应用于微电子机械系统中多孔硅的研究

针对多孔硅在MEMS中作为牺牲层和绝热层的应用,主要研究了电化学腐蚀法制备多孔硅的实验条件与多孔硅深度及其孔隙率间的关系,实验发现电化学腐蚀法制备多孔硅的腐蚀速率在腐蚀前期阶段基本是一定值(电流密度为80mA/cm2时为1.3μm/min,电流密度为40 mA/cm2时为0.4μm/min),但到腐蚀后期阶段随着孔深的增加有所下降.同时发现对于不同的腐蚀电流密度,多孔硅的孔隙率都有随腐蚀时间的延长先增加后降低的趋势,用Beale模型可以很好的解释这一现象.最后,针对多孔硅在制备后易发生龟裂的现象,用拉曼光谱分析了多孔硅的内部应力情况,结果表明随多孔硅孔隙率的上升其内部残余应力有增加的趋势.     

阴阳极间距对碳纳米管薄膜强流脉冲发射的影响

采用酞菁铁高温裂解法在镀有镍金缓冲层的硅基底上生长了碳纳米管薄膜(CNTs),并采用二极结构在单脉冲模式下研究了其强流脉冲发射特性。结果表明:在脉冲电场峰值相同的条件下(~12.1V/μm),阴阳极间距越小,冷阴极的发射电流越大,且冷阴极的开启场强越小;当阴阳极间距为14cm时,CNTs薄膜的强流脉冲发射电流峰值为312A(电流密度为15.9A/cm~2),对应的开启场强为4.3 V/μm;当阴阳极间距为12.8cm时,CNTs薄膜的强流脉冲发射电流峰值为747.2A(电流密度为38.OA/cm~2),对应的开启场强为4.0 V/μm。     

硅基底上热解法生长CNT薄膜的强流脉冲发射特性

采用酞菁铁高温热解方法在直径为5cm的硅基底上生长了定向CNT薄膜,并对其强流脉冲发射特性进行了表征.测试结果表明,在单脉冲条件下,当宏观场强为11.7V/μm时,发射脉冲电流的峰值约为109.4A;而在双脉冲模式下,当第一脉冲峰值宏观场强为8.6V/μm,第二脉冲峰值宏观场强为5.4V/μm时,第一脉冲和第二脉冲峰值...     

适用于微型燃料电池扩散层的多孔硅的可控制备工艺研究

多孔硅以其多孔结构及大的表面体积比等特点被认为是可在基于MEMS技术的微型燃料电池中代替碳 纸、碳布作为扩散层的材料. 本文考虑传统碳纸、碳布作为扩散层的要求, 并结合多孔硅材料的特点, 选用n<100>(0.04～0.15 Ω·cm)单晶硅进行了多孔硅制备工艺的研究; 考察了腐蚀液的浓度、电流密度和氧化处理时间对多孔硅的孔隙率、孔深度及氧化速率 的影响, 实现了多孔硅的可控制备. 孔隙率为40%、孔径为350～700nm、厚度为60μm的多孔硅膜电极经循环伏安测定, 在0.5mol/L H₂SO₄溶液中, 表现出与碳纸相近的电活性, 显示了潜在的应用价值.     

多孔硅对单晶硅少子寿命影响状况的研究

以p型单晶硅片为研究对象,在单晶硅片表面采用化学腐蚀方法制备多孔硅层,通过实验选取制备多孔硅的最佳工艺条件,采用SEM观察多孔硅表面形貌,以及用微波光电导法测试少子寿命的变化情况。结果表明,在相同的腐蚀溶液配比条件下腐蚀11min得到的多孔硅层的表面形貌最好,孔隙率最大。在850℃下热处理150min时样品少子寿命的提高达到最大,不同腐蚀时间的样品少子寿命提高程度不同,腐蚀11min的样品少子寿命提高最大,约有10%左右。多孔层的形成伴随着弹性机械应力的出现,引起多孔层-硅基底界面处产生弹性变形,这有利于缺陷和金属杂质在界面处富集。另外,多孔硅仍具有晶体结构,但其表面方向上的晶格参数要比初始硅的晶格参数大,也有利于金属杂质向多孔层迁移。     

