The effects of MWCNTs on iron–copper nanocomposites thermal-structural properties.

Abstract

The subject studied in the presented thesis is the effect of incorporating different concentrations of multiwall carbon nanotubes into iron-copper — Fe–Cu with a ratio of 4:1; MWCNTs of 0.5, 1.0 and 2.0 vol.%—nanocomposites—made via mechanical milling of different times of 20, 60 and 120 minutes— on the thermal and structural properties. The characterisations conducted were heat flow and thermogravimetry, the relative linear expansion (ΔL L ⁄ 0), coefficient of linear thermal expansion (CTE) for the thermal behaviour, on the other hand for the structural changes, x-ray diffraction, Raman spectroscopy and infrared absorptions were applied. Several temperature ranges were distinguished for the Fe–Cu–MWCNTs nanocomposite by the ΔL L ⁄ 0 (T) and CTE temperature dependences. Effect of CNTs on the ΔL L ⁄ 0 and CTE temperature dependences are different for different temperature ranges, and the magnitude of the effect depends on the CNTs content. The heat flow and thermogravimetry show thermal stability and higher calorific capacity for the samples with longer milling time and containing a higher concentration of CNTs. As for the coefficient of thermal expansion, an improvement in CTE of the Fe–Cu- 1% MWCNTs milled for 120 minutes. The provided x-ray diffraction patterns show a grain refinement for the 120 minutes milling time, also a homogenous distribution of CNTs (the absence of CNTs clusters appearing as carbon graphite) Raman spectroscopy reveals a higher defect density with a longer milling time, except for 60 minutes samples showing a lower defect density which indicates the healing and the recovery of CNTs. Infrared spectroscopy aid in showing the presence of functional groups in the samples and the establishment of multiple bonding types.