• Title/Summary/Keyword: Spectroscopy Analysis

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An Experimental Study on Relationship Between Half-Cell Potential and Corrosion Current Density of Chloride-Induced Corroded Steel in Concrete (염해에 따라 콘크리트 속에서 부식된 철근의 반전지전위와 부식전류밀도의 상관관계에 관한 실험적 연구)

  • Jo, Sang-Hyeon;Kim, Dong-Won;Kee, Seong-Hoon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.6
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    • pp.1-13
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    • 2022
  • This study aims to investigate the feasibility of the half-cell potential (HCP) measurements on the concrete surface for evaluation of corrosion rate (or corrosion levels) of reinforcing steel in concrete. A series of experimental study is performed to measure HCP (or corrosion potential, Ecorr) and corrosion current density (icorr) of reinforcing steel in concrete cube specimens, with a side length of 200 mm. Various corrosion levels in a range of 0% to 20% of the test specimens are accelerated by impressing current to the reinforcing steel in concrete immersed in 3.0 % NaCl solution. HCP is measured in accordance with ASTM C876-15, and corrosion current density is determined by using the Stern-Geary equation and measured polarization resistance measured by electrochemical impedance spectroscopy (EIS). As a result, a numerical formula that relates HCP and icorr in the test specimen is established by a regression analysis of the measured data in this study. It is observed that HCP is linearly correlated with log(icorr) with a R2 greater than 0.87, which is less affected by the experimental variables such as concrete mixture proportion, diameter of reinforcing steel and the amount of applied current in this study. These results exhibit that HCP measurements could be effective for evaluation of corrosion rate (or corrosion levels) of reinforcing steel in concrete in the case of exposed to a certain consistent environment.

Aqueous Boron Adsorption on Carbonized Nanofibers Prepared from Electrospun Polyacrylonitrile(PAN) Mats (전기방사 후 탄소화된 폴리아크릴로니트릴(PAN) 나노섬유의 수용액 중 붕소 흡착)

  • Hong, So Hee;Han, Sun-Gie;Kim, Su Young;Won, Yong Sun
    • Clean Technology
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    • v.28 no.3
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    • pp.210-217
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    • 2022
  • Boron(B) is a rare resource used for various purposes such as glass, semiconductor materials, gunpowder, rocket fuel, etc. However, Korea depends entirely on imports for boron. Considering the global boron reserves and its current production rate, boron will be depleted on earth in 50 years. Thus, a process including proper adsorbent materials recovering boron from seawater is demanded. This research proposed carbonized nanofibers prepared from electrospun PAN(polyacrylonitrile) mats as promising materials to adsorb boron in aqueous solution. First, the mechanism of boron adsorption on carbonized nanofibers was investigated by DFT(density functional method)-based molecular modeling and the calculated energetics demonstrated that the boron chemisorption on the nitrogen-doped graphene surface by a two-step dehydration is possible with viable activation energies. Then, the electrospun PAN mats were stabilized in air and then carbonized in an argon atmosphere before being immersed in the boric acid aqueous solution. Analytically, SEM(scanning electron microscopy) and Raman measurements were employed to confirm whether the electrospinning and carbonization of PAN mats proceeded successfully. Then, XPS(X-ray photoelectron spectroscopy) peak analysis showed whether the intended nitrogen-doped carbon nanofiber surface was formed and boron was properly adsorbed on nanofibers. Those results demonstrated that the carbonized nanofibers prepared from electrospun PAN mats could be feasible adsorbents for boron recovery in seawater.

Phthalate Exposure Levels and Related Factors in the Urban Low-Income Group: Focus on a Residential Disadvantaged Community (도시 저소득층의 프탈레이트 노출수준과 관련 요인: 거주 취약집단을 중심으로)

