Phase Relations in the Si3N4-SiO2-MgO System and Their Interrelations with Strength and Oxidation Resistance. Dense Si3N4: Interrelation between Phase Equilibria,Microstructure and Mechanical Properties.

摘要

Phase equilibria studies between 1400 C and 1750 C have established three important tie lines in the Si3N4-SiO2-MgO system, viz., Si3N4-MgO, Si3N4-Mg2SiO4, and Si2N2O-Mg2SiO4. Strength measurements at 1400 C for fixed Si3N4 molar contents and varying MgO/SiO2 molar ratios show that the maximum high temperature strengths can be obtained for MgO/SiO2 molar ratios that approach zero and infinity. The oxidation of these materials will be discussed in terms of the compatibility of SiO2 (the oxidation product of Si3N4) and the other phases present in the material. (Author)