Sol-gel法制备ZnO:Cd薄膜及性能研究

采用Sol-gel法使用旋转涂覆技术在Si(100)基片上生长了ZnO:Cd薄膜.XRD结果表明:ZnO:Cd薄膜具有与ZnO一样的六角纤锌矿结构,随热处理温度的升高,(002)衍射峰强度逐增,FWHM减小,并沿c轴择优取向生长;透射光谱实验表明:以石英为基底,适度掺镉可降低薄膜的禁带宽度Eg,特别是在800℃、8?条件下,Eg=2.80eV,与纯ZnO的禁带宽度3.30eV相比,明显降低了光学禁带;光致发光谱(PL)实验表明:在吸收边附近均有较强的紫外发射峰,且随热处理温度升高呈规律的变化;电阻率测定表明:掺镉使薄膜导电性增强.     

脉冲激光沉积法室温下ZnO薄膜的制备与表征

在室温条件下,采用脉冲激光沉积技术在玻璃衬底上生长了ZnO薄膜.对薄膜的XRD分析表明,ZnO薄膜为六方纤锌矿结构并沿c轴取向生长,且(002)衍射峰的半高峰宽仅为0.24°.薄膜沿c轴方向受到一定的张应力为1.7×108 N/m2.原子力显微镜分析表明薄膜表面较为平整,平均粗糙度约为6.5 nm,晶粒尺寸约为50 nm.此外,透射光谱分析表明薄膜的禁带宽度为3.25 eV,与ZnO体材料的禁带宽度3.30 eV基本相同.     

超声喷雾热解法制备MgxZn1-xO薄膜及其性能研究

采用超声喷雾热解法在石英玻璃衬底上生长出不同组分的宽禁带MgxZn1-xO薄膜(z=0、0.08、0.16、0.25).通过X射线衍射(XRD)、扫描电子显微镜(SEM)和分光光度计等分析测试手段对MgxZn1-xO薄膜的晶体结构、透光性及禁带宽度进行了研究.结果表明,随着Mg含量的增加,MgxZn1-xO薄膜仍然保持着ZnO的纤锌矿结构,没有生成MgO相,Mg可以有效地溶入ZnO的晶格中.MgxZn1-xO薄膜具有良好的透光性,在可见波段的光透过率达85%以上;此外,随着Mg含量的增加,MgxZn1-xO薄膜的吸收边出现蓝移现象,禁带宽度从3.30eV增大到3.54eV.     

半导体ZnO晶体生长及其性能研究进展

ZnO晶体是直接宽带隙半导体材料，室温下禁带宽度为3.37eV，激子束缚能为60meV。其禁带宽度对应紫外光的波长，有望开发蓝绿色、蓝光、紫外光等多种发光器件。对ZnO晶体的生长方法及研究进展做了简要的叙述。     

LMBE法生长ZnO薄膜的结构和光学性能

利用激光分子束外延方法(LMBE)在单晶Si(100)和玻璃基片上生长了ZnO薄膜.通过XRD谱、拉曼光谱和光致发光(PL)谱研究了ZnO薄膜的结构和光学性能.结果表明,ZnO薄膜具有六方纤锌矿结构,(002)衍射峰较强,c轴择优取向良好.在可见光范围,ZnO薄膜的平均透射率＞80%,而在紫外范围,平均透射率急剧降低.拟合得到ZnO薄膜的禁带宽度为3.31eV.随激发波长增加,PL谱峰位没有变化,但强度发生了变化.同时,随测量温度升高,紫外发光峰强度减弱,峰位红移,半高宽展宽.理论拟合得到ZnO薄膜的活化能为59meV,接近于ZnO体材料的激子束缚能(60meV),说明紫外发光是由自由激子辐射复合引起的.     

