High temperature corrosion of alloy Haynes 556 in carburizing/oxidizing environments

The iron based alloy Haynes 556 has been recently used in hydrocarbon and carbonaceous environments due to its excellent resistance to carburization. This alloy outperforms stainless steels and some of the best commercial carburization‐resistant nickel‐based alloys. This paper is concerned with the behavior of alloy Haynes 556 in high temperature carburizing environments containing trace amounts of oxygen. Thermal cyclic exposures were conducted in 2% and 10% CH₄/H₂ gas mixtures at 800, 900, 1000, and 1100°C for 10 cycles, 50 h each. Carbon activities, oxygen partial pressures, and stabilities of oxides and carbides were used to identify the role played by the reaction products in providing protection. Thermodynamic analyses, weight changes, and microstructural characterization were correlated with environmental parameters and alloy composition to elucidate the causes of its marked resistance to carburization. The results indicate protective character in both gas mixtures under all exposure conditions except the most aggressive, namely 1100°C in 10% CH₄/H₂ gas mixture. Below 1000°C, the formation of Cr, Al, and Si oxides along with Cr carbides provides the primary means of protection. Catastrophic failure at 1100°C was manifested by extensive fracture and crack development within the outer substrate surface in the 10% CH₄/H₂ gas mixture resulting in a dramatic increase in weight gain. This has been attributed to the increased carbon pick‐up, coupled with the loss of the protective outer scales.     

The pulmonary performance and airway reactivity in acute and chronic fascioliasis before and after triclabendazole treatment

The pulmonary performance and airway reactivity were evaluated in 16 acute and 12 chronic fascioliasis patients before and after treatment with triclabendazole in a trial to clarify some underlying pulmonary changes which can explain the chest symptomatology that may accompany this intestinal fluke. Before treatment, the maximum voluntary ventilation was impaired in the acute and chronic cases. In the acute stage, the affection was in the small airways (as denoted by lower values of FEF75% compared to control), while in the chronic stage, the impairment was more generalized including not only the small and large airways (as shown by diminished FVC, FEV1, FEFmax, FEF25%, FEF50% and FEF75%) but also, the upper airway (as noticed by lower values of FIVC and FIF50% compared to the corresponding control values). By individual analysis of the dose response slopes (DRS), 37.5% of acute and 33.3% of chronic cases had bronchial hyperactivity. After triclabendazole treatment and cure of the patients, most of the pulmonary flow rates improved significantly compared to the pre-treatment values. Moreover, all cases regained normal bronchial reactivity and the DRS diminished significantly than during fascioliasis infection. It is concluded that, although the fluke doesn't have a cycle in the lung, yet it may have an impact on the pulmonary performance and airway reactivity which subsides greatly after treatment with triclabendazole.     

Enthalpies of formation of liquid and solid (palladium + indium) alloys

Enthalpies of formation of (Pd + In) alloys have been obtained by direct reaction calorimetry using a very high temperature calorimeter between 1425 and 1679 K in the concentration range 0 <x _Pd < 0.66. They are very negative with a minimum Δ_mix H _o ^m, = -59.6 /2.5 kJ · mol^-1 atx _Pd = 0.59 and independent of temperature within the experimental error. The integral molar enthalpy of mixing is given by Δ_mixΔH _m ^o /· mol^-1 =x(1 -x)·- (-126.94 - 92.653x-83.231.x ₂ - 734.49.x ₃ + 949.07x ⁴), wherex = x _Pd. The limiting partial molar enthalpy of palladium in indium was calculated as Δh _m(Pd liquid in ∞ liquid In) = -127 ± 5 kJ·mol^-1. The results are discussed and compared with the enthalpies of formation of solid alloys. The anomalous behavior of the partial enthalpy of Pd is assumed to be due to the charge transfer of, at most, two electrons of In to Pd. Formerly Ph.D. Student, Université de Provence.     

Generalized Theory of Thermoviscoelasticity and a Half-Space Problem

In this work, the equations of generalized thermoviscoelasticity for a viscoelastic medium are derived. Also, uniqueness and reciprocity theorems for these equations are proved. In addition, a one-dimensional problem for a viscoelastic half space is considered. The Laplace transform technique is used to solve the problem. The solution in the transformed domain is obtained by a direct approach. The inverse transforms are obtained in an approximate analytical manner using asymptotic expansions valid for small values of time. The temperature, displacement, and stress are computed and represented graphically.     

