No abstract

No abstract

The crystal structure of V307 has been determined from three-dimensional X-ray diffractometer data

No abstract

C and Si02 of different types were mixed and heat-treated (1410" to 1550"C), according to a standardized temperature program, in flowing N2 at different pressures. It was found that a starting material combination of C (115 m'/g) and Si02 (50 m'/g) yielded pure SiJN4 after about 2 h at 1550°C and 1.3 MPa. By adjustment of the pressure in the range 2 to 6 MPa, irreversible evaporation of SiO(g) as well as formation of nonequilibrium phases was suppressed, and the amounts of residual C and 0 in the sample were controlled. Even a small amount of CO in the N2 was observed to retard the nitridation. Possible explanations are discussed, based on thermodynamic calculations on the Si-0-N-C system.