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[en] Yittrium iron garnet, Y3Fe5O12 (YIG), is a material used widely in electronic devices for the microwave region as well as the magnetic bubble domain-type memories. Yittrium iron garnet (Y3Fe5O12) was produced by mechanochemical synthesis from Y2O3 and Fe2O3 with particle size of around 150 nm. PMMA/YIG composite films were prepared by solution casting method at different concentration (i.e. 10%, 20% and 40%) of YIG filler. Dielectric permittivity of composite materials were studied over a wide a range of frequency and temperature as a function of filler concentration. The electrical properties of composites were explained by in terms of molecular mobility and interfacial polarization.
[en] Yittrium iron garnet, Y3Fe5O12 (YIG), is a material used widely in electronic devices for the microwave region as well as the magnetic bubble domain-type memories. Yittrium iron garnet (Y3Fe5O12) was produced by mechanochemical synthesis from Y2O3 and Fe2O3 with a particle size of around 150 nm. Dense ceramics with theoretical density of around 95% was obtained from mechanochemically activated powders after sintering at 1425 deg. C for 10 h without calcination step. Ferro-magnetic resonance (FMR) spectrum and microwave absorption spectrum of the YIG nanoparticles were studied at different frequencies and magnetic fields. The signal exhibits a resonance character at each frequency. It was observed that the location of the FMR signal peak at the field axes monotonically shifts to higher field with increasing frequency. The dielectric properties of YIG pellets produced from nanopowder was studied over a wide range of frequency and as a function of temperature. It was observed that the dielectric constant, dielectric loss and electrical conductivity gradually increase with temperature.
[en] Recently, there is a high demand for development of polymeric membrane for their widespread technological applications. Polymer blends incorporation with inorganic composite particles is the most effective strategy for obtaining antifouling, antibacterial, gas and water permeable membrane materials. However, their biological and surface properties are always hindered by the inefficient interaction of filler into polymer matrix because it is distributed into the bulk membrane matrix. In this study, graphene oxide nanosheets are incorporated with metal (Ag)/metal oxide (ZnO) composite filler (MGO) followed by surface modification with quaternary cetyltrimethylammonium bromide (CTAB) to enhance non-covalent interactions between filler and poly methyl methacrylate (PMMA)/polyethylene glycol (PEG) blend membrane. The membrane was utilized for improving antifouling, antibacterial and gas permeability of membrane. Our results indicated that CTAB-modified filler (CTAB@MGO) was bonded to the polymer blend membrane without affecting the membranes’ physicochemical properties. The prepared CTAB@MGO–PMMA/PEG membrane showed excellent antibacterial property against model Escherichia coli bacteria. The antifouling activity and CTAB stability results of modified blend membrane ensured reduced bovine serum albumin adsorption and slow dissociation of surfactant molecules, respectively. The CTAB@MGO–PMMA/PEG blend membrane also showed promising gas permeability results with hydrogen (H2), nitrogen (N2) and carbon dioxide (CO2). The presented approach highlights the potential of surface modification of filler and introduces them in polymeric membrane as a simple, easy and cost-effective strategy for preparing antifouling and gas/water permeable polymeric membranes.
[en] The effect of low energy (300 eV) argon plasma treatment on the morphology of polycarbonate was studied by means of contact angle measurement, X-ray photoelectron spectroscopy (XPS), Vickers' micro hardness indentation and atomic force microscopy (AFM). The surface free energy (SFE) changes from 38.5 mJ/m2 to 74.9 mJ/m2 on increasing the treatment time and the corresponding contact angle was changed from 630 to 170, which shows the enhancement in surface adhesion. The XPS analysis shows the increase of the C-O and C=O functional groups upon treatment. The Vickers' micro hardness was studied in the load range 10-500 gf. The micro hardness of the film increases with the treatment time. Atomic force microscopy (AFM) reveals that average surface roughness increases from 7.0 nm to 27.2 nm as treatment time increases.
[en] The pellets of BaTi4O9 were synthesized via a polymerized complex method and irradiated with 50 MeV Li3+ ions for two different fluences. The dielectric constant (εr), and dielectric loss (tan δ) as a function of frequency (1 kHz-2 MHz) and temperature (40-200 oC) were measured for unirradiated and irradiated samples. The values of εr for unirradiated and irradiated samples decreased with frequency at room temperature which is explained by Koops' model. The increase in dielectric constant after the irradiation shows that the damage occurs during irradiation and produces defects due to electronic processes and/or inelastic collisions. Micro-structural properties revealed that the size of pores/holes and their number increased with irradiation fluence giving rise to volume expansion porous defects.
