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Preparation of Fine-Grained Spinel-Silica Composites

IP.com Disclosure Number: IPCOM000040926D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Giess, EA: AUTHOR [+2]

Abstract

Fine-grained spinel-silica composites can be prepared by the addition of approximately equal amounts of a colloidal silica dispersion to a size classified spinel dispersion.

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Preparation of Fine-Grained Spinel-Silica Composites

Fine-grained spinel-silica composites can be prepared by the addition of approximately equal amounts of a colloidal silica dispersion to a size classified spinel dispersion.

In one part of the process narrowly sized spinel powder is obtained by suspending commercially available spinel powder in an aqueous solution which has been acidified to approximately pH 3.5 using acetic or nitric acid and subsequently size-classifying the resulting dispersion by semi-continuous centrifugation.

Commercially available colloidal silica particles, also used in the composite powder, are preprocessed by dilution with water to a concentration of about 1.5 M, with addition of an ionic exchange resin to remove alkali ions, and adjustment to pH 3.5 using acetic acid.

A composite powder dispersion is then prepared by the slow addition of equal amounts of silica dispersion to vigorously stirred size-classified spinel dispersion. The pH's of both dispersions are matched at 3.5, and silica and spinel concentrations are previously adjusted to about 1.2 M and 0.28 M, respectively. At a pH of 3.5, silica and spinel have opposite surface charges and hence are normally attracted to each other in dispersion. Slow addition of silica to spinel, diluteness of the spinel dispersion, and more highly concentrated silica dispersion all promote the formation of non-flocculated silica-spinel composite powder which is comprised of individual spinel par...