凝胶—发泡法制备多孔氧化铝隔热材料的研究

【作者】 张林；

【导师】 杜景红；

【作者基本信息】 昆明理工大学 ， 材料学， 2011， 硕士

【摘要】 多孔陶瓷由于在化学稳定性、透过性、力学性质、抗高温氧化及抗热震等方面都具有十分优异的性能,而被广泛的应用于保温隔热材料、过滤器、催化剂载体、生物材料、燃料电池材料、热交换器等。多孔陶瓷用于保温隔热材料时,要求气孔以闭口孔为主,但传统的制备方法存在孔径不易控制、气孔分布不均匀等缺点。本文运用凝胶注模和发泡法相结合的方法,即凝胶—发泡法,成功的制备出了闭口孔率高、孔径小、气孔分布均匀的氧化铝多孔陶瓷。本文推导了热导率的计算公式,从理论上分析了热导率的影响因素；对凝胶—发泡法的机理进行了初步的研究,研究了发泡剂对凝胶形成的影响；研究了坯体的DSC—TG曲线,确定了排胶工艺；研究了固相含量、发泡剂添加量、烧结助剂的添加量、烧结温度对样品性能和结构的影响；分析了气孔率对热膨胀性能的影响。得到了以下结论：通过对热导率计算公式的分析表明：气孔率越高,测试温度越低,孔径越小,则氧化铝多孔陶瓷的热导率就越低,其隔热保温效果越好。由于氧阻聚效应,发泡剂的加入会对凝胶的形成产生一定的影响,从而使凝胶时间增加,凝胶强度降低。适当的增加有机单体、交联剂和引发剂的用量,可以在一定程度上减少凝胶时间,增加凝胶强度。有机物的分解温度区间为200℃-500℃,确定排胶工艺为从室温到200℃,升温速率为5℃/min；从200-500℃,升温速率3℃/min；500℃保温一小时浆料的固相含量为45%、发泡剂加入量为1%、烧结助剂加入量为1%、烧结温度为1500℃时,可制备出性能优异的多孔氧化铝陶瓷,此时氧化铝多孔陶瓷的气孔率为56%,其中闭口孔率为51%,抗弯强度为23MPa,气孔分布均匀,孔径约15～120μm。氧化铝多孔陶瓷的热膨胀系数与氧化铝陶瓷的热膨胀系数近似相等,气孔率的变化对多孔氧化铝陶瓷膨胀性能的影响并不明显。更多还原

【Abstract】 Porous ceramics are widely used in thermal insulation materials, filters, catalyst supports, biological materials, fuel cell materials and heat exchangers because of their chemical stability, permeability, mechanical properties, high temperature oxidation and thermal shock, etc.When porous ceramics are used as thermal insulation material, their pores are usually closed pores. But there are many disadvantages in traditional preparation, such as difficultly to control pore size and uneven distribution. In this thesic, alumina porous ceramics were fabricated successfully by gel injection molding and foaming methods, and they were all high closed pore porosity, small aperture and uniformity distribution.Calculating formula of thermal conductivity were derived to analyze their influence factors. Gel-foaming mechanism were studied preliminarily, the gel formation was affected by foaming agent. The row was determined by using to DSC—TG. Properties and structure of sample were impacted by the solid content, foaming agent additive quantity, amount of additives and temperature.and thermal performance was impacted by porosity. The conclusions as follows:According to the analysis of thermal conductivity calculating formula:the higher porosity, the lower testing temperature was, while the smaller aperture of alumina porous ceramics, the less thermal conductivity was, and the better adiabatic effect.Gel formation was influenced by added foaming agent because of oxygen inhibitor effect, and gel time was increased, gel strength was decreased. Gel time was reduced and gel strength was increased to a certain extent, because of appropriate organic monomer, crosslinking agent and initiator.Temperature range of organic decomposition are from 200℃to 500℃, row glue craft as from room temperature to 200℃at 5℃/min, from 200℃～500℃at 3℃/min; and kept warm one hour at 500℃were determined.When the paste solid content was 45%, vesicant addition amount was 1%, sintering fertilizer addition amount was 1%, sintering temperature was 1500℃, the excellent porous alumina ceramic can be prepared, and their porosity was 56% including closed pore porosity 51%, bending strength was 23MPa, distribution uniformity, aperture about 15 120μm.The thermal expansion coefficient of A12O3 porous ceramics were approximately equal to alumina ceramics, and porosity was no effect on expansiveness of A12O3 porous ceramics.更多还原