贱金属Ni电极的制备和性能

使用Ni、B粉和玻璃粉制备贱金属Ni电极浆料,加入松香松油醇作为有机溶剂。两组浆料中Ni粉,B粉和玻璃粉的质量百分比分别为70%、15%、15%和68%、16%、16%。将浆料涂覆在PTC半导瓷上在790~870℃烧结,制备出贱金属Ni电极。用SEM电镜观察电极样品截面的形貌。对不同烧结温度的Ni电极做截面EDX线扫以获取电极和陶瓷各组成元素的原子数的变化。改变浆料的组成和烧结温度调节了电极的匹配性以及体电阻、方阻等电学性能。在810~850℃区间内保温20 min,在PTC等半导瓷上得到的Ni电极具有良好电学性能。根据电极和瓷体主要元素的原子百分比的变化研究了陶瓷与电极的匹配性并分析了温度变化对扩散系数D以及原子浓度百分比变化的影响,探索了客观性质的微观机理。实现了Ni电极与PTC陶瓷的良好匹配。     

Ba0.65Sr0.35TiO3陶瓷材料的制备及介电特性研究

采用溶胶－凝胶工艺制备了Ba0.65Sr0.35TiO3粉体，并利用微波烧结技术对粉体进行了合成和烧结，研究分析了样品的介电特性，并与传统制备工艺获得的样品进行了性能比较。实验结果表明，获得的Ba0.65Sr0.35TiO3粉体颗粒较细，其合成温度和烧结成瓷温度都较传统工艺有大幅度降低，分别为900和1310℃；可以获得晶粒尺寸在1μm以内的陶瓷；随晶粒的减小，材料的相对介电常数变化不大，而介电损耗大大降低。     

Ba0.65Sr0.35TiO3陶瓷材料的制备及介电特性研究

采用溶胶-凝胶工艺制备了Ba_0.65Sr_0.35TiO₃粉体,并利用微波烧结技术对粉体进行了合成和烧结,研究分析了样品的介电特性,并与传统制备工艺获得的样品进行了性能比较.实验结果表明,获得的Ba_0.65Sr_0.35TiO₃粉体颗粒较细,其合成温度和烧结成瓷温度都较传统工艺有大幅度降低,分别为900和1310℃;可以获得晶粒尺寸在1μm以内的陶瓷;随晶粒的减小,材料的相对介电常数变化不大,而介电损耗大大降低.     

掺杂Y_2O_3,Sm_2O_3对氧化铝瓷介电性能的影响

研究了Y2O3、Sm2O3对氧化铝瓷烧结性能、介电性能和显微组织的影响。研究结果表明,Y2O3、Sm2O3在氧化铝瓷的烧结过程中可以显著降低氧化铝瓷的烧成温度,抑制晶粒生长,使晶粒尺寸变小,提高了陶瓷的致密性,降低了试样的结构损耗。掺稀土氧化物的氧化铝瓷在1600℃保温2h烧结后,相对密度达98.8%以上,介质损耗达到4.2×10-3。     

钛酸钡系PTCR半导体陶瓷烧结过程的计算机模拟 Ⅱ.烧结中后期及奥氏熟化过程中的晶粒生长

对Monte-Carlo计算机模拟法的Q－States Potts模型进行了修正,用于模拟BaTiO3系PTCR半导体陶瓷烧结中后期的晶粒生长和奥氏熟以及液相性质对晶粒生长的影响。模拟结果表明：在含有液相的二相系统,钛酸钡半导瓷样品在1240℃附近体积收缩率基本上达到最大值,以后的保温阶段是在液相控制下的晶粒生长和致密化过程,这和大多数实验结果是一致的。     

