SAR - Review

I. Introduction – Scope of the review

The review will try to answer to two main goals: the product classification and the product removal in the nano-size range and specifically applied to wet suspensions. The product classification means the removal of the coarse fraction from a size distribution, targeting specific size regimes (e.g. those > 0.5 μm and those > 100nm). The product recovery is the removal of all particles from a suspension, down to several nanometers. In that case however, the separation may be done differently if the product of interest is the solid (the separation is focused on the recovery of particles in the nano-size range) or the liquid phase (the separation is focused on the liquid phase purification). Usually, one considers that nanoparticles are particles having their three dimensions lower than 100 nm. The size range covered by this review varies from a few nanometers to several microns or even more. One raison is that nanoseparation processes are often not specific technologies but current technologies that have been extended towards the submicronic range.

Abstract

This review describes the packing of powders, and ways to modify it according to practical needs. Packing is affected by the assembling procedure, the container form, the shape, rugosity, and size distribution of grains, the nature of forces at each contact, the ambient fluid and the external loads acting on the packing. The variety of powders properties required by concrete applications precludes the use of universal recipes for packing optimization valid for all of them. Therefore, in this report we discuss ideas and methods that can help engineers to solve their specific technical problems related to packing.

Introduction

The development of strength during compaction of fine powder is a topic with immense importance for a variety of industrial applications. Results related to experimental evaluation of particle to particle interactions, particle-based computational simulation of compaction, and a renewed discussion about proper interpretation of traditional strength tests have been recently finding their way in the literature but have not yet compiled in a single document. In addition, the importance of the particle-to-particle interfaces has been rather understated. The development and evolution of interparticle cohesion during the process is central to the determination of the final compact properties but a quantitative understanding is not available.

This review attempts to contribute towards a more objective and coherent presentation on the subject, which will include the state-of-the-art in our understanding of the problem and will highlight areas where additional knowledge is needed. While experimental results will be incorporated in the discussion, this report is geared towards the discussion of the necessary models that analyze the various phenomena in compaction and post compaction mechanical properties. In such problems with multiple parameters and interactions, experiments offer correlations and often excellent insight but it is only when the physics is understood and modeled that predictive approaches become available and optimization becomes possible without the need for extensive experimentation.