• 한국세라믹학회지
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• 제40권8호
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• pp.751-757
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• 2003

10 wt% A1$_2$O$_3$-Y$_2$O$_3$-CaO를 첨가한 SiC-30 wt% TiC 분말을 스파크 플라즈마 소결(SPS) 방법을 사용하여 급속 치밀화 하였다. SPS 공정은 매우 빠른 승온 속도와 짧은 시간에 완전 치밀한 시편을 얻을 수 있다. 본 실험에서, 승온 속도와 압력은 $100^{\circ}C$/min과 40MPa이고, 소결 온도 범위는$1600^{\circ}C$~$1800^{\circ}C$이었으며, 10min 동한 유지하였다. $Al_2$O$_3$, $Y_2$O$_3$ 및 CaO를 첨가한 SiC-30 wt% TiC 복합체는 $1700^{\circ}C$ 이상 온도에서 스파크 플라즈마 소결 방법으로 완전 치밀화가 이루어졌다. 모든 SPS 공정 온도에서 탄화큐소으 상전이나 YAG 결정상의 형성 없이 3C-SiC와 TiC 만이 XRD에서 나타났다. 급속 소결한 SiC-30 wt% TiC 복합체의 미세구조는 비교적 작은 등축상 SiC 결정립과 비교적 큰 TiC 결정립으로 구성되었다. $1750^{\circ}C$에서 제조한 시편의 이축강도능 635.2MPa이고, 파괴인성은 6.12 MPaㆍ$m^{1/2}$이었다.

• 한국분말재료학회지
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• 제12권6호
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• pp.422-427
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• 2005

The $Al_2O_3$ with various phases were prepared by simple ex-situ hydrolysis and spark plasma sintering (SPS) process of Al powder. The nano bayerite $(\beta-Al(OH)_3)$ phase was derived by hydrolysis of commercial powder of Al with micrometer size, whereas the bohemite (AlO(OH)) phase was obtained by hydrolysis of nano Al powder synthesized by pulsed wire evaporation (PWE) method. Compaction as well as dehydration of both nano bayerite and bohemite was carried out simultaneously by SPS method, which is used to fabricate dense powder compacts with a rapid heating rate of $100^{\circ}C$ per min. under the pressure of 50MPa. After compaction treatment in the temperature ranges from $100^{\circ}C\;to\; 1100^{\circ}C$, the bayerite and bohemite phases change into various alumina phases depending on the compaction temperatures. The bayerite shows phase transition of $Al(OH)_3{\to}{\eta}-Al_2O_3{\to}{\theta}-Al_2O_3{\to}\alpha-Al_2O_3$ sequences. On the other hand, the bohemite experiences the phase transition from AlO(OH) to ${\gamma}-Al_2O_3\;at\;350^{\circ}C.$ It shows AlO(OH) ${\gamma}-Al_2O_3{\to}{\delta}-Al_2O_3{\to}{\alpha}-Al_2O_3$ sequences. The ${\gamma}-Al_2O_3$ compacted at $550^{\circ}C$ shows a high surface area $(138m^2/g)$.

• 한국분말재료학회지
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• 제26권4호
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• pp.299-304
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• 2019

Nb-Si-B alloys with Nb-rich compositions are fabricated by spark plasma sintering for high-temperature structural applications. Three compositions are selected: 75 at% Nb (Nb0.7), 82 at% Nb (Nb1.5), and 88 at% Nb (Nb3), the atomic ratio of Si to B being 2. The microstructures of the prepared alloys are composed of Nb and $T_2$ phases. The $T_2$ phase is an intermetallic compound with a stoichiometry of $Nb_5Si_{3-x}B_x$ ($0{\leq}x{\leq}2$). In some previous studies, Nb-Si-B alloys have been prepared by spark plasma sintering (SPS) using Nb and $T_2$ powders (SPS 1). In the present work, the same alloys are prepared by the SPS process (SPS 2) using Nb powders and hypereutectic alloy powders with composition 67at%Nb-22at%Si-11at%B (Nb67). The Nb67 alloy powders comprise $T_2$ and eutectic ($T_2+Nb$) phases. The microstructures and hardness of the samples prepared in the present work have been compared with those previously reported; the samples prepared in this study exhibit finer and more uniform microstructures and higher hardness.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2582-2590
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• 2021

