Effect of pH on the combustion synthesis of nano-crystalline alumina powder

Synthesis of nano-crystalline alumina powder by a chemical pyrophoric reaction using citric acid and ammonia was investigated by varying the pH of the precursor solution, which played an important role in controlling the morphology of the synthesised powder. The flaky morphology obtained at pH = 2 could be modified to fine desegregated particulate form by varying the pH of the solution to 10. The sluggish decomposition rate at low pH was found to be responsible for the generation of flaky powders, whereas the rapid decomposition at high pH - 10 yielded the fine desegregated powders. The as-prepared powders were amorphous in nature, which yielded the nano-crystalline alumina powder after calcination at elevated temperatures. (C) 2002 Elsevier Science B.V. All rights reserved.