• Polymer(Korea)
• /
• v.27 no.3
• /
• pp.265-270
• /
• 2003

In spite of high ionic conductivity, the polymer gels have poor mechanical properties and high reactivity with lithium metal anode. To solve these problems, the dry solid systems and polymer composites have been intensively studied, due to their good mechanical, thermal, chemical, and electrochemical stability. The objectives of this experiment were to improve ionic conductivity and mechanical properties of the solid polymer electrolytes based on PEO-LiClO$_4$. To obtain higher ionic conductivity and better mechanical properties, ceramic or rubber phase was added in the PEO-LiClO$_4$(8:1) matrix. The results showed that ionic conductivity and mechanical properties were improved. The ionic conductivity of the samples was as high as 10$\^$-5/ S cm$\^$-1/. This value is similar to the best ionic conductivity ever reported in the solid drying system. To obtain better results, we used PEO with various molecular weights (600∼8000) and changed the salt contents. By using DSC, we found that the addition of salt reduced the crystallinity of PEO. The mobility of polymer dependence on salt contents was examined by FT-IR.

• Journal of Information Display
• /
• v.12 no.3
• /
• pp.145-152
• /
• 2011

Since the discovery of fullerenes as a class of nanostructure compounds, many potential applications have been suggested for their unusual structures and properties. The isolated pentagon rule (IPR) states that all pentagonal carbon rings are isolated in the most stable fullerene. Fullerenes $C_n$ are a class of spherical carbon allotrope group with unique properties. Electron transfer between fullerenes and other molecules is thought to involve the transfer of electrons between the molecules surrounding the fullerene cage. One class of electron transfer molecules is the methanofullerene derivatives ([6,6]-phenyl $C_{61}$-butyric acid methyl ester (PCBM), 4-(2-ethylhexyloxy)-[6,6]-phenyl $C_{61}$-butyric acid methyl ester (p-EHO-PCBM), and 4-(2-ethylhexyloxy)-[6,6]-phenyl $C_{61}$-butyric acid (p-EHO-PCBA), 10-12). It has been determined that $C_{60}$ does not obey IPR. Supramolecular complexes 1-9 and 10-12 are shown to possess a previously unreported host.guest interaction for electron transfer processes. The unsaturated, cis-geometry, thiocrown ethers, (1-9) (described as [X-UT-Y], where X and Y indicate the numbers of carbon and sulfur atoms, respectively), are a group of crown ethers that display interesting physiochemical properties in the light of their conformational restriction compared with a corresponding saturated system, as well as the sizes of their cavities. Topological indices have been successfully used to construct mathematical methods that relate structural data to various chemical and physical properties. To establish a good relationship between the structures of 1-9 with 10-12, a new index is introduced, ${\mu}_{cs}$. This index is the ratio of the sum of the number of carbon atoms ($n_c$) and the number of sulfur atoms ($n_s$) to the product of these two numbers for 1-9. In this study, the relationships between this index and oxidation potential ($^{ox}E_1$) of 1-9, as well as the first to third free energies of electron transfer (${\Delta}G_{et(n)}$, for n = 1-3, which is given by the Rehm-Weller equation) between 1-9 and PCBM, p-EHO-PCBM, and p-EHO-PCBA (10-12) as [X-UT-Y]@R(where R is the adduct PCBM, p-EHO-PCBM, and p-EHO-PCBA group) (13-15) supramolecular complexes are presented and investigated.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.1
• /
• pp.699-704
• /
• 2018

One-dimensional nanostructures have attracted increasing attention because of their unique electronic, optical, optoelectrical, and electrochemical properties on account of their large surface-to-volume ratio and quantum confinement effect. Vertically grown nanowires have a large surface-to-volume ratio. The vapor-liquid-solid (VLS) process has attracted considerable attention for its self-alignment capability during the growth of nanostructures. In this study, vertically aligned silicon oxide nano-pillars were grown on Si\$SiO_2$(300 nm)\Pt substrates using two-zone thermal chemical vapor deposition system via the VLS process. The morphology and crystallographic properties of the grown silicon oxide nano-pillars were investigated by field emission scanning electron microscopy and transmission electron microscopy. The diameter and length of the grown silicon oxide nano-pillars were found to be dependent on the catalyst films. The body of the silicon oxide nano-pillars exhibited an amorphous phase, which is consisted with Si and O. The head of the silicon oxide nano-pillars was a crystalline phase, which is consisted with Si, O, Pt, and Ti. The vertical alignment of the silicon oxide nano-pillars was attributed to the preferred crystalline orientation of the catalyst Pt/Ti alloy. The vertically aligned silicon oxide nano-pillars are expected to be applied as a functional nano-material.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.12
• /
• pp.4205-4209
• /
• 2011