The high-energy milling is one of the most extended techniques to produce Oxide dispersion strengthened (ODS) powder steels for nuclear applications. The consequences of the high energy mill process on the final powders can be measured by means of deformation level, size, morphology and alloying degree. In this work, an ODS ferritic steel, Fe-14Cr-5Al-3W-0.4Ti-0.25Y₂O₃-0.6Zr, was fabricated using two different mechanical alloying (MA) conditions (M_std and M_act) and subsequently consolidated by Spark Plasma Sintering (SPS). Milling conditions were set to evidence the effectivity of milling by changing the revolutions per minute (rpm) and dwell milling time. Differences on the particle size distribution as well as on the stored plastic deformation were observed, determining the consolidation ability of the material and the achieved microstructure. Since recrystallization depends on the plastic deformation degree, the composition of each particle and the promoted oxide dispersion, a dual grain size distribution was attained after SPS consolidation. M_act showed the highest areas of ultrafine regions when the material is consolidated at 1100 ℃. Microhardness and small punch tests were used to evaluate the material under room temperature and up to 500 ℃. The produced materials have attained remarkable mechanical properties under high temperature conditions.

• 한국재료학회지
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• 제17권2호
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• pp.107-114
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• 2007

Porous Ti compacts were fabricated by spark plasma sintering (SPS) method and their in vitro and in vivo biocompatibilities were investigated. Alkaline phosphatase (ALP) activity representing the activity of osteoblast was increased when osteoblast-like MG-63 cells were cultured on the Ti powder surface. Some genes related to cell growth were over-expressed through microarray analysis. The porous Ti compact with 32.2% of porosity was implanted in the subcutaneous tissue of rats to confirm in vivo cytotoxicity. 12 weeks post-operation, outer surface and inside the porous body was fully filled with fibrous tissue and the formation of new blood vessels were observed. No inflammatory response was confirmed. To investigate the osteoinduction, porous Ti compact was implanted in the femur of NZW rabbits for 4 months. Active in-growth of new bone from the surrounded compact bone was observed around the porous body. From the results, The porous Ti compacts fabricated by spark plasma sintering might be available for the application of the stem part of artificial hip joint.

• 한국분말재료학회지
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• 제22권6호
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• pp.426-431
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• 2015

Microstructural examination of the Nb-Si-B alloys at Nb-rich compositions is performed. The Nb-rich corner of the Nb-Si-B system is favorable in that the constituent phases are Nb (ductile and tough phase with high melting temperature) and $T_2$ phase (very hard intermetallic compound with favorable oxidation resistance) which are good combination for high temperature structural materials. The samples containing compositions near Nb-rich corner of the Nb-Si-B ternary system are prepared by spark plasma sintering (SPS) process using $T_2$ and Nb powders. $T_2$ bulk phase is made in arc furnace by melting the Nb slug and the Si-B powder compact. The $T_2$ bulk phase was subsequently ball-milled to powders. SPS is performed at $1300^{\circ}C$ and $1400^{\circ}C$, depending on the composition, under 30 MPa for 600s, to produce disc-shaped specimen with 15 mm in diameter and 3 mm high. Hardness tests (Rockwell A-scale and micro Vickers) are carried out to estimate the mechanical property.

