• Title/Summary/Keyword: energy degradation

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Effect of Curing Solution and Pre-Rust Process on Rebar Corrosion in the Cement Composite (시멘트 복합체 내부 철근 부식에 양생 용액과 철근 사전 부식이 미치는 영향)

  • Du, Rujun;Jang, Indong;Lee, Hyerin;Yi, Chongku
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.2
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    • pp.1-8
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    • 2022
  • The corrosion of reinforcement is the main reason for the performance degradation of concrete structures. The pre-rusted parts of rebar in concrete structures are vulnerable to the corrosion, especially if the structure is exposed to wet or chlorinated environments. In this study, effects of different curing solution on corrosion behavior of the pre-rusted rebars in the cement composites were investigated. HCl(3%) and CaCl2(10%) solution were utilized to accelerate the pre-rust of the rebar, and each pre-rust condition rebar including reference (RE) were placed in mortar cylinder. Three kinds of samples then were cured in CaCl2 (3%) solution and tap water respectively for 120 days. Electrochemical polarization and half-cell potential measurement were used to monitor the influence of curing water on the corrosion behavior of pre-rusted steel bar in cement composite. The surface morphology and composition of corroded steel bar were analyzed by scanning electron microscope and energy dispersive X-ray diffraction. The results show that the corrosion rates of pre-rusted samples in both curing water are higher than that of non-pre-rusted samples. The corrosion rates of RE, CaCl2 and HCl pre-rusted samples in salt water were 8.14, 4.48, 13.81 times higher than those in tap water respectively, on the 120th day.

Enhanced Cycle Performance of Bi-layer Structured LMO-NCM Positive Electrode at Elevated Temperature (겹층구조의 LMO-NCM 복합양극을 통한 고온 사이클 수명개선 연구)

  • Yoo, Seong Tae;Ryu, Ji Heon
    • Journal of the Korean Electrochemical Society
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    • v.25 no.4
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    • pp.184-190
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    • 2022
  • Spinel LiMn2O4 (LMO) and layered LiNi0.5Co0.2Mn0.3O2 (NCM) are widely used as positive electrode materials for lithium-ion batteries. LMO and NCM positive electrode materials have a complementary properties. LMO has low cost and high safety and NCM materials show a relatively high specific capacity and better cycle life even at elevated temperature. Therefore, the LMO and NCM active materials are blended and used as a positive electrode in large-size batteries for electric vehicles (xEV). In this study, the cycle performance of a blended electrode prepared by simply mixing LMO and NCM and a bi-layer electrode in which two electrode layers aree sequentially coated are compared. The bi-layer electrode prepared by composing the same ratio of both active materials has similar capacity and cycle performance to the blend electrode. However, the LN electrode coated with LMO first and then NCM is the best in the full cell cycle performance at elevated temperature, and the NL electrode, in which NCM is first coated with LMO has a faster capacity degradation than the blended electrode because LMO is mainly located on the top of the electrode adjacent to electrolyte and graphite negative electrode. Also, the LSTA (linear sweep thermmametry) analysis results show that the LN bi-layer electrode in which the LMO is located inside the electrode has good thermal stability.

The Hydrogen Reduction Behavior of MoO3 Powder (MoO3 분말의 수소환원거동)

  • Koo, Won Beom;Yoo, Kyoungkeun;Kim, Hanggoo
    • Resources Recycling
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    • v.31 no.1
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    • pp.29-36
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    • 2022
  • The hydrogen reduction behavior of molybdenum oxides was studied using a horizontal-tube reactor. Reduction was carried out in two stages: MoO3 → MoO2 and MoO2 → Mo. In the first stage, a mixed gas composed of 30 vol% H2 and 70 vol% Ar was selected for the MoO3 reduction because of its highly exothermic reaction. The temperature ranged from 550 to 600 ℃, and the residence time ranged from 30 to 150 min. In the second step, pure H2 gas was used for the MoO2 reduction, and the temperature and residence time ranges were 700-750 ℃ and 30-150 min, respectively. The hydrogen reduction behavior of molybdenum oxides was found to be somewhat different between the two stages. For the first stage, a temperature dependence of the reaction rate was observed, and the best curve fittings were obtained with a surface reaction control mechanism, despite the presence of intermediate oxides under the conditions of this study. Based on this mechanism, the activation energy and pre-exponential were calculated as 85.0 kJ/mol and 9.18 × 107, respectively. In addition, the pore size within a particle increases with the temperature and residence time. In the second stage, a temperature dependence of the reaction rate was also observed; however, the surface reaction control mechanism fit only the early part, which can be ascribed to the degradation of the oxide crystals by a volume change as the MoO2 → Mo phase transformation proceeded in the later part.

