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On the Competitive Substitutional Partitioning During Nano-pearlitic Transformation in Multicomponent Steels
No full textBulk nano-pearlitic microstructure with apparent interlamellar spacing below 100 nm has been attained by rapidly undercooling a hypereutectoid multicomponent steel below equilibrium eutectoid temperature from the austenitization temperature. The aforementioned processing rendered non-partitioned pearlite growth in the steel, as confirmed by acquiring compositional variation across the austenite/pearlite growth front using scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (STEM-EDS) technique. The post transformation sidewise partitioning of substitutional components between ferrite and cementite has been critically assessed by interrupting the cooling process at various intervals followed by STEM-EDS and atom probe tomography (APT) across the austenite/pearlite and ferrite/cementite interfaces. This partitioning phenomena has been simulated using DICTRA(R) and validated with experimental observations. It is inferred that partitioning kinetics of Mn is fastest in the early stages followed by Cr in the intermediate. However, towards the completion stages of partitioning, Mn and Si have much faster rate as compared to Cr
Ru-supported mesoporous melamine polymers as efficient catalysts for selective hydrogenation of aqueous 5-hydroxymethylfurfural to 2,5-bis-(hydroxymethyl)furan
No full textA Ru-decorated porous melamine polymer is found to be an active catalyst upon selective hydrogenation of aqueous 5-hydroxymethylfurfural to 2,5-bis-(hydroxymethyl)furan (yield > 99%) under mild (20 bar H-2, 30-90 degrees C), base/additive free conditions. Owing to its porous structure and unique surface chemistry presenting abundant weakly basic N-sites (amine and triazine), the polymeric catalyst could outperform various benchmark Ru catalysts (viz. Ru/AC, Ru/SBA-15, Ru/Nb2O5, Ru/NbOPO4, Ru/NC, and Ru/g-C3N4) in terms of activity and desired product selectivity. The catalytic material was also found to be reusable and maintained good performance during multiple recycles under kinetic regime in batch mode. Furthermore, the polymeric catalyst also showed good performance for selective HMF hydrogenation under intensified conditions in a fixed-bed reactor achieving constant BHMF yield during 20-h steady-state operation under relatively mild conditions (70 degrees C, 20 bar, WHSV 0.2 h(-1))
Investigation of Operating Parameters' Effects on Bubble Characteristics in a Co-Current Downflow Bubble Column
No full textBubble columns are frequently employed as multiphase reactors and gas-liquid contactors. In the bubble column, gas is dispersed into the liquid phase. The dispersion of gas into a liquid is the function of bubble size and its distribution. It also includes the complex process of coalescence and the break up of bubbles. The present research intends to examine the operating parameters' effect, including temperature on bubble characteristics in the ejector-induced downflow bubble column (i. d. 0.05 m X 1.6 m height) via Computational Fluid Dynamics (CFD) and experimental methods. Bubbles inside the column are analyzed and mean bubble diameters are obtained using a photographic technique. The effect of superficial gas velocity (4.25x10(-3)-9.68x10(-3) m/s) and liquid velocity (8.5x10(-2)-14.11x10(-2) m/s) on an average Sauter diameter is studied. The gas holdup variation with temperature (60-80 degrees Celsius) is also examined. The temperature distribution at different axial locations (0.48-1.35 m) from the top of the column is observed using the CFD model. An empirical model for predicting the temperature, i.e., Tr (T/Tset), is proposed as a function of the Prandtl number, Weber number, Reynolds number, and Froude number
Cellulose hydrogels: Green and sustainable soft biomaterials
No full textCellulose is a highly abundant, green, sustainable, and biodegradable polymer. These characteristic features of cellulose make it a useful polymer for the synthesis of bio-based hydrogel/or soft material for various applications. This article is focused on the preparation of biodegradable and biocompatible cellulose-based hydrogels using different methods based on the crosslinking agents used and the solvents used for cellulose dissolution. A study on the classification of different types of hydrogels was also reported. This article also discusses the self-healing cellulose-based hydrogel, bacterial cellulose-based hydrogel and includes the use of cellulose hydrogel in agriculture, biomedical field such as wound healing, wound dressing, and tissue engineering, water purification, removal of heavy metal, and in environmentally beneficial supercapacitors
