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Atomic Investigation of Corrosion Mechanism and Surface Degradation of Fe-Cr-Ni Alloy in Presence of Water: Advance Reactive Molecular Dynamics Simulation
No full textSteel is the most versatile engineering and construction material. Construction, power, automobiles, infrastructure, manufacturing, and various industrial sectors are using steel as their most important raw material. It is also the most recycled metal material on earth. But steel is having a major problem of rusting when exposed to water. Interaction of steel products with water is almost unavoidable in majority of the cases like automobiles, construction, water pipes, etc. Thus a detailed atomistic study of steel with water is required to understand the corrosion behavior. At the atomic scale, Fe, Cr, and Ni are the major alloying elements of steel and are highly reactive with water which results in corrosion and degradation of both surface and bulk properties. Therefore, we have used reactive molecular dynamics simulation (RMDS) to investigate reactivity of water with Fe-Cr-Ni substrate. We have carried out a large number of simulations at different initial conditions and found that water molecules split into H and OH. Further, OH predominantly reacts with Cr and forms chromium oxide compounds over the Fe-Cr-Ni substrate. In the next step, variation in potential energy and mean square displacement have been used for quantitative characterization of the reaction between water and Fe-Cr-Ni substrate. This study can provide a detailed perspective on the corrosion behavior of steel in a humid environment
An emerging trend of ionic liquids in the separation of critical metals from spent lithium and nickel based batteries
No full textSeparation of critical metals viz. nickel, cobalt, lithium, manganese, zinc, and copper from scrap rechargeable batteries (LIBs, NiMHs) is still challenging due to its heterogeneous composition. The currently prevailing multistage separation tools like solvent extraction, ion exchange, is being replaced by ionic liquids (ILs) for being ecofriendly and are rapidly replacing organic solvents/resins due to their distinctive properties such as negligible vapour pressure and higher stability, structure tenability, easily recyclable, and low melting point. Creating new cations and anions and incorporating suitable functional groups can impart the exact physical properties essential for each application at the core of the ILs designing process. ILs are classified as imidazolium-based ILs, phosphonium-based ILs (PILs), non-fluorinated, and task-specific ionic liquids (TSILs). PILs and TSILs are receiving an upsurge of interest and are widely used due to their advantages, viz., minimum solute interaction, cost-effectiveness (PILs are reported to be costly), and manageability. The overview describes in vogue the recent advances to extract metals from LIBs, NiMHs, etc., using different types ILs and their comparative assessment of performance-cum-selectivity
Influence of Mechanically Activated Silico-Manganese Slag on Hydration and Properties Development of Blended Cement
No full textSilico-manganese (SiMn) slag is a byproduct of the SiMn alloy production process, which has been blended with clinker to produce Portland slag cement. The influence of mechanical activation (in a vibratory mill) on the heat of hydration, physical properties, and structural changes is elucidated and compared with a ball-milled control sample. Calorimetric studies have shown the variation in hydraulic behavior with the addition of mechanically activated slag. However, reducing peak maxima and appearing later with an increase in fineness is not directly related to its reactivity. Still, it is due to the decrease in the water-to-binder ratio subcutaneously. Typical cement hydration phases such as CH, CSH, and CAH (throughout the study cement abbreviations are used such as C = CaO, A = Al2O3, S = SiO2, H = H2O, etc.) are identified by XRD analysis and further detected by EDX analysis. Formation of dense gel with a well-connected matrix attributes higher compressive strength development with an increase in milling time
Influence of Genesis on Mechanochemical Activation and Reactivity of Boehmite Prepared by Thermal and Hydrothermal Transformation of Gibbsite
No full textThe focus of this paper is on the mechanical activation and reactivity of boehmite (gamma-AlOOH) synthesized by thermal transformation (B-TH) and hydrothermal transformation (B-HT) of the same gibbsite (Al2O33H2O) precursor. The central idea is to emphasize the role of sample genesis. The samples used had similar size distribution and largely differed in their BET surface area, 264 and 2.98 m2/g for B-TH and B-HT, respectively. Mechanical activation was carried out for different durations, up to 240 minutes, using a planetary mill. On milling, the span of change in physicochemical properties, namely geometric specific surface area, BET specific surface area, degree of amorphization, microcrystalline dimension, and macro strain (in /stacking direction of AlO4(OH)2 octahedra layers) was more for B-TH vis-& agrave;-vis B-HT. The anomalous decrease in the BET surface area reported in the literature for B-TH is not observed in B-HT. The nature of alteration in pore size distributions with milling time is used to present a plausible explanation for the contrasting change in BET surface area. The samples also showed the opposite sign for macro strain; a negative sign for B-TH which was characterized by a relatively weaker interlayer bonding. The reactivity of the samples was evaluated in terms of leachability in alkali and the lowering of boehmite to gamma-Al2O3 transformation temperature. In general, higher reactivity was observed for B-TH vis-& agrave;-vis B-HT. The reactivity was correlated with physicochemical changes. Despite wide differences in reactivity, the change in reactivity could be expressed in terms of simple multivariate equations with high correlation coefficients
