IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Vanadium oxide thin films on quartz and Al6061 with reduced phase transition temperature and low solar absorptance for advanced thermal control application in space
No full textDoped and co-doped vanadium oxide (VO) thin films were deposited on quartz substrates with varying concentrations of doping elements by sol-gel spin coating technique. The VO thin films were characterized by the X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), cross-sectional FESEM and X-ray photoelectron spectroscopy (XPS) techniques. The optical properties, e.g., the average solar absorptance (alpha(s)), the average solar reflectance (rho(s)) and the average solar transmittance (tau(s)) of the films deposited on quartz were evaluated by using a solar spectrum reflectometer. Based on the optical characterizations, an optimized doping concentration was identified. Further, a process optimized condition was utilized to grow both doped and co-doped vanadium oxide films on metallic Al6061 substrates; which are generally used in spacecraft. The phase transitions of all as grown vanadium oxide films on Al6061 were characterized by the differential scanning calorimetry (DSC) technique. The thin films showed reversible and repeatable phase transitions at sub-zero level of temperatures e.g., similar to(-23.3 degrees C). Thus, the VO thin films developed in the present work emerge out to be of paramount importance for the smart radiative device applications in spacecraft
An in vitro evaluation of the variation in surface characteristics of bioactive glass coated SS316L for load bearing application
No full textThe present communication reports the variation in surface characteristics of bilayered coating of phosphate free bioactive glass (PFBG) on SS316L substrate at simulated conditions, w.r.t both pH and temperature, to understand the suitability of the same for load bearing applications. The coated substrates were subjected to both physiological (7.4) and pathophysiological (4.5) pH conditions, considering two working temperatures of 37 degrees C and 45 degrees C, related to the real time scenario, in the post implantation period. Herewith, a faster dissolution of the PFBG network could be obtained `at higher temperature (45 degrees C) and acidic pH (4.5) conditions, leading to a degraded surface texture, while the same at 37 degrees C and pH 7.4, exhibited an almoit intact surface. The observation was corroborated using atomic force microscopy which exhibited an exponential increase in the nanoscale surface roughness of the coating at lower pH and at higher temperature conditions. The ionic Ca2+ dissolution kinetics of the PFBG coating followed by their cellular interaction were assessed using MC3T3 cell line, which showed a distinct difference compared to the as prepared PFBG coated substrate. Further, we made an attempt to assess the role of the calcium binding protein, calmodulin and its major target, calcium-calmodulin kinase II alpha (CAMKII alpha) in osteoblast (MC3T3) differentiation, cultured on the PFBG coated SS316L substrates, subject to the experimental parameters as abovementioned. The results indicated significance of the real time conditions at the site of application of a bioactive glass coating on load bearing SS316L based implant material
Studies on Synthesis and Characterization of Magnesia Based Aggregates Derived from Indian Magnesite
No full textRole of different rare earth oxides on the reaction sintering of magnesium aluminate spinel
No full textRole of three rare earth oxides, viz., La2O3, CeO2 and Yb2O3 on reaction sintering of magnesium aluminate spinel having molar ratio of MgO:Al2O3 = 1:2 from its solid oxide precursors was investigated in static and dynamic heating conditions. Effect of these additives (3 wt%) on densification behavior, phase assemblage and microstructure development were studied in the temperatures of 1500–1700 °C. Yb2O3 enhanced the sintering of spinel, while La2O3 and CeO2 negatively impacted the sintering of magnesium aluminate spinel which can be discerned from the shrinkage curve of TMA as well as from static firing regime. This is ascribed to the formation of secondary phases in La2O3 and CeO2 containing samples which have different crystalline structures to that of spinel. This anisotropy due to different crystallinity hindered the pore shrinkage and pore removal and thereby retarded the densification. Whereas, the cubic structure of the secondary phase formed in Yb2O3 containing sample which is isotropic with the crystalline orientation of the parental spinel phase assisted the densification
Wideband optical fiber amplifier with short length of enhanced erbium-zirconia-yttria-aluminum co-doped fiber
No full textA wideband optical amplifier is demonstrated by using an enhanced Zirconia-Yttria-Aluminum erbium doped fiber (Zr-EDF) with a total length of 3.5 m as gain media, in double-pass parallel configuration. At - 10 dBm input signal, the proposed amplifier produces a flat gain of 17.1 dB with gain fluctuation less than 1.5 dB within wavelength region from 1525 to 1600 nm. The noise figure is maintained below 10 dB within the flat gain region
Improvements in mechanical properties of SPS processed 15R-SiAlON polytype through structurally survived MWCNT reinforcement
No full textPresent work reports the effects of multiwalled carbon nanotube (MWCNT) reinforcement on sintering and mechanical properties of additive free, dense (> 96%) 15R-SiAlON polytype. Laboratory made precursor polytype powder, prepared through carbothermal-reduction-nitridation technique and devoid of any external sintering additive, were dispersed with MWCNT and were consolidated using spark plasma sintering at 2000 degrees C for 10 min under 40 MPa. Differential electrical conductivity causing localized heating resulted in improved sintering behaviour in the composites. Apart from formation of both equiaxed and elongated SiAlON grains, various CNT/SiAlON interactions were noticed in the composites. Depending on test load, the 0.5 wt% MWCNT/15R-SiAlON composite offered 9.6-17% and 12-13% higher hardness and indentation fracture toughness, respectively, over the monolith. Indentation size effect and load dependence of indentation toughness of the studied specimens have been reported. Under 20N, > 30% reduction in specific wear rate was observed at only 0.5 wt% MWCNT loading. Self-reinforcement offered by elongated matrix grains, reinforcement by structurally survived CNTs, matrix grain refinement by the dispersed nanotubes and solid lubrication offered by the pulled-out CNTs were the key factors behind obtaining improved tribo-mechanical performance of the composites over pure 15R-SiAlON polytype
