Applications metal nitrides

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 ... 

The c-BN phase was first obtained in 1957 [525] by exposing hexagonal boron nitride phase (h-BN) to high pressures and low temperatures. A pressure of more than 11 GPa is necessary to induce the hexagonal to cubic transformation, and these experimental conditions prevent any practical application for industrial purposes. Subsequently, it has been found that the transition pressure can be reduced to approximately 5 GPa at very high temperature (1300-1800°C) by using catalysts such as alkali metals, alkali metal nitrides, and Fe-Al or Ag-Cd alloys [526-528]. In addition, water, urea, and boric acid have been successfully used for synthesis of cubic boron nitride from hexagonal phase at 5-6 GPa and temperature above 800-1000°C [529]. It has been... 

In February 1909, the results of the experiments on nitride formation had led to the outline of a patent application which covered the preparation of metal nitrides in the presence of auxiliary substances. Following a hypothetical concept of the action of these additions, they were defined as flux promoters." This draft of an application ended with the following sentence Finally, it is also advantageous to add a flux promoter to metals or alloys which serve as catalysts for the ammonia synthesis. This statement was made in view of the early catalytic experiments in which we had observed the synthesis of traces of ammonia in the presence of catalysts similar to those which acted favorably for the nitride formations. 

This chapter summarizes recent experimental findings on transition metal carbides and nitrides and shows, in section 25.2, that measurable surface shifts do exist both in the metal and nonmetal levels. A few application examples are presented in section 25.3. These experimentally determined surface shifts may stimulate new theoretical efforts to explain their existence and lead to a better understanding of the surface electronic properties. To date, no ab initio calculations of surface shifts for transition metal nitrides and carbides, including final state relaxation effects, have... 

Prins summarizes advances in understanding of the reactions in catalytic hydrodenitrogenation (HDN), which is important in hydroprocessing of fossil fuels. Hydroprocessing is the largest application in industrial catalysis based on the amount of material processed. The chapter addresses the structures of the oxide precursors and the active sulfided forms of catalysts such as Ni-promoted Mo or W on alumina as well as the catalytically active sites. Reaction networks, kinetics, and mechanisms (particularly of C-N bond rupture) in HDN of aliphatic, aromatic, and polycyclic compounds are considered, with an evaluation of the effects of competitive adsorption in mixtures. Phosphate and fluorine promotion enhance the HDN activity of catalysts explanations for the effect of phosphate are summarized, but the function of fluorine remains to be understood. An account of HDN on various metal sulfides and on metals, metal carbides, and metal nitrides concludes this chapter. 

Transition-metal nitrides have many properties that make them suitable for industrial applications, including high wear resistance, high decomposition temperature, and high microhardness. 

Other Metal Nitrides Many other metal nitrides are used in ceramic formulations. These include AIN, TiN, VN, and BN. These metal nitride powders are produced by carbothermal reduction of the relevant metal oxide in a nitrogen-containing atmosphere or reaction of the relevant metal with a nitrogen-containing reducing atmosphere. These metal nitrides are used as abrasives and in hi -temperature wear applications. 

Because of the importance of the cubic to hexagonal transition in determining the properties of coatings for particular applications, a series of calculations have been carried out for a number of AlN-MeN systems (MeN is a transition metal nitride). 

For the preparation of technically important metal carbide and metal nitride materials the application of organosilicon compounds as preceramic precursors is advantageous under certain conditions [1-5]. Compared with the conventional metallurgical powder process, one benefit is the utilization of very low process temperatures for the preparation of individual ceramic materials. Another improvement is the high purity of the ceramics obtained from tailor-made preceramic precursors. Usually, after pyrolysis organosilicon compounds afford silicon-containing ceramic powders Likewise, they can also be used under certain conditions for the production of silicon carbide or silicon nitride fibers. 

In the oxide literature, there are several reviews specific to the different families, such as layered transition metal oxides and metal phosphonates. Synthesis of metal nitrides has been discussed by Di Salvo. Precursor synthesis of oxides, chalcogenides and other materials is being pursued with vigour. - Thus, single-molecule precursors of chalcogenide containing compound semiconductors have b n developed. Kanatzidis has reviewed the application of molten poly-chalcophosphate fluxes for the synthesis of complex metal thiophosphates and selenophosphates. 

Nanosized Transition Metal Nitrides and Carbides Advantages and Specific Applications, 116... 

Due to their excellent mechanical properties and high-temperature durability, metal nitrides and carbides have many industrial and technological applications (1). While more details about applications will be given in the next chapter, here the chemical and physical properties of these interesting compounds are addressed. 

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