Journal of advanced materials and processing
Volume:11 Issue: 3, Summer 2023

This study addresses the imperative for advanced gas sensors, particularly for monitoring ‎hazardous carbon monoxide (CO), by enhancing nanocrystalline SnO2 thin film fabrication. ‎Control of parameters in the sol-gel synthesis process is systematically explored to mitigate crack ‎formation and enhance SnO2 film quality on uncoated Al2O3 substrates. Leveraging SnO2's n-‎type semiconductor properties, traditional thin film methods are employed, with a specific focus ‎on overcoming drawbacks through glycerin. Among various fabrication techniques, sol-gel proves ‎cost-effective for producing high-quality, crack-free SnO2 layers tailored for gas sensor ‎applications. The study evaluates sensitivity to CO gas concentrations, improving structural ‎integrity, sensitivity, and stability. X-ray powder diffraction and SEM imaging confirm phase ‎purity and surface morphology, ensuring the absence of impurities or cracks. Integrated with ‎microcontroller-based circuits, the sensors exhibit rapid response and recovery times crucial for ‎real-time gas sensing. The addition of an output circuit with enhanced resolution and stability ‎further enhances sensor performance. Results demonstrate the proposed sensor's capability for ‎rapid response (less than 30 seconds) and recovery times (~39 seconds), crucial for real-time gas ‎sensing. Notably, the sensors demonstrate an admirable sensitivity with a minimum detection ‎limit of as low as 1 ppm of CO gas. Additionally, the study validates the sensor's stability and ‎reliability during prolonged exposure to N2 and 1% CO mixtures, highlighting its potential for ‎personal safety detectors and environmental safety monitoring.‎

This study aims to study the refurbishment of the first-stage Inconel 738 blades for GE-Frame 5 gas turbines through laser cladding and welding techniques. Laser welding employed a pulsed Nd:YAG system outfitted with a manual 0.7mm Inconel 625 filler wire feed. Meanwhile, laser cladding utilized a continuous fiber laser coupled to an automated powder injection system for Inconel 625. Process parameters such as scan speed, laser power output, and powder feeding rate were carefully optimized to refine the laser cladding protocol. Testing revealed laser settings of 400W power, 15g/s powder feed, and 8mm/s scan speed generated coats with superior geometry, eliminated hot cracking entirely, and minimized porosity. Preliminary welds determined optimal settings of 4mm/s scan speed at 5kW maximum power. Subsequently, 20 layers were deposited in simulation of worn blade tip repair welds. Both methods effectively reduced heat-impacted zones through refined parameters. Pulsed laser welding with filler material expanded repair options for gas turbine blades. However, surface hardness in treated areas was somewhat less than the base due to phase transformations during laser cladding and welding.

This study aims to investigate the effect of aging on microstructural evolution and mechanical properties of two ASTM F75 alloys, one without the carbon additive and the other one containing 0.21 wt.% C. Aging on the samples solution-annealed at 1225 °C for 1 hour was performed at 720, 760, and 800°C for 5 hours. The evaluation of the microstructure of both samples after aging showed that the γ→ε transformation led to the formation of two various morphologies of the precipitates in the regions of the ε-phase. At the first stages of aging, the precipitates appeared as a series of straight bands in both samples, while with an increase in the temperature, pearlite-like regions were found at the grain boundaries of only the carbon-containing sample. In the sample without the carbon additive, the microstructure consisted of the σ-phase. In the carbon-containing sample, lamellar M23C6 carbides were formed during aging in the vicinity of the remaining blocky M23C6 carbides. The carbon-containing sample consisted of fine M23C6 carbides after aging at 720°C, which were distributed inside the grains and at the grain boundaries. The appropriate precipitation rate and their optimum distribution in the structure led to an increase in the yield strength by up to 15%, along with an increase in the ultimate tensile strength by up to 6% compared with the as-cast state. However, no significant improvement was found in the ductility of the alloy.

In the face of dwindling energy resources and the alarming surge in harmful greenhouse gas emissions, there is a crucial shift towards embracing renewable energy solutions that minimize environmental impact. For this goal, Microbial Fuel Cells (MFCs) are used as a dual-purpose technology; functioning potentially as great energy generators and environmental cleansers. This study delves into the enhancement of MFCs’ efficiency through the customization of the Nafion proton exchange membrane using sulfuric acid-doped polyaniline. Due to this quality, Polyaniline was selected for its robustness and high electrical conductivity. Later, it was electrochemically deposited onto the Nafion membrane, employing a method rooted in electrochemistry. Experimental trials involved a dual-chamber MFC, employing Escherichia coli and glucose as substrates. Assessing the Nafion membrane's condition using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR), the MFC with the modified Nafion membrane exhibited significantly higher maximum current density (285 mA/cm2) and power density (36 mW/cm2) compared to its pristine Nafion counterpart; titled (165 mA/cm2) and (14.5 mW/cm2) respectively. A comparison with the polarization curve displays an improvement in the microbial fuel cell's performance attributed to the Nafion membrane modification.

In this study, the transient liquid phase bonding of St52 plain carbon steel to WC-Co compound using BNi-2 interlayer with a thickness of 50 μm was investigated. For this purpose, samples were bonded at a temperature of 1050 °C and holding times of 1, 15, 30 and 45 min. After the joining process, the microstructure of the bonded samples was examined using a scanning electron microscope equipped with energy-dispersive X-ray spectroscopy. X-ray diffraction analysis was also used to investigate the effects of bonding parameters on the phase transformations of the bonding region. Microhardness and tensile shear tests were also conducted to study the mechanical properties of the bonded samples. Microstructural studies showed that the formation mechanism of the solidification zone in all samples was isothermal solidification mechanism. The results of the investigations showed that the only phase in the isothermal solidification zone was the nickel base solid solution. The maximum hardness in all samples belonged to WC-Co base materials due to the presence of WC particles in it. The maximum tensile-shear strength was related to the sample with bonding time of 30 min. The mode of failure in all samples was a combination of brittle and ductile fracture.

These days, water has a special importance in human life, and access to safe drinking water is essential to maintaining human health. The presence of residual pharmaceutical compounds as emerging contaminants (ECs) in wastewater deteriorates aquatic life and water quality due to the lack of effective treatment processes to remove them. This paper deals with the degradation and demineralization of acetaminophen (ACT) from its aqueous solution under UV-Vis irradiation using ZnO (UV/ZnO) and K2S2O8 (UV/PS). Detailed batch tests were evaluated to investigate the effect of different variables such as pH, catalyst dose, reaction time, drug concentration and mineralization rate. The results showed the higher performance of the UV/PS process and the UV/ZnO at acidic and natural conditions, respectively. The constant reaction rate for ACT removal in the UV/PS process is almost double that of the UV/ZnO process. The results of the remaining TOC tests show that the processes can convert the ACT in the solution into harmless minerals such as carbon dioxide after degradation. Increasing the dose of catalysts to an optimum amount led to an increase in elimination efficiency. The UV/PS process is able to degrade 20 mg/L of acetaminophen in 50 minutes, while the UV/ZnO process breaks down this amount of acetaminophen in 100 minutes. This work can be developed for the removal of ECs related to the pharmaceutical group from contaminated water.