本文選題：定向冷凍鑄造　切入點：層狀結構　出處：《蘭州理工大學》2017年碩士論文

【摘要】：仿珍珠貝鋁基復合材料具有層狀結構,因而具有高強度、高韌性等優(yōu)良特點。層狀結構多孔陶瓷作為具有代表性的仿珍珠貝鋁基復合材料的增強體,其制備工藝和孔隙結構研究是制備高性能仿珍珠貝結構復合材料的基礎。定向冷凍鑄造法對孔隙方向和結構定向可控,且操作簡單、成本低廉、環(huán)保,已成為制備層狀結構多孔陶瓷的首選工藝。Si C/Al復合材料已經(jīng)得到廣泛應用,但高性能仿珍珠貝Si C/Al復合材料有待近一步研究,因此,本文研究層狀Si C多孔陶瓷,為下一步以層狀Si C多孔陶瓷為增強體制備仿珍珠貝Si C/Al復合材料做準備。以SiC為原料,水為溶劑,卡拉膠、分散劑、PEG、甘油為添加劑,采用定向冷凍鑄造法實現(xiàn)了層狀Si C多孔陶瓷制備,表征了層狀Si C多孔陶瓷微觀孔隙形貌,總結了成孔機制,分析了各因素對層狀Si C多孔陶瓷微觀孔隙形貌的影響,主要研究結果如下:樣品隨著與冷源距離的增大,依次出現(xiàn)致密區(qū)、過渡區(qū)、層狀區(qū),三個區(qū)分別呈現(xiàn)蜂窩狀、柱狀、層狀孔隙形貌,孔徑范圍在10~80μm。成孔機制主要與溶劑的晶體結構和結晶生長動力學有關,而形成層狀孔隙的條件受固相含量、冷凍溫度、顆粒粒徑、甘油含量等因素影響。固相含量由20 vol.%增加到35 vol.%時,孔隙率由68.8 vol.%降低到了52.3 vol.%,孔徑從84μm減小到14μm,陶瓷壁厚從37μm增加到72μm;冷凍溫度為-5?C時,孔隙呈現(xiàn)無序狀,低于-10?C時呈現(xiàn)層狀孔隙形貌,冷凍溫度越低,孔徑越細小,-30?C時平均孔徑為63μm;顆粒粒徑影響孔隙的輪廓線及陶瓷璧表面粗糙度,小顆粒粒徑的多孔陶瓷,輪廓線清晰,表面越光滑,冰晶形貌復制越完整;甘油含量由3 vol.%增加到6 vol.%,孔徑由109μm下降到46μm,陶瓷壁厚由49μm減小到22μm,甘油含量繼續(xù)增加對孔徑和陶瓷壁厚影響不大,孔隙由層狀向蜂窩狀轉變,甘油含量12 vol.%時,孔隙完全轉變?yōu)榉涓C狀。本文采用定向冷凍鑄法制備層狀Si C多孔陶瓷工藝通過控制固相含量、冷凍溫度、甘油含量、顆粒粒徑,調節(jié)層狀Si C多孔陶瓷孔隙形貌、孔隙率,制備出定向的層狀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.
【學位授予單位】：蘭州理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ174.6

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