Raja Ramanna Centre for Advanced Technology

The room-temperature growth, characterization, and electrical transport properties of magnetron sputtered superconducting Ti40V60 alloy thin films are presented. The films exhibit low surface roughness and tunable transport properties. As the sputtering current increases, the superconducting transition moves toward higher temperatures. Rietveld refinement of the two-dimensional XRD pattern reveals the presence of stress in the films, which shifts from tensile to compressive as the sputtering current increases. Additionally, the crystallite size of the films increases with higher sputtering currents. The films exhibit a strong preferential orientation, contributing to their texturing. The crystallite size and texturing are found to be correlated with the superconducting transition temperature (TC) of the films. As the crystallite size and texturing increase, the TC of the films also rises.

Antiferromagnetic Kagome semimetal FeSn has gained significant attention due to the presence of topological flat bands and Dirac fermions. There has been immense interest to tune the bands with doping in FeSn for enhancing the magnetic and transport properties. Here, we report an experimental study of transport, magnetization, and electronic structure of Fe$_{1-y}$Co$_y$Sn as a function of Co-doping concentration (y). Variation in the temperature-dependent resistivity with increasing y is associated with the increase in spin-dependent scattering. Co doping in FeSn gives rise to canted antiferromagnetism with the decrease in the Neel transition temperature ($T_{N}$). The local moment of Co and Fe atoms has been estimated from the analysis of 3s core levels. The decrease in $T_{N}$ with increasing y is due to the decrease in the local moment of Fe atoms. The systematic shift in the valence states away from the Fermi level ($E_{F}$), and the valence band broadening with the increase in y indicate an increase in the electron correlation and hybridization effects in Fe$_{1-y}$Co$_y$Sn. An increase in both electron correlation and hybridization with doping leads to the strong magnetic interaction between the local moments of Fe and Co atoms which gives rise to the canted antiferromagnetism in Fe$_{1-y}$Co$_y$Sn.

In this work, controlled surface rolling (CSR), a novel roller based low plasticity burnishing technique, was developed to mitigate initiation of stress corrosion cracking (SCC) in machined SS304L in chloride environment. This setup utilized a pneumatic system to apply controlled loads (upto 1000 kgf), with CSR performed by varying roller velocity and number of rolling passes. Advanced characterization techniques, like electron back scattered diffraction (EBSD), nanoindentation, and 3D optical profilometer were used to characterize changes in microstructure and surface roughness resulting from CSR. These results were compared with conventional shot peening. The depth up to which misorientation within the grains observed in EBSD, which is an indicator of plastic strain induced on the surface, didn’t increase significantly due to CSR treatment (77 µm) on as-machined sample (62 µm). Residual stresses along both circumferential (σ C ) and radial (σ R ) directions with respect to machining tracks were measured using synchrotron X-ray beam, and correlated to SCC density from ASTM G36 test. The SCC density in as-machined condition reduced by 99% after CSR treatment at 800 kgf, 10 mm/s and 20 passes. A significant reduction in SCC density was also achieved after CSR at 200 kgf due to small reduction in tensile σ C in as-machined condition. While after CSR treatment at 1000 kgf, compressive stresses were observed along both the directions (σ R : − 512 MPa, σ C : − 72 MPa).

We present a comprehensive photoemission study of two Vanadium-based quaternary Heusler alloys, CrFeVGa and CoFeVSb, which are highly promising candidates for spintronics and topological quantum applications. CrFeVGa exhibits large anomalous Hall conductivity due to the large Berry curvature originating from its non-trivial topological bands. In contrast, CoFeVSb displays a spin-valve-like behavior alongside excellent thermoelectric properties, such as ultra-low thermal conductivity and high power factor at room temperature. By utilizing synchrotron x-ray photoemission spectroscopy and resonant photoemission spectroscopy, we have investigated the core levels and valence band of both the alloys. Our analysis shows that the V 3d states are primarily responsible for the electronic states at the Fermi level which result in the high spin polarization, consistent with our theoretical predictions. The presence of the Fermi edge in the valence band spectra in both the systems confirms the predicted metallic or half/semi-metallic features. The observed spectra match qualitatively with our simulated partial density of states. A close inspection of the temperature dependent valence band spectra indicates that some of the intriguing bulk properties reported earlier on these two systems are intimately connected with their unique band structure topology. This in turn facilitate a deeper insight into the origin of such interesting properties of these alloys. Such direct measurements of electronic structure provide a guiding platform towards a better understanding of the anomalous properties of any material in general.

