Preparation and Characterization of CeO2 Superfine Powder

The CeO2 superfine powder was prepared by the co-precipitation method, using the industrial grade Ce2(CO3)3 and NH4HCO3 as starting material and precipitating reagent, respectively. The precipitated precursons and the calcinated products were characterized by the thermogravimetric analysis/thermoanalysis (TGA/DTA), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The results show that using NH4HCO3 as a precipitating reagent,the precipitate decomposed full as it was heated to 360℃. The CeO2 superfine powder formed by calcinating the precipitate belongs to a cubic CaF2-type structure and has the first mean particle diameter 140nm and second mean particle diameter 630nm. The CeO2 powder particles aggregate and grow with raising the calcination temperature.     

Effect of Ca^2＋ and Mg^2＋ on CO2 Corrosion Behavior of Tube Steel

Corrosionfailurecasesobservedinoil fieldaremainlycausedbylocalcorrosion ,whicharealwaysfoundinthedefectareasofcorrosionproductlayer .Thecompositionandmicrostructureofcorrosionprod uctlayeraffectthecorrosionrateandcorrosionmor phologystrongly[1- 3] .Ca2 a…     

Influence of pH on Morphology and Formation Mechanism of CeO2 Nanocrystalline

Nanoparticles of cerium oxide were prepared by common precipitation method using cerium nitrate solution and ammonia reagent. Cerium oxide particles with different morphologies were synthesized through adjusting pH values of the solution. TEM and BET results showed that spherical crystal was gained in acid solution, with the specific surface of 148. 1944 m2·g^-1. The cerium oxide appeared in the form of spherical and rod-like grains under neutral condition, and the specific surface changed to 114.7975 m^2·g^-1. Moreover, in alkaline solution, cerium oxide powders were exhibited in rod-like form with the specific surface of 106.2465 m^2·g^-1. Precipitation formation mechanism of different morphologies was also discussed, which followed decomposition precipitation mechanism and topology reaction mechanism in acid and alkaline solution, respectively.     

Effect of CeO2 on Microstructure and Bond Strength of Fe-Ni-Cr Alloy

The more extreme conditions in which metallicmaterials are required to work lead to the developmentof different surface modification materials, such asnickel based alloy, Fe based alloy and Co based al loy, etc. In general, these …     

Structure and Catalytic Behavior of CuO-ZrO-CeO2 Mixed Oxides

The effect of doping CuO on the structure and properties of zirconia-ceria mixed oxide was studied. The results show that addition of CuO decreases the reduction temperature of ceria, and stabilizes the cubic structure of mixed oxides, and enhances catalytic activity of CuO-ZrO-CeO2 mixed oxides for CO oxidation. Increasing ceria content in the mixed oxides can enhance the catalytic activity, but some impurities such as sulfate make catalytic activity falling. There is little effect of calcination temperature on catalytic activities, implying that these catalysts are effective with good thermal stability.     

Synthesis and Electrical Conductivities of Sm2O3-CeO2 Systems

Solidoxidefuelcell(SOFC)hasattracteda greatattentionasapromisingtechniqueforelectrical powergeneration[1].Thecurrentstate of the art SOFCsusesyttriastabilizedzirconia(YSZ)electro lyte,operatesat800～1000℃duetothelowoxy genionicconductivityoftheYSZelect…     

Influence of reaction of Al2O3 and carbonaceous materials in Al2O3–C refractories on aluminum and carbon pick-up of iron

Carbon-containing Al2O3 refractory crucibles and pure Al2O3 refractory crucible were fabricated to study the effect of carbon-containing Al2O3-C refractories on aluminum and carbon pick-up of iron.Refractory crucibles with pure iron powder were placed in a vacuum induction furnace and heated at 1600℃ for regular time under flowing argon atmosphere.The Al and C contents of iron samples were analyzed,and iron samples were also investigated using a field scanning electron microscope equipped with energy-dispersive spectroscope.The results showed that carbon materials did affect the interac?tion of(Al2O3-C)/Fe system,carbothermal reduction in alumina occurred in the reaction system and the extent of reactions depended on the kinds of carbon materials.     

Effect of Preparation Method on Surface Area and Crystalline Form of CeO2-ZrO2 Solid Solution

TheCeO2 ZrO2 solidsolutionisacrucialcompo nentinthethree waycatalysts(TWCs)usedtocatalyzethesimultaneouspurificationofCO ,HCandNOxfromanautomobileexhaust [1～ 3] .Besidesafeasiblecatalyticactivity ,itshouldhavehighthermalstabilityandoxygenstoragecapacity(OSC) .InordertogainhighperformanceCeO2 ZrO2 solidsolution ,varioustechniqueshavebeendeveloped .ItwasshownthataneffectofpreparationmethodonthesurfaceareaandcrystallineformofCeO2 ZrO2 isveryobvious .Intheearliestwork ,theCeO2 ZrO…     

Effect of CeO_2 on Crystal Structures and Catalytic Properties of the Mn_2O_3 Catalysts

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Effect of AI2O3 on Structure and Wearability of Composite Coating

The composite coating was prepared by thermal spray welding after making composite powder, which is composed of Ni based self melted alloy and AI2O3 ceramic powder including nano, sub-micron and micron powders. The influences of contents and sizes of AI2O3 on the structure and wearability were investigated. The results show that the wear resistance of the coating would be increased greatly by adding AI2O3, but the spray weldability decreases with increasing AI2O3 content. So there is an optimal content of AI2O3 powder. The composite coating with AI2O3 nano or sub micron powder of 0.5% has the best abrasive resistance, while the optimal content of AI2O3a micron powder is 1%.     

