scholarly journals Flash Sintering of YSZ/Al2O3 Composites: Effect of Processing and Testing Conditions

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1031
Author(s):  
Mattia Biesuz ◽  
Andrea Ometto ◽  
Vincenzo Maria Sglavo
Keyword(s):  
Electric Current ◽  
Thermal Insulation ◽  
Homogeneous Material ◽  
Sintering Behavior ◽  
Current Limit ◽  
Flash Sintering ◽  
Relevant Effect ◽  
Strong Relation ◽  
Alumina Composites ◽  
Two Phases

The flash sintering behavior of yttria-stabilized zirconia/alumina composites was investigated to understand the role of the fundamental processing and testing parameters (electric field intensity, electric current limit, thermal insulation, homogeneity and dispersion of the two phases) on densification. A strong relation between the composite compositions and the electric parameters needed to promote flash sintering is revealed. Interestingly, the composite preparation method, which affects the two-phases dispersion homogeneity, was shown to have a relevant effect on the flash onset conditions, where the more homogeneous material is more difficult to be flashed. Moreover, the use of a simple thermal insulation system around the green body allowed to improve the final density of the composites under constant electric current.

scholarly journals Removal of organic matter from pre-treated domestic sewage in anaerobic biological reactor by a combined system of electrolytic and biological aerobic treatment

2019 ◽  
Vol 14 (4) ◽  
pp. 1
Author(s):  
Ariela Araujo Fonseca ◽  
Yovanka Pérez Ginoris ◽  
Norma Mendes Pinheiro Gontijo ◽  
Marco Antonio Almeida de Souza
Keyword(s):  
Organic Matter ◽  
Electric Current ◽  
Phase 1 ◽  
Zooplankton Community ◽  
Batch Reactors ◽  
Phase 2 ◽  
Combined System ◽  
Organic Matter Removal ◽  
Electrolytic Process ◽  
Two Phases

Biological processes are the most widespread methods for wastewater treatment. However, they are limited in their ability to degrade toxic and refractory pollutants, contaminants that electrochemical processes can remove. Therefore, this research explored the possibility of treating sewage by an anaerobic biological process followed by an aerobic system integrated to an electrolytic process. Three sequential batch reactors were operated in an automated way. Each of three reactors represented a process: aerobic biological treatment (BR); electrolytic treatment (ER); and a combination of both, the bio electrolytic reactor (BER). Two phases were ran with different electrodes: (Phase 1) stainless steel and (Phase 2) graphite. The electric current was varied from 0.001 to 0.100 A. COD, TS, SS, turbidity, and the zooplankton community were monitored. The highest organic matter removal efficiencies were 86%, 79% and 87% for BR, ER and BER, respectively. The best weekly BER efficiencies for COD removal were 90% and 98%, with current densities of 0.27 A/m2 (Phase 1) and 0.05 A/m2 (Phase 2). The main conclusions about bio electrolytic process were: (1) it did not achieve organic matter removal high enough to justify its application; (2) inert electrodes are the more indicated; and (3) the zooplankton community was affected by the electric current.

scholarly journals Spark Plasma Sintering Behavior of Nb-Mo-Si Alloy Powders Fabricated by Hydrogenation-Dehydrogenation Method

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3549 ◽  
Author(s):  
Sung Lee ◽  
Ki Park ◽  
Jang-Won Kang ◽  
Yanghoo Kim ◽  
Hyun-Su Kang ◽  
...  
Keyword(s):  
Spark Plasma Sintering ◽  
Sintering Temperature ◽  
Sintering Behavior ◽  
Powder Metallurgy Method ◽  
Composite Powders ◽  
Plasma Sintering ◽  
Formation Behavior ◽  
Spark Plasma ◽  
Two Phases ◽  
Nb5si3 Phase

