Refractory materials, such as molybdenum and niobium, are potential candidates for cladding material due to their high melting temperatures and desirable mechanical properties at higher temperatures than those of zirconium alloys. However, refractory materials have low resistance to oxidation at elevated temperatures. Therefore, this study examined silicide or aluminide surface coatings as protection against rapid oxidation of refractory materials at elevated temperatures for a potential accident-tolerant fuel cladding. Silicide or aluminide layers were formed on refractory metal substrates by using the pack cementation method. The steam oxidation behavior of both coated and uncoated samples was compared by thermogravimetric analysis at 1200°C. The weight changes of the coated samples were greatly reduced than those of uncoated samples. Microstructural analyses demonstrated that the silicide and aluminide layers were oxidized to form a protective surface oxide that prevented rapid oxidation of the refractory substrate at elevated temperatures.

One of the efficient method for DPF(Diesel Particulate Filter) regeneration of diesel engines is using post fuel injection, which is injected into the combustion chamber during the expansion stroke. This method generates a heat for DPF regeneration by oxidation of HC with Pt coated on DOC(Diesel Oxidation Catalyst). This study investigates heat generation of DOC using post fuel injection.

This study involved the heterogenization of a binder pitch (BP) using a small amount of nanocarbon to improve physical properties of the resulting graphite electrode (GE). Heterogenization was carried out by adding 0.5–2.0 wt.% platelet carbon nanofiber (PCNF) or carbon black (CB) to a commercial BP. To evaluate the physical properties of the BPs, we designed a new model graphite electrode (MGE) using needle coke as a filler. The heterogenized binder pitch (HBP) with PCNF or CB clearly increased the coking value by 5–13 wt.% compared to that of the as-received BP. Especially, the model graphite electrodes prepared with HBPs containing 1.0 wt.% PCNF or CB showed significantly improved physical properties compared to the control MGE from the as-received BP. Although the model graphite electrodes prepared with HBPs showed similar properties, they had smaller pore sizes than the control. This indicates that heterogenization of the BP can effectively decrease the pore size in the MGE matrix. Correlating the average pore sizes with the physical properties of the model graphite electrodes showed that, for the same porosity, matrices formed by the HBP with a smaller average pore size can effectively improve the apparent density, tensile strength, and oxidation resistance of the model graphite electrodes.

We report a new route of akaganéite (β-FeOOH) formation and maghemite (γ-Fe2O3) formation. Akaganéite can be produced by stirring Fe2+ at room temperature for a day under mild conditions. We used FeCl2 ·4H2O as the precursor and mixed it with the Na-rich particle from the oxidation debris solution. The role of the concentration ratio between graphene oxide (GO) and NaOH was addressed to generate oxidation debris (OD) on the surface. In particular, the characterization of OD by transmission electron microscope (TEM) imaging provides clear evidence for the crystal formation of Na-rich particle under electron beam irradiation. For the base treatment process, increasing the concentration of a NaOH in Na-rich solution contributed primarily to the formation of γ-Fe2O3. The characterization by scanning electron microscope (SEM) and TEM showed that the morphology was changed from needle-like to small-oval form. In addition, β-FeOOH can be effectively produced directly using GO combined with FeCl2 ·4H2O at room temperature. More specifically, the role of parent material (Hummer's GO and Brodie's GO) was discussed, and the crystal transformation was identified. Our results concluded that β-FeOOH can be formed in basic and acidic conditions.

In this research, in order to increase the oxidation resistance of graphite, kaolin and alumina powder with different ratios (26A-74S, 49A-51S, 72A-28S) and slurry method were used to create an aluminosilicate coating on the graphite substrate. In order to reduce the difference in the coefficients of thermal expansion of graphite with aluminosilicate coating, aluminum metaphosphate coating as an interlayer was prepared on the surface of graphite by cathodic electrochemical treatment. The isothermal oxidation test of the samples was carried out in air at a temperature of 1250 °C for 1, 3 and 5 h. The microstructure, chemical composition, and phase components of the coating were, respectively, analyzed by scanning electron microscope equipped with an energy-dispersive spectrometer and X-ray diffraction. The results indicated that, by increasing the withdrawal speed of the samples in slurry method, the amount of changes in the weight of the samples has increased and therefore had a direct effect on oxidation. In addition, it was approved that, at high-temperature oxidation, AlPO4 glass phase forms on aluminum metaphosphate interlayer which retards graphite oxidation. Along with aluminum metaphosphate, aluminosilicate coating also produces a glass phase which fills and seals the voids on the surface which prevents the oxygen to reach the surface of graphite. The created double-layer coating including an interlayer of aluminum metaphosphate + slurry coating prepared with the ratio of 26A-74S as the optimal coating in this research was able to increase the oxidation resistance of graphite by 73% at a temperature of 1250 °C.

