• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
• /
• pp.295-295
• /
• 2013

Supercapacitors with higher energy and power density are attracting growing attention for their wide range of potential applications such as portable electronic equipments, hybrid vehicle and cellular devices. In various classes of materials for supercapacitors, the redox pseudocapacitive materials such as conducting polymers and metal oxides have been most widely studied recently. The nanostructuring of the electrode surface has also been focused on since it can provide large surface area and consequently easy diffusion of ions in the capacitors. Among the active materials, in this work, we have used polyaniline (PANi) and manganese oxide ($MnO_2$). PANi is one of the promising electrode and active materials due to its desirable properties such as high electrochemical activity, high doping level and stability. $MnO_2$ is also widely studied material for supercapacitors since it is relatively cheap and environmentally friendly. In this work, we fabricated PANi hollow nanospheres by polymerizing aniline monomers on the polystyrene (PS) nanospheres and then dissolving the inner PS spheres. This nanostructuring of the PANi surface can provide large surface area and hence easy diffusion of electrolyte ions. We also incorporated $MnO_2$ nanoparticles into the PANi hollow nanospheres and investigated its electrochemical properties. It is expected that the combination of these two active materials with slightly different working potential windows show synergetic effects such as broader working potential range and enhanced specific capacitance.

• Mycobiology
• /
• 제47권2호
• /
• pp.217-229
• /
• 2019

Two manganese peroxidases (MnPs), MnP1 and MnP2, and a laccase, Lac1, were purified from Trametes polyzona KU-RNW027. Both MnPs showed high stability in organic solvents which triggered their activities. Metal ions activated both MnPs at certain concentrations. The two MnPs and Lac1, played important roles in dye degradation and pharmaceutical products deactivation in a redox mediator-free system. They completely degraded Remazol brilliant blue (25 mg/L) in 10-30 min and showed high degradation activities to Remazol navy blue and Remazol brilliant yellow, while Lac1 could remove 75% of Remazol red. These three purified enzymes effectively deactivated tetracycline, doxycycline, amoxicillin, and ciprofloxacin. Optimal reaction conditions were $50^{\circ}C$ and pH 4.5. The two MnPs were activated by organic solvents and metal ions, indicating the efficacy of using T. polyzona KU-RNW027 for bioremediation of aromatic compounds in environments polluted with organic solvents and metal ions with no need for redox mediator supplements.

• 한국재료학회지
• /
• 제31권2호
• /
• pp.68-74
• /
• 2021

Zinc-ion Batteris (ZIBs) are recently being considered as energy storage devices due to their high specific capacity and high safety, and the abundance of zinc sources. Especially, ZIBs can overcome the drawbacks of conventional lithium ion batteris (LIBs), such as cost and safety issues. However, in spite of their advantages, the cathode materials under development are required to improve performance of ZIBs, because the capacity and cycling stability of ZIBs are mainly influenced by the cathode materials. To design optimized cathode materials for high performance ZIBs, a novel manganese oxide (MnO2) coated graphite sheet is suggested herein with improved zinc-ion diffusion capability thanks to the uniformly decorated MnO2 on the graphite sheet surface. Especially, to optimize MnO2 on the graphite sheet surface, amounts of percursors are regulated. The optimized MnO2 coated graphite sheet shows a superior zinc-ion diffusion ability and good electrochemical performance, including high specific capacity of 330.8 mAh g-1 at current density of 0.1 A g-1, high-rate performance with 109.4 mAh g-1 at a current density of 2.0 A g-1, and remarkable cycling stability (82.2 % after 200 cycles at a current density of 1.0 A g-1). The excellent electrochemical performance is due to the uniformly decorated MnO2 on the graphite sheet surface, which leads to excellent zinc-ion diffusion ability. Thus, our study can provide a promising strategy for high performance next-generation ZIBs in the near future.

