【作者】 凌钦才；

【导师】 孙建中；

【作者基本信息】 浙江大学 ， 化学工程， 2009， 博士

【摘要】 本文介绍线性低密度聚乙烯(LLDPE)/乙烯-辛烯共聚物(POE)基光催化及微波吸收复合材料的制备及表征。以钛酸丁酯作为钛源,分别选用硼酸-氟化铵、硼酸-硝酸铁-硝酸铈和硼酸-硝酸铁-正硅酸乙酯为掺杂体系,通过溶胶-凝胶法分别制备了可见光响应的硼-氮共掺杂二氧化钛、硼-铁-铈三元共掺杂二氧化钛和硼-铁共掺杂二氧化钛/二氧化硅光催化剂。采用X射线衍射(XRD)、X射线光电子能谱(XPS)、紫外-可见吸收光谱(UV-vis DRS)、红外光谱(FT-IR)、氮气吸脱附和扫描电镜(SEM)表征了所制备的共掺杂光催化剂;选用苯酚或2,4-二氯苯酚为模拟污染物在可见光照射下进行降解实验,评价了它们的光催化活性,并与商用二氧化钛P25的催化活性进行比较。结果表明:掺杂可阻止加热条件下二氧化钛由锐钛型向金红石的转化;非金属硼和氮原子或硼原子都已掺入二氧化钛晶格,导致带隙能降低,吸收光谱红移和可见光催化活性,而金属铁和铈原子或铁原子则以氧化物的形式分散在二氧化钛中,抑制光生电子-空穴对的复合,提高光量子效率,改善二氧化钛的光催化活性;二氧化钛和二氧化硅之间存在密切的相互连接,这种连接有利于形成高表面积的光催化剂;掺杂剂用量及热处理温度影响光催化剂的催化活性。催化活性的提高来源于共掺杂原子的协同效应。以LLDPE/POE/碳酸钙拉伸膜为基材,用浸渍法制备了二氧化钛光催化膜。用SEM观察了二氧化钛在催化膜上的分散状态。分别在紫外光和可见光照射下降解甲醛,评价光催化膜的催化活性。结果表明:在紫外照射下,P25光催化膜的催化活性要稍微大于硼-氮共掺杂二氧化钛光催化膜的活性;而在可见光照射下,硼-氮共掺杂二氧化钛光催化膜的活性要明显高于P25光催化膜的活性。以LLDPE/POE为聚合物基体,分别用羰基铁粉、短碳纤维、碳纳米管、炭黑作为微波吸收剂,采用熔融共混法制备了LLDPE/POE基微波吸收复合材料,分别用标量网络分析仪和矢量网络分析仪测试了复合材料的微波吸收性能和电磁参数,分析了微波吸收的来源。用SEM和TEM观察了复合材料的形貌。结果表明:固定吸波剂种类,在材料厚度相同的条件下,随着复合材料中吸波剂含量的提高,复合材料的吸收峰位置都向低频方向移动;为了获得最优吸收效果,每一种吸波剂都有相应的最佳含量;LLDPE/POE/羰基铁粉复合材料的微波吸收既有介电损耗也有磁损耗,而其余复合材料的微波吸收来自于介电损耗;填料粒子都较好地分散在聚合物基体中,表明熔融共混是制备LLDPE/POE基微波吸收复合材料的有效方法。模拟计算则表明:同一种复合材料体系,随着厚度增加,复合材料的吸收峰位置也向低频方向移动。更多还原

【Abstract】 The thesis reported preparation and characterizationof low density polyethylene （LLDPE）/ethylene- octene copolymer （POE） matrix composites with photocatalytic and microwave absorbing properties.Using tetrabutyl titanate as the precursor of titanium, visible-light-driven titania photocatalysts co-doped with boron and nitrogen, with boron and ferrum and cerium, and titania/silica photocatalysts co-doped with boron and ferrum were prepared by sol-gel routes, in which boric acid and ammonium fluoride, boric acid and ferric nitrate and cerium nitrate, and boric acid and ferric nitrate and ethyl silicate were the sources of dopants, respectively. The prepared photocatalysts were characterized by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, UV-Vis diffusive reflectance spectroscopy （UV-vis DRS）, Fourier transform infrared spectroscopy （FT-IR）, N₂ adsorption-desorption isotherm and scanning electron microscopy （SEM）. The decomposition of phenol or 2, 4-dichlorophenol under visible light irradiation was used as probe reaction to evaluate their photocatalytic activities, which were compared with the photoactivity of merchandise titania P25. The results show that the doping can retard the transformation from anatase to rutile at elevated temperatures, that nonmetal boron and nitrogen atoms or boron atoms are weaved into the crystal lattice of titania, resulting in the decreases of band gap, red-shift and visible-light-driven photoactivity, whereas ferrum and cerium atoms or ferrum atoms present in the forms of FeO/Fe₂O₃ and Ce₂O₃/CeO₂ or FeO/Fe₂O₃ and disperse in TiO₂, which can prohibit recombination of the photo-generated electrons and holes, increasing photo quantum efficiency and improving the photoactivity, and there are intimate molecule-level interactions between titania and silica, which are in favor of the preparing the photocatalysts with big surface area. The synergistic effects of co-doping are responsible for the visible light response and high photoactivity.Using microporous film prepared from LLDPE/POE/CaCO₃ as substrate, titania film with photocatalytic property was prepared by dipping. The morphologies were observed by SEM. Degradation of formaldehyde under ultraviolet radiation or visible illumination was used to evaluate the photoactivity of photocatalytic films. The results show that the photocatalytic property of P25 film under ultraviolet radiation is superior slightly to that of boron-nitrogen co-doped titania film, whereas the photocatalytic property of boron-nitrogen co-doped titania film under visible illumination is obviously higher than that of P25 film.Polymer matrix microwave absorbing composites were prepared by melt blend using LLDPE and POE as matrix, and carbonyl iron powder （CIP）, short carbon fiber （SCF）, multi-walled carbon nanobute （MWCNT） and carbon black （CB） as absorbents, respectively. The absorbing properties and electromagnetic parameters of microwave absorbing composites were measured by a scalar network analyzer and a vector network analyzer, respectively. The microwave absorption mechanisms of composites prepared with different absorbents were discussed. The morphologies were observed by SEM and TEM. The results show that the absorbing peak moves to the low frequency as absorbent content in composites increases when absorbent and thickness of composites are fixed, that there is the corresponding optimum content of absorbent in order to gain the best absorbing effectiveness. The microwave absorption can be attributed to a combining contribution of the dielectric loss and magnetic loss for LLDPE/POE/CIP composites, and the dielectric loss for LLDPE/POE/SCF,LLDPE/POE/MWCNT,LLDPE/POE/CB andLLDPE/POE/CB/CaCO₃ composites. The absorbents and filler （CaCO₃） are well dispersed in polymer matrix, demonstrating that LLDPE/POE matrix composites can be fabricated by melt blending. The simulation calculation show that the absorbing peak moves to the low frequency as thickness of composites increases when absorbent and content of absorbent in composites are fixed.更多还原