Ultra-fast firing: Effect of heating rate on sintering of 3YSZ, with and without an electric field

Ji, Wei; Parker, B.A.; Falco, S.; Zhang, J.Y.; Fu, Zhengyi; Todd, Richard I.

doi:10.1016/j.jeurceramsoc.2017.01.033

Cited by 210 publications

(144 citation statements)

References 22 publications

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“…We have recently shown that the same slip cast powder compacts can be sintered to 99% density in ³30 s by rapid heating to 1300°C without applying an electric field or current to the specimen. 20) The confirmation here that similar temperatures are required to reach high sintered density on the same timescale when some of the specimen heating is electrical in origin supports the idea that rapid heating rather than the application of an electric field is the most important factor in accelerating densification in flash sintering.…”

Section: Densification and Grain Growthsupporting

confidence: 65%

“…Others, have shown that the power surge can be explained satisfactorily as thermal runaway resulting from the negative temperature coefficient of resistivity of most ceramics 14)18) whilst comparison with the sintering of powder compacts rapidly heated without an electric field suggests that the high densification rate may be at least in part a consequence of the fast heating in flash sintering. 19), 20) Further progress requires a better understanding of the conditions during flash sintering. This is a complex and dynamic process with transient temperatures, temperature gradients and constantly changing specimen characteristics (electrical resistivity, thermal conductivity, emissivity, dimensions) as sintering removes porosity and densifies the specimen.…”

Section: Introductionmentioning

confidence: 99%

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Measurement and modelling of electrical resistivity by four-terminal method during flash sintering of 3YSZ

Yoshida

Falco

Todd

2018

J. Ceram. Soc. Japan

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Flash sintering is a newly developed technique to quickly densify conductive ceramics in the presence of an electric field. At a critical combination of field and temperature, densification takes place in a few seconds. This paper investigates the electrical resistivity during flash sintering of 3YSZ by the four-terminal method in combination with numerical modelling of electrical heating and temperature distributions. Densification rates were similar to those observed previously in specimens rapidly heated by methods not involving direct electrical heating. Temperature gradients caused by heat loss from the surface and non-uniform electrical heating led to differential sintering, specimen distortion and non-uniform grain size. The four point measurements revealed significant contact resistance at the power supply electrodes and allowed accurate measurement of the resistivity under the high current conditions of flash sintering. The specimen resistivity was lower for a given temperature under high current conditions and this was attributed to electronic conduction. Concurrent sintering led to a progressive reduction of resistivity during heating causing an increase in the apparent activation energy for electrical conduction. When the effect of sintering on resistivity was accounted for, the onset conditions for the "flash event" were accurately predicted on the basis of thermal runaway.

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Section: Densification and Grain Growthsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Measurement and modelling of electrical resistivity by four-terminal method during flash sintering of 3YSZ

Yoshida

Falco

Todd

2018

J. Ceram. Soc. Japan

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“…Furthermore, heat transfer by conduction/convection from the hot nanoparticle surface to its surrounding gas may follow different regimes, depending on the nanoparticle size and the gas composition, as will be shown below. In addition, changing the heating rate led to different sintering rates in both the presence and absence of the electric field [22,38]. Consequently, the heating rate has strong effect on the heat transfer regime and mechanism during sintering hence heat transfer needs careful treatment.…”

Section: Theory Heat Transfer From Nanoparticlesmentioning

confidence: 99%

“…Although the thermal runaway of the Joule heating is a well-accepted description of the process physics [14][15][16], the underlying atomistic mechanisms for the rapid sintering are still under debate. The main question is whether the enhanced mass transport takes place at the nanoparticle surfaces [17][18][19][20], or within their bulk [21], in the solid state [21,22], or liquid-assisted [23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

“…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. Ji et al [22] applied high heating rates without electric field, in addition to conventional, SHS (selfpropagating high-temperature synthesis), and flash sintering, for comparative sintering studies in yttriastabilized zirconia (3YSZ). Sudden insertion of the specimens into the furnace hot zone enabled fast heating rate of * 50°C s -1 .…”

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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Effect of Spark Plasma Sintering Current and Voltage on the Microstructure and Electrical Properties of Borosilicate Glass–Indium Tin Oxide Composites

Rudzik

Gerhardt

2020

Adv Eng Mater

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Borosilicate glass–indium tin oxide (ITO) composites made from glass microspheres and ITO nanoparticles provide a unique model system to monitor the effect of spark plasma sintering (SPS) parameters on the resultant electrical properties of the composites. Composite sets containing different ITO content (up to 10 phr), fabricated under the same SPS conditions, are used as the starting point for the equivalent circuit analysis. The effect of changing the various SPS parameters such as heating rate, hold temperature, and applied pressure on the current and voltage profiles experienced by samples containing 2.5 phr (2.44 wt%) ITO, and their resultant electrical response are reported. Experiments are carried out varying a single SPS parameter at a time while keeping others constant. The applied pressures used range from 5 to 40 MPa; the hold temperature is varied from 610 to 680 °C; and the heating rate is tested between 2 and 200 °C min−1. It is demonstrated that not only do the current and voltage profiles change in all of these instances but also the microstructure and resultant electrical properties of the composite samples being fabricated. Results indicate that all of these parameters are interdependent and can affect the electrical properties of the fabricated samples by many orders of magnitude in some cases.

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Ultra-fast firing: Effect of heating rate on sintering of 3YSZ, with and without an electric field

Cited by 210 publications

References 22 publications

Measurement and modelling of electrical resistivity by four-terminal method during flash sintering of 3YSZ

Measurement and modelling of electrical resistivity by four-terminal method during flash sintering of 3YSZ

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

Effect of Spark Plasma Sintering Current and Voltage on the Microstructure and Electrical Properties of Borosilicate Glass–Indium Tin Oxide Composites

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