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Influence of rare earth metals on inclusion modification of dual phase steel: Influence des métaux de terres rares sur la modification des inclusions de l'acier biphasé
No full textInclusions are very critical in advanced high-strength steels as they are used in automobile and aerospace industries in which modification of inclusions is required. In this investigation, Rare Earth Metals (REM) have been used to control and modify the inclusions in the steel. With the addition of REMs, the total sulphur content present in the steel has been reduced by 22%. An inclusion study has been performed using the inclusion classifier and ISO-4967 method. Total inclusions and the number of inclusions at higher indexes (severity) are reduced by adding REM. The chemistry of the modified inclusions, such as oxides, sulphides and oxysulphides of REM, is compatible with the steel matrix and does not have harmful effects. With the addition of REM, the global cleanliness index value at 1.5, 2, 2.5 and 3 indexes are decreased. This may be attributed to the REM breaking down the stringers. Whereas value has been increased at 0.5 and 1 indexes after the addition of RE metals, inclusions sizes are reduced, which is not harmful to the properties of the steel
The utilization of agricultural and industrial waste in the synthesis of AA7075-based novel lightweight composite
No full textFly ash (FA) and coconut shell ash (CSA) are solid byproducts of industrial and agricultural waste, respectively, that are produced in enormous amounts around the world. It is considered to be a contaminant in the environment. Because of the negative impacts on the environment, research on the use of FA and CSA is being undertaken all over the world. The current study focuses on the use of FA and CSA as reinforcement in an AA7075 alloy matrix through two-step stir casting. The present study also reported on the characteristics of newly developed novel composites and their environmental effects using leaching tests. The inclusion of ceramic particles can enhance the microstructure, mechanical, and corrosion characteristics of AA7075 alloys. Optical and scanning electron microscopes were used to evaluate the homogenous distribution of FA and CSA particles in the matrix. Contrasting with the homogeneous alloy, the hybrid composite, composed of 5 wt% FA and 5 wt% CSA, exhibited a remarkable surge of 27% in maximum hardness and a 19% increase in tensile strength. To explore the corrosion resistance of these newly created composites, polarization tests, and AC impedance spectra were employed. Immersing the meticulously crafted specimens in a 3.5% sodium chloride solution, the corrosion assessment revealed that the composite with 5 wt% FA and 5 wt% CSA outperformed the traditional monolithic AA7075 alloy in terms of corrosion resistance
A Clean Process for the Recovery of Potash Fertilizer from Glauconitic Rock via Hydrogen Gas Pre-treatment and Mild Acid Leaching
No full textPotassium (K) is an essential macronutrient for the healthy growth and development of crops but their conventional resources are only limited to a few countries. Deficiency of potash fertilizer in soil is a widespread problem for countries with no such potash deposits to meet the present as well as future food demands. In view of this, the present work investigates a novel interdisciplinary approach to the recovery of potash fertilizer from widely available glauconitic rocks. The rock sample containing similar to 6-8% K2O can be considered a potential alternative source of K-fertilizer. The characterization study revealed that the quartz, glauconite and K-feldspar are the major mineral phases, and the glauconite occurs in the form of ovoidal-shaped pellets. As potassium is trapped between the di-octahedral T-O-T stable structure of glauconite, a combined process involving hydrogen gas reduction followed by mild hydrochloric acid leaching was developed to enhance the effective recovery of potassium. More than 99% of potassium dissolution was achieved with 20% (v/v) hydrochloric acid leaching at 80 degrees C for the sample reduced at 500 degrees C in the presence of 20 mL/min of H-2 gas flow rate for 2 h. The leach liquor was further treated to recover potassium as muriate of potash (MOP)
Coarsening Behaviour of γ′ Precipitates in High Fe Containing Ni-Fe-Cr-Based Medium Entropy Alloy
