• Journal of the Korean Ceramic Society
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• v.56 no.3
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• pp.211-232
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• 2019

Porous ceramics are promising materials for a number of functional and structural applications that include thermal insulation, filters, bio-scaffolds for tissue engineering, and preforms for composite fabrication. These applications take advantage of the special characteristics of porous ceramics, such as low thermal mass, low thermal conductivity, high surface area, controlled permeability, and low density. In this review, we emphasize the direct foaming method, a simple and versatile approach that allows the fabrication of porous ceramics with tailored microstructure, along with distinctive properties. The wet foam stability is achieved under the controlled addition of amphiphiles to the colloidal suspension, which induce in situ hydrophobization, allowing the wet foam to resist coarsening and Ostwald ripening upon drying and sintering. Different components, like contact angle, adsorption free energy, air content, bubble size, and Laplace pressure, play vital roles in the stabilization of the particle stabilized wet foam to the porous ceramics. The mechanical behavior of the load-displacements curves of sintered samples was investigated using Herzian indentations testes. From the collected results, we found that microporous structures with pore sizes from 30 ㎛ to 570 ㎛ and the porosity within the range from 70% to 85%.

• Macromolecular Research
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• v.17 no.11
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• pp.850-855
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• 2009

Keratin is an important protein used in wound healing and tissue recovery. In this study, keratin was modified chemically with iodoacetic acid (IAA) to enhance its solubility in organic solvent. Poly(hydroxybutylate-co-hydroxyvalerate) (PHBV) and modified keratin were dissolved in hexafluoroisopropanol (HFIP) and electrospun to produce nanofibrous mats. The resulting mats were surface-characterized by ATR-FTIR, field-emission scanning electron microscopy (FE-SEM) and electron spectroscopy for chemical analysis (ESCA). The pure m-keratin mat was cross-linked with glutaraldehyde vapor to make it insoluble in water. The biodegradation test in vitro showed that the mats could be biodegraded by PHB depolymerase and trypsin aqueous solution. The results of the cell adhesion experiment showed that the NIH 3T3 cells adhered more to the PHBV/m-keratin nanofibrous mats than the PHBV film. The BrdU assay showed that the keratin and PHBV/m-keratin nanofibrous mats could accelerate the proliferation of fibroblast cells compared to the PHBV nanofibrous mats.

• Composites Research
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• v.35 no.4
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• pp.232-241
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• 2022

Plasticizers are chemical additives added to polymers to have a desirable effect on mechanical properties such as processability and ductility. In this paper, we explore the use and market of eco-friendly plasticizers that can replace phthalate-based plasticizers that have been traditionally used in the plastics market. Bio plasticizers are derived primarily from biomass sources, including agricultural products, by-products and wastes. Regardless of the source of biomass, an ideal eco-friendly plasticizer should be non-toxic, have high resistance to volatilization, extraction, and migration, have good compatibility and compatibility, and be economical. The global bio plasticizer market is expected to reach USD 2.1 billion by 2030 from USD 1.3 billion in 2020, growing at a CAGR of 5.31% from 2021 to 2030.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.4-4
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• 2012

Proteins enable biology to be viable through molecular interactions (such as in antigen-antibody, ligand-receptor, and drug-target) with

• Journal of Powder Materials
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• v.19 no.3
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• pp.177-181
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• 2012

Copper composite materials have attracted wide attention for energy applications. Especially $CuInS_2$ has a desirable direct band gap of 1.5 eV, which is well matched with the solar spectrum. $CuInS_2$ nanoparticles could make it possible to develop color-tunable $CuInS_2$ nanoparticle emitter in the near-infrared region (NIR) for energy application and bio imaging sensors. In this paper, $CuInS_2$ nanoparticles were successfully synthesized by thermo-decomposition methods. Surface modification of $CuInS_2$ nanoparticles were carried out with various semiconductor materials (CdS, ZnS) for enhanced optical properties. Surface modification and silica coating of hydrophobic nanoparticles could be dispersed in polar solvent for potential applications. Their optical properties were characterized by UV-vis spectroscopy and photoluminescence spectroscopy (PL). The structures of silica coated $CuInS_2$ were observed by transmission electron microscopy (TEM).

• Environmental Engineering Research
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• v.13 no.1
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• pp.19-27
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• 2008

Simultaneous removal of ternary gases of $NH_3$, $H_2S$ and toluene in a contaminated air stream was investigated over 180 days in a biofilter. A commercially available inorganic/polymeric composite chip with a large void volume (bed porosity > 0.80) was used as a microbial support. Multiple microorganisms including Nitrosomonas and Nitrobactor for nitrogen removal, Thiobacillus thioparus (ATCC 23645) for $H_2S$ removal and Pseudomonas aeruginosa (ATCC 15692), Pseudomonas putida (ATCC 17484) and Pseudomonas putida (ATCC 23973) for toluene removal were used simultaneously. The empty bed residence time (EBRT) ranged from 60 - 120 seconds and the inlet feed concentration was $0.0325\;g/m^3-0.0651\;g/m^3$ for $NH_3$, $0.0636\;g/m^3-0.141\;g/m^3$ for $H_2S$, and $0.0918\;g/m^3-0.383\;g/m^3$ for toluene, respectively. The observed removal efficiency was 2% - 98% for $NH_3$, 2% - 100% for $H^2S$, and 2% - 80% for toluene, respectively. Maximum elimination capacity was about $2.7\;g/m^3$/hr for $NH_3$, > $6.4\;g/m^3$/hr for $H_2S$ and $4.0\;g/m^3$/hr for toluene, respectively. The inorganic/polymeric composite carrier required 40 - 80 days of wetting time for biofilm formation due to the hydrophobic nature of the carrier. Once the surface of the carrier was completely wetted, the microbial activity became stable. During the long-term operation, pressure drop was negligible because the void volume of the carrier was two times higher than the conventional packing materials.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.791-806
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• 2020

