Preparation of aluminium hydroxide by reacting sodium aluminate solutions with mineral acid

The preparation of aluminium hydroxide from sodium aluminate solutions by varying the alkaline concentration at a fixed molar ratio of Na₂O: Al₂O₃ has been investigated on addition of hydrochloric or nitric acids. The resulting materials have been examined by X-ray diffraction study, infrared spectrophotometry, thermogravimetrical and differential analyses. As a result, it was found that precipitates generally exist as pseudoboehmite or bayerite, but the formation of bayerite is enhanced by a low rate of addition of acid, higher temperature or higher alkaline concentration. In this case, the composition of the precipitates was little influenced at different molar ratios of Na₂O: Al₂O₃. When the precipitates from sodium aluminate solutions at low and higher alkali concentrations were aged in the mother liquors, pseudoboehmite therein transformed to hydrargillite and bayerite, respectively.     

Near lossless coding of sparse histogram images based on zero-skip quantization

Multimedia Tools and Applications - This paper introduces a zero-skip quantization (ZS.Q) scheme for the near lossless coding of sparse histogram images. Increases in the range of pixel values and...     

Combined ab initio/CALPHAD modeling of fcc-based phase-equilibria in the Ir–Nb system

A preliminary thermodynamic assessment of the Ir–Nb system, one of the key binary systems of the Ir-based refractory superalloys, has been performed by combining ab initio calculations and the CALPHAD (CALculation of PHAse Diagrams) technique. The ground-state formation enthalpies have been calculated by the full-potential linearized augmented plane wave method. The free energies at finite temperatures have been estimated using the cluster variation method, where the effective cluster interaction energies have been extracted from the formation enthalpies by the cluster expansion method. The liquid and A1 phases are modeled as substitutional solutions. The L1₀ and L1₂ phases are described using the four-sublattice model with the formula (Ir,Nb)_1/4(Ir,Nb)_1/4(Ir,Nb)_1/4(Ir,Nb)_1/4, while other solid phases are not considered in the present assessment. The obtained parameter set reproduces well the characteristic features of the experimental phase diagram and thermodynamic quantities.     

Hydrocracking of diphenylmethaneRoles of H2S, pyrrhotite and pyrite

This study presents the role of H₂S other than H-transfer catalyst in the hydrocracking of diphenylmethane with H₂–H₂S-pyrrhotite. The results indicate that the partial pressure of H₂S controls the conversion of pyrrhotite to FeS and FeS₂, which in turn is closely related to the promotional activity of pyrrhotite on the diphenylmethane conversion. Under higher H₂S overpressures, pyrite bands appear in the Mössbauer spectra providing proof of the reversibility of pyrite decomposition under liquefaction conditions. With lower H₂S pressures, low activity troilite forms from the pyrrhotite. An enhanced activity was observed for a partial pressure of H₂S, sufficient for the maintenance of a high iron deficient surface on the pyrrhotite particles. When the partial pressure was increased too much, the formation of FeS₂ was observed with a slight decrease in activity. FeS did not show as great an activity as the non-stoichiometric pyrrhotite.     

Extraction of uranium (VI) from hydrochloric acid solutions by long-chain aliphatic amines

The partition of uranium (vi) between hydrochloric acid solutions and organic solutions of long-chain aliphatic amines has been investigated at different concentrations of hydrochloric acid, solvent and aqueous uranium, and at different temperatures. The effects of amine structure and of organic solvent and the mechanism of uranium extraction are discussed on the basis of the results obtained. From infra-red spectral measurements it is postulated that a chloro complex of uranium (vi) is formed in the extraction of uranium (vi) from hydrochloric acid solution by tri-n-dodecylamine in benzene.     

