• Nuclear Engineering and Technology
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• 제47권5호
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• pp.617-623
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• 2015

$ZrO_2$-based composites reinforced with 6.5 vol.% of carbon foam, carbon fiber, and graphite were fabricated using spark plasma sintering, and characterized using scanning electron microscopy and X-ray diffractometry. Their thermal properties were also investigated. The microstructures of the reinforced composites showed that carbon fiber fully reacted with $ZrO_2$, whereas carbon foam and graphite did not. The carbothermal reaction of carbon fiber had a negative effect on the thermal properties of the reinforced $ZrO_2$ composites because of the formation of zirconium oxycarbide. Meanwhile, the addition of carbon foam had a positive effect, increasing the thermal conductivity from 2.86 to $3.38Wm^{-1}K^{-1}$ at $1,100^{\circ}C$. These findings suggest that the homogenous distribution and chemical stability of reinforcement material affect the thermal properties of $ZrO_2$-based composites.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.848-849
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• 2006

Bulk metallic glass (BMG) composites combining a $Cu_{54}Ni_6Zr_{22}Ti_{18}$ matrix with brass powders or $Zr_{62}A_{l8}Ni_{13}Cu_{17}$ metallic glass powders were fabricated by spark plasma sintering. The brass powders and Zr-based metallic glass powders added for the enhancement of plasticity are well distributed homogeneously in the Cu-based metallic glass matrix after consolidation. The BMG composites show macroscopic plasticity after yielding, and the plastic strain increased to around 2% without a decrease in strength for the composite material containing 20 vol% Zr-based amorphous powders. The proper combination of strength and plasticity in the BMG composites was obtained by introducing a second phase in the metallic glass matrix.

• 한국분말재료학회지
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• 제27권3호
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• pp.203-209
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• 2020

The automotive industry has focused on the development of metallic materials with high specific strength, which can meet both fuel economy and safety goals. Here, a new class of ultrafine-grained high-Mn steels containing nano-scale oxides is developed using powder metallurgy. First, high-energy mechanical milling is performed to dissolve alloying elements in Fe and reduce the grain size to the nanometer regime. Second, the ball-milled powder is consolidated using spark plasma sintering. During spark plasma sintering, nanoscale manganese oxides are generated in Fe-15Mn steels, while other nanoscale oxides (e.g., aluminum, silicon, titanium) are produced in Fe-15Mn-3Al-3Si and Fe-15Mn-3Ti steels. Finally, the phases and resulting hardness of a variety of high-Mn steels are compared. As a result, the sintered pallets exhibit superior hardness when elements with higher oxygen affinity are added; these elements attract oxygen from Mn and form nanoscale oxides that can greatly improve the strength of high-Mn steels.

• 한국분말재료학회지
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• 제11권2호
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• pp.158-164
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• 2004

W-Cu composite has been used for the applications requiring both high strength, good thermal and electrical conductivity. A graded combination of W and Cu will reduce thermal stress concerned with heat conduction, maintaining good thermal conductivity and high mechanical strength. In the present work, an attempt was made to fabricate continuous W-Cu FGM by preparing the graded porous structure of W skeleton using spark plasma sintering (SPS) process followed by infiltrating Cu. The graded porous structure was prepared at 150$0^{\circ}C$ for 60s under pressure of 15MPa by SPS process using a graphite mold with varying crr)ss section in the longitudinal direction. Infiltration of Cu was performed at 115$0^{\circ}C$ for 1 hour under $H_2$. W-Cu composite with graded Cu composition of 14 to 27 wt％ was finally prepared. In this process the gradient of composition could be conveniently controlled by varying the gradient of cross sectional area of graphite mold, temperature and pressure.

• 한국기계가공학회지
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• 제12권6호
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• pp.3-9
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• 2013

Aluminum Oxide($Al_2O_3$) ceramics are excellent candidates for such applications due to their outstanding mechanical, thermal, and tribological properties. However, they are difficult to machine using conventional mechanical methods. Carbon fillers, such as carbon nanotubes(CNT) and graphene nanoplatelets(GNP)can be dispersed in a ceramic matrix to improve the mechanical and electrical properties. In this study, CNT and Graphene reinforced hybrid ceramic composites were fabricated using the spark plasma sintering method at a temperature of $1,500^{\circ}C$, pressure of 40 MPa, and soaking time of 10min. Besides this, the material properties such as microstructure, crystal structure, hardness, and electrical conductivity were analyzed using FE-SEM, XRD, Vickers, and the 4-point probe method. A micro machining test was carried out to compare the effects of the material properties and the machining performance for CNT and Graphene reinforced ceramic composites.

