• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.1-8
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• 2016

Capacity of layered lithium nickel-cobalt-manganese oxide ($LiNi_{1-x-y}Co_xMn_yO_2$) cathode material can increase by raising the charge cut-off voltage above 4.3 V vs. $Li/Li^+$, but it is limited due to anodic instability of conventional electrolyte. We have been screening and evaluating various sulfone-based compounds of dimethyl sulfone (DMS), diethyl sulfone (DES), ethyl methyl sulfone (EMS) as electrolyte additives for high-voltage applications. Here we report improved cycling performance of $LiNi_{0.5}Co_{0.2}Mn_{0.3}O_2$ cathode by the use of dimethyl sulfone (DMS) additive under an aggressive charge condition of 4.6 V, compared to that in conventional electrolyte, and cathode-electrolyte interfacial reaction behavior. The cathode with DMS delivered discharge capacities of $198-173mAhg^{-1}$ over 50 cycles and capacity retention of 84%. Surface analysis results indicate that DMS induces to form a surface protective film at the cathode and inhibit metal-dissolution, which is correlated to improved high-voltage cycling performance.

• Journal of Adhesion and Interface
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• v.21 no.3
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• pp.86-92
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• 2020

We confirmed the effects on the device performances and the charge injection characteristics of organic field-effect transistor (OFET) by selectively differently controlling the surface energies on the contact region of the substrate where the source/drain electrodes are located and the channel region between the two electrodes. When the surface energies of the channel and contact regions were kept low and increased, respectively, the field-effect mobility of the OFET devices was 0.063 ㎠/V·s, the contact resistance was 132.2 kΩ·cm, and the subthreshold swing was 0.6 V/dec. They are the results of twice and 30 times improvements compared to the pristine FET device, respectively. As the results of analyzing the interfacial trap density according to the channel length, a major reason of the improved device performances could be anticipated that the pi-pi overlapping direction of polymer semiconductor molecules and the charge injection pathway from electrode is coincided by selective surface treatment in the contact region, which finally induces the decreases of the charge trap density in the polymer semiconducting film. The selective surface treatment method for the contact region between the electrode and the polymer semiconductor used in this study has the potential to maximize the electrical performances of organic electronics by being utilized with various existing processes to lower the interface resistance.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.60-68
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• 2012

In this study, the manufacturing process of micro capsulized PCM (phase changing material) for thermal storage performance of latent heat was investigated to save energy during the use of buildings: i.e. use of melamine-type resin as the micro-capsule material and paraffin wax as the inner material that are together used in concrete walls. For the manufacturing process of the micro-capsulized PCM, the amount of SDS addition as surfactant was the key variable and the resulting thermal storage performance depended on the SDS amount. With increasing amount of SDS, the micro capsulation became much easier while the capsule surface became harder. The micro capsules became uniform at an optimum SDS addition. The addition of SDS also affected the thermal capacity: with increasing SDS amount, the heat storage and release tendency at melting point was more clearly manifested. The current investigation is part of a study under progress to explore the use of PCM in concrete walls to save building maintenance cost and energy.

• Journal of Adhesion and Interface
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• v.4 no.3
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• pp.33-40
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• 2003

In this work, diglycidyl ether of bisphenol A (DGEBA)/polyetherimide (PEI) blends were cured using 4,4-diaminodiphenyl methane (DDM). And the effects of addition of different PEI contents to neat DGEBA were investigated in the thermal properties and fracture toughness of the blends. The contents of contents of containing PEI were varied in 0, 2.5, 5, 7.5, and 10 phr. The cure activation energies ($E_a$) of the cured specimens were determined by Kissinger equation and the mechanical interfacial properties of the specimens were performed by critical stress intensity factor ($K_{IC}$). Also their surfaces were examined by using a scanning electron microscope (SEM) and the surface energetics of blends was determined by contact angles. As a result, $E_a$ and $K_{IC}$ showed maximum values in the 7.5 phr PEI. This result was interpreted in the increment of the network structure of DGEBA/PEI blends. Also, the surface energetics of the DGEBA/PEI blends showed a similar behavior with the results of $K_{IC}$. This was probably due to the improving of specific or polor component of the surface free energy of DGEBA/PEI blends, resulting in increasing the hydrogen bonding of the hydroxyl and imide groups of the blends.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.27-33
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• 2016

