A.G. Dhere

Correlation between texture and substructure of conventionally and shock-wave-deformed aluminum

Abstract The changes in texture and substructure induced in commercial purity aluminum by conventional (cross-rolling) and shock wave deformation (peak pressure, 5.8 GPa; pulse duration, 2.8 μs) were studied by X-ray diffraction and transmission electron microscopy. Three different grain sizes were investigated (26, 70 and 440 μm) and shock wave deformation did not produce any noticeable change in texture, while cold rolling induced significant changes. The deformation substructure consisted of tangled dislocations after shock loading and of cellular arrays after rolling. Misorientations within the grains were investigated using Kikuchi lines and were found to be small after both shock loading and rolling (to an equivalent hardness).

Twinned colloidal gold particles

Abstract The structural characteristics of colloidal gold particles prepared by reduction of gold chloride were studied. Images and microdiffraction patterns indicate that multiple twinning is commonly present in the gold particles which range in size from 15 to several hundred nm. Very good agreement was found between the twin-fault densities determined by TEM studies and X-ray diffraction results.

Structural characteristics of cobalt particles in a 9.5%Co-ZSM-5 catalyst

A detailed structural study of cobalt particles in a 9.5%Co-ZSM-5 catalyst was made using x-ray diffraction and analytical transmission electron microscopy. The results obtained from these two techniques show the cobalt particles contain a high concentration of basal plane stacking faults. On the average one out of every twelve basal planes is faulted. It is suggested that atoms of a particle which lie at positions on the surface where intersection stacking faults exist may be the origin of active sites.

In situ X-ray diffraction investigation of the structural characteristics of two Co/ZSM-5 catalysts

Two CoZSM-5 catalysts, one prepared by impregnation with a cobalt nitrate/water media and the other impregnated by cobalt carbonyl, were investigated employing an in situ X-ray diffraction chamber mounted on a diffractometer. X-Ray diffraction patterns were obtained following each step in a sequence of processes on each catalyst. The water media-impregnated catalyst displayed the larger particle size and all characteristics remained constant following the initial reduction. The carbonyl-impregnated catalyst showed the formation of a large amount of CoO after exposure to HCO gas of 11 composition at 200 °C. Once the CoO formed it would continue to return after subsequent calcining and reduction treatments.

A method for separation of X-Ray diffraction patterns from Co-ZSM-5 catalysts

Abstract A Fourier method to unfold an X-ray diffraction pattern from a mixture to obtain the X-ray pattern from one component in the mixture is developed. The method is applied to the X-ray pattern from the catalyst mixture of 9.5% Co on a ZSM-5 support to obtain the diffraction pattern from metallic cobalt. Analysis of the details of the cobalt pattern shows the cobalt to be hexagonal in structure and dispersed with an average particle size of 220 A. The shapes of the profiles indicate that the cobalt particles are heavily faulted on the basal plane.

Morphological Developments of Nickel Particles in Supported Metal Catalysts

The morphology of nickel-containing phases at each stage during the treatment of a 12%Ni/Si/sub 2/ catalyst was studied. Liquid impregnated catalyst initially shows nickel nitrate uniformly dispersed on the surface of the silica in the form of a film. After calcining, large rafts of NiO with faceted surface pits are seen. The reduced catalyst contains bunched nickel particles or large rafts on the surface of the silica.

Application of X-Ray Diffraction Techniques to Study the Sintering of Catalysts

An x-ray diffraction single profile analysis method is presented which allows the calculation of the particle size distribution function (PSD). This method is verified by using it to analyze simulated diffraction profiles from single, duplex, triplex, and normal distributions of particle sizes. This method is employed to study the sintering of a nickel catalyst.