【作者】 王春风；

【导师】 顾华志；

【作者基本信息】 武汉科技大学 ， 材料学， 2012， 博士

【摘要】 能源短缺是世界上所有国家面临的共同难题，解决能源短缺最有效的途径是节能，而节能的主要措施之一就是发展和应用隔热材料。膨胀蛭石不但本身具有较低的导热系数和体积密度，而且其颗粒表面的鳞片结构还具有反射热辐射的能力，是一种有潜在应用价值的高温隔热材料。本文采用蛭石与镁橄榄石复合制备出了复合隔热材料，利用灰色关联分析法，对膨胀蛭石-镁橄榄石复合材料的制备工艺进行了优化。优化后工艺制备的膨胀蛭石-镁橄榄石复合材料抗折强度为9.33MPa，耐压强度为15.74MPa，200oC时，热导率在0.19W/m·K左右，300oC时约为0.22W/m·K，600oC时约为0.26W/m·K。基于离子极化理论和结合系统的固化反应机理，分析了膨胀蛭石复合材料强度的影响因素，考察了磷酸二氢铝的浓度及用量、促凝剂镁砂的种类和MgO/P2O5摩尔比对复合材料的显气孔率、体积密度和力学性能的影响。为进一步提高复合材料的高温隔热性能，以热传导的基本原理和协同作用原理为基础，选取了合适的外加剂提高复合材料的隔热性能。K2Ti6O13晶须的添加量为2wt%，二氧化钛添加量为2wt%，添加8wt%BiOCl的膨胀蛭石-镁橄榄石复合材料具有最优的隔热性能。300oC时热导率为0.117W/m·K，600oC时热导率为0.169W/m·K，800oC时热导率为0.184W/m·K，1000oC时热导率为0.190W/m·K。采用原位凝胶法对膨胀蛭石进行了改性，将膨胀蛭石微米级孔隙转化为网状结构的纳米级孔隙，有效改善了复合材料的微观结构，增强了膨胀蛭石复合材料的力学性能和隔热性能，并研究了改性膨胀蛭石的微观结构的影响因素。原位凝胶改性的膨胀蛭石的制备工艺为：n(环氧丙烷):n(A1):n(甲酰胺)):n(乙醇)=5.5:1:0.8:30，非临界干燥。制备的铝凝胶原位改性的膨胀蛭石的结构孔隙中，构成铝凝胶的骨架由近似球状的氧化铝颗粒相互聚结而成，颗粒粒度比较均匀，平均粒径约为40nm，颗粒间形成的孔径约为45nm，孔径分布较均匀。经900oC和1000oC煅烧后4h仍能保持较好的多孔网络结构，没有出现明显的团聚或孔结构塌陷的现象。改性的膨胀蛭石重量百分比越高，膨胀蛭石-镁橄榄石复合材料的热导系数越低，高温隔热性能越好。当改性膨胀蛭石占蛭石总量百分比为50%时，复合材料的热导率最低，在300oC，其热导系数为0.13W/m·K，600oC时为0.157W/M·K，800oC时为0.169W/m·K，900oC时为0.168W/m·K。与未改性的膨胀蛭石复合材料相比，改性的膨胀蛭石复合材料的热导率在300oC降低了约20-30%，600oC下降了30-40%，800oC和900oC约35-45%。为拓展蛭石的应用领域，增加其附加价值，采用离子交换法对蛭石进行无机改性，将聚羟基铝离子插入到蛭石层间，利用煅烧后插层离子在层间留下的微孔和氧化物柱子，进一步改善蛭石的微观结构，并对蛭石柱化的影响因素和离子交换反应的动力学做了基础理论研究。XRD分析表明柱化插层后Al-柱化蛭石001晶面的层间距为18.42，煅烧后的Al-柱化蛭石的层间距为17.26，通过聚羟基铝的插层，蛭石获得了永久的8.82的层间自由空间。采用TEM，TG-DSC，XRD，FT-IR和N-吸附脱附等方法对柱化前后的蛭石微观结构进行了表征，与蛭石原矿相比，经过聚羟基铝离子柱化的蛭石在热稳定性和层间微观结构都有所改善。蛭石与keggin-Al7+13离子的离子交换反应中，粒内扩散步骤为反应的速控步骤，其反应的表观活化能为26.79kJ/mol，动力学方程可表示为：(?)更多还原

