S. Asad Ali¹, Ameer Azam¹,  Rajesh Kumar², S. A. H. Naqvi¹, R. G. Sonkawade³ and Rajendra Prasad^1,4

¹Department of Applied Physics, Z. H. College of Engineering & Technology, Aligarh Muslim University, Aligarh-202002.
²University School of Basic & Applied Sciences, G. G. S. I.P. University, Delhi-110403
³Inter-University Accelerator Center, Aruna Asaf Ali Marg, New Delhi -110067.
⁴Vivekananda College of Technology and Management Aligarh-202002

          Swift Heavy Ion (SHI) 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 beam parameters (ion, energy and fluence) and the polymeric material itself. In the present study, characterization of modification in optical, chemical, structural and electrical properties induced by 145 MeV Ne⁶⁺ ions is carried out. 100 μm thick PTFE Polymer procured from Good fellow, Cambridge Ltd. England (UK), were irradiated by 145 MeV Ne⁶⁺ ions to various fluences at Variable Energy Cyclotron Centre (VECC), Kolkata, India.

        From UV-Vis spectra the optical band gap (E_g), calculated from the absorption edge of the UV spectra of the films in 200-800 nm region varied from 2.23 eV to 1.63 eV for pristine and irradiated samples. At the highest fluence of 10¹³ ions/cm² the maximum change in optical band gap ~26% has been observed.  The cluster size changes from 236 to 443 carbon atoms per cluster. Carbon enriched domains created in the polymer during irradiation may be responsible for the decrease in the band gap. In FTIR spectra, appreciable changes have been observed after irradiation, indicating molecular fragmentation, cross-linking, formation of unsaturated group and free radicals. X-Ray Diffraction (XRD) analyses show significant change in crystallinity with fluence. Dielectric constant (ε') decreases with frequency whereas it increases with the ion fluence. Variation of loss factor (tanδ) with frequency reveals that tan δ increases as the frequency increases. Tanδ also increases with fluence. Tan δ has positive values indicating the dominance of inductive behavior. A sharp increase in A. C.  conductivity in pristine as well as in irradiated samples is observed with frequency. Due to irradiation the increase in conductivity with fluence at a given frequency may be attributed to scissoring of polymer chains, resulting in an increase of free radicals, unsaturation, etc.

 

Syyed Asad Ali*, Aligarh Muslim University, Aligarh, India - 202002, India

*presenting author