• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.196-201
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• 2023

In this study, a CNT fiber flexible electrode grafted with CuO nanoparticles (CuO NPs) and polyaniline (PANI) was developed and applied to a nonenzymatic electrochemical sensor for H₂O₂ detection. CuO NPs/PANI/CNT fiber electrode was fabricated through the synthesis and deposition of PANI and CuO NPs on the CNT fiber surface using an electrochemical method. Surface morphology and elemental composition of the CuO NPs/PANI/CNT fiber electrode were characterized by scanning electron microscope with energy dispersive X-ray spectrometry. And its electrochemical characteristics were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). Compared with a bare CNT fiber as a control group, the CuO NPs/PANI/CNT fiber electrode showed a 4.78-fold increase in effective surface area and a 8.33-fold decrease in electron transfer resistance, which leads to excellent electrochemical properties such as a good electrical conductivity and an efficient electron transfer. These improved characteristics were due to the synergistic effect through the grafting of CNT fiber, PANI and CuO NPs. As a result, this electrode enhanced the H₂O₂ sensing performance.

• Journal of the Korean Geotechnical Society
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• v.23 no.12
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• pp.25-32
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• 2007

This study is to evaluate the effect of chemical attack on durability and deterioration of lining concrete in tunnel. Surface examination, nondestructive inspection, uniaxial compressive strength test, carbonation test, chloride diffusion test, micro-structural analysis were performed to analyze the deterioration of lining concrete in tunnel constructed 70 years ago. From surface examination results, the tunnel had been repaired and reinforced in several times. It has many cracks, water-leakage, efflorescence and exploitation. Compressive strengths obtained from nondestructive inspection and uniaxial compressive strength test have measured $17.5{\sim}34.7MPa$, and $12.8{\sim}40.3MPa$, respectively. Carbonation depth specimen cored from concrete lining has ranged from 3mm to 27mm. From chloride diffusion test, most specimens have low permeability. And the XRD analysis was able to detect ettringite and thaumasite, which were confirmed by SEM and EDS results to be the causes for the deterioration of lining concrete.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.419-425
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• 2023

This paper presents the research results of analyzing the high-temperature corrosion characteristics of three currently commercialized heat exchanger tube materials under actual operating conditions of a biomass power plant. In order to precisely analyze the high-temperature corrosion characteristics of these materials, a high-temperature corrosion evaluation device was installed in the power plant equipment, which allows for adjusting the surface temperature of the heat exchanger tubes. Experiments were conducted for approximately 300 hours under various temperature and operating conditions. In this study, the commercialized heat exchanger tube materials used were SA213T12, SA213T22, and SA213T91 alloys. In order to objectively analyze the high-temperature corrosion characteristics of each material, an international standard-based process to remove corrosion products was applied to obtain the weight change of the specimens, and the average thickness loss and corrosion rate were derived. Thus, the high-temperature corrosion results for each condition were quantitatively compared and analyzed. In addition, in order to increase the reliability of the high-temperature corrosion evaluation method introduced in this study, the surface and cross-sectional corrosion of the specimens were confirmed by using scanning electron microscopy and energy-dispersive X-ray analysis. Based on these analysis results, it was found that the corrosion resistance of the commercial heat exchanger materials increases as the content of chrome and nickel in the composition increases. Additionally, it was found that the corrosion phenomenon is rapidly accelerated as the surface temperature increases. Finally, the replacement period (lifetime) of the heat exchanger tubes under each condition could be inferred through this study.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.5
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• pp.174-180
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• 2023

