In this work we report the synthesis and the characterization of poly(vinyl alcohol) (PVA)-based proton-conducting membranes. In particular, we describe a cross-linking process of PVA with glutaraldehyde, which gives rise to membranes with enhanced morphological, thermal, and electrochemical characteristics. The critical role of the dispersion of a SiO2 -based ceramic filler in promoting liquid retention and in enhancing the proton conductivity of composite PVA-based membranes is also discussed.

Bismuth thermodynamic activities in Ni – Bi liquid solutions have been measured by the modified isothermal isopiestic method at 1723, 1753 and 1773 K. These results are coupled with thermochemical and topological data from literature, in order to achieve reliable re-optimization of the Ni – Bi system by the CALPHAD method. The model of disordered substitutional solutions has been applied to the liquid phase and to the face-centered cubic solid solutions (Ni). The compound NiBi3 is stoichiometric and is modeled by a two-sublattice model corresponding to its formula. The nickel solubility in the solid bismuth is negligible, which is why the phase (Bi) is considered as consisting of bismuth only. The description Bi: Ni, Va has been used for the thermodynamic modeling of the nonstoichiometric NiBi phase.

Influence of Zr on the microstructure and phase characteristics of aluminide diffusion coatings deposited on the nickel substrate has been investigated in this study. The coatings with and without zirconium were deposited by CVD method. The cross-section chemical composition investigations revealed that during the coatings formation, there is an inward aluminum diffusion and outward nickel diffusion in both types of coatings (with and without zirconium), whereas zirconium is located far below the coating surface, at a depth of ∼17 μm, between β-NiAl phase and γ-Ni 3 Al phase. XRD examinations showed that β-NiAl, γ-NiAl and γ-Ni 3 Al were the main components of the deposited coatings. β-NiAl phase is on the surface of the coatings, whereas γ-NiAl and γ-Ni 3 Al form deeper parts of the coatings. Zirconium is dissolved in NiAl on the border between β-NiAl and γ-Ni 3 Al.

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a b s t r a c tThe microstructure of the zirconium doped aluminide coating deposited on the nickel substrate by the CVD method is presented. TEM analysis proved that the ß-NiAl and the γ 0 -Ni3Al are the main phases of the deposited coating. Some dislocations in the nickel substrate and in the coating were observed. The cross section chemical composition examination revealed, that the coating was formed via the inward aluminum diffusion and the outward nickel diffusion. SEM analysis revealed small zirconium content (0.2-0.4 at%) on the cross-section of the aluminide coating. Such zirconium content leads to zirconium dissolution in the aluminide coating. Long time of zirconizing (4 h) caused the appearance of zirconium nano particles at the surface of the coating. TEM investigations confirmed that zirconium formed inclusions on the coating's surface.

The CMSX 4 superalloy was coated with rhodium 0.5-μm thick layer and next aluminized by the CVD method. The coating consisted of two layers: the additive and the interdiffusion one. The outward diffusion of nickel from the substrate turned out to be a coating growth dominating factor. The additive layer consists of the β-NiAl phase, whereas the interdiffusion layer consists of the β-NiAl phase with precipitates of σ and μ phases. Rhodium has dissolved in the coating up to the same level in the matrix and in the precipitates. The oxidation test proved that the rhodium modified aluminide coating showed about twice better oxidation resistance than the nonmodified one.

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