Touch‐free flash sintering with magnetic induction within a reactor activated by the usual flash method

We describe a new system for flash sintering where a reactor is built with walls made from dog‐bone specimens that are held in Stage III of flash under current control. The reactor is placed within a cylindrical space, like a tube, with axial access, for camera, pyrometer, and optical spectrometer....

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Veröffentlicht in:Journal of the American Ceramic Society 2022-11, Vol.105 (11), p.6517-6522
Hauptverfasser: Jalali, Syed I. A., Raj, Rishi
Format: Artikel
Sprache:eng
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Zusammenfassung:We describe a new system for flash sintering where a reactor is built with walls made from dog‐bone specimens that are held in Stage III of flash under current control. The reactor is placed within a cylindrical space, like a tube, with axial access, for camera, pyrometer, and optical spectrometer. A free‐floating green sample (without electrodes) is placed within; it is physically separated from the walls of the reactor. In the present experiments, the reactor wall as well as the “touch free” workpiece were constituted from yttria‐stabilized zirconia. The workpiece is shown to flash, luminesce, and sinter (in a few seconds) when a modest magnetic field is superimposed over the reactor. The final density depends on the strength of the magnetic field, eventually rising to ∼98%. The grain size is highly uniform and nanoscale. Samples of different and arbitrary three‐dimensional shapes have been so sintered. We propose that the walls of the reactor, which are in a constant state of flash, may generate an evanescent plasma that becomes concentrated around the center line of the reactor by the applied magnetic field. The plasma field helps to transfer energy from the reactor walls into the green sample. When the magnetic induction is turned on, the conductive load of the reactor walls on the power supply increases proving the presence of an energy transfer mechanism. The question of impedance matching between the walls, the specimen, and the free space in between is outlined.
ISSN:0002-7820
1551-2916
DOI:10.1111/jace.18601