Although the deformation of the Heisenberg algebra by a minimal length has become a central tool in quantum gravity phenomenology, it has never been rigorously obtained and is often derived using heuristic reasoning. In this study, we move beyond the heuristic derivation of the deformed Heisenberg algebra and explicitly derive it using a model of discrete spacetime, which is motivated by quantum gravity. Initially, we investigate the effects of the leading order Planckian lattice corrections and demonstrate that they precisely match those suggested by the heuristic arguments commonly used in quantum gravity phenomenology. Furthermore, we rigorously obtain deformations from the higher-order Planckian lattice corrections. In contrast to the leading-order corrections, these higher-order corrections are model dependent. We select a specific model that breaks the rotational symmetry, as the importance of such rotational symmetry breaking lies in the relationship between CMB anisotropies and quantum gravitational effects. Based on the mathematical similarity of the Planckian lattice used here with the graphene lattice, we propose that graphene can serve as an analogue system for the study of quantum gravity. Finally, we examine the deformation of the covariant form of the Heisenberg algebra using a four-dimensional Euclidean lattice.

Aluminum-reinforced silicon carbide composite (Al/SiC) has gained popularity as a metal matrix composite for various applications in aerospace, automotive, defense, and other fields due to its high specific strength, lightweight, and wear-resistant characteristics. Due to their excellent material properties, drilling precise holes especially in thick Al/SiC composites is a difficult task. The present research aims for laser beam percussion drilling of precise holes with better accuracy by reducing the hole taper, non-circularity, and spatter size. This study may help figure out the best way to use a laser beam to drill holes in a 4.5 mm thick Al/SiC composite. The experimental results suggest that reducing the pulse width and increasing the assist pressure lead to a decrease in hole taper and better hole circularity. Genetic algorithm optimization technique was used to optimize the hole top circularity, resulting in a notable 7.587% improvement and a 2.736% improvement in the bottom circularity of the hole, respectively. The hole taper was significantly minimized by 31.943%, with spatter size also significantly reduced by 37.796%. This research further indicates the positive contributions of process parameters to improve the drilling efficiency and accuracy.

Coupling between different interactions allows the control of physical aspects in multifunctional materials by perturbing any degrees of freedom. Here, we aim to probe the correlation among structural, electronic, and magnetic observables in Sm2NiMnO6 (SNMO) ferromagnetic insulator double perovskite. Our employed methodology includes thermal evolution of x-ray diffraction, x-ray absorption spectroscopy, and bulk magnetometry. The magnetic ordering in SNMO adopts two transitions, at TC = 160 K due to the ferromagnetic arrangement of Ni–Mn sublattice and at Td = 34 K because of anti-parallel alignment of polarized Sm paramagnetic moments with respect to Ni–Mn network. Signature of Ni/Mn anti-site disorders are evidenced from short-range structure and magnetization analysis. The long-range as well as short-range crystal structure of SNMO undergo changes across TC and Td, observed through temperature dependent variation in Ni/Mn–O bonding characters. Hybridization between Ni, Mn 3d, O 2p electronic states show changes in the vicinity of magnetic transition. The change in crystal environments governs the magnetic response by imposing alteration in metal—ligand orbital overlap. On the other hand, it is observed that application of electric bias causes monotonic reduction in the saturation magnetic moment. By using these experimental methods, we demonstrate how the structural, electronic, and magnetic properties are correlated in SNMO, which makes it a potential platform for technological usage.

