Infrared laser synthesis and properties of magnetic nano-iron-polyoxocarbosilane composites

Abstract

Nano-magnetic, thermally stable iron-based composites were obtained by a one-step procedure consisting of continuous-wave infrared laser-induced and ethylene-sensitized co-pyrolysis of gaseous iron pentacarbonyl and hexamethyldisiloxane in argon. The simultaneously occurring formation of iron from iron pentacarbonyl and that of organosilicon polymer from hexamethyldisiloxane yield iron nanoparticles surrounded by an organosilicon polymer shell. The particles were characterized by spectral analyses, electron microscopy, thermal gravimetry and magnetic measurements. They become superficially oxidized in the atmosphere. Their composition, thermal behaviour and magnetic properties depend on the flow rates of the precursors and the total pressure of the procedure. Magnetization curves, exchange bias H ex at T = 5 K and AC susceptibility were studied in the temperature range 5-400 K. The values of H ex verified the observed degree of the particle surface oxidation. The system of the iron nanoparticles is in a ferromagnetic blocked state and the temperature dependence of the coercivity and susceptibility is in accord with the transmission electron microscopy data.

IR laser-induced chemical vapor deposition of carbon-coated iron nanoparticles embedded in polymer

“…Nanomagnetic particles of iron stabilized by polymers have been prepared by sonolysis of iron pentacarbonyl in the presence of poly(dimethylphenyleneoxide) 9 and by IR laser gas-phase co-decomposition of iron pentacarbonyl and methoxytrimethylsilane 10 or hexamethyldisiloxane. 11 The carbon-coated Fe nanoparticles were produced by simply annealing mixtures of nanoparticles of hematite (Fe 2 O 3 ) and carbon to 1200 uC under nitrogen, 12 annealing mixtures of iron and diamond nanoparticles at 1700 uC in vacuum, 13 heating mixtures of mm-sized powders of Fe 3 O 4 and poly(vinyl chloride) at 1000 uC in Ar flow, 14 or by heating mixtures of ferrocene or Fe(CO) 5 with bis(n-propylamine) at above 800 uC in vacuum, 15 by the Kra ¨tschmer-Huffmann carbon-arc method (arc discharge evaporation of an electrode composed of graphite and Fe), 16,17 by an ion beam sputtering technique applied to graphite/iron target 18 and by IR laser co-pyrolysis of Fe(CO) 5 and acetylene. 19 In this paper we report on two-and three-wavelengths IR laser irradiation of a gaseous mixture of silacyclopent-3-ene (SCP) and Fe(CO) 5 .…”