• 공업화학
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• 제33권4호
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• pp.419-424
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• 2022

The oxidative degradation performance of the Erionyl Navy R dye was studied in this article. The investigation mainly focused on a comparative study between chemical oxidations by sodium hypochlorite (NaClO) and hydrogen peroxide (H₂O₂), and catalytic oxidations including the Fenton (Fe²⁺-H₂O₂) and Fenton-Like (Fe²⁺/ Fe³⁺/Co²⁺/ Mn²⁺-H₂O₂) or modified Fenton-like (Fe²⁺/ Fe³⁺ -NaClO) reactions. A discoloration and degradation of the Erionyl Navy R occurred after 30 minutes, which varies according to the oxidation system involved; 31%, 54%, <20%, 95%, and >96% losses were observed for Co²⁺-H₂O₂, Mn²⁺-H₂O₂, Fe²⁺-NaClO, Fe³⁺-NaClO), and Fe²⁺-H₂O₂ and Fe³⁺-H₂O₂, respectively.

• 한국전기전자재료학회논문지
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• 제21권7호
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• pp.638-644
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• 2008

The effects of $Nb_2O_5$ and $MnO_2$ on the positive temperature coefficient of resistivity (PTCR) behavior of lead-free $Ba_{0.99}(Bi_{1/2}Na_{1/2})_{0.01}TiO_3$ (BaBiNT) ceramics were investigated in order to fabricate a PTC thermistor available at high temperature of > $120^{\circ}C$. In particular, 0.05 mol% $Nb_2O_5$ added BaBiNT ceramic, which has significantly increased Curie temperature (Tc) of $160^{\circ}C$, showed good PTCR behavior; low resistivity at room temperature $(\rho_r)$ of $80.1{\Omega}{\cdot}cm$, a high $\rho_{max}/\rho_{min}$ ratio of $5.65{\times}10^3$ and a large resistivity temperature factor (a) of 18.5%/$^{\circ}C$. Furthermore, the improved $\rho_{max}/\rho_{min}$ of $6.48{\times}10^4$ and a of 25.4%/$^{\circ}C$ along with higher $T_c$ of $167^{\circ}C$ despite slightly increased $\rho_r$ of $569{\Omega}{\cdot}cm$, could be obtained for the BaBiNT + 0.05 mol% $Nb_2O_5$ + 0.02 wt% $MnO_2$ ceramic cooled down at a rate of $200^{\circ}C/h$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.7-10
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• 2001

Orthorhombic type $LiCo_{x}Mn_{1-x}O_{2}$(0 ${\times}$ 0.14) oxides have been synthesized by hydrothermal treatment of $(Co_{x}Mn_{1-x})_{3}O_{4}$ precursors and LiOH aqueous solution at $170^{\circ}C$. As-synthesized powders showed well-ordered ${\beta}-NaMnO_{2}$ structures, and the products were single crystalline particle oxides from TEM observations. The particle size decreased with increasing the amount of Co substituent. Much more improved capacity upon 100 cyclings was clearly seen in orthorhombic $LiCo_{0.1}Mn_{0.9}O_{2}$, comparing to orthorhombic $LiMnO_2$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.7-10
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• 2001

Orthorhombic type $LiCo_{x}Mn_{1-x}O_2$ (0 x 0.14) oxides have been synthesized by hydrothermal treatment of ($Co_{x}Mn_{1-x}$)$_3O_4$ precursors and LiOH aqueous solution at $170^{\circ}C$. As-synthesized powders showed well-ordered ${\beta}$-$NaMnO_2$ structures, and the products were single crystalline particle oxides from TEM observations. The particle size decreased with increasing the amount of Co substituent. Much more improved capacity upon 100 cyclings was clearly seen in orthorhombic $LiCo_{0.1}Mn_{0.9}O_2$, comparing to orthorhombic $LiMnO_2$.

• 한국광물학회지
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• 제3권1호
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• pp.34-43
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• 1990

Crystal-chemical study of hexagonal 7$\AA$ phyllomanganate minerals reveals that they have hexagonal layer structures with variable c dimensions which depend on the nature of interlayer cations and content of water molecules between edge-sharing [MnO6] octahedral layers. Approximately one out of nine octahedral sites is statistically vacant, leading to the general unit cell formula R2xMn4+1-xO2.nH2O, where R=Ca, Mn2+, Mg, K, Na;x=0.09-0.14 ; n-0.37-0.84. Z=1. The minerals of this formula fall under the name of rancieite group. It includes Ca-diminant (rancieite), Mn2+-dominant (takanelite), Na-dominant (birnessite), and Mg-dominant members. Minerals of the rancieite group occur predominantly in two different hydration states, i.e., n shows the values around 0.35 and 0.75. It is suggested that minerals of higher hydration state be called as species(i.e., rancieite, etc.) and those of lower hydration state be called as dehydrated varieties(i.e., dehydrated rancieite,etc.).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.744-747
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• 2004

