• Journal of Ceramic Processing Research
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• 제19권6호
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• pp.483-491
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• 2018

Effects of additives on phase development and physico-mechanical properties of mullite-carbon was investigated. Powdered clay, kaolinite and graphite of predetermined compositions were blended with additives using ball mill for 3 hrs at 60 rev/min. Samples were produced by uniaxial compression and sintered between $1400^{\circ}C$ and $1600^{\circ}C$ for one hr. They were characterized for various properties, developed phases and microstructural features. It was observed that the properties and phase developments in the samples were influenced by the additives. 10 wt % SiC served as nucleating point for SiC around $1400^{\circ}C$. 10wt % $TiO_2$ lead to development of 2.5 wt % TiC at $1500^{\circ}C$ which increased to 6.8 wt % at $1600^{\circ}C$. Ifon clay in the sample leads to development of anorthite and microcline in the samples. 10wt % $TiO_2$ is effective as anti-oxidant for graphite up to $1500^{\circ}C$. Base on strength and absorbed energy, sample C (with 10wt % $TiO_2$) sintered at $1500^{\circ}C$ is considered to be optimum.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.15-18
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• 2001

The composites were fabricated 61 vol% $\beta$-SiC and $39vol%TiB_2$ powders with the liquid forming additives of 8, 12, 16wt% $Al_2O_3+Y_2O_3$ by hot pressing at $1730^{\circ}C$ and subsequent pressed annealing and pressureless annealing at $1750^{\circ}C$ for 4 hours to form YAG. The result of phase analysis of composites by XRD revealed $\alpha$-SiC(6H), $TiB_2$, and YAG($Al_5Y_3O_{12}$) crystal phase. The relative density of composites were increased with increasing $Al_2O_3+Y_2O_3$ contents. The fracture toughness showed the highest value of $7.77MPa{\cdot}m^{1/2}$ for composites added with 12wt% $Al_2O_3+Y_2O_3$ additives at room temperature. The electrical resistivity and the resistance temperature coefficient showed the lowest of $7.3{\times}10^{-4}{\Omega}{\cdot}cm$ and $3.8{\times}10^{-3}/^{\circ}C$, respectively, for composite added with 12wt% $Al_2O_3+Y_2O_3$ additives at room temperature. The electrical resistivity of the composites was all positive temperature coefficient resistance(PTCR) in the temperature range of $25^{\circ}C$ to $700^{\circ}C$.

• 한국세라믹학회지
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• 제37권4호
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• pp.302-307
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• 2000

The objective of this study was to investigate the sintering behavior, crystallization characteristic of glass-ceramic and optimal sintering condition on the glass/ceramic composite for fabricating substrate of LTCC. Glass/ceramic composite was made from alumina powder and glass frit, which was composed of SiO2-TiO2-RO-PbO/(R: Ba, Sr, Ca), and was sintered for 0, 30, 60minutes in the temperature range from 700$^{\circ}C$ to 1000$^{\circ}C$. Properties of frit and glass/ceramic compsoite were analyzed by DTA, XRD, SEM and Network Analyzer and so on. Main sintering mechanism was densification occurred above 730$^{\circ}C$ by viscous flow and crystallization starting about 780$^{\circ}C$ affected sintering also. So viscous flow was affected by sintering temperature, duration time, and creation of crystallization phase etc. From this study, it was possible to fabricate glass/ceramic composite by changing sintering temperature and duration time.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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• pp.72-75
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• 2000

The effect of $Al_2O_3+Y_2O_3$ additives on fracture toughness of ${\beta}-SiC-TiB_2$ composites by hot-pressed sintering were investigated, The ${\beta}-SiC-TiB_2$ ceramic composites were hot-presse sintered and annealed by adding 4, 8, 12wt% $Al_2O_3+Y_2O_3$(6 : 4wt%) powder as a liquid forming additives at low temperature($1800^{\circ}C$) for 4h. In this microstructures, the relative density is over 97% of the theoretical density and the porosity increased with increasing $Al_2O_3+Y_2O_3$ contents because of the increasing tendency of pore formation. But the fracture toughness showed the highest of $7.0MPa{\cdot}m^{1/2}$ for composites added with 12wt% $Al_2O_3+Y_2O_3$ additives at room temperature. The electrical resistivity showed the lowest of $1.59\times10^{-3}\Omega{\cdot}cm$ for composite added with 8wt% $Al_2O_3+Y_2O_3$ additives at room temperature and is all positive temperature coefficient resistance(PTCR} against temperature up to $700^{\circ}C$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.479-481
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• 2000

The effect of $Al_{2}O_{3}+Y_{2}O_{3}$ additives on fracture toughness of $\beta-SiC-TiB_2$ composites by hot-pressed sintering were investigated. The f$\beta-SiC-TiB_2$ ceramic composites were hot-presse sintered and annealed by adding 16, 20, 24wt% $Al_{2}O_{3}+Y_{2}O_{3}$(6 : 4wt%) powder as a liquid forming additives at low temperature($1800^{\circ}C$) for 4h. In this microstructures, the relative density is over 95.88% of the theoretical density and the porosity increased with increasing $Al_{2}O_{3}+Y_{2}O_{3}$ contents because of the increasing tendency of pore formation. The fracture toughness showed the highest of $5.88MPa{\cdot}m^{1/2}$ for composites added with 20wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature. The electrical resistivity showed the lowest of $5.22{\times}10^{-4}\Omega{\cdot}cm$ for composite added with 20wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature and is all positive temperature coefficient resistance (PTCR) against temperature up to $700^{\circ}C$.

