电脉冲空化制备超细镍磷粉体材料的理论与实验研究

本文从热力学和动力学角度分析了利用电脉冲空化制备超细镍磷粉体材料的可能性,并从实验上成功制备出粒径可控的镍磷合金粉体材料,研究结果表明电脉冲空化制备镍磷合金粉体材料的形核与长大过程主要受脉冲能量、脉冲方式、反应时间等多重因素控制.反应初期(60秒以内),反应形核受脉冲能量控制,镍磷合金粉体颗粒数随脉冲放电能量(包括脉冲电压和脉冲次数)的增加而增加;随反应时间延长(超过60秒),脉冲空化导致镍磷非晶合金粉体的反应被激活,溶液中镍磷粉体可自发形核、生长,直至反应完成.     

聚焦超声辅助电火花制备多尺度镍粉时超声功率对镍粉粒径的影响

电火花-超声复合加工技术是一种绿色环保、易于控制的制备微纳米金属粉末的方法。为了研究聚焦超声功率对微纳米金属粉末形貌和粒径分布的影响,本工作通过COMSOL Multiphasic仿真软件模拟超声在工作箱中的声压分布,确定放电位置,并根据仿真结果,采用实验室自制设备以镍棒为电极在纯水中进行实验。实验结束后观察微米尺度与纳米尺度镍粉的形貌,并分析微纳米镍粉的粒径分布。结果表明:聚焦超声的空化和振动效应能有效地破碎固液相中的金属蒸气团簇和金属液滴,便于制备出小尺寸的镍颗粒,并使其均匀地分布在溶液中;声空化产生的冲击波使镍颗粒发生碰撞,大尺寸的镍颗粒在撞击点处产生的高温使镍粉发生烧结,形成金属烧结颈,多个球形颗粒团聚成不规则的大颗粒;小尺寸的镍颗粒由于粒径小,发生碰撞后产生的能量不足以使其团聚。     

超声化学法制备无机纳米材料的研究进展

由于纳米材料具有许多不同于本体材料的优良性能,因此纳米材料的制备与应用是近年来材料科学研究的热点。超声化学法是一种制备特异性能纳米材料的有效途径。超声波对反应体系的作用主要表现在:利用超声能量进行分散,利用空化过程进行高温分解,利用剪切破碎机理对颗粒尺寸进行控制,利用机械搅动影响沉淀的形成过程。本文中介绍了超声化学法制备纳米材料的原理,并详细介绍了超声化学法在制备纳米金属及合金、纳米金属氧化物及其它纳米金属化合物方面的应用。     

反应合成银氧化锡电接触材料抗熔蚀性研究

采用反应合成技术和传统粉末冶金技术制备银氧化锡(AgSnO2)电接触材料，利用千瓦级CO2激光器模仿电弧作用在试样表面产生局部熔化。对AgSnO2块体材料进行抗熔蚀性测试，对块体材料及冷拉拔的AgSnO2线材进行显微组织分析(扫描电镜、透射电镜)。研究结果表明，采用反应合成技术可以在银基体中合成尺寸细小、界面新鲜的SnO2颗粒，制备AgSnO2电接触材料；用反应合成法制备的AgSnO2材料中，微米级的SnO2颗粒系由纳米级的SnO2颗粒聚集而成；用反应合成法制备的AgSnO2电接触材料由于改变了银和SnO2的结合状态使材料的抗熔蚀性得到改善和提高。     

自蔓延法制备ZrO2-Y2O3纳米粒子的影响因素

采用自蔓延法制备ZrO2-Y2O3(YSZ)纳米粒子。研究了反应中柠檬酸与硝酸盐比例(c／n)对反应产物的影响以及对纳米晶粒尺寸的影响，并且探讨了分散剂的作用机理，在制备过程中添加分散剂磷酸酯(PE)对YSZ纳米颗粒尺寸的影响及其作用机制。结果表明，反应中柠檬酸与硝酸盐的最佳比例为0．56，此时可获得的晶粒尺寸为12nm；分散剂PE加入量为ZrOCl2质量的2％时，分散效果最好，获得的纳米颗粒团聚最小(30-70nm)。     

Al2O3/Ni包裹粉体的制备、烧结行为及其显微结构研究

利用非均相沉淀包裹技术,在铝无机盐溶液中制备出氧化铝前驱体包裹纳米镍颗粒的复合粉体,并通过能量发射能谱（EDS）以及俄歇电子能谱（AES）研究包裹粉体的成分构成,发现镍纳米颗料表面均匀地包裹一层氧化铝的前驱体。燃烧后的包裹粉体在氩气氛中进行热压烧结。结果表明,与溶胶－凝胶法制备的粉体相比,包裹粉体可以在较低的温度下达到致密化,烧结后的材料其显微结构明显不同于环磨粉体烧成的材料,否认在氧化铝晶界或晶内,镍颗粒与氧化铝之间都有孔隙,这是由于镍的热膨胀系数与氧化铝的热膨胀系数大引起的,Al2O3/Ni复合材料的断裂方式以及沿晶断裂为主。     

一种制备一维纳米材料的新方法--固相转化法

利用微乳技术和固体反应方法分别合成了锰的氢氧化物和单质锡纳米颗粒前驱体(直径D≤20 nm).首次将熔盐技术应用于一维蚋米材料的合成,以纳米颗粒前驱体为原料制备了一维纳米结构蚋米棒、纳米线和纳米带;并发现了一维蚋米结构生长的新现象,即蚋米颗粒固相自生长.通过TEM,记录了纳米颗粒前驱体生长的中间体--项链状纳米线.实验分析了熔盐介质、热处理温度和颗粒临界尺寸对纳米颗粒自组织生长的影响,提出了固相生长机理模型.     

火焰CVD法制备含碳纳米TiO2的研究

本文报道了工业丙烷/空气火焰气相沉积法制备含碳纳米TiO2颗粒材料的实验与分析结果。讨论了O2／C3H8摩尔比在2—9范围内对火焰温度和火焰长度的影响，火焰温度对含碳纳米TiO2晶型的影响，O2／C3H8摩尔比和火焰中TiO2颗粒浓度对含碳纳米TiO2碳含量的影响，关联了含碳纳米TiO2的平均尺寸与颗粒长大准数的关系。     

电沉积制备纳米镍的拉伸变形行为

为了系统研究纳米材料的超塑性变形特点,用电沉积方法制备了平均晶粒尺寸为70 nm的纳米镍.采用单向拉伸实验研究了其在室温和高温时的力学性能,并用透射电子显微镜TEM、扫描电子显微镜SEM和X射线能谱仪EDS观察分析了纳米镍变形前后的显微组织.实验结果表明:制备的纳米镍在室温时表现出的延伸率很低,但强度可达1000 MPa以上.当温度升高至450℃,应变速率为1.67×10-3 s-1时单向拉伸实验得到380%的延伸率,说明制备的纳米镍具有低温超塑性性能.实验过程中,材料内部的晶粒发生明显的长大与拉长.拉伸过程中形成的氧化物夹杂成为裂纹源,断口表现为沿晶断裂.     

纳米铜及稀土铜合金粉的研究进展

综述了目前纳米铜粉制备过程中解决纳米颗粒容易团聚及防止纳米铜粉氧化的方法，重点介绍纳米稀土对纳米铜粉颗粒团聚的抑制作用。研究中发现稀土元素对铜的性能有极大的促进作用，在此基础上，展望了稀土铜合金粉这种高效产品的应用前景。     

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.……     

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...     

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.……     

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.     

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