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Understanding the phase stability in a multi-principal-component AlCuFeMn alloy
No full textMethod(s) that can reliably predict phase evolution across thermodynamic parameter space, especially in complex systems, are of critical significance in academia as well as in the manufacturing industry. In the present work, the phase stability in an equimolar AlCuFeMn multi-principal-component alloy (MPCA) was predicted using complementary first-principles density functional theory calculations and ab initio molecular dynamics (AIMD) simulations. The temperature evolution of completely disordered, partially ordered, and completely ordered phases was examined based on the Gibbs free energy. Configurational, electronic, vibrational, and lattice mismatch entropies were considered to compute the Gibbs free energy of the competing phases. Additionally, elemental segregation was studied using AIMD. The predicted results at 300 K align well with room-temperature experimental observations using x-ray diffraction and scanning and transmission electron microscopy on a sample prepared using commercially available pure elements. The adopted method could help in predicting plausible phases in other MPCA systems with complex phase stability
Neutral pH Fenton and photo-Fenton activity of Mo-doped iron-pyrite particles
No full textLow H2O2 utilization efficiency for hydroxyl radical generation, acidic pH, and recyclability are critical limitations of heterogeneous Fenton and photo-Fenton catalysts. The present research shows that the optimum Mo doping of FeS2 particles can largely alleviate these catalysis constraints. A solvothermal protocol was followed to prepare polyvinyl pyrrolidone (PVP) stabilized FeS2 and Mo-doped FeS2 particles. XRD observations showed that Mo doping increases the lattice parameters of FeS2. The band gap of the Mo-doped FeS2 particles decreased to 1.58 eV from the 2.24 eV value exhibited by pure FeS2 particles. Structural and electronic structure DFT calculations support these results. The Fenton and photo-Fenton p-nitrophenol (PNP) degradation at neutral pH on PVP-stabilized Mo-doped FeS2 and FeS2 particles were examined. The photo-Fenton results were substantially better than under Fenton conditions. The best PNP degradation photo-Fenton turnover frequency (TOF) recorded was 254.50 mu mol g-1 min-1 on the PVP stabilized 4% Mo-doped FeS2 sample. The Mo-doped FeS2 catalysts were stable under photo-Fenton recycling, and the H2O2 (1.66 mM) required for these reactions was significantly lower than most reports (30-6000 mM). Given the economic importance of the latter in Fenton/photo-Fenton reactions, H2O2 normalized turnover frequency (13.85 and 153.31 mg-1 min-1 L for Fenton and photo-Fenton) values were used to evaluate catalytic activities. Mo-doping enhances FeS2 photo-Fenton activity and recyclability at neutral pH by effective Fe3+ to Fe2+ conversion
Environmental Impact Assessment in the Entire Life Cycle of Lithium-Ion Batteries
No full textThe growing demand for lithium-ion batteries (LIBs) in smartphones, electric vehicles (EVs), and other energy storage devices should be correlated with their environmental impacts from production to usage and recycling. As the use of LIBs grows, so does the number of waste LIBs, demanding a recycling procedure as a sustainable resource and safer for the environment. This review paper analyses and categorizes the environmental impacts of LIBs from mining their constituents, their usage and applications, illegal disposal, and recycling. Compared to recycling, reusing recovered materials for battery manufacturing would lessen the environmental footprints and reduce greenhouse gas emissions (GHG) and energy consumption. Thus, to prevent pollution and safeguard the environment, it is necessary to consider recycling spent LIBs and improving production and disposal methods. The present study offers a comprehensive overview of the environmental impacts of batteries from their production to use and recycling and the way forward to its importance in metal replenishment. The life cycle assessment (LCA) analysis is discussed to assess the bottlenecks in the entire cycle from cradle to grave and back to recycling (cradle)
Development and Assessment of Different Hydrometallurgical Processes for Sustainable Recovery of Rare Earths from Spent NdFeB Magnets
No full textThe utilization of NdFeB magnets is extensive in cutting-edge technologies such as hybrid electric vehicles and wind turbines. These magnets possess a substantial REE (Rare Earth Elements) content, approximately 30%, which significantly surpasses the concentration found in natural REE ores. Due to their pronounced economic significance and the associated supply risks stemming from limited primary resources, REEs are classified as critical metals. With the NdFeB permanent magnet sector experiencing an annual growth rate of 20%, the recycling of end-of-life magnets emerges as a highly effective strategy for mitigating challenges related to the supply of essential raw materials. In the current investigation, three distinct processes have been developed to recover REEs from spent wind turbine magnets. These processes encompass (1) oxidation roasting-acid leaching, (2) chlorination roasting-water leaching, and (3) electrochemical dissolution. Optimization of process parameters has been meticulously undertaken for each of these methods to achieve the production of high-purity rare earth oxide (>99%). Furthermore, a comparative evaluation has been conducted, taking into account energy efficiency and environmental sustainability, to determine the most viable approach for the sustainable recovery of REEs from spent NdFeB magnets
