Time-resolved reflectivity (TRR) measurements have been used to determine the growth kinetics of both the amorphous-to-␥-phase and the ␥-to-␣ phase transformations of alumina films that have been deposited on (0001), (1210), and (0112) sapphire substrates. The activation energies for the amorphous-to-␥-phase and ␥-to-␣ transformations respectively are 4.5 and 5.2 eV, irrespective of the crystallographic orientation of the underlying sapphire substrate. For both transformations, the relative transformation rates seem to reflect the symmetry of the sapphire substrates, with the fastest kinetics being on the lowest symmetry orientation and slowest kinetics being on the highest symmetry orientation. These relative rates are attributed to the differences in step mobility on the different substrate orientations.
This paper presents the results of an in-situ Scanning Electron Microscopy study of the local strain partitioning between ferrite- and martensite-rich regions in a commercial dual-phase steel. A Scanning Electron Microscopy tensile micro-stage, coupled with strain measurement methodologies based on gold micro-grids and digital image correlation, has been used to measure inhomogeneous strain fields at the micron scale. It has been found that when martensite is distributed non-uniformly, local strain partitioning depends significantly on the local spatial phase distribution and morphology. Strain distribution maps can be developed which provide valuable information about local strain paths for both phases. The results suggest that a rather detailed description of the two-phase microstructure of such materials is needed in order to fully understand their mechanical behaviour.
Lead selenide (PbSe), cadmium selenide (CdSe), and selenium (Se) nano-and microcrystals were synthesized by using respective metal acetate salts along with sodium selenite as the Se source in the presence of bovine serum albumen (BSA) as the capping/stabilizing agent. Aqueous phase hydrazine reduction at 85 °C produced fine crystalline morphologies within 48 h. Both PbSe and CdSe reactions produced Se microrods (MRs) as reaction byproduct. The concentrations of metal acetate and sodium selenite used were always 1:1 (i.e., 1.25 mM in each case) and that of hydrazine was fixed at 0.78 M. The amount of BSA was changed systematically from 1-10 × 10 -4 g/mL to determine its influence on the crystal growth of these chalcogenides. Their morphologies and chemical compositions were determined with FESEM, TEM, and EDX analysis. A selective and precise EDX analysis of a single particle helped us to elucidate its shape and chemical composition. Such analyses lead to the finding that both reactions produced Se rods, their sizes varied from the nano to micro scale with an increase of the amount of BSA. PbSe polyhedral nanocrystals were obtained at a low BSA amount, which ultimately attained the shape of thick MRs. However, no rod formation was observed for CdSe particles, which were always present in the form of groups of small nanoparticles along with Se MRs. Protein estimation indicated the presence of adsorbed BSA on the surface of chalcogenide particles. A potential reaction mechanism was proposed to explain the Se MRs formation as byproduct. Finally, the results were discussed on the basis of selective adsorption of denatured BSA on specific crystal planes of the rock salt (PbSe) geometry in order to produce rod like morphologies.
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