BaBi2Ta2O9 based glass-ceramics: Influence of ZrO2 on crystallization kinetics, microstructure and dielectric properties
No full textBaBi2Ta2O9 (BBT) based ferroelectric glass-ceramics (GCs) with different zirconium oxide (ZrO2) content used as nucleating agent are synthesized via glass melt-quenching technique followed by temperature controlled crystallization. The effect of ZrO2 as a nucleating agent on the crystallization mechanism, microstructure and dielectric properties of BBT based GCs has been studied for the first time. Crystallization kinetics studies facilitated successful controlled crystallization of ZrO2 doped BBT based GCs around the exothermic peak temperature using double stage and single-stage heat-treatments, which was otherwise difficult in the undoped glass. The dielectric constant increased while the loss and dissipation factors decreased with increase in zirconia content in the GCs. The dielectric properties obtained from single-stage and double-stage heat-treated GCs have been compared and correlated to the corresponding microstructures of the GCs. With 5 mol % ZrO2, dielectric constant of 181 with loss of 0.04 has been obtained for the sample fabricated by single-stage ceramization around the 2nd crystallization peak temperature. (C) 2019 Elsevier B.V. All rights reserved
Highly selective and stable acetone sensor based on chemically prepared bismuth ferrite nanoparticles
No full textExcellent acetone sensing property with high selectivity and long-term stability has been observed in single phase crystalline bismuth ferrite (BFO) nanoparticles. This phase pure BFO nanoparticles were synthesised via a simple sol-gel method and well characterized using various sophisticated instruments. BFO nanoparticles exhibit remarkable response (S = 1.8) towards 1 ppm of acetone at an operating temperature of 350 degrees C. The prepared sensor is extremely selective towards acetone among different gas analyte and also insensitive to moisture which can be attributed to a particular operating temperature (350 degrees C). Additionally, other important features of the sensor include high reproducibility and long-term stability for around 1 year. Displayed efficient sensing performance of these BFO nanoparticles-based sensors could be a potential candidate for different application e.g non-invasive monitoring of diabetes. (C) 2019 Elsevier B.V. All rights reserved
Flexible piezoelectric energy harvesters using different architectures of ferrite based nanocomposites
No full textElectroactive phase transition in polyvinylidene fluoride (PVDF) can be economically achieved readily by addition of nanofillers. In this work, we have demonstrated the influence of rational design and structural control of nanofillers on nucleation and stabilization of an electroactive polymorph in PVDF. Different architectures of zinc ferrite (ZF) i.e. nearly spherical, nearly cubic, and rod-like were synthesized and further introduced in PVDF as a nucleating agent with different filler to polymer ratios. A comparative study of the dielectric and ferroelectric properties and energy harvesting performance of the corresponding nanocomposite was performed to obtain the best architecture based composite. It has been observed that one dimensional nanofillers are more favorable for polar phase transformation and stabilization with incorporation of a lower fraction of fillers. Thus, they exhibited maximum electrical performance (an energy storage density of 7.68 mJ cm(-3) with an energy discharge efficiency of similar to 77%, and an output piezoresponse of similar to 39.10 V with a power density of 2.96 mu W mm(-3)). This may be due to the preferred ` in-plane' orientation of the nanorod structure in the polymer matrix which helps to accumulate the entire short chain all-trans (TTTT) conformation and form an extended all-trans conformation corresponding to an electroactive ss-polymorph. This study may open a new strategy to design and fabricate ferrite-PVDF based electroactive nanocomposites with desired shapes for high performance energy storage and harvesting application
Nanosecond pulse laser generation at 1.55 and 2 mu m regions by integrating a piece of newly developed chromium-doped fiber-based saturable absorber
No full textThis paper demonstrated the nanosecond pulse laser operation at 1.55 and 2 mu m wavelength regions using a newly develop chromium-doped fiber (CrDF) as a saturable absorber (SA) to convert efficiently continuous-wave laser operation to nanosecond pulse laser operation. The laser uses an erbium-doped fiber (EDF) and thulium-doped fiber as the gain medium. A piece of 10 cm long CrDF was integrated into both laser cavities to generate nanosecond pulse laser operation. In 1.55 region generation, an additional single-mode fiber (SMF) 100 m long was added into the EDF laser cavity. Stable pulse generation occurred at a repetition rate of 1 MHz with a pulse width of 432 ns and a signal-to-noise ratio (SNR) of 66 dB. The highest peak power of 24 mW was obtained at 142 mW pump power. In 2 mu m region generation, the obtained repetition rate was 10 MHz with a pulse width and SNR of 59 ns and 41 dB, respectively. The highest peak power was only 8.3 mW. By looking into the findings, the newly developed CrDF SA has a potential to be further enhanced toward better generation of ultrashort pulse fiber lasers. (C) 2019 Optical Society of Americ