• 제목/요약/키워드: O2O

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Physicochemical and Catalytic Properties of NiSO4/CeO2-ZrO2 Catalyst Promoted with CeO2 for Acid Catalysis

  • Sohn, Jong-Rack;Shin, Dong-Cheol
    • Bulletin of the Korean Chemical Society
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    • 제28권8호
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    • pp.1265-1272
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    • 2007
  • A solid acid catalyst, NiSO4/CeO2-ZrO2 was prepared simply by promoting ZrO2 with CeO2 and supporting nickel sulfate on CeO2-ZrO2. The support of NiSO4 on ZrO2 shifted the phase transition of ZrO2 from amorphous to tetragonal to higher temperatures because of the interaction between NiSO4 and ZrO2. The surface area of 10-NiSO4/1-CeO2-ZrO2 promoted with CeO2 and calcined at 600 oC was very high (83 m2/g) compared to that of unpromoted 10-NiSO4/ZrO2 (45 m2/g). This high surface area of 10-NiSO4/1-CeO2-ZrO2 was due to the promoting effect of CeO2 which makes zirconia a stable tetragonal phase as confirmed by XRD. The role of CeO2 was to form a thermally stable solid solution with zirconia and consequently to give high surface area and acidity of the sample, and high thermal stability of the surface sulfate species. 10-NiSO4/1- CeO2-ZrO2 containing 1 mol% CeO2 and 10 wt% NiSO4, and calcined at 600 oC exhibited maximum catalytic activities for both reactions, 2-propanol dehydration and cumene dealkylation.

$Al_2O_3/Cr_2O_3-ZrO_2/HfO_2$ 계의 기계적 거동 (Mechanical Behavior of $Al_2O_3/Cr_2O_3-ZrO_2/HfO_2$ System)

  • 신동우;오근호;이종근
    • 한국세라믹학회지
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    • 제22권6호
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    • pp.42-52
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    • 1985
  • Several $Al_2O_3$-based polycrystalline which had different dopant ratio in the range of 0.5mol% were prepared by doping pure $Cr_2O_3$ $HfO_2$. Single crystalline which had same composition with above polycrystalline were made by means of floating zone method. This study examined the role of each dopant for enhancing the mechanical properties of $Al_2O_3$-based Ceramics. Optical micrographs $({ imes}200)$ of $Al_2O_3-Cr_2O_3$ single crystal showing not only radial crack (rc) on the specimen surface but median crack(mc) and lateral crack(lc) under surface at the edge of indentation mark. Fracture toughness of Al2O3-based Ceramics was increased with $ZrO_2$ content. Alloying effect of $Cr_2O_3$ contributed to the hardness of $Al_2O_3$ based ceramics.

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6Bi2O3.GeO2 조성 융액의 결정화 (Crystallization from The Melt of 6Bi2O3.GeO2 Composition)

  • 김호건;김명섭
    • 한국세라믹학회지
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    • 제26권4호
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    • pp.479-486
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    • 1989
  • According to the phase diagram, 6Bi2O3.GeO2 composition melts congruently at 93$0^{\circ}C$ and forms a stable ${\gamma}$-6Bi2O3.GeO2 crystal phase below the melting point. But when the melt of this composition was cooled at a rate 1-15$0^{\circ}C$/min without tapping by a glass rod or impurity addition, a metastable $\delta$-6Bi2O3.GeO2 crystal phase was formed. It is due to that as the nucleation energy barrier of $\delta$-6Bi2O3.GeO2 crystals, which have more open and defective structure, is lower than that of ${\gamma}$-6Bi2O3.GeO2 crystals. When impurities or ${\gamma}$-6Bi2O3.GeO2 crystals existed in the melt, stable ${\gamma}$-6Bi2O3.GeO2 crystal phase was formed at various cooling rate. It is because of that the impurities or the ${\gamma}$-6Bi2O3.GeO2 crystals role as a seed crystal and as a result the nucleation energy barrier of ${\gamma}$-6Bi2O3.GeO2 crystals is lowered.

