• Korean Journal of Materials Research
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• v.27 no.3
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• pp.155-160
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• 2017

Doped-$LaCrO_3$ perovskites, because of their good electrical conductivity and thermal stability in oxidizing and/or reducing environments, are used in high temperature solid oxide fuel cells as a gas-tight and electrically conductive interconnection layer. In this study, perovskite $(La_{0.8}Ca_{0.2})(Cr_{0.9}Co_{0.1})O_3$ (LCCC) coatings manufactured by atmospheric plasma spraying followed by heat treatment at $1200^{\circ}C$ have been investigated in terms of microstructural defects, gas tightness and electrical conductivity. The plasma-sprayed LCCC coating formed an inhomogeneous layered structure after the successive deposition of fully-melted liquid droplets and/or partially-melted droplets. Micro-sized defects including unfilled pores, intersplat pores and micro-cracks in the plasma-sprayed LCCC coating were connected together and allowed substantial amounts gas to pass through the coating. Subsequent heat treatment at $1200^{\circ}C$ formed a homogeneous granule microstructure with a small number of isolated pores, providing a substantial improvement in the gas-tightness of the LCCC coating. The electrical conductivity of the LCCC coating was consequently enhanced due to the complete elimination of inter-splat pores and micro-cracks, and reached 53 S/cm at $900^{\circ}C$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.669-673
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• 2011

This study explores the numerical analysis method of fluid dynamics in the reaction section to improve the gas processing efficiency in the hazardous gas removal by atmospheric thermal plasma. This study also intends to contribute in technology advance to improve the processing efficiency and make the process more stable. Numerical analysis of temperature distribution in the reaction section dependent on the change in flow velocity of Ar and plasma temperature change, which are major control variables in the cracking process of HFC-23 using arc plasma, was done. The characteristic of incoming oxygen by temperature suggested that when temperature increased to 1600K, 1700K, 1800K respectively, the range of cracking temperature 1500K increased to 75.0%, 83.3%, 90.2% respectively. The temperature change of Ar by velocity change was widest in the area higher than 1500K when the velocity was 2.5m/s; however, since there was no big difference when the velocity was 2m/s, it is believed that 2 m/s would be most proper.

• Journal of Ocean Engineering and Technology
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• v.15 no.4
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• pp.60-65
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• 2001

Thermal spray coating is formed by a process in which melted particles flying with high speed towards substrate, then crash and spread on the substrate surface cooled and solidified in a very short time, Stacking of the particles makes coating. In this study, the exfoliation of $Al_2$O$_3$ and Ni-4.5wt.%Al thermally sprayed coating which were deposited by an atmospheric plasma spray apparatus are investigated using an AE method. A tensile test is conducted on notch specimens in a stress range below the elastic limit of substrate. The wave forms of AE generated from the three coating specimens can be classified by FFT analysis into two types which low frequency(type I waveform is considered to corresponds exfoliation of coating layers and type II waveform corresponds the plastic deformation of notch tip or the resultant fracture of coating. The fracture of the coating layers can estimate by AE event and amplitude, because AE features increase when the deformation generates.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.82.1-82.1
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• 2017

After a coronal mass ejection occur, plasma blobs are often observed along the post-CME ray. Searching for features related to the plasma blobs would be important in understanding their origin. We investigated the morphology of solar flares at EUV wavelengths, around the estimated times when blobs were formed. We focused on three events - 2013 September 21 and 22, 2015 March 7 and 8, and 2017 July 13 and 14 - observed by Atmospheric Imaging Assembly (AIA) aboard Solar Dynamic Observatory (SDO). Around the blob ejection times on 2013 September 21 and 22 and 2017 July 13 and14, we found regions with recurrent events of pronounced flux increase in EUV images. Around those of 2015 March 7 and 8, however, we could not observe such recurrent flux increase. This illustrates that even though blob ejections along different post-CME rays look similar in the high corona, the assocated features in the low corona may differ. We conclude that magnetic morphology and CME triggering process should be carefully examined in order to classify plasma blobs by their nature.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.99-102
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• 2005

Plasma surface coating is applied to the wood powder to improve its bonding and dispersion with the polypropylene(PP). Some mechanical test results and visual inspection indicates the good compatibility between the wood powder and the PP, and relatively good interfacial adhesion between wood powder and PP matrix was seen. Also, this method is considered as a non-toxic process as compared to other direct chemical method.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1999.10a
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• pp.65-68
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• 1999

A plasma melting system to vitrify ny ash from MSW(Municipal Solid Waste) incinerator has been operated in SHI(Samsung Heavy Industries) since 1996. Waste feeding rate was 200kg/hr. with maximum working power of 500㎾. Because of high melting temperature of fly ash, bottom ash was used as an additive to decrease melting temperature. Data analysis for discharged slag shows volume reduction up to 30% and no leaching of heavy metals such as Pb, Cd, Cr which were an obstacle for landfill and recycle. Atmospheric pollution gas like nitrogen oxides, carbon monoxide, and PCDD/PCDF were restrained below the regulatory limit.

