Effects of Sample Preparation on Particle Size Distributions of Different Types of Silica in Suspensions

Abstract

The granulometric characterization of synthetic amorphous silica (SAS) nanomaterials (NMs) still demands harmonized standard operation procedures. SAS is produced as either precipitated, fumed (pyrogenic), gel and colloidal SAS and these qualities differ, among others, with respect to their state of aggregation and aggregate strength. The reproducible production of suspensions from SAS, e.g., for biological testing purposes, demands a reasonable amount of dispersing energy. Using materials representative for each of the types of SAS, we employed ultrasonic dispersing (USD) at energy densities of 8–1440 J/mL and measured resulting particle sizes by dynamic light scattering and laser diffraction. In this energy range, USD had no significant impact on particle size distributions of colloidal and gel SAS, but clearly decreased the particle size of precipitated and fumed SAS. For high energy densities, we observed a considerable contamination of SAS suspensions with metal particles caused by abrasion of the sonotrode’s tip. To avoid this problem, the energy density was limited to 270 J/mL and remaining coarse particles were removed with size-selective filtration. The ultrasonic dispersion of SAS at medium levels of energy density is suggested as a reasonable compromise to produce SAS suspensions for toxicological in vitro testing.

On the State and Stability of Fuel Cell Catalyst Inks

“…Secondly, while UB has fastest settling bottommost assemblage, UB+S70 has fastest settling topmost assemblage. From this, in line with findings of Retamal Marín et al [62] on silica particles re-agglomeration at high intensity sonication, we can carefully speculate that the energy input during preparation of sample UB+S70 potentially leads to re-agglomeration of broken assemblages, which settled quickly. The results of this section establish transmittograms as an effective way to compare, contrast and study the dispersion state.…”

Nanocomposite coatings obtained by electrophoretic co-deposition of poly(etheretherketone)/graphene oxide suspensions

“…Acoustic cavitation produced during TS promotes highly intense local conditions characterised by short-lifetime hot spots whose temperature rises to 5000°C, reaching pressure values of around 1000 atm, and cooling rates of 10 10 KÁs -1 [60]. Even though propagation of ultrasonic waves in liquids is generally considered as an adiabatic process because of the rapid pressure variation [61], the highly intense local conditions can cause ceramic, metallic, carbonaceous, and polymeric particles to experience, according to their nature, changes of their molecular weight, chemical and crystalline structure, and morphology [32,33,[61][62][63][64][65][66][67]. Hence, the first step was to determine the effects of TS on PEEK particles.…”

The Effect of Extender Particle Size on the Glass Transition Temperature of Model Epoxy Coatings

“…In addition, several different silica types have been used in these studies. It is well-known that fumed, precipitated, and colloidal silica have very different physical properties (particle size, particle size distribution, surface area, pore volume, pore diameter, pore size distribution) which may lead to different dispersibility characteristics of these silica types [6,14] and, therefore, may have been a reason for the mixed results obtained by different researchers. In this work the aim is to investigate the effect of extender particle size and loading (i.e., the amount of extender in component A or in the total formulation) on the T g of model epoxy-amine coatings by using commercially important extenders.…”