Carbide definition

Tbe term structural foam was originally coined by Union Carbide to describe an injection moulded thermoplastic cellular material with a core of relatively low density and a high-density skin. The term has also been used to describe rigid foams that are load bearing. Today it is commonly taken to imply both of the above requirements, i.e. it should be load bearing and with a core of lower density than the skin. In this section the broader load-bearing definition will be used. Whilst structural foams are frequently made from polymers other than polystyrene, this polymer is strongly associated with such products and it is convenient to deal with the topic here. 

Such binary borides (p. 145), carbides (p. 297) and nitrides (p. 417) as are formed have been referred to already. The ability of the metals to absorb molecular hydrogen has also been alluded to above. While the existence of definite hydrides of nickel and platinum is in doubt the... 

Seeding technique, procedure 130, 131 Sequential addition of monomers 164, 167 Silicon-carbide fibers 8 Silicon-nitride fibers 8 Silicone rubber, crosslinked 4, 7-9, 31, 67 Siloxane, definition of 5 Siloxane-acrylate copolymers 27, 29, 56, 57, 64, 70, 71, 73, 74... 

The term ceramics comes from the Greek keramikos, which means potter s clay or burnt stuff. While traditional ceramics were often based on natural clays, today s ceramics are largely synthetic materials. Depending on which ceramic and which definition is to be applied, ceramics have been described as inorganic ionic materials and as inorganic covalent (polymeric) materials. In fact, many ceramics contain both covalent and ionic bonds and can thus be considered to be or not to be (shades of Shakespeare) polymeric materials. Many of the new ceramics, such as the boron nitriles and the silicon carbides, are polymeric without containing any ionic bonds. 

D. africanus Fd III containing reactive [3Fe S] cluster, 38 138-144 definition, 38 117 ferredoxins, 38 126-128 ideal case, 38 124 problems, 38 118, 120-121 recent developments, 38 119-120 sensitivity, 38 125 techniques, 38 125-126 underuse, 38 118 useful features, 38 121-126 u.seful potential range, 38 122 voltammetric response, 38 121 voltammetry of adsorbed protein molecules, 38 122-123 Dysprosium carbides, 11 201 dibromide, 20 4 dichloride, 20 4 preparation of, 20 8 properties of, 20 16-18 di iodide, 20 4... 

The discovery of acetylene in 1836(or 1837) is attributed to Edmond Davy, but it was not until I860 that Berthelot definitely identified and named it(Ref 9, p 101 Ref 16, p 469). The compd obtained by Berthelot from cuprous acetylide was not pure because it contained some vinyl chloride. Acetylene was not produced commercially until Ca carbide was produced in the lab in 1899 by Morehead Willson, by heating a mixt of lime and coke in an electric furnace. They expected to prepare metallic calcium... 

It is clear that the influence of surface geometry upon catalytic activity is extremely complex and many more studies are required before any definitive relationship between catalytic activity and metal particle size can be established. Such studies will require to take cognisance of such factors as the perturbation of surface structure due to the formation of carbidic residues, as noted by Boudart [289] and by Thomson and Webb [95], and by the modification of catalytic properties on adsorption, as noted by Izumi et al. [296—298] and by Groenewegen and Sachtler [299] in studies of the modification of nickel catalysts for enantioselective hydrogenation. Possible effects of the support, as will be discussed in Sect. 6.3, must also be taken into account. 

The term organic has persisted, but the modern definition of organic chemistry lias changed to mean the chemistry of carbon compounds. Sometimes a few carbon compounds are excluded from this category, such as carbon dioxide, CO2 meted carbonates, e.g NajCOs carbonyls. e,g Ni(CO)4 cyanides, e.g, KCN carbides, e.g., CaC- anil a few others, but this exclusion is somewhat arbitrary. The designation organic is still pertinent because the chemistry of carbon compounds is more important to everyday life than that of any other element. 

Equations (287) are again used for the definition of, l2, and l3 in this equation via rate constants of elementary reactions of scheme (292). At lt = 0, (293) becomes (290). This corresponds to stage 2 of scheme (292), being at equilibrium. Thus the reaction kinetics does not provide a possibility for giving preference to the Eidus-Zelinskii theory or the carbide theory. 

The structure of Rhi2(CO)25(C2), reported in Fig. 10, is a further example of carbide stabilization (13). This is the most irregular cluster as yet characterized like Rh8(CO)i9C, it has no symmetry element. This cluster is also derived chemically from the oxidation of [Rh COVC]2-. The 2 central carbide atoms are definitely bonded together (1.47 A) and lead to... 

Several other species have been isolated in the crystalline state and are presently awaiting definite characterization. Great difficulties arise from the fact that these derivatives are only sparingly soluble in inert solvents and often react with polar solvents [sec for instance Eq. (37)]. The octa-nuclear carbide Rh8(CO)i9C polymerizes THF at room temperature (102). 

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