Hydrothermal synthesis of submicrometer alpha-alumina from seeded tetraethylammonium hydroxide-peptized aluminum hydroxide


Submicrometer alpha-alumina powder was successfully synthesized from seeded aluminum hydroxide peptized with tetraethylammonium hydroxide (TENOH) and hydrothermally treated at 200degreesC, using alpha-alumina particles as seeds. The powders were characterized by XRD, SEM, DTA-TG, and BET analyses. Results showed that seeding could greatly enhance the transition to alpha-alumina at 200degreesC without formation of other transient alumina phases. alpha-Alumina with some amount of boehmite formed in the seeded samples, whereas boehmite was the exclusive phase formed in the nonseeded sample. The morphology of alpha-alumina embedded in the boehmite matrix for the seeded samples suggests a direct transition from aluminum hydroxide to alpha-alumina without the formation of transient alumina phases. The formation of alpha-alumina in the seeded samples at temperatures as low as 200degreesC could be attributed to a favored nucleation in the TENOH-peptized aluminum hydroxide and to the subsequent hydrothermal treatment that supplies the necessary activation energy for crystal growth. Transition of boehmite to alpha-alumina in the hydrothermally treated samples with low-seed contents was significantly promoted by heat-treating the samples at 500degreesC.




Materials Science


Yang, J; Mei, S; Ferreira, JMF

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