一种提高金刚石薄膜形核密度的新方法

报导了一种提高火焰法合成高质量金刚石薄膜形核密度的新方法-化学腐蚀法;研究了在化学腐蚀试样表面上金刚石的形核与生长行为、晶粒度与形核密度之间的关系。试验表明:经腐蚀后的样品,金刚石形核均匀致密,2min内便能形成连续的膜。金刚石形核密度随晶粒度的增加而增大。初步分析了化学腐蚀法提高形核密度的原因,认为晶界对金刚石的形核起重要作用。     

WC和Si衬底生长金刚石薄膜的研究

采用ＳＥＭ,Ｒａｍａｎ光谱等手段,较全面系统地研究了ＨＦＣＶＤ法在ＷＣ和Ｓｉ衬底上生长金刚石薄膜时,衬底预处理、碳源深度、热丝及衬底温度等对金刚石形核、生长的影响。并对两种衬底进行了对比与分析,最后总结出影响金刚石形核密度、形核速率、晶形结构及晶形完善性的关键因素。     

采用正交法研究金刚石偏压形核

在微波等离子体化学气相沉积装置中 ,采用正交试验法研究金刚石在镜面抛光的Si( 1 0 0 )面上的偏压形核过程中 ,形核时间、偏压电压、气压及甲烷浓度对形核密度的影响 ,研究结果表明 :形核密度随形核时间的增加而增加 ,适中的偏压电压和沉积气压有利于金刚石的形核 ,而甲烷浓度的影响很小。正交试验所得的最佳形核条件为偏压 -1 5 0V ;时间 1 2min ;气压 4kPa;CH4 比率 5 % ,在该条件下金刚石的形核密度达到 1 0 1 0 个 cm2 。     

大面积长生金刚石相关物理参量的空间分布

研究了在热丝化学气相生长金刚石的过程中,衬底温度、衬底表面附近的气体温度以及气流的质量流密度分布对金刚石膜的形核和生长的影响。模拟计算结果表明,这三个参量是空间位置的参数,在某些区域,这三个参量均匀分布。当热丝阵列面与衬底间距离超过７ｍｍ之后,这三个参量在衬底上有一个较大的均匀区域,在该区域的两侧,各参量值显著变化。在衬底中心的均匀区域,金刚石膜晶形清楚而致密;偏离该区域,这三个参量数值明显下降,形核密度和生长速度较低,三个参量均匀的区域可作为金刚石大面积均匀的形核和生长的位置。     

大面积生长金刚石相关物理参量的空间分布

研究了在热丝化学气相生长金刚石的过程中,衬底温度,衬底表面附近的气体温度以及气流的质量流密度分布对金刚石膜的形核和生长的影响模拟计算结果表明,这三个参量是空间位置的函数,在某些区域,这三个参量均匀分布当热丝阵列面与衬底间距离超过7mm之后,这三个参量在衬底上有一个较大的均匀区域,在该区域的两侧,各参量值显著变化在衬底中心的均匀区域,金刚石膜晶形清楚而致密;偏离该区域,这三个参量数值明显下降,形核密度和生长速度较低,三个参量值均匀的区域可作为金刚石大面积均匀的形核和生长的位置.     

铱衬底上金刚石外延形核与生长:第一性原理计算

异质外延为金刚石晶圆合成提供了一个有效的实现路径,而Ir衬底上金刚石形核生长技术经过20多年的发展已经有能力制备最大直径为3.5英寸的晶体,开启了金刚石作为终极半导体在电子信息产业应用的大门。然而,表面形核、偏压技术窗口、金刚石外延生长等一系列发生在异质衬底上的问题都需要从生长热力学的角度给予解释。本研究针对化学气相沉积气氛中金刚石如何实现外延形核与生长这一关键问题,利用第一性原理计算从原子尺度对金刚石形核生长过程展开了系列探究。研究结果如下:C原子在Ir衬底表面位点吸附比在体相位点吸附更稳定,表明无偏压条件下金刚石形核只能在衬底表面发生;离子轰击作用下非晶氢化碳层中sp3杂化C原子个数随着离子动能的增加呈现先增大后减小的变化规律,证实了金刚石高密度形核存在一定的离子动能与偏压大小窗口;金刚石沿着Ir衬底外延生长时界面结合能最低(约为–0.58 eV/C),意味着界面结合能是决定外延形核生长的主要热力学因素。本研究阐明了偏压辅助离子轰击促进金刚石单晶外延生长的热力学机制,对于指导金刚石及其他碳基半导体生长具有重要意义。     

铱衬底上异质外延单晶金刚石:过程与机理

金刚石因其独特的物理化学性质,在探测器、光电子器件等领域得到了广泛的应用,单晶金刚石更是因为具有大幅度提高这些器件功能的潜力而引起了众多学者的关注。目前在铱(Ir)衬底上异质外延生长的单晶金刚石具有最大尺寸和较为优异的生长质量。本文介绍了可用于外延金刚石的不同结构的衬底以及金刚石在铱(Ir)衬底上的形核和生长过程,重点阐述了金刚石偏压辅助形核(BEN)和外延横向生长(ELO)的机理,以及衬底图形化形核生长技术,指出了目前研究存在的不足,并对金刚石异质外延理论和实验研究方向进行了展望。     

HFCVD金刚石薄膜在Mo基体表面的形核

采用热丝化学气相沉积(HFCVD)方法在Mo基体上沉积金刚石薄膜,使用扫描电镜(SEM)和X射线衍射(XRD)对薄膜样品进行分析检测,研究了表面形核密度随碳源浓度的变化.结果表明:随着碳源浓度增加表面形核密度增大,当碳源浓度达到3%时,表面形核密度质量最佳,当浓度进一步增大时,形核密度下降;随着碳源浓度增加,生长加快,当生长过快时影响形核过程,形核密度下降.     

用于X射线光刻掩模的纳米金刚石膜成核研究

介绍了金刚石膜在下一代X射线光刻掩模中应用的必要性;通过调节衬底温度,改变生长时间、控制甲烷浓度等工艺措施,实验研究了不同参数对成核密度及成核质量的影响,获得了高密度形核的样品;对形核后的预生长期进行了工艺优化,有效地控制了核岛的优势生长,总结出了一套优化的形核方案,即甲烷浓度4％,衬底温度700℃,形核时间14min;这套工艺不仅改善了自支撑金刚石薄膜窗口的光学性能,还有效地降低了膜的内应力。     

红外光学材料硫化锌衬底上沉积金刚石膜的研究

采用微波等离子体化学气相沉积法,在预镀陶瓷过渡层的硫化锌衬底上沉积金刚石膜。在以前的实验中,我们发现在陶瓷过渡层上沉积金刚石膜极其困难,但采用金刚石诱导形核方法后,我们已经在过渡层／硫化锌试样表面获得了很小面积（约1mm宽的环状区域）的金刚石形核。本文对前期的诱导形核工作进行了一定改进,目前已经使形核生长范围大大增加,沉积面积超过原来10倍。此外,本文对金刚石／过渡层／硫化锌试样的红外透过特性以及金刚石膜质量等进行了评价。     

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.……     

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.     

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.     

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 ...