Effects of relative density on microwave heating of various carbon powder compacts microwave-metallic multi-particle coupling using spatially separated magnetic fields

Kashimura, Keiichiro; Hasegawa, Naoya; Suzuki, Shohgo; Hayashi, Miyuki; Mitani, Tomohiko; Shinohara, Naoki; Nagata, Kazuhiro

doi:10.1063/1.4772648

Cited by 15 publications

(7 citation statements)

References 17 publications

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“…However, some researchers have reported that anomalous electrical absorptions can occur when fibers are at appropriate distances without additives. [14,15]. If this special distance is achieved when ZrO 2 is added, this could explain the anomalous behavior we observed.…”

Section: Discussionmentioning

confidence: 80%

“…However, mixed powders with dielectric loss differences typically exhibit high-absorption characteristics at a certain density, which is not expressed by the Maxwell-Garnett prediction. We previously reported [13][14][15] that SiC fiber-γAl 2 O 3 mixtures display anomalous absorption at a weight ratio of W SiC /W total = 0.6. Interestingly, the expanded Clausius-Mossotti formula, which is based on the Maxwell-Garnett prediction, does suggest this special MW absorption.…”

Section: Introductionmentioning

confidence: 99%

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Microwave Heating Behavior in SiC Fiber-MO2 Mixtures (M = Ce, Zr)—Selective Heating of Micrometer-Sized Fibers Facilitated by ZrO2 Powder

et al. 2020

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SiC fiber-MO2 (M = Ce, Zr) mixtures with various compositions were heated by applying an 80 W microwave electric field, to investigate their heating rate, maximum temperature, and dielectric constant. For the SiC fiber-CeO2 mixture, all three parameters continued to increase as the weight ratio of the SiC fiber increased; in contrast, for the SiC fiber-ZrO2 mixture, these parameters reached a maximum value at a certain composition. A thermal gradient of 500 °C was observed at a microlevel in the SiC fiber-ZrO2 mixture, and hot spots were located in regions with a certain composition. This result not only contributes to designing a novel good microwave absorber but also presents new aspects with regard to high-temperature microwave processing, including the mechanism behind the high-temperature gradients on the order of micrometers as well as engineering applications that utilize these high-temperature gradients.

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Section: Discussionmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Microwave Heating Behavior in SiC Fiber-MO2 Mixtures (M = Ce, Zr)—Selective Heating of Micrometer-Sized Fibers Facilitated by ZrO2 Powder

et al. 2020

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“…The plunger was placed at the end of the waveguide. This system enabled us to spatially separate the electric and magnetic fields of the microwaves 26 , 27 . The sample was placed at an electric field node (denoted by E max , where the magnetic field is zero) or magnetic field node (denoted by H max , where the electrical field is zero).…”

Section: Methodsmentioning

confidence: 99%

Manufacturing carbon storage sintered body using microwave-selective and high-speed heating techniques

Kashimura

Oshita

Miyata

et al. 2023

Sci Rep

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Microwave sintering of fly ash samples with large amounts of unburned carbon and CaCO3 was examined in this study. To this end, CaCO3 was mixed with fly ash sintered body to fix CO2. The decomposition of CaCO3 was observed when the raw material was heated to 1000 °C using microwave irradiation; however, a sintered body containing aragonite was obtained when the raw material was heated to 1000 °C with added water. Further, carbides in the fly ash could be selectively heated by controlling the microwave irradiation. The microwave magnetic field created a temperature gradient of 100 °C in a narrow region of 2.7 μm or less in the sintered body, and it helped suppress the CaCO3 decomposition in the mixture during sintering. By storing water in the gas phase before spreading, CaCO3, which is difficult to sinter using conventional heating, can be sintered without decomposing.

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“…The plunger was placed at the end of the waveguide. This system enabled us to spatially separate the electric and magnetic fields of the MWs [22,23]. The sample compact was a 15 vol % graphite fibers–Al 2 O 3 powder (1 µm, Kojundo Chemical Co., Ltd., Saitama, Japan) to eliminate the effect of percolation because the percolation of electrical conductivities is often observed to have a volume ratio of over 30%.…”

Section: Methodsmentioning

confidence: 99%

Effect of Aspect Ratio on the Permittivity of Graphite Fiber in Microwave Heating

et al. 2018

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Microwave (MW) heating has received attention as a new heating source for various industrial processes. Some materials are expected to be a more effective absorber of MW, and graphite is observed as a possible candidate for high-temperature application. We investigated the dependence of the aspect ratio of graphite fibers on both their heating behavior and permittivity under a 2.45 GHz MW electric field. In these experiments, both loss tangent and MW heating behavior indicated that the MW absorption of conductive fibers increases with their aspect ratio. The MW absorption was found to be well accounted for by the application of a spheroidal model for a single fiber. The absorption of graphite fibers decreases with increasing aspect ratio when the long axis of the ellipsoid is perpendicular to the electric field, whereas it increases with the aspect ratio when the long axis is parallel to the electric field. The analytical model indicated that MW heating of the conductive fibers is expected to depend on both the shape and arrangement of the fibers in the electric field.

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Effects of relative density on microwave heating of various carbon powder compacts microwave-metallic multi-particle coupling using spatially separated magnetic fields

Cited by 15 publications

References 17 publications

Microwave Heating Behavior in SiC Fiber-MO2 Mixtures (M = Ce, Zr)—Selective Heating of Micrometer-Sized Fibers Facilitated by ZrO2 Powder

Microwave Heating Behavior in SiC Fiber-MO2 Mixtures (M = Ce, Zr)—Selective Heating of Micrometer-Sized Fibers Facilitated by ZrO2 Powder

Manufacturing carbon storage sintered body using microwave-selective and high-speed heating techniques

Effect of Aspect Ratio on the Permittivity of Graphite Fiber in Microwave Heating

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