Compressive mechanical properties of porous alumina powder compacts

Abstract In this study, compressive mechanical properties, relative density, porosity, grain size, and grain boundary area of porous alumina ceramics, were examined at room temperature to clarify the influence of microstructures. High purity alumina powder of median size 150 nm was dispersed in an aqueous solution at pH 3.0 and consolidated by pressure filtration to achieve a uniform microstructure. The grain boundary development was analyzed using an initial sintering model and the decreased Brunauer–Emmett–Teller specific surface area during sintering. When the alumina compacts were sintered at 500–1400 °C, the relative density (60.2–62.9%) was almost constant up to 1000 °C, while the specific surface area decreased above 800 °C. The Young's modulus and compressive strength of porous alumina compacts increased exponentially with sintering temperature. The abovementioned mechanical properties were well explained by the increased grain boundary area during sintering. Another factor that contributes to the observed increase in the mechanical strength of porous alumina compacts is the increase in packing density, leading to an increase in the total grain boundary area. An effective compressive strength (830 MPa) for dense alumina compacts of 0% porosity was estimated from the relationship between measured compressive strength and grain boundary area, which was 1/4–1/3 times that of the compressive strength reported for dense alumina materials.