Effect of 10% Zn Addition on Fabrication of Al Alloys on Mechanical Properties, Crystal Structure and Micro Structure

Aluminum-based alloy are one of the most alloy beneficial in the industry. Therefore, the research is done on the effect of Zn addition on Al alloys fabrication using powder metallurgy method. The composition of 0% and 10% Zn with sintering temperature varied: 550oC, 600oC, and 650oC respectively at that temperature held for 1 hour. Characterization includes: measurement of hardness, SEM analysis, and XRD analysis. The result of XRD analysis from the results of the rietveld refinement phase using the match program it is found several phases is Al, Zn and ZnO. From the result of SEM analysis it is found that the reaction between Zn and Al so as to form solid solution phase on the addition of 10% Zn with 650oC sintering temperature. From the result of characteristic of mechanical properties, the highest hardness is 99,5 HD at 10% Zn addition for all sintering temperatures. With the addition of Zn the mechanical properties is increasing.

Formation of a solid solution between [N(C2H5)4][BF4] and [N(C2H5)4][PF6] in crystal and plastic crystal phases

The [N(C2H5)4][BF4]–[N(C2H5)4][PF6] binary system form solid solution in both crystal and plastic crystal phases (rock-salt type for plastic crystals).

Sintering of Ultrahigh Density and Highly Conductive ZnO-Ga2O3 Ceramic Targets

The ultrahigh density Gallium (Ga2O3 1 wt%) doped zinc oxide (ZnO, 99wt%) targets were prepared by air sintering. The relative density, conductivity, bending strength, Vickers hardness and shrinkage ratio of GZO targets were measured. The morphologies and microstructures were characterized by XRD and SEM. It turns out that sintered GZO targets achieved a relative density of 98%, square resistance of 7Ω/□, Vickers hardness of 310HV and a bending strength of 90.79MPa. The best sintering temperature is 1300°C. The Ga2O3 added can effectively enter into the ZnO lattice structure to form solid solution during sintering. The second phase of GaZn2O4 turned out when the sintering temperature was 1350°C.

Thermodynamic Analysis of Nb-Cr Powders of Mechanical Alloying

In this study, Nb-Cr binary mixtures were prepared by mechanical alloying. And mechanical alloying process of mixed Nb-Cr(1:2) powders was studied, and the phases of milling powders analyzed by XRD and SEM. It has been found that the powders form solid solution first, then amorphous phase appeared gradually and crystallization of amorphous takes place with the different milling time. A thermodynamic model of MA of Nb-Cr system was developed based on Miedema Semi-experimental theory to explain the phase transformations of Nb-Cr system during milling. Using Miedema semi-empirical model the free energies of the ordered Laves-phase NbCr2 intermetallics, solid solution and amorphous alloy were calculated. From XRD and SEM analysis of Nb/2Cr powders prepared by mechanical alloying in a planetary ball milling, it was found that the calculated results were in accordance with the experiments.

EVOLUTION AND ORDERING OF MULTILAYER Ge QUANTUM DOTS ON Si(001)

Evolution and ordering of multilayer Ge islands (up to 14 layers) on Si (001), prepared by physical vapor deposition at about 550°C; were studied using Scanning Tunneling Microscope (STM). In the growth process, it was observed that long huts split during the deposition of Si buffer layer. It can be explained as a consequence of strain due to lattice mismatch and intermixing of Si and Ge to form solid solution. Such a mechanism of splitting could lead the dots to order and uniformity in the subsequent layers. Apart from splitting of huts, the surface corrugation of Si spacer layer influences the nucleation of Ge islands in the next layer.

