基于EBSD方法测定单晶Cu纳米压痕的各向异性实验

为研究单晶Cu材料的各向异性力学特性,针对单晶连铸技术制备的单晶Cu,采用电子背散射衍射(EBSD)法对其3个不同晶粒的晶面进行定向,利用原位纳米压痕仪在不同晶面进行不同压入载荷的纳米压痕实验.通过EBSD分析,发现用单晶连铸技术制备的单晶Cu在拉拔方向上具有较强的择优取向,单个晶粒较大,且晶粒内部没有(亚)晶界存在.纳米压痕实验结果表明单晶Cu样件在各种压痕载荷下的约化模量为50 GPa～120GPa,材料的晶体取向对纳米压痕载荷-位移曲线和约化模量有很大影响,面(032)比面(119)和面(041)有更大的约化模量.不同载荷下,硬度值在0.8 GPa左右变动,晶体取向对硬度的影响较小.实验所得单晶Cu各晶面约化模量与采用金属弹性力学理论计算所得数值吻合较好.     

MgO表面的第一性原理研究

MgO薄膜被认为是等离子体显示器件中介质保护膜的最理想材料。本文基于第一性原理的密度泛函理论,结合格林函数G和动力学屏蔽库仑相互作用W纠正和Bethe-Salpeter方程的求解,研究了MgO不同晶面取向表面结构的电子特性和光谱特性。在分析不同晶面取向表面能带结构、态密度分布的基础上,估算了相应的二次电子发射系数。结果表明:(100)、(110)和(111)三种晶面取向,(100)禁带宽度最小,二次电子发射系数最大。而(111)晶面吸附氢原子后,禁带宽度显著减小,二次电子发射系数优于(100)晶面,是高Xe、高气压工作气体下等离子体显示器介质保护层材料MgO的优选取向。激子光谱计算结果表明,MgO表面有强激子效应,有利于外电子发射。合理选择MgO晶面取向,可有效提高等离子体显示器放电效率、降低其着火电压,减小Jitter时间。     

锌单晶的制备及不同晶面的电化学行为

通过坩埚下降法制备了单晶锌,同时采用金相实验和XRD分析了所生长的锌单晶,并用塔菲尔曲线外推法、循环伏安法分别研究了锌单晶(002)晶面电极和(100)晶面电极在6.0mol·L-1的KOH溶液中的电化学行为.结果表明:在6.0mol·L-1的KOH溶液中,锌单晶(002)晶面电极的腐蚀速度小于(100)晶面电极;锌单晶(002)晶面电极氧化还原可逆性优于锌单晶(100)晶面电极,锌单晶(100)晶面电极的氧化和还原能力优于锌单晶(002)晶面电极.     

Al-Y-TZP陶瓷的抗热震行为与相变的关系

研究了不同 Y_2O_3添加剂含量的2mol% Al_2O_3-ZrO_2陶瓷的相变增韧和强化以及热震损伤行为。分析了材料的抗热震性和断裂参数(K_(1c),σ_f,γ_f)之间的关系。在实验的基础上阐明了四种 ZrO_2材料的热震损伤行为由抗热震参数(R′,R″,R_(8t))控制,并分别受到下述因素的影响:a.应力诱发相变的增韧和强化;b.抑制四方 ZrO_2相变的内约束力所起的强化作用;c.与无外应力下的相变开裂相关的增韧和强度衰减;d.热震裂纹成核引起的增韧。     

La1-xNdxB6单晶的制备及热电子发射性能

以LaB_6和NdB_6粉末为原料,采用区域熔炼法成功制备了大尺寸、高质量的多元稀土六硼化物La_(1-x)Nd_xB_6(x=0.1~0.3)单晶,并测试了该系列单晶(100)晶面的热电子发射性能。本实验制备的单晶长度大于40mm,直径大于4mm。单晶衍射、劳埃照片、晶面摇摆曲线、单晶断口扫描等检测结果表明单晶质量较高,热发射测试结果表明在1 873K、4 000V下,单晶零场电流发射密度随着Nd含量增加从6.01A/cm~2降为4.83A/cm~2,有效逸出功从2.88eV增大到2.95eV。     

