The extent to which solute atoms influence dislocation mobility in Ni-based solid solution strengthened Alloy 690 is investigated in this work using atomistic methods. The formulated equations are then utilized to inform higher length scale simulations. Experiments are also performed to validate the predictions of polycrystalline behavior. The experiments are conducted under dynamic uniaxial compression at different temperatures, and relevant material characterization is done to extract the initial and final grain orientation distributions. Initially, atomistic simulations of dislocation motion are performed by modeling straight screw, mixed and edge dislocation in Alloy 690. Simulations reveal that at low dislocation velocities, solute pinning governs glide wherein an Arrhenius-type dependence on applied shear stress is envisaged. Dislocation velocities increase with temperature in this regime and character dependence of dislocation motion stems from the character dependence of critical athermal stress. Edge dislocations adopt rough profiles and hence, require higher threshold stresses and line lengths to obtain length independent mobilities. At higher speeds, phonon and relativistic regimes are encountered and mobility parameters significantly depend on dislocation character in relativistic regime. The mobility data is then used to inform dislocation dynamics simulations across seven crystallographic orientations to capture ensuing hardening and obtain the constitutive hardening parameters of crystal plasticity. The parameters tend to follow a statistical normal distribution and the mean parameter values are extracted for crystal plasticity simulations. This work shows how atomistics, discrete dislocations, crystal plasticity and experiments can be coupled in a hierarchical manner while retaining sufficient accuracy garnered at the atomic scales of inception.

Through a synergistic use of atomistic simulations, crystal plasticity finite element analyses and experiments, this work sheds light on non-Schmid effects in solid solution strengthened Ni-based Alloy 690. The ensuing tension-compression asymmetry of yield stress is numerically demonstrated first using molecular dynamics simulations on single crystals at room temperature. Investigation of slip systems and associated resolved stresses leads to a single crystal slip initiation criterion that adequately predicts the non-Schmid effects at the inception of plasticity. Theoretical calculations are also performed to analyze the orientation and loading dependent activation of various twin variants in single crystals. In an attempt to develop an atomistically informed crystal plasticity framework, the non-Schmid coefficients (c1-c5) of well-established yield criterion in crystal plasticity are calibrated from molecular dynamics simulations. Moreover, activation energy parameters for character dependent dislocation glide are also evaluated at the atomistic level in order to establish a more robust multiscale framework. Finally, uniaxial tensile and compression experiments at quasi-static strain rates at room temperature validate the predictions of atomistically informed crystal plasticity model on Alloy 690 aggregate.

In this work, laser surface re-melting of Zr-8wt

Bismuthinite (Bi2S3) nanostructures have garnered significant interest due to their appealing photoresponsivity which has positioned them as an attractive choice for energy conversion applications. However, to utilize their full potential, a simple and economically viable method of preparation is highly desirable. Herein, we present the synthesis and characterization including structural elucidation of a new air- and moisture-stable bismuth-pyrimidylthiolate complex. This complex serves as an efficient single-source molecular precursor for the facile preparation of phase-pure Bi2S3 nanostructures. Powder X-ray diffraction (PXRD), Raman spectroscopy, electron dispersive spectroscopy (EDS) and electron microscopy techniques were used to assess the crystal structure, phase purity, elemental composition and morphology of the as-prepared nanostructures. This study also revealed the profound effects of temperature and growth duration on the crystallinity, phase formation and morphology of nanostructures. The optical band gap of the nanostructures was tuned within the range of 1.9-2.3 eV, which is blue shifted with respect to the bulk bandgap and suitable for photovoltaic applications. Liquid junction photo-electrochemical cells fabricated from the as-prepared Bi2S3 nanostructure exhibit efficient photoresponsivity and good photo-stability, which project them as promising candidates for alternative low-cost photon absorber materials.