Photodegradation Characteristics of Oxygen Vacancy-fluorinated WO3 Photocatalysts Controlled by Plasma and Direct Vapor Fluorination (플라즈마 및 직접 기상 불소화에 의해 제어된 산소결핍 불소화 WO3 광촉매의 광분해 특성)

  • Lee, Hyeryeon;Lee, Raneun;Kim, Daesup;Lee, Young-Seak
    • Applied Chemistry for Engineering
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    • v.33 no.2
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    • pp.159-165
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    • 2022
  • To enhance the photocatalytic activities of WO3 photocatalysts, fluorine doping was performed to induce the oxygen vacancies. Both plasma and direct vaper fluorination were carried out for fluorine doping, and photocatalytic activities were examined by using methylene blue dye. Oxygen vacancies of the plasma and direct vaper fluorinated WO3 photocatalysts were measured to be 14.65 and 18.59%, which increased to about 23 and 56% at pristine WO3 photocatalysts. The degradation efficiency of methylene blue was also determined about 1.7 and 3.4 times higher than pristine WO3 photocatalysts, respectively, depending on oxygen vacancies increased. In addition, it was confirmed that the bandgap process energy decreased from 2.95 eV to 2.64 and 2.45 eV after fluorine doping. From this result, it is considered that the direct vaper fluorination has an advantage for increasing the photocatalytic activities of WO3 compared to that of the plasma fluorination.

Evaluation of Serviceability and Flexural Performance for RC Hollow Slab by Hollow Ratio and Damping Ratio (중공율과 감쇠율을 이용한 RC 중공 슬래브의 사용성 및 휨성능 평가)

  • Jong Hoon Kim;Dong Baek Kim;Yong Gon Kim;Jae Won Lee;Jeong Ho Choi
    • Journal of the Society of Disaster Information
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    • v.18 no.4
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    • pp.930-935
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    • 2022
  • Purpose: The purpose of this study is to evaluate the stiffness reduction and damping ratio of reinforced concrete hollow slabs and to analyze their performance, and to study the effect of the damping effect of hollow bodies and the stiffness reduction on the serviceability of slabs. Method: Test specimen was made in a size of 0.6m*0.21m*3.6m to evaluate the vibration effect of the slab, and the hollow ratio was set in six steps from 0.0% to 30% to measure the change in rigidity and damping according to the change in the hollow ratio. Result: As the hollow ratio increases, rigidity decreases and the natural frequency decreases, but as the mass decreases, the natural frequency increases gradually. Since energy is hardly dissipated up to the hollow ratio of 20%, the hollow ratio should be reduced by 30%. Conclusion: It was found that the bending strength degradation of the slab with a hollow ratio of about 30% is minimized, but an appropriate natural frequency can be maintained, and a certain damping effect can be obtained.

Flash Lamp Annealing of Ag Organometallic Ink for High-Performance Flexible Electrode (플래시 기반 유기금속화합물 열처리를 통한 고성능 유연 전극 제조)

  • Yu Mi Woo;Dong Gyu Lee;Yun Sik Hwang;Jae Chan Heo;SeongMin Jeong;Yong Jun Cho;Kwi-Il Park;Jung Hwan Park
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.36 no.5
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    • pp.454-462
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    • 2023
  • Flash lamp annealing (FLA) of metal nanoparticle (NP) ink has provided powerful strategies to fabricate high-performance electrodes on a flexible substrate because of its rapid processing capability (in milliseconds), low-temperature process, and compatibility with to roll-to-roll process. However, metal NPs [e.g., gold (Au), silver (Ag), copper (Cu), etc.] have limitations such as difficulty in synthesizing fine metal NPs (diameter less than 10 nm), high price, and degradation during ink storage and FLA processing. In this regard, organometallic ink has been proposed as a material that can replace metal NPs due to their low-cost (usually 1/100 times cheaper than metal nano inks), low-temperature processability, and high material stability. Despite these advantages, the fabrication of flexible electrodes through FLA treatment of organometallic compounds has not been extensively researched. In this paper, we experimentally guide how to determine the optimal conditions for forming electrodes on flexible substrates by considering material parameters, and flashlight processing parameters (energy density, pulse duration, etc) to minimize the difficulties that may arise during the FLA of organometallic ink.

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.

Effects of fermentation on protein profile of coffee by-products and its relationship with internal protein structure measured by vibrational spectroscopy

