K. Kang, Y. Xiong, C. Lee, Hanyang University, Seoul, South Korea
In this study, multi-walled carbon nanotube (MWCNT) aluminum composite powders which have different MWCNT fractions were manufactured through optimized mechanical milling process. The MWCNT aluminum composite coating and pure aluminum coating were built-up through kinetic and high velocity oxygen-fuel (HVOF) spraying process. The significantly distinguishable characteristics of two spraying processes, in terms of thermal history of particles, in-flight particle velocity and deposition mechanism, lead to significant differences in deposition characteristic, microstructure and physicochemical interaction between the MWCNT and aluminum matrix. The transmission electron microscopy on the microstructure and interaction between MWCNTs and aluminum matrix of coatings revealed that the MWCNT fraction of kinetic spraying coating is higher than that of HVOF spraying as high thermal energy provided from HVOF process dissociated the MWCNTs and activated the interaction between the MWCNTs and aluminum. These MWCNT fraction and interaction in the coating in conjunction with aluminum matrix microstructure induces the significant differences in electrical and mechanical properties of coatings, e.g., electrical resistivity, micro-hardness, and wear resistance. Based on the microstructure and MWCNT reaction, coating property evaluation results are discussed.
Summary: In this study, multi-walled carbon nanotube (MWCNT) aluminum composite powders which have different MWCNT fractions were manufactured through optimized mechanical milling process. The MWCNT aluminum composite coating and pure aluminum coating were built-up through kinetic and high velocity oxygen-fuel (HVOF) spraying process. The significantly distinguishable characteristics of two spraying processes, in terms of thermal history of particles, in-flight particle velocity and deposition mechanism, lead to significant differences in deposition characteristic, microstructure and physicochemical interaction between the MWCNT and aluminum matrix. The transmission electron microscopy on the microstructure and interaction between MWCNTs and aluminum matrix of coatings revealed that the MWCNT fraction of kinetic spraying coating is higher than that of HVOF spraying as high thermal energy provided from HVOF process dissociated the MWCNTs and activated the interaction between the MWCNTs and aluminum. These MWCNT fraction and interaction in the coating in conjunction with aluminum matrix microstructure induces the significant differences in electrical and mechanical properties of coatings, e.g., electrical resistivity, micro-hardness, and wear resistance. Based on the microstructure and MWCNT reaction, coating property evaluation results are discussed.
