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Athermal Field Effects in Spark Plasma Sintering and Flash Sintering...
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Athermal Field Effects in Spark Plasma Sintering and Flash Sintering

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (31 December 2019) | Viewed by 14479

Special Issue Editor

Dr. Salvatore Grasso

E-Mail Website
Guest Editor
Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, China
Interests: ceramics; spark plasma sintering; cold sintering; flash sintering; strong magnetic field alignment; ultra-fast high temperature sintering; solid state batteries; transparent ceramics; low energy processing

Special Issue Information

Dear Colleagues,

Electricity is a noble form of energy, which enables energy saving materials processing (sintering, joining, synthesis and forming). Since the discovery of Joule effect in 1843, researchers working on field-assisted techniques realized that by passing a current across a material it could led to “something special” not seen otherwise. That “something special” found little use for more than 150 years because of poor controls over the processing parameters. Nowadays, even if these issues have been surpassed, there is still a lot unknown about the interaction between matter and intense electric fields at high temperature (T > 0.4 Tm). The special issue invites submissions on aspects of material processing where the use of an electrical field plays a key role in the triangle properties-microstructure-processing. The focus is on athermal field effects where experiments and simulation are conceived to distinguish between field and temperature induced effects. Intrinsic fields effects include ionic and electro migration, waveform/frequency, polarity, electroluminescence/arcing, thermokinetics, electroplasticity/softening, anisotropic lattice distortion, Peltier effect, electrochemistry, in situ diagnostic (impedance spectroscopy, crystallography, etc.) and multiscale differential heating (from point defects to sample size).

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Prof. Dr. Salvatore Grasso
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Flash sintering
  • Spark Plasma Sintering
  • Electro -plasticity -softening-migration -luminescence
  • electrochemistry
  • metastability and defects

Published Papers (4 papers)