Cholesterol is prone to oxidation, which results in the formation of cholesterol oxidation products (COPs). This occurs because it is a monounsaturated lipid with a double bond on C-5 position. Cholesterol in foods is mostly non-enzymatically oxidized by reactive oxygen species (ROS)-mediated auto-oxidative reaction. The COPs are found in many common foods of animal-origin and are formed during their manufacture process. The formation of COPs is mainly related to the temperature and the heating time the food is processed, storage condition, light exposure and level of activator present such as free radical. The level of COPs in processed foods could reach up to 1-10 % of the total cholesterol depending on the foods. The most predominant COPs in foods including meat, eggs, dairy products as well as other foods of animal origin were 7-ketocholesterol, 7 α-hydroxycholesterol (7α-OH), 7β-hydroxycholesterol (7β-OH), 5,6α-epoxycholesterol (5,6α -EP), 5,6β-epoxycholesterol (5,6β-EP), 25-hydoxycholesterol (25-OH), 20-hydroxycholesterol (20-OH) and cholestanetriol (triol). They are mainly formed non-enzymatically by cholesterol autoxidation. The COPs are known to be potentially more hazardous to human health than pure cholesterol. The procedure to block cholesterol oxidation in foods should be similar to that of lipid oxidation inhibition since both cholesterol and lipid oxidation go through the same free radical mechanism. The formation of COPs in foods can be stopped by decreasing heating time and temperature, controlling storage condition as well as adding antioxidants into food products. This review aims to present, discuss and respond to articles and studies published on the topics of the formation and inhibition of COPs in foods and key factors that might affect cholesterol oxidation. This review may be used as a basic guide to control the formation of COPs in the food industry.

Bioreactors are devices used by sewage treatment plants to process sewage and which produce active sludge, and sediments separated by solid-liquid are treated in anaerobic digestion tanks. In anaerobic digestion tanks, the volume of active sludge deposits is reduced and biogas is produced. After dehydrating the digestive sludge generated after anaerobic digestion, anaerobic digested wastewater, which features a high concentration of organic matters, is generated. In this study, the decomposition of organic carbon and nitrogen was studied by advanced oxidation process. Ozone-microbubble flotation process was used for oxidation pretreatment. During ozonation, the TOC decreased by 11.6%. After ozone treatment, the TOC decreased and the removal rate reached 80.4% as a result of the Ultra Violet-Advanced Oxidation Process (UV-AOP). The results with regard to organic substances before and after treatment differed depending on the organic carbon index, such as CODMn, CODCr, and TOC. Those indexes did not change significantly in ozone treatment, but decreased significantly after the UV-AOP process as the linkage treatment, and were removed by up to 39.1%, 15.2%, and 80.4%, respectively. It was confirmed that biodegradability was improved according to the ratio of CODMn to TOC. As for the nitrogen component, the ammonia nitrogen component showed a level of 3.2×102 mg/L or more, and the content was maintained at 80% even after treatment. Since most of the contaminants are removed from the treated water and its transparency is high, this water can be utilized as a resource that contains high concentrations of nitrogen.