Comparison of low cycle fatigue behaviour of additively manufactured and wrought Inconel625 alloys
No full textThe present investigation highlights a comparison of strain-controlled low cycle fatigue (LCF) behaviour between the additively manufactured (AM) and wrought (WR) Inconel625 alloys at the total strain amplitude levels of +/- 0.4, +/- 0.5, +/- 0.6 and +/- 0.8 % at 650 degrees C. The cyclic life has been found to be lower in the AM alloy as compared to the WR alloy. The evolution of precipitates such NbC and gamma '' are found in both type of alloys after LCF tests. However, the AM alloy has shown a significant presence of (Cr,Mo)23C6 along the grain boundaries, which acts as a potential source of generation of the intergranular cracks during cyclic deformation. Although, a relatively fine grain structure and enhanced number density of high-angle boundaries have been identified in the LCF-tested samples of AM alloy through EBSD analyses, the formation of intergranular cracks in the AM alloy has resulted in the reduction of cyclic life of the AM alloy
An experimental investigation and predictive modeling using machine learning technique for reclamation of metal values from scrap NdFeB magnets
No full textNeodymium-Iron-Boron (NdFeB) magnets are widely used in various industries due to their exceptional magnetic properties, such as high coercivity, remanence, and maximum energy product. These magnets consist of rare earth elements (REEs) viz., neodymium (Nd), praseodymium (Pr), and Dysprosium (Dy), along with other metals. With the ever increasing demand for REEs and the need to bridge the supply gap, it is crucial to develop alternative methods for their extraction. Recycling metal from scrap magnets is a promising approach to address the pressure on the supply chain and work towards sustainable development. The primary goal of this study is to generate a predictive model based on machine learning to determine the optimal conditions for metal recovery from scrap NdFeB magnets through water leaching after chloridizing roasting. Bench-scale leaching experiments were carried out to generate a dataset for statistical process optimization and machine learning analysis. The leaching kinetics of neodymium was also explored, and mixed-controlled shrinking core model was found to be most suitable, with an activation energy of 58.11 kJ/mol in the temperature range of 25- 95 degrees C. This study is the first to utilize a machine learning approach to analyze the potential process variables and their impact on metal recovery from calcined NdFeB magnet powder. A comparative analysis between experimental and machine learning approaches is presented to predict the optimal conditions for selective recovery of metal values from scrap NdFeB magnets. The maximum efficiency of extraction of metal ions was found to occur at a temperature of 95 degrees C, solid to liquid ratio of 125 g/l, and leaching duration of 60 min
Harnessing hetero-atom doped CQDs from Pyrostegia venusta for latent fingerprint and anti-counterfeit applications
No full textThe development of innovative techniques for latent fingerprint (LFP) analysis and anti-counterfeiting applications is crucial for addressing various societal challenges. Quantum dot (QD)-based fluorescent staining offers a promising approach due to its high sensitivity. However, the toxicity of traditional heavy metal-containing QDs necessitates the exploration of eco-friendly alternatives. This study presents a facile and environmentally sustainable method for synthesizing heteroatom (nitrogen, phosphorus, and potassium)-doped carbon quantum dots (N-P-K@CQDs) derived from the flower extract of Pyrostegia venusta. Characterization revealed spherical CQDs with an average size of approximately 4.7 nm, a quantum yield of 25 %, and excellent water solubility, photostability, and greenish-fluorescent properties. N-P-K@CQDs were incorporated into a cornstarch nanocomposite phosphor, which exhibited greenish fluorescence under UV excitation. The nanocomposite was utilized as a fluorescent marker for LFP analysis using a customized smartphone-based dactyloscope. Pythonbased image processing algorithms were employed to enhance and analyze the fluorescence images of the developed LFPs. Additionally; a proof-of-concept anti-counterfeiting tag was demonstrated using CQDs-based ink, enabling the detection of concealed security marks. The findings highlight the potential of eco-friendly NP-K@CQDs as a versatile platform for both LFP analysis and anti-counterfeiting applications
Effect of Structural Refinement and Modification on the Mechanical Properties of Al-7Si Alloy
No full textIn this present research, the effects of grain refiner (Ti-B) and eutectic modifier (Sr) on the microstructural
feature, casting defects, and mechanical properties of Al-7Si alloys are studied. Addition of grain refiner