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Research

20 pages, 9057 KiB  
Article
Passive Film Properties of Bimodal Grain Size AA7075 Aluminium Alloy Prepared by Spark Plasma Sintering
by Wenming Tian, Zhonglei Li, HuiFeng Kang, Fasong Cheng, Fangfang Chen and Guoxing Pang
Materials 2020, 13(14), 3236; https://doi.org/10.3390/ma13143236 - 21 Jul 2020
Cited by 12 | Viewed by 2299
Abstract
The bimodal-grain-size 7075 aluminium alloys containing varied ratios of large and small 7075 aluminium powders were prepared by spark plasma sintering (SPS). The large powder was 100 ± 15 μm in diameter and the small one was 10 ± 5 μm in diameter. [...] Read more.
The bimodal-grain-size 7075 aluminium alloys containing varied ratios of large and small 7075 aluminium powders were prepared by spark plasma sintering (SPS). The large powder was 100 ± 15 μm in diameter and the small one was 10 ± 5 μm in diameter. The 7075 aluminium alloys was completely densified under the 500 °C sintering temperature and 60 MPa pressure. The large powders constituted coarse grain zone, and the small powders constituted fine grain zone in sintered 7075 aluminium alloys. The microstructural and microchemical difference between the large and small powders was remained in coarse and fine grain zones in bulk alloys after SPS sintering, which allowed for us to investigate the effects of microstructure and microchemistry on passive properties of oxide film formed on sintered alloys. The average diameter of intermetallic phases was 201.3 nm in coarse grain zone, while its vale was 79.8 nm in fine grain zone. The alloying element content in intermetallic phases in coarse grain zone was 33% to 48% higher than that on fine grain zone. The alloying element depletion zone surrounding intermetallic phases in coarse grain zone showed a bigger width and a more severe element depletion. The coarse grain zone in alloys showed a bigger electrochemical heterogeneity as compared to fine grain zone. The passive film formed on coarse grain zone had a thicker thickness and a point defect density of 2.4 × 1024 m−3, and the film on fine grain zone had a thinner thickness and a point defect density of 4.0 × 1023 m−3. The film resistance was 3.25 × 105 Ωcm2 on coarse grain zone, while it was 6.46 × 105 Ωcm2 on fine grain zone. The passive potential range of sintered alloys increased from 457 mV to 678 mV, while the corrosion current density decreased from 8.59 × 10−7 A/cm2 to 6.78 × 10−7 A/cm2 as fine grain zone increasing from 0% to 100%, which implied that the corrosion resistance of alloys increased with the increasing content of fine grains. The passive film on coarse grain zone exhibited bigger corrosion cavities after pitting initiation compared to that on fine grain zone. The passive film formed on fine grain zone showed a better corrosion resistance. The protectiveness of passive film was mainly determined by defect density rather than the thickness in this work. Full article
(This article belongs to the Special Issue Athermal Field Effects in Spark Plasma Sintering and Flash Sintering )
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13 pages, 5534 KiB  
Article
Densification and Phase Transformation in Multi-Layered Graded Si3N4–TiN Components Produced by Field-Assisted Sintering
by Dong-Tao Lin, Li-Juan Yuan, Peng-Jie Zhang, Fei Zuo, Kevin Plucknett, Salvatore Grasso, Hong-Jian Wang and Hua-Tay Lin
Materials 2019, 12(18), 2900; https://doi.org/10.3390/ma12182900 - 08 Sep 2019
Cited by 3 | Viewed by 2097
Abstract
The structural and/or functional design of multiphase ceramics, along with their processing, are timely research topics in the area of field-assisted sintering techniques, such as spark plasma sintering, especially for systems containing both electrically insulating and conductive phases. In the present study, spark [...] Read more.
The structural and/or functional design of multiphase ceramics, along with their processing, are timely research topics in the area of field-assisted sintering techniques, such as spark plasma sintering, especially for systems containing both electrically insulating and conductive phases. In the present study, spark plasma sintering of Si3N4–TiN composites was investigated by changing the TiN particle size and electrical current waveform. Their combined effects on both the densification behavior and α-to-β phase conversion of the Si3N4 matrix was studied and compared by means of a thermodynamic approach and dilatometric measurements. Through the control of TiN phase characteristics and heating mode, double-layered Si3N4-based components were also prepared using a one-step spark plasma sintering process, which was compared with conventional hot-pressing. It was shown that the size of the conductive TiN phase has a significant influence on the particle rearrangement, with the formation of a liquid phase, and the solution–diffusion–precipitation process, through the field-induced local heating and electrowetting mechanisms. Moreover, the contribution of current pulsing to the densification and α-to-β conversion of the layered Si3N4-based components was mostly dependent upon the particle size distribution and content of the TiN phase, indicating that the electric-field effect is dependent upon current path. Full article
(This article belongs to the Special Issue Athermal Field Effects in Spark Plasma Sintering and Flash Sintering )
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9 pages, 742 KiB  
Article
Liquid-Film Assisted Mechanism of Reactive Flash Sintering in Oxide Systems
by Rachman Chaim and Yaron Amouyal
Materials 2019, 12(9), 1494; https://doi.org/10.3390/ma12091494 - 08 May 2019
Cited by 14 | Viewed by 2129
Abstract
Reactive flash sintering in oxide systems is analyzed assuming the formation of a liquid film at the particle contacts at the flash onset temperature. Formation of intermediate phases, as well as phase assemblage, are predicted upon optimal conditions of the electric field and [...] Read more.
Reactive flash sintering in oxide systems is analyzed assuming the formation of a liquid film at the particle contacts at the flash onset temperature. Formation of intermediate phases, as well as phase assemblage, are predicted upon optimal conditions of the electric field and current density. In single-phase impure oxides, the solidus and the solubility limit determine the flash onset temperature. In reacting binary systems, the composition of the liquidus determines primarily the reaction products during the cooling. In multicomponent systems, the oxide with the lowest flash temperature forms the interfacial liquid film, and the solid phase assemblage follows the equilibrium phase diagram. Examples from literature are consistent with reactive flash sintering and flash sintering assisted by a transient liquid film. Full article
(This article belongs to the Special Issue Athermal Field Effects in Spark Plasma Sintering and Flash Sintering )
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15 pages, 4567 KiB  
Article
Investigation of Electrochemical, Optical and Thermal Effects during Flash Sintering of 8YSZ
by Mattia Biesuz, Lorenzo Pinter, Theo Saunders, Mike Reece, Jon Binner, Vincenzo M. Sglavo and Salvatore Grasso
Materials 2018, 11(7), 1214; https://doi.org/10.3390/ma11071214 - 14 Jul 2018
Cited by 153 | Viewed by 7401
Abstract
This paper reports the electrochemical, optical and thermal effects occurring during flash sintering of 8 mol % yttria-stabilized zirconia (8YSZ). In-situ observations of polycrystalline and single crystal specimens revealed electrochemical blackening/darkening during an incubation period prior to flash sintering. The phenomenon is induced [...] Read more.
This paper reports the electrochemical, optical and thermal effects occurring during flash sintering of 8 mol % yttria-stabilized zirconia (8YSZ). In-situ observations of polycrystalline and single crystal specimens revealed electrochemical blackening/darkening during an incubation period prior to flash sintering. The phenomenon is induced by cathodic partial reduction under DC fields. When using a low frequency AC field (0.1–10 Hz) the blackening is reversible, following the imposed polarity switching. Thermal imaging combined with sample colour changes and electrical conductivity mapping give a complete picture of the multi-physical phenomena occurring during each stage of the flash sintering event. The partial reduction at the cathode causes a modification of the electrical properties in the sample and the blackened regions, which are close to the cathode, are more conductive than the remainder of the sample. The asymmetrical nature of the electrochemical reactions follows the field polarity and causes an asymmetry in the temperature between the anode and cathode, with the positive electrode tending to overheat. It is also observed that the phenomena are influenced by the quality of the electrical contacts and by the atmosphere used. Full article
(This article belongs to the Special Issue Athermal Field Effects in Spark Plasma Sintering and Flash Sintering )
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