IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Permeability behavior of silicon carbide-based membrane and performance study for oily wastewater treatment
No full textPorous SiC ceramic is considered as a suitable material for hot gas filtration, microfiltration, and many others industrial applications. However, full utilizations of porous SiC ceramics have been limited by high-processing costs. In this study, mullite-bonded porous SiC ceramics membranes were prepared using commercial SiC powder, alumina, clay, and different sacrificial pore formers. The effect of different pore formers on the microstructure, mechanical strength, porosity and pore size distribution, air, and water permeability of porous SiC ceramics were investigated. The average pore diameter, porosities, and flexural strength of the final ceramics varied in the range 3.7-6.5 mu m, 38-50 vol. %, and 28-38 MPa, respectively, depending on the characteristics of pore former. The Darcian (k(1)) and non-Darcian (k(2)) permeability evaluated from air permeation behavior at room temperature was found to vary from 1.48 x 10(-13) to 4.64 x 10(-13) m(2) and 1.46 x 10(-8) to 6.51 x 10(-8) m, respectively. All membranes showed high oil rejection rate (89%-93%) from feed wastewater with oil concentration of 1557 mg/L. The membrane with porosity similar to 48 vol% and mechanical strength 31.5 MPa showed and highest pure water permeability of 13 298 Lm(-2)h(-1)bar(-1)
Synthesis of pure 15R-SiAlON polytype phase & its crystal structure under carbothermal-reduction-nitridation
No full textSynthesis of pure 15R-SiAlON polytype phase, unexplored so far, through carbothermal-reduction-nitridation (CRN) of a mixture of alumina with stoichiometrically proportionate silica has been successfully attempted. The probable reaction sequences of formation are described in terms of the obtained phases. It is argued that the role of CRN process is limited to the formation of intermediate phases, AlN and beta-SiAlON, which finally react to form the polytype phase. FTIR studies provide supportive evidence for the different chemical reactions taking place. Formed particles are mostly agglomerated which are actually consisted of fine crystallites (100-300 nm). The powder is well sinterable without external densification aid under spark plasma sintering process producing plate-like elongated grains. The refinement of X-Ray data revealed lattice parameters, lattice volume, crystallite size, microstrain as well as atom coordinates and the corresponding Wycoff positions of the obtained 15R-SiAlON. Six independent atom sites in the unit cell, one (Si/Al) site at 3a, two (Si/Al) sites at 6c and three (O/N) sites at 6c are found. The crystal structure as revealed is silicon rich, ordered but distorted with respect to both bond length and direction for the presence of N4- electronic state
Photocatalytic Evaluation of Anatase TiO2 Coating on Ceramic Tiles by Raman Spectroscopy
No full textThe present work reports a convenient way to evaluate the photocatalytic activity of anatase TiO2 films by monitoring the degradation of methylene blue (MB) directly on the TiO2 coated tiles under simulated solar light (1 sun condition; AM 1.5G simulator) using Raman spectroscopy. For this purpose, nanocrystalline TiO2 films of aesthetic quality (thickness similar to 80 +/- 5 nm) were deposited by the sol-gel method on the glazed tiles. XRD and Raman studies of the calcined coatings (500 degrees C/2 h in air) confirmed the formation of anatase phase of TiO2. The water contact angle (theta) value of the coated tiles was found to be 20 +/- 1 degrees (hydrophilic) and no significant change of theta was noticed after storing in ambient condition for 3 months. The MB decomposition on the TiO2 coating under 1 sun condition was monitored by recording the Raman spectra with respect to time. Using this technique, the apparent rate constant (k(app)) value of MB degradation was found to be 0.2554 min(-1). The total photo-decomposition of dye and its repeatability studies through direct Raman monitoring of the coating surface ensured the self-cleaning ability of the TiO2 coatings
Processing of Si-Mo-SiC composite by infiltration of silicon metal alloy into coir fibre derived bio-preform
No full textFibreboards made of coir fibres were converted to carbon templates by controlled thermal processing which were further infiltrated and reacted with Mo-Si alloy containing 90.4wt% Si, at 1400-1550 degrees C in vacuum. Depending on infiltration temperature the composition of the final composite varied containing mainly SiC, MoSi2, unreacted Si and C. Morphology and the phase distribution of the final Si-Mo-SiC composite determined by scanning electron microscopy and X-ray diffraction technique. Micro-hardness test at different loads was carried out using a Vicker's micro-hardness tester. The sample prepared at 1400 degrees C showed best hardness property
Effect of cation ratio on microstructure and optical absorbance of magnesium aluminate spinel
Get PDFThis work is pertaining to the synthesis of fine magnesium aluminate spinel (MgAl2O4) powders of varied trivalent:bivalent cation ratio along line of homogeneity of the solid solution (MgO. xAl(2)O(3), x = 1, 1.25, 1.50, 1.75, and 2) via gel combustion method. Magnesium- and aluminum- nitrate were used as the oxidants in combustion reaction fuelled by urea in combination with stoichiometric formaldehyde solution acting as reductant. Synthesized powders were characterized in terms of microscopic analysis and optical absorbance measurements. The cation ratio, through a change in gel structure influences the nature of crystallization of the product, while on the other hand does not affect grain shapes and sizes. Distinct enhancement in both absorption intensity and the corresponding estimated energy band gap has been observed against increasing excess than stiochiometric alumina concentrations. Evaluated optical band gaps were widened in proportion to the Al: Mg ratio which may be attributed to Burstein-Moss effect in consequence of substitutional insertion of introduced Al3+ ions in spinel lattices
