Evolution of microstructure and electromagnetic interference shielding performance in thermal decomposition process of ZrC precursor

In this work, a polymer-derived ZrC ceramic with excellent electromagnetic interference (EMI) shielding performance was developed to meet the requirement in ultra-high temperature. Thermal decomposition process of ZrC ceramic organic precursor was studied, and the evolution of phase composition, microstructure, and EMI shielding performance was revealed. The carbothermal reduction reaction begins to occur at 1300℃, and the transformation from ZrO₂ to ZrC was completely at 1700℃. With the increase of annealing temperature, the tetragonal zirconia (t-ZrO₂) gradually transforms into monoclinic zirconia (m-ZrO₂), and the transformation is complete at annealing temperature of 1500℃ due to the consumption of large amount of carbon phase. The average total shielding effectiveness was 11.63, 22.67, 22.91, 22.81 and 34.73 dB when the polymer-derived ZrC (PDC-ZrC) was annealed at 900, 1100, 1300, 1500 and 1700℃, respectively. In the thermal decomposition process, the graphitization degree and phase distribution of free carbon plays the dominant role to affect the shielding performance. The typical core-shell structure, composed of carbon and ZrC, can be formed at the annealing temperature of 1700℃, resulting in the excellent shielding performance.