Preparation And Magnetic Properties Of Transition Metal Nanotubes/Wires

With the development of science and technology,components tend to be miniaturized,and the application of magnetic materials is also very wide,so it is very important to perform the research of magnetic materials.In his thesis,the transition metal nanotube/wire arrays have been synthesized by porous anodic aluminum oxide template-assisted electrodeposition methods.The morphology of the sample is characterized by scanning electron microscopy,the crystal structure is determined by X-ray diffraction instrument,the composition is analyzed by X-ray energy dispersive spectrometry,and the magnetic properties are measured by vibrating sample magnetometer.Based on templates,metal nanotubes and nanowires are prepared by electrochemical methods,which are favored for their simplicity,low cost and easy manipulation.In this experiment,firstly,porous alumina template is obtained by electrochemical method,namely two-step anodic oxidation,and 0.3mol/L oxalic acid solution is selected as the electrolyte.Then Fe,Co and Ni nanotubes/wires are deposited,respectively,into the above self-made template and the commercial template with the pore diameter of 100 nm and 200 nm.The results show that compared with the nanotubes/wires of the three elements,the growth morphology of the Ni nanotubes/wires is the best,and the nanotubes/wires of Fe,Co and Ni are all crystal structures at room temperature.The preferred growth orientation of the Co nanotubes/wires is(002),and the preferred growth orientation of the Fe and Ni nanotubes/wires is(111).Compared with hysteresis loops of Co and Ni nanotubes/wires,hysteresis loops of Ni nanotubes/wires are typical soft magnetic materials with slender hysteresis loops and small coercivity and remanence.The hysteresis loop of Co nanotubes/wires deviates from the center.The reason is that some of the Co nanotubes/wires are oxidized to form the Co/CoO interface during the preparation process,and there is exchange bias.The commercial template with pore diameter of 100 nm is selected to deposit Ni-Fe and Ni-Co nanotubes/wires at different voltages.It is found that the components of nanotubes/wires prepared with different voltages are the same,but the percentages of each component are different.In the Ni-Fe nanotubes/wires,the percentage of iron atoms decreases and the percentage of nickel atoms increases with the negative increase of deposition voltage.In Ni-Co nanotubes/wires,the percentage of nickel atoms decreases and the percentage of cobalt atoms increases with the negative increase of deposition voltage.The XRD pattern shows that both Ni-Fe and Ni-Co nanotubes/wires are crystal structures at room temperature,and their peaks gradually weaken with the negative increase of deposition voltage.Hysteresis loop indicates that the Ni-Co nanotubes/wires to magnetize more easily in the direction perpendicular to the nanotubes/wires than in the direction parallel to the nanotubes/wires,and with the negative increase of the deposition voltage,the saturation magnetization increases gradually,while the coercivity and remanence both decrease gradually.