Abstract
Infuences of binders, grain sizes, gap gradings, forming methods, sintering temperature, sintering atmospheres, etc. on properties of both green and sintered silicon nitride bodies were determined. The binders used in this study were C.M.C., Maxelon M (Wax Emulsion), polyethylen glycol 4000, camphor, ethylsilicate, colloidal silica sodium silicate, aluminum hydroxide, Monophix (aluminum phosphate solution), colloidal alumina, and bentonite. One sample was moulded without binders using ageing method.
The results are as follows :
(1) C.M.C. and aluminum bearing materials were good for binders of green bodies of silicon nitride. The maximum modulus of rapture was 14.0kg/cm2 in the case of C.M.C.
(2) The modulus of rupture of sintered body increased when alumina bearing binders such as Al(OH) 3 was used. The maximum modulus of rupture was 246kg/cm2.
(3) Ageing of silicon nitride powder on modulus of rupture was effective. The maximum modulus of rupture was 202kg/cm2. The longer the ageing time, the higher the maximum modulus was.
(4) Better results were obtained by using the dry mixing of the binders such as ethylsilicate, colloidal alumina, and collidal silica than using the wet mixing. The modulus of rupture increased about 30-40% by using the dry mixing. (5) In general, the modulus of rupture of 60 mesh grain bodies after sintering in NH 3 atmo-sphere was higher than that of 200 mesh grain bodies. The maximum modulus of rupture of the 60 mesh grain body was the ageing sample of 202kg/cm2, and for 200 mesh grain body was 167kg/cm2, Al(OH) 3 binder sample.
(6) In the case of binders such as C.M.C. and Al(OH) 3, better results were obtained at temperatures higher than 1, 420°C for sintering, but in the case of bentonite and non-addition of ageing sample, 1, 420°C was better the other temperatures.
(7) In the case of Al(OH) 3, bentonite and non-addition, N 2 atmosphere was better than NH 3 for sintering. The modulus of rapture was increased 1.5 to 2 times.
(8) The expansion which have been occurred at the sintering was less than 2%.
