The thermal stability of anodic alumina membranes at high temperatures

Abstract

Nano-structured anodic alumina membranes are ideal templates and have wide applications. However, anodic alumina materials begin to curl up at high temperatures. To better understand and overcome this problem, the thermal stability of anodic alumina membranes was investigated. Anodic alumina membranes obtained in oxalic acid electrolyte were heat treated in air at different annealing temperatures up to 1200• C. Our results show that the sub-pores produced during the annealing process are responsible for the curling. The repulsive forces between neighboring pores caused by mechanical stress at the metal nucleus/oxide interface promote the formation of the sub-pores. Annealing under a suitable pressure provided thermal stability to the membranes, because it avoided or minimized curling and cracking phenomena. Scanning electron microscopy images showed that the sub-pores disappeared when annealed under a suitable pressure.

Liquid permeation and chemical stability of anodic alumina membranes

“…The most convenient way involves oxolation and partial crystallization of hydroxides to crystalline alumina phases having extremely low solubility products. Unfortunately, thermal treatment of anodic alumina films is known to be accompanied by increasing brittleness and possible membrane curling [24–25]. However, none of the pure chemical methods (phosphate or chromate treatment) results in the necessary stability improvement towards dissolution.…”

Structural stability and optical properties of 1D photonic crystals based on porous anodic alumina after annealing at different temperatures

“…The phase transition into corundum at 1100 °С induces a noticeable reduction (shrink) of the d H and d L layer pairs (figure 4(d)). The PAA is considered as an optical platform with the high-temperature structural stability [46][47][48]53], but our results show that it is not always correct. The shrink is more prominent in the d L layer as compared to reduction in the d H layer, which is probably due to a higher porosity of the latter.…”

“…The applicability of the PAA-based PCs depends on the preservation of the periodically modulated pore structure upon annealing. Most articles regarding the microstructural stability of PAA after high-temperature thermal treatment focus on the macro-and microanalysis to the PAA's surface [46][47][48][49][52][53][54]. However, one of the most important aspects of microstructural stability is temperature-dependent morphological evolution along the PAAs cross-section.…”