• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.404-405
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• 2008

In this work, we investigated the effect of the functionalized SWNT-polymer composites for increasing sensitivity and imparting selectivity to nanotube sensors. To do this, CNT -based gas sensors were fabricated with two types of dispersed SWNT solution involving different polymer resin of TEOS (Tetraethyl orthosilicate) or MTMS (Methyl trimethoxysilane) which is blended to adhere to substrate well. As the surfaces of TEOS and MTMS surrounding SWNTs remain functionalized to -OH and $-CH_3$ groups respectively after hardening, gas adsorption will be affected differently according to the type of gases. In the experiment, we examined the response of electrical conductance for alcohol vapour gas. As the result, the conductance in the sensors using TEOS decreased considerably while that of MTMS was nearly invariable.

• 한국전기전자재료학회논문지
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• 제21권9호
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• pp.783-788
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• 2008

We suggest a CNT-based gas sensor for breath alcohol measurement. The sensor was composed of single-walled carbon nanotubes (SWCNTs) thin film on flexible PES (polyethersulfone) substrate, and the SWCNTs thin film was formed by multiple spray-coating with SWCNTs solution which was well-dispersed, highly controlled and functionalized in ethanol solvent. In this work, three types of SWCNTs thin films were deposited with changes in the number of spray-coatings to 20, 40 and 60 times in order to compare electrical response properties of the SWCNTs thin films. from the fabricated sensors, conductance and capacitance responses were measured and discussed. Alcohol gas sensors have been commercialized widely as gauge for breath alcohol measurement which is applicable to checking whether car drivers are drinking-driving or not. Our alcohol gas sensors showed good sensitivity and linearity even at room temperature.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.368-371
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• 2003

The humidity sensors with a stable characteristics and gas sensors operating at room temperature have been fabricated, and a multi-functional sensor system which has gas sensor, humidity sensor, temperature sensor and control circuit has been applied to the microwave oven system. For a suitable cooking state, the humidity sensors was more applicable to heating and defrosting condition than gas sensors, however, the dynamic characteristics of gas sensors were obtained in the easy burning food such as pop corn.

• 한국전기전자재료학회논문지
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• 제22권12호
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• pp.1089-1094
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• 2009

Carbon nanotubes (CNTs) have excellent electrical, chemical stability, mechanical and thermal properties. In this paper, networks of Multi-walled carbon nanotube (MWCNT) materials were investigated as resistive gas sensors for ethanol ($C_2H_5OH$) detection. Sensor films were fabricated by air spray method for the multi-walled CNTs solution on glass substrates. Sensors were characterized by resistance measurements in the sensing system, in order to find the optimum detection properties for the ethanol gas molecular. The film that was sprayed with the MWCNT dispersion for 60 see, was 300 nm thick. And the electric resistivity is $2{\times}10^{-2}\;{\Omega\cdot}cm$. Also, the sensitivity and the linearity of MWVNT sensor for ethanol gas are 0.389 %/sec and 17.541 %/FS, respectively. The MWCNT film was excellent in the response for the ethanol gas molecules and its reaction speed was very fast, which could be using as ethanol gas sensor. The conductance of the fabricated sensors decreases when the sensors are exposed to ethanol gas.

• 센서학회지
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• 제32권1호
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• pp.55-61
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• 2023

The objective of this study is to determine the concentrations of mixed gases by establishing a diagnosis method of a transformer using tunable-wavelength optical infrared sensors. Absorption of infrared light by methane, acetylene, and ethylene gases injected is measured from the outputs of the infrared sensors. Regression analysis equations of the gas concentrations are acquired from their respective measured absorption. The obtained concentrations are as follows: -3-9 % errors above 600 ppm(methane), 3 % errors above 1200 ppm(acetylene), and 10 % errors above 500 ppm(ethylene). The concentration inference equations obtained using the individual gases are applicable when the absorption wavelength bands do not overlap. The results of the fault analysis of a transformer using the Duval triangle method and the tunable infrared gas sensors are as follows: temperature faults with -1-1% errors and energy faults with -7-7 % errors.

• 한국재료학회지
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• 제21권9호
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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.

