超细Al₂O₃-TiC-Co复合粉体的制备及复合材料的研究

【作者】 张超；

【导师】 凌国平；

【作者基本信息】 浙江大学 ， 材料学， 2004， 硕士

【摘要】 为了得到品粒细小、均匀，力学性能优异的Co-Al₂O₃-TiC（ATC）复合陶瓷，解决陶瓷的脆性问题，本文在化学镀钴制备高性能ATC复合陶瓷的基础上，采用超声波化学镀方法，以提高钴在陶瓷粉末以及Al₂O₃与TiC陶瓷颗粒之间的分布均匀性，以期进一步提高ATC陶瓷的力学性能。其后，以获得纳米金属陶瓷复合材料为目标，对纳米Al₂O₃、TiC采用超声波化学镀Co，制备纳米ATC复合粉末，并进行烧结试验。在保证复合陶瓷中各相均匀性的同时，减小复合陶瓷的品粒尺寸，从而获得具有高力学性能的复合材料。 用超声波化学镀装置，对微米、纳米Al₂O₃、TiC陶瓷粉体表面镀覆钴，研究各组成分布均匀的ATC复合粉末最佳制备工艺参数，以及复合粉末中钴含量的控制；用HIGH-MULTI 10000型多功能烧结炉对复合粉末进行热压烧结制备ATC复合陶瓷；用HRD-150型电子洛氏硬度机硬度计测定复合陶瓷的硬度；用三点弯曲法和单边切口梁法方法测定了ATC陶瓷的抗弯强度与断裂韧性；用X-ray衍射仪、扫描电子显微镜、能谱成分分析仪、透射电子显微镜对复合粉末和烧结材料的结构、微观形貌进行了观察分析。 对陶瓷粉末化学镀钴法制备金属陶瓷复合粉末的研究表明：通过在粉体化学镀中引入超声波，使得反应可以在较低温度下进行，防止了镀液的自分解。同时相比较传统的机械搅拌分散工艺，超声波分散具有明显的优势，可以大大提高颗粒的分散性，使复合粉末中各组成更为均匀。其最佳的工艺参数为：硫酸钴25g／l、次亚磷酸钠25g／l、柠檬酸钠52.3g／l、硼酸25g／l、pH值10.0、温度45℃、超声波功率40KHZ，并且，通过调整化学镀时的装载量，可以控制复合粉末中钴的含量。 超声波化学镀复合粉末通过热压烧结制备的微米ATC陶瓷力学性能，与常规化学镀钴法制备的ATC陶瓷相比得到明显提高。其断裂韧性达到11.28MPa／m^1／2。 对纳米ATC粉体烧结工艺的研究表明：真空保护试样各项力学性能均优于氮气保护试样。氮气保护试样表而各元素分布很不均匀，晶粒大小相差很大，有较多的异常长大相。随着烧结温度的升高，超细ATC陶瓷硬度先上升后下降，浙江大学硕卜学位论文张超超细A120;一Tic一CO复合粉体的制各及复合材料的研究20043其抗弯强度和断裂韧性均随烧结温度的升高而下降。超细A丁C陶瓷硬度随钻含量的增加而降低，而抗弯强度则随钻含量的增加而增加，断裂韧性则随着钻含量的增加先降低，后升高。超细A」，C陶瓷主要的断裂方式是沿晶断裂，伴有部分穿品断裂及塑性断裂。 与微米ATC陶瓷相比，已₁纳米ATC粉体制成的超细ATC陶瓷硬度较高，断裂韧性和抗弯强度较低，综合性能较好。更多还原

【Abstract】 To obtain the ultra fine ATC ceramic with fine, uniform grain and high mechanical properties and solve the problem of brittle of ceramic, the technique of electroless cobalt plating under low temperature and ultrasonic was used to get a cobalt deposition on nano/micro Al2O3, TiC ceramic. The nano/micro Al2O3-TiC-Co composite powder with different cobalt content was prepared by changing the load. The composite powder was then hot-pressed into a ultra fine composite ceramic. The technique of electroless plating and hot-press, the microstructure, mechanical properties and toughen mechanism of the ultra fine composite ceramic were investigated.The best parameters of electroless plating were observed. Results demonstrated that by utilizing the ultrasonic into the electroless plating, the reaction can reacted in lower temperature and the self-decomposition of the solution can be prevented. The ultrasonic can also afford the energy that the electroless plating need so that the coating speed is rapider than the normal low-temperature electroless plating, then reduce the cost. The ultrasonic has great advantage in dispersion compared with the normal mechanical mixing.The mechanical properties of micro ATC ceramic is much higher than the AT ceramic and ATC ceramic prepared by normal electroless plating. The analysis on the micro structure demonstrated that the cobalt can prevent the ceramic’s growth and the reaction between different ceramic. The cobalt along grain boundary can change the "hard" type bonding of ceramic interface and improve the toughness of the composite ceramic by plastic deformation. The loading and hot stress of the dispersed brittle ceramic can be relaxed by the cobalt which is in three-dimensional net structure. The cobalt can also be strengthened by the difference of the hot expansion coefficient between cobalt and ceramic. These all can improve the strength and toughness of thebulk ceramic.The research on the hot-press parameter of the nano ATC composite powder demonstrated that the ceramic prepared under vacuum has better mechanical properties than the ceramic prepared under N2. The hardness of the ultra fine ATC ceramic grows first and then fall down with the growing sinter temperature. The bending strength and fracture toughness of the ultra fine ATC ceramic all fall down with the growing sinter temperature. When the cobalt content grows, the hardness and bending strength fall down and the fracture toughness fall down first and then grow.The main fracture model of ultra fine ATC ceramic is intergranular fracture. The analysis on the microstructure of the ultra fine ATC ceramic demonstrated that the ceramic is intergranular-transgranular structure. The residual hot stress caused by the difference of the hot expansion coefficient between cobalt and ceramic can strengthen the grain boundary and disperse the energy of crack. The cobalt in the grain causes stress concentration and makes the crack through the sub-grain-boundary, which can increase the path of crack.更多还原