Direct large-scale synthesis of perovskite barium strontium titanate nano-particles from solutions

This paper reports a wet chemical synthesis technique for large-scale fabrication of perovskite barium strontium titanate nano-particles near room temperature and under ambient pressure. The process employs titanium alkoxide and alkali earth hydroxides as starting materials and involves very simple operation steps. Particle size and crystallinity of the particles are controllable by changing the processing parameters. Observations by X-ray diffraction, scanning electron microscopy and transmission electron microscopy TEM indicate that the particles are well-crystallized, chemically stoichiometric and ∼50 nm in diameter. The nanoparticles can be sintered into ceramics at 1150 °C and show typical ferroelectric hysteresis loops.     

Photorechargeable Properties of Metal Hydride-SrTiO3 Electrode

A photosensitive metal hydride electrode was prepared by modification with perovskite-type SrTiO3 photocatalyst. The photorechargeable properties of the prepared electrodes were investigated by using electrochemical cyclic voltammetry and EIS measurements. The results showed that the modified electrode exhibited the obvious photorechargeable properties. The reduction current increased remarkably under the xeon light irradiation compared with the unmodified electrode. During the photocharging process, the potential of the modified electrode shifted quickly to negative direction and a potential plateau of about -0.90V (vs. Hg/HgO) occurred at the end of light irradiation. The corresponding discharge capacity of the electrode was about 5.4 mAh/g.     

Co-SrTiO3上光催化分解水制氢的性能研究

氢能在使用过程中不会给环境带来任何污染,是未来最理想的能源。但目前的氢气生产方法能耗较高,同时伴随着严重的环境污染,显然不适合大规模生产能源用氢气。洁净化生产氢气方法的开发备受世人的关注,吸引了大量的科研人员从事这方面的研究。其中以半导体氧化物为催化剂,光催化分解水制氢被认为是最有前途的方法。经过几十年的努力,取得了很大的进步,先后开发出在紫外光照射下可以将蒸馏水分解为氢气和氧气的光催化剂,如TiO2犤1犦、SrTiO3犤2犦、Na2Ti6O13犤3犦、BaTi4O9犤4犦、K2La2Ti3O10犤5犦、K4Nb6O17犤6犦、ZrO2犤7犦等;可见…     

Ba0.6Sr0.4TiO3/聚偏氟乙烯-聚甲基丙烯酸甲酯复合材料的制备及其介电性能

采用流延热压工艺制备Ba_0.6Sr_0.4TiO₃(BST)/聚偏氟乙烯(PVDF)?聚甲基丙烯酸甲酯(PMMA)复合薄膜,研究了PMMA含量对复合材料微观组织结构和介电性能的影响规律。结果表明,BST相能够均匀分散在聚合物基体中,归因于PMMA与PVDF良好的相容性,2种聚合物之间的界面不分明;随着PMMA含量的增加,复合材料的介电常数先降低后升高,耐击穿强度和介电可调性先增加后减少。PMMA含量(体积分数)为15%的BST/PVDF?PMMA₁₅复合材料的综合性能最佳:介电常数为23.2,介电损耗为0.07,耐击穿强度为1412 kV·cm^-1,在550 kV·cm^-1偏压场下,介电可调性为26.2%。     

La0.8Sr0.2Fe1-xScxO3-δ催化剂的制备、表征及甲烷催化燃烧性能

采用甘氨酸-硝酸盐溶液燃烧法制备了钙钛矿型氧化物催化剂La_0.8Sr_0.2Fe_1-xSc_xO_3-δ (LSFS, x=0, 0.3,0.4, 0.5, 0.6, 0.8, 1), 利用X射线衍射(XRD)、H₂程序升温还原(H₂-TPR)、扫描电子显微镜(SEM)和比表面积测试等手段对催化剂进行了系统表征, 并在常压微型固定床反应器上考察了催化剂对甲烷燃烧的催化性能. 结果表明, 经空气气氛下900 °C煅烧5 h制备的LSFS均具有单一的钙钛矿结构, 在La_0.8Sr_0.2FeO_3-δ (LSF)中掺杂Sc有助于改善催化剂的抗烧结性能, 提高催化剂的比表面积. 当LSF 中的Sc 掺杂量为0.4-0.6 时, 所形成的LSFS表现出良好的甲烷催化燃烧活性, 其中Sc 掺杂量为0.5 时, 其起燃温度(T₁₀)和完全转化温度(T₉₀)分别为406和563 °C, 与La_0.8Sr_0.2FeO_3-δ和La_0.8Sr_0.2ScO_3-δ相比, T₁₀分别降低了14和87 °C; T₉₀分别降低了59和95 °C.     

