Ranjini Menon

Surface stiffening and enhanced photoluminescence of ion implanted cellulose - polyvinyl alcohol - silica composite

Novel Cellulose (Cel) reinforced polyvinyl alcohol (PVA)-Silica (Si) composite which has good stability and in vitro degradation was prepared by lyophilization technique and implanted using N(3+) ions of energy 24keV in the fluences of 1×10(15), 5×10(15) and 1×10(16)ions/cm(2). SEM analysis revealed the formation of microstructures, and improved the surface roughness on ion implantation. In addition to these structural changes, the implantation significantly modified the luminescent, thermal and mechanical properties of the samples. The elastic modulus of the implanted samples has increased by about 50 times compared to the pristine which confirms that the stiffness of the sample surface has increased remarkably on ion implantation. The photoluminescence of the native cellulose has improved greatly due to defect site, dangling bonds and hydrogen passivation. Electric conductivity of the ion implanted samples was improved by about 25%. Hence, low energy ion implantation tunes the mechanical property, surface roughness and further induces the formation of nano structures. MG63 cells seeded onto the scaffolds reveals that with the increase in implantation fluence, the cell attachment, viability and proliferation have improved greatly compared to pristine. The enhancement of cell growth of about 59% was observed in the implanted samples compared to pristine. These properties will enable the scaffolds to be ideal for bone tissue engineering and imaging applications.

Influence of low-energy Argon ions on thermal and surface properties of polycarbonate films

ABSTRACT Low-energy Argon ions from electron cyclotron resonance ion source were bombarded on polycarbonate films. The interaction of ions with the surface of the material was studied by using X-ray diffraction analysis, Fourier transform infrared spectroscopy, thermo-gravimetric analysis and atomic force microscopy. The study reveals that the surface roughness of the films increases with the modification of the surface morphology induced by ion irradiation. Thermal decomposition zone of irradiated samples has extended and hence thermal stability has also improved. Changes in the structural parameters and functional groups were observed after irradiation. These ion-induced changes and their significance were discussed in this paper.

Effects of low energy ions on the optical, structural and chemical properties of polycarbonate

Low energy Argon (Ar+) and Hydrogen (H+) ions were made to fall on the surface of Polycarbonate (PC) films. The depth profile calculations of ions on the material were carried out using Stopping and Range of Ions in Matter (SRIM-2008) code. The influence of bombarded ions with regard to the optical, structural and chemical properties was studied using UV-Visible spectroscopy (UV-Vis), X-Ray Diffraction (XRD) analysis and Fourier Transform Infra Red (FTIR) spectroscopy. The obtained results from UV-Visible study show a slight shift in the absorption edge towards higher wavelength region. The optical band gap found to be decreased after irradiation. XRD analysis showed minor changes in the structural parameters. The obtained FTIR spectra show reduction in the intensity of vibration bands for irradiated samples.

Positron Annihilation Study of Zr-2.5 wt.% Nb alloy Irradiated by Ar9+ heavy ions

Zr-2.5 Nballoy is used as a pressure tube material in pressurized heavy water reactor (PHWR). It is one of the most critical component which decides the lifespan of the reactor. The in-reactor degrading phenomenon of prime concern is dimensional changes caused by irradiation induced creep and growth processes. The present study aims to understand the mechanism of irradiation damage by irradiating the alloy with heavy ion. Such type of irradiation study would facilitate larger damage of material in a shorter time. Zr-2.5Nb alloy samples were irradiated using 315 keV Ar9+ ion for different durations. The irradiation doses were varied in the range of 3.1X1015 to 4.17X1016 Ar9+/cm2. SRIM calculation was carried out to evaluate damage profile in the irradiated samples. Beam based Positron Annihilation Spectroscopy (PAS) technique was used for depth profiling to characterize defect distribution in the alloys. The no. of defects generated is seen to increase with the increase in the fluence.

Micro fabrication by low energy ion beam from plasma based ion sources

An inductively coupled plasma ion source based micro machining system is being developed. The system parameters, in which mainly the source parameters like brightness, ion energy spread and source size, are optimized for increasing the efficiency of the system. Preliminary tests show 6 KeV Argon ion beam focused to 1.4 micron size with current density 600 mA/cm2. Possibilities of micro fabrication on silicon and copper target are explored. The paper describes inductively coupled plasma ion source based micro machining system, the preliminary results and challenges and benefits of using plasma generated ions for micro fabrication techniques.