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Geochemical characteristics of the Rajmahal coals in Dhulia North Block, Eastern India: implication to their utilization and environment
No full textThe borehole coal samples of Dhulia North Block from the Rajmahal Basin, Eastern India, were systematically analyzed based on the chemical composition and concentration of major and trace elements (including rare earth elements, REEs) to assess the distribution of REEs and their environmental implications with utilization potential. The Dhulia North Block coals are characterized by the predominant major oxides of SiO2, Al2O3, and Fe2O3, accounting for 94% of the total ash composition, indicating the presence of quartz, clay-rich minerals, and pyrite. Compared with the average world coal ash, the total REE content in the analyzed samples ranged from 341.0 to 810.4 ppm, which is substantially higher. Hot humid climate conditions with intermediate igneous source rocks of the basin were demonstrated by the major oxide ratios (Al2O3/TiO2 < 20) and plots of TiO2 with Al2O3 and Zr. The redox-sensitive elements such as V, Ni, Cr, and Co found in the Dhulia North Block coal indicate that an oxic sedimentary environment existed in the basin when coal was formed. The low sulfur content (1% in most samples) indicates freshwater conditions in the basin at the time of organic matter deposition. The outlook coefficient (C-outl) varies between 0.7 and 1.6, indicating that the Dhulia North Block coals are a prospective source of REEs. The Dhulia North Block coals are characterized by low H/C and O/C atomic ratios ranging from 0.56 to 0.90 and 0.10 to 0.22, respectively, and contain type-III kerogens, indicating gas-prone source rock. Further, the basic-to-acid oxide ratio suggested that Dhulia North Block coals were suitable for utilization during combustion processes
Microstructural, Mechanical, and Corrosion Behaviour of Ni-Fe-Cr-Al and Ni-Fe-Cr-Al-Co Alloys
No full textHigh entropy alloys (HEAs) with excellent strength-ductility combinations are considered potential candidates for various structural and aerospace applications. Despite its promising mechanical properties, there have been contradictory observations related to the corrosion behaviour of HEAs. Therefore, the present study aimed to design low-density cost-effective medium entropy alloys exhibiting the popular & gamma;-& gamma; MODIFIER LETTER PRIME microstructures of superalloys and to evaluate their mechanical properties and corrosion behaviour. The CALPHAD-based approach was used to design two alloy systems, Ni-Fe-Cr-Al (0Co) and Ni-Fe-Cr-Al-Co (14Co). These alloys were produced through induction melting and casting routes. The microstructure and room-temperature mechanical properties of the alloys were thoroughly investigated employing various characterization tools. Further, the corrosion behaviour of the developed alloys was investigated through electrochemical and gravimetric techniques, followed by surface topography studies. Both the alloys exhibited excellent strength-ductility synergy and the addition of Co significantly improved the mechanical properties. It is interesting to note that 0Co alloy exhibited better corrosion resistance compared to 14Co alloy in an electrochemical test using 3.5wt.% NaCl solution. Moreover, no significant influence of Co could be confirmed during the immersion test in 6wt.% FeCl3 solution. Further, the potentiodynamic results obtained for both the studied alloys exhibited corrosion rates comparable to SS304 as well as other studied HEAs while possessing better room-temperature mechanical properties
Grain boundary assembly in a 316 L steel produced by selective laser melting and annealing
