• Journal of Powder Materials
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• v.27 no.4
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• pp.293-299
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• 2020

W₂C is synthesized through a reaction-sintering process from an ultrafine-W and WC powder mixture using spark plasma sintering (SPS). The effect of various parameters, such as W:WC molar ratio, sintering temperature, and sintering time, on the synthesis behavior of W₂C is investigated through X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) analysis of the microstructure, and final sintered density. Further, the etching properties of a W₂C specimen are analyzed. A W₂C sintered specimen with a particle size of 2.0 ㎛ and a relative density over 98% could be obtained from a W-WC powder mixture with 55 mol%, after SPS at 1700℃ for 20 min under a pressure of 50 MPa. The sample etching rate is similar to that of SiC. Based on X-ray photoelectron spectroscopy (XPS) analysis, it is confirmed that fluorocarbon-based layers such as C-F and C-F2 with lower etch rates are also formed.

• Journal of Ceramic Processing Research
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• v.22 no.1
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• pp.86-90
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• 2021

Fabrication of infrared (IR) transparent ZnS ceramics by spark plasma sintering (SPS) suffers from carbon contamination due to the graphite mold in the SPS system. In the present work, we consolidated transparent ZnS ceramics by SPS using Mo metal foil to prevent the generation of carbonate and/or carbon impurities in the sintered product. The effect of Mo foil on carbon contamination and IR transmittance was investigated. The Fourier transform infrared spectroscopy (FTIR) results revealed that the C-O absorption peak was significantly reduced, however, sulfur vacancies were generated, thus, deteriorating the overall transmittance. The sulfur vacancies were eliminated by post-annealing the specimen in a nitrogen atmosphere, whereby the overall IR transmittance was partially recovered. The results indicate that metal foil wrapping of green bodies could be potentially applicable for the fabrication of carbon contamination-free ZnS ceramics via SPS system.

• Journal of Powder Materials
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• v.10 no.3
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• pp.176-180
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• 2003

Pure WC powders which does not include a binder phase were consolidated by spark plasma sintering (SPS) process at 1600~185$0^{\circ}C$ for 0~30 min under 50 MPa. Microstructure alid mechanical properties of binderless WC prepared by SPS were investigated. With increasing sintering temperature, sintered density and Vickers hardness of binderless WC increased. The fracture toughness of binderless WC was 7~15 MPa $m^{1/2}$ depending on the sintered density and decreased with increasing the Vickers hardness. It is found that the binderless WC prepared by SPS at 175$0^{\circ}C$ for 10 min under 50 MPa showed nearly full densification with fine-grained structure and revealed excellent mechanical properties of high hardness (~HV 2400) and considerably high fracture toughness (~7 MPa $m^{1/2}$).

• Journal of Powder Materials
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• v.15 no.5
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• pp.405-410
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• 2008

SOFC (Solid Oxide Fuel Cell) Ni-YSZ anode was fabricated by the spark plasma sintering (SPS) process and its microstructure and electrical properties were investigated in this study. The spark plasma sintering process was carried out at $800{\sim}1000^{\circ}C$ for holding time of 5 min under 40 MPa. To fabricate Ni-YSZ anode, the SPS processed specimens were reduced at $800^{\circ}C$ under $H_2$ atmosphere. The reduced specimens showed relative density of $48.4{\sim}64.8%$ according to sintering temperature. And also, the electrical conductivity of reduced specimens after sintering at 900 and $1000^{\circ}C$ showed $480{\sim}600$ (S/cm) values at the measuring range of $600{\sim}900^{\circ}C$.

• Korean Journal of Metals and Materials
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• v.49 no.9
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• pp.678-685
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• 2011

The aim of this study was to determine the effect of applied pressure and sintering temperature on the microstructure and mechanical properties for spark plasma sintering (SPS) from commercial pure titanium (CP-Ti) powders. Spark plasma sintering is a relatively new sintering technique in powder metallurgy which is capable of sintering metal and ceramic powers quickly to full density at a fairly low temperature due to its unique features. SPS of -200 mesh or -400 mesh CP-Ti powders was carried out in an $Ar+H_2$ mixed gas flowing atmosphere between $650^{\circ}C$ and $750^{\circ}C$ under 10 to 80 MPa pressure. When SPS was carried out at relatively low temperatures ($650^{\circ}C$ to $750^{\circ}C$), the high (>60 MPa) pressure had a marked effect on densification and grain growth suppression. The full density of titanium was achieved at temperatures and pressures above $700^{\circ}C$ and 60 MPa by spark plasma sintering. The crystalline phase and microstructure of titanium sintered up to $700^{\circ}C$ consisted of ${\alpha}$-Ti and equiaxed grains. Vickers hardness ranging from 293 to 362 Hv and strength ranging from 304 to 410 MPa were achieved for spark plasma sintered titanium.