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SIMS를 이용한 SiO2/PSG/SiO2/Al-1%Si 및 SiO2/TEOS/SiO2/Al-1%Si 적층 박막내의 Na 게터링 분석 (Analysis of the Na Gettering in SiO2/PSG/SiO2/Al-1%Si and SiO2/TEOS/SiO2/Al-1%Si Multilevel Thin Films using SIMS)

  • 김진영
    • 한국표면공학회지
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    • 제51권2호
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    • pp.110-115
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    • 2018
  • The Na low temperature gettering in $SiO_2/PSG/SiO_2/Al-1%Si$ and $SiO_2/TEOS/SiO_2/Al-1%Si$ multilevel thin films was investigated using dynamic SIMS(secondary ion mass spectrometry) analysis. DC magnetron sputter, APCVD and PECVD techniques were utilized for the deposition of Al-1%Si thin films, $SiO_2/PSG/SiO_2$ and $SiO_2/TEOS/SiO_2$ passivations, respectively. Heat treatment was carried out at $300^{\circ}C$ for 5 h in air. SIMS depth profiling was used to determine the distribution of Na, Al, Si and other elements throughout the $SiO_2/PSG/SiO_2/Al-1%Si$ and $SiO_2/TEOS/SiO_2/Al-1%Si$ multilevel thin films. XPS was used to analyze chemical states of Si and O elements in $SiO_2$ passivation layers. Na peaks were observed throughout the $PSG/SiO_2$ and $TEOS/SiO_2$ passivation layers on the Al-1%Si thin films and especially at the interfaces. Na low temperature gettering in $SiO_2/PSG/SiO_2/Al-1%Si$ and $SiO_2/TEOS/SiO_2/Al-1%Si$ multilevel thin films is considered to be caused by a segregation type of gettering.

온디맨드 O2O(Online to Offline)서비스에 대한 소비자의 심리적 애착과 즐거움 및 신뢰성이 서비스만족도와 태도에 미치는 영향 (The Impact of Consumer's Psychological Attachment and Enjoyment, Trust on Satisfaction and Attitude toward On-Demand O2O(Online to Offline) Service)

  • 이윤선
    • 융합정보논문지
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    • 제8권6호
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    • pp.399-407
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    • 2018
  • 본 연구는 O2O서비스에 대한 선행 연구와는 달리 온디맨드 O2O 서비스에 대한 소비자의 심리적 요인에 중점을 두었다. 이를 위해 152명을 대상으로 정량, 정성 조사를 통해 자료를 수집하고 분석하였으며 위계적 회귀분석을 통해 가설을 검증하였다. 정성조사로서 O2O 서비스에 대한 소비자의 지각을 살펴보고, 정량조사를 통해 소비자의 심리적 요인이 서비스의 만족도에 미치는 영향을 살펴보기 위해 서비스에 대한 애착과 즐거움, 신뢰성을 중심으로 살펴보았다. 연구결과, 온디맨드 O2O서비스에 대한 만족도에 가장 큰 영향력을 미치는 심리적 요인은 서비스에 대한 신뢰성이며, 서비스태도에서는 소비자의 심리적 애착이 가장 높은 영향을 미치는 것으로 나타났다. 본 연구는 소비자의 입장에서 온디맨드 O2O 서비스에 대한 소비자의 심리적 요인을 살펴보았다는 점에서 의의가 있으며, 본 연구 결과를 통해 온디맨드 O2O서비스의 확장을 위해서는 소비자의 심리적 애착과 신뢰성을 우선적으로 고려해야 할 것이다.

입도분포에 따른 하상퇴적물의 지구화학적 분산 및 부화 (Geochemical Dispersion and Enrichment of Fluvial Sediments Depending on the Particla Size Distribution)

