Maghemite (γ-Fe2O3) Fiber-in-tube And Tube-in-tube Nanostructures

Inspired by the nanowire-in-microtube structure, Jian-guo Guan and colleagues proposed a facile and effective nonequilibrium heat-treatment approach combined with electrospinning for fabrication of maghemite (γ-Fe2O3) fiber-in-tube and tube-in-tube nanostructures. The pre cursor was composed of PVP and iron citrate. Fig. 5.21 shows SEM images and corresponding TEM images of as-obtained γ-Fe2O3 fiber-in-tube and tube-in-tube fibers. The figure reveals that the tips of the inner structures are totally separated from the outer tube, and the inner and outer tubes have a closed end. The resultant γ-Fe2O3 fiber-in-tube and tube-in-tube nanostructures may have important applications in a number of fields, such as magnetic separable catalysts or catalyst-supporting mate rials, sensors, absorbents, microreactors, and so forth, because of their structural characteristics and good magnetic properties. This method can intentionally control the contraction direction of the precursor nanofibers during the heat-treatment process by adjusting only heating rate (R) of the calcination, as R can be easily utilized to tune the temperature gradient established in