This study examined the effects of a variety of metallurgical factors on the electrochemical corrosion behavior of superaustenitic stainless steel welds. First, the effects of the sigma (σ)-phase on the corrosion behavior were studied by means of a three-dimensional-atom probe. Cr and Mo depletion areas formed around the σ-phases which are precipitated in the interdendritic area were clearly observed. Second, the effects of oxide inclusion on the pitting corrosion of the steel welds were analyzed. The utilization of high resolution transmission electron microscope clearly demonstrated that the thickness and Cr content of the passive film formed on the steel surface decreased significantly with decreasing distance to the oxide inclusion, resulting in a deterioration of the corrosion resistance. Third, the effects of alloying elements, Cu and Al, were evaluated using an electrochemical polarization technique. This confirmed that Cu has a detrimental effect on the resistance to localized corrosion of the steel. The addition of Al up to 0.25 wt% had no significant effects on corrosion resistance in a chloride environment despite the presence of an Al-based oxide layer (Al2O3) on the outermost surface.

The catalytic activity of Pt nanoparticles (NPs) significantly influences the electrochemical performance of direct methanol fuel cells. Information about the factors that influence the electrochemical activity of the catalyst themselves is scarce; hence, guidelines for the preparation of Pt NPs that yields the best performances are lacking. With consideration for this situation, we systematically investigated the relationship(s) between the characteristics of Pt NPs and their electrochemical performance. The general characteristics of Pt NPs, such as the average size, loading density, and dispersion status on the support, were varied in the presence of poly(acrylic acid)-wrapped multiwalled carbon nanotubes by controlling the preparation conditions, including the pH of the aqueous solution, the reaction temperature, and the reaction time. The enhanced catalytic activity is attributable to higher degree of dispersion, specific surface area, and electrochemically active surface area of Pt NPs. The optimized catalyst exhibits a ∼165% higher catalytic activity toward methanol oxidation than the commercial E-TEK.

Plasma doping (PLAD) process utilizing PH3 plasma to fabricate n-type junction with supplied bias of −1 kV and doping time of 60 sec under the room temperature is presented. The RTA process is performed at 900 °C for 10 sec. A defect-free surface is corroborated by TEM and DXRD analyses, and examined SIMS profiles reveal that shallow n+ junctions are formed with surface doping concentration of 1021atoms/cm3. The junction depth increases in proportion to the O2 gas flow when the N2 flow is fixed during the RTA process, resulting in a decreased sheet resistance. Measured doping profiles and the sheet resistance confirm that the n+ junction depth less than 52 nm and minimum sheet resistance of 313 Ω/□ are feasible.

Titanium dioxide nanopowders were synthesized by in-flight oxidation of titanium nitride (TiN) in radio-frequency (rf) induction thermal plasma. The powders were characterized by x-ray diffraction, high-resolution transmission electron microscopy, field emission scanning electron microscopy, Raman spectroscopy, and optical microscopy to reveal the mechanisms of phase selection and particle morphology evolution. The reaction began with surface oxidation of TiN particles, leading to the formation of core-shell composites with oxidized shells and TiN cores, followed by gas-phase condensation of TiO2 nanoparticles. Phase selection of the resultant TiO2 powders was found to largely depend on the oxidation potential of the thermal plasma rather than on the heat transfer itself. Anatase content of the products increased steadily with increasing the O2 input, and TiO2 nanoparticles (∼50 nm) containing ∼90% of anatase were obtained through O2/Ar plasma treatment. Phase-pure rutile nanoparticles (∼50 nm, on average) were also synthesized in H2/Ar plasma injected with O2 as the powder carrier gas.