【作者】 王美荣；

【导师】 贾德昌；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2011， 博士

【摘要】 本文以天然偏高岭土、硅酸钾溶液、漂珠等为原材料制备了铝硅酸盐聚合物和漂珠/铝硅酸盐聚合物复合材料。采用X射线衍射、傅里叶变换红外光谱、固体核磁共振、扫描电镜、高分辨透射电镜等分析手段,研究了高岭土向偏高岭土转变过程及偏高岭土形成机制;探讨了影响偏高岭土化学活性的因素及以化学合成的偏高岭土为原料的铝硅酸盐聚合物的聚合机制;系统研究了铝硅酸盐聚合物材料的制备工艺、偏高岭土的化学活性对铝硅酸盐聚合物组织和性能的影响及漂珠/铝硅酸盐聚合物复合材料的组织、结构和性能。研究结果表明,在高岭土的热转变过程中,高岭土的脱羟基是发生结构转变的前提条件,但是脱羟基和结构转变是两个独立的过程。当高岭土失去羟基后,结构重组使Al–O和Si–O结构单元发生变化,从而形成无序状态的偏高岭土。偏高岭土的化学活性采用四配位AlO₄含量来衡量,四配位AlO4含量越大则化学活性越大。随着煅烧温度的提高（600⁹00°C）铝硅酸盐聚合物的化学活性逐渐增大;随着保温时间的延长（1⁸h）,其化学活性先增大后降低。当煅烧温度为900°C,保温时间为4h时,偏高岭土获得最大化学活性。铝硅酸盐聚合物的反应–生成机理:当偏高岭土颗粒与碱性的硅酸盐溶液混合后,首先由颗粒表面开始溶解,即偏高岭土中的结构单元Q4（1Al）和四、五和六配位的Al原子结构单元溶解,使Si–O–Si键和Si–O–Al键水解断裂,形成[Al（OH）₄]^–、[AlO（OH）₃]^2–、[Al（OH）₄（OH₂）]^–、[Al（OH）₅]^2–、[Al（OH）₄（OH₂）₂]^–和[Al（OH）₅（OH₂）]^2–和[SiO（OH）₃]^–为主的单体以及少量的[SiO₂（OH）₂]^2–单体。随着反应的进行,单体相互之间发生缩聚反应,脱去水分子,最终生成一种Si以Q4（3Al）和Q4（2Al）结构单元形式存在、Al全部以四配位原子结构单元形式存在的网络状混合结构组成的铝硅酸盐聚合物。随着养护温度的升高（25⁹0°C）和养护时间的延长（4²8d）,铝硅酸盐聚合物的性能先增大后降低。当养护温度为80°C,养护时间为19d时,铝硅酸盐聚合物的体积密度最大、开孔孔隙率最低抗压强度最大,分别为1.45g·cm–3、8.5%和124.8MPa。采用具有不同化学活性的偏高岭土可制备具有不同性能的铝硅酸盐聚合物材料。分别以800MK和900MK为原料所制备铝硅酸盐聚合物的体积密度分别为1.43g·cm–3和2.29g·cm–3,抗弯强度分别为8.7MPa和32.1MPa,抗压强度分别为73.0MPa和111.0MPa,导热系数分别为0.23W·m^–1·K^–1和1.10W·m^–1·K^–1。添加漂珠后,其复合材料的体积密度和导热系数均大幅度降低。当添加40vol.%漂珠后,其漂珠/铝硅酸盐聚合物复合材料的抗压强度为36.5MPa、体积密度为0.82g·cm^–3和导热系数为0.173W·m^–1·K^–1,其综合性能优于目前使用的漂珠砖的抗压强度7.84MPa、体积密度0.80g·cm⁽–3_和导热系数1.59W?m^–1?K^–1。更多还原

【Abstract】 In this paper, metakaolin, potassium silicate and fly ash cenosphere, etc, were used to fabricate geopolymer and cenosphere/ aluminosilicate geopolymers composite. Transformation mechanism from kaolin to metakaolin and factors which have great effect on the chemical activity of metakaolin were systematically investigatedanalyzed by XRD, SEM, NMR and HRTEM et al. The geopolymerization mechanism was studied using the synthesized metakaolin. Effects of manufacture parameters and chemical activity of metakaolin on the structure and properties of the resulted aluminosilicate geopolymer were investigated. Based on the above studies, fly ash cenosphere/ aluminosilicate geopolymers composites were successfully prepared and structure, microstructure and properties were systematically researched.The result revealed that dehydroxylation of kaolin is the precondition of the structural rearrangements, while dehydroxylation and structural rearrangements are two separate processes. After the dehydroxylation of kaolin, the structural rearrangements of Al–O structural site occured, resulting in the amorphous metakaolin. The chemical activity of metakaolin was measured by the content of four tetrahedral Al, and the more four tetrahedral Al content, the greater chemical activity of the metakaolin. With the increasing of calcined temperature （600⁹00°C） and calcined time （1⁸h）, the chemical activity of metakaolin increased and the highest chemical activity were obtained when calcined temperature and time are 900°C and 4h, respectively.The geopolymerization mechanism of aluminosilicate geopolymers based on synthetic metakaolin are: after mixing metakaolin particles with alkali silicate solution, dissolving of metakaolin started from its surface, i.e., Q4（1Al） sites and four, five and six coordinates of Al–O sites dissolved, together with the Si–O–Si bond and Si–O–Al bound hydrolysis, resulting in the [Al（OH）₄]^–, [AlO（OH）₃]^2–, [Al（OH）₄（OH₂）]^–, [Al（OH）₅]^2–, [Al（OH）₄（OH₂）₂]^–, [Al（OH）₅（OH₂）]^2–, [SiO（OH）₃]^– and a small amount of [SiO₂（OH）₂]^2– monomers. With reaction, the Si species condense with Al species to form aluminosilicate with network structure where Si is in the form of Q4（3Al） and Q4（2Al） and Al in four coordinate.With increasing the curing temperatures （25⁹0°C） and time （4²8d）, when curing temperature and time are 80°C and 19d, respectively, open porosity is the lowest, bulk intensity and compressive strength of aluminosilicate geopolymers reach the highest values, which are 18.5%, 1.45g·cm^–3 and 124.8MPa, respectively. Properties of aluminosilicate geopolymers based on metakaolin with various chemical activities were also different. Using metakaolin caclined under 800°C and 900°C separately, compressive strengths, flexural strengths, bulk intensities and thermal conductivities of the resulted geopolymers were 73.0MPa and 111.0MPa, 8.7MPa and 32.1MPa, 1.43g·cm^–3 and 2.29g·cm^–3, 0.23W·m^–1·K^–1 and 1.10W·m^–1·K^–1, respectively.After the addition fly ash cenosphere, bulk density and coefficient of thermal conductivity of the composite significant decline. With 40vol.% fly ash cenosphere, the compressive strength, bulk density and thermal conductivity of the composite are 36.5MPa, 0.82g·cm^–3, 0.173W·m^–1·K^–1, respectively, which are much better than the common cenosphere-brick material of 7.84MPa, 0.80g?cm^–3 and1.59W·m^–1·K^–1, respectively.更多还原