【作者】 赵振璇；

【导师】 戴洪兴；

【作者基本信息】 北京工业大学 ， 化学工程与技术， 2010， 硕士

【摘要】 具有特定形貌(如纤维状、层状、片状、棒状、管状等)的纳微米无机材料已广泛应用于功能材料的改性和高性能复合材料的制备,特定形貌和晶体结构无机化合物的可控制备成为材料化学领域极具吸引力和挑战性的热点研究课题。传统的碳酸钙和氧化镁是在物理与化学领域均有重要用途的无机材料,而特定形貌和多孔结构的碳酸钙和氧化镁具有更为优越的物化性质。因此,探求高比表面积特定形貌和多孔结构的碳酸钙和氧化镁的可控制备方法及揭示其物化性质具有重要意义。本论文采用表面活性剂辅助的溶剂热法和水热法合成具有特定形貌或多孔结构的碳酸钙和氧化镁纳微米粒子,并利用XRD、HRSEM、HRTEM/SAED、TGA/DSC、FT-IR和BET等技术表征这些纳微米材料的物化性质,得到如下结果:1.以CTAB、P123、PVP、SDS或PEG为表面活性剂,以不规则氧化钙粒子为钙源,以OA/EtOH (或EG)、OAM或H2O为溶剂,采用溶剂热或水热法合成出花状、带状、珊瑚状、网状、六方状和四方状六方相碳酸钙纳微米粒子。以P123、F127、CTAB、PVP或PEG为表面活性剂,以不规则氧化镁粒子为镁源,以OA、DA或H2O为溶剂,采用溶剂热或水热法合成出花状、六方片状、六棱柱状和介孔立方相氧化镁纳微米粒子。表面活性剂、溶剂以及溶剂(水)热温度对碳酸钙和氧化镁纳微米粒子形貌有着重要影响。2.提高溶剂(水)热温度可增加所得碳酸钙样品的比表面积。采用表面活性剂辅助的OA/EtOH或OA/EG溶剂热法所合成的碳酸钙纳微米粒子的比表面积(8~21 m2/g)高于采用表面活性剂辅助的OAM溶剂热法所合成的碳酸钙纳微米粒子的比表面积(2~6 m2/g)。由PEG辅助的水热法在240 oC条件下水热处理72 h可获得最高比表面积(134 m2/g)的六方状和四方状介孔碳酸钙纳微米粒子。3.由P123、F127或OMA辅助的OA溶剂热法可合成出较高比表面积(122~161 m2/g)的立方相氧化镁纳米粒子,其中由OAM辅助的OA溶剂热法所获得氧化镁具有最高的比表面积(161 m2/g),由P123或F127辅助的OA溶剂热法所制得的六方状和四方状氧化镁粒子的比表面积次之,无表面活性剂辅助的OA溶剂热法合成的比表面积(122 m2/g)最低。由PEG辅助的水热法经240 oC水热处理72 h所得六棱柱状介孔氧化镁纳微米粒子的比表面积最高可达201 m2/g。4.具有六方状和四方状形貌且高比表面积(134 m2/g)的介孔碳酸钙纳微米粒子可在800 oC以下分解成相似形貌的高比表面积(110 m2/g)介孔氧化钙纳微米5.粒子。这种特定形貌和介孔结构的碳酸钙在较低温下表现出优异的可逆吸附与再生性能,使其在酸性气体的吸附和分离以及催化等领域有着重要用途。更多还原

【Abstract】 Nano/microstructured inorganic materials with specific (e.g., fiber-, layer-, plate-, rod-, tube-like, etc.) morphologies have been utilized extensively in the modification of functional materials and the synthesis of high-performance composite materials. The controlled fabrication of inorganic compounds with desired crystalline structures and well-defined shapes is an attractive and challenging hot topic in the research of modern materials chemistry. Conventional calcium carbonate and magnesia are inorganic materials useful in the fields of physics and chemistry, however, their counterparts with specific morphologies and porous structures possess better physicochemical properties. Therefore, it is of significance to explore controllable making strategies and to clarify the physicochemical properties of high-surface-area porous CaCO3 and MgO with specific morphologies. The present thesis was focused on the surfactant-assisted solvo- or hydrothermal fabrication of CaCO3 and MgO nano/microparticles that possessed well-defined morphologies and/or porous structures, and on the physicochemical property characterization of these materials by means of the techniques, such as X-ray diffraction (XRD), high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), and nitrogen adsorption-desorption measurements (BET). The results obtained are as follows:1. Hexagonally crystallized CaCO3 nano/microparticles with flower-, belt-, coralloid-, network-like, hexagonal, and rectangular parallelepiped morphologies were fabricated by adopting the solvo- or hydrothermal strategy with cetyltrimethylammonium bromide (CTAB), triblock copolymer EO20PO70EO20 (Pluronic P123), poly(N-vinyl-2-pyrrolidone (PVP), sodium dodecyl sulfate (SDS) or polyethylene glycol (PEG) as surfactant, irregularly morphological CaO powders as Ca source, oleic acid (OA)/ethanol (EtOH) (or ethylene glycol (EG)), oleylamine (OAM) or H2O as solvent. Cubically crystallized MgO nano/microparticles with flower-like, hexagonal, and hexagonal prism morphologies and mesopores were generated by adopting the solvo- or hydrothermal strategy with P123, triblock copolymer EO106PO70EO106 (Pluronic F127), CTAB, PVP or PEG as surfactant, irregularly morphological MgO powders as Mg source, and OA, decylamine (DA) or H2O as solvent. It is found that the morphologies of the CaCO3 and MgO nano/microparticles were dependent upon the nature of the surfactant and solvent and the solvo- or hydrothermal temperature.2. Increasing the solvo- or hydrothermal temperature favored the enhancement in surface area of the as-fabricated CaCO3 product. The surfactant-assisted solvothermally derived CaCO3 samples possessed higher surface areas (8?21 m2/g) in an OA/EtOH or OA/EG medium than those (2?6 m2/g) in an OAM medium. The mesoporous CaCO3 sample generated hydrothermally with PEG at 240 oC for 72 h exhibited hexagonal and rectangular parallelepiped morphologies and the highest surface area of 134 m2/g.3. Cubic MgO nanoparticles with higher surface areas (122?161 m2/g) were fabricated solvothermally with P123, F127 or OAM as surfactant and OA as solvent, in which the OAM-assisted derived MgO sample possessed the highest surface area (161 m2/g), the surfactant-free derived MgO sample displayed the lowest surface area (122 m2/g), and the P123- or F127-assisted derived MgO samples with hexagonal and rectangular parallelepiped morphologies exhibited surface areas between those of the above MgO samples. The hexagonal prism-like MgO sample obtained hydrothermally with PEG at 240 oC for 72 h possessed the highest surface area of 201 m2/g.4. The high-surface-area (134 m2/g) mesoporous CaCO3 nano/microparticles with hexagonal and rectangular parallelepiped morphologies generated hydrothermally with PEG at 240 oC for 72 h could decompose below 800 oC to similarly morphological mesoporous CaO nano/microparticles with a higher surface area (110 m2/g). The excellent reversible adsorption and regeneration behavior at lower temperatures between CaO and CaCO3 with well-defined particle shapes and mesoporous architectures makes such materials useful in the applications of acidic gas adsorption and separation as well as catalysis.更多还原