No full textThe effect of recrystallization annealing on the grain boundary assembly of a 316 L-type austenitic stainless steel produced by selective laser melting was studied. The primary recrystallization readily developed upon heating to 1373-1473 K. Using the orientation imaging microscopy, the recrystallization development could be evaluated using the grain orientation spread and/or the kernel average misorientation. The recrystallization kinetics was mainly controlled by the grain nucleation rate rather than the grain growth rate. The recrystallized microstructures were characterized by large fractions of special sigma 3n CSL (coincident site lattice) grain boundaries above 0.7 that were associated with a high number density of annealing twins. The change in the fraction of sigma 3n SCL boundaries could be expressed by a unique linear function of the recrystallized fraction irrespective of annealing temperature. The development of sigma 3n CSL boundaries interrupted the network of ordinary grain boundaries when the number of triple junctions with 3 ordinary boundaries decreased and that with 1 ordinary and 2 sigma 3n CSL boundaries increased. An increase in the fraction of triple junctions with 1 ordinary and 2 sigma 3n SCL boundaries correlated with the recrystallized fraction
Magnetostriction of Fe-rich FeSiB(P)NbCu amorphous and nanocrystalline soft-magnetic alloys
No full textThe compositional effect of magneto-elastic and magnetostriction properties of Fe-rich Fe81B15-xPxSi2Nb1Cu1 (ii) Fe(82)B(14-x)PxSi(2)Nb(1)Cu(1) and (iii) Fe83B13-xPxSi2Nb1Cu1 (x = 0, 4, 8) amorphous and annealed nanocrystalline alloy ribbons were investigated. The present study adds knowledge to the limited magnetostriction literature available for Fe-rich nanocrystalline alloys by systematically varying the Fe and P content. A combination of Becker-Kersten and small angle magnetization rotation (SAMR) techniques has been employed for the magnetostriction (lambda s) evaluation. Both the as-quenched and nanocrystalline ribbons exhibit large positive magnetostriction and show strong compositional dependence to the P content. In the as-quenched condition, 4 at% P addition shows maximum magneto-elastic response and magnetostriction constant, with Fe81B11P4Si2Nb1Cu1 alloy exhibiting a maximum of + 52 ppm and P-free Fe83B13Si2Nb1Cu1 alloy exhibiting a minimum of + 27 ppm. In the nanocrystalline state, a slight reduction of magnetostriction is seen for all alloys, with a maximum of + 32 ppm (4 at% P) and a minimum of + 22 ppm (P-free) in Fe83 at% alloys. The unusual large magnetostriction of optimally annealed samples is attributed to the relatively low crystal volume fraction (30-45%) of nano-crystalline ribbons. The lowest magnetostriction of Fe83B13Si2Nb1Cu1 alloy in both as-quenched and annealed state is explained based on ribbon structural heterogeneity consisting of crystal nuclei and textured alpha-Fe surface crystallization. The study reveals a contradictory response of magneto-crystal anisotropy (grain size reduction) and magneto-elastic anisotropy to the P addition and ribbon structural heterogeneity. The study discusses the implications of the large magneto-elastic anisotropy associated with Fe-rich nanocrystalline ribbons and the way forward for improving their magnetic softness. (C) 2023 Elsevier B.V. All rights reserved
Nanostructure-induced inhibition of oxygen evolution and enhancement of methanol electrooxidation on engineered anodized brass
No full textTo capitalize the improved electrical contact feature, a self-supported hybrid binary/ ternary copper and zinc oxides (i.e., ZnO-Cu2O and Cu2O-ZnO-CuO) nanostructures have been generated via a simple potentiostatic mode of anodization on alpha brass in an alkaline medium. The catalyst nanostructuring i.e., wheat-grain-like to nanograss type structure has improved the mass transport, and sluggish kinetics of the methanol electrooxidation reaction process, and hindered the competitive oxygen evolution reaction (OER) of direct methanol fuel cell. The catalytic poisoning phenomenon has not been noticed due to two different reaction processes in two potential regions. Interestingly, a significant reduction of 236 mV and 350 mV, respectively. The enhancement of current density has been explained through an inductive circuit perspective. So, the present study provides a better insight into the design and utilize non-precious metal/alloy-based catalysts with hindered OER and (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
Artificial neural network-based sensitivity analysis and experimental investigation of liquid–solid fluidization technique for low-grade coal upgradation
Get PDFLiquid-solid fluidization technique is being applied where low-grade coal or minerals enrichment
is mostly density-based. Static and dynamic behavior of particles in a fluid medium has been
extensively investigated over the years because of its dynamic applications across various industries.
