Chemical Structure and Morphology of Magnetic Ultrafine Particles Synthesized from a Ternary Gaseous Mixture Involving Cobalt Tricarbonyl Nitrosyl

摘要

From a ternary gaseous mixture of cobalt tricarbonyl nitrosyl (Co(CO)(3)NO),iron pentacarbonyl (Fe(CO)(5)), and 2-propenyltrimethylsilane (allyltrimethylsilane) (ATMeSi), magnetic black fibrous material composed of amorphous ultrafine particles were produced under irradiation with intense Nd:YAG laser light at 355 nm. Chemical structures were studied from FT-IR and Raman spectra. It was shown that Co(CO)(3)NO and Fe(CO)(5) molecules evolved terminal C=O groups, and Co and Fe atoms were connected via bridging C=O groups. ATMeSi also coordinated to Co atoms via C=C double bond of allyl group. The chemical compositions and the morphology of the magnetic particles were analyzed by scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS) and HRTEM images. Small amorphous particles with sizes of less than 50 nm joined together to form fibers, and crystalline spheres similar to the structure of Co0.7Fe0.3 were involved in some particles. Magnetization of the ultrafine particles was measured with a SQUID magnetometer. Magnetic susceptibility, chi, of the ultrafine particles was evaluated to be similar to 2 X 10(-2) emu/g, and temperature dependence of chi supported the ferromagnetic behaviors of the particles. Under a magnetic field of 1-5 T, super-paramagnetic ultrafine particles were also produced in addition to ferromagnetic particles. Existence of several kinds of crystalline spheres was responsible to magnetic properties of the ultrafine particles.