Effect of ZnO on sintering and microwave dielectric properties of 0.5CaTiO3-0.5 (Li0.5La0.5) TiO3 ceramics

The novel calcium titanate-lithium lanthanum titanate doped with zinc oxide (0.10, 0.30, and 0.50 mol. %) ceramic samples were prepared by solid-state reaction route. The phase formation, microstructure, densification, and microwave dielectric properties were investigated. It was found that the doping with zinc oxide led to a decrease in sintering temperature by 25 ^oC as compared with pure calcium titanate lithium lanthanum titanate due to the liquid phase effect. Also, the calcium titanate lithium lanthanum titanate (10ZCTLLT&30ZCTLLT)) doped with lower zinc oxide (0.10 and 0.30 mol. %) led to higher densification parameter. This was followed by increasing the zinc oxide doping up to (0.50 mol. %) which resulted in a decrease in densification and microwave dielectric properties which may be attributed to increase in porosity and grain growth upon the evaporation of zinc and oxygen vacancy. This led to the increase in dielectric loss (≈10 × 10^?4) value with 50ZCTLLT. Hence, the best result of microwave dielectric characteristics was obtained for 0.5CaTiO₃–0.5(Li_0.5La_0.5)TiO₃ with (0.10 and 0.30 mol. % ZnO) 10ZCTLLT and 30ZCTLLT ceramic samples sintered at 1175 ^oC/2h, with low dielectric constant (ε_r) = 4.4–10.5, very low dielectric loss = 1.07-2.23 × 10^?4 and high quality factor (Q x ?) ≈59-55 × 10⁴ at 8 GHz. Consequently, they can be used not only in wireless satellite communications technology but also can be used in the fifth-generation telecommunication 5G technology construction.     

Al_2O_3包覆Ba_(0.6)Sr_(0.4)TiO_3复合粉体制备及表征

采用液相包覆法制备了Al2O3包覆的Ba0.6Sr0.4TiO3复合粉体。通过SEM,TEM,TG-DSC,XRD,XPS和ζ电位测试对包覆前后粉体的表面形貌、组织结构、等电点进行了测试和分析。结果表明:Al2O3以无定形结构成功的包覆在Ba0.6Sr0.4TiO3粉体表面,形成了Ba-O-Al、Sr-O-Al和Ti-O-Al键,Ba0.6Sr0.4TiO3颗粒的等电点由包覆前的pH=3.2增大至pH=8。     

氧化硅柱层状镧钛酸盐的制备和表征

本文报道通过先用正己胺盐酸盐水溶液与K₂La₂Ti₃O₁₀发生离子交换得到正己铵离子柱撑的层状镧钛酸盐，然后再与氨基丙基三乙氧基硅烷的正八面体多聚体作用，最后将层间的有机物焙烧分解掉后可得新型氧化硅柱层状镧钛酸盐。采用X射线衍射(XRD)、红外光谱(IR)、差热--热重分析(TG/DTA)、透射电子显微镜(TEM)和比表面测定等方法对该新材料进行了表征。结果表明，所得氧化硅柱层状镧钛酸盐具有很高的热稳定性(>800℃)     

Rh, Co, Ru and Pd complex catalyzed hydroformylation of ethylene using triphenylphosphine, triphenylarsine and triphenylstibine as ligands

Summary Zn-promoted Cu-ZSM-5 catalysts are active and selective for CO oxidation in the presence of H₂. This high activity was attributed to the improved reducibility of copper species in exchanged samples.</o:p>