IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Enhancement of Li+ ion kinetics in boehmite nanofiber coated polypropylene separator in LiFePO4 cells
No full textBoehmite (gamma-AlO(OH)) nanofibers (length 90-140 nm; dia. -15 nm) synthesized by low temperature (180 degrees C) hydrothermal method and coated onto both sides of surface modified polypropylene. Ceramic coated composite separator (ALO-PP) shows enhanced thermal and dimensional stability over uncoated polypropylene (PP). Optimum coating thickness is found to be 8 mu m in each side. Electrochemical properties are investigated by assembling 2032-type coin cells using LiFePO4 as cathode against Li/Li+ in half-cell and Mesocarbon microbeads (MCMB) in full-cell configuration respectively. It is found that composite separator results in improved cell kinetics due to better electrolyte uptake and formation of a Li+ ions buffer reservoir facilitating fast ion transport at high current rates. About 16% higher capacity is observed for ALO-PP over PP at a current rate of C/5. Present results show that nanostructured boehmite could be a promising coating material for surface modification of polyolefin separators not only with improved safety but also with enhanced rate performance
Fabrication and characterization of sol-gel-based coatings on quartz glass to obtain antireflective effect at 1054 nm for optics of high power Nd:phosphate glass laser
Get PDFIn order to obtain higher laser-induced damage threshold (LIDT) and lower loss of laser radiation, the incident radiation must have an insignificant absorbance and high anti-reflectance. In this work, a single-layer porous SiO2-based anti-reflective (AR) coating for the optics of Nd:phosphate laser system has been developed on quartz glass optics adopting sol-gel dip coating technique, following quarter wavelength optical design. As measured by spectroscopic ellipsometer, the refractive index (RI) of the coated layer is found to be similar to 1.2. A maximum transmittance of similar to 99% in single-layer-coated quartz glass has been achieved at 1054 nm. In addition, the non-quarter wavelength-based double layer with an optical design (glass/ 0.7153 M / 1.134 L / air) and triple-layer AR coating with an optical design (glass / 0.28 H / 1.65 M / 1.03 L / air, where H, M and L indicate one-quarter wave thick layers of high, medium and low RI materials) have been fabricated. The deposition of M and H layers has been made from mixed metal oxide precursor sols of zirconia-silica, while L has been made from silica precursor sol to obtain porous silica coating. A maximum transmittance of about 98.1 and 97.6% was found at 1054 nm in double- and triple-layer AR-coated samples, respectively. The LIDT values have been measured on the AR coatings. Based upon the number of layers in the AR coatings, the LIDT values varied in the range of 8.7-2.4 J cm(-2) starting from single to double to triple layer. The AR coatings developed by sol-gel dip coating technique could find application in Nd:phosphate high power laser system
In vitro biocompatibility and degradation assessment of tantalum oxide coated Mg alloy as biodegradable implants
No full textIn the present study, the sputtering process deposited tantalum oxide thin film onto AZ31B alloy, and the biocompatibility and degradation resistance were evaluated. The phase analysis by X-ray diffraction (XRD) and transmission electron microscopy (TEM) was carried out to understand the Ta-based thin films' crystalline and amorphous nature thin film. The thin film surface chemical composition was investigated by X-ray Photoelectron Spectroscopy (XPS) which showed the elemental signals of O, Ta without any other impurities. Contact angle measurements verified the hydrophobic nature of the coated specimens. The corrosion studies revealed that corrosion resistance was significantly enhanced for the Ta-based thin-film coated Mg alloys than the uncoated bare counterpart by reducing corrosion current density from 2.886 x 10(-4) to 1.20 x 10(-5) A/cm(2). Bioactivity of the coated specimens in SBF immersion showed apatite formation in 5 days. The hemocompatibility studies of the coatings showed the echinocytes morphology of the RBCs. In vitro, MIT assay exhibited more significant cell proliferation and cell viability of 100% at 7 days of incubation. The cell morphology studies showed improved cell attachment and cell growth by controlling magnesium ions' release into the cell culture media. (C) 2022 Elsevier B.V. All rights reserved
Biocompatibility and corrosion evaluation of niobium oxide coated AZ31B alloy for biodegradable implants
No full textBiodegradable magnesium (Mg) based implants have considerable interest in the biomedical field as their use nullifies the necessity for implant removal surgery and avoids the long-standing adverse reaction of permanent bioimplants. The degradation resistance and biocompatibility of the Mg alloys can be improved by coating them with a suitable thin film. Here, thin films of niobium and niobium oxide were developed on the AZ31B Mg alloy by sputtering technique and their biocompatibility and corrosion resistance was examined. X-ray diffraction (XRD) and Transmission electron microscope (TEM) techniques confirmed the crystallinity of the thin films. Subsequently, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques were employed to evaluate the morphology and chemical composition of the thin film surfaces, respectively. Thin-film coated Mg alloys revealed good corrosion resistance compared to their uncoated bare counterparts in simulated body fluid (SBF). The contact angle study was performed on the coated specimens to investigate their wettability which revealed their hydrophobic character. The cell viability studies on thin-film coated specimens exhibited significant cell proliferation, and cell morphological studies showed good cell attachment and growth. The in vitro MTT assay on mouse osteoblast precursor cells (MC3T3-E1) indicated that the Nb-based coatings are cytocompatible and promote cell proliferation
