导　　师： 丁恩勇

学科专业： 070305

授予学位： 博士

作　　者： ;

机构地区： 华南理工大学

摘　　要： 随着科技的高速发展，工业生产不断扩大，人类的生存环境则日益恶化。如何有效开发利用功能性材料治理环境污染，实现经济的可持续发展，已经成为人类社会亟待解决的共同问题。纳米TiO/_2作为一种重要的宽禁带半导体材料，因其化学性质稳定，成本低廉，对生物无毒，光催化活性高，降解污染物无选择性且无二次污染等优点，在过去的几十年里得到了迅速的发展。本文以自制的纳米微晶纤维素为诱导剂，以四氯化钛为主要原料，采用水解法在30-80°C的温度下制备了具有不同形貌和晶体结构的TiO/_2纳米晶体。纳米纤维素表面富含大量羟基，可通过氢键相互作用，促进TiO/_2生长基元在其表面异质成核，在温和的反应条件下生长发育为形貌规整、结晶完善的纳米晶体。本文具体的研究工作包括以下几个方面。 首先，采用无机酸水解法、碱再生法和高压均质技术制备了具有不同微观结构和结晶相态的纳米微晶纤维素HNCC、LNCC和RNCC。分别将此三种纤维素和羧甲基纤维素加入四氯化钛的水解体系中，诱导制备TiO/_2纳米晶体，研究纤维素的微观结构和结晶相态对TiO/_2晶体结构和性能的影响，并通过对比实验对纤维素诱导机理进行了初步探讨。 其次，选择极具代表性的HNCC纳米纤维素作为诱导剂，通过大量的探索性实验研究了反应温度、时间、反应物浓度、外加无机酸和表面活性剂等因素对TiO/_2纳米晶体形貌和晶体结构的影响，制备了具有正方形状、花状、纳米针状、球形、刺球形和板栗球状等各种微观形貌的TiO/_2纳米晶体，采用TEM、HRTEM、SEM、XRD、BET比表面积等测试手段对制得的TiO/_2样品进行表征，并以甲基橙溶液模拟染料废水，考察了各样品的光催化活性。 再次，采用光还原法和化学还原法，成功在花状TiO/_2晶体表面负载了一层纳米金属银单质，制备了Ag//TiO/_2复合物，探讨了负载方法、外加助剂和AgNO3浓度对纳米Ag颗粒在TiO/_2晶体表面分散性、均一性及粒径大小的影响。以甲基橙溶液为目标分解物，对各Ag//TiO/_2样品进行光催化性能测试，结果表明，以NH3H2O和NaOH为助剂，采用光还原法，在AgNO3浓度为0.2/%和0.5/%条件下制备的Ag//TiO/_2样品，光催化活性提高较为明显。以金黄色葡萄球菌和大肠杆菌为实验菌种，采用抑菌圈法，对制备的Ag//TiO/_2复合物进行抗菌性能测试，表明各样品均具有较好的抗菌性能。 最后，以聚对苯二甲酸乙二醇酯无纺布和玻璃纤维为负载基体，先对其进行表面接枝改性处理，再采用原位生长的方法，在两种基体表面成功沉积上一层TiO/_2纳米晶体，分析测试结果表明，TiO/_2纳米晶体以化学键的方式牢牢接枝固定在基体表面，光催化降解实验证明，制备的TiO/_2//PET和TiO/_2//GF复合材料在紫外光照和自然光照下均表现出较好的光催化活性，尤其是TiO/_2//GF效果更佳。TiO/_2纳米粒子的接枝固定化，解决了悬浮体系中催化剂难以分离回收的问题。 With the development of science and industry, the environment is getting worse andworse. So how to develop useful and efficient functional materials to solve the problems ofenvironmental pollution has been of great importance for all the human beings. As animportant semiconductor with wide forbidden band, TiO/_2nanocrystals has attracted greatattention during the past decades, due to its superior performances, such as chemical stability,low-cost, nontoxic, high photoreactivity and causing no secondary pollutions. In the presentdissertation, TiO/_2nanocrystals with different morphologies and crystal structure wereprepared by hydrolysis of TiCl4in aqueous solution at a low temperature of30-80°C, usingnanocrystalline cellulose as inducing agent. Nanocrystalline cellulose /(NCC/) whose surfacepossesses of abundant hydroxyl groups acted as as hydrophilic substrate and morphologyinducing agent to promote the heterogeneous nucleation and crystal growth of TiO/_2nanocrystals at low temperatures through strong hydrogen bonding with growth unit of TiO/_2.Well-defined TiO/_2nanocrystals can be obtained under the mild condition without calcinationsin the presence of NCC. The major research contents of this present work were as follows: Firstly, nanocrystalline cellulose with different microstructure and crystalline phase wasprepared by degrading natural cotton fiber in strong acid or alkaline environment. Highcrystallinity NCC /(HNCC/) was prepared by acid degradation process. Low crystallinity