【作者】 熊金钰；

【导师】 徐国财；

【作者基本信息】 安徽理工大学 ， 应用化学， 2005， 硕士

【摘要】 利用超声空化产生的独特的分散、碎化、活化和引发等作用,制备纳米银粒子、纳米银/聚合物复合粒子,用UV、IR、TEM、HRTEM、DSC-TG、XRD,激光粒度分析仪对所得产物进行了表征。 以硝酸银（AgNO₃）为银源,聚乙烯醇（PVA）为稳定剂,利用超声波的空化作用,制备纳米银及其分形生长成的有序体。用紫外--可见分光光度计、激光粒度仪和透射电子显微镜表征纳米银的生长过程和结构。实验表明,在超声辐射下,不需任何还原剂,Ag⁺可被还原成银原子,进而聚集成纳米银微粒,尺寸在15—25nm,这种纳米银能够分形生长,最终成为树枝状的有序聚集体。 超声辐射不含引发剂、还原剂而仅含有银盐的甲基丙烯酸甲酯乳液,原位合成了纳米Ag/PMMA复合粒子。这种复合粒子的IR、HRTEM、XRD表征结果显示,以纳米银为核的复合粒子具有很好的分散性,且纳米银为多晶体,结晶为高度有序的结构,纳米银粒子与聚合物间存在化学作用。聚合物的含量对银粒子的结晶行为有一定的影响。通过考察反应过程中各因素对反应物转化率、聚合物分子量等的影响情况,发现一个有趣的现象:不存在AgNO₃时,MMA几乎不聚合,而AgNO₃存在时,MMA不但能聚合,而且在一定浓度范围内,转化率随AgNO₃增加而增大,说明银离子的存在能够促进单体的聚合。纳米Ag/PMMA复合物的热分析表明银粒子的存在可能催化复合材料中PMMA的分解,导致分解温度提前。 这种双原位合成技术能够在室温常压下实施,银离子的还原和单体的聚合同时发生,相对简单、省时,有望用于制备其它不同尺寸和组成的无机/聚合物纳米复合材料。更多还原

【Abstract】 The ultrasonic radiation technique was introduced to synthesize nanomaterials, and nanosilver particles, nanosilver/polymer composites particles were prepared through ultrasonic cavitation with unique dispersion, crushing, activation, initiation action. The obtained nanomaterials were characterized by means of ultraviolet-visible spectra (UV), infrared spectroscopy (IR), high resolution transmission electron microscopy (HRTEM), transmission electron microscopy (TEM), differential scanning calorimetry-thermogravimetry (DSC-TG), X-ray diffraction (XRD), Laser Zetasizer analysis and so on.The mixture solution consisted of the silver nitrate and polyvinyl alcohol(PVA) dissolved in water was acted by ultrasound wave and the silver ion in the solution was reduced to silver atom, then silver clusters during the process of ultrasonicating. The results of UV Spectra suggested that the nano-silver was formed and the maximal absorbing peak shifted to long wave. The photos of TEM showed that the average size of nano-silver particulate was about 15—25 nm, which was equal to that by Zetasizer, and that nano-silver particulate were fractal assembling into ordered dendritical aggregation structure.Silver-polymethyl methacrylate nanocomposites were successfully synthesized in the emulsion containing methyl methacrylate monomers and silver salt but neither initiator nor reductant contained in situ by ultrasonic radiating. The resultant Ag/PMMA nanocomposites were characterized by IR, HRTEM and XRD, and the results showed that nano-silver as core within the composites particles was uniform, polycrystalline and high order crystalline, and that there existed some degree of interaction between silver particles and polymer matrix. The content of polymer in the composites had some effect on nano-silvers crystallization. The effects of the experimental conditions such as systemic temperature and contents of components on the final conversion of monomer and molecular weight of PMMA were also researched. The interesting phenomenon was found that the polymerization was promoted by silver clusters, and the polymerization of monomer didn’t occur without silver nitrate. The polymerization of monomer procreated easily in the presence of silver nitrate and the monomer conversion increased with silver nitrate increasing below its critical concentration. The thermal analysis results of the composites particles showed that decomposition of PMMA as shell within the更多还原