Thermal conductivity improvement of heat-storage composite filled with milling modified carbon nanotubes

Abstract

ABSTRACTCarbon nanotubes (CNTs) were modified through ball milling. The influence of the ball milling time on the dispersion of CNTs was studied. CNTs composite phase change materials (PCMs) were prepared with paraffin and the modified CNTs. The influence of the ball milling time on the thermal properties of the modified CNTs/paraffin was studied. Functional groups of the modified CNTs were tested by a Fourier Transform Infrared (FTIR). The microstructure of the modified CNTss was characterized by a scanning electron microscopy (SEM). The dispersion of CNTs in the molten paraffin was tested by an UV-visible spectrophotometer. A thermal constant analyzer was used to test the thermal conductivity of CNTs/paraffin. The results showed that the optimum time of ball milling of CNTs is 3 h, the thermal conductivity of paraffin was increased by 61% when paraffin was compounded by 1 wt% modified CNTs that were milled for 3 h. With the prolongation of milling time, the increase rate of thermal conductivity decreases gradually. The reason for this phenomenon is that, CNTs were damaged seriously and the dispersion of CNTs was decreased if the ball milling time is too long.