The Polycrystalline ceramic samples with formula unit Bi2V1-xTix/2Alx/2O5.5-δ (x = 0.1 and 0.175) were synthesized. The specimens were characterized by AC Impedance Spectroscopy for dielectric studies. The variation of dielectric parameters: dielectric constant ( ), dielectric loss (tan ), complex electric modulus and AC conductivity, as a function of frequency and temperature, have been analyzed. The dielectric loss peaks and AC conductivity plots revealed different relaxation mechanisms i.e. electrode-electrolyte, conduction and dipolar occurring at low, intermediate and high-frequency regimes respectively. The shifting of the dielectric relaxation peaks and hopping frequency in AC conductivity plots towards higher frequency sides with an increase in temperature imply these materials are ionic conductor.
India honors Dr. Sudam Kate with highest civilian award ‘Padma Shri’ for work on Sickle Cell
In the present work, we have estimated the vacancy migration energy in a single crystal of hcp Zr and also determined the mean energy path for this transition using molecular dynamics based simulations. The vacancy migration energy is estimated to be about 1.02 eV, which is quite close to the experimental and DFT data for hcp-Zr.
The present work focuses on the systematic study of the removal of diary industrial pollutants from effluent of MILMA – Kerala Co-operative Milk marketing Federation limited, Calicut through electrocoagulation process (EC). An electrocoagulation batch reactor with aluminium as anode and mild steel as cathode were designed and used for the treatment process. Optimization of various operating parameters such as operating time, pH and current Density on COD and Turbidity removal were studied. The results indicates that the operating time and the applied current density has a positive relationship with the removal efficiency. Higher removal efficiency was found at neutral to alkaline region pH of 7 to 9. Over 95.00 % of pollutants removal efficiently was observed by conducting the EC treatment at current density (CD) of 33.33 A/m2, pH of 7 and EC time of 75 min. The effect of multielectrode system was studied with the obtained optimized parameters in which Monopolar and Bipolar configurations were tested. Out of which Monopolar configuration was found to be most effective in reduction of COD.
La2Mo2O9 based Tb-doped compound, La2-xTbxMo2O9 (x=0.1, 0.2, 0.5), was synthesized and characterised by EIS studies. The frequency and temperature dependent dielectric, electric modulus and ac conductivity studies have been done. Different formalisms have been used to understand relaxation mechanism in our compound. The conductivity in these specimens appears to be due to mobility of oxygen ions.
: The global alarms of energy security and change of environment have prompted strong research in the field of renewable energy to lessen the impact of environmental effects and health hazard. The present study addresses with pyrolysis kinetics of water hyacinth using thermogravimetric analysis (TGA). The TGA analysis was conducted in the temperature range of 30 to 900 ᵒC with four heating programs (10, 15, 20 and 30 C/min). TGA result shows that the pyrolysis of water hyacinth is categorized by three different stages and most decomposition was observed in the 2nd pyrolysis stage. The activation energy in this study was determined using isoconversional method i.e. Flynn–Wall–Ozawa and the preexponential coefficient were calculated using Kissinger’s equation. From the analysis it was observed that the average value of activation energy of water hyacinth obtained as 238.75 kJ/mol in the conversion range of 0.1 – 0.8. With the increasing of heating rates, the pre-exponential coefficient was found to decreased and maximum value was obtained at α = 0.6.
Four new molecules 1,3,5-trinitrooctahydropyrrolo[3,4-d]imidazole (1), 1,4,6-trinitrooctahydro-1H-pyrrolo[3,4-b]pyrazine (2), tetranitrodecahydropyrrolo [3, 4-f] [1, 3, 5] triazepine (3), 1,2-dinitro-4-(3-nitro-1,3-diazetidin-1-yl)pyrazolidine-3,5-dione (4) were designed and studied the theoretical properties using DFT calculations. All the four molecules were found to exhibit better or comparable properties with the commercially available, widely used explosives RDX, HMX and useful for propellant and explosive applications.
Porous layers from activated carbon with macro-molecular cyclic amines based on PVC and modyfied by primary amines were synthesized and its properties were described. Layers were grafted to the surface of a PVC film, cotton medical gauze and asbestos fabric. The nature of benzyl alcohol solvatation and the mechanism of suspension formation within layers of macro-molecular cyclic amines were investigated by methods of IR-spectroscopy and luminescence spectroscopy and described. The structural features of grafted PVC was identified and the influence of the substrate nature on the structure was traced. Upon contact of particles with benzyl alcohol molecules from solvatocomplexes PVC-related aromatic groups replace benzyl alcohol in solvatocomplexes. This leads to non-covalent binding of groups on the surface of the particles. It was shown that sorption of organic molecules does not affect the number of structural types of oxoamines.
Based on our own research work and results, I try to analyze the developments/progress in the area of photocatalysis and its realistic applications.
