Controlling Surface Composition and Zeta Potential of Chemical Vapor Synthesized Alumina‐Silica Nanoparticles

Abstract

Ultrafine alumina-silica powders with varying composition gradients within the particles have been produced by chemical vapor synthesis in a hot-wall reactor using the precursors tetraethoxysilane (TEOS) and aluminiumtrisecbutylate (ASB). The surface chemistry at the particle/liquid interface in aqueous dispersions can be adjusted by varying the process parameters. The powders have been characterized by nitrogen adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) with local energy dispersive X-ray (EDX) analysis, X-ray fluorescence (XRF) analysis, and electrophoretic mobility measurements.

Interparticle forces in spherical monodispersed silica dispersions: Effects of branched polyethylenimine and molecular weight

“…The zeta potential approaches nearly asymptotically an isoelectric point (pI) in the neighbourhood of pH 2.7. This pI is in good agreement with values in the vicinity of 2.0-3.0 previously reported for silica powder dispersed in aqueous media [14,15] while Leong [16] has reported that a charge reversal was not observed.…”

“…Silica has a particularly low Hamaker constant in water of about 4.3 zJ or $1 kT at 25°C [11]. This means that the van der Waals attraction between silica particles in the flocculated state is very weak compared with most other oxides [15]. Direct force measurements also found short-range repulsive hydration forces for interactions between silica surfaces [21,22].…”

Microgranules and Nanoparticles on Their Surfaces

“…The composition of individual granules and nanoparticles can be determined by EDX spectrometry. Using these techniques, Sieger et al [55] determined the SiO 2 : Al 2 O 3 ratio in the central and peripheral parts of aluminosilicate microgranules while optimizing the synthesis process.…”

“…An effective process for the preparation of SiO 2 , Al 2 O 3 , and mixed-oxide particles is vaporization of volatile precursors, followed by thermal decomposition in a reactor [55]. In addition, this process, called the "aerosol" method [56], can be used to produce porous SiO 2 microgranules with a pore size of 8 nm [57].…”

In‐Situ Coating of Silica Nanoparticles with Acrylate‐Based Polymers

“…As nanoparticles exhibit a large specific surface area, it is expected that a change in the surface chemistry will drastically affect the overall characteristics of the powder (e.g., dispersability, corrosion resistance, optical, and electronic properties). Srdic et al [1] as well as Sieger et al [2] used CVS to prepare zirconia and silica particles, respectively, surface doped with alumina and reported the influence of doping on the interface properties in dispersions. The Karlsruhe microwave plasma process (KMP) has been used to apply coatings of oxides (e.g., ZrO 2 ) [3] or polymers (e.g., PMMA) [4] on ceramic nanoparticles.…”