• 한국안전학회지
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• 제19권4호
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• pp.25-30
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• 2004

Unidirectional fiber-metal matrix composites have superior mechanical properties along the longitudinal direction. However, the applicability of continuous fiber reinforced MMCs is somewhat limited due to their relatively poor transverse properties. Therefore, the transverse properties of MMCs are significantly influenced by the properties of the fiber/matrix interface. In this study, the interfacial stress states of transversely loaded unidirectional fiber reinforced metal matrix composites investigated by using elastic-plastic finite element analysis. Different fiber volume fractions $(5-60\%)$ were studied numerically. The interface was treated as thin layer (with different properties) with a finite thickness between the fiber and the matrix. The fiber is modeled as transversely isotropic linear-elastic, and the matrix as isotropic elastic-plastic material. The analyses were based on a two-dimensional generalized plane strain model of a cross-section of an unidirectional composite by the ANSYS finite element analysis code.

• 한국세라믹학회지
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• 제45권3호
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• pp.150-156
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• 2008

Pitch-binded activated carbon fiber(ACF)/$TiO_2$ composite photocatalysts were prepared by Carbon Tetra Chloride (CTC) solvent mixing method with different mixing ratios of anatase to ACF. The result of the textural surface properties demonstrated that there is a slight increase in the Brunauer, Emmett and Teller (BET) surface area of composites with an increase of the amount of ACF. The surfaces structure morphologies of the composites were observed using an Scanning Electron Microscope (SEM). In the XRD patterns for all ACF/$TiO_2$ composites, the diffraction peaks showed the formation of anatase crystallites. The EDX spectra showed the presence of C, O and Si with strong Ti peaks. Most of these samples were richer in carbon and major Ti metal than any other elements. From the photo-decomposition results, the excellent activity of the ACF/$TiO_2$ composites between c/$c_0$ for methylene blue and UV irradiation time could be attributed to both the effects of the photocatalysis of the supported $TiO_2$ and adsorptivity of activated carbon fiber and another carbon derived from pitch.

• 한국재료학회지
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• 제9권3호
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• pp.263-268
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• 1999

본 연구에서는 Al-기지 복합재료의 새로운 개념과 in-situ 공정의 가능성을 Al-Ti계의 연구결과들을 토대로 제시하고자 하였다. 가스아토마이제이션법에의해 $Al_3Ti$가 미세한 편상형상을 갖도록 Al-10%Ti 조성의 합금분말을 제조하고, 고온 압출 공정을통하여 25V/o $Al_3Ti/Al $ 복합재를 제조하였다. 복합재의 미세구조를 광학현미경, SEM, TEM 등을 이용하여 조사하였고, 상온과 고온에서의 기계적 특성을 인장시험을 통하여 측정하였다. 제조된 복합재료의 미세구조 및 고온 기계적 성질을 상용되고 있는 $SiC_w/2124$ 복합재료와 유사한 거동을 보여준다. 제조된 $Al_3Ti/Al$ 복합재료의 장점과 단점이 물성향상의 가능성과 더불어 제시되었다.

• 한국세라믹학회지
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• 제33권2호
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• pp.192-202
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• 1996

In Li0.4Ca0.05AlP0.5Si0.75O4.5 composition glass, glass-ceramic having a near 100% crystallinity after nucleation heat treatment of 74$0^{\circ}C$/2 h and crystallization heat treatment of 90$0^{\circ}C$/2 h and in-situ TiO2 whisker reinforced glass-ceramic after heat treatment of 105$0^{\circ}C$ for 20 h were fabricated with the addition of 4% TiO2 as a nucleating agent. With these materials a ball-on-disc type wear test was conducted in order to examine the effect of TiO2 whisker prepcipitation on ambient and high temperature wear properties of the glass-ceramic. Wear test results indicated that all specimens exhibited micro-fracture wear mechanism in ambient temperature. As temperature increased the wear rates of the materials were increased. However the in-situ TiO2 whisker reinforced glass-ceramic exhibited the lowest wear rate over the test temperature range. This resulted from the improvement of harness and fracture toughness of the material as the glass converted into the glass-ceramic followed by precipitation of TiO2 whiskers throughout the glass-ceramic matrix.

• Composites Research
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• 제16권3호
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• pp.1-8
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• 2003

금속복합재료 개발을 위한 고온가압 성형공정은 기지재료의 비탄성거동과 성형체 내부의 기공에 대한 충진 과정을 수반하며 이러한 강화공정은 압력, 온도 그리고 강화재와 모재의 상대부피분률과 같은 공정변수의 영향을 받게 된다. 특히 티타늄금속기 복합재료의 강화공정은 강화재와 모재 사이의 기계적 혹은 열적 특성 차이 및 생산환경으로 인한 다양한 형태의 손상이 발생할 수 있으며 따라서 이들을 극복하기 위한 재료특성, 작용압력, 온도, 시간조건 등과 공정에 따른 조직의 진전 등 미소역학적 연구가 수반된 최적의 고온가압강화공정의 개발이 요구되어진다. 이를 위하여 본 연구는 VHP방식을 이용한 SiC／Ti-6Al-4V 연속섬유강화 금속기 복합재료의 강화공정실험을 수행하였으며 특히 미시역학적 접근에 따른 다공성 재료의 구성방정식을 이용하여 보강재와 기지재료의 변형거동과 고온가압공정에 필요한 다양한 조건들을 실험결과와 비교 연구하였으며 유한요소해석을 통해 공정변수와 그에 따른 결과들을 고찰하였다.