• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1090-1098
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• 1998

$RuO_2$ thin films were deposited on Si and Ru/Si substrates by rf magnetron reactive sputtering and annealed in oxygen atmosphere(1atm) to investigate their thermal stability and diffusion barrier property. $RuO_2$ thin films were thermally stable up to 700\ulcorner for 10min. in oxygen atmosphere and showed excellent barrier property against the interdiffusion of silicon and oxygen. After annealing at $750^{\circ}C$ , however, volatilization to higher oxide occurred at the surface and inside of $RuO_2$ thin film and diffusion barrier property was also deteriorated. When annealed at $800^{\circ}C$, $RuO_2$thin film showed a different microstructure from that of $RuO_2$ thin film annealed at 75$0^{\circ}C$. It is likely that surface defect structure of $RuO_2$, $RuO_3$, and excess oxygen had an influence on the mode of volatilization with increasing annealing temperature.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.11 no.1
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• pp.21-31
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• 1985

The effect of dispersed phase on the stability of emulsion system with polyoxyethylene dodecyl ethers and their variation of ethylene oxide moles was studied by such methods as interfacial tension measurement, centrifugation and droplet size variation with time. The experiments showed that, in interfacial tension measurement, long chain alkanols into dispersed phaes are more effectively adsorbed onto interface, while long chain alkanes nearly not, and in centrifugation, dispersed phase with alkanols is less separated than that with alkanes. On the other hand, alkanes help more stabilyzing emulsion than alkanols in droplet size variation. And the addition of NaCl or Urea, and variation of E.O. moles have very slight effects on the stability with alkanes than with alkanols. Moreover, the longer carbon chain length is, dispersed phase is more effective on emulsion stability. Supposed from these facts is that more stable emulsion can be made with alkanes which retard molecular diffusion by water solubility decrease rather than alkanols which raise resistance to coalescence by rigid interfacial mixed monolayers formation. In conclusion, the stabilities of these emulsions are proved to be more influenced by molecular diffusion than coalescence.

• Journal of the Korean Chemical Society
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• v.55 no.1
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• pp.50-56
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• 2011

The electrochemical reduction of (2,4-difluoro-phenyl)-(2-phenyl-1H-quinolin-4-ylidene)-amine was investigated in 0.1 M tetrabutylammoniumbromide in N,N-dimethylformamide at glassy carbon electrode (GCE) using the technique of cyclic voltammetry at the room temperature (290 K). The reduction of imines occurs in two successive steps, involving one electron in each. In this medium the first peak was observed at about -0.793 V (vs Ag/$Ag^+$) at the glassy carbon electrode surface, which is more stable and well defined as compared to the second peak. The diffusion coefficient ($D_0$) of imine in the investigated solvent media has been calculated using the modified Randles-Sevcik equation. The electron transfer coefficient ($\alpha$) of the reactant species has also been calculated.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.211-217
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• 2016

Boride coating applied on steam turbine parts of power plants has provided good particle erosion resistance under temperature of $550^{\circ}C$, but it isn't able to protect the parts effectively any more in ultra super critical (USC) steam turbine which is being operated up to temperature of $650^{\circ}C$. To ensure stable durability for USC steam turbine parts, an alternative coating replacing boride coating should be developed. In this study, multi-component boride coatings containing elements such as chromium (Cr) and vanadium (V) were formed on base metal (B50A365B) using thermochemical treatment method called by pack cementation. The thermochemical treatments involve consecutive diffusion of boron(B) and Cr or/and V using pack powders containing diffusion element sources, activators and diluents. The top layer of Cr-boride coating is primarily consisted of $Cr_2B_3$ and $Cr_5B_3$, while that of V-boride coating is mostly consisted of $VB_2$ and $V_2B_3$. The (Cr,V)-boride coating is consisted of $Cr_2B_3$, $Cr_5B_3$ and $V_2B_3$ mostly. The top surfaces of 3 multi-component boride coatings show hardness of $3200-3400H_v$, which is much higher than that of boride, about $1600-2000H_v$. In 5 wt.% NaCl solution immersion tests, the multi-component boride coatings show much better corrosion resistance than boride coating.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.1
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• pp.28-35
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• 2018

In order to analyze the flammability limit and structure of the gaseous methane-gaseous oxygen diffusion flame formed through a shear coaxial injector, combustion experiments were carried out according to the condition of injector recess and propellant mass-flow rate. As a result, it was confirmed that stable anchored flame was observed even at the high oxygen Reynolds number as the propellant momentum flux ratio increased, and that the recess had no significant influence on the flame shape and flammability limit. The anchored flame visualized through a chemiluminescence showed the maximum OH radical emission intensity at a specific position, irrespective of the propellant injection condition, and the radical intensity was greatly reduced by the injector recess.

• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.646-652
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• 2022

The dead-end anode (DEA) system is a method that closes the anode outlet and supplies fuel by pressure. The DEA method could improve fuel usage and power efficiency through system simplification. However, flooding occurs due to water and nitrogen back diffusion from the cathode to the anode during the DEA operation. Flooding is a cause of decreased fuel cell performance and electrode degradation. Therefore, tthe structure and components of polymer electrolyte membrane fuel cell (PEMFC) should be optimized to prevent anode flooding during DEA operation. In this study, the effect of a porous flow field with metal foam on fuel cell performance and fuel efficiency improvement was investigated in the DEA system. As a result, fuel cell performance and purge interval were improved by effective water management with a porous flow field at the cathode, and it was confirmed that cathode flow field structure affects water back-diffusion. On the other hand, the effect of the porous flow field at the anode on fuel cell performance was insignificant. Purge interval was affected by metal foam properties and shown stable performance with large cell size metal foam in the DEA system.

