Influence of ZnO Nanoparticles on Thermal Behavior of Poly Vinyl Alcohol Films

Thermal behavior and thermal stability of PVA and PVA-ZnO(5mol% - 20mol%) nanocomposite films prepared by solution casting method were studied by various techniques such as Differential Scanning Calorimetry (DSC), Thermogravimetry (TG) and Differential thermal analysis(DTA). Nano ZnO used as filler was prepared by low temperature solution combustion synthesis. Dehydration temperature (TD), glass transition temperature (Tg), and melting temperature(Tm) were estimated using DSC. Heat of enthalpy and specific heat capacity (Cp) of the samples are also estimated from these studies. Thermogravimetric analysis showed significant decrease in weight loss in nanocomposite films compared to pure polyvinyl alcohol indicating increase in thermal stability of the host matrix due to the incorporation of nano ZnO. The composite of 15mol% ZnO is found to exhibit the highest thermal stability. First order derivative of weight loss supports the results obtained from the DSC studies and shows extension of final degradation temperature of composite films in comparison with pure PVA. Differential thermal analysis reveals the existence of three endothermic peaks and an exothermic one corresponding to various physical and chemical changes taking place in pure polymer and composite films subjected to heating

Preparation and Investigation of Suitability of Gadolinium Oxide Nanoparticle Doped Polyvinyl Alcohol Films for Optoelectronic Applications

Gd2O3 nanoparticles synthesized by solution combustion method were used to prepare PVA-Gd2O3 nanocomposite films of varying concentrations (2 wt%–6 wt% of filler) by solution casting method. Being a rare earth oxide, gadolinium oxide was expected to exhibit good photoluminescence and the nanocomposite was expected to be flexible as well. The Gd2O3 nanoparticles prepared were found to be in cubic phase with an average size of 19 nm. Raman spectra showed the incorporation of Gd2O3 into the polymer matrix. Scanning electron microscope images revealed that the particles were porous in nature, agglomerated and distributed evenly on the surface of the film in the form of clusters. The UV–Visible absorption spectra gave direct optical energy band gap value in the range 5.78–4.86 eV. Both band gap as well as the Urbach energy are seen to decrease with increasing concentration of the dopant. Four prominent photoluminescence peaks were observed in all the three composite films in the UV region (318 nm), deep blue region (396 nm), blue region (477 nm) and green region (553 nm). The color purity of the films using CIE coordinates was found to be the highest, 82.81%, in the 2 wt% film making this film a promising material for blue OLED's and blue flexible screen

Synthesis, characterization and optical properties of polyvinyl alcohol-​cerium oxide nanocomposite films

Nanocomposite films of CeO2 doped polyvinyl alc. (PVA) of varying concns. were prepd. by a soln. casting technique using nanoparticles synthesized by a soln. combustion method. Energy Dispersive X-​ray (EDX) confirmed the presence of constituent elements in the composite films. The characterization by X-​ray Diffraction (XRD) gave the structure of the CeO2 nanoparticles as cubic fluorite and the size of the nanoparticles in the composites as 6.5-​44 nm. SEM (SEM) and High Resoln. Transmission Electron Microscopy (HRTEM) show homogenous dispersion of nanoparticles with increasing size and some agglomeration for concns. upto 12.5 wt​% while the 25 wt​% film is radically different showing a tape-​like structure in SEM images and a string of beads-​like formation of nanoparticles in the HRTEM images. Raman spectra exhibit shifts as well as new bands in the composites confirming structural change and formation of a new material. The UV-​Visible spectrum of the composites exhibit a red shift in the optical band gap with respect to pure PVA and both red and blue shift with respect to nano CeO2 depending on the concn. of the filler. Good absorption in the UV (2.5 wt​% and 25 wt​%) and visible range (12.5 wt​% and 25 wt​%) suggest possible use in filters and solar cells. Photoluminescence studies reveal three emission peaks corresponding to the UV region and blue-​green regions of the visible range. The max. PL intensity, nearly equal to that of nano CeO2, was obsd. for 2.5 wt​% films suggesting that this concn. is most suitable for optoelectronic applicat

Poly Vinyl Alcohol-CeO2 Nanocomposite Films: A Promising Material for No2 Sensors at High Temperatures

Nanoparticles of CeO2 were dispersed in Poly vinyl Alcohol to form nanocomposite films of various concentrations. Thick films of thickness around 100 μm were prepared by solution casting and pure PVA, PVA-2.5 wt% CeO2 and PVA-25 wt% CeO2 films were tested for their response as sensors to various gases. It was found that the PVA-2.5 wt% CeO2 film showed the best response of nearly 40% increase in resistance to 100 ppm of NO2 gas at 423 K. This indicated that it could be useful as a high temperature sensor for NO2 gas. Three of the above samples were also prepared by spin coating technique as thin films of thickness 1 μm, 5 μm and 50 μm, on a glass substrate and tested for sensing action of the same gases at 3 ppm concentration. It was seen that 2.5 wt% CeO2 film of 1 μm thickness gave the best response of 16% increase for NO2 gas, amongst all the films. The increase in resistance of the films in the presence of NO2 gas is due to chemisorption on the CeO2 nano fillers and the mechanism seems to be effective even at low concentration of the filler. The results of sensing in these films are better than that of other similar materials and suggest that they can be used as high temperature sensors

