Wetting Behavior and Reactivity Between AlTi6 Alloy and Carbon Nanotubes

Wetting behavior between molten AlTi6 alloy and nanoporous carbon substrate (carbon nanotubes paper) was investigated by a sessile drop method in vacuum at 800, 900, and 1000 A degrees C. In order to avoid the effect of native oxide film on metal sample, an advanced capillary purification technique coupled with non-contact heating was applied. The AlTi6 drop did not wet the MWCNT paper immediately after deposition on the substrate at 800 A degrees C, forming a contact angle of theta A = 153A degrees. The increase in temperature up to 900 A degrees C and holding the system for 15 min also did not affect the contact angle (theta = 153 +/- A 1). Further heating above 930 A degrees C at a rate of 5 A degrees C/min caused a gradual lowering of contact angle down to similar to 130A degrees and after about 10-min interaction at 1000 A degrees C, it reached the final value of 123A degrees. Structural investigations of solidified sessile drop AlTi6/MWCNT couple by scanning and transmission electron microscopy showed that high-temperature interaction between MWCNTs and molten AlTi6 alloy is accompanied with liquid metal infiltration of MWCNT substrate, fragmentation of MWCNTs, and formation of TiC in the form of rod-like crystallites and fine particles uniformly distributed in the metal matrix. The mechanism of MWCNT -> TiC transformation in the AlTi6/MWCNT system by high-temperature liquid-assisted process is discussed.