• Journal of Pharmaceutical Investigation
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• v.1 no.1
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• pp.101-108
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• 1971

The stability and toxicity test for p.p'-DDT, DDVP and dipterex that put to used sample in this study effects is follows A. about p.p'-DDT (1) In elevating the stability of p.p'-DDT, best stabilizing solvent was benzene. (2) The stability-agent has no difficulty as long as it not contain metal ion for instance $Z_n^{2+}$,$C_r^{3+}$,$Al^{3+}$,and $Fe^{2+or3+}$ but in case of contain $F_e^{3+}$, the combination of salicylaminoguanidine is best effective. (3) Using this product for water-suspension, We must use span 40 for stability agent and adding it at the same time. (4) We must use container which does not week alkali and metal ion but it is to preserved in tight light-resistant container. (5) The stopper of container is adapted with above-mentioned condition of container, but it is better not to use metal material. (6) This product needs opening ventilation more than 30 minutes after diffusion or spray and in the room we remove cause of remained poison by cleaning the bottom. B. about DDVP and Dipterex (1) Benzene or toluene in best solvent to preserve stability of DDVP and Dipterex. (2) Span 40 is superior for stability agent of this product and second is span 80. (3) The pH of solution is very stable in pH 5-6 and comparative stable in alkali more than p,p'-DDT. (4) Container is to preserved in tight, lightresistant container and especially be careful of outflow and inflow of water. (5) Because this product is centeral stimulant poison, we must pay attention to prevent cause of contact diadermic toxicity after use.

• Journal of Powder Materials
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• v.23 no.3
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• pp.240-246
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• 2016

In order to improve the high-temperature oxidation stability, sintered 434L stainless steel is studied, focusing on the effect of the addition of metallic oxides to form stable oxide films on the inner particle surface. The green compacts of Fecralloy powder or amorphous silica are added on STS434L and oxidized at $950^{\circ}C$ up to 210 h. The weight change ratio of 434L with amorphous silica is higher than that of 434L mixed with Fecralloy, and the weight increase follows a parabolic law, which implies that the oxide film grows according to oxide diffusion through the densely formed oxide film. In the case of 434L mixed with Fecralloy, the elements in the matrix diffuse through the grain boundaries and form $Al_2O_3$ and Fe-Cr oxides. Stable high temperature corrosion resistance and electrical resistivity are obtained for STS434L mixed with Fecralloy.

• Corrosion Science and Technology
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• v.2 no.1
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• pp.18-25
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• 2003

Effects of the precipitation of $\sigma$ phase on the metastable pitting as a precursor of stable pitting corrosion and also on the progress of stale pitting of the 25Cr-7Ni-3Mo-0.25N duplex stainless steel were investigated in chloride solution. Electrochemical potential and current noises of the alloy were measured in 10 % ferric chloride solution ($FeCl_3$) with zero resistance ammeter (ZRA), and then analyzed by power spectral density (PSD) and by corrosion admittance ($A_c$) spectrum. With aging at $850^{\circ}C$, the passive film of the alloy was found to get significantly unstable as represented by power spectral density (PSD) and a transition from metastable pitting state to stable one was observed. In the corrosion admittance spectrum, the number of negative $A_c$ corresponding to the state of localized corrosion increased with aging, suggesting that the precipitation of $\sigma$ phase considerably degraded the passive film by depleting Cr and Mo around it at $\alpha/\sigma$ or $\gamma/\sigma$ phase boundaries, thereby leading to the initiation of the pitting corrosion. However, the Cr and Mo at $\alpha/\sigma$ or $\gamma/\sigma$ phase boundaries which were once depleted due to the precipitation of the $\sigma$ phase were partly replenished by the diffusion of Cr and Mo from the surrounding matrix with aging time longer. The initiation of pitting seems to be associated with the precipitation density of the $\sigma$ phase with an effective size needed to induce the sufficient depletion of Cr and Mo around it.

• Nuclear Engineering and Technology
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• v.46 no.2
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• pp.169-182
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• 2014

High-performance research reactors require fuel that operates at high specific power to high fission density, but at relatively low temperatures. Research reactor fuels are designed for efficient heat rejection, and are composed of assemblies of thin-plates clad in aluminum alloy. The development of low-enriched fuels to replace high-enriched fuels for these reactors requires a substantially increased uranium density in the fuel to offset the decrease in enrichment. Very few fuel phases have been identified that have the required combination of very-high uranium density and stable fuel behavior at high burnup. U-Mo alloys represent the best known tradeoff in these properties. Testing of aluminum matrix U-Mo aluminum matrix dispersion fuel revealed a pattern of breakaway swelling behavior at intermediate burnup, related to the formation of a molybdenum stabilized high aluminum intermetallic phase that forms during irradiation. In the case of monolithic fuel, this issue was addressed by eliminating, as much as possible, the interfacial area between U-Mo and aluminum. Based on scoping irradiation test data, a fuel plate system composed of solid U-10Mo fuel meat, a zirconium diffusion barrier, and Al6061 cladding was selected for development. Developmental testing of this fuel system indicates that it meets core criteria for fuel qualification, including stable and predictable swelling behavior, mechanical integrity to high burnup, and geometric stability. In addition, the fuel exhibits robust behavior during power-cooling mismatch events under irradiation at high power.