• Journal of the Korean Vacuum Society
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• v.7 no.2
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• pp.141-149
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• 1998

The W thin films were deposited on Si3N4 by a PECVD technique. The effects of substrate temperature and gas flow ratio on the properties of the W films were investigated. The deposition of W films were limited by surface reaction at the temperature range of 150>~$250^{\circ}C$, W films had the deposition rate of 150~530 $\AA$/min and stress of 0.85~$14.35\times10 ^9 \textrm {dynes/cm}^2}$ at various substrate temperatures and $SiH_4/WF_6$ flow ratios. $SiH_4/WF_6$ flow ratio affected the deposition rate and stress of the W films, expecially, excessive flow of SiH4 abruptly changed the structure, chemical bonding, and stress of the W films. Among the deposited W films on TiN, Ti, Mo, NiCr and Al adhesion layer, the one on the Al had the best adhesion property.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1538-1540
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• 2003

The composites were fabricated respectively 61vol.% ${\beta}$-SiC and 39vol.% $TiB_2$ spray-dried powders with the liquid forming additives of 12wt% $Al_2O_3+Y_2O_3$ by pressureless annealing at $1700^{\circ}C,\;1750^{\circ}C\;1800^{\circ}C$ for 4 hours. 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, the Young's modulus and fracture toughness showed respectively the highest value of 92.97%, 92.88Gpa and $4.4Mpa{\cdot}m^{1/2}$ for composites by pressureless annealing temperature $1700^{\circ}C$ at room temperature. The electrical resistivity showed the lowest value of $8.09{\times}10^{-3}{\Omega}{\cdot}cm$ for composite by pressureless annealing tempe rature $1700^{\circ}C$ at $25^{\circ}C$. The electrical resistivity of the SiC-$TiB_2$ composites was all positive temperature cofficient resistance (PTCR) in the temperature ranges from $25^{\circ}C$ to $700^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.26 no.3
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• pp.409-415
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• 1989

Si3N4-TiN electro-conductive ceramic composites with 7wt% Al2O3＋3wt% Y2O3 or 5wt% MgO as sintering aids were fabricated by pressureless sintering at 1,80$0^{\circ}C$ for 1h. The 3pt. flexural strength, KIC and Vickers hardness were measrued in order to investigate the effects of TiN on the mechanical properties. Also oxidation behavior was observed by measuring the weight gain after exposure to air at 1,10$0^{\circ}C$ for 100h. the reaction products between Si3N4 and TiN was not detected by XRD and EDS. Mechanical properties of the composites were not influenced by the addition of TiN less than 30vol%, but oxidation resistance of the composites was rapidly decreased with the amount of added TiN.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.75-77
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• 2001

The mechanical and electrical properties of the pressureless annealed SiC-$TiB_2$ electro conductive ceramic composites were investigated as functions of the transition metal of $TiB_2$. The result of phase analysis for the SiC-$TiB_2$ composites by XRD revealed $\alpha$-SiC(6H). $TiB_2$, and YAG($Al_5Y_3O_{12}$) crystal phase. The relative density showed the lowest 84.8% for the SiC-$TiB_2$ composites added with 39vol.%$TiB_2$. Owing to crack deflection, crack bridging and YAG of fracture toughness mechanism, the fracture toughness showed the highest value of $7.8\;MPa{\cdot}m^{1/2}$ for composites added with 39vol.%$TiB_2$ under a pressureless annealing at room temperature. The electrical resistivity of the SiC-27vol.%$TiB_2$ composites was negative temperature coefficient resistance(NTCR), and the electrical resistivity of the besides SiC-27vol.%$TiB_2$ composites was all positive temperature coefficient resistance(PTCR) in the temperature range of $25^{\circ}C$ to $700^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.28 no.5
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• pp.406-414
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• 1991