The $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ silicate was prepared by blending of $Li_2MnSiO_4$ and $Li_2FeSiO_4$ precursors with same molar ratio. The one of the silicates of $Li_2FeSiO_4$ is known as high capacitive up to ~330 mAh/g due to 2 mole electron exchange, and the other of $Li_2FeSiO_4$ has identical structure with $Li_2MnSiO_4$ and shows stable cycle with less capacity of ~170 mAh/g. The major drawback of silicate family is low electronic conductivity (3 orders of magnitude lower than $LiFePO_4$). To overcome this disadvantage, carbon composite of the silicate compound was prepared by sucrose mixing with silicate precursors and heat-treated in reducing atmosphere. The crystal structure and physical morphology of $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ was investigated by X-ray diffraction, scanning electron microscopy, and high resolution transmission electron microscopy. The $Li_2Mn_{0.5}Fe_{0.5}SiO_4$/C nanocomposite has a maximum discharge capacity of 200 mAh/g, and 63% of its discharge capacity is retained after the tenth cycles. We have realized that more than 1 mole of electrons are exchanged in $Li_2Mn_{0.5}Fe_{0.5}SiO_4$. We have observed that $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ is unstable structure upon first delithiation with structural collapse. High temperature cell performance result shows high capacity of discharge capacity (244 mAh/g) but it had poor capacity retention (50%) due to the accelerated structural degradation and related reaction.

• Applied Chemistry for Engineering
• /
• v.28 no.2
• /
• pp.153-157
• /
• 2017

Gel type internal electrolytes were synthesized by varying hydroxyethyl-cellulose (HEC) amounts and their durability and conductivity were measured. The ionic conductivity decreased as the content of HEC increased thus the internal electrolyte containing more than 12% of HEC could not be used as a reference electrode. Based on durability test results, as the HEC amount decreased carrier density resulting in increasing of the amount of KCl coming out of the porous membrane. Therefore in order to use long time at ballast water treatment systems, we selected 10% HEC for gel type internal electrolyte. The resolution test for total residual oxidants (TRO) was carried out using the TRO sensor and the gel type reference electrode made of 10% HEC. A 50 mV potential was applied to the TRO sensor for 30 sec and changes in the current were measured. It was confirmed that the TRO concentrations ranging from 0 to 15 mg/L could be separated at salinity conditions of 0.2~30 PSU. The results indicated that the TRO concentration at sea water and at fresh water was successfully measured by the TRO sensor constructed with the reference electrode using gel-type internal electrolyte of HEC.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.8
• /
• pp.877-885
• /
• 2013

A seawater pipe of the engine room in the ships is being surrounded with severely corrosive environments caused by fast flowing of the seawater, containing aggressive chloride ion and high conductivity etc.. Therefore, the leakage of the seawater from its pipe have been often occurred due to its local corrosion by aggressive chloride ions. Subsequently, its leakage area is usually welded by AC shielded metal arc welding with various electrodes. In this study, when the sea water pipe is welded with several types of electrodes such as E4301, E4311, E4313 and E4316, a difference of the corrosion resistance on the welding metal zones was investigated using an electrochemical method, observing microstructure, measuring polarization behaviors and hardness. The weld metal zone welded with E4313 electrode exhibited the lowest value of hardness compared to other weld metal zones. In addition, its zone indicated also the best corrosion resistance than those of other weld metal zones. Furthermore, all of the weld metal zones revealed a relatively better corrosion resistance than those of the base metal zones. and also showed higher hardness than the base metal zones.

