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Ni-based composite microstructures fabricated by femtosecond laser reductive sintering of NiO/Cr mixed nanoparticles

Ni-based composite micropatterns were fabricated by the femtosecond laser reductive sintering of NiO/Cr mixed nanoparticles. A NiO/Cr mixed nanoparticle solution including ethylene glycol and polyvinylpyrrolidone was irradiated with focused femtosecond laser pulses. The X-ray diffraction spectra of the fabricated micropatterns indicated that NiO nanoparticles were well reduced under atmospheric conditions in the laser scanning speed range of 5–15 mm/s. In contrast, micropatterns including NiO were formed at a laser scanning speed of 1 mm/s, indicating that the reduced Ni was reoxidized by overheating. These results were supported by those of energy-dispersive X-ray spectrometry analysis and the electrical resistivity of the micropatterns. The compositions such as Ni, NiO, Cr2O3, and Ni–Cr in the fabricated micropatterns depended on laser scanning speed. The selective fabrication of a ferromagnetic free microgear from the substrate and an axis fixed on the substrate was demonstrated by controlling the laser scanning speed. The fabrication process for Ni-based composite microstructures is useful for the fabrication of ferromagnetic microdevices.