A UNIT CELL APPROACH TO MODEL AND CHARACTERIZE THE METAL POWDERS AND METAL-DIELECTRIC COMPOSITES AT MICROWAVE FREQUENCIES

A unit cell based numerical approach to model the metal powders and metal-dielectric composites at microwave frequencies is proposed. The unit cell based numerical modeling helps to compute the equivalent re∞ection and transmission coe-cients of these materials, which are commonly used measured parameters at RF and microwave frequencies. The computation of the re∞ection and transmission coe-cients of these artiflcial dielectric samples also facilitates the determination of their efiective constitutive properties, deflned in terms of the efiective permittivity and permeability, using the re∞ection transmission approach. The applicability of the proposed unit cell method is flrst verifled for some mixed dielectrics using the classical mixing formulas, and the standard waveguide approach. Once the validity of the proposed approach is ascertained, the efiective constitutive properties of copper powder is determined. A detailed parametric analysis is also carried out in order to study the efiect of various parameters such as the packing fraction, the grain size and the gap between adjacent spherical shaped metal particles, on the efiective constitutive properties of the copper powder compact. This detailed analysis is quite helpful in order to optimize various parameters of the microwave sintering of metal powders and metal-dielectric composites before the actual start of the sintering process using microwaves.