低温应变测量技术

第三讲低温下材料或结构部件裂纹扩展的电测技术一、前方任何材料或结构部件,由于内部存在缺陷、气孔及腐蚀等原因,使其在使用过程中发生裂纹,而裂纹的产生与传播会造成结构的损坏。在低温环境下,由于材料自身的冷脆性,加速了材料或结构部件的裂纹产生与扩展速度,增加了材料或结构破坏的危险性。为确保结构在使用或运行中的安全,充分掌握各种材料或结构部件裂纹的产生及传播过程,对材料研究和结构设计人员来说都是非     

低温真空截止阀真空性能分析

介绍了真空截止阀在低温环境下真空度的性能,对低温真空度和传热进行了分析探讨,通过实验计算为低温真空阀在生产加工和实际应用中提供了有利的指导和理论依据,对于低温材料选择,结构设计具有一定参考价值。     

国际低温材料会议ICMC-88在沈阳举行

国际低温材料会议 ICMC-88于1988年6月7—10日在沈阳召开。根据国际低温材料理事会(International Cryogenic Materials Conference Board)的建议,会议由中国科学院金属研究所主办,宝鸡稀有金属加工研究所和国际低温材料理事会协助。该理事会主席 E.W.Collings 和国际知名科学家多人参加了会议。理事会理事15人中有8人     

刚柔复合式路面裂缝反射预防材料开发及结构表征

针对现有刚柔复合式路面裂缝反射预防材料高温软化、低温断裂的缺点,以沥青材料的高温软化点和低温延度为指标研发了适用于防治裂缝反射的有机复合材料,通过红外光谱试验(FTIR)和差示扫描热(DSC)试验探究了有机添加剂对沥青官能团的影响和裂缝反射预防材料在工作环境下温度变化对热稳定性的影响,并通过板带拉伸试验深入分析了裂缝反射预防材料的抗拉和抗变形能力。结果表明,裂缝反射预防材料具有较好的高温稳定性和低温抗裂性,能够满足在高温施工不软化流淌、低温环境受拉不断裂的要求;两种高分子材料加入到沥青中形成了有利于提高材料延展性和降低温度敏感性的基团;同时,裂缝反射预防材料在辅助以玻纤布后具有了与强力材料相同的弹性变形阶段、强化阶段、屈服阶段和缩颈阶段,其抗拉与抗变形性能可以在刚柔复合式路面中发挥良好的裂缝反射预防功效。     

电子冷冻加工的特点与应用研究

针对采用热电制冷的冷冻加工方式的特点与应用进行了研究,对于特殊工件的加工提出了一种全新的加工方式,它改革了传统的工件夹持方法,为超小、超薄、异形、低强度脆性材料的工件的加工提供了一种可能,同时电子冷冻加工使低温加工成为现实,可解决一般常用材料及某些特殊材料的加工问题,特别适宜于薄片件,韧、粘性材料的加工,结构简单,温度可调,成本低,无粉尘和气味,可应用于各行各业的机械加工中.     

一种高速铁路用新型鱼尾板材料的性能评价

对一种新型非调质贝氏体鱼尾板材料在常温和低温下的拉伸性能和冲击性能进行了全面评价.研究结果表明:该材料的显微组织为晶粒细小的粒状贝氏体,常温和低温下材料的拉伸、冲击性能均高于国内现用的B7钢及日本鱼尾板材料,在室温和-55℃下材料的屈服强度分别为722,738MPa,伸长率分别为60.7%和41.7%.观察了不同温度下的拉伸断口和冲击断口形貌,并讨论了材料的断裂方式.     

低温高压锻造容器研制

从设计方案的确定、总体结构的设计压容器的设计和加工过程.该2 m3容器在20 K的低温和18 MPa的高压下工作,根据其工作性质、加工制造周期等因素,采用堆积绝热形式.在容器外采用LN2夹套,内容器采用锻焊结构.该容器为国内首次设计压力最高,温度最低,采用锻造技术加工的低温高压容器.加工完成后经使用单位检验、调试与试验表明,该容器满足设计和使用要求.     

基于DMA方法的玻璃态转变温度与沥青混合料低温性能研究

为进一步探究沥青与沥青混合料玻璃态转变温度与沥青混合料低温性能的相关性,以交通运输部公路科学研究院足尺环道(RIOHTrack)为依托,采用动态力学分析仪在弯拉受力模式下用沥青和沥青混合料试件进行温度扫描试验,通过函数拟合确定材料的玻璃态转变温度,进而比较不同定义方式下材料的玻璃态转变温度的变化趋势,探究沥青与沥青混合料相态转变温度的相关性。最后通过与低温弯曲小梁试验的实验结果的相关性和灰关联度分析,讨论利用沥青与沥青混合料的玻璃态转变温度评价沥青混合料低温性能的可行性。结果表明:(1)对于同一种材料,不同的玻璃态转变温度定义下获得的玻璃态转变温度之间存在良好的相关性;(2)在相同级配和相同试验条件下,沥青是影响沥青混合料玻璃态转变温度的主要因素;(3)在弯拉受力模式下沥青与沥青混合料的玻璃态转变温度与材料的低温性能相关性良好,但通过灰关联度分析发现采用沥青混合料的玻璃态转变温度评价混合料的低温性能更加合理。     

