Iron encapsulated carbon nanotube composites embedded in alumina with enhanced magnetic properties

Abstract Alumina is an essential ceramic insulator, while carbon nanotubes (CNTs) have intriguing mechanical, thermal, electrical, and magnetic properties. We report on the synthesis of CNTs/Al2O3 nanocomposites using the chemical vapor deposition (CVD) process using iron as a catalyst. The as-prepared composite's structure and morphology are characterized by transmission electron microscope, scanning electron microscope, X-ray diffractometer, thermogravimetric analyzer, and Mossbauer spectroscopy. The experimental results show that these composites contain CNTs of an average diameter of 40 nm distributed homogenously within the alumina matrix. The percentage of CNTs within the composites is at 7%. The CNT/Al2O3 nanocomposites demonstrate a dramatic enhancement of ferromagnetic properties during vibrating sample magnetization measurements. As compared to the magnetization of 0.03 e.m.u./g at an applied field of 1.5 T for the Fe-catalyzed Al2O3, the saturation magnetization of CNT/Al2O3 is 1.78 e.m.u./g, which represents an increment of ∼5800%. The coercivity of CNTs/Al2O3 composites increased from 0.036 T at 300 K to 0.285 T at 5 K. This study provides a relatively simple approach to blending the magnetic properties with potential thermoelectric materials.