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Mechanical-load and temperature-engendered degradation of α-CsPbI3: reactive molecular dynamics simulation
No full textInorganic halide perovskite materials are widely used to make efficient solar cells; however, they have a number of stability issues. Furthermore, due to the inadequate spatiotemporal resolution in experimental tests, the impact of mechanical-load and temperature-induced stresses on the degradation mechanism of halide perovskite materials is poorly understood. Here, we investigate the effect of mechanical and temperature-induced stresses on the degradation of the cubic (α) perovskite CsPbI3 using reactive molecular dynamics. As per the detailed investigation, major structural degradation of α-CsPbI3 was observed at around a temperature of T = 850 K. As a result, we evaluated the structural stability and subsequent relaxation over a wide range of temperatures (T = 300 K to 800 K) and external loads (Fz = 0.007 pN to 35 pN) applied along the z-axis. The number of dissociating bonds (ξ) in the structure is calculated to be in the following order at Fz = 1.74 pN and T = 300 K: ξ(Pb—I,Pb–Pb) > ξ(Cs–Cs,I–I,Cs–Pb) > ξ(Cs–I). Furthermore, the ξ value of these bonds is found to be in inverse order with temperature. Moreover, it shows a saw-tooth or stick-slip pattern during bond dissociation at T = 300 K and low pulling force (<0.07 pN). It is also observed that the impact of applied force along the z-axis differs from that along the x-axis. We also investigated the bond dissociation and formation of all connected bonds over a wide range of applied forces and temperatures, as well as the subsequent relaxation process, to better understand the feasibility of restoring the perovskite structure of degraded products. The data show that, during the relaxation of the applied force and at high temperatures, the dissociated atoms of the structure aggregate and the degraded products are unable to reform the perovskite structure. We anticipate that our findings will help researchers better grasp the stability of perovskite materials under external-load and temperature-driven stresses
Microstructural Phase Detection in Steel Components by Magnetic NDE Sensor
No full textSteel is the most widely used material in structural components due to its superior strength, ductility, and corrosion properties both at room temperature and
elevated temperatures. The microstructural phase detection by NDE techniques is advantageous for the identification of any structural damage in steel structures and components so as to avoid any catastrophic failure. With this viewpoint, a magnetic NDE sensor, MagStar, is developed by CSIR-NML in collaboration with M/s, Technofour, Pune (India). The sensing head of this device is placed in contact with steel
components and important soft magnetic parameters like coercivity and Barkhausen voltage are measured. Two important steels, interstitial free (IF) and rail steels, are chosen for this research and different annealing treatment is done to generate different microstructural phases. The annealing treatment generates strain-free recrystallized microstructure in cold rolled IF steel and decarburized ferrite layer in rail steel. These structural changes are related to increasing magnetic softness in IF and rail steel, monitored by MagStar. Therefore, the electromagnetic NDE sensor is found a potential tool for monitoring microstructural phases of steel during its processing and service exposure as the components
Structure-Dependent Corrosion Behavior of Electrodeposited Zn Coating
No full textIn the present work, zinc (Zn) coating was developed on an interstitial-free (IF) steel from Zn sulfate bath using direct current (DC) and pulse current (PC) electrodeposition techniques at different current densities of 10, 30, and 60 mA/cm(2). The x-ray diffraction (XRD) analysis of the coatings reveals that the higher atomically dense (0002) crystal plane of the pure Zn in the PC deposits is pronounced as compared to the DC deposits. The scanning electron microscopic (SEM) study displays finer and compact morphology of the PC deposits as compared to the DC deposits. The electrodeposits change from coarser to finer morphology with an increase in current density in both the electrodeposition techniques. All the PC deposits show a higher water contact angle (WCA) as compared to the DC deposits at each applied current density. The finer and compact coating morphology, higher WCA values with the dominance of a higher atomically dense (0002) crystal plane as well as the higher fraction of simonkolleite phase lead to the higher corrosion resistance of the PC deposits than the DC deposits
Enhancing the properties of Al-Ni added medium Mn steel by tailoring B2-NiAl precipitates through aging treatment