金/硅纳米孔柱阵列的场发射

利用浸溃技术在硅纳米孔柱阵列(silicon nanoporous pillar array(简称Si-NPA))上制备了复合纳米薄膜Au/Si-NPA.测试了其场发射性能.测试结果显示,Au/Si-NPA的开启电场为约2V/μm;在7.59V/μm的外加电场下,其发射电流密度为67μA/cm2;在外加电压2000V时,其电流浮动率为21%.导致Au/Si-NPA优良的发射性能是由于其独特的表面形貌和结构所致.     

缓冲层对碳纳米管强流脉冲发射特性的影响

为了研究缓冲层对碳纳米管薄膜(CNTs)强流脉冲发射特性的影响,采用酞菁铁高温热解方法分别在镀镍和不镀镍硅基底上生长了碳纳米管薄膜(Ni-CNTs和Si-CNTs),镍层采用化学镀方法制备,强流脉冲发射特性采用二极结构在单脉冲下进行测试。实验发现,通过引入镍缓冲层,CNTs的强流脉冲发射能力显著增强。在峰值为～10.4 V/μm的脉冲场强下,平均开启电场强度从Si-CNTs的5.0V/μm下降到Ni-CNTs的4.3V/μm,而峰值发射电流和电流密度从Si-CNTs的70A和3.5 A/cm2升高到Ni-CNTs的162 A和8.1 A/cm2,Ni-CNTs的峰值电流比Si-CNTs提高了1.3倍。     

强流脉冲电子束FV520B钢表面改性组织及耐腐蚀性能

利用强流脉冲电子束进行FV520B钢表面改性,处理参数包括加速电压27 k V,能量密度5 J/cm2,脉冲次数1到25次。使用扫描电镜、电子探针和X射线衍射分析样品表层形貌、元素分布和相组织变化。经强流脉冲电子束改性后,样品表面形貌细密均匀,晶粒尺寸降至2μm以下,重熔层厚度约4μm并形成沿(200)择优方向的柱状凝固组织。样品表层深约10μm范围内的沉淀硬化颗粒得到有效溶解,成分分布均匀化。在3.5%(质量比)Na Cl溶液中测试电化学腐蚀性能,25次脉冲处理样品的腐蚀电位由原始样品的-0.213 V升至0.038 V,腐蚀速率降低约一个数量级。     

阳极氧化电流密度和时间对多孔硅形貌和电子发射特性的影响

为了应用于场发射显示器,采用电化学阳极氧化,快速热氧化和磁控溅射等方法制备出了金属/多孔硅/硅基底/金属结构的多孔硅电子发射体,并运用扫描电子显微镜观察了多孔硅的微观形貌,结果发现多孔硅的孔径随着电化学阳极氧化电流密度的增加而增加,多孔硅层的厚度随着阳极氧化电流密度和时间乘积的增加而增加。在真空系统中测量了多孔硅的电子发射特性,电子发射的阈值电压Vth随着多孔硅层厚度的增加而增加;最大的发射效率η为7.5‰,此效率出现在孔径6~16 nm,多孔硅层厚度为11.06μm的样品中,对应的器件电压Vps为30V。     

非晶碳/Mo2C混合膜的场发射特性

以镀有Mo过渡层的A12O3衬底,在微波等离子体增强化学气相沉积(MPCVD)系统中,制备了非晶碳/Mo2C混合结构薄膜,反应气体为CH4和H2.在高真空室中测量了样品场发射特性.开启场强为0.55V/μm,在1.8V/μm电场下样品的发射电流密度为6.8mA/cm2.发射点点密度＞103/cm2.用SEM观察了表面形貌,Raman和XRD谱分析了薄膜的微观结构和成分.实验结果表明该薄膜是一种好的场致电子发射体.     

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.     

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.     

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.……     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.