Controllable synthesis of defective carbon nanotubes/Sc ₂ Si ₂ O ₇ ceramic with adjustable dielectric properties for broadband high-performance microwave absorption

High-performance carbon nanotubes (CNTs) with adjustable electro-conductivity have been widely used as electromagnetic (EM) waves absorption materials to achieve stealth of weapons and equipment. Chemical vapor deposition technology is used for the simple preparation of CNTs on porous Sc ₂ Si ₂ O ₇ matrix. As expected, well-matched impedance and EM dissipation of CNTs/Sc ₂ Si ₂ O ₇ ceramics are synthesized. Curls of CNTs formed a three-dimensional network structure and large amounts of interfaces, resulting in multiple reflections and scattering of EM waves. The defect concentrations can be optimized by tuning reaction times. The existing defects will produce dipole polarization and affect the band gap of CNTs as well. Using density functional theory as first principle calculations, we calculate and simulate the relationship between band gap and vacancy-defects of CNTs. The results show that the appropriate contents of vacancy-defects will increase the band gap of CNTs, which regulate the conductivity loss of CNTs/Sc ₂ Si ₂ O ₇ . Hence, the excellent microwave absorption performance of CNTs/Sc ₂ Si ₂ O ₇ (loading content of 1.56 wt%) is RC _min of −33.5 dB at the thickness of 2.85 mm, achieving an effective absorbing bandwidth of 4.2 GHz covering the whole X-band. The exploration results provide a useful reference to EM wave absorption materials with strong absorption, wide bandwidth and thin thickness.