Spark Plasma Sintered High-Entropy Alloys: An Advanced Material for Aerospace Applications

High-entropy alloys (HEAs) are materials of high property profiles with enhanced strength-to-weight ratios and high temperature-stress-fatigue capability as well as strong oxidation resistance strength. HEAs are multi-powder-based materials whose microstructural and mechanical properties rely strongly on stoichiometry combination of powders as well as the consolidation techniques. Spark plasma sintering (SPS) has a notable processing edge in processing HEAs due to its fast heating schedule at relatively lower temperature and short sintering time. Therefore, major challenges such as grain growth, porosity, and cracking normally encountered in conventional consolidation like casting are bypassed to produce HEAs with good densification. SPS parameters such as heating rate, temperature, pressure, and holding time can be utilized as design criteria in software like Minitab during design of experiment (DOE) to select a wide range of values at which the HEAs may be produced as well as to model the output data collected from mechanical characterization. In addition to this, the temperature-stress-fatigue response of developed HEAs can be analyzed using finite element analysis (FEA) to have an in-depth understanding of the detail of inter-atomic interactions that inform the inherent material properties

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Thickness dependent chemical and microstructural properties of DC reactive magnetron sputtered titanium nitride thin films on low carbon steel cross-section

Polished samples of low carbon steel (LCS) rod cross-sections were sputtered with different thicknesses of TiNx thin film using DC reactive magnetron sputtering technique. While other process parameters such as target power (200 W), substrate position (150 mm) and sputtering pressure (1.33 Pa) were kept constant during the deposition, the deposition time was varied from 5 to 20 min. Physical and chemical characterizations of the samples were done using Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and optical microscopy. Vickers micro-hardness tester was used for the hardness test. The optimum value of the Vickers hardness was found to be 267.9 for the film deposited at 20 min. The inter-planar spacing was found to be from 2.0362 Å to 2.0890 Å, while corresponding lattice parameter was calculated to be from 4.0724 Å to 4.1780 Å. Scanning electron microscopy observation of the films gave an indication of fine-grained microstructure, which confirms the good adhesion and hardness properties of titanium nitride layer on the LCS substrate. The XRD spectra show that the multiphase reflections TiO2 (110) and TiN (111) for thinner film samples which shift to a preferred orientation (200) for thicker films, indicating a largely TiNx phase. This strongly suggest remarkable changes in crystal orientations of the TiNx films with deposition time. Ion beam (RBS) results showed increase in amount of nitrogen contents (47–64%) in TiNx films with thickness and deposition time. Keywords: Low carbon steel, Sputtering, Magnetron, Micro-hardness, Inter-planar spacin

Data on environmental sustainable corrosion inhibitor for stainless steel in aggressive environment

This data article contains data related to the research article entitled “enhanced corrosion resistance of stainless steel Type 316 in sulphuric acid solution using eco-friendly waste product” (Sanni et al., 2018). In this data article, a comprehensive effect of waste product and optimized process parameter of the inhibitor in 0.5 M H2SO4 solution was presented using weight loss and potentiodynamic polarization techniques. The presence of the inhibitor (egg shell powder) influenced corrosion resistance of stainless steel. Inhibition efficiency value of 94.74% was recorded as a result of inhibition of the steel by the ionized molecules of the inhibiting compound of the egg shell powder influencing the redox mechanism reactions responsible for corrosion and surface deterioration. Keywords: Corrosion, Stainless steel, Inhibitor, Sulphuric aci

Effect of dissolved CO2 and Syzygium malaccense leaf DNA concentrations on carbon steel within a carbonic acid equilibrium

The corrosion of CO2 is a multifaceted process. This study investigated the impact of Syzygium malaccense DNA in combating the corrosion of dissolved CO2 in water on mild steel. The increase in the concentration of CO2 and of course the carbonic acid increases the corrosion rate of mild steel by speeding up the cathodic reaction. However, with regards to inhibitor efficiency, no evidence was found for a direct reaction of CO2 on mild surface. The adsorption of Syzygium malaccense DNA inhibitor in all the concentrations of dissolved CO2 media on mild steel surfaces obeyed the Freundlich adsorption isotherm as all linear correlation coefficient (R2) values were close to 1. The inhibition mechanism was ascribed to the electrostatic interaction ensued amid the negatively charged surface of the mild steel and the positively charge DNA inhibitor molecule. All surfaces of tested samples were characterized by XRD and SEM. The 0 mg/L DNA in 1627 mg/L dissolved CO2 led to formation of high rough surface. The XRD patterns depict that the mild steel mainly constitutes Fe and FeCO3