Thermodynamic Analysis of Grain Aspect Ratio in Fibrous Microstructures of Silicon Nitride

Abstract

Needlelike, free-floating ␤-crystals of silicon nitride, precipitated within a supersaturated Y-Si-Al-O-N oxynitride glass, apparently approach an equilibrium value of the aspect ratio. An expression that relates this aspect ratio to the anisotropy in the interfacial energies of the longitudinal and transverse interfaces of the crystal is derived. The prediction agrees reasonably well with theoretical estimates of the interfacial energies. Kinetic and stearic effects that often lead to nonequilibrium values of the aspect ratio are discussed.

Phase transformation and interface segregation behavior in Si3N4 ceramics sintered with La2O3–Lu2O3 mixed additive

“…Once it has been understood that RE ions segregate at the interface, next question would be how it should be related to the grain growth behaviors, and several research groups proposed plausible mechanisms that evidently conflict each other as follows:…”

“… It was considered that the interfacial segregation would reduce the free energy of the total system, and thus, the interfacial energy decreased as a result of segregation, which should increase the surface area of β‐grain to enhance the elongated grain shape . Since the grain aspect ratio is higher for RE ion with larger radius, much more reduction of interface energy is expected for RE ion with larger radius.…”

“…Once it has been understood that RE ions segregate at the interface, next question would be how it should be related to the grain growth behaviors, and several research groups proposed plausible mechanisms 14,15,[19][20][21][22][23][24] that evidently conflict each other as follows: 1. It was considered that the interfacial segregation would reduce the free energy of the total system, and thus, the f1 100g interfacial energy decreased as a result of segregation, which should increase the f1 100g surface area of b-grain to enhance the elongated grain shape.…”

Gas Pressure Sintering of Arbitrary Porous Silicon Nitride Ceramics with High Mechanical Strength

“…1. As a side note, the aspect ratio of fibrous β‐Si 3 N 4 grains depends on the interfacial energy anisotropy between the longitudinal and the transverse surfaces 17 …”

Experiment and modeling on the compressive behaviors for porous silicon nitride ceramics

“…In present work, we mainly evaluate the quantitative influences on overall Young's modulus and compression strength, caused by grain aspect ratio and mechanical properties of grain boundaries. [40][41][42]. Fig.…”