IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Wire electrical discharge machining and microstructural analysis of hot-pressed boron carbide
No full textBoron carbide powder was hot-pressed at 2070 degrees C with 30 MPa uniaxial pressure and 90 min soaking. The mechanical, microstructure and other related properties were evaluated. XRD of the boron carbide powder and sintered samples, shows the presence of B13C2 phase of high electrical conductivity. Crystal lattice parameters, space group, cell angle, cell parameters, etc. were found from Rietveld refinement. The micro Vicker's hardness was 26.98 +/- 0.98 GPa at 4.9 N load, fracture toughness 3.54 +/- 0.26 MPa/Mt and Young's modulus 461.50 +/- 4.5 GPa. The hot-pressed boron carbide was found to be electrically conducting, which can be machined using a wire electrical discharge machine (WEDM)
Bismuth-doped fiber Q-switcher in erbium-doped fiber laser cavity
No full textWe propose a simple design of all-fiber Q-switched erbium-doped fiber laser (EDFL). The laser is passively Q-switched by splicing bismuth-doped fiber into a ring cavity. The design has been experimentally demonstrated at the emission wavelength of 1560.48 nm. A single-mode Q-switched pulse with pulse duration of 1.18 mu s and pulse energy of 15.6 nJ was obtained with 980 nm pump power of 178 mW. Stable and typical Q-switched pulses were achieved at the repetition rate changing from 63.3 to 94.6 kHz. To the best of our knowledge, it is the first time to demonstrate bismuth-doped fiber as an effective saturable absorber for erbium-doped fiber laser
Manifestation of Hall-Petch breakdown in nanocrystalline electrodeposited Ni-MoS2 coating and its structure dependent wear resistance behavior
No full textThis work reports successful development of pure Ni and Ni-MoS2 bulk nano-crystalline electrodeposited coatings and it's mechanical and wear behavior. The crystallite size of the Ni in the Ni-MoS2 coatings varies from 31.6 to 146.8 nm at different loading levels of MoS2 (1, 2, 5, 10 and 20 g/l) in the deposition bath. The nanocrystalline Ni in the Ni-MoS2 coatings follow inverse Hall-Petch relation, as the hardness value is observed to decrease with decrease in crystallite size of the Ni below 62.2 nm. The wear mechanism of the electrodeposited pure Ni and NiMoS2 electrodeposits has been analyzed using micro-scratch technique with progressive load of 100 to 1000 mN. Moreover, all the Ni-MoS2 coatings display significantly improved wear resistance than the pure Ni electrodeposit due to the higher hardness of the Ni-MoS2 coatings caused by dispersion hardening. Moreover, the wear behavior of the Ni-MoS2 coatings has been correlated with crystal orientation, coating morphology and hardness to establish the possible abrasive wear mechanism
Comprehensive characterization of Ba1-x,SrxTiO3: Correlation between structural and multifunctional properties
No full textConsidering the superior multifunctional performance and beautiful structural tunability, Ba(1- x)SrxTiO3 (0 <= x <= 1) samples were synthesized in this work by following a conventional solid state reaction technique. The structural, vibrational, optical and dielectric properties of the synthesized materials were characterized extensively throughout the work. Band gap energy of all the materials was evaluated from optical characterizations and correlated with structural properties. Study of leakage characteristics rendered fruitful explanation for electrical properties. At x = 0.4, a structural phase transition from ferroelectric to paraelectric state was observed. All the functional properties were correlated with structural properties. The Ba0.6Sr0.4TiO3 sample showed maximum room temperature dielectric permittivity (similar to 4000 at 1 kHz) with good frequency and thermal stability. The dielectric loss tangent of this composition was reduced to similar to 0.0098 (at 1 kHz) which was even much lower than that of undoped BaTiO3. The detail temperature dependent dielectric and impedance characteristics of this sample were also evaluated. The activation energy, calculated from dielectric characterizations, was found to be similar to 1 eV suggesting the governance of doubly ionized oxygen vacancy for conduction and relaxation mechanism. (C) 2021 Elsevier B.V. All rights reserved
Screen-printed MgAl2O4 semi-thick film based highly sensitive and stable capacitive humidity sensor
No full textIn this paper we have reported on the excellent humidity sensing properties of screen-printed magnesium aluminate (MgAl2O4) porous, semi-thick film, capacitive sensor in the range of 2%-98% RH. MgAl2O4 nanoparticles were prepared by a facile solid-state reaction route. Screen printing technique was employed to prepare the MgAl2O4 porous semi-thick film. The binders used in screen-printing generated pores on the film surface during firing of the film. The as prepared nanoparticles and the thick film were characterized by different sophisticated techniques, viz. X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), BET-surface area analysis, laser diffraction-based particle size analysis, and contact angle measurement. Parallel plate capacitive configuration was used whereby the sensor film was interposed between copper bottom and silver top electrodes. The sensor exhibited high and stable response up to 98%RH with a detection lower limit of 2%, which is seldom reported. Further we observed low dissipation (<2), fast response (-66 s) and recovery (-71 s) times, low hysteresis (-109 pF at 89% RH), excellent repeatability (at least 15 cycles), and long-term stability (at least 6 months). This sensor is suitable for commercial applications in tea industry, food packaging, hospitals etc
Comparative investigation of coating and friction stir processing on Mg-Zn-Dy alloy for improving antibacterial, bioactive and corrosion behaviour
