Reaction sequences in the synthesis of silicon nitride from quartz

doi:10.1016/0272-8842(91)90064-7

Ceramics International

Volume 17, Issue 3, 1991, Pages 171-179

https://doi.org/10.1016/0272-8842(91)90064-7 Get rights and content

Abstract

Carbothermal reduction and nitridation of pure silica have been performed to synthesize pure Si₃N₄ powder. Iron was used to serve as a catalyst. The reduction reaction was studied with respect to different parameters such as temperature, soaking time and gas flow rate, etc. Almost pure Si₃N₄ powder with predominating β-phase could be synthesised at 1540°C. Below this temperature SiC and Si₂N₂O are the associated phases. SiC is unstable to Si₃N₄ in nitrogen atmosphere and disappears at 1540°C or under a longer holding at 1440°C. There is a critical flow rate of the nitrogen gas of 1·32 × 10⁴ litre m⁻² h⁻¹, above which the yield on nitridation almost flattens. It has been suggested through thermodynamic arguments that the Si₃N₄ formation at 1440°C takes place through the intermediate formation of SiC and Si₂N₂O as follows: $SiO_{2} (s ) + 2SiC(s) + 2N_{2} (g) = Si_{3} N_{4} (s) + 2CO(g)$ $SiO_{2} (s) + Si_{2} N_{2} O(s) + 3C(s) + N_{2} (g) = Si_{3} N_{4} (s) + 3CO(g)$ At 1540°C the following reaction may predominate: $3SiO_{2} (s) + 6C(s) + 2N_{2} (g) = Si_{3} N_{4} (s) + 6CO(g)$

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Recently, much attention has been focused on the utilization of plant biomass to produce engineering materials, encompassing the technological/scientific aspects as well as the economic, environmental and social issues. Amongst the variety of agricultural wastes or biomasses available, rice-husk (RH) occupies a preeminent position, not only in terms of its amount produced worldwide, but also because of its unique chemistry-related features. In this sense, some attempts have been made to produce advanced materials – including SiO₂, SiC, Si₃N₄, elemental Si, Mg₂Si and more recently, active carbon –, using RH. The production of those mentioned advanced materials depends largely on the treatments used (physical and/or chemical) and the reactions involved in the process, such as pyrolysis, carbothermal and reduction processes. In this contribution, a critical review on the processing and application of rice husks (RHs) for the production of various silicon-based materials and of active carbon is presented. The review addresses the different processing methods, the effects of various process parameters on the pyrolysis stage, the influence of physical, chemical and thermal treatments, activating conditions and activated carbon consolidation mechanisms. A flow chart with all the possible routes to produce SiO₂ was purposely constructed.
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Rice husk was digested by using various concentrations of HNO₃ at 60°C and it was found that rice husk containing about 29% carbon and about 79% silica was produced by digestion with 12m HNO₃ for 3 h. The carbon and silica obtained are in stoichiometric ratio for the overall carbothermal reduction reaction. An equiaxed, submicrometre and high α-phase silicon nitride powder was obtained by heating pyrolysed digested husk at about 1430°C under flowing nitrogen. The homogeneity of the carbon and silica is the main factor that allows completion of the reaction.

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Reaction sequences in the synthesis of silicon nitride from quartz

Abstract

J. Eur. Ceram. Soc.

Ceram. Int.

The preparation of silicon nitride from silica

Synthesis of the α-form of silicon nitride from silica

J. Mat. Sci.

Reactions in the SiO2CN2 systems

The kinetics of Si3N4 formation from Korean rice hulls

J. Kor. Ceram. Soc.

The preparation of silicon nitride from silica by sol-gel processing

Synthesis of silicon nitride powder from silica reduction

J. Am. Ceram. Soc.

Preparation of some high purity ultrafine nonoxide powders

Preparation of silicon nitride powder from silica

Preparation of silicon nitride from silica

J. Am. Ceram. Soc.

Reductive nitridation of cristobalite with carbon in N2 atmosphere

J. Ceram. Soc. Jap.

The influence of iron on the preparation of silicon nitride from silica

J. Mat. Sci.

Synthesis of silicon nitride powder by carbothermal nitriding of silica

Silicon nitride: Part 2

Powder. Metal. Int.

Reactions in the SiO₂CN₂ systems

The kinetics of Si₃N₄ formation from Korean rice hulls

Reductive nitridation of cristobalite with carbon in N₂ atmosphere