Corrosion Resistance of Coatings Produced by Spraying Powders Under a Laser Beam in a Saline Environment NaCl 3% by the Electrochemical Method

The manuscript focuses on the study of corrosion resistance in NaCl medium of a 304L type stainless steel after application of protective nickel-based and cobalt-based coatings produced by powder spraying under a continuous CO2 laser (10.6 µm wavelength) beam. Using polarization and electrochemical impedance spectroscopy methods, the results found confirm that metallic coatings produced under high energy beams offer excellent protection up to an efficiency of E = 98.12% in aggressive environments with salinity to 3%.

EFFECT OF CRYSTALLINITY TO OVERPOTENTIAL ON Ni₃Fe ALLOY AS ELECTROCATALYST IN HYDROGEN EVOLUTION REACTION

EFFECT OF CRYSTALLINITY TO OVERPOTENTIAL ON Ni3Fe ALLOY AS ELECTROCATALYST IN HYDROGEN EVOLUTION REACTION. Ni-Fe alloys can be used as electrocatalyst for the hydrogen evolution reaction (HER) in an alkaline solution. HER consumed highly energy and overpotential driven. The overpotential value corresponding to the electron transfer in reaction can be affected either by metal combination or alloy as a cathode. Ni₃Fe alloy had been successfully synthesized by the electrodeposition method using direct-current (DC) on a 304 L type stainless steel substrate. The modified Watts bath deposition was used NiCl2·6H2O and FeCl3·6H2O as precursors of the alloy. The optimum conditions of the reaction were obtained at pH of the solution is 2.20±0.02 with 25 mA/cm² current density at 55 °C for 160 minutes. Ni₃Fe alloy was characterized by Powder X-ray Diffraction (PXRD), Energy-Dispersive X-ray Spectroscopy (EDX), and Scanning Electron Microscopy (SEM). The electrocatalytic property of Ni3Fe alloy was electrochemically measured in 1 M KOH solution by polarization method using a Tafel plot with a scanning rate of 1 mV/s. As a result, the mass ratio of Ni²+ /Fe³+ in bath deposition influenced the electrocatalytic property of Ni₃Fe alloy. Ni₃Fe alloy with a higher crystallinity lowered the overpotential value of HER up to 67% compared to Ni metal.

Increasing Temperature and Relative Humidity Accelerates Inactivation of SARS-CoV-2 on Surfaces

ABSTRACT Coronavirus disease 2019 (COVID-19) was first identified in China in late 2019 and is caused by newly identified severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Previous studies had reported the stability of SARS-CoV-2 in cell culture media and deposited onto surfaces under a limited set of environmental conditions. Here, we broadly investigated the effects of relative humidity, temperature, and droplet size on the stability of SARS-CoV-2 in a simulated clinically relevant matrix dried on nonporous surfaces. The results show that SARS-CoV-2 decayed more rapidly when either humidity or temperature was increased but that droplet volume (1 to 50 μl) and surface type (stainless steel, plastic, or nitrile glove) did not significantly impact decay rate. At room temperature (24°C), virus half-life ranged from 6.3 to 18.6 h depending on the relative humidity but was reduced to 1.0 to 8.9 h when the temperature was increased to 35°C. These findings suggest that a potential for fomite transmission may persist for hours to days in indoor environments and have implications for assessment of the risk posed by surface contamination in indoor environments. IMPORTANCE Mitigating the transmission of SARS-CoV-2 in clinical settings and public spaces is critically important to reduce the number of COVID-19 cases while effective vaccines and therapeutics are under development. SARS-CoV-2 transmission is thought to primarily occur through direct person-to-person transfer of infectious respiratory droplets or through aerosol-generating medical procedures. However, contact with contaminated surfaces may also play a significant role. In this context, understanding the factors contributing to SARS-CoV-2 persistence on surfaces will enable a more accurate estimation of the risk of contact transmission and inform mitigation strategies. To this end, we have developed a simple mathematical model that can be used to estimate virus decay on nonporous surfaces under a range of conditions and which may be utilized operationally to identify indoor environments in which the virus is most persistent.

On the Strength of a 316L-Type Stainless Steel Subjected to Cold or Warm Rolling Followed by Annealing

The ultrafine-grained microstructures and their effect on the yield strength of a 316L-type austenitic stainless steel processed by large strain cold/warm rolling and subsequent annealing were studied. A kind of continuous recrystallization developed during annealing, resulting in the evolution of uniform ultrafine-grained microstructures with relatively high residual dislocation densities. The development of such microstructure at 973 K led to excellent combination of tensile properties including high yield strength (σ0.2 > 900 MPa) and satisfactory plasticity (δ > 15%). A unique power law function between the annealed grain size and the dislocation density with a dislocation density exponent of −0.5 was obtained for these continuously recrystallized microstructures. A physically justified explanation of the observed structural/substructural strengthening is introduced.

Metallurgical Interaction among BNi-9 and Waspaloy, FSX-414 or 304-Type Stainless Steel under TLP Cycle

The metallurgical interaction of BNi-9 filler metal paste with Waspaloy, Ni-coated Waspaloy, FSX-414, and 304-SS is studied in a brazing treatment under an argon atmosphere with an isothermal hold for one hour at 1150 °C. The Waspaloy alloys were brazed under both solubilized and aging conditions. Before brazing, some Waspaloy samples were electrochemically coated with an Ni layer 35-40 μm thick. The microstructures of the FSX-414 and 304-SS alloys showed that the thickness of the isothermal solidification zones was approximately 50 μm, while this thickness was not well defined in the Waspaloy samples. The Ni-coated solubilized Waspaloy showed a wider diffusive zone, which was associated with an increase in the penetration extension of the liquid films. The analysis of grain orientation in all brazed zones of the Waspaloy samples showed aleatory characteristics. Plastic factors in the different brazed zones were also obtained by nanoindentation under 350 mN loads. It was observed that the plastic factor was low when the width of the diffusive zone increased. The plastic factor in the Ni-coated Waspaloy was the lowest, while the diffusive zone in this sample had the largest width. The BNi-9 wettability is better in FSX-414, and 304-SS than in Waspaloy. Ni coating in Waspaloy improves BNi-9 wettability.