ZnO压敏陶瓷的晶粒生长和电学性能

研究了不同价态Co、Mn添加物对低压ZnO压敏陶瓷晶粒生长和电学性能的影响,分析了由于不同价态Mn和Co掺杂所产生的缺陷类型,应用晶粒生长的动力学方程：Gⁿ=Dtexp(-E/RT)确定了晶粒生长的动力学指数和激活能．实验结果表明：对于低压ZnO压敏陶瓷,其晶粒生长的动力学指数n＝6,激活能E＝224±17kJ／mol,随着Mn、Co价态的增加,ZnO压敏陶瓷的平均晶粒大小增加,提高烧结温度,ZnO压敏陶瓷的压敏场强E1mA降低,漏电流IL增加,非线性系数α降低．在低压ZnO压敏陶瓷的制备过程中,烧结温度以不超过1250℃为宜．     

锌硼玻璃掺杂低压ZnO压敏电阻电性能及晶粒生长动力学研究

研究了锌硼玻璃掺杂量对低压ZnO压敏电阻微观结构和电性能的影响.结果表明,当掺杂量x=0.1wt%时,可以得到较好综合性能的ZnO压敏电阻:E1mA=36.7V/mm,α=30.4,IL=0.1μA.并应用晶粒生长动力学唯象理论研究了锌硼玻璃掺杂低压ZnO压敏电阻的晶粒生长规律,探讨了锌硼玻璃掺杂对低压ZnO压敏陶瓷晶粒生长的作用机理.当烧结温度T≤1000℃时,其晶粒生长动力学指数n≈4.54,激活能Q≈316.5kJ/mol,这是由于未熔融的锌硼玻璃通过颗粒阻滞机理阻碍了ZnO压敏陶瓷晶粒的生长;而当T1000℃时,其晶粒生长动力学指数n≈2.92,激活能Q=187kJ/mol,这是由于熔融的锌硼玻璃通过液相烧结机理促进了晶粒的生长.     

多元纳米复合氧化锌压敏陶瓷的晶粒生长

研究了多元纳米复合ZnO电压敏粉体在高温下的烧结行为.应用晶粒生长的动力学方程Gn-G0=K0texp(-Q/RT),确定了晶粒生长的动力学指数n和激活能Q.实验结果表明,随着烧结温度的提高和保温时间的延长,ZnO压敏陶瓷的晶粒不断长大,其动力学指数n=3.2,激活能Q=(185±28)kJ/mol.     

微波烧结氧化锌压敏电阻的致密化和晶粒生长

研究了微波烧结的ZnO压敏电阻的致密化和生长动力学, 微波烧结温度从900～1200℃, 保温时间从20min～2h. 研究表明, 微波烧结ZnO压敏电阻的物相组成和传统烧结的样品没有区别; 微波烧结有助于样品的致密化, 并降低致密化温度. 随着烧结温度的升高, 致密化和反致密化作用共同影响样品的密度, 其中Bi的挥发是主要影响因素. 微波烧结ZnO压敏电阻的晶粒生长动力学指数为2.9～3.4, 生长激活能为225kJ/mol, 传统烧结的ZnO压敏电阻的晶粒生长动力学指数为3.6～4.2, 生长激活能为363kJ/mol. 液相Bi₂O₃、尖晶石相和微波的“非热效应”是影响微波烧结ZnO压敏电阻陶瓷晶粒生长的主要因素.     

铝掺杂对氧化锌压敏陶瓷电性能的影响

研究了微量铝(Al)掺杂对氧化锌(ZnO)压敏陶瓷显微结构、电性能和本征点缺陷浓度等方面的影响及其作用机理。研究结果表明, 介电损耗峰值能够在一定程度上反映ZnO压敏陶瓷本征点缺陷浓度, 微量Al掺杂能够引起ZnO压敏陶瓷本征点缺陷浓度的显著降低。氧空位缺陷对应的损耗峰峰值从88.82下降到1.74, 锌填隙缺陷对应的损耗峰峰值从133.38下降到8.14。随着Al掺杂量的增加, ZnO压敏陶瓷平均晶粒尺寸从9.15 μm逐渐下降到6.24 μm, 而压敏电压从235 V/mm逐渐提高到292 V/mm。可见Al掺杂抑制了ZnO压敏陶瓷中本征点缺陷的形成, 而本征缺陷浓度的降低导致材料显微结构和电性能发生明显变化。本文阐述了Al掺杂对ZnO压敏陶瓷本征缺陷的影响机理, 建立了ZnO压敏陶瓷显微形貌、电性能、介电性能和本征点缺陷之间的联系。     

