Abstract
Based on the principle of maximum bond energy, a structural model is proposed for Si3N4 + 60 wt % MoSi2 + 5 wt % Y2O3 + 1.5 wt % Al2O3 ceramics. In this model, Si3N4 clusters form a star-like structure with columnar pores 0.45 and 1.5 nm in size. The smaller pores are filled with MoSi2 molecules, and the larger pores are filled with Y2O3 and Al2O3 clusters. The solubility of MoSi2 molecules in silicon nitride is 70 wt %, and those of Y2O3 and Al2O3 are 5.45 wt %. The energies of intercluster interaction in two mutually perpendicular directions are 3.2 and 5.5 eV, which is comparable to bond energies in structural metallic materials. The lattice parameters of molybdenum disilicide are determined by x-ray diffraction. The formation of MoO3 and SiO2 molecules during thermal cycling has an insignificant effect on the structure of the material.
Published Version
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