No full textPresent work evaluates the coarsening kinetics of gamma ' precipitates in gamma-gamma '-based microstructure of a high Fe-containing low-density low-cost Ni-29.8Fe-11.1Cr-3.7Al (wt pct) medium entropy alloy. The experimentally estimated mean size of the gamma precipitates, during isothermal ageing of the alloy at 600 degrees C for the varying duration, agrees well with the theoretical prediction by considering interfacial energy of 10 mJ/m(2). This investigation suggests the sluggish coarsening kinetics with the diffusion of Cr across the gamma-gamma interface as the rate-controlling factor
Mini-Review on Organic Electrode Materials: Recent Breakthroughs and Advancement in Metal Ion Batteries
No full textRedox-active organic materials/composites/polymers for next-generation energy storage systems have attracted significant attention for developing cost-efficient, lightweight, flexible, and sustainable batteries. Organic electrode materials (OEMs) can provide several advantages over traditional inorganic ones, such as increased energy density, improved cycle life, tunable energy storage and voltage output, and structural diversity. Herein, an in-depth knowledge of OEMs developed from carbonyl and conducting polymers is highlighted. The challenges and latest scientific strategies to build better organic batteries like covalent organic frameworks (COFs), donor-acceptor, and all acceptor-type material-based electrodes, modified electrolytes, organic-inorganic hybrids electrolytes, ceramic-type electrolytes, COF-based electrolytes, and organic liquid electrodes are highlighted. This Review also covers a brief overview of the present electrolytes and the recent advances in the field of electrolytes like organic-inorganic hybrids, ceramic-type electrolytes, and COFs-based electrolytes and their improvement directions
Characterization of sputter-deposited hydrophobic chromium doped nickel aluminide coatings for mechanical and high-temperature oxidation-resistant applications
No full textNi3Al and Cr-Ni3Al films were deposited on Inconel-718 using the DC magnetron sputtering at a substrate temperature of 400 degrees C. The evolution of phase, microstructure, surface topography, and mechanical properties of the deposited films have been characterized using XRD, FESEM, AFM, and nanoindentation, respectively. The results of nanoindentation showed that the hardness, modulus, and adhesive strength of the coatings increased with increase in Cr concentration in the host Ni3Al matrix. The maximum hardness and modulus of 10.62 and 150.42 GPa respectively are shown by 5.7 at% of Cr-Ni3Al films. The cyclic oxidation tests were performed at elevated temperatures of 900 degrees C, 1000 degrees C, and 1100 degrees C in the open-air environment to study the actual oxidation attack. The results of the test showed that the rate of oxidation in Ni3Al and Cr-Ni3Al films was low as compared to the uncoated substrate. Ni3Al film doped with 5.7 at% of Cr-Ni3Al has resulted in providing better protection to the substrate against oxidation attacks. The surface morphology and elemental composition of the oxidized samples were investigated using FESEM and EDS to elucidate the surface scale analysis and mechanism of oxidation due to the formation of different oxide layers
Investigating the influence of post-deposition heat treatment (PDHT) on the characteristic changes in wire arc additively manufactured 410 martensitic stainless steel thin-wall structure
No full textObtaining the desired material characteristics of an as-deposited martensitic stainless steel (MSS) structure fabricated by wire arc additive manufacturing (WAAM) is challenging due to several factors like inhomogeneity, precipitation, phase transition, etc. This investigation elucidates the impact of post-deposition heat treatment (PDHT) on the microstructural and mechanical properties of the WAAM-processed 410 MSS thin-wall structure and compares it with the as-deposited 410 thin-wall structure. The MSS thin-wall structure consists of retained austenite (gamma), delta (delta) ferrite, martensite laths and Cr-rich M23C6 type carbide. The M23C6 volume fraction increases by up to 18 %, and the gamma-phase fraction reduces by up to 40 % by applying PDHT. The PDHT process significantly changed the texture from {110} to {001}. The PDHT process increases the dislocation density (1.974 x 10(-15) m(-2)) than the as-deposited condition (0.924 x 10(-15) m(-2)). The total low energy boundary (LAGB+CSL) contribution of the as-deposited sample is 19.5 %, whereas the PDHT sample demonstrated a higher fraction of low energy boundaries of 32.4 %. The PDHT sample showed a much smaller distribution of grains with an average grain size of 11 mu m compared to the as-deposited condition. The overall hardness increases from 468 HV to 487 HV after PDHT compared to the as-deposited condition with lower inhomogeneity across the build direction. The mean 0.2 % proof stress, ultimate tensile stress, and elongation of the PDHT sample increased by 17 %, 5 %, and 60 %, respectively, compared to the as-deposited sample
