• B A MARINKOVIC

      Articles written in Bulletin of Materials Science

    • Negative thermal expansion and cationic migration in zeolite Y used in FCC catalysts

      A DOSEN B A MARINKOVIC

      More Details Abstract Fulltext PDF

      The influence of extra-framework cations on the intrinsic negative thermal expansion (NTE) of calcined ultrastable and lanthanum-exchanged zeolites Y was analysed. High-temperature thermal behaviour, cationic migration and dealumination were examined by in situ high temperature X-ray powder diffraction and thermogravimetric (TG) analyses. We analysed protonated ultrastable zeolite Y and zeolite Y containing 13% La$_2$O$_3$ (LaY), and investigated howthe presence of La$^{3+}$ influences thermal behaviour of zeolite Y. Uncalcined LaY was also analysed to observe the La$^{3+}$ migration before calcination. Mass loss up to 990$^{\circ}$C was accompanied by TG analyses. X-ray powder diffraction data were analysed by Rietveld method. Our data show that lanthanum migration from supercages to sodalitic cavities is not reversible. However, some La$^{3+}$ migration occurs above 400$^{\circ}$C and we observe emptying of site I$^{\prime}$, migration to site I and to some extent to site II$^{\prime}$. Furthermore, we examined the dealumination process as well. Both samples showtwo distinct thermal behaviours, positive or near-zero thermal expansion up to 500$^{\circ}$C and NTE above this temperature. Together with intrinsic NTE in faujasite type zeolites, the dealumination process is largely responsible for NTE at high temperatures.

    • Effects of different polymers and solvents on crystallization of the NaYF$_4$:Yb/Er phase

      M VUKOVIC I DINIC M G NIKOLIC B A MARINKOVIC A M L M COSTA K RADULOVIC O MILOSEVIC L MANCIC

      More Details Abstract Fulltext PDF

      Up-converting NaYF$_4$:Yb,Er nanoparticles were obtained by polymer-assisted solvothermal synthesis using a common solution of hydrated RE nitrates in ethanol or ethylene glycol. It was shown that polymer choice (polyacrylic acid—PAA, polyvinylpyrrolidone—PVP and chitosan—CS) controls the size and shape of NaYF$_4$:Yb,Er nanoparticles, while the solvent type and pH value affect their crystallinity. Consequently, the spherical nanoparticles of a cubic ($\alpha$) phase, the average size of which ranged from 60 to 140 nm, were obtained either when PVP/ethanol or PVP/ethylene glycol were used solely during synthesis, whereas NaOH addition induced hexagonal ($\beta$) phase nucleation. The formation of the hierarchically organized spherical aggregates and nanofoils was observed when CS and PAA were used during synthesis, respectively. The average crystallite size, microstrain, doping level, lattice parameters, as well as, the presence of the certain ligands on the particle surface were determined and correlated with the intensity of visible-light emission observed under 980 nm laser-diode excitation.

  • Bulletin of Materials Science | News

    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.