• 한국세라믹학회지
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• 제55권1호
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• pp.1-20
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• 2018

Semiconducting nanomaterials have attracted considerable interest in recent years due to their high sensitivity, selectivity, and fast response time. In addition, for portable applications, they have low power consumption, lightweight, simple in operation, a low maintenance cost. Furthermore, it is easy to manufacture microelectronic sensor structures with metallic oxide sensitive thin layers. The use of semiconducting metal oxides to develop highly sensitive chemiresistive sensing systems remains an important scientific challenge in the field of gas sensing. According to the sensing mechanisms of gas sensors, the overall sensor conductance is determined by surface reactions and the charge transfer processes between the adsorbed species and the sensing material. The primary goal of the present study is to explore the possibility of using semiconducting mixed metal oxide nanostructure as a potential sensor material for selective gases.

• 한국산학기술학회논문지
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• 제13권1호
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• pp.456-461
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• 2012

본 연구에서는 글리세롤과 우레아를 이용하여 글리세롤카보네이트를 합성하는 반응을 진행하였다. ZnO와 Zn-Al 이원계 금속 산화물 촉매를 제조하고, 제조되어진 촉매를 사용하여 글리세롤의 전환율과 글리세롤카보네이트의 수율을 확인하였고, Al의 첨가에 따른 촉매 특성의 분석과 글리세롤카보네이트 합성반응에서의 역할에 대해 확인하였다. 글리세롤카보네이트 합성 반응에서 ZnO를 단독으로 촉매를 사용한 경우보다 Zn-Al 혼합 산화물을 촉매로 사용하여 반응하였을 때, 부반응이 억제되어 전환율 및 수율이 증가함을 확인하였다.

• 공업화학
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• 제19권6호
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• pp.624-628
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• 2008

$N_2O$는 주요 온실가스 성분의 하나로서 광화학 스모그의 유발, 산성비의 전구체 등 온실효과에 상당한 기여를 하고 있는 물질이다. 이러한 $N_2O$ 및 질소산화물을 제거하기 위하여 환원제를 이용한 Selective Catalytic Reduction (SCR) 반응 공정이 널리 사용되고 있다. 본 연구에서는 Hydrotalcite 형태의 전구체로부터 Mixed Metal Oxide 촉매를 제조하고 그를 사용하여 $N_2O$ 분해를 위한 메탄 SCR 반응 및 CO의 생성효과를 비교 연구하였다. 실험결과 $CH_4$ 환원제의 첨가는 $N_2O$의 분해 반응에 긍정적인 영향을 미치며, 최적화된 $O_2/CH_4$ 비율의 조건에서 메탄의 부분산화에 의한 SCR 반응이 가장 높은 효율을 나타내는 것을 확인할 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.339-339
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• 2010

The metallic nanoparticles (Pt, Au, Ag. Cu, etc.) supported on ceria-titania mixed oxide exhibit a high catalytic activity for the water gas shift reaction ($H_2O\;+\;CO\;{\leftrightarrow}\;H_2\;+\;CO_2$) and the CO oxidation ($O_2\;+\;2CO\;{\leftrightarrow}\;2CO_2$). It has been speculated that the high catalytic activity is related to the easy exchange of the oxidation states of ceria ($Ce^{3+}$ and $Ce^{4+}$) on titania, but very little is known about the ceria titanium interaction, the growth mode of metal on ceria titania complex, and the reaction mechanism. In this work, the growth of $CeO_x$ and Au/$CeO_x$ on rutile $TiO_2$(110) have been investigated by Scanning Tunneling Microscopy (STM), Photoelectron Spectroscopy (PES), and DFT calculation. In the $CeO_x/TiO_2$(110) systems, the titania substrate imposes on the ceria nanoparticles non-typical coordination modes, favoring a $Ce^{3+}$ oxidation state and enhancing their chemical activity. The deposition of metal on a $CeO_x/TiO_2$(110) substrate generates much smaller nanoparticles with an extremely high activity. We proposed a mechanism that there is a strong coupling of the chemical properties of the admetal and the mixed-metal oxide: The adsorption and dissociation of water probably take place on the oxide, CO adsorbs on the admetal nanoparticles, and all subsequent reaction steps occur at the oxide-admetal interface.

• 공업화학
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• 제18권6호
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• pp.618-624
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• 2007

Cu/Fe/Zr 혼합 산화물 매체 상에서의 2단계 열화학 메탄 개질 반응을 고정층 적외선 반응로를 이용하여 수행했다. 첫 번째 단계에서 금속 산화물은 CO, $H_2$ 및 환원된 금속 산화물을 생성하기 위하여 1173 K의 온도에서 메탄으로 환원되었다. 두번째 단계에서 환원된 금속 산화물은 $H_2$와 금속 산화물을 생성하기 위하여 973 K의 온도에서 재산화되었다. 본 연구에서는 Cu/Fe/Zr 혼합 산화물 내 Cu 첨가량에 따른 반응 특성과 사이클 반응을 평가하였다. Cu/Fe/Zr 혼합 산화물 매체 내 Cu 첨가량 증가에 따라 첫 번째 단계에서 $CH_4$ 전환율, $CO_2$로의 선택성 및 $H_2/CO$ 몰 비는 증가하였으며, CO로의 선택성은 감소하는 경향을 나타냈다. 한편, 두 번째 단계에서 $H_2$ 생성량은 Cu 첨가량 증가에 따라 감소하는 것으로 나타났다. Cu의 첨가량이 x = 0.7인 $Cu_xFe_{3-x}O_4/ZrO_2$ 매체는 내구성이 우수한 매체임을 지시하듯이 10회의 사이클 순환 반응에서 우수한 재생 성능을 나타냈다. 더 나아가 물 분해 단계에서 침적된 탄소의 가스화 반응은 매체 내 Cu 첨가에 의해 촉진되었다.

• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.311-324
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• 2018

Herein,the Neodymium ion ($Nd^{3+}$) doped CoAl-LDH have been successfully prepared via co-precipitation method and was used as a precursor of Nd-doped CoAl-mixed metal oxides (MMO). The photocatalytic activity of doped LDH and MMO was investigated in the degradation of an azo dye, C.I. Acid Red 14, under visible light irradiation. DRS and PL analysis demonstrated decreasing in the band gap energy and recombination of photo-induced charge carriers of Nd-doped LDH and MMO compared with the pristine CoAL-LDH. Due to significant difference in photocatalytic performance. A power law empirical kinetic model was obtained for predicting the photocatalytic degradation efficiency.

• 한국재료학회지
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• 제14권5호
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• pp.322-327
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• 2004

Copper-based leadframe sheets were oxidized in two kinds of hot alkaline solutions to form brown-oxide or black-oxide layer on the surface. The oxide coated leadframe sheets were molded with epoxy molding compound (EMC). After post mold curing, the oxide-coated EMC-leadframe joints were machined to form sandwiched Brazil-nut (SBN) specimens. The SBN specimens were used to measure the fracture toughness of the EMC/leadframe interfaces under mixed-mode (mode I + mode II) loading conditions. Fracture surfaces were analyzed by various equipment to investigate failure path. The results revealed that the failure paths were strongly dependent on the oxide type. In case of brown oxide, hackle-type failure was observed and failure path lay near the EMC/CuO interface with a little inclining to CuO at all case. On the other hand, in case of black oxide, quite different failure path was observed with respect to the distance from the tip of pre-crack and phase angle. Different failures occurred with oxide type is presumed to be due to the difference in microstructure of the oxides.

• Transactions on Electrical and Electronic Materials
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• 제16권5호
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• pp.254-259
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• 2015

This paper reports the optimized mixed-signal performance of a high-voltage (HV) laterally double-diffused metaloxide-semiconductor (LDMOS) field-effect transistor (FET) with a dual gate oxide (DGOX). The fabricated device is based on the split-gate FET concept. In addition, the gate oxide on the source-side channel is thicker than that on the drain-side channel. The experiment results showed that the electrical characteristics are strongly dependent on the source-side channel length with a thick gate oxide. The digital and analog performances according to the source-side channel length of the DGOX LDMOS device were examined for circuit applications. The HV DGOX device with various source-side channel lengths showed reduced by maximum 37% on-resistance (R_ON) and 50% drain conductance (g_ds). Therefore, the optimized mixed-signal performance of the HV DGOX device can be obtained when the source-side channel length with a thick gate oxide is shorter than half of the channel length.

• 청정기술
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• 제16권4호
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• pp.284-291
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• 2010

온실가스로 알려진 $N_2O$의 촉매 분해는 최소한 670 K 이상의 온도가 요구되는 난해한 공정으로 알려져 있다. 본 연구는 CO 환원제와 더불어 473 K의 저온에서도 $N_2O$를 전량 분해될 정도로 높은 활성을 나타내는 혼합금속산화물(mixed metal oxide: MMO) 촉매에 Ce을 첨가함으로서 나타나는 $N_2O$ 분해활성에의 영향을 검토하기 위하여 수행되었다. MMO 촉매는 Co 및 Al 외에 Rh과 Pd을 사용하고, 여기에 Ce을 미량 첨가하여 공침전법으로 제조하였으며, 결과적으로 Ce 함량이 증가함에 따라 촉매 표면적은 감소하고 $N_2O$의 직접분해 활성이 감소하는 현상이 나타났다. 그러나 CO 환원제의 분위기 하에서는 이러한 활성 감소를 상쇄하고도 남을 정도의 높은 $N_2O$ 분해활성을 나타냈으며 Ce 첨가비율에 따른 활성저하도 줄일 수 있어서 MMO 촉매의 물리적 안정성 증대를 위해 Ce을 첨가할 경우 CO 환원제에 의한 $N_2O$ 환원 반응계의 활성 안정성도 유지될 수 있는 것으로 확인되었다.

• 동력기계공학회지
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• 제11권2호
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• pp.44-50
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• 2007

The oxidation behavior of commercial pure titanium is investigated in the temperature range of $727^{\circ}C{\sim}950^{\circ}C$ in mixed gases. The weight change is measured by TGA during oxidation in mixed gases. The oxidation behavior indicated by weight gain or the growth of oxide layer is based on the linear rate law at high temperatures. The structure of the oxide scale formed during oxidation is analysed by optical microscopy, electron probe microanalyzer, scanning electron microscope and x-ray diffraction. Oxide scales have a $TiO_2$ structure, and are constituted with multi-layered or two layered porous external one and a dense internal one. Ti-O solid solution region is formed at the interface of metal and scale layer. The formation of oxide scale is influenced by the oxidation temperature, time, crystal structure and the condition of atmosphere.