Gd Added Mg Alloy for Biodegradable Implant Applications
No full textMicrostructure, mechanical, in vitro and in vivo behavior of extruded Mg alloys with varying Zn/Gd ratios, Mg-2Gd-2Zn-0.5Zr (Zn/Gd = 1), Mg-2Gd-6Zn-0.5Zr (Zn/Gd = 3), and Mg-10Gd-1Zn-0.5Zr (Zn/Gd = 0.1) were investigated. The results revealed that the major secondary phases such as W (Mg3Zn3Gd2), (Mg,Zn)3Gd, LPSO (Long period stacking order) and I (Mg3Zn6Gd) phase in alloys depended on Zn/Gd ratio. These second phases influenced the mechanical as well as biological characteristics of the alloys. Among studied alloys, Mg-10Gd-1Zn-0.5Zr alloy showed the highest yield strength and tensile strength of 270 (+/- 9.29) and 330 MPa (+/- 15.8), respectively, with a reasonably good elongation of 12% (+/- 2.36). The presence of Gd2O3 in the degradation film of Mg-10Gd-1Zn-0.5Zr enhanced the resistance offered by the film, which resulted in its lowest biodegradation, better viability, and cell proliferation under in vitro condition. The short term (subcutaneous implantation in rats for 1 month) in vivo studies showed that the alloy Mg-10Gd-1Zn-0.5Zr degraded at a rate of 0.35 mm/y (+/- 0.02) and did not induce any toxicity to the vital organs
Tailoring rGO-Cu-Cu2O as a three-dimensional catalytic system in boosting of methanol electro-oxidation reaction
No full textTailoring a reduced graphene oxide-Cu-Cu2O (rGO-Cu-Cu2O) as a three-dimensional (3D) integrated catalytic system via an in-situ potential-controlled electrodeposition approach is a feasible pathway to boost methanol oxidation reaction (MOR) for direct methanol fuel cell. The enhancement in catalytic functionality and performances is due to the synergistic interaction between the in-situ electroreduced graphene oxide (rGO) and copper metal ions over it. The sequential and synergistic effect of the co-deposition potential, optimized time, and probable corrosion-promotion effect (formation of a galvanic cell between rGO and copper due to entrapped dissolved oxygen) is believed to be responsible for the structural growth of as-developed 3D catalytic systems. The MOR results suggest that the composite material deposited at the higher cathodic deposition potential (-1.2 V vs SCE), i.e., rGO-Cu (c) featured the remarkable lowest onset oxidation potential (i.e., +0.37 V), peak potential (i.e., +0.73 V), peak current density (135.76 mAcm(-2)), potentiostatic durability at +0.6 V after 3.5 h (similar to 65.85 mAcm(-2)) and outstanding cyclic stability (similar to 97.7 % current retention after 500 cycles), which is superior to the other modified composite electrodes. The enhanced performances are due to the effective dissociative adsorption of methanol from the available active catalytic site's and the presence of hydroxyl groups which has probably improved the oxidation of adsorbed intermediates from the surface. Further, Fourier- transform infrared (FT-IR) experiments revealed that formate as an active intermediate is being generated on all three rGO-Cu-Cu2O modified electrodes and follows the non-CO reaction pathway for direct oxidation of methanol
Kinetics and mechanism of gallic acid as an ecofriendly corrosion inhibitor for steel rebars in mortar
No full textChloride-induced corrosion of steel rebars embedded in mortar was effectively controlled by blending of gallic acid in wet mixture. Mixing of optimized concentration of gallic acid (GA) inhibitor (0.125%) in mortars considerably increased the charge transfer resistance of embedded rebars (80.11 Ω cm2) in comparison to that noted for the control mortars (3.36 Ω cm2) after 37 cycles of wet/dry treatments. The corrosion inhibition efficiency after this cycle of exposure was of the order of 95%. The studied inhibitor also improved the workability (% flow of wet mix) from 25% for control to 43% at its optimum dosing. It is suggested that GA transforms into negatively charged gallate anions in an alkaline-pore solution of concrete and electrostatically attracted to the positively charged calcium ions, forming a complex with a partial positive charge. This complex interacts with the negatively charged maghemite film formed on rebar surface and forms a protective film of FeO− Ca++– GA anion, isolating it from the aggressive electrolyte. The experimental results showed that Ca++ ion of the concrete had a strong synergistic effect in boosting the inhibitive performance of the GA. The inhibition efficiency increased from 84.1% in the presence of GA only to 97.9% for the mixture of GA and calcium ions