Fabrication and properties of Epoxy/ CCTO and Silicone Rubber/ CCTO composite.

A lot of researches have been carried up to produce the ceramics with very high dielectric properties, such as Al2O3, BaTiO3, ZrO3, Bi2/3Cu3Ti4O12 and TiO2. Some of them have even raised up to 60,000 of dielectric constant of the materials, but not as high as CaCu3Ti4O12 (CCTO), which can reach up to 100,000. On the other hand, some polymers possess great flexibility but low in dielectric constant. Thus, with the aim to produce flexible materials with great dielectric constant, this research had been conducted by combining synthesized CCTO with thermoset materials (epoxy and silicone rubber). The experiment was started by synthesizing the CCTO from raw powders of CaCO3, CuO and TiO2. The materials had undergone mixing process at certain stoichiometry, pressing and calcination. Calcination process had been done at different temperature in case of obtaining the optimum processing temperature. The best CCTO sample which possessed great dielectric constant while keeping low dielectric lost had been chosen to be blend with polymer. Whilst, the polymer were blend with hardener at certain curing ratio. The optimized polymer was with the lesser curing time recorded. The blending of the selected CCTO and polymer had been done at different percentage ranging from 10, 20, 30, 40 and 50wt% of CCTO. The samples had undergone XRD analysis, morphological test, dielectric tests and tensile test. XRD analysis had confirmed that both the epoxy/CCTO and silicone rubber/CCTO had been reacted when blend together and the crystal structure changed from their original phase of CCTO, epoxy and silicone rubber respectively. FESEM tests show that the epoxy/CCTO with lower wt% (10, 20 & 30) displayed the pure and clean surface rather than higher wt% (40 & 50) displayed the rougher surface finish. But, it was a great differ of silicone rubber/CCTO which shows great cohesion of silicone rubber had created greater surface finish even at high wt%. The particle packing also determined the characteristics of the composite on dielectric properties and even mechanical properties. For epoxy/CCTO, at 1kHz frequency, the CCTO loaded at 50wt% is 25, while the CCTO loaded at 10wt% was only 17 in dielectric constant whilst for silicone rubber/CCTO, the CCTO loaded at 50wt% was 42, while the CCTO loaded at 10wt% is only 10 dielectric constant. Whilst value of Modulus of elasticity increased as the higher amount of CCTO was used. The epoxy/CCTO increased from 357 - 14400MPa whilst for silicone rubber/CCTO increased from 33-150MPa from 10 to 50wt%. Through Response Surface Methodology (RSM) analysis, it is also proved that the higher particle packing provide higher dielectric constant and greater mechanical properties of both composites. Comparing those two composites, it can be concluded that the best flexible materials with high dielectric constant is silicone rubber/CCTO that suitable to be used as capacitor or dielectric resonator antenna.