Effects of phase transformation on properties of alumina ceramic membrane: A new assessment based on quantitative X-ray diffraction (QXRD)

Alumina ceramic membranes were synthesized by pressing boehmite into disc form and sintering at different temperatures. Quantitative X-ray diffraction (QXRD) analysis was firstly used for determining the compositions of different types of alumina in membrane products. The result quantitative determined that alumina membranes experienced a series of phase transition from boehmite → γ-alumina → δ-alumina → θ-alumina → α-alumina from 450 to 1300 °C. Below 850 °C, no significant alumina transformation (i.e. γ-alumina was the dominate phase) was detected in fabricated membranes, which corresponded to stable membrane properties (i.e. porosity, BET surface area, pore size and chemical stability). At 950–1300 °C, substantial phase transformation was detected as follows, θ-alumina significantly increased from 1.21 to 61.6% (950–1125 °C), and α-alumina increased gradually from 3.98 to 100% (1100–1300 °C). Accordingly, the substantial phase transformation lead to the significant change in membrane properties at 950–1300 °C. Lower temperature (1150 °C) membrane containing 8.2% θ-alumina and 91.8% α-alumina showed comparable properties with 1300 °C consist of 100% α-alumina sintered products due to the similar alumina composition in the products. The overall results indicated that the properties of membrane were accordingly determined by the structure and content of alumina phases in membrane products. This strategy proposed a valuable method for production of lower temperature alumina-based ceramic membrane.