No full textIn the present work, the effect of aging treatment and the role of precipitates in improving the strength-ductility combination of intercritically annealed Fe-8Mn-4Al-3.5Ni-0.6Si-0.2C (wt.%) medium Mn steel has been studied. The steel has been intercritically annealed at 750 degrees C for 1 h and subjected to two different aging treatments, one-stage aging treatment at 500 degrees C for 3 h, and two-stage aging comprising first stage at 650 degrees C for 3 h followed by water quenching and second stage at 500 degrees C for 3 h. The microstructure, precipitates characteristics, mechanical properties and deformation behavior of the aged samples have been investigated. It was observed that after one-stage and two-stage aging treatment, the strength-ductility product of the steel improved significantly. The one-stage aging led to the formation of nano-sized NiAl precipitates in both ferrite and austenite, which resulted in an increment of yield strength (YS) by 300 MPa, with no notable decrease in ductility, as compared to the inter critically annealed sample. The two-stage aging led to phase-selective precipitation of NiAl of varying sizes in ferrite and austenite during the first and second stages of aging respectively. A combination of TRIP-TWIP effect and precipitation strengthening by the NiAl in austenite phase was observed in the two-stage aged sample, which led to sustained three-stage work-hardening during deformation resulting in improved elongation and strength-ductility combination
Role of phosphorus as micro alloying element and its effect on corrosion characteristics of steel rebars in concrete environment
No full textThis communication reports the effect of phosphorus (P) added in micro concentration range in steel on kinetics, mechanism and growth of passive film in contact of chloride contaminated concrete. Electrochemical impedance spectroscopy, direct-current polarization, mass loss and Raman spectroscopic techniques were used to arrive at the findings. The results showed that an intentional addition of P in steel (0.064%) makes it more prone to uniform and localized corrosion (about 1.1 and 1.7 times) than the steel having low phosphorus (< 0.016%, present as tramp element) exposed under wet/dry conditions in simulated pore solution added with chloride and in the absence of this ion. A similar effect is also noted for the rebars embedded in mortars. Identification of corrosion products formed on steel rebars surface by Raman spectroscopy reveals thermodynamically stable maghemite and goethite phases on the surface of low P content steel. Unstable phase of lepidocrocite is recorded on the surface of higher phosphorus steel rebars. The findings are discussed with experimental evidence and taking clues from the published literature to arrive at plausible mechanism for this behaviour
The Influence of Arc Welding Process on the Mechanical and Microstructural Characteristics of Low Carbon Steel in a Corrosive Environment
No full textThe study is fundamentally geared toward the investigation of the influence of Manual Metal Arc (MMA) welding on the mechanical and microstructural properties of low carbon steel immersed in a 0.5 M nitric acid environment having a pH of 0.3. The corrosion and mechanical behavior of the substrates are investigated prior to and after 336 h of immersion in the test environment. The outcome of the experiment shows that the structural integrity of the immersed substrates is affected due to corrosion in the test environment. Prior to immersion, the bending resistance is seen to decrease at the welded joints relative to the blank sample and then decrease further after immersion in the test solution respectively as 3.95, 3.53, and 4.21KN. Similarly, the tensile strength of the immersed substrate decreases as compared to the unexposed and blank samples; exposed to test environment (30.60%), welded unexposed to test environment (33.25%) and for the control sample (36.33%). Furthermore, the hardness value is observed to be higher at the heat-affected zone (HAZ) of the test substrate than at the weldment and parent metal, respectively, as 11.3, 17.7, and 15.7HV. Optical micrographs prior to and after immersion have evidently revealed that heat input during welding has caused recrystallization leading to coarser grains at the HAZ
Recovery of valuable metals from cathodic active material of spent lithium-ion batteries: Leaching and kinetic aspects
No full textThis work is focussed on the processing of cathodic active material of spent lithium ion batteries (LIBs) to ensure resource recovery and minimize environmental degradation. The sulfuric acid leaching of metals was carried out for the recovery of all the valuable metals including nickel and manganese along with the frequently targeted metals like lithium and cobalt. The process parameters such as acid concentration, pulp density, time and temperature for the leaching of metals from the cathode powder containing 35.8% Co, 6.5% Li, 11.6% Mn and 10.06% Ni, were optimized. Results show the optimized leach recovery of 93.4% Li, 66.2% Co, 96.3% Ni and 50.2% Mn when the material was leached in 1 M H2SO4 at 368 K and 50 g/L pulp density for 240 min. The need of a reductant for improved recovery of cobalt and manganese has been explained by the thermodynamic analysis (Eh–pH diagram) for these metals. Leaching of the valuable metals was found to follow the logarithmic rate law controlled by surface layer diffusion of the lixiviant reacting with the particles. The mode of leaching of the metals from the spent LIBs was further examined by chemical analysis of the samples at various stage of processing which was further corroborated by characterizing the untreated sample and the leach residues by XRD phase identification and the SEM-EDS studies
