• 센서학회지
• /
• 제31권5호
• /
• pp.343-347
• /
• 2022

Recently, the problem of global warming caused by greenhouse gases is getting serious due to the development of industry and the increase in transportation means. Accordingly, the need for a technology to reduce carbon dioxide, which accounts for most of the greenhouse gas, is increasing. Among them, a catalyst for converting carbon dioxide into fuel is being actively studied. Catalysts for reducing carbon dioxide are classified into thermal catalysts and photocatalysts. In particular, the photocatalyst has the advantage that carbon dioxide can be reduced only by irradiating ultraviolet rays at room temperature without high temperature or additional gas. TiO₂ is widely used as a photocatalyst because it is non-toxic and has high stability, but has a disadvantage of low carbon dioxide reduction efficiency. To increase the reduction efficiency, 1-propanol was used in the synthesis process. This prevents agglomeration of the catalyst and increases the specific surface area and pores of TiO₂, thereby increasing the surface area in contact with carbon dioxide. As a result of measuring the CO₂ reduction efficiency, it was confirmed that the efficiency of TiO₂ with 1-propanol and TiO₂ without 1-propanol was 19% and 12.3%, respectively, and the former showed a 1.5 times improved efficiency.

• 센서학회지
• /
• 제24권6호
• /
• pp.379-384
• /
• 2015

An infrared image sensor is a core device in a thermal imaging system. The fabrication method of a focal plane array (FPA) is a key technology for a high resolution infrared image sensor. Each pixels in the FPA have $Si_3N_4/SiO_2$ membranes including legs to deposit bolometric materials and electrodes on Si readout circuits (ROIC). Instead of polyimide used to form a sacrificial layer, the feasibility of an amorphous silicon (${\alpha}-Si$) was verified experimentally in a $8{\times}8$ micro-bolometer array with a $50{\mu}m$ pitch. The elimination of the polyimide sacrificial layer hardened by a following plasma assisted deposition process is sometimes far from perfect, and thus requires longer plasma ashing times leading to the deformation of the membrane and leg. Since the amorphous Si could be removed in $XeF_2$ gas at room temperature, however, the fabricated micro-bolomertic structure was not damaged seriously. A radio frequency (RF) sputtered nickel oxide film was grown on a $Si_3N_4/SiO_2$ membrane fabricated using a low stress silicon nitride (LSSiN) technology with a LPCVD system. The deformation of the membrane was effectively reduced by a combining the ${\alpha}-Si$ and LSSiN process for a nickel oxide micro-bolometer.

• 센서학회지
• /
• 제9권2호
• /
• pp.146-152
• /
• 2000

고주파 마그네트론 스퍼터링법으로 Li이 도핑된 ZnO(ZnO:Li) 박막을 코닝 7059 글라스 기판상에 증착하였다. 도핑량은 스퍼터링용 ZnO타겟내의 $Li_2CO_3$의 첨가량을 달리하여 조절하였다. 타겟내의 $Li_2CO_3$의 첨가량에 따른 구조적 특성을 XRD, AFM 및 SEM으로 조사하였으며 기판온도, 고주파출력 및 $O_2/Ar$ 가스비에 따른 Li이 도핑된 ZnO박막의 전기적 특성을 조사하였다. 타겟내의 $Li_2CO_3$의 첨가량과 증착조건이 막의 구조적 및 전기적 특성에 미치는 영향을 조사하였다. $Li_2CO_3$의 첨가량이 1wt%이하인 타겟으로 기판온도 $200^{\circ}C$, $O_2$/Ar 가스비 100%, 고주파 출력 100W에서 스퍼터된 ZnO:Li 박막이 표면거칠기가 낮은 우수한 표면형상, 강한 c-축 우선배향성 및 $10^8{\Omega}cm$ 이상의 큰 비저항을 보였다.

