【作者】 和平；

【导师】 陈建峰；

【作者基本信息】 北京化工大学 ， 化学工程， 2007， 硕士

【摘要】 在充满生机的二十一世纪,新材料的创新,尤其是以纳米材料为基础的新技术、新产品的创新将是对社会发展、经济振兴、国力增强最具影响力的战略研究领域之一。无机纳米颗粒的制备是这一战略研究领域极为重要的组成部分,具有重要的科学意义和应用前景。为此,本论文选择具有广阔市场前景的钙钛矿型电子陶瓷材料—SOx粉体材料作为研究对象,探索合成纳米材料的新方法和新工艺,研究调控纳米材料性能的手段和策略,并在此基础上合成了三种钛酸钡基钙钛矿型纳米粉体,考查了这三种粉体的性能。首先以S2、C2和T4为原料,采用低温液相合成法(LTAS)在常压100℃以下制备了钙钛矿型纳米SOx(SOx, SCT)粉体,其反应步骤简单,且生成的速率较快。利用TEM和XRD表征手段对粉体的形貌和物相进行了剖析,研究结果表明采用低温液相合成法制备的SOx纳米粉体为外边缘毛糙的松团状球形,粉体中含有一定量富T无定形物质。当掺杂C2+离子量少于80mol%时,C2+离子可均匀的进入母体晶格,形成完全互溶的固溶体,平均粒径随x增加(从0.3增至0.9)从220nm逐渐变小到45nm。为了进一步改善低温液相合成法制备的粉体性能,对粉体浆料进行水热后处理,通过TEM、FE-SEM、XRD、FT-IR、TG和ICP等表征手段与水热前粉体进行了性能上的比较。结果表明,水热后Sox粉体在0.1=x=0.4范围形成以CT3为基的斜方晶型SOx固溶体,并随着S含量的增加逐渐过渡到立方相,且颗粒形貌变得规整,不含有富T无定形物质,结晶度提高,羟基缺陷以及C032-杂质显著减少。该法克服了LTAS法的不足,为制备各种高纯、高性能的SOx固溶体粉体提供了可能。在SCT粉体制备工艺基础上,用超重力沉淀法制备了BS2、BS2和BSZ2固溶体粉体并采用焙烧预处理方法对粉体做进一步处理改善,再进行烧结。结果说明,超重力反应沉淀法制备的BZ2、BS2和BSZ2粉体室温下呈立方相钙钛矿晶体结构,颗粒形貌近似为球形松团状,但粉体结晶度不好,且含有BaCO3杂质。经焙烧处理后,粉体晶体结构没有变化,结晶度显著提高,BaCO3杂质已脱除,颗粒外边缘变得光滑呈实心类球形。焙烧处理的粉体,不论在成型还是在烧结上都显示比未焙烧处理粉体优越。在1320℃烧结时,1000℃焙烧处理的BZ2、BS2和BSZ2粉体对应陶瓷体室温介电常数分别为3054、1857和2411,而未焙烧粉体对应陶瓷体室温介电常数仅为1582、1008和731。粉体焙烧处理能够有效的降低粉体比表面积以及吸附空气和湿气等,促进烧结致密化程度,提高陶瓷体介电性能。更多还原

【Abstract】 In the vibrant21st century, innovation of new materials, especially technologies and products based on nanomaterials, will greatly influence society development, economic growth and enhancement of national status. Preparation of inorganic nanomaterials is one of the most important parts in this strategic research field. With this in mind, we selected an important perovskite-type electro-ceramic material, SOx materials, as research objects. Novel synthesis route and controllable strategy of powder properties were studied. Based on these, we prepared three kinds of barium-based perovskite-type nano-powders in RPB, and studied their sintering and dielectric properties after the powders been precalcined.Firstly, nano-sized SOx solid-solution powders have been prepared by low temperature aqueous synthesis method (LTAS) at temperature below100℃and under ambient pressure from cheap starting materials of S2, C2and T4. The as-obtained powders were analyzed by TEM and XRD measurements. It is shown that the as-obtained particles are in form of homogeneous solid solutions when C2+content is lower then80mol%. The morphology of particles is rounded single crystal with somewhat "knobbly" around the edges, and the particle size is decreased from220nm to45nm with the content of the composition S increased.To optimize the performance of the powders, the hydrothermal post-treatment was followed. After the post-treatment, the powders were analyzed by TEM, XRD, FT-IR, TG and ICP measurements. It is shown that the crystal structure of the as-treated powders is orthorhombic phase when the composition is0.1=x=0.4, and it is turned to cubic phase with the content of Sr increased. Compared with the powders prepared by LTAS method, the powders after hydrothermal post-treatment showed much less hydroxyl defects, higher purity, uniform morphology and better crystallinity.Based on the preparation method of SCT, we prepared BZ2, BS2and BSZ2powders in RPB. The as-prepared powders are all single cubic phase perovskite, however, the crystallinity of the powders is inferior and the powders contain the impurity of BaCO3. In order to improve the properties of the particles, the precalcining-treatment was followed. Afer the precalcining, the powders become more pure and better crystallized. The precalcining method improves the shaping and sintering abilities of as-obtained powders. The BZ2, BS2and BSZ2powders precalcined at1000℃show better room temperature dielectric constant of3054,1857and2411, respectively, when unprecalcined powders show room temperature dielectric constant of1582,1008and731. The precalcining procedure could reduce the specific surface area and adsorbing air and water of powders, promote their sintering densification and the dielectric properties.更多还原