Sb掺杂对ZnO-V2O5多元系压敏电阻的影响

本文研究了V/Sb预合成粉、SbVO4和Sb2O3等三种不同形式的Sb掺杂对ZnO-V2O5基压敏陶瓷结构和性能的影响.化学计量比不变情况下,上述Sb掺杂方式的改变,使烧结过程中Sb3 离子在陶瓷样品中的浓度上升,促进Zn7Sb2O12型尖晶石相形成,材料晶粒随之细化.同时材料的压敏电压出现大幅上升,而非线性系数和漏电流密度受Sb掺杂形式的变化影响不大.Sb以V/Sb预合成粉进行掺杂可以获得较大尺寸的晶粒,有利于材料在低压方面的应用.     

V2O5-B2O3掺杂钛酸锌陶瓷的相转变及晶粒生长动力学

通过化学法结合固相烧结技术制备了钛酸锌陶瓷,掺杂V2O5和B2O3降低了陶瓷的烧结温度,研究了V2O5-B2O3掺杂钛酸锌陶瓷的低温烧结行为、降温机制、相转变机制以及晶粒生长动力学特性.结果表明,V2O5-B2O3掺杂有效地将钛酸锌陶瓷烧结温度从1100℃降至900℃以下;V2O5-B2O3复合掺杂缩小了六方相分解的温度区间;高V2O5含量的复合掺杂试样中,产生了异常长大的晶粒,随B2O3加入量增加,晶粒趋于均匀一致;采用TPRE(Tradition Phenomenological Rate Equation)描述晶粒生长机制,计算得晶粒生长激活能为315.5kJ/mol,晶粒生长表达式为G=K07√texp(-315.5×103/RT).     

Fe元素对ZnO陶瓷晶界电性能的影响机理研究

研究了不同浓度的Fe2O3掺杂对ZnO陶瓷压敏特性的影响,实验表明,随Fe掺杂量增加,ZnO平均晶粒尺寸逐渐变大,压敏电压升高,非线性系数先增大后减小,漏电流先减小后增大.分析认为,Fe元素掺杂对ZnO陶瓷电性能的影响不仅与电子的能级有关,还与其自旋特性紧密相连.ZnO中掺杂的Fe元素随机取代其中的部分Zn原子后,Fe3+或Fe2+在ZnO中产生局域磁矩,会对与其取向不同的自旋电子产生强的散射,这样可增大ZnO陶瓷的电阻率,Fe元素在晶界的偏析可产生和提高其非线性特性.     

稀土氧化物Pr2O3掺杂对高压ZnO压敏电阻性能的影响

采用低温固相化学反应法制备了Pr2O3掺杂的ZnO纳米复合粉体,并用此粉体在不同烧结温度下制备了高压ZnO压敏电阻.采用X射线衍射、比表面测试、透射电镜、扫描电镜等手段对制备的ZnO纳米复合粉体及高压ZnO压敏电阻进行了表征,并与未掺杂ZnO压敏电阻进行了对比研究,探讨了稀土氧化物Pr2O3掺杂对高压ZnO压敏电阻电性能的影响机制.结果表明:较低的烧结温度(1030～1130℃)时,掺杂的稀土氧化物Pr2O3偏析于ZnO晶界中,有活化晶界、促使晶粒生长的作用;同时,Pr2O3掺杂导致1080℃烧结的ZnO压敏陶瓷体中晶体相互交织形成晶界织构,比未掺杂的更均匀和致密,这有助于高压ZnO压敏电阻晶界性能的改善,从而提高其综合电性能.当烧结温度为1080℃时,Pr2O3掺杂的高压ZnO压敏电阻的综合电性能最佳:电位梯度为864.39 V/mm,非线性系数为28.75,漏电流为35 μA.     

