• Journal of Powder Materials
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• v.23 no.2
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• pp.120-125
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• 2016

P-type ternary $Bi_{0.5}Sb_{1.5}Te_3$ alloys are fabricated via mechanical alloying (MA) and spark plasma sintering (SPS). Different ball sizes are used in the MA process, and their effect on the microstructure; hardness, and thermoelectric properties of the p-type BiSbTe alloys are investigated. The phases of milled powders and bulks are identified using an X-ray diffraction technique. The morphology of milled powders and fracture surface of compacted samples are examined using scanning electron microscopy. The morphology, phase, and grain structures of the samples are not altered by the use of different ball sizes in the MA process. Measurements of the thermoelectric (TE) transport properties including the electrical conductivity, Seebeck coefficient, and power factor are measured at temperatures of 300-400 K for samples treated by SPS. The TE properties do not depend on the ball size used in the MA process.

• Korean Journal of Materials Research
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• v.30 no.2
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• pp.74-80
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• 2020

Synthesis of composite powders for the Fe₂O₃-Zn system by mechanical alloying (MA) has been investigated at room temperature. Optimal milling and heat treatment conditions to obtain soft magnetic composite with fine microstructure were investigated by X-ray diffraction, differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM) measurement. It is found that α-Fe/ZnO composite powders in which ZnO is dispersed in α-Fe matrix can be obtained by MA of Fe₂O₃ with Zn for 4 hours. The change in magnetization and coercivity also reflects the details of the solid-state reduction process of hematite by pure metal of Zn during MA. Densification of the MA powders was performed in a spark plasma sintering (SPS) machine at 900 ~ 1,000 ℃ under 60 MPa. Shrinkage change after SPS of sample MA'ed for 5 hrs was significant above 300 ℃ and gradually increased with increasing temperature up to 800 ℃. X-ray diffraction results show that the average grain size of α-Fe in the α-Fe/ZnO composite sintered at 900 ℃ is in the range of 110 nm.

• Journal of Powder Materials
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• v.20 no.6
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• pp.425-431
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• 2013

Microstructural and mechanical properties of Ni-YSZ fabricated using SPS processing have been investigated at various sintering temperatures. Our study shows samples to be applied as a SOFC anode have the proper porosity of 40% and high hardness when processed at $1100^{\circ}C$. These results are comparable to the values obtained at $100-200^{\circ}C$ higher sintering temperature reported by others. This result is important because when the fabrication processes are performed above $1100^{\circ}C$, the mechanical property starts to decrease drastically. This is caused by the fast grain coarsening at the higher temperature, which initiates a mismatch between thermal expansion coefficients of Ni and YSZ and induces cracks as well.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.87-87
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• 2009

The composites were fabricated by adding 30, 40, 50, 60[vol.%] Zirconium Diboride(hereafter, $ZrB_2$) powders as a second phase to Silicon Carbide(hereafter, SiC) matrix. SiC-$ZrB_2$ composites were sintered by Spark Plasma Sintering(hereafter, SPS) in argon gas atmosphere. The relative density SiC+30[vol.%]$ZrB_2$, SiC+40[vol.%]$ZrB_2$, SiC+50[vol.%]$ZrB_2$ and SiC+60[vol.%]$ZrB_2$ composites are 94.98[%], 99.57[%], 96.58[%] and 93.62[%] respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.105-105
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• 2009

The composites were fabricated by adding 30, 35, 40, 45[vol.%] Zirconium Diboride(hereafter, $ZrB_2$) powders as a second phase to Silicon Carbide(hereafter, SiC) matrix. $SiC-ZrB_2$ composites were sintered by Spark Plasma Sintering(hereafter, SPS) in vacuum or argon gas atmosphere. The relative density of SiC+40[vol.%]$ZrB_2$ composites reveal high 99.57[%] in argon gas atmosphere and pressure 50MPa.

• Journal of Powder Materials
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• v.8 no.1
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• pp.35-41
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• 2001

$BaTiO_3$ fine powder was synthesized by hydrothermal process from the mixture of titania-hydroxide($TiO_2{\cdot}xH_2O$) and barium hexa-hydroxide ($Ba(OH)_2{\cdot}8H_2O$) as starting materials. Fine powder(< 100 nm) was made under the reaction conditions of 18$0^{\circ}C$,10 atm, 1.5 hr in autoclave and showed cubic structure. The powders were sintered by a spark plasma sintering technique from 1050~115$0^{\circ}C$ for 5 min. The grains of sample sintered at 110$0^{\circ}C$ were about 0.9${\mu}m$ in average size and showed the mixture of cubic and tetragonal structures.

