【作者】 郭孝孝；

【导师】 段雪；

【作者基本信息】 北京化工大学 ， 应用化学， 2010， 博士

【摘要】 层状双羟基复合金属氧化物(LDHs)是一类阴离子型层状功能材料,因其具有层板组成可调、层板电荷密度可调、层间客体可调及离子尺寸可调等多方面的可调变性能,已经在高性能催化材料、吸附材料、分离材料、功能性助剂材料、生物材料和医药材料等多个领域得到了研究和应用。近些年,基于器件化应用为背景,研究者们将LDHs粉体组装到各种基体上得到了LDHs薄膜,极大地扩展了其应用领域。本论文以原位生长法制备不同取向结构的LDHs薄膜为手段,以简化制备工艺、扩展LDHs在不同领域的应用为目标,分别在金属铝、玻璃、聚乙烯醇(PVA)及生物材料蛋壳膜(ESM)四种不同材质的基体上原位生长得到了取向LDHs薄膜,其中分别包括了c轴平行于基体的LDHs薄膜、c轴垂直于基体的LDHs薄膜及三维网状结构LDHs薄膜；文中还探讨了LDHs薄膜的取向机制,并对所制备薄膜的性能进行了探索性研究,考察了薄膜结构和性能之间的关系,将为LDHs薄膜应用领域的扩展提供一定的实验及理论基础。具体的研究内容和实验结果如下：1、针对c轴平行于基体的LDHs薄膜,分别在金属铝基体上原位生长得到了ZnAl-LDHs薄膜和MgAl-LDHs薄膜,在无机非金属材料玻璃基体上得到了MgAl-LDHs薄膜,并对所得到的薄膜进行了系统的表征和性能探索：(1)首先通过氨水络合的方法在金属铝基体上一步原位生长制备得到了c轴平行于基体的取向ZnAl-NO3--LDHs薄膜；薄膜连续、致密,和基体之间的结合力强；采用极化曲线、交流阻抗(ESI)及浸泡实验等手段对薄膜的防腐蚀性能进行了研究,发现薄膜对基体Al有长久有效的防腐蚀作用；对薄膜的防腐蚀机理进行分析,认为致密的LDHs薄膜可以抑制基体和其周围离子间的电荷传输,从而阻碍了腐蚀的发生；另外由于NO3--LDHs可以将周围的侵蚀性离子如Cl-交换进入层间,通过层板和层间离子之间强的相互作用对侵蚀性离子进行固定,亦可阻碍其对基体的侵蚀。(2)通过尿素分解的方法在金属铝基体上一步原位生长制备得到了c轴平行于基体的取向MgAl-CO32--LDHs薄膜；构成薄膜的六方片状的LDHs粒子相互交错排列,形成了丰富的孔隙结构,有效降低了薄膜的密度；500℃焙烧以后,LDHs薄膜转化为MgAl-MMO薄膜,MMO薄膜维持了前体薄膜的形貌；对MMO薄膜的介电常数进行测试,结果显示由于薄膜丰富的孔隙结构,其介电常数较低；通过改变LDHs前体薄膜的制备条件,实现了对薄膜形貌的规律性调控,进而实现了对MMO薄膜介电常数的有效调控；文中还采用数学曲面插值理构筑了金属离子浓度、晶化时间和MMO薄膜介电常数的三维曲面方程,实现了对薄膜介电常数在2.0-4.7范围内的理论预测。(3)通过尿素分解的方法在无机非金属材料玻璃基体上一步原位生长制备得到了c轴平行于基体的取向MgAl-LDHs薄膜,500℃焙烧以后,得到了复合金属氧化物MgAl-MMO薄膜；抗菌性能进行测试显示,在较高的浓度梯度下MMO薄膜对大肠杆菌和金黄色葡萄球菌的抗菌率均达到了99.9%；分析其抗菌机理认为由LDHs前体法得到的MMO薄膜,由于Al2O3的存在,MgO可以在纳米尺度均匀分散。纳米MgO表面存在Fs+色心,色心可以和氧分子反应生成活性很强的超氧离子O2-,进而对细菌起到杀灭作用。该薄膜无需在光照条件下即可实现抗菌,对抗菌玻璃的制备提供了一条简便易行、成本低廉的途径。2、针对c轴垂直于基体的LDHs薄膜,我们采用聚乙烯醇(PVA)为结构诱导剂对玻璃基体进行改性后,原位生长得到了目标取向的MgAl-LDHs薄膜；对薄膜的取向机理进行分析,认为PVA含有的丰富的羟基和LDHs层板上的羟基之间可以形成氢键作用,从而诱导了薄膜c轴垂直于基体取向生长。3、针对三维复杂结构的LDHs薄膜,我们采用生物模板法,原位生长得到了具有网状结构的水滑石／蛋壳膜(LDHs/ESM)复合薄膜,对薄膜的组成、结构及形貌进行了分析,并对其吸附Cr(VI)性能进行了研究,复合薄膜显示出了良好的吸附性能,热力学研究表明其吸附行为符合Langmuir吸附模型。更多还原