In the present work, stability of Nb2C and (Nb,Zr)C phases, encountered in the Nb-1Zr-0.1 C alloy, is being assessed under the influence of fast neutron and 250 keV Ne ion irradiation, respectively. Microstructural investigations revealed a reduction in the volume fraction of the Nb2C phase in as-solidified alloy as a function of irradiation dose when irradiated with neutrons to a dose of-0.65 dpa. On the other hand, (Nb,Zr)C phase in the recrystallized alloy was also observed to dissolve during in situ assessment as a function of irradiation dose when irradiated with Ne ions to a dose of-32 dpa. With the help of DFT, SPECTER and SRIM simulations, it is rationalized that out of the various possible mechanisms of dissolution, the dissolution of these carbide phases proceeds through ejection of atoms from the precipitates to the matrix phase. Dissolution of Nb2C phase proceeds through the ejection of carbon atoms from the precipitate to the matrix phase, which is envisaged by segregation of carbon at the grain boundaries in the form of Nb2C phase and nucleation of (Nb,Zr)C precipitates within the matrix phase observed in neutron irradiated specimens. Dissolution of (Nb,Zr)C precipitates, on the other hand, is rationalized in terms of ejection of C/ Zr/Nb atoms from the precipitate to the matrix phase. & COPY; 2023 Elsevier B.V. All rights reserved.

This study explored the effect of pre-corrosion damage on the tribology behavior of the austenitized and the different tempered conditions of 13 wt.% Cr martensitic stainless steel under dry sliding conditions using a “ball on plate” configuration. Corrosion immersion experiments were performed in 5 wt.% HNO3 solution at room temperature for 30 min. The austenitized and the tempered at 300 °C (T300) specimens displayed the attack along the prior austenitic grain boundaries, whereas the specimens tempered at 550 (T550) and 700 °C (T700) showed intergranular plus interlath corrosion and uniform corrosion, respectively. Subjecting this corrosion-damaged specimens to dry sliding revealed non-monotonic friction and wear behavior with tempering temperature. The microstructure and the type of corrosion attack together determined the overall wear performance of the tempered conditions. The specific wear rate (k) decreased in the order kT700 > kT550 > kT300 ~ kaustenitized. The k value of the austenitized and the T300 specimens (~ 32 − 35 × 10−6 mm3/Nm) is observed to be 12 and 15 times lower than the k value of T550 (~ 408 × 10−6 mm3/Nm) and T700 (~ 495 × 10−6 mm3/Nm) specimens, respectively. The reason for the lower k value is due to the continuous, thick (~ 4 μm thickness) Cr-rich tribo-film that formed on the wear track and acted as solid lubricant. The T550 and T700 specimens had a discontinuous Fe-rich tribo-film on the wear tracks; therefore, rubbing in the presence of harder and loose Fe-rich oxides particles led to severe adhesion plus galling in T550 and smearing plus plastic deformation in T700 specimens. It was also found that the wear rate and surface damage are reduced for pre-corroded austenitized and T300 specimens compared to the respective unattacked pristine specimens; however, the opposite effect was observed in T550 and T700 specimens.

In the present work, a new thermo-mechanical processing route with reduced deformation temperature has been developed for Nb-5Mo-1Zr-0.1C (wt%) alloy. For this purpose, the as-cast Nb-5Mo-1Zr-0.1C alloy was processed through two different processing routes: 1) Warm Rolling (WR) and 2) Cold Rolling (CR) routes. In the WR route, the as-cast alloy was deformed by warm rolling (WR) and subsequently re-crystallized by heat treating at 1400 degrees C for 4 h. In the CR route, prior to deformation by cold rolling (CR), the as-cast alloy was heat treated at 1400 degrees C for 16 h. Detailed microstructural characterization of heat treated samples by electron microscopy revealed that Nb2C carbides, which were present in the as-cast micro-structure got dissolved during the heat treatment process and in place excess carbon reprecipitated as (Nb,Zr)C carbides. This change in the carbide phase led to the successful deformation of the heat treated alloy by CR up to 75% of thickness reduction. The CR samples were heat treated at the same temperature of WR samples to get the recrystallized microstructure. The mechanical testing of the recrystallized samples obtained through both the routes (WR & CR) showed similar mechanical properties and it is attributed to nearly identical microstructure consisting of spherical morphology of (Nb,Zr)C carbides in the recrystallized Nb grains. Therefore, the developed low temperature processing route (CR route) can be used as alternative to the WR processing route for bulk scale of fabrication of components of Nb alloy. This study also shows that by addition of 5 wt% Mo in Nb-1Zr-0.1C alloy, the strength of the alloy can be increased to twofold by solid solution strengthening. In addition to the processing, the carbide transformation mechanism in cold rolled route from Nb2C to needle morphology of (Nb,Zr)C and to spherical morphology of (Nb,Zr)C has been studied in detail.(c) 2023 Elsevier B.V. All rights reserved.

