【作者】 李芳；

【导师】 杨瑞成；

【作者基本信息】 兰州理工大学 ， 材料学， 2011， 博士

【摘要】 磁性纳米材料是一种应用潜力巨大的磁记录材料,在生物医学领域也有广泛的用途,是纳米材料研究的热点之一。本文主要综述了FePt纳米材料的研究最新进展,并利用XRD、TEM、VSM等手段对所制FePt/Fe₃O₄纳米颗粒进行表征。主要内容如下:1.选择Fe（acac）₃和H₂PtCl₆ 6H₂O作为制备FePt纳米颗粒的前驱体,分别利用NaBH₄一步还原;NaBH₄和Vc多重还原;1,2十二烷二醇多元醇还原法制备出了单分散FePt纳米颗粒。考查了表面活性剂对FePt纳米颗粒尺寸形貌以及磁性能的影响。2.利用NaBH₄一步还原法制备单分散的FePt纳米颗粒。考查该体系下表面活性剂对FePt纳米颗粒尺寸形貌以及磁性能的影响。结果显示:表面活性剂PVP的用量对所制备FePt纳米颗粒的尺寸无明显作用,但却影响FePt纳米颗粒相变:PVP对FePt纳米颗粒的相变起“催化”作用,适量的PVP诱导纳米颗粒的相变。当调节表面活性剂PVP单体与FePt前驱体的摩尔比（PVP/FePt）为7时,所制得的FePt纳米颗粒经过500℃保温30min热处理后,矫顽力高达5.2KOe;3.选择CTAB作为表面活性剂,在NaBH₄一步还原体系下,制备出了蠕虫状FePt纳米颗粒。颗粒的尺寸与CTAB的浓度有关,随着CTAB浓度的增加而变大。CTAB双层微胶束结构的形成对于各向异性纳米结构的生长起到关键作用。我们推测CTAB自发形成了蠕虫状的纳米胶束,为FePt纳米颗粒的形貌控制提供软模板,同时也使得磁性能也大不相同。4.选用十二烷基苯磺酸钠（SDBS）作为表面活性剂,利用NaBH₄一步还原法,通过控制表面活性剂与前驱体的摩尔比（SDBS/FePt）,成功制备出球形、不规则片状和树枝状纳米结构。当SDBS/FePt为9:1时显示磁能积相对最大,这与FePt纳米颗粒的形貌有关。5.选用聚乙二醇作为表面活性剂,室温下制备出了花状自组装的FePt纳米颗粒。颗粒形貌主要由平均粒径分别为19.2 nm和4.9 nm的梭形和球形颗粒组成。这些梭形的“花瓣”和球形的“花蕊”自组装形成大小不等的花状结构。我们推测,纳米颗粒的花状自组装主要是表面活性剂集合的结果。VSM显示饱和磁化强度Ms是相同条件下PVP作为表面活性剂时的18倍。6.选择复配型表面活性剂柠檬酸和聚乙二醇（PEG）、油酸和油胺,以及单一型表面活性剂十二烷基苯磺酸钠（SDBS）对FePt纳米颗粒进行修饰,比较了三者在FePt纳米颗粒形貌及磁性能上的作用区别。复配型表面活性剂有利于诱导生成各向异性纳米结构,聚合物表面活性剂PEG和柠檬酸复配诱导生成了棒状和米粒状纳米结构;室温下颗粒的饱和磁化强度Ms差别很大,球形颗粒Ms相对最大,而棒状颗粒Ms相对较小。7.以多元醇1,2-十二烷二醇为还原剂,在表面活性剂油酸和油胺及二苄醚的环境中,成功制备出单分散的FePt纳米颗粒。通过改变油酸油胺的体积比,制备出2.3-8.8nm的FePt纳米颗粒,随油酸/油胺体积比的增加,颗粒粒径逐渐减小,四边形颗粒的数目也随着减小。8.用NaBH₄和抗坏血酸Vc多重还原法制备FePt纳米颗粒,考查了热处理温度对FePt纳米颗粒磁性能的影响。随着热处理温度的升高矫顽力变大,600℃时可达3kOe,但是在高温区（550℃及以上）矫顽力的变化并不明显,这主要是由高温退火过程中纳米颗粒的团聚导致的。9.在表面活性剂油酸和油胺,液相环境二苄醚体系中,采用多元醇还原法,利用1,2-十二烷二醇还原前驱体乙酰丙酮铁Fe（acac）₃,通过表面活性剂和金属前驱体以及液相环境的共同作用,制备出了单分散六边形Fe₃O₄纳米颗粒,考查了表面活性剂油酸油胺的浓度对纳米颗粒尺寸形貌的影响。结果显示:与未使用表面活性剂相比,油酸油胺的使用抑制了颗粒的生长,颗粒尺寸明显变小;适量浓度的表面活性剂使颗粒的尺寸和形貌更均匀。更多还原

