Sn掺杂ZnO纳米带的制备及其光致发光性能研究

采用热蒸发法制备了单晶Sn掺杂ZnO纳米带,其中Sn的掺杂含量约为5%(原子分数).X射线衍射(XRD)结果表明Sn掺杂ZnO纳米带为单相纤锌矿结构.X射线光电子能谱(XPS)表明样品中Sn的价态为4+.样品的室温光致发光谱(PL)在445.8nm处存在较强的蓝光发射峰,对其发光机制进行了分析.     

Al掺杂浓度对氧化锌纳米棒结构和光学性能的影响

采用水热合成法以15min的溅射时间,0.7Pa的溅射压强制备的ZnO种子层玻璃片为衬底,制备出具有较好光致发光性能的Al掺杂ZnO纳米棒。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和光致发光谱(PL)谱表征了样品的晶体结构、表面形貌和光致发光性能。结果表明,不同的Al掺杂浓度对于ZnO纳米棒产生了一定的影响,适当的Al掺杂使ZnO纳米棒的c轴择优取向更好,改善了ZnO的近紫外发光和蓝色发光特性。其结晶质量随着Al掺杂量的增加而降低,而且纳米棒的顶端在逐渐变细。随着Al~(3+)浓度的增加,纳米棒的光学性能先变好后变差,在Zn~(2+)与Al~(3+)的浓度比为1∶0.02时,纳米棒的光学性能效果最佳,紫外发光峰强度最大,并且出现了蓝移。     

ZnO纳米带梳的制备及生长机理的研究

采用化学气相沉积(CVD)法成功制备出ZnO纳米带梳,实验过程不需要催化剂.X射线衍射仪(XRD)分析结果表明,ZnO纳米带梳为高度结晶的六方纤锌矿结构;利用扫描电子显微镜(SEM)观测,所制样品是由纳米带组成梳状形貌,纳米带梳的形成经过两个步骤:先通过VS机制形成微米带,而梳的齿通过自催化生长平行于(0001)极性面形成.对样品的光致荧光(PL)谱测量发现了位于～395nm和495nm处的室温光致发光峰.     

水热法制备掺铝氧化锌纳米棒阵列及其光学特性

采用水热法,在ZnO种子层上制备出不同Al掺杂量的ZnO纳米棒阵列薄膜,利用XRD、SEM、TEM、PL等检测手段对样品进行结构、形貌和发光性能分析.结果表明,纳米棒属于六方纤锌矿结构,具有垂直基底沿[002]方向生长的特征,PL谱上存在强的近紫外辐射峰.随着掺杂量的增加,纳米棒直径略有减小,近紫外辐射峰蓝移,强度先增加后减小,证明掺杂会形成非辐射中心,探讨了Al掺杂ZnO纳米棒阵列的发光机理.     

Zn_(1-x)Mn_xS稀磁半导体的水热法制备及其性能

以乙二胺为修饰剂,采用水热法合成了不同掺杂比例的Zn_(1-x)Mn_xS(x=0,0.02,0.05,0.07)稀磁半导体材料,并通过XRD、FESEM、HRTEM、XEDS、光致发光光谱(PL)和振动样品磁强计(VSM)对样品的晶体结构、形貌、光学性能和磁学性能进行表征。实验结果表明:本方法制备的所有样品具有结晶良好的纤锌矿结构,没有杂峰出现;样品形貌为一维的纳米棒状,分散性良好;掺杂的Mn2+以替代Zn2+的形式进入到ZnS晶格中,随着Mn掺杂量的增加晶格常数呈现收缩趋势;样品的PL光谱存在明显的紫外发光峰、蓝光发光峰和绿光发光峰,而且峰位发生蓝移;同时一定量的Mn掺杂ZnS纳米晶在室温条件下具有铁磁性。     

