IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Studies on Structure-Property Correlation in Some Functional Ceramic Based Gas Sensing Materials Using Various Experimental Techniques
No full textRole of silane grafting in the development of a superhydrophobic clay-alumina composite membrane for separation of water in oil emulsion
No full textHydrophobic composite kaolin-coated clay-alumina membranes are unique choices for water in oil emulsion separation. In this work, a membrane fabrication approach is presented using kaolin clay coating in the clay -alumina tubular composite support tube and subsequently grafting by different concentrations of fluoroalkyl silane (FAS: 1H, 1H, 2H, 2H, -Perfluorooctyltriethoxysilane) on the membrane surface. Different concentrations of fluoroalkyl silane formed distinctive hierarchical structures which exhibited hydrophobicity of the membrane surface. The pore property, surface roughness properties, and thermogravimetric properties can be suitably tailored by tuning the silane concentration in the grafting solution. The surfaces of comparatively higher silane content grafted (M50 and M100) composite membranes were found to be superhydrophobic. Comparably, our optimal composite membrane (M100) displayed a moderate steady flux rate of 80-100LMH (Lm-2h-1) and excellent water rejection (> 99%) properties during the separation of water in hexane and toluene emulsion at a cross-flow transmembrane pressure of 1 bar. The role of silane concentration on permeated hexane and toluene flux rate, water rejection rate, surface wettability, microstructure, and hydrophobic stability reveals new dis-tinguishing insights into the hydrophobic clay-alumina composite membrane fabrication
Realization of optical fiber regenerated gratings by rapid cooling and split annealing
Get PDFRapid cooling, or quenching, during regeneration of seed gratings in standard single-mode silica optical fiber is explored. It is shown that regeneration can be broken up into stages in time. The novel, to the best of our knowledge, method of ``split annealing'' offers a unique tool for optimiz-ing regeneration and studying fundamental glass science within a one-dimensional bi-material system. We demon-strate regeneration at temperatures as high as T= 1200 degrees C for the first time as well as opening up an approach suited to batch processing of regenerated gratings. (c) 2022 Optica Publishing Grou
Chemiresistive NH3 detection at sub-zero temperatures by polypyrrole- loaded Sn1-xSbxO2 nanocubes
No full textChemiresistive gas sensors operate mainly at high temperatures, primarily due to the need of energy for surface adsorption-desorption of analytes. As a result, the operating temperature of the chemiresistive sensors could be reduced only to room temperature. Hence, a plethora of sensing requirements at temperatures below ambient have remained outside the scope of chemiresistive materials. In this work, we have developed an antimony-doped SnO2 nanocube-supported expanded polypyrrole network that could detect low ppm ammonia gas (<= 20 ppm) at sub-zero temperatures with high response (similar to 4), selectivity, and short response and recovery times. The low temperature chemiresistive sensing has been explained in terms of the interplay of an extended conducting network of an in situ deposited polymer, effective transport properties of majority charge carriers and a loosely bound exciton-like electron-hole pair formation and breakage mechanism
Effects of Ni doping at Co-site on dielectric, impedance spectroscopy and AC-conductivity in La2CoMnO6 double perovskites
No full textMultifunctionalities of double perovskites depend strictly on the 3d/4d/5d-transition metals that can be purposefully tuned by doping effect at the transition metal-site. In the present study, the effects of Ni doping at the Co-site on the dielectric, magnetodielectric, complex impedance, complex modulus and ac-conductivity are investigated in detail for the La2Co1-xNixMnO6 (x = 0, 0.1, 0.5) double perovskites. At room temperature, all the compounds exhibited monoclinic crystal symmetry (space group P2(1)/n). No structural phase transition and/or impurity phases were observed after doping. The dielectric behavior is investigated over a wide frequency (100-1 MHz) and temperature (100-300 K) ranges, revealing an enhancement in the dielectric constant for the doped samples compared to parent La2CoMnO6. The magnetodielectric effect is also observed for x = 0 and x = 0.1 samples under 3 T magnetic field. The contributions of grain and grain boundaries at high and low frequencies become evident from the complex impedance spectroscopic and modulus studies. The corresponding carrier activation energies for all the samples are estimated from the Arrhenius fittings. The Nyquist plots are fitted well with an equivalent circuit consisting of two parallel resistance-capacitance elements connected in series, representing the grain and grain boundary effects. The behaviour of the temperature-dependent unitless exponent function predicts the Overlapping Large Polaron Tunneling mechanism in the parent system, while the non-overlapping Small Polaron Tunneling model best describes the doped x = 0.5 system. We confirmed by dc-conductivity study that the samples exhibited semiconductor-like nature in a wide temperature range. By revealing the dielectric, impedance and conductivity behaviours of Ni-doped La2CoMnO6, our study broadens the scope of further research on the doping effect at transition metal-sites in perovskites
White light emission of wide-bandgap silicon carbide: A review
No full textWhite light-emitting diodes (LEDs) are the most promising alternative to the conventional lighting sources due to their high efficacy and energy saving in illumination. Silicon carbide (SiC) has a wide optical bandgap and could be tailored to emit light at different wavelengths across the entire visible spectrum by introducing different dopants. Donor and acceptor (DA) co-doped fluorescent SiC (f-SiC) is a potential candidate for replacing phosphor material in white LEDs, as it has been observed as a good wavelength converter overcoming the disadvantages of rare earth-containing phosphors, such as poor color-rendering index (CRI), short lifetime, and short degradation time. The current study attempts to present an overview on the available approaches to fabricate f-SiC for generating the white light emission and challenges in fundamental research issues to enhance quantum efficiency, color rendering performance, stability, reproducibility of color quality, and lifetime of f-SiC
