2011 Postgraduate Research Competition - UNSW Science - The ...

Page |25
Structure analysis and modelling of the packing of
ternary mixtures of spheres
Liangyu Yi and Aibing Yu
School of Materials Science & Engineering
Abstract
The packing of multi-sized particles is important to many industrial processes. While the
packing structure often determines the process performance, it is not easy to be obtained
experimentally and the fundamental understanding of it is far from well known. This work has
presented a numerical study of the packing of ternary mixture of spheres with size ratios of
24.4/11.6/6.4 (approximately 4:2:1) by means of the discrete element method (DEM). Good
agreement between the simulated and measured coordination numbers was obtained,
which validated the DEM model at a particle scale. By the reliable and well controllable
numerical experiments, rich and detailed data were generated and analysed, and a model
was established to predict the coordination number of the ternary system with any volume
fraction ratios of the components. The structure was further analysed by the so-called radical
tessellation, which divides the whole packing into unit cells, each containing a single particle.
The detailed topological and metric properties of radical polyhedron were studied and
modelled against particle size distribution. The present study provides a comprehensive and
insightful understanding of the packing structure of the ternary mixtures of spheres, and could
be further extended to the general multi-sized systems.
Abstract
Highly Photocatalytic Titanium Dioxide Spheres
Xiaohong Yang and Aibing Yu
School of Materials Science and Engineering
Monodispersed titanium dioxide (TiO2) spheres with enhanced photocatalytic activity have
been synthesized via a simple but efficient method at room temperature. By this method, the
monodispersed titanium glycolate colloids can be first generated with diameters of 60-1000
nm by optimizing experimental parameters (e.g., concentration, time, and temperature). The
proposed approach shows a few unique features, including: short reaction time (within a few
minutes), high yield, and reproducibility. These titanium glycolate colloids can be further
processed to be TiO2 particles with large surface areas via hydrothermal treatment at 100 o C
or calcinations at around 500 o C, confirmed by various advanced techniques (TEM, TGA,
FTIR, XRD, BET and ESI). Interestingly, the enhanced photocatalytic activity of these TiO2
nanoparticles was finally confirmed by measuring the decolourization of organic dye
molecules (e.g., phenolphthalein) under UV irradiation.
|energy + materials technologies