• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.134-142
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• 2020

In this study, in order to evaluate the self-healing performance of cement composites the self-healing test method and the analysis method were suggested by applying constant water head permeability test, chloride migration test and repeated bending test. The method of making a cracked specimen and controlling crack width are also proposed. Constant head water permeability test can evaluate the healing performance by using the decreasing rate of water flow passing through the crack zone of a specimen. Furthermore, the equivalent crack width can be used to intuitively investigate the healing effect with healing period. The chloride migration test can evaluate the healing rate by the decreasing rate of the diffusion coefficient obtained by ASTM C 1202. Mechanical healing performance can be evaluated using ISR and IDR estimated from load vs. CMOD relationship graph obtained through the repeated bending test. Finally, the applicability of proposed self-healing evaluation methods was examined by testing mortar specimens with or without self-healing agents.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.957-962
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• 2009

Sialon was produced by hot-pressing the mixtures of $Si_3N_4$, AlN and $Y_2O_3$ powders. All fracture tests were performed on a three-point loading system with a 30 mm bending span. Fracture toughness and Vickers hardness of smooth specimen were average 7.05 $MPa{\cdot}m^{0.5}$ and Hv = 1580, respectively. Density of three kinds of specimens, smooth specimen, smooth and healed specimen, smooth with $SiO_2$ colloidal coating and healed specimen, had beyond 99 % of theoretical density. Bending strength of smooth healed specimens had high strength more than 1 GPa. Crack healed specimens recovered as strength as smooth specimen. That is, cracked specimen with $SiO_2$ colloidal coating on cracked part recovered strength by heat treatment, completely. Crack healing of $Si_3N_4$ composite ceramics had contributed glassy $SiO_2$ to strength recovery. Limiting high temperature for bending strength of heat treated smooth specimen for bending strength was about 1273 K.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.150-153
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• 2005

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.35-42
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• 2014

Thermal analysis properties and adhesive properties of self-healing agents were evaluated through differential scanning calorimetry, reaction heat measurement, and adhesive shear test. D1E0, D3E1, D1E1, D1E3, and D0E1, depending on the mixing ratio of DCPD and ENB, were considered as self-healing agents. The amount of Grubbs' catalyst, depending on the type of self-healing agents, was varied from 0.1 wt% to 1.5 wt%. In the case of DCPD, the polymerization reaction occurred faster and the stabilized adhesive strength increased as the amount of catalyst increased; however, a large amount of catalyst was required. ENB had excellent reactivity with a small amount of the catalyst; however, high reaction heat was observed at the early stage of polymerization. Thermal analysis properties and adhesive properties of self-healing agents can be controlled by varying a mixing ratio of DCPD and ENB. Among the self-healing agents used for this study, the D3E1 would be one of the most preferable candidates with regard to maximum adhesive strength, reaching time to maximum adhesive strength, stabilized adhesive strength, and reaction heat.

• Archives of Pharmacal Research
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• v.26 no.10
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• pp.855-860
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• 2003

The effect of silver sulfadiazine (SSD) on the proliferation of human dermal fibroblast (HDF) was studied to determine the impact of the drug on the wound healing process and dermal mechanical strength. Human dermal fibroblasts were cultured to 80% confluency using DMEM with 10% FBS and viability of the cell was estimated using neutral red assay. In addition, the $2^{nd}$ degree burn wound was prepared on the anterior part of rabbit ear skin and dressings containing SSD were applied for 96 h. Presence of inflammatory cells and degree of re-epithelialization were investigated in the wound. After 15 day of the induction of burn wounds, the treated area was excised and dermal mechanical strength was quantitatively measured with a constant speed tensiometer. SSD was found to be highly cyto-toxic in cultured HDF cells. The topical application of SSD (2%) could control the infection as evidenced by the lack of accumulation of inflammatory cells in histological evaluation. Therefore, these observations suggested that the impairment of dermal regeneration and decreased mechanical strength of dermal tissue was resulted from the cyto-toxic effect of SSD on dermal cells. Since the decreased mechanical strength may lead to reduction in resilience, toughness and maximum extension of the tissue, the identification of optimum dose for SSD that limits infection while minimizes the cyto-toxic effect may be clinically relevant.

