Al在单晶SiC和碳纳米管上的润湿性及界面结构
发布时间：2018-11-25 22:28
【摘要】：对于高性能、轻量化材料的迫切需求使传统的SiC陶瓷和新兴的碳纳米管增强Al基复合材料成为研究热点。采用液相制备工艺时，增强体与基体间的润湿性及界面化学是复合材料制备的关键因素。尽管很多学者对Al/SiC体系的润湿性进行过研究，但结果却很分散，且他们对该体系真实润湿性、润湿动力学以及反应性等问题所持的观点也存在分歧。对于Al/碳纳米管体系，目前几乎未有人对其润湿性进行过专门的研究。鉴于此，本文采用先进的改良座滴装置和测试方法，对Al在(0001)单晶α-SiC、碳纳米管两种基板上的润湿性和界面化学进行了较深入的研究，获得的主要结果如下： (1) SiC表面极性对Al/SiC体系的润湿性及反应性有显著的影响。与熔融Al接触时，6H-SiC单晶C终结面化学稳定性远高于Si终结面，这可能与两极性面表面微观结构存在差异有关。Al与Si终结面反应非常迅速，，铺展先受基板表面的去氧化控制，后受Al4C3产物层的生成控制，最终为Al[ Si]([ Si]为界面反应生成)熔体在Al4C3产物层上的润湿，平衡接触角为56o。C终结面去氧化相对缓慢，且界面反应较微弱，最终(2h)为Al[ Si]熔体在SiC和Al4C3复合界面上的润湿，但润湿性却好于Si终结面。 (2)纯净的Al与洁净(表面无氧化膜)的SiC之间很可能具有很好的润湿性，尤其是C终结面，界面上Al4C3的生成不一定真正促进了该体系的润湿。传统上认为Al/SiC体系润湿性差、界面生成Al4C3促进润湿的观点在很大程度上是受到了Al和SiC表面存在氧化膜以及界面上Al4C3的快速生成阻碍真实Al/SiC固/液界面建立的影响。 (3) SiC晶体结构(4H、6H)对Al/SiC体系的润湿性影响较小。纯Al在4H和6H-SiC上的润湿动力学及最终润湿性基本无差异。纯Al在多晶SiC和单晶SiC的Si终结面上的润湿动力学过程类似，最终的固/液界面也均为Al[ Si]/Al4C3界面，虽产物层形貌不同，但最终润湿性相同。 (4)合金元素Si对Al/SiC体系的润湿性有显著的影响。对于Si终结面，Si含量决定了固/液界面性质，从而决定最终润湿性，即当Si含量低于临界含量(完全抑制Al4C3生成的Si含量)时，添加Si对最终润湿性无影响；Si含量达到或超过临界含量时，界面反应几乎被完全抑制，同时润湿性得到显著改善。对于C终结面，添加Si则会恶化该体系最终润湿性，且Si含量越大恶化作用越大。 (5) Al与碳纳米管(CNTs)间的本征润湿性很差，甚至比Al/多晶石墨体系差，其本征润湿角大于140o。Al/CNTs体系属于界面反应驱动润湿体系，因CNTs稳定性高于多晶石墨，Al/CNTs体系界面反应比Al/多晶石墨体系更慢，致其铺展速度慢于后者。Al/CNTs体系反应性与CNTs结构完整性密切有关。与熔融Al接触时，高结晶程度碳管管壁有非常高的稳定性，即便温度高达1173K，也不易与铝发生反应或反应缓慢。存在结构缺陷的部位稳定性则低得多。开口端部在较低温度(973K)下就会发生溶解，但溶解速度比较缓慢，短时间内(10min)管状结构不会严重破坏。而高温下(T≥1073K)开口端部溶解速度很快，且碳管管壁缺口处(石墨片层不连续)、大曲率弯曲部位易被熔融Al侵蚀，加速碳管管状结构的破坏。
[Abstract]:The urgent need for high performance and light-weight materials has made the traditional SiC ceramic and the new carbon nanotube-reinforced Al-based composite material become the hot spot. In the process of liquid phase preparation, the wettability and interface chemistry between the reinforcement and the matrix are the key factors in the preparation of the composite. Although many scholars have studied the wettability of the Al/ SiC system, the results are very dispersed, and their views on the real wettability, wetting kinetics and reactivity of the system are different. In the case of the Al/ carbon nanotube system, no special research has been carried out on the wettability of the Al/ carbon nanotube system. In view of this, this paper studies the wettability and interface chemistry of Al in (0001) single-crystal silicon-SiC and carbon nano-tube, and the main results are as follows: (1) The surface polarity of SiC is significant to the wettability and reactivity of the Al/ SiC system. The chemical stability of the C-terminated surface of the 6H-SiC single crystal is much higher than that of the Si-terminated surface when in contact with the molten Al, which may be different from the microstructure of the two-polar surface. 鏈夊叧.Al涓嶴i缁堢粨闈㈠弽搴旈潪甯歌繀閫
本文编号：2357551
[Abstract]:The urgent need for high performance and light-weight materials has made the traditional SiC ceramic and the new carbon nanotube-reinforced Al-based composite material become the hot spot. In the process of liquid phase preparation, the wettability and interface chemistry between the reinforcement and the matrix are the key factors in the preparation of the composite. Although many scholars have studied the wettability of the Al/ SiC system, the results are very dispersed, and their views on the real wettability, wetting kinetics and reactivity of the system are different. In the case of the Al/ carbon nanotube system, no special research has been carried out on the wettability of the Al/ carbon nanotube system. In view of this, this paper studies the wettability and interface chemistry of Al in (0001) single-crystal silicon-SiC and carbon nano-tube, and the main results are as follows: (1) The surface polarity of SiC is significant to the wettability and reactivity of the Al/ SiC system. The chemical stability of the C-terminated surface of the 6H-SiC single crystal is much higher than that of the Si-terminated surface when in contact with the molten Al, which may be different from the microstructure of the two-polar surface. 鏈夊叧.Al涓嶴i缁堢粨闈㈠弽搴旈潪甯歌繀閫
本文编号：2357551
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