• 한국응용과학기술학회지
• /
• 제12권1호
• /
• pp.125-131
• /
• 1995

Ultra thin films of Tetra-3-hexadecylsulphamoylcopperphthalocyanine(HDSM-CuPc) were formed on various substrates by Langmuir-Blodgett method, where HDSM-CuPc was synthesized by attaching long-chain alkylamine(hexa-decylamine) to CuPc. The reaction product was identified with FT-IR, UV-visible absorption spectroscopies, elemental analysis and thin layer chromatography. The formation of Ultrathin Langmuir-Blodgett(LB) films of HDSM-CuPc was confirmed by FT-IR and UV-visible spectroscopies. A quartz piezoelectric crystal coated with LB films of HDSM-CuPc was examined as a gas sensor for $N0_2$ gas. HDSM-CuPc LB films were transferred to a quartz crystal microbalance(QCM) in the form of Z-type multilayers. Response characteristics of film-coated QCM to $NO_2$ gas concentrations over a range of $100{\sim}600ppm$ have been tested with a thickness of $5{\sim}20$ layers of HDSM-CuPc. Changes in frequency by adsorption of $NO_2$ were increased With the number of LB layers and $NO_2$ concentration, but the response time was slow.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.416-417
• /
• 2006

Nanostructured ceria powder was synthesized by a thermochemical process and investigated its applicability for an oxygen gas sensor. An amorphous precursor powders prepared by spray drying a cerium-nitrate solution were transformed successfully into nanostructured ceria by heat-treatment in air atmosphere. The powders were a loose agglomerated structure with extremely fine $CeO_2$ particles about 15 nm in size, resulting in a very high specific surface area $(110\;m^2/g)$. The oxygen sensitivity and the response time $t_{90}$ measured at sintered sample at $1000^{\circ}C$ was about -0.25 and very short, i.e., $3{\sim}5$ seconds, respectively.

• 전기화학회지
• /
• 제2권3호
• /
• pp.130-133
• /
• 1999

본 연구에서는 음주 측정에 적용할 수 있는 다공질 실리콘층으로 된 저농도의 캐퍼시턴스형 알코올 가스 측정용 센서를 제작하고, 상온에서 그 특성을 측정하였다. 기존의 $SnO_2$등의 금속 산화물 반도체를 이용한 센서는 저농도의 알코올을 정확하게 검지하기에 어려울 뿐만 아니라 감도를 높이기 위해 $200\~400^{\circ}C$로 가열이 필요하였다. 이에 비해 다공질 실리콘층을 이용한 센서는 넓은 표면적을 갖고 있어 상온에서도 감도가 양호할 뿐만 아니라 집적화 센서로 제작이 용이한 점을 갖고 있다. 실험은 증류수에 희석한 알코올 수용액을 체온과 같은 $36^{\circ}C$를 비롯하여 25와 $45^{\circ}C$로 유지한 상태에서 0에서 $0.5\%$의 농도범위에 대해서 $0.05\%$의 간격으로 120 Hz와 1 kHz의 두 주파수에서 측정하였다. 그 결과, 양호한 선형성과 함께 120 Hz의 주파수에서 측정하였을 때, $0.1\%$의 알코올 농도의 증분마다 $25,\;36,\;45^{\circ}C$의 알코올 수용액의 온도에 대해 각각 1.1, 2.6 및 $4.6\%$로 캐퍼시턴스의 증가율을 보였다.

• 한국산학기술학회논문지
• /
• 제20권5호
• /
• pp.81-86
• /
• 2019

금속산화물/그래핀 복합체는 고감도 가스센서 및 고용량의 이차전지와 같은 첨단 응용 분야에 활용될 수 있는 유망한 기능성 소재로 알려져 있다. 본 연구에서는 이산화주석($SnO_2$) 나노구조물을 두 영역 전기로 장치를 이용하여 화학적으로 합성된 그래핀 나노시트 위에 성장시켰다. 대면적의 그래핀 나노시트는 Cu foil 위에 열화학기상증착 장비를 이용하여 메탄가스와 수소가스로 합성하였다. 화학적으로 합성된 그래핀 나노시트는 PMMA를 이용하여 세척된 Si 기판위에 전사시켰고, $SnO_2$ 나노구조물은 그래핀 나노시트 위에 $424^{\circ}C$, 3.1 Torr 조건에서 3시간동안 성장시켰다. 합성된 그래핀의 품질과 성장된 $SnO_2$ 나노구조물의 결정학적 특성을 Raman 분광학으로 확인하였다. 그래핀 위에서 성장된 $SnO_2$ 나노구조물의 표면형상은 전계방출 주사전자현미경으로 조사하였다. 그 결과 합성된 그래핀 나노시트는 이중층 그래핀이었고, 그래핀 위에서 성장된 산화주석은 $SnO_2$ 상을 가지고 있었다. 그래핀 위에서 성장된 $SnO_2$ 나노구조물은 복잡한 표면형상을 나타내었는데, 이것은 Si 기판 위에서 성장된 $SnO_2$ 나노구조물이 nano-dots 형태인 것과 비교된다. 그래핀 위에서 성장된 $SnO_2$ 나노구조물이 복잡한 형상을 갖는 것은 그래핀 표면의 기능기의 영향인 것으로 판단된다.

