• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.43-44
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• 2007

SiO and graphite composite has been prepared by adopting high energy ball milling technique. The anode material shows high initial discharge and charge capacity values of 1138 and 568 mAh/g, respectively. Since the materials formed during initial discharge process the nano silicon/$Li_4SiO_3\;and\;Li_2O$ remains as interdependent, it may be expected that the composite exhibiting higher amount of irreversible capacity$(Li_2O)$ will deliver higher reversible capacity. In this study, pretreatment method of constant current-constant voltage (CC-CV) Provided high coulombic efficiency of SiO/C composite electrode removing the greater part of irreversible capacity.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.487-492
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• 2021

In this study, the electrochemical properties of pitch coated silicon sheets/graphite anode materials were investigated. Using NaCl as a template, silicon sheets were prepared through the stöber method and the magnesiothermic reduction methode. In order to synthesize the anode composite, the silicon sheets and graphite were combined with SDBS. The pitch coated silicon sheets/graphite was synthesized using THF as a solvent for the anode material composite. The physical properties of the prepared anode composites were analysed by XRD, SEM, EDS and TGA. The electrochemical performances of the prepared anode composites were performed by the current charge/discharge, rate performance, cyclic voltammetry and EIS tests in the electrolyte LiPF₆ dissolved solvents (EC:DMC:EMC=1:1:1 vol%). As the silicon composition of silicon sheets/graphite composite material increased, the discharge capacity also increased, but the cycle stability tended to decrease. The anode material of pitch coated silicon sheets/graphite composite (silicon sheets:graphite=3:7 weight ratio) showed the initial discharge capacity of 1228.8 mAh/g and the capacity retention ratio of 77% after 50 cycles. From these results, it was found that the cycle stability of pitch coated silicon sheets/graphite was improved.

• Journal of Marine Bioscience and Biotechnology
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• v.7 no.2
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• pp.58-70
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• 2015

Injectable RGD-bioconjugated Mussel Adhesive Proteins (RGD-MAPs) composite hydroxypropyl methylcellulose (HPMC) hydrogels provide local periodontal tissue for bone filling in periodontal surgery. Previously we developed a novel type of injectable self-supported hydrogel (2 mg/ml of RGD-MAPs/HPMC) based porcine nano hydroxyapatite (MPH) for dental graft, which could good handling property, biodegradation or biocompatibility with the hydrogel disassembly and provided efficient cell adhesion activity and no inflammatory responses. Herein, the aim of this work was to evaluate bone formation following implantation of MPH and collagen membrane in rabbit calvarial defects. Eight male New Zealand rabbits were used and four circular calvarial defects were created on each animal. Defects were filled with different graft materials: 1) collagen membrane, 2) collagen membrane with MPH, 3) collagen membrane with bovine bone hydroxyapatite (BBH), and 4) control. The animals were sacrificed after 2 and 8 weeks of healing periods for histologic analysis. Both sites receiving MPH and BBH showed statistically increased augmented volume and new bone formation (p < 0.05). However, there was no statistical difference in new bone formation between the MPH, BBH and collagen membrane group at all healing periods. Within the limits of this study, collagen membrane with MPH was an effective material for bone formation and space maintaining in rabbit calvarial defects.

• Journal of Powder Materials
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• v.10 no.6
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• pp.443-447
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• 2003

Nano-sized $TiB_2$ was in situ synthesized in copper matrix through self-propagating high temperature synthesis (SHS) with high-energy ball milled Ti-B-Cu elemental mixtures as powder precursors. The size of $TiB_2$ particles in the product of SHS reaction decreases with time of preliminary mechanical treatment ranging from 1 in untreated mixture to 0.1 in mixtures milled for 3 min. Subsequent mechanical treatment of the product of SHS reaction allowed the $TiB_2$ particles to be reduced down to 30-50 nm. Microstructural change of $TiB_2$-Cu nanocomposite during spark plasma sintering (SPS) was also investigated. Under simultaneous action of pressure, temperature and electric current, titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a interpenetrating phase composite with a fine-grained skeleton.

• Journal of Surface Science and Engineering
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• v.42 no.2
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• pp.73-78
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• 2009

Quinary Ti-Al-Si-C-N films were successfully synthesized on SUS 304 substrates and Si wafers by a hybrid coating system combining an arc ion plating technique and a DC reactive magnetron sputtering technique. In this work, the effect of Si content on the microstructure and mechanical properties of Ti-Al-C-N films were systematically investigated. It was revealed that the microstructure of Ti-Al-Si-C-N coatings changed from a columnar to a nano-composite by the Si addition. Due to the nanocomposite microstructure of Ti-Al-Si-C-N coatings, the microhardness of The Ti-Al-Si-C-N coatings significantly increased up to 56 GPa. In addition the average friction coefficients of Ti-Al-Si-C-N coatings were remarkably decreased with Si addition. Therefore, Ti-Al-Si-C-N coatings can be applicable as next-generation hard-coating materials due to their improved hybrid mechanical properties.