  • Dahee, Han;Jiyun, Kang;Seohui, Han;Su Hyeon, Kim;Hohyun, Jin;Chahun, Kim;Hosub, Im;Ki-Tae, Kim;Yong Min, Cho
    • Journal of Environmental Health Sciences
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    • v.48 no.6
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    • pp.315-323
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    • 2022
  • Background: Socioeconomical disadvantaged communities are more vulnerable to environmental chemical exposure and associated health effects. However, there is limited information on chemical exposure among vulnerable populations in Korea. Objectives: This study investigated chemical exposure among underprivileged populations. We measured urinary metabolites of phthalates in urban disadvantaged communities and investigated their correlations with residential environment factors and relative socioeconomic vulnerability. Methods: Urine samples were collected from 64 residents in a disadvantaged community in Seoul. A total of eight phthalate metabolites were analyzed by liquid chromatography-mass spectroscopy. Analytical method used by the Korean National Environmental Health Survey (KoNEHS) was employed. Covariate variance analysis and general linear regression adjusted with age, sex and smoking were performed. Results: Several phthalate metabolites, namely monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), and mono-n-butyl phthalate (MnBP) had higher levels than those reported in the adults of 4th KoNEHS. Notably, the MnBP level was higher in the lower socioeconomic group (geometric mean [GM]=47.3 ㎍/g creatinine) compared to non-recipients (GM=31.9 ㎍/g creatinine) and the national reference level (GM=22.0, 28.2 and 32.2 ㎍/g creatinine for adults, 60's and 70's, respectively.). When age, sex and smoking were adjusted, MEP and MnBP were significantly increased the lower socioeconomic group than non-recipients (p=0.014, p=0.023). The lower socioeconomic group's age of flooring were higher than non-recipients, not statistically significant. Conclusions: These results suggest that a relatively low income and aged flooring could be considered as risk factors for increased levels of phthalate metabolites in socioeconomic vulnerable populations.

Physicochemical properties of a calcium aluminate cement containing nanoparticles of zinc oxide

  • Amanda Freitas da Rosa;Thuany Schmitz Amaral;Maria Eduarda Paz Dotto;Taynara Santos Goulart;Hebert Luis Rossetto;Eduardo Antunes Bortoluzzi;Cleonice da Silveira Teixeira;Lucas da Fonseca Roberti Garcia
    • Restorative Dentistry and Endodontics
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    • v.48 no.1
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    • pp.3.1-3.14
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    • 2023
  • Objectives: This study evaluated the effect of different nanoparticulated zinc oxide (nano-ZnO) and conventional-ZnO ratios on the physicochemical properties of calcium aluminate cement (CAC). Materials and Methods: The conventional-ZnO and nano-ZnO were added to the cement powder in the following proportions: G1 (20% conventional-ZnO), G2 (15% conventional-ZnO + 5% nano-ZnO), G3 (12% conventional-ZnO + 3% nano-ZnO) and G4 (10% conventional-ZnO + 5% nano-ZnO). The radiopacity (Rad), setting time (Set), dimensional change (Dc), solubility (Sol), compressive strength (Cst), and pH were evaluated. The nano-ZnO and CAC containing conventional-ZnO were also assessed using scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Radiopacity data were analyzed by the 1-way analysis of variance (ANOVA) and Bonferroni tests (p < 0.05). The data of the other properties were analyzed by the ANOVA, Tukey, and Fisher tests (p < 0.05). Results: The nano-ZnO and CAC containing conventional-ZnO powders presented particles with few impurities and nanometric and micrometric sizes, respectively. G1 had the highest Rad mean value (p < 0.05). When compared to G1, groups containing nano-ZnO had a significant reduction in the Set (p < 0.05) and lower values of Dc at 24 hours (p < 0.05). The Cst was higher for G4, with a significant difference for the other groups (p < 0.05). The Sol did not present significant differences among groups (p > 0.05). Conclusions: The addition of nano-ZnO to CAC improved its dimensional change, setting time, and compressive strength, which may be promising for the clinical performance of this cement.

Thermal Performance Evaluation of Composite Phase Change Material Developed Through Sol-Gel Process (졸겔공법을 이용한 복합상변화물질의 열성능 평가)

  • Jin, Xinghan;Haider, Muhammad Zeeshan;Park, Min-Woo;Hu, Jong-Wan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.43 no.5
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    • pp.555-566
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    • 2023
  • In this study, a composite phase change material (CPCM) produced using the SOL-GEL technique was developed as a thermal energy storage medium for low-temperature applications. Tetradecane and activated carbon (AC) were used as the core and supporting materials, respectively. The tetradecane phase change material (PCM) was impregnated into the porous structure of AC using the vacuum impregnation method, and a thin layer of silica gel was coated on the prepared composite using the SOL-GEL process, where tetraethyl orthosilicate (TEOS) was used as the silica source. The thermal performance of the CPCM was analysed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC results showed that the pure tetradecane PCM had melting and freezing temperatures of 6.4℃ and 1.3℃ and corresponding enthalpies 226 J/g and 223.8 J/g, respectively. The CPCM exhibited enthalpy of 32.98 J/g and 27.7 J/g during the melting and freezing processes at 7.1℃ and 2.4℃, respectively. TGA test results revealed that the AC is thermally stable up to 500℃, which is much higher than the decomposition temperature of the pure tetradecane, which is around 120℃. Moreover, in the case of AC-PCM and CPCM thermal degradation started at 80℃ and 100℃, respectively. The chemical stability of the CPCM was studied using Fourier-transform infrared (FT-IR) spectroscopy, and the results confirmed that the developed composite is chemically stable. Finally, the surface morphology of the AC and CPCM was analysed using scanning electron microscopy (SEM), which confirmed the presence of a thin layer of silica gel on the AC surface after the SOL-GEL process.

