A Comparative Analysis of the Flow Properties between Two Alumina-Based Dry Powders

Milene Minniti De Campos,Maria Do Carmo Ferreira

doi:10.1155/2013/519846

Milene Minniti De Campos, Maria Do Carmo Ferreira

Open Access

https://doi.org/10.1155/2013/519846

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Abstract

We measured and compared the flow properties of two alumina-based powders. The alumina powder (AP) is irregularly shaped and has a smooth surface and moisture content of 0.16% (d.b.), and the ceramic powder (CP), obtained after atomization in a spray dryer, is spherical and has a rough surface and moisture content of 1.07%. We measured the Hausner ratio (HR), the static angle of repose (AoR), the flow index (FI), the angle of internal friction, and the wall's friction angle. The properties measured using aerated techniques (AoR and HR) demonstrated that AP presents true cohesiveness (and therefore a difficult flow), while CP presents some cohesiveness and its flow might be classified as half way between difficult and easy flow. Their FI values, which were obtained using a nonaerated technique, enable us to classify the alumina as cohesive and the ceramic powder as an easy-flow powder. The large mean diameter and morphological characteristics of CP reduce interparticle forces and improve flowability, in spite of the higher moisture content of their granules. The angles of internal friction and of wall friction were not significantly different when comparing the two powders.

Highlights

Alumina-based ceramic powders can be used in a variety of industries such as aerospace, automotive, medical, chemical, electronics, and environmental technologies because these powders can be applied in manufacturing cutting tools, car parts, dentistry, heat exchangers, filters, and refractory tiles [1,2,3]
A mixture of particles of different sizes is common in powders meant for applications into the ceramic field
This paper presents the measured flow properties of two alumina-based powders with different sizes and morphology

Summary

Introduction

Alumina-based ceramic powders can be used in a variety of industries such as aerospace, automotive, medical, chemical, electronics, and environmental technologies because these powders can be applied in manufacturing cutting tools, car parts, dentistry, heat exchangers, filters, and refractory tiles [1,2,3]. The flow index (FI) is calculated either as the inverse of the flow function slope [8] or as the inverse of the slope of a line cutting the flow function at a particular point of major consolidation stress and passing through the origin of coordinates [9]. These curves of cohesive strength versus consolidating pressure are measured in direct or annular shear cells, according to detailed procedures described by the ASTM standards D6128-06 and D6773-08, respectively, [10, 11]. Data obtained by shear testers may provide further information

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