Theoretical and phenomenological analogies between flash sintering and dielectric breakdown in α-alumina

Biesuz, Mattia; Luchi, Piero; Quaranta, A.; Sglavo, Vincenzo M.

doi:10.1063/1.4964811

Cited by 55 publications

(41 citation statements)

References 43 publications

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“…Recent percolation model showed the possibility for nanoparticle surface softening/melting at temperatures resembling plasma and in excess of the melting points [13]. This was in agreement with observed dielectric prebreakdown in alumina [10,34]. In addition, several teams challenged recently the electric field effects in flash sintering, by conducting high heating rate sintering experiments in the absence of the electric field.…”

Section: Introductionsupporting

confidence: 66%

“…The photoluminescence signals the transition to the nonlinear behavior of the compact's electric conductivity, which otherwise is almost linear with the increase in the temperature [8,9]. Immediate after the flash event, the initial voltage control mode (i.e., constant voltage) exchanged into the current control mode (i.e., constant current) in order to prevent damage of the specimen and the flash sintering system [10,11].…”

Section: Introductionmentioning

confidence: 99%

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On thermal runaway and local endothermic/exothermic reactions during flash sintering of ceramic nanoparticles

Chaim

Estournès

2018

J Mater Sci

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OATAO is an open access repository that collects the work of some Toulouse researchers and makes it freely available over the web where possible. ABSTRACTNumerical analysis of the heat balance at the flash event during flash sintering of granular ceramic nanoparticles was performed assuming continuum solid state as well as simultaneous surface softening/liquid formation and current percolation through the nanoparticle contacts. Assuming inter-particle radiations in the specimen volume, the electric Joule heat generated at the nanoparticle contacts partially lost by radiation from the specimen external surfaces. Considering the thermal effects due to rapid heating rate and freemolecular heat conduction regime, high-temperature gradients between the nanoparticle surfaces and the surrounding gas were developed. The attractive capillary forces, induced by the particle surface softening/liquid at the percolation threshold, lead to rapid rearrangement and densification of the nanoparticles. The excess Joule heat, already at the flash event, suffices the excess internal heat that is necessary for partial or full melting. Particle surface softening/liquid formation is a transient process, hence followed by crystallization immediate after the nanoparticle rearrangement. Thermal runaway is associated with local surface softening/melting and its solidification.

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Section: Introductionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

On thermal runaway and local endothermic/exothermic reactions during flash sintering of ceramic nanoparticles

Chaim

Estournès

2018

J Mater Sci

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“…After such phenomenon, the power supply starts to work in current control and the electrical power stabilizes. The time needed for reproducing this sort of transition from insulator to semiconductor‐like, called incubation time, clearly depends on the applied field: the samples treated at higher electrical filed are characterized by shorter incubation times, this being similar to the behavior shown by other crystalline ceramics …”

Section: Resultsmentioning

confidence: 95%

“…During flash sintering, the sample is connected to a power supply and, at a certain combination of electrical field and temperature, an abrupt decrease in electrical resistivity is observed, the material undergoing to a sort of transition from electrical insulator to conductor. 1,2,4 This phenomenon is followed by an intense light emission 1,5,6 and an almost instantaneous densification occurs in few seconds. Although the first FS experiments were carried out on ionic conductors (YSZ, GDC, etc.…”

Section: Introductionmentioning

confidence: 99%

Porcelain stoneware consolidation by flash sintering

Biesuz

Abate

2017

J Am Ceram Soc

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Porcelain stoneware was consolidated by flash sintering under DC polarization using current densities in the range 4-20 mA/mm 2 . The results show the applicability of this innovative sintering technology to a material whose densification occurs by vitrification, thus allowing to extend the possible application field of flash sintering to traditional ceramics. Using appropriate current density, the flashsintered samples are dense, homogeneous, and well-vitrified. XRD and microstructural analysis points out the formation of primary mullite while secondary mullite is only sporadically observed. In addition, comparison between flash sintering and fast firing shows that the densification obtained in the selected ceramic system via the former route cannot be reproduced just by a rapid heating process. K E Y W O R D Sfield-assisted sintering technology, porcelain, sinter/sintering

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“…Many other reports were published applying this technique to other materials [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], studying the dependence on the amplitudes of the electric field and current density [31], on the average particle size [32], on the porosity [33], and searching for an explanation of such events [34][35][36][37][38][39][40].…”

Section: Introductionmentioning

confidence: 99%

Electrical Behavior and Microstructural Features of Electric Field-Assisted and Conventionally Sintered 3 mol% Yttria-Stabilized Zirconia

Carvalho¹,

Muccillo²,

Muccillo

2018

Ceramics

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ZrO 2 : 3 mol % Y 2 O 3 (3YSZ) polycrystalline pellets were sintered at 1400 • C and by applying an alternating current (AC) electric field at 1000 • C. An alumina sample holder with platinum wires for connecting the sample to a power supply was designed for the electric field-assisted sintering experiments. The apparent density was evaluated with the Archimedes technique, the grain size distribution by analysis of scanning electron microscopy images, and the electrical behavior by the impedance spectroscopy technique. Sintering with the application of AC electric fields to 3YSZ enhances its ionic conductivity. An explanation is proposed, based on the dissolution back to the bulk of chemical species, which are depleted at the grain boundaries, leading to an increase in the oxygen vacancy concentration. For the enhancement of the grain boundary conductivity, an explanation is given based on the diminution of the concentration of depleted chemical species, which migrate to the bulk. This migration leads to a decrease of the potential barrier of the space charge region, known to be responsible for blocking the oxide ions through the intergranular region. Moreover, the heterogeneity of the distribution of the grain sizes is ascribed to the skin effect, the tendency of the AC current density to be largest near the surface, decreasing towards the bulk.

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Theoretical and phenomenological analogies between flash sintering and dielectric breakdown in α-alumina

Cited by 55 publications

References 43 publications

On thermal runaway and local endothermic/exothermic reactions during flash sintering of ceramic nanoparticles

On thermal runaway and local endothermic/exothermic reactions during flash sintering of ceramic nanoparticles

Porcelain stoneware consolidation by flash sintering

Electrical Behavior and Microstructural Features of Electric Field-Assisted and Conventionally Sintered 3 mol% Yttria-Stabilized Zirconia

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