This study used optical and scanning electron microscopy to analyze the surface oxidation phenomenon that accompanies a γ'-precipitate free zone in a directional solidified CM247LC high temperature creep specimen. Surface oxidation occurs on nickel-based superalloy gas turbine blades due to high temperature during use. Among the superalloy components, Al and Cr are greatly affected by diffusion and movement, and Al is a major component of the surface oxidation products. This out-diffusion of Al was accompanied by γ' (Ni3Al) deficiency in the matrix, and formed a γ'-precipitate free zone at the boundary of the surface oxide layer. Among the components of CM247LC, Cr and Al related to surface oxidation consist of 8 % and 5.6 %, respectively. When Al, the main component of the γ' precipitation phase, diffused out to the surface, a high content of Cr was observed in these PFZs. This is because the PFZ is made of a high Cr γ phase. Surface oxidation of DS CM247LC was observed in high temperature creep specimens, and γ'-rafting occurred due to stress applied to the creep specimens. However, the stress states applied to the grip and gauge length of the creep specimen were different, and accordingly, different γ'-rafting patterns were observed. Such surface oxidation and PFZ and γ'-rafting are shown to affect CM247LC creep lifetime. Mapping the microstructure and composition of major components such as Al and Cr and their role in surface oxidation, revealed in this study, will be utilized in the development of alloys to improve creep life.

강황 분말의 첨가가 마요네즈의 품질특성, 항산화활성 및 산화안정성에 미치는 영향에 대해 평가하였다. 들기름으로 제조된 마요네즈에 강황 분말을 0.5%, 1%, 2%, 3% 농도로 첨가하여 4°C에서 12주 동안 저장하였으며, 강황 분말 무첨가구와 비교하였다. 강황 분말 첨가량이 많아짐에 따라 들기름 마요네즈의 L* (명도) 값은 유의적으로 감소하였고, a* (적색도)는 모든 실험구에서 negative (-)값이었으며, b* (황색도)값은 유의적으로 증가되는 경향이었다(p<0.05). 강황 분말 첨가량이 많아짐에 따라 총 페놀 함량 및 항산화 활성이 유의적으로 증가하였다(p<0.05). 마요네즈를 저장하는 동안 과산화물가는 유의적으로 증가하였으나, 강황 분말 첨가 시료에서는 유의적으로 낮았다(p<0.05). 마요네즈의 유화안정성은 저장 초기에 비해 저장 기간이 길어질수록 감소되는 경향이었으나, 0.5%의 강황 분말 첨가구는 무첨가구에 비해 유의적으로 높은 유화안정성을 보였으며, 1%의 강황 분말 첨가구는 무첨가구와 유의차를 보이지 않았다. 점도는 저장 기간이 경과됨에 따라 감소되었으나, 무첨가구에 비해 1% 이상의 강황 분말 첨가구에서 유의적으로 높았다. 들기름 마요네즈에 강황 분말 첨가 시 항산화 활성 증대 및 과산화물의 생성 억제에 효과적이었으며, 특히 0.5~1% 첨가시 마요네즈의 유화안정성 및 점도 개선에 도움이 될 것으로 판단된다.

본 연구의 목적은 남자 대학 엘리트 조정선수의 2000 m 로잉 에르고미터 수행 후 저온침수 처 치를 통해 혈중 젖산, LDH, MDA 및 SOD의 변화에 긍정적인 영향을 주어 피로 회복에 미치는 영향을 구명하는 데 있다. 이에 남자 대학 엘리트 조정선수 10명을 대상으로 고강도 로잉 에르고미터 2,000 m 수 행 후 비 처치와 저온 침수 처치의 효과를 비교하였다. 측정 변인들에 대한 결과를 검증하기 위해 처치 및 시기 간 상호작용 효과를 분석하기 위해 ANOVA를 실시하였고 각 항목별 유의수준 .05로 설정하여 다음 의 결과를 도출하였다. 젖산은 시기 간 주효과가 나타났고(p<.001) 그룹 내 시기별 차이가 났다(p<.001). 또한, LDH는 그룹 내 시기별 차이가 나타났다(p<.05). MDA는 그룹×시기 간 상호작용 효과가 나타났고 (p<.05), 그룹 간(p<.05), 시기 간(p<.001) 주효과가 나타났다. SOD는 그룹 간, 시기 주효과가 나타났고 (p<.05) 회복 30분 후 그룹 간 차이가 나타났다(p<.05). 이를 종합해 볼 때, 본 연구에서 실시한 저온침수처치가 조정 선수의 혈중 피로 물질, 활성산소 및 항산화 효소에 유의한 효과를 나타냈다. 따라서 운동선수 의 고강도 훈련 후 저온침수를 적극 활용할 것을 권장한다.

