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Waste remediation: Low‑temperature synthesis of hybrid Cu(OH)2/CuO and CuO nanostructures from spent printed circuit boards and their dye degradation studies
No full textThe demand for environmentally friendly and sustainable resource utilization techniques for recycling waste printed circuit boards is significant due to their status as valuable secondary resources, containing high-purity copper and precious metals. In this context, Cu(OH)2/CuO and CuO nanostructures were fabricated using alkaline precipitation and low-temperature aging methods using the strip solution originated from laboratory-scale spent mobile phone printed circuit board recovery process. XRD, FTIR, FESEM-EDX, and TEM were utilized to characterize the as-recovered nanoproducts. A hybrid structure of Cu(OH)2/CuO was formed at 70°, and monoclinic CuO phase was formed at 80 °C aging time. The results show that Cu(OH)2/CuO nanoflakes have an average crystallite size of 24.06 nm and a particle width of 22 ± 3 nm. Cu(OH)2/CuO nanoflakes formed at 70 °C aging temperature and 24-h residence time have finer crystallite and particle sizes than CuO-ridged nanospheres formed at 80 °C aging temperature. The optical band gap energy of Cu(OH)2/CuO and CuO nanostructures formed was found to be 2.28 eV and 2.22 eV, respectively. The hybrid Cu(OH)2/CuO nanostructure photocatalyzed the decomposed 97.28% rhodamine blue using a visible light source, whereas the CuO nanostructure degraded only 14.64% rhodamine blue dye under similar conditions. A surfactant-less hybrid structure is developed without the use of any chemical precursor. Thus, a high value-added product is produced using one waste material to remove another waste in wastewater treatment
Hydrometallurgical recovery of copper from the leach liquor of waste PCBs
No full textThe present work is focused on the recovery of pure copper metal from leach liquor of discardedprinted circuit boards (PCBs) using solvent extraction and electrowinning techniques. Leach liquorcontaining copper was produced from PCBs of scrap computers using pretreatment followed bythe leaching technique. The obtained leach liquor contained 19.35 g/L of copper and 6 M con-centration of nitric media. From the obtained leach liquor, systematic solvent extraction andelectrowinning studies were carried out for maximum extraction of copper, leaving other metalsto be present as impurities. Various process parameters of solvent extraction viz. effect of pH,contact time, phase ratio, and so on were studied and optimized. McCabe–Thiele diagram wasplotted, which shows that complete recovery of copper can be achieved in three stages using 40%LIX 84IC and O/A ratio 1/1 at equilibrium pH 2.2 in a mixing time of 20 min. The loaded copper wasstripped using 10% H2SO4. The obtained strip solution containing 19.35 g/L Cu was electrowinnedat the optimized condition, i.e., 8 hours’ time and 205 A/m2 cathode density with 99.99% currentefficiency. 99.8% pure copper metal was obtained. The developed process is environmentally sustainable and has potential to be commercialized after scale-up studies
Engineering lithium nickel cobalt manganese oxides cathodes: A computational and experimental approach to bridging gaps
No full textLithium-ion batteries (LIBs) have transformed our envisioned future into a reality where induction motor engines power electric vehicles (EVs). While LIBs offer impressive advantages compared to other energy storage systems for EVs, they face practical deployment challenges in performance, cost, and scalability. One critical component of LIBs that has garnered significant attention is the cathode, primarily due to its high cost, stemming from expensive cobalt metals and limited capacity, which cannot meet the current demand. However, layered lithium nickel cobalt manganese oxide (NCM) materials have achieved remarkable market success. Despite their potential, much current research focuses on experimental or theoretical aspects, leaving a gap that needs bridging. Understanding the surface chemistry of these oxides and conducting operando observations is crucial. Combining advanced surface analysis techniques with theoretical calculations (viz., quantum mechanics) is proposed to bridge this knowledge gap. This review delves into recent performance achievements (viz., projected driving performance, current EVs model, and battery specifications), challenges, and opportunities associated with various NCM materials as cathode materials. It also explores cutting-edge developments in experimental and theoretical techniques that analyze battery operations, address frontier challenges, and provide novel insights. Furthermore, the review comprehensively discusses the concept of single-crystal (SC) NCM and its practical implications in EVs. Finally, the review provides an outlook on future guidelines for designing NCM cathodes for LIBs, emphasizing the convergence of experimental and computational/theoretical approaches to achieve superior performance
Designing of novel microstructure and its impact on the improved service temperature mechanical performance of 2nd and 3rd generation advanced intermetallic TiAl alloys
