Iron oxide-based catalyst of (Fe1-xMgx)O·Fe2O3 with well-dispersed active sites favoring carbon nanotubes growth for high-performance microwave absorption

Abstract

Traditional catalysts for carbon nanotubes growth require specific substrates to prevent catalyst aggregation, then designing environmentally friendly and efficient catalysts remains enormous challenges. Herein, we developed an iron oxide-based catalyst of (Fe1-xMgx)O·Fe2O3 with catalytic active sites for the low-cost growing of carbon nanotubes (CNT) in chemical vapor deposition (CVD) system. This (Fe1-xMgx)O·Fe2O3 was prepared by solid-phase sintering of iron oxide and magnesium oxide uniformly mixed in mass ratio of 3%∼20 wt% MgO at 1400 °C. The introduction of magnesium oxide possesses some advantages of reducing the decomposition temperature of iron oxide and hindering the aggregation of as-formed Fe catalyst during CVD process. Furthermore, the in-situ growing CNT wrapped up the magnetic (Fe1-xMgx)O·Fe2O3 catalyst to form the 3D CNT/(Fe1-xMgx)O·Fe2O3 with the high-performance of microwave absorption. The maximum absorption of the three-dimensional carbon nanocomposites at 11.8 GHz with a thickness of 2.0 mm is −37.3 dB. The coupling of dielectric loss of CNTs and magnetic loss of (Fe1-xMgx)O·Fe2O3 results in the enhancement of microwave absorption. Therefore, this study provides a low-cost and green route to design the efficient catalyst for carbon nanotubes as well as high-performance absorbing materials.