In Situ Monitoring of Microwave Processing of Materials at High Temperatures through Dielectric Properties Measurement

García-Baños, Beatriz; Catalá-Civera, J.M.; Peñaranda‐Foix, Felipe L.; Plaza-Gonzalez, P.J.; Llorens-Vallés, Gabriel

doi:10.3390/ma9050349

Cited by 31 publications

(21 citation statements)

References 21 publications

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“…There is a wide range of reported experimental techniques to determine the dielectric properties of materials as a function of temperature from very low frequencies to several hundred gigahertzes (a brief overview of these methods can be found 18 ). For most of the permittivity experiments in the GHz range, especially around the Industrial Scientific and Medical (ISM) frequencies 0.915 GHz and 2.45 GHz, the thermal process was carried out by increasing the temperature of the materials using conventional means (infrared, electric) to moderate temperatures (200 °C to 500 °C), which does not allow us to observe microwave effects with the monitoring of permittivity changes with temperature.…”

Section: Introductionmentioning

confidence: 99%

Temperature Assessment Of Microwave-Enhanced Heating Processes

García-Baños

Reinosa

Peñaranda‐Foix

et al. 2019

Sci Rep

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In this study, real-time and in-situ permittivity measurements under intense microwave electromagnetic fields are proposed as a powerful technique for the study of microwave-enhanced thermal processes in materials. In order to draw reliable conclusions about the temperatures at which transformations occur, we address how to accurately measure the bulk temperature of the samples under microwave irradiation. A new temperature calibration method merging data from four independent techniques is developed to obtain the bulk temperature as a function of the surface temperature in thermal processes under microwave conditions. Additionally, other analysis techniques such as Differential Thermal Analysis (DTA) or Raman spectroscopy are correlated to dielectric permittivity measurements and the temperatures of thermal transitions observed using each technique are compared. Our findings reveal that the combination of all these procedures could help prove the existence of specific non-thermal microwave effects in a scientifically meaningful way.

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Section: Introductionmentioning

confidence: 99%

Temperature Assessment Of Microwave-Enhanced Heating Processes

García-Baños

Reinosa

Peñaranda‐Foix

et al. 2019

Sci Rep

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“…The homogeneous mixtures of the raw materials were thermally treated in different ways for comparison purposes between conventional and MW heating sources. Hence, frit was obtained in a laboratory MW prototype manipulated by Garcia‐Baños et al in batch of ~2 cm 3 of sample and in a pre‐industrial MW process in batch of 10 kg/h. The scale up MW oven was designed to evaluate the MW energy consumption at the pre‐industrial scale step (Figure ).…”

Section: Methodsmentioning

confidence: 99%

“… In MW laboratory equipment (thereafter LAB_frit) from Garcia‐Baños et al where the MW cell is a cylindrical cavity designed to operate simultaneously in two modes, one for heating and the other one for measuring in situ the dielectric properties of the sample. The heating mode TE 111 designed to resonate near the ISM standard frequency of 2.45 GHz, is fed into the cavity by a probe inserted through the side wall, while the measuring mode TM 010 is fed by another probe through the bottom wall of the cavity.…”

Section: Methodsmentioning

confidence: 99%

Feasible glass‐melting process assisted by microwaves

Reinosa

García-Baños

Catalá-Civera

et al. 2019

Int J of Appl Glass Sci

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The advantages of microwave (MW) energy processing have been verified in the sintering of a ceramic frit at a pre-industrial scale. The challenge of achieving high temperature using MW energy at such dimensions was overcome and a mix of natural raw materials was heated until its fluxing point. Changes in dielectric properties of the raw materials mix were also measured in situ with the increase in temperature, being in accordance to thermal processes of a conventional heating process. The properties of the resulting ceramic frit were compared with the same frit obtained by the conventional sintering method. Both frits showed similar thermal behavior regarding DTA-TGA, heating microscopy and XRD (only glassy phase was present). A Raman study confirms the existence of the mentioned glass phase. The application of the frits as glazes were performed and their properties were studied. As a result, glazes with similar properties were obtained which confirms that the MW energy processed frit is suitable for its application as a ceramic glaze. K E Y W O R D Sceramic frit, ceramic glaze, CO 2 emissions, MW dielectric properties, MW energy, time saving

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“…3. Removing all constant terms and substituting Equation (3) and regular terms (2) into Equation (4), we can get:…”

Section: Algorithm Model Constructionmentioning

confidence: 99%

“…The dielectric property of material mainly relies on the frequency and temperature. In the high power application of microwaves, the microwave frequency is usually fixed, and the interaction between microwaves and matter at different temperature, especially high temperature, should be investigated [1][2][3][4][5]. Meanwhile, in the microwave heating process, thermal runaway always happens.…”

Section: Introductionmentioning

confidence: 99%

Design of High Temperature Complex Dielectric Properties Measuring System Based on XGBoost Algorithm

Zhu

et al. 2020

Materials

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This paper aims to propose an online relative complex permittivity measurement system at high temperature based on microwave interferometer. A ridge waveguide with a TE10 mode was used in which the sample was heated and measured simultaneously at a frequency of 2450 MHz, and the microwave interferometer is used to collect the amplitude and phase difference of the incident signal. The Extreme Gradient Boosting (XGBoost) algorithm trained by the corresponding simulation data is used to construct the inversion model to calculate the complex dielectric coefficient of the tested material. Besides, this paper uses linear regression algorithm (LR) to calibrate the measurement system in order to improve the measurement accuracy. The entire system was tested using different materials at room temperature, and the maximum error of the measurement accuracy is less than 8% compared to the theoretical data. The robustness of the entire system was also tested by measuring Macor materials up to 800 °C. This proposed method provides an effective way to understand the mechanism between microwaves and matter at high temperatures.

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In Situ Monitoring of Microwave Processing of Materials at High Temperatures through Dielectric Properties Measurement

Cited by 31 publications

References 21 publications

Temperature Assessment Of Microwave-Enhanced Heating Processes

Temperature Assessment Of Microwave-Enhanced Heating Processes

Feasible glass‐melting process assisted by microwaves

Design of High Temperature Complex Dielectric Properties Measuring System Based on XGBoost Algorithm

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