Silica diffraction effects

We have shown a new concept for selective chemical sensing based on composite core/shell polymer/silica colloidal crystal films. The vapor response selectivity is provided via the multivariate spectral analysis of the fundamental diffraction peak from the colloidal crystal film. Of course, as with any other analytical device, care should be taken not to irreversibly poison this sensor. For example, a prolonged exposure to high concentrations of nonpolar vapors will likely to irreversibly destroy the composite colloidal crystal film. Nevertheless, sensor materials based on the colloidal crystal films promise to have an improved long-term stability over the sensor materials based on organic colorimetric reagents incorporated into polymer films due to the elimination of photobleaching effects. In the experiments... 

Silica from zeolite migrates less readily. In the magnesia-alumina system, spinel, as identified by X-ray diffraction, is inactive for SO2 removal. The effect of temperature on steam stability, oxidative adsorption and reductive desorption of SO2 are described. Five commercial catalyst types are ranked for SOx removal. 

The effect the deliberate addition of water on the crystalization of silica sodalite was investigated in a separate series of experiments where increasing amounts of water were added to the system. Addition of water up to water/ethylene glycol ratios of 0.05 had no observable effect, x-ray diffraction showing 100 percent silica sodalite. Above this ratio increasing amounts of meta sodium silicate were formed until this became the only product at water/ethylene glycol ratios above 0.5. 

Effect of disagglomeration of a fumed silica suspension on the results of laser diffraction (a) and ultrasonic... 

Palladium-silica catalysts prepared from tetra-ammine palladous nitrate (to avoid chlorine introduction) showed a marked reduction effect , viz, the specific activity for benzene hydrogenation decreased with increased reduction temperature, i.e., 573 or 723Various explanations were considered, including a metal-support interaction. After reduction at 873 K, X-ray diffraction provided clear evidence of chemical reaction and at lower temperatures silicon insertion into palladium might still occur, which could either disrupt the palladium ensembles required for benzene adsorption or modify the properties of single palladium atoms, if these are the active sites. 

A series of catalysts was prepared to study the effect of substituting titanium, zirconium, or tin for antimony in the USb3O2 Q lattice. The crystalline phases present in these materials were determined by X-ray powder diffraction. To provide a basis for comparison with the prior art, catalyst 1 listed in Table I was prepared following the published recipe ( ). This catalyst represents the old uranium-antimony oxide catalyst without any silica binder. The crystalline phases detected in catalyst 1 were USb3O2 Q and Sb20 as expected (3,4). 

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