Effect of Feedstock Powders on the Microstructural and Electrical Characteristics of 8 mol% Yttria-Stabilized Zirconia Plasma-Sprayed Coatings

Plasma-sprayed coatings of 8 mol% yttria-stabilized zirconia (YSZ) were fabricated using the feedstock powders obtained from co-precipitation (PPT) and spray-drying (SD) processes. Particle size and the specific mass (SM) of the feedstock powder were found to be the critical parameters that influence the microstructural and electrical properties of the coatings. While dense and larger particle-sized PPT powder resulted in a porous microstructure, dense coatings were obtained for SD powders with relatively lower SM. Electrical conductivity values of SD-coatings were found to be 30% higher than that of PPT-coatings. Electrical conductivity values of plasma-sprayed PPT-coatings improved significantly on decreasing the particles size. However, the size effect was only subtle in the case of SD coatings. PPT-coatings fabricated from smaller particle-sized powders had the necessary electrical conductivities appropriate for solid oxide fuel cell electrolyte applications.     

Compressive Creep Behavior of Spark Plasma Sintered 8 mol% Yttria Stabilized Cubic Zirconia

The present paper describes compressive creep behavior of cubic 8 mol% Yttria-stabilized Zirconia, fabricated by spark plasma sintering, in the temperature range of 1300-1330 °C at a stress level of 78-193 MPa in vacuum. The pre- and post-creep microstructures, along with the values of the stress exponent (n = 1.7-2.7) and the activation energy (Q = 711-757 kJ/mol) suggest that a mixed mode of plastic deformation, dominated by grain boundary sliding, occurred in this material. The relatively high activation energy observed was related to the pinning of the grain boundaries by voids during creep, leading to microcrack formation, shear strain-induced grain exfoliation, and finally creation of new voids at grain boundaries.     

Electrochemical Synthesis and Physicochemical Properties of Nanostructured Al2O3–ZrO2–MgO Oxide Systems

Protection of Metals and Physical Chemistry of Surfaces - Based on the use of electrogenerated reactants, a method for producing Al2O3–ZrO2–MgO oxide systems has been proposed. Their...     

Preparation, Characterization and Photocatalytic Property of Cubic α-Fe2O3 Nanoparticles

设计了一种简单的水热合成法合成晶型可控的立方结构的α-Fe2O3,通过扫描电子显微镜,透射电子显微镜,和X射线衍射对所制备产物的结构和形态特征进行了分析。制备的立方结构的α-Fe2O3的尺寸范围在130~150 nm之间。研究结果表明,α-Fe2O3纳米材料作为一种有效的光催化剂,在过氧化氢存在的条件下可以用来光催化降解废水中的有机物（如罗丹明B）,这为设计和开发高效率可见光催化剂在去除工业废水中有机染料的应用提供了新的探索和基础。     

Synthesis and Properties of Molybdotungstogallic Heteropoly Complexes

ＳｙｎｔｈｅｓｉｓａｎｄＰｒｏｐｅｒｔｉｅｓｏｆＭｏｌｙｂｄｏｔｕｎｇｓｔｏｇａｌｌｉｃＨｅｔｅｒｏｐｏｌｙＣｏｍｐｌｅｘｅｓＷｕＱｉｎｇｙｉｎａｎｄＳｏｎｇＹｕｌｉｎ（吴庆银）（宋玉林）（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，Ｌｉａｏｎｉｎｇ...     

Mo—La2O3阴极La2O3表面富集研究

采用俄歇电子能谱法研究了 Mo- L a2 O3阴极材料中 L a2 O3向表面的富集过程。结果表明 ,在高温下 ,L a2 O3以 L a3+ ,O2 - 离子的形式分别向表面扩散 ,然后在表面上重新结合成分子。在 112 3 K～ 142 3 K范围内 ,L a3+ ,O2 -离子的扩散系数分别为 :DL a=3.6 70 3× 10 - 1 6 exp (- 1.0 16 39× 10 5 / RT) m2 / s;DO=1.5 12 2× 10 - 1 6 exp (- 8.130 6 6× 10 4/ RT) m2 / s     