Comparative study on thermal cyclic resistance of glass-ceramic-bonded TBC system and conventional TBC system
No full textThermal barrier coatings (TBCs) are provided to protect the metallic parts of gas turbines from high inlet temperature. In the present study, two types of TBCs, namely conventional TBC having NiCoCrAlY bond coat, 8-YSZ top coat and a new TBC with glass-ceramic bond coat keeping the top coat same, were considered to investigate their thermal cyclic resistance at 1000celcius for 500 cycles. Assessment of weight change, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis were performed for both TBCs after thermal cycling. Weight change measurement indicated that oxidative weight gain dominated over the coating spallation in case of conventional TBCs. On the contrary, oxidative weight gain could not considerably govern over coating spallation for glass-ceramic bond-coated TBCs. Furthermore, thermally grown oxide (TGO) layer was not observed at the bond coat-top coat interface of glass-ceramic bond-coated TBC system whereas the same was observed clearly at the interfacial region of bond coat and top coat of conventional TBC system after completion of 500 cycles at 1000 degrees C
Charge Compensation Mechanism and Multifunctional Properties of Bi1-xBaxFeO3 (x=0, 0.05, 0.1) Ceramics
No full textThe charge compensation mechanism of Ba2+ ion doped BiFeO3 (BFO) has been studied here in detail. The most common problem of high leakage current of ceramic BFO was noticeably resolved by significant reduction of charge defects through Ba2+ doping. The leakage current density of Bi1-xBaxFeO3 (x = 0, 0.05, 0.1) was found to be reduced to similar to 3.13 x 10(-8) A cm(-2) for x = 0.1 from a value of 2.26 x 10(-4) A cm(-2) for x = 0 at an applied field of 500 V cm(-1). This reduction of leakage current was caused by the reduction of charge defects which was verified through the X-ray photoelectron spectroscopy (XPS). The dielectric and ferroelectric properties of undoped and Ba2+ doped BFO were also studied here explicitly and correlated with charge compensation mechanism. The structural and vibrational characterization proved the phase pure formation and the presence of metal-oxide bonds. The optical characterization showed the reduction in energy band gap with increased Ba2+ doping in BFO (2.18, 1.71 and 1.56 eV for x = 0, 0.05 and 0.1, respectively). Another common problem of BFO, namely low remanent magnetization, was also significantly resolved through Ba2+ doping in it and the strong antiferromagnetic BFO started showing weak ferromagnetic nature with increased doping concentration. (C) 2022 The Electrochemical Society (''ECS''). Published on behalf of ECS by IOP Publishing Limited
Multiferroic BiFeO3-based hydrophobic polymer composites for polarization rationalization-induced piezo-tribo hybrid energy harvesting and versatile self-powered mechanosensing
No full textBiFeO3-poly(vinylidene fluoride) (BFO-PVDF) and BiFO3-polydimethylsiloxane (BFO-PDMS) piezoelectric composite films have been fabricated herein and used to develop flexible piezoelectric-triboelectric hybrid nanogenerators by forming different combinations with aluminium (Al) electrodes (PVDF-Al, PDMS-Al and PDMS-PVDF) using the contact-separation mode. The dielectric permittivity of both the PVDF- and PDMS-based composites has been found to increase from similar to 9 and 3.2 for a filler loading of 3 wt% to similar to 16.6 and 4.7, respectively, for 10 wt% BFO concentration within their matrix. The mechanical stimulus-driven output voltage has also been found to be increased from similar to 7.5 V and 35 V to similar to 18 V and 100 V for the respective films. The rational augmentation of the polarization of PVDF and PDMS induced by the gradually increased BFO filler concentration in their matrix, as confirmed from the above-mentioned results, have been found to significantly affect the output performance of the fabricated piezo-tribo hybrid nanogenerators. Among the three types of fabricated hybrid devices, the combination of 10 wt% BFO-incorporated PDMS with an aluminium electrode shows the best output performance both theoretically and experimentally. Hence, this combination has been used to develop a flexible multi-unit hybrid nanogenerator (M-HNG), which shows further performance enhancement (output power density: similar to 600 mu W cm(-2)). The M-HNG was then used for biomechanical energy harvesting, powering small electronics and different self-powered mechanosensing applications including motion sensing, pressure sensing, water drop counting and phonation monitoring
Disorder-induced crossover of Mott insulator to weak Anderson localized regime in an argon-irradiated NdNiO3 film