In this work, bed characterization studies and experiments have been conducted to study
coal washing ability of the liquid-solid fluidized bed separator. Results have been recorded in
terms of ash rejection%, combustible recovery% and separation efficiency%. Minimum fluidization
velocity and pressure drop values have been predicted using existing theoretical correlations and
compared with the experimental values. A three-layered (4:5:3) feedforward back-propagation
(FFBP) neural network model was developed using Levenberg-Marquardt algorithm, LOGSIG and
MSE as training, transfer and performance functions respectively. Garson’s algorithm and connection
weight approach have been employed for sensitivity analysis to interpret the neural network
results physically. Coefficients of correlation, all R (including training, validation & testing datasets)
obtained for outputs ash rejection (R¼0.9960), combustible recovery (R¼0.9952) and separation
efficiency (R¼0.9944) suggest that predicted values are in agreement with the experimental values
and the developed model is a good fit
Effect of Alloying Elements on the Dry Sliding Wear Characteristics of Gravity-Cast Mg-Sn Based Alloys
No full textThe effect of solo and combined addition of Al (3wt. %) and Zn (1wt. %) into gravity-cast Mg-10 wt. % Sn binary alloy on the dry sliding wear test has been investigated using pin-on-disk configuration with varying rotational speed (100 and 200 rpm) under a range of test loads (10, 20, 30, and 40 N). Microstructural characterization and phase analysis of the as-cast Mg-Sn alloys using scanning electron microscope and x-ray diffraction, respectively, have revealed the refinement of the binary alloy microstructure in terms of smaller dendritic arm spacing, uniform and discrete distribution of eutectic phase mixture at the interdendritic locations owing to the alloying additions. Moreover, a significant improvement in microhardness is achieved with increase in amount (wt.%) of alloying elements, depicting the highest hardness in the Mg-10Sn-3Al-1Zn (wt.%) alloy. Simultaneously, the alloying addition even in micro-concentration has been found to reduce the specific wear rate than that of the binary alloy over the entire loading range. The post-wear topographical surface features and chemical analysis using scanning electron microscope and energy-dispersive x-ray spectroscopy of the investigated alloys have suggested the oxidation and abrasion as dominant wear mechanisms. The reduced wear rates in the Al containing alloys are ascribed to the protective and continuous mechanically mixed oxide scale formation during test, which acts as a lubricating layer between the pin and the rotating disk. The discrete oxide island formation at the Zn-lean regions of Zn containing alloys is responsible for their accelerated wear rates
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 a 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 & DEG, C, and a monoclinic CuO phase was formed at 80 & DEG; 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 & plusmn; 3 nm. Cu(OH)(2)/CuO nanoflakes formed at 70 & DEG; C aging temperature and 24-h residence time have finer crystallite and particle sizes than CuO-ridged nanospheres formed at 80 & DEG; 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
Assessment of the internal chemistry nexus of coke and biomass-based sinters
No full textThe present study highlights the differences/similarities in the sinter’s microstructure that are essentially caused due to the adjustment in the fuel framework. In general, sintering draws energy from fuel to initiate the melt phase formation which is significant for sinter bond formation. Thus, it is possible that changing the fuel and its proportion may reflect various phenomena while sintering, and that can propagate changes in the mineralogy, morphology, and subsequently the sinter strength and metallurgical properties. Here, two types of sinters (a) conventional coke-based sinter and (b) biomass-coke blend-based sinter at a 70:30 ratio are assessed based on the comparative investigation of the microstructural and morphological aspects, which further relate to the sinter indices. Sinters are characterized for acquiring their internal chemistry, phase transitions, phase identification, textural transformations, bond phase distribution, elemental distribution, and metallurgical indices. The findings are similar for both the sinter types that concluded the technical feasibility of the biomass blend-based sinters. When biomass proportion went higher than 30%, the extent of phase transition started to subside,
and some unreacted hematite phases started to surface as the effect of underheating. However, 30% coke
substitution with biomass feasibly ensured a cleaner sinter production with energy sustainability without
compromising the internal chemistry nexus
Structural and magnetic behaviors of Fe‑based glassy alloys prepared by industrial raw materials and different processing routes
No full textThree types of Fe-based metallic glass alloys with nominal compositions of Fe74.5B5Si2C4P10Cr2Mo2Mn0.5(#A1), Fe73.5B5Si3C4P10Cr2Mo2Mn0.5(#A2), and Fe72.5B6Si3C4P10Cr2Mo2Mn0.5(#A3) are developed using commercial pure raw materials in the forms of ribbon, rod, and powder. The structural and thermal properties are investigated by X-ray diffractometer (XRD) and differential scanning calorimetry (DSC), respectively. The alloy #A1 displays complete crystallinity in powder form while dispersion of crystallites in amorphous matrix found in
ribbon and rod. The replacement of Fe by Si in #A1 causes complete amorphous structure for all forms of alloy #A2 and ribbon and rods of alloy #A3. More B atoms in alloy #A3 enhance glass transition and crystallization temperatures than alloys #A1 and #A2. The additional B and Si atoms in #A2 and #A3 influence the lowering of saturation magnetization compared to alloy #A1. However, the alloy
#A3 possess the lowest coercivity, sustaining its good magnetic softness even after post-annealing at 770 K. The optimized composition in alloy #A3 is found with high amorphous-forming ability and good sphericity in powders, which would be beneficial for improving the alloy performance at further processing like additive manufacturing