基于相对关联度的工程选材决策模型及应用

 根据灰色关联度反映候选材料的理想解之间曲线形状的相似性,在综合考虑正、负理想解影响的基础上,通过构造相对关联度,建立工程选材决策模型.以低温存储罐材料选择为例,根据专家评分得到所选8种评价指标的权重,确定理想解和负理想解,继而分别计算10种候选低温材料的相对关联度,进行选材决策.结果表明：全硬态301型不锈钢的相对关联度最高,是最佳的低温存储罐材料,这与实际应用和加权性质分析法得出的选择结果一致,而且所得其他候选材料的测评效果排序也更加合理.该模型同时反映候选材料的理想解和负理想解之间曲线的相似性,物理含义更加明确,分析问题更加全面、客观,是工程选材决策的有力工具.     

低温温度测量与控制系统研究

简要介绍了G-M制冷机在低温实验中的的应用.针对低温实验过程中的温度测量与控制要求,提出在G-M制冷机内部设置加热器调节被测温度,解决低温下温度的测量控制问题.该系统可应用于低温下材料热物性测量和固体接触界面热阻实验等.温度控制范围为30 K-200 K,测量精度优于1 K,对于低温实验技术具有重要意义.     

Physics,fabrication, and characterization of thin films

Superconducting tunnel junctions as well as transition edge thermometers could benefit from high quality thin films. We point out the important features of various cryo detectors and show where high purity, or even epitaxially grown films are advantageous for detector performance. Some fabrication methods are discussed and methods of film characterization introduced. Photolithography has proven necessary to fabricate the complex structure of the present cryo detectors.     

Design,fabrication and applications of soft network materials

Soft network materials represent a class of emerging cellular materials that have well-organized micro-architectures inspired by network microstructures found in many soft biological tissues. Apart from a good combination of low density, high stretchability and high air permeability, the high degree of design flexibility of soft network materials allows precise customization of mechanical properties by rationally tailoring their microstructural architecture and optimizing selections of constituent materials. These intriguing properties have enabled a range of promising applications in cutting-edge technologies, such as bio-integrated electronics and regenerative medicine. This review summarizes the latest progress in the design and fabrication of soft network materials, as well as their representative applications in biomedical devices, tissue engineering and other areas. It focuses on fundamental principles, design concepts and fabrication techniques of soft network materials that consist of either periodically or randomly distributed microstructures. Rational designs of these soft network materials result in customized mechanical properties that mimic or even exceed those of soft biological tissues. Finally, perspectives on the remaining challenges and open opportunities are provided.     

Microstructured Fibers for the Production of Food

Food engineering faces the difficult challenge of combining taste, i.e., tailoring texture and rheology of food matrices with the balanced intake of healthy nutrients. In materials science, fiber suspensions and composites have been developed as a versatile and successful approach to tailor rheology while imparting materials with added functionalities. Structures based on such types of physical (micro)fibers are however rare in food production mainly due to a lack of food‐grade materials and processes allowing for the fabrication of fibers with controlled sizes and microstructures. Here, the controlled fabrication of multi‐material microstructured edible fibers is demonstrated using a food compatible process based on preform‐to‐fiber thermal drawing. It is shown that different material systems based on gelatin or casein, with plasticizers such as glycerol, can be thermally drawn into fibers with various geometries and cross‐sectional structures. It is demonstrated that fibers can exhibit tailored mechanical properties post‐drawing, and can encapsulate nutrients to control their release. The versatility of fiber materials is also exploited to demonstrate the fabrication of food‐grade fabrics and scaffolds for food growth. The end results establish a new field in food production that relies on fiber‐based simple and eco‐friendly processes to realize enjoyable yet healthy and nutritious products.     

骨组织工程多孔支架材料性质及制备技术

多孔性生物可降解支架的选择和制备是组织工程技术成功运用的关键。从骨架的材料要求、常用的骨架材料、骨架的制备技术等几个方面对组织工程和生物降解支架的研究进行了综述 ,并对该研究的前景进行了展望     

Synthesis of 2D micro-assemblies using the interface of immiscible liquids: boundary control of self-assembled structures

We present a novel technique for the fabrication of multi-function microstructures which is a more efficient and economical alternative in the range 10–200 μm to current fabrication methods (e.g., photolithography and standard ink-jet printing). It is a modification of the classical drop-drying technique in which the material content and evaporation of water droplets are controlled by a toluene/water interface. This allows for sequential introduction of materials inside the droplets, with the possibility of in-drop controlled chemical reactions while keeping the form and a pinned contact line for each micro-droplet. It also makes the technique fully compatible with ink-jet printing methods, rendering it amenable to the fabrication of large-scale multi-function micro-arrays. As an illustration of its versatility, the technique is applied to the fabrication of microstructures from colloidal suspensions of nanoparticles, deposition of biological materials, in-drop fabrication of single crystals from water soluble materials, and fabrication of supported and free-standing polymer-based microstructure films.     