Low-Energy Processing of a Local Boltwoodite Ore as Intermediate in Nuclear Fuel Cell
No full textThe industrial demand for pure uranium and uranium compounds is tremendously increasing due to its wide array of utilities most especially in nuclear industries. Consequently, the treatment of a local boltwoodite ore containing albite (Na2.00Al2.00Si6.00O16.00: 96-900-1634), boltwoodite (Na2.00K2.77U3.00Si6.00O9.00H4.00: 96-900-7219), thorite (Th4.00Si4.00O16.00: 96-9007625), and quartz (Si6.00O6.00: 96-900-5019) was examined in sulphuric acid media. The experimental parameters such as leachant concentration, reaction temperature, and particle size on uranium ore dissolution were investigated. At optimal leaching conditions (2.5 mol/L H2SO4, 75 degrees C, and 75 mu m), an 89.1% dissolution rate was achieved within 120 min. The estimated activation energy of 20.70 kJ/mol supported the diffusion control reaction mechanism as the rate-determining step. The leach liquor obtained at established conditions was further beneficiated to produce an industrial grade sodium diuranate (Na2U2O7: 00-064-0473, density = 6.51 g/cm(3), melting point = 1654 +/- 2 degrees C) proposed to serve as intermediate raw-material in a nuclear fuel cell
Utilizing a sustainable surfactant from Cucurbita pepo seeds for eco‑friendly flotation of non‑coking coal in sustainable energy applications
No full textFatty acids are being explored as promising collectors in coal flotation as they consist of both polar heads and non-polar aliphatic tails. In the present study, the fatty acid–rich oil extracted from Cucurbita pepo (Cp) seeds by Soxhlet extraction was used as a bio-based surfactant to reduce ash in non-coking coal by flotation. The FTIR and GCMS were used to investigate the functional groups and free fatty acid composition of the extracted oil respectively. The molecular conformation was identified using NMR spectroscopy. The extracted Cp oil was primarily composed of linoleic acid (64.17%) and oleic acid (11.54%). The extracted oil was utilized as a bio-based surfactant to float high ash non-coking coal, taking advantage of the oil’s fatty acid content. Taguchi’s design of experiments was used to optimize flotation process parameters such as collector dosage (extracted Cp oil), frother dosage (MIBC), and airflow rate. ANOVA analysis was conducted to determine
the significance of the process parameters. It was observed that frother dosage played the most significant role in achieving optimal ash rejection, followed by collector dosage and airflow rate. The optimized conditions for combustible recovery were an airflow rate of 2.0 l pm, collector dosage of 3.5 ml, and frother dosage of 0.35 ml. For optimal combustible recovery (92.15) and separation efficiency (67.77), the airflow rate had the highest impact, followed by collector and frother dosages. From the XRD analysis, it was found that the major gangue, namely, quartz and kaolinite present in the non-coking coal, were significantly reduced in the final concentrate (float). Thus, the oil extracted from the seeds of Cucurbita pepo can be used as a bio-based surfactant in high ash, non-coking coal flotation
Implementation of different scanning strategy to improve the mechanical and wear properties of 15-5 PH stainless steel fabricated by laser-directed energy deposition
No full textIn this work, the effect of three different scan patterns (island scan pattern, island alternative scan pattern, and cross-hatch pattern) on mechanical and wear properties is investigated for 15-5 Precipitation-hardened (PH) stainless steel by using laser-directed energy deposition (L-DED). Six rectangular blocks are deposited with constant laser power and scanning speed. Currently, studies on the control of anisotropic behavior to improve the mechanical and wear properties by using different scan strategy, especially in the case of 15-5 PH grade stainless steel is relatively sparse. Therefore, it is necessary to learn how mechanical and wear properties are improving in these three different scan pattern samples. At first, the temperature data at a specific point is captured by using a non-contact type pyrometer during printing and the detailed microstructural characterization of that particular region is analyzed. All three different scan pattern samples mostly show delta-ferrite and lath martensite (alpha') structure. The X-ray diffraction shows, there is the formation of secondary precipitation phases like NbCr2, NbC, and Cu-rich precipitation in all three different scan pattern samples. The electron back-scattered diffraction (EBSD) result exhibits that the island alternative scan pattern samples have mostly mixed orientation direction, a high fraction of retained austenite ((similar to)0.004), and high angle grain boundaries (HAGBs) compared to the island scan pattern and cross-hatch pattern samples. The island alternative scan pattern samples show maximum improved mechanical properties i.e. average ultimate tensile strength (UTS) of 1316 MPa and up to 20% elongation amongst all deposited samples. Similarly, the alternative island scan pattern samples exhibit a high coefficient of friction (COF) irrespective of the applied load. The SEM image of the worn surfaces demonstrates abrasion and adhesion type wear in all three different scan pattern samples
