• Title, Summary, Keyword: $CO_2-O_2$ mixture

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Low Temperature Sintering and Dielectric Properties of CaCO3-Al2O3 Mixture and Compound with CAS-based Glass (CAS계 유리가 첨가된 CaCO3-Al2O3 혼합물 및 화합물의 저온 소결 및 유전 특성)

  • Yoon, Sang-Ok;Kim, Myung-Soo;Kim, Kwan-Soo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.5
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    • pp.397-404
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    • 2009
  • Effects of ceramic filler types and dose on the low temperature sintering and dielectric properties of ceramic/$CaO-Al_{2}O_{3}-SiO_2$ (CAS) glass composites were investigated. All of the specimens were sintered at $850{\sim}900^{\circ}C$ for 2 h, which conditions are required by the low-temperature co-firing ceramic (LTCC) technology. Ceramic fillers of $CaCO_3$, $Al_{2}O_{3}$, $CaCO_3-Al_{2}O_{3}$ mixture, and $CaCO_3-Al_{2}O_{3}$ compound ($CaAl_{2}O_{4}$), respectively, were used. The addition of $Al_{2}O_{3}$ yielded the crystalline phase of alumina, which was associated with the inhibition of sintering, while, $CaCO_3$ resulted in no apparent crystalline phase but the swelling was significant. The additions of $CaCO_3-Al_{2}O_{3}$ mixture and $CaAl_{2}O_{4}$, respectively, yielded the crystalline phases of alumina and anorthite, and the sintering properties of both composites increased with the increase of filler addition and the sintering temperature. In addition, the $CaAl_{2}O_{4}$/CAS glass composite, sintered at $900^{\circ}C$, demonstrated good microwave dielectric properties. In overall, all the investigated fillers of 10 wt% addition, except $CaCO_3$, yielded reasonable sintering (relative density, over 93 %) and low dielectric constant (less than 5.5), demonstrating the feasibility of the investigated composites for the application of the LTCC substrate materials.

Combustion Kinetics of Pulverized Indian Coal-Char in Different CO2-O2 Mixture Isothermally (여러 CO2-O2 혼합기체에서 인도산 분말숯의 등온 연소반응)

  • Saravanan, V.;Shivakumar, R.;babu, P. Niruguna;Ramakrishna
    • Journal of the Korean Chemical Society
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    • v.53 no.6
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    • pp.635-639
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    • 2009
  • Experimental work was carried out to study the combustion kinetics of the Indian coal-char in the varying mixture of carbon dioxide-oxygen ($CO_2-O_2$). The coal sample was pulverized and sieved to less than 58 microns and charred using volatile furnace by passing the nitrogen gas. The experiments were carried out using the Thermo Gravimetric Analyzer (TGA-50) at CPRI, Bangalore, different proportions of ($CO_2-O_2$) gas was allowed in to the TGA-50 (80-20, 60-40, 40-60, 20-80) mole basis were used to study the combustion kinetics of coal Isothermally, kinetic parameters like Activation energy (E) and the pre-exponential factors (A) are calculated using the unification approach and modified Arrhenius equation.

Heterogeneous Ignition of $H_2/O_2/CO_2$ Mixture Over Platinum Catalyst (수소/산소/이산화탄소 혼합기의 백금촉매반응특성 : 비균일 반응의 점화 온도)

  • Nam, Chang-Ho;Shin, Hyun-Dong
    • 한국연소학회:학술대회논문집
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    • pp.90-96
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    • 2001
  • Catalytic ignition of $H_2/O_2/CO_2$ mixtures over platinum catalyst is experimentally investigated by using microcalorimetry. For comparison, $N_2$ and Ar is also used as diluent gas. The gas mixture flows toward platinum foil heated by electric current at atmosphere pressure and ambient temperature. The ignition temperature range 350-445K according to the fuel ratio, dilution ratio and diluent gas. It increases as the fuel ratio and dilution ratio increase. $H_2/O_2$ mixture with $CO_2$ ignites at higher temperature than with other diluents by 30-50K. Several experimental evidences show the inhibition effects of $CO_2$ in $H_2-O_2$ heterogeneous reaction is considerable

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Effect of Abnormal Expansion in the Equimolecular Mixture BaCO3 and TiO2 Added Excess BaCO3 (BaTiO3이론조성과 BaCO3가 과잉인계에서 팽창과 상의 관한 연구)