The composition of base glass was selected as MgO 8, Al2O3 24, SiO2 68 in weight percent. TiO2 and ZrO2 were added to the base glass to investigate their effects as nucleating agents. In the case of ZrO2 addition, the optimum temperature for nucleation, which was related to the precipitation of tetragonal ZrO2, was 80$0^{\circ}C$. The optimum growth condition for the crystal was 87$0^{\circ}C$ for 8 hrs, and the major crystal phases precipitated in the samples were $\beta$-quartz ss. and mullite. The light transmissivity turned out to be around 80 per cent. On the other hand, when the TiO2 was added, it was difficult to determine the nucleating temperature, because the samples turned easily into translucency during the heat treatment. Therefore, it was almost impossible to retain transparency in the samples. The light transmissivity was below 30 per cent.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.381-384
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• 2001

The $\beta$-SiC+ZrB$_2$ and $\beta$-SiC+TiB$_2$ceramic electroconductive composites were pressureless-sintered and annealed by adding l2wt% A1$_2$ $O_3$+Y$_2$ $O_3$(6 : 4wt%) powder as a function of sintering temperature. The relative density showed highest value of 84.92% of the theoretical density for SiC-TiB$_2$ at 190$0^{\circ}C$ sintering temperature. The phase analysis of the composites by XRD revealed of $\alpha$-SiC(6H), TiB$_2$, $Al_{5}$Y$_2$ $O_{12}$ and $\beta$-SiC(15R). Flexural strength showed the highest of 230 MPa for SiC-ZrB$_2$ composites sintered at 190$0^{\circ}C$. The vicker's hardness increased with increasing sintering temperature and showed the highest for SiC-ZrB$_2$ composites sintered at 190$0^{\circ}C$. Owing to YAG, the fracture toughness showed the highest of 6.50 MPa . m$^{1}$2/ for SiC-ZrB$_2$ composites at 190$0^{\circ}C$. The electrical resistivity was measured by the Rauw method from $25^{\circ}C$ to $700^{\circ}C$. The electrical resistivity of the composites showed the PTCR(Positive Temperature Coefficient Resistivity).).

• Corrosion Science and Technology
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• v.15 no.3
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• pp.129-134
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• 2016

The effects of Ti on the high temperature oxidation of Ni-based superalloys were investigated by cyclic oxidation at $850^{\circ}C$ and $1000^{\circ}C$. The oxide scale formed at $850^{\circ}C$ consists of $Cr_2O_3$, $Al_2O_3$, and $NiCr_2O_4$ layers, while a continuous $Al_2O_3$ layer was formed at $1000^{\circ}C$. The oxidation rate of the alloy with higher Ti content was higher than the alloy with less Ti content at $850^{\circ}C$, possibly due to the increase in the metal vacancy concentration in the $Cr_2O_3$ layer involved by incorporation of $Ti^{4+}$. However, Ti improved the oxidation resistance of the superalloy at $1000^{\circ}C$ by reducing oxygen vacancy concentration in $Al_2O_3$ layer.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.4
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• pp.141-146
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• 2002

The mechanical and electrical properties of the pressureless sintered SiC-TiB$_2$electroconductive ceramic composites were investigated as functions of the transition metal of TiB$_2$. The result of phase analysis for the SiC-TiB$_2$ composites by XRD revealed $\alpha$-SiC(6H), TiB$_2$, and YAG(Al$_{5}$Y$_3$O$_{12}$) crystal phases. The relative density showed the lowest 84.8% for the SiC-TiB$_2$composites added with 39vol.%TiB$_2$. Owing to crack deflection, crack bridging and YAG of fracture toughness mechanism, the fracture toughness showed the highest value of 7.8 MPa.m$^{1}$2/ for composites added with 39vol.%TiB$_2$under a pressureless annealing at room temperature. The electrical resistivity of the SiC-27vol.%TiB$_2$ composites was negative temperature coefficient resistance(NTCR), and the electrical resistivity of the besides SiC-27vol.%TiB$_2$composites was all positive temperature coefficient resistance(PCTR) in the temperature range of $25^{\circ}C$ to $700^{\circ}C$.EX>.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.626-633
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• 1998