Synthesis and characterization of CoFe2O4 nanoparticles

The reverse microemulsion composition consisting of 37.0% cyclohexane, 26.0% surfactant （TX-10 and AEO9）, 13.0% n-pentanol and 24.0% aqueous phase was investigated and chosen for the preparation of cobalt ferrite nanoparticles. Then silicon dioxide was coated onto the surface of the magnetite nanoparticles. The two kinds of nanoparticles were characterized by means of X-ray diffractometry（XRD）, scanning electron microscopy （SEM）, infrared spectroscopy （IR）, and energy dispersion spectrometry （SEM-EDS）. The SEM results indicate that both nanoparticles have narrow size distribution, less agglomeration and are in the size range of 10 -60 nm. XRD patterns show that there is not any peak detected except for the peaks of CoFe2O4, and imply that the coated silicon dioxide is amorphous. IR absorption spectra of the samples show the characteristic bands of Si—O—Si group and Fe—O group. SEM-EDS indicates that the molar ratio of Fe to Si is 96.11 ： 3.89. These results prove that a thin film of SiO2 is coated on the surface of the magnetite nanoparticles. And the characterization of cobalt ferrite nanoparticles prepared by conventional precipitation method are compared.     

Synthesis and character of spinel LiMn2O4

1　INTRODUCTIONTheincreasingconcernsonportableelectricele mentsdemandmoreandmoreelectrochemicalener gy .Countriesallovertheworldhaveputlargequan tityofmanuallabors ,materialresourcesandfinancialresourcesonbasicresearchanddevelopmentonnewtypeofrechargeablebatteries[1,2 ] .However ,thisnewtypeofbatteriesisbasedonstudyinganddevel opingperfectperformanceofmaterials ,especiallyonmaterialsofthelithiumbatteries.LixMn2 O4 cathodematerialshavebeenwidelystudiedoverthelasttwodecadesasapotentialcand…     

Hot Corrosion of Yttria-Stabilized Zirconia Coating,in a Mixture of Sodium Sulfate and Vanadium Oxide at 950 °C

Yttria-stabilized zirconia thermal barrier coating along with CoNiCrAlY bondcoat was deposited using air plasma spray on Inconel-X750 superalloy. The coated samples were exposed at 950 °C in a mixture of Na₂SO₄ and V₂O₅. The exposed specimens were investigated using XRD and SEM. The formation of spinel and perovskite structures was revealed at the interface of topcoat and the bondcoat. Further, the chemical composition profile of all samples helped to analyze the diffusion behavior of different constituent elements of bondcoat and substrate. XRD analyses of the samples confirmed the phase transformation of the tetragonal zirconia into monoclinic zirconia and yttrium vanadate. The shift of high angle peaks indicated lattice distortion, which was directly related to the stresses in the coating.     

Friction and wear behaviors of Al2O3–13 wt%TiO2 coatings

Nanostructured and conventional Al2O3-13 wt%TiO2 coatings were manufactured by air plasma spray. Friction and wear behaviors of coatings were investigated at room and elevated temperatures using an SRV wear test machine. The nanostructured coating has "two regions" microstructure, while the conventional coating has typical layered microstructure with obvious interfaces among splats. The coefficient of friction decreases with rising of temperature because of the formation of tribo-layer at elevated temperatures. The wear resistance of the nanostructured coatings is higher than that of the conventional coating, and the wear threshold of applied load is 30 N for conventional coating and 40 N for nanostructure coating. The wear resistance difference is related to the "two regions" microstructure of nanostructure coating, which could blunt or branch the cracks propagation. In our test ranges, the wear rates rising are more sensitive with the applied wear load rising than with the temperature rising.     

