• Title/Summary/Keyword: $SiO_2$Microstructure

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Electrical Properties of SiC Composites by Transition Metal (천이금속에 따른 SiC계 복합체의 전기적 특성)

  • Shin, Yong-Deok;Seo, Je-Ho;Ju, Jin-Young;Ko, Tae-Hun;Kim, Young-Bek
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.1303-1304
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    • 2007
  • The composites were fabricated, respectively, using 61[vol.%]SiC-39[vol.%]$TiB_2$ and using 61[vol.%]SiC-39[vol.%]$ZrB_2$ powders with the liquid forming additives of 12[wt%] $Al_{2}O_{3}+Y_{2}O_{3}$ by hot pressing annealing at $1650[^{\circ}C]$ for 4 hours. Reactions between SiC and transition metal $TiB_2$, $ZrB_2$ were not observed in this microstructure. ${\beta}{\rightarrow}{\alpha}$-SiC phase transformation was occurred on the SiC-$TiB_2$ and SiC-$ZrB_2$ composite. The relative density, the flexural strength and Young's modulus showed the highest value of 98.57[%], 226.06[Mpa] and 86.38[Gpa] in SiC-$ZrB_2$ composite at room temperature respectively. The electrical resistivity showed the lowest value of $7.96{\times}10^{-4}[{\Omega}{\cdot}cm]$ for SiC-$ZrB_2$ composite at $25[^{\circ}C]$. The electrical resistivity of the SiC-$TiB_2$ and SiC-$ZrB_2$ composite was all positive temperature coefficient resistance (PTCR) in the temperature ranges from $25[^{\circ}C]$ to $700[^{\circ}C]$. The resistance temperature coefficient of composite showed the value of $6.88{\times}10^{-3}/[^{\circ}C]$ and $3.57{\times}10^{-3}/[^{\circ}C]$ for SiC-$ZrB_2$ and SiC-$TiB_2$ composite in the temperature ranges from $25[^{\circ}C]$ to $700[^{\circ}C]$.

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Phase Formation and Physical Properties of SiAlON Ceramics Fabricated by Gas-Pressure Reactive Sintering (가스압 반응소결로 제조된 SiAlON 세라믹스의 상형성과 물리적 특성)

  • Lee, Soyul;Choi, Jae-Hyeong;Han, Yoonsoo;Lee, Sung-Min;Kim, Seongwon
    • Journal of Powder Materials
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    • v.24 no.6
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    • pp.431-436
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    • 2017
  • SiAlON-based ceramics are some of the most typical oxynitride ceramic materials, which can be used as cutting tools for heat-resistant super-alloys (HRSA). SiAlON can be fabricated by using gas-pressure reactive sintering from the raw materials, nitrides and oxides such as $Si_3N_4$, AlN, $Al_2O_3$, and $Yb_2O_3$. In this study, we fabricate $Yb_{m/3}Si_{12-(m+n)}Al_{m+n}O_nN_{16-n}$ (m=0.3, n=1.9, 2.3, 2.7) ceramics by using gas-pressure sintering at different sintering temperatures. Then, the densification behavior, phase formation, microstructure, and hardness of the sintered specimens are characterized. We obtain a fully densified specimen with ${\beta}$-SiAlON after gas-pressure sintering at $1820^{\circ}C$ for 90 min. under 10 atm $N_2$ pressure. These SiAlON ceramic materials exhibited hardness values of ~92.9 HRA. The potential of these SiAlON ceramics for cutting tool application is also discussed.

Wear Behavior of Silicon Nitride Depending on Gas Pressure Sintering Conditions

  • Kim, Sung-Ho;Lee, Soo-Wohn;Park, Yong-Kap
    • The Korean Journal of Ceramics
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    • v.6 no.3
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    • pp.193-200
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    • 2000
  • Si$_3$N$_4$powder with 2 wt% $Al_2$O$_3$and 6 wt% $Y_2$O$_3$additives was sintered by the gas pressure sintering (GPS) technique. The unlubricated wear behavior depending on sintering conditions such as sintering temperature, pressure, and sintering time was investigated. When the sintering temperature and time increased, the larger elongated grains were formed and the microstructural heterogeneity increased. When sintering pressure increased, grain growth, however, was impeded. Also, the wear properties depended on microstructure and friction coefficient were related to grain size. Based on the experimental results, the wear properties were associated with initial friction coefficients as well as mechanical properties including fracture toughness and flexural strength.