【Abstract】 Layered double hydroxides (LDHs) are a calss of anionic lamellar functional materials. They have a wide variety of applications including as additives in polymers, as precursors to magnetic materials, in biology and medicine, in catalysis and environmental remediation. Recently, ways have been reported to organize LDH microcrystals into large uniform films, which have widened the range of applications of LDH as catalysts, metallic anti-corrosion coatings, and in optical, electric, magnetic devices.In this dissertation, we successfully achieve to fabricate LDH films with different orientations (i.e., the c-axis of the LDH crystallites parallel and perpendicular to the substrate and three dimentional LDH composite membranes with network structure) through in-situ growth methods. To widen the application area of the LDH films, aluminum, glass, poly (vinyl alcohol) (PVA) and eggshell membrane (ESM) were chosen as substrates which represent metal, inorganic material, polymer and biomaterial four typical textures respectively. The effect of the different texture on the morphology of the LDH films was also investigated. The growth mechanisms of the LDH films with different orientations were discussed and compared. The properties of the resulting films were explored and tuned by varying the preparation conditions. The details are shown below:1. For the LDH films with c-axis parallel to the substrate, we obtained ZnAl-LDH films and MgAl-LDH films on aluminum substrate, and MgAl-LDH films on glass substrate. The films were characterized in detail and the properties were investigated respectively.(1) We obtained ZnAl-NO3--LDH films with c-axis parallel to the aluminum substrate by using one-step in-situ growth method. The films were continous and densely packed on the substrate with strong adhesion. The anti-corrosion ability of the films on the aluminum was investigated by polarization curve tests, electrochemical impedance spectroscopy (EIS) tests and immersion tests, and it results that the film could provide long-term protection to the substrate. The densely oriented LDH films could serve as passive layers with high charge transfer resistance contributing to the anticorrosion ability. In addition, the NO3--LDH could exchange the corrosive ions, such as Cl-, into the interlayer, and the ions would be immobilized by the strong interaction between the host layer and the interlayer anions.(2) MgAl-CO32--LDH films with c-axis perpendicular to the aluminum substrates were fabricated by using urea hydrolysis method. The hexagonal platelet-like LDH crystallites are interlaced with each other forming a network of vacant pockets which results in a low density of the film. After being calcined at 500℃, the LDH films were transferred to MgAl-MMO films which could retain the morphology of the precursor films. Dielectric tests showed that the low density of the MMO film results in a low k-value. Furthermore, we successfully controlled the microstructure of the MMO films by varying the crystallization conditions (metal ion concentration, and crystallization time) of the corresponding precursor LDH films. Relatively low k-values in the range 2.0-4.7 were achieved.(3) MgAl-CO32--LDH films with c-axis perpendicular to the glass substrates were fabricated by using urea hydrolysis method. After being calcined at 500℃, the LDH films were transferred to MgAl-MMO films. Bactericidal experiments with colon bacillus and S. aureus were carried out using the as-synthesized MgO-Al2O3 composite film, and both the bactericidal efficiency could reach 99.9% at high concentration gradient. It seems that there are rich Fs+ colour centers on the surface of the highly dispersive nano MgO particles, and highly active superoxide ions O2-could be produced on these colour centers, which can react with the peptide linkages in the cell wall of bactrials and thus destroy them.2. For the LDH films with c-axis perpendicular to the substrate, we obtained this aimed oriented MgAl-LDH films on substrate through in-situ growth method by using PVA as structure-direct agent. We propose that the hydroxyl groups in PVA interact with the Mg/Al-bound hydroxyl groups on the surface of the LDH crystallites via hydrogen bonding which finally orients the metal hydroxide sheet of the LDH crystallites with their c-axis perpendicular to the substrate.3. For the three-dimensional LDH films with complicated structure, we fabricated a LDH/ESM composite membrane by using ESM as the substrate as well as template. SEM images showed that the LDH crystallites could grow on the protein fiber of the ESM, and the final composite membrane retained the network structure of the ESM. Further investigate showed that the inorganic-bio composite membrane could be used as highly efficient adsorbent for hexavalent chromium Cr(VI) removal even when the pH value of the Cr(VI) solution was not further adjusted by addition of acid, which is of practical significance in a wastewater treatment plant. The adsorption isotherm showed a good fit with the Langmuir isotherm model.更多还原