In this study, the sintering behaviors of Nb-6Mo-20Si-3Cr (at percentage) in situ composite powders were studied. The Nb alloy powder was fabricated by a hydrogenation-dehydrogenation method, and both the alloy ingot and powders consisted of two phases: An Nb metal phase and the α-Nb5Si3 phase. Consolidation of the alloy powders was performed at 1500, 1600, and 1700 °C using spark plasma sintering, and the microstructures and phases formed at various sintering temperatures were analyzed. Micropores were observed in the compact sintered at 1500 °C due to the lack of complete densification at that temperature. The densification was completed at 1600 °C and the microstructure was slightly coarsened at 1700 °C compared to the microstructure of the compact sintered at 1600 °C. The microstructures prepared by the powder metallurgy method were finer than the microstructure of the ingot prepared by the casting method. The phase formation behavior varied according to the sintering temperature. Specifically, the α-Nb5Si3 phase, which is a stable structure of the Nb5Si3 phase at a low temperature, was transformed to the β-Nb5Si3 phase (which is stable at a high temperature) with an increasing sintering temperature.

scholarly journals Gd/Sm-Pr Co-Doped Ceria: A First Report of the Precipitation Method Effect on Flash Sintering

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1218 ◽  
Author(s):  
Luca Spiridigliozzi ◽  
Lorenzo Pinter ◽  
Mattia Biesuz ◽  
Gianfranco Dell’Agli ◽  
Grazia Accardo ◽  
...  
Keyword(s):  
Ammonia Solution ◽  
Current Control ◽  
Precipitation Method ◽  
Precipitation Process ◽  
Sintering Behavior ◽  
Method Effect ◽  
Flash Sintering ◽  
Co Precipitation ◽  
First Time ◽  
Flash Event

In this work, ceria-based ceramics with the composition Gd0.14Pr0.06Ce0.8O2-δ and Sm0.14Pr0.06Ce0.8O2-δ, were synthesized by a simple co-precipitation process using either ammonium carbonate or ammonia solution as a precipitating agent. After the calcination, all of the produced samples were constituted by fluorite-structured ceria only, thus showing that both dopant and co-dopant cations were dissolved in the fluorite lattice. The ceria-based nanopowders were uniaxially compacted and consequently flash-sintered using different electrical cycles (including current-ramps). Different results were obtained as a function of both the adopted precipitating agent and the applied electrical cycle. In particular, highly densified products were obtained using current-ramps instead of “traditional” flash treatments (with the power source switching from voltage to current control at the flash event). Moreover, the powders that were synthesized using ammonia solution exhibited a low tendency to hotspot formation, whereas the materials obtained using carbonates as the precipitating agent were highly inhomogeneous. This points out for the first time the unexpected relevance of the precipitating agent (and of the powder shape/degree of agglomeration) for the flash sintering behavior.

scholarly journals Flash Sintering of Commercial Zirconium Nitride Powders

2021 ◽  
Author(s):  
Diego Dubois ◽  
Amirali Eskandariyun ◽  
Suprabha Das ◽  
Andriy Durygin ◽  
Zhe Cheng
Keyword(s):  
Ceramic Powder ◽  
External Pressure ◽  
Zirconium Nitride ◽  
Electrical Field ◽  
Electrical Field Strength ◽  
Current Limit ◽  
Flash Sintering ◽  
Compact Pressure ◽  
Short Period ◽  
A Current

Flash sintering is an electrical field-assisted densification technique that requires passing a current through a ceramic powder compact. Pressure-assisted flash sintering of commercially available Zirconium Nitride (ZrN) powders has been demonstrated. Near fully dense samples can be obtained within a short period of time. The influences of parameters such as electrical field strength, voltage ramping rate, current limit, external pressure, pre-heating, and holding time on the onset of the flash event were investigated. Some post-flash sintered samples were subjected to the same condition to observe if the material would experience repeated flash. In addition, material properties such as density and hardness were measured and correlated with SEM and XRD. Implications of the observations on underlying flash sintering mechanism will also be discussed.

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