• Journal of the Korean institute of surface engineering
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• v.41 no.6
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• pp.255-263
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• 2008

Generally, deposition mechanism of diamond particle is mainly embedding effect in the kinetic spray process. Accordingly, in spite of high cost, helium gas was employed as process gas to get high diamond fraction in the composite coating. In this study, the deposition behavior of bronze/diamond by kinetic spray process was compared using different process gas (helium and nitrogen). Bare (mean size of $5{\mu}m$, $20{\mu}m$) and nickel coated diamond (mean size of $26{\mu}m$) were deposited on Al 6061-T6 substrate with fixed process temperature and pressure. For comparison with experimental results, plastic deformation behavior of nickel layer was simulated by finite element analysis (using ABAQUS/Explicit 6.7-2). The size, broken ratio, and fraction of diamond in the composite coating were analyzed through scanning electron microscopy and image analysis method. The uniform distribution and deposition efficiency of diamond particles in the coating layer could be achieved by tailoring the physical properties of the feedstock.

• Korean Journal of Materials Research
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• v.22 no.5
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• pp.249-252
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• 2012

Fe doped $TiO_2$ nanoparticles were prepared under high temperature and pressure conditions by mixture of metal nitrate solution and $TiO_2$ sol. Fe doped $TiO_2$ particles were reacted in the temperature range of 170 to $200^{\circ}C$ for 6 h. The microstructure and phase of the synthesized Fe doped $TiO_2$ nanoparticles were studied by SEM (FE-SEM), TEM, and XRD. Thermal properties of the synthesized Fe doped $TiO_2$ nanoparticles were studied by TG-DTA analysis. TEM and X-ray diffraction pattern shows that the synthesized Fe doped $TiO_2$ nanoparticles were crystalline. The average size and distribution of the synthesized Fe doped $TiO_2$ nanoparticles were about 10 nm and narrow, respectively. The average size of the synthesized Fe doped $TiO_2$ nanoparticles increased as the reaction temperature increased. The overall reduction in weight of Fe doped $TiO_2$ nanoparticles was about 16% up to ${\sim}700^{\circ}C$; water of crystallization was dehydrated at $271^{\circ}C$. The transition of Fe doped $TiO_2$ nanoparticle phase from anatase to rutile occurred at almost $561^{\circ}C$. The amount of rutile phase of the synthesized Fe doped $TiO_2$ nanoparticles increased with decreasing Fe concentration. The effects of synthesis parameters, such as the concentration of the starting solution and the reaction temperature, are discussed.

• Korean Journal of Materials Research
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• v.22 no.5
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• pp.243-248
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• 2012

ZrN nanoparticles were prepared by an exothermic reduction of $ZrCl_4$ with $NaN_3$ in the presence of NaCl flux in a nitrogen atmosphere. Using a solid-state combustion approach, we have demonstrated that the zirconium nitride nanoparticles synthesis process can be completed in only several minutes compared with a few hours for previous synthesis approaches. The chemistry of the combustion process is not complex and is based on a metathesis reaction between $ZrCl_4$ and $NaN_3$. Because of the low melting and boiling points of the raw materials it was possible to synthesize the ZrN phase at low combustion temperatures. It was shown that the combustion temperature and the size of the particles can be readily controlled by tuning the concentration of the NaCl flux. The results show that an increase in the NaCl concentration (from 2 to 13 M) results in a temperature decrease from 1280 to $750^{\circ}C$. ZrN nanoparticles have a high surface area (50-70 $m^2/g$), narrow pore size distribution, and nano-particle size between 10 and 30 nm. The activation energy, which can be extracted from the experimental combustion temperature data, is: E = 20 kcal/mol. The method reported here is self-sustaining, rapid, and can be scaled up for a large scale production of a transition metal nitride nanoparticle system (TiN, TaN, HfN, etc.) with suitable halide salts and alkali metal azide.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.11a
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• pp.343-343
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• 2002