Carbon/carbon composites are widely used in re-entry engineering applications thanks to their excellent mechanical properties at high temperatures, but they are easily oxidized in the oxygenated atmosphere. It is important to research their residual mechanical properties influenced by oxidation behaviour, in order to ensure the in-service safety. A microscale degradation model is proposed to predict the oxidation behavior based on the mass conservation and diffusion equations, the derived equivalent steady recession rate of composite is employed to evaluate the residual mechanical properties of the oxidized composite theoretically. A numerical strategy is proposed to investigate the oxidation mechanism of this composite. The differences in the degradation rate between the fiber and the matrix resulted in the steady state and an unchanged shape of the front. Residual mechanical properties of composite with three different domains of oxidation were simulated with a multiscale coupled model. The numerical results demonstrated that the mechanical properties of this composite decreased by 24–32% after oxidation for 30 min at 850 °C. Oxidation also caused the stress redistribution inside components, with the stress concentration diminishing their load-bearing capacity. The local areas of increased stress in the pyrocarbon matrix provided new ways for diffusion of oxygen into the pyrocarbon matrix and fibers.

Volatile organic compounds (VOCs) are a paramount factor in air pollution of the environment. VOCs are vastly present in the wastewater discharged by the pharmaceutical industries. As it is evaporative in nature, it enters the environment spontaneously and causes air pollution, global warming, acid rain and climate change. VOCs must be treated before discharging or any other aerobic methods using an efficient catalyst. As the catalytic oxidation in the liquid phase is facile compared to the gas phase, this study investigated on catalytic liquid-phase oxidation of VOCs in model and real pharmaceutical wastewater. The model compounds of toluene-, ethylbenzene- and chlorobenzene-contaminated waters were treated separately along with the VOCs present in real pharmaceutical wastewater using a tungsten-based carbon catalyst. The tungsten was impregnated on the low-cost activated carbon matrix as it has good selectivity and catalytic property toward VOCs for facile catalytic operations. The metal catalysts were characterised by Fourier transform infrared spectroscopy, X-ray diffraction studies, and scanning electron microscopy with elemental and mapping analysis. The treatability was monitored by total organic carbon, ultra-violet spectroscopy and high-pressure liquid chromatography analysis. The tungsten-impregnated activated carbon matrix (WACM) has a catalytic efficiency toward toluene by 85.45 ± 1.78%, ethylbenzene by 93.9 ± 1.16%, chlorobenzene by 85.9 ± 2.26% and pharmaceutical VOCs by 85.05 ± 1.73% in 20 treatment cycles. The results showed that WACM worked efficiently in VOCs treatment, preventing the environment from air pollution. Furthermore, liquid-phase oxidation could easily be implementable on an industrial scale.

수도권에 위치한 S매립장 내 3개의 매립장을 대상으로 매립가스 배출 및 주요 경로별 표면 발산과 관련된 분석을 하였다. 전체 매립가스 발생비율 10.9%인 LS1이 총 표면발산 비중은 49.4%를 차지하고 있었다. 3개 매립장에서의 메탄의 총 표면발산은 13.6 Nm3/min로서, LS1 8.4 Nm3/min (61.7%), LS2 4.0 Nm3/min(29.4%), LS3 1.2 Nm3/min(8.9%)이고, 발산경로별로는 상부 7.3 Nm3/min (53.2%), 사면 6.4 Nm3/min(46.7%), 다이크 0.02 Nm3/min(0.1%)이었다. 3개 매립장의 주요 배출경로 별 산화율은 다이크가 87.5%로 가장 크고, 상부 72.3%, 사면 71.8% 순이었다. 메탄을 기준으로 표면발 산 기여율은 매립장 별로 LS1이 전체의 61.7%로 가장 컸다. 주요 배출경로별로는 LS1의 사면이 전체의 41.7%, LS2의 상부 24.4%, LS1의 상부 20.0%로서 S매립장의 전체 메탄 표면발산량의 86.1%를 차지함 에 따라 향후 집중적인 관리가 필요할 것으로 판단되었다.