A study of mechanical properties and WEDM machinability of spark plasma sintered ZrB2-B4C ceramic composites
No full textFour different compositions of ZrB2-B4C composites (i.e., 5, 15, 20, 25 Wt. % of B4C) were fabricated by Spark Plasma Sintering Technique (SPS) at 2000 degrees C temperature. The composites were characterized by the evolution of physical and mechanical properties; X-Ray Diffraction (XRD) analysis was also done for phase analysis of the composites. The relative density values were obtained in the range of 96.14-97.78 % of all the composites. The addition of B4C in ZrB2 matrix led to an enhancement in hardness (15.38 GPa at 5 wt.% B4C to 20.49 GPa at 25 wt.% B4C measured at 1.0 kgf load) and fracture toughness (from 2.93 MPa-m(0.5) at 5 wt.% B4C to 4.13 MPa-m(0.5) at 25 wt.% B4C measured at 1.0 kgf load). The composite samples were processed by wire electrical discharge machining (WEDM) process with three different parameters set for the study of machining speed, surface roughness. The composite with 25 wt.% of B4C shows highest machining speed of 10.56 mm(2)/min. The average surface roughness (R-a) of the WEDM processed composite surfaces lies in the range of 1.26-5.64 mu m
Measurement and analysis of pocket milling features in abrasive water jet machining of Ti-6Al-4V alloy
No full textThe present work deals with the size effect of abrasive water jet milling parameters on the square pockets of Ti-6Al-4V alloy. In this study, the abrasive mesh size, water jet pressure and traverse rate were chosen as milling variables and their effect on pocket features such as depth of cut, undercut, material removal rate, and surface roughness were examined. This study also characterizes the milled pocket surfaces under different milling conditions. Most of the measurements and surface characterizations were done using the Dino-Lite Digital Microscope. For both #80 and #100 abrasives, the AWJ-milled pockets were formed with variations in depth milled and rugged surface by increasing the water jet pressure from 175 to 200 MPa under all the selected traverse rate conditions. Also, the variations of depth of cut in successive trajectories found to have a speed bump effect. At these settings, distribution of energy to the work material was more due to deceleration of jet in the boundary close by and changes made in the feed directions in raster path from 0 & DEG; to 90 & DEG; at a step-over distance of 0.2 mm. This yielded undercuts in the milled pocket corners. However, there was a significant reduction in the undercut with a water jet pressure of 125 MPa and a traverse rate of 3500 mm/min were employed. Besides, the abrasive mesh size #100 had a better surface topography, and also strong jet footprints were observed with mesh size of #80. Based on the experiments results, the size effect of different milling parameters was seen having influence on the pocket geometry and surface features
Temperature-dependent dielectric properties of CsPb2Br5: a 2D inorganic halide perovskite
No full textTwo dimensional (2D) CsPb2Br5 have been successfully synthesized via the chemical precipitation method. Detailed structural, morphological, optical, and dielectric studies of these materials have been performed. These 2D CsPb2Br5 plates (of thickness around 200-300 nm) are ascribed to a tetragonal lattice system with I4/mcm space group. The dielectric attributes such as dielectric constant, electrical modulus, loss factor, and the DC, and AC conductivities, are observed to be varying appreciably with temperature over an extensive frequency window of 10 Hz-50 MHz. The Nyquist plots are investigated using the Maxwell-Wagner equivalent circuit model, which shows the impact of grains and grain boundaries on the overall impedance. Both the free charge conductivity and space charge increase with an increment in temperature, as revealed from the modified Cole-Cole plot. The relaxation time and relaxation mechanism of 2D CsPb2Br5 are estimated using the Kohlrausch-Williams-Watts equation. Variation in DC conductivity and relaxation time, as a function of temperature, closely resembles Arrhenius' behavior. Value of activation energy calculated from the DC conductivity corroborates with the same derived from relaxation time. The observation of high dielectric constant and nominal dielectric loss for CsPb2Br5 perovskite offers enormous potential in energy harvesting and storage devices
Strategies Involved in Enhancing the Capacitive Energy Storage Characteristics of Poly(vinylidene fluoride) Based Flexible Composites
No full textFunctional Materials and Devices Division (FMDD) With the progress of the daily lifestyle of modern human being, the need for flexible dielectric energy storage devices for high field applications has become inevitable. PVDF and its co-polymers, which exhibit excellent flexibility, high breakdown strength, good piezoelectric and ferroelectric properties and low cost, have become very useful in this purpose and hence being investigated widely all over the world. Different strategies including versatile device fabrication techniques and momentous materials engineering have been employed to promote the energy storage characteristics of PVDF based composites. In this paper, we review the current trend of research in the field of PVDF based energy storage devices with the main focus on the strategies involved in enhancing their energy storage performance. Upon extensive literature survey, it has been found that the breakdown characteristics of the composite films are the main determining factor of their high field energy storage applications. The strategies, which can enhance the said performance of PVDF-based composites, have been elaborately discussed here step-by-step and the fruitful approaches for the desired performance enhancement have been proposed. Considering the numerous attraction of research in this field, the gaps and huge future scopes of research have also been comprehensively discussed here