• Journal of the Korean Society of Safety
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• v.16 no.3
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• pp.41-44
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• 2001

The removal characteristics of nitrogen oxides (NOx) by the dielectric ($Al_2O_3$) packed-bed plasma reactor are experimentally investigated Reactor is packed with 5[mm] diameter $Al_2O_3$ beads, and was desisted to remove NOx at atmospheric pressures from the moving pollution source such as diesel automobile. The experiments were conducted for applied voltages from 5 to 10[kV], flue gas rate from 2 to 5[l/min] and frequency from 0.5 to 2[kHz]. The NOx removal efficiency significantly increasing with increasing applied voltage. Especially removal rate significantly increased with increasing frequency. However, in this experiment discharged poler n relatively high.

• Resources Recycling
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• v.26 no.6
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• pp.3-9
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• 2017

In this study, plasma arc remelting behaviors according to arc current, arc voltage, and types of plasma gas were investigated using Kroll processed Ti sponges as anode. In the discharge pressure range of vacuum pump ($200{\sim}300kgf/cm^2$), the arc voltage did not vary greatly with the increase of discharge pressure at a given arc length. This means that the pressure in the vacuum chamber during operation hardly changes and the atmospheric pressure maintains. Under various conditions of arc currents (700~900A), the arc voltage slightly increased with arc current. The effects of anode materials and operational variables on the arc length-arc voltage relationship were compared with the results in previous studies. When the atmospheric gas changed from argon to helium, double effect of improvement on the output of the steady state was observed. The increase of output in the plasma arc device was accompanied by an increase in the melting rate of the Ti sponge and the quality of the ingot surface was also improved. The plasma arc remelting of the new scrap titanium and the old scrap zirconium alloy could result in the fabrication of an ingot with high surface quality.

• Journal of the Korea Convergence Society
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• v.13 no.3
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• pp.281-289
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• 2022

Plasma ozone is utilized in a variety of applications in the field of sterilization due to its high sterilization performance. Dielectric materials used in DBD(dielectric barrier discharges) are mainly polymer, quartz and ceramics. These dielectric layers have the advantage of limiting the amount of supplied electron charge and allowing plasma to occur evenly on the surface of dielectric. Actually, the target or environment for sterilization is often a complex structure, so research and academic study are needed by utilizing the concept of space sterilization. In this study, the device is applied to generate DBD plasma at atmospheric pressure for disinfection due to the effectiveness in producing radicals and ozone. The generator of plasma ozone is a basic structure of dielectric barrier discharge by placing ceramic tube dielectrics and stainless steel electrical conductors at regular intervals. Various applications can be developed based on the proposed design method. Plasma ozone generation for space sterilization device is recognized as an excellent sterilization device. Through the design and verification of the device, we intend to establish an optimal design of the spatial sterilization device and provide the basis data for sterilization applications.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.4
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• pp.495-503
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• 1999

Airborne particulate matter $(PM_{10})$ collected using high volume air sampler and silica fiber filter were analyzed by Instrumental Neutron Activation Analysis(INAA), Inductively Coupled Plasma Atomic Emission Spectrometry(ICP-AES) and Atomic Absorption Spectrometry(AAS), and the results were compared with each other. 30~40 trace elements in environmental standard reference materials(NIST SRM 1648 and NIES CRM No.8) were analyzed for the analytical quality control. The relative error for two-third of elements detected was less than 10%, and the standard deviation was less than 15%. During the sampling period for 24 hours, the mass concentration of total suspended particulate was 36.1$\mu\textrm{g}$/㎥ and the value is lower than the critical level in Korea. In the results of NAA, the elements of Al, As, Ba, Fe, La, Mg, Na, Sb, Zn were well agreed with those of other methods. In statistical estimation between different methods, the deviation of Al, Ba, Cr, Fe was less than 10% and quite reliable.