Transformation of β-Ni(OH)2 to NiO nano-sheets via surface nanocrystalline zirconia coating: Shape and size retention

Shape and size of the synthesized NiO nano-sheets were retained during transformation of sheet-like β-Ni(OH)₂ to NiO at elevated temperatures via nano-sized zirconia coating on the surface of β-Ni(OH)₂. The average grain size was 6.42 nm after 600 °C treatment and slightly increased to 10 nm after 1000 °C treatment, showing effective sintering retardation between NiO nano-sheets. The excellent thermal stability revealed potential application at elevated temperatures, especially for high temperature catalysts and solid-state electrochemical devices.     

Effect of cobalt oxide on surface structure of alumina supported molybdena catalysts studied by in situ Raman spectroscopy

A set of Co promoted 10% Mo/Al₂O₃ samples have been characterized by means of Raman spectroscopy under ambient as well as in situ dehydrated conditions. Under ambient conditions, the degree of the polymerization of surface molybdenum oxide species decreases with increasing Co loading. Under dehydrated conditions, the polymeric molybdenum oxide species is absent with the addition of only 0.2% Co. At low Co loadings (2%), before the formation of CoMoO₄ compound, the spectral features are very similar under ambient conditions. Dehydration causes the upward shift of the Mo=O symmetric stretching mode. A broad band around 920–930 cm^–1 was thus observed. This band has been suggested to be associated with the Co-Mo interaction species. In contrast to crystalline CoMoO₄, this species shows a reversibility on H₂ reduction-O₂ reoxidation treatments. From the results obtained, it is proposed that cobalt oxide interacts with the most polymerized molybdenum oxide species to form Co-Mo interaction species and/or crystalline CoMoO₄; therefore, the amount of the surface molybdenum oxide species decreases with a change in the molecular structure as a function of the Co concentration.     

Kinetics of the methanation of carbon dioxide over a supported Ni-La2O3 catalyst

The kinetics of the methanation of carbon dioxide was investigated using an alumina supported Ni-La₂O₂ catalyst in a differential and integral reactor. In the differential reactor the molar ratio of H₂ to CO₂ was varied from 0.6 to 30. In the integral reactor the rates were measured with up to 90% conversion. Both reactor tests were carried out at temperatures between 513 and 593 K. The experimental results were described by a Langmuir-Hinshelwood type equation. The kinetics can be explained by assuming equilibrium of dissociative carbon dioxide and hydrogen adsorption, and assuming hydrogenation of surface carbon as the rate determining step.     

Oxidative coupling of methane over CaO-MgO mixed oxide

Mixed oxide catalyst prepared by co-precipitating magnesium oxide and calcium oxide showed an excellent activity for the oxidative coupling of methane. The high performances were presumed to arise from the high basicity of the mixed oxide.     

锌精矿制酸三级旋风除尘器的设计与实践

介绍了锌精矿制酸系统采用三级旋风除尘器替代电除尘器的设计及运行情况。为了提高旋风除尘器的除尘效率，硫酸系统各工序作了适当调整。运行实践表明，三级旋风除尘器除尘效果良好，硫酸系统能长期稳定运行。     

Influence of silicon on the growth of barrier-type anodic films on titanium

Amorphous anodic titania, stabilised by incorporation of silicon species, is shown to grow to high voltages on sputter-deposited, single-phase Ti-Si alloys during anodizing at a constant current density in ammonium pentaborate electrolyte. The films comprise two main layers, with silicon species confined to the inner layers. An amorphous-to-crystalline transition occurs at ∼60 V on the Ti-6 at.% Si alloy, while the transition is suppressed to voltages above 140 V on alloys with 12 and 26 at.% silicon. The crystalline oxide, nucleated at a depth of ∼40% of the film thickness, is associated with the presence of a precursor of crystalline oxide in the pre-existing air-formed oxide. The modified structure of the air-formed oxide due to increased incorporation of silicon species suppresses the amorphous-to-crystalline transition until the onset of dielectric breakdown. The transport numbers of cations and anions during growth of the anodic oxides are independent of the concentration of silicon species in the inner layer, despite the marked change in the field strength.     

环氧丙烷生产工艺进展

综述了近年来环氧丙烷合成工艺的新进展,包括对现有环氧丙烷生产工艺的革新、直接氧化法、光催化环氧化等方法,并对各种方法的特点和发展前景进行了讨论.     

Effect of particle size on the surface oxidation and flotation behavior of galena particles in lime system

ABSTRACT

In this research, the effect of particle size on the surface oxidation and flotation behavior of galena in the lime system was studied. Coarse (?0.074 + 0.038 mm), intermediate (?0.038 + 0.025 mm) and fine (?0.025 mm) galena particles were used in the experiment. The dissolution tests, flotation tests, and sorption tests were accomplished. Through further analysis by XPS, the effect of particle size and lime was observed. The decrease of mineral particle sizes increased the adsorption ratio of collector and the dissolution of galena, while the hydrophilic product OH^?/Ca(OH)⁺ produced by dissolution occupied the dominant position, which led to the minerals hydrophilic.     

电石渣在环氧丙烷生产中的循环利用

总结了电石渣生产环氧丙烷工艺中的设计与应用。运行情况表明，该工艺具有明显的经济效益和社会效益。     

Sintering of Ceramic Particulate Composites: Effect of Matrix Density

Composites consisting of a fine-grained, polycrystalline zinc oxide matrix and <10 vol% coarse, rigid silicon carbide inclusions were prepared by the same mixing procedure and then compacted to produce samples with matrix densities of 0.45 and 0.68 of the theoretical. The samples were sintered under identical temperature profiles in separate experiments that employed either a constant rate of heating of 4°C/min or near isothermal heating at 735°C. The ratio of the densification rate of the composite matrix to the densification rate of the unreinforced zinc oxide was found to be independent of the initial matrix density. This ratio increased significantly with temperature in the constant-heating-rate experiments but was relatively constant in the isothermal experiments. The results indicate that microstructural coarsening may be an important mechanism for explaining the reduced sinterability of polycrystalline matrix composites.