  • 김종옥;이풍헌;임대영
    • Journal of the Korean Ceramic Society
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    • v.26 no.6
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    • pp.783-788
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    • 1989
  • The reason of abnormal expansion in BaTiO3 synthesized in the equimolecular mixture and synthesized in Ba-rich region were investigated at the point of crystal and microstructure. The shrinkage and the expansion of the mixtures in BaCO3-TiO2 system were determined by the mass of BaCO3 added to the equimolecular BaCO3 and TiO2, Ba2TiO4 which was much formed and BaTi2O3 were important crystal in the reaction of Ba-rich region. Sintering phenomena of unreacted BaCO3 activity and the secondary phase caused to generate microcracks in the specimens.

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Effect of Cobalt Oxide on Carbothermal Reduction of Spray Dried Titanium-Cobalt-Oxygen Based Oxide Powder (분무건조법에 의해 제조된 Ti-Co-O계 산화물 분말의 환원/침탄반응에 미치는 코발트 산화물의 영향)

  • Lee, Gil-Geun;Kim, Chan-Young
    • Journal of Korean Powder Metallurgy Institute
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    • v.12 no.5
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    • pp.336-344
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    • 2005
  • In the present study, the focus is on the effect of cobalt oxide powder in the carbothermal reduction of the titanium-cobalt-oxygen based oxide powder by solid carbon for the optimizing synthesis process of ultra fine TiC/Co composite powder. The titanium-cobalt-oxygen based oxide powder was prepared by the combination of the spray drying and desalting processes using the titanium dioxide powder and cobalt nitrate as the raw materials. The titanium-cobalt-oxygen based oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under flowing argon atmosphere. Changes in the phase structure and thermal gravity of the mixture during carbothermal reduction were analysed using XRD and TGA. Titanium-cobalt-oxygen based oxide powder desalted at $600^{\circ}C$ had a mixture of $TiO_2\;and\;Co_{3}O_4$. And the one desalted at $800^{\circ}C$ had a mixture of $TiO_2\;and\;CoTiO_3$. In the case of the former powder, the reduction of cobalt oxide powder in the titanium-cobalt-oxygen based oxide powder occurred at lower temperature than the latter one. However, the carbothermal reduction of titanium dioxide powder in the titanium-cobalt-oxygen based oxide powder with a mixture of $TiO_2\;and\;Co_{3}O_4$ occurred at higher temperature than the one with a mixture of $TiO_2\;and\;CoTiO_3$. And also, the former powder showed a lower TiC formation ability than the latter one.

Preparation of M Type Hexa-Ferrite Using the Mill Scale (Mill Scale을 이용한 M형 Ferrite의 합성)

  • 오영우
    • Journal of the Korean Magnetics Society
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    • v.6 no.4
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    • pp.204-210
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    • 1996
  • M type hexa-ferrites were prepared by means of a solid state reaction using mill scale, $Fe_{2}O_{3}$, and the mixture of mill scale and $Fe_{2}O_{3}$. The mixture of powders were calcined at $1150^{\circ}C$ for 2 hrs. and sintered at $1250^{\circ}C$ for 2 hrs, with varing the mole ratio of $Fe_{2}O_{3}$/$BaCO_{3}$, by 5.2~6.0. And the magnetic properties and morphologies of Baferrites with impurities such as $SiO_{2},\;Al_{2}O_{3},\;MgO,\;CaO\;and\;Na_{2}O$ in the mill scale were investigated. The magnetic properties were worsened by the addition of $Na_{2}O because of non-reacted iron oxide and intermediate compound of $BaFe_{2}O_{4}$ but they were improved apparently by the addition of $Si_{2}$ and $Al_{2}O_{3}$ in the composition of $BaO.5.6Fe_{2}O_{3}$. Moreover, $M_{s}$ decreased but $_{B}H_{C}$ increased through the addition of $Al_{2}O_{3}$ in Ba-ferrite. ${(BH)}_{max}$ of sintered BM($BaCO_{3}$, mill scale mixture) and BFM($BaCO_{3}$, $Fe_{2}O_{3}$, and null scale mixture) were 0.86 and 1.04 MGOe, respectively, and the magnetic properties were changed around $440^{\circ}C$.

