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On Fabrication of Inconel 718 Slab by Wire Arc Additive Manufacturing: Study of Built Microstructure and Mechanical Properties
No full textA slab of dimension (152 × 25 × 18) mm3 is successfully fabricated through Cold Metal Transfer + Metal Inert Gas-based Wire Arc Additive Manufacturing (WAAM). 4.3 kg/h deposition rate is achieved. WAAMed Inconel 718 exhibits dendritic microstructure which grows along the build direction. In the solid solution matrix of Ni–Cr–Fe, Laves phase, Nb-rich MC-type carbides and delta (δ) phases are detected. The average tensile strength along horizontal direction is obtained as ~ 824 MPa. Location-specific microstructure evolution causes significant extent of property anisotropy predominantly along the build
direction. The horizontal tensile specimen extracted from the bottom region of the slab exhibits the highest tensile strength (UTS), while the lowest tensile strength is obtained for the specimen extracted from the middle zone of the fabricated slab. Temperature data as recorded by the thermocouples are utilized to understand the complex heat interaction phenomena during WAAM process. Laves phase is completely dissolved during homogenization treatment thus microstructure of aged specimen only consists of strengthening phase, i.e., γ (Ni3Nb) and Nb-rich MC carbides
Detrapping of the carriers from shallow states in a highly responsive, fast, broadband (UV-vis-NIR), self-powered SnSe/Si photodetector with asymmetric metal electrodes
No full textTin-selenide (SnSe), as an eco-friendly and low-cost semiconductor material, has exhibited great potential to detect weak signals and has wide applications in imaging and optical communication. Here, self-powered SnSe-based photodetectors (PDs) via asymmetric metal electrodes are fabricated to achieve weak light detection for broad spectral ranges from 385 to 1064 nm with high response and
fast response (on/off) times. The results show that the SnSe PDs are highly sensitive in a wide spectral range from UV to NIR, even at 0 V applied bias. They exhibit an excellent responsivity (R) of 54.7 mA W1 and detectivity (D) of 7.87 1010 Jones, corresponding to rise/decay times of 26/47 ms
under 1064 nm illumination at 0 V applied bias, respectively. With increasing the bias, detrapping of the
carriers can be seen from the shallow trap states arising from the secondary phases in the SnSe. The results suggest that SnSe-based PDs obtained from the evaporation method have great potential in developing low-cost, next generation, and self-powered optoelectronics
Strength and toughness balance in 7 %Ni steel by formation epsilon martensite, retained austenite and Low matrix strain
No full textIn the current study, 7 wt.%Ni alloy steel was prepared, hot rolled, and heat treated according to popular quenching, lamellarization, and tempering treatments. The inter-critical lamellarization temperature was varied and the microstructure-property correlation was evaluated in each stage of heat treatment to understand the metallurgical aspects. Optical and detailed electron microscopic techniques were used to characterize and quantify the microstructures. Mechanical responses under uniaxial and impact loading were also recorded for all the studied samples. Tempered martensite with blocky and lamellar morphology, along with retained austenite and ε-martensite, were observed in the microstructures after the above-mentioned heat treatment. The lamellarization at 700 ℃ leads to a more uniform distribution of alloying elements and, therefore, promotes the formation of finer retained austenite with uniform distribution, compared to 650 ◦C lamellarization temperature. The presence of lower matrix strain and uniformly distributed fine retained austenite provides the highest toughness with moderate strength in the 700 ◦C samples. ε-martensite is expected to provide the necessary strength to balance the softening arising due to tempered martensite and retained austenite. Moreover, the
uniformly distributed fine and filmy-shaped retained austenite provides thermal stability, and arrests crack
propagation, enhancing toughness. The XRD results after impact toughness show that the γ-ε-α transformation takes place during the -196 ◦C temperature, and during impact toughness testing, ε-α transformations also provide the toughening in the Ni-700+590 sample
Evaluation of Different Fly Ash-Blast Furnace Slag Formulations for Design of Geopolymers in Radioactivity Disposal Applications