For the fabrication of low temperature cofirable glass/ceramic with high dielectric constant, crystallizing glass [$SiO_2-TiO_2-RO (RO:BaO, CaO:SrO)$] was formed. The glass/ceramic composites were made by mixing this glass and alumina ceramic as filler, and its characteristics was investigated. With this glass compositon, it was possible to fabricate the glass which could be crystallized under $900^{\circ}C$. And it was found that the crystallizing temperature was changed in accordance with the composition of RO in glass. By adding $Bi_2O_3$ as flux, using $Al_2O_3$ as filler and sintering at $860^{\circ}C$, low temperature cofirable glass/ceramic with high dielectric constant was fabricated. The density of that composites was 3.96 g/$\textrm{cm}^3$, dielectric constant was 17 and Q. f was 600.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.71-71
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• 2000

본 연구에서는 차세대 마이크로파 유전체 소자로서의 응용을 목적으로 펄스 레이저 방식에 의하여 증착된 MgTiO3 박막의 전기적 특성을 종합적으로 연구 분석하였다. 이를 바탕으로 MgTiO3 박막의 유전손실 등과 같은 열화를 야기시키는 박막 내부 또는 박막과 기판간의 결함의 특성을 파악하여 열화 메카니즘을 분석하였다. MgTiO3는 마이크로파 영역에서의 우수한 유전특성과 같은 낮은 유전손실을 가지며, 온도 안정성 또한 우수하다. 현재까지 벌크 세라믹 MgTiO3 의 응용 광범위하게 연구되어 왔으나 박막의 제조공정 및 전기적 특성 분석은 미흡한 형편이다. 따라서 벌크 세라믹과는 특성이 상이한 박막의 전기적 특성분석 및 연구가 필요하다. 분석을 위한 소자의 기본 구조로서 Metal-Insulator-Semiconductor(MIS) 구조를 채택하였다. MgTiO3 박막을 증착하기 위한 기판으로는 n형 Si(100)기판과 p형 Si(100)기판을 사용하였고, Si 기판 위에 급속 열처리기 (RTP)를 이용하여 SiO2를 ~100 두께로 성장시킨 것과 성장시키지 않은 것으로 구분하여 제작하였다. MgTiO3 박막은 펄스 레이저 증착 방식(PLD)에 의하여 약 2500 두께로 증착되었으며, 200mTorr 압력의 산소 분위기 하에서 기판의 온도를 40$0^{\circ}C$~55$0^{\circ}C$까지 5$0^{\circ}C$간격으로 변화시키며 제작하였다. 상하부의 전극 금속으로는 Al을 이용하였으며, 열증발 증착기로 증착하였다. 증착된 MgTiO3 박막의 결정구조를 확인하기 위하여 XRD 분석을 수행하였으며, 박막의 전기적 특성을 분석하기 위해 Boonton7200 C-V 측정기와 HP4140P를 이용한 경우에는 C-V 곡선에 이력현상이 나타났으나, MgTiO3/SiO2를 이용한 경우에는 이력현상이 나타나지 않았고, 유전율은 감소하는 것으로 나타났다. I-V 측정 결과, 절연층으로 MgTiO3/SiO2를 이용한 경우에는 MgTiO3만을 절연층으로 사용한 경우에 비해 동일한 전계에서 낮은 누설전류 값을 가짐을 알 수 있었다. 또한 박막의 증착온도가 증가함에 따라서 C-V 곡선의 위치가 양의 방향으로 이동함을 확인하였다. 위의 현상은 기판의 종류에 관계없이 발생하는 것으로 보아 벌크 또는 계면에 존재하는 결함에 의한 것으로 추정된다. 현재 C-V 곡선의 이동 원인과 I-V 곡선의 누설전류 메카니즘을 분석 중에 있으며 그 결과를 학회에서 발표할 예정이다.