Challenges in Spark Plasma Sintering of Cerium (IV) Oxide

Prasad, Anil; Malakkal, Linu; Bichler, Lukas; Szpunar, Jerzy A.

doi:10.1002/9781119423829.ch19

Cited by 11 publications

(11 citation statements)

References 17 publications

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“…This change in color indicates the partial reduction of GDC10-HP powder during FAST/SPS sintering. As mentioned above, similar result was reported by the research groups, which used micrometer sized CeO 2 powder [ 39 , 40 ]. The authors stated that fragmentation can be caused by partial reduction of CeO 2 in contact with graphite and discussed related chemical expansion and abrupt contraction after exposition to air as crucial effects.…”

Section: Resultssupporting

confidence: 86%

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Field-Assisted Sintering/Spark Plasma Sintering of Gadolinium-Doped Ceria with Controlled Re-Oxidation for Crack Prevention

et al. 2020

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Gadolinium-Doped Ceria (GDC) is a prospective material for application in electrochemical devices. Free sintering in air of GDC powder usually requires temperatures in the range of 1400 to 1600 °C and dwell time of several hours. Recently, it was demonstrated that sintering temperature can be significantly decreased, when sintering was performed in reducing atmosphere. Following re-oxidation at elevated temperatures was found to be a helpful measure to avoid sample failure. Sintering temperature and dwell time can be also decreased by use of Spark Plasma Sintering, also known as Field-Assisted Sintering Technique (FAST/SPS). In the present work, we combined for the first time the advantages of FAST/SPS technology and re-oxidation for sintering of GDC parts. However, GDC samples sintered by FAST/SPS were highly sensitive to fragmentation. Therefore, we investigated the factors responsible for this effect. Based on understanding of these factors, a special tool was designed enabling pressureless FAST/SPS sintering in controlled atmosphere. For proof of concept, a commercial GDC powder was sintered in this tool in reducing atmosphere (Ar-2.9%H2), followed by re-oxidation. The fragmentation of GDC samples was avoided and the number of micro-cracks was reduced to a minimum. Prospects of GDC sintering by FAST/SPS were discussed.

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Section: Resultssupporting

confidence: 86%

“…The authors even concluded that FAST/SPS is not a suitable technology to sinter CeO 2 . Prasad et al investigated FAST/SPS of other commercial CeO 2 powder (ACROS Organics) with a particle size of ~20 µm [ 40 , 41 ]. After sintering at 1400 °C, with 60 MPa pressure and 5 min dwell, a relative density of 91% was achieved.…”

Section: Introductionmentioning

confidence: 99%

Field-Assisted Sintering/Spark Plasma Sintering of Gadolinium-Doped Ceria with Controlled Re-Oxidation for Crack Prevention

et al. 2020

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“…However, for the benefit of the readers, it is important to note that as the sintering temperature increased (>1500 °C), the CeO 2 reduced to Ce 2 O 3 . Moreover, in our previous work 47 , it was observed that at a high sintering temperature (>1100 °C) and reductive atmosphere CeO 2 exhibited a range of stoichiometry and such non-stoichiometric oxide had been susceptible to chemical expansion 48 leading to the disintegration of the sintered pellets. It was for this reason that the experimental determination of thermal conductivity was limited to two samples sintered at 1000 °C and 1100 °C.…”

Section: Resultsmentioning

confidence: 93%

“…The pellets of CeO 2 with varying densities were made by controlling the sintering parameters such as the sintering temperature, pressure, hold time, and the sintering atmosphere. The more detailed description of the sintering conditions and its effect on density and the microstructure of CeO 2 are given in our previous work 47 . Therefore for brevity, discussions would be limited to the samples on which the thermal conductivity measurements were made.…”

Section: Resultsmentioning

confidence: 99%

Atomistic and experimental study on thermal conductivity of bulk and porous cerium dioxide

Malakkal

Prasad

Oladimeji

et al. 2019

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Cerium dioxide (CeO 2 ) is a surrogate material for traditional nuclear fuels and an essential material for a wide variety of industrial applications both in its bulk and nanometer length scale. Despite this fact, the underlying physics of thermal conductivity ( k L ), a crucial design parameter in industrial applications, has not received enough attention. In this article, a systematic investigation of the phonon transport properties was performed using ab initio calculations unified with the Boltzmann transport equation. An extensive examination of the phonon mode contribution, available three-phonon scattering phase space, mode Grüneisen parameter and mean free path (MFP) distributions were also conducted. To further augment theoretical predictions of the k L , measurements were made on specimens prepared by spark plasma sintering using the laser flash technique. Since the sample porosity plays a vital role in the value of measured k L , the effect of porosity on k L by molecular dynamics (MD) simulations were investigated. Finally, we also determined the nanostructuring effect on the thermal properties of CeO 2 . Since CeO 2 films find application in various industries, the dependence of thickness on the in-plane and cross-plane k L for an infinite CeO 2 thin film was also reported.

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“…Similarly, several works described the FS of doped ceria, [23][24][25][26][27] emphasizing the cost and sintering efficiency of the process. Recently, the formation of sub-stoichiometric ceria by reduction of Ce(IV) to Ce(III) was observed during SPS 28 or FS 29 of pure ceria, possibly leading to phase and volume changes. These effects can have crucial impact on the final pellet structure possibly leading to mechanochemical disintegration.…”

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confidence: 99%

Power‐controlled flash spark plasma sintering of gadolinia‐doped ceria

et al. 2020

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Flash spark plasma sintering (FSPS) is a newly developed technique for consolidation of powder materials into dense compacts. This method belongs to the group of electrical field-assisted sintering (FAST) techniques. It combines the voltage/current characteristics of flash sintering (FS), 1,2 usually performed in pressure-less dog-bone configuration, with the sintering cell design typical of spark plasma sintering (SPS). 3 Recent investigations in FSPS 4-8 use mostly a modification of the classical SPS to achieve FS conditions. This is usually done through the insertion of a nonconductive sleeve (eg, BN 9) between the powder (or pre-compacted/partially pre-sintered pellet) and the graphite die, or alternatively in a die-free configuration. Commercial instruments enabling FSPS processing with higher voltage characteristics (>10 V), using independent external heating of the die or precise time application of the electric field, are under development or in early application stage. In the presented paper, we describe the pressure-assisted FS compaction of powder in an SPS configuration using such a newly developed instrument. We have chosen ceria as a sintering probe not only for its

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Challenges in Spark Plasma Sintering of Cerium (IV) Oxide

Cited by 11 publications

References 17 publications

Field-Assisted Sintering/Spark Plasma Sintering of Gadolinium-Doped Ceria with Controlled Re-Oxidation for Crack Prevention

Field-Assisted Sintering/Spark Plasma Sintering of Gadolinium-Doped Ceria with Controlled Re-Oxidation for Crack Prevention

Atomistic and experimental study on thermal conductivity of bulk and porous cerium dioxide

Power‐controlled flash spark plasma sintering of gadolinia‐doped ceria

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