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551.
Synthesis, NMR Spectroscopic Characterization and Structure of Bis(1,2-dimethoxyethane-O,O′)barium Bis[1,3-bis(trimethylsilyl)-2-phenyl-1-aza-3-phosphapropenide] Barium-bis[bis(trimethylsilyl)phosphanide] 1 reacts with two equivalents of benzonitrile to give barium bis[1,3-bis(trimethylsilyl)-2-phenyl-1-aza-3-phosphapropenide]; the choice of the solvent determines whether a tris-(tetrahydrofuran)- or a bis(1,2-dimethoxyethane)-complex 2 can be isolated. 2 crystallizes from DME as red cuboids (monoclinic, C2/c, a = 1627.0(3), b = 1836.6(3), c = 1602.5(2) pm; β = 96.071(12)°; V = 4761.7(12); Z = 4; wR2 = 0.0851). The phosphorus atom displays a pyramidal surrounding in contrast to the planar coordination sphere of the nitrogen atom. In addition a twist within the P? C? N skeleton of the heteroallyl anion is observed. 相似文献
552.
Guoqing Xu Hongliang MaMinjian Zhong Jiong ZhouYuezhong Yue Zhengming He 《Journal of magnetism and magnetic materials》2006
BaFe12O19 powders with nanocrystalline sizes were produced by sol–gel auto-combustion. Fe3+ and Ba2+, in a molar ratio of 11.5, were chelated by citric acid ions at different pH. After dehydration, auto-combustion and calcinations, BaFe12O19 powders were formed. TG/DSC indicated the action to form BaFe12O19 first occurred at about 800. XRD patterns of the annealed powders showed that the well-crystalline powder was produced when pH=10. In addition, the data from XRD showed the lattice parameters a and c, and the unit-cell volume V had a little decrease and the density went up with the increasing pH. The data from PPMS exhibited that pH in the starting solution had an important influence on magnetic properties. In this case, BaFe12O19 powder, of maximum magnetization M(3 T)≈60 A m2/kg, the remanent magnetization Mr≈33 A m2/kg and the intrinsic coercive Hc≈432 kA/m, was produced under the molar ratio of citric acid to the metal nitrate of 1.5 when pH=10. 相似文献
553.
Hongwei Chen Chuanren Yang Chunlin Fu Li Zhao Zhiqiang Gao 《Applied Surface Science》2006,252(12):4171-4177
Barium strontium titanate (BST) thin films were prepared by RF magnetron sputtering. The dielectric constant-voltage curves and the hysteresis loops of BST thin films with different grain sizes and film thicknesses were investigated. When the grain size increases from 12 nm to 35 nm, remarkable increases in dielectric constant and tunability were observed. Above 12 nm, the BST films exhibited size effects, i.e. a decrease in maximal polarization (Pm) and an increase in coercive electric field (Ec) with reduction in grain size. In our investigation, the dielectric constant, tunability and maximal polarization increased as the film thickness increased. Furthermore, the size dependence of the dielectric constant and tunability of Ba0.6Sr0.4TiO3 thin films is determined by that of the maximal polarization and the coercive electric field. 相似文献
554.
Barium sulfate particles were synthesized in the presence of EDTA at room temperature. X-ray diffractometry (XRD), Fourier transform infrared resonance (FTIR) and scanning electron microscopy (SEM) were used to characterize the structure and morphology of BaSO4 particles. The effect of the preparation parameters on the particle size distribution and morphology was investigated. The conditional formation constants of Ba-EDTA at different pH values were calculated. The results show that the size and morphology of BaSO4 particles can be effectively controlled by adding EDTA in the precipitation process. Among all the operation conditions, the pH value has significant effect on the particle size. The obtained barium sulfate particles are spherical and well dispersed at pH = 9-10. Zeta potentials of BaSO4 were measured at different pH. The isoelectric point (IEP) of barium sulfate colloid appears at pH 6.92. The model of the solid-solution interface at a particle of BaSO4 was presented. The FTIR result indicates that the surface of the prepared BaSO4 absorbs the functional groups of EDTA, which lower the IEP of the barium sulfate particles. 相似文献
555.
