钕掺杂锆钛酸铅纳米粉体的溶胶-凝胶法合成研究

以乙二醇为溶剂,硝酸钕为钕源,采用改进的溶胶-凝胶法制备了钕掺杂锆钛酸铅纳米粉体Pb1-3x/2NdxZr0.52Ti0.48O3(PNZT).通过FTIR、XRD、TG-DTA讨论了溶胶经热处理制备纳米粉体的反应机理,PNZT的热处理温度较PZT高50～100℃.采用XRD、SEM、TEM对纳米粉体进行表征.研究表明,钕掺杂增加了晶格畸变程度.与PZT相比,随着钕掺杂量增加晶格参数a和V下降,而参数c和c/a则不同,少量钕掺杂导致参数c和c/a增加,随着钕掺杂量增加逐渐下降.当钕掺杂量≤9%(摩尔分数)时可生成粒径约为20～50nm的钙钛矿型粉体, Nd3 离子取代Pb2 离子与Ti4 离子、O2 离子形成稳定的钙钛矿型结构.     

Lu2O3:Yb3+, Ho3+纳米粉体的发光性能研究

采用共沉淀工艺合成了Yb3 离子和Ho3 离子共掺杂的Lu2O3纳米粉体,研究了粉体的斯托克斯(Stokes)和反斯托克斯(Anti-Stokes)发光特性以及煅烧温度对粉体发光性能的影响.在氙灯447.5nm和半导体激光器980nm激发下样品均发射出明亮的绿光,观察到了不同Ho3 离子浓度掺杂的纳米粉体的浓度淬灭现象.发射强度与激发功率的关系表明Anti-Stokes发光是双光子过程,能量转移是主要的上转换机制.Ho3 离子的5F4,5S2能级在不同波长激发下的衰减时间也证实了浓度淬灭及能量转移现象.     

稀土元素(La、Ce、Nd、Pr、Sm)掺杂纳米TiO2相对介电常数的研究

采用溶胶-凝胶法制备纳米TiO2以及稀土元素(La、Ce、Nd、Pr、Sm)掺杂纳米TiO2粉体.采用TEM和XRD研究了粉体形貌和晶体结构,利用TH2816型宽频LCR数字电桥测试分析了粉体介电特性.结果表明,所有稀土元素的掺杂均提高了纳米TiO2的相对介电常数和介电损耗,其原因是稀土离子取代钛离子产生了更多的感应偶极矩以及稀土离子进入晶体内部使晶格畸变有利于极化.在Nd/纳米TiO2复合粉体中,最佳掺杂浓度为Nd2.5%(原子分数)时,样品相对介电常数达到峰值.     

ZAO纳米粉体的制备及其在红外隐身中的应用研究

采用溶胶-凝胶法制备了铝掺杂氧化锌(ZAO)纳米粉体.使用X射线衍射仪(XRD)研究了Al2O3掺杂对ZnO物相结构和晶粒度的影响,结果表明,Al离子的掺杂并没改变ZnO的晶体结构,Al抖对Zn2 的替位掺杂使晶格发生畸变,衍射角偏离,随Al离子掺杂浓度的增加,晶体的平均粒径减小.对ZAO纳米粉体样品的红外吸收特性分析表明:随Al离子掺杂浓度的增加,红外吸收出现蓝移.理论分析得出适当调节ZAO栽流子浓度可以制备低红外发射率材料.     

Fe基合金的微结构与频率特性

用高能球磨的方法制备铁基纳米晶铁钴和铁镍合金,研究材料的结构与频率特性.结果表明:具有体心立方晶体结构样品的颗粒尺寸在0.5~5μm之间,尺寸分布较宽;而具有体心立方和面心立方混合晶体结构样品的在5~20μm之间,尺寸分布较窄.含钴样品的钴含量有提高样品截止频率的作用;样品的磁导率实部在掺杂量为7.69%(原子分数)时均出现极大值.Co掺杂的样品显示出弛豫型磁谱特征,而Ni掺杂样品则显示出共振型磁谱特征.Fe-Co样品在高频区域磁导率虚部随着掺杂量的增大而减小,同时随着掺杂量的增加,磁导率虚部最小值向高频区域移动.Fe-Ni样品的磁导率虚部最小值也随着掺杂量的增加向高频区域移动.纯铁样品则在高频区域磁导率虚部小于掺杂样品.     

