Polytypic transformations of aluminum hydroxide: A mechanistic investigation--颗粒学报PARTICUOLOGY

Thimmasandra Narayan Ramesh. (2012). Polytypic transformations of aluminum hydroxide: A mechanistic investigation. Particuology, 10(3), 359–364. https://doi.org/10.1016/j.partic.2011.08.003

Polytypic transformations of aluminum hydroxide: A mechanistic investigation

Thimmasandra Narayan Ramesh^*

Centre for Advanced Materials and Department of Chemistry, Tumkur University, Tumkur 572103, India

10.1016/j.partic.2011.08.003

Volume 10, Issue 3, June 2012, Pages 359-364

Received 3 April 2011, Revised 13 August 2011, Accepted 29 August 2011, Available online 4 January 2012.

E-mail: adityaramesh77@yahoo.com

Highlights

Abstract

The diffusion of ammonia vapors into a solution of aluminum nitrate or ferric nitrate results in the precipitation of their respective hydroxides and oxyhydroxides. Polymorphic phase formation of aluminum hydroxide is controlled by the rate of crystallization. The PXRD patterns of products obtained via vapor phase diffusion revealed that poorly ordered aluminum hydroxide is formed during the initial stages of crystallization. After 8 days, the formation of the bayerite phase of aluminum hydroxide was observed. Upon prolonged exposure to ammonia vapors, bayerite was transformed into gibbsite. The infrared spectrum of the product confirmed the presence of different polytypic phases of aluminum hydroxide. The results demonstrated that the crystal structure of metal hydroxides is controlled by the rate of crystallization, nature of the metal ion, site selectivity and specificity and preparative conditions.

Graphical abstract

Keywords

Vapor phase diffusion; Aluminum hydroxide; Gibbsite; Bayerite; Polytypism

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