Shing-Chung Wong

One-dimensional multiferroic bismuth ferrite fibers obtained by electrospinning techniques

We report the fabrication of novel multiferroic nanostructured bismuth ferrite (BiFeO(3)) fibers using the sol-gel based electrospinning technique. Phase pure BiFeO(3) fibers were prepared by thermally annealing the electrospun BiFeO(3)/polyvinylpyrrolidone composite fibers in air for 1 h at 600 °C. The x-ray diffraction pattern of the fibers (BiFeO(3)) obtained showed that their crystalline structures were rhombohedral perovskite structures. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed that the BiFeO(3) fibers were composed of fine grained microstructures. The grains were self-assembled and self-organized to yield dense and continuous fibrous structures. The magnetic hysteresis loops of these nanostructured fibers displayed the expected ferromagnetic behavior, whereby a coercivity of ∼ 250 Oe and a saturation magnetization of ∼ 1.34 emu g(-1) were obtained. The ferroelectricity and ferroelectric domain structures of the fibers were confirmed using piezoresponse force microscopy (PFM). The piezoelectric hysteresis loops and polar domain switching behavior of the fibers were examined. Such multiferroic fibers are significant for electroactive applications and nano-scale devices.

The technique of electrospinning for manufacturing core-shell nanofibers

ABSTRACT On account of their low cost coupled with acceptable efficiency, electrospinning can be considered to be both a viable and feasible method for the production of continuous nanofibers having a uniform structure. With noticeable developments in the areas spanning catalysis, fluidics, purification and even separation, nanofibers having a core-shell nanostructure have been both examined and studied with the primary purpose of achieving a uniform structure. With sustained efforts in the domain of both research and development, two electrospinning methods, namely (i) coaxial electrospinning and (ii) emulsion electrospinning, did emerge as potentially viable choices for the preparation of continuous nanofibers having a core-shell nanostructure. In this research paper, the discovery and progress made with specific reference to the techniques of coaxial electrospinning and emulsion electrospinning are examined. A prudent use of the two techniques for the preparation of hollow nanofibers is examined. Potential applications of core-shell nanofibers, prepared using the method of electrospinning, for the purpose of self-healing and drug release are examined and discussed. An outline is provided of the work that is currently being done on aspects related to both theory and experiments with the primary purpose of gaining an understanding of the two techniques.