Magnetic property and crystallinity of a Ni-P hollow microfiber affected by immersion in a NaOH aqueous solution

抄録

An amorphous nickel-phosphorus (Ni-P) hollow microfiber is prepared by template-synthesis with a hydrogen-bonded fibrous supramolecular template by Pd-promoted electroless deposition. To let the Ni-P microfiber show conductivity and magnetic property in this study, we carried out thermal annealing at 500 °C under an argon atmosphere in different two ways. One is the annealing after template removal with a 1 mol dm-3 NaOH aqueous solution. Another is the annealing without template removal, which was intended to reduce fabrication procedures. As a result, an annealed Ni-P hollow microfiber showed a different saturated magnetization value of 14 emu g'1 in the former and 9 emu g'1 in the latter. To understand the phenomena, we investigated the two kinds of annealed Ni-P microfibers by transmission electron microscopy (TEM), inductively coupled plasma atomic emission spectrometry (ICP-AES), and X-ray diffractometry (XRD). Although the powder conductivity and chemical composition were hardly affected, formation of an f.c.c. nickel phase related to the magnetic property was significantly suppressed in the latter case of annealing without template removal. It was suggested that carbonization of the supramolecular template upon annealing suppressed the formation of an f.c.c. nickel crystalline phase.