• Korean Journal of Materials Research
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• v.19 no.2
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• pp.55-60
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• 2009

In this study, Ti powder was fabricated from Ti scrap by a hydrogenation-dehydrogenation (HDH) method. The Ti powders were compacted by Spark plasma sintering (SPS) and the microstructure and mechanical properties of the powders were investigated. A hydrogenation reaction of Ti scrap occurred at temperatures near $450^{\circ}C$ with a sudden increase in the reaction temperature and a decrease in the pressure of the hydrogen gas as measured in a furnace during the hydrogenation process. In addition, a dehydrogenation process was carried out at $750^{\circ}C$ for 2hrs in a vacuum of $10^{-4}torr$. The Ti powder sizes obtained by hydrogenation-dehydrogenation and mechanical milling processes were in the range of $1{\sim}90{\mu}m$ and $1{\sim}100{\mu}m$, respectively. To fabricate Ti compacts, Ti powders were sintered under an applied uniaxial punch pressure of 40 MPa at in a range of $900{\sim}1200^{\circ}C$ for 5 min. The relative density of a SPSed compact was 99.6% at $1100^{\circ}C$, and the tensile strength decreased with an increase in the sintering temperature. However, the hardness increased as the sintering temperature increased.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.1
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• pp.16-20
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• 2005

In order to improve electrical conductivity and mechanical properties of 8YSZ SOFC electrolyte material, we used Al₂O₃ as an additive and applied the spark plasma sintering (SPS) method. The sintered bodies were densified above 96 ％ of theoretical density at 1200℃ and possessed microstructures composed of homogeneous grains less than 1 ㎛ in size. The addition of Al₂O₃ improved fracture toughness and bending strength by inhibiting grain growth of 8YSZ and increased total ionic conductivity because grain interior conductivity appeared to remain constant and grain boundary conductivity increased. It was assumed that the dissolution of Al₂O₃ into 8YSZ which was inevitable problem at commercial sintering method was effectively prohibited by the SPS technique with a relatively low sintering temperature and the reaction between Al₂O₃ and SiO₂ present at grain boundary to produce the crystalline Al/sub 2-x/Si/sub l-y/O/sub 5/ phase, resulting in the increase of grain boundary conductivity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.3
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• pp.115-119
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• 2001

Hydroxyapatite-yttria stabilized zirconia bioceramics containing fine zirconia particles were prepared as 3-layered functionally graded materials (FGMs) using a spark plasma sintering (SPS) and hot pressing (HP) apparatuses. The pretreatment of the raw hydroxyapatite promoted the sinterability of hydroxyapatite. The maximum density of pretreated FGM composites could be obtained at lower temperature than that for he untreated FGM samples. No decomposition from hydroxyapatite to three calcium phosphate (TCP) was observed in FGMs of HAp-$ZrO_2$ sintered below $1200^{\circ}C$ for 8 min under 10 MPa by SPS. However, the transformation of the tetragonal zirconia to the cubic modification had occurred in FGMs at this temperature. The presence of zirconia i.e. stress induced transformation of zirconia may be expected to enhance the mechanical properties of HAp-$ZrO_2$ FGM. The SPS is concluded as a better method to fabricated the FGM with dense and high strength compared with HP process.

• Korean Journal of Metals and Materials
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• v.49 no.6
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• pp.493-497
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• 2011

The basic properties and electrical characteristics of sputtering films deposited with a commercial cast target and spark plasma sintering (SPS) were compared and analyzed. The results, revealed that, the Al film prepared by heating at $60^{\circ}C/min$ (SPS process) showed a specific resistance similar to the commercial cast Al film. In addition, the results of XRD, SIMS and TEM, showed that there was not much difference in the crystal structure and impurities between the two films. Consequently, the SPS Al target was found to have properties quite similar to the commercial one and it is expected to be applied in future research to the metal wiring material for semiconductor/display devices.