Optimization of factors affecting current generation,biofilm formation and rhamnolipid production by electroactive Pseudomonas aeruginosa FA17

Microbial electrochemical cells (MXCs) have been developed as promising devices mainly for energy generation and wastewater treatment. Among the well-defined electroactive bacteria, Pseudomonas aeruginosa has been demonstrated for its electroactivity through mediated electron transfer in MXCs. In addition to phenazine pigments that mediate external electron transfer (EET), biofilm formation and rhamnolipid production are considered important factors affecting electricity generation by P. aeruginosa in MXCs. In the present study, a local electroactive strain of P. aeruginosa was isolated. Bacterial identification was done by Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and 16S rDNA as P. aeruginosa FA17. Cyclic voltammetric studies showed the appearance of oxidation peaks which contributes to pyocyanin. Plackett-Burman designs were employed to optimize the composition of artificial wastewater (AWW) media for current generation (represented the mediated electron transfer), biofilm formation and rhamnolipid production by FA17. Ammonium chloride was the significant variable affecting electron transfer of FA17 for current generation in three-electrode set-up by using cyclic voltammetry analyses. While phosphate, Sodium dodecyl sulfate (SDS) and chlorides were the major factors influencing biofilm formation by FA17, phosphate, inoculum size, MgSO₄.7H₂O, pH, and SDS were the significant variables for rhamnolipid production. This study provides knowledge about the electrochemical behavior of mediated electron transfer catalyzed by P. aeruginosa FA17, biofilm formation, and rhamnolipid production in response to medium composition, which leads to the possibility for the future development of power produced by MXCs using the electroactive FA17.     

Numerical evaluation of the performance of a Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) under different loading conditions

This paper presents the results of a finite element (FE) numerical analysis that was developed to simulate the fully-instrumented Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS) at the Maree Michel Bridge in Louisiana. Four different loading conditions were considered in this paper to evaluate the performance of GRS-IBS abutment due to dead loading, tandem axle truck loading, service loading, and abnormal loading. The two-dimensional FE computer program PLAXIS 2D 2016 was selected to model the GRS-IBS abutment. The hardening soil model proposed by Schanz et al., (1999) that was initially introduced by Duncan and Chang (1970) was used to simulate the granular backfill materials; a linear-elastic model with Mohr-Coulomb frictional criterion was used to simulate the interface between the geosynthetic and backfill material. Both the geosynthetic and the facing block were modeled using linear elastic model. The Mohr-Coulomb constitutive model was used to simulate the foundation soil. The FE numerical results were compared with the field measurements of monitoring program, in which a good agreement was obtained between the FE numerical results and the field measurements. The range of maximum reinforcement strain was between 0.4% and 1.5%, depending on the location of the reinforcement layer and the loading condition. The maximum lateral deformation at the face was between 2 and 9 mm (0.08%–0.4% lateral strain), depending on the loading condition. The maximum settlement of the GRS-IBS under service loading was 10 mm (0.3% vertical strain), which is about two times the field measurements (～5 mm). This is most probably due to the behavior of over consolidated soil caused by the old bridge. The axial reinforcement force predicted by FHWA (Adams et al., 2011b) design methods were 1.5–2.5 times higher than those predicted by the FE analysis and the field measurements, depending on the loading condition and reinforcement location. However, the interface shear strength between the reinforcement and the backfill materials predicted by Mohr-Coulomb method was very close to those predicted by the FE.     

Dyeability improvement of proteinic and polyamide fabrics pretreated with saccharin sodium salt: A kinetic approach

Improvement of the dyeability of wool, silk, and polyamide fabrics with cationic dye was achieved by their pretreatments with saccharin sodium salt. The acquired color values of the dyed materials were significantly enhanced by the aforementioned treatment. Kinetic investigations of the dyeing process were performed by determining the half dyeing time, specific dyeing rate constant, and diffusion coefficient. Fastness properties to crocking (dry and wet) and washing of the pretreated dyed fabrics were significantly improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Non-precious co-catalysts boost the performance of TiO2 hierarchical hollow mesoporous spheres in solar fuel cells

A main challenge hindering the development of efficient solar fuel cell systems is the identification of robust, cost-effective, and abundant catalysts. Herein, we demonstrate the ability to synthesize photoactive, relatively cheap and abundant catalyst for the solar-assisted water splitting. The proposed catalyst is a composite of CoCu/graphene immobilized on hierarchical hollow mesoporous Titania. Diffuse Reflectance analysis showed visible light absorption for (CoCu) _2%TiO₂/RGO with an estimated band gap of 2.41 eV, as compared to 3.13 eV for Titania. Photoluminescence spectra showed a significant decreasing in recombination rate of photogenerated electron-hole pair for (CoCu) _2%TiO₂/RGO nanocomposites. Upon their use as photoanodes in solar fuel cells, the fabricated nanocomposites show 14-fold increase in photocurrent density compared to Titania. This enhancement was confirmed via the measurement of electron and phonon life times. The results attained in this study demonstrate a step toward using non-precious co-catalysts to boost the performance of photocatalysts in solar fuel cells.     

A modified linear algorithm for power system contingency analysis

This paper introduces an algorithm for fast linear contingency analysis which computes linearized system line real power flow changes due to system outages. It implements the relation between bus injected real powers and bus phase angles, taking into account the second-order changes in the relation due to the system contingencies. The effects of these changes greatly improve the DC load flow results over similar methods used previously for this type of problem.