16th International Conference
on Microwave and High Frequency Heating

18-21 September 2017, Delft, The Netherlands
11:00   Dielectric properties measurement (2)
Chair: Felipe L. Penaranda-Foix
15 mins
Li Wu, Zili Hu, Jianbo He, Kama Huang
Abstract: Accurate values of dielectric properties of materials under high temperature are crucial for many applications [1-2], especially in the microwave metallurgy industry. However, most of the existed measure methods raise the temperatures of materials by heat conduction from the high-temperature sample holder heated by an extra equipment [2-5]. These means may lead to longer heating time and uneven temperature distribution of the materials, having negative impacts on the accuracy of the measurement. In view of these problems, this paper proposes a setup for measurements of the permittivity from room temperature up to 1600 °C using a ridge waveguide, since it can heat the media quicker and more uniformly. An artificial neural network is trained with the corresponding setup simulation data and used to reverse the permittivity. Measurements on the laterite ore powder samples are performed in order to evaluate the performance of the setup and the procedure that is used to determine the permittivity from the transmission power and reflection power measured by the power meters. The preliminary experiments prove the feasibility of this system.
15 mins
Shiyue Wu, Xiaoqing Yang, Lanshuo Li, Yang Yin, Kama Huang
Abstract: The measured permittivity of binary liquid mixture with hydrogen bonds is larger than that of any component at some proportions or at some frequencies, which is not accurately consistent with Bruggeman’s formula. Mathematical analysis about this phenomenon was made and compared with experimental data, the results indicates that there is a limitation of Bruggeman’s formula about liquid mixture. Furthermore, a correction term was introduced by Debye relation model about binary liquid mixture with 1 hydrogen acceptor and donator. The numerical results obtained from modified Bruggeman’s formula agrees approximately with experimental results.
15 mins
Dhidik Prastiyanto, Guido Link, John Jelonnek, Manfred Thumm
Abstract: Due to its high strength to mass ratio and corrosion resistance, fiber reinforced polymers are used as construction materials in automotive, avionic and other engineering industries. As a light weight material it can provide significant energy savings during use, although the production of those materials is still very energy consuming. One potential technology to reduce the energy consumption in production is the application of high power microwave technology in the curing process. For a successful system and process design profound knowledge about the dielectric properties of the resin and its change during chemical reaction is inevitable. Therefore, a fully automated test set for temperature dependent dielectric measurements at 2.45 GHz, based on the waveguide transmission and reflection method, has been developed. Epoxy resins with different catalysts and fillers were investigated. Based on the dielectric data obtained, a model for description of the curing kinetics was developed. This allows a precise prediction of the curing state, what was validated by use of DSC analysis.
15 mins
Jingyi Wang, Junwu Tao, Laura Severac, David Mesguich, Christophe Laurent
Abstract: Nanostructured materials and nanocomposites have specific properties thanks to their nanoscale and are serious candidates in mechanical, electrical, chemical and environmental applications. Among their many physical properties, their capacity to interact with electromagnetic waves is particularly interesting because potentially source of new functionalities. In this paper, the simultaneous characterization of the permittivity and the permeability of the samples of a new nanostructured material in the frequency band 40 MHz and 1500 MHz will be presented. First, the Nicolson-Ross-Weir algorithm (NRW) [1] will be applied to the scattering parameters measured with a vectorial network analyzer on a microstrip transmission line cell on which a rectangular slab sample is added. The effective complex permittivity and permeability of central part consisting of the plate on a reference planar line will be deduced. This central part will then be modeled as a section of multilayer planar transmission line including the sample to be characterized. The permittivity and permeability of the materials will be determined by an inverse modeling method based on the use of the fullwave modified transverse resonance method (MTRM) [2]. The weak point of the NRW algorithm lies in the fact that the reactive electromagnetic energy in the discontinuities regions is not taken into account. This reactive energy contributes to modifying the effective length of the central section, thus introducing a potentially large source of error. We propose an iterative procedure to minimize the error induced by the presence of this reactive energy by modeling it by a lumped reactive element, deduced from a 3D electromagnetic simulation of a simple junction. This technique has been validated on several samples of known dielectric materials. The results will be presented at the conference as well as the results on the sample of nanostructured materials. References [1] Nicolson, A.M., Ross, G. F., IEEE Trans. on IM, 1970, 19, 377–382 [2] Tao, J., IEEE Trans. on MTT, 1992, 40, 1966–1969