【作者】 车如心；

【导师】 高宏；

【作者基本信息】 大连交通大学 ， 材料加工工程， 2008， 博士

【摘要】 材料的复合化是材料发展的必然趋势之一,复合材料己成为21世纪最重要、最有发展潜力的领域。本文利用溶胶-凝胶燃烧合成法、溶胶-凝胶包裹法及胶溶法制备了纳米复合碱土(稀土)永磁材料以及复合磁性液体,所得样品主要用于吸波材料、磁记录、磁存储介质和润滑。在深入进行了大量实验研究的基础上,查明了各种工艺条件对所制备复合磁性材料物相结构、粒度及磁学性能影响的规律,确定了最佳制备工艺;利用X射线衍射仪(XRD)和红外光谱仪(IR)确定样品物相,扫描电镜(SEM)观察样品的形貌,振动样品磁强计(VSM)进行磁性测量,热重-差热分析仪(TG/DTA)研究凝胶的燃烧和析晶过程。本研究的主要内容如下:一、制备了新型纳米复合永磁粉体并建立了溶胶-凝胶包裹法1、在查明了最佳工艺条件的基础上,制备了软硬磁相复合、粒径细小(20nm左右)、粒度均匀且磁性能优良的纳米复合碱土及稀土永磁粉体,即BaFe12O19/γ-Fe2O3、SrFe12O19/γ-Fe2O3、SmFeO3/γ-Fe2O3及NdFeO3/γ-Fe2O3。2、将溶胶-凝胶法和液相包裹法相结合,建立了一种兼具二者优点的纳米粉体合成方法——溶胶-凝胶包裹法。该方法能较好的解决纳米粉体团聚问题。3、应用所制备的纳米复合永磁粉体作为吸波剂进行了一定的分析和研究。二、纳米复合碱土永磁粉体通过溶胶-凝胶燃烧法制备了纳米复合碱土永磁粉体BaFe12O19/γ-Fe2O3和SrFe12O19/γ-Fe2O3。1、研究了原料配比与粉末的磁学性能之间的关系。柠檬酸配比对粉末的物相结构影响不大,随着柠檬酸用量的增加,粉末的磁学性能明显得到改善。2、得到溶胶-凝胶燃烧合成法制备纳米复合永磁粉体的最佳工艺及参数。纳米复合样品的剩磁和最大磁能积比分段煅烧样品的单相有了较大提高,与前人合成的样品相比有了较大的改善。同时也证明了纳米复合粒子间产生了硬磁相和软磁相之间的交换耦合。三、纳米复合稀土永磁粉体通过溶胶-凝胶包裹法制备了纳米复合稀土永磁粉体SmFeO3/γ-Fe2O3及NdFeO3/γ-Fe2O3。1、利用溶胶-凝胶包裹法在纳米尺度上对核壳复合粒子的结构和组成进行设计和剪裁,并较好地改善了纳米粉末的分散性。由此粉体制作出的块状磁晶纳米复合磁体最大磁能积可达221 kJ·m-3。2、溶胶-凝胶包裹法制备的复合永磁体中稀土含量比传统快淬法和机械合金化法生产的稀土永磁体含量低,成本得以降低,并具有较高的磁性能。同时,由于具有纳米结构并含有软磁相,因此断裂韧性也得到改善。四、复合磁性液体制备了Fe3O4和CoFe2O4作为磁性粒子的煤油基、水基、辛烷基磁性液体。1、采用改进的胶溶法制备出纳米Fe3O4及CoFe2O4磁性粒子,确定了合成最佳工艺条件。将制备的Fe3O4和CoFe2O4颗粒在一定条件下包覆表面活性剂后分散在基载液中,制备出复合磁性液体。探讨了表面活性剂种类的选择及其用量、改性温度、改性时间、酸碱条件、超声波分散作用、离心分离等对磁性液体的影响。对磁性液体的物理性质如密度、粘度也进行了测定。2、利用磁性液体中总铁Fe[x]含量来表示磁性液体的稳定性,讨论了重力、离心力、存放条件等对磁性液体中总铁Fe[x]含量的影响,进而讨论了对磁性能的影响。更多还原

