Abstract
In the present work, the influence of addition of some dispersing agents employed for maximizing the solid loading of alumina concentrated suspensions has been investigated. Two commercially available deflocculants were used: a sodium tripolyphosphate and a sodium polyphosphate. Rheological tests were carried out at 25°C under continuous flow conditions by using the rate-controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-osc., measuring device SV2P with serrated surfaces. The application of rheological techniques permitted the evaluation of the efficiency and the optimum dosage of the dispersing agents employed upon the alumina slips examined, that is, the critical concentration at which the maximum reduction in viscosity is detected.
Highlights
Alumina is widely used in a lot of industrial applications which presuppose the employment of concentrated suspensions
The application of rheological techniques permitted the evaluation of the efficiency and the optimum dosage of the dispersing agents employed upon the alumina slips examined, that is, the critical concentration at which the maximum reduction in viscosity is detected
The present work is aimed at studying the influence of the addition of a sodium tripolyphosphate and a sodium polyphosphate on the flow characteristics of suspensions prepared with an alumina powder of high purity
Summary
Alumina is widely used in a lot of industrial applications which presuppose the employment of concentrated suspensions. The addition of dispersants to alumina suspensions induces particle repulsion and a viscosity decrease until the saturation adsorption limit of dispersing agent is reached; this phenomenon takes place in correspondence to a critical dispersant concentration (optimum dosage) at which electrostatic or electrosteric stabilization occurs. The present work is aimed at studying the influence of the addition of a sodium tripolyphosphate and a sodium polyphosphate on the flow characteristics of suspensions prepared with an alumina powder of high purity. When organic surfactants are used in the colloidal ceramic processing (mixing, dispersing, and forming) stages, they have to be removed later by thermal decomposition. This process causes materials to shrink and generates gaseous wastes. The inorganic dispersants as an alternative processing aid will eliminate or reduce these problems because the majority of the inorganic surfactants will be converted to ceramic materials
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