Preparation and Fluorescence Properties of TiO2 ：Eu Nano-Materials

A series of europium-doped titanium dioxide (TiO2) fluorescent nano-materials prepared by sol-gel method is presented. The phase structure and crystalline sizes of TiO2:Eu, which is doped with different europium content and then heat-treated at different temperature, were investigated by XRD ,TG, DTA and TEM. The results show that europium could be introduced into TiO2 under high temperature and it can suppress the structural phase transition from anatase to rutile and the crystal growth of TiO2 in TiO2:Eu nano-materials. The fluorescence spectra were examined by fluorescence spectrophotometer, and the results show that the fluorescence intensity is the strongest when europium content is 2.68% (molefraction) and the heat-treated temperature is 700℃. From the measurement results of the fluorescence lifetimes, it can be seen that the fluorescence lifetime could be prolonged when europium is incorporated in TiO2.     

Preparation and Characterization of Nanocrystalline CeO2 by Precipitation Method

CeO2 nanocrystalline particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD spectra show that the synthesized CeO2 has cubic crystalline structure of space group OH^H-FM3M, when calcination temperature is in the range of 250 - 800 ℃. TEM images reveal that CeO2 particles are spherical in shape. The average size of the particles increases with the increase of calcination temperature. Thermogravimetric analysis indicates that the weight loss of precursor mainly depends on the calcination temperature, and little depends on the calcination time. Measurements of CeO2 relative density show that the relative density of CeO2 nanocrystalline powders increases with increasing CeO2 particle size.     

Preparation and Photocatalytic Behaviors of Nanoporous Polyoxotungstate-Anatase TiO2 Composites

Nanoporous anatase TiO2 crystalline particles coupled with Keggin or Wells-Dawson unit, H3PW12O40/TiO2 or H6P2W18O62/TiO2, were prepared at a low temperature （200℃ ） using sol-gel method combined with hydrothermal treatment at programmed temperature. The as-prepared composites have uniform anatase phase, and they exhibit both micrand mesoporosities with pore sizes of 0.6 and 4.0 nm, respectively, and their average size is lower than 10 nm. Photocatalytic tests show the composites exhibit relatively higher photocatalytic activities to decompose the organocholorine pesticide hexachlorobenzene（HCB） than anatase TiO2, the starting polyoxotungstates, and EuEOa/TiO2 prepared by using sol-gel method, and this was attributed to （ 1 ） the synergistic effect of photoactive anatase TiO2 with the polyoxotungstate, and （2） the fascinating physical and chemical properties of the porous materials.     

Microstructure and Mechanical Properties of Hot Pressed TiB_2－ZrO_2 Composites

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Characteristics and Controlling of LaB_6-ZrB_2 Eutectic Microstructure

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Effect of TiO2 on Sintering and Grain Growth Kinetics of MgO from MgCl2·6H2O

The effect of TiO₂ on the grain growth kinetics of MgO prepared from MgCl₂·6H₂O was studied by the tradition phenomenological rate equation. The results showed that the addition of TiO₂ decreased the activation energy of MgO grain growth, accelerated the growth rate of MgO grain, and markedly promoted the sintering of MgO. Without TiO₂ addition, the MgO grain growth exponent $ n $ was 3, the grain growth activation energy $ Q $ was 556.9 kJ·mol^?1, and the process was considered as volume diffusion controlled. With 0.2 wt pct TiO₂ addition, the MgO grain growth exponent $ n $ was 2, the grain growth activation energy $ Q $ was 272.8 kJ·mol^?1, and the process was considered as interface diffusion controlled. The apparent and closed porosities of MgO-0.2 wt pct TiO₂ sample were decreased significantly, and the bulk density increased to 3.49 g·cm^?3 (relative density is 97.5 pct). The main mechanism of TiO₂ promoting the sintering of MgO was that TiO₂ solubilized in MgO to form unequivalence substitutional solid solutions and cation vacancies that were favorable to cation diffusion.     

Preparation of CeO2-TiO2/SiO2 and Its Removal Properties for Fluoride Ion

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Synthesis and Characterization of Quaternary Complex of Sm-CH_3C(CH_2OH)_2COOH-Phen

Asrareearthionshaveexcellentfluorescentproperty ,theirapplicationsandresearcheshavere ceivedunabatedattention .Aseriesofcomplexesofrareearthwithfluorescentpropertyhasbeensynthesized[1～ 4] .Throughorbitaltransitionofrareearthions ,UVlightabsorbedcanbechan…     

Effects of ZrO2 Content on Structure and Performance of Cu/CeO2-ZrO2 Catalysts for Water-Gas Shift Reaction

Water-gas shift(WGS)is a critical step in fuelprocessors for preli minary COclean-up and additionalhydrogen generation prior to the CO clean-up stage,which opened up new potential applications for WGScatalysts.Recently several formulations of noble-met-al…     

Effect of La2O3 on Microstructure and Transmittance of Transparent Alumina Ceramics

Optically transparent alumina ceramics were fabricated by conventional process and sintered without pressure in H2 atmosphere. The results indicate that relative densities of alumina specimens increase to theoretical densities （T. D. ） with increasing content of La2O3. With increasing holding time during sintering, much less pores and larger grains were found in the sintered alumina samples. Higher transmittance was achieved in alumina codoped with MgO and La2O3 as compared with that doped with MgO only. The total-transmittance of alumina sample is up to 86% at twavelength range of 300 - 800 nm.