Low temperature synthesis of carbon nanotube-reinforced aluminum metal composite powders using cryogenic milling

Abstract

temperature synthesis of carbon nanotube-reinforced aluminum metal composite powders using cryogenic milling. "J. Mat. Sci. 29, 2644(2014 Carbon nanotube (CNT)-reinforced aluminum composite powders were synthesized by cryogenic milling. The effects of different cryogenic milling parameters and CNT contents on the structural characteristics and mechanical properties of the resulting composite powders were studied. Detailed information on powder morphology and the dispersion and structural integrity of the CNTs is crucial for many powder consolidation methods, particularly cold spray (CS), which is increasingly utilized to produce metal-based nanocomposites. While all of the produced composite powders exhibited particle sizes suitable for spray application, it was found that with increasing CNT content, the average particle size decreased and the size distribution became narrower. The dispersion of CNTs improved with milling time and helped to maintain a small Al grain size during cryogenic milling. Although extensive milling allowed for substantial grain size reduction, the process caused notable CNT degradation, leading to a deterioration of the mechanical properties of the composite.

Metallurgical Challenges in Carbon Nanotube-Reinforced Metal Matrix Nanocomposites

“…These characteristics are controlled by two competing mechanisms during the milling: (i) Cold working, which results in decreased ductility, particle fracturing, and reduced particle size; and (ii) Cold welding, which results in increased particle size [40,82,83].…”

“…The higher the energy imposed on the powder blend, the higher the volume fraction of defective nanotubes will be [82]. In contrast, high energy milling can evenly embed CNTs in the metallic powders, while the planetary milling is usually incapable of uniformly dispersing CNTs.…”

“…It seems that the utilization of a chemical modification or a processing control agent as well as the low energy milling technique can successfully reduce the structural damages of CNTs [82].…”

“…Therefore, such methods are able to reduce the processing time and bring forth finer grains with the lowest possibility of chemical reactions. Interestingly, if the cryogenic milling is conducted with the presence of carbon-containing PCA such as stearic acid, their carbons may react with metallic powders and form carbides during the milling or subsequent sintering processes [82].…”

“…Interestingly, if the cryogenic milling is conducted with the presence of carbon-containing PCA such as stearic acid, their carbons may react with metallic powders and form carbides during the milling or subsequent sintering processes [82]. The CNTs are uniformly dispersed and embedded in Al powders during high energy ball milling.…”