【作者】 李晶；

【导师】 赵天波；

【作者基本信息】 北京理工大学 ， 化学， 2016， 硕士

【摘要】 莫来石是一种硅铝酸盐,作为结构材料,在高温方面有广泛应用。目前,通过伴随相分离的溶胶-凝胶方法,已合成了具有双连续大孔-介孔结构的莫来石整体材料。环氧丙烷(PO)作为酸性调节剂用以调控凝胶过程,聚环氧乙烷(PEO)是相分离诱导剂和孔道结构形成剂。六结晶水合氯化铝AlCl3·6H2O为铝源。本文分别运用有机硅源正硅酸甲酯(TMOS)和正硅酸乙酯(TEOS),以及更低廉的无机硅源含水硅溶胶(Aq)合成多级孔道莫来石整体材料。考察了水量、醇量、硅铝比、相分离剂加入量、酸性调节剂用量、NaF等因素对多级孔道莫来石材料的影响。同时,采用不同相对分子量相分离剂,调变其在不同体系中的用量,得到了孔径可调控的多级孔道莫来石整体材料。运用扫描电子显微镜法(SEM),热重法-差热分析法(TG-DTA),X射线衍射法(XRD),傅里叶变换红外光谱法(FT-IR)以及氮气吸附-脱附法等表征方法,对其微观结构变化及合成机理进行了对比研究。发现不同体系中,相分离剂最佳用量、凝胶时间、硬度、收缩率、孔尺寸、莫来石的转化温度、转化过程及相对结晶度均有所不同。实验表明,这些不同主要取决于前驱体混合程度及适宜的相分离和凝胶过程。与无机硅源相比,有机硅源更适宜在较低的转化温度下合成相对结晶度较高的多级孔道莫来石整体材料。通过改变相分离剂的相对分子量和添加量,在无机硅源和有机硅源体系中,均得到孔径可调变的多级孔道莫来石整体材料,为此材料提供了更广阔的应用前景。更多还原

【Abstract】 Hierarchical porous mullite monoliths have been prepared via sol-gel process accompanied by phase separation. Propylene oxide(PO) acted as an acid scavenger to mediate the gelation, poly(ethylene oxide)(PEO) as the phase-separation inducer and network former, alμminμm chloride hexahydrate(Al Cl3·6H2O) as the alμminμm source. The route was improved by using hypotoxic tetraethylorthosilicate(TEOS) and nontoxic aqueous colloidal silica(Aq) instead of tetramethoxysilane(TMOS). The hierarchical porous mullite monoliths is prepared by adjusting the amount of H2 O, Et OH, Si/Al, PEO, PO and Na F, and aging temperature via sol-gel method. In addition, changing the amount of different relative molecular weight of phase-separation agent is necessary to synthesize hierarchical porous mullite monoliths with controllable macropores. The synthesis mechanism and microstructural development were comparatively investigated by scanning electron microscopy(SEM), thermogravimetry-differential thermal analysis(TG-DTA), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR) and nitrogen adsorption-desorption. The optimμm amount of PEO, gel times, hardness, shrinkage, transformation temperature and relative crystallinity of mullite phase, and pore size with different silicon sources are not the same. It was found that the mixing degree of precursors and concurrent process of gelation and phase separation are key elements to get well-defined hierarchical porous mullite monoliths. In addition, the monoliths with high relative crystallinity are more likely to be obtained under low transformation temperature in organic silicon sources system. By adjusting the relative molecular weight and the amount of phase separation agent in inorganic silicon source and organic silicon source system, hierarchical porous mullite monoliths with adjustable pore size are successfully prepared. It may provide a broader prospect for this materials.更多还原