Field assisted and flash sintering of alumina and its relationship to conductivity and MgO-doping

Cologna, Marco; Francis, John S. C.; Raj, Rishi

doi:10.1016/j.jeurceramsoc.2011.07.004

Cited by 323 publications

(280 citation statements)

References 23 publications

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“…, similar to thermal runaway, is shown in Figure 13(b) [33]. This is because the heating of MgO results in a significant increase of its electrical conductivity.…”

Section: Fs Of Insulators and Semiconductorsmentioning

confidence: 56%

“…Out of a total of 88 papers published on FS, 53 of them involve pressure-less mode [33,38,[47][48][49], while 23 involve pressure-assisted (Figure 4(b) and (c)) [35,42,50]. In the pressure-less configurations, silver (Ag) or platinum (Pt) pastes were employed in order to achieve good electrical contact (minimising contact resistance) between the sample and the electrodes.…”

Section: Experimental Configurations For Fsmentioning

confidence: 99%

“…The initial suggestion [33,66] that the average sample temperature (T S ) was close to the furnace temperature (T F ) has been disproven by modelling [67] and afterwards by experiments [39,62]. At present, an accurate T S measurement system with high time resolution (<1 ms) has not yet been achieved.…”

Section: Sample Shrinkage During Fsmentioning

confidence: 99%

“…In the case of pure alumina, the presence of MgO-doping (0.25 wt-% MgO) [33] promoted FS behaviour. The preferential segregation of Mg [131] to the grain boundaries might significantly affect electrical conductivities, FS temperature distribution and grain-boundary mobility.…”

Section: Proposed Mechanisms In Fsmentioning

confidence: 99%

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Review of flash sintering: materials, mechanisms and modelling

Grasso

McKinnon

et al. 2016

Advances in Applied Ceramics

393

248

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Flash sintering (FS) is an energy efficient sintering technique involving electrical Joule heating, which allows very rapid densification (<60 s) of particulate materials. Since the first publication on flash-sintered zirconia (3YSZ) in 2010, it has been intensively researched and applied to a wide range of materials. Going back more than a century ago, we have found a close similarity between FS of oxides and Nernst glowers developed in 1897. This review provides a comprehensive overview of FS and is based on a literature survey consisting of 88 papers and seven patents. It correlates processing parameters (i.e. electric field magnitude, current density, waveforms (AC, DC) and frequency, furnace temperature, electrode materials/ configuration, externally applied pressure and sintering atmosphere) with microstructures and densification mechanisms. Theorised mechanisms driving the rapid densification are substantiated by modelling work, advanced in situ analysis techniques and by established theories applied to electric current assisted/activated sintering techniques. The possibility of applying FS to a wider range of materials and its implementation in industrial scale processes are discussed.

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“…, similar to thermal runaway, is shown in Figure 13(b) [33]. This is because the heating of MgO results in a significant increase of its electrical conductivity.…”

Section: Fs Of Insulators and Semiconductorsmentioning

confidence: 56%

Section: Experimental Configurations For Fsmentioning

confidence: 99%

Section: Sample Shrinkage During Fsmentioning

confidence: 99%

Section: Proposed Mechanisms In Fsmentioning

confidence: 99%

See 2 more Smart Citations

Review of flash sintering: materials, mechanisms and modelling

Grasso

McKinnon

et al. 2016

Advances in Applied Ceramics

393

248

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“…Flash sintering (FS) is a novel technique, whereby simultaneous application of electric and thermal fields lead, within few seconds, to ultrafast densification of the ceramic nanoparticles compact [1,2]. The sudden densification takes place at appropriate combinations of the electric field and temperature and accompanied by the photoluminescence flash [3].…”

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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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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