Monodisperse single-crystalline α-cristobalite nanospheres have been synthesized by hydrocarbon-pyrolysis-induced carbon deposition on amorphous silica aerosol nanoparticles, devitrification of the coated silica at high temperature, and subsequent carbon removal by oxidation. The nanosphere size can be well controlled by tuning the size of the colloidal silica precursor. Uniform, high-purity na...

Silica, or silicon dioxide (SiO2), is a group IV metal oxide, which naturally occurs in both crystalline and amorphous forms (i.e. polymorphic; NTP, 2005). The various forms of crystalline silica are: α-quartz, β-quartz, α-tridymite, β-tridymite, α-cristobalite, β-cristobalite, keatite, coesite, stishovite, and moganite (NIOSH, 2002). The most abundant form of silica is α-quartz, and the term q...

We have used Monte Carlo simulations to study the formation of the MCM-41 mesoporous silica material, with a new lattice model featuring explicit representations of both silicic acid condensation and surfactant self-assembly. Inspired by experimental syntheses, we have adopted the following two-step "synthesis" during our simulations: (i) high pH and low temperature allowing the initial onset o...

Examination of clays from surface and basal horizons of four Scottish soils by differential thermal analysis, before and after heating to 600~ and by infra-red spectroscopy indicates that these contain a proportion of highly hydrated amorphous material, resembling allophane in its properties, and that this component is particularly high in clays from the surface horizons with the greatest organ...

Coaxial nanocables of single-walled carbon nanotubes (SWNTs) sheathed with amorphous silica were synthesized by using an arc discharge method. The as-obtained nanocables were characterized by TEM, SEM and laser Raman. It was found that the nanocalbes are usually tens of microns in length and about 50 nm in diameter, and each of the cylinder-shaped nanocabels contains one to several SWNTs at the...

We report a case study in grid computing with associated data and metadata management in which we have used molecular dynamics to investigate the anomalous compressibility maximum in amorphous silica. The primary advantage of grid computing is that it enables such an investigation to be performed as a highly-detailed sweep through the relevant parameter (pressure in this case); this is advantag...

Amorphous silica density at ambient pressure is known to depend on thermal history (through the quenching rate) but also, at room temperature, on the maximum pressure applied in the past. Here we show that beyond density, a mechanical loading can endow the structure with an orientational order. Molecular dynamics simulations show evidence that amorphous silica develops a permanent anisotropic s...

In this work, the interfacial thermal transport across silicene and various substrates, i.e., crystalline silicon (c-Si), amorphous silicon (a-Si), crystalline silica (c-SiO2) and amorphous silica (a-SiO2) are explored by classical molecular dynamics (MD) simulations. A transient pulsed heating technique is applied in this work to characterize the interfacial thermal resistance in all hybrid sy...

Plasticity in amorphous silica is unusual: The yield stress decreases with hydrostatic pressure, in contrast to the Mohr-Coulomb response commonly found in more compact materials such as bulk metallic glasses. To better understand this response, we have carried out molecular dynamics simulations of plastic response in a model glass with open structure. The simulations reproduce the anomalous de...

Hydrophobic silica titanium nanoparticles (STNPs) were successfully synthesized by the sol-gel process using liquid modification. Fourier transform infrared (FTIR) and X-ray fluorescence (XRF) studies were demonstrated the attachment of titanium on the silica surface. Titanium content enhanced the agglomeration of particles as shown in topography results. The N2 adsorption-desorption followed T...