaxy is tin growdi on the (100) surfaces of InSb or CdTe a = 6.49 A) [14]. At room temperature, elemental tin is metallic and adopts a bet crystal structure ( white tin ) with a lattice constant of 5.83 A. However, upon deposition on either of the two above-mentioned surfaces, tin is transfonned into the diamond structure ( grey tin ) with a = 6.49 A and essentially no misfit at the interface. Furtliennore, since grey tin is a semiconductor, then a novel heterojunction material can be fabricated. It is evident that epitaxial growth can be exploited to synthesize materials with novel physical and chemical properties. [Pg.927]

The structural differences between graphite and diamond are reflected in their differing physical and chemical properties, as outlined in the following sections. [Pg.276]

Hardness on the Mohs scale is often above 8 and sometimes approaches 10 (diamond). These properties commend nitrides for use as crucibles, high-temperature reaction vessels, thermocouple sheaths and related applications. Several metal nitrides are also used as heterogeneous catalysts, notably the iron nitrides in the Fischer-Tropsch hydriding of carbonyls. Few chemical reactions of metal nitrides have been studied the most characteristic (often extremely slow but occasionally rapid) is hydrolysis to give ammonia or nitrogen ... [Pg.418]

Structural chemistry is an essential part of modern chemistry in theory and practice. To understand the processes taking place during a chemical reaction and to render it possible to design experiments for the synthesis of new compounds, a knowledge of the structures of the compounds involved is essential. Chemical and physical properties of a substance can only be understood when its structure is known. The enormous influence that the structure of a material has on its properties can be seen by the comparison of graphite and diamond both consist only of carbon, and yet they differ widely in their physical and chemical properties. [Pg.1]

A number of chemical elements, mainly oxygen and carbon but also others, such as tin, phosphorus, and sulfur, occur naturally in more than one form. The various forms differ from one another in their physical properties and also, less frequently, in some of their chemical properties. The characteristic of some elements to exist in two or more modifications is known as allotropy, and the different modifications of each element are known as its allotropes. The phenomenon of allotropy is generally attributed to dissimilarities in the way the component atoms bond to each other in each allotrope either variation in the number of atoms bonded to form a molecule, as in the allotropes oxygen and ozone, or to differences in the crystal structure of solids such as graphite and diamond, the allotropes of carbon. [Pg.94]

They all have different physical properties but have the same chemical properties. Even diamond and graphite bum in air to form carbon dioxide. [Pg.63]

The differences in the physical properties of diamond and graphite are because of the manner in which the carbon atoms are arranged. Their chemical properties, however, are the same. They both bum in air to form carbon dioxide. They are allotropes of carbon. [Pg.64]

Owing to its extraordinary chemical stability, diamond is a prospective electrode material for use in theoretical and applied electrochemistry. In this work studies performed during the last decade on boron-doped diamond electrochemistry are reviewed. Depending on the doping level, diamond exhibits properties either of a superwide-gap semiconductor or a semimetal. In the first case, electrochemical, photoelectrochemical and impedance-spectroscopy studies make the determination of properties of the semiconductor diamond possible. Among them are the resistivity, the acceptor concentration, the minority carrier diffusion length, the flat-band potential, electron phototransition energies, etc. In the second case, the metal-like diamond appears to be a corrosion-stable electrode that is efficient in the electrosyntheses (e.g., in the electroreduction of hard to reduce compounds) and electroanalysis. Kinetic characteristics of many outer-sphere... [Pg.209]

The physico-chemical properties of surface initial diamond, are, in their turn, due to chemical composition of the powder surface, the nature of adsorption processes proceeding on the surface of their [7, 8],... [Pg.551]

In addition to silicon and metals, a third important element being deposited as thin films is diamond (Celii and Butler, 1991 May, 2000). For many years, diamonds were synthesized by a high pressure/high temperature technique that produced bulk diamonds. More recently, the interest in diamonds has expanded to thin films. Diamond has a slew of properties that make it a desired material in thin-film form hardness, thermal conductivity, optical transparency, chemical resistance, electrical insulation, and susceptibility to doping. Thin film diamond is prepared using chemical vapor deposition, and we examine the process in some detail as a prototypical chemical vapor example. Despite its importance and the intensity of research focused on diamond chemical vapor deposition, there remains uncertainty about the exact mechanism. [Pg.131]

These multiple roles operate in parallel with a complex structural chemistry giving rise to families of chemically vastly different modifications of the element. It is a special characteristic of carbon chemistry that many of these modifications cannot be obtained as phase-pure materials. This limits the exact knowledge ol physical and chemical properties to a few archetype modifications, namely graphite and diamond. [Pg.100]