溶胶-凝胶法制备ZnO基稀释磁性半导体薄膜

用溶胶－凝胶法制备了具有良好光学性质和C轴取向的ZnO:Fe薄膜。ZnO:Fe薄膜具有尖锐的带边发光，禁带宽度约为3.3eV，半高宽13nm。磁性测量表明，ZnO：Fe薄膜在室温下具有铁磁性，饱和磁化强度约为10^-3emu量级，矫顽力为30奥斯特（Oe)。     

Zn1-xMgxO的溶胶凝胶法合成及其特性研究

由溶胶凝胶法、利用草酸盐在水相中合成了干凝胶前体粉末,经过热处理得到了纳米Zn1-x MgxO(x≤0．15)粉体;XRD表明所制得的材料具有ZnO的六方晶系结构;经UV—Vis分析,比较了量子尺寸的ZnO与热处理的ZnO和Mg掺杂的ZnO及其混合溶胶的紫外吸收差异;通过Mg的掺杂,使ZnO的禁带宽度从3、31eV调节至3．65eV。     

In掺杂和退火对磁控溅射制备ZnO薄膜的结构和光电性质的影响

用射频磁控溅射技术在石英玻璃衬底上制备出ZnO和In掺杂的ZnO(ZnO∶In)薄膜,研究了In的掺杂和退火对薄膜的结构和光电性质的影响。所制备的薄膜为纤锌矿结构的ZnO相,In的掺杂有利于ZnO薄膜的c轴择优生长,并且使其表面更加致密平整,退火提高了薄膜的结晶行为,但使得薄膜的表面有部分团聚形成。由于In3+替代了Zn2+,提供了一个多余的电子,ZnO薄膜的电阻率从28.9Ω.cm降低到4.3×10-3Ω.cm。由于载流子浓度的增加和晶格尺寸的拉长,In的掺杂使得ZnO薄膜的禁带宽度增加;空气中退火后薄膜的载流子浓度降低和晶格尺寸的减小,使得禁带宽度降低。ZnO薄膜在可见光范围的透光率在90%以上,受In的掺杂和退火的影响不大。室温下用325 nm的激发光源测试了样品的光致发光(PL)谱,发现In的掺杂对薄膜的PL谱影响不大,而退火后的ZnO薄膜在446 nm处的蓝光发射明显增强,更适合于作为蓝色发光器件。     

热处理对溶胶-凝胶TiO2薄膜的晶相转变和性能影响

以钛酸丁酯（TPOT）为有机醇盐前驱体，采用溶胶－凝胶技术制备了TiO2溶胶。为测量方便起见，分别制备了凝胶粉体和薄膜，并对样品进行了不同温度的热处理。X射线衍射（XRD）、椭偏仪和紫外－可见光谱（UV－vis)的测量表明：随热处理温度的升高，TiO2的结构由非晶到锐钛矿再到金红石相转变，400℃为锐钛矿相，600℃开始出现金红石相，800℃完全转变为金红石相；晶粒尺寸随热处理温度的升高而逐渐增大，锐钛矿结构的晶粒尺寸范围是2.5-5.5nm，金红石结构的晶粒尺寸范围是5.9-6.8nm；TiO2薄膜的折射率随热处理温度的升高而增大，同时薄膜厚度降低；禁带宽度随热处理温度的升高而增大，同时薄膜厚度降低；禁带宽度随热处理温度升高而变窄，锐钛矿结构的禁带宽度为3.45eV，而金红石结构的禁带宽度为3.30eV。     

氧化锌的能带工程

ZnO由于具有3.4eV的宽直接禁带和60meV的高激子束缚能,近年来引起了研究者的广泛兴趣,被认为是制备室温或高温蓝光或紫外光发光二极管以及激光二极管的理想材料.ZnO的能带工程是发展高效率的ZnO发光器件的关键,这已经成为ZnO领域的研究热点.近年来,大量的研究表明,可以通过ZnO与Mgo或BeO形成MgZnO或BeZnO合金来增大ZnO的禁带宽度,通过ZnO与CdO形成CdZnO合金来减小ZnO的禁带宽度,从而在保持单一六方结构的情况下实现了室温禁带宽度在1.8～10.6eV范围内的可调节.总结了ZnO能带工程的国内外研究进展,系统地介绍了MgZnO、BeZnO和CdZnO合金、ZnO基量子阱和超晶格的制备方法、晶体结构、光学性能等.     

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.