Effects of OCF content and oxidation treatment on thermal conductivity and corrosion resistance of CF/BN/EPN coating

Abstract

The effects of oxidation time and content of oxidized carbon fiber (OCF) on the thermal conductivity (TC) and corrosion resistance of the OCF/BN/EPN coating are investigated. The results show that the oxidation treatment does not change the chemical organization of OCF, while the amount of carboxyl group grafting and the roughness of OCF surface increase with the increase in the oxidation time. Moreover, SEM results show that the higher content OCF fillers causes the more severe contact in the coatings. As the oxidation time increases, the TC gradually enhances, whereas the EIS results increase firstly and then decrease. This can be attributed to the dual effect of the oxidation treatment and content of OCF. The positive effect of oxidation treatment is that it enhances the interfacial compatibility between the coating and the OCF, improving the thermal conductivity and corrosion resistance of the coating. The downside is that the increase in the amount of carboxyl groups on the surface of the OCF with the oxidation time increases the hydrophilicity of the coating, which reduces the corrosion resistance. In terms of content, it significantly shortens the transmission distance of phonons between fillers and improves phonon transmission efficiency but leads to the increase in the number of defects between the filler and resin interfaces, thus enhancing the thermal conductivity of the coating and reducing the corrosion resistance. As a result, when the oxidation time of the OCF is 1.5 h and 15 wt% OCF is added, the best comprehensive performance can be obtained, i.e., and the TC of the coating reaches 1.4 W/m·K while the impedance modulus at 0.1 Hz is 4.6 × 109 Ω·cm2. This work provides an important guidance for the design of heat exchanger coatings with excellent TC and corrosion resistance.