• Journal of Information Display
• /
• 제1권1호
• /
• pp.35-41
• /
• 2000

Manganese-doped $Zn_2SiO_4$ phosphors well known as a green emitter with high luminescence efficiency were prepared by the homogeneous precipitation method, and their photoluminescence properties under vacuum-ultraviolet (VUV) excitation were investigated. $Zn_2SiO_4$:Mn phosphors obtained by this method have exhibited a high luminance of property and a spherical shape of particles. In particular, the green emission intensity of zinc orthosilicate prepared as containing around 2 mole% of manganese was much stronger than that of the commercial $Zn_2SiO_4$:Mn phosphor, while the decay time was longer. However, addition of $Al^{3+}$ and $Li^+$ into $Zn_2SiO_4$:Mn composition has significantly diminished the decay time of the phosphor without much degradation of the emission intensity.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집A
• /
• pp.205-210
• /
• 2001

Fatigue crack growth tests were carried out using high manganese cast steel under constant amplitude loading. Average crystal grain sizes of the material are $200{\mu}m$ and $1000{\mu}m$. For this material, ${\Delta}K_{th}$ is about $8MPa{\sqrt{m}}$ which is quiet large as compared to the general structural steels and the crack growth rate is lower than the general structural steels especilly in the low ${\Delta}K$ regsion. The reason of this behavior is crack closure due to fracture surface roughness and fretting oxide. The relationship between da/dN and the ${\Delta}K_{eq}$ was represented by narrow band regardless of the stress ratio.

• 펄프종이기술
• /
• 제29권2호
• /
• pp.83-90
• /
• 1997

An unbleached hardwood kraft pulp was bleached in vitro with partially purified manganese peroxidase (MnP) from the fungus Phanerochaete sordida YK-624 without the addition of MnSO$_4$ in the presence of oxalate, malonate or gluconate known as manganese chelator, When the pulp was treated without the addition of MnSO$_4$, the pulp brightness increased by about 10 points in the presence of 2 mM oxalate, but the brightness did not significantly increase in the presence of 50 mM malonate. Residual MnP activity decreased faster during the bleaching with MnP without MnSO$_4$ in the presence of malonate than in the presence of oxalate. Oxalate reduced MnO$_2$ which already existed in the pulp or was produced from $Mn^{2+}$ by oxidation with MnP and thus supplied $Mn^{2+}$ to the MnP system. Thus, bleaching of hardwood kraft pulp with MnP, using manganese originally existing in the pulp, became possible in the presence of oxalate, a good manganese chelator and reducing reagent. Properties of partially purified MnPs from liquid cultures of white rot fungi, Ganoderma sp. YK-505, Phanerochaete sordida YK-624 and Phanerochaete chrysosporium were compared. MnP from Ganoderma sp. YK-505 was superior to MnPs from P. sordida YK-624 and P. chrysosporium in stabilities against high temperature and high concentration of $H_2O$$_2$. The MnP from Ganoderma sp. YK-505 differed in pH-activity profile from other MnPs. These data suggest that MnP from Ganoderma sp. YK-505 has different structure from those of other fungi. Bleaching of hardwood kraft pulp using the MnP from ganoderma sp. YK-505 is now in progress.

• Journal of Periodontal and Implant Science
• /
• 제34권2호
• /
• pp.357-366
• /
• 2004

Chronic exposure to high levels of manganese leads a pronounce and debilitating disorder known as manganism. Research on the toxic manifestation of manganese have focused primarily on its neurological effects because exposure to high levels of the metal produces a distinct and irreversible extrapyramidal dysfunction resembling the dystonic movements associated with Parkinson's physiological and biochemical systems in the body. The purpose of this study was to evaluate the effect of manganeses on primary rat calvarial cell growth and toxicity. The experimental groups were in concentration of 0, 10, 30, 60, 100, 300 ${\mu}M$. Cell activity was assessed at day 1 and day 3 using a fluorescent molecular probe. Cell proliferation was evaluated at day 1 and day 3 by MTT assay. The amount of total protein synthesis was measured at day 3 and day 7. The results were as follows: The proliferation of primary rat calvarial cells were inhibited by $MnCl_2$ in the concentration exceeding $100{\mu}M$. The primary rat calvarial cells treated with $MnCl_2$ showed similar protein synthesis to the control group except in 100 ${\mu}M$. These result suggest that manganese suppress the viability and protein synthesis of primary rat calvarial cells in concentration exceeding $100{\mu}M$.

