Fabrication And Properties Research Of Carbon Nannotubes-Cu Composite With Interpenetrating Networks

Since discovered in 1999, carbon nanotubes(CNTs) has sparked considerable interests in various fields such as physics, chemistry and material science. Due to their unique structure and exellent properties, CNTs is an ideal reinforcement addictive for metal matrix composite. However, because of their strong Van der Waals'forces, CNTs can not be dispersed uniformly in matrix, and the interfacial adhesion is poor, which limits their application. Therefore, it is of huge significance to blaze a novel compounding way. Composite with interpenetrating networks possesses homogeneous dispersion, thus it presents well mechanical, thermal and tribological performances. In this paper, we tried using two synthesis routes to fabricate CNTs-Cu composite with interpenetrating networks.Firstly, after treated in mix-acid and ammonia, CNTs self-assembled to microspheres with regular shape in invert microemulsion without the addition of emulsor. The effect of oil system with different molecular weight, the content of CNTs in water, the extent of acid treatment and the stirring temperature for emulsion were also studied. It was found that the in castor oil system, with CNTs acid-treated for 1.5 h, CNTs microspheres with a diameter of 2~20μm were synthesized after vigorous stirring at 85℃. The formation mechanism for carbon nanotubes microspheres was also discussed: because the surfaces were amidated after treated in mix-acid and ammonia, CNTs self-assembled to stable sphere structure, by means of the electrostatic effect and chemical effect of function groups. The test of specific surface area and pore size distribution results shows that compared to the pristine CNTs, the specific surface area of microspheres decreased slightly, while the total pore volume increased. Afterwards, Cu was infiltrated to the microspheres which acted as a skeleton. However, due to the poor wettability of Cu for CNTs, the infiltration was not successful.Secondly, the CNTs were modified by gelatin, then Cu powders were embedded during the formation process of CNTs skeleton. Subsequently, CNTs-Cu composite with interpenetrating networks was fabricated followed by solidification, carbonization, reduction and vacuum sintering. The SEM images indicate that CNTs and Cu were already interpenetrated to net-liked structure. The results of friction and wear test demonstrate that the tribological properties were enhanced significantly. CNTs distributed in Cu matrix with a net-like structure acted as loading-bearing and load-tansferring like steel backbone, inhibiting the dislocation motion of Cu matrix during dry sliding wear process. At the same time, lubricating carbon nanotubes film exposed to the worn surface served as spacers restraining rough scuffing and adhesion of Cu matrix under dry sliding against the steel pin. The results of thermophysics tests show that the thermal expansion of composite with 9 wt% CNTs is 27% of that of pure copper, while the thermal conductivity and electric conductivity decreased with increasing CNTs content. In addition, the influences of different sintering temperature, sintering pressure and raw materials on the properties were also explored.