• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2017년도 춘계공동학술대회
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• pp.108-108
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• 2017

In this study, biocomposite filaments with agricultural by-products can be used in extrusion-based 3D (Three-dimensional) printing. Extrusion-based 3D printing stands as a promising technique owing to its versatility. We hypothesized that bio-filament composite consisted of something derived from agricultural by-products could be used as 3D printing materials that could overcome the drawbacks of PCL (poly-caprolactone). Bio-filament mixed with PCL and agricultural by-products was defined as r-PCL in this study. In order to find it out the optimal mixing ratio of filaments, we had investigated PCL, r-PCL 10%, r-PCL 20%, r-PCL 50% separately. The morphological and chemical characteristics of the filaments were analyzed by FE-SEM (Field emission scanning electron microscope) and EDX (Energy-dispersive X-Ray spectroscopy), and the mechanical properties were evaluated by stress-strain curve, water contact angle, and cytotoxicity analysis. Results of this study have been shown as a promising way to produce eco-friendly bio-filaments composite for FDM (Fused deposition modeling) method based 3D printing technology. Thus, we could establish biomimetic scaffolds based on bio-printer filaments mixed with agricultural by-product.

• 한국재료학회지
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• 제26권10호
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• pp.521-527
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• 2016

Geopolymers have many advantages over Portland cement, including energy efficiency, reduced greenhouse gas emissions, high strength at early age and improved thermal resistance. Alkali activated geopolymers made from waste materials such as fly ash or blast furnace slag are particularly advantageous because of their environmental sustainability and low cost. However, their durability and functionality remain subjects for further study. Geopolymer materials can be used in various applications such as fire and heat resistant fiber composites, sealants, concretes, ceramics, etc., depending on the chemical composition of the source materials and the activators. In this study, we investigated the thermal properties and microstructure of fly ash and blast furnace slag based geopolymers in order to develop eco-friendly construction materials with excellent energy efficiency, sound insulation properties and good heat resistance. With different curing times, specimens of various compositions were investigated in terms of compressive strength, X-ray diffraction, thermal property and microstructure. In addition, we investigated changes in X-ray diffraction and microstructure for geopolymers exposed to $1,000^{\circ}C$ heat.

• 한국분말재료학회지
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• 제27권3호
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• pp.247-255
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• 2020

Recently, interest in technology for eco-friendly energy harvesting has been increasing. Polyvinylidene fluoride (PVDF) is one of the most fascinating materials that has been used in energy harvesting technology as well as micro-filters by utilizing an electrostatic effect. To enhance the performance of the electrostatic effect-based nanogenerator, most studies have focused on enlarging the contact surface area of the pair of materials with different triboelectric series. For this reason, one-dimensional nanofibers have been widely used recently. In order to realize practical energy-harvesting applications, PVDF nanofibers are modified by enlarging their contact surface area, modulating the microstructure of the surface, and maximizing the fraction of the ν-phase by incorporating additives or forming composites with inorganic nanoparticles. Among them, nanocomposite structures incorporating various nanoparticles have been widely investigated to increase the β-phase through strong hydrogen bonding or ion-dipole interactions with -CF₂/CH₂- of PVDF as well as to enhance the mechanical strength. In this study, we report the recent advances in the nanocomposite structure of PVDF nanofibers and inorganic nanopowders.

• Elastomers and Composites
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• 제55권1호
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• pp.13-19
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• 2020

4,4'-Methylenebis(2-chlorobenzenamine) (MOCA)-free fast curing polyurethanes were prepared. In this study, the processibility of a fast curing polyurethane system was characterized by assessing the pot life. The obtained pot life of the polyurethane was 6-8 s, indicating that this prepolymer-curative system is appropriate for ribbon flow casting. The influence of the NCO index on the viscosity and mechanical properties was evaluated. The viscosity, tensile strength, tear strength, and hardness of the as-prepared polyurethanes showed an increasing trend, with an increase in the NCO index, whereas the elongation at break increased initially and then decreased with an increase in the NCO index. The gel fraction and crosslink density showed a direct correlation with the NCO index, which substantiated the improved mechanical properties at the higher NCO index. The coefficients of friction and abrasion deteriorated with an increase in the NCO index.

• Elastomers and Composites
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• 제55권3호
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• pp.215-221
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• 2020

Silica/SBR (styrene-butadiene rubber) compounds are the primary constituents of tire treads. Furthermore, the excellent dynamic viscoelastic properties of silica lead to good fuel efficiencies. However, the silanol group on the surface of silica does not mix well with non-polar rubber because of its polarity. This incompatibility causes aggregation due to the occurrence of hydrogen bonding between the hydroxyl groups, thereby reducing the dispersibility of silica. Recently, the wet master batch (WMB) process has been applied to overcome these disadvantages, and research on silica dispersants that can be used in the WMB process has been increasing. In this study, we prepared silica/SBR compounds by using three types of eco-friendly cellulose-based dispersants in the WMB process, namely: cellulose-, sodium carboxymethyl cellulose, and nanocellulose-based dispersants. Subsequently, we compared the vulcanization characteristics, viscoelastic properties, and mechanical properties of the compounds. The silica dispersibility in the rubber compounds was improved with the addition of the nano-cellulose dispersant, resulting in the enhancement of the workability, hardness, tensile strength, and wear resistance of the SBR compound.