Porcelain (white ware, celadon ware) coated with a ferrous sulfate and ferrous/cobalt sulfate was sintered at 1250℃. The specimens were investigated by HR-XRD, FE-SEM, HR-EDS, and UV-vis spectrophotometer. Through X-ray rietveld quantitative analysis, quartz and mullite were found to be the main phases for white ware, and mullite and plagioclase were found to be the main phases for celadon ware. When the pigment of ferrous/cobalt sulfate was applied, were identified as an andradite phase for celadon ware and a spinel phase for the white ware, and the amorphous phase, respectively. The L^* value, which was the brightness of the specimen, was 72.01, 60.92 for white ware and celadon ware, respectively. The ferrous and ferrous/cobalt pigment coated porcelain had L^* values of 44.89, 52.27 for white ware and celadon ware, respectively; with a^* values of 2.12, 1.40, an d at b^* values of 1.45 and 13.79. As for the color of the specimens, it was found that the L^* value was greatly affected by the white ware, and the b^* value differed greatly depending on the clay. It was thought to be closely related to the production of the secondary phase such as Fe₂O₃ and andradite phase produced in the surface layer.

• Korean Journal of Heritage: History & Science
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• v.56 no.4
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• pp.216-228
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• 2023

The purpose of this study is to apply the handheld Raman spectrometer to identify the coloring materials used in a large Buddhist painting (of Maitreya Buddha) at Janggoksa Temple through cross-validation with HH-XRF. An in situ investigation was performed together with use of a digital microscope and HH-XRF analysis to verify the properties of pigments used in the gwaebul ("large Buddhist painting") via a non-destructive method. However, the identification of coloring materials composed of light elements and mixed or overlaid pigments is difficult using only non-destructive analysis data. Unlike in situ investigation, laboratory analysis often required samples yet the sampling is restricted to a small quantity due to the cultural heritage characteristic. Thus, it is necessary to develop a non-destructive in situ method to supplement the HH-XRF data. The large Buddhist painting at Janggoksa Temple was painted mainly using white, red, yellow, green, and blue colors. The Raman spectroscopy provides molecular information, while XRF spectroscopy provides information about elemental composition of the pigments. Analysis results identified various coloring materials: inorganic pigment, such as lead white, minium, cinnabar, and orpiment, as well as organic pigment such as gamboge and indigo. Therefore, it is possible to obtain more information for the identification of pigments; organic pigment and mixed or overlaid pigments, while at the same time minimizing the collection sample and simplifying the analysis procedure compared to previously used methods. The results of this study will be used as basic data for the analysis of painting cultural heritage through a non-destructive in situ method in the future.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.263-270
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• 2024

In this study, impact factors for dehydration with KOMIR-Tube system using flocculant and dewatering tube were evaluated for mine drainage sludges. The experiments were conducted on semi-active facility sludges with water contents above 90 % using KOMIR-Tube system. The flocculant and input amount were determined from laboratory experiment and the dewatering efficiency was verified onsite experiment. The sludge characteristics were identified by instrumental analysis such as zeta potential measurement, particle size analysis, XRD, XRF and SEM-EDS. Selection of flocculants for sludge dewatering treatment need to consider not only precipitated rate but also filterated rate. Floc size has to keep at least 0.7 mm. From on-site experiments, sludge dewatering using KOMIR-Tube system suggests to carry out April and May that is low rainfall and humidity considering to climate conditions. Also, dewatering rate depends on the crystal degree of mineral that mainly makes up sludges. Particularly, goethite of the iron hydroxides has better dewatering rate than ferrihydrite. Ferrihydrite is low degree of crystallinity and uncleared or broad shaped crystal, goethite is good crystallinity with needle shaped crystal so that the effect of flocculation and dewatering showed to depend on the crystal. In results, impact factors of dewatering for mine drainage sludges are related to flocculant, climate, crystallinity and shape of iron hydroxides.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.2
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• pp.169-181
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• 2007

