高熵合金熔覆涂层的研究进展

高熵合金熔覆涂层以其简单的结构、优异的性能、较大的应用潜力在材料表面工程中受到广泛关注。综述了高熵合金熔覆涂层的研究进展,探讨了热处理工艺等对高熵合金熔覆涂层的影响,总结了高熵合金熔覆涂层的应用研究,展望了高熵合金熔覆涂层的发展方向。     

INCO718高温合金钎焊工艺研究

对于高温合金,把合金元素及化合物充分固溶于基体内,才能获得良好的高温性能。本文主要介绍了INCO718高温合金的应用及工艺特点,并对该材料的焊接性能进行了深入的研究分析,总结出高温合金表面氧化问题、钎焊热循环的影响、钎料与钎焊金属成分的影响、焊缝间隙和钎料量的多少、钎焊温度的影响以及真空钎焊设备的性能,都将直接决定着INCO718高温合金钎焊接头的焊接质量。本文着重阐述了高温合金表面氧化问题的解决和不同牌号的钎料对于高温合金钎焊质量的影响。     

新型高温合金的液相连接

简要介绍了粉末冶金高温合金,定向凝固高温合金,单晶合金,镍铝系金属间化合物结构材料等新型高温合金钎焊和过渡液相扩散焊领域的发展现状,主要包括其钎料或中间层合金,连接方法及工艺和接头的高温持久性能。     

电火花沉积高熵合金涂层的研究现状与展望

基于高熵效应的多主元合金克服了传统高熵合金(HEA)的弊端,形成了综合性能优异的简单固溶体.最初,高熵合金的设计理念主要通过块状高熵合金来实现,随着人们对高熵合金的深入研究,高性能高熵合金涂层的概念被提出来.但是,现有的磁控溅射、热喷涂和激光熔覆技术制备高熵合金涂层存在厚度低、孔隙率高、对异形关键部件涂层可达性差等问题,严重阻碍了高熵合金涂层在航空航天领域的应用.电火花沉积技术不但具有绿色、节能、省材等优势,而且针对细长管内壁和弯曲弧面等结构特征的关键件,电火花沉积高熵合金涂层的厚度均匀、可达性良好.除了对涂层制备工艺的探索外,众多学者还通过高熵合金涂层设计的五大效应之一"鸡尾酒效应"改变组元进行调配以及添加WC等硬质颗粒和稀土元素来达到涂层所需的组织和性能.最后,研究者往往会在涂层制备之前采用正交试验等手段优化高熵合金涂层制备的工艺参数,提高涂层所需要的性能.本文详细介绍了高熵合金设计原理及不同技术制备高熵合金涂层的研究进展,总结了不同高熵合金涂层体系结构与性能之间的关系,并指出利用电火花沉积高熵合金涂层作为表面改性手段的发展前景.     

电流辅助下CoFeCrNiCuTi2高熵合金钎焊SiC陶瓷接头组织与性能

采用电流辅助连接技术，以CoFeCrNiCuTi₂高熵合金为连接层材料，在1125℃的温度下，实现了SiC陶瓷的快速钎焊，提高了连接效率的同时保证了元素的充分扩散，系统研究了钎焊温度对连接接头界面微观结构和力学性能的影响。结果表明：所获得的钎焊接头无明显缺陷，焊缝组织主要由高熵FCC相、TiC相、Cr₂₃C₆相组成。界面致密的TiC反应层的形成在一定程度上抑制了高熵合金的分解和金属间化合物的生成，并缓解了SiC基体界面与高熵合金钎料之间的热应力。同时，由于高熵合金钎料的迟滞扩散效应，焊缝中心主体钎料仍保持高熵合金的FCC结构。力学性能测试表明：钎焊接头强度随钎焊温度升高呈先降低后增大的变化趋势。当连接温度为1125℃时，碳化硅接头获得最大弯曲强度，达到37 MPa,高于普通镍基钎料约21.3 MPa。     

