定向冷冻铸造工艺制备层状SiC多孔陶瓷的研究

发布时间：2018-03-26 05:38

本文选题：定向冷冻铸造　切入点：层状结构　出处：《兰州理工大学》2017年硕士论文

【摘要】：仿珍珠贝铝基复合材料具有层状结构,因而具有高强度、高韧性等优良特点。层状结构多孔陶瓷作为具有代表性的仿珍珠贝铝基复合材料的增强体,其制备工艺和孔隙结构研究是制备高性能仿珍珠贝结构复合材料的基础。定向冷冻铸造法对孔隙方向和结构定向可控,且操作简单、成本低廉、环保,已成为制备层状结构多孔陶瓷的首选工艺。Si C/Al复合材料已经得到广泛应用,但高性能仿珍珠贝Si C/Al复合材料有待近一步研究,因此,本文研究层状Si C多孔陶瓷,为下一步以层状Si C多孔陶瓷为增强体制备仿珍珠贝Si C/Al复合材料做准备。以SiC为原料,水为溶剂,卡拉胶、分散剂、PEG、甘油为添加剂,采用定向冷冻铸造法实现了层状Si C多孔陶瓷制备,表征了层状Si C多孔陶瓷微观孔隙形貌,总结了成孔机制,分析了各因素对层状Si C多孔陶瓷微观孔隙形貌的影响,主要研究结果如下:样品随着与冷源距离的增大,依次出现致密区、过渡区、层状区,三个区分别呈现蜂窝状、柱状、层状孔隙形貌,孔径范围在10~80μm。成孔机制主要与溶剂的晶体结构和结晶生长动力学有关,而形成层状孔隙的条件受固相含量、冷冻温度、颗粒粒径、甘油含量等因素影响。固相含量由20 vol.%增加到35 vol.%时,孔隙率由68.8 vol.%降低到了52.3 vol.%,孔径从84μm减小到14μm,陶瓷壁厚从37μm增加到72μm;冷冻温度为-5?C时,孔隙呈现无序状,低于-10?C时呈现层状孔隙形貌,冷冻温度越低,孔径越细小,-30?C时平均孔径为63μm;颗粒粒径影响孔隙的轮廓线及陶瓷璧表面粗糙度,小颗粒粒径的多孔陶瓷,轮廓线清晰,表面越光滑,冰晶形貌复制越完整;甘油含量由3 vol.%增加到6 vol.%,孔径由109μm下降到46μm,陶瓷壁厚由49μm减小到22μm,甘油含量继续增加对孔径和陶瓷壁厚影响不大,孔隙由层状向蜂窝状转变,甘油含量12 vol.%时,孔隙完全转变为蜂窝状。本文采用定向冷冻铸法制备层状Si C多孔陶瓷工艺通过控制固相含量、冷冻温度、甘油含量、颗粒粒径,调节层状Si C多孔陶瓷孔隙形貌、孔隙率,制备出定向的层状Si C多孔陶瓷。
[Abstract]:The aluminum matrix composite material of Pearl shell has the advantages of high strength and high toughness because of its layered structure. The porous ceramic with layered structure is used as the reinforcement of the representative aluminum matrix composite of Pearl shell. The preparation process and pore structure study are the basis for the preparation of high performance pearl shellfish structural composites. The directional freezing casting method can control the orientation and structure of the pore, and is easy to operate, low in cost and environmentally friendly. Si C/Al composites have been widely used in the preparation of layered porous ceramics. However, the high performance imitated Pearl Bay Si C/Al composites need to be further studied. Therefore, the layered sic porous ceramics are studied in this paper. In order to prepare the Si-like C/Al composites with layered sic porous ceramics as reinforcements, using SiC as raw material, water as solvent, carrageenan, dispersant PEG and glycerol as additives, Layered sic porous ceramics were prepared by directional freezing casting. The micropore morphology of layered sic porous ceramics was characterized, the mechanism of pore formation was summarized, and the influence of various factors on the micropore morphology of layered sic porous ceramics was analyzed. The main results are as follows: with the increase of the distance between the sample and the cold source, the dense region, the transition zone, the stratified zone and the three regions respectively appear honeycomb, columnar and layered pore morphology. The pore formation mechanism is mainly related to the crystal structure and crystal growth kinetics of the solvent, and the formation conditions of layered pores are determined by solid content, freezing temperature and particle size. The porosity decreased from 68.8 vol.% to 52.3 vol.0.The pore diameter decreased from 84 渭 m to 14 渭 m, the wall thickness of ceramics increased from 37 渭 m to 72 渭 m, and the freezing temperature was -5? At C, the porosity is disordered, lower than -10? The lower the freezing temperature, the smaller the pore size is. The average pore size at C is 63 渭 m, the particle size affects the profile of pores and the surface roughness of ceramic, and the porous ceramics with small particle size have clear outline and smooth surface, and the more complete the ice crystal morphology is, the more complete the shape of ice crystal is. The content of glycerol increased from 3 vol.% to 6 vol.um, the pore diameter decreased from 109 渭 m to 46 渭 m, and the thickness of ceramic wall decreased from 49 渭 m to 22 渭 m. The increase of glycerin content had little effect on pore size and ceramic wall thickness. The preparation of layered sic porous ceramics by directional freezing casting was carried out by controlling solid content, freezing temperature, glycerol content, particle size, pore morphology and porosity of layered sic porous ceramics. Directional layered sic porous ceramics were prepared.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ174.6

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