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Rheological behavior of coal-water slurry using sodium tripolyphosphate as a dispersant
No full textThe rheological nature of coal-water suspensions of an Indian coal variety is reported in the shear rate range of 60-160 s(-1). Sodium tripolyphosphate (STPP) is used as a dispersant or chemical additive for the slurries. The effects of percentage solid loading, dispersant dosage and pH on the rheological nature are comprehensively studied. The rheological data is fitted for power-law model to categorize the slurry flow nature with reference to the calculated flow behavior index of the model. At lower solid loadings (10% 20%), the shear stress-shear rate relation did not alter with the dispersant dosage or pH and the slurries of exhibited dilatant behavior. The effects of the slurry parameters are quite predominant at higher solid loadings (30%, 40%, and 50%). For pH >= 8.0, dilatancy of the slurries were observed for 30% solids loadings with dispersant in some cases. Excluding this, the higher percent solid loadings exhibited shear thinning behavior. For a fixed shear rate, the shear stress decreased with increasing pH at higher dispersant dosages which confirms the sharp effect of pH on the slurry rheology with the dispersant addition. The increased adsorption of the anionic dispersant (STPP) on the solids at higher pH values is the reason for this trend
Characterization and Assessment of Mold Flux for Continuous Casting of Liquid Steel Using an Inverse Mold Simulator
No full textThis investigation discusses the experimental methods to characterize and evaluate the mold flux performance during continuous casting of liquid steel. The mold fluxes are initially characterized by the conventional techniques for particle size, phase identification, phase transformation during the heating process, viscosity, break temperature, and other high-temperature properties. Subsequently, the initial solidification behavior of the peritectic and interstitial free (IF) steel in the presence of respective molten mold flux has been simulated using an in-house designed and developed inverse mold simulator. This simulator takes into account the physical, thermal, and fluid properties of mold flux, liquid steel to be cast, and casting parameters (casting speed, mold oscillation frequency, and stroke length), to assess the performance of liquid steel casting in the continuous caster. A suitable mathematical model has also been developed to predict the transient heat flux and hot face surface temperature of mold at the meniscus level. The current study successfully concludes the importance of a mold simulator along with the conventional characterization techniques to completely evaluate the performance of any mold flux
Spectroscopic and molecular docking studies for the binding and interaction aspects of curcumin-cysteine conjugate and rosmarinic acid with human telomeric G-quadruplex DNA
No full textThe binding and interaction aspects of potential anticancer ligands like: curcumin-cysteine (CC) and rosmarinic acid (RA) with human telomeric G-quadruplex DNA, a novel anticancer target, have been probed by spectroscopic and molecular docking approach. The circular dichroism study unravels the conformational switching from mixed hybrid to parallel structure for the short sequence of human telomeric G-quadruplex structure in the presence of both the ligands. Further a good correlation for binding affinity has been established from the emission and absorption binding spectrum analysis. Further our spectroscopic and molecular docking studies have suggested that the CC having better binding capability than RA to human telomeric G-quadruplex. The presence of L-cysteine moiety in CC ligand is responsible factor for its binding via both minor as well as major groove of human telomeric G-quadruplex DNA where-as RA binds only via minor groove of telomeric G-DNA. (c) 2021 Published by Elsevier B.V
Application of Hydrodynamics Using CFD in Evaluating Efficacy of External Loop Air-lift Reactor Biochemical Leaching of Sea Nodules
No full textBiochemical leaching of sea nodules using Bacillus circulans was carried in an external circulation-loop
airlift bioreactor. In contrast to the slightly high recovery (92% Cu, 73% Ni, 72% Co, 38% Mn, and 17% Fe)
with fine particles (<75 μm) on shake flasks in 25d, the leaching of metals using coarser lumps (1190–
250 μm size fraction) were found to be 76% Cu, 69% Ni, 65% Co, 29% Mn and 12% Fe in the same duration
in an air-lift reactor with airflow of 500L min−1. The use of air flow assisted in retaining good metal
recoveries with reduced grinding costs in the air lift reactor. Computational Fluid Dynamics (CFD) with
a multiphase mixture model was used to describe the mass transfer and hydrodynamics vis-à-vis its role in
improved leaching efficacy. The leach liquor was treated to eliminate iron, followed by selective extraction
of copper by 10% Acorga M5640. The remaining leach liquor with Mn, Co and Ni were separated as
respective salts by sulfide/carbonate precipitation
Role of Synthetic Slag Treatment on the Morphology of Non-Metallic Inclusions and Subsequent Cold Drawability of the High Carbon Wire Rod Steel
No full textThe present work discusses the evolution of microstructure and non-metallic inclusions during wire drawing process in a synthetic slag-treated 5.5 mm diameter high carbon wire rod steel. It has been observed that failure of the as-received wire rod (without synthetic slag treatment) takes place at different stages of deformation during wire drawing operation. However, in case of the synthetic slag-treated wire rods (TW specimen), failure takes place consistently at similar to 95% reduction in the cross-sectional area of the wire. In a quest to understand the failure mechanisms during wire drawing process, a systematic study has been carried out by analyzing the microstructures and non-metallic inclusions in the steel wires drawn at various stages of deformation. The improved drawability of the treated wire specimens is attributed to the decrease in the amount of unfavourable non-deformable inclusions in the steel matrix, and this stems from the synthetic slag treatment of the liquid steel. Microstructural investigation also confirms the complete realignment of pearlite colonies along the wire drawing direction followed by thinning and disintegration of cementite lamellae at higher deformation, particularly in case of the synthetic slag-treated wire rod steel. Graphic abstract