NCC/(LNCC/) was produced via alkali regeneration followed by being homogenized with a highpressure homogenizer. Regenerated nanocrystalline cellulose /(RNCC/) was obtained by alkaliregeneration of HNCC. The obtained HNCC, LNCC and RNCC were used as inducing agentseparately to make out the influence of crystal phase and microstructure of cellulose on thenucleation and crystal growth of TiO/_2crystals. The growth mechanism was discussed on thebasis of the results of comparative experiments. Secondly, plenty of experiments were carried out to investigate the effect of temperature,reaction time, the concentration of TiCl4and additive on the morphology and structure ofTiO/_2crystals in the presence of high crystallinity NCC. Cubic, flower-like, needle-like,spherical, thorny ball, chestnut-like TiO/_2nanocrystals were obtained, and they were characterized by TEM, HRTEM, SEM, XRD and BET surface area analyzer. Thephotocatalytic activity of all the samples was detected by the decolourization of methylorange. Thirdly, metallic Ag nanoparticles were deposited on the flower-like TiO/_2nanocrystalsby photoreduction and chemical reduction methods, obtaining Ag//TiO/_2nanocomposites. Theinfluence of preparation technology, additive and concentration of AgNO3solution on thediameter and decentrality and of Ag particles was discussed. The photodegradationexperiment of MO solution indicated that the photocatalytic activity of Ag//TiO/_2nanocomposites prepared by photoreaction method in the presence of NH3H2O and NaOHincreased obviously when the concentration of AgNO3solution was0.2/%and0.5/%. Theantibacterial performance of Ag//TiO/_2samples were tested by inhibition zone method, S.cereus /(ATCC29213/) and E. coli /(ATCC8739/) were chosen as the experimental strains. Lastly, flower-like and cubic TiO/_2nanocrystals were in situ grown on polyethyleneterephthalate /(PET/) non-woven fabric and glass fiber /(GF/) by hydrolysis of TiCl4in aqueoussolution in the presence of nanocrystal cellulose grafted PET fabric /(HNCC-g-PET/) and GF/(HNCC-g-GF/) at a low temperature of70°C. Characteristic results showed that strongchemical bondings were established between substrates and TiO/_2nanocrystals. Thephotocatalytic activity of the obtained TiO/_2//PET and TiO/_2//GF composites was examined bydegradation of orange methyl under natural solar light and high-pressure mercury lamp. Theresults indicated that the TiO/_2//PET composites exhibited good photocatalytic activity, and theTiO/_2//GF showed even higher photoactivity. Loading TiO/_2nanoparticles on supportingmaterials with large surface area where pollutants can be condensed can solve the difficulty infiltration and separation of fine particles in aqueous solution.

关 键 词： 纳米 纳米微晶纤维素 形貌控制 负载

分 类 号： [TB383.1 TQ134.11]

领　　域： [一般工业技术] [化学工程]