Modulated Nanowires Preparation And Characterization

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...