Electrochemical Corrosion Behavior of Magnetron-Sputtered Al-Mo Gradient-Coated Steel in 3.5 wt.% NaCl Solution

A gradient three-layer Al-Mo coating was deposited on steel using magnetron sputtering method. The corrosion properties of the coating were studied in 3.5 wt.% NaCl solution using electrochemical techniques, whereas the hydrogen-induced cracking (HIC) resistance was examined by constant-load tests using notched tensile specimens. These results were compared with conventional electroplated cadmium-coated steel. The results show that the gradient Al-Mo coating exhibits better corrosion and HIC resistance when compared to electroplated cadmium. This was due to the excellent corrosion resistance of the bottom aluminum-rich layer, while the top Mo-rich layer provided good lubrication properties.     

Cu promoted Ni-Co/hydrotalcite catalyst for improved hydrogen production in comparison with several modified Ni-based catalysts via steam reforming of ethanol

Enhanced hydrogen production via catalytic steam reforming of ethanol has a huge potential. In the present investigation, several combinations of mixed metal oxide supported catalysts were evaluated for efficient and economical hydrogen generation from ethanol. The comparison was carried out in terms of ethanol conversion, hydrogen yield and cyclic stability over various catalyst-support systems. Several nickel based supported catalysts namely, Ni/MgO, Ni/Al₂O₃, Ni/CeO₂ and Ni/ZrO₂ were studied in this work among which Ni/MgO and Ni/Al₂O₃ showed satisfactory activity and stability for hydrogen production. Thereafter Ni/hydrotalcite (HTc)-type material was employed to combine features of the above catalysts which showed more than 90% ethanol conversion and yielded 82 mol% of hydrogen at optimized conditions. Finally, a novel combination of Cu promoted Ni-Co/HTc was synthesized and tested for improved hydrogen production. It showed almost complete conversion of ethanol (98.3%) with hydrogen yield of 83% at much lower temperature (673 K). The process conditions were optimized by studying effects of temperature, S/C ratio and GHSV on hydrogen production. Cu-Ni-Co/HTc also remained stable for up to 4 cycles justifying its multi-cycle activity, selectivity and durability. Such novel combination of catalyst-support system assists in improved hydrogen production in a sustainable manner.     

Parametric analysis of desiccant wheel for air conditioning application

A one‐dimensional mathematical model is developed to evaluate the operating and design parameters of the desiccant wheel for air conditioning application. In this paper, dehumidification coefficient of performance (DCOP) and sensible energy ratio (SER) are adopted as a combined performance index to reflect the dehumidification and thermal performance of the desiccant wheel. The analysis of the results reveals that for lower SER, suitable wheel length, wall thickness, channel pitch, and channel height should be 100 mm, 0.2 mm, 3 mm, and 5 mm, respectively. These design parameters have been analyzed under different operating conditions and it was found that for higher DCOP, rotational speed, regeneration temperature, process and regeneration velocity should be 20 rph, 60°C, and 2 m/s.     

Corrosion of Inconel 690 in N<Subscript>2</Subscript>-0.1%H<Subscript>2</Subscript>S gas at 700-800 °C

Inconel 690 superalloy was corroded at 700 °C and 800 °C for up to 70 h in N₂-0.1% H₂S gas. It corroded almost linearly with large weight gains, displaying little protectiveness. Its corrosion rates were quite fast when compared with its corrosion in air or Ar-1%SO₂ gas. The formed scales were thick, fragile, and nonadherent. They consisted primarily of Cr₂O₃ with some NiCr₂O₄, Ni₃S₂, CrS, and Cr₂S₃. The H₂S gas accelerated the corrosion significantly by forming nonprotective sulfides and dissolving hydrogen in the scale and in the internal corrosion zone that consisted of discrete chromium-sulfides and some oxide particles. The marker test indicated that the scales grew by the outward diffusion of metallic ions such as Ni, Cr, Fe, and Mn, whilst the internal corrosion zone thickened by the inward migration of oxygen and sulfur through the lattice, grain boundaries, and microcracks.     

