Papers by Keyword: Stoichiometry

Abstract: Synthesis of YSAG:Yb ceramic powders with different stoichiometry by chemical precipitation method was carried out. It has been established that scandium can replace both dodecahedral and octahedral positions of garnet. It is shown that scandium is embedded in those positions that become available to it when the YAG:Yb composition deviates from stoichiometric. Thus, scandium can compensate for the lack of one of the components of the oxide composition Y₂O₃, Yb₂O₃, and Al₂O₃ during the formation of the garnet phase.

Abstract: Anaerobic ammonium oxidation (anammox) process is a heated researched biotechnology for nitrogen removal in wastewater. The application of the process is limited due to its long start-up time and sensitivity to organic matters. This paper discussed the effects of acetate on anammox process. The nitrogen removal rate of anammox process was elevated at low acetate content (1 mmol/L) and decreased at high acetate content (3 and 4 mmol/L). The ratios among NH₄⁺-N, NO₂^--N and NO₃^--N were not related acetate content and remained at 1:1.50:0.07, but the ratios between acetate and three forms of nitrogen were acetate dependent.

Abstract: Nanocrystalline BaTiO₃ powder was directly synthesized by a convenient one-step solvothermal route. 8~10 nm BaTiO₃ with different Ba/Ti ratios are obtained by adjusting the raw material ratios. The optimum raw material ratio of Ba/Ti is obtained. And the as-prepared BaTiO₃ nanoparticles are all small and uniform. Influence of the nominal Ba/Ti ratios on diameter of nanocrystalline BaTiO₃ powder was investigated by XRD, TEM and XRF analyses. It was found that the Ba/Ti ratios of the raw materials have a great influence on the process of powder fabrication. When the raw material Ba/Ti ratio is low (<0.9), the reaction cannot be finished and strong BaCO₃ peaks were founded as the alkalinity of the system at the later reaction stage is too low. Besides, the Ba/Ti ratio of the product rises as the raw material Ba/Ti ratio increases.

Abstract: Near-stoichiometric lithium tantalite (LiTaO₃) crystals were grown by the top-seed solution pulling method in congruent melt with the addition of K₂O. The crystals were characterized by measurement of the ultraviolet absorption edge, ability of photo-damage resistance, and the domain structure analysis. Compared with the congruent crystal shows that, the ultraviolet absorption edge of the near-stoichiometric crystals has a blue shift towards a shorter wavelength and curie temperature is also improved; the domain structure of near-stoichiometric LiTaO3 crystals is hexagonal; and the photo-damage resistance of the crystals is greatly improved.

Abstract: It has a significant practical value to research a compound inhibitor for low temperature for the protecting of power plant devices with low working-temperature. In this paper, a new kind of film-forming inhibitor based on octadecylamine for low temperature has been proposed. Coupon test has been taken with autoclave simulating the on-site water-vapor environment; the film-forming effect of the metal specimen has been evaluated by hydrophobic test, acid copper sulfate drip test and AC impedance test. The result shows that the inhibitor filmed well after compounded, and has an important practical value.

Abstract: Nutrient elements from litter decomposition was viewed as the main source of essential elements for normal growing of the forest tree. In this study, selected litter leaves of several typical desert plants as study materials, and deferent element contents of the litter leaves were analyzed. The main results are as belows: (1) There were significant differences in the levels of C, N, P, K, Ca, Mg and K between litter leaves of different desert plants (p < 0.01). (2) Significant differences were found in the nutrition re-utilization rate of the withered leaves of different plants, with P > K > N. Haloxylon ammodendron has the highest N utilization rate of 88.33%. Calligonum mongolicum has the lowest P utilization rate of 95.13%. Elaeagnus angustifolia has the highest K utilization rate of 77.49%.

Abstract: This paper focused in details about dielectric properties of BT with different stoichiometry. In this research, BT was synthesis by solid state reaction between TiO₂ and BaCO₃ at constant sintering temperature of 1350 °C. Five different ratio of BT was characterized by using SEM, XRD, and IS. There have production of secondary phase when Ba was excessive. Impedance plot shows the relation between dielectric properties and stoichiometry of BT where the highest value of dielectric properties is comes from sample with Ba/Ti ratio equal of 1:1.

Abstract: CuIn_0.8Ga_0.2Se₂ (CIGS) thin films have been successfully deposited on soda lime glass substrate at different working (Ar gas) pressures by Pulsed laser deposition (PLD). The effect of working pressure on the structural, electrical and optical properties of CIGS thin films has been investigated. All deposited CIGS thin films are found to be polycrystalline in nature with preferred orientation along (112). Crystallinity of CIGS thin films has been improved with decreasing of working pressures in PLD chamber. Stoichiometry of CIGS thin films has been maintained for all working pressures. Optical transmittance and electrical sheet resistance of CIGS thin films have been found to decrease with decrease of working pressure. The results of the present study signify that desired structural, electrical and optical properties of CIGS thin films can be obtained by changing the processing parameter in PLD method.Keywords: CIGS, XRD, Stoichiometry, UV-Vis-NIR spectrophotometer.

Abstract: The effects of Fe stoichiometry and degree of order on mechanical properties of intermetallics Ni₃Fe were investigated. The experimental results showed that the phase composition and the grain size of Ni₃Fe alloy was independent on Fe stoichiometry. The Ni₃Fe alloy with the normal stoichiometry had the lowest elongation in the ordered and disordered alloys. The tensile strength of Ni₃Fe alloy depended on Fe stoichiometry of alloy. The effect of Fe stoichiometry on the mechanical properties of the ordered alloy was larger than that of disordered alloy. There were more point defects in lattice when the alloy stoichiometry deviating from the normal stoichiometry in the Ni₃Fe alloy. The changes of the concentration of the point defects and degree of order altered the deformation behavior of the Ni₃Fe alloy.

Abstract: Tin Selenide thin films have been deposited using thermal evaporation technique on chemically and ultrasonically cleaned glass substrates. The stoichiometry of deposited films has been studied using Energy Dispersive Analysis of X-rays (EDAX).The orthorhombic structure and polycrystalline nature of the films were also revealed by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) analysis. The well characterized thin film of SnSe was then used to fabricate Ag/p-SnSe/In Schottky barrier diode. The I-V characteristics of prepared diodes have been investigated over the temperature range of 303 K to 393 K. The forward biased I-V characteristics of prepared structure has been analyzed using TE theory and different device parameters have been evaluated and discussed in present paper. The Richardson constant was also determined from the conventional Richardson plot and it is found close to the reported value.