One step synthesis and characterization of high aspect ratio network-like carbon nanotubes containing calcium aluminate cement composite powders

Abstract

The poor water dispersion and oxidation resistance of carbon has restricted the widely industrial application of carbon containing castables. High aspect ratio network-like carbon nanotubes containing calcium aluminate cement composite powders were synthesized by carbon-bed sintering method using calcium acrylate and activated alumina as raw materials, and nickel nitrate as catalyst. Meanwhile the effects of catalyst content on the structure and morphology of carbon nanotubes were also studied. The synthesized products were characterized by X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The results indicated that the phase compositions of composite powders were similar to that of commercial Secar71. The length of carbon nanotubes was ca. 25 μm, and the diameter of carbon nanotubes was 55 nm. The aspect ratio of carbon nanotubes is ca. 450. The formation process and mechanism of carbon nanotubes was studied by thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. The growth temperature of carbon nanotubes was 700 °C, and the growth of carbon nanotubes agrees with vapour–solid (V–S) model. In addition, the thickness of floating layer, floating ratio and oxidation ratios of the synthesized product were lower than those of the same carbon containing Secar71 cement (S71CB) composite powders, implying that the water dispersion and oxidation resistance of carbon nanotubes were improved because the high aspect ratio network-like carbon nanotubes were not easily separated from calcium aluminate cement and the carbon nanotubes were encased in calcium aluminate cement.