调制型纳米线的制备及其表征

【作者】 何凤英；

【导师】 郭光华；

【作者基本信息】 中南大学 ， 物理学， 2011， 硕士

【摘要】 多孔阳极氧化铝(AAO)模板法是目前人们制备各种纳米一维材料的常用方法。本文围绕高度有序的调制型AAO模板的制备工艺以及基于AAO模板法电沉积结构或成分调制的磁性纳米线的中心内容,分别做了以下几个方面的研究：1.在采用二次阳极氧化法研究了电解液类型和浓度、温度以及氧化电压等对AAO模板有序度、孔间距以及孔径的影响的基础上,采用非对称阳极氧化法,通过改变相邻两次氧化过程的工艺条件,在草酸、硫酸和磷酸的电解液中制备了高度有序的、结构调制的AAO模板。采用场发射扫描电镜对其形貌进行表征,研究了结构调制型AAO模板的制备工艺。所制备的结构调制型AAO模板,孔径大小比值可在一定范围内变化,最大值可达2：1,而且孔径大小可实现周期性变化。2.在自制的结构调制型AAO模板上,采用直流电沉积方法制备了单根纳米线线径大小比约为8：5的调制型钴、镍单质纳米线。利用和x射线衍射分析(XRD)对其形貌和晶体结构进行表征；采用振动样品磁强计(VSM)对其磁性进行了分析。结果表明,钴单质纳米线呈现六方相和面心立方相的复合相结构,镍单质纳米线呈现单一面心立方相结构并沿(220)择优取向。磁滞回线分析表明,它们都呈现明显的磁各向异性：平行于纳米线长轴方向为易磁化方向,而垂直于纳米线长轴方向为难磁化方向。3.在AAO模板上,采用多电位直流电化学沉积方法,在单槽溶液中制备了多层纳米线阵列。通过控制不同子层的电沉积时间,我们制备出了钴子层厚度在30～110nm间而铜子层厚度在30-50nm间变化的多层纳米线。XRD分析表明,钴单质呈现六方相和面心立方相的复合相结构；铜单质呈现单一面心立方相结构。磁滞回线分析表明,不同调制波长和子层厚度的多层纳米线阵列,磁化情况相似,外加磁场垂直或平行于纳米线长轴方向时,矫顽力和矩形比都很小,多层纳米线没有呈现出磁各向异性。更多还原

【Abstract】 Anodic aluminium oxide (AAO) template method is one of the main technologies in manufacturing various kinds of one dimensional nanomaterials for the time being. In this paper, we studied the preparing process of gaining highly ordered and structural modulated AAO templates and the process of electrodeposing magnetic nanowires with modulated structure or modulated element, based on AAO templates. To reach these objectives, we conducted a series of reseaches as follows:(1)Now that our team had figured out the effects of the type、the concentration and the temperature of the electrolytes, as well as the effects of the anodic voltage on the ordering degree、pore interval distance and pore diameter of AAO templates,with the traditional two-step anodazion method,we figured out a new technology,which was named asymmetric anodic oxidation method, to prepare highly ordered and structural modulated AAO templates. During this new process,we had to change the type of electrolytes(including oxalic、sulfuric and phosphoric acid), and other process conditions used in the two adjacent anodization steps. We characterized the surface topography of samples with the field emission scanning electron microscope(FE-SEM), and set up the process conditions to manufacture structural modulated AAO templates.The pore diameter rates could be changed,and the biggest rate we could gain was up to 2:1,and we turned out AAOs with periodically various pore diameters.(2) We electrodeposited Co、Ni nonawires with modulated wire diameter into our self-made structural modulated AAO templates,using direct current electrodeposition method. We characterized and analyzed the samples with、FE-SEM and X-ray diffraction analysis (XRD).We studied the magnetic propertis via vibrating sample magnetometer(VSM), analyzed the effect of modulated wire diameters on the hysteresis loop. The wire diameter rate in a Co or Ni nanowire was around 8:5. XRD analysis showed the Co nanowires had compound phase structure of hexagonal phase and face centered cubic phase, while the Ni nanowires had single face centered cubic phase structure and preferred orientation along (220).The hysteresis loops indicated that Co and Ni nanowires had magnetization distinct anisotropy:the easy magnetization direction was parallel to the long axis of nanowire and the hard magnetization direction was vertical to the long axis of nanowire.(3)We electrodeposited Co-Cu multilayer nanowires into AAO templates in a single groove by the multi-electric potential direct current electrodeposition method. We figured out the relationship between the electrodeposition time and the thickness of the sublayer.We studied how the variations of the wavelength modulation and different sublayer thicknesses affected the hysteresis loop via the VSM. We could change the thickness of Co layers between 30-110nm, and Cu layers between 30-50nm. XRD analysis implied that in the Co-Cu multilayer nanowires,Co element had compound phase structure of hexagonal phase and face centered cubic phase, while the Ni element had single face centered cubic phase structure.Though the modulated wavelength and sublayer thickness of the Co-Cu nanowires were different,the magnetization was almost the same, without any indication of magnetization anisotropy更多还原