三甲基镓,三乙基铝直接气相色谱分析方法的研究

用直接气相色谱法对三甲基镓和三乙基铝进行了分析,探讨了不同条件下的色谱行为。对有机杂质碘甲烷等进行了定性和定量分析。     

芯-壳结构/GaAs-AlGaAs纳米线中AlGaAs壳材料均匀性研究

Ⅲ-Ⅴ族半导体纳米线材料被认为是高速光电探测器最有前途的材料之一。采用金属有机化学气相沉积法在GaAs(111)B衬底上生长芯-壳结构/GaAs-AlGaAs纳米线材料,GaAs芯材料的生长机制为气相-液相-固相,而AlGaAs壳材料的生长机制为气相-固相。采用场发射扫描电子显微镜和微区光荧光谱仪等测试分析手段研究了AlGaAs壳材料横向、轴向和生长方向的均匀性,探讨了生长机制对均匀性的影响。在此基础上获得了组分均匀的高晶体质量的AlGaAs壳材料,其Al组分为0.14。     

烷基镓化合物的生产工艺

在以金属卤化物作为辅助碱的条件下,卤化镓化合物与烷基卤化铝反应生产烷基镓化合物。最好使用与氯化镓相应的金属卤化物和第Ⅰ—Ⅲ族金属氯化物作辅助碱。由于作为副产物而得到的二烷基铝卤化物在镓-卤键上不能进一步的烷基化,更何况烷基铝二卤化物。出人意料,目前人们发现当加入辅助碱,如第Ⅰ主族和第Ⅱ主族卤化物时,烷基铝二卤化物完全能够同镓上的卤原子定量地交换烷基。此外在相同的反应条件下,也可使用二烷基铝卤化物和三烷基铝以及与烷基铝二氯化物的混合物(即工     

无催化β-Ga2O3纳米棒的可控制备

由于氧化镓(Ga₂O₃)纳米棒具有独特的物理和化学性质,在纳米光电子器件等领域具有广泛的应用前景,因此氧化镓纳米棒的可控制备具有十分重要的意义。本文采用化学气相沉积(CVD)的方法,在无催化条件下,在硅Si(100)衬底上成功生长出β-Ga₂O₃纳米棒。通过X射线衍射仪、场发射扫描电子显微镜等表征,发现氧化镓纳米棒按照气-固(V-S)机制生长,当生长温度从850℃升高到950℃时,纳米棒的密度、直径和长度增加,纳米棒的形貌从杂乱无序的随机生长转变为沿衬底垂直且具有不同夹角方向生长。结果表明,反应温度和氧气浓度决定了氧化镓纳米棒的形貌和尺寸,通过控制温度和氧气浓度能够有效调控氧化镓纳米棒的形貌和光学性能。     

美开发出合金制氢新工艺

我的汽车只"喝"水美国普度大学的研究人员最近开发出一种利用铝镓合金加水制造氢气的新工艺。将水添加到铝镓合金时,铝通过吸收氧气分解水,在此过程中产生氢气。合金中的镓是关键成分,因为铝和氧结合后在铝的表面形成一层氧化铝膜,而镓能阻止这个膜的形成,使反应继续下去,直到所有的铝都被用来产生氢气。     

反应温度对碳纳米管的影响

本文利用化学气相沉积( CVD)法,以乙烯为碳源气体,二茂铁为催化剂,在二氧化硅上制备出一系列碳纳米管,并通过拉曼光谱和扫描电子显微镜( SEM)对其形貌、结构和组分进行表征,分析反应温度对碳纳米管的影响.研究发现:当反应温度为860℃时,有均匀的碳纳米管薄膜生成,其管径和长度分别达到104 nm和95 μm,同时结构缺陷少,非碳管杂质较少,纯度较高.     

圆柱形光子晶体微波反应腔的加热效率和均匀性研究

微波加热具有瞬时、可控、高效等优点,已被广泛应用于新材料制备、核工业、名贵药材干燥、化学反应催化、食品加热等方面。微波反应腔作为微波加热系统的关键设备,其更加合理的设计对提升微波加热的效率、均匀性、可控性都具有决定性意义。基于光子晶体对电磁波的布拉格散射特性,将微波波段的光子晶体引入到传统圆柱形微波反应腔中,设计了一款新型圆柱形光子晶体微波反应腔。在此基础上,仿真研究了光子晶体对加热效率和均匀性的影响规律。研究结果表明,相较传统圆柱形微波反应腔,圆柱形光子晶体微波反应腔具有更高的加热效率和均匀性。     

三级冷阱预浓缩—气相色谱/质谱法测定气体包装容器中有机物

研究采用苏玛罐系统预浓缩技术对气体包装容器中有机物进行预浓缩,以气相色谱毛细管色谱柱分离,质谱定性定量,建立了三级冷阱预浓缩-气相色谱/质谱法测定气体包装容器中苯乙烯等51种有机物组分的方法.实验探究了色谱柱温度及预浓缩温度对样品检测的影响,完成的苯乙烯等51种组分检测方法标准曲线线性相关系数在0.994～1.000,回收率在61.28％ ～111.4％,相对标准偏差在0.48％ ～11.73％.该方法操作简单,在极低浓度水平下,线性浓度范围内具有线性关系良好、测定精密度好及回收率较高等特点,该方法可应用于实际标准气体、高纯气体包装气瓶等容器及其盛装的产品气中有机物的检测.     

CVD法SiC纤维的强度与表面状态

采用射频加热ＣＶＤ法制备出连续ＳｉＣ纤维，观察和分析了纤维表面微观形貌与纤维强度及制备工艺参数之间的关系。结果表明，纤维强度与纤维表面光滑性，晶粒生长的均匀性，致密性有直接关系。而ＣＶＤ过程的温度、反应气体组分及流量、钨丝载体清洁度是决定ＳｉＣ纤维表面微观形貌的关键因素。     

银/碳微球复合材料的制备和表征

用强酸和二氯化锡对化学气相沉积法制备的碳微球(CMSs)进行活化之后,在含活化CMSs的悬浮液中顺序加入聚乙烯砒咯烷酮、硝酸银及水合肼,在加热条件下制备了银纳米颗粒/CMSs复合物.研究了反应过程中硝酸银溶液和水合肼溶液的用量对产物形貌的影响.用场发射扫描电子显微镜、透射电子显微镜和x射线衍射仪表征了产物的形貌和结构特征.结果表明:经过混酸及二氯化锡处理的CMSs在乙醇溶液中与硝酸银、水合肼在加热条件下反应,可以在其表面沉积尺寸较小、分布均匀的银纳米颗粒.     

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.