• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.368-369
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• 2006

The pure $LiFePO_4$, carbon added $LiFePO_4(LiFePO_4/C$) and pyrene added $LiFePO_4(LiFePO_4/P$) are synthesized by using solid-state reaction. XRD patterns show no impurity phase in the three kinds of the cathode materials. The 10wt% pyrene added $LiFePO_4$ shows around 140mAh/g of discharge capacity at 3rd cycle compared to the pure $LiFePO_4$. The carbon added $LiFePO_4$ shows 145mAh/g of discharge capacity at 3rd cycle and stable cycle-life compared to the others.

• Journal of Sensor Science and Technology
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• v.4 no.1
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• pp.35-42
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• 1995

Conventional ball-milling technique was used to synthesize NASICON powders. The NASICON powders were made from three kinds of component powders : coarse($ZrO_{2}$, $Na_{3}PO_{4}$, $SiO_{2}$), fine ($ZrO_{2}$, $Na_{3}PO_{4}$, $SiO_{2}$) and fine ($ZrSiO_{4}$, $Na_{3}PO_{4}$) powders. The fine component powders were easily reacted to form the desired product at $1100^{\circ}C$ or higher, whereas incomplete reaction due to the coarse component powders occurred even at $1170^{\circ}C$. The finer the grain size of the starting powders was, the higher the bulk density of NASICON electrolyte after sintering was observed. Almost single phase NASICON electrolytes with more than 95% of the theoretical density, $3.27g/cm^{3}$, could be fabricated by sintering for $40{\sim}60$ hours at temperatures between 1150 and $1170^{\circ}C$.

• Journal of the Korean Electrochemical Society
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• v.17 no.4
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• pp.229-236
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• 2014

In this study, the method to improve the electrochemical performance of $LiFePO_4$ by carbon coating and morphology control into porous structure was studied. The synthesis of $LiFePO_4$ was done by coprecipitation method by two step procedure. In the first step $FePO_4$ precursor was synthesized by coprecipitation method, followed by impregnation of lithium into the precursor at $750^{\circ}C$. The carbon coating was done by both physical and chemical coating processes. Using the physical coating process, the amount of coating layer was 6% and the capacity achieved was 125 mAh/g. In case of chemical coating process, the active material delivered 130~140 mAh/g, which is about 40% improvement of delivered capacity compared to uncoated $LiFePO_4$. For the morphology control into porous structure, we added nano particles of $Al_2O_3$ or $SiO_2$ into the active materials and formed the nanocomposite of ($Al_2O_3$ or $SiO_2$)/$LiFePO_4$. Between them, $SiO_2/LiFePO_4$ porous nanocomposite showed larger capacity of 132 mAh/g.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05a
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• pp.66-70
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• 2001

The partial discharge testing is widely used in diagnostic measuring technology because it gives low stress to power equipment which is undertaken tests. Therefore it is very useful method compare to previous destructive methods and effective diagnosis method in power system that requires on-line/on-site diagnosis. But partial discharges have very complex characteristics of discharge pattern, so it is required continuous research to development of precise analysis method. In recent, the study of partial discharge is carrying out discover of initial defect of power equipment through condition diagnosis and system development of degradation diagnosis using HFPD(High Frequency Partial Discharge) detection. In this study, simulated system is manufactured and HFPD occurred from those simulator is measured with broad-band antenna in real time, the degradation grade of system is analyzed through produced patterns in simulated target according to the AI/statistics processing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05b
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• pp.75-78
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• 2001

Recently, the HFPD measurement testing is widely used in partial discharge measurement of HV machines because HFPD measurement testing receives less influence of external noise and has a merit of good sensitivity. Also HFPD testing is able to offer the judgement standard of degradation level of HV machine and can detect discharge signals in live-line. Therefore it is very useful method compare to previous conventional PD testing method and effective diagnosis method in power transformer that requires live-line diagnosis. But partial discharges have very complex characteristics of discharge pattern so it is required continuous research to development of precise analysis method. In recent, the study of partial discharge is carrying out discover of initial defect of power equipment through condition diagnosis and system development of degradation diagnosis using HFPD(High Frequency Partial Discharge) detection. In this study, simulated transformer is manufactured and HFPD occurred from transformer is measured with broad band antenna in real time, the degradation grade of transformer is analyzed through produced patterns in simulated transformer according to applied voltages.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1337-1345
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• 1994

Glasses in the system of 45CaO-25TiO2-30P2O5 containing 1 mole% of M2O(M=Li, Na, K) were melted and crystallized. And their crystal phases were Ca3(PO4)2, CaTi4(PO4)6, and TiO2. Porous glass-ceramics with skeleton of two crystal phase CaTi4(PO4)6 and TiO2 were prepared by selective leaching of Ca3(PO4)2 with 0.1 N-HCl. Glass transition temperature(Tg) and crystallization temperature(Tc) were decreased by addition of 1 mole% alkali metal oxide. Pore size of porous glass-ceramics was increased with increasing heat treatment temperature and its dependence on heat treatment temperature was decreased with addition of Na2O and K2O. It was found that porous glass-ceramics of parent glass and containing 1mole% M2O(M=Li, Na, K) composition had maximum specific surface area, porosity and maximum of crystallzed phase by heat treatment at 80$0^{\circ}C$, 76$0^{\circ}C$, 78$0^{\circ}C$, 80$0^{\circ}C$ respectively.