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Synthesis of Nanocrystalline BaTiO3 Powder by the Combination of High Energy Ball Milling of BaCO3-TiO2 Mixture and Solid-State Reaction (고에너지 볼밀링된 BaCO3와 TiO2 혼합분말의 고상반응에 의한 나노결정 BaTiO3 분말 합성)

  • Ryu, Sung-Soo
    • Journal of Korean Powder Metallurgy Institute
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    • v.19 no.4
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    • pp.310-316
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    • 2012
  • Nanocrystalline $BaTiO_3$ powder could be synthesized by solid-state reaction using the mixture which was prepared by a high energy milling process in a bead mill for $BaCO_3$ and nanocrystalline $TiO_2$ powders mixture. Effect of the milling time on the powder characteristic of the synthesized $BaTiO_3$ powder was investigated. Nanocrystalline $BaTiO_3$ with a particle size of 50 nm was obtained at $800^{\circ}C$. High tetragonal $BaTiO_3$ powder with a tetragonality(=c/a) of 1.009 and a specific surface area of $7.6m^2/g$ was acquired after heat-treatment at $950^{\circ}C$ for 2 h. High energy ball milling was effective in decreasing the reaction temperature and increasing the tetragonality.

Nanometer-scale etching of CoFeB thin films using pulse-modulated high density plasma

  • Cho, Doo Hyeon;Lee, Jae Yong;Choi, Jae Sang;Chung, Chee Won
    • Current Applied Physics
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    • v.18 no.9
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    • pp.968-974
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    • 2018
  • Pulse-modulated inductively coupled plasma reactive ion etching of nanometer-scale patterned CoFeB thin films was performed in $CH_4/O_2/Ar$ gas mixture. As the pulse on-off duty ratio decreased, the etch selectivity of CoFeB/TiN slightly increased and the etch profiles were improved. Moreover, the etch selectivity of the CoFeB films and the etch profiles were improved with the increase in the pulse frequency of the plasma. X-ray photoelectron spectroscopy revealed that during the pulse-modulated etching in the $CH_4/O_2/Ar$ gas mixture, some polymeric layers were formed on the CoFeB films, which helped prevent the lateral etching and increased the etch selectivity. Consequently, nanometer-scale etching of CoFeB thin films patterned with TiN hard masks could be achieved using pulsed-modulated plasma in $CH_4/O_2/Ar$ gas mixture.

Characteristics of Diamond Films Deposited on Cemented Tungsten Carbide Substrate (초경합금기판 위에 성장되는 다이아몬드 막의 특성)

  • 김봉준;박상현;박재윤
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.53 no.7
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    • pp.387-394
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    • 2004
  • Diamond films were deposited on the cemented tungsten carbide WC-Co cutting insert substrates by using both microwave plasma chemical vapor deposition(MWPCVD) and radio frequency plasma chemical vapor deposition (RFPCVD) from $CH_4$$-H_2$$-O_2$ gas mixture. Scanning electron microscopy and X-ray diffraction techniques were used to investigate the microstructure and phase analysis of the materials and Raman spectrometry was used to characterize the quality of the diamond coating. Diamond films deposited using MWPCVD from $CH_4$$-H_2$$-O_2$ gas mixture show a dense, uniform, well faceted and polycrystalline morphology. The compressive stress in the diamond film was estimated to be (1.0∼3.6)$\pm$0.9 GPa. Diamond films which were deposited on the WC-Co cutting insert substrates by RFPCVD from $CH_4$$-H_2$$-O_2$ gas mixture show relatively good adhesion, very uniform, dense and polycrystalline morphology.

A Numerical Study on Charactericstics of Mixture Composition in Superdeonative Mode Ram Accelerator (초폭굉 모드 램가속기의 혼합기 강도 특성에 대한 수치적 연구)

  • Sung, Kun-Min;Jeung, In-Seuck
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.244-247
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    • 2008
  • Based on ISL' S225 superdetonative mode ram accelerator, numerical simulation is conducted for strong mixture cases ($2H_2+O_2+3CO_2,\;2H_2+O_2+2.5CO_2$). For 3.0CO2 case, projectile is not acclerated, but 2.5CO2 case has sucessful acceleration. It shows that superdetonative mode ram accelerator can be operated when using mixture which strong enough to ignition.

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