No full textGeopolymers in radioactive waste management have in recent times gained dominance in disposal module acceptance. Here is a comparative study on formulations prepared from industrial wastes to be utilized as radionuclide disposal barriers in near surface disposal facilities (NSDFs). Different tools such as isocalorimetry, compressive strength, chemical durability were utilized for screening the formulations. Water leaching of the samples shows that the release of the ions to the leachant is minimal. Durability studies in acids (H2SO4, HCl and HNO3) show that the samples are mostly acid resistant. X-ray tomography suggests low pore volume change over a period of 2 years. The study concludes that the NSDF requirement of low permeability of water and better chemical durability criterion is met by the optimized geopolymerization formulation
Evaluating porosity formation in gas metal arc directed energy deposition of an aluminium alloy
No full textPorosity formation in gas metal arc directed energy deposition of aluminium alloys is a critical challenge as it affects the structural integrity of build parts. An experimental investigation is reported here to examine the influence of energy input on pore size and area fraction in single- and multi-layer build samples of an aluminium alloy for short-circuiting and pulsed current gas metal arc. The energy input is estimated from real-time current and voltage transients. The porosity distribution in deposited samples is measured using an image segmentation approach. The pulsed current mode yielded 16-22% lower pore area fraction in comparison to short-circuiting mode. For the range of process conditions considered, an increase in energy input reduced pore area fraction significantly
Synergistic effect of benzo triazole with polyethoxylated sorbitan monooleate in inhibiting corrosion of rebars and chloride diffusion through mortars
No full textIt is found that mixture of 1,2,3 benzo triazole (BTAH) with polyethoxylated sorbitan monooleate, a non-ionic surface-active agent (NIS) effectively improves the properties of the cast concrete as well as significantly reduces the chloride induced corrosion of steel reinforced bars, when added in freshly prepared paste of mortar mixture. The addition of this mixture in the cast mortars is noted to reduce the water absorption in comparison to the control mortars cast using identical materials and under similar cast conditions. Electrochemical impedance spectroscopy and polarization studies of the rebars embedded in mortars and exposed in cement slurry have been performed to study the role of synergistic mixture on kinetics and mechanism of corrosion of rebars. The characterisation of corrosion products formed on the surface of rebars was carried out by X-ray diffraction, Scanning electron microscopy and EDX analysis. It is proposed that the synergistic boosting in protection is caused due to the shielding of NIS around anionic BTA-, thus minimizing their electrostatic repulsion. This facilitates the migration of additional ionic BTA towards the double layer which increases their concentration at the corroding interface leading to reduced susceptibility to corrosion
Effect of process parameters and orientation on the tensile and low cycle fatigue properties of low-carbon steel builds manufactured by directed energy deposition-gas metal arc process
No full textDirected energy deposition-gas metal arc (DED-GMA) process has recently gained considerable attention due to its inherent capability to produce large metallic components, with moderate complexity, at substantially high deposition rate compared to other additive manufacturing techniques. The effect of wire feed rate, energy input per unit length and orientation on the tensile and low cycle fatigue behaviour of multi-layer builds of low-carbon steel ER70S-6 is systematically studied in the present work. In addition, a detailed microstructural characterization is also carried out for better understanding of the microstructural evolution during deposition and its influence on the mechanical behaviour of the build. In general, insignificant variation of the tensile properties of DED-GMA specimens at different orientations signifies an overall isotropic behaviour. The vertically oriented samples, printed at highest energy input, show superior fatigue life. The number of cycles to failure, for the vertically oriented samples, at highest wire feed rate of 10 m/min and deposition travel speed of 1 m/min, are found to be around 718, 450 and 366 at strain amplitudes of +/- 0.6, +/- 0.8 and +/- 1.0%, respectively. It is envisaged that the control of energy input by adjusting wire feed rate and deposition travel speed is crucial to improve the tensile and fatigue properties of the build