In this paper, we report and discuss the semi-permanently hydrophilic (SPH) treatment of polyester fabric using plasma polymerization and oxidation based on atmospheric pressure dielectric barrier discharge (APDBD) technology. SiOxCy (-H) was coated on polyester fabric using Hexamethylcyclotrisiloxane (HMCTSO) as a precursor, and then plasma oxidation was performed to change the upper layer of the thin film to SiO2-like. The degradation of hydrophilicity of the SPH polyester fabrics was evaluated by water contact angle (WCA) and wicking time after repeated washing. The surface morphology of the coated yarns was observed with scanning electron microscopy, and the presence of the coating layer was confirmed by measuring the Si peak using energy dispersive x-ray spectroscopy. The WCA of the SPH polyester fabric increased to 50 degrees after 30 washes, but it was still hydrophilic compared to the untreated fabric. The decrease in hydrophilicity of the SPH fabric was due to peeling of the SiOxCy(-H) thin film coated on polyester yarns.

High-temperature oxidation of a Ni-based superalloy was analyzed with samples taken from gas turbine blades, where the samples were heat-treated and thermally exposed. The effect of Cr/Ti/Al elements in the alloy on high temperature oxidation was investigated using an optical microscope, SEM/EDS, and TEM. A high-Cr/high-Ti oxide layer was formed on the blade surface under the heat-treated state considered to be the initial stage of high-temperature oxidation. In addition, a PFZ (γ’ precipitate free zone) accompanied by Cr carbide of Cr23C6 and high Cr-Co phase as a kind of TCP precipitation was formed under the surface layer. Pits of several μm depth containing high-Al content oxide was observed at the boundary between the oxide layer and PFZ. However, high temperature oxidation formed on the thermally exposed blade surface consisted of the following steps: ① Ti-oxide formation in the center of the oxide layer, ② Cr-oxide formation surrounding the inner oxide layer, and ③ Al-oxide formation in the pits directly under the Cr oxide layer. It is estimated that the Cr content of Ni-based superalloys improves the oxidation resistance of the alloy by forming dense oxide layer, but produced the σ or μ phase of TCP precipitation with the high-Cr component resulting in material brittleness.

This study was performed to investigate the effects of water molecules on ozone oxidation of acetaldehyde using a manganese oxide catalyst at room temperature. The catalytic ozone oxidation was conducted at different relative humidity (RH) conditions of 0%, 50%, and 80%. As the RH increased, both ozone and acetaldehyde removal efficiencies dropped due to competitive adsorption on the surface of the catalyst. At the highest RH of 80%, the oxidation reaction was severely retarded, and oxidation by-products such as acetic acid were formed and adsorbed on the surface. After the ozone oxidation of acetaldehyde, the regeneration of the catalyst using ozone alone was tested, and the further oxidation of accumulated organic compounds was investigated under the RH conditions of 0%, 50%, and 80%. When the highest relative humidity was introduced in the regeneration step, the ozonation reaction with the by-products adsorbed on the catalyst surface decreased due to the competitive reaction with water molecules. These findings revealed that, only when relative humidity was low to minimize the formation of by-products, the ozone oxidation of acetaldehyde using the manganese oxide catalyst at room temperature can be feasible as an effective control method.

This study assessed the changes in the fiber properties of virgin and recovered fibers from lab-scale and pilot-scale depolymerization reactors based on the thermal air oxidation-resistance characteristics. Lab-scale and pilot-scale depolymerization reactors had different depolymerization volumes. Results showed that the lab-scale and pilot-scale peak solvent temperatures were 185 °C and 151 °C, respectively. The lab-scale had highest solvent temperature rate increase because of the small depolymerization volume and the dominant role of the cavitation volume. The structural properties of the recovered and virgin fibers were intact even after the depolymerization and after the pretreatment and oxidation-resistance test. We observed 1.213%, 1.027% and 0.842% weight loss for the recovered (lab-scale), the recovered (pilot-scale) and virgin fibers because of the removal of impurities from the surface and chemisorbed gases. Further, we observed 0.8% mass loss of the recovered fibers (lab-scale) after the oxidative-onset temperature because of the “cavitation erosion effect” from the dominant of the cavitation bubbles. The “cavitation erosion effect” was subdued because of the increased depolymerization volume in the pilot-scale reactor. Therefore, negligible impact of the pilot-scale mechanochemical recycling process on the structure and surface characteristics of the fibers and the possibility of reusing the recovered fibers recycling process were characteristic. Representative functional groups were affected by the thermal oxidation process. We conducted HPLC, HT-XRD, TGA– DSC, XPS, SEM, and AFM analysis and provided an extensive discussion of the test thereof. This study highlighted how misleading and insufficient small-lab-scale results could be in developing viable CFRP depolymerization process.

