Reaction-bonded Silicon Nitride Research Articles

Silicon nitride as a rolling bearing material—A preliminary assessment

Using a simple, accelerated service simulation test silicon nitride has been compared in a preliminary manner with En31 ball bearing steel, high speed tool steels and tungsten carbide under conditions of heavily loaded, lubricated, unlubricated and elevated temperature rolling contact. Low density, porous, heterogeneous reaction bonded silicon nitride does not appear to be a suitable rolling bearing material. Under lubricated test conditions hot-pressed silicon nitride was not as effective a material as En31 and high speed tool steels. Under unlubricated conditions it was inferior to tungsten carbide. Further work to allow a fuller assessment is suggested.

Method of production of reaction bonded silicon nitride ceramic matrix composite materials : Parr N.L., May E.R.W., Godfrey D.J., Lindley M.W. and Brown R.L. UK Patent Specification, 1,198,906 (15 July 1970)

Method of production of reaction bonded silicon nitride ceramic matrix composite materials : Parr N.L., May E.R.W., Godfrey D.J., Lindley M.W. and Brown R.L. UK Patent Specification, 1,198,906 (15 July 1970)

Structural and Electrical Properties of Silicon Nitride Ceramic

The effects of structural properties on the d.c. and a.c. electrical properties of different weight gain reaction bonded silicon nitride (RBSN) have been studied in this work. The degree of nitridation is assessed by the ‘weight gain’ of the ceramic, the percentage by which the weight is increased in the nitriding reaction. From X-ray diffraction (XRD) patterns, it is observed that a higher degree of nitradation sample has strong α-silicon nitride peaks. Intensity of α-silicon nitride peaks decreases with decreases weight gain. The higher degrees of nitridation, the samples have less significant Si peak. XRD patterns were recorded to calculate the lattice parameters of RBSN. The lattice parameters for three weight gain RBSN samples are found to be a =b = 7.7727 Å, c= 5.6565 Å (26% weight gain), a=b= 7.6272 Å, c= 5.6374 Å (42% weight gain) and a=b=7.6158 Å, c= 5.7732 Å (58.27% weight gain) and are in good agreement with the reported values from XRD patterns. Porosity (%) and surface morphology was observed by SEM. Keywords: Silicon nitride ceramic; electrical properties; structural properties. DOI: http://dx.doi.org/10.3329/diujst.v7i1.9648 Daffodil International University Journal of Science and Technology Vol.7(1) 2012 50-58

Multipurpose vacuum furnace with induction electron beam and resistance heating

The mechanical and thermal properties, before and after thermal shock testing, of reaction bonded silicon nitride (RBSN) produced by slip casting, were studied. Slips with solids contents of 27 wt% and 50 wt% silicon powder were used to produce bend bars. Metals casting ladles, with wall thicknesses of 8 mm and 24 mm, were cast from the 50 wt% slip. Nitridation was conducted at 1500 °C for 4 h. X-ray diffraction (XRD) showed α and β phases of Si3N4 were formed. It was found that increasing the solids content increased the density and flexural strength of the bars. After thermal shock testing the flexural strength decreased. The 24 mm ladle which was exposed to 700 °C aluminum fractured after one exposure, while the 8 mm ladle withstood five exposures before failure. This was attributed to the difference in thermal strain.