No full textWe show that an introduction of disorder in a controlled way using 1 MeV argon (Ar) ion irradiation, suppresses the correlation driven metal-insulator transition (MIT) in NdNiO3 films. The films make a crossover to a heavily disordered conductor governed by weak localization (WL) and at even higher disorder, an Anderson localized state. The disorder (atomic displacement up to 2% of the total atoms) in the NdNiO3 films was created using 1 MeV Ar4+ ion irradiation. We show that the pristine films of NdNiO3 exhibit an MIT with the conduction process being governed by variable range hopping (VRH). For disorder up to 1% of the displaced atoms or lower, the insulating state arising from a gap in the density of states (DOS) at the Fermi level (E-F) as in a Mott insulator is suppressed and the conduction in the film shows a WL behavior with finite conductivity at temperature T -> 0. This behavior is expected ina disordered conductor that does not have a gap in DOS at E-F. At higher fluences the conductivity reduces substantially but the electrical conduction shows a power-law temperature dependence with a small but finite zero temperature conductivity Sigma (T = 0) which is expected in a solid with electrons that are Anderson localized. A similar experiment was performed on the La substituted NdNiO3 films (Nd1-xLaxNiO3) with x = 0.3 that are grown in the same way. La substitution in NdNiO3 suppresses the temperature driven transition and leads to a metallic state with critical composition at x approximate to 0.3. The pristine as well as films irradiated with lowest fluence shows metallic or marginally metallic behavior grown on LaAlO3 and SrTiO3 substrates, respectively. However, at higher fluences they too exhibit a convergence in electronic transport and Sigma shows a power-law temperature dependence at low T with Sigma (T = 0) ???0. Evidence of suppression of correlated behavior can also be seen in the irradiated films where the non-Gaussian nature of resistance fluctuation at T approximate to T-MI, a signature of correlated electron systems, is suppressed on irradiation that leads to collapse of the MIT. Evidence for progressing disordering of the films on irradiation were observed in Raman spectroscopy as well as x-ray studies that show the basic integrity of the NiO6 octahedra is preserved and the structure retains its crystallinity
Permeation Behavior of Oxide Bonded SiC Ceramics at High Temperature and Prediction of Pressure Drop in Candle Filters
No full textOxide-bonded silicon carbide supports of porosity ranging from 33% to 47% were prepared by heating powder compacts (SiC, clay and alumina) at 1400 degrees C in air with graphite acting as a pore former. The supports were spray-coated with an aqueous slurry of fine SiC powder (d(50)=15 mu m), then sintered to produce a filtering layer with thickness ranging from 116 to 200 mu m and average pore size ranging from 5 to 20 mu m. Airflow tests were performed on both supports and coated filters at temperatures ranging from 25 degrees to 700 degrees C and superficial velocities ranging from 0.02 to 0.9 m.s(-1). Experimental permeability coefficients were used to simulate the pressure drop behavior of hypothetical candle filters for industrial combustion/gasification processes (biomass combustion in water-tube steam boilers (BCSB), pressurized fluidized-bed combustion (PFBC) and integrated gasification combined cycle (IGCC)). The simulated permeation properties of the hypothetical candles were compared to those of commercial hot gas filters
Ln(2)Te(6)O(15) (Ln = La, Gd, and Eu) ``Anti-Glass'' Phase-Assisted Lanthanum-Tellurite Transparent Glass-Ceramics: Eu3+ Emission and Local Site Symmetry Analysis
No full textThe presence of lanthanide-tellurite ``anti-glass'' nanocrystalline phases not only affects the transparency in glass-ceramics (GCs) but also influences the emission of a dopant ion. Therefore, a methodical understanding of the crystal growth mechanism and local site symmetry of doped luminescent ions when embedded into the precipitated ``anti-glass'' phase is crucial, which unfolds the practical applications of GCs. Here, we examined the Ln(2)Te(6)O(15) ``anti-glass'' nanocrystalline phase growth mechanism and local site symmetry of Eu3+ ions in transparent GCs produced from 80TeO(2)-10TiO(2)-(5 - x)La2O3-5Gd(2)O(3)-xEu(2)O(3) glasses, where x = 0, 1, 2. A crystallization kinetics study identifies a unique crystal growth mechanism via a constrained nucleation rate. The extent of ``anti-glass'' phase precipitation and its growth in GCs with respect to heat-treatment duration is demonstrated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analysis. Qualitative analysis of XRD confirms the precipitation of both La2Te6O15 and Gd2Te6O15 nanocrystalline phases. Rietveld refinement of powder X-ray diffraction patterns reveals that Eu3+ ions occupy ``Gd'' sites in Gd2Te6O15 over ``La'' sites in La2Te6O15. Raman spectroscopy reveals the conversion of TeO3 units to TeO4 units with Eu2O3 addition. This confirms the polymerizing role of Eu2O3 and consequently high crystallization tenacity with increasing Eu2O3 concentration. The measured Eu3+ ion photoluminescence spectra revealed its local site symmetry. Moreover, the present GCs showed adequate thermal cycling stability (similar to 50% at 423 K) with the highest activation energy of around 0.3 eV and further suggested that the present transparent GCs would be a potential candidate for the fabrication of red-light-emitting diodes (LEDs) or red component phosphor in W-LEDs