This work reported the electrochemical and photoelectrochemical (PEC) properties of a new photoelectrode based on hematite Co-Fe2O3@NiO, a photoactive semiconductor, was prepared using a process involving a combination of the co-precipitation and microwave-assisted synthesis of Fe2O3, Co-Fe2O3 and Co-Fe2O3@NiO, respectively. The obtained products were characterized by X-Ray powder Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray analysis (EDX), Ultraviolet–Visible (UV–vis) analysis, Fourier Transform Infrared spectroscopy (FT-IR). X-ray diffraction (XRD) pattern of the sample determined the crystal structure of α-Fe2O3 nanoparticles. The SEM image shows spherical nanoparticles. FTIR spectrospy spectrum confirmed the phase purity and chemical bond for the sample. Optical studies show a variation of band gap from 2.118 to 2.07 eV. The electrochemical and photoelectrochemical (PEC) performance of the films were examined by cyclic voltammetry, linear sweep voltammetry and chronoamperometry. The electrochemical oxidation of water achieved by Cobalt-doped Fe2O3@ GCE modified electrode exhibited the current density of 21 mA/g at 0.5 V vs. SCE for 5 at% of Co and reveals enhanced specific capacitance of 352.11 F/g. The catalytic performance of urea oxidation was measured by cyclic voltammetry on Co-Fe2O3@NiO nanoparticles modified glassy carbon electrode (GCE) in alkaline medium. The electrode Co-Fe2O3@NiO without annealing showed a peak current density of 1.59 mA/cm2 at 0.1 M urea in 1.0 M NaOH, which was 3.6 fold higher than that of Co-Fe2O3@NiO with annealing. In another part, this work reported the photoelectrochemical (PEC) properties of photoanode prepared by spin coating. The highest photocurrent 0.042 mA/cm2 at 0.5 V Vs SCE was obtained for 5% Co-Fe2O3@NiO while the photocatalytic oxidation of urea.

Designing and producing a low-cost, high-current-density electrode with good electrocatalytic activity for the oxygen evolution reaction (OER) is still a major challenge for the industrial hydrogen energy economy. In this study, nanostructured Fe-doped CuCo(OH)2 was discovered to be a precedent electrocatalyst for OER with low overpotential, low Tafel slope, good durability, and high electrochemically active surface sites at reduced mass loadings. Fe-doped CuCo(OH)2 nanosheets are made using a hydrothermal synthesis process. These nanosheets are clumped together to form a highly open hierarchical structure. When used as an electrocatalyst, the Fe-doped CuCo(OH)2 nanosheets required an overpotential of 260 mV to reach a current density of 50 mA cm−2. Also, it showed a small Tafel slope of 72.9 mV dec−1, and superior stability while catalyzing the generation of O2 continuously for 20 hours. The Fe-doped CuCo(OH)2 was found to have a large number of active sites which provide hierarchical and stable transfer routes for both electrolyte ions and electrons, resulting in exceptional OER performance.

Conventional wastewater treatment plants (WWTPs) do not fully remove micropollutants. Enhanced treatment of sewage effluents is being considered or implemented in some countries to minimize the discharge of problematic micropollutants from WWTPs. Representative enhanced sewage treatment technologies for micropollutant removal were reviewed, including their current status of research and development. Advanced oxidation processes (AOPs) such as ozonation and UV/H2O2 and adsorption processes using powdered (PAC) and granular activated carbon (GAC) were mainly discussed with focusing on process principles for the micropollutant removal, effect of process operation and water matrix factors, and technical and economic feasibility. Pilot- and full-scale studies have shown that ozonation, PAC, and GAC can achieve significant elimination of various micropollutants at economically feasible costs(0.16-0.29 €/m3). Considering the current status of domestic WWTPs, ozonation and PAC were found to be the most feasible options for the enhanced sewage effluent treatment. Although ozonation and PAC are all mature technologies, a range of technical aspects should be considered for their successful application, such as energy consumption, CO2 emission, byproduct or waste generation, and ease of system construction/operation/maintenance. More feasibility studies considering domestic wastewater characteristics and WWTP conditions are required to apply ozonation or PAC/GAC adsorption process to enhance sewage effluent treatment in Korea.