Beneficiation of lithium bearing pegmatite rock: a review
No full textThe need for lithium in energy storage systems has risen dramatically due to the development of
renewable energy technology, portable devices, and electric cars. The current review focuses on the
existing worldwide resources of lithium ore, along with the production, demand, and mineralogy of
lithium-bearing minerals, in addition to lithium recovery from hard pegmatite ore using different beneficiation
techniques. Lithium ore is beneficiated using various methods, including magnetic separation,
gravity concentration, electrostatic separation, and flotation to separate gangue minerals. Flotation is the
most frequently utilized beneficiation technique. It is found that gravity concentration and flotation are
the main beneficiation methods used in many plants around the world. In flotation, reagent chemistry,
surface properties, and water quality were critical in spodumene’s efficient recovery. A summary of several
reagent regimes, surface properties, flotation conditions, and prospective future studies for technical
viability are provided. The current review paper also discusses the beneficiation flowsheet widely used to
recover spodumene, lepidolite, and petalite from pegmatite ore. Also, it is tried to discuss the key future
research areas along with the cost economics aspect of processing such ore deposits to recover lithium
Recovery of Nickel from Waste Printed Circuit Boards of Personal Computers
Get PDFPresent study reports, the application-oriented process for the recovery of nickel from printed circuit boards (PCBs) of scrap personal computers. The PCBs were initially depopulated, crushed, pulverized, and beneficiated to get the metallic concentrate. The concentrate was further processed by hydrometallurgical leaching and solvent extraction processes to extract nickel and copper. At first,
leaching studies were carried out in sulphuric acid at different process parameters such as acid concentration, reaction time, temperature, etc., to dissolve the metals. Results show that 99% of Ni and Cu was leached in 20% H SO at 75°C for 2 h maintaining the pulp density of 100 g/L in the presence of 20% H O . The obtained leach liquor was further processed by solvent extraction technique to separate the Cu and Ni. It was found that 99% Cu and Ni were selectively extracted with LIX-984 N at pH: ±2.5 and ±4.5, respectively. Electrolysis, evaporation and crystallization processes could be used to obtain the pure metal and its salt from the pure metallic solutions
Investigation of non-classical creep behavior of Inconel 617 alloy at 700 degrees C and 800 degrees C through interrupted tests and microstructural characterizations
No full textThe 'non-classical creep behavior' of the Inconel 617 alloy consisting of the miniscule primary and secondary creep regimes followed by a prolonged tertiary creep regime, has been investigated through interrupted tests at 700 degrees C/275 MPa and 800 degrees C/95 MPa, having nearly similar time to rupture (-3500 h) to understand the role of microstructural evolution. A steady state tertiary creep region present at 800 degrees C/95 MPa, is found to be absent at 700 degrees C/275 MPa. The microstructural changes including formation of gamma' and fine secondary carbide precipitates, and twin boundary generation observed on interrupting the creep tests at both the aforementioned conditions after varying durations, have been investigated using optical, scanning and transmission electron microscopy, electron back scattered diffraction (EBSD) and thermal analysis. The formation of ample fine gamma' precipitates along with the fine secondary carbides in the samples subjected to creep tests at 700 degrees C with interruptions after varying fractions of time to rupture lead to increase in hardness, which is found to be lower for similar tests at 800 degrees C due to the absence of gamma' precipitates. Moreover, the EBSD analysis has confirmed a higher length fraction ratio of twin boundary (TB) to high angle grain boundary (HAGB) in the samples exposed to the steady state tertiary creep regime (almost 95% of total rupture time) at 800 degrees C. The increased TB to HAGB length fraction ratio is responsible for improving the creep resistance by delaying the damage accumulation, as the TBs are typical coincident site lattice boundaries with lower energy and greater packing density