• Nano
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• 제13권11호
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• pp.1850135.1-1850135.8
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• 2018

A one-step high-temperature solvothermal approach to the synthesis of monolayer or bilayer $MoS_2$ anchored onto reduced graphene oxide (RGO) sheet (denoted as $MoS_2/RGO$) is described. It was found that single-layered or double-layered $MoS_2$ were synthesized directly without an extra exfoliation step and well dispersed on the surface of crumpled RGO sheets with random orientation. The prepared $MoS_2/RGO$ composites delivered a high reversible capacity of $900mAhg^{-1}$ after 200 cycles at a current density of $200mAg^{-1}$ as well as good rate capability as anode active material for lithium ion batteries. This one-step high-temperature hydrothermal strategy provides a simple, cost-effective and eco-friendly way to the fabrication of exfoliated $MoS_2$ layers deposited onto RGO sheets.

• Elastomers and Composites
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• 제54권3호
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• pp.220-224
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• 2019

Herein, three polymer compounds were manufactured using three polymer combination methods, ethylene-vinyl acetate/ethylene-propylene-diene-copolymer (EPDM), ethylene-vinyl acetate (EVA)/polyethylene-A (PE-A; density: 0.870), and ethylene-vinyl acetate (EVA)/polyethylene-B (PE-B; density: 0.885), for making cable sheath for use in the shipping industry. In this study, EVA, EPDM, PE-A, and PE-B were used as matrix polymers, and EVA-grafted maleic anhydride was used as a coupling agent for compounding with various compounds such as a fire retardant, cross-linking agent, filler, and other additives, besides the plasticizer. ${\Delta}T$, Mooney viscosity, and tensile strength increased in order of EPDM < PE-A < PE-B, the probable reason is due to the different crosslinking effect. The three compounds showed similar results for fire resistance and aging resistance after compounding process, but they showed excellent cold resistance owing to the non-polarity of the polymers and sufficient plasticizer content.

• Membrane and Water Treatment
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• 제14권3호
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• pp.121-128
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• 2023

This study introduces a NaOH/Zn-assisted hydrothermal method for the synthesis of zeolites derived from coal ash (CA). A zeolite/Zn adsorbent is successfully prepared by the activation of CA with NaOH and Zn; it is characterized by a high surface area and a negative surface charge.Methylene blue (MB) and methyl orange (MO) are selected as dye pollutants, and their adsorption onto the zeolite/Zn adsorbent is investigated. Results show the high adsorption capacities of MB and MO and that the negative surface charge facilitates electrostatic interactions between the adsorbates and adsorbents. The zeolite/Zn adsorbents shows the selective adsorption of positively charged dye MB via electrostatic interactions between the =NH+ group (positive dipole) and the oxygen functional group of the adsorbents (negative dipole). The selectivity for the positively charged dye is sufficiently high, with the removal efficiency reaching 99.41% within 10 min. By contrast, the negatively charged dye MO exhibits negligible absorption. These findings confirm the role of electrostatic interactions in the adsorption of MB, in addition to the effect of a large surface area. The results of this study are expected to facilitate the development of simple, eco-friendly, and cost-effective zeolite-based adsorptive composites from CA residuals for the selective removal of dye pollutants from CA waste.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.51-52
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• 2023

A new shape-stable composite phase change material (PCM) have been produced via an easy and simple vacuum impregnation method. The composite PCM have been derived from almond shell biochar (ASB) as supporting material and capric acid (CA) as phase change material. Cost effective waste almond shells (AS) are renewable, eco-friendly, and rich in pores which enhance the possibility of CA impregnation. Therefore, in this study, three different ratios of CA (1:1, 1:2 and 1:3) have been incorporated in ASB to produce shape-stabilized phase change composites (ASCAs). Different techniques such as scanning electron microscopy (SEM), Fourier transform-infrared spectroscope (FT-IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) have been applied to evaluate the characteristics of ASCAs. The attained composite PCMs have exhibited shape stability with high latent heat storage, that makes it suitable for thermal energy storage applications.

• Tribology and Lubricants
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• 제33권1호
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• pp.15-22
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• 2017

Because the running speed of vehicles is increasing and a shorter braking distance is required, high heat-resistant brake pads are needed to satisfy the requirements of customers and car makers. In the near future, hazardous materials such as Cu, Cr, Zn, and Sb will be restricted from use in friction materials. Ceramic composites reinforced by carbon fibers are good candidates for eco-friendly friction materials. In this study, we develop ceramic composite friction materials. The friction materials are composed of carbon fibers, Si, SiC, graphite, and phenol resin and are prepared by hot forming and heat treatment at high temperatures. The density, void ratio, and compressive strength are $1.59-1.66g/cm^3$, 16.6-20, and 70-90 MPa, respectively. Friction and wear tests are performed using a pin-on-plate-type reciprocating friction tester at 25, 100, and $200^{\circ}C$. The counterpart material is a CrMoV steel extracted from a KTX brake disc. Friction coefficient, wear amount, and wear mechanism are measured and examined. We determine that the friction coefficients depend on the temperature and the fluctuation of the friction coefficients is larger at higher temperatures. The amount of wear increases with the surface temperatures of the specimens. The tribological properties of the developed composites are similar to those of a Cu-based sintered friction material. Through this study, it is confirmed that ceramic composite materials can be used as friction materials.