Electrical and Optical Properties of O6þ Ion Beam–Irradiated Polymers (original) (raw)
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Optical and electrical properties of some electron and proton irradiated polymers
Ion beam treatment studies have been carried out to investigate the potential for improvements in conductivity properties of the polymers Polytetra¯uroethylene (PTFE), Polyimide (PI), Polyethyleneterepthalate (PET) and Polypropylene (PP), after 2 MeV electron and 62 MeV proton irradiation. The shift in optical absorption edges as observed by UV±VIS spectra of the irradiated polymers has been correlated to the optical band-gap using TaucÕs expression. A decrease in the optical band-gap has been observed in irradiated PP and PTFE, but no considerable change was found for the optical band-gaps of PET and PI. Further AC conductivity measurements con®rmed an increase in conductivity in electron irradiated PP. Ó
Ion irradiation induced chemical changes of polymers used for optical applications
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1997
Polymers are a class of materials widely used in different fields of applications. In the field of optical telecommunication, polymers are discussed as a new class of materials for the fabrication of passive optical devices. Ion irradiation is a promising method to generate structures with a modified index of refraction, which is necessary for the guidance of light with different wavelengths in an optical device. The behaviour of different polymers which fulfil the requirements of high transparency has been studied during and after ion irradiation. Mass spectroscopy measurements of the reaction products outgassing during ion irradiation were performed as well as infrared (IR) measurements after irradiation. Ion induced chemical changes will be discussed in relation to modified macroscopic properties such as the index of refraction.
Infrared analysis of ion beam irradiated polymers
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2009
Irradiation with heavy ions can produce several modifications in the chain structure of polymers. These modifications can be related to scissioning and cross-linking of chemical bonds, which depend on the ion fluence and the density of energy deposited in the material. Stacked thin film Makrofol-KG Ò samples were irradiated with 350 MeV Au 26+ ions and FTIR absorption spectroscopy was used to determine the bond changes in the samples. Data on the absorption bands as a function of the fluence indicated a higher probability for simple-bonds scissioning than for double-bonds scissioning and no dependence on the number of double bonds breaking with ion fluence. Since sample irradiation was done in a non-trackoverlapping regime, a novel process for double bonds formation is suggested: the excitation of a site in the material by only one incident ion followed by a double bond formation during the de-excitation process.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1991
The keV-MeV ion irradiation of polymers produces deep changes in their physical and chemical properties associated with the breaking and rearrangement of original bonds. The modification of chain structure occurs within a well defined ion fluence range which depends on the ion linear energy transfer as well as on the target parameters. At low ion fluences (≈1014 ions/cm2) crosslinks between chains and chain-scissions are detected with a chemical yield in the range 0.05–0.3, depending on the ion mass. With increasing ion fluence (1015 ions/cm 2) the original polymer structure is heavily modified and the irradiated films exhibit properties close to those of hydrogenated amorphous carbon. At very high fluences (≈1016 ions/cm 2) graphitization of the material occurs.
Advances in Polymer Technology, 2014
Polytetrafluoroethylene (PTFE) polymer samples were irradiated by 50 MeV Li 3+ ion beams to the fluences of 1 × 10 10 , 1 × 10 11 , and 1 × 10 12 ions/cm 2. The structural, optical, and chemical properties were studied by X-ray diffraction (XRD), UV-visible (UV-vis) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy, respectively. The XRD analyses showed amorphization of the polymer sample at fluences of 1 × 10 10 and 1 × 10 11 ions/cm 2. Crystallite size (calculated by applying the Scherrer formula) decreased for irradiated samples at fluences of 1 × 10 10 and 1 × 10 11 ions/cm 2. The other factors like microstrain (ε), dislocation density (δ), and distortion parameters (g) showed variations at these fluences. However, there was no change in the interchain separation (R) and interplanar distance (d) for all irradiated samples. UV-vis showed a shift of the absorption edge of irradiated samples towards the visible region. The band gap energy (E g) was calculated using Tauc's relation, and its value decreased with an increase of ion fluence for all irradiated samples. The number of carbon atoms per conjugation length (N) increased for the irradiated samples. The FTIR results revealed the liberation of CF 2 groups and the appearance of some new bands after irradiation.
