The Raja Ramanna Centre for Advanced Technology is a unit of Department of Atomic Energy, Government of India, engaged in R&D in non-nuclear front-line research areas of lasers, particle accelerators and related technologies.
Magnetic permeability is an important factor while considering austenitic stainless steel for construction of vacuum chambers of particle accelerators. The presence of ferromagnetic δ-ferrite in the weld metal of austenitic stainless steel is desirable to prevent hot cracking, but its presence enhances magnetic permeability which compromises the functionality of component. The purpose of the present study is to develop a sustainable tungsten inert gas welding technology for achieving better productivity by increasing metal penetration with simultaneous betterment in weld quality and control of magnetic permeability. The study has been carried out using an active flux (SiO2 TiO2) and nitrogen addition (2-3
In this work, D2205 duplex stainless steel has been laser shock peened without an ablative layer. The effect of shock peening on the microstructure, tensile strength, wettability, protein adsorption and biocompatibility has been studied. Due to thermal effect of the high-energy pulsed laser used for peening, lattice micro-strain and dislocation density decreased, and lattice parameters and grain size increased in the vicinity of the shock peened surface. However, beneath the heat affected area, the nature of residual stress changed from compressive in ferrite and tensile in austenite to compressive for both. Within 1 mm distance from the shock peened surface, induced residual compressive stress and grain refinement led to increase in nano-hardness from similar to 3.8 GPa to similar to 4.3 GPa. In addition, the yield and ultimate tensile strengths increased to 709 MPa and 845 MPa, respectively on the shock peened surface compared to 611 MPa and 750 MPa, respectively on the unpeened side. Laser shock peening led to decrease in surface energy and increase in hydrophobicity, indicated by increase in contact angle in the sessile drop test. Protein adsorption got decreased on the shock peened surface due to increase in hydrophobicity. Cell proliferation and decrease in secretion of pro-inflammatory cytokines indicated better biocompatibility.
Abstract This study investigates the role of oxygen defects in europium (Eu)-doped (Na0.41K0.09Bi0.5)TiO3 (NKBT) perovskite ceramics, focussing on their impact on piezoelectric properties. Using X-ray photoelectron spectroscopy (XPS) and temperature-dependent Ac-conductivity measurements, this study presents evidence of the amphoteric nature of Eu ions in the NKBT host matrix. The XPS analysis shows the presence of oxygen vacancies, with O-1 s core level spectra showing distinct peaks corresponding to lattice oxygen (binding energy: ~ 529 eV) and oxygen vacancies (binding energy: ~ 532 eV). The concentration of oxygen vacancies reduces with low Eu doping concentrations (≤ 1.0 at%), corresponding to Eu ions absorbing the A-site (Na/K/Bi), where Eu act as donor dopants which lowers the oxygen vacancy concentration and enhancing piezoelectric properties. Conversely, at higher doping levels (> 1.0 at%), Eu ions favourably substitute the B-site (Ti4⁺), behaving as acceptor dopants, which increases the oxygen vacancy concentration and shows a deterioration in piezoelectric performance. Conductivity measurements further verify these findings and verifying their foremost role in conduction mechanisms for the reason that the activation energy values aligning with oxygen vacancy migration. This study not only clarifies the amphoteric behaviour of Eu ions in NKBT but also highlights the critical role of oxygen defects in tuning the material’s electromechanical properties.
Synergistic integration of Al-doped ZnO, a SiO 2 electron-blocking interlayer, and a MoS 2 –PDMS nanocomposite results in a flexible high-output triboelectric nanogenerator capable of lighting 400 LEDs and maintaining long-term operational stability.
Thermoelectric materials offer a promising route for efficient heat-to-power conversion. In search of materials functional at high and low operating temperatures, we investigate the thermoelectric properties of two-dimensional lead halide Janus layers (JLs) using density functional theory. The electronegativity difference between halides in JLs significantly modulates the electronic structure, particularly the strong Pb-F bonding in PbIF JLs leads to pronounced band curvature and a unique direct bandgap. Estimated through three-phonon interactions, the lattice thermal conductivity is intrinsically low, primarily due to acoustic phonon contributions and suppressed optical phonon transport. The thermoelectric coefficients are enhanced with carrier doping, resulting in figures of merit as high as 1.48 at room temperature and up to 4.93 at elevated temperatures. Up to 30% of heat-energy conversion efficiency is acheived at 1000 K in PbIBr JL. These findings establish two-dimensional lead halide Janus layers, particularly the PbIBr layer, as optimal candidates for thermoelectric conversion, and the insights into their elemental and electronic characteristics offer a valuable basis for the future design of high-performance lead-based thermoelectric materials.