This study examines the influence of long-range transport of dust particles and air pollutants on both local/regional DMS oxidation chemistry and the distribution of sulfur compounds at Jeju Island (33.17$^{\circ}$ N. 126.10$^{\circ}$ E) during the Asian dust-storm(ADS) period in April 2001. The atmospheric concentrations of these sulfur species were measured at a ground station on Jeju Island. Korea as Part of the ACE-Asia intensive operation. Three ADS events were observed during the periods of 10-12, 13-14. and 25-26 April. respectively. The concentrations of DMS and CS$_2$ were higher during the ADS period than during the non-Asian-dust-storm (NADS) period. Conversely. a difference in SO$_2$ levels during the ADS period was not distinguishable from those during the NADS period. The diurnal variation pattern of DMS observed was largely different from that in the remote marine boundary layer. DMS loss by NO$_3$ in the atmospheric boundary layer was dominant due to significantly high NOx levels influenced by the long-range transport of pollutants from East Asia to Jeju Island The DMS maximum during the ADS period was observed in the late afternoon. The oceanic fluxes of DMS during the ADS and NADS periods were estimated to be 5.7$\pm$2.3 and 2.9 (+2.8/-1.5) mole m$^{-2}$ day$^{-1}$ . respectively. The contribution of oxidized DMS to SO$_2$ levels at Jeju Island during the study period was found to be insignificant.

• Journal of Environmental Health Sciences
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• v.45 no.2
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• pp.126-133
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• 2019

Objectives: In this study, a nine-stage cascade impactor was used to collect dust, and the concentration of $PM_{2.1}$ & $PM_{10}$ and alveolar deposition ratio were investigated. Methods: This study was conducted at Kunsan National University from May to June 2016. A nine-stage Cascade Impactor was used to analyze the concentrations of fine and ultrafine dust and to estimate the alveolar deposition rate by particle size of atmospheric dust particles. The pore size of each stage of the collector used in this study gradually increased from F to 0, with the F-stage as the last stage. Results: The mass fraction of PM showed a bimodal distribution divided into $PM_{2.1}$ & $PM_{10}$ based on $2.1-3.1{\mu}m$. The average mass fraction of particulate matter in the range of $2.1-3.1{\mu}m$ was 44%, and the area occupied by $PM_{2.1}$ was similar. Therefore, the Gunsan area is considered to be a region where there are similar effects from anthropogenic and natural sources. Conclusion: Dust collecting efficiency increased with the stage of collecting fine dust, and the efficiency of collection was very low at the stage of collecting ultra-fine dust. The seasonal overall efficiency of the Cascade Impactor was 44% in spring and 37.4% in summer, and the average overall efficiency was 40.7%. The alveolar deposition rate of $PM_{2.1}/PM_{10}$ during the sampling period was estimated to be about 75% deposited in the alveoli.

• 보존과학연구
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• s.22
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• pp.115-132
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• 2001

No. 3 Tomb of Bogam-ri, in Naju City, Chollanam-do Province, was a site excavated and inspected from 1996 to 1998 and had a various grave forms, including jar-coffins, stone-chambers and stone-cists. Although most of the metal artifacts excavated from it were severely corroded, we could implement microstructure investigation by collecting samples from the iron axes, iron coffin-nails and iron clamps in which the metal parts were remained. The metal structures were inspected by using metallographic microscope and SEM, and fine components analysis was implemented by ICP. To examine the hardness differences in accordance with the structure distribution, we measured the hardness by structures with Vickers hardness testing machine. As a result of the metal structure inspection, most of them were pure iron, ferrite, and also pearlite, cementite and widmannstaten structures were displayed. We could confirm carbonization was formed on the surface of the iron axes-B, iron coffin-nails-B, and iron clamps-A. There was no carbonization in the rest of the artifacts, and it is not certain that whether the carbonized parts were peeled off through extreme corrosion or they were not carbonized when they were made. In the particular part of a blade, the quality of the material was strengthened through processing. Due to the processing re-grain was caused and fine grain particles were formed. As a result of the ICP component analysis, there were no addition atoms because pure irons were used as materials. In the mean time, No. 17 jar-coffin where the iron axes-A are excavated, is chronologically ordered as from the late-fourth century to the mid-fifth century, and No. 1 and No. 2 stone chambers, where the rest of the artifacts were excavated, as the early-sixth century. It was difficult to relate the periodic differences with the manufacture technique artifacts which we inspected because there were no distinct characteristics of the manufacture technique of the metal structures and it is impossible to conclude the artifacts and sites are at the same period although their periods are different.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.2
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• pp.165-174
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• 1995

