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        검색결과 445

        3.
        2023.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        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.
        4,600원
        4.
        2023.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        PURPOSES : The current research aims to evaluate the impact of coating materials and temperature on the percentage of bead loss in pavement markings. METHODS : Five mixtures with varying numbers of coating layers (C0, C1, C2, C3, and C4) were prepared to assess the effect of coating layers on bead loss. The effect of stripping was simulated using a modified Hamburg Wheel Tracking test. Furthermore, the influence of temperature and coating material on bead loss was examined using control mixture (without coating), YR, and SY coating mixtures. The percentage bead loss was evaluated by a developed image analysis program. RESULTS : The results demonstrated a substantial reduction in bead loss as the number of coating layers increased, with the C4 mixture showing an impressive 4.3% bead loss after 500 HWT braking cycles compared to 27.4% for the C0 mixture. Higher testing temperatures resulted in increased bead loss, with the control mixture exhibiting the highest percentage loss at 7,500 HWT rolling cycles. Conversely, the YR and SY coating mixtures displayed superior resistance to bead loss. Statistical analysis confirmed the significance of coating layers in reducing bead loss, further supporting the effectiveness of coatings in preserving bead adhesion during HWT cycles. CONCLUSIONS : The findings highlight the potential of coating materials as a key protective measure for enhancing the longevity and performance of pavement markings.
        4,000원
        5.
        2023.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The tribology characteristics of the graphene coated PA6 were evaluated with scratch experiments. As a result, the following conclusions were obtained. The PA6 of the graphene coating shows a 0.1 improvement in friction coefficient and a lower abrasion depth than PA6 in the variable pressure-type scratch experiments. PA6 of the graphene coating showed a lower friction coefficient of 0.2 or more than PA6 in the friction coefficient in the static pressure scratch experiments, indicating that wear resistance was improved. In both the variable and the static pressure type scratch experiments, the tip depth of graphene-coated PA6 shows a thinner wear depth than PA6, showing the effect of graphene. The graphene content showed excellent tribology characteristics at 3%, and there was no difference in tribology characteristics at higher contents.
        4,200원
        6.
        2023.11 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Recently, the electron transport layer (ETL) has become one of the key components for high-performance perovskite solar cell (PSC). This study is motivated by the nonreproducible performance of ETL made of spin coated SnO2 applied to a PSC. We made a comparative study between tin oxide deposited by atomic layer deposition (ALD) or spin coating to be used as an ETL in N-I-P PSC. 15 nm-thick Tin oxide thin films were deposited by ALD using tetrakisdimethylanmiotin (TDMASn) and using reactant ozone at 120 °C. PSC using ALD SnO2 as ETL showed a maximum efficiency of 18.97 %, and PSC using spin coated SnO2 showed a maximum efficiency of 18.46 %. This is because the short circuit current (Jsc) of PSC using the ALD SnO2 layer was 0.75 mA/cm2 higher than that of the spin coated SnO2. This result can be attributed to the fact that the electron transfer distance from the perovskite is constant due to the thickness uniformity of ALD SnO2. Therefore ALD SnO2 is a candidate as a ETL for use in PSC vacuum deposition.
        4,000원
        14.
        2023.11 구독 인증기관·개인회원 무료
        Wide-area surface decontamination is essential during the sudden release of radioisotopes to the public, such as nuclear accidents or terrorist attacks. A spray coating composed of a reversible complex between poly (vinyl alcohol) (PVA) and phenylboronic acid-grafted poly (methyl vinyl ether-alt-mono-sodium maleate) (PBA–g–PMVE–SM) was developed to remove radioactive cesium from surfaces. The simultaneous spay of PVA and PBA–g–PMVE–SM aqueous polymer solutions containing Cs adsorbent to contaminated surfaces resulted in the spontaneous formation of a PBA–diol ester bond-based gel-like coating. The Cs adsorbent suspended in the gel-like coating selectively removed Cs-137 from the Cs-contaminated surface. The used gel-like coating were removed from surfaces by simple water rinsing. This recovery way has advantages compared with costly incineration to remove the organic materials for final disposal/storage of the radioactive waste. Thus, our spray coating is suitable for practical wide-area surface decontamination. In radioactive tests, the hydrogel containing Cs-adsorbent showed substantial Cs-137 removal efficiencies of 96.996% for painted cement and 63.404% for cement, which are 2.33 times better than the values for the commercial surface decontamination coating agent DeconGel.
        15.
