Flash sintering incubation in Al2O3/TZP composites

Bichaud, Emmanuelle; Chaix, Jean‐Marc; Carry, C.; Kleitz, M.; Steil, M.C.

doi:10.1016/j.jeurceramsoc.2015.02.033

Cited by 103 publications

(63 citation statements)

References 18 publications

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“…This is further aided by the very low aspect ratio of the sample, effectively reducing internal thermal gradients and maximizing the intimate thermal contact with the electrodes, thus allowing the electrodes to serve as effective heat sinks. A similar effect has been reported for the flash sintering of zirconia, where the onset of flash was significantly delayed in low aspect ratio samples (Bichaud et al, 2015). To verify that the absence of flash sintering is a result of the thermal sink effect of the electrode configuration in our apparatus, a single sample was pressed from the same powder in the shape of a dog bone using method taught by Francis et al (2012) and an attempt was made to sinter the sample using the flash sintering technique.…”

Section: Resultssupporting

confidence: 68%

Improving NASICON Sinterability through Crystallization under High-Frequency Electrical Fields

Lisenker

Stoldt

2016

Front. Energy Res.

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The effect of high-frequency (HF) electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP) ion conducting ceramic was investigated. LAGP with the nominal composition Li1.5Al0.5Ge1.5(PO4)3 was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300 V/cm at 1 MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using X-ray diffraction, scanning electron microscope, TEM, and electrochemical impedance spectroscopy to compare conventionally and field-sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 h of sintering were minor with measured sintering strains of 31 vs. 26% with and without field, respectively. Ionic conductivity of the sintered pellets was evaluated, and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

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Section: Resultssupporting

confidence: 68%

Improving NASICON Sinterability through Crystallization under High-Frequency Electrical Fields

Lisenker

Stoldt

2016

Front. Energy Res.

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“…Bichaud et al [118] showed that 3Y-TZP with up to 40% alumina added will flash sinter at 1100 120V/cm [20], and pure alumina, which will not flash sinter without doping under these conditions [87], it seems that the properties of the composite are clearly not entirely predictable from the parent materials in both studies. This suggests that in composite materials undergoing flash sintering some interaction between the defect states from the parent materials can affect the flash sintering process.…”

Section: Composite Materialsmentioning

confidence: 90%

“…Flash sintering behaviour has also been studied in zirconia-based materials with additions of alumina [118], silicon carbide whiskers [119], and yttrium aluminium garnet (YAG) with alumina [120]. Liu et al [119] showed that the flash sintering of silicon carbide whiskers in a 3Y-TZP matrix resulted in a dense (>95%) microstructure under 120-140V/cm, 80mA/mm 2 and at 1000 o C. The process was carried out in air without significant oxidation of the silicon carbide whiskers.…”

Section: Composite Materialsmentioning

confidence: 99%

Flash sintering of ceramic materials

Dancer¹

2016

Mater. Res. Express

160

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During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sintering methods carried out to date, and compares the properties of the materials obtained to those produced by conventional sintering. The flash sintering process is described for oxides of zirconium, yttrium, aluminium, tin, zinc, and titanium; silicon and boron carbide, zirconium diboride, materials for solid oxide fuel applications, ferroelectric materials, and composite materials. While experimental observations have been made on a wide range of materials, understanding of the underlying mechanisms responsible for the onset and latter stages of flash sintering is still elusive. Elements of the proposed theories to explain the observed behaviour include extensive Joule heating throughout the material causing thermal runaway, arrested by the current limitation in the power supply, and the formation of defect avalanches which rapidly and dramatically increase the sample conductivity.Undoubtedly, the flash sintering process is affected by the electric field strength, furnace temperature and current density limit, but also by microstructural features such as the presence of second phase particles or dopants and the particle size in the starting material. While further experimental work and modelling is still required to attain a full understanding capable of predicting the success of the flash sintering process in different materials, the technique nonetheless holds great potential for exceptional control of the ceramic sintering process.

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“…Recent FS works support the thermal runaway model as a dominating process at the flash set point [8,10,28]. Several significant processes may take place if the actual local temperature at the contact point surpasses the melting point of the solid particle at contact due to the Joule heating.…”

Section: Analysis and Discussionmentioning

confidence: 99%

“…Therefore, all ceramic powder compacts subjected to an electric field are prone to flash sintering, once critical flash conditions attained. The flash onset condition is mainly controlled by the amount of the applied electric power density [28], and leads to local melting at the particle contacts. The non-linear electric conductivity is associated with this local melting.…”

Section: Analysis and Discussionmentioning

confidence: 99%

Liquid Film Capillary Mechanism for Densification of Ceramic Powders during Flash Sintering

Chaim

2016

Materials

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Recently, local melting of the particle surfaces confirmed the formation of spark and plasma during spark plasma sintering, which explains the rapid densification mechanism via liquid. A model for rapid densification of flash sintered ceramics by liquid film capillary was presented, where liquid film forms by local melting at the particle contacts, due to Joule heating followed by thermal runaway. Local densification is by particle rearrangement led by spreading of the liquid, due to local attractive capillary forces. Electrowetting may assist this process. The asymmetric nature of the powder compact represents an invasive percolating system.

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Flash sintering incubation in Al2O3/TZP composites

Cited by 103 publications

References 18 publications

Improving NASICON Sinterability through Crystallization under High-Frequency Electrical Fields

Improving NASICON Sinterability through Crystallization under High-Frequency Electrical Fields

Flash sintering of ceramic materials

Liquid Film Capillary Mechanism for Densification of Ceramic Powders during Flash Sintering

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