• Journal of Adhesion and Interface
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• v.15 no.2
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• pp.69-76
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• 2014

Two kinds of epoxy-functionalized alkoxysilane (EAS) compounds (EAS-MS and EAS-ES) were successfully synthesized through the reaction between epoxy resin (YD-128) and aminopropyl trimethoxysilane (APTMS) or aminopropyl triethoxysilane (APTES). By the hydrolysis-polycondensation reaction of EAS compounds with 3-Glycidyloxypropyl trimethoxysilane (GPTMS) and Tetraethyl orthosilicate (TEOS), silica/epoxy nanohybrids could be prepared at various compositions of EAS to GPTMS/TEOS. Prepared nanohybrids were yellow transparent and miscible with various organic solvents. By the reaction silica/epoxy nanohybrids with curing agents (TETA or acrylic acid), cured hybrids films could be obtained. These cured films showed higher thermal stability and mechanical property compared to cured neat epoxy resin. TEM and AFM images showed formation of nano-sized silica nanoparticles within cured hybrid films.

• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1569-1579
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• 2021

This study aims to provide microstructural characterization for the matrix graphite which molten salt reactors (MSRs) use, and improve resistance to molten salt infiltration of the matrix graphite for fuel elements. Mesocarbon microbeads (MCMB) densified matrix graphite A3-3 (MDG) was prepared by a quasi-isostatic pressure process. After densification by MCMBs with average particle sizes of 2, 10, and 16 ㎛, the pore diameter of A3-3 decreased from 924 nm to 484 nm, 532 nm, and 778 nm, respectively. Through scanning electron microscopy, the cross-section energy spectrum and time-of-flight secondary ion mass spectrometry, resistance levels of the matrix graphite to molten salt infiltration were analyzed. The results demonstrate that adding a certain proportion of MCMB powders can improve the anti-infiltration ability of A3-3. Meanwhile, the closer the particle size of MCMB is to the pore diameter of A3-3, the smaller the average pore diameter of MDG and the greater the densification. As a matrix graphite of fuel elements in MSR was involved, the thermal and mechanical properties of matrix graphite MDG were also studied. When densified by the MCMB matrix graphite, MDGs can meet the molten salt anti-infiltration requirements for MSR operation.

• Applied Chemistry for Engineering
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• v.32 no.2
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• pp.157-162
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• 2021

In this study, 3D printing filaments using recycled polypropylene (rPP) were produced by a single screw extruder. Graphene composite filament was also prepared using electrochemically exfoliated graphene (EEG) as a composite filler by adding 10, and 20 wt% of EEG to rPP. The graphene and rPP were successfully dispersed with great homogeneity, so that 3D filaments were uniformly produced, and their thermal properties increased as the graphene content increased. The mechanical property was also improved when EEG was 10 wt% but decreased when EEG was 20 wt% compared to that of rPP. 3D structures were successfully manufactured using prepared 3D filaments by a conventional 3D printer, and great advantages can be expected in terms of environmental and economical perspective by adopting plastic waste.

• Advances in concrete construction
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• v.8 no.1
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• pp.21-31
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• 2019

The rich recipe of ultra high performance concrete (UHPC) offers the higher mechanical, durability and dense microstructure property. The variable like cement/sand ratio, amount of supplementary cementitious material, water/binder ratio, amount of fiber etc. alters the UHPC hardened properties to any extent. Therefore, to understand the effects of these variables on the performance of UHPC, inevitably a stage-wise development is required. In the present experimental study, the effect of sand/cement ratio, the addition of finer material (fly ash and quartz powder) and, hybrid fiber on the fresh, compressive and microstructural property of UHPC is evaluated. The experiment is conducted in three phases; the first phase evaluates the flow value and strength attainment of ingredients, the second phase evaluates the efficiency of finer materials (fly ash and quartz powder) to develop the UHPC and the third phase evaluate the effect of hybrid fiber on the flow value and strength of ultra high performance hybrid fiber reinforced concrete (UHP-HFRC). It has been seen that the addition of fly ash improves the flow value and compressive strength of UHPC as compared to quartz powder. Further, the usage of hybrid fiber in fly ash contained matrix decreases the flow value and improves the strength of the UHP-HFRC matrix. The dense interface between matrix and fiber and, a higher amount of calcium silicate hydrate (CSH) in fly ash contained UHP-HFRC is revealed by SEM and XRD respectively. The dense interface (bond between the fiber and the UHPC matrix) and the higher CSH formation are the reason for the improvement in the compressive strength of fly ash based UHP-HFRC. The differential thermal analysis (DTA/TGA) shows the similar type of mass loss pattern, however, the amount of mass loss differs in fly ash and quartz powder contained UHP-HFRC.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2395-2407
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• 2022