• Corrosion Science and Technology
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• v.21 no.1
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• pp.41-52
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• 2022

Herein, we report polyvinyl butyral composites coatings containing various loadings of 72-h bath sonicated hexagonal boron nitride particles (5 ㎛) to enhance barrier properties of coatings. Barrier properties of coatings were determined in 3.5 wt% NaCl after different time periods of immersion via electrochemical techniques such as open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization test. Coatings containing sonicated hexagonal boron particles exhibited improved corrosion resistance for longer periods of immersion compared to neat coating. We also discussed effects of hexagonal boron nitride on healing properties of polyvinyl butyral. Coatings containing 1.0 wt% loading of sonicated hexagonal boron nitride showed improved long-term barrier properties than coatings with other compositions. The presence of hexagonal boron nitride also affected the healing properties of polyvinyl butyral coatings besides their barrier properties. Such improved barrier properties of composites coatings were attributed to the high aspect ratio, plate-like shape, and electrically insulated nature of the filler.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.40.2-40.2
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• 2009

Using the favorable resorption behavior of amorphous Calcium phosphate (CaP) we fabricated a gelatin basednano fibrous mat by electrospinning for using as a fast healing patch for minorbone defects. Bone is predominantly formed by an inorganic phase of nano-crystalline HAp materials and nano fibrous protein material of collagen. The osteoblast cells, which are the bone formation cells and are key to the new bone formation, receive these materials to form new bone. Taking these considerations we make a new nano fibrous mat of amorphous CaP and gelatin, which is derived from collagen itself. A polymer carrier of poly caprolactone(PCL) was used in the system to stabilize the materials in biological condition. The electrospinning conditions were optimized for smooth mat without any droplet formation. The fabricated mat was characterized for its morphologyby SEM. Mechanical properties like tensile strength was evaluated. To investigate the bio-compatibility we performed the MTT assay and investigated its resorption behavior and apatite formation behavior by SBF immersion.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.7
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• pp.652-657
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• 2009

Strength characteristics of $Si_3N_4$ composite ceramics has been studied as functions of heat-treatment temperature and additive $SiO_2$. $SiO_2$ colloidal could significantly increase the bending strength. Crack healing temperature decreased 300 K by additive $TiO_2$. Bending strength of specimen added $SiO_2$ is higher than that of non-added $SiO_2$. Moreover, bending strength of specimen with $SiO_2$ colloidal coating is much higher that of non-coated specimen. In in-situ observation, crack-healed specimen at 1,573 K shows phenomenon like a fog on the surface. By SPM, both crack-healed specimen, non-coating and coating of $SiO_2$ colloidal, at 1,273 K were healed completely but both of 1,573 K exist crack. This was made by evaporation of $SiO_2$ at high temperature. Crack-healing materials of $Si_3N_4$ composite ceramics is crystallized $Y_2Si_2O_7$, $Y_2Ti_2O_7$ and $SiO_2$. A large amount of Si and O, and little C were detected by EPMA. Si and O increase but C decreases according to heat treatment temperature. Specimens with additive $SiO_2$ were more detected Si and O than that of non-additive $SiO_2$. Specimen with $SiO_2$ colloidal coatings were much more detected O.

• Journal of Ocean Engineering and Technology
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• v.27 no.5
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• pp.10-15
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• 2013

The crack-healing behavior and corrosion resistance of SiC ceramics were investigated. Heat treatments were carried out from $900^{\circ}C$ to $1300^{\circ}C$. A corrosion test of SiC was carried out in acid and alkaline solutions under KSL1607. The results showed that heat treatment in air could significantly increase the strength. The heat-treatment temperature has a profound influence on the extent of crack healing and the degree of strength recovery. The optimum heat-treatment temperature was $1100^{\circ}C$ for one hour at an atmospheric level. In the two kinds of solutions, the cracks in a specimen were reduced with increasing time, and the surface of the crack healed specimen had a greater number of black and white spots. The strength of the corroded cracked specimen was similar to that of the cracked specimen. The strength of the corroded crack healed specimen decreased 47% and 75% compared to that of the crack healed specimen in the acid and alkaline solutions, respectively. Therefore, the corrosion of SiC ceramics is faster in an alkaline solution than in an acid solution.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.3
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• pp.53-59
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• 2018

When manufacturing self-healing concrete using bacteria, nutrients are added to increase the activity of the bacteria. Although many researches have focused on the effects of nutrients containing bacterial healing agent on concrete, few have studied the effects of sole nutrient on self-healing of cement composites. Bacterial nutrients, like commercial chemical admixtures, affect hydration characteristics such as flow, setting, hydration heat, mechanical strength of cement composites and also affect the self healing of cement composites by hydration of unhydrated particles. In this study, effect of the four nutrient commonly used in the existing literature on the hydration characteristics of cement composites by its addition was investigated. Flow, setting time, hydration heat, compressive strength have studied for each nutrients added by 1.5% and 3% of cement weight. Experimental results shows that urea and calcium-nitrate can be used up to 3% without significant detrimental effect on cement composites. Addition of calcium-lactate up to 1.5% show better compressive strength than control, but addition of 3% show almost non-hydration. Yeast extract shows detrimental effects on the composites regardless of the amount added.