【Abstract】 Magnetic nanoparticle is an important class of recording media with huge potential application in the biomedicine fields which has become one of the hot points for nanotechnology research. This paper reviews recent advances in FePt nanoparticles research progress and chose XRD, TEM, VSM techniques to characterize the as‐synthesized FePt/Fe3O4nanoparticles. The main contents are following:1. Using Fe（acac）₃ and H2_PtCl₆ 6H₂O as precursors, via NaBH₄ one‐step reduction combine with Vc two‐step reduction as well as polyol reduction process to synthesis FePt nanoparticles. We study the effect of surfactant on the size, morphology and magnetic properties of the as‐synthesized FePt nanoparticle.2. A method of one‐step reduction by NaBH₄ in the presence of surfactant poly（N‐vinyl‐2‐pyrrolidone） （PVP） was employed to produce monodisperse FePt nanocrystals. The results confirm that the PVP contents have an effect on the transition degree while no significant effect on the particles size. We consume the PVP most probably plays the role of the“catalyst”, proper amount of PVP induces the easier transformation of the nanocrystals. The highest coercivity of 5.2 KOe was obtained with the adjusted PVP / FePt molar ratio of 7 when annealed at 500℃for 30 min.3. A convenient surfactant CTAB was chose to assist synthesis of worm‐like FePt nanoparticles. The shape and size evolution ranging from worm‐like to spherical and from 4 to 8 nm were observed, respectively. Growth of worm‐like nanoparticles was monitored by nano‐micelles formed by surfactant CTAB. Further magnetic analysis also revealed the modification of Ms arise from anisotropic shape of nanoparticles4. FePt nanoparticles with different morphologies were successfully prepared in the presence of surfactant sodium dodecyl benzene sulfonate （SDBS） with the addition of different molar ratio of surfactant SDBS to precursors FePt （SDBS/FePt） by a one‐step NaBH₄ reduction approach. And the morphologies show spherical, irregular schistose and dendritic structure when changing the molar ratio of SDBS/FePt. And the magnetic energy product show the largest at SDBS/FePt = 9:1. We deduce this is the result of differences in nanoparticle morphology.5. FePt nanoparticles with flower‐like assembly are synthesized at room temperature when chose PEG as the surfactant. The shapes are composed of fusiform and spherical with the mean sizes of 19.2 nm and 4.9 nm respectively. These fusiform“petals”and spherical“stamens”were found to assemble into flower‐like structures. We suggest the formation of flower‐like assemble of FePt nanoparticles is result from the surfactant assemblage. VSM indicates that Ms nearly eighteen‐fold increase when compared to nanoparticles synthesized under identical conditions except for using PVP as surfactant.6. The complex surfactants oleic acid and oleylamine; citric acid and polyethylene glycol （ PEG） as well as single surfactant sodium dodecyl benzene sulfonate（ SDBS）were chose to stabilize the FePt nanoparticles. The characterizations indicate that the complex surfactants induced to produce anisotropic morphologies, and the complex surfactants PEG and citric acid lead to rice‐shape and rod‐shape nanostructure. VSM results show that the spherical particles have the largest Ms while the rod‐shape nanoparticles possess the smallest Ms.7. FePt nanoparticles are synthesized at room temperature by polyol 1, 2‐dodecanediol reduction in the presence of oleic acid, oleylamine and dibenzyl ether. The particles size were tuned from 2.3‐8.8nm by varying the volume ratio of oleic acid / oleylamine, the size and number of quadrilateral particles increase with the amount of oleylamine.8. Multi‐step NaBH₄ combine with ascorbic acid reduction process was chose to synthesis FePt nanoparticles. The effects of annealing temperatures on the magnetic properties of FePt have been investigated. The results confirmed that The annealing treatment caused an increase of coercivity as high as 3KOe at 600℃. However the increscent of coercivity was slight at high temperatures of 550℃which may be caused by the agglomeration of nanoparticles during the annealing treatment.9. Based on the cooperation of surfactants, metal precuesor and liquid environment, monodisperse magnetite （Fe₃O₄） nanoparticles have been prepared by 1, 2‐dodecanediol reduction of iron acetylacetonate （Fe（acac）₃） in the presence of oleic acid, oleylamine and dibenzyl ether. The effect of surfactants concentration on the particles size and morphology were examined. Compared with particles synthesized without surfactants, the use of oleic acid and oleylamine suppressed the growth of magnetite nanoparticles and gave rise to smaller particle size. In addition, suitable concentration of surfactants makes for the uniformity of particles size and shape.更多还原