• Journal of Sensor Science and Technology
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• v.9 no.6
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• pp.430-439
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• 2000

$In_2O_3$-based thin film sensor with 500-600 nm thick was fabricated for the detection of CO gas by rf magnetron sputtering. In order to improve both sensitivity to CO gas and selectivity to hydrogen gas containing -CH, ultra-thin transition metal Co catalyst was sputtered over $In_2O_3$ thin film and annealed at $500^{\circ}C$. Sensitivity to CO was maximum at the thickness of Co 2.1 nm and $300^{\circ}C$, and that to $C_3H_8$ was at the thickness of Co 1.4 nm and $350-400^{\circ}C$. From the x-ray photoelectron spectroscopy (XPS) result, ultra-thin Co was existed into CoO covered with $Co_2O_3$ on $In_2O_3$ particles, and thus p-n junction of $In_2O_3(n-type)$-CoO(p-type) was thought to be formed. In this p-n junction type sensors, sensing mechanism with reducing gases can be explained by the variation of depletion layer thickness formed in the interface.

• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.128-132
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• 2020

Total organic carbon (TOC) analysis equipment, which was previously used to prevent eutrophication in advance, is heavy, bulky, and expensive; therefore, so it is difficult to be carried and has been used as an experimental unit. In this study, a through-carbon analysis chip that integrates pretreatment through photocatalytic oxidation and carbon dioxide measurement using a pH indicator was investigated. Both the total carbon - inorganic carbon method and the nonpurgeable organic carbon (NPOC) measurement method require an acidification part for injecting an acid solution for inorganic carbon measurement and removal, an oxidation part for total carbon or NPOC oxidation and a measurement part for Carbon dioxide (CO₂) measurement. Among them, the measurement of oxidation and CO₂ requires physical technology. The proposed TOC analysis chip decomposed into CO₂ as a result of the oxidizing of organic carbon using a photocatalyst, and the pH indicator that was changed by the generated CO₂ was optically measured. Although the area of the sample of the oxidation part and the pH indicator of the measurement part were distinguished in an enclosed space, CO₂ was quantified by producing an oxidation part and a measurement part that shared the same air in one chip. The proposed TOC analysis chip is less expensive and smaller, cost and size are disadvantages of existing organic carbon analysis equipment, because it does not require a separate carrier gas to transport the CO₂ gas in the oxidation part to the measurement part.

• Korean journal of food and cookery science
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• v.14 no.5
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• pp.541-546
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• 1998

Volatile flavor components in leaf and petiole of fresh Pleurospermum kamtschaticum H$\_$OFFM/ were extracted by SDE (simultaneous steam distillation and extraction) method using diethyl ether as solvent. Essential oils were analyzed by gas chromatography (GC) and combined gas chromatography-mass spectrometry (GC-MS). Identification of volatile flavor components was based on the Rl of GC and mass spectrum of GC-MS. A total of 31 components, including 15 hydrocarbons, 4 aldehydes, 1 ketone, 5 alcohols, 2 esters, 3 acids and 1 oxide were identified in the essential oils. (Z)-${\beta}$-Farnesene, (Z, E)-${\alpha}$-farnesene and farnesene were the major volatile flavor components in fresh Pleurospermum kamtschaticum. Volatile flavor patterns of Pleurospermum kamtschaticum were analyzed using electronic nose. Sensor T30/1 and PA2 that were sensitive to alcohols had the highest resistance for fresh Pleurospermum kamtschaticum. Resistance of six metal oxide sensors was decreased in dried sample compared with fresh one.

• 한국연소학회:학술대회논문집
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• 2000.12a
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• pp.168-174
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• 2000

A diode laser sensor system based on absorption spectroscopy techniques has been developed to measure $CO_2$ concentration and temperature non-intrusively in high temperature combustion environments using a 2.0 ${\mu}m$ DFB(Distributed Feedback) laser. Two optics was fabricated in pig-tail fashion and all optical components were implemented in a single box. The evolution of measurement sensitivity was done using test cell by changing sweep frequency and $CO_2$ concentration. Gas temperature was determined from the ratio of integrated line strengths. Species concentration was determined from the integrated line intensity and the measured temperature. The result show that the system has 2% error in wide operation frequency range and accuracy of $CO_2$ concentration was about 3%. The system was applied to measure temperature and concentration in the combustion region of a premixed $CH_4$ +air triangular flame. The measurement results of gas temperature agreed well with thermocouple results. Many considerations were taken into account to reduce optical noise, etalon effect, beam steering and base line matching problem. The evaluations results and actual combustion measurement demonstrate the practical and applicability for in-situ and real time combustion monitoring in a practical system.

