• Macromolecular Research
• /
• 제16권6호
• /
• pp.555-560
• /
• 2008

A series of hydroxyl-group containing polyimides (HPIs) were prepared in order to investigate the structure-gas permeation property relationship. Each polymer membrane had structural characteristics that varied according to the dianhydride monomers. The imidization processes were monitored using spectroscopic and thermog-ravimetric analyses. The single gas permeability of He, $H_2$, $CO_2$, $O_2$, $N_2$ and $CH_4$ were measured and compared in order to determine the effect of the polymer structure and functional -OH groups on the gas transport properties. Surprisingly, the ideal selectivity of $CO_2/CH_4$ and $H_2/CH_4$ increased with increasing level of -OH incorporation, which affected the diffusion of $H_2$ or the solubility of $CO_2$ in HPIs. For $H_2/CH_4$ separation, the difference in the diffusion coefficients of $H_2$ and $CH_4$ was the main factor for improving the performance without showing any changes in the solubility coefficients. However, the solubility coefficient of $CO_2$ in the HPIs increased at least four fold compared with the conventional polyimide membranes depending on the polymer structures. Based on these results, the polymer membranes modified with -OH groups in the polymer backbone showed favorable gas permeation and separation performance.

• 전자공학회논문지A
• /
• 제30A권12호
• /
• pp.69-76
• /
• 1993

The statistical methodology using RSM (response surface method) was used too ptimize the deposition conditions of selective CVD tungsten process for improving the deposition rate and the adhesion property. Temperature, flow rate of SiH$_4$ and WF$_6$ and H$_2$ and Ar carrier gases were chosen for the deposition variables and process characteristics due to carrier gas were intensively investigated. It was observed that temperature was the main factor influencingthe deposition rate in the case of H$_2$ carrier gas while the reactant ratio, $SiH_{4}/WF_{6}$, had the principal effect on the deposition rate in the case of Ar carrier gas. The increased deposition rate and the good adhesion to Si were obtained under Ar carrier gas compared to H$_2$ carrier gas. The optimum conditions for deposition rate and antipeeling property were found to be the temperature range of 300~32$0^{\circ}C$ and the reactant ratio, $SiH_{4}/WF_{6}$, of 0.5~0.6.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 추계학술대회 논문집
• /
• pp.471-475
• /
• 2000

P-type (100) Si wafer patterned with 1000$\AA$ SiO$_2$island was used as substrate and the Si films were deposited under low pressure using Si$_2$H$_{6}$-H$_2$gas mixture where the total gas flow rate and deposition pressure were 16.6sccm and 3.5mtorr, respectively. In this condition, we selectively obtained high-quality epitaxial Si layer of the 350~1050$\AA$ thickness. In order to extend the incubation period, we kept high pressure H$_2$ environment without Si$_2$H$_{6}$ gas for few minutes after first incubation period and then we conformed the existence of second incubation period.iod.

• Bulletin of the Korean Chemical Society
• /
• 제32권10호
• /
• pp.3735-3737
• /
• 2011

We report a simple method for fabricating ZnO gas sensors via a sonochemical route and their $H_2$ gas sensing properties. Vertically aligned ZnO nanorod arrays as a sensing material were synthesized on a Pt-electrode patterned alumina substrate under ambient conditions. The advantage of the proposed method is a high speed of processing. The gas sensor based on ZnO nanorod arrays with large specific surface area showed a high response to $H_2$ and a detection limit of 70 ppm at $250^{\circ}C$. Also, their response and recovery time were relatively short and a complete regeneration was observed. A mechanism for sensing $H_2$ gas on the surface of ZnO nanorods is proposed.

• Journal of Applied Biological Chemistry
• /
• 제51권6호
• /
• pp.307-314
• /
• 2008

To explore the optimal conditions for the removal of $H_{2}S$ gas by biofiltration, various conditions, including inlet $H_{2}S$ concentration, flow rate, moisture, and cell number, were examined. Heterotrophic bacteria were isolated from the compost of the animal excreta. A strain that effectively removed $H_{2}S$ was selected and identified as Rhodococcus rhodochrous B261 by analysis of its 16S rDNA sequence. A cell number of $10^{7}\;cfu/g^{-}compost$ was sufficient to dominate the microbiota, and an effective removal was observed at $H_{2}S$ gas concentrations below 220 mg/L. The moisture content of 33-38% was suitable for activation of the microbial activity and delaying the desiccation. Higher flow rates resulted in lower removal rates of the $H_{2}S$ gas. Under the conditions of $10^7\;cfu/g^{-}compost$, $H_{2}S$ gas concentrations of 220 mg/L, and moisture content of 33-38%, the inlet $H_{2}S$ gas concentrations of 120 and 400 mg/L were completely removed for 34 and 12 days, respectively. The amount of sulfur removed was $2.99{\times}10^{-9}H_{2}S-S/cell$, which was suggested as the amount of sulfur removed by a single cell. The biofilter consisting of the compost and R. rhodochrous B261 could be suitable for a long-term biofilteration for the removal of $H_{2}S$ and other malodorous compounds.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2008년도 Asian Magnetics Conference
• /
• pp.22.2-22.2
• /
• 2008

