• Journal of the Korean Ceramic Society
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• v.43 no.8 s.291
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• pp.469-471
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• 2006

The effects of $Cr_2O_3$ on the microstructural evolution and mechanical properties of $Al_2O_3$ polycrystalline were investigated. The microstructure of $Al_2O_3-Cr_2O_3$ composites (ruby) was carefully controlled in order to obtain dense and fine-grained ceramics, thereby improving their properties and reliability with respect to numerous applications related to semiconductor bonding technology. Ruby composites were produced by Ceramic Injection Molding (CIM) technology. Room temperature strength, hardness, Young's modulus and toughness were determined, as well as surface strengthening induced by thermal treatment and production of a fine-grained homogenous microstructure.

• Ceramist
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• v.9 no.6
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• pp.18-23
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• 2006

In this article, the present activities regarding research and development of continuous SiC fiber reinforced ceramic matrix composites (CFCC) in Japan are reviewed. The key technologies in SiC fiber composites are interphase between fiber and matrix and its oxidation resistance. To improve oxidation resistance of interphase, various kinds of technologies such as environment barrier coating, high dense matrix, unti-oxidation matrix, multi-layered intephase have been developed. It is suggested that high performance, affordable processing cost, and excellent reliability will be important factors to be in practical use of CMCs in future.

• Journal of the Korean Ceramic Society
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• v.33 no.12
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• pp.1403-1413
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• 1996

• Journal of Information Display
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• v.5 no.3
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• pp.25-29
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• 2004

Effects of additing various types of ceramic fillers to the BZB-based glass on the thermo-chemical stability, optical reflectance, and mechanical properties were investigated. The glass system demonstrated the feasibility to host various types of ceramic fillers to form micro-composites at the processing temperature suitable for PDP systems. The optical reflectance and mechanical strength of the filler-glass composites were improved as compared to the glass itself. These results demonstrate the feasibility of applying the Pb-free BZB-based glass system as a matrix for employing various types of crystalline ceramic fillers to be used as barrier rib materials in plasma display panels.

• Journal of Powder Materials
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• v.8 no.3
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• pp.186-191
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• 2001

Several fabrication processes, corresponding nanostructural features and multifunctionality as well has been investigated for oxide ceramic based nanocomposites with metal nanodispersion (i.e., ceramic/metal nanocomposites). Transition metal (Ni, Co, etc) dispersed alumina and zirconia based nanocomposites have been synthesized by reducing and hot-press sintering of ceramic and metal oxide mixtures prepared by several method. Improved fracture strength (1.1 and 1.9 GPa for $Al_2O_3/Ni$ and $ZrO_2/Ni$ nanocomposites, respectively) of these composites have been achieved according to their nanostructures. In addition, ferromagnetic characteristic has been kept. The variation of magnetization with an applied stress has found to be more sensitive as smaller as the magnetic metal dispersion is. This result thus suggests the possibility of fracture and/or stress sensing of the composites by simple magnetic measurement.

• Journal of the Korean Ceramic Society
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• v.34 no.10
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• pp.1092-1098
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• 1997

Electrical discharge machining (EDM) was attempted on a ceramic matrix composite containing non-conductive alumina as a matrix and conductive titania as a second phase, and was found successful. As the current or duty factor increased, the material removal rate (MRR) increased and the surface roughness also increased. The EDMed surface was covered with a number of craters of a circular shape having 100-200 microns of diameter. The melting and evaporation was suggested for the EDM mechanism. The bending strength decreased 44% after EDM, but the Weibull modulus increased more than twice. Combination of EDM and barre이 polishing resulted in the maintenance of the bending strength level. Temperature distribution near a spark in the sample was computer-simulated by use of finite element method, and was found to have similar shape to the one which the observed craters have.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1065-1066
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• 2006

The aging behavior of sintered Al composites with various ceramic contents was investigated. 2xxx series blended powder was used as the starting powder. Ceramic contents were 0wt.% and 5wt.%. The blended powders were compacted at 250MPa. The sintering process was performed at $620^{\circ}C$ for 60min in a $N_2$ atmosphere. Each part was solution-treated at $518^{\circ}C$ for 60min and aged at $180^{\circ}C$. The Rockwell hardness at the peak aging time increased with ceramic contents. However, the peak aging time at maximum hardness was reduced with increased ceramic contents.

• Journal of the Korean Ceramic Society
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• v.43 no.6 s.289
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• pp.338-343
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• 2006

The effects of lead-borosilicate glass frits on the sintering behavior and microwave dielectric properties of ceramic-glass composites were investigated as functions of glass composition of glass addition ($10{\sim}50vol%$), softening point (Ts) of the glass, and sintering temperature of the composites ($500{\sim}900^{\circ}C$ for 2 h). The addition of 50 vol% glass ensured successful sintering below $900^{\circ}C$. Sintering characteristics of the composites were well described in terms of Ts. PbO addition in to the glass enhanced the reaction with $Al_{2}O_3$ to form liquid phase and $PbAl_{2}Si_{2}O_8$, which was responsible to lower Ts. Dielectric constant(${\epsilon}_r$), $Q{\times}f_0$ and temperature coefficient of resonant frequency (${\tau}_f$) of the composite with 50 vol% glass contents ($B_{2}O_{3}:PbO:SiO_{2}:CaO:Al_{2}O_3$ = 5:40:45:5:5) demonstrated 8.5, 6,000 GHz, $-70\;ppm/^{\circ}C$, respectively, which is applicable to substrate requiring a low dielectric constant. When the same glass composition was applied sinter $MgTiO_3\;and\;TiO_2,\;at\;900^{\circ}C$ (50 vol% glass in total), the properties were 23.8, 4,000 GHz, $-65ppm/^{\circ}C$ and 31.1, 2,500 GHz, $+80ppm/^{\circ}C$ respectively, which is applicable to filter requiring an intermidiate dielectric constant.

• Journal of the Korean Magnetics Society
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• v.22 no.6
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• pp.216-220
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• 2012

Magnetic properties of composite materials consisting of polymer filled with ferromagnetic powders (MnZn ferrite, Fe-Si alloy) were investigated in this study. The volume fraction of magnetic powders as fillers was varied from 70 % to 95 %. This paper presents the fabrication method of polymer magnetic composites in an effort to produce the 0-3 types of MnZn ferrite and FeSi as fillers with a proper complex permeability through the optimization of some experimental parameters. The polymer matrix composites were prepared by mixing the crushed ferrites and flaky FeSi powders homogenously with low-density resins (EPDM, epoxy). The relationships among the manufacturing technology of these materials, their filler volume fraction, as well as their complex permeability were measured and analyzed.

• Journal of the Korean Ceramic Society
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• v.49 no.3
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• pp.272-278
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• 2012

Effects of ceramics on the microwave dielectric properties of polytetrafluoroethylene (PTFE) composites filled with $MgTiO_3$ (MTi) and/or $MgTa_2O_6$ (MTa) were investigated. The dielectric constant ($K$), quality factor ($Qf$), and temperature coefficient of resonant frequency ($TCF$) of the composites were dependent on the type and volume fraction ($V_f$) of the ceramics. For the composites mixed with MTa and MTi, the $K$ and $TCF$ values decreased with increasing MTi content. The $Qf$ values of the composites were affected by relative density. The measured $K$ values of the composites were compared with those predicted by several theoretical models. Good microwave dielectric properties with values of $K$=3.6, $Qf$ = 7,788 GHz, and $TCF$ = -0.19 ppm/$^{\circ}C$ were obtained for the composites with 0.1 $V_f$ ceramics (mixed 0.025MTa and 0.075MTi).