【Abstract】 The permanent magnetic nanocomposite with alkali-earth and rare-earth powders, magnetic fluid were firstly synthesized using novel techniques---sol-gel combustion synthesis method, sol-gel packing method and sol-gel process. Samples are using as compound absorber, medium of magnetic record, magnetic memory and lubricant. Based on theoretical analysis and experimental studies, the effects of the pH of solution, the kinds and amounts of complexing agents, the adding of dispersant, and the condition in heat treatment of the gel on crystal phase, particle size and magnetic properties of ultra-fine powders were firstly investigated systematically to clarify the optimum forming conditions.The thermal analyse of dried gel was carried out by means of differential thermal analysis (DTA) with a heating rate of 10℃/ min. The phase of the samples was determined by X-ray diffraction (XRD) and infrared spectrometer (IR). The microstructure was observed by scanning electronic microscope (SEM). Magnetic measurements were conducted by vibrating sample magnetometer (VSM). Some important results are summarized as follows:Ⅰ. Preparation of new pattern permanent magnetic nanocomposite and foundation of sol-gel packing method.1 On the base of clarifying the optimum forming conditions, BaFe12O19/γ-Fe2O3, SrFe12O19/γ-Fe2O3, SmFeO3/γ-Fe2O3 and NdFeO3/γ-Fe2O3 were prepared, which are new pattern permanent magnetic nanocomposite with small size (about 20nm), narrow size distribution and high magnetic properties. These four powders are not seen to report.2 Sol-gel packing method was founded, which combines sol-gel with liquid packing.this method can solve powder dispersing preferably.3 The permanent magnetic nanocomposite as compound absorber and medium of magnetic record is analyzed and studied.Ⅱ. The permanent magnetic nanocomposite powders with alkali-earth The permanent magnetic nanocomposite powders with alkali-earth BaFe12O19/γ-Fe2O3 and SrFe12O19/γ-Fe2O3 were synthesized by sol-gel combustion synthesis method1 The automatism combustion of the gel is correlation with the mol ratio of nitrate and citric acid. The ratio influence little on the structure of powders, but the magnetic properties will be improved when the amount of citric acid increase.2 The optimum forming conditions is gained, these small magnetic particles allow effective exchange coupling between hard and soft magnetic phases and result in the simultaneous enhancement of the magnetic properties.Ⅲ. The permanent magnetic nanocomposite powders with rare-earthThe permanent magnetic nanocomposite powders with rare-earth were synthesized by sol-gel packing method1 Sol-gel packing method can design and clipping the pit-shell composite particles in the structure and can improve the disperse of nano-powders. The (BH)max of its block is 221 kJ m-3.2 The permanent magnetic nanocomposite prepared by sol-gel packing method has less rare-earth than tradition quench quickly, mechanical alloying method, and the cost is depressed, which display enhancement of permanent magnetic and antisepsis properties. The tenacity property has been improved because the permanent magnetic nanocomposite contains soft magnetic.Ⅳ. Magnetic fluidThe magnetic fluid of Fe3O4 and CoFe2O4 were prepared, which take the coal oil, water and alkyl as the carrier liquid .1 Fe3O4 and CoFe2O4 magnetic particles were prepared by novel sol-gel process. The optimum parameter of prepared Fe3O4 and CoFe2O4 nanoparticles were determined. When the pH was about 7, the particles modified by the surfactant were scattered in the carrier liquid. The magnetic fluid was prepared. The factors, which influence magnetic fluid properties, such as type of surfactant, quantity of surfactant, modified temperature, modified time, pH, action of ultrasonic, centrifugal effect, were discussed. The density and the viscosity of magnetic fluid were also measured.2 The total iron—Fe[x] in the magnetic fluid was used to express the stability of magnetic fluid, The effects on the stability of magnetic fluid were discussed, such as the gravity, the centrifugal force, the depositing condition, then the effects on the magnetism of magnetic fluid were discussed.更多还原