Analysis of Electrical Properties of Li 3+ ion Beam Irradiated Lexan Polycarbonate
The electrical properties of polymers are a subject which is inherently interdisciplinary in nature. The development of intrinsically conductive polymers has benefited immensely from the contributions of synthetic chemists. Electrical properties are closely allied with the mechanical properties of polymers studied by both physicists and engineers. A primary objective is, thus to produce semiconductive properties to the polymers. One of the best methods to increase the conductivity is to irradiate the polymers with swift heavy ions. In the present investigations the influence of 40MeV Li 3+ ion beam in the range of 3x10 11-3x10 13 ions/cm 2 on the electrical properties of lexan has been studied. The variations in dielectric constant and dielectric losses in the polymer have been investigated before and after irradiation. It has been observed that the ion beam irradiation enhances the degradation processes of lexan and helps in increasing the conductivity of the polymer.
Polymer Engineering and Science, 2008
Thin films of poly(ethylene terephthalate) (PET) having a thickness of 100 μm were exposed to different ion fluence of swift heavy ions of carbon in the range of 5 × 1011 – 5 × 1013 ions/cm2. The effect of ion beam on structural and electrical modification has been studied by UV/vis, FTIR, X-ray diffraction (XRD), Differential Scanning Calorimetery (DSC), and AC electrical measurement techniques. On irradiation, a shift in absorption wavelength toward the red end of spectrum with increase of ion fluence was observed. The intensity of crystalline IR bands and main diffraction peak in XRD pattern were found to decrease with increase in ion fluence. It indicates the loss of crystallinity induced by ion-beam irradiation. The crystallite size was found to increase on irradiation. The melting temperature (Tm) of PET films increased at a low ion dose (5.0 × 1012 ions/cm2), while it decreased at higher ion fluence (50.0 × 1012 ions/cm2). The dielectric constant (ε′) of PET films was increased with increase of ion fluence. The modifications brought about in the dielectric constant are correlated with chemical and molecular structural changes occurring on irradiation. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.
Optical absorption studies in heavy ion irradiated polymers
Radiation Effects and Defects in Solids, 2001
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50 MeV lithium ion beam irradiation effects in poly vinylidene fluoride (PVDF) polymer
2000
Physical and chemical changes induced by 70 MeV carbon ions 12 C 5 have been investigated in bulk polyvinylidene 9¯uoride (PVDF) polymer. The induced changes have been studied with respect to their optical, chemical and structural response using UV±visible, FTIR and XRD techniques. The ion¯uences ranging from 2:5 Â 10 11 to 9 Â 10 13 ions cm À2 have been used to study the irradiation eects. It has been observed that at the¯uence of 9 Â 10 13 ions cm À2 the PVDF sample became brittle and practically it was not possible to handle it for any further measurements. The recorded UV± visible spectra show that the optical absorption increases with increasing¯uence, indicating maximum absorption at 200 nm. An interesting feature of UV±visible spectra is that dips change into peaks and vice versa with increase of 15¯uence. In the FTIR spectra, development of new peaks at 1714 and 3692 cm À1 along with disappearance of peaks at 2363 and 3025 cm À1 and shifting of peak at 2984±2974 cm À1 have been observed due to high energy irradiation, indicating the chemical changes induced by 12 C 5. The diraction pattern of PVDF indicates that this polymer is semicrystalline in nature; a large decrease in the diraction intensity indicates decrease in crystallinity. Increase in crystallite size has also been observed due to heavy ion irradiation.
Dielectric response of makrofol-KG polycarbonate irradiated with 145 MeV Ne6+ and 100 MeV Si8+ ions
Indian Journal of Physics, 2009
The passage of heavy ions in a track detector polymeric material produces lattice deformations. These deformations may be in the form of latent tracks or may vanish by self annealing in time. Heavy ion irradiation produces modifications in polymers in their relevant electrical, chemical and optical properties in the form of rearrangement of bonding, cross-linking, chain scission, formation of carbon rich clusters and changes in dielectric properties etc. Modification depends on the ion, its energy and fluence and the polymeric material. In the present work, a study of the dielectric response of pristine and heavy ion irradiated Makrofol-KG polycarbonate is carried out. 40 μm thick Makrofol-KG polycarbonate films were irradiated to various fluences with Si 8+ ions of 100 MeV energy from Pelletron at Inter University Accelerator Centre (IUAC), New Delhi and Ne 6+ ions of 145 MeV from Variable Energy Cyclotron Centre, Kolkata. On irradiation with heavy ions dielectric constant ( ) decreases with frequency where increases with fluence for both the ions. Variation of loss factor (tan ) with frequency for pristine and irradiated with Si ions reveals that tan increases as the frequency increases. Tan also increases with fluence. While Ne irradiated samples tan shows slight variation with frequency as well as with fluence. Tan has positive values indicating the dominance of inductive behavior.