单晶取向及其分布两种测定方法的对比

单晶取向的判断是单晶生长和加工过程中的重要环节，比较研究了摇摆曲线法和旋转定向法两种测定方法在判断单晶取向性问题中的优缺点。结果表明：对于生长较好的单晶材料，摇摆曲线法定义材料结晶质量的准确性较高；而旋转定向法能很好地解决取向性材料晶面间距相同的重叠峰的分离问题。     

单晶La_(0.2)Ce_(0.8)B_6的制备、表征及热发射性能研究

采用区域熔炼法制备了大尺寸、高质量多元稀土六硼化物La_(0.2)Ce_(0.8)B_6单晶体。结合X射线劳埃定向法对(110)和(310)晶面进行了定向,并系统研究了热发射性能。结果表明,当阴极温度为1 673,1 773和1 873K时(110)和(310)晶面最大电流密度分别为3.60,7.73,12.44A/cm~2和3.25,11.67,16.93A/cm~2。表明晶面间发射性能存在"各向异性"的特点。不同发射温度下的(110)和(310)晶面平均有效逸出功分别为2.85和2.80eV,表明单晶La_(0.2)Ce_(0.8)B_6具有良好的热发射性能。     

CH3NH3PbI3晶体的晶轴对其光电性能的影响

通过逆温结晶的方法制备了CH_3NH_3PbI_3单晶,用扫描电子显微镜观察晶体形貌、X射线粉末衍射仪测量晶体结构、拉曼光谱仪测量晶体光谱。此外,通过X射线单晶衍射仪确定了晶面方向,分别沿平行和垂直于晶体c轴方向对晶体进行切割,经打磨、抛光后在其对应的晶面上蒸镀电极进而制备出基于CH_3NH_3PbI_3单晶的光探测器。采用不同波长和偏振方向的激光照射光探测器的受光面后,测试了器件的光电特性。实验结果表明,当激光的电场分量E平行于晶体的晶轴时光探测器的光电流密度比电场分量E垂直于晶轴时(垂直样品)的光电流密度大两个数量级。通过计算得到,激光的电场分量E平行于晶体晶轴时,光探测器的光响应度(R)是垂直样品的58倍、光暗电流比(P)的10倍和外量子效率(EQE)的66倍。发现CH_3NH_3PbI_3单晶的晶轴对晶体的光电性能影响很大。     

方形γ-MnOOH单晶的水热法制备

在150℃水热条件下, 用HMnO₄氧化Mn(CH₃COO)₂, 制备出了方形γ-MnOOH单晶. 反应过程中使用HMnO₄为氧化剂, 不引入任何金属阳离子杂质. 通过XRD、SEM、TEM、HRTEM、TG等方法研究发现, γ-MnOOH单晶的形成经过两个主要阶段: (1)反应初期生成γ-MnO₂晶须; (2)在水热系统中, 晶须按照吸附生长机理生长, 由于各个晶面的表面能的不同, (111)晶面首先快速生长, 再沿其他方向生长, 形成方形γ-MnOOH单晶. 反应时间是影响晶体形态的主要因素. TG结果证明γ-MnOOH单晶在350℃下开始转化成MnO₂.     

一种测定晶体取向及其分布的简便XRD方法

提出了旋转定向测试法，其原理是使试样的在粉末X射线衍射仪上进行θ扫描的同时绕其端面法线自转，增加了晶面法线通过衍射平面的机会。通过这种方法可直观地区分取向多晶，准单晶或者单晶体，评定研制过程中准单晶和择优取向材料的晶体品质，确定单晶，准单晶及择优取向等材料的晶面相对宏观端面的晶向偏离角和取向分散度，还可对单晶体材料进行三维晶面定向。旋转定向法测试晶体取向具有快速简便，一机多用，精度高等优点，在电子、光学、磁性，机械等材料研究领域具在广泛的应用。     

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.     

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.……     

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 ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.