【作者】 吴有金；

【导师】 洪若瑜；

【作者基本信息】 苏州大学 ， 应用化学， 2009， 硕士

【摘要】 本论文主要围绕制备粒径小、粒度均匀的YIG及Bi掺杂粉体展开的。通过强化粉体制备过程(如分别采用共沉淀、微乳液法、明胶模板等方法制备Bi-YIG粉体,外加微波场,采用盐熔融法煅烧粉体等)控制粉体粒径,对制备的Bi-YIG粉体进行表面改性,提高其与聚合物的相容性;选用MMA单体与Bi-YIG粉体进行原位聚合制得Bi-YIG/PMMA磁旋光复合材料。改善材料的加工性能,降低成本,以期达到制备高性能且低成本纳米磁旋光复合材料的目的。具体如下:(1)以十六烷基三甲基溴化铵/正辛烷/正丁醇体系,采用微乳液法制备了YIG(Y3Fe5O12),并与共沉淀法所制备的样品进行了对比。采用热分析(TG-DTA)对其前驱体进行表征,粉末X射线衍射(XRD)、透射电镜(TEM)及振动样品磁强计(VSM)等方法研究YIG颗粒大小及其特性。将YIG颗粒分散到MMA单体中,进行本体聚合,得到YIG/PMMA复合材料,并用法拉第磁光仪对复合材料进行表征。结果表明:与共沉淀法相比,微乳液法制备的YIG在颗粒大小和磁光等方面都呈现出较好的性能。(2)以硝酸铁、硝酸钇和硝酸铋为原料,通过共沉淀法制备了不同Bi含量掺杂的石榴石BixY3-xFe5O12纳米颗粒,并系统的研究了制备过程中各种条件的影响。其中包括Bi含量对YIG粉体成相温度及性能的影响;热处理温度对磁性颗粒大小及饱和磁化强度的影响;不同类型表面活性剂对Bi-YIG性能的影响;外加微波场对Bi-YIG性能的影响。另外,将制得Bi-YIG纳米颗粒分散在MMA单体中,通过本体聚合制备得到Bi-YIG/PMMA复合材料,通过法拉第磁光效应仪研究其磁光性能。结果表明:复合材料的磁光效应随着入射波长的缩短而增大;随着Bi含量的增加,Bi掺杂石榴石(Bi-YIG)成相温度降低、饱和磁化强度降低、Bi-YIG/PMMA复合材料法拉第磁光旋转角也随之增大。通过在共沉淀过程中加入表面活性剂和微波辐射可以制得性能较好的Bi-YIG。其中,阳离子表面活性剂(CTAB)效果最好、非离子表面活性剂(PEG-20000)次之、阴离子表面活性剂(SDS)效果最差;引入微波辐射能得到均匀性较好的Bi-YIG纳米颗粒。采用盐熔融法煅烧前驱体,Bi-YIG的成相温度较低(盐熔融工艺:600℃开始形成Bi-YIG相,650℃能得到纯的Bi-YIG,而普通热处理:650℃开始形成Bi-YIG相,700℃能得到纯的Bi-YIG)、得到的Bi-YIG性能较好(如颗粒的均匀性、大小、较低的Ms、光吸收小和较好的磁光性能)。(3)采用明胶模板法制备Bi-YIG并研究了明胶浓度对Bi-YIG性能的影响。探讨了明胶模板法制备纳米颗粒的机理,并采用乳液法对所制备的Bi-YIG进行了表面改性。产物经TEM、XRD、VSM及磁光测试,结果表明:明胶模板法制备Bi-YIG的成相温度为700℃,明胶浓度对材料的性能有较大影响。明胶浓度越大,制得的Bi-YIG性能越好。当明胶浓度为20%时,Bi-YIG/PMMA复合材料的磁光性能最好,复合材料在532nm处的磁优值为2.66°。采用乳液法改性,能够改善Bi-YIG在MMA中的分散性,提高Bi-YIG/PMMA复合材料的磁光性能。改性后的Bi-YIG/PMMA复合材料在532nm处的磁优值得到很大的提高(3.29°)。更多还原

【Abstract】 Bi-YIG nanoparticles with narrow size distribution were prepared. Three methods have been employed to prepare YIG and substituted ones, such as co-precipitation, microemulsion and gelatin-template. To enhance the dispersibility of Bi-YIG nanoparticles in the organic monomer (e.g. MMA), the emulsion-based bottom-up self-assembly (EBS) method was used to modify Bi-YIG nanoparticles. To invest the magneto-optical properties of Bi-YIG, Bi-YIG/PMMA composite was prepared by in-situ bulk polymerization. The composite shows great potential for magneto-optical applications.(1) Yttrium iron garnet (YIG, Y3Fe5O12) was prepared in reverse microemulsion consisting of water, CTAB, octane and n-butanol, and subsequent heating treatment. A contrastive experiment has been conducted to study the properties of YIG powders prepared by microemulsion and co-precipitation. Particles were characterized by thermal gravity-differential thermal analysis (TG-DTA), X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), respectively. Moreover, the transparency and Faraday rotation of the polymethyl methacrylate slices filled with yttrium iron garnet (YIG/PMMA) were investigated by visible spectrophotometer and Faraday rotation meter, respectively. All results reveal that both of particles prepared by microemulsion and co-precipitation show great potential for magneto-optical applications and the microemulsion-based powders show better properties with respect to particle size and Faraday rotation.(2) Bismuth substituted yttrium iron garnet (Bi-YIG, BixY3-xFe5O12) particles were prepared by co-precipitation using ammonia aqueous solution as precipitant. The influences of surfactants, microwave, and anneal process on the properties of Bi-YIG particles were investigated. Results suggest that Bi-YIG phase transition temperatures and Ms of Bi-YIG particles decrease, the magneto-optical properties of Bi-YIG/PMMA composite increase as the increasing Bi content. Bi-YIG nanoparticles with good magneto-optical properties can be prepared by the addition of surfactant and the irradiation of microwave at the co-precipitation process. Homogenous Bi-YIG nanoparticles were also successfully synthesized by molten-salt method in NaCl-KCl flux at a relatively low temperature (650 oC), and the molten-salt-based powders exhibit better properties than common heat process-based powders, e.g., more homogenized and better particles, lower Ms, lower UV-vis optical absorption and better magneto-optical properties.(3) Bi-substituted yttrium iron garnet (Bi-YIG, Bi1.8Y1.2Fe5O12) particles with homogeneous size have been prepared by a gel-network co-precipitation method using gelatin as template. The influence of gelatin concentration on the properties of Bi-YIG particles was studied, and emulsion-based bottom-up self-assembly (EBS) method was used to modify the prepared Bi-YIG nanoparticles. The obtained products were characterized by XRD, TEM, dynamic light scattering (DLS) and VSM, respectively. Moreover, the transparency and Faraday rotation of Bi-YIG/PMMA composite were investigated by visible spectrophotometer and Faraday rotation meter, respectively. Results show that Bi-YIG particles exihibit better properties as the increasing gelatin concentration, and Bi-YIG particles modified by EBS exhibit better properties with respect to particle size and magneto-optical properties.更多还原