• 전기학회논문지
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• 제60권11호
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• pp.2083-2087
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• 2011

The SiC-$ZrB_2$ composites were produced by subjecting a 40:60 vol.% mixture of zirconium diboride($ZrB_2$) powder and ${\beta}$-silicon carbide (SiC) matrix to spark plasma sintering(SPS). Sintering was carried out for 60sec at $1400^{\circ}C$ (designation as TP145 and TP146), $1500^{\circ}C$(designation as TP155 and TP156) and uniaxial pressure 50MPa, 60MP under argon atmosphere. The physical, electrical, and mechanical properties of the SiC-$ZrB_2$ composites were examined. The relative density of TP145, TP146, TP155 and TP156 were 94.75%, 94.13%, 97.88% and 95.80%, respectively. Reactions between ${\beeta}$-SiC and $ZrB_2$ were not observed via x-ray diffraction (hereafter, XRD) analysis. The flexural strength, 306.23MPa of TP156 was higher than that, 279.42MPa of TP146 at room temperature, but lower than that, 392.30MPa of TP155. The properties of a SiC-$ZrB_2$ composites through SPS under argon atmosphere were positive temperature coefficient resistance (hereafter, PTCR) in the range from $25^{\circ}C$ to $500^{\circ}C$. The electrical resistivities of TP145, TP146, TP155 and TP156 were $6.75{\times}10^{-4}$, $7.22{\times}10^{-4}$, $6.17{\times}10^{-4}$ and $6.71{\times}10^{-4}{\Omega}{\cdot}cm$ at $25^{\circ}C$, respectively. The densification of a SiC-$ZrB_2$ composite through hot pressing depend on the sintering temperature and pressure. However, it is convinced that the densification of a SiC-$ZrB_2$ composite do not depend on sintering pressure under SPS.

• 한국재료학회지
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• 제33권6호
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• pp.242-250
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• 2023

Titanium, which has excellent strength and toughness characteristics, is increasingly used in the aerospace field. Among the titanium alloys used for body parts, more than 80 % are Ti-6Al-4V alloys with a tensile strength of 931 MPa. The spark plasma sintering (SPS) method is used for solidification molding of powder manufactured by the mechanical milling (MM) method, by sintering at low temperature for a short time. This sintering method avoids coarsening of the fine crystal grains or dispersed particles of the MM powder. To improve the mechanical properties of pure titanium without adding alloying elements, stearic acid was added to pure titanium powder as a process control agent (PCA), and MM treatment was performed. The properties of the MM powder and SPS material produced by solidifying the powder were investigated by hardness measurement, X-ray diffraction, density measurement and structure observation. The processing deformation of the pure titanium powder depends on the amount of stearic acid added and the MM treatment time. TiN was also generated in powder treated by MM 8 h with 0.50 g of added stearic acid, and the hardness of the powder was higher than that of Ti-6Al-4V alloy when treated with MM for 8 h. When the MM-treated powder was solidified in the SPS equipment, TiC was formed by the solid phase reaction. The SPS material prepared as a powder treated with MM 8 h by adding 0.50 g of stearic acid also formed TiN and exhibited the highest hardness of Hv1253.

• 한국분말재료학회지
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• 제14권6호
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• pp.399-404
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• 2007

The Cu-based bulk metallic glass (BMG) composite was fabricated by spark plasma sintering (SPS) using of gas-atomized metallic glass powders and ductile brass powders. No defect such as pores and cavities was observed at the interface between the brass powder and the metallic glass matrix, suggesting that the SPS process caused a severe viscous flow of the metallic glass and brass phases in the supercooled liquid region, resulting in a full densification. The BMG composites shows some macroscopic plasticity after yielding, although the levels of strength decreased.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.725-726
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• 2006

Ultra-fine grained and dispersion-strengthened titanium materials (Ti-Si, Ti-C, Ti-Si-C) have been produced by high energy ball milling and spark plasma sintering (SPS). Silicon or/and carbon were milled together with the titanium powder to form nanometer-sized and homogeneously distributed titanium silicides or/and carbides as dispersoids, that should prevent grain coarsening during the SPS compaction and contribute to strengthening of the material. The microstructures and the mechanical properties showed that strength, hardness and wear resistance of the sintered materials have been significantly improved by the mechanisms of grain refinement and dispersion strengthening. The use of an organic fluid as carrier of the dispersoid forming elements caused a significant increase in ductility.