The ability to detect the ethanol rapidly and sensitively in ethanol–gasoline blends has become important in recent times, both for engine performance and for fuel economy. In order to achieve this, a deterministic methodology based on Raman spectroscopy is employed for quantitative estimation of ethanol in commercial ethanol–gasoline blends of fuel. The different concentrations of anhydrous ethanol were mixed with pure gasoline to calibrate the Raman spectroscopy measurement setup. The variation in the ratio of the heights of Raman peaks at wavenumbers ∼885 and 1005 cm –1 is found to be linear with the fractional volumes of ethanol and gasoline in the blends. Using this methodology, the volume percentage of ethanol in commercial gasoline is determined to be ∼10%. This methodology can also be adopted for detection of other additives/adulterants in commercial gasoline.

Stem cells (SC) based therapies are proving to be the mainstay of regenerative medicine. Despite the significant potential, direct grafting or implantation of SCs for regenerative therapy encounters various translational roadblocks such as paucity of implantable cells, decreased potency, cell death post-implantation, cell damage caused by the pre-existing inflammation and immune rejection. Hence, an emerging avenue is cell-free approach; use of SC secretome. Although priming approaches based on pharmacological molecules/chemicals, cytokines and growth factors are being explored to elicit enhanced secretome production, the potential concerns include the need for continuous replenishment and potential chemical contamination during secretome isolation. To alleviate these concerns, various non-pharmacological approaches for invigorating SCs are also being investigated and among these, use of photobiomodulation (PBM) has garnered considerable interest. Notwithstanding the positive outcomes, standardized parameters are yet to be established for reproducible results. Moreover, the mechanisms of PBM based SC stimulation and secretome production are poorly elucidated and significant knowledge gaps exist on influence of cell type, culture conditions on PBM. This review aims to provide insight into the current status of this emerging field emphasizing on novel avenues and potential challenges for clinical translation. We also summarize the studies on PBM based proliferation, differentiation and secretome production according to SC cell type and culture conditions. Further, as a fixed PBM based protocol for SC proliferation, differentiation and secretome is lacking, the knowledge on functional targets and pathways in PBM based SC stimulation needs upgradation. Consequently, putative mechanisms for PBM based SC secretome have been proposed.

Soft switching of primary‐side semiconductor switches across the full operational range, high‐frequency transformer nonidealities, and the high reactive energy in the resonant tank circuit is key challenges in the design of focusing magnet DC power supplies (FMDPS). To address these issues, this paper presents a simplified and optimized design method for an LLC resonant converter (LLC‐RC)‐based FMDPS in high‐power linear accelerators (LINACs). The proposed LLC‐RC power converter, with its optimal design approach, effectively resolves these challenges, achieving zero voltage switching (ZVS) at turn‐ON across the entire operational range. Additionally, transformer nonidealities such as leakage inductance and magnetizing inductance are absorbed within the resonant tank and utilized to advantage. The proposed converter is designed with an optimal quality factor (Q), minimizing the total reactive energy in the circuit. The work also presents a steady‐state analysis of the proposed topology, along with derived expressions for voltage gain, input impedance, and resonant frequencies. To validate the concept, a 600‐W experimental prototype (input: 250 V; output: 30 V/20A) featuring soft switching throughout the full operating range was developed, achieving a maximum efficiency of 95.99%. The experimental results closely align with the theoretical design and simulation outcomes.

The present study investigated the influence of deposition angle of sputtered atoms on the microstructure, morphology, mechanical and electrical properties of niobium (Nb) thin films by varying it from 0° to 50° in a step of 10°. It was found that the deposition rate follows cosine distribution with deposition angle. The root mean square (rms) surface roughness increases from 0.40 ± 0.05 to 1.5 ± 0.2 nm, and density decreases from 8.5 to 7.7 (± 0.2) g/c.c as the deposition angle increases while no significant change in crystallites size was observed. Room temperature electrical resistivity rises from 79 to 293 µΩ-cm with increasing deposition angle due to enhanced electron scattering. The residual stresses remain compressive but shift towards tensile as the deposition angle increases. Atomic force microscopy confirms the increase in surface roughness and showing columnar growth at higher deposition angle. This work provides some insights into the how the deposition angle of sputtered atoms affects the growth of Nb films and optimal deposition angular range of sputtered atoms to coat Nb films on irregular surfaces.

