低维镍纳米结构材料的绿色和简易制备工艺与磁性能

发布时间：2018-06-21 00:39

本文选题：Ni纳米线 + 滴注法　；参考：《安徽工业大学》2017年硕士论文

【摘要】：通过纳米材料结构和形态的可控制备,来裁剪材料的物理、化学和机械性能,已成为材料科学发展的一个重要前沿研究课题。由低维纳米结构单元(零维、一维、二维纳米材料)构筑而成的多级纳米结构材料,因为它们独特的结构-性能依赖性,在电子、磁传感器、靶向药物载体等生物医学领域的出色应用而备受关注。通常实现纳米材料结构与形貌的有效调控方法大多需要借助于各种软和硬模板、表面活性剂、或外加磁场等辅助手段,合成方法既繁琐、昂贵、又不环保,从而限制了它们的进一步应用。本文尝试采用简易、绿色方法制备一维Ni纳米线和碳包裹Ni纳米材料,以获得低维纳米材料的优化制备工艺。主要研究结果如下:一、一维镍纳米线的简易制备工艺与磁性能选择乙二醇为溶剂,水合肼还原剂,在不借助外加辅助磁场和不添加表面活性剂条件下,采用改进的滴注法,直接制备出一维Ni纳米线,并系统研究了制备工艺参数(Ni~(2+)离子浓度、反应温度、碱浓度、和外加磁场强度等)对Ni纳米线合成、结构以及磁性的影响,主要研究结果如下:(1)Ni盐浓度的影响:结果显示,用简易的滴注法制备的Ni纳米线形貌和磁性敏感地依赖于Ni盐浓度的变化(0.05-0.7 mol/L)。当浓度从0.05增加到0.3 mol/L时,由絮状Ni转变为一维Ni纳米线的数量增多,纳米线长度增长,表面凸起晶粒细化,导致晶体沿[111]晶轴取向度提高、表面原子磁矩有序度增强,以及Ni纳米线饱和磁化强度Ms增强。当Ni盐浓度提高到0.7 mol/L时,纳米线表面出现约10 nm厚的片状微结构,部分纳米线团聚成块状,从而导致晶体沿[111]晶轴取向度降低、表面原子磁矩无序度增高,合成产物Ms下降。(2)碱浓度的影响:研究发现,当NaOH从0.3 g增加到1.2 g时,由疏松絮状的纳米颗粒逐渐形成Ni纳米线的数量增多,纳米线纵横比增大、表面变光滑。碱浓度的提高,促使Ni纳米线沿[111]易磁化方向的取向度增高,饱和磁化强度增强。(3)反应温度的影响:当反应温度较低(60℃)时,只形成部分镍纳米线,表面存在刺状纳米颗粒。反应温度升高到80℃时,Ni纳米线数量增多、纵横比增大。再继续提高到100℃时,镍纳米线变短,部分团聚结块,导致Ms显著降低。(4)外加磁场的影响:外加磁场可以使Ni纳米线变直,沿[111]易磁化方向的取向度显著提高,在外加磁场强度为100 mT时,饱和磁化强度Ms达到81.8 Am2·kg-1,相比块体Ni材料的Ms(55 Am2·kg-1)高出近50%。二、碳包裹镍纳米材料的绿色制备工艺与其磁性能采用天然多元醇蓖麻油为溶剂,在不添加任何其它表面活性剂和催化剂的条件下,采用简易的二步法制备了碳包裹Ni纳米颗粒,研究了材料制备工艺参数(Ni~(2+)离子浓度、退火温度、退火时间等)对Ni纳米颗粒合成的影响规律,获得了二步法制备纳米级零价镍的最佳工艺条件:(1)蓖麻油还原金属Ni盐分两个阶段:第一阶段是液相化学反应,在此阶段,蓖麻油酸中的阴离子型活性官能团吸附Ni~(2+)离子,形成Ni的前驱体中间物;第二阶段是湿法化学还原反应,经低中温退火将Ni~(2+)离子还原为零价Ni金属,在此过程中蓖麻油酸长分子链起到修饰作用,从而得到性能稳定的金属Ni纳米晶材料。(2)Ni~(2+)离子浓度的影响:Ni金属盐浓度在3-5 mol/L时,可以制备纯FCC-Ni纳米颗粒,平均晶粒尺寸在28-35 nm之间,在低于3 mol/L或高于6 mol/L时,金属Ni易被氧化而生成NiO杂相。(3)退火温度和时间的影响:在液相(~120℃)温度下化学反应2 h,再经400℃退火1-2 h,可以制备出非晶态碳包裹的零价Ni纳米晶颗粒。在超出以上制备工艺参数范围时,还原出的金属Ni纳米晶易被氧化而生成NiO杂相。(4)磁性测量表明,碳包裹Ni纳米颗粒的饱和磁化强度Ms随Ni盐浓度及退火时间的提高而增强,最高值Ms=11 Am2·kg-1。该值比近期文献报道的用蓖麻油制备Ni纳米棒的最高Ms~3 Am2·kg-1高出数倍。采用该方法制备的金属镍产量相对低,但Ni纳米晶的矫顽力可达Hc~16.4 kA/m,比体块Ni矫顽力有明显的增强。
[Abstract]:The structure and morphology controlled preparation of nano materials to cut material, physical, chemical and mechanical properties, has become an important frontier research topic in the development of material science. By the low dimensional nano structure unit (zero dimensional, one-dimensional, two-dimensional nano materials) hierarchical nanostructure material form, because of their unique dependence the structure and properties And in the electronic, magnetic sensor, excellent application to target biomedical fields such as drug carrier and concern. Most often need the help of all kinds of soft and hard template method to achieve effective control of the morphology and structure of nano materials, surface active agent, or other external magnetic field assistant, synthesis method is complicated, expensive, and not environmental protection thus, the limit For their further development. This paper tries to use the simple preparation of one-dimensional Ni nanowires and carbon coated Ni nano material green method, preparation process to obtain the optimization of preparation of low dimensional nanomaterials. The main results are as follows: first, one-dimensional Ni nanowires with simple preparation process and magnetic properties of selected ethylene glycol as solvent. Hydrazine hydrate reduction agent in By means of external magnetic field and adding surfactant conditions by dripping method, the direct preparation of one-dimensional Ni nanowires, and researched the preparation technology parameters (Ni~ (2+) ion concentration, reaction temperature, alkali concentration, and external magnetic field intensity) on the synthesis of Ni nano line structure and the magnetic effect, the main results are as follows: ( 1) effects of Ni salt concentration: the results showed that changes in simple infusion of prepared Ni nanowires depends sensitively on the morphology and magnetic properties of Ni salt concentration (0.05-0.7 mol/L). When the concentration increased from 0.05 to 0.3 mol/L, the number of change from Ni as the flocculent of one-dimensional Ni nanowires increased, nanowires the length of growth, raised surface grain refinement, lead