• Composites Research
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• v.35 no.1
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• pp.1-7
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• 2022

The activated carbon is a very good choice for using as supercapacitor electrode materials. Herein, the flower of Shorea robusta, a bio-waste material was successfully used to synthesize the activated carbons for application as supercapacitor electrode materials. The activated carbon was synthesized through chemical activation process followed by thermal treatment at 700℃ in presence of N₂ atmosphere using KOH, ZnCl₂ and H₃PO₄ as the activating agents. The physicochemical analyses demonstrate that the obtained activated carbons are graphitic in nature and the degree of disorder of the graphitic carbons is changed with the activating agents. The activated carbon obtained from Shorea robusta flower (ACSF-K) electrode shows the specific capacitance of ~610 F g^-1 at 2 A g^-1 current density, which is higher than ACSF-Z (560 F g^-1) and ACSF-H (470 F g^-1) electrode material under the identical current density. The synthesized graphitic carbons also demonstrated good rate capability and high electrochemical stability as supercapacitor electrode.

• Steel and Composite Structures
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• v.47 no.5
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• pp.601-613
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• 2023

Numerous methods have been proposed in predicting formability of sheet metals based on microstructural and macro-scale properties of sheets. However, there are limited number of papers on the optimization problem to increase formability of sheet metals. In the present study, we aim to use novel optimization algorithms in neural networks to maximize the formability of sheet metals based on tensile curve and texture of aluminum sheet metals. In this regard, experimental and numerical evaluations of effects of texture and tensile properties are conducted. The texture effects evaluation is performed using Taylor homogenization method. The data obtained from these evaluations are gathered and utilized to train and validate an artificial neural network (ANN) with different optimization methods. Several optimization method including grey wolf algorithm (GWA), chimp optimization algorithm (ChOA) and whale optimization algorithm (WOA) are engaged in the optimization problems. The results demonstrated that in aluminum alloys the most preferable texture is cube texture for the most formable sheets. On the other hand, slight differences in the tensile behavior of the aluminum sheets in other similar conditions impose no significant decreases in the forming limit diagram under stretch loading conditions.

• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.334-339
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• 2004

Microstructures and mechanical properties of SPSed monolithic HAp, HAp-Ag, and HAp-ZrO$_2$sintered bodies were investigated by the XRD, SEM, and TEM techniques. The nano-sized HAp powders were successfully synthesized by precipitation of Ca(NO$_3$)$_2$4$H_2O$ and (NH$_4$)HPO$_4$solution. In the HAp-Ag composite, the shrinkage cavities were observed at the interfaces between HAp and large sized Ag particles due to the mismatch of their thermal expansion coefficients. However, no found the defect at the interfaces between HAp and fine-sized Ag particles. In the HAp-ZrO$_2$composite. nano-sized ZrO$_2$particles were almost dispersed at the grain boundaries of HAp phase. The fracture toughness of HAp-Ag and HAp-ZrO$_2$ composites were increased due to the plastic deformation and phase transformation mechanisms of the dispersed fine Ag and ZrO$_2$phase in the HAp matrix, respectively.

• Polymer(Korea)
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• v.36 no.5
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• pp.612-616
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• 2012

In this work, the effect of chemical treatments of multi-walled carbon nanotubes (MWNTs) on the mechanical interfacial properties of carbon fiber fabric-reinforced composites was investigated. The surface properties of the MWNTs were determined by acid and base values, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. The mechanical interfacial properties of the composites were assessed by interlaminar shear stress (ILSS) and critical stress intensity factor ($K_{IC}$). The chemical treatments based on acid and base reactions led to a significant change of surface characteristics of the MWNTs, especially A-MWNTs/carbon fibers/epoxy composites had higher mechanical properties than those of B-MWNTs and non-treated MWNTs/carbon fibers/epoxy composites. These results were probably due to the improvement of interfacial bonding strength, resulting from the acid-base interaction and hydrogen bonding between the epoxy resins and the MWNT fillers.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.1
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• pp.35-41
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• 2022

In the era of Fifth-Generation (5G), technology requirements such as Artificial Intelligence (AI), Cloud computing, automatic vehicles, and smart manufacturing are increasing. For high efficiency of electronic devices, research on high-intensity circuits and packaging for miniaturized electronic components is important. A solder paste which consists of small solder powders is one of common solder for high density packaging, whereas an electroplated solder has limitation of uniformity of bump composition. Researches are underway to improve wettability through the addition of nanoparticles into a solder paste or the surface finish of a substrate, and to suppress the formation of IMC growth at the metal pad interface. This paper describes the principles of improving the wettability of solder paste and suppressing interfacial IMC growth by addition of nanoparticles.