Effects of barium on the nonlinear electrical characteristics and dielectric properties of SnO2-based varistors

The effects of barium on electrical and dielectric properties of the SnO_2·Co_2O_3·Ta_2O_5 varistor system sintered at 1250℃ for 60min were investigated. It is found that barium significantly improves the nonlinear properties. The breakdown electrical field increases from 378.0 to 2834.5V/mm, relative dielectric constant (at 1kHz) falls from 1206 to 161 and the resistivity (at 1kHz) rises from 60.3 to 1146.5kΩ·cm with an increase of BaCO_3 concentration from 0mol% to 1.00mol%. The sample with 1.00mol% barium has the best nonlinear electrical property and the highest nonlinear coefficient (α=29.2). A modified defect barrier model is introduced to illustrate the grain-boundary barrier formation of barium-doped SnO_{2}-based varistors.     

电化学法测定几种稀土贮氢合金的热力学函数

贮氢材料由于能可逆地吸放氢,得到了广泛地应用.特别是以贮氢材料为负极制成的氢镍二次电池,容量为同类型镉镍电池的1.5～2倍,且电压又相近,是镉镍电池的理想换代产品,受到人们普遍的关注。LaNi_(4.5)Mn_(0.5),LaNi_(4.9)Sn_(0.1)和La_(0.8)Nd_(0.2)Ni_(2.5)Co_(2.4)Al_(0.1)是电化学性能较优越的贮氢合金。LaNi_(4.5)Mn_(0.5)的电化学容量高,理论容量可达400mAh.g~(-1).LaNi_(4.9)Sn_(0.1)和La_(0.8) Nd_(0.2)     

金属酞菁化合物在TiO2表面的分散研究

Dispersion of copper(Ⅱ) phthalocyanine (CuPc), copper(Ⅱ) phthalocyaninesulfonate (CuPcS) and cobalt(Ⅱ)phthalocyaninetetrasulfonate (CoPcTS) on the surface of titanium dioxide was investigated by XRD, XPS, FT-IR and UV-Vis techniques. Results show that interaction between CuPc and TiO2 was very weak and CuPc was difficult to disperse on the surface of the support. While partly sulfurized CuPcS could be dispersed on the surface of support through sulfo-groups and its dispersion capacity was determined to be 0.085 g CuPcS/g TiO2. Completely sulfurlzed CoPcTS could also be dispersed on the surface of TiO2 as a monolayer and its dispersion capacity was 0.12 g CoPcTS/g TiO2. Interactions of the sulfo-groups as well as the electrons of CoPcTS with the surface of TiO2 could be evidenced by FT-IR characterization. Therefore, it was suggested that CoPcTS molecules be adsorbed on the surface of TiO2 in a flat-lying mode while CuPcS in a slanting one. UV-Vis spectra show that the dispersed CuPcS and CoPcTS molecules exist in both forms of monomers and dimers.     

Cu（Ⅱ）—胱氨酸络合物吸附波的研究及蛋白质中胱氨酸的测定

研究了Cu(Ⅱ)-胱氨酸络合物极谱波的性质;提出了一种用示波极谱法测定蛋白质中胱氨酸的新方法,可在8.0×10~(-4)mol/L Cu~(2+)+8.0×10~(-3)mol/L三乙醇胺的溶液中测定0.05～20mg/L的胱氨酸。     

Underpotential Deposition Study and Determination of Bismuth on Gold Electrode by Using Voltammetry

ＴｈｅｃｏｍｂｉｎａｔｉｏｎｏｆｓｔｒｉｐｐｉｎｇｖｏｌｔａｍｍｅｔｒｙｗｉｔｈＵＰＤｃａｎｌｅａｄｔｏｔｈｅｉｍｐｒｏｖｅｍｅｎｔｏｆｓｅｎｓｉｔｉｖｉｔｙ ,ｓｅｌｅｃｔｉｖｉ ｔｙａｎｄｒｅｖｅｒｓｉｂｉｌｉｔｙｆｏｒｅｌｅｃｔｒｏａｎａｌｙｔｉｃａｌｐｕｒｐｏｓｅａｎｄａｖｏｉｄｔｈｅｕｓｅｏｆｔｏｘｉｃｍｅｒｃｕｒｙａｓｔｈｅｗｏｒｋｅｌｅｃｔｒｏｄｅ1ａｎｄｔｈｅｎａｎａｌｙｔｉｃａｌａｐｐｌｉｃａｔｉｏｎｓｈａｖｅｂｅｅｎｄｅｓｃｒｉｂｅｄ .2 4 Ｉｎｔｈｉｓｗｏｒｋ ,ｗｅｄｅｖｅｌｏ…     

MgSiO3掺杂对ZnO压敏电阻器电学性质的影响

采用传统陶瓷工艺制备了MgSiO3掺杂的防雷用ZnO压敏电阻。实验发现,掺杂0.04%的MgSiO3(物质的量)能显著提高其电流–电压非线性、通流能力和电压梯度E1.0,且能降低样品的漏电流IL以及残压比V40kA/V1mA。其非线性系数α和压敏电压梯度分别高达120,180V/mm,样品正反面各五次通流40kA、8/20μs波后,残压比和压敏电压变化率?V1mA/V1mA分别仅为2.56和–2.9%,且漏电流变化很小。对样品的微观结构分析显示,其电学性能的提高和晶粒的均匀程度有关。     

非穿透激光焊等离子体光信号与熔深的关系

在一定工艺条件下,焊缝熔合面积随线能量的增加线性增长,而在激光功率与焊接速度二者之中,激光功率对熔深有更为显著的影响,焊接速度则对熔宽影响较大.400nm~600nm波段的等离子体光信号可以较好地反映非穿透激光深熔焊熔深的变化,其均方根值与熔深成严格的二次曲线关系,另外还分析了等离子体光信号与焊缝熔深之间内在联系.研究结果为非穿透激光深熔焊熔深的实时监测或预测提供了理论与实验依据.     

硅电极/溶液界面开路电位-时间谱和原子力显微镜在化学镀Ag中的应用研究

用开路电位-时间谱技术,表征了在硅（100）表面化学镀银的硅电极/溶液界 面吸附态。所得结果与原子力显微镜在纳米尺寸上的面结构信息分析结果作了对比 。同时也将该结果与循环伏安法（CV）结果作了比较。证明当硅电极表面具有单层 吸附Ag~+离子、表面单层吸附Ag~+离子发生沉积反应、Ag~+离子发生本体沉积时的 开路电位-时间曲线有完全不同的特征。     

聚乙二醇类表面活性剂对硅表面无电沉积Ag膜光滑作用研究

应用原子力显微镜技术及开路电位～时间谱技术,研究了非离子表面活性剂聚乙二醇2000,6000,20000对硅(100)表面无电沉积银膜的光滑作用.实验表明硅(100)表面无电沉积银的光滑程度以及镀层的质量均随聚乙二醇聚合度的增加而变好.     

激光烧蚀辅助激光焊接的焊缝气孔率抑制研究

激光烧蚀辅助的激光焊接可以调节气孔率,进一步提高抗拉强度。在优选焊接参数后,研究了激光烧蚀密度对表面氧含量和表面形貌的影响。0 J/cm²时,表面氧含量(体积分数,下同)为8.91%,表面较为平整。激光烧蚀后,氧含量先减少后增加。8.75 J/cm²时,氧含量为2.75%,仅为0 J/cm²的30.86%,且形成了均匀的火山坑形貌。之后,过高的能量引起热氧化和不规则的烧蚀形貌。用σ_a和σ_b分别作为等离子体/金属蒸气喷发和熔池波动的标准偏差进行定量分析。σ_a和σ_b在0 J/cm²时为0.173和0.045。8.75 J/cm²时,分别为0.176和0.049,最接近0 J/cm²。35 J/cm²时则相反。0 J/cm²时,发现了大量的气孔,气孔率为1.85%。分析了在匙孔和熔池行为影响下三类气孔形成位置。8.75 J/cm