Oxynitride ceramics

Figure 1. The conversion degree for the gaseous mixture containing 1% CO, 1% CH4, 1% C3H8 in the presence of SHS oxynitride ceramic powder as a function of temperature(W=l 8- lO h ).

Recently, there has also been a considerable thrust in the direction of producing transparent oxynitride ceramics, the aim being to overcome the longstanding... 

SiAION (silicon aluminium oxynitride) ceramics for engineering applications can be synthesised from aluminosilicates by carbothermal reduction and nitridation (CRN), in which a mixture of the aluminosilicate with carbon is fired in nitrogen at 1400 C. Composites of potassium aluminosilicate geopolymers with graphite, when fired for lOhr under these conditions, have been found to produce predominantly p-SiAlON (Figure 10) by a reaction such as ... 

Vapor—sohd reactions (13—17) are also commonly used ia the synthesis of specialty ceramic powders. Carbothermic reduction of oxides, ia which carbon (qv) black mixed with the appropriate reactant oxide is heated ia nitrogen or an iaert atmosphere, is a popular means of produciag commercial SiC, Si N, aluminum nitride [24304-00-3], AIN, and sialon, ie, siUcon aluminum oxynitride, powders. 

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. 

In conclusion, it can be stated that Si3N4 ceramics are polyphased materials including mainly /fss, ass, secondary phases (mainly oxide nitrides, in ceramic literature generally called oxynitrides) and an amorphous phase, all having characteristic morphologies and can be arranged in a manifold of microstructures (Sect. 6). 

Mandal H, Hoffmann MJ (2000) Hard and Tough a-SiALON Ceramics. In Hampshire S, Pomeroy MJ (eds) Nitrides and Oxynitrides. Trans Tech Publications Ltd, Switzerland, p 219... 

Oxynitride glasses - glass ceramics composites S Hampshire, University of Limerick, Ireland 560... 

Oxynitride glasses may be heat treated to form glass-ceramics, effectively multi-phase composites. The process involves heat treatment at two different temperatures, firstly to induce nucleation, then to allow crystal growth of the nuclei. The crystalline phases formed depend on both the composition of the parent glass and the temperatures used for heat treatment. The extent of their formation and growth, the relative amounts and distributions of different phases (including residual glass) and their characteristics will determine the overall properties of the particular composite. The formation of these types of materials and their properties is outlined below. 

Crystallisation of oxynitride glasses to form multi-phase glass-ceramic composites... 

As with other silicate glasses, oxynitride glasses may be heat treated at appropriate temperatures to crystallise as glass-ceramics (Leng-Ward and Lewis, 1990 Thompson, 1992 Hampshire, 1993). The crystalline phases formed depend on both the composition of the parent glass and the heat-... 

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