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Effect of Oxygen on the Microstructure and Mechanical Properties of Cr-O-N Coatings (Oxygen 함량에 따른 Cr-O-N 코팅막의 미세구조 및 기계적 특성에 관한 연구)

  • Yun, Jun-Seo;Kwon, Se-Hun;Park, In-Wook;Lee, Jeong-Du;Kim, Kwang-Ho
    • Journal of the Korean institute of surface engineering
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    • v.42 no.5
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    • pp.220-226
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    • 2009
  • Cr-O-N coatings having different oxygen contents were deposited on Si wafer and SUS 304 substrates by an arc ion plating technique using Cr target in $Ar/O_2/N_2$ gaseous atmosphere. As increasing oxygen content in the coating, the microstructure of Cr-O-N coating changed from polycrystalline having NaCl structure to amorphous structure. Further increase of oxygen content resulted in phase transformation from amorphous to rhombohedral structure. From the variations of d value and average grain size, it was revealed that the maximum solubility of oxygen in Cr-O-N coating was about 21 at.%. And the maximum micro-hardness of 2751HK was obtained in this composition. The lowest friction coefficient was measured in the coating having 34.8 at.% of oxygen. However, more narrow width of wear track was found in the coating having 30.1 at.% of oxygen.

A Study on the Thermal, Structural and Dielectric Properties of Photo Machinable Glass-Ceramics

  • Lee, Myung-won;Kang, Won-ho
    • Journal of Electrical Engineering and information Science
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    • v.3 no.1
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    • pp.68-72
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    • 1998
  • The photomachinable glass-ceramics of Ag and CeO2 doped Li203-SiO2 (LAS)glass system was investigated as a function of UV irradiation time. After the expose and the non-exposed samples were heated, they went under crystalline phase with DTA, SEM, TEM and XRD of normal/high temperature. In this work, crystalline phases, microstructure and dielectric properties were studied under the various time of UV irradiation and heat treatment.

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Effect of modifiers on the properties of glass-ceramics containing coal bottom ash (석탄 바닥재가 포함된 결정화 유리의 특성에 미치는 수식제의 영향)

  • Kang, Seung-Gu
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.20 no.1
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    • pp.53-57
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    • 2010
  • The influence of CaO addition on the crystallization temperature, crystal types, and microstructure of L-A-S ($Li_2O-Al_2O_3-SiO_2$) glass-ceramics system fabricated from a coal bottom ash, produced at thermal power plant, was studied. The glass transition and crystallization temperatures were shifted to the higher temperature position with increasing CaO content in a non-isothermal analysis using a DTA. The major crystalline phases of L-A-S glass-ceramics system produced were identified as ${\beta}$-spodumene ($LiAlSi_2O_6$) and eucryptite ($LiAlSiO_4$). The glass-ceramics showed a bulk and surface crystallization behavior at a time. With increasing CaO content, the ${\beta}$-spodumene peak in XRD increased and some CaO-related phases were formed. The surface crystal grown from the exterior to the center in glass-ceramics showed various shapes by amount of CaO added. Some cracks were generated at the glass-ceramics containing CaO above 9 wt% due to the mismatch of thermal expansion coefficients between a ${\beta}$-spodumene and CaO-related crystal phases.

Microstructure and Electrical Properties of SrBi$_2$Ta$_2$O$_9$ Ferroelectric Thin Films Prepared by RF Magnetron Sputtering Method (R-F magnetron sputtering 법으로 제조된 SrBi$_2$Ta$_2$O$_9$ 강유전성 박막의 미세구조 특성 및 전기적 특성)

