超细(Ba,Sr,Cd)TiO3基多层陶瓷电容器陶瓷的研究

采用溶液-溶胶-凝胶法制备(Ba0.70Sr0.25Cd0.05)TiO3纳米粉体,利用所得到的纳米粉体研究了(Ba0.70Sr0.25Cd0.05)TiO3基多层陶瓷电容器用超细陶瓷的制备.对比研究了超细电容器陶瓷和传统固相法电容器陶瓷的性能.采用扫描电镜分析了两种方法得到的陶瓷的显微结构.结果表明:采用纳米粉体制备的(Ba0.70Sr0.25Cd0.05)TiO3基电容器陶瓷具有晶粒尺寸约为1μm,其性能为:介电常数为140 9.44,介质损耗为0.017 5,陶瓷的密度是5.22 g*cm-3,烧结温度为1300 ℃,大大降低了烧结温度,比传统固相法的陶瓷性能有较大的改善.     

Secondary ketonization of primary alcohol over LaMn-based mixed oxides with perovskite-like structure

LaMnO₃-based mixed oxides with perovskite-like structure both bulk and supported on La–Al₂O₃, show high catalytic activity in dehydrogenation of n-butanol to an aldehyde, which then undergoes a secondary reaction to produce a symmetrical ketone. Partial substitution of Cu, V or Sr into LaMnO₃ structure does not destroy the perovskite-like structure and enables to control the acid–base surface properties. It allows linking up these qualitative and quantitative features with activity and selectivity of these materials. The degree of n-butanol conversion depends on the total concentration of basic and acidic sites. Selectivity to butyraldehyde can be related with the share of basic sites. Selectivity to dipropyl ketone is affected both by the acidity and concentration of acidic sites. LaMnO₃/La–Al₂O₃ seems to posses an optimum set of surface characteristics for the examined ketonization of a primary alcohol.     

Electric properties of La0.8Sr0.2CoO3 nanoceramics

The electric measurements were carried out for La_0.8Sr_0.2CoO₃ nanoceramics by using impedance spectroscopy methods. The resistance of sample was practically independent of frequency in measurement range. Its dependence on reciprocal temperature showed quite complicated mechanism of conduction. The most striking property of investigated sample was its resistance decreasing with increasing applied polarization.     

Studies on the structure and microstructure of lead strontium titanate thin films

Pb1-xSrxTiO3 （0≤x≤0.9） thin films on Si （100） substrate were prepared by the sol-gel process and their characteristics were investigated as a function of strontium content（x）. With increasing of the strontium content, the tetragonality （c/a） was slightly decreased, the splitting peaks become less prominent and the splitting peaks tend to merge into a single peak. Furthermore, the grain size of the films was systematically reduced with the increase in strontium content.     

Strontium Zirconate and Strontium Titanate Ceramics for High-Voltage Applications: Synthesis, Processing, and Dielectric Properties

The synthesis, processing, and electrical properties of SrZrO₃ and SrTiO₃ materials have been examined. Phase-pure powders of SrZrO₃ and SrTiO₃ materials were synthesized using the Pechini method. Powder processing routes that used water and 2-propanol as carrier fluids were developed to achieve high green densities, which resulted in sintered densities of >99% of the theoretical density. The relative permittivity and average breakdown strength for carefully processed SrZrO₃ were 60 and 40 V/μm; the corresponding values for SrTiO₃ were 400 and 35 V/μm. The higher breakdown strengths suggest that these materials can be used in high-voltage capacitor applications.     

Synergistic effect of La and Co co-doping on room-temperature ferromagnetism enhancement of TiO2 nanoparticles

The synergistic influence of lanthanum and cobalt co-doping on room temperature ferromagnetism (RTFM) of TiO₂ system is investigated. A series of Ti_0.97?xCo_0.03La_xO₂ nanoparticles were prepared and their structures and properties were systematically studied with X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, UV–vis spectrophotometer, Raman spectra and magnetic measurement techniques, respectively. Detailed experimental characterizations indicate that the as-prepared La and Co co-doped samples exhibit single anatase phase, and all the samples exhibit strong visible photoluminescence associated with oxygen vacancies and a clear ferromagnetic hysteresis loop, both of which were dramatically enhanced with La and Co co-doping, and the maximum saturation magnetization (M_s) reaches 1.38 emu/g at the La content of 6 mol%. It is speculated that oxygen vacancies modulated by ionic La play an important role in the enhanced RTFM, which can be attributed to the bound magnetic polarons (BMPs) formed via ferromagnetic coupling between two neighboring Co²⁺ ions mediated by oxygen vacancy (F⁺ center). Our results present an alternative method to obtain high performance RTFM.     

Solid superbase derived from lanthanum–magnesium composite oxide and its catalytic performance in the knoevenagel condensation under solvent-free condition

We report for the first time the synthesis of a novel solid superbase that was derived from lanthanum–magnesium composite oxide and KOH through thermal treatment. The as-prepared material shows base strength (H_–) above 26.5 and is a high-efficiency catalyst for solvent-free Knoevenagel condensation at room temperature. The results of the present study open up a new dimension for the use of composite oxides as new support materials in the synthesis of superbases.     

Performance improvement by metal deposition at the cathode active site in solid oxide fuel cells

In this study, the performance improvement of the SOFC single cell and its underlying mechanism was investigated. Furthermore, an application of the identified electrochemical mechanism is proposed and tested experimentally. The deposition of Platinum (Pt) at electrochemically active sites for the oxygen reduction reaction is determined to be responsible for the improved performance. Pt migration from a current collector to the cathode active sites originates from the oxygen partial pressure difference between current collector and triple phase boundary, and the electrochemical reduction reaction. It is supported by the confirmation of Pt particles at the cathode active sites by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and calculations of the thermodynamic equilibrium partial pressure values. In addition, correlation of the initial performance change and the quantities of Pt deposition are investigated. This selective Pt deposition mechanism at the active sites is applied to the LSCF cathode, as well.     

聚锑酸离子交换剂的制备及分离锶和钇

以三氧化二锑为原料,双氧水为氧化剂,经氧化回流法制备聚锑酸无机离子交换剂.该聚锑酸离子交换剂对锶-钇混合溶液中的锶具有较好的选择性吸附能力.通过正交实验设计法对反应影响因素进行了优化,结果表明,在60 ℃时加入40 mL水和12 mL H_2O_2氧化10 g Sb_2O_3固体,反应120 min可制得对Sr~(2+)和Y~(3+)具有较高分离系数的聚锑酸离子交换剂.理化性能研究表明,产物是一种阳离子交换剂,对溶液中的Sr~(2+)和Y~(3+)的动态吸附分离具有较高的选择性.     

Improvement of Fracture Toughness Lanthanum Zirconate

Thermalbarriercoatings(TBCs)havefoundan increasingnumberofapplicationsinprotectinghigh temperaturemetalliccomponents,forexample,TBCsaredepositedontransitionpieces,combustion lines,first stagebladesandvanes,andotherhot pathcomponentsofgasturbineseithertoincreasethe inlettemperaturewithaconsequentimprovementof theefficiencyortoreducetherequirementsfora coolingsystem[1].Thereareseveralceramicsthat havebeenevaluatedasTBCmaterials[2].Lanthanum zirconatewasrecentlyproposedasapromisingTBC materia…