A solid‐state laser is preferred for generating light in a photoacoustic (PA) system because of its high energy and coherence. However, conventional Nd:YAG lasers are bulky, complex, and expensive. This article introduces a portable alternative: a custom‐built Nd:YAG laser with an in‐house power supply that delivers 0–30 A current pulses with a 1500 μs pulse width, providing efficient thermal management. A pockels cell driver generates 10 ns pulses with 3.84 mJ/c m ² laser energy density. Implemented for noninvasive breast cancer diagnosis, The peak frequency obtained from three different samples was 0.23 ± 0.1, 0.26 ± 0.13, and 1.80 ± 0.14 MHz, respectively, for Normal, Fibrotic, and Tumor tissues. In addition to the dominant frequency peaks the spectral energy of the PASR spectra has also been investigated to characterize the breast tissue samples. The developed laser successfully differentiates between carcinoma, fibrocystic disease, and normal breast tissue based on quantitative PA spectral parameters.

A simple method to self-start a Mamyshev oscillator (MO) using an optical beam shutter (OBS) in the cavity is presented. OBS is placed inside the cavity to introduce a strong optical fluctuation by switching its state (open/close). Stable mode-locking operation is achieved in fiber MO by using an OBS without requiring any external mode-locked seed source or pump modulation.

The development of a metallic copper‐based catalyst system remains a significant challenge. Herein, we report the synthesis of highly stable, active, and reusable Cu⁰ catalyst for the carboboration of alkynes using carbon electrophiles and bis(pinacolato)diboron (B2pin2) as chemical feedstocks to afford di‐ and trisubstituted vinylboronate esters in a regio‐ and stereoselective manner with appreciable turnover number (TON) of up to 2535 under mild reaction conditions. This three‐component coupling reaction works well with a variety of substituted electrophiles and alkynes with broad functional group tolerance. In addition, a wide range of terminal and challenging internal alkynes were efficiently converted into hydroborated products in up to >99 % yield with excellent regioselectivity in the absence of carbon electrophiles. X‐ray photoelectron spectroscopy and X‐ray absorption near‐edge spectroscopy (XANES) analysis confirm that the oxidation state of the copper in the catalyst is zero. The broad range of organic transformations, effectiveness, and recyclability of this Cu⁰ catalyst are the major achievements that provide an environmentally friendly route for the efficient production of tri‐ and tetrasubstituted olefins, key intermediates in organic synthesis. The gram‐scale reaction and synthetic transformations further highlights the usefulness of these methods.

The current manuscript undertakes a systematic analysis of sequential layer-by-layer laser remelting (SLLR) within the context of laser-directed energy deposition (LDED) of Hastelloy-X (HX) bulk structures. Comparative analysis is conducted between the surface and bulk properties of LDED-built samples and those incorporating SLLR. Integrating SLLR with LDED results in a notable decrease in surface roughness by 71.5% and porosity by eight times. While both lack of fusion and gas porosity are evident in the as-built sample, the combination of SLLR with LDED shows only gas porosity. Moreover, microstructural refinement is observed after SLLR without preferential growth along (100), unlike in samples without SLLR. Analysis reveals segregations of Mo, Si, and C and the presence of Mo-rich carbides in both LDED and SLLR samples. The finer dendritic microstructures observed in SLLR samples contribute to a 12% increase in microhardness and a 7% rise in yield strength along the build direction compared to samples without SLLR. This study lays the path for fabricating dense components with tailored microstructures and mechanical properties during LDED through the utilisation of SLLR.

