Graphene-coated copper foam interlayer for brazing carbon/carbon composite and niobium

Problems such as poor structural integrity, inhomogeneous dispersion, and agglomeration of graphene in the brazing seam are typically encountered for graphene additives in a brazed joint interface. To resolve these problems, a plasma-enhanced chemical vapor deposition process was employed for in-situ preparation of a high-quality graphene-coated copper (Cu) foam composite interlayer prior to be applied for brazing carbon/carbon composite and niobium. The prepared graphene and the brazed joints were characterized via Raman spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The results revealed that graphene was evenly distributed in the brazing seam with the help of the Cu foam, which was characterized by interconnected porosity. Simultaneously, the excellent chemical inertia of graphene inhibited the collapse of the Cu foam, based on which the thermal residual stress in the joint was effectively mitigated due to the synergistic reinforcement effect of the Cu foam (with good plastic deformation capacity) and graphene (with extremely low coefficient of linear expansion). This effect led to significant improvement in the average shear strength of the joint.     

TC4合金与SiO2复合材料钎焊接头界面结构及性能

采用AgCu-4.5Ti钎料直接钎焊TC4钛合金与SiO2复合材料,研究了接头界面组织结构及形成机理,分析了不同工艺参数下界面变化对接头抗剪强度的影响。研究表明：接头界面典型结构为SiO2复合材料/TiSi2/Cu4Ti3+Cu3Ti3O/ Ag(s,s)+Cu(s,s)/TiCu/Ti2Cu/α,β-Ti/TC4;钎焊温度的升高可促进两侧母材界面反应层厚度的增加,同时钎缝中部的AgCu共晶组织消失,化合物相增多;随着接头界面结构的变化,接头抗剪强度表现出先升高后降低的趋势：当钎焊温度为850 ℃,保温10 min时,接头室温最高抗剪强度达到7.8 MPa     

BaCe0.7Zr0.1Y0.1Yb0.1O3-δ质子导电陶瓷与不锈钢的空气反应钎焊分析

针对质子陶瓷燃料电池堆中BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3-δ (BCZYYb)质子导电陶瓷与Crofer22APU不锈钢的连接难题展开研究,探究了Ag-CuO钎料在BCZYYb陶瓷表面的润湿性能,分析了CuO与陶瓷反应对钎料润湿的驱动作用. 研究了Ag-CuO钎料的空气反应钎焊工艺,在1010 ℃/20 min工艺条件下实现了质子导电陶瓷与不锈钢的无缺陷连接,分析了接头两侧界面连接特性以及接头元素分布规律. 结果表明,CuO与陶瓷基体中BaO的反应促进了钎料润湿,钎料扩散进入陶瓷基体形成了较厚的渗透层,CuO与不锈钢保护层 (Mn, Co)₃O₄的反应促进了保护层致密化,保护层在连接过程对不锈钢基体起到了良好的保护作用. 系统分析了CuO含量对接头组织与性能的影响规律,采用Ag-CuO(2%,质量分数)钎料获得了最高接头剪切强度(21.6 MPa),综合评定了钎缝两侧界面反应对接头性能的影响.     

轻质金属与陶瓷连接研究综述

轻质金属由于其高比强度的优点,在航空航天、能源、汽车、建筑、包装与交通运输等诸多领域中得到了广泛的应用。然而大多数轻质金属的高温强度较低,将轻质金属与陶瓷连接起来制备成复合结构有助于获得质量较轻,高温性能优良的构件。本文综述了钛合金,铝合金,锆合金与Ti Al金属间化合物等常用轻质金属与Al_2O_3、Zr O_2、Si C、Si O_2、Si_3N_4与MAX相等常见陶瓷及Si O_2f/Si O_2和Cf/Si C等陶瓷基复合材料的钎焊,扩散焊的研究现状,并介绍了如中间层法,复合钎料法与界面结构设计等常用的缓解轻质金属与陶瓷接头中残余应力的方法,综述了中间层与复合钎料中增强相的选取原则,讨论了目前轻质金属与陶瓷连接中存在的问题与发展趋势。     

石墨烯包覆泡沫铜复合中间层钎焊碳/碳复合材料与铌的工艺与性能

针对石墨烯增强相在焊缝中难以分散均匀、结构完整性差、易团聚等问题. 采用等离子增强化学气相沉积(PECVD)方法在泡沫铜表面原位制备高质量石墨烯,得到石墨烯增强泡沫铜复合中间层. 使用该复合中间层钎焊碳/碳(C/C)复合材料与铌(Nb). 采用Raman, SEM, HRTEM方法表征石墨烯以及钎焊接头的微观组织结构. 结果表明,泡沫铜独特的多孔网络结构使其表面原位生长的高质量石墨烯在焊缝中均匀分布. 同时,石墨烯优异的化学惰性保证了泡沫铜骨架的完整性,并协同石墨烯自身的低线膨胀系数充分发挥了缓解残余应力的作用,有效提高了接头的抗剪强度.     