• Microbiology and Biotechnology Letters
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• v.8 no.2
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• pp.77-85
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• 1980

This experiment was conducted to investigate the conditions for production and the characteristics of pretenses. Aspergillus oryzae KC-15, which is selected as a superior strain for the production of the protease, was used in this study. The results obtained were as follows: 1. The optimum culture time for the production of acid, neutral and alkaline protease on wheat bran medium were about 48, 48 and 72hr, respectively. The protease-produced by the strain were mainly alkaline and neutral one, but the production of acid protease was feeble extremely. 2. The addition of NaH$_2$PO$_4$, Na$_2$HPO$_4$, glucose, rice powder and Na-glutamate respectively to wheat bran media were effective for the production of alkaline and neutral protease, and the addition of (NH$_4$)$_2$HPO$_4$, glucose and rice powder respectively were effective for the production of acid protease. 3. Characteristics of professes(equation omitted) 4. As a heat resistance agent, NaH$_2$PO$_4$was the most effective one. The optimum amount of NaH$_2$PO$_4$was 10mg for alkaline and neutral protease, and 5mg for acid protease. 5. The heat resistance of the Protease by NaH$_2$PO$_4$was not recognized mostly above 6$0^{\circ}C$. 6. After the treatment of enzyme solution with 10mg of NaH$_2$PO$_4$for 30 minutes at 55$^{\circ}C$, the residual activities measured for alkaline, neutral and acid protease were 58, 57 and 55％ respectively.

• Membrane Journal
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• v.19 no.4
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• pp.302-309
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• 2009

A block copolymer of polystyrene-b-poly (hydroxyl ethyl methacrylate), PS-b-PHEMA, was synthesized via atom transfer radical polymerization (ATRP) and crosslinked with 4,5-imidazole dicarboxylic acid (IDA) via esterification of the -OH groups of PHEMA in the block copolymer and the -COOH groups of IDA. Upon doping with $H_3PO_4$ to form imidazole-$H_3PO_4$ complexes, the proton conductivity of the membranes continuously increased as the content of $H_3PO_4$ increased. In addition, both the tensile strength and the elongation at break increased with IDA content. A proton conductivity of 0.01 S/cm at $100^{\circ}C$ was obtained for the PS-b-PHEMA/IDA/$H_3PO_4$ membrane with [HEMA]:[IDA]:[$H_3PO_4$] = 3:4:4 under anhydrous conditions. All of the PS-b-PHEMA/IDA/$H_3PO_4$ membranes were thermally stable up to $350^{\circ}C$, as revealed by thermal gravimetric analysis (TGA).

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.E1
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• pp.21-28
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• 2003

An auxiliary device, called Post Cyclone (PoC). had been introduced and primarily examined in earlier works which proved the reduction of the emission of fine dust from the gas-solid cyclones without incurring significant increase of cost and pressure drop. It has been known that the PoC has some advantages over other secondary dust treatment devices such as (a) simple design, (b) low cost of manufacture, (c) minimum additional pressure drop, (d) high recoverbility of the product dust, and (e) simplicity of operation. Despite the potential advantage, however, lack of practical data confined its plausible application in wide areas. Thus, in this work, a few serial experiments were conducted in terms of a few operation conditions, and the particle trajectories throughout the cyclone set-up were visually analyzed by using a commercial computer simulation program (FLUENT).

• Bulletin of the Korean Chemical Society
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• v.6 no.1
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• pp.11-15
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• 1985

Electrical conductivites of polycrystalline yttrium sesquioxides containing 1.6 and 3.2 mol % of holmium sesquioxdes have been measured from 650 to $1050^{\circ}C$ under oxygen partial pressures of $1{\times}10^{-5}$ to $2{\times}10^{-1}$ atm. Plots of log conductivity vs. 1/T at constant oxygen partial pressures are found to be linear away from the two inflection points. The low- and high-temperature dependences of conductivity show different defect structures of yttrium sesquioxide. The plots of log conductivity vs. log $PO_2$ are found to be linear at $PO_{2'}$s of $10^{-5}$ to $10^{-1} atm. The electrical conductivity dependences on $PO_2$ are found to be $1}5.3$ at $950-1050^{\circ}C$, $\frac{6}{1}$ at $800-950^{\circ}C$ and ($\frac{6.2}{1}$) - ($\frac{6.5}{1}$) at $650-800^{\circ}C$, respectively. The defect structures and conduction mechanisms have been suggested.