No full textAdvanced lightweight TiAl-based intermetallic systems, capable of surviving elevated temperatures, have been a topic of interest, considering their ever-increasing demands in aerospace industries. The optimization of solidification and processing methods stands as a pivotal factor in microstructural engineering for TiAl systems, aiming to attain desired mechanical properties. The present study focuses on two distinct alloy systems, a commercial grade 2nd generation, i.e., Ti-48Al-2Cr-2Nb (at. %), and a newly developed 3rd generation, i.e., Ti-45Al-2Cr-7.5Nb-0.2B (at. %) alloys. Interestingly, the variation in the solidification path, triggered by higher Nb content along with a minor amount of B, accounts for the substantial microstructural refinement for the 3rd generation TiAl alloy. Nevertheless, prominent segregation of Nb and Cr to the 130 phase is observed in both the as-cast microstructure, which restricts the applicability of the alloys. Remarkably, a novel bilamellar-globular (BLBG) microstructure consisting of gamma and alpha 2 phases in both lamellar and globular morphologies is achieved through heat treatment for both categories of alloy. Elevated temperature tensile testing depicts an exceptional strength-ductility combination for 3rd generation BLBG microstructure. Excellent twin-twin activity and twin-induced plasticity effect are observed to govern the deformation mechanism. Overall, the path of solidification, phase distribution, and its effect on the deformation mechanism are thoroughly analyzed, which is of particular interest from a design and application point of view
Creep strain prediction in power plant material via ANN modeling of nonlinear ultrasonic test results
No full textReliable and accurate prediction of the creep life of power plant components is crucial for both economic and safety reasons. Existing prediction models, based on creep test data, can be complex and time-consuming. Nonlinear ultrasonic (NLU) is a widely accepted non-destructive testing (NDT) technique for evaluating damage progression in crept specimens. The information from NLU measurements alone is insufficient to forecast the life of any component. In real-time applications, intelligent NDT protocols are needed to enable fast and accurate life prediction of such components. A methodology for creep life prediction using artificial neural networks (ANN) has been introduced based on NLU test results of crept P92 steel specimens. The technique involved creep tests of P92 specimens exposed to a temperature of 625SUPERSCRIPT ZEROC with applied stress ranging from 120MPa to 160MPa, NLU measurements at each step load, and prediction of creep life of the material with an ANN trained with creep strain and NLU test data. The technique involves prediction from previously generated historical data, thus saving both cost and time of conducting continuous experiments. This approach for ANN modeling of NLU data can be considered a reliable, time-saving, and effective technique for assessing creep damage progression in power plant components
Solid-State Direct Regeneration of Spent Lithium Cobalt Oxide Cathodes for Li-Ion Batteries
No full textRegeneration of spent lithium-ion battery (LIB) electrode materials is essential for sustainable development of the LIB energy storage sector and resource management of critical metals such as Li, Co, Ni, and Mn. Enormous use of LIBs has been seen in the last two decades in portable electronic devices. In addition, now it is predicted that LIBs will be exploited in electric vehicles and stationary energy storage systems in the coming decades. Wider exploitation of LIB energy storage technologies creates an alarming situation, especially for the resource management of critical metals and the environment. In this work, we report the direct regeneration of a spent lithium cobalt oxide (LCO) cathode material. The deficiency of Li concentration in spent cathode material is fulfilled by the solid-state regeneration process just by heating with the required amount of Li2CO3 at 740 degrees C for 6 h. In particular, the Li void in the defective LCO crystal structure has been repaired, and the morphology is restored into the pristine LCO. The elemental analysis confirmed the increase of Li content to 7.4% in the relithiated cathode material in comparison to the spent cathode (5.28% Li). The X-ray diffraction study revealed the repair of degraded phase cobalt oxide to pristine phase LCO. XPS analysis also indicated the repair of the degraded phase from Co2+ to Co3+ in the regenerated LCO. Scanning electron microscopy analysis showed the improvement of microcrystals in the regenerated LCO. Cyclic voltammetry analysis showed the enhancement of electrochemical properties in the regenerated LCO and exhibited an enhanced initial charge specific capacity to 148.31 mAh/g at 0.1C rate in comparison to the spent LCO. This work demonstrated a simple and cost-effective regeneration process of spent LCO compared to pyrometallurgy and hydrometallurgy where the critical metals are recycled in the form of alloys and individual salts, respectively
An Insight into the Pre-reduction Mechanism of Manganese Ores Using Elemental Sulfur for Ferromanganese Production
No full textThe pre-reduction of manganese ore using elemental sulfur under an inert atmosphere at temperatures above 600 degrees C is required for maximum MnO formation. Under atmospheric conditions, SO2 formation via sulfur oxidation leads to MnSO4, which again will dissociate to lower Mn oxides. Thus, excess energy is required for this conversion, thereby decreasing the overall energy efficiency. The optimum pre-reduction condition obtained is 800 degrees C, with a holding time of 4 hours at 0.5 S/Mn ratio
Graphite from Dead Li-Ion Batteries: A "Powerful" Additive for Fabrication of High-Performance Li-Ion Capacitors