La2O3-Gd2O3-Mo secondary emission material

A new kind of materials La2O3-Gd2O3-Mo has been produced by powder metallurgy method.The composition and microstructure of the material were studied by XRD and SEM.It shows that no chemical reaction takes place among La2O3,Gd2O3,Mo and the rare earth oxides exist along molybdenum grain boundaries and in the pores.The emission property measurement results of this material show that adding rare earth oxide into molybdenum can improve the secondary emission coefficient of the emitter,and the emission property depends on the activation temperature.After La2O3-Gd2O3-Mo was activated at 1360℃,the maximum secondary emission coefficient can be high to 2.62,which has exceeded that for practical uses(2.0).     

Synthesis and catalytic property of Cu-Mn-Ce／γ-Al2O3 complex oxide

A new type of catalytic material for purification of automobile exhaust, Cu-Mn-Ce-O/γ-Al2O3, has been studied. The factors affecting its catalytic activity, such as calcination temperature and the period of calcinations and so on have been investigated. Its catalytic activity after SO2-poisoning was determined in a hxed-bed reactor by exposing the sample to the atmosphere of 160 mL/min SO2/air. The study reveals that the catalyst has shown high catalytic activities for the conversion of NH3 oxidation by NO after sulfate. The conversion of NO reduction over the sulfated catalyst is somewhat higher than that over the fresh catalyst except that the optimum temperature has increased about 100℃. Also at the optimum process for the experiment, the selective catalytic oxidation of CO by NO is Over 76 % and the conversion of NO reduction is over 80 % by NH3.     

Synthesis of TiAl-Al2O3 composites by high energy milling and hot-press sintering

A sub-microstructure titanium aluminide alloy/Al2O3 （3A） composite was obtained by crystallization of the amorphous powders, which were prepared by mechanical alloying （MA） in a planetary ball milling system using Ti-AI-TiO2 as raw materials. The experimental results show that, when the milling time increases up to 30 h, the hep Ti（Al） supersaturated solid solution disappears, only amorphous phase is left. The compact samples were synthesized by hot-press to 1 200 ℃ with the amorphous as a precursor; the final phases of the matrix and strengthened phase are y-TiAl and Al2O3. The phases come from in situ crystallization and transformation. The samples, fabricated from the amorphous phase by hot press sintering, have high bending strength and fracture toughness.     

Synthesis of Al2O3／WC powder by aluminothermic reduction and carbonization method

Al2O3/WC powder was synthesized by means of aluminothermic reduction-carbonization with metallic Al powder, yellow tungsten oxide and carbon black or graphite as raw materials under the protection of coke granules.The effects of Al2O3 content, temperature, C/WO3 molar ratio, and atmosphere on the synthesis of Al2O3/WC powder were studied. The results show that the relative content of WC and W2C is strongly influenced by the factors mentioned-above. Carbon black has higher reactivity than graphite. Al2O3-WC composite is easier to obtain under the protection of coke granules than under argon atmosphere. The CO in the coke layer can easily react witht ungsten to form WC and to transfer from W2C to WC.     

Synthesis and characterization of Al2O3–TiC nano-composite by spark plasma sintering

Al₂O₃–10TiC composite was synthesized by high energy ball milling followed by spark plasma sintering (SPS) process. Microstructure of the sintered composite samples reveals homogeneous distribution of the TiC particles in Al₂O₃ matrix. Effect of sintering temperature on the microstructure and mechanical properties was studied. The sample sintered at 1500 °C shows a measured density of 99.97% of their theoretical density and hardness of 1892 Hv with very high scratch resistance. These results demonstrate that powder metallurgy combined with spark plasma sintering is a suitable method for the production of Al₂O₃–10TiC composites.     

Synthesis of crystalline γ-Al2O3 with high purity

Crystalline γ-AlO(OH) was synthesized by the precipitation of sodium aluminate and oxalic acids in aqueous solution. And then γ-AlO(OH) was successfully transferred to γ-Al₂O₃ after subsequent high temperature heat treatment. The effects of reaction conditions on formation of γ-AlO(OH) and γ-Al₂O₃ were further investigated in detail. The XRD analysis shows that the complete formation of crystalline γ-Al₂O₃ is at pH 8–9, reaction temperature of 93–96 °C and calcination temperature of higher than 400 °C. The product of γ-Al₂O₃ contains impurity, including iron, calcium and silicon ion with a low content of about 0.01% and has large specific surface area and high pore volume of 269.9 m²/g and 0.57 mL/g, which can be applied in catalysts and catalyst supports.     