退火温度对ZnO陶瓷薄膜低压压敏特性的影响

应用新型溶胶-凝胶法制备了ZnO陶瓷薄膜,研究了退火温度对ZnO陶瓷薄膜低压压敏电阻电性能的影响.结果表明,采用溶胶掺杂在550℃退火条件下可形成Zn7Sb2O12及ZnCr2O4相,且在退火温度范围内(550～950℃)基本上没有焦绿石相形成.当退火温度达到750℃以后,Sb2O3已全部转变为稳定性好的尖晶石相,同时存在Bi2O3、ZnO的挥发.采用适当的退火温度,可得到具有优良电性能的ZnO陶瓷薄膜低压压敏电阻,其压敏电压低于5 V,非线性系数可达20,漏电流密度小于0.5μA/mm2.     

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.     

Effect of Permeable Crystalline Material on Steel Reinforcement Corrosion of Concrete

Permeable crystalline materialcan permeate into pores and cracks of concrete and catalyze the reaction between Ca(OH) 2and unhydrated cement to generate a great quantity needle non-soluble crystals, which can stop up the pores and cracks of concrete, and increase the impermeability of concrete. This paper reported the results of a study conducted to evaluate steel reinforcement corrosion of concrete specimens uncoated and coated with permeable crystalline material as well as mixed with the permeable crystalline material. The properties evaluated for corrosion test were water impermeability, water absorption, compressive strength and potential. The results of water impermeability, water absorption, compressive strength clearly showed that the permeable crystalline material could prohibit water, any soluble salts and moisture from penetrating the concrete to cause corrosion, leaking, and other problems, and it did increase the compressive strength, which was favorable for protection of corrosion of reinforcing steel. Moreover, it was concluded from the potential-time curve that the steel reinforcement of uncoated specimen was in the state of activation whereas that of other specimens coated and mixed with the permeable crystalline material was in the state of inactivation. Above all, it was indicated that the permeable crystalline materialis very effective to protect the steel reinforcement of concrete from corrosion.     

The Research and Application About "Dry Peeling Off" Technology for Airplane Surface Paint Layer

In this paper, the principle of spurting take off lacquer were introduced; and with orthogonal method the unsaturate polyester was prepared ;it was easy to peel airplane paint layer off with this material and equipment.     

Quality Study of Honeycomb Core Shaping Without Wax Stabilization

Sandwich panels utilizing honeycomb cores result in lightweight, high-strength units that are very rigid. Indeed, they give honeycomb panels the best strength-to-weight ratio of any construction type available. Conventionally, the wax is poured into the cell of the core to strengthen the structure and prevent the core from being crushed during milling. Much time and labor is required to wax, mill, and clean the cores. In this study, the process of pouring wax into the core was skipped. In other words, the cutter directly milled the core. Experiments showed that the compressive strength of the core produced without wax stabilization was only 3% lower than that of cores produced using the traditional method. In addition, the drum peel strengths of cores produced without wax stabilization were 38.4% higher than cores produced using the traditional method, in which residual wax seriously polluted the adhesive. It was also found that eliminating the wax process can reduce costs.     

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.     

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.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

In-process thermal treatment of polylactic acid in fused deposition modelling

Polylactic acid (PLA) is one of the most widely used open source fused filament fabrication materials due to its ease of extrusion, biodegradability, and mechanical strength. The mechanical strength of PLA largely depends on the proper growth of its semi-crystalline structure, which can be severely impaired by a low rate of crystallization, particularly in open source printers. This can be further aggravated by the non-uniform thermal distribution of heat that causes improper curing among the extruded beads of the printing material. As a result, PLA printed on open source printers does not achieve the best mechanical properties. This research, for the first time, proposes an additive-free solution implemented through a detailed set of experimentation to improve the curing rate through in-process temperature variations to cure the joints among the beads. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy is used to confirm the improvements in the bead joints. This work is conducted in two phases of experiments. In the first phase, a full factorial ANOVA is used to investigate various process parameters and the important variables are used in the second phase to print test specimens in four different sets.