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The oxidation kinetics of a grade 300 maraging steel in air at temperatures ranging from 300 to 600°C have been determined using Auger electron spectroscopy in conjunction with argon ion sputtering. A limited-thickness type of growth was observed up to the relatively high temperature of 480 OC. Above 480 "C, the kinetics were parabolic.A thin gold layer sputtered onto the surface before oxidation resulted in a change in the kinetics from limitedthickness to approximately parabolic growth at temperatures below 480"C, while it remained parabolic above 480 "C.The limited-thickness oxide growth is described in terms of space-charge effects, as outlined by the theory of Fromhold. Tbe insulating properties of a thin mixed spinel oxide present at the metaloxide interface is critical in bringing about the space charge in tbe oxide. A change in the electrical conductivity of the mixed spinel is associated with a change in the oxidation kinetics

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Herein, we describe the synthesis of titanium dioxide (TiO2) nanoparticles by the hydrolysis and condensation of titanium tetrachloride. The resulting nanoparticles were immobilized on polyacrylonitrile (PAN) based nanofibres by an electrospinning technique in order to allow simple isolation and reuse of titania semiconductor photocatalyst. The composite nanofibres were heat treated to convert the polymer nanofibres to carbon nanofibres and to convert amorphous TiO2to crystalline TiO2. X-ray diffraction (XRD) analysis showed that the rutile phase was the major phase and the equatorial peaks of PAN disappeared after heat treatment at 600°C. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analysis confirmed that some TiO2nanoparticles were encapsulated whereas some were surface residing on the electrospun nanofibres. The TiO2nanoparticles were found to lower the cyclization temperature of PAN as indicated by differential scanning colorimetry (DSC) and differential thermal analysis (DTA). Photocatalytic studies on the degradation of methyl orange dye under UV light irradiation showed that composite nanofibres were capable of degrading organic contaminants in water. The carbon nanofibres with surface residing titanium dioxide nanoparticles (TiO2/CNF-SR) showed the highest photocatalytic activity (59.35% after 210 minutes) due to direct contact between the TiO2photocatalyst and methyl orange.