Yield and quality optimization for MWNT prepared by catalytic CVD

Multi-walled nanotubes are grown by chemical vapor deposition (CVD) in ethane+hydrogen mixture over 20þ/SiO2 catalyst, and the influence of ethane and hydrogen space velocities on carbon yield and crystalline quality of the reaction products is systematically investigated. It is found that higher carbon yields are paid with loss of selectivity and consequent worsening of the phase purity of the carbonaceous deposits. The most satisfactory results are achieved by inletting into the reactor a gas mixture, composed by 50% ethane + 50% hydrogen, at ∼45 min-1 space velocity.