  • 김효영;박상준;장건익
    • Journal of the Microelectronics and Packaging Society
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    • v.6 no.2
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    • pp.51-61
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    • 1999
  • $SrBi_2Ta_2O_9$ thin films were prepared on $Pt/SiO_2$/Si p-tyPp (100) substrate by r.f. magnetron sputtering method. The films were annealed at $800^{\circ}C$ and characterized in terms of micro-structures and electrical properties depending on film deposition conditions. XRD patterns of SBT films annealed at $800^{\circ}C$ indicated the typical SBT phase of (006), (111), and (200) with BiPt additional peaks. SEM images show that crystal gram become to grow with increasing the substrate temperature and decreasing the gas pressure. The remanant polarization(2Pr) and the coercive field(Ec) of 200nm thickness SBT film which was deposited at 10$0^{\circ}C$ under 50mtorr gas pressure and annealed at $800^{\circ}C$ were 20.07$\mu$C/$\textrm {cm}^2$ and 79kV/cm, respectively.

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Tailoring the Dielectric and Mechanical Properties of Si3N4 Ceramics (질화규소 세라믹의 유전 및 기계적 특성 제어에 관한 연구)

  • Lee, Seung Jun;Yong, Seok-Min;Park, Jin-Woo;Choi, Jaeho;Baek, Seungsu
    • Journal of the Korea Institute of Military Science and Technology
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    • v.21 no.6
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    • pp.760-766
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    • 2018
  • The present study investigates the effect of PMMA and BN content on microstructure, mechanical and dielectric properties of silicon nitride($Si_3N_4$) ceramics in $Y_2O_3-Al_2O_3$ additive system. The total additive content was fixed at 8 wt.% and the amount of PMMA varies from 0 to 40 wt.% and BN varies from 0 to 36 wt.%, respectively. The crystalline phases of the samples were determined by X-ray diffraction analysis. All the sintered sample shows complete transformation of ${\alpha}$ to ${\beta}-Si_3N_4$ during the sintering process indicated that the phase transformation was unaffected by the PMMA or BN content. However, the microstructure shows that the residual porosity increased with increasing PMMA and BN content. In addition, the flexural strength and the dielectric constant decrease with addition of PMMA and BN due to the residual porosity. This article provides empirical study of design parameters for $Si_3N_4$-based radome materials.

Synthesis and Photoactivity of SnO2-Doped TiO2 Thin Films (SnO2가 도핑된 TiO2 박막의 합성 및 광촉매 효과)

  • Jung, Mie-Won;Kwak, Yun-Jung
    • Journal of the Korean Ceramic Society
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    • v.44 no.11
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    • pp.650-654
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    • 2007
  • [ $SnO_2$ ]-doped $TiO_2$ thin films were prepared from tin (IV) bis (acetylacetonate) dichloride and titanium diisopropoxide bis (acetylacetonate) with pluronic P123 or degussa P25 as a structural-directing agent. These hydrolyzed sol were spin coated onto Si(100) wafer substrate. The microstructure, morphology and bonding states of thin films were studied by field-emission scanning electron microscopy (FE-SEM), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of these films was investigated by using indigo carmine solution.

Dielectric Properties of Complex Microstructure for High Strength LTCC Material (고강도 LTCC 소재을 위한 복합구조의 유전특성)

  • Kim, Jin-Ho;Hwang, Seong-Jin;Sung, Woo-Kyung;Kim, Hyung-Sun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.06a
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    • pp.309-309
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    • 2007
  • The LTCCs (low-temperature co-fired ceramics) are very important for electronic industry to build smaller RF modules and to fulfill the necessity for miniaturization of devices in wireless communication industry. The dielectric materials with sintering temperature $T_{sint}$<$900^{\circ}C$ are required. In this study, we investigated with glass-ceramic composition, which was crystallized with two crystals. The microstructure, crystal phases, thermal and mechanical properties, and dielectric properties of the composites were investigated using FE-SEM, XRD, TG-DTA, 4-point bending strength test and LCR measurement. The starting temperature for densification of a sintered body was at $779{\sim}844^{\circ}C$ and the glass frits were formatted to the crystal phases, $CaAl_2Si_2O_8$(anorthite) and $CaMgSi_O_6$(diopside), at sintering temperature. The sintered bodies exhibited applicable dielectric properties, namely 6-9 for ${\varepsilon}_r$. The results suggest that the glass-ceramic composite would be potentially possible to application of low dielectric L TCC materials.

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