【作者】 李顺；

【导师】 刘家臣；

【作者基本信息】 天津大学 ， 材料学， 2010， 博士

【摘要】 本论文结合微波升温迅速、选择性加热、高效节能、瞬时无污染等特性,设计保温装置,选择金属Al粉、纳米Si粉、Al-Si合金粉及含Al-Si合金的微膨胀ZTM复合中间层为研究对象,在系统研究金属Al粉、纳米Si粉、Al-Si合金粉的吸波升温特性、润湿特性基础上,通过制定相应的微波连接制度（如时间、功率、压力及装置等）,实现了以金属Al粉、纳米Si粉、Al-Si合金粉以及微膨胀ZTM复合中间层的95-Al₂O₃陶瓷的微波连接,并通过对界面结构、物相、元素线扫描分析得出结论如下:粒径小于100μm金属Al粉、纳米Si粉、Al-Si合金粉均能吸波并迅速升温至熔点以上,实现微波选择性加热。选用金属Al粉为中间层时,金属Al粉微波加热过程中迅速升温、氧化、熔融,熔体体积膨胀,破壳铺展。增大微波功率和外界压力促进连接。选用纳米Si粉为中间层时,1KW/20min→2KW/20min→3KW/20min→0KW可成功连接95-Al2O3陶瓷。微波连接过程伴随着中间层的快速升温、氧化、熔融、铺展、渗透,通过液相形成连接;微波热处理促进了界面两侧的元素交换,随中间层的氧化,与基体化合生成莫来石,界面消失,微观结构均匀一致;活性添加剂Mg含量在5wt%以下时有利于发生界面反应,促进界面生成。选用Al-Si合金粉为中间层时,微波连接制度为2KW/20min→自然冷却时可获得陶瓷/合金连接界面,中间层快速升温熔融,在界面上流动、渗透,在冷却中凝固形成陶瓷/合金连接界面;纯Al-Si合金粉由于氧化膨胀剧烈,升温过程难以控制,很难实现无缺陷的陶瓷/陶瓷连接界面。以20wt%ZrO2、23.7wt%Al-Si、33wt%Al₂O₃、22.3wt%SiO₂和1wt%Y₂O₃为原料的微膨胀ZTM复合中间层在1KW/20min→2KW/20min→3KW/20min→2KW/20min→1KW/20min→0KW微波作用下和5.71KPa外加压力作用下可实现95-Al₂O₃陶瓷的微波连接,连接界面消失,连接强度略低于基体,为324±36MPa;微膨胀ZTM复合中间层微波连接95-Al₂O₃陶瓷的连接机制综合了Al-Si合金粉体、SiO₂粉体微波连接的优点,同时避免了由于过分体积膨胀而引起的界面缺陷,是液相连接、固相反应连接、原位氧化连接、界面化合反应连接的共同作用结果。更多还原

【Abstract】 95-Al₂O₃ ceramics were successfully joined by microwave selective heating in industrial microwave furnace. In this paper, temperature-rising characteristics of Al power, nano-Si powder, Al-Si alloy powder and 95-Al₂O₃ ceramic in a self-making microwave heating system were experimentally investigated, based on which the wetting properties and the interfacial bonding properties of Al powder, Al-Si alloy powder and nano-Si powder to 95-Al₂O₃ ceramics were studied. Combination the advantages of Al-Si alloy powder and nano-Si powder, ZTM ceramic composites with micro-expansive effects, consisted of ZrO₂, Al-Si alloy, Al₂O₃,SiO₂ and Y₂O₃ for raw materials, were successfully prepared. The ZTM ceramic composites contain the different absorbing microwave elements at different temperature. 95-Al₂O₃ ceramics were effectively joined by using Al power, nano-Si powder, Al-Si alloy powder and ZTM powder containing Al-Si alloy powder. The results indicate that:Al powders which are less than 100μm, nano-Si powders and Al-Si alloy powders, used as active component, absorb microwave strongly and rise in temperature over the fusion temperature. Microwave selective heating can be performed at targeted regions during joining 95-Al₂O₃ ceramics with the above intermediates.95-Al₂O₃ ceramics were effectively joined by using Al power. During microwave joining process, microwave raises the Al powder to fusion temperature, at which Al-Si alloy powder melt immediately to form molten metal. The molten metal spread over the surface of 95-Al₂O₃ ceramics after breaking the oxide shell into fragments. Increasing the microwave power and the impressed pressure promote the joint’s forming.At the following microwave heating process: 1KW/20min→2KW/20min→3KW/20min→0KW, 95-Al₂O₃ ceramics were effectively joined by using nano-Si powder as interlayer. During microwave joining process, nano-Si powder absorb microwave and be heated to high temperature combining with oxidation, fusion, spreading and penetrating. The joints are formed by liquid phase. Microwave heat-treatment promotes the elemental diffusion. Al₂O₃ ceramic joints were obtained with unobvious bond line, homogeneous microstructure finally following the oxidazing of the interlayer. When the content of Mg is less than 5wt%, Mg will facilitate the interfacial reaction and promote the forming of joint.95-Al₂O₃ ceramics were effectively joined by using the Al-Si alloy powder at 2KW/20min→0KW. During microwave joining process, micrwowav raises the Al-Si alloy to fusion temperature, at which Al-Si alloy powder melt immediately to form molten metal. The molten metal fills the interfacial gaps and the in-situ oxidation of Al-Si on the interface facilitates joint formation. Because of the volumetric expansion caused by the oxidation reactions and combination reaction at the interface are too strongly to control the heating process, the flawless joint is too difficult to obtain.At the following microwave heating process: 1KW/20min→2KW/20min→3KW/20min→2KW/20min→1KW/20min→0KW, 95-Al₂O₃ ceramics were effectively joined by using the ZTM ceramic composites with 20wt%ZrO₂, 23.7wt%Al-Si, 33wt%Al₂O₃, 22.3wt%SiO₂ and 1wt%Y₂O₃ as the interlayer. Al₂O₃ ceramic joints were obtained with unobvious bond line, homogeneous microstructure and high micro-hardness at the interface. The bond strength, which is 324±36MPa, is near to the matrix strength. The joining mechanism of joint formation are associated with the liquid joining, in-situ oxidation reaction joining, solid reaction joining, interfacial combination reaction joining and rapid inter diffusion across the interface. At the same time, pressure promotes the formation of the joint.更多还原