Microwave-assisted rapid synthesis of titanium phosphate free phosphorus doped Ti3C2 MXene with boosted pseudocapacitance
No full textPhosphorus (P) doping is well-known for a variety of energy materials with improved energy storage performances; however, it remains rarely explored for Ti3C2 MXene. The primary bottleneck of developing P doped Ti3C2 (P-Ti3C2) is the formation of undesired electrochemically inferior titanium phosphate phases during doping. Herein, for the first time, we presented a solution to this problem by producing titanium phosphate free P-Ti3C2 through a rapid microwave (MW)-assisted doping method (P-Ti3C2-MW). Various prevailing experimental features like the effects of different doping methods (conventional heating vs. MW assisted heating), use of different varieties of doping sources, tunable mixing ratios of functionalized Ti3C2 (Ti3C2Tx) with doping sources (1 : 0 to 1 : 15), MW power (500-1000 W) and time (30 s to 5 min) have been optimized for obtaining titanium phosphate free P-Ti3C2-MW with superior energy storage properties. Detailed mechanistic studies unveil that homogeneous mixing of Ti3C2Tx and doping sources like phytic acid (PA) through electrostatic attraction and the extraordinary MW absorption ability of multilayered Ti3C2Tx, PA and H2O direct the formation of titanium phosphate free P-Ti3C2-MW, whereas the conventional heating fails to do so and mainly produces phosphates (P-Ti3C2-An). The best titanium phosphate free P-Ti3C2-MW electrode exhibits a high volumetric capacitance of 1702 F cm(-3) at 1 A g(-1), a capacitance retention of 82% on moving from 1 A g(-1) to 2.5 A g(-1) and a capacitance retention of 91% after 10 k cycles at 5 A g(-1) by enabling improved pseudocapacitance through an enlarged interlayer spacing of 1.18 nm, which facilitates the intercalation of ions, abundance of P-containing redox active sites, optimized electronic conductivity, and an improved surface area. Furthermore, a parallel-type flexible symmetric supercapacitor made of the titanium phosphate free P-Ti3C2-MW electrode has been able to produce a maximum volumetric capacitance of 1357 F cm(-3) with excellent energy and power densities of 41.7 W h L-1 and 712.5 W L-1, respectively. This work has enormous potential to generate further interest towards the development of titanium phosphate free P-Ti3C2 based various composites suitable for energy generation, catalysis, and energy storage
The Synergistic Effects among Crystal Orientations, Creep Parameters, Local Strain, Macro-Microdeformation, and Polycrystals' Hardness of Boron Alloyed P91 Steels
No full textThis article induces proficient microstructure--creep reciprocity by electron backscatter diffraction (EBSD) and impression creep measurements (ICM). The article has further contributed to understanding the synergistic effects of boron in extenuating microstructural degradation. Herein, 22 and 100 ppm boron alloyed P91 steels (P91 and P91B steels, respectively) are subjected to ICM, assessing stress exponent (n), threshold stress (sigma(Th)), effective activation volume (V-eff), and activation energy. Base metal and narrowed crept realm of each steel are measured by employing EBSD. ICM results are correlated with crystal orientations and 1) strain accumulation, 2) macroscopic and 3) microscopic deformation resistance, and 4) hardness of grain in polycrystals by calculating kernel average misorientation (KAM), elastic stiffness, grain reference orientation deviation (GROD), and Taylor factor (M) within microstructure before and after ICM. Measurements of P91B steel show a small value of n and V-eff and a high value of sigma(Th) and activation energy as regards P91 steel. Lower KAM and stiffness before and after creep, higher GROD in base metal, and lower GROD in the crept realm in P91B steel as regards P91 steel corroborate microstructural homogeneity. M indicates both steels are hard before creep, while ICM moderates hardness. Finally, this study reveals synergistic effects of crystal orientations, KAM, stiffness, GROD, M, and creep
Evaluation of microstructure and mechanical properties of M-SIMA processed Al-7Si alloy
No full textIn this research article, the effect of the strain-induced melt activation (SIMA) process on the microstructure and mechanical properties of the Al-7Si alloy has been investigated. The morphology of alpha-Al grains is changed from dendritic to fine spherical and flaky type eutectic Si to a fine fibrous eutectic Si after the modified strain-induced melt activation (M-SIMA) process. The intermetallic compounds are refined and distributed uniformly throughout the matrix after the M-SIMA process. The mechanical properties have been improved due to fine spherical grain formation with refined eutectic Si. A high tensile strength (UTS: 204 MPa) with a remarkable improvement in ductility (El: 30%) is achieved after the M-SIMA process at 585 degrees C for 30 min in comparison to the as-cast Al-7Si alloy (UTS: 117 MPa, El: 16%)