The technical synthesis of graphite, diamond and a variety of other forms of sp2 carbons (Fig. 3) is described in a review [39] and is not covered here. As the unintended formation of carbon in deactivation processes and the modification of primary carbon surfaces during chemical treatment (in catalytic service and during oxidative reactivation) and their chemical properties arc frequent problems encountered in catalytic carbon chemistry, it seems appropriate to discuss some general mechanistic ideas which mostly stem from the analysis of homogeneous combustion processes (flame chemistry) and from controlled-atmosphcre electron microscopy. [Pg.110]

In the different fields of science and engineering during the past few years the interest in diamond powders as the multipurpose materials with a wide set of physico-chemical properties has considerably increased. So, the production of diamond powders with specific propetries, particularly with specific chemical and energy properties of a diamond grain surface, is the important research and technology topics. [Pg.503]

Relationship between physico-chemical properties of the crystallization medium ( Ni-Mn-Ga-C and Ni-Mn-Si-C systems) and physico-mechanical, physico-chemical properties and performance characteristics of synthesized diamond powders. [Pg.506]

So, our investigations allow us to establish the correlation between physico-chemical properties of the crystallization media (capillary properties of the diamond-metal melt interface, carbon supersaturation in the melt with respect to diamond) and adsorption-structure and energy proreties of the produced diamond powders. Our findings permit us to extend scientific and technological potentialities for production of diamond grinding and micron powders having unique properties. [Pg.508]

Diamond, graphite, and the fullerenes differ in their physical and chemical properties because of differences in the arrangement and bonding of the carbon atoms. Diamond is the densest (3.51 vs 2.22 and 1.72 g cm-3 for graphite and Cw, respectively), but graphite is more stable than diamond, by 2.9 kJ mol-1 at 300 K and 1 atm pressure it is considerably more stable than the fullerenes (see later). From the densities it follows that to transform graphite into diamond, pressure must be applied, and from the thermodynamic properties of the two allotropes it can be estimated that they would be in equilibrium at 300 K under a pressure of —15,000 atm. Of course, equilibrium is attained extremely slowly at this temperature, and this property allows the diamond structure to persist under ordinary conditions. [Pg.209]

Upon reaching the outdoor environment, POPs experience fate processes that are consistent with their physical-chemical properties and that of the receiving environment. Most compounds released to the city from indoor ventilation are exported via air advection only a small proportion (typically 1-20%) is either retained in a city s soils or moves from impervious surfaces into surface waters (Diamond et al, 2001 Jones-Otazo et al, 2005). Unlike a typical forested environment, cities are poor sinks for chemicals (Priemer and Diamond, 2002 Diamond and Hodge, 2007) (see Chapter 7). [Pg.244]

Its unique combination of excellent physical and chemical properties make diamond one of the most technologically advanced materials available today. Most uses of diamond require depositing a highly adherent thin diamond film onto a non-diamond substrate. [Pg.152]

Carbon exists in a number of allotropic forms. Allotropes are forms of an element with different physical and chemical properties. Two allotropes of carbon have crystalline structures diamond and graphite. In a crystalline material, atoms are arranged in a neat orderly pattern. Graphite is found in pencil lead and ball-bearing lubricants. Among the noncrystalline allotropes of carbon are coal, lampblack, charcoal, carbon black, and coke. Carbon black is similar to soot. Coke is nearly pure carbon formed when coal is heated in the absence of air. Carbon allotropes that lack crystalline structure are amorphous, or without crystalline shape. [Pg.103]

Carbon atoms crystallize in several forms. Graphite and diamond are well known carbon polymorphs. Fullerenes, which were discovered in the 1980 s, have also been well characterized. Carbon materials show a variety of different physical and chemical properties. Because of this the electronic structure of carbon materials has been investigated using a number of different experimental techniques, for example, XPS, UPS and XANES. Theoretical studies of carbon materials have been also performed. However, experimentally observed spectra are not always consistent with theoretical predictions. Recently, in order to understand the various kinds of observed electronic spectra, DV-Xa calculations have been performed on a small cluster model. [1] In the present paper, we report results of DV-Xa calculations performed on the carbon materials graphite, alkali graphite intercalation compounds (GIC), fullerene, and fluorinated fullerenes. [Pg.302]

Structural Studies. In a number of communications,22-26 correlations have been sought between both the spectroscopic and chemical properties of the various carbon allotropes and their structures. Thus, an electron-energy-loss spectroscopic study22 of diamond, graphite, and amorphous carbon has shown that the differences in the X-shell ionization loss spectra of the three allotropes (Figure 1) might be the basis of a technique for distinguishing... [Pg.193]

The choice of the ingredients used for mechanical polishing (felt or cloth, alumina powder or diamond paste, etc.) is dictated by the hardness of the metal and its chemical properties. Soft metals (such as gold) are more difficult to polish than hard metals because the polishing material can possibly be buried into the metal and consequently modify the chemical composition of the electrode surface (see Section IV.6). [Pg.33]


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See also in sourсe #XX -- [ Pg.278 ]

See also in sourсe #XX -- [ Pg.278 ]




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