A data-driven approach to model the martensitic transformation temperature in strain-induced metastable austenitic steels
Full text linkStrain-induced metastable austenitic stainless steels form an important class of materials in metallurgical industries for their wide range of applications. These steels undergo austenite-martensite phase transformation at temperatures above martensite start temperature, Ms, at which martensite is formed on mechanical deformation, also known as the Md temperature. Md temperature depends on several factors related to the steel and is important from alloy design perspective. In the literature, there are quite a few equations based on composition of the steels for the prediction of Md temperature. However, it is well known that the transformation from austenite to martensite is dependent on the austenite grain size as well as deformation conditions i.e. strain, strain rate and temperature of deformation. In the present work, the role of those parameters has also been considered. The model is implemented using fourteen input parameters viz., composition, grain size, amount of strain, temperature of deformation, and strain rate. The architecture of the neural network model is optimized rigorously to predict the Md temperature on a par with actual value. It has been shown that grain size and strain rate have very negligible influence whereas strain and temperature of deformation have quite strong role. Md temperature is increased with increasing strain whereas the temperature of deformation shows opposite dependence on it. An empirical equation thus, has been established to calculate the Md temperature of a steel as a function of its composition, grain size, temperature of deformation and strain. The final optimized model is then deployed to predict the Md temperature of different steels and predictions are found to be in close agreement to the experimentally measured Md temperatures. The developed model is general and can be extended to include other parameters as well as various other steel alloys
Enhancing the tribological characteristics of the biocompatible Ti-6Al-4 V alloy via heat treatment: An experimental analysis
No full textThe tribological behaviour of the Ti-6Al-4 V biocompatible alloy fabricated using laser powder bed fusion (LPBF) was experimentally investigated for prosthesis implants. Annealing heat treatment was executed to improve its tribological performance. The microstructure and microhardness characterization were performed using scanning electron microscope (SEM) and Vickers microhardness. The wear test was processed using a SS304 spherical ball in simulated body fluid (SBF) at body temperature. The ball on a flat tribometer was used to determine wear rate, depth, width, and friction coefficient at 15 N. The results revealed that a needle-like martensite alpha' structure was noticed on the as-deposited sample. Microstructural characterization significantly affects wear morphologies. The heat-treated specimen showed a more desirable wear performance than the as fabricated
Sputter-deposited zirconium doped nickel-aluminide coatings for high-temperature oxidation-resistant applications
No full textZr-Ni3Al coatings were deposited over the Inconel-718 substrate using DC cosputtering. The deposition was carried out in a custom-designed chamber at a substrate temperature of 400 degrees C. The evolution of phases, microstructure, surface topography, and elemental composition were characterized using x-ray diffraction, field emission scanning electron microscopy (FESEM), atomic force microscopy, and energy dispersive spectroscopy (EDS), respectively, whereas the adhesion strength and the mechanical properties of the coatings were characterized using nanoindentation. The oxidation properties of the coatings were studied at 900, 1000, and 1100 degrees C in open air to determine the kinetics of oxidations. The results reveal that with the increase in Zr concentration in the host Ni3Al matrix, the adhesive strength and mechanical properties of the films increase. The highest hardness and Young's modulus of similar to 9.2 and similar to 150.3 GPa, respectively, are observed for 30 W Zr-Ni3Al coatings. Additionally, 1.51 at. % of Zr in Ni3Al coatings has shown the best oxidation resistance properties at all temperatures. However, an increase in the rate of oxidation has been observed with an increase in exposure temperature. The formation of different oxide layers after oxidation has been elucidated using FESEM and EDS after looking into the surface morphologies of the oxidized coatings