On prominent TRIP effect and non-basal slip in a TWIP high entropy alloy during high-pressure torsion processing
No full textSevere plastic deformation response of a face centered cubic (FCC) twinning induced plasticity (TWIP) high entropy alloy (HEA), Fe40Mn40Co10Cr10, subjected to high-pressure torsion (HPT) is investigated. The so-called TWIP HEA demonstrated an extensive transformation induced plasticity (TRIP) effect even in 1/2 turn (shear strain, gamma = 15) of HPT processing, which increased further with increasing the number of turns to 2 (gamma = 68). Additionally, HPT induced nano-structuring and heavily dislocated structure; dislocation density was of the order of 1015 m- 2. c/a ratio of the transformed HCP phase was found to be <1.633 and it did not change with increasing the extent of shear strain. This was manifested as the occurrence of at least 50% non-basal slip in the HCP phase. For the first time, the fraction of c c+a dislocations are quantified and their evolution are discussed in the purview of the studied alloy. The micro-mechanism of strain accommodation is correlated with increasing hardness of the HEA upon sequential HPT processing. The present work provides a viewpoint that the deformation induced HCP phase in a metastable FCC HEA can have tailored c/a ratio which triggers non-basal slip, leading to a strong and ductile material
Strain ratio effect on microstructural evolution during low cycle fatigue exploitation of nickel base superalloy IN 740H
No full textStrain ratio (Re) is varied during isothermal strain-controlled fatigue tests of nickel-base superalloy IN740H at 760 degrees C; R-epsilon = -1, 0, 0.5. Unlike most alloys, highest fatigue life is observed under R-epsilon = 0 test condition compare to R-epsilon = -0.5 and -1. From extensive electron microscopy, i.e. energy-filtered TEM (EF-TEM), WDS and EDS studies, it is confirmed that the creep effect due to tensile mean stress under R-epsilon = 0 condition was offset due to segregation of Nb at dislocation and formation of Nb(CN) at grain boundaries, which proved to be fatigue strengthening. Debonding of Nb(CN) and. matrix provided preferential fatigue crack initiation sites and resulted in lowering the fatigue life for R-epsilon = 0.5 test condition
Formability study of bake hardening steel and its correlation with microstructure
No full textIn the present study, the bake hardening (BH 240) steel sheet's formability behavior is studied experimentally based on the Nakajima test method. A forming limit diagram is successfully constructed using universal sheet metal forming machine by offline measuring the strains of deformed specimens. In-process strain measurement based on a digital image correlation technique is also performed for a few selected samples to compare the results with manual strain measurement techniques. All the deformed specimens are also characterized to correlate the sample geometries with hardness values and microstructure. It is observed that the hardness value gradually decreases with an increase in sample width for all the deformed specimens up to the width of 150 mm, except for full-width sample of 200 mm. Microstructural analysis reveals that the morphology of ferrite grains changes with the sample geometry in all the deformed specimens. Microstructural characterization at the top surface of the specimen demonstrates that the aspect ratio of grains is maximum for a 25 mm width sample due to uni-axial stretching. It is also noted that grain's aspect ratio is close to one (minimum) for a 200 mm width sample due to almost equi-biaxial elongation in grains. It is also observed that the aspect ratio of grains obtained from specimen cross-section indicates that the ratio increases gradually from 25 to 200 mm width samples
Establishment of transition point in operating mode for Constant Current Constant Voltage (CC-CV) charging of Li-ion batteries
No full textThe present-day Li-ion batteries when operated, needs precise monitoring of the charging voltage. Several charging techniques have been tested so far with varying degrees of success. One of the most widely used charging techniques is the CC-CV (constant current constant voltage) charging. When performing this, the safety considerations must be maintained with respect to over voltage charging which is a very common problem during constant current charging. In order to prevent over voltage charging, the charging mode must be then shifted from CC to CV mode. So, this transition point of the charging mode from CC to CV is very crucial for the safe operation and health of the battery in the long run. The problem is that, this transition point doesn’t remain the same for the battery. So, in this paper the factors on which it depends are discussed and a Li-ion battery was charged in a few different charging rates using the CC-CV technique to demonstrate the process
Developing Feasible Processes for the Total Recycling of WEEE to Recover Rare Metals
Get PDFThe present paper reports several application-oriented processes developed for the recovery of various non-ferrous (Cu, Ni, Al, Pb, Sn), rare (Li, Co, In), precious (Au, Ag, Pt, and Pd), and rare earth metals (Nd, Ce, La, Y, Eu) from various urban ores, i.e., waste electrical and electronic equipment (WEEE), liquid crystal displays (LCD), batteries, magnets, fluorescent tubes, etc. Initially, the WEEE and
various wastes were classified and dismantled. Further, the materials were pretreated to separate plastics, epoxy, ceramics, rubber, iron covers, and metallic concentrates.
Based on their properties, plastic, epoxy, and rubber could be either pyrolysed for production of marketable low-density oil and saleable activated carbon or directly recycled. The pre-treated metallic concentrates were processed by hydrometallurgical techniques, i.e., leaching, solvent extraction, ion exchange, and electro-winning for
maximum recovery of metals. Various flow sheets discussed for rare metal extraction and processing strictly comply with environmental regulations