【Abstract】 Energy shortage is an important problem faced by all countries in the world, and the mosteffective way to solve the energy shortage is energy saving. The most effective way to save energyis development and application of insulation materials. Expanded vermiculite itself has low thermalconductivity and bulk density, moreover, the scale structure of its granule surface has the ability toreflect thermal radiation. It is a potential insulation refractory material with high application value.In this work, the insulation material was prepared from expanded vermiculite and forsterite.Based on analysis of grey relational degree, the preparation process of expandedvermiculite-forsterite composites was optimized. Prepared by the optimized preparation process, theinsulation material can endure rupture strength of9.33MPa and compression strength of15.74MPa.At the temperature of200oC, its thermal conductivity is about0.19W/m·K, at300oC, about0.22W/m·K，at600oC, about0.26W/m·K.Based on the polarization theory and curing mechanism of bond system, the bond system ofcomposites was optimized, and the relationship between the properties of composites and manyfactors were studied, such as the concentration and dosage of aluminum dihydrogen phosphate, thetypes of magnesia and MgO/P2O5molar ratio. Based on the synergistic effect theory, we try toimprove the thermal insulation propertiy of composites by way of selecting appropriate admixtureto improve the intensity and thermal insulation of composites material. The addictive amount ofK2Ti6O13whisker is2wt%, Titanium dioxide2wt%, BiOCl8wt%, which can produce the bestheat-resistance of expanded vermiculite and forsterite composites material. At the temperature of300oC, its thermal conductivity is0.117W/m·K, at600oC0.169W/m·K, at800oC0.184W/m·K, at1000oC0.190W/m·K.In order to improve the microstructure of composites material, furthermore to enhance themechanical and thermal insulation properties of composites, we adopted method of gel in situ tomodify expanded vermiculite and research the conditions for preparation process of modifiedexpanded vermiculite. Through modification of gel-in situ, the pore structure of expandedvermiculite varied from micrometers to nanometer. So the microstructure of composites can beimproved, and the mechanical strength and thermal insulation properties of composites increase. Theoptimized preparation process of gel in situ modification is: n(epoxy propane):n(A1):n(methanamide)):n(alcohol)=5.5:1:0.8:30, ambient drying. As is shown in SEM of expanded vermiculite after being optimizedby aluminum gel in situ, the framework of aluminum gel in situ is made up of sphere-like Al2O3particles, the particle size is fairly regular, the mean particle diameter is40nm, the pore size amongparticles is45nm, and the distribution of pore size is fairly regular. After being calcined under the temperature of900oC and1000oC for4hours, it can be still kept in good multi-porous network,without any distinct signs of conglobation or porous structure collapse.By means of in-situ modification to expanded vermiculite, thermal conductivity of compositesmaterial has been remarkably reduced. The higher proportion the modified expanded vermiculitetakes up in total weight of vermiculite, the lower the thermal conductivity of composites material is,and the better the thermal insulation. When modified expanded vermiculite takes up50wt%of totalamount of vermiculite, the thermal conductivity of composites material is the lowest. At thetemperature of300oC, its coefficient of thermal conductivity is0.13W/m·K, at600oC0.157W/m·K,at800oC0.169W/m·K, at900oC0.168W/m·K. Compared with non-modified expanded vermiculitecomposites material, the modified expanded vermiculite composites material can reduce thermalconductivity by20-30%at300oC,30-40%at600oC,35-45%at800oC or900oC.In order to expand the application of vermiculite and increase its added value, we adopted ionexchange method to modify vermiculite by inorganic salt, insert polynuclear Al into the layers ofvermiculite, and take advantage of the micro holes and oxidized pillars in inter-layers of inserting ionsafter calcination. In order to furthermore improve microstructure of vermiculite, we also discuss thepreparation process of pillared vermiculite, and research the dynamics of ion exchange reaction. Theanalysis of XRD indicates that after being pillared, the interlayer spacing of A1pillared vermiculitecrystal face is18.42, the interlayer spacing of calcinated Al pillared vermiculite is17.26.Through inserting layer of polynuclear Al, vermiculite gains perpetual8.82interlayer free space.From the characterization of vermiculite microstructures before and after pillarization by means ofTEM, TG-DSC, XRD, FT-IR and nitrogen sorption isotherms, we find out that polynuclear Alpillared vermiculite is much better than raw vermiculite in thermal stability and interlayermicrostructure. During the ion exchange of vermiculite and keggin-Al7+13, intra-particle diffusionprocess is controlling step, the apparent activation energy of its reaction is26.79kJ/mol, and itskinetic equation can be denoted as follows:(?)更多还原