$M\""{o}ssbauer$ Effet Studies on Nanocrystalline $Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_6$ Alloy (초미세결정립 $ Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_6$ 합금의 $M\""{o}ssbauer$ 효과 연구)

  • 신영남;김재경;양재석;조익한;강신규
    • Journal of the Korean Magnetics Society
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    • v.4 no.1
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    • pp.12-19
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    • 1994
  • The crystallization behavior of the amorphous $Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_{6}$ alloy with isothermal annealing at $552^{\circ}C$ was studied by $M\"{o}ssbauer$ spectroscopy. The amorphous phase was revealed to coexist together with $Do_{3}-FeSi$ nanocrystalline and Cu-duster in annealed alloys by $M\"{o}ssbauer$ spectrum analysis. At the early stage of crystallization, Si content of FeSi is high due to the creation of Cu-cluster, and decreases with annealing until 60 minutes, which results in the increase in the mean hyperfine field of FeSi, and thereafter keeps constant. After 60 minutes, the decrease in the mean hyperfine field of the residual armrphous, in spite of a slight change in the volume fraction of the FeSi and the residual armrphous, is caused by the increase in the content of Nb and B in residual amorphous phase. Both directions of the hyperfine field, those of the FeSi and the residual amorphous, become randomly oriented in about 60 minutes. For FeSi and Cu-duster, the Avrami exponents are 0.51 and O.65, the activation energies are 2.35 eV and 2.44 eV, and the incubation times are 2.4 minutes and 0.8 minutes respectively. Earlier formation of Cu-duster than that of FeSi is coincidence with the fact that Cu atom promotes the nucleation of the FeSi.

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Low Temperature CO Oxidation over Cu-Mn Mixed Oxides (Cu-Mn 혼합산화물 상에서 일산화탄소의 저온산화반응)

  • Cho, Kyong-Ho;Park, Jung-Hyun;Shin, Chae-Ho
    • Clean Technology
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    • v.16 no.2
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    • pp.132-139
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    • 2010
  • The Cu-Mn mixed oxide catalysts with different molar ratios of Cu/(Cu+Mn) prepared by co-precipitation method have been investigated in CO oxidation at $30^{\circ}C$. The catalysts used in this study were characterized by X-ray Diffraction (XRD), $N_2$ sorption, X-ray photoelectron spectroscopy (XPS), and $H_2$-temperature programmed reduction $(H_2-TPR)$ to correlate with catalytic activities in CO oxidation. The $N_2$ adsorption-desorption isotherms of Cu-Mn mixed oxide catalysts showed a type 4 having pore range of 7-20 nm and BET surface area was increased from 17 to $205\;m^2{\cdot}g^{-1}$ with increasing of Mn content. The XPS analysis showed the surface oxidation state of Cu and Mn represented $Cu^{2+}$and the mixture of $Mn^{3+}$ and $Mn^{4+}$, respectively. Among the catalysts studied here, Cu/(Cu+Mn) = 0.5 catalyst showed the highest activity at $30^{\circ}C$ in CO oxidation and the catalytic activity showed a typical volcano-shape curve with respect to Cu/(Cu+Mn) molar ratios. The water vapor showed a prohibiting effect on the efficiency of the catalyst which is due to the competitive adsorption of carbon monoxide on the active sites of catalyst surface and finally the formation of hydroxyl group with active metals.

