SiO2-乙酰胺复合储热相变材料的制备

采用溶胶-凝胶法将有机相变材料乙酰胺嵌入到SiO2网络空间内,制备了复合储热相变材料.通过对比实验,研究了相变材料的种类、相变材料的加入量及催化剂种类对复合材料性能的影响.研究结果表明:采用氨水作催化剂,乙酰胺作相变材料,可制备出储热能力高、疏松多孔的复合材料,复合材料的相变温度为69.1℃,相变潜热高达124.2J/g;且复合材料中包含相变材料的质量分数越高,其储热能力越高.     

石蜡/泡沫碳相变复合材料的制备及蓄热实验

以石蜡类正二十烷相变材料为填充材料,泡沫碳为基体材料,制备了石蜡/泡沫碳相变复合材料。采用差示扫描量热法(DSC)分析了正二十烷相变材料的热物性,通过扫描电子显微镜(SEM)分别获得了泡沫碳和正二十烷/泡沫碳相变复合材料的表面形态图像。搭建了相变蓄热装置实验台,对3种不同材料的相变蓄热装置进行蓄放热对比实验,记录并分析了相变蓄热装置温度测试数据。与正二十烷的结果对比,泡沫材料的填充大幅提高相变材料的传热性能。在蓄热过程中,泡沫复合相变材料的升温速率明显降低;在放热过程中,正二十烷/泡沫碳相变复合材料温度恢复至室温的时间比纯二十烷恢复至室温的时间减少约30%。     

无机盐/陶瓷基复合蓄热材料高温稳定性的研究

通过理论分析和XRD、DSC及传统热分析等实验手段研究了新型无机盐/陶瓷基复合蓄热材料的高温稳定性。结果表明,相变材料Na2SO4在1000℃高温下具有热力学稳定性,适合作为复合材料的相变介质;Na2SO4/SiO2复合蓄热材料具有良好的高温热稳定性,经100次热循环后,其热失重率低于1.26%、潜热值降低约6.19%、相变温度基本保持恒定,且熔化-凝固特性和热震稳定性良好。Na2SO4/SiO2复合材料适合作为工业炉高温蓄热器储能用蓄热材料。     

聚乙二醇改性相变微胶囊-木粉/高密度聚乙烯复合材料的制备与热性能

通过原位聚合法制备了以正十二烷醇(DA)为芯材,密胺树脂(MF)或聚乙二醇改性密胺树脂(PMF)为壁材的相变微胶囊DA@MF和DA@PMF,并将相变微胶囊添加到木粉/高密度聚乙烯复合材料(WF/HDPE)中,制备了具有相变蓄热能力的DA@MF-WF/HDPE和DA@PMF-WF/HDPE复合材料。采用DSC、TG和红外热成像等方法对DA@MF、DA@PMF和相变微胶囊-WF/HDPE的热性能进行了分析与表征。测试结果表明,DA@PMF的结晶和熔融热焓值分别提高了35.0J/g和21.5J/g,快速失重温度提高了19.9℃;蓄热能力测试表明,DA@PMF成功添加至WF/HDPE中,且在制备过程中损失较小;DA@PMF-WF/HDPE的相变温度(27.2、11.3℃)、相变潜热(31.6、20.3J/g)和热稳定性(256.9℃,DA开始失重)等性能表明其具备成为相变蓄热材料的潜力。     

PNIPAm凝胶为载体的复合相变蓄热材料的制备和性能

以聚N-异丙基丙烯酰胺(PNIPAm)热敏凝胶为载体,棕榈酸和月桂酸的混合物为相变蓄热材料,制备了一种无需容器盛装的复合相变蓄热材料.通过IR、DSC 、TG、SEM对其结构和性能进行分析.结果表明,脂肪酸与PNIPAm凝胶之间没有发生化学变化,脂肪酸在复合材料中仍保持原来的性质.随脂肪酸含量的增加,相变焓增大,可达100J/g以上;相变起始温度基本上保持不变,而峰值温度和终止温度增大.TG曲线表明材料具有较好的热稳定性.     