No full textMagnesium based alloys are well-known materials for temporary implant applications. However, failures due to early degradation and bacterial infection are limiting their applications. To overcome these problems, in the present work a Mg-Zn-Dy alloy based composite surface was prepared using coating and friction stir processing (FSP) techniques. Herein, hydroxyapatite (HA) and silver (Ag) particles were deposited on Mg-Zn-Dy alloy to obtain HA and Ag coated surface (C-HAg). Later, FSP was carried out on the C-HAg surface to develop a Mg-Zn-Dy alloy based composite surface (F-HAg). Field emission scanning electron microscope (FESEM) and energy dispersive X-ray analysis (EDS) confirm the mixing of HA and Ag particles with the Mg-Zn-Dy substrate. Antibacterial studies reveal that both C-HAg and F-HAg samples inhibit Escherichia coli and Staphylococcus aureus bacteria. In vitro cytotoxicity study indicates that the both samples are non-toxic in nature. Results of in vitro corrosion study reveal a significant reduction (72%) in corrosion rate of F-HAg sample when compared to C-HAg sample. The F-HAg samples showed simultaneous improvement in corrosion resistance and antibacterial properties with good biocompatibility. The results of this study indicate that the developed composite surface is a promising material for antibacterial and biodegradable implant applications
Mode-Field Matched Pump-Signal Combiner for High Power Fiber Laser in Advanced Manufacturing
No full textStable output and beam profile at high power laser operation is a prime requirement for precision high-end manufacturing. The stability of laser charateristics during power scaling in a single-oscillator is limited by several unavoidable non-linear effects. Hence, kW-level power scaling through multiple amplification stages or using signal combination are feasible solutions. In a master oscillator power amplifier (MOPA) architecture, pump-signal combiner with high pump coupling efficiency and low loss signal transmission maintaining seed beam quality during coupling from a single mode fiber into a large mode area fiber, is an important component. In this respect, an effective method of fabricating mode-field matched pump-signal combiner has been presented employing a section of intermediate fiber, having adiabatically tapered core and uniform cladding, along with a conventional signal fiber (termed hybrid signal fiber) inside the input fiber bundle to obtain effective mode-field matching of signal light in between the input fiber bundle and the output fiber. Additionally a taper-less signal combiner design has been proposed for scaling laser power through incoherent combination. The reduced-clad signal fiber with low loss core guidance supports bundling of the input fibers inside an economic low-OH silica tube to obtain good transmission efficiency and beam profile
Cube shaped FAPbBr(3) for piezoelectric energy harvesting devices
No full textIn order to meet the ever-increasing call for alternative energy, a plethora of novel materials have been explored to harvest energies. Amongst them, organic-inorganic halide perovskites belong to a relatively new class of compounds. In this work, we have prepared FAPbBr(3) cubes via solution process and explored its candidature in energy harvesting. Piezoelectric nanogenerator (PNG) based on the composite of FAPbBr(3) and poly (vinylidene fluoride) (PVDF) showed noticeable output performance. To get benchmark level output response, concertation of perovskite was optimized in composites. PNG fabricated with 3.0 wt% FAPbBr(3) in PVDF exhibited an instantaneous output voltage of similar to 200 V and current of similar to 650nA. It also showed long cycle stability (10,000 cycles) and durability under robust conditions. Energy generated from the PNG was further utilized to charge a capacitor and light up commercial LEDs. As obtained results are of great importance and open the feasibility of novel smart device using this kind of perovskites
Label-free immunosensing by long period fiber gratings at the lowest order cladding mode and near turn around point
No full textA long period fiber grating has been fabricated by combining two sensitivity enhancement techniques, the turn around point (TAP) and the maximum enhancement of the evanescent field by obtaining the lowest order cladding mode (LP0,2 cladding mode). A label-free immunoglobulin G/anti immunoglobulin G (IgG/anti-IgG) immunoassay in serum has been performed with the sensor inside a thermostated closed flow cell. Real time kinetics of the IgG and anti-IgG binding has been monitored and evaluated. By measuring the dual peak resonance of the LP0,2 cladding mode, a limit of detection of 0.16 ng/ml (1.06 pM) for anti-IgG has been achieved
Microstructure stability during high temperature deformation of CoCrFeNiTa eutectic high entropy alloy through nano-scale precipitation
No full textDual-phase microstructures arising out of eutectic reactions offer several advantages: ease of casting, composite properties and tunable characteristic length scale of the phases. Eutectic high entropy alloys (EHEA) with a multi-component solution phase and a hard intermetallic phase are candidate materials to identify alternate high-temperature materials. Alloying elements can be chosen to improve the resistance to lamellar microstructure degradation and coarsening. In this work, we present the CALPHAD guided design of a hypo-eutectic high entropy alloy CoCrFeNiTa0.395 with primary dendritic FCC phase and fine eutectic (FCC solution + Laves phase) microstructure possessing good high-temperature mechanical properties. The primary FCC phase fraction is 0.42 +/- 0.02. The interlamellar spacing of the eutectic is 0.69 +/- 0.12 mu m. The alloy exhibited a balanced yield strength of 1303 +/- 18 MPa, a fracture strength of 2237 +/- 23 MPa and a fracture strain of 0.3 under mom temperature compression testing. The mechanism for change in the lamellar morphology during deformation at temperatures beyond 0.8 T-E is explained schematically. Strain field distribution obtained by FEM simulation correlates well with the observed microstructure gradients in the deformed samples. The formation of nano-scale precipitates in the low strain rate deformation is attributed to thermal effects. High-temperature precipitation of two types of precipitates (L1(2) ordered and Ni3Ta type) in the FCC-solution phase extended the useable temperature range of this alloy