IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Dark pulse mode-locked fibre laser with zirconia-based erbium-doped fibre (Zr-EDF) and Black phosphorus saturable absorber
No full textA dark pulse multi-wavelength mode-locked fibre laser was demonstrated via the enhanced zirconia-yttria-aluminium co-doped silica fibre (Zr-EDF) as a gain medium with the utilisation of black phosphorus as saturable absorber (BPSA). A self-started dark pulse was accomplished by increasing the pump power and carefully rotating a polarisation controller (PC). Five lasing lines of multi-wavelength were generated with small constant channel spacing of 0.6 nm. The measured fundamental repetition rate was 1 MHz with a pulse duration of 3.46 ps. At output power 9.89 mW, the calculated pulse energy was 9.89 nJ, whereas the optical signal to noise ratio (OSNR) was as high as 74.8 dB, which confirmed the stability of the dark pulse train
3D printing of modified soybean hull fiber/polymer composites
No full textHerein, we have evaluated the soybean hull derived fibers as reinforcements to manufacture thermoplastic copolyester (TPC) composites using 3D printing process namely fused filament fabrication (FFF). The hulls were subjected to physical and chemical treatments to understand their influence on the microstructural and mechanical properties of the composites. We found strong dependence of surface quality, printing defects and interbead/interlayer bonding on the fiber treatment. The composites made using dilute acid hydrolysis treated fibers increased the relative density of the composites to 99% and reduced the pore size from 81 mu m to 39 mu m. Defect free fiber-matrix interfacial characteristics in these composites enhanced the elastic modulus from 36 MPa to 54 MPa. Similarly, the toughness and stress at 50% strain of these composites were similar to 30% and 50% higher than the pure TPC, respectively. Our results clearly demonstrated that the low-cost and abundantly available soybean hulls when modified using dilute acid hydrolysis have a strong potential in the fabrication of natural fiber reinforced composites
Effect of Oxygen Diffusion Constraints on the Performance of Planar Solid Oxide Fuel Cells for Variable Oxygen Concentration
No full textPerformance enhancement of solid oxide fuel cell (SOFC) has been a very prominent research problem of the present era. One of the key performance-limiting factors is diffusional constraint encountered in SOFC cathodes during operation with air. While attempts at improving cell performance have been made through the optimization of geometries, flow rates, and operating conditions, very few studies have reported the potential for performance enhancement through the optimization of cathode gas composition. The present study takes an experimental as well as theoretical approach to examine the extent to which SOFC performance can be enhanced through alterations in the oxygen concentration of cathode gas (without varying the oxygen molar flow rate). An SOFC is operated for various cathodic oxygen concentrations, and the experimental protocol is simulated using a parametric computational fluid dynamics study. The results depict remarkable nonlinearities in the dependence of cell performance indicators on cathode gas oxygen concentration, which opens up a new dimension for the optimization of cell efficiency, contingent on the availability of oxygen, and the design and operational constraints unique to specific SOFC development ventures
Wideband Fiber Bragg Grating Accelerometer Suitable for Health Monitoring of Electrical Machines
No full textA fiber Bragg grating (FBG) accelerometer suitable for health monitoring of electrical machines has been proposed. A polymer composite material is used to design the cantilever of the accelerometer. Thus it is ensured that there are no conducting parts in the accelerometer. Detailed finite element analysis of the cantilever is done to optimize the sensitivity and the resonant frequency. The sensitivity is significantly improved compared to the conventional FBG accelerometer having similar bandwidth of operation. Two different configurations, one having sensitivity 14.4 pm/g with resonant frequency 444 Hz, and the other having sensitivity 7.5 pm/g with resonant frequency 940 Hz have been designed and fabricated. The wide band optical accelerometers will enable monitoring of vibration modes of critical components of electrical machines and more importantly using commercially available standard FBG interrogators, instead of using any complex interrogation techniques. A good match between the simulation and experimental results was observed
Synthesis and characterization of PCL-DA:PEG-DA based polymeric blends grafted with SMA hydrogel as bio-degradable intrauterine contraceptive implant
