A Survey of Complementary Methods for the Characterization of Dense Colloidal Silica

Abstract

The aim of this study is to enhance existing knowledge of different techniques developed for the characterization of stability and particle sizing of nanoparticles in dense dispersions subjected to interparticulate and hydrodynamic forces. Silica suspension, commercially known as Klebosol® 30R50 and consisting of a particle size of 80 nm on average, was investigated in the study over a wide range of concentrations. The investigations were carried out using different optical and acoustic techniques such as laser diffraction, multiple light scattering, photon correlation spectroscopy and acoustic spectroscopy. The study details the capabilities and limitations of these modern techniques based on the different physical principles behind the characterization of the size distribution of particles in suspensions. The results are presented in terms of particle size ranges, solid concentration and technological aspects such as online and offline analysis. An important finding is that many of these modern techniques need to be improved for applications at higher concentrations since the standard models become practically invalid because of the complex interaction of acoustic and optical waves with particles in suspensions of silica.

Effects of Rod‐like Particles on the Microstructure and Strength of Porous Silica Nanoparticle Composites

“…In addition, 34 wt% silica colloidal suspension (Ludox TMA, Sigma‐Aldrich, St. Louis, MI), sodium chloride (NaCl, AR grade, Mallinckrodt, Paris, KY), and deionized water were mixed together with the nanorods to form the solutions to be freeze cast. The silica nanospheres in the Ludox suspension had a nominal diameter of 22 nm (manufacturer reported), a density of 2.37 g/cm 3 , and were well dispersed in deionized water.…”

Effects of concentration of dispersions on particle sizing during production of fine particles in wet grinding process

“…For these dispersions, acoustic attenuation spectra were determined with the help of acoustic attenuation spectrometer. M. Tourbin and C. Frances [15] have given the expression for the attenuation spectrum of water as a function of frequency (f) as:…”

“…Nonlinearity observed in acoustic curves (attenuation plotted as a function of concentration) may indicate the presence of multiple scattering [15,17]. The method adopted by M. Tourbin and C. Frances [15] was followed to confirm the existence of multiple scattering. The method takes into consideration the excess of attenuation which may be described as [15]:…”

“…Based upon the theory behind the technique (Section 2.2), hydrodynamic diameter may be regarded as the diameter of the particle plus the thickness of the layer of ions surrounding the particle, at both ends of the diameter [15]. Approximately, D H = D + 2/k (where D H = hydrodynamic diameter, D = diameter of particle and 1/k = thickness of layers of ions around the particle, known as Debye length) [15]. The value of the thickness of the layer of ions (from both ends of diameters) may be subtracted from the hydrodynamic diameter in order to get diameter of the particle (D).…”

“…The method adopted by M. Tourbin and C. Frances [15] was followed to confirm the existence of multiple scattering. The method takes into consideration the excess of attenuation which may be described as [15]:…”