ICMCTF2005 Session AP: Symposium A Poster Session

CrN coatings deposited by PVD techniques exhibit excellent corrosion and wear properties, and have better oxidation resistance, as well as better adhesion to tool steel. Earlier work concluded that Cr(N,O) films deposited by cathodic arc deposition exhibit better mechanical properties when compared to CrN. However, it is expected that macroparticles accompanied with cathodic arc deposition result in defects of the films. Increasing amount of researches found that multilayers combined the properties of the constituent materials had led to improved properties when compared to the individual single layer films.

In this study, the Cr(N,O)/CrN double-layered coatings on tool steel was conducted using cathodic arc deposition process. CrN layer was first deposited on tool steel as an interlayer to ensure better adhesion. The following procedure was deposited with Cr(N,O) as a surface layer. The Cr(N,O) was designed with various composition by various O/N gas flow ratio during the process. The chemical composition, structure and morphology of coatings was analyzed by XRD, XPS and SEM, respectively. The corrosion behavior of Cr(N,O)/CrN double-layered coatings was investigated using polarization and immersion tests. Polarization properties of coatings were carried out under the condition of 3.5 wt% NaCl solution. In the immersion test, Cr(N,O)/CrN double-layered coatings were exposed under H₂SO₄, HCl, NaOH environment for 25, 50 and 50 hours, respectively. The results show that the corrosion resistance of Cr(N,O)/CrN coating is similar to diamond like carbon (DLC) films, but better than that of CrN single layer.

The co-deposition of Al-Si coatings on ferritic steels (P-91, P-92 and HCM-12A) were produced by Chemical Vapour Deposition in Fluidized Bed Reactors (CVD-FBR). The initial parameters of the processes were determined by means of thermochemical calculations using the Themo Calc Sofware. Metal sub-halide chemistry was used to produce the gas precursors for the deposition. The thermodynamic analysis of system consists of Al and Si powder as donator, HCl as activator, H₂ as reducing agent and Ar as inert gas. The most important precursors for Al and Si in a range o temperature from 450°C up to 600°C were AlCl₃, Al₂Cl₆, AlHCl₂, AlCl, and Cl₁H₃Si, respectively. With this method Al-Si coatings 4 μm thick were obtained at low deposition temperatures and short deposition time.

The effect of diffusion heat treatment that was performed under argon flow a 700°C for 2 hours on coating was studied in order to allow the phase transformation from Fe₂Al₅ to another iron aluminides. The coating morphology, composition and mechanical properties were characterized using optical microscopy (OM), Scanning Electron Microscopy (SEM), Electron Probe Microanalysis, X-ray diffraction and the mechanical properties were measurement using Vickers microhardness tester. The heat treatment at 700°C brings about transport of different elements, which in turn give rise to thicker coatings and phase change of intermetallic compounds.

Titanium dioxide is a widely studied material due its numerous applications in optics, optoelectronics or photocatalysis, in relation with its favourable physical, chemical and optoelectronical properties associated with a high stability. Extensive efforts have been made by several authors for the development of titanium dioxide coatings that can efficiently use solar or indoor light [1, 2]. Numerous techniques are available to synthesise photocatalytic anatase thin films, such as sol-gel, chemical vapour deposition, pulsed laser deposition or physical vapour deposition.

In this paper, we present results of nitrogen doped titanium dioxide coatings deposited on glass slides by reactive magnetron sputtering of a titanium target in the presence of various reactive argon-oxygen-nitrogen mixtures. In a first part, we investigate the influence of the deposition pressure and of the annealing temperature in case of TiO₂ coatings in relation with their morphology and their grain size, determined respectively by scanning and transmission electron microscopy. The second part is ascribed to the nitrogen substitution in the TiO_2-xN_x anatase structure as a function of the N₂ to O₂ ratio in the reactive atmosphere. Finally, photocatalytic measurements, performed by irradiating samples covered by orange-G, are discussed in relation with the films composition, microstructure and morphology.

[1] Y. Suda, H. Kawasaki, T. Ueda, T. Ohshima, Thin Solid Films 453-454 (2004), 162

[2] L. Shivalingappa, J. Sheng, T. Fukami, Vacuum 48 5 (1997), 413.

Sputter deposition has been investigated as a tool for manufacturing proton-exchange membrane fuel cell (PEMFC) elecrodes with improved performance and catalyst utilization vs. commercial and metal chemical electrode. Nanosize (diameter 2-5 nm) platinum cluster has been deposited on gas diffusion electrode (carbon paper + PTFE/C diffusive layer) and the activity for methanol oxidation resulted highly increased (about 30 times) compared to commercial catalyst, with loading of 0.006 mg/cm₂.

We measured and studied the electrochemical performance also of nanosized films deposited on Nafion membrane and of the entire cell (membrane electrode assembly, MEA), prepared by bonding the catalysed electrodes to the catalysed proton exchange polymer membrane.

SEM-FEG, XRD and XPS measurements were carried out to understand the performaces and beahvior of the Pt electrocatalyst as both cathode and anode of a polymer electrolyte fuel cell.

Lanthanum manganite of perovskite structure are potential candidates for numerous applications in energy generation [1] or environmental applications [2] due to their catalytic properties. Their use as thin films should constitute a useful way to improve devices functionality such as solid oxide fuel cells or air cleaning systems using the concept of electrochemical promotion of catalysis. In this paper, we investigate the deposition of La_{1-x√sub x}MnO₃ coatings by co-sputtering of La_{0.9√sub 0.1}and Mn metallic targets on a rotating substrate-holder in the presence of reactive argon-oxygen mixtures. After a short description of the reactor equipped with a conventional optical emission spectroscopy (OES) system and an original optical transmittance interferometry (OTI) device developed at the laboratory, the structure of the as-deposited coatings is investigated by X-ray diffraction as a function of their composition, measured by electron probe micro analysis (EPMA), resulting from the power dissipated on each target. The structural evolution of the coatings, initially amorphous, is then presented as a function of the annealing temperature. Finally, electrical conductivity measurements performed by the four probe method are presented in relation with the coatings structure.

[1] M. Gaudon, C. Laberty-Robert, F. Ansart, P. Stevens, A. Rousset, Solid State sciences 4 (2002) 125.

[2]J.J. Spivey, Ind. Eng. Chem. Res., 26 (1987) 2165.

Keywords: Lanthanzirconate, TGO growth, EB-PVD-technique, thermal cycle test.

Under a severe gas turbine environment it is expected from thermal barrier coatings (TBCs) to provide not only thermal insulation to the metallic components by preserving a low thermal conductivity but also to protect them from oxidation, hot corrosion and wear damage.

In this paper, a TBC system is investigated with regard to performance under high temperature corrosion exposure in molten salts. The investigated TBC system comprises an atmospheric plasma-sprayed ZrO₂-8wt%Y₂O₃ top coat and a vacuum plasma-sprayed NiCoCrAlY bond coat deposited on a stainless steel substrate. The surface of the ceramic top coat has been previously laser-glazed by a high power continuous wave CO₂ laser to generate an external dense layer.

The hot corrosion investigation was carried out by subjecting the specimens to an isothermal air furnace testing under Na₂SO₄ and/or V₂O₅ deposits in a temperature of approximately 1000°C for 1 hour cycles. The corrosion mechanisms were investigated from post-test image analysis using scanning electron microscopy (SEM) and from structural changes by X-ray diffraction (XRD). Energy dispersive X-ray analysis (EDX) was also used to map the elements deriving from the corrosive compounds along through-thickness. Bond coat corrosion and top coat destabilization mechanisms are discussed.