No full textPresently available long-acting reversible female contraceptive implants are said to be an effective way of preventing unintended pregnancy. Unacceptable side effects attributed by these contraceptive implants act as a major drawback for the practitioners. These problems pave the way for the development of a new form of long acting non-hormonal female contraceptive implant, especially in the developing countries. PCL-DA: PEG-DA polymeric scaffold is grafted with Styrene Maleic Anhydride (SMA) based hydrogel, and their physicochemical, thermal and biological parameters are being explored for developing a bio-degradable form of the non-hormonal intrauterine contraceptive implant. With the fixed ratio of PEG-DA: PCL-DA polymer, SMA hydrogel was added at four different concentrations to determine the optimum concentration of SMA hydrogel for the development of a promising long-acting biodegradable intrauterine contraceptive implant. Structural elucidation of the polymers was confirmed using H-1 and C-13 NMR spectroscopic analyses. The physiochemical characterization report suggests that SMA hydrogel interacts with the PCL-DA: PEG-DA polymeric scaffold through intermolecular hydrogen bonding interaction. The in-vitro spermicidal activity of the polymeric scaffold increases when the concentration of SMA based hydrogel in the polymer samples is increased without showing any significant toxicological effects. From the study results, it may be concluded that SMA hydrogel grafted PCL-DA: PEG-DA scaffold can be developed as intra-uterine biodegradable non-hormonal female contraceptive implant due to its excellent bio-compatibility and spermicidal activity
Printability studies of Ti-6Al-4V by metal fused filament fabrication (MF3)
No full textPredicting the influence of material composition on the printability of highly filled metal powder-polymer systems present a significant challenge in metal fused filament fabrication (MF3). The current work presents an approach to evaluate new material compositions used to fabricate filaments for their printability. In this study, filaments with 59 vol.% (87 wt.%) of Ti-6Al-4V powder with two particle size distributions {fine (D-50 = 13 mu m) and coarse (D-50 = 30 mu m)} dispersed in a polymer matrix were examined. The respective forces to overcome the pressure drop, for successful printing, were found to increase with an increase in the feed rate, and were also dependent on the feedstock viscosity. In addition, shear forces estimated from the filament shear strength were found to be limiting conditions for successful printing. Based on these observations, a criterion has been proposed to evaluate filament printability from the predicted limiting force for filament failure and the required force to achieve continuous material flow for successful printing. Under present experimental conditions, successful printing was achieved up to 2 mm/s and 8 mm/s for fine and coarse powder filaments, in good agreement with the model predictions. The model was experimentally tested and found to be applicable for other compositions. The results demonstrate a new printability criterion to design novel materials for MF3
Synthesis and characterization of SmFeO3 and its effect on the electrical and energy storage properties of PVDF
No full textHere we report an anomalous electrical properties and energy storage performance of SmFeO3-Poly(vinylidene fluoride) (SFO-PVDF) composites fabricated by a simple solvent casting technique with SmFeO3 concentration varying from 1 to 10 wt% with respect to PVDF content. Dielectric permittivity and ferroelectric parameters of PVDF initially decreased for 1 wt% SmFeO3 incorporation and then started increasing with further increase of SFO concentration. However, in contrary to our expectation, all the composites exhibited lower values of dielectric permittivity compared to neat PVDF. The observed unexpected trend of variation of dielectric permittivity and electric displacement was explained by considering a local electric field approximation model followed by the mechanism of polymer chain movement and dipole orientation of PVDF
Development of nano-porous hydroxyapatite coated e-glass for potential bone-tissue engineering application: An in vitro approach