Mg掺杂对ZnO纳米纤维发光性能的影响

采用静电纺丝法在Si基底上制备了不同Mg掺杂浓度的ZnO纳米纤维膜,利用扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、光致发光(PL)等手段对不同Mg掺杂浓度ZnO纳米纤维膜的表面形貌、晶体结构、化学成分、发光性能进行研究。SEM结果表明MgxZn1-xO纳米纤维的直径在50~300nm。XRD结果表明在Mg掺杂浓度低于15%(x=0.15)时,晶体呈现ZnO六角纤锌矿结构,当掺杂浓度达到20%(x=0.2)时,晶体出现MgO的分相。XPS结果表明Mg已成功掺入到ZnO纳米纤维中。PL谱表明MgxZn1-xO纤维膜具有较强的紫外发射,而可见发射几乎观察不到,随着Mg掺杂浓度的增加,紫外发光峰明显蓝移且发光强度增加。     

Cu掺杂ZnO纳米粒子的光学性能及铁磁性

利用溶胶凝胶法制备了纳米结构的Cu掺杂ZnO基稀磁半导体,通过X射线衍射分析表明,样品为纯相ZnO纤锌矿结构,磁性测量表明样品在室温下呈室温铁磁性,铁磁性来源为氧化锌晶格中的缺陷与Cu2+离子之间的交换作用。室温光致发光(PL)谱观察到紫外带边和可见光区两个发射峰,且随着Cu掺杂量增加,紫外峰淬灭,可见峰发射增强。     

Cr掺杂ZnO薄膜晶体结构及光学性能的研究

采用磁控溅射法在载玻片上制备了不同Cr掺杂浓度的ZnO薄膜,并对其紫外发光性能做了初步研究.XRD结果表明,所制备的样品具有纤锌矿结构,呈c轴择优取向生长;透射谱表明,改变Cr掺杂浓度可以使ZnO薄膜的吸收边向短波方向移动,并且薄膜的禁带宽度连续可调;光致发光(PL)谱表明,所有样品的PL谱由发光中心位于370nm的紫外发光峰组成,且该峰的峰位蓝移,与吸收边缘移动的结果吻合.2.0%(原子分数,下同)的Cr掺杂可以提高ZnO的紫外发光强度,而过量的Cr掺杂反而会降低其紫外发光强度.     

ZnO缓冲层上低温生长Al掺杂的ZnO薄膜

采用射频磁控溅射法在ZnO缓冲层上制备了不同Al掺杂量的ZnO（AZO）薄膜。利用X射线衍射（XRD）、扫描电子显微镜（SEM）和光致发光（PL）等表征技术,研究了AZO薄膜的微观结构、表面形貌和发光特性。结果表明,随着Al掺杂量的增加,ZnO薄膜的择优取向性发生了改变,且当Al的掺杂量为0.81%（原子分数）时,（002）衍射峰与其它衍射峰强度的比值达到最大,表明适合的Al掺杂使ZnO薄膜的择优取向性得到了改善。在可见光范围内薄膜的平均透过率超过70%。通过对样品光致发光（PL）谱的研究,发现所有样品出现了3个发光峰,分别对应于以444nm（2.80eV）、483nm（2.57eV）为中心的蓝光发光峰和以521nm（2.38eV）为中心较弱的绿光峰。并对样品的发光机理进行了详细的探讨。     

Mn、Co掺杂ZnO薄膜结构及发光特性研究

利用脉冲激光沉积(PLD)方法在Si(100)衬底上制备了ZnO、Zn0.8Mn0.2O、Zn0.8Co0.2O薄膜.薄膜的晶体结构和表面形貌采用X射线衍射仪和原子力显微镜测试.表明薄膜具有明显的c轴择优生长取向,薄膜表面较为平整,颗粒尺寸在纳米量级,薄膜中晶粒的生长模式为"柱状"模式.此外,Mn、Co掺入后,薄膜的X射线衍射峰有小角度偏移,这与 Mn2 、Co2 离子半径有关.PL谱显示Mn、Co掺杂ZnO薄膜的蓝、绿发光峰的位置相对纯的ZnO薄膜没有改变,还出现了紫外发光峰,其中Mn掺杂的蓝、绿光峰的强度减弱,Co掺杂的蓝光峰强度减弱,绿光峰强度增强.这是因为Mn、Co掺入改变了ZnO本征缺陷的浓度,发光峰的强度也随之而改变.     

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.     

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.……     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

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.