Influence of water vapour and additives on the surface area stability of gamma-Al₂O₃

International audienceThe influence of water vapour and additives on the decrease in surface area of gamma Al2O3 at 1378 K, before its transformation into alpha Al2O3, was investigated. The experimental rate of this decrease was found to vary as P H2O at constant value of surface area and for a value of water vapour pressure ranging from 0.1 to 1 kPa. This reduction in surface area was inhibited by a slight addition of Mg2+, Ca2+, La3+, Th4+ or Zr4+ ions but its rate was drastically increased by increasing both additive content up to 4% (cationic fraction) and oxygen pressure. The influence of water vapour can be explained quantitatively using a mechanistic model for initial sintering of oxide powders. This model is based on a description of material transport by means of structural elements of alumina, point defects, and their chemical interaction with the calcination atmosphere