Optical and dielectric properties of organic laser dye Rhodamine 6G doped silica xerogels with the variation of the sol-gel parameters

413-420The effect of sol-gel parameters such as pH of the alcosol, R6G/TEOS, H2O/TEOS and EtOH/TEOS molar ratios on the optical and dielectric characteristics of R6G doped silica xerogels are reported here. Optical absorption and emission have been studied in the visible range. The dielectric property such as dielectric permittivity (') is carried out for pure and the R6G doped silica xerogels in the frequency range of the applied field (f) from 100 Hz to 1 MHz. It has been found that the optical and dielectric properties of the R6G doped silica xerogels are strongly dependent on the sol-gel parameters. Monolithicity and transparency of the R6G doped silica xerogels have also been studied. There is a remarkable shrinkage with the variation of the sol-gel parameters

A new route for preparation of sodium-silicate-based hydrophobic silica aerogels via ambient-pressure drying

An in-depth investigation into the synthesis of hydrophobic silica aerogels prepared by the surface derivatization of wet gels followed by subsequent drying at ambient pressure is reported. The following sol–gel parameters were examined for their effect on the physical properties of the derived aerogels: number of gel washings with water, percentage of hexane or methanol in silylating mixture, molar ratio of tartaric acid: Na2SiO3, gel aging period, weight% of silica, trimethylchlorosilane (TMCS) percentage, and silylation period. These parameters were varied from 1 to 4, 0 to 100%, 0.27 to 1.2, 0 to 4 h, 1.5 to 8 wt.%, 20 to 40% and 6 to 24 h, respectively. The properties of hydrophobic silica aerogels synthesized by this new route were investigated in terms of bulk density, percentage volume shrinkage, percentage porosity, thermal conductivity and contact angle with water, and by Fourier transform infrared spectroscopy (FTIR). The as-prepared hydrophobic silica aerogels exhibited high temperature stability (up to approximately 435 °C) as measured by thermogravimetric/differential thermal analysis (TGA-DTA). The optimal sol-gel parameters were found to be a molar ratio of Na2SiO3:H2O : tartaric acid : TMCS of 1 : 146.67 : 0.86 : 9.46, an aging period of 3 h, four washings with water in 24 h and the use of a 50% hexane- or methanol-based silylating mixture. Aerogels prepared with these optimal parameters were found to exhibit 50% optical transparency in the visible range, 84 kg m−3 density, 0.090 W mK−1 thermal conductivity, 95% porosity and a contact angle of 146° with water

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Not AvailableProcessing of fish involves mainly the application of various preservation techniques for retaining a superior quality and enhancing shelf life. It also covers aspects like value-addition to produce a wide variety of products. But during these fish processing operations large quantity of effluents, which contain active microorganisms in various forms are being generated. Depending on the processing operation involved, the level of contamination varies. This high-strength wastewater from fish processing industry is of great concern world-wide and hence recently stringent liquid effluent policies are being adopted. A number of treatment strategies at different levels are applicable for reducing this risk, however biological treatment is one of the best options for fish processing wastewater, rich in organic matter. Biological treatment includes both aerobic and anaerobic processes. Aerobic processes such as activated sludge, lagoons, trickling filter and rotating biological contactor are suitable for organics removal. The anaerobic processes can also remove 80-90% organics and produce biogas. A combination of both anaerobic digestion and aerobic process is regarded as an effective approach to reduce the contaminants in fish processing wastewater.Not Availabl