Synthesis and electromagnetic wave reflectivity of Si3N4 ceramic with gradient Fe3O4 distribution.

A Si 3 N 4 ceramic with gradient distribution of tri–iron tetroxide (Gradient–Si 3 N 4 –Fe 3 O 4 ) was fabricated with a combined technique of chemical precipitation and directional infiltration. Electromagnetic wave could enter Gradient–Si 3 N 4 –Fe 3 O 4 with little reflection because of weak impedance mismatch at its surface. Also the electromagnetic wave entering the Gradient–Si 3 N 4 –Fe 3 O 4 propagated with small reflection due to continuous and gradual change of impedance resulting from the gradient Fe 3 O 4 distribution, and was absorbed completely by Fe 3 O 4 of the gradient structure. [ABSTRACT FROM AUTHOR]