Metals oxynitrides

If this qualitative argument is of general importance, one may predict that simple nonstoi-chiometric transition-metal oxynitrides are inferior candidates when it comes to the search for magnetic materials, simply because they possess more internal, structural degrees of freedom that will suppress spin-polarization. 

Cr, Mn, Co), from the nitridation of bimetallic oxide precursors with ammonia via TPR at the final reaction temperatures of 890-1110 K (70). The oxide precursors were prepared by conventional solid-state reactions. All the synthesized oxynitrides have face-centered cubic structures and large surface areas of 45-118 m /g. In addition, bimetallic and ternary-metallic oxynitrides were prepared by ammonolysis of metal salt precursors and NH3 gas in the various temperatures from 973 to 1023 K (71). 

Based on the results with metal oxides and nitrides, research on the catalytic behavior toward ORR of metal oxynitrides has been intensified in the last few years. Nitrides and oxynitrides of subgroup IV and V elements have been intensively investigated as photo-catalysts for water oxidation showing remarkable stabilities and electrochemical activities in acidic electrolytes [51, 52]. Due to their partly high metal d-band concentration at the Fermi level, these materials might also be promising as ORR catalysts. 

It is beheved that the search for alternative supports for Fe-N-C catalysts will become dominant in the future. Especially, different transition metal oxynitrides (TiOxNy, TaOxNy, ZrO Ny), and Nb- or Sb-doped Ti02 or Sn02 or PANI appear to be promising in this context [55, 224—227]. It will remain a major challenge to enable the implementation of molecular centers onto the surface of the new support material. It has already been pointed out that PANI possesses a considerable potential with this respect [189]. Since none of the other promising support materials contain carbon, it is questionable how catalytically active Fe-N-C catalysts could be implemented. 

Aguiar, R., Logvinovich, D., Weidenkaff, A., Rachel, A., Reller, A., and Ebbinghaus, S.G. (2008) The vast colour spectrum of ternary metal oxynitride pigments. Dyes Pigm., 76, 70-75. 

Gate oxide dielectrics are a cmcial element in the down-scaling of n- and -channel metal-oxide semiconductor field-effect transistors (MOSEETs) in CMOS technology. Ultrathin dielectric films are required, and the 12.0-nm thick layers are expected to shrink to 6.0 nm by the year 2000 (2). Gate dielectrics have been made by growing thermal oxides, whereas development has turned to the use of oxide/nitride/oxide (ONO) sandwich stmctures, or to oxynitrides, SiO N. Oxynitrides are formed by growing thermal oxides in the presence of a nitrogen source such as ammonia or nitrous oxide, N2O. Oxidation and nitridation are also performed in rapid thermal processors (RTP), which reduce the temperature exposure of a substrate. 

Silicon-containing ceramics include the oxide materials, silica and the silicates the binary compounds of silicon with non-metals, principally silicon carbide and silicon nitride silicon oxynitride and the sialons main group and transition metal silicides, and, finally, elemental silicon itself. There is a vigorous research activity throughout the world on the preparation of all of these classes of solid silicon compounds by the newer preparative techniques. In this report, we will focus on silicon carbide and silicon nitride. 

Phosphorus oxynitride, PON, is a useful starting product, as a phosphorus and nitrogen source, to prepare various nitridooxophos-phates, in particular phosphorus oxynitride glass compositions (211). Moreover, it shows as a material excellent chemical stability with potential applications in several domains. In microelectronics, for example, PON has been used to form by evaporation insulating films for the passivation of III-V InP substrates and the elaboration of MIS (metal-insulator-semiconductor) structures (190, 212-215). PON could have also valuable properties in flame retardancy (176,191,216). 

Nitrides and Oxynitrides. Crystalline films of NbN and Nb Nj have been prepared. Electron-diffraction studies showed that the former has a NaCl-type structure and the latter is isomorphous with Ti405 and Ta Nj. " The phase 0-TaN, 0 has been prepared by nitriding Ta metal powder with ammonia gas at 850—1200°C. Although it could not be obtained pure, the phase was characterized by X-ray diffraction studies. The free energy of formation of TajNj has been determined as -272 42 kJ mol and that of TaO, 05N0.95 as -396 21 kJ moP. ... 

Nitrides can be sub-divided into ionic, covalent and interstitial types.An alternate general classification of nitrides, based on bonding classification, as ionic, covalent and metallic has also been applied. Ionic or salt-like nitrides are formed by electropositive elements such as Li, Mg, Ca, Sr, Ba, Cu, Zn, Cd and Hg and possess formulae which correspond to those expected on the basis of the combination of the metal ion with ions. A range of covalent nitrides are known and are exhibited by less electropositive elements such as B, S, P, C and Si. Interstitial nitrides are formed by some transition metals and refer to compounds which can be described in terms of the occupancy of interstitial sites in close packed metallic structures by nitrogen atoms. Oxygen can also be accommodated within these structures and a range of oxynitrides are known to... 

Generally, metal nitride and oxynitride catalysts have been prepared by the temperature programmed ammonolysis method. This technique was originally applied by Volpe and Boudart to M0O3 precursors to produce y-Mo2N which was pseudomOrphic with the precursor, with surface areas up to 225 m g The resultant surface area of materials is known to be a strong function of the synthesis parameters as demonstrated in Table 1. ... 

Extensive studies describe the development of new materials, such as transition-metal nitrides and oxynitrides, as new potential catalysts for hydroprocessing operations. Studies were performed to acquire information on the effect of high levels of ZSM-5 additive on light olefins and gasoline composition in FCC.289 It was found that ZSM-5 can substantially increase propylene and butenes, and... 

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