High temperatures gas-solid reactivity of aluminum-carbon nanotubes composites

• Published in: Thermochimica acta 2016-09, Vol.640, p.8-18
• Main Authors: Di Pascasio, F., Genova, V., Gozzi, D., Latini, A., Lazzarini, L.
• Format: Article
• Language: English
• Subjects: Carbides; Carbon nanotubes; Composite materials; Differential thermal analysis (DTA); Electron microscopy (STEM, TEM and SEM); Nanostructures; Sintering
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2016.07.015

[Display omitted] •DTA up to 1200°C shows that the composites do not behave as two independent phases.•CNTs reduce by a few degrees the Al melting temperature.•The reactivity in O2, synthetic air, CO2, H2-Ar (5% v/v) and Ar was studied.•Al-CNTs sintered samples were studied at temperatures below and above Al melting.•The formation of Al4C3 occurs only in presence of molten Al. The gas-solid reactivity of metal-carbon matrix composites such as aluminum-carbon nanotubes (Al-CNT) sintered samples was studied at temperatures below and above the melting point of Al in O2, synthetic air, CO2, H2-Ar (5% v/v) and Ar. Small cylindrical samples of different composition with “single-walled” CNTs (SWCNTs) or “multi-walled” (MWCNTs) were sintered in Ar at 625°C and the resulting materials showed densities ranging from 92.2 to 99.0% of the theoretical density of bulk Al. Thermogravimetric analysis (TG) with simultaneous differential thermal analysis (DTA) up to 1200°C shows that the Al-CNT composites do not behave as a two independent phases system. This is mainly demonstrated by the following phenomena: i. The lowering of the melting point of Al, the magnitude of which cannot be explained by the expected very low solubility of C in Al at this temperature; ii. The amount of α-Al2O3 grown in oxidizing atmospheres and at the highest temperatures depends from the CNT content in the composite; iii. The formation of Al4C3 occurs only in presence of molten Al as shown by environmental X-ray diffraction “XRD”. Field emission scanning electron microscope “FESEM” and high-resolution analytical transmission electron microscopy “HRTEM” investigations confirm that at the sintering temperature no detectable chemical interaction exists between Al and CNT.