Nanostructured hybrid carbon nanotube-ceramics heterostructures: Microstructure and forming mechanism

The interest in carbon nanotubes (CNTs) as reinforcements for ceramic and ceramic matrix composites has been growing considerably. Herein, we have proposed an original catalytic method based on zirconium (Zr) and boron (B)-contained precursors to synthesize CNTs-ZrB₂-ZrO₂ nanostructured composites. Observations show that the in-situ grown CNTs are homogeneously dispersed at each section of the ZrB₂-ZrO₂ matrix. The fragments of CO, CH₄, CO₂ resulting from the ZrB2 polymeric precursor are identified to be the main carbon sources for CNTs growth. The m-ZrO₂ and t-ZrO₂ are produced at 1100-1300^oC, and some ZrO₂ further transforms into ZrB2 pyrolysized at 1500oC. There are two kinds of grown CNTs existed in the produced hybrid heterostructures: (i) the worm-like, disordered and incomplete graphitization CNTs; (ii) the long-length and completely graphitized CNTs. The nucleation and growth of CNTs are dominated and controlled by homogeneous vapor-liquid-solid reactions.