Synthesis and characterization of aminated SiO2/CoFe2O4 nanoparticles

A kind of newly aminated CoFe2O4 nanoparticles were synthesized by grafting process for biomedical applications, which were coated primarily with silicon dioxide（SiO2）. The characterizations of aminated SiO2/CoFe2O4（ASCN） and SiO2-coated CoFe2O4（SCN） nanoparticles were investigated using elemental analysis, thermogravimetric analysis（TGA）, differential thermal analysis（DTA）, infi＇ared spectroscopy（IR）, atomic force microscopy（AFM）, zeta-potential measurement and vibrating sample magneto-metry（VSM） The AFM micrograph shows that the ASCN nanoparticles are approximately spherical with an average diameter of 30 nm. Based on IR and TGA results, it is suggested that the surface of the SiO2-coated CoFe2O4 nanoparticles are graiied with amino compounds. The elemental analysis also shows the presence of 0.98 mmol/g of organic moieties immobilized on the surface ofASCN nanoparticles. Zeta-potential data ofASCN nanoparticles also reveal that amino compounds are bonded onto the surface of SiO2-coated CoFe2O4 nanoparticles by ether linkage. The magnetic parameters show that ASCN nanoparticles still have good magnetic property.     

Synthesis of ZrO2-SiC composite powder and effect of its addition on properties of Al2O3-C refractories

ZrO2-SiC composite powder was synthesized by carbothermal reduction of zircon in argon atmosphere, and it was used as the additive to prepare Al2O3-C refractories. The effects of heating temperature on the synthesis process and the addition of the synthesized composite powder on the properties of the Al2O3-C refractories were investigated. The results show that the synthesized composite powder can be easily obtained by heating the mixture of zircon and carbon black at 1 873 K for 4 h in argon atmosphere, and the relative contents of ZrO2 and SiC in sample reach about 83.7% and 16.3%, respectively. The bulk density, crushing strength and thermal shock resistance of the Al2O3-C refractories can be improved obviously by the addition of the synthesized ZrO2-SiC composite powder.     

Synthesis and Characterization of La0.8Sr0.2Ga0.8Mg0.2-xCox O3-δ Electrolyte Materials

分别采用甘氨酸硝酸盐法(GNP)和固相法(SSR)分别制备了La0.8Sr0.2Ga0.8Mg0.2-xCoxO3-δ(x=0.05,0.085,0.1),简称LSGMC并通过容忍因子和平均电负性差计算得出LSGMC电解质材料能够形成一种稳定钙钛矿结构。LSGMC电解质材料的非化学计量值随着Co含量的增加而不断增加,显示出随Co含量增加吸附在LSGMC晶格中的氧减少。固相法制备的LSGMC电解质材料比甘氨酸硝酸盐法制备的LSGMC电解质材料要致密,而甘氨酸硝酸盐法制备的LSGMC电解质材料粉末分布范围要窄一些。制备的LSGMC电解质材料具有优良的电导率,在800和750℃分别达到0.217和0.193 S/cm。     

Synthesis of GdF3 from the Gd2O3-NH4HF2 system

GdF3 was synthesized with Gd2O3 and NH4HF2 under atmospheric pressure and vacuum. The effects of pressure,temperature,and reactant ratio on the reaction process were investigated. A new mechanism for the synthesis of GdF3 was proposed. Powdered Gd2O3 started to react with NH4HF2 at low temperature,and the products were GdNH4F4,NH4F,NH3,and H2O. GdNH4F4 decomposed to GdF3 and NH4F after further high-temperature treatment,accompanying the volatilization and decomposition of NH4F. The whole process could be divided into three steps： synthesis,decomposition,and deamination. The initial and final reaction temperatures decreased under vacuum condition. An optimized process for the preparation of GdF3 was obtained： synthesis under atmospheric pressure at low temperature and decomposition and deamination under vacuum at high temperature.