碳纳米管最新性质--光学相关性

本文对碳纳米管最新的光学性质--光致发光和电致发光进行详细讨论.光致发光方面采用红外激光激发高定向碳纳米管,观察到强烈而稳定的白炽光,通过发光曲线证明发射光谱主要由于光致发光而非热辐射所致.电致发光方面碳纳米管被做成灯丝,与普通钨丝球形灯进行发光比较,证明发光光谱为以电致发光为主,伴有热辐射的综合效应.实验结果显示碳纳米管具有优越的光致发光和电致发光特性.     

SiCP/Al复合材料的真空扩散钎焊

文中采用Al/Cu/Al复合箔扩散钎焊SiC_P/Al复合材料,采用SEM,EDS,XRD分析接头界面组织,研究了钎焊温度对接头界面组织及力学性能的影响,并结合Al-Cu二元相图分析接头形成机制.结果表明,固定连接压力为1 MPa,保温时间为10 min,当钎焊温度从590℃升至640℃,接头界面产物由Al₂Cu+αAl共晶组织转变为断续的Al₂Cu金属间化合物,Al-Cu液相向两侧母材扩散的距离增加,接头的抗剪强度呈现先增大后减小的变化趋势.当钎焊温度为620℃,保温时间为10 min,连接压力为1 MPa时,接头的抗剪强度达到最大值69 MPa.     

Synthesis and characterization of carbon nanotubes reinforced Al-Si-Cu brazing powder

In this paper, an approach to synthesizing carbon nanotubes （ CNTs ） reinforced A1-Si-Cu brazing powder was studied, which was accomplished by in-situ growth of the CNTs on the Al-Si-Cu powder at a relatively low temperature by plasma enhanced chemical vapor deposition （ PECVD ）. The synthesis parameters were optimized. The component of brazing powder was analyzed by X-ray diffraction （ XRD ）. The microstracture and dispersity of as-grown CNTs were investigated by scanning electron microscopy （SEM）. The graphitization and defects were characterized by Raman spectroscopy. The asgrown CNTs on Al-Si-Cu powder disperse uniformly and have moderate length and density, meanwhile its sp2 structure dominates minor quantity of amorphous carbons and defected carbon structures.     

BNi2+TiH2复合钎料钎焊C/C复合材料与GH99镍基高温合金

采用BNi2+TiH₂复合粉末钎料成功实现C/C复合材料与GH99镍基高温合金的钎焊,对焊后接头界面组织及力学性能进行了分析.结果表明,焊后接头典型界面结构为C/C复合材料/Cr₃C₂+MC+Ni(s,s)/MC+Ni(s,s)/Ni₃Si+Ni(s,s)/Cr₃C₂+MC+Ni(s,s)/GH99高温合金.钎料中加入TiH₂,可促进C/C复合材料母材的溶解,并在钎缝中部形成MC碳化物颗粒.随着TiH₂含量的增加,钎缝中部MC形态由细小弥散向大片状转变.当TiH₂含量为3%时,接头室温及800,1000℃高温抗剪强度最高,分别可达40,19及10 MPa,接头强度高于BNi2钎料钎焊接头强度,并可有效保证接头高温使用性能.     

新工科理念下的焊接与连接前沿与进展课程改革与实践探索

在“新工科”的教育理念和教育改革背景下,面向国家重大发展战略和新兴产业的蓬勃发展对创新拔尖人才的需求,文中以焊接与连接前沿技术与创新进展为主题,在《焊接与连接前沿与进展》研究生核心课程中进行多学科交叉融合设计,采取设计理论与实践并重的教学内容和教学模式,组建“学术+工程大师领航”跨学科教学团队,编订多学科交叉融合的新形态教材,建立跨学科的创新实践平台及多元化的科学考核评价体系,培养适应国家建设需要的高水平综合性创新拔尖人才。