Sejal Shah

Surface modification of polycarbonate by plasma treatment

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.

Ion Beam Modification of Polymethyl methacrylate (PMMA) Polymer Matrix Filled with Organometallic Complex

A Nickel Dimethylglyoxime (Ni‐DMG) compound was dispersed in polymethyl methacrylate (PMMA) films at different concentrations. PMMA was synthesized by a solution polymerization technique. These films were irradiated with 120 MeV Ni10+ ions at the fluences of 1×1011 and 1×1012 ions/cm2. The radiation induced changes in dielectric properties and average surface roughness were investigated by using an LCR meter in the frequency range 50 Hz to 10 MHz and atomic force microscopy (AFM), respectively. The electrical properties of irradiated films are found to increase with the fluence and also with the concentration of Ni‐DMG. 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 α 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 (ii) convert the polymeric structure in to hydrogen depleted carbon network due to the emission of hydrogen gas and/or other volatile gases. Atomic force microscopy (AFM) shows that the average surface roughness and surface morphology of irradiated films are observed to change.

Radiation-induced modification of organometallic compound dispersed polymer composites

Polymethyl methacrylate (PMMA) was synthesized by solution polymerization technique. Films of polymer composites were prepared by dispersion of different concentrations of nickel dimethylglyoxime in PMMA. These films were irradiated with 3 MeV proton beam at a dose of 1.48×105 Gy. The dielectric, structural properties and surface morphology of pristine and irradiated samples were studied by means of an LCR meter, X-ray diffraction (XRD) analysis and atomic force microscopy (AFM), respectively. The dielectric properties are observed to enhance with increase in metal compound concentration as well as with irradiation dose. This may be due to metal/polymer bonding and conversion of polymeric structure into hydrogen-depleted carbon network. AFM shows that the surface average roughness decreases after irradiation. Crystallite size of organometallic compound is observed to decrease after irradiation as revealed from XRD analysis.

Modification of Polymer Composite by Proton Beam Irradiation

Composite films of the thermoplastic polymer (Polymethyl methacrylate) filled with different concentration of organometallic compound was prepared by chemical method. These films were irradiated with 3 MeV proton beam at the fluences of 6×1012 and 1×1013 ions/cm2. The dependence of a.c. conductivity of pristine and irradiated films on frequency, fluence of proton beam, and filler concentration was studied. The result shows that the conductivity increases with increase in the concentration of the filler and also with fluence. Microhardness of the films was studied for the applied load ranging from 10–1000 mN. The hardness is observed to increase with the fluence. This may be due to the conversion of polymeric structure in to hydrogen depleted carbon network, which makes polymer more conductive and harder. Surface morphology was studied by means of atomic force microscopy (AFM). It reveals that the average surface roughness decreases after irradiation. Structural changes in the polymer structure due to irradiation have been studied using Fourier Transform Infrared (FTIR) spectroscopy.

Study of Dielectrical Properties of Swift Heavy Ion Induced Modifications in Metal Oxide/PMMA Nanocomposites

Fe2O3 nanoparticles were synthesized by co-precipitation method and different concentrations (6 and 10 wt%) of it were dispersed in a poly (methyl methacrylate) (PMMA) matrix, through a soft chemical casting method. These films were irradiated with 50 MeV Li+3 ions at a fluence of 5 × 1012 ions/cm2. Dependence of dielectric properties of pristine and irradiated samples on frequency, ion beam fluence and with filler concentration was studied. The results reveal the enhancement in dielectric properties after dopping nanoparticles and also upon irradiation. The average surface roughness values decreased from 21 nm to 16 nm and 24 nm to 18 nm respectively for 6 and 10 wt% of Fe2O3 dispersed PMMA composites after irradiation as revealed from AFM analysis. Differential scanning calorimetry analysis revealed an increase in the glass transition temperature from 77.4°C to 78.7°C upon irradiation, which may be attributed to cross linking structure due to ion beam irradiation. ATR-FTIR spectroscopy analysis revealed that the few peaks enhanced after dopping and irradiation which corroborates the change in the environment of these groups.

Effect of ion beam irradiation on palladium (II) acetyl acetonate dispersed in polymer matrix

Composites, containing different concentrations of palladium (II) acetylacetonate in polymethyl methacrylate (PMMA) matrix were prepared by vigorous mixing. PMMA was prepared by solution polymerization technique. The composites were irradiated with a 120 MeV Ni10+ beam at two different fluences of 1×1011 and 5×1012 ions/cm2 to study ion-induced effects on their dielectric, structural properties and surface morphology. AC electrical properties of these samples were studied in the frequency range 100 Hz to 10 MHz. The dielectric permittivity/loss shows frequency dependent behavior and it obeys the universal law of dielectric (i.e. ϵα f n−1) for pristine and irradiated samples at high frequency. The crystalline size and crystallinity of the composites were studied by X-ray diffraction analysis. Decrease in peak intensity after irradiation signifies the amorphization which is also responsible for decrease in T g as obtained by means of differential scanning calorimetry measurement. Fourier transform infrared spectra also support this result. Surface roughness increases upon irradiation as observed from scanning electron microscopy.

Sensitivity, property P and uniform entropy

We give a sufficient condition for sensitivity of continuous maps defined on a uniform space. We also study property P for uniformly continuous maps defined on a uniform space and its relation with uniform entropy.

On collective sensitivity for -actions

ABSTRACT We define and study here the notion of k-type collective sensitivity and related notions for a -action on a metric space. A characterization of collective sensitivity for a -action on a compact metric space is obtained and its relation with k-type weak mixing is studied. We prove that k-type collective sensitivity is preserved under uniform conjugacy and finite product.

Ion Beam Induced Modification of Metal Nanoparticles Dispersed Polymeric Films

Thin films of Fe dispersed polyimide (PI) were prepared on glass and silicon substrates by RF sputtering technique. Different concentrations of Fe viz 0.5, 1 and 5% were dispersed by simultaneous sputtering of polymer and Fe-metal. These films were irradiated with 120 MeV Ni10+ ion beam at a fluence of 5 × 1012 ions/cm2. Ion induced modification in optical, structural, surface and magnetic properties were studied. Optical study of these samples was carried out by using UV-VIS spectroscopy. Small shift in band gap is observed with increase in metal concentration. However no significant change was observed after irradiation as polyimide is highly radiation resistive material. AFM analysis reveals that average surface roughness of the samples increases after irradiation. Magnetic properties were studied by means of MFM and SQUID. MFM images reveal that the magnetic contrast increases with increasing the concentration of Fe in the composites which shows strong magnetization due to metal doping. However the contrast decreases after irradiation. SQUID also supports the MFM results.