Dielectric and electrical properties of nano-Ag/C3AH6 nanocomposites

The microstructure, phase composition, thermal stability, electrical property and dielectric behaviors of tricalcium aluminate hexahydrate [3CaO-Al2O3-6H(2)O (C3AH6)] cement hydrate-based nanocomposites were systematically investigated. Conductive Ag nanoparticles (Ag-NPs) were used as a filler. Pellet samples of Ag-NPs/C3AH6 nanocomposites with various filler volume fractions (fAg-NPs) were fabricated using a hot-press sintering method. Microstructural analysis revealed that C3AH6 nanoparticles were formed and Ag-NPs homogeneously dispersed in the C3AH6 matrix. Interestingly, the dielectric permittivity (epsilon') of the nano-composite with f(Ag-NPs) = 0.15 increased by a factor of 4 over the measured frequency range, while the dielectric loss tangent slightly decreased. These effects usually cannot be obtained simultaneously. Such an enhanced epsilon' value was due to interfacial polarization between the interface of conductive Ag-NPs and an insulating C3AH6 phase. With further increases above f(Ag-NPs)= 0.16, the epsilon' values at 100 Hz, 1 kHz and 10 MHz of the nanocomposite were significantly enhanced by factors of 484, 47 and 16, respectively. This rapid change in epsilon' can be described by the percolation model. Surprisingly, the dielectric behavior still followed the percolation model even at 10 MHz.