粉料埋烧的TiO2瓷半导化和电学非线性研究

基于一次烧结工艺，采用埋烧和裸烧两种方法制备组分相同(Sr，Bi，Si，Ta)掺杂的TiO2陶瓷。通过复阻抗特性、晶粒电阻、晶界电阻、压敏电压、非线性系数及势垒高度的测定，研究埋烧与裸烧工艺对TiO2陶瓷的半导化以及电学非线性特性的影响。结果表明，采取粉料埋烧有利于晶粒半导化，降低压敏电压。     

Nb掺杂TiO2压敏陶瓷的施主掺杂固溶度

研究了不同烧结温度TiO2压敏陶瓷的显微结构、施主掺杂固溶度和电学性能。采用SEM和EDS测试了其显微结构和晶粒化学组成。随烧结温度增加,TiO2晶粒迅速长大,显微结构均匀致密,但过高的烧结温度将导致较多气孔。1350℃为比较合适的烧结温度,其晶粒大小为15μm左右。在施主掺杂浓度一定的条件下,施主掺杂离子Nb5+在TiO2晶粒中的固溶度、晶粒电子浓度和电导率随烧结温度上升而增加,晶粒电阻率随烧结温度上升而下降。以能谱中O为参考确定TiO2晶格数量计算得到的固溶度及其电学性能更符合实验测试结果。     

钇稳定氧化锆纳米粉体烧结工艺的研究

实验研究了钇全稳定氧化锆(8YSZ)纳米粉体的烧结工艺,根据阿基米德原理测瓷体密度,通过测定烧结前后瓷片尺寸获得烧结线收缩率,使用扫描电子显微镜观测样品微观形貌,并探讨了纳米粉体烧结的致密化过程,分析了烧结工艺对致密度和晶粒大小的影响,得到了8YSZ纳米粉体合理的烧结工艺为:采用两步烧结,首先升温到1500℃,升温速率为3℃/min,然后降低温度到1450℃,烧结时间为4h.结果显示,采用该工艺,可以得到相对密度98%,晶粒尺寸小于3μm的性能优异的8YSZ瓷体.研究发现,粉体粒度对烧结性能影响较大,纳米粉体比普通粉体具有较低的开始烧结温度,双粒度混合粉体可以进一步提高其烧结性能.     

烧结温度对Zn-Bi系压敏陶瓷晶界的影响

采用传统的固相烧结法制备了Zn-Bi-Mn-Cr-Si(ZBMCS)压敏陶瓷样品,研究了烧结温度对ZBMCS压敏陶瓷相组成、微观结构、电学性能的影响。烧结温度的持续升高使得样品平均晶粒尺寸逐渐增大,压敏场强逐渐减小。对不同烧结温度下样品EDS分析可知,烧结温度的升高显著降低了Bi的含量,Mn, Cr、Si参与了Zn₂SiO₄和其他第二相的形成过程。当烧结温度为990℃时,样品的综合性能达到最好,此时非线性系数最大值为43.36,漏电流密度最小值为1.89μA/cm²,击穿场强为435.10 V/mm,在10³～10⁶ Hz外电场作用下其损耗角正切值最大仅为0.07。     

V~(5+)-Sr~(2+)共掺杂对TiO_2基压敏陶瓷性能的影响

研究了V~(5+)-Sr~(2+)共掺杂对TiO_2基压敏陶瓷电学性能的影响。采用固相烧结方法制备V~(5+)-Sr~(2+)共掺杂TiO_2样品。利用XRD衍射仪检测物相和SEM测定显微结构。用压敏电阻直流参数仪测定V~(5+)-Sr~(2+)共掺杂TiO_2样品在不同烧结温度和掺杂量下的电学性能。结果表明:掺杂0.35mol%的V_2O_5,XRD衍射仪没有检测到第二相的产生。随着SrCO_3掺杂量以及烧结温度的增加,样品压敏电压和非线性系数都有不同的变化趋势。当烧结温度为1 300℃、Sr~(2+)掺杂量为0.5mol%时,样品的各项电学性能最优:V~(5+)-Sr~(2+)共掺杂TiO_2样品压敏电压达到16.3V/mm,非线性系数α达到5.6。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.