John A. Ajao

Synthesis and Characterization of Electrospun Poly(ethylene oxide)/Europium-Doped Yttrium Orthovanadate (PEO/YVO4:Eu3+) Hybrid Nanofibers

Europium-doped yttrium orthovanadate/polyethylene oxide nanofibers were fabricated by firstly, synthesizing crystalline YVO4:Eu3+ nanoparticles using an aqueous precipitation method followed by electrospinning of PEO/YVO4:Eu3+ polymer composites. X-ray diffraction patterns showed that the nanoparticles exhibited well-defined peaks that were indexed as the tetragonal phase of YVO4. No additional peaks of other phases were observed indicating that Eu3+ ions were effectively built into the YVO4 host lattice. The photoluminescence spectra for the nanofibers showed peaks at 593, 615, 650, and 698 nm which was ascribed to the 5D0− 7F1, 5D0− 7F2, 5D0− 7F3 and 5D0− 7F4 transitions of Eu3+. Due to an efficient energy transfer from vanadate groups to Eu3+, the composite nanofibers showed a strong red emission under ultraviolet excitation characteristic of the red luminescence of the europium ion. The results demonstrate that this synthetic approach could prove to be viable for the fabrication of rare earth/polymer composite nanofibers intended for luminescent device applications.

Preparation and characterization of melt-spun nickel-based alloys containing heavy metals

Abstract The solidification behaviour and morphology of some nickel-based hardfacing alloys containing heavy metals such as tungsten have been studied by scanning electron microscopy and transmission electron microscopy. These alloys are very sensitive to different cooling rates (from as cast to melt spinning). At low cooling rates, these alloys present as primary phases, i.e. the stable carbide M 7 C 3 or the double carbide M 6 C (η type), according to the silicon content. For high cooling rates, the alloys occur as either amorphous (high silicon content) or microcrystallized structures depending on silicon level. In this latter case, the solid solution Ni(α) and the metastable carbide M 23 C 6 are observed.

Porous and non-porous electrospun fibres from discarded expanded polystyrene

In this study, we report the electrospinning of expanded polystyrene (E-PS) in xylene and tetrahydrofuran to produce microfibres. The aim is to develop a viable technique for waste polystyrene electrospun fibers for various applications. The E-PS was dissolved in xylene and tetrahydrofuran (THF), spun at voltage range of 10 to 28 kV keeping the spinning distance constant. The E-PS was characterized with Fourier transform infra red spectrophotometer (FTIR) and fibres obtained were characterized by scanning electron microscopy (SEM). The diameter of the fibres formed is in the range of 1.0 to 25.0 µm. The results obtained clearly justify the use of discarded E-PS as an inexpensive substitute for the specialized polymer carriers commonly used in electrospinning work.