Fe3O4 magnetic nanoparticles, synthesized using co-precipitation method, were epoxy functionalized via plasma polymerization of 2,3-epoxypropylmethacrylate (EPMA) precursor. The EPMA-functionalized Fe3O4 nanoparticles (EPMA-f-MN) were employed as templates for facile, one-step covalent immobilization of laccase enzyme at room temperature. Samples were rigorously characterized by FTIR, TGA, SEM, TEM, XRD techniques, while Mössbauer spectroscopy (MöS) and vibrating sample magnetometry (VSM) confirmed the supermagnetic nature of Fe3O4 nanoparticles. Activities of free and immobilized laccase (ImLac) were assayed by spectrophotometrically monitoring the enzymatic reduction of substrate 2,2-azino-bis(3-ethylthiazoline-6-sulfonate) (ABTS) at 420 nm, corresponding to the λmax of ABTS.+. In addition to possessing higher thermal stability and a broader pH tolerance window compared to free laccase, the supermagnetic property of the Fe3O4 renders the ImLac system conveniently recoverable and recyclable. Practical applicability of ImLac towards catalytic degradation of industrial dyes was also ably demonstrated using Acid Blue 193 (AB 193) as a commercially used model textile dye, which belongs to the family of azo dyes. Over 95% degradation of the dye was achieved within a period of 4 hours. ImLac could be used for more than 10 dye degradation cycles with >90 % of retention in enzyme activity.

Tungsten inert gas welding (TIG) has remained a worldwide utilized welding technology in the industry to till date. Activated tungsten inert gas welding (ATIG) is also an advanced variant of TIG to enhance the penetration depth and reduce the width of the weld bead in single-pass compared to traditional TIG welding. The current study focuses on utilizing the Inconel interlayer approach to link dissimilar cold-rolled super duplex and austenitic stainless steels, which are mostly used in the offshore and marine industries. A systematic strategy is used to emphasize the studies conducted after using the ATIG interlayer procedure over the traditional TIG interlayer welding process. The research also studies and compares the microstructure, elemental mapping of the weld interface, phase identification and mechanical properties of dissimilar welded super duplex and austenitic steel samples.

The present study deals with the determination of fracture properties of a cracked Ni3Al-based intermetallic single crystal turbine blade subjected to tensile load. The analysis has been carried out by accounting the effect of microstructure, strain hardening and damage development under monotonic loading. A continuum damage criterion combined with crystal plasticity model incorporating non-Schmid effects was employed to evaluate material damage owing to highly localised deformation. The damage evolution was defined as the function of a microstructure variable. The present coupled model was used to replicate the stress-strain behaviour of Ni3Al single crystals until material softening due to damage after necking. The model parameters were ascertained by a close match of the computed data with the available experimental data. Using the model, damage evolution near crack tip of a cracked Ni3Al turbine blade was assessed for randomly varying secondary orientations, while maintaining primary orientations same as that of along the solidification direction. The analysis helped to calculate the fracture initiation toughness (Ji) of turbine blade for various crystallographic orientations. Combined by damage formulation, analysis was continued to estimate the Ji values for different crack lengths in all the cases of orientation. Finally, triaxiality quotient (q) was computed to characterise the estimated Ji values as a function of crack tip constraints. The approach provides a useful way to analyse orientation dependent fracture behaviour of single crystal components with crack under mechanical loading.

