改进Stoeber法制备光子晶体用SiO2微球

为获得光子晶体用单分散性较好、表面光滑的SiO2球形颗粒,对传统Stoeber法进行改进,分析了氨水和正硅酸乙酯（TEOS）浓度对SiO2微球粒径的影响,提出了单分散SiO2微球的形成机理,利用X射线衍射分析仪（XRD）和场发射扫描电子显微镜（SEM）对样品结构和形貌进行了表征。XRD分析表明,合成的SiO2微球为无定形态;SEM照片显示SiO2微球粒径在292-750nm范围内,微球粒径偏差均在5％以下。     

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。     

生物模板法制备具有特殊表面形貌的二氧化硅中空微球

利用油菜花粉作为生物模板,通过溶胶在花粉颗粒表面包裹,再经高温烧结去除花粉颗粒的方法制备了具有特殊表面形貌的二氧化硅中空微球. 并通过调节溶胶中醇盐与水的比例,实现了不同表面形貌的二氧化硅中空微球的制备. 利用差热（DSC）、热重（TG）、X射线能谱仪（EDS）、扫描电子显微镜（SEM）等对花粉颗粒和所制备的二氧化硅中空微球进行了表征,并对不同表面形貌的形成机理进行了探讨. 结果表明,花粉内壁在200℃时即可完全消除,从而形成中空结构,而外壁及其表面的网格状结构在较高温度仍能保持完好,从而保证该结构在微球表面的复制,而溶胶浓度则是形成微球表面不同形貌的决定因素,随着胶体粒子在花粉表面沉积量的不同,微球表面的微孔结构也将随之变化.     

超声辅助电火花放电制备微纳米镍颗粒中超声功率对颗粒粒径的影响

超声辅助电火花放电是一种绿色环保、易于控制的制备微纳米金属粉末的方法.为研究超声功率对微纳米金属粉末粒径分布的影响,本工作通过COMSOL仿真软件模拟声压在工作液中随时间的变化趋势,得出不同换能器功率下工作液中的最大声压值.利用测量得到的最大声压值与工作液理论空化阈值的比较确定了换能器的功率值,通过理论计算得到了不同超声功率对粒径的影响范围.最后采用实验室自制设备制备镍粉,通过SEM观测制备的镍粉的形貌,采用激光粒度分析仪分析镍粉的粒径分布,验证了理论分析结果.结果表明:超声的空化与振动效应能够破碎火花放电产生的汽化和熔融金属液滴;工作液中的空化泡破裂所产生的冲击波使小粒径的镍粉颗粒发生碰撞,动能转换成热能,产生的高温使镍颗粒烧结形成金属烧结颈,使多个小颗粒团聚成不规则的大颗粒.     

改进Stober法制备光子晶体用SiO2微球

为获得光子晶体用单分散性较好、表面光滑的SiO2球形颗粒.对传统Stober法进行改进,分析了氨水和正硅酸乙酯(TEOS)浓度对SiO2微球粒径的影响,提出了单分散SiO2微球的形成机理,利用X射线衍射分析仪(XRD)和场发射扫描电子显微镜(SEM)对样品结构和形貌进行了表征.XRD分析表明,合成的SiO2微球为无定形态;SEM照片显示SiO2微球粒径在292～750nm范围内,微球粒径偏差均在5%以下.     

SHS/PHIP法合成TiB2陶瓷的研究

采用自蔓延高温合成结合准热等静压（SHS／PHIP）工艺制备了TiB2陶瓷材料，并进行了X射线衍射（XRD）、扫描电镜（SEM）、力学性能等实验研究。XRD结果表明反应生成了高纯度的TiB2，没有其他相生成，这与热力学计算结果相吻合，材料SEM分析发现，TiB2陶瓷颗粒形貌为近等轴状，尺寸细小且较均匀，在TiB2陶瓷颗粒间还存在“烧结颈”，由于SHS反应所产生的高温，造成了TiB2陶瓷颗粒表面的圆化。合成产物的致密度较低，气孔主要存在于TiB2陶瓷颗粒交界处，较低的致密性导致了材料具有较低的硬度、弯曲强度和断裂韧性等力学性能。     

电爆法制备纳米铜颗粒的微结构特征及其氧化行为研究

本文利用扫描电镜（SEM）、高分辨透射电镜（HRTEM）、X-射线衍射（XRD）和热分析技术等,对电爆法制备的纳米铜（Cu）颗粒的微观形貌、晶体结构特征,以及高温氧化性能进行了较为详细的表征和测试。实验发现,1）纳米铜（Cu）颗粒具有完整的晶体结构,有轻微的软团聚,粒径分布在60～80nm之间,平均粒径约为78nr／l;颗粒表面有一层钝化的非晶态膜。2）在空气气氛中,从室温加热到1200℃时,其氧化过程中的相转变为Cu→CuO2→CuO→CuO2,即,在198℃开始被氧化,在275℃后完全被氧化;低温时,主要产物为CuO;而高温时,主要为Cu2O。     

两步退火形成钛硅化物和氮化物的研究

模拟自对准硅化物技术的两步退火工艺，对超高真空（UHV）下制备的Ti／Si样品依次进行低温退火、腐蚀和高温退火。利用俄歇微探针（AES）和X射线衍射（XRD）分析样品的组分及晶相。发现高温退火后，薄膜内同时生成了Ti的硅化物及氮化物，这对发展MOS器件工艺中自对准硅、氮化物技术很有意义。另外，还利用扫描电镜（SEM）观察了薄膜形貌，用VandePauw法测量了薄膜电阻。     

聚乙烯吡咯烷酮对羟基磷灰石结晶和形貌的影响

采用化学均相沉淀法,在水热条件下以Ca(NO3)2.4H2O和(NH4)2HPO4为原料,合成了具有特殊形貌的羟基磷灰石(HA)微球。在合成过程中加入聚乙烯吡咯烷酮(PVP)为模板剂,研究了PVP的加入和浓度对HA晶体形貌和粒径的影响。结果表明,PVP的加入改变了HA晶体的生长方式,颗粒是由针片状HA晶体组成的微球;HA颗粒的形貌和粒径可以通过调节PVP浓度来控制,当PVP浓度从0%(质量分数,下同)增加到12%时,HA颗粒的形貌逐渐由不规则的絮状团聚物转变为规整的微球,组成微球的结构单元也随PVP浓度的变化有所不同。     

不同工艺条件对球形纳米硫酸钙制备的影响

制备纳米硫酸钙(CaSO4)颗粒的关键在于采用适宜的制备工艺条件配制反相微乳液,使CaSO4晶体在理想的环境中生长。采用AOT、OP-10复合表面活性剂/环己烷/正戊醇/水溶液反相微乳液反应体系,在水与表面活性剂的摩尔比(水表比)ω=20、反应物浓度n([Ca2+])/n([SO24-])=0.125mol/L、陈化时间t=10min的条件下,制备出了形貌均一,平均粒径为70nm的球形CaSO4颗粒。用扫描电子显微镜(SEM)对产物形貌和大小进行了表征。实验分析了水表比ω、反应物浓度n([Ca2+])/n([SO24-])值、陈化时间t等因素对纳米CaSO4颗粒粒径的影响。     

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 ...