[en] Ferric oxalate was used as organometallics fillers in polyvinyl chloride (PVC) to form polymer matrix composite films at different concentration of filler. These films were irradiated with 80 MeV O6+ ions at the fluences of 1 x 1011 and 1 x 1012 ions/cm2. The radiation induced modifications in dielectric properties, microhardness, surface morphology and surface roughness of polymer composite films have been investigated at different concentration (i.e. 5%, 10% and 15%) of filler. It was observed that hardness and electrical conductivity of the films increase with the concentration of the dispersed ferric oxalate and also with the fluence. From the analysis of frequency, f, dependence of dielectric constant, ε, it has been found that the dielectric response in both pristine and irradiated samples obey the Universal law given by ε ∝ f n-1. The dielectric constant/loss is observed to change significantly due to the irradiation. This suggests that ion beam irradiation promotes (i) the metal to polymer bonding and (ii) convert the polymeric structure into hydrogen depleted carbon network. Thus irradiation makes the polymer harder and more conductive. Atomic force microscopy (AFM) shows that average roughness (R a) of the irradiated films is lower than that of unirradiated films. Surface morphology of irradiated polymer composite films is observed to change. Scanning electron microscopy (SEM) results show that partial agglomeration of fillers in the polymer matrix
[en] Different concentration of ferric oxalate (organometallic compound) was dispersed in polymethyle methacrylate (PMMA) films. PMMA was synthesized by solution polymerization technique. These films were irradiated with 3 MeV protons at a fluence of 1x1013ions/cm2. The frequency dependent dielectric behavior was studied both in pristine and irradiated samples in the frequency range from 100 Hz to 10 MHz. The contribution to the dielectric response is due to the conductive phase formed by organometallic compound. From the analysis of frequency dependence of dielectric constant it was observed that the dielectric response in both pristine and irradiated samples obey Jonscher's power law. These results were corroborated with structural changes observed in Fourier transform infrared (FTIR) spectra of pristine and irradiated samples
[en] The films of polymethyl methacrylate (PMMA) were synthesized by solution polymerization technique. Nickel dimethylglyoxime (Ni-DMG) compound was dispersed in polymethyl methacrylate (PMMA) films at different concentrations. These films were irradiated with 120 MeV Ni10+ ions at the fluences of 1 x 1011 and 1 x 1012 ions/cm2. These irradiated films were characterized by means of X-ray diffraction (XRD), Vickers' microhardness tester, atomic force microscopy (AFM) and scanning electron microscopy (SEM). X-ray diffraction patterns revealed that the particle size of Ni-DMG nanoparticles is reduced upon irradiation. It indicates that there is a significant interaction of ion beam with Ni-DMG particles in polymer matrix which leads to deposition of large amount of energy and resulted in splitting/melting of nanometric grains. It also revealed that semi crystalline phase of pristine films has been changed with respect to concentration and with the fluence. It is observed that the hardness of the film increases as fluence increases. This suggests that ion beam irradiation promotes (i) the metal to polymer bonding (ii) convert the polymeric structure in to hydrogen depleted carbon network due to the emission of hydrogen gas and/or other volatile gases. The surface average roughness increases as concentration of filler increases and decreases due to ion beam irradiation as revealed from AFM studies. SEM micrographs show partial agglomeration of filler and flake-like structure upon irradiation
[en] The effects of 80 MeV O6+ ions irradiation on polycarbonate (makrofol-DE) have been studied by different characterization techniques, viz. Fourier transform IR spectroscopy, Vickers' microhardness tester, LCR meter, thermogravimetric analysis and differential scanning calorimetry. It is observed that the hardness of the film increases as fluence increases. This may be attributed to the cross-linking effects as corroborated with FTIR spectra. There is an exponential increase in conductivity with log frequency and the effect of irradiation is significant at higher fluences. The dielectric constant/loss is observed to change with the fluence. From the analysis of frequency dependence of dielectric constant it has been observed that the dielectric response in both pristine and irradiated samples obey Jonscher's power law. The results are also explained on the basis of structural modification of polymer due to heavy ion irradiation. TGA/DSC thermograms indicate that there is no significant change in the stability of polymer and glass transition temperature up to the fluence of 2.4 x 1013 ions/cm2
[en] The surfaces of polycarbonate films were treated by nitrogen plasma, in order to understand the effect of low energy ions on the surface modification of polycarbonate. The modified samples were characterized by micro-hardness tester, optical micrograph/atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and FTIR spectroscopy. It was observed that the hardness of the film increases as fluence increases. This may be attributed to the cross-linking effect as corroborated with FTIR spectra. XPS analysis indicates that chemical bonding on the surface of the film, especially C=O, C-O and C-C/C-H functional groups, was found to change due to plasma treatment. AFM analysis reveals that average surface roughness increases from 5.9 nm to 42.7 nm as fluence increases.