Nanorods zirconia

Template-based methods have so far been the only successfiil strategies to obtain zirconia nanorods or nanotubes with high aspect ratios. Hollow zirconia nanotubes were first prepared by Rao et al., using carbon nanotubes as templates... 

Figure 8.11 Zirconia nanotubes with tunable wall thicknesses (a-e) and nanorods (f) obtained using anodic alumina templates [120]. Reproduced from Ref. [120], with kind permission of Springer Science + Business Media.

AAO can only be removed by etching at either high or low pH. Although etching with KOH or NaOH proved effective for the selective removal of alumina in the presence of zirconia nanostructures, this led concurrently to the formation of nanowire bundles (see Figure 8.14). A soUd-gas-phase reaction method was also reported to enable the synthesis of boron nitride nanotubes filled with zirconia nanorods. The formation of these composite nanotubes was achieved simply from zirconium diboride and ammonium chloride as solid-state precursors [128]. 

Unlike zirconia nanoparticle synthesis, the preparation of anisotropic zirconia nanomaterials has been rarely reported, with the preparation of nanoparticles with a rice- or fiber-hke morphology having been achieved in solution-based processes, and the underlying mechanisms not yet understood. Template-based processes, both in solution and in gas phase, have however been successfully employed to prepare nanorods and nanotubes, using common polymer-based membranes and anodic alumina as templates. 

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