Synthesis of CNTs on stainless steel microfibrous composite by CVD: Effect of synthesis condition on carbon nanotube growth and structure

CNT-microfibrous (CNT-MF) composites are synthesized by thermal chemical vapor deposition (CVD) method. The effects of deposition temperature, deposition time, gas flow rate and acid pretreatment on the structure of CNT-MF are investigated. Results show that with increase of temperature, the yield of CNT is increased due to the increasing CNT growth rate and the evolution of surface roughness of the composite. The quality of the CNT is increased first and then decreased. With increase of gas flow rate, the yield of CNT is increased first and then decreased due to the increase of carbon diffusion rate and decrease of contact time between carbon precursor and catalysts. The CNT crystalline perfection is improved. With increase of deposition time, the yield and quality of CNT is increased and the CNT growth form changes as deposition time increases. Acid pretreatment can change the surface structure of the support. 1 mol/L HCl pretreatment forms uniform small particles so the yield of CNT is increased, but the quality of CNT is decreased. When the acid concentration is increase to 2 mol/L, the mechanical strength of the substrate is destroyed badly and flaky grains are formed, causing the decrease of the CNT yield and quality.