钙钛矿复合氧化物中空微纳颗粒的控制合成与气敏性能研究

This application uses perovskite oxides as the research subject and aims at "Controllable fabrication and gas sensor properties of perovskite oxide hollow micro- and nanoparticles. Sol-gel theory has claimed that the aggregated particles were size-controllable by altering the thickness of the double eletric layer of colloids. The interparticle forces are altered by adjusting the electrolyte concentration of a sol to adjust the sizes of the aggregated particles. Thus, aggregated particles will form with various size. Hydrothermal treatment of these aggregated particles will promote the Ostwald ripening process to hollowing these particles. Hollow particles are then formed with adjustable and controllable size and shell thickness. A hydrothermal route will be developed to synthesize perovskite oxide hollow particles. Furthermore, (heterogeneous) multi-shell hollow micro- or nanoparticles can be readily fabricated by using layer-by-layer deposition method. On the other hand,the addition of electrolyte is well-known to elevate the boiling temperature of a solution for most solutes. We have also found that the boiling temperature of highly concentrated base solutions was over 180 centi degree, which is high enough for most reactions that occur under hydrothermal conditions. From this view, many hydrothermal reactions are possibly replaced by simple reflux method. So, on the light of the synthetic parameters of hydrothermal reactions, reflux method will be also utilized to prepare hollow micro- and nanoparticles of perovskite oxides. The reactions under stirring are propitious to improve the monodispersity of the hollow particles. The relations between boiling temperature, conductivity and concentrations of highly conncentrated solutions will also be studied. The influence of thses parameters on the formation of hollow particles is also a research goal of this program. Several synthetic system of perovskite oxides will be investigated to develope a general method for preparing perovskite oxide hollow particles with samll size distribution. This method features simplicity, process controllable and up-scalable. After various hollow particles of perovskite oxides are isolated, we will study the gas sencitivity of the perovskite oxide hollow particles to humidity, carbon dioxide, ethanle, etc.We will also investigate the influences of the particle size,shell number and thickness, and composition on the gas sensor properties.

在大量预研基础上，针对多元氧化物以及（异质）多壳层中空微纳颗粒在粒径、单分散性、壳层厚度与层数等可控制备的难点，以钙钛矿型复合氧化物为对象，基于溶胶-凝胶理论中改变电解质浓度可以调节胶体颗粒双电层厚度，使胶体颗粒在不同尺度聚沉，实现聚沉颗粒大小的可调可控，进而在水热、加热回流条件下利用Ostwald熟化作用使聚沉颗粒转变为中空微纳颗粒，通过控制反应时间和温度实现颗粒尺度与壳层厚度的可调可控，搅拌下的加热回流可提高产物的单分散性；以所制备的钙钛矿型复合氧化物中空微纳颗粒为基体，采用层层沉积技术制备（异质）多壳层材料，通过沉积液浓度与沉积次数控制沉积层的层数与厚度，开发出过程可控、具有一定普适性和易于规模化的无模板制备方法。在材料制备的基础上，研究中空微纳颗粒对CO2、水蒸气、乙醇等气体的气敏性能，考查粒径、组成、壳层厚度与层数对气敏性的影响。

中空微纳颗粒具有低密度、高比表面积、良好的稳定性和表面渗透性等特点，在化学、生物技术、材料科学领域具有极其广泛的应用前景。本项目利用熟化作用及纳米尺度的Kirkendall效应，主要研究了中空微纳颗粒的控制合成。首先根据胶体颗粒的聚沉过程受电解质浓度的影响，实现了聚沉颗粒尺度的可调可控，并通过水热条件下的熟化过程，实现了BaZrO3、SrZrO3、BaHfO3、SrHfO3四种复合氧化物中空微纳颗粒的控制合成，粒径在50-200nm可调可控，并将该方法推广至简单化合物SnO2中空颗粒的合成，颗粒尺度在122-270nm间可调可控。以BaZrO3为基体研究了Y3+、Ti4+、Al3+、Rb+等元素在钙钛矿型中空微纳颗粒在A位或B掺杂对样品的光致发光强度的调节作用。合成了SrTiO3中空纳米颗粒，发现其具有较好的光催化降解染料的性能。基于高浓度溶液高沸点的特性，开发了常压回流法制备氧化物中空微纳颗粒的简易方法，合成了BaZrO3、SrZrO3、BaHfO3、SrHfO3复合氧化物及SnO2中空颗粒。水热熟化法制得了CuO/Cu(OH)2CO3梭形复合中空微粒，高度弥散分布的两相颗粒增大了CuO与气体的接触面积，提高了CuO对乙醇和丙酮的气敏性能。以静电纺聚丙烯腈复合纤维为前驱体，通过碳化、氧化，制得了含有氧化铁、氧化钴或氧化镍中空纳米颗粒的复合碳纳米纤维，以其为锂电负极材料表现出高容量和良好的倍率及循环稳定性。我们还探索了碳基纳米复合材料的制备及其电化学性能，以多孔芳香骨架纳米粒为硫载体，在75wt%的高载硫下充放电1000周，单周容量衰减仅为0.074%，循环稳定性优异。以葡萄糖为生物质碳源，尿素为氮源，制得了高氮掺杂的碳镍复合材料，镍纳米颗粒仅为2.26nm，该材料作为乙醇燃料电池电极表现出优异性能。在1M乙醇溶液中的面电流达到327mA/cm2，与文献中的非贵金属电极材料相比为最高值。由于乙醇的消耗，反应500周后，面电流保持89%，更换新鲜的乙醇溶液，面电流恢复到初始的96.8%，表现出极佳的稳定性。