• Title/Summary/Keyword: ${B_4}C-{Al_2}{O_3}$

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High Temperature Oxidation of NiCoCrAlY-(Ta, Re, Ir) Coatings for Gas Turbines (가스터빈 엔진부품용 NiCoCrAlY-(Ta, Re, Ir) 코팅의 고온산화특성)

  • Choi, J.H.;Lee, D.B.
    • Journal of the Korean institute of surface engineering
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    • v.39 no.3
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    • pp.129-136
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    • 2006
  • The high velocity oxy-fuel sprayed coatings of 38Ni-23Co-20Cr-11Al-3Y-5Ta, 25Ni-34Co-20Cr-11Al-3Y-2Re and 32Ni-34.5Co-22Cr-11Al-0.5Ir (in wt%) were oxidized at 1000 and $1100^{\circ}C$ in air in order to find the alloying effect of Ta, Re and Ir on the oxidation properties of the NiCoCrAlY-base coatings. The primary phase of the coatings was $Ni_3Al$. The oxides formed on the coatings consisted primarily of ${\alpha}-Al_2O_3$, together with some $CoCr_2O_4,\;CoAl_2O_4$, and $Al_5Y_3O_{12}$. Tantalum oxidized to $Ta_2O_5$ and $Ta_2O_{22}$. However, no oxides of Re and Ir were detected by XRD owing to their thermodynamic inertness and/or their small amount.

Formation of Mo(NAr)(PMe₃)₂Cl₃and Mo₂(PMe₃)₄Cl₄from Reduction of Mo(NAr)₂Cl₂(DME) with Mg in the Presence of PMe₃[Ar=2,6-diisopropylphenyl]

  • 정건수;박병규;Lee, Soon W.
    • Bulletin of the Korean Chemical Society
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    • v.18 no.2
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    • pp.213-217
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    • 1997
  • Magnesium reduction of Mo(N-C6H3-2,6-i-Pr2)2Cl2(DME) in the presence of trimethylphosphine led to a mixture of Mo(N-C6H3-2,6-i-Pr2)(PMe3)2Cl3, 1, and Mo2(PMe3)4Cl4, 2. In solution 1 is slowly air-oxidized to Mo(N-2,6-i-Pr2-C6H3)(OPMe3)(PMe3)Cl3, 3. 1 is chemically inert to carbon nucleophiles (ZnMe2, ZnEt2, AlMe3, AlEt3, LiCp, NaCp, TlCp, NaCp*, MeMgBr, EtMgBr), oxygen nucleophiles (LiOEt, LiO-i-Pr, LiOPh, LiOSPh), and hydrides (LiBEt3H, LiBEt3D). Crystal data for 1: orthorhombic space group P212121, a=11.312(3) Å, b=11.908(3) Å, c=19.381(6) Å, Z=4, R(wR2)=0.0463 (0.1067). Crystal data for 2: monoclinic space group Cc, a=18.384(3) Å, b=9.181(2) Å, c=19.118(3) Å, b=124.98(1)°, Z=4, R(wR2)=0.0228 (0.0568). Crystal data for 3: orthorhombic space group P212121, a=11.464(1) Å, b=14.081(2) Å, c=16.614(3) Å, Z=4, R(wR2)=0.0394 (0.0923).

Friction and Wear at Ceramic Coated Surfaces of Aluminum Alloy (알루미늄 합금표면에 코팅된 세라믹재의 마찰마멸 특성)

  • 공호성;권오관;김형선
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.12
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    • pp.3083-3093
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    • 1993
  • Friction and wear at ceramic coated surfaces of aluminum alloy were experimentally studied using a Ring-on-Block wear test machine. Ceramic materials coated on aluminum alloy surfaces were WC, CrC, $Al_{2}O_{3}$ by a plasma spray; and $Al_{2}O_{3}$,$Al_{2}SiO_{5}$, $Na_{2}B_{4}O_{7}$,$Na_{4}P_{2}O_{7}$, and $Al_{2}O_{3}-ZrO_{2}$ composite coating by an Anodic Spark Depositon. They were tested under the sliding wet contact and compared with aluminum alloys and steels. Test results showed that ceramic coated surfaces, in general, have better anti-wear property than those of aluminum alloys due to increase in the surface hardness ; however, they also showed higher coefficients of friction and changes in wear mechanisms, resulting in brittle fractures.

