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The effects of the modification of the pH in 0.1 M cerium nitrate solutions in the elaboration and corrosion resistance of ceria based coatings on carbon steel are investigated. Increasing the concentration of acetic acid impedes an efficient electrodeposition. At low concentrations, acetic acid seems to prevent the precipitation of Ce(OH)3 and the formation of even films of cerium oxides is favored. The increase of pH through the addition of NaOH to the cerium nitrate solutions with 0.008 M of acetic acid is shown to provide superior corrosion resistance for exposures in air and immersed in 0.5 M NaCl for 30 days. The effects of the modification of the pH in 0.1 M cerium nitrate solutions in the elaboration and corrosion resistance of ceria based coatings on carbon steel are investigated. Increasing the concentration of acetic acid impedes an efficient electrodeposition. The increase of pH through the addition of NaOH to the cerium nitrate solutions with 0.008 M of acetic acid is shown to provide superior corrosion resistance. [ABSTRACT FROM AUTHOR]

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The influence of the as-cast and fully heat-treated microstructures on the isothermal behaviour of the Ni-based single crystal superalloy AM1 was investigated at 850-1050 °C. It appears that the kinetics transition regime is a function of time, temperature and also of bulk microstructure. The various characterisation techniques allowed elucidating that the growth of a continuous inner layer of α-Al 2 O 3 governs the oxidation mechanisms, irrespective of the microstructure. Such layer is favoured for high oxidation temperatures, long exposure times and high γ' precipitate surface fraction. However, the chemical segregation of the as-cast state is responsible for the growth of inhomogeneous oxide layers. • Differences in oxidation unveiled for as-cast and FHT AM1 Ni-based superalloy. • Oxidation mechanism governed by internal Al 2 O 3 scale on the γ/γ' structure of AM1. • Transition regime linked to the allotropic transformation of Al 2 O 3 and of Cr. • None of the AM1 microstructure develops Al 2 O 3 at low temperatures and short times. • Chemical segregation in as-cast AM1 is responsible for the uneven growth of oxides. [ABSTRACT FROM AUTHOR]

A single-phase ZrW2O8 was prepared by the hydrothermal route via decomposition of ZrW2O7(OH1.5,Cl0.5)·2H2O at 843 K. TEM , in situ high-temperature XRD and TG-DTA analyses of the ZrW2O8 synthesized were performed. The morphology of the material was represented as elongated particles with an intrinsic block structure. The stability fields of ZrW2O8 were determined. The ZrW2O8 demonstrated a negative thermal expansion behavior from 298 to 1023 K. [ABSTRACT FROM AUTHOR]

• Failure mode in VHCF conditions (1,000 °C/R ε = -1/f = 20 kHz) of slurry-coated Ni-based SX superalloys. • The competition between surface and internal crack initiation for slurry-coated Ni-based SX superalloys. • The interaction between the casting pore, the interdiffusion zone and the rough zone developed around internal casting pores. The failure mode in the very high cycle fatigue (VHCF) regime of four different nickel-based single-crystal (SX) superalloys coated with a slurry aluminide has been investigated at high temperature (1,000 °C) and under fully-reversed conditions (R ε = -1). The 3rd generation superalloy CMSX-4 Plus presented a lifetime one to two order(s) of magnitude higher than AM1, CMSX-4 and Rene N5 for the same applied alternating stress (180 MPa). The crack initiation zones were distinct. CMSX-4 Plus samples failed from the interdiffusion zone (IDZ) while AM1, CMSX-4 and Rene N5 samples failed from casting pores close to the IDZ. The interaction between the casting pore, the IDZ and the rough zone is believed to control the premature crack initiation. A new crack initiation mode in VHCF for coated specimens is proposed in this article and the competition between crack initiation from a casting pore or from the surface is considered and discussed. [ABSTRACT FROM AUTHOR]

The effects of chromium and silicon modification on the microstructure and hot corrosion resistance of slurry aluminide coatings applied on pure nickel was studied by in-depth microscopic analyses. The simple and the Cr-modified aluminide coatings provided limited protection in Type II hot corrosion conditions but the Si-modified coating exhibited outstanding resistance with no sign of attack after 300 h of isothermal exposure at 700 °C. The synergistic dissolution between NiO and Al 2 O 3 /Cr 2 O 3 appears responsible for the onset of the corrosion attack for the simple and Cr-modified coatings while silicon is shown to extend the incubation period. [Display omitted] • Experimental evidence for a two-stage corrosion mechanism following initiation and propagation. • Onset of hot corrosion attack occurs after an incubation period and is triggered by NiO. • Chromium improves resistance through formation of Cr 2 O 3 and promoting α-Al 2 O 3. • Silicon significantly improves the resistance of the aluminide coating by prolonging the incubation period. • Aluminium surface concentration of the coating also plays a role, mainly by delaying the formation of NiO. [ABSTRACT FROM AUTHOR]

A water-based slurry aluminide coating was elaborated on high-purity nickel and tested in synthetic air, synthetic air + 0.5 % SO 2 /SO 3 and synthetic air + 0.5 % SO 2 /SO 3 with sodium sulphate (Na 2 SO 4) deposit at 700 °C. The developed coating considerably increased the oxidation-sulphidation resistance of nickel in the absence of salt through the formation of thin and adherent alumina scales. In contrast, the presence of sodium sulphate decreased the corrosion resistance. Microstructural investigations indicated that aluminium depletion and the related formation of Ni-rich oxides is mainly responsible for the onset of the corrosion attack following sulphation reaction and fluxing mechanisms. [Display omitted] • Coating based on β-NiAl increases sulphidation resistance through protective α-Al 2 O 3. • Coating offers limited protection after the incubation period when in contact with solid Na 2 SO 4. • Initiation of the attack due to fluxing and synergistic dissolution of NiO and Al 2 O 3. • Aluminium surface concentration and phase transformation are key factors on the onset of the hot corrosion attack. • Microstructural observations confirm the formation of the eutectic Na 2 SO 4 -NiSO 4 in Type II conditions. [ABSTRACT FROM AUTHOR]

Coevolution can sculpt remarkable trait similarity between mutualistic partners. Yet, it remains unclear which network topologies and selection regimes enhance trait matching. To address this, we simulate coevolution in topologically distinct networks under a gradient of mutualistic selection strength. We describe three main insights. First, trait matching is jointly influenced by the strength of mutualistic selection and the structural properties of the network where coevolution is unfolding. Second, the strength of mutualistic selection determines the network descriptors better correlated with higher trait matching. While network modularity enhances trait matching when coevolution is weak, network connectance does so when coevolution is strong. Third, the structural properties of networks outrank those of modules or species in determining the degree of trait matching. Our findings suggest networks can both enhance or constrain trait matching, depending on the strength of mutualistic selection.