Atomistic Structure of Calcium Silicate Intergranular Films in Alumina Studied by Molecular Dynamics Simulations

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Abstract
Molecular dynamics simulations of calcium silicate (CaSiO3)intergranular films that were formed during the liquid‐phase sintering of alumina (Al2O3)ceramics were conducted. A constant‐pressure algorithm was used in the simulations to accommodate changes in the sample size during heat treatment and tensile tests. A model of the grain boundary that was wetted by glass was created by melting the silicate film between two Al2O3surfaces with the basal orientation. Samples with different film thicknesses and CaO contents were studied. The presence of an ordered interface in the atomistic structure of the mostly amorphous films was revealed. Calcium additives segregated preferentially into the ordered SiO2/Al2O3interface regions. Increased addition of calcium further promoted the ordering and increased stability of the films. Tensile strength was evaluated and showed an increase with low calcium additions, followed by strength reduction at higher CaO additions. Two modes of fracture were observed in the simulations.