• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.327-328
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• 2006

We have demonstrated that textured $Al_2O_3-mullite-SiC$ nanocomposites can be fabricated by slip casting followed by partial oxidation - reaction sintering of mixed suspensions of $Al_2O_3$ and SiC powders in a high magnetic field. The sintered density was changed by the degree of oxidation at 1200C and 1300C. The degree of orientation of alumina in the nanocomposite was examined on the basis of the X-ray diffraction patterns and scanning electron micrographs. It is confirmed that alumina-oriented nanocomposites were fabricated. The three-point bending strength at room temperature was observed for the nanocomposites.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.455-456
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• 2006

We have demonstrated that textured $Al_2O_3-mullite-SiC$ nanocomposites can be fabricated by slip casting followed by partial oxidation. reaction sintering of mixed suspensions of $Al_2O_3$ and SiC powders in a high magnetic field. The sintered density was changed by the degree of oxidation at 1200C and 1300C. The degree of orientation of alumina in the nanocomposite was examined on the basis of the X-ray diffraction patterns and scanning electron micrographs. It is confirmed that aluminaoriented nanocomposites were fabricated. The three-point bending strength at room temperature was observed for the nanocomposites.

• Journal of Powder Materials
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• 제23권5호
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• pp.397-401
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• 2016

A lean alloy is defined as a low alloy steel with a minimum amount of the alloying element that maintains the characteristics of the sintered alloy. It is well known that the addition of elements such as Cr, P, Si, or Mn improves the mechanical characteristics of the alloy, but decreases the sinterability. The mother alloy is used to avoid an oxidation reaction with the alloying elements of Cr, P, Si or Mn. The purpose of this study is to determine the change in the mechanical properties of Fe-P-Mo and Fe-P-Mn alloys as a result of the addition of Si. In this article, the Fe-P-Mo and Fe-P-Mn alloys to which Si is added are compacted at $7.0g/cm^3$ and then sintered in $H_2-N_2$ at $1120^{\circ}C$. The P around the macropores and large grains reduces due to the formation of $SiO_2$ as the Si content increases. This is caused by the increase in strength owing to reducing intergranular fracture by suppressing the reaction with oxygen.

• Journal of Powder Materials
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• 제28권1호
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• pp.51-58
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• 2021

The conversion of carbon preforms to dense SiC by liquid infiltration is a prospectively low-cost and reliable method of forming SiC-Si composites with complex shapes and high densities. Si powder was coated on top of a 2.0wt.% Y2O3-added carbon preform, and reaction bonded silicon carbide (RBSC) was prepared by infiltrating molten Si at 1,450℃ for 1-8 h. Reactive sintering of the Y2O3-free carbon preform caused Si to be pushed to one side, thereby forming cracking defects. However, when prepared from the Y2O3-added carbon preform, a SiC-Si composite in which Si is homogeneously distributed in the SiC matrix without cracking can be produced. Using the Si + C → SiC reaction at 1,450℃, 3C and 6H SiC phases, crystalline Si, and Y2O3 were generated based on XRD analysis, without the appearance of graphite. The RBSC prepared from the Y2O3-added carbon preform was densified by increasing the density and decreasing the porosity as the holding time increased at 1,450℃. Dense RBSC, which was reaction sintered at 1,450℃ for 4 h from the 2.0wt.% Y2O3-added carbon preform, had an apparent porosity of 0.11% and a relative density of 96.8%.

• Journal of Mechanical Science and Technology
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• 제14권8호
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• pp.830-835
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• 2000

The thermodynamical estimation of the interfacial reaction and the impact properties of $Nb/MoSi_2$ laminate composites containing SiC, $NbSi_2$ or $ZrO_2$ particles are investigated. Laminate composites, which comprise alternating layers of $MoSi_2$ with the particle and Nb foil, were fabricated by the hot press process. It is clearly found out that the interfacial reaction of $Nb/MoSi_2$ can be controlled by the addition of $ZrO_2$ particle to the $MoSi_2$ phase. The addition of $ZrO_2$ particle increases both the impact value and the sintered density of Nb/McSij, The suppression of the interfacial reaction is caused by the formation of $ZrSiO_2$ in $MoSi_2-ZrO_2$ matrix mixture.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제5권3호
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• pp.291-298
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• 1995

Abstract The growth and dissolution behaviour of reaction phase was studied during dissolution reaction between sintered alumina and $CaMgSiO_4$ at $1600^{\circ}C$ for various times. The formation of $CaO{\cdot}6Al_2O_3$ an intermediate reaction phase, and $CaMgSiO_4$ spinel, the final reaction product were observed during dissolution reaction of alumina into $CaMgSiO_4$ liquid phase. The growth and dissolution shape of $CaO{\cdot}6Al_2O_3$, an intermediate phase, was quite different.

