多孔氧化物陶瓷的可控烧结制备及性能研究

发布时间：2018-05-12 05:54

本文选题：多孔陶瓷 + 陶瓷膜　；参考：《中国科学院大学(中国科学院过程工程研究所)》2017年博士论文

【摘要】：多孔陶瓷具有耐高温、抗酸碱、耐有机腐蚀、良好的生物惰性、使用寿命长、再生性能好等优点,广泛应用在过滤、隔热、吸音及生物骨骼等领域中。目前,多孔陶瓷制备所用的原料多为形貌不规则的颗粒,这些颗粒在烧结过程中的可控性差,存在不均匀的团聚收缩,导致陶瓷中出现死孔、半通孔,并伴随孔率的烧结损失,影响了多孔陶瓷的实际应用效果。本论文针对陶瓷孔结构难以调控的问题,提出采用热等离子体制备的球形致密颗粒进行多孔陶瓷制备。球形颗粒堆积体经过烧结,获得孔结构均匀、贯通、可调的多孔陶瓷。主要工作为:(1)以球形致密的SiO_2颗粒为原料进行紧密堆积造孔,球形颗粒堆积体经过烧结,相互接触的颗粒之间形成颈部连接,获得孔隙均匀贯通的多孔氧化硅陶瓷。结合动力学分析,对多孔陶瓷的烧结行为进行研究,结果发现球形致密的SiO_2颗粒具有热稳定性,在颗粒间颈部强化过程中孔隙得到完好的保留,制备的多孔陶瓷具有很好的烧结可控性。研究了颗粒堆积紧密度对陶瓷结构和机械强度的影响,分析了球形颗粒造孔的特点。同时,获得了原料粒径对陶瓷孔径的调控规律。最后,开展了 SiO_2多孔陶瓷渗透性研究,并探索了其在固液分离、油水分离和颗粒粒径分级上的应用性能。(2)为应用于高温环境,采用球形致密的Al_2O_3颗粒制备具有均匀贯通孔道的Al_2O_3多孔陶瓷。采用硅溶胶包覆原料颗粒的方法,有效降低了高强度氧化铝陶瓷的烧结温度,同时完好地保留了均匀、贯通、光滑的孔结构。分析了硅溶胶包覆层与氧化铝颗粒在烧结中生成莫来石颈部的过程,同时结合动力学分析开展了颈部生成的控制机理研究,结果表明莫来石颈部的生成受Al_2O_3颗粒表面Al3+释放速率的控制。根据陶瓷微观孔结构的烧结变化,优化了硅溶胶包覆量。同时,对莫来石强化陶瓷的作用机理进行了研究。最后,验证了氧化铝多孔陶瓷的高渗透性。(3)以超细球形Al_2O_3颗粒为原料堆积造孔,制备孔径更小的Al_2O_3陶瓷膜。研究了超细球形Al_2O_3颗粒的烧结演化行为,发现球形颗粒堆积孔经过均匀的烧结演化,成为均匀贯通的孔结构,展现出良好的烧结可控性。从超细球形颗粒的传质机理研究中,发现球形颗粒通过表面扩散进行传质,烧结活化能达到721±12kJ/mol,说明颗粒有很好的热稳定性。在膜层与过渡层的匹配研究中,得到了膜层的优化厚度4.8μm和适宜的烧结区间1200-1400℃。通过膜层和过渡层的一步烧结机理研究,发现介稳相的纳米球形Al_2O_3颗粒转化为稳定的α相后才发生颗粒间的传质烧结,然而相转化温度与过渡层颗粒的烧结温度基本一致,使两层膜能够实现一步烧结。最后,将陶瓷膜用于悬浮颗粒分离,证明了其良好的应用性能。(4)将孔结构的可控烧结技术运用到闭孔隔热陶瓷领域,利用SiO_2空心颗粒壳体致密、高强的特点,制备了闭孔结构支撑的SiO_2隔热陶瓷。通过调控烧结温度和烧结助剂,研究了隔热陶瓷孔结构的烧结可控性,结果发现致密的颗粒壳体能够很好地保护陶瓷闭孔结构,在高强颈部形成过程中,空心颗粒仅收缩3.3%。同时,通过添加烧结助剂进行了陶瓷晶型结构的调控研究,揭示了方石英对隔热陶瓷性能的影响机理。通过调节空心颗粒的大小和壁厚,实现了多孔陶瓷结构和性能的调控。最后,建立了闭气孔支撑结构的隔热性能模拟模型,模拟结果与实验结果一致。
[Abstract]:Porous ceramics have the advantages of high temperature resistance, acid alkali resistance, organic corrosion resistance, good biological inertness, long service life, good regeneration performance and so on. It is widely used in the fields of filtration, heat insulation, sound absorption and biological skeleton. At present, the materials used in the preparation of porous ceramics are mostly irregular particles, and the controllability of these particles in the sintering process is poor. The existence of uneven agglomeration contraction leads to the appearance of dead pores, half through holes in ceramics and the sintering loss of pore ratio, which affects the practical application effect of porous ceramics. In this paper, spherical compact particles prepared by thermal plasma are prepared for porous ceramics. Through sintering, porous ceramics with uniform pore structure, through and adjustable are obtained. The main work is as follows: (1) dense spherical SiO_2 particles are used as raw materials for tight packing and pore formation. The sintering behavior of porous ceramics was studied. The results showed that the spherical compact SiO_2 particles had thermal stability. The pores were retained well during the strengthening of the intergranular neck. The prepared porous ceramics had good sintering controllability. The effects of particle packing tightness on the structure and mechanical strength of the ceramics were studied, and the spherical particles were analyzed. At the same time, the regulation of pore size of the raw material was obtained. Finally, the permeability of SiO_2 porous ceramics was studied and its application performance on solid liquid separation, oil water separation and particle size classification was explored. (2) the preparation of spherical compact Al_2O_3 particles for the application in high temperature environment has uniform penetration. The Al_2O_3 porous ceramics of the channel. The sintering