• Korean Journal of Materials Research
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• v.26 no.4
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• pp.187-193
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• 2016

Fabrication of iron oxide/carbon nanotube composite structures for detection of ammonia gas at room temperature is reported. The iron oxide/carbon nanotube composite structures are fabricated by in situ co-arc-discharge method using a graphite source with varying numbers of iron wires inserted. The composite structures reveal higher response signals at room temperature than at high temperatures. As the number of iron wires inserted increased, the volume of carbon nanotubes and iron nanoparticles produced increased. The oxidation condition of the composite structures varied the carbon nanotube/iron oxide ratio in the structure and, consequently, the resistance of the structures and, finally, the ammonia gas sensing performance. The highest sensor performance was realized with $500^{\circ}C/2h$ oxidation heat-treatment condition, in which most of the carbon nanotubes were removed from the composite and iron oxide played the main role of ammonia sensing. The response signal level was 62% at room temperature. We also found that UV irradiation enhances the sensing response with reduced recovery time.

• Journal of Sensor Science and Technology
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• v.7 no.5
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• pp.327-333
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• 1998

A new human sensibility (kansei) meter that can measure human sensibility at the indoor environment is developed in this paper. Four sensors that can measure temperature, humidity, $CO_2$ and $C_4H_{10}$ concentrations are used. Among these sensors, the first three are used to determine the human sensibility. And the last to protect human from the harmful gas. First of all, human sensibilities are defined for each sensor datum, and then those are linearly combined to make a final human sensibility (kansei). The efficiency and usefulness of the meter are verified using a simulator on Windows 95 and a stand-alone system constructed using a microprocessor.

• Journal of Sensor Science and Technology
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• v.5 no.1
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• pp.63-70
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• 1996

Silicon epitaxial films of submicron level were successfully grown by the RTCVD method. For the growth of silicon epitaxial layers, $SiH_{2}Cl_{2}\;/\;H_{2}$ gas mixtures and various process parameters including $H_{2}$ prebake process were used. The growth conditions were varied to investigate their effects on the interface abruptness of doping profile, the film growth rates and crystalline properties. The crystallinity of the undoped silicon was excellent at the growth temperature of $900^{\circ}C$. The doping profiles were measured by SIMS technique. The abruptness of doping profile would be controlled within about $200{\AA}/decade$ in the structure of undoped Si / $n^{+}-Si$ substrate.

• Journal of Sensor Science and Technology
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• v.17 no.2
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• pp.143-146
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• 2008

Polymer-coated film SAW sensors have been fabricated and their sensing properties for toxic chemicals have been extensively investigated. Four types of the toxic chemical compounds of hydrogen cyanide(AC), carbonyl dichloride(CG), pinacolyl methylfluorophosphonate(GD), 2,2'-dichlorodiethylthio ether(HD) were used as target gases. SAW sensors using five different kinds of polymers were used to detect toxic chemicals and their gas sensing characteristics were investigated. The polymers used as the sensing materials were polyisobutylene(PIB), polyepichlorohydrin(PECH), polydimethylsiloxane(PDMS), polybutadiene(PBD) and polyisoprene(PIP). The recommendable mixing ratio of PIB, PECH, PDMS, PBD and PIP to solvents were 1:30, 1:40, 1:10, 1:30 and 1:30, respectively. The sensing characteristics of the SAW sensors were measured by using E-5061A network analyzer.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.222-227
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• 2018

$Zn_{1-x}Co_x$ Zeolitic Imidazolate Framework (ZIF) (x = 0~0.05) were prepared by the co-precipitation of $Zn^{2+}$ and $Co^{2+}$ using 2-methylimidazole, which were converted into pure and Co-doped ZnO nanoparticles by heat treatment at $600^{\circ}C$ for 2 h. Homogeneous Zn/Co ZIFs were achieved at x < 0.05 owing to the strong coordination of the imidazole linker to $Zn^{2+}$ and $Co^{2+}$, facilitating atomic-scale doping of Co into ZnO via annealing. By contrast, heterogeneous Zn/Co ZIFs were formed at $x{\geq}0.05$, resulting in the formation of $Co_3O_4$ second phase. To investigate the potential as high-performance gas sensors, the gas sensing characteristics of pure and Co-doped ZnO nanoparticles were evaluated. The sensor using 3 at% Co-doped ZnO exhibited an unprecedentedly high response and selectivity to trimethylamine, whereas pure ZnO nanoparticles did not. The facile, bimetallic ZIF derived synthesis of doped-metal oxide nanoparticles can be used to design high-performance gas sensors.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.2
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• pp.21-26
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• 2015

Mesoporous ceramic materials were applied in various fields such as adsorbent and gas sensor because of low thermal conductivity and high specific surface area properties. This structure could be divided into open-pore structure and closed-pore structure. Although closed-pore structure mesoporous ceramic materials have higher mechanical property than open-pore structure, it has a restriction on the application because the increase of specific surface area is limited. So, in this work, specific surface area of closed-pore structure $TiO_2$ was increased by anneal time. As increased annealing time, crystallization and grain growth of $TiO_2$ skeleton structured material in mesoporous structure induced a collapse and agglomeration of pores. Through this pore structural change, pore connectivity and specific surface area could be enhanced. After anneal for 24 hrs, porosity was decreased from 36.3% to 34.1%, but specific surface area was increased from $48m^2/g$ to $156m^2/g$. CO gas sensitivity was also increased by about 7.4 times due to an increase of specific surface area.