Ni–Mo–Cr–Ti alloys are one of the proposed structural materials for molten salt breeder reactors. In the current work, the evolution of precipitates in the alloy at various stages of thermo-mechanical processing followed by thermal ageing at 750 °C is studied. The microstructure after thermal ageing for various durations shows the presence of ‘MC’-type carbides with different morphologies and compositions. Formation of carbide networks with bulky titanium-rich ‘MC’ carbides of irregular morphology and spherical ‘MC’ around it is observed in the early stages, while fine uniform dispersion of ‘MC’-type needle-like carbides that possess a cube-on-cube orientation relationship with the FCC matrix is observed in the latter stages. High-resolution transmission electron micrograph reveals the presence of misfit dislocations on the semi-coherent interface between the fine needle-like MC carbides and the matrix which is attributed to the lattice parameter mismatch between them.

Facile and selective synthesis of phase pure photo-responsive InSe and In2Se3 nanostructures employing air-stable In[Sepym(Me-4,6)2]3 as a novel molecular precursor.

Copper selenide (Cu1.8Se) and silver selenide (Ag2Se) have garnered unprecedented attention as efficient absorber materials for cost-effective and sustainable solar cells. Phase pure preparation of these exotic materials in a nano-regime is highly desirable. This account outlines a simple and easily scalable pathway to Cu1.8Se and Ag2Se nanocrystals using novel complexes [Cu{2-SeC5H2(Me-4,6)2N}]4 (1), [Ag{2-SeC5H2(Me-4,6)2N}]6 (2) and [Ag{2-SeC5H3(Me-5)N}]6·2C6H5CH3 (3·2C6H5CH3) as single source molecular precursors (SSPs). Structural studies revealed that the Cu and Ag complexes crystallize into tetrameric and hexameric forms, respectively. This observed structural diversity in the complexes has been rationalized via DFT calculations and attributed to metal-metal bond endorsed energetics. The thermolysis at relatively lower temperature in oleylamine of complex 1 afforded cubic berzelianite Cu1.8Se and complexes 2 and 3 produced orthorhombic naumannite Ag2Se nanocrystals. The low temperature synthesis of these nanocrystals seems to be driven by the observed preformed Cu4Se4 and Ag6Se6 core in the complexes which have close resemblance with the bulk structure of the final materials (Cu1.8Se and Ag2Se). The crystal structure, phase purity, morphology, elemental composition and band gap of these nanocrystals were determined from pXRD, electron microscopy (SEM and TEM), EDS and DRS-UV, respectively. The band gap of these nanocrystals lies in the range suitable for solar cell applications. Finally, these nanocrystal-based prototype photo-electrochemical cells exhibit high photoresponsivity and stability under alternating light and dark conditions.

As a part of its clean nuclear energy program, India is developing Fast Breeder nuclear reactor. High level nuclear wastes, which are likely to be produced upon reprocessing of its spent fuel will contain platinum group of elements in concentrations higher than their respective solubility limits within borosilicate melts. Towards this, interaction study of palladium telluride (PdTe) with sodium barium borosilicate base glass and waste glass were carried out. Mostly, spherical PdTe got settled down at the bottom of ceramic crucibles without any compositional exchanges with base glass. However, significant compositional variations took place in case of waste glass. Interaction studies between Alloy 690 and base glasses show development of wide reaction zones (including intergranular attacks within Alloy 690 coupons, formation of Cr2O3 layer and crystallization of needle shaped phases within adjacent glass domains) at the interfaces. In case of waste glass, tiny PdTe beads crystallized at the reaction zone/borosilicate glass interfaces.

This article investigates the deformation behaviour and fracture characteristics of copper single crystals by uniaxial tensile experiments and compares the results with crystal plasticity simulations. Quasi-static tensile tests were carried out to include different stress–strain states by varying the crystal orientation with respect to specimen axis after determining the initial orientation by Electron Backscatter Diffraction. The different ductile modes of failure of single crystals due to shear after loading were examined. Thereafter, by employing the scanning electron microscopy and theoretical slip trace analysis, orientations of slip traces of deformed crystals were determined. Experimental results were then rationalised by performing crystal plasticity finite element simulations, presuming cross-slip and associated dislocation dissociation into partials play an influential role on the orientation dependence of the material. A continuum ductile damage criterion was coupled with plasticity on capturing the slip localisation caused by material softening. Comparison between experimentally measured and numerically obtained stress–strain data, texture evolution and fracture angles were subsequently evaluated. An evaluation has also been made by comparing the identities of active slip modes attained from experiments with that of determined from simulations.