  • 이현구
    • 자원환경지질
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    • 제32권3호
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    • pp.247-260
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    • 1999
  • Geochermical characteristics of the fluvial sediments deprnding on particle size distribution size were investigated in the respect of majir, minor and rare eath element chemisitry. Ratios of $Al_{2}O_{3}/Na_{2}O$ and $K_{2}O/Na_{2}O$ of the sediments show the homogeneous valus, and partly positive correlation with $SiO_{2}/Al_{2}O_{3}$, respecively. Characteristics of minor element ratios (V/Ni, Cr/V, Ni/Co and Zr/Hf)are within the lower and narrow range. Thesesuggested that sediment sources may be acidic to intermediate granitic rock, and may be explained by simple weathering and sedimentation. With increasing SiO2 contents, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO and MgO decreased, but those of $K_{2}O$ and $Na_{2}O$ increased, Concentrations of Ba, Be, Cs, Cu, Li, Ni, Sr, V and Zr show comparatively normal negative and some positive trends. Compared with the mean composition of granite, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, MnO, CaO and MgO in the sediments of the study area were highly enriced. Among some minor and rare earth elements, concentrations of As, Cd, Cu, and V were enriched, but those of Be, Ce, Rb, Sc, Sr and Zn were depleted when compared with average composition of granite. By decreasing of particle size fractions, SiO2, Rb and Sr conterts decreased, but concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO, MgO, $TiO_{2}$, MgO, $P_{2}O_{5}$, Be, Cu, Hf, Pb, V and Zr increased. From the correlations between particle size fractions and element concenreations, some elements of $Fe_{2}O_{3}$, CaO, MgO, $P_{2}O_{5}$, Cu, Ni, Zn and Zr showed typical trends in the secondary contramination sediments. These trends are typically shown under 100 mesh fractions. It indicates that the fraction of minus 100 mesh is the optimum size fraction for geochemical and environmental survey.

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Comparative Investigation of Interfacial Characteristics between HfO2/Al2O3 and Al2O3/HfO2 Dielectrics on AlN/p-Ge Structure

  • Kim, Hogyoung;Yun, Hee Ju;Choi, Seok;Choi, Byung Joon
    • 한국재료학회지
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    • 제29권8호
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    • pp.463-468
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    • 2019
  • The electrical and interfacial properties of $HfO_2/Al_2O_3$ and $Al_2O_3/HfO_2$ dielectrics on AlN/p-Ge interface prepared by thermal atomic layer deposition are investigated by capacitance-voltage(C-V) and current-voltage(I-V) measurements. In the C-V measurements, humps related to mid-gap states are observed when the ac frequency is below 100 kHz, revealing lower mid-gap states for the $HfO_2/Al_2O_3$ sample. Higher frequency dispersion in the inversion region is observed for the $Al_2O_3/HfO_2$ sample, indicating the presence of slow interface states A higher interface trap density calculated from the high-low frequency method is observed for the $Al_2O_3/HfO_2$ sample. The parallel conductance method, applied to the accumulation region, shows border traps at 0.3~0.32 eV for the $Al_2O_3/HfO_2$ sample, which are not observed for the $Al_2O_3/HfO_2$ sample. I-V measurements show a reduction of leakage current of about three orders of magnitude for the $HfO_2/Al_2O_3$ sample. Using the Fowler-Nordheim emission, the barrier height is calculated and found to be about 1.08 eV for the $HfO_2/Al_2O_3$ sample. Based on these results, it is suggested that $HfO_2/Al_2O_3$ is a better dielectric stack than $Al_2O_3/HfO_2$ on AlN/p-Ge interface.

Study of properties of $YBa_2Cu_3O_x$ with PbO and $BapbO_3$ additives

  • Soh, Dae-Wha;Fan, Zhanguo
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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    • pp.543-546
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    • 2004
  • The melting temperature and critical temperature(Tc) of $YBa_2Cu_3O_x$ with deferent content impurities of PbO and $BaPbO_3$ were studied. When the PbO was used as addition in $YBa_2Cu_3O_x$, although the melting point could be reduced, the superconductivity(the transition width, ${\Delta}T_c$) became poor. From the XRD pattern of the sintered mixture of $YBa_2Cu_3O_x$ and PbO it was known that there is a reaction between $YBa_2Cu_3O_x$ and PbO, and the product is $BaPbO_3$. In the process of the reaction the superconducting phase of $YBa_2Cu_3O_x$ was decreased and in the sample $BaPbO_3$ became the main phase. Therefore the superconductivity was reduced. $BaPbO_3$ was chosen as the impurity for the comparative study. The single phase BaPbO3 was synthesized by the simple way from both mixtures of $BaPbO_3$ and PbO, $BaPbO_3\;and\;PbO_2$. Deferent contents of $BaPbO_3$(10%, 20%, 30%) were added in the $YBa_2Cu_3O_x$. By the phase analysis in the XRD patterns it was proved that there werenot reactions between $YBa_2Cu_3O_x$ and $BaPbO_3$. When $BaPbO_3$ was used as impurity in $YBa_2Cu_3O_x$ the superconductivity was much better than PbO as impurity in $YBa_2Cu_3O_x$. But the melting point of $YBa_2Cu_3O_x$ with $BaPbO_3$ could not be found when the temperature was lower than $1000^{\circ}C$ in the DTA measurement.