高熵合金基复合材料研究进展

高熵合金基复合材料以其结构简单、性能优异以及较大的应用潜力在材料表面工程方面日益受到人们的关注。综述了块状高熵合金基复合材料及高熵合金基复合材料涂层的研究现状,并着重介绍了上述复合材料的制备工艺及性能特点。     

碳纤维复合材料与金属连接及接头力学性能测试

碳纤维复合材料因其强度高、质量轻、导热性能出众,在外空间和核工业等领域中的关键部件中得以应用.碳纤维复合材料与金属主要是通过螺栓、胶结、钎焊或扩散焊连接在一起.其中,在钎焊过程中,多数钎料在这类复合材料表面并不润湿,通常采用活性钎料,在高温和高真空的条件下进行;钎料的种类不同,钎焊接头的强度差异也很大.本文对碳纤维复合材料与金属铜、钛、铌、铝等金属的连接方法和相关研究进展作了总结,对其接头的力学性能测试方法作了介绍,并对该领域的研究方向发展做了展望.     

SiC/SiC-哈氏合金异质连接机制及其氟熔盐腐蚀特性分析

以Cu-2.67Ni钎料, 采用钎焊工艺获得了SiC/SiC复合材料-哈氏合金异质接头, 并研究了其在800 ℃的FLiNaK熔盐中的腐蚀行为。利用不同手段表征了接头微观结构和氟熔盐腐蚀行为。结果表明, Ni、Cr、Mo等合金元素以及SiC中的Si元素发生互扩散。Cr元素替代Ni元素, 在焊料-复合材料界面富集并形成不连续碳化物层。高温钎焊加速Ni扩散并侵蚀SiC, 低温钎焊导致焊料熔融不充分。钎焊过程中的元素扩散改变了哈氏合金的组成,导致其耐腐蚀性能恶化。Cr与Si的选择性溶出导致钎焊接头及合金的腐蚀损伤, 这与热力学计算结果一致。     

SiC/SiC-哈氏合金异质连接机制及其氟熔盐腐蚀特性分析（英文）

以Cu-2.67Ni钎料,采用钎焊工艺获得了SiC/SiC复合材料-哈氏合金异质接头,并研究了其在800℃的FLiNaK熔盐中的腐蚀行为。利用不同手段表征了接头微观结构和氟熔盐腐蚀行为。结果表明, Ni、Cr、Mo等合金元素以及SiC中的Si元素发生互扩散。Cr元素替代Ni元素,在焊料–复合材料界面富集并形成不连续碳化物层。高温钎焊加速Ni扩散并侵蚀SiC,低温钎焊导致焊料熔融不充分。钎焊过程中的元素扩散改变了哈氏合金的组成,导致其耐腐蚀性能恶化。Cr与Si的选择性溶出导致钎焊接头及合金的腐蚀损伤,这与热力学计算结果一致。     

镍基高温粘带钎料

目前,在航空发动机的高温合金和不锈钢的钎焊中,常用的高温钎料为Ni-Cr-Si-B系合金,因为它有良好的高温综合性能。但是由于Si和B的含量较高,使得这种钎料很脆,无法轧制变形.起初只能以粉状或膏状使用。近来为使用方便,出现了粘带钎料。     

Gender differences in publication productivity in psychology in India

An analysis of gender differences in psychology in India provides quantitative and qualitative assessment of R&D output contributed by psychologists with the indication of the trend of growth, skewness, relatedness, co-authorship pattern of productivity.     