• Corrosion Science and Technology
• /
• 제7권2호
• /
• pp.69-76
• /
• 2008

Common methods for large scale hydrogen production, such as steam reforming and coal gasification, also involve production of carbonaceous gases. It is therefore necessary to handle process gas streams involving various mixtures of hydrocarbons, $H_2$, $H_2O$, CO and $CO_2$ at moderate to high temperatures. These gases pose a variety of corrosion threats to the alloys used in plant construction. Carbon is a particularly aggressive corrodent, leading to carburisation and, at high carbon activities, to metal dusting. The behaviour of commercial heat resisting alloys 602CA and 800, together with that of 304 stainless steel, was studied during thermal cycling in $CO/CO_2$ at $650-750^{\circ}C$, and also in $CO/H_2/H_2O$ at $680^{\circ}C$. Thermal cycling caused repeated scale separation, which accelerated chromium depletion from the alloy subsurface regions. The $CO/H_2/H_2O$ gas, with $a_C=2.9$ and $p(O_2)=5\times10^{-23}$ atm, caused relatively rapid metal dusting, accompanied by some internal carburisation. In contrast, the $CO/CO_2$ gas, with $a_C=7$ and $p(O_2)=10^{-23}-10^{-24}$ atm caused internal precipitation in all three alloys, but no dusting. Inward diffusion of oxygen led to in situ oxidation of internal carbides. The very different reaction morphologies produced by the two gas mixtures are discussed in terms of competing gas-alloy reaction steps.

• Transactions on Electrical and Electronic Materials
• /
• 제13권1호
• /
• pp.27-30
• /
• 2012

This paper proposes a micro gas sensor for measuring $H_2S$ gas. This is based on a $SnO_2$-CuO multi-layer thin film. The sensor has a silicon diaphragm, micro heater, and sensing layers. The micro heater is embedded in the sensing layer in order to increase the temperature to an operating temperature. The $SnO_2$-CuO multi layer film is prepared by the alternating deposition method and thermal oxidation which uses an electron beam evaporator and a thermal furnace. To determine the effect of the number of layers, five sets of films are prepared, each with different number of layers. The sensitivities are measured by applying $H_2S$ gas. It has a concentration of 1 ppm at an operating temperature of $270^{\circ}C$. At the same total thickness, the sensitivity of the sensor with multi sensing layers was improved, compared to the sensor with one sensing layer. The sensitivity of the sensor with five layers to 1 ppm of $H_2S$ gas is approximately 68%. This is approximately 12% more than that of a sensor with one-layer.

• 한국재료학회지
• /
• 제18권11호
• /
• pp.628-633
• /
• 2008

ZnO nanopowders were synthesized by the sol-gel method using hydrazine reduction, and their gas responses to 6 gases (200 ppm of $C_2H_5OH$, $CH_3COCH_3$, $H_2$, $C_3H_8$, 100 ppm of CO, and 5 ppm of $NO_2$) were measured at $300\;{\sim}\;400^{\circ}C$. The prepared ZnO nanopowders showed high gas responses to $C_2H_5OH$ and $CH_3COCH_3$ at $400^{\circ}C$. The sensing materials prepared at the compositions of [$ZnCl_2$]:[$N_2H_4$]:[NaOH] = 1:1:1 and 1:2:2 showed particularly high gas responses ($S\;=\;R_a/R_g,\;R_a$ : resistance in air, $R_g$ : resistance in gas) to 200 ppm of $C_2H_5OH$($S\;=\;102.8{\sim}160.7$) and 200 ppm of $CH_3COCH_3$($S\;= 72.6{\sim}166.2$), while they showed low gas responses to $H_2$, $C_3H_8$, CO, and $NO_2$. The reason for high sensitivity to these 2 gases was discussed in relation to the reaction mechanism, oxidation state, surface area, and particle morphology of the sensing materials.

• 한국전기전자재료학회논문지
• /
• 제15권10호
• /
• pp.909-913
• /
• 2002

The luminance and discharge characteristics of ac PDP may be significantly affected by a small amount of impurity gas in working gas. These impurity gases such as O$_2$, O, C and H$_2$ can be mixed in the manufacturing and /or discharge process. In this paper a small amount of impurity gas in acPDP are introduced quantitatively and the relationship between the amount of impurity gas and the luminance/discharge characteristics are investigated. The luminous efficiency decreased seriously with increase in the partial pressure of impurity gases, especially in H$_2$, O$_2$ and CO$_2$. Under the condition of the impurity gas ratio of 2${\times}$10$\^$-3/ for Ar, N2, H$_2$, CO$_2$ and O$_2$, the luminous efficiency decreased about 8%, 8%, 32%, 36% and 50%, respectively.