No full textTo reconstruct the defects caused by craniectomies autologous, bone grafting was usually used, but they failed most commonly due to bone resorption, infections and donor-site morbidity. In the present investigation, an effort has been made for the first time to check the feasibility and advantage of using hydroxyapatite (HAp) coated e-glass as component of bone implants. Sol-gel synthesized coatings were found to be purely hydroxyapatite from XRD with graded and interconnected pores all over the surface observable in TEM. The interconnected porous nature of ceramics are found to increase bioactivity by acting to up-regulate the process of osseointegration through enhanced nutrient transfer and induction of angiogenesis. From TEM studies and nano indentation studies, we have shown that pores were considered to be appropriate for nutrient supply without compromising the strength of sample while in contact with physiological fluid. After SBF immersion test, porous surface was found to be useful for nucleation of apatite crystals, hence increasing the feasibility and bioactivity of sample. However, our quasi-dynamic study showed less crystallization but had significant formation of apatite layer. Overall, the in vitro analyses show that HAp coated e-glass leads to significant improvement of implant properties in terms of biocompatibility, cell viability and proliferation, osteoinductivity and osteoconductivity. HAp coating of e-glass can potentially be utilized in fabricating durable and strong bioactive non-metallic implants and tissue engineering scaffolds
Hierarchically structured alpha-nickel hydroxide based superhydrophobic and antibacterial coating on cellulosic materials for oil-water separation
No full textInspired by hierarchical surface structure of lotus leaf and insect wings, a uniform coating of disorderly oriented semi crystalline alpha-Ni(OH)(2) nanosheets for creating dual scale (micro-nano) has been developed on cellulosic materials (cotton and wood) by a one-step facile solution process. The coating shows an innate superhydrophobic nature with a static water contact angle (SCA) similar to 157 degrees and water shedding angle (WSA) similar to 10 degrees. Growth pattern, morphology and microstructure, thermogravimetric mass loss behaviour and chemical bonding of alpha-Ni(OH)(2) with commercially available cotton fabric as well as antibacterial activity of the coated fabric towards gram positive and negative bacteria have been studied systematically. For long term use as a filter cloth for oil-water separation, the coating is further modified with hexadecyltrimethoxysilane (HDTMS) restoring the hierarchical structure of alpha-Ni(OH)(2). The dual scale surface roughness as well as low surface energy long chain HDTMS layer renders the coating a stable SCA similar to 162 degrees and WSA similar to 8 degrees. The superhydrophobic and superoleophilic alpha-Ni(OH)(2)-HDTMS coating shows self-cleaning ability, similar to 99% oil-water separation efficiency including reusability over 50 separation cycles. The coated sample also shows excellent chemical and mechanical stability as well as laundering fastness. This facile fabrication process can make an avenue for development of other transition metal hydroxides based superhydrophobic and superoleophilic coatings on cellulosic materials
Elucidating the structure and optimising the photoluminescence properties of Sr2Al3O6F: Eu3+ oxyfluorides for cool white-LEDs
No full textHerein, Sr2Al3O6F in hexagonal symmetry was synthesized via a solid-state methodology. The X-ray diffraction pattern of Sr2Al3O6F was refined by the Rietveld refinement with lattice parameters a = 17.8232(1) angstrom and c = 7.2168(0) angstrom. The stability of the crystal structure is further confirmed from the results of bond valence sums and the global instability index. The theoretical calculations of the electronic and optical behaviors of the Sr2Al3O6F were analyzed by density functional theory and the obtained results of the lattice parameters and direct bandgap were found close to the experimental data. The chemical states and elemental composition of Sr2Al3O6F were also authenticated by X-ray photo-electron spectroscopy (XPS). To evaluate the suitability of the Sr2Al3O6F structure as high efficient red phosphor, a series of Eu3+ doped Sr2-xEuxAl3O6F (x = 0.0 to 0.10) were synthesized, which showed intense red-orange emission (D-5(0)-> F-7(1,2)) at UV and blue excitations. The photoluminescence intensity corresponding to D-5(0)-> F-7(2) transition decreased significantly for x = 0.10 due to the luminescence quenching. Nevertheless, further enhancement in photoluminescence of Sr1.9Al3O6F: Eu-0.1 sample was realized with the substitution of 0.1 mol Ba2+ ion for 0.1 mol Sr2+ ion. The various radiative properties of the emission bands were also analyzed through the Judd-Ofelt theory. The optimized Sr1.8Al3O6F: Ba-0.1/Eu-0.1 phosphor showed high red color purity (>95%), and moderate thermal stability of around 72% at 150 degrees C, suggesting that it could be an ideal red component for white-LEDs. A white-LED comprising the commercial yellow phosphor and the optimized sample showed bright white light having the CRI of 80.5%, CCT of 5510 K, and CIE of (0.33, 0.36) indicating that Sr1.8Al3O6F: Ba-0.1/Eu-0.1 phosphor is an appropriate red component for cool white-LEDs. (C) 2020 Published by Elsevier B.V