Metal hydride carbidization

In both metal lattices and closo polyhedral metal clusters there are cavities present, whose dimensions are a function of the number of vertices, the shape of the polyhedral moiety, and the interatomic separation. Partial occupation of these sites within the metal lattice by main group elements results in the formation of interstitial alloys such as, for example, metal hydrides, carbides, and nitrides. Occupation of the cavity within a molecular metal cluster gives rise to interstitial clusters. Although close topological relationships are sometimes found between interstitial alloys and interstitial clusters, the greater degree of freedom of a molecular assembly of metals, in comparison to a three dimensional infinite array of metals, increases the possible number of interstitially lodged elements... 

Chlorides. Anhydrous ThCl [10026-08-1] has usually been prepared by direct interaction of thorium metal, hydride, or carbide with chlorine. 

Carbides of the Actinides, Uranium, and Thorium. The carbides of uranium and thorium are used as nuclear fuels and breeder materials for gas-cooled, graphite-moderated reactors (see Nuclearreactors). The actinide carbides are prepared by the reaction of metal or metal hydride powders with carbon or preferably by the reduction of the oxides uranium dioxide [1344-57-6] UO2 tduranium octaoxide [1344-59-8], U Og, or thorium... 

Drying agents that combine irreversibly with water include the alkali metals, the metal hydrides (discussed in Chapter 2), and calcium carbide. 

The interstitial carbides are compounds formed by the direct reaction of a d-block metal and carbon at temperatures above 2000°C. In these compounds, the C atoms occupy the gaps between the metal atoms, as do the H atoms in metallic hydrides (see Fig. 14.9). Here, however, the C atoms pin the metal atoms together into a rigid structure, resulting in very hard substances with melting points often well above 3000°C. Tungsten carbide, WC, is used for the cutting surfaces of drills, and iron carbide, FesC, is an important component of steel. 

The SRNL hybrid microwave concept design is shown in Figure 1. Metal tritide powder is slightly susceptible to conventional microwave frequency, so to obtain the high temperature needed a Silicon Carbide (SiC) susceptor is used to generate the hot temperature. This susceptor is used for all metal hydride materials regardless of the individual susceptibility of the sample. 

Hybalines. A family of novel metal hydride coordination compds, both liq solid, trade name of Union Carbide Corp, New York. The company s R D program at its South Charleston, West Virginia technical center suggests Hybalines may find use as high-energy liq fuels and as additives in high-energy solid proplnts... 

When discussing metal alloys (Section 4.3), we saw that atoms of non-metallic elements such as H, B, C, and N can be inserted into the interstices (tetrahedral and octahedral holes) of a lattice of metal atoms to form metal-like compounds that are usually nonstoichiometric and have considerable technological importance. These interstitial compounds are commonly referred to as metal hydrides, borides, carbides, or nitrides, but the implication that they contain the anions H, B3, C4, or N3- is misleading. To clarify this point, we consider first the properties of truly ionic hydrides, carbides, and nitrides. 

Union Carbide showed the possibility of developing D-size hydrogen-nickel batteries with satisfactory performance. However, safety and cost considerations have restricted the applications of such units and the discovery of hydrogen storage alloys led to the development of the nickel-metal hydride secondary cell which was described in Chapter 6. 

The use of metal alkyls, metal aryls, metal hydrides, and metal carbides for preparing alcoholates of carbohydrates in inert, aprotic solvents has not yet been reported. 

Tetraamminelithium dihydrogenphosphide, 4590 Thorium dicarbide, 1023 Titanium carbide, 0558 Trimercury tetraphosphide, 4611 Tungsten carbide, 0560 Uranium carbide, 0559 Uranium dicarbide, 1024 Zinc phosphide, 4870 Zirconium dicarbide, 1025 METAL ACETYLIDES N-METAL DERIVATIVES METAL HYDRIDES METAL OXIDES METAL SULFIDES NITRIDES... 

Rednction of boron trihaUdes to elemental boron can be accomplished by heating with alkali metals, alkaline earth metals, or hydrogen. Under the proper conditions, rednctions of this type can also yield diborane and, under selected conditions, boron subhalides (see below). Metal hydrides also react with boron trihalides to give diborane. Boron nitride and boron carbide have been prepared by the high-temperature reductions of boron trihalides with ammonia and methane, respectively, and deposited on metal substrates by CVD. 

Ignition or explosive reaction with metals (e.g., aluminum, antimony powder, bismuth powder, brass, calcium powder, copper, germanium, iron, manganese, potassium, tin, vanadium powder). Reaction with some metals requires moist CI2 or heat. Ignites with diethyl zinc (on contact), polyisobutylene (at 130°), metal acetylides, metal carbides, metal hydrides (e.g., potassium hydride, sodium hydride, copper hydride), metal phosphides (e.g., copper(II) phosphide), methane + oxygen, hydrazine, hydroxylamine, calcium nitride, nonmetals (e.g., boron, active carbon, silicon, phosphoms), nonmetal hydrides (e.g., arsine, phosphine, silane), steel (above 200° or as low as 50° when impurities are present), sulfides (e.g., arsenic disulfide, boron trisulfide, mercuric sulfide), trialkyl boranes. 

In the first experiments in which chemistry of metal clusters was demonstrated, the reactant was present in the carrier gas. The problem with this approach is that the reactant is also decomposed during the high-temperature vaporization process, and thus reactive radical fragments are present which may participate in the cluster growth process. Although not exploited, this may be a good method to synthesize metal cluster carbides, oxides, nitrides, sulfides, and hydrides, to name a few. It is not a viable mode of operation for the measurement of reactivity toward molecular species, but has been used to examine the stoichiometry of metal cluster compounds. ... 

Carbide powder is manufaetured by carburization of the metal, metal oxide or metal hydride with nuclear-pure graphite at ca. 2000°C. Carbide powder pellets (see Section 5.5.5.1.5) or beads up to 0.6 mm in diameter are formed and sintered using ceramic process technology. Reaction sintering is commonly used for the manufacture of uranium earbide fuel beads, in whieh uranium oxide and carbon are first mixed then annealed to form the carbide and then are sintered to 90 to 95% of the theoretical density. An... 

If single-source precursors are unavailable, carbides can be produced by reacting a metal halide or metal hydride with a hydrocarbon gas. Often the hydrocarbon is methane, and the carbide formation reaction may be written as follows ... 

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