Durability Evaluation of Cement Concrete Using Ferrosilicon Industrial Byproduct (페로실리콘 산업부산물 활용 시멘트 콘크리트의 내구성능 평가)

  • Chang-Young Kim;Ki Yong Ann
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.11 no.1
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    • pp.89-96
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    • 2023
  • In this paper, a ferrosilicon by-product was evaluated to confirm the feasibility of recycling it as supplementary cementitious material of ordinary Portland cement in concrete. Three different levels of replacement ratio (10 %, 20 % and 30 % of total binder) were applied to find which is the most beneficial to be used as a binder. Ferrosilicon concrete was initially assessed at setting time and compressive strength. Durability was evaluated by the resistance to chloride penetration test(RCPT) and alkali-silica reaction(ASR) with a comparison to silica fume concrete due to their similarity in chemical composition. The porosimetry and X-ray diffraction analysis along with energy dispersive X-ray spectroscopy give information on the microstructural characteristics of the ferrosilicon concrete. It was found that 10 % ferrosilicon concrete has higher strength while 20 %, 30 % have lower strength than OPC concrete. However, chemical resistance to chloride attack is higher when replacement is increased. Compared to silica fume, the durability of ferrosilicon might be less efficient however, it is obviously beneficial than OPC. High SiO2 content in ferrosilicon results in producing more C-S-H gel which could make denser pore structure. Most of the risk of alkali silica reaction to silicate binders through length change tests was less than 0.2 %, and both mortar using ferrosilicon and silica fume showed better resistance to alkali silica reaction as the substitution rate increased.Reuse of industrial waste rather than producing highly refined additives might reduce environmental load during manufacture and save costs.

Effects of Dielectric Curing Temperature and T/H Treatment on the Interfacial Adhesion Energies of Ti/PBO for Cu RDL Applications of FOWLP (FOWLP Cu 재배선 적용을 위한 절연층 경화 온도 및 고온/고습 처리가 Ti/PBO 계면접착에너지에 미치는 영향)

  • Kirak Son;Gahui Kim;Young-Bae Park
    • Journal of the Microelectronics and Packaging Society
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    • v.30 no.2
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    • pp.52-59
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    • 2023
  • The effects of dielectric curing temperature and temperature/humidity treatment conditions on the interfacial adhesion energies between Ti diffusion barrier/polybenzoxazole (PBO) dielectric layers were systematically investigated for Cu redistribution layer applications of fan-out wafer level package. The initial interfacial adhesion energies were 16.63, 25.95, 16.58 J/m2 for PBO curing temperatures at 175, 200, and 225 ℃, respectively. X-ray photoelectron spectroscopy analysis showed that there exists a good correlation between the interfacial adhesion energy and the C-O peak area fractions at PBO delaminated surfaces. And the interfacial adhesion energies of samples cured at 200 ℃ decreased to 3.99 J/m2 after 500 h at 85 ℃/85 % relative humidity, possibly due to the weak boundary layer formation inside PBO near Ti/PBO interface.

Nutritional analysis of amino acid composition and zinc bioavailability in plant-based meats (대체육의 아미노산 조성 및 아연 생체 이용률의 영양학적 분석)

  • Seohyun Kang;Solmin Lee;Min Seo Chang;Soorin Kim;Young-gyun Lim;Yujin Kim;Wonhyeong Jang
    • Analytical Science and Technology
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    • v.37 no.3
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    • pp.155-165
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    • 2024
  • This study aimed to assess whether plant-based meat substitutes can effectively replace animal meat products in terms of amino acid composition and zinc bioavailability. The evaluation was conducted in response to the growing demand for meat substitutes, driven by the increasing vegan population and the expansion of vegan culture. For this purpose, a chicken product and two plant-based meat substitutes in tender form were selected. The amino acid content and composition were measured using HPLC, while the levels of trace elements like zinc and calcium were determined through ICP-AES. Additionally, the presence of phytic acid, which inhibits zinc bioavailability, was extracted and quantified using UV-Vis spectroscopy. The results were analyzed in the context of daily product consumption. The findings revealed that certain essential amino acids, such as valine and lysine, were found to be deficient in plant-based meat substitutes compared to animal meat products. It was challenging to meet the recommended daily intake of these amino acids solely through the use of meat substitutes. Regarding zinc bioavailability, the inhibitory effect of calcium on zinc bioavailability was expected to be minimal. The zinc bioavailability of the meat substitutes varied significantly depending on the zinc and phytic acid content of the ingredients. Therefore, ingredients of plant-based meat substitutes should be carefully modulated to reach appropriate zinc bioavailability by selecting and processing plant materials with high zinc and low phytic acid content.