Statement of problem: Titanium is well known as a proper metal for the dental restorations, because it has an excellent biocompatibility, resistance to corrosion, and mechanical property. However, adhesion between titanium and dental porcelains is related to the diffusion of oxygen to the reaction layers formed on cast-titanium surfaces during porcelain firing and those oxidized layers make the adhesion difficult to be formed. Many studies using mechanical, chemical and physical methods to enhance the titanium-ceramic adhesion have been actively performed. Purpose: This study meant to comparatively analyse the adhesion characteristics depending on different titanium surface coatings after coating the casts and wrought titanium surfaces with Au and TiN. Material and method: In this study, the titanium specimens (CP-Ti, Grade 2, Kobe still Co. Japan) were categorized into cast and wrought titanium. The wrought titanium was cast by using the MgO-based investment(Selevest CB, Selec). The cast and wrought titanium were treated with Au coating($ParaOne^{(R)}$., Gold Ion Sputter, Model PS-1200) and TiN coating(ATEC system, Korea) and the ultra low fusing dental porcelain was fused and fired onto the samples. Biaxial flection test was done on the fired samples and the porcelain was separated. The adhesion characteristics of porcelain and titanium after firing and the specimen surfaces before and after the porcelain fracture test were observed with SEM. The atomic percent of Si on all sample surfaces was comparatively analysed by EDS. In addition, the constituents of specimen surface layers after the porcelain fracture and the formed compound were evaluated by X-ray diffraction diagnosis. Result: The results of this study were obtained as follows : 1. The surface characteristics of cast and wrought titanium after surface treatment(Au, TiN, $Al_2O_3$ sandblasting) were similar and each cast and wrought titanium showed similar bonding characteristics. 2. Before and after the biaxial flection test, the highest atomic weight change of Si component was found in $Al_2O_3$ sandblasted wrought titanium(28.6at.% $\rightarrow$ 8.3at.%). On the other hand, the least change was seen in Au-Pd-In alloy(24.5at.% $\rightarrow$ 9.1at.%). 3. Much amount of Si components was uniformly distributed in Au and TiN coated titanium, but less amount of Si's was unevenly dispersed on Al2O3 sandblasting surfaces. 4. In X-ray diffraction diagnosis after porcelain debonding, we could see $Au_2Ti$ compound and TiN coating layers on Au and TiN coated surfaces and $TiO_2$, typical oxide of titanium, on all titanium surfaces. 5. Debonding of porcelain on cast and wrought titanium surface after the biaxial flection is considered as a result of adhesion deterioration between coating layers and titanium surfaces. We found that there are both adhesive failure and cohesive failure at the same time. Conclusion: These results showed that the titanium-ceramic adhesion could be improved by coating cast and wrought titanium surfaces with Au and TiN when making porcelain fused to metal crowns. In order to use porcelain fused to titanium clinically, it is considered that coating technique to enhance the bonding strength between coating kKlayers and titanium surfaces should be developed first.

• Development and Reproduction
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• v.4 no.2
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• pp.215-220
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• 2000

Most of endocrine disrupters (EDs) have been reported to exhibit estrogenic or anti-androgenic activity and thereby may disrupt reproductive development in human or wildlife. This study was performed to investigate the effects of estrogen (E$_2$), bisphenol (BP) and octylphenol (OP) on the mouse Leydig cell line (TM3). TM3 originated from testis of 11~13-daly-old BALB/c nu/＋ mice was cultured in DMEM supplemented with 10％ FBS alone or medium with estrogen (E$_2$), bisphenol (BP) and octylphenol (OP; 1 pM, 1 nM, 1 $\mu$M, 1 mM, respectively) for 48 hours. After culture, total cell number and viability were assessed by heamocyto-meter and trypan blue stain. Expression of cytochrome P450scc (CYPscc) mRNA whose product is involved in steroid hormone biosynthesis and estrogen receptor $\alpha$(ER $\alpha$) mRNA were detected by RT-PCR. As a result, treatment of TM3 with E$_2$, BP and OP(1 mM, respectively) significantly decreased the viability but not all of groups as high as 1 $\mu$M. Exposure of TM3 to OP significantly reduced the total cell number but not E$_2$ or BP. The expression of CYPscc mRNA was slightly reduced in BP (1 nM, 1 $\mu$M) and significantly decreased in OP (1 nM, 1 $\mu$M) treated TM3, except E$_2$ group. But the expression of ER $\alpha$ mRNA was sightly increased in all treated groups. In conclusion, BP and OP (high concentration) might inhibit steroidogenesis by decreasing the CYPscc mRNA expression in the mouse testis. These results suggest that BP and OP might impair spermatogenesis and subsequently disturb testicular function.

• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.187-196
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• 2005

Structural sites which cations can occupy in garnet structure are centers of the tetrahedron, octahedron, and distorted cube sharing edges with the tetrahedron and octahedron. Among them, the size of cation occuping at tetrahedral site (the center of tetrahedron) is closely related with the size of a unit cell of garnet. Accordingly, garnet containing iron with relative large ionic radii in tetrahedral site can be considered as a promising matrix for the immobilization of the elements with large ionic radii, such as actinides in radioactive wastes. We synthesized several garnets with the batch composition of $Ca_{1.5}GdCe_{0.5}ZrFeFe_3O_{12}$, and studied their properties and phase relations under various conditions. Mixed samples were fabricated in a pellet form under a pressure of $200{\~}400{\cal}kg/{\cal}cm^2$ and were sintered in the temperature range of $1100\~1400^{\circ}C$ in air and under oxygen atmospheres. Phase identification and chemical analysis of synthesized samples were conducted by XRD and SEM/EDS. In results, garnet was obtained as the main phase at $1300^{\circ}C$, an optimum condition in this system, even though some minor phases like perovskite and unknown phase were included. The compositions of garnet and perovskite synthesized from the batch composition of $Ca_{1.5}GdCe_{0.5}ZrFeFe_3O_{12}$ were ranged $[Ca_{l.2-1.8}Gd_{0.9-1.4}Ce_{0.3-0.5}]^{VIII}[Zr_{0.8-1.3}Fe_{0.7-1.2}]^{VI}[Fe_{2.9-3.1}]^{IV}O_{12}$ and $Ca_{0.1-0.5}Gd_{0.0-0.8}Ce_{0.1-0.5}\;Zr_{0.0-0.2}Fe_{0.9-1.1}O_3$, respectively. Ca content was exceeded and Ce content was depleted in the 8-coordinated site, comparing to the initial batch composition. This phenomena was closely related to the content of Zr and Fe in the 6-coordinated site.

• Journal of The Korean Society of Grassland and Forage Science
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• v.30 no.2
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• pp.169-178
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• 2010

The present study was conducted with four ruminally fistulated cattle to examine the fermentation characteristics and effective degradability (ED) in the rumen, and whole tract digestibility and TDN values of various silages (whole crop rye, RS; whole crop barley, BS; Italian ryegrass, IRGS and sudangrass, SGS) which were produced in Korea. The pH of rumen fluid were not greatly affected by silage at most times after feeding but SGS decreased (p<0.049) the ruminal ammonia-N concentration as 7.28 mg/100 ml at 3h after feeding compared to other silages. An acetate proportion from SGS feeding was higher at 1h (p<0.018), 3h (p<0.004) and 6h (p<0.019) after feeding than those from other silages. The propionate ($C_2$) proportion, however, was greater (p<0.001~p<0.042) for the RS and BS than the corresponding values of other silages up to 6h after feeding while the lowest $C_2$ proportion was observed from SGS. The butyrate proportion was lowest (p<0.007~p<0.027) in the cattle fed BS at 1~6h after feeding among silages. An ED of dry matter (DM) in the rumen was highest (P<0.048) for RS as 59.64%, and was reduced in the order of BS (56.12%), IRGS (55.64%) and SGS (54.02%). Similar tendency was observed in the EDs of crude protein (p<0.014) and organic matter (OM, p<0.039). The whole tract digestibility of DM (p<0.032), neutral detergent fiber (NDF, p<0.034) and OM (p<0.041) of SGS was greatly reduced. The TDN value based on whole tract digestibility of silages was highest for RS as 61.1%, and TDN values of BS, IRGS and SGS were 57.1%, 57.9% and 50.7%, respectively. Based on the results obtained from the present study, components in various whole crop silages produced in Korea might affect the ruminal VFA proportion, and especially, NDF content could greatly influence on the TDN value of silage calculated based on the NDF content.