The sodium-cooled fast reactor is among the innovative nuclear technologies selected in the framework of the development of Generation IV concepts, allowing the irradiation of uranium-plutonium mixed oxide fuels (MOX). A fundamental step for the safety assessment of MOX-fuelled pins for fast reactor applications is the evaluation, by means of fuel performance codes, of the integral thermal-mechanical behaviour under irradiation, involving the fission gas behaviour and release in the fuel-cladding gap. This work is dedicated to the performance analysis of an inner-core fuel pin representative of the ASTRID sodium-cooled concept design, selected as case study for the benchmark between the GERMINAL and TRANSURANUS fuel performance codes. The focus is on fission gas-related mechanisms and integral outcomes as predicted by means of the SCIANTIX module (allowing the physics-based treatment of inert gas behaviour and release) coupled to both fuel performance codes. The benchmark activity involves the application of both GERMINAL and TRANSURANUS in their "pre-INSPYRE" versions, i.e., adopting the state-of-the-art recommended correlations available in the codes, compared with the "post-INSPYRE" code results, obtained by implementing novel models for MOX fuel properties and phenomena (SCIANTIX included) developed in the framework of the INSPYRE H2020 Project. The SCIANTIX modelling includes the consideration of burst releases of the fission gas stored at the grain boundaries occurring during power transients of shutdown and start-up, whose effect on a fast reactor fuel concept is analysed. A clear need to further extend and validate the SCIANTIX module for application to fast reactor MOX emerges from this work; nevertheless, the GERMINAL-TRANSURANUS benchmark on the ASTRID case study highlights the achieved code capabilities for fast reactor conditions and paves the way towards the proper application of fuel performance codes to safety evaluations on Generation IV reactor concepts.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.112-119
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• 2022

Recently, as carbon neutrality has been important factor in the construction industry, many studies have been conducted on the high-volume fly ash concrete. High volume fly ash concrete(HVFC) is usually made by replacing more than 50% of cement with fly ash. However, HVFC has a disadvantage of low compressive strength in early age. To overcome this shortcoming of HVFC, improve this, interest in techonolgy using nanomaterials is increasing. Nano silica is expected to improve the early age strength of HVFC as a pozzolanic material. This study investigated the effect of nano silica on the early hydration reaction and microstructure of HVFC. The early hydration reaction of HFVC was analyzed through setting time, isothermal calorimeter, compressive strength and thermal weight analysis. In addition, the microstructure of HVFC was measured by mercury intrusion porosimetry. From the test results, it was confirmed that nano silica increased the early age strength and improve the microstructure of HVFC.

• The Korean Journal of Pain
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• v.35 no.3
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• pp.271-279
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• 2022

Background: Inflammation is known to underlie the pathogenesis in neuropathic pain. This study investigated the anti-inflammatory and neuroprotective mechanisms involved in antinociceptive effects of co-administration of acetaminophen and L-carnosine in chronic constriction injury (CCI)-induced peripheral neuropathy in male Wistar rats. Methods: Fifty-six male Wistar rats were randomly divided into seven experimental groups (n = 8) treated with normal saline/acetaminophen/acetaminophen + L-carnosine. CCI was used to induce neuropathic pain in rats. Hyperalgesia and allodynia were assessed using hotplate and von Frey tests, respectively. Investigation of spinal proinflammatory cytokines and antioxidant system were carried out after twenty-one days of treatment. Results: The results showed that the co-administration of acetaminophen and L-carnosine significantly (P < 0.001) increased the paw withdrawal threshold to thermal and mechanical stimuli in ligated rats compared to the ligated naïve group. There was a significant (P < 0.001) decrease in the levels of nuclear factor kappa light chain enhancer B cell inhibitor, calcium ion, interleukin-1-beta, and tumour necrotic factor-alpha in the spinal cord of the group coadministered with acetaminophen and L-carnosine compared to the ligated control group. Co-administration with acetaminophen and L-carnosine increased the antioxidant enzymatic activities and reduced the lipid peroxidation in the spinal cord. Conclusions: Co-administration of acetaminophen and L-carnosine has anti-inflammatory effects as a mechanism that mediate its antinociceptive effects in CCI-induced peripheral neuropathy in Wistar rat.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.2
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• pp.61-68
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• 2023

