نتایج جستجو برای: amorphous silica
تعداد نتایج: 61469 فیلتر نتایج به سال:
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...
Palladium catalysts deposited over different types of silica (amorphous silica, mesoporousmolecular sieves, solids obtained by co-condensation of silicate precursors and many others) modified with suitable donor moieties have gained enormous importance due to their wide application as catalysts for cross-coupling and other synthetically useful organic reactions. This work provides an overview o...
[1] Theoretical geochemical modeling has been used to evaluate the formation conditions of amorphous silica during aqueous alteration of typical Martian igneous rocks at 0 C. The models show that some silica can form during low-temperature alteration of mafic to ultramafic rocks over a large range of pH and water/rock ratios. Silica-dominated deposits, like those found at the Columbia Hills in ...
In this paper we present a fast model system for monitoring the recrystallization of quench-cooled amorphous xylitol using Raman spectroscopy and wide-angle X-ray scattering. The use of these two methods enables comparison between surface and bulk crystallization. Non-ordered mesoporous silica micro-particles were added to the system in order to alter the rate of crystallization of the amorphou...
The fundamental interactions of dimethyl methylphosphonate (DMMP) and dimethyl chlorophosphate (DMCP) on amorphous silica nanoparticles have been investigated with transmission infrared spectroscopy and temperature-programmed desorption (TPD). DMMP and DMCP both adsorb molecularly to silica through the formation of hydrogen bonds between isolated silanols and the phosphoryl oxygen of the adsorb...
We present a reformulation of the Tangney-Scandolo interatomic force field for silica [J. Chem. Phys. 117, 8898 (2002)], which removes the requirement to perform an Ewald summation. We use a Yukawa factor to screen electrostatic interactions and a cutoff distance to limit the interatomic potential range to around 10 Å. A reparametrization of the potential is carried out, fitting to data from de...
Rice husk is an abundant agricultural by-product reaching the output of 80 million tons annually in the world. The most common treatment method of rice husk is burning or burying, which caused serious air pollution and resource waste. In order to solve this problem, a new method is proposed to comprehensively utilize the rice husk in this paper. Firstly, the D-xylose was prepared from the semic...
We have developed structure/toxicity relationships for amorphous silica nanoparticles (NPs) synthesized through low-temperature colloidal (e.g., Stöber silica) or high-temperature pyrolysis (e.g., fumed silica) routes. Through combined spectroscopic and physical analyses, we have determined the state of aggregation, hydroxyl concentration, relative proportion of strained and unstrained siloxane...
Computational simulations are a new branch of science where one can perform computational experiments by simulating a model system. The model contains an approximation of a real system with simplified physical laws and reduced size in order to make it computationally tractable. Many physical systems cannot be analytically solved and also experimentally not everything can be measured. Computatio...
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