Development of electroless (Ni-P)/BaNi_(0.4)Ti_(0.4)Fe_(11.2)O_(19) nanocomposite powder for enhanced microwave absorption

摘要

Ni-, Ti-substituted nanocrystalline M-type barium hexaferrite powder (BaNi_xTi_xFe_(12-2x)O_(19) (x= 0.4) of size approx 10 nm) was coated with Ni-P by electroless (EL) coating technique to form EL Ni-P/BaNi_(0.4)Ti_(0.4)Fe_(11.2)O_(19), a radar absorbing material (RAM) nanocomposite powder. Under TEM, the particle size of RAM powders before and after Ni-P coating were found to be in the range of 10-15 nm and 15-25 nm respectively. A uniform layer of 5-10 nm thick coating is deposited due to the controlled growth of EL Ni-P nanoglobules onto the powder. A growth mechanism was proposed to understand the deposition of EL Ni-P layer onto the RAM powder. The reflection loss (RL) of the EL (Ni-P)/RAM nanocomposite powder in Ku band (12.4 - 18GHz) was evidently enhanced to - 28.70 dB, as compared to the EL Ni-P nanoglobules (- 16.20 dB) and nanocrystalline RAM powder (- 24.20 dB). After annealing at 400 deg C for 4h, the RL and bandwidth of EL (Ni-P)/RAM nanocomposite powder was further improved from - 24.20 to - 35.90 dB and 1.50 to 4.00 GHz respectively. The RL enhancement mechanism was explained on the basis of VSM study (hysteresis loops) and electromagnetic theory.