铈掺杂钛酸钡微粉制备与微波吸收特性研究

采用溶胶一凝胶法制备了稀土铈掺杂钛酸钡纳米晶粉体,借助XRD、Raman、SEM以及矢量网络分析仪等分析测试手段对样品晶相、晶格常数、粒径、表面形貌及微波吸收特性进行了研究.结果表明:铈掺杂样品均形成四方相钛酸钡微晶,晶粒发育良好.随着铈掺杂量增大,晶粒逐渐细化,晶格常数a变大,晶格常数c减小;与未掺杂钛酸钡相比,在2-18GHz频率范围内,稀土铈掺杂材料(掺杂量0.2%)的反射损耗明显地提高,反射峰发生蓝移,尤其5.8GHz和7GHz处反射损耗分别提高了15dB和30dB,频带拓宽近2倍.由此可见铈掺杂有利于改善钛酸钡材料的微波吸收特性.     

还原气氛烧成Y5V型瓷粉的结构与介电性能

运用SEM、TEM、XRD等手段研究了掺杂组分对钛酸钡基Y5V陶瓷的结构和性能影响.结果表明:由于掺杂组分的存在,烧结情况得到了明显的改进.掺杂钛酸钡陶瓷的烧结包括固-固烧结和液-固烧结.Zr和稀土元素能够扩散进入钛酸钡晶格并促进固-固烧结,SiO2主要聚集在晶界并促进液-固烧结烧结.Nd5 聚集在晶界并促进针状颗粒生成,XRD的结果表明样品中有新相形成.由于掺杂的引入,材料的居里温度向低温方向移动,材料的介温曲线较纯钛酸钡材料的介温曲线更趋平坦.研究的结果还表明,由于在还原气氛中烧结,材料的介电损耗上升.     

Mn在BaTiO3中的固溶及其对BaTiO3结构影响的研究

运用XRD、SEM、HRTEM研究了Mn2O3掺杂对钛酸钡陶瓷结构的影响.随着烧结温度上升,发现Mn2O3掺杂钛酸钡样品的晶格常数在c轴方向增大.在烧结温度相同的情况下,Mn2O3掺杂能够抑制钛酸钡晶粒的生长,Mn3 在烧结的过程中逐渐的固溶进入钛酸钡晶格.从结构角度出发,提出了Mn固溶进入晶格后,在其周边微区可能产生压应力,这是样品在还原气氛下烧结仍保持高电阻现象的原因之一.     

828nm激发下Nd~(3+)掺杂TiO_2上转换发光的研究

采用溶胶-凝胶法制备了掺杂稀土离子Nd3+的TiO2纳米晶体,考察了样品在828nm激发光源作用下,不同的稀土离子掺杂量、不同的焙烧温度对其上转换发光特性的影响,在828nm波长激光激发下,室温时检测到了蓝绿(493nm)黄(565nm)的上转换荧光,它们分别对应4G9/2→4I9/2、4G7/2→4I9/2跃迁时的发射,并对Nd3+掺杂的上转换发光机制进行了探讨。     

溶胶-凝胶法制备Co掺杂ZnO纳米粉体的实验研究

采用溶胶．凝胶法制备了钴掺杂氧化锌纳米粉体，研究了反应物浓度、掺杂比例、退火温度对样品微结构的影响．XRD测试结果表明：所有样品均为六角纤锌矿结构，而且低浓度的反应物易于形成钴掺杂含量相对较高的固溶体．依据测试结果计算发现：钴的掺杂比＜5％时，由于杂质钴在氧化锌晶体中可能以间隙原子的形式存在，所以样品的晶格常数比未掺杂ZnO的晶格常数大；而钴的掺杂比〉5％时，由于离子半径小的CO^2＋替代Zn^2＋离子使得样品晶格常数变小。而且提高退火温度，可以增大晶粒尺寸，有利于样品呈现室温铁磁性.     

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.