Metrology in Chemistry in Germany

The system for Metrology in Chemistry in Germany is described. At the national standards level, a network of high-level chemistry institutes coordinated by the national metrology institute, PTB, provides the primary references for chemical measurements. A dissemination mechanism employs chemical calibration laboratories accredited within the framework of the German Calibration Service (DKD). They act as “multipliers” between the national standards level and the user level by providing the user with calibration means which are traceable to the SI via national standards. Traceability structures in clinical chemistry, electrochemistry, elemental analysis and gas analysis are described     

Natural radioactivity in drinking water in private wells in Finland

Natural radioactivity in drinking water was determined in population-based random study of 472 private wells. The mean concentrations of (222)Rn, (226)Ra, (234)U, (238)U, (210)Pb and (210)Po in drilled wells were 460, 0.05, 0.35, 0.26, 0.04 and 0.05 Bq l(-1), and in wells dug in the soil were 50, 0.016, 0.02, 0.015, 0.013 and 0.007 Bq l(-1), respectively. Approximately 10% of the drilled wells exceeded a radon concentration of 1000 Bq l(-1) and 18% a uranium concentration of 15 microg l(-1). The mean annual effective dose from natural radionuclides for a drilled well user was 0.4 mSv and 0.05 mSv for a user of a well dug in the soil. The effective dose arising from (222)Rn was 75% of the total of all natural radionuclides for drilled well users. As regards long-lived radionuclides, (210)Po and (210)Pb caused the largest portion of the effective dose. The dose arising from (238)U, (234)U and (226)Ra was only 8% of the total of all natural radionuclides.     

Natural radioactivity in drinking water in private wells in Finland

Radiation Protection Dosimetry     

Optische in situ Schichtdickenmessung in Bedampfungsanlagen. Optical in situ film thickness monitoring in coating systems

Optical film thickness monitoring is more precise than crystal monitoring. The optical measurement makes use of the fact that the intensity of a monochromatic light beam which is reflected on a film will change periodically with increasing film thickness. The measurement is performed at an exchangeable test glass that is positioned beside the substrates and is therefore coated in the same way as the substrates. The accuracy of cut‐off is achieved by a “fit” of a theoretical curve shape to the measured values. Order filters are used to ensure that, at a certain wavelength, higher deflection orders do not influence the measurement when a monochromator grating is used.     

Spanish experience in education and training in radiation protection in medicine

In most of its publications, the International Commission on Radiological Protection has highlighted the importance of education and training in radiation protection (RP) for medical exposures. Spain, like other Member States of the European Union, has implemented the Directive and the Guidelines in the medical area. The purpose of this paper is to present the Spanish experience in RP education and training in medicine, the different objectives established according to professional levels, existing regulations and feedback obtained from various RP actions.     

Differences in coagulation in clotting of vascular access in hemodialysis patients

Arteriovenous graft (AVG) thrombosis is a frequent cause of graft failure. We evaluated coagulation protein concentrations, platelet function, and viscoelasticity factors in 20 hemodialysis (HD) patients with AVGs. The goal was to determine whether significant differences in protein concentrations, platelet function, and viscoelasticity factors exist among dialysis patients requiring frequent AVG declot procedures vs. those who do not. Twenty HD patients were enrolled: 10 frequent clotters (>3 declots in the previous year) and 10 were nonclotters. Patients on antiplatelets or chronic anticoagulation were excluded. Laboratories were drawn pretreatment and heparinase was added to counteract any potential heparin effect. Coagulation protein concentrations including tissue factor (TF), thrombin/antithrombin III complex (TAT), and prothrombin fragment 1 + 2 (F₁₊₂) were assayed. The time to clot onset was measured by force onset time (FOT). Platelet contractile force (PCF) measured the force produced by platelets during clot retraction, whereas clot rigidity was measured as clot elastic modulus (CEM). FOT, CEM, and PCF were measured by Hemodyne. Both groups had upregulation of the TF pathway, as TF, TAT, and F₁₊₂ levels were similarly increased over baseline levels. Hemodialysis patients with frequent AVG clotting had higher levels of both PCF and CEM compared with nonclotters. Additionally, the frequent clotters had a lower FOT relative to nonclotters, although both were considered in the normal range. Our study suggests that HD patients with recurrent AVG thrombotic events form clots with higher tensile strength compared with HD patients without recurrent graft thrombosis.