Wear resistant NiCrFeSiBC hardfacing alloy bushes for fast breeder reactor applications are fabricated through direct laser energy deposition (DLED) using CO 2 laser with optimized parameters for laser power (2.5 kW), scan speed (4.2 mm/s), powder feed rate (4 g/min) and 60% of track to track overlap. DLED bushes have significantly different microstructure than weld deposited ones. As-deposited bushes have predominantly uniform fine dendritic solidification structure of γ-Ni + Ni 3 B, γ-Ni + Ni 3 B + Cr 3 C 2 and Ni-B-Si eutectics with low volume fractions of Cr-rich borides and carbides. Microstructural heterogeneity is observed only in layer overlap regions characterized by coarsening of carbides that resulted in lower hardness (625 ± 11 HV0.1) compared to layer interiors (740 ± 19 HV0.1). Effect of aging at 550 °C on the microstructure and properties of the bushes is investigated using experimental and thermo-kinetic simulation techniques. Microstructure of the bushes remains stable without significant coarsening of the γ-Ni + Ni 3 B eutectic structures even after heat treatment for 4000 h. However, precipitation and coarsening behavior of Cr 7 C 3 and Cr 23 C 6 carbides are affected by aging which is reflected in the variation in hardness. Hardness of the bushes increases up to 100 h of aging due to the precipitation of fine Cr-rich carbides, and with increase in the duration of aging, carbides coarsen thereby reducing the hardness. Based on the study, it is concluded that direct laser energy deposited bushes may have better stability with respect to microstructure and properties at service temperatures.

The study investigates the solid polymer composite (SPC) made using solution casting with PVA as the host polymer and KI as the dopant. The SPC was exposed to electron beam doses ranging from 0 to 300 kGy to study its microstructural, optical, thermal, electrical, and dielectric properties. XRD, FTIR, and TGA were used to study the structural and thermal properties. Results showed variations in crystalline phase, charge transfer complex formation, and defects due to crosslinking and chain scission processes. The activation energy for thermal decomposition values matches the onset temperature. UV–Vis studies revealed changes in optical properties with radiation dose, attributed to molecular ordering changes, defects formation, and charge transfer complexes. Electric and dielectric properties were studied using impedance spectroscopy. The highest ac conductivity was achieved for 300 kGy-irradiated SPC, attributed to free radical production. The correlated barrier hopping model was found to be the best fit for characterizing the electrical conduction mechanism of the system. Dielectric measurements revealed non-Debye behavior and substantial dielectric dispersion in the frequency range, increasing with irradiation dose. The results suggest the SPC is a potential candidate for solid-state energy storage and conversion applications.

The orbital-free density functional theory (OF-DFT) based method is a convenient tool to carry out electronic structure calculations scaling almost linearly with the number of electrons. However, the main impediment in the application of this method is the unavailability of the accurate form for the non-interacting kinetic energy functional in terms of electron density. The Pauli kinetic energy functional is the unknown part of the kinetic energy functional, and the corresponding Pauli potential appears in the governing Euler equation. In the present study, we present a feed-forward neural network (NN) approach to represent the Pauli potential of a group of atomic systems possessing spherically symmetric ground-state densities. This NN-based representation of Pauli potential combined with the Hohenberg–Kohn variational principle yields self-consistent radial densities that accurately exhibit the correct atomic shell structure. For this approach, the electron density in the form of a grid serves as the input to the NN model. In addition, we calculated the non-interacting kinetic energy by summing the Pauli kinetic energy, derived from the NN-based Pauli potential, and the von Weizsäcker kinetic energy. Our results demonstrate high accuracy for smaller atoms, while larger atoms exhibit greater deviations when compared with smaller atoms. The method presented in this paper provides an efficient way to calculate the Pauli potential and the Pauli kinetic energy without the need for functional derivatives. Our study represents a significant step forward in the application of machine learning techniques to OF-DFT, showcasing the potential of NNs in improving the accuracy and efficiency of quantum mechanical calculations in atomic systems.