Influence of nickel-based buttering material on welded joint between SA508 low alloy steel and 304LN stainless steel
No full textABS T R A C T Dissimilar metal welded joints were fabricated between SA508 low alloy and 304LN stainless steel using IN82, IN182, and IN152 as buttering alloys. In-situ tensile testing of the welds demonstrated that the crack initiation and propagation were away from the fusion boundary between low alloy steel and buttering material. The heterogeneities like clustered lath martensite with high dislocation density, Type-I boundary, and Type-II boundary near the interface have a meager role in influencing the tensile properties of the welds. On the con-trary, grain structure and second phase distribution in re-solidified buttering alloy played a dominant role in determining the tensile properties of welds. This understanding may pave the way to modify the welding pa-rameters, select appropriate welding consumables, and explore the failure-prone location for such kind of transition joints
Recycling of plastic wastes generated from COVID-19: A comprehensive illustration of type and properties of plastics with remedial options
No full textPlastic has contributed enormously to the healthcare sector and towards public health safety during the COVID-19 pandemic. With the frequent usage of plastic-based personal protective equipment (PPEs) (including face masks, gloves, protective body suits, aprons, gowns, face shields, surgical masks, and goggles), by frontline health workers, there has been a tremendous increase in their manufacture and distribution. Different types of plastic polymers are used in the manufacture of this equipment, depending upon their usage. However, since a majority of these plastics are still single-use plastics (SUP), they are not at all eco-friendly and end up generating large quantities of plastic waste. The overview presents the various available and practiced methods in vogue for disposal cum treatment of these highly contaminated plastic wastes. Among the current methods of plastic waste disposal, incineration and land filling are the most common ones, but both these methods have their negative impacts on the environment. Alongside, numerous methods that can be used to sterilize them before any treatment have been discussed. There are several new sorting technologies, to help produce purer polymers that can be made to undergo thermal or chemical treatments. Microbial degradation is one such novel method that is under the spotlight currently and being studied extensively, because of its ecological advantages, cost-effectiveness, ease of use, and maintenance. In addition to the deliberations on the methods, strategies have been enumerated for combination of different methods, vis-a-vis studying the life cycle assessment towards a more circular economy in handling this menace to protect mankind
An innovative approach to replace bentonite in hematite ore pelletizing with organic binder
No full textThere is a continuous endeavor to replace bentonite with any other suitable inorganic or organic binders. Organic binders generally burn at around 300-350 degrees C and lose their binding property and cause crumbling in most cases. This study aimed to develop a process to use a suitable organic binder for the development of blast furnace quality pellets using some additives which can overcome the strength loss of pellets during induration. The wastes generated from pulp industries viz. Ca-lignosulphonate (Ca-LS) and Na-lignosulphonate (Na-LS) have been used as binders in hematite ore pellets. To alleviate the strength loss at 300-350 degrees C, lower iron oxide (FeO and Fe3O4) containing materials viz. Linz-Donawitz (LD) sludge and mill scale have been added. FeO and Fe3O4 in these materials will be oxidized at the mild oxidizing atmosphere of the induration strand and initiate diffusion bonding at around 300 degrees C. Therefore, the strength loss due to burning will be compensated by the strength gain due to diffusion bonding. From the experimental study, it has been found that Ca-LS is a better binder than Na-LS and LD-sludge (LDS) is a better additive than mill scale. A combination of 0.4% Ca-LS with 5% LDS addition can prevent strength deterioration at 300-350 degrees C during drying and gives a good-quality pellet in terms of strength, thermal shock resistance, reducibility, reduction degradation, and swelling index, which is comparable with bentonite added pellet. Thus, 04% Ca-LS with 5% LDS shows its good application potential to replace bentonite in hematite ore pelletizing