Papers by Keyword: La

Abstract: A new type of AZ31-1.3Ca-1.0Sm-0.3La alloy was obtained in this study by adding Ca, Sm and La to AZ31 alloy. Detailed analysis results on second phases showed that Al₂Ca phases, Al₂Sm phases with two kinds of morphologies formed in as-cast AZ31-1.3Ca-1.0Sm-0.3La alloy besides Mg₁₇Al₁₂ phases, and La atoms mainly dissolved in Al₂Ca/Sm phases. The average grain size of as-cast AZ31-1.3Ca-1.0Sm-0.3La alloys was 212 μm and the grain sizes distributions were uniform. After the hot extrusion, the average grain size decreased to 5.4 μm and the grain sizes distributions were uneven. The base texture of as-extruded AZ31-1.3Ca-1.0Sm-0.3La alloy was strong, and the maximum density value was 3.25. The yield strength, ultimate tensile strength and elongation of as-extruded AZ31-1.3Ca-1.0Sm-0.3La alloy was 216 MPa, 280 MPa and 16% at RT, and 145 MPa, 188 MPa and 42% at 150°C, respectively, which are much higher than those of the common MB2 alloy both at the room temperature and 150 °C.

Abstract: The effect of Ca and RE metal additions on the precipitation and microstructure of as-cast AZ91 alloy was systematically investigated. It was found that Ca and RE additions could result in phase and microstructure changes. The XRD pattern showed the crystallite phase of as-cast AZ91 alloys consists of α-Mg matrix and β-Mg₁₇Al₁₂, however, after adding 1.5wt. % Ca and 0.8wt. % RE (0.5wt. % Sm and 0.3wt. % La), peaks coincident with Al₂Ca, Al₂Sm and Al₁₁La₃ intermetallic compounds were found, suggesting the generation of relative precipitates. The SEM images indicated that in as-cast alloys, the Al₂Ca intermetallic compound was located at grain boundaries with a lamellar structure, and the Al₂Sm intermetallic compound was homogeneously distributed in the α-Mg matrix or near the grain boundaries with a polygonal structure, and the Al₁₁La₃ intermetallic compound was located at grain boundaries with a needlelike structure. These intermetallic compounds could reduce the amount of β-Mg₁₇Al₁₂ and refine the microstructure of as-cast AZ91 alloy.

Abstract: Butyl titanate as titanium source, anhydrous ethanol as solvent, glacial acetic acid as inhibitor, La-WO₃/TiO₂, La/TiO₂, WO₃/TiO₂ and pure TiO₂ photocatalysts were prepared through sol-gel method; At the same time, both of which were characterized by infrared spectrometer and uv-vis spectrophotometer; With methyl orange as simulated target degradation material, heat treatment temperature、different dopants, etc. on photocatalytic performance influences of TiO₂ were studied by spectrophotometer. Experimental results show that doping can improve obviously the photocatalytic activity of TiO₂. When calcination temperature is 500 ℃, dosage of catalyst is 0.25 g, pH is 1, and methyl orange concentration is 10 mg/L, La-WO₃/TiO₂ photocatalytic effect is best, and degradation rate is 46.18%.

Abstract: Twelve vinegars from different production areas in China were evaluated by the Portable Electronic Nose 3 (PEN3), and the data detected by PEN3 were analyzed by principal component analysis (PCA), linear discriminant analysis (LDA) and loadings analysis (LA). The results of PCA and LDA all showed that the electronic nose could clearly discriminate the vinegars of difference production areas, but had very little discrimination on same production area vinegars. The results of LD showed that these sensors, including W1S, W2S, W5S, W2W, W1W, W5C, were appropriate to evaluate and compare the aroma of vinegars, especially W1S, W2S, W5S. Loadings analysis also indicated that these compounds in twelve vinegars had great differences, such as acids, esters, alcohols, alkanes, while aromatics compounds, sulfur-containing compounds and alkenes had some distinctions.