• Tribology and Lubricants
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• 제24권5호
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• pp.269-274
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• 2008

Carbon nanotube composite is considered to be a good candidate material for composite material because of its excellent mechanical property and low density under high temperature as well as good wear and frictional properties. In this study, tribological characteristics of carbon nanotube aluminum composite were evaluated using pin-on-disk wear tester. Spark Plasma Sintering method is more effective than Hot Pressing method in terms of wear and friction. The composite with 1% CNT has the lowest friction and wear characteristic.

• 대한금속재료학회지
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• 제49권3호
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• pp.250-255
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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. From the results, the Cu film prepared heating $60^{\circ}C/min$ (SPS process) showed a similar specific resistance compared to the commercial cast Cu film. Also, auording to the results of XRD, SIMS, and TEM. There was not much difference in the crystal structure and impurities between the two films. Consequently, the SPS Cu target was found to have quite similar properties with the commercial one and it is expected to be applied in futare research to the metal wiring material for semiconductor/display devices.

• Archives of Metallurgy and Materials
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• 제65권3호
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• pp.1001-1004
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• 2020

We investigated the austenite stability and mechanical properties in FeMnNiC alloy fabricated by spark plasma sintering. The addition of Mn, Ni, and C, which are known austenite stabilizing elements, increases its stability to a stable phase existing above 910℃ in pure iron; as a result, austenitic microstructure can be observed at room temperature, depending on the amounts of Mn, Ni, and C added. Depending on austenite stability and the volume fraction of austenite at a given temperature, strain-induced martensite transformation during plastic deformation may occur. Both stability and the volume fraction of austenite can be controlled by several factors, including chemical composition, grain size, dislocation density, and so on. The present study investigated the effect of carbon addition on austenite stability in FeMnNi alloys containing different Mn and Ni contents. Microstructural features and mechanical properties were analyzed with regard to austenite stability.

• 한국세라믹학회지
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• 제40권6호
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• pp.553-559
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• 2003

PDP(Plasma Display Panel) rib은 고정세의 패턴 설계 및 복잡, 다양한 공정으로 제조되고 있다. Rib은 PDP제조 공정 및 역할상 매우 중요한 부분의 하나이며 rib의 소결 정도는 cross-talk와 같은 현상을 방지하는 데에 중요한 역할을 한다. 저렴하고 높은 양산성을 가진 rib은 주로 스크린 프린팅법에 의해 제작되지만, 인쇄, 소성 등 일련의 제조 공정을 거친 후 얻어진 수백 $\mu\textrm{m}$ 미세규격의 격벽 소결체의 소결도를 정확히 평가하기는 쉽지 않다. 본 연구에서는 rib의 소결도를 직접적 판단할 수 있는 방법에 대한 연구의 일환으로서 주로 소결 말기에 나타나는 기공의 응집, 성장을 potentiostat로 기공에서의 절연 파괴, 전계 집중의 원리를 이용함으로서 소결도를 측정했다 이 측정값은 각 온도에서 열처리한 시편에 대한 밀도값과 유사한 경향성이 나타남을 확인할 수 있었다 개기공, 폐기공의 분포에 따라 예상될 수 있는 측정오차는 온도에 따른 미세구조의 변화를 수차례의 전자 현미경 관찰을 통해 확인, 검증하여 미세규격 rib 소결도의 판단을 전기화학적 방법으로 예측 가능하다는 것을 알 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.314-314
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• 2010

The SiC-$ZrB_2$ composites were fabricated by combining 40vol.% of Zirconium Diboride(hereafter, $ZrB_2$) powders with Silicon Carbide(hereafter, SiC) matrix. TheSiC+40vol.%$ZrB_2$ composites were manufactured through Spark Plasma Sintering(hereafter, SPS) under argon atmosphere, uniaxial pressure of 50MPa, heating rate of $100^{\circ}C$/min, sintering temperature of $1,500^{\circ}C$ and holding time of 5min. But one on/off pulse sequence(one pulse time: 2.78ms) is 10:9(hereafter, SZ10), and the other is 48:8(hereafter, SZ48). The physical and mechanical properties of the SZ12 and SZ48 were examined. Reactions between $\beta$-SiC and $ZrB_2$ were not observed via X-Ray Diffraction(hereafter, XRD) analysis. The apparent porosity of the SZ10 and SZ48 composites were 9.7455 and 12.2766%, respectively. The SZ10 composite, 593.87MPa, had higher flexural strength than the SZ48 composite, 324.78MPa, at room temperature. The electrical properties of the SiC-$ZrB_2$ composites had Positive Temperature Coefficient Resistance(hereafter, PTCR).