Via a mild thermal precipitation and aging process, polycrystalline hydrated nickel oxalate nanofibers were synthesized using nickel chloride and ammonium oxalate as raw materials, with pH 8.0 and temperature 60 ？C. Atomic absorption spectrometer （AAS）, organic elemental analyzer （OEA）, fourier transform infrared spectroscopy （FT-IR）, thermogravimetry-derivative thermogravimetry （TG-DTG）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM） were used to characterize the products properties. The results demonstrated that the product was hydrated nickel oxalate. The sizes of hydrated nickel oxalate nanofibers were 100-150 nm in diameter, and 0.5-5.0 μm in length. A rational mechanism based on coordination self-assembly was discussed for the selective formation of the polycrystalline hydrated nickel oxalate nanofibers.
Nickel tartrate precursor particles were synthesized by the liquid phase precipitation method in an ethanol-water-ammonia mixed solution, with tartaric acid and using nickel chlorate as raw materials, with the pH value controlled at 4.0, and the temperature controlled at 50 ℃. Nickel particles with complicated morphology were prepared by the decomposition of nickel taratrate precursor particles at temperatures of 360, 380 and 400 ℃, respectively. The study of infrared spectroscopy （IR） indicated that the product was pure nickel tartrate. The studies of the atomic absorption spectrometry （AAS） and organic elemental analysis （OEA） indicated that the molar ratio of Ni2＋ to （C4H4O6）2- is close to 1：1. The studies of the differential scanning calorimeter and thermo-gravimetric analysis （DSC-TG） indicated that the chemical formula Niz（C4H4O6） 2.5H2O was confirmed. The studies of X-ray diffractions （XRD） indicated that the silvery white metal powders were pure Ni, with a face-centered cubic crystal structure. The images of scanning electron microscopy （SEM） showed that the morphology of metal Ni particles was obvious spherical and radiate. The diameter of nickel tartrate particles was about 60 μm, which consisted of many nanolathes; and the diameter of metal Ni particles was about 30 μm, which consisted of many lathes about 0.5 μm in thickness.
