TY - JOUR

T1 - Annealing induced structural and phase transitions in anodic aluminum oxide prepared in oxalic acid electrolyte

AU - Roslyakov, I. V.

AU - Kolesnik, I. V.

AU - Levin, E. E.

AU - Katorova, N. S.

AU - Pestrikov, P. P.

AU - Kardash, T. Yu

AU - Solovyov, L. A.

AU - Napolskii, K. S.

PY - 2020/1/15

Y1 - 2020/1/15

N2 - Anodic aluminum oxide (AAO) films with uniform cylindrical pores are widely used as templates and membranes. The annealing of initially amorphous AAO enhances its chemical stability, but simultaneously changes its morphology and phase composition. Here we study the effect of annealing in the temperature range up to 1150 °C on structural and phase transitions in porous AAO films prepared by Al anodization in oxalic acid. Full-profile analysis of high-resolution X-ray diffraction patterns using the Rietveld method reveals the sequence of phase transformations (amorphous alumina → a mixture of γ-Al2O3 and θ-Al2O3 → a mixture of γ-Al2O3, δ-Al2O3, and θ-Al2O3 → α-Al2O3) and is used for quantitative phase analysis. Decomposition of oxalate-impurities, induced by the AAO crystallization, is studied using combined Fourier-transform infrared spectroscopy and thermogravimetry analysis. The removal of impurities results in the formation of mesopores in the AAO cell walls with a consequence increase in the specific surface area up to 80 m2·g− 1. The apparent activation energies of the removal of water (~35 kJ·mol− 1) and of the decomposition of carbon-containing impurities (~350 kJ·mol− 1) are calculated. Morphology-dependent kinetics of the impurities removal is described in the framework of the limited mass-transport of oxalate decomposition products through the cell walls.

AB - Anodic aluminum oxide (AAO) films with uniform cylindrical pores are widely used as templates and membranes. The annealing of initially amorphous AAO enhances its chemical stability, but simultaneously changes its morphology and phase composition. Here we study the effect of annealing in the temperature range up to 1150 °C on structural and phase transitions in porous AAO films prepared by Al anodization in oxalic acid. Full-profile analysis of high-resolution X-ray diffraction patterns using the Rietveld method reveals the sequence of phase transformations (amorphous alumina → a mixture of γ-Al2O3 and θ-Al2O3 → a mixture of γ-Al2O3, δ-Al2O3, and θ-Al2O3 → α-Al2O3) and is used for quantitative phase analysis. Decomposition of oxalate-impurities, induced by the AAO crystallization, is studied using combined Fourier-transform infrared spectroscopy and thermogravimetry analysis. The removal of impurities results in the formation of mesopores in the AAO cell walls with a consequence increase in the specific surface area up to 80 m2·g− 1. The apparent activation energies of the removal of water (~35 kJ·mol− 1) and of the decomposition of carbon-containing impurities (~350 kJ·mol− 1) are calculated. Morphology-dependent kinetics of the impurities removal is described in the framework of the limited mass-transport of oxalate decomposition products through the cell walls.

KW - Annealing

KW - Anodic aluminum oxide

KW - Kinetic analysis

KW - Quantitative phase composition

KW - Rietveld method

KW - Specific surface area

KW - GAMMA

KW - MEMBRANES

KW - THERMAL-DECOMPOSITION

KW - DESORPTION

KW - ANODIZATION

KW - TEMPERATURE

KW - CATALYTIC-PROPERTIES

KW - KINETICS

KW - PROFILE REFINEMENT

KW - FABRICATION

UR - http://www.scopus.com/inward/record.url?scp=85075858100&partnerID=8YFLogxK

U2 - 10.1016/j.surfcoat.2019.125159

DO - 10.1016/j.surfcoat.2019.125159

M3 - Article

AN - SCOPUS:85075858100

VL - 381

JO - Surface and Coatings Technology

JF - Surface and Coatings Technology

SN - 0257-8972

M1 - 125159

ER -