Abstract: The extraction kinetics and mechanism of La (III) by P204-kerosine from phosphoric acid were investigated by constant interfacial cell with laminar flow. The effects of stirring speed, temperature, specific interface area on extraction rate were studied. The results indicated that a plateau region is appeared at the stirring speed of over 115r/min. The extraction apparent activation energy was calculated to be-13.40kJ/mol and the extraction process is controlled by a mixed mechanism of diffusion and chemical reaction. The rate equation of extraction was deduced. Under conditions of 25°C and interfacial area 19.64cm2, the extraction rate constant was 2.08×10-6 m·s-1·. Through the derivation of the reaction mechanism the reaction zone is at the liquid-liquid interface.

Abstract: The performance of ZrO₂-La promoted silica supported cobalt catalyst (100Co/15ZrO₂/ 100Aerosil/0.66La) was compared to the ZrO₂-Ru promoted one, 100Co/15ZrO₂/100Aerosil/0.66Ru, in Fischer-Tropsch synthesis (FTS). These catalysts were prepared by co-precipitation and incipient wetness impregnation methods. The characterization by XRD confirmed the cobalt phase of Co3O4 in both catalysts. For their catalytic activity on FTS reaction, the results preliminarily showed the higher methane fraction (60-80%) and lower C₂-C₄ (10-20%) and C₅₊ (10-20%) fractions in ZrO₂-La promoted catalyst compared to the fractions of methane (20-40%), C₂-C₄ (20-50%), and C₅₊(10-60%) from the ZrO₂-Ru promoted catalyst. During reaction, the maximum n-paraffin selectivity of 40% was at C₃ and the hydrocarbon chain was up to C₆ for the ZrO₂-La promoted catalyst. For the ZrO₂-Ru promoted catalyst, the result showed the maximum n-paraffin of C₃ at 30 min of reaction time. When the reaction time increased, the maximum n-paraffin selectivity shifted toward higher C number but levelled off (15%) and the hydrocarbon chain was up to C₁₆.

Abstract: The study of this paper is La and Ba(La⁄Ba=1:1) doped modifying alumina. And we focus on the need for influence on content(La+Ba) and calcination temperature on the S.A of modified alumina. Factors considered were the S.A, it’s attenuation and phase in calcined etc. Screening out the sample of better comprehensive performance. At the same time the less content(La+Ba) can reduce the manufacturing cost of the catalyst.

Abstract: Nanocrystalline samples of titanium dioxide (TiO₂) monodoped or co-doped with La and Y were prepared by a facile method, using Ti(OC₄H₉)₄ as the precursor. All products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and UV-visible diffuse reflectance spectra (DRS), respectively. Photocatalytic activities of the products were assessed by the photocatalytic decomposition of methyl orange (MO). Both of undoped TiO₂ and doped-TiO2 samples exclusively consist of primary anatase crystallites, which further form spherical aggregates with diameters ranging from 14 to 21 nm. The photocatalytic performances of rare earth (RE) element co-doped samples were much higher than that of single doped and pure TiO2 under UV-visible-light irradiation. It indicated that a strong La-Y synergistic interaction appeared to play a decisive role in driving the excellent photocatalytic performance of LYT.

Abstract: Semisolid A356 alloy was prepared by low superheat pouring. The effects of La as a kind of refinement on the size and morphology of the primary phase in semisolid A356 alloy were researched. The results indicated that semisolid A356 alloy contained certain La addition with particle-like and rosette-like primary phase could be prepared by low superheat pouring. The size and morphology of primary phase in A356 alloy are markedly improved by the suitable addition of La. The refining mechanism of La on the size and morphology of the primary phase in semisolid A356 alloy were concerned with the eutectic reaction induced by La in the alloy.

Abstract: Dehydrogenation process of organic chemical hydrides was improved by modifying the catalyst of nickel-activated carbon (Ni/AC) with lanthanum (La). The catalysts were prepared in impregnation method with different amounts of La and Ni. The textural properties and morphology of catalyst were analyzed by nitrogen adsorption and transmission electron microscope equipped with energy dispersive spectrometer respectively. The effects such as metal content and granule size on the dehydrogenation of cyclohexane were investigated in fixed bed reactor. The results show that the metallic active components can be well dispersed on the support, and the elements analysis indicates the metal species tend to assemble on the surface layer rather than being distributed equally in the whole catalyst. The La modified catalyst LaNi/AC exhibited superior catalytic performance to Ni/AC and the conversion was 45% for LaNi/AC catalyst at 673K, while only 34 % for Ni/AC under the same conditions.