正十八烷/泡沫相变复合材料蓄热实验研究

通过实验对相变复合材料的相变过程进行研究,将相变材料正十八烷(C18)分别填充到泡沫铜和泡沫碳中来提高相变材料的导热性能,采用差示扫描量热法(DSC)分析了正十八烷相变材料的热物性。利用相变蓄热装置对三种不同材料(C18、C18/泡沫碳、C18/泡沫铜)进行蓄放热对比实验,记录温度测试数据,分析这三种不同材料的温控性能与蓄热能力,并与正十八烷的结果对比。结果表明:泡沫材料的填充大幅提高相变材料的温控性能,使蓄热装置温度分布更均匀。     

室温相变蓄热复合材料的制备及研究

选用十酸和十二酸2种脂肪酸作为相变材料,采用溶胶一凝胶法制备脂肪酸/SiO_2相变蓄热复合材料.分别采用差示扫描量热仪(DSC)、红外光谱仪(IR)和扫描电镜(SEM)对所制备的复合材料的相变温度、相变焓和微观结构进行了测试和表征.DSC测试结果表明,该复合材料的相变温度在室内舒适温度范围具有较高的相变潜热、相变焓和相变温度;IR分析表明,脂肪酸与SiO_2之间是简单的嵌合关系;SEM表明,复合材料表面具有多孔结构,改善了相变可逆性.     

复合相变蓄热材料研究进展

相变材料是目前热门的功能材料,在储存和释放能量的过程中,温度保持不变或稳定在一定的温度区间内,使得相变材料不仅能实现热量储存且具有温度调控功能。复合相变材料由于具有多种单一材料的性质而成为研究热点,并广泛应用在建筑节能、电子器件热管理等方面。本文分类归纳了相变材料的特征,并根据化学成分不同将复合相变蓄热材料分为有机-有机、无机-无机和有机-无机三大类,结合研究现状分类梳理了不同类型复合相变蓄热材料的优缺点,并对其蓄热特性进行归纳对比。总结了复合相变蓄热材料的应用现状,结合能源应用现状和环境情况进一步分析了今后的研究和发展方向,认为未来的复合相变材料应该是高效蓄热、灵敏准确、价格低廉、环保可降解的新型复合相变材料。     

聚乙二醇/乙基纤维素复合相变蓄热材料的制备及性能

以聚乙二醇(PEG)为功能材料、乙基纤维素(EC)为支撑材料,根据有机相分离法制备了聚乙二醇/乙基纤维素(PEG/EC)复合相变材料,其中PEG的含量最大可达84.6%(质量分数)。采用扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FT-IR)、差示扫描量热仪(DSC)、热重分析仪(TG)等技术考察了PEG/EC复合相变蓄热材料的微观形貌、相容性及化学结构、蓄热性能及稳定性。结果表明,PEG/EC复合相变材料为不规则颗粒状粉末,PEG与EC的相容性较好,分子间形成氢键而没有形成新的化学键。由于EC与PEG间形成的氢键及分子链缠绕等作用,使PEG/EC复合材料呈网络结构,使得PEG发生固-液相变时失去了流动性。PEG/EC复合材料作为固-固相变材料,最大相变焓可达151.8J/g,在温度低于80℃范围发生相变,稳定性可靠。     

利用纳米石墨强化正癸酸-十四醇复合相变材料的导热性能

作为常用的有机相变材料,脂肪酸具有循环熔融/结晶稳定的热性能以及无毒、无腐蚀性等优点,但脂肪酸体系的导热系数(0. 1～0. 3 W·m~(-1)·K~(-1))低,限制了它的工业应用范围。为了提高正癸酸(CA)-十四醇(TA)复合相变材料的导热性能,本实验选用CA与TA物质的量比为7∶3的复合相变材料为基液,通过添加不同质量分数的纳米石墨制备出正癸酸-十四醇/纳米石墨复合相变材料体系。研究发现,当添加纳米石墨的质量分数为0. 1%～0. 9%时,能形成较为稳定的悬浮液。通过SEM、DSC和Hot Disk导热系数测定仪对复合材料的主要热物理性能进行表征,分析结果表明,正癸酸-十四醇/纳米石墨复合相变材料的导热系数相对原基液有较大幅度的提高,而相变潜热和相变温度没有太大变化。当添加纳米石墨的质量分数为0. 6%时,所制备的正癸酸-十四醇/纳米石墨复合相变材料的综合性能最佳,其固态和液态导热系数分别提高了39. 5%、35. 2%,相变温度和相变潜热分别为20. 42℃、154. 25 k J/kg,并且具有良好的热稳定性。     

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.     

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...     

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.     

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.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

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.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.