多孔硅基热敏薄膜的制备与性能

对MEMS用具有绝热性能的多孔硅基底上沉积的热敏感薄膜进行了研究．首先用电化学方法制备多孔硅,分别在多孔硅基底和硅基底上通过溅射镀膜方法沉积氧化钒、Cu、Au热敏薄膜,测试多孔硅基底和硅基底上的氧化钒及金属薄膜电阻的热敏特性．结果表明,在多孔硅基底表面沉积的热敏薄膜具有与硅基表面热敏薄膜同样的热敏特性且表现出更高的灵敏度;此外,对沉积在不同制备条件得到的多孔硅上的氧化钒薄膜电阻热敏特性进行比较,发现随着孔隙率和厚度的增加,多孔硅的绝热性能提高,其上沉积的氧化钒薄膜电阻热敏特性增强．     

MEMS中多孔硅绝热技术

主要介绍了多孔硅的制备方法(化学法、电化学法及原电池法等)、多孔硅导热系数测试的几种常用手段(温度传感器法、显微拉曼散射法及光声法等)、导热系数的理论模型及影响因素．此外,采用不同方法制备了多孔硅样品,分析了其表面形貌并用显微拉曼光谱法测定了导热系数．结果发现,化学法制备的多孔硅孔径尺寸大于微米量级,而利用大孔硅电化学和原电池法得到的样品孔径尺寸小(约20nm),属于介孔硅．由于腐蚀条件的不同,多孔硅的孔隙率和厚度也不同,多孔硅的导热系数随孔隙率和厚度的增大而迅速减小．     

红外微测辐射热计用纳米氧化钒薄膜的制备和性能研究

具有优异热敏性能的氧化钒薄膜材料是红外测辐射热计的首选热敏电阻材料，合适的薄膜电阻及高温度电阻系数的氧化钒薄膜的制备是实现高探测率红外测辐射热计的保证．利用新型对靶反应磁控溅射工艺制备了具有纳米颗粒的氧化钒薄膜材料，确定了最佳工艺参数．对其组成、结构和性能进行了分析，原子力显微镜AFM形貌分析表明薄膜具有均匀致密的表面，X射线光电子能谱分析XPS确定了其组成成分主要为V2O5,VO2和少量的V2O3.在常用作微测辐射热计结构层材料的氮化硅基底上，该薄膜材料在室温附近具有合适的薄膜电阻（大约为每方14kΩ）以及高的温度电阻系数（-3．17％／℃），有望适用于非致冷红外测辐射热计探测器．     

测量超低温用NTC热敏电阻的制备和性能研究

采用Pechini法制备La掺杂的Fe-Co-Mn-Ni系尖晶石型负温度系数(negative temperature coefficient,NTC)热敏陶瓷,使用X射线衍射仪和扫描电镜表征了复合陶瓷的相组成和微观结构,测量了其电学性能和老化.结果表明,制备的NTC热敏陶瓷20K时电阻值在90～120kΩ之间;在20～45K温度范围内电阻灵敏度在0.5～45kΩ/K之间,测试电流在2～15μA内变化时引起的温度测量误差<0.1K,热敏电阻常数B20K/40K值在180～210K之间,制备的NTC热敏电阻性能稳定.     

氧化法热处理温度对氧化钒薄膜热敏特性的影响

采用直流磁控溅射法制备氧化钒薄膜,并采用不同的温度对其进行氧化法热处理,通过XRD、SEM、四探针薄膜电阻测试,分析了不同热处理温度对氧化钒薄膜的晶相特性与热敏特性的影响。实验分析证明热处理温度升高后(400℃)得到的薄膜热敏特性良好,其室温电阻为160KΩ·cm,室温电阻温度变化系数为-2.4%/℃,变温过程中(20~98℃)其平均值约-1.98%/℃,表明温度升高有利于改善薄膜热敏特性,在非制冷红外探测器应用方面具有发展潜力。     

多孔硅层孔隙率对其热绝缘性能的影响

研究了多孔硅层孔隙率对其热绝缘性能的影响机制.以P 型硅片为基底,通过双槽电化学腐蚀法制备多孔硅.采用微拉曼光谱法对多孔硅的热导系数进行了测量,结果表明,多孔硅的热导系数随其孔隙率的增大而明显下降,实验中热导系数最低可达到0.624W/(m·K),从而通过降低热导系数使多孔硅的绝热性能得到了增强.     

多孔硅的电化学制备与研究

以电化学方法制备了多孔硅材料并通过表面轮廓测试仪、原子力显微镜、显微拉曼光谱仪等设备对制备多孔硅的孔隙率、厚度、表面形貌、以及热导率进行了表征.结果发现,本实验制备的多孔硅属于介孔硅(15～20nm),其孔隙率随腐蚀时间和腐蚀电流的变化有先增大后减小的趋势.增加多孔硅的厚度和孔隙率,可以使得多孔硅的热导率显著降低(最低可低至0.62W/m·K).     

反应离子束溅射沉积和还原退火工艺制备VO_x多晶薄膜

通过反应离子溅射沉积和后退火工艺制备出优质微测辐射热计用的氧化钒薄膜。对薄膜退火前后进行了扫描电子显微镜分析,结果表明,制备的VOx多晶薄膜致密均匀,退火后晶粒尺寸变大。电学测试表明,在室温时薄膜的方块电阻约为50kΩ,电阻温度系数为-0.022/K,满足制作高性能微测辐射热计的要求。     

PEEK基底上厚度为6.4 nm的金薄膜导热导电性能研究

运用高真空溅射镀膜仪在聚醚醚酮(PEEK)薄膜和纤维表面分别制备了厚度为6. 4 nm的金薄膜,并通过瞬态电热技术(TET)测量了该金薄膜的导热性和导电性。PEEK薄膜基底上厚度为6. 4 nm的金薄膜的导热系数、导电系数和洛伦兹数分别为283. 97 W·m~(-1)·K~(-1)、2. 46×10~7Ω~(-1)·m~(-1)和3. 49×10~(-8)W·Ω·K~(-2)。PEEK纤维基底上厚度为6. 4 nm的金薄膜的导热系数、导电系数和洛伦兹数分别为81. 11 W·m~(-1)·K~(-1)、1. 20×10~7Ω~(-1)·m~(-1)和2. 17×10~(-8)W·Ω·K~(-2)。研究发现,在不同基底材料上制备的金薄膜的导热系数、导电系数和洛伦兹数均不同。这种差异可以归因于以下两点:一方面,不同基底材料上制备的金薄膜的晶粒尺寸不同;另一方面,不同的基底材料会引起基底与金薄膜结合界面的平整度不同。金薄膜晶粒尺寸越小,其电子的导热系数、导电系数越小;金薄膜与基底的结合界面平整度越差,其声子的导热系数越小。     

氧化钒薄膜的厚度对薄膜电学特性的影响

利用直流反应磁控溅射法在表面覆盖有Si3N4薄膜的Si(100)基片上制备了不同厚度的氧化钒薄膜.用光谱式椭偏仪对薄膜的厚度进行了测试.采用四探针测试系统对制备的薄膜进行了方阻和方阻温度系数的分析,发现薄膜的厚度对薄膜的电学特性有很大的影响.实验结果表明氧化钒薄膜的厚度调整可作为调控氧化钒薄膜性能的一种重要工艺手段.     

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.……     

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 ...