• Polymer(Korea)
• /
• v.29 no.4
• /
• pp.403-407
• /
• 2005

In this work, the solid polymer electrolyte (SPE) composites, which are composed of poly(ethylene oxide) (PEO), mesoporous mobil crystalline material-41 (MCM-41), and lithium salt, are prepared in order to investigate the influence of MCM-41 contents on the ionic conductivity of the composites. The crystallinity of the SPE composites was evaluated using differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The ionic conductivity of the SPE composites was measured by the frequency response analyzer (FRA). As a result, the addition of MCM-41 into the polymeric mixture prohibited the growth of PEO crystalline domain due to the mesoporous structures of the MCM-41. The $P(EO)_{16}LiClO_4$/MCM-41 electrolytes show an increased ion conductivity as a function of MCM-41 content up to 8 $wt\%$ and a slightly decreased conductivity over 8 $wt\%$. These ion conductivity characteristics are dependent on a change of polymer crystallinity in the presence of MCM-41 system.

• Analytical Science and Technology
• /
• v.13 no.5
• /
• pp.630-635
• /
• 2000

The concentration of neurotransmitters in rat brain was determined by HPLC-ECD (electrochemical detection) method and the effects of methanol extracts of some crude drugs, such as Polygala Radix, Myristicae Semen, Zizyphi Semen, Acori graminei Rhizoma, Visci Herba, Liriopsis Tuber, Myrrha on the concentration of neurotransmitters in the ethanol-treated rat brain were investigated. By the administration of ethanol, dopamine (DA), 3, 4-dihydroxyphenyl acetic acid (DOPAC) and serotonin (5-HT) levels in frontal cortex and 5-HT level in hippocampus were significantly increased compared with the neurotransmitter levels in the brain of saline-treated rats. The ${\gamma}$-aminobutyric acid (GABA) level in frontal cortex was decreased by the same treatment. There was a tendency that the DA level in frontal cortex and striatum of ethanol-treated rats were increased by the administration of crude drug extracts. Especially, Myrrha and Visci Herba significantly increased the DA level of frontal cortex in ethanol-treated rats, while they significantly decreased the 5-HT level in the same region of the brain. GABA level in striatum of ethanol-treated rats was significantly decreased by Myristicae Semen, Visci Herba and Myrrha. These results suggest that the tested crude drug extracts have selective interaction with neurotransmitters in specified region of central nervous system.

• Applied Chemistry for Engineering
• /
• v.19 no.4
• /
• pp.407-412
• /
• 2008

As an activation procedure, in this study, the oxidation treatment of needle cokes with a dilute nitric acid and sodium chlorate $(NaClO_3)$, combined with heat treatment, was attempted. The structures of acid-treated and pyrolyzed coke were examined with XRD, FESEM, elemental analyzer, BET, and Raman spectroscopy. The behavior of double layer capacitance was investigated with the analysis of charge and discharge. The structure of needle coke treated with acid was revealed to a single phase of (001) diffraction peak after 24 h. On the other hand, thecoke oxidized by heat treatment was reduced to a graphite structure of (002) at $300^{\circ}C$. The distorted graphene layer structure, derived from the process of oxidation and reduction of the inter-layer, makes the pores by the electric field activation at the first charge, and generates the double layer capacitance from the second charge. The cell using pyrolyzed coke with 24 h acid treatment and $300^{\circ}C$ heat treatment exhibited the maximum capacitance per weight and volume of 33 F/g and 30 F/mL at the two-electrode system in the potential range of 0~2.5 V.

• Journal of Hydrogen and New Energy
• /
• v.12 no.1
• /
• pp.29-38
• /
• 2001

The alloys $ZrMn_2Ni_x$ (x=0.0, 0.3, 0.6, 0.9 and 1.2) as the alloys of Zr-Mn-Ni three component system were prepared and their hydrogen-storage properties and their electrochemical properties were investigated. The C14 Laves phase formed in all the alloys $ZrMn_2Ni_x$. Among these alloys $ZrMn_2Ni_{0.6}$ was activated relatively easily(after about 11 charge-discharge cycles), and had the largest discharge capacity(max. 45mAh/g). For all the alloys Zr was dissolved most easily into the 6M KOH solution. More Mn and Ni were dissolved from the $ZrMn_2Ni_{0.6}$ alloy than from the other alloys. Due to the active charge and discharge of the $ZrMn_2Ni_{0.6}$ alloys, related to the easier activation and the larger discharge capacity, Zr, Mn and Ni in this alloy were considered to be dissolved more easily into the 6M KOH solution, compared with the other alloys.