temperature of high strength alumina ceramics was effectively reduced by the method of coating material particles by silica sol. At the same time, the uniform, through and smooth pore structure were well preserved. The process of producing mullite neck in the sintering of the silica sol coating and alumina particles in the sintering was analyzed, and the kinetic analysis was combined. The control mechanism of the neck formation was studied. The results showed that the formation of mullite neck was controlled by the Al3+ release rate on the surface of Al_2O_3 particles. According to the sintering changes of the micro pore structure of the ceramics, the coating amount of the silica sol was optimized. At the same time, the mechanism of the action of mullite strengthened ceramics was studied. Finally, the porous alumina ceramics were verified. High permeability. (3) the pore forming of superfine spherical Al_2O_3 particles was deposited and the Al_2O_3 ceramic membrane with smaller pore size was prepared. The sintering evolution behavior of the ultrafine spherical Al_2O_3 particles was studied. It was found that the spherical particles accumulated through the uniform sintering evolution and became uniform and permeable Kong Jie structure, showing good sintering controllability. In the study of mass transfer mechanism of the particles, it is found that the spherical particles are mass transfer through the surface diffusion, and the activation energy of the sintering is 721 + 12kJ/mol, indicating that the particles have good thermal stability. In the matching study of the film layer and the transition layer, the optimum thickness of the film layer is 4.8 Mu and the suitable sintering interval is 1200-1400 degrees. One step through the diaphragm and transition layer is obtained. The sintering mechanism was studied. It was found that the spherical Al_2O_3 particles in the metastable phase were converted to the stable alpha phase only after the mass transfer sintering. However, the phase conversion temperature was basically consistent with the sintering temperature of the transition layer particles, which made the two layers a one-step sintering. Finally, the ceramic membrane was applied to the separation of suspended particles, which proved its good application. (4) the controllable sintering technology of the pore structure is applied to the field of closed heat insulation ceramics. The SiO_2 insulation ceramics with closed structure support are prepared by using the compact and high strength characteristics of the SiO_2 hollow particle shell. The sintering controllability of the porous structure of the insulating ceramic is studied by controlling the sintering temperature and the sintering aids, and the compact particle shell is found. In the forming process of high strength neck, the hollow particles only shrink 3.3%., and the crystal structure of ceramics is regulated by adding sintering aids. The influence mechanism of the quartz on the properties of the insulating ceramics is revealed. The porous ceramic structure is realized by adjusting the size of the hollow particles and the thickness of the wall. Finally, a simulation model of the thermal insulation performance of the closed hole supporting structure is established, and the simulation results are consistent with the experimental results.

【学位授予单位】：中国科学院大学(中国科学院过程工程研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ174.1

【参考文献】