Papers by Author: K. Ramachandran

Abstract: A detailed analysis on the depth profiles of 30 keV H+ ion implanted n-GaAs for various doses from 1014 to 1017 cm-2 was carried by using Secondary ion mass spectrometry (SIMS), to identify the buried amorphous layer. The results are correlated with Raman and XRD strain parameter studies. Various thermal parameters are computed for the 30 keV H+ ion implanted n-GaAs and SIMS study reported for the first time.

Abstract: Self-diffusion, both cationic and anionic diffusion, in ZnS nanoparticles is studied here following reaction coordinate theory. The jump frequencies, at various temperatures are computed. The isotope effect reveals the self-diffusion in nano ZnS is mainly through interstitial migration.

Abstract: In this paper, the application of photoacoustic methods to study thermal properties of Al-Li alloy is described. The photoacoustic measurements are carried out for thermal properties on Al-Li alloy and studied for various thicknesses. The theoretical basis for quantitative measurements is discussed together with the advantages and limitations of these methods as compared with conventional measurements. Applications to spectroscopic and depth-profile analysis and also to thermal property measurements in Al-Li samples heat-treated at 755K per hour and annealed at 505K are discussed. The results are compared with literature values, and discussed.

Abstract: Zircaloy-2, an useful nuclear material is studied here by photoacoustics to correlate with the measurements of X-rays. The microstructure variations observed in X-rays could be explained on the basis of thermal diffusivity measured by photoacoustics technique.

Abstract: The nuclear material, Zircaloy-2 is studied here by photoacoustics and the results are correlated with ultrasonic measurements and metallographic microstructures. Precipitation of hard intermetalics and formation of α-martensite, due to thermal aging are also explained through photoacoustic studies.

Abstract: Alloy D9 is a candidate material for core components of fast breeder reactors. This alloy has been 20% cold worked and thermally aged at 1073 K for different time durations and their thermal properties have been studied using photoacoustic (PA) measurements. The results of the PA measurements have been correlated well with the ultrasonic velocity and hardness measurements.

Abstract: New software using VEE Pro was developed to integrate the various components of photoacoustic spectrometer through RS-232 interface and this is the first time such an effort is made not only to integrate but also to automatically acquire the data for depth profile and wave length scanning. The performance and validity was rigorously tested for repeatability and standard error for samples like air, glass and silicon wafer. As an application towards NDE, the thermal parameters obtained from photoacoustics are compared with ultrasonics and discussed.

Abstract: Defect modes in ZnS:Mn and CdS:Mn nanoparticles are investigated by means of Fourier transform infrared spectroscopy and the Raman technique for local vibrational modes (LVM), and the observed modes are explained theoretically by using a molecular model.

Abstract: An experimental and theoretical investigation of defect modes in tin-doped cupric oxide (Sn-doped CuO) nanoparticles synthesized via a one-step solid-state reaction was reported. The defect mode at 455 cm^-1 due to Sn doping in CuO nanoparticles, calculated using a molecular model, was compared with the experimental value of 458 cm^-1 obtained from the FTIR vibrational spectrum. The Debye-Waller factor (DWF) of CuO nanoparticles was determined using Rietveld refinement of the XRD pattern and the Wilson’s plot, and the results were discussed on the basis of the number of surface atoms and thermal vibrations. The effect of defect modes upon the DWF of Sn-doped CuO nanoparticles was also discussed.

Abstract: Self-diffusion, both cationic and anionic, in ZnO nanoparticles was studied here in accord with reaction coordinate theory. The jump frequencies at various temperatures were computed. The isotope effect revealed that self-diffusion occurred mainly via a vacancy mechanism in nano ZnO; a result not previously reported in the literature.