No full textLithium-ion capacitors (LICs) are considered a promising next-generation energy storage system with high energy density and power capability. The conductive additive is a passive and indispensable material in deciding the electrochemical performance of an energy storage device during high current charging and discharging processes. The incorporation of a suitable conductive additive into the layers of an electrode improves electronic conductivity. It reduces the internal resistance and polarization of the electrode resulting in the enhanced performance of the charge-storage system. Herein, recovered graphite (RG) is reported from dead Li-ion batteries as an excellent conductive additive that can improve the electronic conductivity of the electrode material. Compared with commercial conductive additive acetylene black (AB), the TiO2 anode material with 5% RG delivered a high discharge capacity of 163 mAh g-1 at a current rate of 0.15 A g-1 with a coulombic efficiency of approximately to 99% after 500 cycles in half-cell assembly. The fabricated AC/TiO2@5%RG LIC displays an excellent electrochemical performance with a maximum energy density of approximately to 50 Wh kg-1 at a current density of 0.15 A g-1. Notably, the LIC rendered promising performance at different temperature conditions (0, 10, 25, and 50 degrees C). The role of graphitic and amorphous carbonaceous materials is explored as potential additives and their application to the Li-ion capacitor, especially for high rates. The graphitic carbon is recovered from the spent Li-ion battery and milled with TiO2 hybrid. imag
Influence of Surface Mechanical Attrition Treatment Parameters on the Residual Stress of EN8 Steel
No full textThe present article addresses the influence of surface mechanical attrition treatment (SMAT) parameters such as the size of the balls (2, 5, and 8 mm circle divide 316L stainless steel (SS) balls) and treatment time (15, 30, 45 and 60 min) on the microstructural features, deformation characteristics, surface roughness and compressive residual stress induced on EN 8 steel. The effective deformation is similar to 25 mu m from the top surface along with elongated grains in the near subsurface region. The decrease in crystallite size and an increase in micro-strain become more pronounced during SMAT using balls with a larger diameter and for a longer treatment time. A similar trend is observed in surface roughness. This is mainly attributed to the involvement of higher kinetic energy imposed by SMAT on EN 8 steel. The residual stress induced during SMAT of EN 8 steel measured by x-ray diffraction (XRD) measurements is higher when treated using 2 mm circle divide SS balls when compared to those treated using 5 and 8 mm circle divide SS balls for a similar time duration. Irrespective of the size of the balls, an increase in treatment time has led to a decrease in the residual stress of EN8 steel. Overworking of EN8 steel that creates surface cracking has been considered responsible for the decrease in residual stress of EN8 steel treated using 5 and 8 mm circle divide SS balls for any given time duration as well as with an increase in treatment time for a given size of the balls. The development of surface cone cracks and material removal from the surface evidenced by the microstructure validates such an occurrence. When the duration of SMAT is limited to 15 min, a large difference in residual stress values is observed for the EN8 steel treated using 2, 5, and 8 mm circle divide balls, whereas, with a further increase in treatment time, the difference between them becomes marginal. Hence, to achieve better mechanical properties, the treatment time employed for SMAT of carbon steels should be carefully optimized. The other option available is to choose lower-size balls for SMAT. The change in residual stress of EN8 steel as a function of process parameters employed for SMAT and the correlation between the ball size and treatment time with the residual stress are discussed
A Quantitative Approach to Precipitate Characterization in Wire Arc Additive Manufactured Inconel 600 Series Alloys
No full textIn this work, wire arc additive manufactured (WAAM-ed) Inconel 617- and 625-wmo grade alloys are characterized in detail for the type and distribution of precipitates in as-built and heat-treated conditions. The analyses are carried out near (similar to 1 mm) and away (similar to 10 mm) from the substrate along the build direction to investigate the effect of the substrate on the nature of precipitate formation. For each analysis location, morphological and chemical information of at least 400 precipitate features was identified and classified using stoichiometric analysis of SEM-EDS data combined with feature analytics. Carbides and carbonitrides are present in both Inconel 600 series alloys but Laves phase precipitates are identified only in the case of Inconel 625 wmo alloy. It is observed that the nature of precipitate size distribution is not altered significantly when compared between the two analyzed locations for a particular grade. Furthermore, Laves phase precipitates closer to the substrate (1 mm) are richer in iron because of the effect of mild steel substrate on precipitation characteristics in Inconel 625 alloy. Our novel characterization approach will pave the way for comparing the microstructures of additively manufactured samples printed using different process parameters and variations