The Loading Of Conductor Into Porous Ceramics And The Study On Their Electromagnetic Properties

Porous ceramic material is of great significance in aviation, military, energy, chemical industry, metallurgy and environmental protection field. New functional characteristics can be created when functional phase such as conductor and magnet is loaded into porous ceramics, and it is significant in the exploring of negative permittivity and negative permeability. These composites have important application backgrounds in military platinotron and so on.Stable Al2O3 ceramic and ferrimagnetic YIG ceramic is selected as matrix, they are high-temperature, corrosion resistance and non-aging. Conductive phase is loaded into porous ceramics via impregnation method, and ceramic matrix composites have been fabricated. The composites’electromagnetic parameters are tuned by the changing of matrixes, conductive phases, contents and microstructures. XRD, SEM, VSM and HP4991 impendance is used to test the composites, and the porcolation phenomenon, equivalent circuit and free-electron model is used to analysis the electromagnetic behavior. Negative permittivity and negative permeability was realized in a certain frequency band.CO/Al2O3 and C/Al2O3 composites were fabricated with Al2O3 as matrix. In CO/Al2O3 composites, three-dimensional cobalt networks were hosted in porous alumina matrix uniformly as the metal content increasing. The electromagnetic parameters were tuned from moderate to extremely high for composites near the percolation threshold. Shunt inductances were account for the negative permittivity behavior in percolative composites. Negative permeability was obtained due to vortex resonance of invented metal rings and magnetic resonance. Morphology changes in the structure of the metal phase after post-treatment resulted in dramatic changes in the electromagnetic characteristics, and the metal networks which were significant to negative permittivity and negative permeability were weakened by lower-dimension structures such as sheets; In C/Al2O3 composites, film-like carbon was formed on the wall of Al2O3 after carbonization. The increasing carbon content enhanced the film continuity and thickness, which made the conductivity paths increased under high-frequency electromagnetic field. When the carbon content reached 14 wt%, negative permittivity was obtained in the test frequency due to plasma resonance, the permeability showed diamagnetic property.Co/YIG and C/YIG composites were fabricated with YIG as matrix. In Co/YIG composites, cobalt networks which composed by cobalt particles were hosted in porous YIG matrix. Double negative properties were realized in 575 M-1 G when the cobalt content of Co/YIG was 35 wt%. The mechanism of negative permittivity was similar to CO/Al2O3, and the negative permeability was caused by the domain wall resonance, magnetic spin resonance of matrix and vortex resonance of conductive networks; In C/YIG composites, particle and slice layer carbon was formed. The conductive property got better with the carbon content increasing, and negative permittivity came true in the whole test frequency and show diamagnetic.