Hydrocracking of diphenylmethane

This study presents the role of H₂S other than H-transfer catalyst in the hydrocracking of diphenylmethane with H₂–H₂S-pyrrhotite. The results indicate that the partial pressure of H₂S controls the conversion of pyrrhotite to FeS and FeS₂, which in turn is closely related to the promotional activity of pyrrhotite on the diphenylmethane conversion. Under higher H₂S overpressures, pyrite bands appear in the Mössbauer spectra providing proof of the reversibility of pyrite decomposition under liquefaction conditions. With lower H₂S pressures, low activity troilite forms from the pyrrhotite. An enhanced activity was observed for a partial pressure of H₂S, sufficient for the maintenance of a high iron deficient surface on the pyrrhotite particles. When the partial pressure was increased too much, the formation of FeS₂ was observed with a slight decrease in activity. FeS did not show as great an activity as the non-stoichiometric pyrrhotite.     

3D structuring of dense alumina ceramics using fiber-based stereolithography with interparticle photo-cross-linkable slurry

In this paper, we demonstrated optical fiber-based stereolithography of alumina ceramics using concentrated slurry with low monomer content for enabling rapid firing of the printed green objects. Photo-cross-linkable alumina slurries were designed using a partial complex of polyethyleneimine and oleic acid (PEI-OA) as reactive polymer dispersants and multifunctional acrylates (MA) as monomers. The effects of the processing parameters, such as oleic acid contents, MA contents, particle contents, and particle sizes, on photocuring properties were systematically investigated. We found that the reactive amine sites of PEI-OA attached to particles and MA volume concentrations in the liquid phase were the most dominant factors to improve the photocuring properties. Therefore, a slurry composed of larger alumina particles with higher solid contents and PEI-OA with lower OA contents was more favorable for achieving photocuring under reduced MA content. The designed photocurable slurry was then applied to ceramic stereolithography using optical fiber. 3D alumina green parts were drawn by passing blue laser beam through an optical fiber in a droplet of photocuring slurry and dense sintered alumina were successfully fabricated by rapid drying (<10 min) and debinding (<1 h) without any structural collapse.     

Aligning vapor-grown carbon fibers in polydimethylsiloxane using dc electric or magnetic field

A trace amount of vapor-grown carbon fibers (VGCFs), which, as received, had an aggregated lump form, was completely dispersed in polydimethylsiloxane, a nonpolar viscous liquid, at room temperature by mechanical stirring. Using this uniformly dispersed sample as a starting material, a dc electric or magnetic field was applied to induce the formation of an aligned structure. In situ transmission optical microscopy was carried out to observe the structural development of VGCFs in polydimethylsiloxane under the dc electric or magnetic field, which was applied both parallel and perpendicular to the observation direction. Upon application of a dc electric field, an aligned ramified network structure of VGCFs developed between the electrodes. In the formation of the network structure, ends of VGCFs became connected to ends of other VGCFs, which was followed by rotation and orientation of the VCGFs. On the other hand, upon application of a magnetic field, the VGCFs were only rotated, without the formation of a network. The electric resistivity of the network structure was evaluated. Additionally, the influence of the viscosity of the polydimethylsiloxane matrix on the structural formation process was examined.     

Efficient spin resolved spectroscopy observation machine at Hiroshima Synchrotron Radiation Center

Highly efficient spin- and angle-resolved photoelectron spectrometer named ESPRESSO (Efficient SPin REsolved SpectroScopy Observation) machine has been developed at the beamline BL-9B in Hiroshima Synchrotron Radiation Center. Combination of high-resolution hemispherical electron analyzer and the high-efficient spin detector based on very low energy electron diffraction by the ferromagnetic target makes the high-energy resolution and angular resolution compatible with spin- and angle-resolved photoemission (SARPES) measurement. 7.5 meV in energy and ±0.18° in angular resolution have been achieved with spin resolution. The ESPRESSO machine, combination of quick energy-band dispersion measurement and Fermi surface mapping by two-dimensional electron detector for the spin integrated ARPES and the high-efficient spin analysis by the efficient spin detector realizes the comprehensive investigation of spin electronic structure of materials.