Nomenclature
CAS number: 12033-89-5
Trisilicon tetranitride.
N
4Si
3; mol wt 140.28.
N 39.94%, Si 60.06%.
Si
3N
4.
Description and references
Non-oxide ceramic material of high thermal
stability. Manuf by direct nitridation of pure silicon. Prepn by
pyrolysis of silicon diimide (Si(NH2)2): O.
Glemser, P. Naumann, Z. Anorg. Allg. Chem. 298, 134 (1954); and characterization: K. S. Mazdiyasni,
C. M. Cooke, J. Am. Ceram. Soc. 56, 628 (1973); eidem, US 3959446 (1976 to USA); by pyrolysis
of silazanes: D. Seyferth et al., J. Am. Ceram. Soc. 66, C-13 (1983); eidem, US 4397828 (1983 to M.I.T.). Brief review: D. L. Segal, Chem. Ind. (London) 1985, 544.
Properties
Exists in two crystalline forms, α-Si3N4 and β-Si3N4. α-Form occurs when
powdered Si3N4 is heated to 1200° >4 hr;
increasing the temperature to >1450°C for 2 hr produces the β-form.
White when pure but often brown or black powder. mp 2173°K (sublimes). d 3.2 kg/dm3. Coefficient
of thermal expansion K-1: 2.5 × 10-6.Use
As high temp engineering material for use in gas
turbines, diesel engines.