        2023.11 구독 인증기관·개인회원 무료
        Domestic commercial low- and intermediate-level radioactive waste storage containers are manufactured using 1.2 mm thick cold-rolled steel sheets, and the outer surface is coated with a thin layer of primer of 10~36 μm. However, the outer surface of the primer of the container may be damaged due to physical friction, such as acceleration, resonance, and vibration during transportation. As a result, exposed steel surfaces undergo accelerated corrosion, reducing the overall durability of the container. The integrity of storage containers is directly related to the safety of workers. Therefore, the development of storage containers with enhanced durability is necessary. This paper provides an analysis of mechanical properties related to the durability of WC (tungsten carbide)-based coating materials for developing low- and intermediate-level radioactive waste storage containers. Three different WC-based coating specimens with varied composition ratios were prepared using HVOF (high-velocity oxy-fuel) technique. These different specimens (namely WC-85, WC-73, and WC-66) were uniformly deposited on cold-rolled steel surfaces ensuring a constant thickness of 250 μm. In this work, the mechanical properties of the three different WCbased coaitng materials evaluated from the viewpoints of microstructure, hardness, adheision force between substrate and coating material, and wear resistance. The cross-sectional SEM-EDS (Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy) images revealed that elements W (tungsten), C (carbon), Ni (nickel), and Cr (chromium) were uniformly distributed within the each coating layers which was approximately 250 μm thick. The average hardness values of HWC-85 and HWC-73 were found to be 1,091 Hv (Vickers Hardness) and 1,083 Hv, respectively, while the HWC-66 exhibited relatively lower hardness value of 883 Hv. This indicates that a higher WC content results in increased hardness. Adhesion force between and substrates and coating materials exceeded 60 MPa for all specimens, however, there were no significant differences observed based on the tungsten carbide content. Furthermore, a taber-type abrasion tester was used for conducting abrasion resistance tests under specific conditions including an H-18 load weight at 1,000 g with rotational speed set at 60 RPM. The abrasion resistance tests were performed under ambient temperatures (RT: 23±2°C) as well as relative humidity levels (RH: 50±10%). Currently, the ongoing abrasion resistance tests will include some results in this study.
        16.
        2023.11 구독 인증기관·개인회원 무료
        This study focuses on the development of coatings designed for storage containers used in the management of radioactive waste. The primary objective is to enhance the shielding performance of these containers against either gamma or neutron radiation. Shielding against these types of radiation is essential to ensure the safety of personnel and the environment. In this study, tungsten and boron cabide coating specimens were manufactured using the HVOF (High-Velocity Oxy Fuel) technuqe. These coatings act as an additional layer of protection for the storage containers, effectively absorbing and attenuating gamma and neutron radiation. The fabricated tungsten and boron carbide coating specimens were evaluated using two different testing methods. The first experiment evaluates the effectiveness of a radiation shielding coating on cold-rolled steel surfaces, achieved by applying a mixture of WC (Tungsten Carbide) powders. WC-based coating specimens, featuring different ratios, were prepared and preliminarily assessed for their radiation shielding capabilities. In the gamma-ray shielding test, Cs-137 was utilized as the radiation source. The coating thickness remained constant at 250 μm. Based on the test results, the attenuation ratio and shielding rate for each coated specimen were calculated. It was observed that the gammaray shielding rate exhibited relatively higher shielding performance as the WC content increased. This observation aligns with our findings from the gamma-ray shielding test and underscores the potential benefits of increasing the tungsten content in the coating. In the second experiment, a neutron shielding material was created by applying a 100 μm-thick layer of B4C (Boron Carbide) onto 316SS. The thermal neutron (AmBe) shielding test results demonstrated an approximate shielding rate of 27%. The thermal neutron shielding rate was confirmed to exceed 99.9% in the 1.5 cm thick SiC+B4C bulk plate. This indicates a significant reduction in required volume. This study establishes that these coatings enhance the gamma-ray and neutron shielding effectiveness of storage containers designed for managing radioactive waste. In the future, we plan to conduct a comparative evaluation of the radiation shielding properties to optimize the coating conditions and ensure optimal shielding effectiveness.
        17.
        2023.11 구독 인증기관·개인회원 무료
        Radioactive waste is typically disposed of using standard 200 and 320 L drums based on acceptance criteria. However, there have been no cases evaluating the disposal and suitability of 200 L steel drums for RI waste disposal. There has been a lack of prior assessments regarding the disposal and suitability of 200 L steel drums for the disposal of RI waste. Radioactive waste is transported to disposal facilities after disposal in containers, where the drums are loaded and temporarily stored. Subsequently, after repackaging the disposal drums, the repackaged drums are transported to disposal facilities by vehicle or ship for permanent disposal. Disposal containers can be susceptible to damage due to impacts during transportation, handling, and loading, leading to potential damage to the radiation primer coating during loading. Additionally, disposal containers may be subject to damage from electrochemical corrosion, necessitating the enhancement of corrosion resistance. Metal composite coatings can be employed to enhance both abrasion resistance and corrosion resistance. The application of metal composite coatings to disposal containers can improve the durability and radiation shielding performance of radioactive waste disposal containers. The thickness of radioactive waste disposal containers is determined through radioactive shielding analysis during the design process. The designed disposal containers undergo structural analysis, considering loading conditions based on the disposal environment. This paper focuses on evaluating the structural improvements achieved through the implementation of metal composite coatings with the goal of enhancing corrosion and abrasion resistance.
        18.
