• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.863-870
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• 2016

We investigated the physical/chemical phenomena that a slow loss of $CO_2$ inventory into sodium after the sodium-$CO_2$ boundary failure in printed circuit heat exchangers (PCHEs), which is considered for the supercritical $CO_2$ Brayton cycle power conversion system of a sodium-cooled fast reactor (SFR). The first phenomenon is plugging inside narrow sodium channels by micro cracks and the other one is damage propagation referred to as wastage combined with the corrosion/erosion effect. Experimental results of plugging shows that sodium flow immediately stopped as $CO_2$ was injected through the nozzle at $300{\sim}400^{\circ}C$ in 3 mmID sodium channels, whereas sodium flow stopped about 60 min after $CO_2$ injection in 5 mmID sodium channels. These results imply that if pressure boundary of sodium-$CO_2$ fails a narrow sodium channel would be plugged by reaction products in a short time whereas a relatively wider sodium channel would be plugged with higher concentration of reaction products. Wastage by the erosion effect of $CO_2$ (200~250 bar) hardly occurred regardless of the kinds of materials (stainless steel 316, Inconel 600, and 9Cr-1Mo steel), temperature ($400{\sim}500^{\circ}C$), or the diameter of the $CO_2$ nozzle (0.2~0.8 mm). Velocities at the $CO_2$ nozzle were specified as Mach 0.4~0.7. Our experimental results are expected to be used for determining the design parameters of PCHEs for their safeties.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.348-351
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• 2006

Bipolar plate, which forms about 50% of the stack cost, is an important core part with polymer electrolyte membrane in PEMFC. Bipolar plates have been commonly fabricated from graphite meterial having high electrical conductivity and corrosion resistance. Lately, many researchers have concentrated their efforts on the development of metallic bipolar plate and stainless steel has been considered as a potential material for metallic bipolar plate because of its high strength, chemical stability, low gas permeability and applicability to mass production. However, it has been reported that its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions and an increase in contact resistance by the growth of passive film therefore, its corrosion resistance as well as contact resistance must be improved for bipolar plate application. In this work, several types of coating were applied to 316L and their electrical conductivity and corrosion resistance were evaluated In the simulated PEMFC environment. Application of coating gave rise to low interfacial contact resistances below $19m{\Omega}cm^2$ under the compress force of $150N/cm^2$. It also made the corrosion potential to shift in the posit ive direct ion by 0.3V or above and decreased the corrosion current from ca. $9{\mu}A/cm^2$ to ca. $0.5{\mu}A/cm^2$ in the mixed solution of $0.1N\;N_2SO_4$ and 2ppm HF A coat ing layer under potentiostatic control of 0.6V and $0.75V_{SCE}$ for 500 hours or longer showed some instabilities, however, no significant change in coat Ing layer were observed from Impedance data. In addition, the corrosion current maintained less than $1{\mu}A/cm^2$ for most of time for potentiostatic tests. It indicates that high electrical conductivity and corrosion resistance can be obtained by application of coatings in the present work.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.939-944
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• 1997

The films of zeolite X on the surface of metal sieve were prepared by continuous crystallization method. It is known that the growth of zeolite crystal on the surface of metal is mainly dependent on the surface composition of metal sieve. In the present work, the zeolite nuclei could be easily formed as Cr content on the metal surface was removed by acid treatment. In order to investigate the proedure growing of zeolite crystal by the continuous crystallization method, the composition of zeolite X($6.36Na_2O-Al_2O_3-5.3SiO_2-190.8H_2O$)was supplied every 12hour. Then the mechanism and inter-relationship between the metal surface and nucleation are investigated. The results show that as the content of silica increases in the gel mixture, the nuclei of zeoilite are easily formed on the metal surface. Also, it was confirmed that the particle of zeolite stuck on the metal surface continues the linear growth. The particles are combined by the reaction of polycondensation, and finally become the shape of crystal. The sample synthesized by the film type was confirmed as zeolite X by the analyses of SEM and XRD.