• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.49-55
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• 1997

Destruction phenomena of structure by gas explosion is due to the explosion pressure and heat. Explosion pressure is a kind of energy converted from the gas mixture explosion. In this paper, we tried to find the relationship between explosion characteristics and combustion heat of the hydrocarbon-oxygen mixtures. Experiment were carried out with the volume of $5916cm^3$ cylindrical explosion vessel. Hydrocarbon gases which used in this study were methane, ethylene, propane, and buthane Experimental parameter was the concentration of the gas mixtures. Explosion characteristics were measured with strain type pressure transducer through the digital storage oscilloscope. From the experimental result, it was found that explosion pressure depend upon the combustion heat.

• Journal of Sensor Science and Technology
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• v.5 no.2
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• pp.21-27
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• 1996

Thick film $TiO_{2}/WO_{3}$ butane gas sensors were fabricated by the screen printing method and their gas sensing characteristics were investigated. The sensitivity of $TiO_{2}/WO_{3}$ thick film was higher than that of pure $WO_{3}$ film to butane. The $WO_{3}$ film with 2wt.% $TiO_{2}$ showed the highest sensitivity to butane. And the optimum heat treatment temperature was $650^{\circ}C$. That film showed the highest sensitivity to butane at the operating temperature of $350^{\circ}C$. The sensitivity of the film to 20000ppm butane in air was 80% at the operating temperature of $350^{\circ}C$.

• Journal of Sensor Science and Technology
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• v.6 no.6
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• pp.476-482
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• 1997

A portable electronic nose system has been fabricated and characterized using an oxide semiconductor gas sensor array and pattern recognition techniques such as principal component analysis and back-propagation artificial neural network. The sensor array consists of six thick-film gas sensors whose sensing layers are Pd-doped $WO_{3}$, Pt-doped $SnO_{2}$, $TiO_{2}-Sb_{2}O_{5}-Pd$-doped $SnO_{2}$, $TiO_{2}-Sb_{2}O_{5}-Pd$-doped $SnO_{2}$ + Pd coated layer, $Al_{2}O_{3}$-doped ZnO and $PdCl_{2}$-doped $SnO_{2}$. The portable electronic nose system consists of an 16bit Intel 80c196kc as CPU, an EPROM for storing system main program, an EEPROM for containing optimized connection weights of artificial neural network, an LCD for displaying gas concentrations. As an application the system has been used to identify 26 carbon monoxide/hydrocarbon (CO/HC) car exhausting gases in the concentration range of CO 0%/HC 0 ppm to CO 7.6%/HC 400 ppm and the identification has been successfully demonstrated.

• Journal of the Korean Wood Science and Technology
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• v.34 no.4
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• pp.22-30
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• 2006

The volatile organic compound (VOC) Analyzer is a portable device to measure the four main aromatic hydrocarbon gases: toluene, ethylbenzene, xylene and styrene. With the VOC Analyzer, a semiconductor gas sensor eliminates the need for the carrier gas which is required for conventional gas chromatographs. In addition, since the semiconductor gas sensor is supersensitive to gas components, it is not necessary to use a conventional gas concentrator or other complicated equipment. Compared with other measurement methods, the VOC analyzer is useful for measuring toluene, ethylbenzene, xylene and styrene in wood-based panel because of its ease in obtaining field results and repeating the test. The VOC Analyzer primarily measures four VOC in the air. In this study, we designed a test method of VOC measurement for particle board. A specimen was sealed in 3L polyester bag, after 96hours we could measure maximum VOC emission level that is a stabilized VOC Value. For easy, fast and economic testing of TVOC emission from wood-based panel, we developed the test method with the VOC Analyzer. The VOC Analyzer is expected to gain widespread use in the manufacturing field where a quick and easy test for VOC emission from wood-based panel is required. Furthermore, the VOC Analyzer promises to become an easier, faster and more economic technique than the currently used standard methods.

• Korean Journal of Materials Research
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• v.21 no.9
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• pp.486-490
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• 2011

Nano-indium-coated ZnO:In thick films were prepared by a hydrothermal method. ZnO:In gas sensors were fabricated by a screen printing method on alumina substrates. The gas sensing properties of the gas sensors were investigated for hydrocarbon gas. The effects of the indium concentration of the ZnO:In gas sensors on the structural and morphological properties were investigated by X-ray diffraction and scanning electron microscopy. XRD patterns revealed that the ZnO:In with wurtzite structure was grown with (1 0 0), (0 0 2), and (1 0 1) peaks. The quantity of In coating on the ZnO surface increased with increasing In concentration. The sensitivity of the ZnO:In sensors was measured for 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity to $CH_4$ gas and $CH_3CH_2CH_3$ gas of the ZnO:In sensors was observed at the In 6 wt%. The response and recovery times of the 6 wt% indiumcoated ZnO:In gas sensors were 19 s and 12 s, respectively.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.23.1-23.1
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• 2010