        2023.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구에서는 Monopile 방식 풍력발전기 강구조물의 부식을 방지하기 위하여 S355 steel의 표면 거칠기에 따른 용사 코팅 상태에 관한 연구를 수행했다. 일차적으로는 시편별 서로 다른 표면거칠기를 부여하기 위해 밀링머신에 페이스 커터를 결합하여 시편별로 다른 조건의 Ra값 기준 표면거칠기를 부여했다. 실험 조건으로는 시편 가공 시 4가지의 회전속도(60, 400, 1200, 2000 rpm), feed rate 150(mm/min) 조건을 선정했다. 2차로는 와이어 용융 방식의 아크 용사 코팅을 실시했다. 코팅 조건으로는 분사 거리 200mm, 전압 24V, 전류 120A, 분사 압력 5bar, 와이어 삽입 속도 30g/mm, 와이어 직경 2mm이다. 용사 코팅 후 FE-SEM으로 표면을 관찰한 결과 모든 시편의 S355 면과 코팅층(아연-알루미늄) 사이에 유격이 발생하지 않고 성공적으로 안착이 되었음을 확인할 수 있었다.
        4,000원
        19.
        2023.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study focused on improving the phase stability and mechanical properties of yttria-stabilized zirconia (YSZ), commonly utilized in gas turbine engine thermal barrier coatings, by incorporating Gd2O3, Er2O3, and TiO2. The addition of 3-valent rare earth elements to YSZ can reduce thermal conductivity and enhance phase stability while adding the 4-valent element TiO2 can improve phase stability and mechanical properties. Sintered specimens were prepared with hot-press equipment. Phase analysis was conducted with X-ray diffraction (XRD), and mechanical properties were assessed with Vickers hardness equipment. The research results revealed that, except for Z10YGE10T, most compositions predominantly exhibited the t-phase. Increasing the content of 3-valent rare earth oxides resulted in a decrease in the monoclinic phase and an increase in the tetragonal phase. In addition, the t(400) angle decreased while the t(004) angle increased. The addition of 10 mol% of 3-valent rare-earth oxides discarded the t-phase and led to the complete development of the c-phase. Adding 10 mol% TiO2 increased hardness than YSZ.
        4,000원
        20.
        2023.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        PURPOSES : The increase in particulate matter due to increased air pollutant emissions has become a significant social issue. According to the Ministry of Environment, air pollutants emitted from large-scale businesses in 2022 increased by 12.2% compared to the previous year, indicating that air pollution is accelerating owing to excessive industrialization. In this study, TiO2, which is used to reduce airborne particulate, was used. The TiO2 coating fixation and dynamic pressure coating-type TiO2 fixation methods were used to solve the material peeling phenomenon caused by gravity, which is a limitation when the TiO2 penetration method is applied to a vertical concrete structure along the road. The long-term durability and performance were analyzed through environmental resistance and NOx removal efficiency evaluation experiments. These analyses were then assessed by comparing the NOx removal efficiency with the dynamic pressure permeationtype TiO2 fixation method used in previous studies. METHODS : To evaluate the long-term durability and performance of the TiO2 coating fixation method and dynamic pressure coating TiO2 fixation method for vertical concrete structures, specimens were manufactured based on roadside vertical concrete structures. Environmental resistance tests such as the surface peeling resistance test (ASTM C 672) and freeze-thaw resistance test (KS F 2456) were conducted to evaluate the long-term durability. To evaluate the long-term performance, the NOx removal efficiency of TiO2 concrete owing to road surface deterioration during the environmental resistance test was evaluated using the NOx removal efficiency evaluation equipment based on the ISO 22197-1 standard. This evaluation was compared and analyzed using the dynamic pressure infiltration TiO2 fixation method. RESULTS : The long-term durability of the TiO2 coating fixation and dynamic pressure coating TiO2 fixation methods were evaluated using environmental resistance tests. During the surface peeling resistance test, the TiO2 material degraded and partially detached from the concrete. However, the NOx removal efficiency was ensured by the non-deteriorated and fixed TiO2 material. The long-term performance was confirmed through a freeze-thaw resistance test to evaluate the NOx removal efficiency after 300 cycles of surface deterioration. The results showed that when the TiO2 coating fixation and dynamic pressure infiltration TiO2 fixation methods were applied to vertical concrete structures, the durability of the structure was not compromised. In comparison to the dynamic pressure infiltration TiO2 fixation method, the NOx removal efficiency observed during the surface peeling resistance test was lower, while the freeze-thaw test exhibited notably higher removal efficiency. CONCLUSIONS : To solve the material peeling phenomenon caused by gravity, the long-term durability and performance were evaluated by applying the TiO2 coating fixation and dynamic pressurized coating TiO2 fixation methods to vertical concrete specimens. Long-term durability was confirmed through environmental resistance tests, and long-term utility was secured by measuring the NOx removal efficiency according to surface degradation. These findings show that implementing the TiO2 coating fixation method and dynamic pressure coating TiO2 fixation methods on-site effectively reduce NOx.
        4,600원
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