Corrosion Behavior and Passive Film Composition of Alloy 825 in High Temperature and High H2S-CO2 Containing Environment

The effect of high temperature on corrosion behavior and passive film composition of Ni-based alloy 825 in H2S-containing environment was investigated by Confocal Laser Microscope (CLM), Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS), and X-ray Photoelectron Spectroscopy (XPS). The experiment was carried out at 150 and 230°C in NaCl solution. The partial pressure of H2S was set to 1.2 MPa and CO2 was set to 3.2 MPa. The results showed that Ni-based alloy 825 presented good general corrosion resistance. Pitting corrosion was likely to occur at 230°C because of Cr depleted in the passive film. NiS appeared at high temperature and is damaging to protectiveness of passive film.

Growth of LixLaySrzMnO3 thin films by pulsed laser deposition: complex relation between thin film composition and deposition parameters

LixLaySrzMnO3 thin films of various compositions (x,y,z) have been grown using pulsed laser deposition. The compositions of the films have been studied as a function of deposition temperature, target-to-substrate distance and deposition pressure with respect to different cation ratios of the targets by inductively coupled plasma mass spectrometry. When growing multi-elemental oxide thin films containing lithium (with its large mass difference to other elements), lithium loss is most probably inevitable. But the desired thin film composition can be achieved by selecting specific growth conditions and different target compositions. The experiments also elucidate some of the mechanisms behind the incongruent lithium transfer from the targets to thin films.

Fabrication, micro-structure characteristics and transport properties of co-evaporated thin films of Bi2Te3 on AlN coated stainless steel foils

N-type bismuth telluride (Bi2Te3) thin films were prepared on an aluminum nitride (AlN)-coated stainless steel foil substrate to obtain optimal thermoelectric performance. The thermal co-evaporation method was adopted so that we could vary the thin film composition, enabling us to investigate the relationship between the film composition, microstructure, crystal preferred orientation and thermoelectric properties. The influence of the substrate temperature was also investigated by synthesizing two sets of thin film samples; in one set the substrate was kept at room temperature (RT) while in the other set the substrate was maintained at a high temperature, of 300 °C, during deposition. The samples deposited at RT were amorphous in the as-deposited state and therefore were annealed at 280 °C to promote crystallization and phase development. The electrical resistivity and Seebeck coefficient were measured and the results were interpreted. Both the transport properties and crystal structure were observed to be strongly affected by non-stoichiometry and the choice of substrate temperature. We observed columnar microstructures with hexagonal grains and a multi-oriented crystal structure for the thin films deposited at high substrate temperatures, whereas highly (00 l) textured thin films with columns consisting of in-plane layers were fabricated from the stoichiometric annealed thin film samples originally synthesized at RT. Special emphasis was placed on examining the nature of tellurium (Te) atom based structural defects and their influence on thin film properties. We report maximum power factor (PF) of 1.35 mW/m K2 for near-stoichiometric film deposited at high substrate temperature, which was the highest among all studied cases.