Saravanamuthu Maheswaran

High energy ion beam studies of ion exchange in a Na2O–Al2O3–SiO2 glass

As part of understanding the processes leading to sodium release and ion exchange, the surface and near surface reaction regions on several specimens of a Na2O–Al2O3–SiO2 glass have been examined after exposures to isotopically labeled aqueous solutions. The majority of the analyses described here have been carried out using energetic ion beam analysis. Rutherford backscattering spectrometry (RBS) has been used to measure the overall glass composition and to determine the profiles and amounts of Na released from the surface. An important part of the ion exchange process is the uptake and incorporation of hydrogen and oxygen in the glass from the solution. To facilitate this analysis, the glasses were exposed to a solution containing 18O and D and analyzed by accelerator based nuclear reaction analysis. To confirm some of the RBS depth profile data very near the surface, x-ray photoelectron spectroscopy depth profiles were collected on some samples. Although the Na concentration is decreased in the near su...

Investigation of alkali ion exchange processes in waste glasses using Rutherford backscattering spectrometry and nuclear reaction analysis

A series of dissolution experiments using isotopic labeled (D2 18O) aqueous solution were carried out to investigate the ion exchange mechanism in Na2O-Al2O3-SiO2 glasses with fixed Na2O and variable Al2O3 concentrations. The sodium removal and the deuterium and oxygen uptake in the glass coupons were measured using ion beam methods such as Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). Both RBS and NRA experimental spectra were simulated using the SIMNRA simulation code with a thin layer approximation. Na, D, and 18O concentrations as a function of depth in reacted and non-reacted glasses were determined using simulated spectra. On the basis of the depth distributions of these elements, three different zones (reaction, transition, and diffusion zones) were identified in both samples.

High energy ion beam analysis of buried α-Fe2O3(0001)/α-Al2O3(0001) interface

We have investigated the disordering at the buried interface of α-Fe2O3(0001)/α-Al2O3(0001) interface using Rutherford backscattering spectrometry (RBS) and channeling techniques. Although expitaxially-grown α-Fe2O3(0001)/α-Al2O3(0001) thin films exhibit about 1.5–2.5% of minimum yield, disordering at the interface is visible due to the misfit dislocations because of the lattice mismatch between the substrate and the film. Theoretical simulations of surface and interface peak areas were simulated using VEGAS program and compared with the experimental data.We have investigated the disordering at the buried interface of α-Fe2O3(0001)/α-Al2O3(0001) interface using Rutherford backscattering spectrometry (RBS) and channeling techniques. Although expitaxially-grown α-Fe2O3(0001)/α-Al2O3(0001) thin films exhibit about 1.5–2.5% of minimum yield, disordering at the interface is visible due to the misfit dislocations because of the lattice mismatch between the substrate and the film. Theoretical simulations of surface and interface peak areas were simulated using VEGAS program and compared with the experimental data.