• G Ranga Rao

      Articles written in Bulletin of Materials Science

    • Characterization of combustion synthesized zirconia powder by UV-vis, IR and other techniques

      H Ranjan Sahu G Ranga Rao

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      Fine powders of zirconia were prepared by employing combustion method with varying fuel to pre-cursor molar ratios. The zirconia powders contained more amount of monoclinic phase as the fuel content was increased. This aspect was studied using XRD, IR and UV-vis diffuse reflectance techniques. The surface acid-base properties of these samples were also investigated by indicator titration method. The catalytic activity was probed with transfer hydrogenation reaction in liquid phase. It was found that combustion synthesized zirconia did not provide required active sites for transfer hydrogenation reactions in liquid phase unlike hydrous zirconia.

    • Preparation of Sm–Ru bimetallic alloy films on Ru(0001) surface by vapour-deposition and annealing

      G Ranga Rao H Nozoye

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      Sm–Ru intermetallic surface alloy films were prepared by vacuum deposition and annealing of rare earth Sm on single crystal Ru(0001) surface. The Ru 3𝑑 and Sm 3𝑑 core level spectra clearly show the formation of surface alloy layers. XPS measurements on surface alloy film revealed an induced peak in the Ru3𝑑 region at lower binding energy by 1 eV compared to the bulk Ru (elemental) suggesting an electronic effect of alloying and Sm–Ru bond formation. The Sm 3𝑑5/2 photoemission peak of Sm film consists of strong features characteristic of Sm(II) with electron configuration 4𝑓6 (5𝑑\ 6𝑠)2 and Sm(III) with electron configuration 4𝑓6 (5𝑑\ 6𝑠)3. It is observed that the Sm(II) feature decreases in intensity upon alloy formation with surface Ru atoms. Oxidation of these films with carbon monoxide indicates alloy breakdown due to the oxidation of Sm atoms selectively. Alloy oxidation also shows a clear shift of Sm 3𝑑5/2 feature.

    • Promoting effect of CeO2 on cyclohexanol conversion over CeO2-ZnO mixed oxide materials prepared by amorphous citrate process

      Braja Gopal Mishra G Ranga Rao

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      CeO2-ZnO materials were prepared by amorphous citrate process and characterized by TGA, XRD, UV-DRS and surface area measurements. TGA showed that the citrate precursors decompose in the range 350-550°C producing CeO2-containing catalytic materials. XRD and DRS results indicated the formation of well-dispersed interstitial Zn$_{x}$Ce$^{4+}_{1-2x}$Ce$^{3+}_{2x}$O2 solid solution on ZnO matrix. Addition of CeO2 to ZnO produced high surface area mixed oxide materials in citrate method. Cyclohexanol conversion reaction was carried out on these catalytic materials to investigate the effect of rare earth oxide on the activity and selectivity. It was found that CeO2 promotes the activity of ZnO without affecting the selectivity to cyclohexanone significantly. The factors such as reaction temperature and WHSV have turned out to be important for cyclohexanol conversion over CeO2-containing ZnO catalyst materials.

    • Infrared reflection absorption study of water interaction with H-terminated Si(100) surfaces

      G Ranga Rao

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      Water adsorption on clean and hydrogenated Si(100) surfaces was studied under ultra high vacuum conditions using surface infrared spectroscopy. The study shows that H–Si–Si–OH and SiH2 species are formed on Si(100)–(2 × 1) and Si(100)–(2 × 1)–H surfaces, respectively. The reactivity behaviour of Si(100)–(3 × 1)–H and Si(100)–(1 × 1)–H is similar, both stabilizing oxygen inserted silicon dihydrides.

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