Determining the size distribution-defined aspect ratio of platy particles

a r t i c l e i n f o Mineral particles are used in many industrial applications as fillers, in coatings, as ad-and absorbers or in catalysis. In these manifold fields the particle size and shape control the final performance and properties of the minerals. Much has been published using different techniques to describe the aspect ratio of platy particles. This study describes a simple method to calculate aspect ratios for platy particles based on particle size data and specific surface area determined by nitrogen adsorption, exemplified with three different talc grades which vary in their amount of specific surface area and geological origin, as well as with one nano-sized synthetic Laponite (Laponite® RD) to illustrate the sensitivity to input parameters and their physical interpretation. The contrast between mass/volume and number probability distribution of particle size is discussed and illustrated. Mineral particles are used as fillers in a range of applications, including paper, decorative and functional coatings, plastics and ceramics (Baudet et al. Frequently, the morphology of the particles constituting the mineral within a desired particle size distribution can be a key factor in determining the functionality of the end use. Mineral particles like talc are found in paper coatings and as paper fillers in the bulk of the fibrous sheet. They are also applied as filtration aids or as a component in fixed bed reactors (Aris, 1957; Casal et al., 1985), and found in cosmetic products (Papirer et al., 1992). In all these application fields, the particle shape is of great importance. For example, in paper, platy talc or acicular aragonite provide for coating coverage and internal bulk, respectively. Minerals may also expose different surface properties, depending on the orientation of the particulate in respect to its morphology. The ratio of anisometric surfaces may control properties such as wettability to certain liquids, which can affect mineral processing and end-use function or the rheological behaviour of a particle suspension A typical example was given by Yekeler et al. (2004) and Yildirim (2001) in respect to the specific adsorption potential of a mineral in relation to its surface differential properties. Similarly, minerals used as catalysts owe their functionality to the exposure of the required reactive surface. Thus, for simple planar and longitudinal geometries, it is crucial for assessing particle-related performance to ascertain a representation of the aspect ratio (Li et al., 2002). Aspect ratio expresses the relative abundance of …