  • Samadi;Xin Feng;Luciana Prates;Siti Wajizah;Zulfahrizal;Agus Arip Munawar;Peiqiang Yu
    • Animal Bioscience
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    • v.36 no.8
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    • pp.1190-1198
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    • 2023
  • Objective: To our knowledge, there are few studies on the correlation between internal structure of fermented products and nutrient delivery from by-products from coffee processing in the ruminant system. The objective of this project was to use advanced mid-infrared vibrational spectroscopic technique (ATR-FT/IR) to reveal interactive correlation between protein internal structure and ruminant-relevant protein and energy metabolic profiles of by-products from coffee processing affected by added-microorganism fermentation duration. Methods: The by-products from coffee processing were fermented using commercial fermentation product, called Saus Burger Pakan, consisting of various microorganisms: cellulolytic, lactic acid, amylolytic, proteolytic, and xylanolytic microbes, for 0, 7, 14, 21, and 28 days. Protein chemical profiles, Cornell Net Carbohydrate and Protein System crude protein and CHO subfractions, and ruminal degradation and intestinal digestion of protein were evaluated. The attenuated total reflectance-Ft/IR (ATR-FTIR) spectroscopy was used to study protein structural features of spectra that were affected by added microorganism fermentation duration. The molecular spectral analyses were carried using OMNIC software. Molecular spectral analysis parameters in fermented and non-fermented by-products from coffee processing included: Amide I area (AIA), Amide II (AIIA) area, Amide I heigh (AIH), Amide II height (AIIH), α-helix height (αH), β-sheet height (βH), AIA to AIIA ratio, AIH to AIIH ratio, and αH to βH ratio. The relationship between protein structure spectral profiles of by-products from coffee processing and protein related metabolic features in ruminant were also investigated. Results: Fermentation decreased rumen degradable protein and increased rumen undegradable protein of by-products from coffee processing (p<0.05), indicating more protein entering from rumen to the small intestine for animal use. The fermentation duration significantly impacted (p<0.05) protein structure spectral features. Fermentation tended to increase (p<0.10) AIA and AIH as well as β-sheet height which all are significantly related to the protein level. Conclusion: Protein structure spectral profiles of by-product form coffee processing could be utilized as potential evaluators to estimate protein related chemical profile and protein metabolic characteristics in ruminant system.

Application of ZVI/TiO2 towards Clean-up of the Contaminated Soil with Polychlorinated Biphenyls (ZVI/TIO2를 이용한 폴리염화비페닐로 오염된 토양 정화)

  • Jae Wook Park;Yun Jin Jo;Dong-Keun Lee
    • Clean Technology
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    • v.29 no.2
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    • pp.118-125
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    • 2023
  • Once a site is contaminated with polychlorinated biphenyls (PCBs), serious environmental and human health risks are inevitable. Therefore, innovative but economical in situ remediation technologies must be immediately applied to the contaminated site. Recently, nanoscale zero-valent iron (nano-ZVI) particles have successfully been applied for the dechlorination of various chlorinated organic compounds like TCE, PCE and DDT, and they are considered to be environmentally safe due to the high abundance of iron in the earth's crust. Nano-ZVIs are much more reactive than granular ones, but tend to agglomerate due to their high surface energy and magnetic properties. In order to prevent them from being agglomerated toward larger particles, TiO2 was used as a support to immobilize the nano-ZVI particles as much as possible. 10wt% ZVI/TiO2 was prepared by adding NaBH4 slowly into an FeSO4/TiO2 aqueous slurry. In spite of their non-uniformity in size, the nano-ZVI particles were quite successfully dispersed onto the exterior surface of a non-porous TiO2 powder. The ZVI/TiO2 was then employed to degrade Aroclor 1242, a kind of PCBs standard, in spiked soil, and its reactivity towards the degradation of Aroclor 1242 was investigated. The fabricated ZVI/TiO2 degraded Aroclor 1242 in soil quite effectively, but the creation of remaining dechlorinated compounds, possibly high molecular weight hydrocarbons, in the soil was unavoidable.

Biodegradation of VOC Mixtures using a Bioactive Foam Reactor II: Analysis of Microbial Community (계면활성제 미생물반응기의(혼합 VOCs) 생분해 II: 미생물의 군집해석)

  • Jang, Hyun Sup;Shin, Shoung Kyu;Song, Ji Hyeon;Hwang, Sun Jin
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.6B
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    • pp.695-701
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    • 2006
  • A toluene-degrading bacterial strain was isolated from a mixed culture that was maintained using toluene as a sole carbon and energy source. The isolated bacterium was classified as Pseudomonas sp. TBD4 based on the close relationship to bacteria belonging to this genus. A bottle study to determine biodegradation rates of individual aromatic compounds showed that the biodegradation was faster in the order of toluene, benzene, styrene, and p-xylene. However, when various mixtures were subjected to TDB4, styrene was degraded at the highest rate, indicating that both toluene and p-xylene could stimulate the degradation of other substrates whereas styrene played as an inhibitor. In addition, the mixed culture and TDB4 were inoculated to the bioactive foam reactor (BFR), and the reactor performance and the corresponding change of microbial community were monitored using the fluorescent in situ hybridization (FISH) method. When an inlet concentration of the VOC mixture increased to greater than 250 ppm, the overall removal efficiency dropped significantly. The FISH measurement demonstrated that the ratio of TDB4 to the total bacteria also decreased to less than 20% along with the decline in removal efficiency in the BFR. As a result, the periodic addition of the pre-grown TDB4 might have been beneficial to achieve a stable performance in the BFR operated over an extended period.