Synthesis, characterization and optical properties of hybrid PVA-ZnO nanocomposite: A composition dependent study

Nanocomposites of poly vinyl alcohol (PVA) and ZnO have been synthesized using the solution casting technique for different concentrations of nano ZnO powder prepared by low temperature solution combustion method. The formation of polymer nanocomposite and changes in the structural and micro structural properties of the materials were investigated by X-ray diffraction, Energy dispersive X ray spectroscopy and optical microscopy techniques (FTIR and UV-Visible). The surface morphology of PVA-ZnO nanocomposite films were elucidated using Scanning Electron Microscopy. The optical absorption spectrum of nano ZnO shows blue shift in the optical band gap energy with respect to characteristic bulk ZnO at room temperature, whereas PVA-ZnO hybrid films show red shift with respect to nano ZnO. The photoluminescence studies show that the intensity of the blue emission (470 nm) varies with change in concentration of ZnO with an optimum intensity observed at 10 mol of ZnO. © 2014 Elsevier Ltd

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Not AvailableThe residual effect on soil properties on application of composts made out of composting enzyme industrial wastes and municipal solid wastes namely MEES compost (multiple effect evaporator salts + municipal solid waste) and primary sludge (PS) compost (Primary sludge + municipal solid waste) were evaluated in this study. Application of composts recorded a marginal increase in soil pH towards harvest (6.70 and 6.68) in treatment T8 (50% N through MEES + 50 % N) through FYM and T7 (PS compost @ 10 t ha - 1 respectively) in comparison to the initial pH and a higher organic carbon content of 0.56 and 0.57 per cent at 30 DAS and 0.52 and 0.53 in T6 (MEES Compost @10 t ha-1) and T7 (PS Compost @ 10 t ha-1) respectively after the harvest of cowpea which was grown as the residual crop. A positive residual effect was evident in compost treatments with an increased status of available major and micro nutrients.Not Availabl

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Not AvailableThe field evaluation of composts prepared out of enzyme industrial wastes and municipal solid waste was carried out in farmer’s field in Bangalore, India using maize as a test crop in a randomized complete block design with nine treatments and 3 replications. Two composts: MEES compost and PS compost and fertilizers were used to know the effects on soil properties and agronomic characteristics and nutrient uptake by maize plants. Application of MEES compost and PS compost resulted in increased soil pH and organic carbon content, but the increase was insignificant. The available nutrient concentration was slightly higher than the initial soil on application of organics like composts and waste materials. The application of 100 % NPK +FYM @ 10 tha-1 recorded higher growth, grain yield (6341.47 kg ha-1) and straw yield (11416.46 kg ha-1) of maize. The status of available nutrients in soil, nutrient contents in maize and uptake by maize was higher with the application of 100 % NPK +FYM @ 10 tha-1. The application of both MEES compost and PS compost resulted in grain yields of 5517.48 and 5249.12 kg ha-1 and stalk yields of 9931.47 and 9448.41 kg ha-1 respectively and the performance was on par with each other. Application of composts did not result in heavy metals (Ni, Cd, Pb and Cr) accumulation in the soil as well as maize grain and stalk. The study thus revealed the suitability of enzyme industry wastes composts as organic nutrient source for use in agriculture.Not Availabl

Temperature dependent dielectric and conductivity studies of polyvinyl alcohol-ZnO nanocomposite films by impedance spectroscopy

Dielectric and conductivity behaviors of nano ZnO doped polyvinyl alcohol (PVA) composites for various concentrations of dopant were investigated using impedance spectroscopy for a wide range of temperatures (303 K-423 K) and frequencies (5 Hz-30 MHZ). The dielectric properties of host polymer matrix have been improved by the addition of nano ZnO and are found to be highly temperature dependent. Anomalous dielectric behavior was observed in the frequency range of 2.5 MHz-5 MHz. Increase in dielectric permittivity and dielectric loss was observed with respect to temperature. The Cole-Cole plot could be modeled by low resistance regions in a high resistance matrix and the lowest resistance was observed for the 10 mol. films. The imaginary part of the electric modulus showed asymmetric peaks with the relaxation following Debye nature below and non-Debye nature above the peaks. The ac conductivity is found to obey Jonscher's power law, whereas the variation of dc conductivity with temperature was found to follow Arrhenius behavior. Two different activation energy values were obtained from Arrhenius plot indicating that two conduction mechanisms are involved in the composite films. Fitting the ac conductivity data to Jonscher's law indicates that large polaron assisted tunneling is the most likely conduction mechanism in the composites. Maximum conductivity is observed at 423 K for all the samples and it is optimum for 10 mol. ZnO doped PVA composite film. Significant increase in dc and ac conductivities in these composite films makes them a potential candidate for application in electronic devices. © 2015 AIP Publishing LLC