Abstract
Aluminum nitride (AlN)/boron nitride (BN) bishell hollow nanofibers (HNFs) have been fabricated by successive atomic layer deposition (ALD) of AlN and sequential chemical vapor deposition (CVD) of BN on electrospun polymeric nanofibrous template. A four-step fabrication process was utilized: (i) fabrication of polymeric (nylon 6,6) nanofibers via electrospinning, (ii) hollow cathode plasma-assisted ALD of AlN at 100 °C onto electrospun polymeric nanofibers, (iii) calcination at 500 °C for 2 h in order to remove the polymeric template, and (iv) sequential CVD growth of BN at 450 °C. AlN/BN HNFs have been characterized for their chemical composition, surface morphology, crystal structure, and internal nanostructure using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction. Measurements confirmed the presence of crystalline hexagonal BN and AlN within the three dimensional (3D) network of bishell HNFs with relatively low impurity content. In contrast to the smooth surface of the inner AlN layer, outer BN coating showed a highly rough 3D morphology in the form of BN nano-needle crystallites. It is shown that the combination of electrospinning and plasma-assisted low-temperature ALD/CVD can produce highly controlled multi-layered bishell nitride ceramic hollow nanostructures. While electrospinning enables easy fabrication of nanofibrous template, self-limiting reactions of plasma-assisted ALD and sequential CVD provide control over the wall thicknesses of AlN and BN layers with sub-nanometer accuracy.
Highlights
Recent technological developments for creation of novel nano structured materials have promoted the control over structure, composition, and uniformity of nanomaterials
In contrast to metallic or semiconducting carbon nanotubes (CNTs), BN nanotubes (BNNTs) exhibit band gap values of ∼5.5 eV, which is found to be independent of tube chirality and morphology.[18]
Low-temperature sequential chemical vapor deposition (CVD) of boron nitride (BN): Following the calcination of aluminum nitride (AlN)-coated polymeric nanofibers, AlN hollow nanofibers (HNFs) were introduced into the same atomic layer deposition (ALD) reactor and coated with BN at 450 ◦C to obtain AlN/BN bishell HNFs. 1000 growth cycles of BN were carried out utilizing TEB and N2/H2 plasma sequentially as boron and nitrogen precursors with Ar as carrier and purge gas
Summary
Recent technological developments for creation of novel nano structured materials have promoted the control over structure, composition, and uniformity of nanomaterials. Fabrication of AlN/BN bishell hollow nanofibers by electrospinning and atomic layer deposition
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