In this study, a block shear strength test was conducted to compare and analyze the strength and failure mode on the glued laminated timber, CLT, and Ply-lam CLT, which are mainly used for the construction of wood construction as engineering wood. Through this, the Ply-lam CLT manufacturing conditions for optimum production, such as the type of lamina, plywood, adhesive, and layer composition, were investigated. The results are as follow. Through block shear strength test, it showed high strength in the order of glued laminated timber, Ply-lam CLT and CLT. In particular, the shear strength of Ply-lam CLT, which is made of a composite structure of larch plywood and larch lamina, passed 7.1 N/㎟, which is a Korean industrial standards for block shear strength of structural glued laminated timber. In addition, in this study, there was no different in shear strength according to the adhesive type used for glulam, CLT, and Ply-lam CLT adhesion. However, in the case of Ply-lam CLT, the difference in shear strength of Ply-lam CLT was shown according to the type of lamina and plywood. The results showed high strength in the order of Larix kaempferi > Mixed light hardwood ≒ Pinus densiflora, sieb, et, Zucc plywood. The optimal configuration of Ply-lam CLT is when larch plywood and larch lamina are used, and it is decided that the adhesive can be used by selecting PRF and PUR according to the application. The results of block shear strength failure mode by type of wood based materials were analyzed. The failure mode showed shear parallel-to-grain for glulam, rolling shear for CLT, and shear parallel-to-grain and rolling for ply-lam CLT. This is closely related to shear strength results and is decided to indicate higher shear strength in Ply-lam CLT than in CLT due to rolling shear.

• Journal of Sensor Science and Technology
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• v.31 no.5
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• pp.312-317
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• 2022

Piezoelectric energy harvesting has attracted increasing attention over the last decade as a means for generating sustainable and long-lasting energy from wasted mechanical energy. To develop self-powered wearable devices, piezoelectric materials should be flexible, stretchable, and bio-eco-friendly. This study proposed the fabrication of stretchable piezoelectric composites via dispersing perovskite-structured BaTiO₃ nanoparticles inside an Ecoflex polymeric matrix. In particular, the stretchable piezoelectric sensor array was fabricated via a simple and cost-effective spin-coating process by exploiting the piezoelectric composite comprising of BaTiO₃ nanoparticles, Ecoflex matrix, and stretchable Ag coated textile electrodes. The fabricated sensor generated an output voltage of ~4.3 V under repeated compressing deformations. Moreover, the piezoelectric sensor array exhibited robust mechanical stability during mechanical pushing of ~5,000 cycles. Finite element method with multiphysics COMSOL simulation program was employed to support the experimental output performance of the fabricated device. Finally, the stretchable piezoelectric sensor array can be used as a self-powered touch sensor that can effectively detect and distinguish mechanical stimuli, such as pressing by a human finger. The fabricated sensor demonstrated potential to be used in a stretchable, lead-free, and scalable piezoelectric sensor array.

• Journal of the Korean Wood Science and Technology
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• v.35 no.5
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• pp.58-66
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• 2007

The objective of this research was to develop environment-friendly adhesives for face fancy veneer bonding of engineered flooring. Urea-formaldehyde (UF)-tannin and melamine-formaldehyde (MF)/PVAc hybrid resin were used to replace UF resin in the formaldehyde-based resin system in order to reduce formaldehyde and volatile organic compound (VOC) emissions from the adhesives used between plywoods and fancy veneers. Wattle tannin powder (5 wt%) was added to UF resin and PVAc (30 wt%) to MF resin. These adhesive systems showed better bonding than commercial UF resin with a similar level of wood penetration. The initial adhesion strength was sufficient to be maintained within the optimum initial tack range. The standard formaldehyde emission test (desiccator method) and VOC analyzer were used to determine the formaldehyde and VOC emissions from engineered flooring bonded with commercial UF resin, UF-tannin and MF/PVAc hybrid resin. By desiccator method, the formaldehyde emission level of UF resin showed the highest but was reduced by replacing with UF-tannin and MF/PVAc hybrid resin. MF/PVAc hybrid satisfied the $E_1$ grade (below $1.5mg/{\ell}$). VOC emission results by VOC analyzer were similar with the formaldehyde emission results. TVOC emission was in the following order: UF > UF-tannin > MF/PVAc hybrid resin.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.722-726
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• 2008

Silica microsphere is a world leading innovative material used in adsorbent packing materials in HPLC technology. The application of microsphere lies in the ability to the surface modification of silica with the special materials such as polymers, metals and bio-active materials. Collagen is a major structural protein of connective tissues and has a good biocompatibility. In this study, we prepared the purified silica porous microsphere, having micro diameters in the range of a pore volume at least 50% by the aggregation procedure of colloidal silica with the polymerization method (PICA). The microspheres were modified by collagen hydrogel to improve the biocompatible properties for biomedical product. The silica/collagen microsphere composite doped with silver nanoparticles was prepared and investigated the capabilities of biomaterial application through the evaluation of the structure characteristics of the microsphere composit.