Blue Cooperative Luminescence In Yb3+-Doped Barium Gallogermanate Glass Excited At 976 nm 总被引:1,自引:0,他引:1
The Yb3+-doped barium gallogermanate glass has been prepared via the conventional melt method. The absorption spectra, the near infrared
emission spectra, the upconversion emission spectra and the differential scanning calorimetry have been measured. Bright blue
upconversion emission centered at 476 nm has been observed under the 976 nm laser diode excitation at room temperature. The
blue upconversion emission mechanism has been discussed on the blue emission intensity and the measured lifetime. The slope
of the log-log plot of the blue emission intensity versus the pump power is equal to 1.98, and the blue luminescence decay
time is half of the near infrared fluorescence decay time, confirming that the blue emission comes from Yb3+-Yb3+ pairs cooperative upconversion mechanism. The result of differential scanning calorimetry suggests that this type of glass
is suitable as a potential candidate for fiber drawing. 相似文献
556.
橘黄色波段固体激光器在基于荧光探测的生物医学诊断和显示等众多方面有着广泛的实际应用. 报道了利用532 nm的Nd∶YAG倍频激光抽运外置喇曼腔内的硝酸钡晶体,获得高效率的599 nm橘黄色喇曼激光的实验结果.对外置喇曼腔实验装置和运转参量进行了优化,喇曼振荡腔由对二阶斯托克斯光有最优化反射率的腔镜构成,对实验中所得到的二阶斯托克斯喇曼激光脉宽压缩及出现双尖峰的现象进行了分析.当抽运光功率达到4.1 W时,获得二阶斯托克斯喇曼激光功率为710 mW,输出光中心波长为599.38 nm,半峰全宽(FWHM)为1.1 nm,激光器最大光光转换效率为17.5%,斜率效率为24.8%. 相似文献
557.
Nanocomposite polymer electrolytes (NCPEs) composed of poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP) as a host polymer, Poly(vinyl acetate) (PVAc) as an additive, Ethylene Carbonate (EC) as a plasticizer, Lithium Perchlorate as dopant salt and Barium Titanate (BaTiO3) as a filler were prepared for various concentrations of BaTiO3 using solvent casting technique. Thermal stability of the sample having maximum ionic conductivity was found using TG/DTA analysis. Nano composite polymer electrolytes were subjected to ac impedance analysis spectra for acquiring the ionic conductivity values at different temperature. Surface structure of the sample was analysed using scanning electron microscope and the complexations of samples were analysed using X-ray diffraction analysis. It was noted that the polymer electrolyte contains 8 wt. % of BaTiO3 showed maximum ionic conductivity than the other ratios of BaTiO3. 相似文献
558.
采用水热法合成单斜相纺锤形纳米二氧化锆(ZrO2),建立单斜相纺锤形纳米ZrO2富集分离电感耦合等离子体质谱(ICP-MS)测定水中痕量Ba(Ⅱ)的方法。对Ba(Ⅱ)的检出限为0.007 ng·mL-1,相对标准偏差为0.13%(n=11);系统的研究纳米ZrO2对Ba(Ⅱ)的最佳富集分离条件,在pH 10.0时,纳米ZrO2对Ba(Ⅱ)的吸附率可达99%以上,以2 mL 0.5 mol·L-1的HCl为洗脱剂,可定量洗脱纳米ZrO2上吸附的Ba(Ⅱ),洗脱率达98%以上;考察了纳米ZrO2对Ba(Ⅱ)的静态吸附容量为196.6 μg·g-1、富集倍数可达250倍;通过再生实验、共存离子的影响以及与普通ZrO2的对比实验探讨了纳米ZrO2的性能,并将纳米ZrO2的富集分离性能应用于实际样品中Ba(Ⅱ)的分析,使用ICP-MS进行测定,结果满意。 相似文献