A study on the properties of the Electrocondutive Ceramic $SiC-TiB_2$ Composites according to Annealing Temperature. (Annealing 온도 변화에 따른 $\beta-SiC-TiB_2$ 도전성 세라믹 복합체의 특성 연구)

  • Shin, Yong-Deok;Ju, Jing-Young;Choi, Kwang-Soo;Oh, Sang-Soo;Lee, Dong-Yoon
    • Proceedings of the KIEE Conference
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    • 2002.11a
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    • pp.106-108
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    • 2002
  • The composites were fabricated 61vol.% $\beta-SiC$ and 39vol.% $TiB_2$ powders with the liquid forming additives of l2wt% $Al_2O_3+Y_2O_3$ by pressureless annealing at $1700^{\circ}C,\;1750^{\circ}C,\;1800^{\circ}C$ for 4 hours respectively. 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 and the Young's modulus showed the highest value of 92.9701% and 92.884Gpa for composites by pressureless annealing temperature $1700^{\circ}C$ at room temperature.

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Synthesis of Tialite Ceramic Pigments and Coloring in Glazes (Tialite계 세라믹 안료의 합성 및 유약에서의 발색)

  • Kim, Yeon-Ju;Lee, Byung-Ha
    • Korean Journal of Materials Research
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    • v.21 no.8
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    • pp.450-455
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    • 2011
  • [ $Al_2TiO_5$ ]has a high refractive index and good solubility of the chromophore in the $Al_2TiO_5$ lattice, which allows this structure to be a good candidate for the development of new ceramic pigments. However, pure $Al_2TiO_5$ is well known to decompose on firing at $900{\sim}1100^{\circ}C$. However, this process can be inhibited by the incorporation of certain metal cations into its crystalline lattice. In this study, the synthesis of gray ceramic pigment was performed by doping cobalt on the $Al_2TiO_5$ crystal structure. The $Al_2TiO_5$ was synthesized using $Al_2O_3$ and $TiO_2$, and doped with $Co_3O_4$ as a chromophore material. In order to prevent the thermal decomposition during the cooling procedure, MgO was added to samples by 0.05 mole, 0.1 mole, and 0.15 mole as a stabilizer. The samples were fired at $1500^{\circ}C$ for 2 hours and cooled naturally. The crystal structure, solubility limit, and color of the synthesized pigment were analyzed using XRD, Raman spectroscopy, UV, and UV-vis. $Al_2O_3$ was available for the formation of $CoAl_2O_4$, which should also be considered in order to explain the small amount of this phase detected in the sample with the higher $Co^{2+}$ content (${\geq}$ 0.03 mole). It was found that the solubility limit of $Co^{2+}$ in the $Al_2TiO_5$ crystal was 0.02 mole% through an analysis of Raman spectroscopy. Through the addition of a pigment with 0.02 mole% of $Co^{2+}$ to lime-barium glaze, stabilized gray color pigments with 66.54, -2.35, and 4.68 as CIE-$L^*a^*b^*$ were synthesized.

Studies on the Glaze for High Expansion Glass Ceramics (고팽창 결정화 유리의 유약에 관한 연구)

  • 박용완;강은태;박찬성;전문덕
    • Journal of the Korean Ceramic Society
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    • v.17 no.4
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    • pp.213-216
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    • 1980
  • A glass-ceramics material of composition %SiO_2$: 38.50, $Al_2O_3$: 26.00, $Na_2O$: 18.00, CaO: 6.00, MgO: 4.00, $TiO_2$: 7.50 was strengthened by coating a series of glazes$(SiO_2-B_2O_3-Al_2O_3-CaO-PbO-Na_2O-)$, which has lower thermal expansion coefficient than that of the glass-ceramics. The thermal expansion coefficient of the glazes ranges $80~90{\times}10^{-7}$cm/cm/$^{\circ}C$, whereas that of the glass-ceramics is $115{\times}10^{-7}$cm/cm/$^{\circ}C$. The glass-ceramics was identified to be composed of nepheline, carnegieite low form, and meta sodium silicate crystal by X-ray diffraction phase analysis. The glaze, having lower melting point and appropriate thermal expansion coefficient, was tried to be stable and good at secondary heat treatment.

