• Applied Chemistry for Engineering
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• v.3 no.3
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• pp.527-534
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• 1992

Raney nickel was used as catalyst in the hydrogen electrode for an alkaline fuel cell. The hydrogen electrode manufactured with the Raney nickel catalyst which was sintered at $700^{\circ}C$ was found to have the highest electrode performance. Using the Raney nickel powder of average particle size $90{\AA}$ for the electrode, the current density which had been measured was $450mA/cm^2$ at $80^{\circ}C$ using 6N KOH solution as an electrolyte. The effects of PTFE addition were investigated with CO-chemisorption, polarization curves and Tafel slope. CO-chemisorption had shown the optimum value when the Raney nickel was mixed with 5wt% of PTFE, but from the current density and Tafel slope at porous Raney nickel electrode, the appropriate value of PTFE addition was 10wt%. Recommendable Ni and Al portion for Raney nickel was 60 : 40 and loading amount was $0.25g/cm^2$. Also the influence of pressing pressure for manufacturing catalytic layer and for junction with gas diffusion layer was examined. The morphology of catalyst surface was investigated with SEM. The influence of reactivation time and heat-treatment temperature were also studied.

• Corrosion Science and Technology
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• v.7 no.2
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• pp.69-76
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• 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 of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.692-699
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• 2006

In this work, $TiO_2$ nanoparticles were synthesized using $N_2-diluted$ and Oxygen-enriched co-flow hydrogen diffusion flames. The effect of flame temperature on the crystalline structure of the formed $TiO_2$ nanoparticles was investigated. The measured maximum centerline temperature of the flame ranged from 2,103k for oxygen-enriched flame to 1,339K for $N_2-diluted$ flame. The visible flame length and the height of the main reaction zone were characterized by direct photographs. The crystalline structures of $TiO_2$ nanoparticles were analyzed by XRD. From the XRD analysis, it was evident that the crystalline structures of the formed nanoparticles were divided into two sorts. In the higher temperature region, over the 1,700K, the fraction of formed $TiO_2$ nanoparticles having anatase-phase crystalline structure increased with increasing the flame temperature. On the contrary, in the lower temperature region, below the 1,600K, the fraction of anatase-phase nanoparticles increased with decreasing the flame temperature.

• Korean Journal of Materials Research
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• v.28 no.4
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• pp.247-253
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• 2018

We examined the characteristics of indium tin zinc oxide (ITZO) thin film transistors (TFTs) on polyimide (PI) substrates for next-generation flexible display application. In this study, the ITZO TFT was fabricated and analyzed with a SiOx/SiNx gate insulator deposited using plasma enhanced chemical vapor deposition (PECVD) below $350^{\circ}C$. X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) results revealed that the oxygen vacancies and impurities such as H, OH and $H_2O$ increased at ITZO/gate insulator interface. Our study suggests that the hydrogen related impurities existing in the PI and gate insulator were diffused into the channel during the fabrication process. We demonstrate that these impurities and oxygen vacancies in the ITZO channel/gate insulator may cause degradation of the electrical characteristics and bias stability. Therefore, in order to realize high performance oxide TFTs for flexible displays, it is necessary to develop a buffer layer (e.g., $Al_2O_3$) that can sufficiently prevent the diffusion of impurities into the channel.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.2
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• pp.315-322
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• 2008

Titanium and its alloys have excellent corrosion resistance, high strength to weight ratios and creep properties in high temperature, which make them using many various fields of application. Especially, pure titanium, which has outstanding resistance for the stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion, brings out to the best material for the heat exchanger, ballast tank, desalination facilities, and so on. Responding to these needs, welding processes for titanium are also being used GTAW, GMAW, PAW, EBW, LBW, resistance welding and diffusion bonding, etc. However, titanium is very active and highly susceptible to embrittlement by oxygen, nitrogen, hydrogen and carbon at high temperature, so it needs to shield the weld metal from the air and these gases during welding by non-active gas. In this study, it was possible to get sound beads without humping and spatter with a decrease of peak power according to increase of pulse width, change of welding speed and overlap rate for heat input control, and shield conditions at pulsed laser welding of titanium plates for Lap welding.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.6
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• pp.593-603
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• 2005