Alkanethiol (CH3(CH2)nSH) 자기 조립 박막은 금, 은, 팔라듐 그리고 구리와 같은 금속 물질과 결합하여 산화 방지 보호막, 생화학적 멤브레인 그리고 케미컬 센서로 널리 이용되었다. 전도성을 가진 많은 금속 분말 중에서, 구리는 뛰어난 열, 전기 전도성과 풍부한 양으로 다른 귀금속에 비교하여 경제성까지 갖춘 물질이다. 그러나 이러한 구리 나노 분말은 대기에 노출된 구리 분말이 쉽게 산화된다는 결정적인 단점 때문에 그동안 널리 이용되지 못하였다. 이러한 구리의 단점을 극복하고 뛰어난 전도성의 특징을 이용하고자, Langmuir-Blodgett (LB), layer by layer (LbL), electrophoretic deposition (EPD), self-assembled monolayer (SAM)과 같은 구리 나노 분말 위에 유기 박막을 형성하고자 하는 많은 방법이 시도되어왔다. 이러한 방법들 대부분은 습식 방법으로 진행되었으며, 약 2-nm 두께의 SAM 구조를 형성할 수 있음이 많은 연구를 통하여 확인되었다. 그러나 습식 기반의 SAM 구조는 단지 수일 동안만 유효하며, 이는 코팅을 수행하면서 점차 떨어지는 source solvent의 순도와 적합하지 않은 코팅 조건, 그리고 이러한 원인으로 형성된 부실한 막질 구조 때문으로 추측된다. 게다가 이러한 습식 기반 공정은 코팅 막의 두께 조절과 코팅 시 solvent의 순도를 일정하게 유지하는 것이 매우 복잡하고 어려운 작업으로 알려져 왔다. 본 실험에서는 고 진공 챔버 (< $4.0{\times}10-6$ torr) 시스템을 이용하여 습식 기반 공정의 문제점을 극복하고 구리 나노 분말의 산화를 막기 위한 실험을 진행하였다. 1-octanethiol (CH3(CH2)7SH)은 중간 길이의 hydrocarbon (n=7) 구조를 가진 특징 때문에 코팅 물질로 사용되었다. 게다가, alkanethiol 족 특유의 물질인 황(sulfur)은 구리와 결합하여 산화방지 보호막의 역할을 수행할 수 있다. 저 진공 조건에서는 10-nm의 multilayer가 일괄적으로 코팅됨을 확인할 수 있었다. 본 실험에서는 약 10-nm 두께의 자기 조립 박막(self assembled monolayers: SAMs)이 고 진공 조건에서 구리 나노 분말 표면 위에 코팅 조건의 변경을 통해서 5-nm에서 10-nm 두께의 1-octanethiol SAMs 구조를 얻어낼 수 있었다. 이는 고 진공 조건에서 1-octanethiol SAMs의 코팅 두께를 조절함으로 다양한 크기의 분말에 코팅 물질로 쓰일 수 있음을 알 수 있다.

• Korean Journal of Materials Research
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• v.23 no.4
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• pp.211-214
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• 2013

The effects of a Ni coating on the sensing properties of nano ZnO:Ni based gas sensors were studied for $CH_4$ and $CH_3CH_2CH_3$ gases. Nano ZnO sensing materials were prepared by the hydrothermal reaction method. The Ni coatings on the nano ZnO surface were deposited by the hydrolysis of zinc chloride with $NH_4OH$. The weight % of Ni coating on the ZnO surface ranged from 0 to 10 %. The nano ZnO:Ni gas sensors were fabricated by a screen printing method on alumina substrates. The structural and morphological properties of the nano ZnO : Ni sensing materials were investigated by XRD, EDS, and SEM. The XRD patterns showed that nano ZnO : Ni powders with a wurtzite structure were grown with (1 0 0), (0 0 2), and (1 0 1) dominant peaks. The particle size of nano ZnO powders was about 250 nm. The sensitivity of nano ZnO:Ni based sensors for 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas was measured at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity of the ZnO:Ni sensor to $CH_4$ gas and $CH_3CH_2CH_3$ gas was observed at Ni 4 wt%. The response and recovery times of 4 wt% Ni coated ZnO:Ni gas sensors were 14 s and 15 s, respectively.

• Korean Journal of Materials Research
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• v.22 no.7
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• pp.358-361
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• 2012

Co and Ni as catalysts in $SnO_2$ sensors to improve the sensitivity for $CH_4$ gas and $CH_3CH_2CH_3$ gas were coated by a solution reduction method. $SnO_2$ thick films were prepared by a screen-printing method onto $Al_2O_3$ substrates with an electrode. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a chamber. The structural properties of $SnO_2$ with a rutile structure investigated by XRD showed a (110) dominant $SnO_2$ peak. The particle size of the $SnO_2$:Ni powders with Ni at 6 wt% was about 0.1 ${\mu}m$. The $SnO_2$ particles were found to contain many pores according to a SEM analysis. The sensitivity of $SnO_2$-based sensors was measured for 5 ppm of $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air to that in the target gases. The results showed that the best sensitivity of $SnO_2$:Ni and $SnO_2$:Co sensors for $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature was observed in $SnO_2$:Ni sensors coated with 6 wt% Ni. The $SnO_2$:Ni gas sensors showed good selectivity to $CH_4$ gas. The response time and recovery time of the $SnO_2$:Ni gas sensors for the $CH_4$ and $CH_3CH_2CH_3$ gases were 20 seconds and 9 seconds, respectively.

• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.65-72
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• 2007

The VOC (volatile organic compound) analyzer is devised to measure the four main aromatic hydrocarbon gases: toluene, ethylbenzene, xylene and styfene. It is not affected by ambient temperature and humidity. In addition, standby and measuring time of VOC Analyzer is a short as below 30 min and 8 min, respectively. Since the semiconductor gas sensor is supersensitive to gas components, it is not necessary to use a conventional gas concentrator or other complicated equipment. In this study, VOC emission behavior from 4 types paints (lacquer, urethane vanish, water-base paint, enamel paint) for wood-based panel was investigated using VOC Analyzer. After a specimen was spreaded on aluminum foil ($6.32{\times}6.32cm$) in $3{\ell}$ polyester bag, after 24 hours we could measure maximum VOC emission level that is a stabilized VOC value. Xylene of VOCs was high emitted from lacquer, urethane vanish and water-based paint, and TVOC (Toluene + Ethylbenzene + Xylene + Styrene) of lacquer was the highest emission concentration than another.