Complex Permittivity and Permeability of SiO2 and Fe3O4 Powders in Microwave Frequency Range between 0.2 and 13.5 GHz

Hotta, Masahiro; Hayashi, Miyuki; Nishikata, Atsuhiro; Nagata, Kazuhiro

doi:10.2355/isijinternational.49.1443

Cited by 62 publications

(34 citation statements)

References 8 publications

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“…This permittivity and permeability measurement technique has been described in elsewhere. 6,10) In order to confirm the feasibility of this method, the e r Ј value of air was measured using the teflon tubes. As a result, it has been found that the obtained values of e r Ј are between 1 and 1.3.…”

Section: )mentioning

confidence: 99%

“…In the previous paper, the authors have measured the values of m r Ј, m r Љ, e r Ј, and e r Љ for bulk SiO 2 in the frequency range between 0.2 and 13.5 GHz, and have found that the values at lower frequencies are considered to contain large errors, as demonstrated by the large standard deviations of the repeatedly measured values of m r Ј, m r Љ, e r Ј, and e r Љ. 6) According to the previous study, we can consider that the e r Ј, e r Љ, m r Ј and m r Љ values of a-Fe 2 O 3 powder at the lowest frequencies contain large errors. It can also be seen from Figs.…”

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confidence: 99%

“…Therefore, it is very important to measure these properties for raw materials and refractories as a function of microwave frequency. In the previous papers, 6) the effects of various factors such as relative density, microwave frequency and particle size of powder SiO 2 and Fe 3 O 4 samples on the complex permittivity and permeability has been investigated by using coaxial transmission line method using a network analyzer. It has been found that the e r Ј values of powder SiO 2 and Fe 3 O 4 samples with the relative density below 1 are smaller than the values estimated using the linear relation between e r Ј and the relative density, and larger than those estimated using the Lichtenecker's logarithm mixed law.…”

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Complex Permittivity and Permeability of α-Fe2O3 and Fe1−xO Powders in the Microwave Frequency Range between 0.2 and 13.5 GHz

2010

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Nowadays, CO 2 emission reduction and energy conservation are urgent tasks owing to the initiation of Kyoto Protocol adopted for the prevention of global warming. Since large fraction of CO 2 emission is attributed to the blast furnace-type iron making in Japan in spite of the fact that Japanese blast furnace technology has been already advanced, new iron making process should be invented based on innovative theories and mechanisms. We have focused on the microwave heating as a new heating source for iron making. 1-4)Ishizaki et al.2) have produced the highly-pure pig iron from the carbon composite iron ore pellet composed of the mixture of magnetite ore (Romeral) and coal (Robe River) powders by means of a 2.45 GHz microwave furnace. The temperature reached 1 350°C ca. 500 s after the onset of the heating, and subsequently the power was switched off. This study implies that iron making from powder raw materials using microwave heating could yield the low temperature operation and the highly-pure pig iron production: The production of highly-pure pig iron is considered to be relevant to the rapid heating of raw materials. 5)Microwave absorption of materials is caused by Joule loss, dielectric loss and magnetic loss, which are dependent on the electrical conductivity and imaginary parts of permittivity and permeability, respectively. Therefore, it is very important to measure these properties for raw materials and refractories as a function of microwave frequency. In the previous papers, 6) the effects of various factors such as relative density, microwave frequency and particle size of powder SiO 2 and Fe 3 O 4 samples on the complex permittivity and permeability has been investigated by using coaxial transmission line method using a network analyzer. It has been found that the e r Ј values of powder SiO 2 and Fe 3 O 4 samples with the relative density below 1 are smaller than the values estimated using the linear relation between e r Ј and the relative density, and larger than those estimated using the Lichtenecker's logarithm mixed law. It has also been found that the imaginary part of complex permeability of Fe 3 O 4 powder with a particle size of 50 nm-180 mm show the peaks in the frequency range of 706 MHz to 2.99 GHz, depending on the particle size. The imaginary part of complex permittivity of Fe 3 O 4 powder is quite large having a peak around 10 GHz.On the other hand, it is very important to measure the complex permittivity and permeability of a-Fe 2 O 3 because most widely used iron ore contains a-Fe 2 O 3 rather than Fe 3 O 4 . Moreover, it is also of industrial importance to measure the complex permittivity and permeability of wüstite (Fe 1Ϫx O) to evaluate the changes of the microwave absorption characteristics in the course of reduction reaction of raw materials. Fe 1Ϫx O is an nonstoichiometric compound and the value of x ranges from 0.05 to 0.15 depending on the temperature and the oxygen partial pressure. Therefore, it is scientifically interesting to elucidate the x value dependencies of these ...

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Complex Permittivity and Permeability of α-Fe2O3 and Fe1−xO Powders in the Microwave Frequency Range between 0.2 and 13.5 GHz

2010

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“…18,19) The molar ratios of FeO(OH):C were chosen to be 1:1 and 1:2. The sample weight was also varied at the molar ratio of 1:1 to determine the effect of apparent density.…”

Section: Determination Of Penetration Depth Of Microwavementioning

confidence: 99%

“…This trial mainly focuses on the pretreatment of poor iron ores involving limonite or pisolite as well as that of sludge in which hydroxides are dominant. Permittivity [17][18][19] of the mixture of FeO(OH) and graphite powder has been measured in the microwave frequency at 2.45 GHz to determine the efficiency to assess how deep microwave can penetrate with various conditions.…”

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Dehydration Behavior of Goethite Blended with Graphite by Microwave Heating

et al. 2011

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In ironmaking and steelmaking processes, dehydration of wet substances and minerals combined by H2O are often recognized to be a key to stable practices. This study aims at understanding dehydration behavior of goethite blended with graphite by microwave treatment simulating drying wet sludge and poor iron ore with combined water.Firstly blend specimens with various conditions, powdery or pelletized, were heated by microwave apparatus. Dehydration rate of goethite increased with increasing temperature. Denser specimen of pelletized was confirmed to be less effective to heat up the whole part. It was found that surplus addition of graphite decreased efficiency in dehydration rate. Thus, it was estimated that a specimen with smaller amount of graphite, whose blend ratio of FeO(OH):C was 1:1, had sufficiently larger distance between graphite particles, through which microwaves could adequately penetrate into the core of the specimen. To prove this hypothesis, Network Analyzer helped evaluate penetration depth of microwave by the measurement of permittivity. The measured results showed that penetration depth decreased with increasing apparent density consistently with the heating behavior by microwave treatment. At the blend ratio of 1:2 of FeO(OH):C, however, the specimen was estimated to behave as if it was under percolation.

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