• 열처리공학회지
• /
• 제23권5호
• /
• pp.245-248
• /
• 2010

Sn doped $In_2O_3$ (ITO) and ITO/Ni/ITO (INI) multilayer films were deposited on the glass substrates with a reactive magnetron sputtering system without intentional substrate heating and then the influence of the Ni interlayer on the methanol gas sensitivity of ITO and INI film sensors were investigated. Although both ITO and INI film sensors have the same thickness of 100 nm, INI sensors have a sandwich structure of ITO 50 nm/Ni 5 nm/ITO 45 nm. The changes in the gas sensitivity of the film sensors caused by methanol gas ranging from 100 to 1000 ppm were measured. It is observed that the INI film sensors show the higher sensitivity than that of the ITO single layer sensors. Finally, it can be concluded that the INI film sensor have the potential to be used as improved methanol gas sensors.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
• /
• pp.802-806
• /
• 2004

For the protection of the local air quality and the global atmosphere, the emissions of trace species including nitric oxides (NO and NO$_2$) from gas turbines are regulated by local governments and by the International Civil Aviation Organization. In-situ measurements of such species are needed not only for the development of advanced low-emission combustion concepts but also for providing emissions data required for the sound assessment of the effects of the emissions on environment. We have been developing a laser absorption system that has a capability of simultaneous determination of NO and NO$_2$concentrations in the exhaust jets from aero gas turbines. A diode laser operating near 1.8 micrometer is used for the detection of NO while a separated visible tunable diode laser operating near 676 nanometers is used for NO$_2$. The sensitivities at elevated temperature conditions were determined for simulated gas mixtures heated up to 500K in a heated cell of a straight 0.5 m optical path. Sensitivity limits estimated as were 30 ppmv-m and 3.7 ppmv-m for NO and NO$_2$, respectively, at a typical exhaust gas temperature of 800K. Experiments using the simulated exhaust flows have proven that $CO_2$ and $H_2O$ vapor - both major combustion products - do not show any interference in the NO or NO$_2$ measurements. The measurement system has been applied to the NO/NO$_2$ measurements in NO and NO$_2$ doped real combustion gas jets issuing from a rectangular nozzle having 0.4 m optical path. The lower detection limits of the system were considerably decreased by using a multipass optical cell. A pair of off-axis parabola mirrors successfully suppressed the beam steering in the combustion gas jets by centralizing the fluctuating beam in sensor area of the detectors.

• Journal of Microbiology and Biotechnology
• /
• 제14권5호
• /
• pp.991-995
• /
• 2004

Immobilized sensor spots were applied for online measurement of dissolved $O_2$, in test tubes. Oxygen transport was quantified at varied shaking frequency and filling volumes. The k$_{L}$ a increased with increasing shaking frequency and decreasing filling volume. In non-baffled tubes the maximum $k_{L}a$ value was $70h^{-1}$, equivalent to a maximum $O_2$ transfer capacity of 15mMh^{-1}$. Monitoring of the hydrodynamic profile revealed that the liquid bulk rotated inside the tube with an inclined liquid surface, whereby the angle between the surface and tube wall increased with increasing shaking frequency. The $k_{L}a$ clearly correlated to the surface area. Placement of four baffles into the tubes improved the oxygen transfer up to 3-fold. The highest increase in $k_{L}a$ was observed at high filling volume and high shaking frequency. The maximum $k_{L}a$ in baffled tubes was $100 h^{-1}$.