Passive sampler using 4-amino-3-hydrazino-5-mercapto-1, 2, 4-triazole (AHMT) was developed to determine formaldehyde in indoor environment. The chromatography paper cleaned by $3\%$ hydrogen peroxide solution was experimently determined as a optimum absorbtion filter for the collection of formaldehyde. The passive sampler with a broad cross-sectional area and a short diffusion length was quite good in sensitivity. The passive sampler and the active sampling method with an impinger were strongly correlated with a correlation coefficient of 0.9848. The limits of detection and quantification of the passive sampler for the measurement of formaldehyde in the indoor environment were 7.5 and 10.2 ppb, respectively. Temperature ($19\∼28^{circ}C$) and relative humidity ($30\∼90\%$) had slight influence on the sampling rate of the passive sampler. However, the increase of flow velocity on the surface of sampler resulted in the increase of sampling rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.5
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• pp.955-961
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• 2009

Present, a portable battery have problem that the volume increases according to capacity Increase. Direct Methanol Fuel Cell is alternative by solution plan of this problem. In this paper, the characteristics of DMFC are analyzed by change in concentration and discharge of fuel in natural convection and room temperature condition. According to the analysis result, polarization by delay of diffusion velocity of hydrogen ion appeared in methanol of low concentration. And if have a lot of supplies of methanol, generation power declines by electric cell cooling effect.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.5
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• pp.38-45
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• 1989

We have studied the electrical characteristics of the hydrogenated amorphous silicon (a-Si:H) ambiploar thin film transistors (TET'S)using 100ppm boron-doped a-Si:H as an active layer. The enhancement of drain current due to the double injection behavior has been observed in the p-channel operation of the TFT. The drain current decreases with time in streched exponential form when the gate voltage is positive. The result indicates that the dangling bonds created by electron accumulation show identical time dependence as the diffusion of hydrogen in the film. We observed the experimental evidence that the doping efficiency changes either when the gate bias is applied or when the light is illuminated on boron-doped a-Si:H.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.428-433
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• 2000

The consolidation behavior of multicomponent particles prepared by the flame hydrolysis deposition process is examined to identify the effects of Si substrate temperature. To fabricate multi-component particles, a vapor-phase ternary mixture of $SiCl_4(100 cc/min),\;BCl_3(30cc/min)\;and\;POCl_3,(5cc/min)$ was fed into a coflow diffusion oxy-hydrogen flame burner. The doped silica soot bodies were deposited on silicon substrates under various deposition conditions. The surface temperature of the substrate was measured by an infrared thermometer. Changes in the chemical states of the doped silica soot bodies were examined by FT-IR(Fourier-transformed infrared spectroscopy). The deposited particles on the substrate were heated at $1300^{\circ}C$ for 3h in a furnace at a heating rate of 10K/min. Si-O-B bending peak has been found when surface temperature exceeds $720^{\circ}C$. Correspondingly, the case with substrate temperatures above loot produced good consolidation result.

• Mycobiology
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• v.36 no.4
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• pp.260-265
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• 2008

Cyclic voltammetric measurements were performed for Co(II), Ni(II), Cu(II) and Zn(II) complexes of 1 : 1 alternating copolymer, poly(3-nitrobenzylidene-1-naphthylamine-co-succinic anhydride) (L) and Ni(II) and Cu(II) complexes of 1 : 1 alternating copolymer, poly(3-nitrobenzylidene-1-naphthylamine-co-methacrylic acid) ($L^1$). The in vitro biological screening effects of the investigated compounds were tested against the fungal species including Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans and bacterial species including Staphylococcus aureus, Escherichia coli, Klebsiella pneumaniae, Proteus vulgaris and Pseudomonas aeruginosa by well diffusion method. A comparative study of inhibition values of the copolymers and their complexes indicates that the complexes exhibit higher antimicrobial activity. Copper ions are proven to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium. The nuclease activity of the above metal complexes were assessed by gel electrophoresis assay and the results show that the copper complexes can cleave pUC18 DNA effectively in presence of hydrogen peroxide compared to other metal complexes. The degradation experiments using Rhodamine B dye indicate that the hydroxyl radical species are involved in the DNA cleavage reactions.