• 한국재료학회지
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• 제20권5호
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• pp.267-270
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• 2010

Sn doped $In_2O_3$ (ITO) and ITO/Cu/ITO (ICI) multilayer films were prepared on glass substrates with a reactive radio frequency (RF) magnetron sputter without intentional substrate heating, and then the influence of the Cu interlayer on the methanol gas sensitivity of the ICI films were considered. Although both ITO and ICI film sensors had the same thickness of 100 nm, the ICI sensors had a sandwich structure of ITO 50 nm/Cu 5 nm/ITO 45 nm. The ICI films showed a ten times higher carrier density than that of the pure ITO films. However, the Cu interlayer may also have caused the decrement of carrier mobility because the interfaces between the ITO and Cu interlayer acted as a barrier to carrier movement. Although the ICI films had two times a lower mobility than that of the pure ITO films, the ICI films had a higher conductivity of $3.6{\cdot}10^{-4}\;{\Omega}cm$ due to a higher carrier density. The changes in the sensitivity of the film sensors caused by methanol gas ranging from 50 to 500 ppm were measured at room temperature. The ICI sensors showed a higher gas sensitivity than that of the ITO single layer sensors. Finally, it can be concluded that the ICI film sensors have the potential to be used as improved methanol gas sensors.

• Design & Manufacturing
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• 제16권1호
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• pp.15-20
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• 2022

This paper is about elimination the situation in which gas sensor data becomes inaccurate due to temperature control when a semiconductor gas sensor is driven. Recently, interest in semiconductor gas sensors is high because semiconductor sensors can be driven with small and low power. Although semiconductor-type gas sensors have various advantages, there is a problem that they must operate at high temperatures. First temperature control was configured to adjust the temperature value of the heater mounted on the gas sensor. At that time, in controlling the heater temperature, gas sensor data are fluctuated despite supplying same gas concentration according to the temperature controlled. To resolve this problem, gas and temperature are extracted as a data. And then, a relation function is constructed between gas and temperature data. At this time, it is included low pass filter to get the stable data. In this paper, we can find optimal gain and parameters between gas and temperature data by using genetic algorithm.

• 한국재료학회지
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• 제25권4호
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• pp.171-176
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• 2015

We present the detection characteristics of nitrogen monoxide(NO) gas using p-type copper oxide(CuO) thin film gas sensors. The CuO thin films were fabricated on glass substrates by a sol-gel spin coating method using copper acetate hydrate and diethanolamine as precursors. Structural characterizations revealed that we prepared the pure CuO thin films having a monoclinic crystalline structure without any obvious formation of secondary phase. It was found from the NO gas sensing measurements that the p-type CuO thin film gas sensors exhibited a maximum sensitivity to NO gas in dry air at an operating temperature as low as $100^{\circ}C$. Additionally, these CuO thin film gas sensors were found to show reversible and reliable electrical response to NO gas in a range of operating temperatures from $60^{\circ}C$ to $200^{\circ}C$. It is supposed from these results that the p-type oxide semiconductor CuO thin film could have significant potential for use in future gas sensors and other oxide electronics applications using oxide p-n heterojunction structures.

• 센서학회지
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• 제22권3호
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• pp.197-201
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• 2013

This paper describes the fabrication and characterization of graphene based carbon dioxide ($CO_2$) gas sensors. Graphene was synthesized by thermal decomposition of SiC. The resistivity $CO_2$ gas sensors were fabricated by pure graphene and graphene decorated Au nanoparticles (NPs). The Au NPs with size of 10 nm were decorated on graphene. Au electrode deposited on the graphene showed Ohmic contact and the sensors resistance changed following to various $CO_2$ concentrations. Resulting in resistance sensor using pure graphene can detect minimum of 100 ppm $CO_2$ concentration at $50^{\circ}C$, whereas Au/graphene can detect minimum 2 ppm $CO_2$ concentration at same at $50^{\circ}C$. Moreover, Au NPs catalyst improved the sensitivity of the graphene based $CO_2$ sensors. The responses of pure graphene and Au/graphene are 0.04% and 0.24%, respectively, at $50^{\circ}C$ with 500 ppm $CO_2$ concentration. The optimum working temperature of $CO_2$ sensors is at $75^{\circ}C$.