Preparation And Characterization Of Nickel And Nickel-based Nano-materials

Synthesis of nickel nanomaterials of different structure and shape has attracted much attention recently because nano-structure nickel have potential applications in magnetic sensors and memory devices. Nickel-based materials have more potential applications in many fields such as hydrogen storage alloy, superconductor, et al.. LaNi₅, Mg₂Ni are potential excellent hydrogen storage alloy. Preparation of nano-alloy may be an efficient approach to improve utility and performance of hydrogen storage alloy. NiO is a promising functional material. Since the superconducting behavior of RENi₂B₂C (RE=Y or rare earth elements) was reported, the carbide superconductors with rare earth elements and Ni have been widely studied because of the coexistence of magnetism and superconductivity in them. Therefore, it is an interesting work to study the preparation of LaNiC₂ superconductor.Preparation of nano-crystalline nickel and nickel-based materials was been studied by different methods, especially, the solvothermal route. Nano-crystalline Ni, NiO and MgNi₂ alloy were synthesized via combustion process in our present work. They are sphere-shape particles with diameters about 50 nm, 10 nm and 200 nm, respectively. Mg₂Ni had not been observed in this route. Finely dispersed nickel with hexagonal closed-packed (hcp) structure was prepared in the solvothermal process. Different reaction condition such as temperature, time and organic solvent have large effect on crystal phase transition of nickel, from face-center cubic (fcc) phase to hcp phase. Furthermore, preparation of LaNi₅ alloy and LaNiC₂ was studied in the solvothermal process.Nickel and LaNis alloy are excellent catalyst. Different carbonaceous materials were prepared with LaNis alloy, in-situ La/Ni and nickel as catalyst in the solvothermal process. Cabon nanotubes with diameter of 100nm and length of several micrometers were synthesized used in-situ La/Ni as catalyst in the toluene at 350℃. The yield of carbon nanotubes was estimated through SEM to be about 70%. In this process, carbon nanotubes could be obtained only at 500℃ when LaNis alloy was used as catalyst. Carbon micro-beads (CMB) with regular and perfect shape, high yields and narrow sizedistributions were obtained via an alcohol-thermal reduction process in a stainless autoclave at 500 °C. In this route, LaNis alloy and in-situ nickel were used as catalyst, respectively. Most of carbon micro-beads are spheres with smooth surface, diameters ranging from 2 to 5 V- m. There are some carbon micro-beads with lemon-like in the sample, diameters ranging from 2 to 4 u m and lengths ranging from 3 to 10 u m.