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Fabrication of Ceramic Particulate Reinforced Steel Composites by Liquid Pressing Infiltration Process (용융가압함침공정을 이용한 세라믹 입자 강화 철강복합재료의 제조성 검증)

  • Cho, Seungchan;Lee, Yeong-Hwan;Ko, Seongmin;Park, Hyeon Jae;Lee, Donghyun;Shin, Sangmin;Jo, Ilguk;Lee, Sang-Kwan;Lee, Sang-Bok
    • Composites Research
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    • v.31 no.4
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    • pp.117-121
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    • 2018
  • Various ceramic particulate such as TiC, $TiB_2$, $Al_2O_3$ reinforced SUS431 matrix composites were successfully fabricated by a novel liquid pressing infiltration process. Microstructures of the SUS431 composite were analyzed to determine manufacturability of composites. $Al_2O_3$-SUS431 composite had lots of defects due to poor wettability between the $Al_2O_3$ and steel matrix. On the other hand, TiC was uniformly dispersed in the SUS431 matrix than $TiB_2$ and $Al_2O_3$ due to good wettability and interfacial properties.

Effect of Sintering Temperature on Properties of $\beta$-SiC-$ZrB_2$ Composites Manufactured by Pressureless Sintering (상압소결법에 의해 제조한 $\beta$-SiC-$ZrB_2$ 복합체의 특성에 미치는 소결온도의 영향)

  • Ju, Jin-Young;Shin, Yong-Deok
    • Proceedings of the KIEE Conference
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    • 2001.07c
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    • pp.1436-1438
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    • 2001
  • The $\beta$-SiC + $ZrB_2$ ceramic electroconductive composites were pressureless-sintered and annealed by adding 12wt% $Al_2O_3$ + $Y_2O_3$ (6 : 4wt%) powder as a function of sintering temperature. The relative density showed the highest value of 81.1% at 1900$^{\circ}C$ sintering temperature. The phase analysis of the composites by XRD revealed of $\alpha$-SiC(6H), $TiB_2$, $Al_5Y_2O_{12}$ and $\beta$-SiC(15R). Flexural strength showed the highest value of 230 MPa for composites sintered at 1900$^{\circ}C$. The vicker's hardness and the fracture toughness showed the highest value of increased with increasing sintering temperature and showed the highest of 9.88 GPa and 6.05 $MPa{\cdot}m^{1/2}$ at 1900$^{\circ}C$. The electrical resistivity was measured by the Pauw method from 25$^{\circ}C$ to 700$^{\circ}C$. The electrical resistivity of the composites showed the PTCR (Positive Temperature Coefficient Resistivity).

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Properties of ${\beta}$-SiC-$TiB_2$ Electrocondutive Ceramic Composites by Spray Dry (Spray Dry한 ${\beta}$-SiC-$TiB_2$ 도전성(導電性) 세라믹 복합체(複合體)의 특성(特性))

  • Shin, Yong-Deok;Ju, Jing-Young;Choi, Kwang-Soo;Oh, Sang-Soo;Lee, Dong-Yoon;Yim, Seung-Hyuk
    • 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 $700^{\circ}C$.

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Effect of Pressure on Properties of the SiC-$TiB_2$ Electroconductive Ceramic Composites (SiC-$TiB_2$ 전도성(電導性) 복합체(複合體)의 특성(特性)에 미치는 가압(加壓)의 영향(影響))

  • Shin, Yong-Deok;Seo, Je-Ho;Ju, Jin-Young;Ko, Tae-Hun;Lee, Jung-Hoon
    • Proceedings of the KIEE Conference
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    • 2008.07a
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    • pp.1228-1229
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    • 2008
  • The composites were fabricated 61[vol.%] ${\beta}$-SiC and 39[vol.%] $TiB_2$ powders with the liquid forming additives of 12[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid by pressure or pressureless annealing at 1,650[$^{\circ}C$] for 4 hours. Reactions between SiC and transition metal $TiB_2$ were not observed in the microstructure and the phase analysis of the SiC-$TiB_2$ electroconductive ceramic composites. Phase analysis of SiC-$TiB_2$ composites by XRD revealed mostly of ${\alpha}$-SiC(6H), $TiB_2$, and In Situ $YAG(Al_5Y_3O_{12})$. The relative density, the flexural strength and the Young's modulus showed the highest value of 88.32[%], 136.43[MPa] and 52.82[GPa] for pressure annealed SiC-$TiB_2$ composites at room temperature. The electrical resistivity showed the lowest value of 0.0162[${\Omega}{\cdot}cm$] for pressure annealed SiC-$TiB_2$ composite at 25[$^{\circ}C$]. The electrical resistivity of the pressure annealed SiC-$TiB_2$ composite was positive temperature coefficient resistance (PTCR) but the electrical resistivity of the pressureless annealed SiC-$TiB_2$ composites was negative temperature coefficient resistance(NTCR) in the temperature ranges from 25[$^{\circ}C$] to 700[$^{\circ}C$].

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