• 한국응용과학기술학회지
• /
• 제30권1호
• /
• pp.71-77
• /
• 2013

알루미늄 테르밋 반응의 환원제로서 알루미늄 분말은 200 메쉬 이하의 미분이 필요하나, 알루미늄의 높은 인성과 분말 제조비 때문에 경제적으로 용이하지 않다. 그러므로 $Mn_3O_4$ 분진 환원용 알루미늄 미분의 제조 코스트를 낮추기 위해, 알루미늄 합금분말의 제특성이 검토되었다. 망간을 다량 함유한 알루미늄 합금괴는 취성이 큰 금속간 화합물을 함유하고 있기 때문에 쉽게 파쇄할 수 있다. 또 망간은 망간 합금철의 주성분이다. Al-15%Mn 합금분말을 기계적 파쇄법으로 저렴하게 제조할 수 있다. Al 분말 대신에 Al-15%Mn 합금분말을 사용한 테르밋 반응 결과는 환원제로 순 알루미늄 분말을 사용한 경우와 같이 고순도 망간 합금철을 얻을 수 있었다. Al-15%Mn 합금분말를 이용한 $Mn_3O_4$ 분진의 망간 회수율은 알루미늄 분말을 이용한 경우의 약 65% 보다 높은 약 70%의 높은 수준을 보였으며, 이는 비산이 적은 것에 기인한다.

• 한국재료학회지
• /
• 제12권11호
• /
• pp.860-864
• /
• 2002

$Li^{+}$ extraction reactions with ion-exchange type lithium manganese oxide in an aqueous phase were examined using chemical and x-ray diffraction (XRD) analysis. In the process of extraction reaction, the lithium manganese oxide showed a topotactic extraction of $Li^{+ }$ in the aqueous phase mainly through an ion-exchange mechanism, and the $Li^{+}$ extracted samples indicated a high selectivity and a large capacity for $Li^{+}$ . The electronic structures and chemical bonding properties were also studied using a discrete variational (DV)-X$\alpha$ molecular orbital method with cluster model of (Li$Mn_{12}$ $O_{40}$ )$^{27-}$ for tetrahedral sites and ($Li_{7}$ Mn $O_{38}$ )$^{3}$ for octahedral site in $Li_{1.33}$ $Mn_{1.67}$ / $O_{4}$ respectively. Li in the manganese oxides is highly ionized in both sites, but the net charge of Li was greater for tetrahedral sites than octahedral. These calculations suggest that the tetrahedral sites have higher $Li^{+}$ $H^{+}$ exchangeability than the octahedral sites, and are preferable for the selective adsorption for L $i^{+}$ ions.s.

• 자원환경지질
• /
• 제45권5호
• /
• pp.477-486
• /
• 2012

북동태평양 대한민국 망간단괴 광구중 하나인 KR1 지역에서 망간단괴의 분포특성을 파악하기 위하여 정밀수심 측량과 망간단괴의 특성(외형, 조직, 크기, 금속함량) 분석을 수행하였다. 작고(<2 cm), 매끄럽고(s-형), 불규칙하고(I-형), Fe의 함량이 높은 망간단괴가 KR1의 북동부(KR1-2) 지역에 우세하게 분포하는 것에 비하여, KR1의 남서부(KR1-1) 지역에서는 상대적으로 Mn, Cu, Ni의 함량이 높고, 크고(2~4 cm), 거칠고(t-형, d-형), 원반형(D-형)의 망간단괴가 우세하게 분포하는 것으로 나타났다. 정밀수심 자료에 의하면 상대적으로 KR1-1 지역은 수심이 깊고(3,838~4,799 m; 평균 4,599 m), KR1-2 지역은 3,940~4,664 m (평균: 4,451 m)의 수심을 보이며 소규모의 해저산이 발달해 있다. KR1 지역에서 나타나는 이러한 수심과 망간단괴에 포함된 Mn, Cu, Ni의 함량과의 상관성은 태평양 전역에 걸쳐 나타나는 일반적인 특성과도 일치한다. 또한 망간단괴의 크기와 형태와 관련하여, KR1-2 지역에 분포하고 있는 소규모 해저산에서부터 망간단괴의 핵으로 사용되는 암편의 공급이 원활하기 때문에 작고 매끄럽고 불규칙한 초기 형태의 망간단괴가 주로 분포하고 있는 것으로 판단된다. 이러한 연구결과는 망간단괴의 분포특성에 있어서, 수심과 더불어 해저지형의 특성이 중요한 변수로 작용할 수 있음을 보여준다.