Million tons of coals are being burned every year to meet the electric power requirement in India. Fly ash powder, a by-product recovered from the gases of burning pulverized coal in thermal power plants contains alumina, silica, iron oxide and other heavy metals as well and cause air, soil and water pollution. So, in this present study, attempt have been made to investigate the potential utilization of fly ash collected from north eastern region of India to make some valuable products which will be used in construction industry. Authors have adapted a green technology i.e. geopolymerization technology for making the same. Geopolymerization process is associated with the alkali activation of materials which are rich in amorphous alumino-silicate. In this present investigation, sodium hydroxide is used as an alkaline activator for the dissolution of fly ash powder. The geopolymerization process has been performed using 8 M, 10 M and 12 M sodium hydroxide solution cured under artificial conditions. The mechanical property (compressive strength) was determined by using compression testing machine. Further, the strength data of the geopolymeric samples were co related with the results obtained from various characterization techniques such as scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR).
TiO2 has been shown to be excellent photoactive material in the presence of UV light. In order to make TiO2 a more efficient photocatalyst several attempts are being made. The present work attempts to address the issue through WO3-TiO2 (TW sample) and Nb2O5-TiO2 (TN sample) composites. Both the composite were synthesized through sol-gel process. The composites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and UV–Visible spectrophotometer. The composites lower band gap value than DP25. This effect also seems to be reflected in photo-degradation experiment. Photo-degradation of methylene blue (MB) dye, in the presence of Nb2O5-TiO2, WO3–TiO2 composite and DP25 under UV irradiation was studied. WO3–TiO2 composites have superior photoactivity than Degussa P25 (DP25) while Nb2O5-TiO2 composite seems to have deteriorating effect on photoactivity of TiO2.
Effects of sintering temperature on structural and electrical properties of La2Mo2O9 synthesized via solution combustion method are addressed in this work. Single phase of La2Mo2O9 was obtained at relatively lower calcination temperature ( about 700 oC) than the conventional route. The synthesized specimen was sintered at three different temperatures 800 oC, 900 oC and 1000 oC for 12 hours and was subjected to structural & electrical characterizations. X-Ray diffraction pattern confirms the formation of monoclinic phase with space group P213 for all three sintering temperatures. Lattice parameters were calculated using Reitveld technique and found to be increased with the sintering temperature. α to β phase transition is prominent in the Arrhenius plot of all the sintered samples but the transition temperature is lower than the powders obtained by the solid state technique. Conductivity was found to be increased slightly at lower and intermediate temperatures for 900 oC and 1000 oC as compared to specimen sintered at 800 oC. In the intermediate temperatures, grain boundary contribution to the total resistance is more distinguished in the Nyquist plot of the sample sintered at 800 oC which causes the decrement in the conductivity. Activation energy in the temperature range 600 oC - 750 oC for the sample sintered at 800 oC, 900 oC and 1000 oC are 0.5298 eV, 0.35896 eV and 0.35805 eV respectively. The sample sintered at 1000 oC exhibited highest ionic conductivity 0.0391 S.cm-1 at 750 oC.
Bioremediation with the help of biosurfactant is one of the promising technologies in treating the hydrocarbon and heavy metal contaminated sites. Biosurfactant was produced naturally by microorganism and hence biodegradable, which is alternative to chemical surfactant for various applications. In this study the biosurfactant producing strain Brevibacillus sp. AVN 13 was used for hydrocarbon and heavy metal remediation. The biosurfactant enhanced biodegradation assay of used engine oil by Brevibacillus sp. AVN 13 was carried out using Erlenmeyer flask experiment and the degradation of hydrocarbon removal rate was analyzed by gas chromatography. The Brevibacillus sp. AVN 13 is having ability to degrade 72 % of hydrocarbon. Then biosurfactant assisted chromium removal process was carried out. The effect of initial chromium concentration, effect of pH, incubation time and concentration of biosurfactant were studied. The removal rate of chromium using biosurfactant was found to be 72.54 % under optimized conditions. Overall this study proved that, biosurfactant from Brevibacillus sp. AVN13 can be effectively used for degradation of oil spilled and heavy metals contaminated sites.
PbS/CdS core-shell quantum dots have been synthesized through chemical route. PbS shows polycrystalline cubic structure and CdS shows hexagonal structure. The photoluminescence study shows a blue shift of near band gap emission of core PbS when coated with shell CdS. PbS shows a band gap of 2.2 eV and CdS shows 2.7 eV whereas the PbS/CdS nanocomposite shows a reduction of band gap 1.5 eV. The observed optical properties are clearly carrying evidences of cationic exchange between the lead and cadmium ion complexes. The quantum yield of the composite is greatly enhanced implying its potential for application in optoelectronic devices.
A study on growth of ZnSe nanostructures in wet chemical bath deposition has been made. The structural and optical characterizations of the samples are done by XRD, UV-VIS and PL spectroscopy. XRD shows the dominant wurtzite structure along with the oxide trace. Oxidation broadens the absorption edges and lowers the band gaps. PL spectra show near band gap emissions in the range 418 nm-421 nm along with the additional impurity emissions around 462 nm, 488 nm & 532 nm. These impurity emissions may be attributed to inherent defects on the surface that can emit band-trap emissions.
Various high energetic materials (HEMs) like RDX and HMX are crystalline solids that are sensitive to shock. Suitable fluorinated polymeric binders will be a potential replacement to the conventional stable but un-energetic hydroxyl-terminated polybutadiene (HTPB) for processing them in a shock insensitive and machinable form without decreasing the overall energy. Synthesis of fluorosubstituted epoxy monomer followed by synthesis of the corresponding fluorinated polymeric binder via cationic ring-opening polymerization is discussed in this paper.