Ti and Ti alloys are used in the automobile and aerospace industries due to their high specific strength and excellent corrosion resistance. However their application is limited due to poor formability at room temperature and high unit cost. In order to overcome these issues, dissimilarly jointed materials, such as cladding materials, are widely investigated to utilize them in each industrial field because of an enhanced plasticity and relatively low cost. Among various dissimilar bonding processes, the rolled cladding process is widely used in Ti alloys, but has a disadvantage of low bonding strength. Although this problem can be solved through post-heat treatment, the mechanical properties at the bonded interface are deteriorated due to residual stress generated during post-heat treatment. Therefore, in this study, the microstructure change and residual stress trends at the interfaces of Ti/Al cladding materials were studied with increasing post-heat treatment temperature. As a result, compared to the as-rolled specimens, no difference in microstructure was observed in the specimens after postheat treatment at 300, 400, and 500℃. However, a new intermetallic compound layer was formed between Ti and Al when post-heat treatment was performed at a temperature of 600℃ or higher. Then, it was also confirmed that compressive residual stress with a large deviation was formed in Ti due to the difference in thermal expansion coefficient and modulus of elasticity between Ti Grade II and Al 1050.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.884-894
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• 2023

Design and safety assessment of fuel pins for application in innovative Generation IV fast reactors calls for a dedicated nuclear fuel modelling and for the extension of the fuel performance code capabilities to the envisaged materials and irradiation conditions. In the INSPYRE Project, comprehensive and physics-based models for the thermal-mechanical properties of U-Pu mixed-oxide (MOX) fuels and for fission gas behaviour were developed and implemented in the European fuel performance codes GERMINAL, MACROS and TRANSURANUS. As a follow-up to the assessment of the reference code versions ("pre-INSPYRE", NET 53 (2021) 3367-3378), this work presents the integral validation and benchmark of the code versions extended in INSPYRE ("post-INSPYRE") against two pins from the SUPERFACT-1 fast reactor irradiation experiment. The post-INSPYRE simulation results are compared to the available integral and local data from post-irradiation examinations, and benchmarked on the evolution during irradiation of quantities of engineering interest (e.g., fuel central temperature, fission gas release). The comparison with the pre-INSPYRE results is reported to evaluate the impact of the novel models on the predicted pin performance. The outcome represents a step forward towards the description of fuel behaviour in fast reactor irradiation conditions, and allows the identification of the main remaining gaps.

• Advances in materials Research
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• v.11 no.2
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• pp.121-146
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• 2022

In the recent years, the use of agricultural waste in green cement mortar and concrete production has attracted considerable attention because of potential saving in the large areas of landfills and potential enhancement on the performance of mortar. In this research, microparticles of palm oil fuel ash (POFA) obtained from a multistage thermal and mechanical treatment processes of raw POFA originating from palm oil mill was utilized as a pozzolanic material to produce high-performance cement mortar (HPCM). POFA was used as a partial replacement material to ordinary Portland cement (OPC) at replacement levels of 0, 5, 10, 15, 20, 25, 30, 35, 40% by volume. Sand with particle size smaller than 300 ㎛ was used to enhance the performance of the HPCM. The HPCM mixes were tested for workability, compressive strength, ultrasonic pulse velocity (UPV), porosity and absorption. The results portray that the incorporation of micro POFA in HPCMs led to a slight reduction in the compressive strength. At 40% replacement level, the compressive strength was 87.4 MPa at 28 days which is suitable for many high strength applications. Although adding POFA to the cement mixtures harmed the absorption and porosity, those properties were very low at 3.4% and 11.5% respectively at a 40% POFA replacement ratio and after 28 days of curing. The HPCM mixtures containing POFA exhibited greater increase in strength and UPV as well as greater reduction in absorption and porosity than the control OPC mortar from 7 to 28 days of curing age, as a result of the pozzolanic reaction of POFA. Micro POFA with finely graded sand resulted in a dense and high strength cement mortar due to the pozzolanic reaction and increased packing effect. Therefore, it is demonstrated that the POFA could be used with high replacement ratios as a pozzolanic material to produce HPCM.