Phenolic resin has excellent heat resistance and good mechanical properties as a thermosetting resin. However, its thermosetting characteristics cause it to produce a non-recyclable waste in the form of sprue and runner which is discarded and represents up to 15~20% of the overall products. Forty thousand tons of phenolic resin sprue and runner are disposed of (annually). The (annual) cost of such domestic waste disposal is calculated to be 20 billion won. In this study, discarded phenol resin scraps were pulverized and treated by silanes to improve their interfacial adhesion with HDPE. The sizes of the pulverized pulverulent bodies and fine particles were (100um~1000um) and (1~100um), respectively. The pulverized phenol resin was treated with 3-(methacryloyloxy) propyltrimethoxysilane and vinyltrimethoxy silane and the changes in its characteristics were evaluated. The thermal properties were evaluated by DSC and HDT. The mechanical properties were assessed by a notched Izod impact strength tester. When the silane treated phenol resin was added, the heat distortion temperature of HDPE increased from $77^{\circ}C$ to $96^{\circ}C$ and its crystallinity and crystallization temperature also increased. Finally, its impact strength and tensile strength increased by 20% and 50%, respectively, in comparison with the non-treated phenol resin.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.14-18
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• 2019

The conductivity of a semiconductor is primarily determined by the carriers. To achieve higher conductivity, the number of carriers should be high, and an energy trap level is created so that the carriers can cross the forbidden zone with low energy. Carriers have a crystalline binding structure, and interfacial mismatching tends to make them less conductive. In general, high-concentration doping is typically used to increase mobility. However, higher conductivity is also observed in non-orthogonal conjugation structures. In this study, the phenomena of higher conductivity and higher mobility were observed with space charge limiting current due to tunneling phenomena, which are different from trapping phenomena. In an atypical structure, the number of carriers is low, the resistance is high, and the on/off characteristics of capacitances are improved, thus increasing the mobility. ZTO thin film improved the on/off characteristics of capacitances after heat treating at $150^{\circ}C$. In charging and discharging tests, there was a time difference in the charge and discharging shapes, there was no distinction between n and p type, and the bonding structure was amorphous, such as in the depletion layer. The amorphous bonding structure can be seen as a potential barrier, which is also a source of space charge limiting current and causes conduction as a result of tunneling. Thus, increased mobility was observed in the non-structured configuration, and the conductivity increased despite the reduction of carriers.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.413-419
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• 2019

In the recent, as a world demand of energy resources has been transformed from fossil fuels to hydrogen-based clean energy resources, a huge attention has been attracted to increase the performance and decrease a production cost of core materials in fuel cell technology. The utilization of reinforced composite membranes as electrolytes in the polymer electrolyte membrane fuel cells can reduce the use of high cost perfluorosulfonic acid (PFSA), mitigate the cell impedance, and improve the dimensional stability as well as the interfacial stability, giving rise to achieve both an improved performance and a reduction of production costs of the fuel cell devices. In this study, we investigate the effects of physical characteristics and cell performances according to the various ionomer solvents in the solution based manufacturing process of reinforced composite electrolyte membrane.