(0.1 wt.% Ti) into Al-7Si melt can significantly change the morphology of dendritic a-Al phase to finer equiaxed grains and eutectic modifier (0.05 wt.% Sr) changes the plate-type eutectic Si particles into fine fibrous-/spherical-type particles leads to improve mechanical properties. AFM analysis reveals that combined effect of grain refiner and eutectic modifier on Al-7Si alloy can easily reduce the surface roughness and casting defects such as porosity and shrinkage. The formation of TiAl3 and Ti7Al5Si14 precipitates refines the a-Al grains, and SrSi2Al2 precipitate modifies eutectic Si particles during solidification. Both the precipitates are identified by XRD and TEM analysis. The ultimate tensile strength (UTS, MPa), yield strength (YS, MPa), and elongation to fracture (El, %) of developed AS4 alloy are 164, 91 MPa, and 30%, respectively, which are significantly higher than those of developed as-cast AS1 alloy (UTS: 117 MPa, YS: 78 MPa, and El: 16%). The developed microstructural features are correlated with mechanical properties of the alloy by using a liner equation. This correlation suggests that SDAS and morphology of eutectic Si particles play a vital role in the enhancement of mechanical properties (UTS, MPa) of the developed alloys. The grain-refined and eutectic modified alloy exhibit more dimple formation on the fracture surface
indicating more ductility
Lipophilic EDTA-based ligands in different diluents for the extraction of rare earths: Preliminary results with Nd(III), Dy(III) and Pr(III) in chloride and nitrate media
No full textA separation method for the recovery of neodymium(III) from two different media, chloride and nitrate, by implementing solvent extraction technique with a novel lipophilic diamide derivative of ethylenediamine tetraacetic acid (EDTA), namely 2,2’-N,N′-didecyl-dioxo-N,N′,N″,N″’ tetraazatetratriacontane-N″,N″’-diyl diacetic
acid (H2E-4C10), has been investigated. Initial screening results demonstrated acceptable solubility (ca. 15 mM)
of the diamide in 1,3-diisopropylbenzene (DiPB) and in a 93:7 v:v n-dodecane: n-octanol mixture (DOm) as nonpolar diluents. Further investigations aiming at determining operational parameters associated with the befitted
extractant systems were conducted at pH ranging from 2 to 4 in chloride and nitrate media. A pH-dependent performance of the proposed systems revealed loading capacity peaking at pH = 3 with the respective values of 1.7 and 2.0 g L− 1 in nitrate and chloride media. The extraction efficiency, the distribution coefficients, and the separation factor (E%, D and SF, respectively) were determined for an equimolar mixture of neodymium (Nd) and two other potential competitive lanthanides, namely dysprosium (Dy) and praseodymium (Pr). The best selectivity was observed in the chloride medium at pH = 4 yielding SFNd/Pr = 1.48 and SFNd/Dy = 2.03. Neodymiumto-extractant stoichiometry was evidenced in chloroform to be 1:1 H2E:Nd at pH = 2. Thermodynamic constants related to the considered extraction equilibrium have been determined by using the Van’t Hoff relation and the slope analysis method. It appeared within the selected pH-range that the mechanism of the Nd3+ transfer was strongly influenced by the nature of the diluent. This was illustrated by the enthalpy-driven transfer when Nd3+ was extracted with the H2E-4C10-Dom system (aliphatic diluent) while the transfer became entropy-driven when the extraction was performed with the H2E-4C10-DiPB system (aromatic diluent). The complexation of Nd3+ involved mainly the participation of both the amide and carboxylic functional groups. The transfer of the cation
to the organic phase might occur through the formation of the Nd(HE)A2 complex (where A is either a nitrate or a chloride anion), allowing for the lowest associated standard Gibbs free energy of transfer (− 28 < ΔG◦ < − 24 kJ
mol− 1) regardless of the aqueous feed
Effect of microwave treatment on structural characteristics and energy bandgap of electrochemically synthesized hydrated tungsten oxide quantum dots
No full textQuantum Dots (QDs) of hydrated tungsten oxide were synthesized via electrolysis using sintered tungsten carbide-6 wt% cobalt (WC - 6Co) scrap as an anode, Ti plate as cathode, and sulfuric acid as an electrolyte at room temperature. The as-synthesized powder was characterized using X-ray diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transforms infrared spectroscopy (FTIR), Raman spectroscopy, Electron paramagnetic resonance spectroscopy (EPR), and Ultraviolet-visible spectroscopy (UV - Vis). The XRD analysis confirmed the formation of orthorhombic hydrated tungsten oxide (WO 3 . H 2 O) QDs via electrochemical oxidation of WC. As-synthesized WO 3 . H 2 O QDs were thermally treated using microwave radiation and conventional furnaces at 150 degrees C for 8 min and 45 min, respectively. Thermal treatment of as-synthesized QDs produced partially dehydrated powder consisting of both orthorhombic WO 3 . H 2 O and cubic WO 3 . H 0.5 crystal structures. The TEM analysis showed that the average particle size of QDs was 7.60 nm. Further, an increase in lattice strain was observed on microwave treatment owing to the non-equilibrium phase transformation (i.e., rapid heating) from orthorhombic to cubic crystal structure resulting in the generation of oxygen vacancies. The increase in oxygen vacancy concentrations in QDs on microwave heating was confirmed by XPS, FTIR, EPR, and Raman spectroscopy. The energy bandgaps of as-synthesized and thermally-treated QDs were in the range of 2.4307 - 2.4979 eV. The relatively low energy bandgap of QDs is attributed to the change in crystal structure and increase in the oxygen vacancy concentration. An improved CO gas sensing characteristics of microwave-treated QDs were noted