Buoyancy‐Driven Gradients for Biomaterial Fabrication and Tissue Engineering

The controlled fabrication of gradient materials is becoming increasingly important as the next generation of tissue engineering seeks to produce inhomogeneous constructs with physiological complexity. Current strategies for fabricating gradient materials can require highly specialized materials or equipment and cannot be generally applied to the wide range of systems used for tissue engineering. Here, the fundamental physical principle of buoyancy is exploited as a generalized approach for generating materials bearing well‐defined compositional, mechanical, or biochemical gradients. Gradient formation is demonstrated across a range of different materials (e.g., polymers and hydrogels) and cargos (e.g., liposomes, nanoparticles, extracellular vesicles, macromolecules, and small molecules). As well as providing versatility, this buoyancy‐driven gradient approach also offers speed (<1 min) and simplicity (a single injection) using standard laboratory apparatus. Moreover, this technique is readily applied to a major target in complex tissue engineering: the osteochondral interface. A bone morphogenetic protein 2 gradient, presented across a gelatin methacryloyl hydrogel laden with human mesenchymal stem cells, is used to locally stimulate osteogenesis and mineralization in order to produce integrated osteochondral tissue constructs. The versatility and accessibility of this fabrication platform should ensure widespread applicability and provide opportunities to generate other gradient materials or interfacial tissues.     

Cryo‐EM‐On‐a‐Chip: Custom‐Designed Substrates for the 3D Analysis of Macromolecules

The fight against human disease requires a multidisciplinary scientific approach. Applying tools from seemingly unrelated areas, such as materials science and molecular biology, researchers can overcome long‐standing challenges to improve knowledge of molecular pathologies. Here, custom‐designed substrates composed of silicon nitride (SiN) are used to study the 3D attributes of tumor suppressor proteins that function in DNA repair events. New on‐chip preparation strategies enable the isolation of native protein complexes from human cancer cells. Combined techniques of cryo‐electron microscopy (EM) and molecular modeling reveal a new modified form of the p53 tumor suppressor present in aggressive glioblastoma multiforme cancer cells. Taken together, the findings provide a radical new design for cryo‐EM substrates to evaluate the structures of disease‐related macromolecules.     

Atomic Layer Deposition of Nanostructured Materials for Energy and Environmental Applications

Atomic layer deposition (ALD) is a thin film technology that in the past two decades rapidly developed from a niche technology to an established method. It proved to be a key technology for the surface modification and the fabrication of complex nanostructured materials. In this Progress Report, after a short introduction to ALD and its chemistry, the versatility of the technique for the fabrication of novel functional materials will be discussed. Selected examples, focused on its use for the engineering of nanostructures targeting applications in energy conversion and storage, and on environmental issues, will be discussed. Finally, the challenges that ALD is now facing in terms of materials fabrication and processing will be also tackled.     

Fabrication and Machining of Metal Matrix Composites: A Review

Intrinsically smart, metal matrix composites (MMCs) are lightweight and high-performance materials having ever expanding industrial applications. The structural and the functional properties of these materials can be altered as per the industrial demands. The process technologies indulged in fabrication and machining of these materials attract the researchers and industrial community. Hybrid electric discharge machining is a promising and the most reliable nonconventional machining process for MMCs. It exhibits higher competence for machining complex shapes with greater accuracy. This paper presents an up-to-date review of progress and benefits of different routes for fabrication and machining of composites. It reports certain practical analysis and research findings including various issues on fabrication and machining of MMCs. It is concluded that polycrystalline tools and diamond-coated tools are best suitable for various conventional machining operations. High speed, small depth of cut and low feed rate are a key to better finish. In addition, hybrid electrical discharge machining has proved to be an active research area in critical as well as nonconventional machining since last few years. This paper incorporates year-wise research work done in fabrication, conventional machining, nonconventional machining, and hybrid machining of MMCs. Conclusions and future scope are addressed in the last section of the paper.     

形变原位铜基复合材料的研究进展

综述了形变原位铜基复合材料的制备方法、组织演变及综合性能特点,介绍了该类材料的强化和导电机理.分析指出:形变原位铜基复合材料兼顾了高强度和高导电性,已成为高强高导铜基导电材料研发领域的热点之一,降低生产成本、研究产业化制备工艺、深入完善基础理论是该类材料的发展趋势.最后探讨了该类材料的应用前景.