Luc Deriemaeker

Inversion of static light scattering measurements for particle size distributions

Abstract The inversion of static light scattering measurements (SLS) for the evaluation of particle size distributions is reported. The performances of two inversiion methods, i.e., the maximum entropy method and a constrained regularization method (Contin), are illustrated with simulated data and experiments on samples with unimodal, bimodal, and trimodal distributions of spherical particles and on a sample with a broad size distribution. Some experimental results are compared to assessments by photon correlation spectroscopy (PCS) and electron microscopy (EM). It appears that a significantly better resolution in particle size is obtained by SLS than by PCS. However, for a sample with a broad distribution in particle sizes, not all details of the distribution observed by EM were resolved.

Singular value analysis and reconstruction of photon correlation data equidistant in time

The application of the algorithm of Zeiger and McEwen to the analysis of noisy photon correlation data is investigated. For the particular case where the data are sampled at equidistant time intervals a complete solution is given allowing reliable reconstruction of the spectrum of exponential decay rates without any a priori knowledge. A particular attractive feature of the method is that the singular value analysis of the Hankel matrix of autocorrelation functions offers a practical criterion for the decomposition of the data into a signal and a noise part. Some tests of the method are illustrated with experiments on monodisperse latices, gold sols, and binary mixtures of monodisperse latices. In the latter case comparable and even better results are obtained in significantly shorter computing time when compared to an analysis with Contin and the maximum entropy method. Since the present method does not require any a priori parameter setting, it is also complementary to these methods.

Shape and Size Determination by Laser Diffraction: Feasibility of Data Analysis by Neural Networks

The feasibility of the inversion of laser diffraction data for size and shape distribution by neural networks has been investigated by computer simulation. Neural networks trained with diffraction patterns of elliptical particles with different sizes and aspect ratios (axis ratios) were able to recover simultaneously both the size and aspect ratio distributions in a few milliseconds on a common PC.

Shape and Size Determination by Laser Diffraction:Feasibility of Data Analysis by Physical Modeling

The feasibility of the inversion of laser diffraction data for size and shape distributions by a constrained regularization method (Contin) has been investigated by computer simulation. Diffraction data are simulated for particles with elliptical projections. An iterative procedure is proposed to calculate the size and shape distribution. This method was able to recover both the size and shape distribution from simulated diffraction patterns of elliptical particles with different sizes and aspect ratios.

Ostwald ripening and solubilization in alkane in water emulsions stabilized by different surfactantsPresented at the 17th Conference of the European Colloid & Interface Science Society, Firenze, Italy, September 21?26, 2003.

The Ostwald ripening (OR) and the solubilization of alkanes in water emulsions stabilized by the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) and the non-ionic surfactants hexaoxyethylene glycol n-dodecyl ether (C12E6) and polyoxyethylene (20) sorbitan monolaurate (Tween20) were investigated. For the emulsions stabilized by the anionic SDBS the mass transport in both OR and solubilization is molecular diffusion of the oil through the continuous phase and no contribution of a micellar mediated transport is observed. For the emulsions stabilized by the non-ionic surfactants three different situations occur. For emulsions prepared in one single step under the high shear conditions of a microfluidizer, the mass transport is also mainly molecular diffusion. For already prepared emulsions to which extra surfactant is added, there is, besides molecular diffusion, a small contribution by a micellar mediated mechanism. Finally, in the solubilization studies the mass transport is a fusion–fission mechanism rather than molecular diffusion.