Thermal Expansion and Phase Transformation up to 1200 °C of Metastable Aluminas Produced by Flame Spraying

Abstract

The transition aluminas δ1 and the cubic, non-spinel-type η-Al2O3 were detected in addition to α-Al2O3 in flame-sprayed material. Their transitions from room temperature up to 1200 °C were investigated by high-temperature XRD measurements. Structural changes with time and temperature were observed for all transition aluminas (η-, δ1- and θ-Al2O3). The phases followed the expected transition sequence of η→δ1→θ→α and showed mainly linear, temperature-independent transition rates. Based on the determined thermal expansion of the phases, it is proposed that the metastable transitions are at least partly mechanically induced. In addition, a second-order phase transition from η→θ might be indicated around 1050–1075 °C by the determined trends of density.

Enhancing responsivity and detection limit in tunable nano-electromechanical system resonator mass sensors

“…The results indicate that reducing T leads to improvements in both R and dM. Notably, the Al 2 O 3 substrate, with a higher a D th 36) in relation to MoS 2 , exhibits a more significant improvement in R and dM compared to the SiO 2 /Si substrate. 37) This can be attributed to the more pronounced strain changes induced by T variation on the Al 2 O 3 substrate.…”