高压PLD法生长ZnO和Zn1-xMgxO纳米棒及其荧光性能

利用自主设计、组装的高压脉冲激光沉积(PLD)系统,研究了温度、靶材、催化剂厚度等生长参数对ZnO和Zn1-xMgxO纳米棒生长的影响,并对ZnO纳米棒的生长机理和Zn1-xMgxO纳米棒的光致发光性能进行了探讨.实验发现,当金膜催化剂厚度为2 nm、温度为925℃时,在单晶Si衬底上生长了直径均匀的ZnO纳米棒阵列,且具有明显的(002)择优生长取向.实验发现温度与催化剂厚度是影响ZnO纳米棒的直径和生长密度的重要因素.据此提出了ZnO纳米棒阵列的高压PLD生长过程应为气–液–固和气–固相结合的生长机制.通过在ZnO靶材中掺入氧化镁,获得了Zn1-xMgxO纳米线和纳米带结构,但生长无明显的择优取向.光致发光谱测量表明,镁掺杂明显增大了ZnO的带隙,但也在其禁带中引入了缺陷能级,导致可见发光明显增强.     

一维纳米氧化锌的场发射性能和光学性能研究

采用真空热蒸发法在不同的制备温度下,制备出了准阵列状和阵列状一维纳米ZnO结构。并利用X射线衍射、扫描电子显微镜、场发射测试仪、光致发光谱对ZnO纳米材料的结晶质量、形貌及场发射性能进行了分析研究。阵列状纳米氧化锌有较明显的择优生长取向。准阵列状纳米氧化锌的场发射性能优于阵列状纳米氧化锌。并通过对PL谱的对比分析得出,准阵列状纳米结构的结晶质量较好,阵列状纳米结构中存在的缺陷较多。     

脉冲激光沉积(PLD)法生长纳米ZnO薄膜的探索

在Si衬底上用脉冲激光沉积法生长C轴取向高度一致的ZnO纳米薄膜.实验制备ZnO纳米结构,其颗粒尺寸的控制是关键.通过改变衬底温度(400～700℃)和沉积时间,获得不同的ZnO纳米结构.SEM观察,在600℃时颗粒均匀且间隔明显,且该薄膜结构为不连续膜,这与其他衬底温度下所形成的薄膜结构有很大差异.XRD显示,600～700℃结晶良好.     

纳米碳管/氧化锌异质结构的合成及发光性质

以纳米碳管（CNTs）为基体、铜为催化剂,采用催化碳热还原方法直接合成出具有异质结构的纳米碳管/氧化锌（CNT/ZnO）复合材料。利用扫描电镜、透射电镜及X射线衍射等手段研究了异质结构CNT/ZnO复合材料的形态和结构。发现氧化锌纳米线在纳米碳管表面的生长过程遵循催化剂诱导的汽-液-固（VLS）机制;氧化锌纳米线与铜催化剂和纳米碳管之间分别存在明显的界面,并且氧化锌纳米线与纳米碳管均保持了规整的晶体结构。同时也发现在大直径纳米碳管上易于形成高密的氧化锌纳米线;随沉积温度的升高ZnO的形态由线到棒最后形成颗粒。异质结构CNT/ZnO复合材料的诱导发光性能不同于氧化锌纳米线和纳米碳管,在蓝光区域的发光强度远大于紫外发光强度。     

聚乙二醇辅助电沉积ZnO纳米棒阵列的研究

以聚乙二醇（PEG-400）为添加剂,采用恒电位方法直接在ITO导电玻璃上制备了ZnO纳米棒阵列膜,用扫描电子显微镜（SEM）、X射线衍射仪（XRD）等分析手段对ZnO纳米棒阵列的形貌和结构进行了表征。结果表明所得ZnO纳米棒为六方纤锌矿型单晶结构,沿着垂直于基底的c轴极性生长,呈现出均匀的六方棒状形貌;在电沉积初期,PEG-400通过其大分子链的空间位阻作用及包覆作用对ZnO成核粒子的形貌和分散性产生显著影响,进而可以有效调整进一步生长所得ZnO纳米棒阵列的密度和垂直度,当PEG-400在电沉积液中的体积分数为2%时,可以得到取向良好垂直度高的纳米棒阵列;光电性能测试表明,ZnO纳米棒阵列膜电极的光电流随着阵列规整度提高而增大。     