Stibnite Sb2S3 and tetrahedrite Cu12Sb4S13 nanostructures being economical, environmentally benign and having a high absorption coefficient are highly promising materials for energy conversion applications. However, producing these materials especially tetrahedrite in the phase pure form is a challenging task. In this report we present a structurally characterized single source molecular precursor [Sb(4,6-Me2pymS)3] for the facile synthesis of binary Sb2S3 as well as ternary Cu12Sb4S13 in oleylamine (OAm) at a relatively lower temperature. The as-prepared Sb2S3 and Cu12Sb4S13 nanostructures were thoroughly checked for their phase purity, elemental composition and morphology by powder X-ray diffraction (pXRD), electron dispersive spectroscopy (EDS) and electron microscopy techniques. pXRD and EDS studies confirm the formation of phase pure, crystalline orthorhombic Sb2S3 and cubic Cu12Sb4S13. The SEM, TEM and HRTEM images depict the formation of well-defined nanorods and nearly spherical nanocrystals for Sb2S3 and Cu12Sb4S13, respectively. The Sb2S3 nanorods and Cu12Sb4S13 nanocrystals exhibit an optical bandgap of ∼1.88 and 2.07 eV, respectively, which are slightly blue-shifted relative to their bulk bandgap, indicating the quantum confinement effect. Finally, efficient photoresponsivity and good photo-stability were achieved in the as-prepared Sb2S3 and Cu12Sb4S13 nanostructure-based prototype photo-electrochemical cell, which make them promising candidates for alternative low-cost photon absorber materials.

An air and moisture stable Pd(II) complex with a pyridyl based selenoether ligand was synthesized and characterized with microanalysis, UV-Vis and NMR spectroscopy. The molecular structure of the complex was established by single crystal XRD analysis. The complex upon thermolysis in oleyl amine (OAm) at higher temperatures about 270 degrees C afforded Pd17Se15 nanoparticles of average dimensions around 14-19 nm. Phase purity, crystal structure and morphology of nanomaterials were assessed by pXRD, EDS and electron microscopy. Growth duration of nanoparticles was found to have profound effect on the particle size of Pd17Se15 nano-particles. Time dependent studies indicate that the preparation of Pd17Se15 nanoparticles from molecular pre-cursor proceeds via the involvement of Pd nanoparticles.

Magnesium alloys are being rapidly used in automobile and aerospace industries due to their low density, high specific strength, high specific stiffness, good damping characteristics, and excellent machinability and castability. Despite their appealing range of mechanical qualities, Mg alloys’ low strength at ambient and elevated temperatures, as well as poor resistance to wear and corrosion, pose a substantial hurdle to their widespread use, which is keeping them from being as commonly employed as Al alloys. This study looks at the characterization, mechanical characteristics, and tribological behavior of a magnesium-silver alloy. Microstructural analysis and phase analysis are used to characterize the material. The material was subjected to tensile test and Vickers hardness test, and it was observed that the tensile strength and hardness of magnesium had been increased due to the addition of silver. Microstructure analysis showed a reduction in the grain size of alloy which in turn can be considered responsible for heightening the mechanical properties of the material. L9 Taguchi orthogonal array was used in designing experiments for the pin-on-disk wear test considering the input parameter sliding distance (500, 750, and 1000 m), normal load (50, 75, and 100 N), and speed (500, 1000, and 1500 rpm). The findings were analyzed using analysis of variance (ANOVA) to determine the impact of each parameter on volume wear, wear rate, and wear loss. The analysis portrayed that speed has the highest influence on the output characters. Finally, ANN and regression mathematical models were used to develop a predictive model to know the effectiveness of results and if the models showed any deviation before predicting an adequate model.