Effect of Cr doping on secondary phases and electrical properties of zinc oxide ceramic thick film varistors

In order to get high-performance low voltage varistors, Cr2O3 doped ZnO ceramic thick films were fabricated by modified sol-gel process. The precursors were fabricated by dispersing doped-ZnO ceramic nano-powders in the sols, which were prepared by dissolving zinc acetate dihydrate into 2-methoxyethanol and stabilized by diethanolamine and glacial acetic acid and doped with a concentrated solution of bismuth nitrate, phenylstibonic acid, cobalt nitrate, manganese acetate and chromium nitrate. The results show that ZnCr2O4 phase can form in ZnO based ceramic films doped 1.0% （mole fraction） Cr2O3. Three secondary phases, such as Bi2o3, Zn7Sb2O12, and ZnCr2O4 phases, are detected in the thick films. The Raman spectra show that the intensity and the position of Raman bands of Zn7Sb2O12 and ZnCr2O4 phases change obviously with increasing Cr203 doping. The nonlinearity coefficient α of ZnO thick films is 7.0, the nonlinear voltage is 6 V, and the leakage current density is 0.7 μA/mm^2.     

基体对金刚石厚膜质量的影响研究

采用MPCVD法在钼基体上制备金刚石厚膜,测量了等离子体发射光谱,并利用XPS、Raman和SEM对金刚石厚膜进行表征.研究了Mo原子进入金刚石中的机制及其对金刚石厚膜的影响.结果表明:除了热扩散,Mo原子还会以蒸发进入等离子体的方式进入金刚石.金刚石中的Mo原子是以Mo+4、Mo+6以及介于Mo+4-Mo+6之间的化...     

Fabrication of a porous material with a porosity gradient by a pulsed electric current sintering process

A porous structure with a porosity gradient can be applied to the preparation of continuous FGM, where liquid or chemical vapor of the second phase is infiltrated into the graded pores. It also has applications in skeletal implant materials and ultrafiltration media. An attempt was made to fabricate a porous material with a porosity gradient by means of a pulsed electric current sintering (PECS) process. The present work describes not only the measured value of the temperature difference between the upper and lower part of the specimen, which brings about a gradual change in pore distribution, but also the sintering characteristics of the porous structure obtained by the pressureless PECS process.     

Effects of substrate temperature and annealing on the anisotropic magnetoresistive property of NiFe films

Ni83Fei7 films with a thickness of about 100 ran were deposited on thermal oxidized silicon substrates at ambient temperature, 240, 350, and 410℃ by DC magnetron sputtering. The deposition rate was about 0.11 nm/s. The as-deposited films were annealed at 450, 550, and 650℃, respectively, in a vacuum lower than 3 x 10-3 Pa for 1 h. The Ni83Fei7 films mainly grow with a crystalline orientation of [111] in the direction of the film growth. With the annealing temperature increasing, the [111] orientation enhances. For films deposited at all four different temperatures, the significant improvement on anisotropic magnetoresistance occurs at the annealing temperature higher than 550℃. But for films deposited at ambient temperatures and 240 ℃, the anisotropic magnetoresistance can only rise to about 1% after 650 ℃ annealing. For films deposited at 350℃ and 410℃, the anisotropic magnetoresistance rises to about 3.8% after 650℃ annealing. The atomic force microscopy (AFM) observation shows a significant i     

电位对天然黄铜矿表面膜层性质的影响

采用循环伏安（CV）、扫描电子显微镜（SEM）和电化学阻抗谱（EIS）研究黄铜矿在含有5×10-4mol/L乙黄药溶液中的电化学行为以及电位对黄铜矿表面膜层成分和性质的影响。结果表明：在开路电位（OCP）下,天然黄铜矿表面发生黄药阴离子的吸附过程;在阳极电位范围-0.11～0.2V内,主要发生黄药阴离子氧化形成疏水双黄药膜层的电化学过程。形成的双黄药膜层在电位为0V时具有较高覆盖度和较大的厚度,随着电位的增加表面双黄药膜层的覆盖度和厚度减小。当电位高于0.2V时,黄铜矿表面发生以自身活化溶解为主的电化学过程,黄铜矿表面由双黄药膜层转化成为大量具有多孔和疏松结构的含有Cu（Ⅱ）和Fe（Ⅲ）的氧化物。     

离子掺杂对纳米TiO2薄膜光催化性能的影响

采用溶胶凝胶法制备含有不同掺杂离子的TiO2溶胶和纳米粉,采用浸渍提拉法将溶胶涂敷在自制的多孔陶瓷膜件上,考察其对蚁酸溶液(1%)的光降解作用。研究结果表明,在适宜掺杂浓度(1?3 ,0.5%La3 (摩尔浓度))下,Fe3 /La3 -TiO2膜的光催化性能最好。采用X射线衍射仪分析、原子力电子显微镜和吸收光谱仪等研究单独掺杂Fe3 、La3 和复合掺杂Fe3 /La3 离子的作用及膜的性能,从而确定出提高TiO2光催化活性的最佳掺杂工艺。     