Fine Piercing with Rubber for Counter Force in a Double Action Hydraulic Press

The present work addresses to evolving a sub-press equipment using rubber for counter force by which only two actions would be required to ensure fine piercing of 03 mm thickness, 25 mm diameter (shear area of 235 mm²) (a) Al, (b) EDD steel, (c) alpha brass and (d) 304 stainless steel sheet as opposed to five actions demanded with rigid tools (conventional-fine cutting). The errors with optimal conditions of impingement and rubber counter forces were compared with those reported in literature with rigid tools. The results obtained from the present work were quite promising. Errors were close to those achievable with rigid tools. For smooth shear of 95 % and above, the individual forces were registered and evaluated for a shear area of 235 mm², so that, with this normalization, evaluation of individual forces for other material, thickness and perimeter could be enabled. Analogue parameters of the individual forces using that of commercially pure Al as the basis were then evaluated. These were evolved and furnished for both the ultimate tensile strength (R_m) as well as strength coefficient K of the flow equation of the form σ_F = K × εⁿ. Such analogue parameters for R_m and K were compared and found to have a correlation factor of 0.93–0.99 reflecting the reliability of the present work. The techno-economics has thus been shown.     

Selectivity engineering in the synthesis of value added chemicals: Oxidation of 1-octanol to 1-octanal over nano-fibrous Ag-OMS-2 catalysts

Oxidation of 1-octanol to 1-octanal is commercially very attractive, since the product is used extensively in the fragrance industry. Among the various methods, selective air oxidation with a suitable heterogeneous catalyst will be green and clean. In this work, novel cryptomelane type octahedral molecular sieve type 2 (Ag-OMS-2) catalysts, with Ag loading from 5 to 15%, w/w, were synthesized and evaluated in air oxidation of 1-octanol in a fixed bed vapour phase reactor. All catalysts were fully characterized to understand the activity and selectivity. The conversion increased with Ag loading but the selectivity was the highest for 10% Ag-OMS-2. A systematic study was conducted to ascertain the effects of various parameters. Use of toluene as a diluant leads to better conversion and selectivity. The optimized conditions are: catalyst mass/molar flow rate of 1-octanol (W/F_A0)- 20 g h/mol, 523 K, toluene to 1-octanol molar ratio- 4:1, weight hourly space velocity (WHSV)- 16.74 h⁻¹, air flow rate- 6 L/h, air pressure- 101.3 kPa. It follows the Mars-van Krevelen mechanism and is intrinsically kinetically controlled. The activation energy is 14.39 kcal/mol using 10%, w/w Ag-OMS-2. It provides a better green process than those reported so far.     

Evolution of atomic and electronic structure of magnetic Gd-doped gold clusters

The evolution of atomic and electronic structure of small Au _n (n = 1–16, and 55) clusters doped with a Gd atom has been investigated using density functional theory within generalized gradient approximation for the exchange–correlation energy. Pure gold neutral clusters with n up to 15 are planar. However, with the doping of a Gd atom, the atomic structure of gold clusters changes, and there is a transition from planar-like structures to three dimensional structures at n = 10. The electronic structure of Gd-doped gold clusters shows a sharp increase in the highest occupied–lowest unoccupied molecular orbital (HOMO–LUMO) gap for certain sizes giving rise to their magic behavior. All clusters are magnetic with large magnetic moments ranging from 6 to 8 μ_B primarily due to the localized 4f electrons on Gd. This makes such clusters with large HOMO–LUMO gaps magnetic superatoms. The main interaction between gold and gadolinium atoms in the clusters is due to hybridization between Au-6s and Gd-5d6s orbitals. Our results indicate the emergence of a wheel structure for Gd@Au₇, a symmetric cage structure at n = 15 for Gd@Au₁₅ and n = 16 for Gd@Au₁₆ ⁺ and Eu@Au₁₆ corresponding to an electronic shell closing at 18 valence electrons leaving aside the f electrons on Gd while for Gd-doped Au₅₅ corresponding to 58 valence electrons, a Au₉Gd@Au₄₆ core–shell structure is obtained in which the Gd atom connects the core of Au₉ with the Au₄₆ shell. The binding energy shows odd–even oscillations with enhancement due to Gd doping compared with pure gold clusters. Such magnetic clusters of gold could have multifunctional biological applications in drug delivery, sensor, imaging, and cancer treatment.     

An efficient algorithm based on artificial neural networks and particle swarm optimization for solution of nonlinear Troesch’s problem

Neural Computing and Applications - In this article, a simple and efficient approach for the approximate solution of a nonlinear differential equation known as Troesch’s problem is proposed....