Validation of measured microwave absorption and temperature change for development of a single-mode-type microwave heating thermogravimetry apparatus

The ongoing development of high-temperature processes with the use of microwaves requires new microwave absorbers that are useful at these temperatures. In this study, we propose Al4SiC4 powders as important and efficient microwave absorbers. We investigated both the behavioural microwave heating and electrical permittivity characteristics of Al4SiC4 powders with various particle sizes at 2.45 GHz. The TE103 single-mode cavity indicated that Al4SiC4 powder samples yielded different heating behaviours and dielectric constants for each particle size compared with SiC. By microwave heating ∅50 mm × 5 mm disks of Al4SiC4 and SiC, we demonstrate that for specific sizes, Al4SiC4 can be heated at a higher temperature than SiC. Finally, the results of the two-dimensional two-colour thermometer show that an energy concentration appears at the interface of the microwave-heated Al4SiC4. These phenomena, which are inconsistent in individual physical property values, can be explained without contradicting microwave heating physics.

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Materials processed by indirect microwave heating in a single-mode cavity

Ceramics International ◽

10.1016/j.ceramint.2005.06.017 ◽

2006 ◽

Vol 32 (8) ◽

pp. 911-915 ◽

Cited By ~ 25

Author(s):

D. Grossin ◽

S. Marinel ◽

J.-G. Noudem

Keyword(s):

Microwave Heating ◽

Single Mode ◽

Single Mode Cavity

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Phase transformations in Si-based alloy powder mixtures induced by microwave heating in a 2.45 GHz single-mode applicator

Intermetallics ◽

10.1016/j.intermet.2010.06.004 ◽

2010 ◽

Vol 18 (11) ◽

pp. 2030-2033 ◽

Cited By ~ 2

Author(s):

Song Li ◽

Guoqiang Xie ◽

Dmitri V. Louzguine-Luzgin ◽

Ziping Cao ◽

Noboru Yoshikawa ◽

...

Keyword(s):

Phase Transformations ◽

Microwave Heating ◽

Alloy Powder ◽

Single Mode ◽

Powder Mixtures

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Stuy on Microwave-Assisted Grinding of Low-Grade Ludwigite

Materials Science Forum ◽

10.4028/www.scientific.net/msf.814.214 ◽

2015 ◽

Vol 814 ◽

pp. 214-219

Author(s):

Ya Jing Liu ◽

Tao Jiang ◽

Zhi Deng ◽

Xiang Xin Xue ◽

Pei Ning Duan

Keyword(s):

Energy Consumption ◽

Microwave Heating ◽

Microwave Absorption ◽

Heating Temperature ◽

Microwave Absorption Property ◽

Low Grade ◽

Absorption Property ◽

Microwave Assisted ◽

Mineral Compositions ◽

Grinding Efficiency

The low-grade ludwigite is one of the complex and refractory ores. Based on the high energy consumption and inefficient in the grinding process and according to the microwave-assisted grinding principle, this paper studied the microwave absorption property of ludwigite and researched the effect of microwave heating on the grinding efficiency of it. The non-microwaved and microwaved samples were characterized with regard to the chemical components, mineral compositions, macroscopic structure and microstructure, grinding efficiency by methods of the chemical analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and grain size analysis, etc. The results indicated that ludwigite, with good microwave absorption property, was suitable for microwave processing. The grindability of microwaved ludwigite was related to the microwave power and microwave heating temperature. By the microwave heating temperature attained 500~650°C, many macro-cracks and micro-cracks were produced by thermal stress between different mineral interfaces, which resulted in the decrease of strength of ludwigite and easy levigation, but the mineral compositions had no obviously changed, which would not affect the subsequent magnetic separation. It was concluded that short, high-power treatments were most effective but over-exposure of the sample led to reductions in efficiency. Under the same conditions, the grinding efficiency of ludwigite was improved 24.54% higher than untreated ore, which significantly improved the grinding efficiency and reduced energy consumption.