Mn含量对梯度多孔Mg-Mn合金微弧氧化膜组织与性能的影响

研究了Mn含量对梯度多孔Mg-Mn合金微弧氧化过程中电压-时间曲线、微弧氧化膜层显微组织、膜层厚度、物相组成以及耐腐蚀性能的影响。结果表明,随Mn元素含量的增加,微弧氧化电压-时间曲线中的起始电压U1、击穿电压U2和稳定电压U3均下降,但是当Mn含量超过2%后,U1、U2、U3均上升,随着Mn元素含量的增加,微弧氧化膜层厚度先降低而后增加。当Mn含量为2%时,梯度多孔Mg-Mn合金表面形成的氧化膜质量最好,孔隙细小、分布均匀,膜层厚度为39.6μm。结合XRD和EDS分析表明,微弧氧化处理后试样表面膜层由Mg2Si O4和Mg O两相组成。随着在模拟体液中浸泡时间的延长,添加2%Mn元素的梯度多孔Mg-Mn合金的质量损失最少,析氢量最低,耐腐蚀性最佳。     

The effect of a high thermal gradient on sintering and stiffening in the top coat of a thermal barrier coating system

Superalloy substrates coated with plasma-sprayed CoNiCrAlY bond coats and yttria-stabilized zirconia top coats (TCs) have been subjected to a high heat flux under a controlled atmosphere. The sintering exhibited by the TC under these conditions has been studied and compared with the behavior observed during isothermal heating. Sintering has been characterized by (a) microstructural examinations, (b) dilatometry, in both the in-plane and through-thickness directions, and (c) stiffness measurements, using both cantilever bending and nanoindentation. A numerical model has been used to explore the stress state under isothermal and thermal gradient conditions. Dilatometry data indicate significant linear contractions during holding at elevated temperatures, particularly in the through-thickness direction. This is largely attributed to microstructural changes associated with sintering, with any volume changes due to phase transformations making relatively small contributions. Sintering proceeds faster at higher temperatures but is retarded by the presence of tensile stresses (from differential thermal expansion between the coating and substrate) within the TC. Thus, it occurs preferentially near the free surface of the TC under gradient conditions, not only due to the higher temperature, but also because the in-plane stress is more compressive in that region.     

Roles of Te and Mn in the two phases of manganite with nominal composition La_（0.6）Sr_（0.1）Te_xMnO_3

Powder samples with nominal composition La<,0.6>Sr<,0.1>Te<,x>MnO<,3> (x = 0.00, 0.05, 0.10, 0.15, 0.20) were prepared using the sol-gel method with thermal treatment up to 1473 K. On the basis of powder X-ray diffraction (XRD), thermogravimetric and magnetic measurements, it was found that almost all of the Te and a few of the Mn ions were lost from the samples when they were calcined at 1473 K. The reason for the Te loss and a quantitative phase analysis for the samples calcined at 1473 K are discussed in detail.     

Interfacial reactions of liquid Sn and Sn-3.5Ag solders with Ag thick films

The interfacial reactions of liquid Sn and Sn-3.5Ag solders with Ag thick films are investigated in the temperature range from 250–325 °C, and the morphology of intermetallic compounds formed after such soldering reactions is observed. In kinetics analysis of the growths of intermetallic compounds, it was found that both Sn/Ag and Sn-3.5Ag/Ag reactions were interfacial-controlled, and the growth rates for both cases were similar. The rate of Ag dissolution into liquid solder attendant on the formation of interfacial intermetallic compounds after Sn/Ag reaction was about four times higher than that after Sn-3.5Ag/Ag reaction, as evidenced by experimental results.     

自蔓延烧结法制备Al_4C_3涂覆金刚石复合材料

采用Ti/Al/石墨/金刚石粉体为原料,通过自蔓延高温烧结技术制备铝-碳化钛基结合金刚石复合材料,制备了Al-TiC结合剂金刚石复合材料,在金刚石表面合成了碳化铝涂层。采用X射线衍射(XRD)、扫描电镜(SEM)结合能谱仪(EDS)分析试样。研究结果表明:各种原料经自蔓延高温烧结后,产物主相为Al、TiC和金刚石。同时,在金刚石表面形成了致密的Al4C3涂层,当Al质量分数较高时(80%),Al4C3涂层组织细小,约为1~5μm;随着Al质量分数减少至60%,Al4C3涂层组织粒度逐渐变大,同时析出较多5~20μm的花蕾状析出物。但是当Al质量分数较少(40%)时,金刚石易发生碎裂现象。