crystal The improved [111] crystal axis orientation, surface atomic magnetic moment order enhancement, and Ni nanowires with the saturation magnetization of Ms increased. When Ni concentration increased to 0.7 mol/L, about 10 nm thick sheet structure micro nano wire surface, nano line aggregate block, resulting in crystals along the [111] crystallographic axis orientation reduced surface atomic magnetic moment disorder The degree of increase of synthetic product Ms decreased. (2) effect of alkali concentration: the study found that when NaOH increased from 0.3 g to 1.2 g, the number of nanoparticles by loose flocculent gradually formed Ni nanowires increased, the nanowire aspect ratio increases, the surface is smooth. The alkali concentration increased, the higher the degree of orientation Ni nanowires along the [111] direction of easy magnetization, saturation magnetization Strength. (3) the effect of reaction temperature when the reaction temperature is low (60 C), only form part of nickel nanowires, surface spinelike nanoparticles. The reaction temperature to 80 DEG C, Ni nanowires increased, the aspect ratio is increased. Further increased to 100 DEG C, Ni Na vermicelli shorter, some agglomerate cause Ms decreased significantly., (4) magnetic field The effects of applied magnetic field can make the Ni nanowires straight along the [111] direction of easy magnetization orientation degree is greatly improved, when the external magnetic field strength is 100 mT, the saturation magnetization of Ms reached 81.8 Am2 - kg-1, compared to bulk Ni materials Ms (55 Am2 kg-1) was nearly two 50%., carbon coated nickel nanomaterials green preparation process and their magnetic properties by Natural polyols of castor oil as solvent, without adding any other surfactant and catalyst, carbon encapsulated Ni nanoparticles were synthesized by two step method simple, the effects of the process parameters of material preparation (Ni~ (2+) ion concentration, annealing temperature, annealing time) on the effect of Ni nanoparticles synthesis, obtained by two step method Preparation of nano zero valent nickel optimum conditions: (1) reduction of metal salt of castor oil Ni two stages: the first stage is the chemical reaction in liquid phase, in this stage, the adsorption of anionic active functional groups in Ni~ ricinoleic acid (2+) ion, the formation of the precursor intermediates of Ni; the second stage is the wet chemical reduction in response, the low temperature annealing of Ni~ (2+) Reduced to zero valence metal ion Ni, in the process of ricinoleic acid long molecular chain to modification, so as to obtain the Ni metal nanocrystalline materials with stable performance. (2) Ni~ (2+) the effect of ion concentration: Ni metal salt concentration at 3-5 mol/L, to the preparation of pure FCC-Ni nanoparticles, the average grain size between 28-35 nm and below 3 mol/L or above 6 mol/L, Ni metal is easily oxidized to generate the phase of NiO. (3) the effect of annealing temperature and time in liquid phase (~120 C) chemical reaction temperature of 2 h, 1-2 h after annealing at 400 DEG C, can be prepared by amorphous carbon coated zero valent Ni nanocrystalline particles. The preparation process parameters in the range beyond the above, metal nanocrystalline Ni reduction is easy to be oxidized To generate the phase of NiO (4). Magnetic measurements show that the saturation magnetization Ms of carbon encapsulated Ni nanoparticles with Ni salt concentration and the annealing time increased, the maximum value of Ms=11 Am2 kg-1. the value than recently reported in the literature with castor oil Ni nanorods prepared by Ms~3 Am2 kg-1, the highest is several times higher. The preparation method of metal nickel production relative Low, but Ni nanocrystalline coercivity was Hc~16.4 kA/m, significantly enhanced than bulk Ni coercivity.
【学位授予单位】：安徽工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TQ138.13

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