Silicon nitride Si3N4 synthesis

There are many examples of rational synthesis. A good example is Sialon, in which A1 and oxygen were partly substituted for Si and nitrogen in silicon nitride, Si3N4. The fast Na+ ion conductor Nasicon was synthesized based on understanding the coordination preferences of cations and the nature of oxide networks formed by them. The zero-expansion ceramic CaQ5Ti2P30j2, possessing the Nasicon framework, was later synthesized based on the idea that the property of zero expansion would be exhibited by two- or three-coordination polyhedra linked in to leave substantial empty space in the network [3]. 

Synthesis of Silicon Nitride (Si3N4) and Oxynitrides by Non-Thermal Plasma Conversion of Silane (Sil-14)... 

All silicon nitride ceramics are derived from synthetic materials, exclusively. The first report on the synthesis of Si3N4 was in 1859 by Sainte-Claire Deville and Wohler [3]. Among the problems of greatest concern to chemists in those days was the utilisation of atmospheric nitrogen for agricultural and industrial purposes. In particular, there was a need for a highly effective... 

Kubo N, Futaki S, Shiraishi K (1987) Synthesis of ultrafine Si3N4 powder using the plasma process and powder characterisation. In Somiya S, Mitomo M, Yoshimura M (eds) Silicon Nitride I. Elsevier, London, p 93... 

Brink R, Lange H (1994) Investigations on the Synthesis of fine-grained, high-purity j8-Si3N4 Powder by Crystallization of amorphous Precursors. In Hoffmann MJ, Becher PF, Petzow G (eds) Silicon Nitride 93. Key Eng Mat 89-91. Trans Tech Publications Ltd, Switzerland, p 73... 

Organometallic precursors are used in the synthesis of a variety of semiconducting materials and superconducting cuprates. Organoaluminium silicate precursors have been used for the synthesis of aluminosilicates [25], while polymeric methylsilyl-amines have been used to obtain SiC-Si3N4 fibres [26], Silicon nitride can also be made using organometallic precursors. 

The thermodynamics of the above-elucidated SiC/C and SijN Si composites are determined by the decomposition of silicon carbide and silicon nitride, respectively, into their elements. The chemistry of ternary Si-C-N composites is more complex. If producing Si-C-N ceramics for applications at elevated temperature, reactions between carbon and silicon nitride have to be considered. Figure 18.2, which exhibits a ternary phase diagram valid up to 1484°C (1 bar N2) displays the situation. The only stable crystalline phases under these conditions are silicon carbide and silicon nitride. Ceramics with compositions in the three-phase field SiC/Si3N4/N are unknown (this is a consequence of the thermal instability of C-N bonds). Although composites within the three-phase field SiC/Si3N4/Si are thermodynamically stable even above 1500°C, such materials are rare. The reasons are difficulties in the synthesis of the required precursors and silicon melting above 1414°C. The latter aspect is of relevance, since liquid silicon dramatically worsens the mechanical properties of the derived ceramics. 

Silicon nitride (SisNJ is another synthetic mineral. It occurs in two crystalline forms. The lower temperature a form is usually preferred as a raw material because the transformation to the P form during sintering favors the development of an elongated crystal structure. Several routes are available for the synthesis of Si3N4 powder, similar to those used to form AIN ... 

Material System. There are two basic techniques for the industrial synthesis of Si3N4 powder, although other methods are available (36). The older and most widely used method is the nitridation of silicon Silicon is heated in a nitrogen [7727-37-9] atmosphere at temperatures of 1100—1450°C in... 

Many catalysts are known for the synthesis of cBN at high pressures (7,13) (Table 9). They are alkali metals (15), alkaline earth metals (15,219), their hydrides (236), their nitrides (15,219-221,228,230,235), their borides (234) and boron nitrides (101,110,219-221,223,235), other metals (15,83), water (237-240,245), fluoride and fluoronitride compositions (241), ammonia compounds (240,241,244,245), hydrochloric acid (246), aluminum nitride (247-250,251), and silicon and its compounds (251,252). Other materials such as Al-Ni, Al-Co, Al-Mn, inconel, Si3N4, ZnO, and LiSrBN2 have been reported in patents. The pressure-temperature cBN synthesis conditions for some catalysts (or solvents) are shown in Fig. 40. The best catalyst (or solvent) for providing good cBN crystals under relatively low-pressure, low-temperature conditions is unknown at present. 

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