• Composites Research
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• 제13권5호
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• pp.31-36
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• 2000

The effect of several important processing variables was investigated on formation of porous mullite with acicular microstructure. Experimental results demonstrated that microstructure and porosity of porous mullite are depending on concentration of $AlF_3$, holding time at $900^{\circ}C$ and starting material. Acicular mullite was developed by increasing amount of $AlF_3$ and holding time at $900^{\circ}C$. Mullite began to be formed at $1200^{\circ}C$ and the resultant microstructure sintered at this temperature is similar to those at higher temperatures. Porosity increases with increase in amounts of $AlF_3$ and holding time at $900^{\circ}C$ . Therefore, it is found that microstructure of reaction-sintered porous mullite can be controlled by governing the amount of $AlF_3$ and holding time at $900^{\circ}C$.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제57권11호
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• pp.2015-2022
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• 2008

The effect of content of $Al_2O_3+Y_2O_3$ sintering additives on the densification behavior, mechanical and electrical properties of the pressureless-sintered $SiC-ZrB_2$ electroconductive ceramic composites was investigated. The $SiC-ZrB_2$ electroconductive ceramic composites were pressurless-sintered for 2 hours at 1,700[$^{\circ}C$] temperatures with an addition of $Al_2O_3+Y_2O_3$(6 : 4 mixture of $Al_2O_3$ and $Y_2O_3$) as a sintering aid in the range of $8\;{\sim}\;20$[wt%]. Phase analysis of $SiC-ZrB_2$ composites by XRD revealed mostly of $\alpha$-SiC(6H), $ZrB_2$ and In Situ YAG($Al_5Y_3O_{12}$). The relative density, flexural strength, Young's modulus and vicker's hardness showed the highest value of 89.02[%], 81.58[MPa], 31.44[GPa] and 1.34[GPa] for $SiC-ZrB_2$ composites added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at room temperature respectively. Abnormal grain growth takes place during phase transformation from $\beta$-SiC into $\alpha$-SiC was correlated with In Situ YAG phase by reaction between $Al_2O_3$ and $Y_2O_3$ additive during sintering. The electrical resistivity showed the lowest value of $3.l4{\times}10^{-2}{\Omega}{\cdot}cm$ for $SiC-ZrB_2$ composite added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at 700[$^{\circ}C$]. The electrical resistivity of the $SiC-TiB_2$ and $SiC-ZrB_2$ composite was all negative temperature coefficient resistance (NTCR) in the temperature ranges from room temperature to 700[$^{\circ}C$]. Compositional design and optimization of processing parameters are key factors for controlling and improving the properties of SiC-based electroconductive ceramic composites.

• Journal of Powder Materials
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• 제20권5호
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• pp.366-370
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• 2013

The effects of $B_4C$ on the mechanical properties of WC/Ni-Si hardmetal were analyzed using sintered bodies comprising WC(70-x wt.%), Ni (28.5 wt.%), Si (1.5 wt.%), and $B_4C$ (x wt.%), where $$0{\leq_-}x{\leq_-}1.2$$ wt.%. Samples were prepared by a combination of mechanical milling and liquid-phase sintering. Phase and microstructure characterizations were conducted using X-ray diffractometry, scanning electron microscopy, and electron probe X-ray micro analysis. The mechanical properties of the sintered bodies were evaluated by measuring their hardness and transverse rupture strength. The addition of $B_4C$ improved the sinterability of the hardmetals. With increasing $B_4C$ content, their hardness increased, but their transverse rupture strength decreased. The changes of sinterability and mechanical properties were attributed to the alloying reaction between $B_4C$ and the binder metal (Ni, Si).

• Composites Research
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• 제25권6호
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• pp.172-177
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• 2012

For the manufacture of low resistance Si-SiC composite, the properties of reaction sintering in the green body of various mixed ${\alpha}$-SiC powder size with the various carbon contents from 0wt% to 20wt% were investigated. The samples preparation was green body by CIP method under this condition, molten silicon infiltration process was conducted to reaction bonded silicon carbide. the results of sintered density, 3-point bending strength and resistance of analysis showed that varied carbon and silicon melt reacted to convert to fine ${\beta}$-SiC particle and the structure was changed to dense material. The amount of fine ${\beta}$-SiC particle was gradually increased as carbon content increase. According to mixed composite, it's mechanical and specific resistivity properties was strongly influenced by carbon content within 10wt% more then carbon content 10wt% was strongly influenced by phase transition.