• Archives of Metallurgy and Materials
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• v.63 no.3
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• pp.1477-1480
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• 2018

The mechanical behavior and the change of retained austenite of nanocrystalline Fe-Ni alloy have been investigated by considering the effect of various Ni addition amount. The nanocrystalline Fe-Ni alloy samples were rapidly fabricated by spark plasma sintering (SPS). The SPS is a well-known effective sintering process with an extremely short densification time not only to reach a theoretical density value but also to prevent a grain growth, which could result in a nanocrystalline structures. The effect of Ni addition on the compressive stress-strain behavior was analyzed. The variation of the volume fraction of retained austenite due to deformation was quantitatively measured by means of x-ray diffraction and microscope analyses. The strain-induced martensite transformation was observed in Fe-Ni alloy. The different amount of Ni influenced the rate of the strain-induced martensite transformation kinetics and resulted in the change of the work hardening during the compressive deformation.

• Korean Journal of Metals and Materials
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• v.50 no.6
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• pp.469-475
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• 2012

A high-energy mechanical milling (HEMM) process was introduced to improve sinter-ability, and rapid sintering of spark plasma sintering (SPS) under pressure was used to make ultra fine grain (UFG) of Ti-Nb-Mo-CPP composites, which have bio-attractive elements, for increasing mechanical properties. Ti-Nb-Mo-CPP composites were successfully fabricated by SPS at $1000^{\circ}C$ within 5 minutes under 70 MPa using HEMMed powders. The Vickers hardness of the composites increased with increased milling time and addition of CPP contents. Biocompatibility and corrosion resistance of the Ti-Nb-Mo alloys were improved by addition of CPP, and the Ti-35%Nb-10%Mo-10%CPP alloy had better biocompatibility and corrosion resistance than the Ti-6Al-4V ELI alloy.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.383-387
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• 2018

Highly transparent $Y_2O_3$ ceramics were produced using spark plasma sintering (SPS) at $1600^{\circ}C$ and 30 MPa for 5 min. When the SPS process was applied with various amounts of $La_2O_3$ as dopant. The specimen doped with 3 mol% $La_2O_3$ showed the highest density, and rapid particle growth and pore growth occurred, exhibiting that the relative density and average grain size are 99.2% and $17.2{\mu}m$, respectively. The specimen showed excellent transmittance of 79.44% in the visible light region (600 nm), resulting that $La_2O_3$ would be a useful dopant for improving the transmittance and mechanical properties of transparent $Y_2O_3$ ceramics produced with SPS.

• Journal of Powder Materials
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• v.12 no.5 s.52
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• pp.351-356
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• 2005

Nanoscale Al powder with thin layer of alumina was produced by Wire Electric Explosion (WEE) process. Spark-Plasma Sintering (SPS) was performed for the produced powder to confirm the effectiveness of SPS like so-called 'surface-cleaning effect' and so on. Crystallite size and alumina content of produced powder varied with the ratio of input energy to sublimation energy of Al wire ($e/e_s$): Increase in ($e/e_s$) resulted in the decrease of crystallite size and the increase of alumina content. Shrinkage curve during SPS process showed that the oxide surface layer could not be destroyed near the melting point of Al. It implied that there was not enough or no spark-plasma effect during SPS for Al/Alumina powder.

• Journal of Powder Materials
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• v.12 no.1
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• pp.70-78
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• 2005

Mechanical alloying using high-energy ball mill and subsequent spark plasma sintering (SPS) process was applied to understand mechanical alloying processing of Al-Fe alloy system. The thermal stability of mechanically alloyed Al-Fe alloy was intended to be enhanced by SPS process. Various analytical techniques including particle size analysis, density measurement, micro-Vickers hardness test, SEM, TEM, and X-ray diffractometry were adopted to find optimum processing conditions for mechanical alloying and subsequent SPS and to estimate thermal stability of the prepared alloy. It was found from the treatment of mechanically alloyed Al-8wt.%Fe powder mixture that needle-shaped $Al_3Fe$ precipitates was formed in the Al-Fe matrix, and the alloy compact showed enhanced densification and reached its full density with little loss of its fine microstructure. After heat treatment at $500^{\circC}$, it was also shown that the thermal stability of Al-8wt.%Fe alloy fabricated in the present study was enhanced, which was due to its fine microstructure developed by fast densification of SPS.