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CaTiO$_3$및 CaTiO$_3$-TiO$_2$세라믹스의 마이크로파 유전특성 (Microwave Dielectric Properties of CaTiO$_3$and CaTiO$_3$-TiO$_2$Ceramics)

  • 홍석경;윤중락;김경용
    • 한국통신학회논문지
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    • 제18권8호
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    • pp.1102-1107
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    • 1993
  • CaO-TiO2 이성분계에서 40~50 mol% CaO 조성범위를 선택하여 CaTiO3과 CaTiO3-TiO2세라믹스의 마이크로파 유전특성을 조사하였다. CaTiO3 단일상 (50 mol% CaO조성)일 때 유전율(er) 178, 공진주파수 (fo)의 온도계수(r,)+1000ppm/C, 픔질계수인 Q값 2760(fo=2.7 GHz)으로 가장 큰 값을 나타내었다. CaTiO3와 TiO2상이 혼합상으로 있는 유전체에서는 CaO 함량이 감소함에 따라서 유전율과 공진주파수의 온도계수는 점차 감소하였으나 Q값과 밀도는 47 mol% CaO조성에서 가장 낮았다. 이것은 이상 혼합 세라믹에서 TiO2상의 감소로 인해 CaTiO3의 결정립 성장이 급속하게 일어남으로써 입계와 입내에 큰 기공이 존재하지 때문으로 생각된다.

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치관 보철용 CaO-MgO-$SiO_2-P_2O_5-TiO_2$계 글라스 세라믹의 합성과 경도 (Synthesis and Hardness of Glass Ceramics for Dental Crown Prosthetic Application in the system CaO-MgO-SiO2-P2O5-TiO2)

  • 정인성;김갑진;정호근;이종일
    • 대한치과기공학회지
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    • 제21권1호
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    • pp.5-14
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    • 1999
  • Glass ceramics for dental crown prosthesis were prepared by crystallization of CaO-MgO-SiO2-$P_2O_5-TiO_2$ glasses. Their crystallization behaviors have been investigated as a function of heattreatment temperature, holding time and chemical composition in relation to mechinical properties. Crystallization peak temperatures were determined by differential thermal analysis(DTA). Crystalline phases and mircostructures of heat-treated sample were determined by the means of powder X-ray diffraction(XRD) and scanning electron microscopy(SEM). The final crystalline phase assemblages and the microstructures of the samples were found to be dependent on glass compositions, heattreatment temperature, and holding time. 1st crystallization peak temperature(TP), affected strongly by apatite, was found to be increased or decreased. From the experiment, the following results were obtained : 1. The crystallization peak temperature($T_P$) formed by apatite increased until adding up to 9wt% $TiO_2$ to base glass composition, then decreased above that. 2. Apatite($Ca_{10}P_6O_{25}$), whitlockite(${\beta}-3CaO-P_2O_5$), $\beta$-wollastonite($CaSiO_3$), magnesium tianate($MaTiO_3$) and diopside(CaO-MgO-$2SiO_2$) crystal phase were precipitated in MgO-CaO-$SiO_2-TiO_2-P_2O_5$ glass system containing 9wt% and 11wt% of $TiO_2$ 3. Vickers hardness of samples increased with increasing heat-treatment temperature and Vickers hardness of S415T9 samples heat-treated at 1075 was approxi-mately 813Kg $mm^{-2}$ as maximum value. 4. Vickers hardness of samples increased due to precipitation of apatite, whitlockite, $\beta$-wollastonite, magnesium titanate, and diopside crystal phases within glass matrix.

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