Particle & Particle Systems Characterization

A simple device to characterize the tribo-electric charging propensity of powders is presented. The device measures the net change of powder charge upon defined shaking in a cup. The operation of this test device is investigated for different powders and surface materials and the influence of operational parameters is shown.

In this paper different methods to obtain the particle size distribution (PSD) of SiO₂ spherical nanoparticles from small angle X-ray scattering (SAXS) are compared. Furthermore, PSDs obtained from transmission electron microscopy and analytical ultracentrifuge are compared. The respective strengths and limitations of the different methods are discussed in detail.

An image analysis method for 3D re-construction of particle shape from silhouette and an estimate of intra-particular porosity of agglomerates is presented and applied to dehydrated milk agglomerates. Furthermore, a fractal dimension can be derived. Finally, this elucidates how instant properties of agglomerated powders are linked to the size and structure of constituting agglomerates.

Rainbow refractometry has been investigated numerically for small droplets under ultrashort pulse illumination. It is shown, that this technique works for pulse lengths as short as 10 fs and droplet diameters down to 5  μm. Overall, the possibility of improved in situ temperature measurements with Rainbow refractometry for small particles was shown to be feasible.

The particle size distribution (PSD) of dilute latex suspensions was estimated through a general regression neural network (GRNN) that was supplied with multiangle dynamic light scattering (MDLS) measurements. The results were compared to a standard Thikonov regularization technique as well as independent measurements showing very good results for the GRNN method.

The X-ray diffraction pattern from gallium phosphide nanoparticles showed the presence of the diamond (111) diffraction peak. Analysis of the Raman scattering and the X-ray photoelectron spectroscopy spectrum was applied too. The results indicate the presence of oxidized disordered graphite and diamond phases.

This work presents a model that calculates re-entrainment in analogy to transport processes between fluid phases, which are well known in chemical engineering. Applying film theory a parameter determining the re-entrainment rate is needed. This parameter was determined by a microscopic model. It is shown that the model is able to reproduce experimental data of the re-entrainment quite well.

This study compares the performance of particle size distribution (PSD) approximation functions when applied to chromite ores comminuted by different devices. It is shown that depending on the breakage mode different function types work better. Furthermore, a piecewise regression proved to be very useful to improve the PSD fit.