Zinc-Ion Batteries: Promise and Challenges for Exploring the Post-Lithium Battery Materials
No full textThe current dominance of high-energy-density lithium-ion batteries (LIBs) in the commercial rechargeable battery market is hindering their further development because of concerns over limited lithium resources, high costs, and the instability of organic electrolytes on a large scale. However, rechargeable aqueous zinc-ion batteries (ZIBs) offer a promising alternative to LIBs. They provide eco-friendly and safe energy storage solutions with the potential to reduce manufacturing costs for next-generation battery technologies. Although ZIBs face challenges, such as dendrite formation, lower energy density, and limited cycle life, they are increasingly becoming more cost-competitive and gaining market acceptance. This article explores the potential of ZIBs as a future energy source, emphasizing their advantages and the recent technological progress in utilizing zinc, which is both abundant and inexpensive. We delve into the various mechanisms employed by ZIB electrodes and discuss the latest developments in electrode materials for anodes and cathodes, as well as the essential electrolytes and separator materials required for assembling ZIBs. Consequently, with their cost-effective materials, enhanced safety, and ongoing technological advancements, ZIBs are emerging as a promising solution for reliable and sustainable energy storage
Flow-Assisted Corrosion of API 5L X56 Steel: Effect of Flow Velocity and Dissolved Oxygen
No full textFlow-accelerated corrosion (FAC) is a complex mechanism of material degradation and depends upon the fluid hydrodynamic parameters, material microstructure and compositions, and environmental chemistry. The effect of flow velocity and dissolved oxygen on FAC behavior of API 5L X56 steels in 0.3 M NaCl solution is investigated. Electrochemical and weight loss measurements were taken in a closed-loop corrosion evaluation system at flow velocities of similar to 0.25, 1.0, 1.6, and 2.3 m/s and dissolved oxygen (DO) contents of similar to 50, 500, 1500, 2500, and 4500 ppb. The corrosion rate observed to increase with flow velocity and dissolved oxygen content. The post-corrosion topography and corrosion products were investigated using 3D profilometry, scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), and Raman spectroscopy techniques. The corrosion products mainly contained hematite (alpha-Fe2O3), lepidocrocite (gamma-FeOOH), goethite (alpha-FeOOH), and magnetite ( Fe3O4). The wall shear stress (tau) induced on specimen surface was simulated through CFD approaches and correlated with corrosion resistance of the steel at different flow velocities
Evaluating the carbon footprint of sulphur recovery unit: A comprehensive analysis
No full textDesulphurising of oil-based fuels and industrial gases is a widespread practice. The combustion process in the sulphur recovery unit (SRU) involves the reaction of H2S with oxygen to produce SO2, which is then converted to elemental sulphur through a series of catalytic reactions. Oxygen enrichment is a technique used to enhance the performance and efficiency of the SRU. By introducing a higher concentration of oxygen into the combustion process, the overall combustion reaction can be optimized, resulting in an increased sulphur recovery from sour gas and reduced emissions of sulphur compounds. The present study analyses the gate-to-gate comparative environmental impact of air versus oxygen-enriched air used for combustion to recover 1.0-ton sulphur using GaBi software (8.5.0.79 version). The primary data was collected from the literature. The GaBi Indian extension database is used for the secondary data source. The results are reported using midpoint impact assessment methods CML 2001. The global warming potential for oxygen-enriched SRU is 232 kg CO2 eq. compared to 276 kg CO2 eq. for air-enriched SRU. Similarly, the potential for abiotic depletion (elements + fossil), acidification, eutrophication, human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, photochemical ozone creation and terrestric ecotoxicity are higher for air-based SRU than oxygen-enriched SRU. The analysis concludes that oxygen enrichment technology is a highly effective way to reduce the environmental impact of the SRU