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Studies of Nonthermal Effects During Intense Microwave Heating of Crystalline Solids

MRS Proceedings ◽

10.1557/proc-269-137 ◽

1992 ◽

Vol 269 ◽

Cited By ~ 5

Author(s):

John H. Booske ◽

Reid F. Cooper ◽

Leon McCaughan ◽

Sam Freeman ◽

Binshen Meng

Keyword(s):

Field Strength ◽

Electric Field ◽

Microwave Heating ◽

Microwave Absorption ◽

Relative Magnitude ◽

Material Surface ◽

Absorption Coefficients ◽

Ion Energy ◽

Absorbing Materials ◽

Theoretical Analyses

ABSTRACTReports of enhanced sintering rates associated with microwave heating may be due to nonthermal lattice fluctuation statistics. Recent theoretical analyses reviewed in this paper confirm the feasibility of this phenomenon for a wide variety of situations involving very different microwave absorption mechanisms. For materials with weak microwave absorption coefficients, the effect is expected to be uniformly distributed throughout the volume. For strongly absorbing materials, however, the effect is expected to be concentrated near the material surface, with a characteristic exponential penetration depth of Lnt ∼ 10 - 100 μm. An “observable” nonthermal effect depends on the relative magnitude of the microwave electric field strength |E| and the lattice ion energy relaxation rate γ with the most pronounced effects occurring for larger values of |E| and smaller values of γ.

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Experimental Observations of Thermal Spikes in Microwave Processing of Ceramic Oxide Fibers

MRS Proceedings ◽

10.1557/proc-347-539 ◽

1994 ◽

Vol 347 ◽

Cited By ~ 1

Author(s):

Gerald J. Vogt ◽

Wesley P. Unruh ◽

J. R. Thomas

Keyword(s):

Microwave Heating ◽

Hot Spots ◽

Hot Spot ◽

Single Mode ◽

Microwave Cavity ◽

X Ray Diffraction ◽

Thermal Spike ◽

X Ray ◽

Heating Behavior ◽

Fiber Processing

ABSTRACTMicrowave heating of alumina/silica fiber tows in a single-mode microwave cavity at 2.45 GHz has produced a surprising thermal spike behavior on the fiber bundles. During a thermal spike, a “hot spot” on the tow brightens rapidly, persists for a few seconds, and then rapidly extinguishes. A hot spot can encompass the entire tow in the cavity or just a localized portion of the tow. Some local hot spots propagate along the fiber. Thermal spikes are triggered by relatively small (<15%) increases in power, thus having obvious implications for the development of practical microwave fiber processing systems. A tow can be heated through several successive thermal spikes, after which the tow is left substantially cooler than it was originally, although the applied microwave electric field is much larger. X-ray diffraction studies show that after each temperature spike there is a partial phase transformation of the tow material into mullite. After several excursions the tow has been largely transformed to the new, less lossy phase and is more difficult to heat. Heating experiments with Nextel 550 tows are examined for a plausible explanation of this microwave heating behavior.

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A single-mode microwave heating for essential oil extraction of perovskia atriplacifolia

2016 Progress in Electromagnetic Research Symposium (PIERS) ◽

10.1109/piers.2016.7735586 ◽

2016 ◽

Author(s):

N. Faqeryar ◽

Y. Mori ◽

T. Matsumura

Keyword(s):

Essential Oil ◽

Microwave Heating ◽

Single Mode ◽

Oil Extraction

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Optimization of the Microwave-Assisted Carbothermical Reduction Process for Metals from Electric Arc Furnace Dust with Biochar

Metals ◽

10.3390/met11111765 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1765

Author(s):

Anton Anzulevich ◽

Leonid Butko ◽

Dmitrii Kalganov ◽

Dmitrii Pavlov ◽

Valentin Tolkachev ◽

...

Keyword(s):

Microwave Heating ◽

Effective Permittivity ◽

Plane Waves ◽

Reduction Process ◽

Single Mode ◽

Spherical Particles ◽

Source Distribution ◽

Eaf Dust ◽

Valuable Metals ◽

Heat Source Distribution

The main purpose of this work was to extract valuable metals from EAF dust with the addition of biochar, using microwaves to control and optimize the carbothermical reduction process. To achieve better microwave penetration and the most homogeneous electromagnetic heat source distribution possible in a sample, the content of EAF dust and biochar in centimeter-size spherical particles prepared by the pelletization process was considered to be radially heterogeneous. The content of EAF dust was determined experimentally and the effective permittivity, permeability, and thermal conductivity of the EAF dust as well as biochar–EAF powder mixture were determined using effective medium approximation. The microwave heating of a multilayered pellet of biochar-containing EAF dust was simulated and investigated. The influence of the distribution of the components within the pellet on the effectiveness of the microwave heating was investigated, as was the influence of the biochar conductivity. The interaction of the pellet with both plane waves in free space and with H10 mode waves in a single-mode waveguide was considered. The most optimal distribution of EAF dust and biochar within the pellet for the reduction process was determined.

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