Ag纳米颗粒对ZnO纳米棒阵列膜的光电响应和持续光电导的调控

通过两步法合成了表面修饰Ag纳米颗粒的ZnO纳米棒阵列膜,并检测了该纳米棒阵列膜在波长为365 nm的紫外光照下的时域光电流曲线。与纯ZnO纳米棒阵列膜相比,Ag纳米颗粒修饰后ZnO纳米棒阵列膜在光电响应阶段有更大的响应值,最大达到7 490,约为纯ZnO纳米棒阵列膜响应值的50倍。而且,Ag纳米颗粒对ZnO纳米棒阵列膜弛豫阶段呈现的持续光电导(PPC)效应有很好的调控作用。相同恢复时间内,纯ZnO纳米棒阵列膜光电流恢复效率为25%,Ag纳米颗粒修饰后达到87%。Ag浓度越大,持续光电导(PPC)效应越不明显,这个现象使得通过简单改变表面Ag纳米颗粒的浓度来调控ZnO纳米棒阵列膜的PPC效应成为可能。     

ZnO纳米棒阵列膜的制备及其光电化学性能研究

采用化学溶液沉积法,在ZnO纳米颗粒膜修饰的FTO导电玻璃基底上,制备了ZnO纳米棒阵列。用X射线衍射仪（XRD）、场发射扫描电子显微镜（FESEM）、透射电子显微镜（TEM）对样品进行表征。研究结果表明所制备的ZnO纳米棒为六方纤锌矿相单晶结构,沿c轴择优取向生长,平均直径约为40nm,长度约为900nm;ZnO纳米棒阵列生长致密,取向性较一致。以曙红Y敏化的ZnO纳米棒阵列膜为光阳极制作了染料敏化太阳能电池原型器件,在光照强度为100mW/cm2下,其开路电压为0.418V,短路电流为0.889mA/cm2,总的光电转换效率为0.133%。     

在二氧化钛修饰的基体上生长氧化锌纳米棒阵列的研究

以硝酸锌和六亚甲基四胺为主要原料,采用简单、低温的水热法在预先用金红石二氧化钛薄膜修饰过的硅基体上生长了高取向性的ZnO纳米棒阵列．运用扫描电子显微镜(SEM),透射电子显微镜(TEM)和X射线衍射(XRD)对产物的结构和形貌进行了表征．并且讨论了溶液浓度对ZnO形貌的影响．测试结果表明,在0．025mol／L的Zn(NO3)2·6H2O和C6H12N4水溶液中70℃反应4h后的ZnO纳米棒的平均直径为100nm,平均长度为1μm,属于六方纤锌矿结构且沿c轴择优取向生长．并且对制备出的ZnO纳米棒阵列薄膜进行了室温下的荧光测试,发现ZnO纳米棒阵列膜在389nm处具有很强的紫外发射峰,在466nm处有一个比较弱的发射峰．     

氧化锌纳米棒形貌对ZnO/Cu2O异质结太阳能电池光伏性能的影响

采用电化学沉积法制备了ZnO纳米棒,首先讨论了电化学沉积参数对氧化锌(ZnO)纳米棒形貌的影响,并对不同长度ZnO纳米棒的光吸收和反射等性质进行了研究.实验发现沉积时间是影响纳米棒长度、直径的重要因素,ZnO纳米棒的微观形貌对其光学性质有重要影响.然后以氧化锌纳米棒为n型材料,以氧化亚铜为p型材料,通过电化学沉积法构筑了ZnO/Cu2O异质结太阳能电池,并测试了其光伏性能,研究表明增长纳米棒阵列的长度使得开路电压、短路电流密度及光电转换效率等性能得到提升.最后,综合分析了氧化锌纳米棒形貌与所组装电池的性能之间的关系,发现调控氧化锌纳米棒的形貌是提高ZnO/Cu2O异质结太阳能电池光伏性能的有效途径.     

阵列纳米ZnO的一种新颖的制备方法及其光致发光特性研究

将锌粉、炭粉和氧化锌粉末混合,用简单的热蒸发方法一步就合成了大量的尖锥状纳米ZnO阵列,该方法克服了其它制备方法需要先单独制备催化剂再合成ZnO的缺点而且得到产物不含杂质.用SEM、EDX、XRD和PL对样品进行了形貌、结构和发光特性分析.结果表明,生成的锥状阵列纳米ZnO为六方纤锌矿结构,产物中氧的含量不足,初步探讨了阵列纳米ZnO结构的生长机理和光致发光性质.     

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.     

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.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

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.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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.     

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.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...