A stable suspension with a colloidal $ZrO_2$ particle was prepared by an adsorption of PV A and investigated to the effects of PV A on the dispersion and particle growth within suspension. With a suspension added the optimum concentration of PYA (about 500 ppm in this study), it was shown the property of a stable sol due to the formation of adsorbed PV A layer on surface and the reduction of an agglomeration among the particles. Most of nucleation in colloidal $ZrO_2$ were occured in the early stage of hydrolysis reaction and the plate-like monoclinic $ZrO_2$ particle were grown with an aging time. The rate of particle growth and yield for a reaction were decreased with an addition of PV A. The compact prepared from well- dispersed suspension by an addition of PV A was contained the homogeneous particle arrangement and pore distribution.

• Resources Recycling
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• v.7 no.4
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• pp.43-49
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• 1998

We investigated the effects of the powder characteristics of various domestic iron oxides (${\alpha}Fe_2O_3$) on the magnetic properties of Sr-ferrites The particle size and the distribution of iron oxides were classified hy three different rerinning methods, and greatly a affected on the magn$\xi$tic prope$\pi$ies and the mmphology of Sr-ferntes. The agglomeration of Ruthner iron oxides and the large particles of Chemirite (CY) above $0.80{\mu}\textrm{m}$ were degraded the prope며es of Sr-fcrrites. The optimal magnetic prope$\pi$ies of Srt territes, showing 68.2 emu/g of saturation magnetization and 4300 Oe of intrinsic coerClvity, were achieved at the following c conditions; Chemirite (P2EP) iron oxides of $0.14{\mu}\textrm{m}$ molar ratio of 5.8. and calcination of $1150^{\circ}C$/1 hr.

• Plant Resources
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• v.4 no.1
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• pp.41-47
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• 2001

This study was conducted to investigate the occurrence of Soil borne wheat mosaic virus(SbWMV) in barley fields in Korea and to examine the host pathogenicity of SbWMV. By using the ELISA test, SbWMV was detected in the six regions : Suwon, Milyang, Jinju, Youngkwang, Iksan, and Chonju. SbWMV was isolated from the two strains, Albori strain from Jinju and Eunpamil strain from Milyang. SbWMV was collected from leaves showing mosaic, yellowing and necrosis stripes. SbWMV was inoculated mechanically on 1∼1.5 leaf stages with leaf-rubbing to identify the host pathogenicity of 36 Korean barley cultivars, a wheat cultivar, two rye cultivars, three Japanese barley cultivars and Chenopodium amaranticola. Viral sympoms of inoculated leaves appeared on moulted loaves about 4 to 6 weeks of inoculation. Baegdong and Tapgolbori, infected from Albori strain and Eunpamil strain infected from Samdobori showed much higher susceptibility than C. amaranticola and C. quinoa which showed ring spots and chlorotic spots respectively. Virus particles were observed by the electron microscope. They were rod-shapes, which are bipartite, of 142 nm or 281 nm in length with 20 nm diameter on infected leaves. Specific detection and identification of SbWMV was set up using the RT-PCR. PCR fragments of SbWMV(0.5kb) were obtained by using the designed primers for SbWMV RNA 2.

• Journal of the Korean Geotechnical Society
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• v.23 no.8
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• pp.97-106
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• 2007

In this study, experiments are conducted to find out the effect of waste leachate on landfill clay liner system. Tensile test, hydrometer analysis and crack pattern test were conducted on sand-bentonite mixtures with different pH values of water. The tensile strength of specimen compacted with pH 9 of water is smaller than that of specimen compacted with for pH 3 and 6 of water. That is, the higher the pH value, the smaller the tensile strength, because a higher pH solution decreases flocculation phenomenon. The percent finer also increased with high pH value in particle size distribution of fine grained soil (<0.075 mm), because the velocity of particles settling decreases. This trend becomes the clearer as the content of bentonite, becomes the larger, because the higher pH value decreases flocculation structure of fine soils. The results of the crack pattern tests also showed the effect of pH values of water.