[ $0.96[Bio_{0.5}(Na_{0.84}K_{0.16})_{0.5}TiO_3]+0.04SrTiO_3+0.3wt%Nb_2O_5+0.2wt%La_2O_3+xwt%MnO_2$ ], were studied in order to develope the superior dielectric and piezoelectric properties of Lead-free Piezoelectric ceramics. With increasing amount of $MnO_2$ addition, density showed the maximum value of $5.79[gcm^3$] at 0.1wt% $MnO_2$ addition, and electromechanical coupling factor($k_p$) and dielectric constant decreased, and mechanical quality factor($Q_m$) increased and showed the maximum value of 161 at 0.3wt% $MnO_2$ addition.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.186-190
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• 2011

Periodically ordered mesoporous manganese oxides were synthesized in a single and double replication procedure. Mesoporous SBA-15 and -16 silica and their reverse replica carbons were successively used as hard templates. The silica and carbon pore systems were infiltrated with $Mn(NO_3)_2{\cdot}xH_2O$ or $Mn(AcAc)_2$, which was then converted to $Mn_2O_3$ at 873 K; the silica and carbon matrix were finally removed by NaOH solution or calcinations in air. The structure of the mesoporous $Mn_2O_3$, using a carbon template, corresponds to that of the original SBA-15 and SBA-16 silica. The products consist of hexagonally arranged cylindrical mesopores with crystalline pore walls or cubic mesoporous pores. The structure of replica has been confirmed by XRD, TEM analysis, and its electrochemical properties were tested with cyclic voltammetry. Formation of $Mn_2O_3$ inside the mesoporous carbon pore system showed much improved electrical properties.

• Korean Chemical Engineering Research
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• 제46권1호
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• pp.94-98
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• 2008

비정형 $MnO_2$의 초고용량 캐폐시턴스 특성을 향상시키기 위하여 망간산화물을 높은 전기전도를 갖는 나노탄소섬유(vapour-grown carbon nanofibers, VGCF)와 복합화하여 나노탄소섬유/망간 산화물(VGCF(40 wt%)/$MnO_2$) 복합 전극을 제조하여 cyclic voltammetry(CV), impedance spectroscopy 및 chronopotentiometric charge/discharge 기법을 사용하여 1.0M $Na_2SO_4$ 전해질에서 초고용량 캐폐시터 특성을 조사하였다. 40 wt% VGCF를 포함한 복합전극에서 $0.8mg/cm^2$ 망간산화물을 로딩한 $VGCF/MnO_2$ 복합전극은 주사속도 20 mV/s에서는 380 F/g, 500 mV/s에서는 230 F/g의 비용량 값을 나타냈다. 또한, $2.0mA/cm^2$의 일정전류로 충방전 실험을 수행한 결과 3,000회에서 97%의 초기용량을 유지하였다.

• 한국세라믹학회지
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• 제29권11호
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• pp.900-904
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• 1992

High temperature electrical conductivity was measured for perovskite La0.98Sr0.02MnO3 at 200~130$0^{\circ}C$ as a function of Po2 and 1/T. Perovskite La1-xSrxMnO3 system is the typical oxygen electrode in solid oxide fuel cell (SOFC). Acetate precursors were used for the preparation of mixed water solution and the calcined powders were reacted with Na2CO3 flux in order to obtain highly reactive powders of perovskite La0.98Sr0.02MnO3. The relative density was greatly increased above 90% because of the homogeneous sintering. From the conductivity ($\sigma$)-temperature and conductivity-Po2 at constant temperature, the defect structure of La0.98Sr0.02MnO3 was discussed. From the slope of 1n($\sigma$) vs 1/T, the activation energy of 0.069 and 0.108eV were evaluated for above 40$0^{\circ}C$, respectively. From the relationship between $\sigma$ and Po2, it was found that the decomposition of La0.98Sr0.02MnO3 was occurred at 10-15.5 atm(97$0^{\circ}C$) and 10-11 atm(125$0^{\circ}C$). It is supposed that the improvement of p-type conductivity may be leaded by the increase of Mn4+ concentration through the substitution of divalent/monovalent cations for La site in LaMnO3.

• 한국세라믹학회지
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• 제33권8호
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• pp.928-934
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• 1996

X-선 형광분석법을 사용하여 표준검정곡선법으로 시멘트 중의 주, 부성분들을 정량하고 습식법과 분석결과를 비교하였다. 이때, 표준시료 및 미지시료는 용융 케스트 비드법으로 준비하였다. 표준시멘트(227A372)의 오차분석결과 주성분인 CaO, SiO2, Al2O3, Fe2O3 및 부성분중의 MgO, SrO는 상대오차가 1% 이내이었으며, 부성분중 So3, K2O, TiO2, Na2O P2O5 및 Mn2O3는 5% 이하의 상대오차를 가졌다. 부성분의 상대오차는 시료준비오차가 가장 큰 부분을 차지하였다. X-선 형광분석과 습식분석을 비교한 결과 시멘트 분석의 측정값간의 최대혀용범위를 만족하므로, X-선 형광분석법을 시멘트 화학분석에 적용할 수 있을 것으로 판단된다. 그리고, 기존의 습식법으로 분석하기 어려운 시멘트내에 존재하는 미량성분인 P2O5, SrO 및 Mn2O3 의 정밀정확한 분석 또한 가능하였다.