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Access type: UnknownSubject: search.filters.subject.Microwave hybrid heating

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    Enhancement of thermoelectric properties in rapidly synthesised β-Cu2Se using optimized Cu content and microwave hybrid heating
    (2024-01-15)
    Sakulkalavek, Aparporn
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    Rudradawong, Chalermpol
    ;
    Gobpant, Jakrit
    ;
    Harnwunggmoung, Adul
    ;
    Limsuwan, Pichet
    To our knowledge, this is the first study to successfully synthesise high-temperature-phase copper selenide (β-Cu<inf>2</inf>Se) at room temperature using rapid microwave hybrid heating (MHH). Controlling the starting Cu/Se ratio is the critical parameter for adjusting the content of α- and β-phases in the as-synthesised sample. The relatively low Cu composition causes impurities to form in the Cu<inf>3</inf>Se<inf>2</inf> phase, deteriorating the thermoelectric (TE) properties of the Cu<inf>2</inf>Se material. The β phase formation at room temperature promotes electrical conductivity. The thermal conductivities of the Cu<inf>2.0</inf>Se samples were 0.5–0.8 Wm<sup>−1</sup>K<sup>−1</sup> at 303–673 K. A strong electronic-phonon interaction may potentially couple electronic thermal conductivity (κ<inf>e</inf>) and lattice thermal conductivity (κ<inf>L</inf>), resulting in incomplete separability of κ<inf>L</inf> and κ<inf>e</inf> in the β-Cu<inf>2.0</inf>Se sample. The Cu<inf>2.0</inf>Se exhibited a ZT value of 0.65 at 523 K because of its considerably lowered thermal conductivity.
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    A STUDY ON SiC SUSCEPTOR CONFIGURATION FOR MICROWAVE HYBRID HEATING
    (2023-01-01)
    Ngamkiatpaisan, Akawat
    ;
    Hankoy, Montree
    ;
    Kitiwan, Mettaya
    ;
    Keawprak, Nittaya
    ;
    Tunthawiroon, Phacharaphon
    Microwave hybrid heating (MHH) is a novel method to enhance ceramic sintering at high temperatures. The heating mechanism by MHH involves two directions of heat transfer for materials: microwaves heat the sample from the inside out, while the susceptor provides conventional heating from the outside. This unique heating mechanism offers several advantages, including uniform heating, rapid sintering, and enhanced microstructure and properties of materials. This study investigates the configuration of silicon carbide (SiC) susceptors for microwave hybrid heating. The microwave oven (multi-mode, 2.45 GHz, 1.2 kW) was modified with a ceramic insulator housing to maintain the temperature in the chamber. The effects of different configurations of SiC susceptors and microwave powers on the heating rate and maximum temperature were investigated. SiC susceptor plates were placed in the microwave oven using 3 different configurations, and for each condition, the microwave power was varied at 40, 60, 80, and 100% (480, 720, 960, and 1,200 W). The temperature in the microwave chamber was recorded until it reached 900°C or after 30 min of heating. Using two plates of SiC susceptor at 100 % power resulted in the highest heating rate of 62°C/min to reach 925°C. The results of this study offer guidance for the selection of appropriate heating conditions for individual ceramic materials, which can lead to more effective sintering processes.
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    Energy-saving synthesis and β-phase enhancement of Cu2Se thermoelectric materials via the microwave hybrid heating technique
    (2021-10-25)
    Rudradawong, Chalermpol
    ;
    Sukwisute, Pisan
    ;
    Limsuwan, Pichet
    ;
    Harnwunggmoung, Adul
    ;
    Horprathum, Mati
    Thermoelectric generators harvest energy from waste heat and convert it to electricity. β-Cu<inf>2</inf>Se is a candidate for them due to its outstanding thermoelectric properties and its environmentally friendly component elements. A microwave hybrid heating (MHH) method was used for the fast synthesis and enhancement of β-Cu<inf>2</inf>Se materials. The effects of the MHH reaction time on the phase microstructure and thermoelectric properties of the Cu<inf>2</inf>Se material were investigated, and the MHH method was compared with the conventional heating method. The X-ray diffraction patterns of samples, synthesized via the MHH method, showed monoclinic- (α) and cubic- (β) Cu<inf>2</inf>Se crystalline structures, whereas a single monoclinic-(α) structure was identified in a sample, synthesized via a conventional heating method. In addition, the β-Cu<inf>2</inf>Se phase was enhanced with increased MHH reaction time. The carrier concentration increased with β-Cu<inf>2</inf>Se content, which increased electrical conductivity and decreased the Seebeck coefficient. The Cu<sup>+</sup> ions in the β-Cu<inf>2</inf>Se phase led to the reduced thermal conductivity. A low thermal conductivity of 0.86 W m<sup>−1</sup> K<sup>−1</sup> and a maximum dimensionless figure of merit of 0.32 at 523 K were realized for 10 min MHH sample. Finally, MHH showed very low energy consumption and saved time, which are essential for industrialization.