氧化铁基纳米棒（颗粒）的可控合成与磁性能研究

发布时间：2018-05-17 16:42

本文选题：磁性材料 + 氧化铁　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：磁性纳米材料作为功能纳米材料的一个重要分支,由于其在纳米级有趣的磁学性质和潜在的应用而受到了广泛的关注和研究。根据矫顽力的大小,磁性材料可以分为硬磁材料和软磁材料。磁性纳米粒子具有许多不同于体相材料的特殊磁性质,例如,高矫顽力、超顺磁性、低居里温度等,这些性质主要是由表面效应和小尺寸效应决定的。此外,磁性纳米粒子的矫顽力和饱和磁化强度,不仅和纳米粒子本身的晶体结构有关,还和它的尺寸,形貌,化学组成和分散性有关。纳米氧化铁是一种非常有前景的无机非金属功能材料,具有无毒,抗腐蚀性能强,储存量丰富,多价态等特点,并且由于其可接受的磁学性能和高度的稳定性,能够广泛应用于磁存储,磁记录,电磁吸收,生物医学,超级电容器负极材料,传感器,能源催化等领域。本论文中,我们首先以氯化铁为前驱体,十六烷基三甲基溴化铵(CTAB)为表面活性剂,在120oC用水热法合成了α-Fe_2O_3纳米粒子和β-FeOOH纳米粒子。借助场发射扫描电子显微镜(FESEM),电子衍射能谱(EDS),X射线衍射(XRD),震动样品磁强计(VSM)等表征手段,研究α-Fe_2O_3纳米粒子和β-FeOOH纳米粒子的形貌,结构和磁性能。晶体的形貌和尺寸可以通过改变前驱体的浓度来控制,当氯化铁浓度比较低时,合成出了菱形、球形和立方体的α-Fe_2O_3纳米粒子;当氯化铁浓度较高时,得到了不同纵横比的β-FeOOH纳米棒。将β-FeOOH纳米棒在不同温度下煅烧,得到了不同尺寸的α-Fe_2O_3纳米棒,并对其磁性进行表征,探索了煅烧温度对相转变的影响。最后,将得到的α-Fe_2O_3纳米棒在不同温度下用H_2还原,得到了Fe,Fe_3O_4和Fe_2O_3@Fe_3O_4复合物。其次,以氯化铁和氯化钴为前驱体,以CTAB为表面活性剂,以尿素为络合剂,合成出了具有高饱和磁化强度和高矫顽力的CoFe_2O_4球形纳米粒子,研究了络合剂,前驱体浓度,反应温度,反应时间,超声,外加磁场等条件对纳米粒子尺寸形貌和磁性能的影响,通过SEM,EDS,XRD,VSM对产物进行表征。最终,我们得出,在氯化铁浓度0.04 M,氯化钴浓度为0.02 M,尿素浓度为0.6 M,反应温度为150oC,反应时间为12 h,超声时间为0.5 h的最优条件下,得到了粒径尺寸为60 nm的球形CoFe_2O_4纳米粒子,其矫顽力为3.57 kOe,饱和磁化强度34.743 emu·g-1。
[Abstract]:As an important branch of functional nanomaterials, magnetic nanomaterials have received extensive attention and research due to their interesting magnetic properties and potential applications. According to the size of coercivity, magnetic materials can be divided into hard magnetic materials and soft magnetic materials. Magnetic nanoparticles have many special magnetic properties, such as high coercivity, superparamagnetism and low Curie temperature, which are mainly determined by surface effect and small size effect. In addition, the coercivity and saturation magnetization of magnetic nanoparticles are not only related to their crystal structure, but also to their size, morphology, chemical composition and dispersion. Nanocrystalline iron oxide is a promising inorganic nonmetallic functional material with the advantages of non-toxic, strong corrosion resistance, abundant storage, multivalent state, etc., and due to its acceptable magnetic properties and high stability, Can be widely used in magnetic storage, magnetic recording, electromagnetic absorption, biomedical, supercapacitor anode materials, sensors, energy catalysis and other fields. In this thesis, 伪 -Fe _ 2O _ 3 nanoparticles and 尾 -FeOOH nanoparticles were synthesized by hydrothermal method using ferric chloride as precursor and cetyltrimethylammonium bromide (CTAB) as surfactant in 120oC. The morphology, structure and magnetic properties of 伪 -Fe _ 2O _ 3 nanoparticles and 尾 -FeOOH nanoparticles were studied by means of field emission scanning electron microscopy (SEM), electron diffraction spectrum (EDS), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The morphology and size of the crystal can be controlled by changing the concentration of the precursor. When the concentration of ferric chloride is low, the rhombic, spherical and cubic 伪 -Fe _ 2O _ 3 nanoparticles are synthesized; when the concentration of ferric chloride is high, the 伪 -Fe _ 2O _ 3 nanoparticles are synthesized. 尾 -FeOOH nanorods with different aspect ratios were obtained. 伪 -Fe2O3 nanorods with different sizes were obtained by calcining 尾 -FeOOH nanorods at different temperatures. The magnetic properties of 伪 -Fe2O3 nanorods were characterized, and the effect of calcination temperature on phase transition was explored. Finally, the 伪 -Fe2O3 nanorods were reduced by H _ 2 at different temperatures, and the Fe-Fe _ 3O _ 4 and Fe_2O_3@Fe_3O_4 complexes were obtained. Secondly, CoFe_2O_4 spherical nanoparticles with high saturation magnetization and high coercivity were synthesized by using ferric chloride and cobalt chloride as precursors, CTAB as surfactant and urea as complexing agent. The effects of reaction temperature, reaction time, ultrasonic and applied magnetic field on the size, morphology and magnetic properties of the nanoparticles were investigated. Finally, under the optimum conditions of ferric chloride 0.04 M, cobalt chloride 0.02 M, urea 0.6 M, reaction temperature 150oC, reaction time 12 h, ultrasonic time 0.5 h, the spherical CoFe_2O_4 nanoparticles with particle size of 60 nm were obtained. The coercivity is 3.57 KOe and the saturation magnetization is 34.743 emu g-1.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34;TB383.1

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