Electrical Conductivity of Zirconia-Mn Oxide Mixture

ABSTRACTMn2O3 was added to YSZ (8 mol% yttria- doped zirconia) either to form solid solution or two-phase (Mn2O3 and Mn2O3 doped-YSZ) mixed-conducting oxide. The electrical conductivity was measured between 600 and 1000°C in air using 4-probe d.c. method in a wide composition range to determine composition-dependent conductivity. Up to 12 mol% MnO1.5 addition, the conductivity decreases and the activation energy increases. With further increase of MnO1.5 content, the conductivity of composite begins to increase slowly and then increases rapidly after 30 mol% due to the interconnected, conductive Mn2O3 particles. Above 35 Mol% MnO1.5 content, the activation energy is nearly the same as that of Mn2O3. Hysteresis behavior shown in the conductivity of composite also provides the evidence of percolation by MnO1.5.

Effect of calcium modification on the microstructure and oxidation property of submicron spherical palladium powders

Ca-modified spherical palladium particles were prepared from the mixed solution of Pd(NO3)2 and Ca(NO3)2 by ultrasonic spray pyrolysis. Pure palladium powder and that modified with less than 55 ppm Ca were composed of single crystal particles. However, Ca addition of more than 500 ppm resulted in polycrystalline particles. Crystallite size of the particles decreased with the increase of Ca addition and changed dramatically at the addition of some hundred ppm. Ca additive did not form solid solution with palladium but formed CaPd3O4 on the surface and grain boundary of the particles. 50 ppm−1% of Ca addition significantly reduced the oxidation of palladium powder. More addition of Ca resulted in excess oxidation due to the reaction between palladium and calcium oxide.

Crystal Chemistry and Microstructures of Uranyl Phosphates

ABSTRACTThe crystal chemistry and microstructures of saleeite (Mg(UO2PO4)2•10H2O) and metatorbernite (Cu(UO2PO4)2•8H2O), from Koongarra, Australia and Shinkolobwe, Congo, were examined by X-ray diffraction analysis, infrared spectroscopy (IR), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis, transmission electron microscopy (TEM) and analytical electron microscopy. The uranyl phosphates consist of uranyl phosphate layers with cations and waters in the interlayers. The IR spectra of saleeite and metatorbernite show the presence of hydroxyls in the interlayers in addition to water molecules. The d002 spacings of the hydrated phases of saleeite and metatorbernite up to 300°C reveal that the uranyl phosphate layers themselves are quite stable in the temperature range although the interlayer water molecules are lost easily. The presence of a mixed phase of saleeite and metatorbernite is confirmed in the micrometer and nanometer scales. However, SEM and TEM examination suggest saleeite and metatorbemite generally grow separately, and rarely form solid solution or interstratification. The results imply that U is retained in uranyl phosphate minerals even when the temperature at around repositories increases, and that saleeite and metatorbernite precipitate independently from solution according to their solubilities even when Mg2+ and Cu2+ coexist in solution.

FORMATION OF NEW CRYSTALLINE ENZYMES FROM CHYMOTRYPSIN

A solution of chymotrypsin on slight hydrolysis undergoes an irreversible change into new proteins, two of which are enzymes and have been isolated in crystalline form. The new crystalline enzymes, called beta and gamma chymotrypsins, differ from the original chymotrypsin as well as from each other in many physical and chemical respects, such as molecular weight, crystalline form, solubility, and combining capacity with acid. The new enzymes still possess the same enzymatic properties as chymotrypsin. It thus appears that the irreversible change from chymotrypsin to the new enzymes does not affect the structure responsible for the enzymatic activity of the molecule. The solubility curves of the new enzymes agree approximately with the curves for a solid phase of one component and furnish very good evidence that the preparations represent distinct substances. The various enzymes when mixed at the proper pH have a tendency to form mixed crystals of the solid solution type. Thus at pH 4.0 gamma chymotrypsin combines to form solid solution crystals with either alpha or beta chymotrypsin. Hence at this pH separation of gamma from either alpha or beta by means of fractional crystallization is impossible. At pH 5.0–6.0, however, each material crystallizes in its own characteristic form and at its own rate; thus a fractional separation of the various enzymes from each other becomes feasible.