• Journal of the Korean Electrochemical Society
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• v.3 no.2
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• pp.109-114
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• 2000

The relation between the phase-shift profile fur the intermediate frequencies and the Langmuir adsorption isotherm at the poly-Ir/0.1 M $H_2SO_4$ aqueous electrolyte interface has been studied using ac impedance measurements, i.e., the phase-shift methods. The simplified interfacial equivalent circuit consists of the serial connection of the electrolyte resistance $(R_s)$, the faradaic resistance $(R_F)$, and the equivalent circuit element $(C_P)$ of the adsorption pseudoca-pacitance $(C_\phi)$. The comparison of the change rates of the $\Delta(-\phi)/{\Delta}E\;and\;\Delta{\theta}/{\Delta}E$ are represented. The delayed phase shift $(\phi)$ depends on both the cathode potential (E) and frequency (f), and is given by $\phi=tan^{-1}[1/2{\pi}f(R_s+R_F)C_P]$. The phase-shift profile $(-\phi\;vs.\;E)$ for the intermediate frequency (ca. 1 Hz) can be used as an experimental method to determine the Langmuir adsorption isotherm $(\theta\;vs.\;E)$. The equilibrium constant (K) for H adsorption and the standard free energy $({\Delta}G_{ads})$ of H adsorption at the poly-Ir/0.1 M $H_2SO_4$ electrolyte interface are $2.0\times10^{-4}$ and 21.1kJ/mol, respectively. The H adsorption is attributed to the over-potentially deposited hydrogen (OPD H).

• Journal of Korean Society of Transportation
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• v.8 no.2
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• pp.119-131
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• 1990

Physico-chemical properties of asphalt, aggregate, and asphalt-aggregate mixture that might influence stripping were summarized in Table 1, based on the fundamental theories concerning stripping. It was found that although physical properties of aggregate affected stripping, there was no strong correlation between the physical properties of aggregate, such as pore volume and surface area, and the stripping propensity of the aggregate. Chemical and electrochemical properties of aggregate surface in the presence of water were most important factors for stripping. All mineral aggregates tested in this study imparted distinctive pH values to the contacting water and possessed distinctive electrochemical properties as measured by zeta potential. It was found that aggregates which had relatively higher surface potential in water and/or which imparted relatively higher pH to the contacting water were more susceptible to stripping. The functionalities contained in antistripping additives tested were primary and secondary amines and those of organic nitrogen compounds. The functionalities were determined by examining their infrared spectra. Based on the interfacial energy concept, the contact angle of an asphalt drop on an aggregate surface immersed in water related to the stripping propensity. The contact angle and stripping propensity were markedly reduced by the presence of an antistripping additive. In general, all the additives tested improved stripping resistance to some extent, depending on their concentration in the asphalts. The optimum dosage of an additive varied with different asphalts, as well as different aggregates. All antistripping additives tested in this study lost their effectiveness and failed to function to some extent when maintained for hours in a hot asphalt.

• Journal of the Korean Electrochemical Society
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• v.3 no.1
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• pp.25-30
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• 2000

The relation between the phase-shift profile for the intermediate frequencies and the Langmuir adsorption isotherm at the poly-$Pt/0.1\;M\;H_2SO_4$ aqueous electrolyte interface has been studied using ac impedance measurements, i.e., the phase-shift methods. The suggested interfacial equivalent circuit consists of the serial connection of the electrolyte resistance ($R_S$), the faradaic resistance $(R_F)$ and the equivalent circuit element $(C_P)$ of the adsorption pseudocapacitance $(C_\varphi)$. The delayed phase shift $(\varphi)$ depends on both the cathode potential (E) and frequency (f), and is given by $\varphi=-tan^{-1}[1/2{\pi}f(R_s+R_F)C_p]$. The phase-shift profile $(\varphi\;vs.\;E)$ for the intermediate frequency (ca. 6Hz) can be used as an experimental method to determine the Langmuir adsorption isotherm (9 vs. E). The equilibrium constant (K) for H adsorption and the standard free energy $({\Delta}G_{ads})$ of H adsorption at the poly-$Pt/0.1\;M\;H_2SO_4$ electrolyte interface are $1.8\times10^{-4}\;and\;21.4kJ/mol$, respectively. The H adsorption is attributed to the over-potentially deposited hydrogen (OPD H).