凝胶—发泡法制备多孔氧化铝隔热材料的研究
发布时间：2019-06-29 17:33
【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。
[Abstract]:Porous ceramics have been widely used in thermal insulation materials, filters, catalyst carriers, biomaterials, fuel cell materials, heat exchanger and so on because of their excellent properties in chemical stability, permeability, mechanical properties, high temperature oxidation resistance and thermal shock resistance. When porous ceramics are used in thermal insulation materials, pores are required to be mainly closed holes, but the traditional preparation methods have some shortcomings, such as difficult to control pore size, uneven distribution of pores and so on. In this paper, alumina porous ceramics with high closed porosity, small pore size and uniform pore distribution were successfully prepared by using the method of gel injection mould and foaming method, that is, gel foaming method. In this paper, the calculation formula of thermal conductivity is deduced, and the influencing factors of thermal conductivity are analyzed theoretically; the mechanism of gel-foaming method is studied, and the effect of foaming agent on gel formation is studied; the DSC-TG curve of billet is studied, and the gel discharge process is determined. The effects of solid phase content, foaming agent addition, sintering assistant addition and sintering temperature on the properties and structure of the sample are studied. The effect of porosity on thermal expansion was analyzed. The following conclusions are obtained: the higher the porosity, the lower the test temperature and the smaller the pore size, the lower the thermal conductivity and the better the thermal insulation effect of alumina porous ceramics. Due to the effect of oxygen inhibition, the addition of foaming agent will have a certain effect on the formation of the gel, so that the gel time increases and the gel strength decreases. By properly increasing the amount of organic monomer, crosslinker and initiator, the gel time can be reduced and the gel strength can be increased to a certain extent. The decomposition temperature range of organic matter is 200 鈩，
本文编号：2507991
[Abstract]:Porous ceramics have been widely used in thermal insulation materials, filters, catalyst carriers, biomaterials, fuel cell materials, heat exchanger and so on because of their excellent properties in chemical stability, permeability, mechanical properties, high temperature oxidation resistance and thermal shock resistance. When porous ceramics are used in thermal insulation materials, pores are required to be mainly closed holes, but the traditional preparation methods have some shortcomings, such as difficult to control pore size, uneven distribution of pores and so on. In this paper, alumina porous ceramics with high closed porosity, small pore size and uniform pore distribution were successfully prepared by using the method of gel injection mould and foaming method, that is, gel foaming method. In this paper, the calculation formula of thermal conductivity is deduced, and the influencing factors of thermal conductivity are analyzed theoretically; the mechanism of gel-foaming method is studied, and the effect of foaming agent on gel formation is studied; the DSC-TG curve of billet is studied, and the gel discharge process is determined. The effects of solid phase content, foaming agent addition, sintering assistant addition and sintering temperature on the properties and structure of the sample are studied. The effect of porosity on thermal expansion was analyzed. The following conclusions are obtained: the higher the porosity, the lower the test temperature and the smaller the pore size, the lower the thermal conductivity and the better the thermal insulation effect of alumina porous ceramics. Due to the effect of oxygen inhibition, the addition of foaming agent will have a certain effect on the formation of the gel, so that the gel time increases and the gel strength decreases. By properly increasing the amount of organic monomer, crosslinker and initiator, the gel time can be reduced and the gel strength can be increased to a certain extent. The decomposition temperature range of organic matter is 200 鈩，
本文编号：2507991
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