Crystallization and kinetics studies of Ti20Zr20Cu60-xNix (x=10, 20, 30 and 40) metallic glasses
Get PDFSynthesis and characterization of Ti20Zr20Cu60-xNix (x = 10, 20, 30 and 40) metallic glasses are reported in this paper. Glassy ribbons are produced by rapid quenching using the standard copper wheel roller technique in argon atmosphere. Their structural characterization is carried out by X-ray diffraction (XRD) and thermal behaviour (crystallization) study by differential scanning calorimetry (DSC). Results of XRD on both sides of each ribbon sample confirmed that each sample was indeed amorphous/glassy as only a very broad peak in XRD pattern was observed. Metallic glass Ti20Zr20Cu50Ni10 shows three crystallization peaks in non-isothermal DSC scans while other three samples show only a single crystallization peak. The activation energy of crystallization for each sample has been calculated using three available models, namely, those of Kissinger, Augis-Bennett and Ozawa. All the three models gave nearly similar activation energies for a given sample within 10%
Agreement on Commercial Utilization of High Power Optical Amplifier based on cladding pump Er/Yb codoped fibers for Free Space Communication
No full textEmulsion based solvothermal synthesis of CuO grainy rod via the formation of quasi-quadrangular prism shaped Cu-2(OH)(3)Br for recyclable catalyst of 4-nitrophenol reduction
No full textQuasi-quadrangular prism shaped Cu-2(OH)(3)Br particles were synthesized by emulsion based solvothermal process followed by their transformation to hierarchical copper oxide grainy rods by calcination at 450 degrees C/2 h. In this process, we employed cetyltrimethyl ammonium bromide (CTAB) as cationic surfactant as well as bromide source, 1-butanol as co-surfactant, cyclohexane as organic (oil) medium, copper acetate as aquo-based copper precursor and hexamethylenetetramine ((CH2)(6)N-4) as the source of ammonia under hydrolyzing condition. The length/diameter of hierarchical CuO grainy rods was found to be around 2.5-10 mu m/0.5-1.5 mu m comprising of smaller grain (20-30 nm) assembly. The proposed reaction trajectory based on anion-exchange mechanism was proposed for the transformation of Cu-2(OH)(3)(CH3COO) to Cu-2(OH)(3)Br. The product showed excellent catalytic performance for 4-nitrophenol reduction. The apparent rate constant values increased from 0.532 min(-1) to 1.038 min(-1) with catalyst amount increased from 1 to 3 mg. This investigation refers the novel synthesis approach of CuO grainy-rod from quasi-quadrangular prism shaped Cu-2(OH)(3)Br precursor, and its role as catalyst for 4-nitrophenol reduction
Frequency dependent energy storage and dielectric performance of Ba-Zr Co-doped BiFeO(3)loaded PVDF based mechanical energy harvesters: effect of corona poling
No full textBi0.95Ba0.05Fe0.95Zr0.05O3(BBFZO) nanoparticles were synthesized by a sol-gel technique to develop a filler material with lower leakage current and oxygen vacancies compared to the host BiFeO3. In this work, we report the enhanced dielectric, ferroelectric, energy storage and energy harvesting performance of BBFZO incorporated PVDF composites. 15 wt% BBFZO loaded PVDF (15BBFZO) exhibited improved polarity (F(EA) = 77.42%) compared to neat PVDF (F(EA) = 37.01%). At an applied field of similar to 14 kV cm(-1)(1 Hz), this film (15BBFZO) exhibited a maximum energy storage density of 151.18 mu J cm(-3)(at 1 Hz). Upon repeated human finger tapping, an average open circuit peak to peak a.c. voltage (V-OC) similar to 20 V was obtained from 15BBFZO. A comprehensive study of frequency dependentD-Eloops and an extensive study of the effect of electrical poling on the output performance of the developed composite films have been performed. An improvement of the dipolar polarization was established through a frequency dependentD-Eloop study of unpoled and poled 15BBFZO and from other experiments. After poling the energy storage density andV(OC)of 15BBFZO were 154.66 mu J cm(-3)(at 1 Hz) and similar to 30 V, respectively. After rectification this output electrical signal was able to charge a 10 mu F commercial capacitor up to similar to 5.5 V. After poling, the energy storage efficiency (eta) of 15BBFZO also improved from 52.49% to 67.85% (at 1 Hz). The frequency dependence of the storage efficiency for all the samples has also been extensively investigated here. At 1 kHz,eta improved to 93.30% for poled 15BBFZO
Compositional dependence of red photoluminescence of Eu3+ ions in lead and bismuth containing borate glasses
No full textHerein, heavy metal borate glasses activated with different concertation of Eu2O3 were prepared via the melt quench method. The Eu3+ concentration effect on photoluminescence (PL) properties of prepared glasses was investigated and discussed in detail to understand their utility in solid-state lighting and other photonic applications. The present work explains the suitability of two heavy metal oxides such as PbO and Bi2O3 for Eu2O3 doping to develop the glassy materials for photonic applications. The PL intensity was increased with an increase in Eu3+ content in PbO framed borate glasses while in Bi2O3 containing borate glasses the PL intensity was decreased at higher concentration due to concentration quenching. The Judd-Ofelt parameters and the radiative properties suggest the heavy metal borate glass hosts activated with 1 mol % of Eu3+ were potential materials for red light-emitting devices under blue light excitations. The Lifetime values of the PbO framed glasses were greater compared to Bi2O3 framed borate glasses which suggest the borate glass host containing high PbO content is more precisely suitable than Bi2O3 containing borate glass for solid-state lighting applications under blue light excitation