• 제목/요약/키워드: $Mn^{2+}$ ion

검색결과 593건 처리시간 0.023초

Temperature Dependence of Mn2+ Paramagnetic Ion in a Stoichiometric LiNbO3 Single Crystal

  • Yeom, Tae Ho;Lee, Soo Hyung
    • Journal of Magnetics
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    • 제18권3호
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    • pp.221-224
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    • 2013
  • Electron paramagnetic resonance (EPR) spectra of $Mn^{2+}$ impurity ion in Stoichiometric $LiNbO_3$ single crystal (SLN) was investigated with an X-band EPR spectrometer in the temperature range of 3 K~296 K. The intensity of EPR spectrum of $Mn^{2+}$ ion was increased to 20 K and decreased again below 20 K as the temperature decreases. The zero-field splitting parameter D decreased as the temperature increases. It was suggested that $Mn^{2+}$ ion substitute for $Nb^{5+}$ ion instead of $Li^+$ ion. No changes for hyperfine interaction of $Mn^{2+}$ ion was obtained in the temperature range of 3 K~296 K.

Electron Spin Resonance Study of Manganese Ion Species Incorporated into Novel Aluminosilicate Nanospheres with Solid Core/Mesoporous Shell Structure

  • Back, Gern-Ho;Kim, Ki-Yub;Kim, Yun-Kyung;Yu, Jong-Sung
    • 한국자기공명학회논문지
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    • 제14권2호
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    • pp.55-75
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    • 2010
  • An ion-exchanged reaction of $MnCl_2$ with Al-incorporated solid core/mesoporous shell silica (AlSCMS) followed by calcinations generated manganese species, where average oxidation state of manganese ion is 3+, in the mesoporous materials. Dehydration results in the formation of $Mn^{2+}$ ion species, which can be characterized by electron spin resonance (ESR). The chemical environments of the manganese centers in Mn-AlSCMS were investigated by diffuse reflectance, UV-VIS and ESR spectroscopic methods. Upon drying at 323 K, part of manganese is oxidized to higher oxidation state ($Mn^{3+}$ and $Mn^{4+}$) and further increase in (average) oxidation state takes place upon calcinations at 823 K. It was found that the manganese species on the wall of the Mn-AlSCMS were transformed to tetrahedral $Mn^{3+}$ or $Mn^{4+}$ and further changed to square pyramid by additional coordination to water molecules upon hydration. The oxidized $Mn^{3+}$ or $Mn^{4+}$ species on the surfaces were reversibly reduced to $Mn^{2+}$ or $Mn^{3+}$ species or lower valances by thermal process. Mn(II) species I with a well resolved sextet was observed in calcined, hydrated Mn-AlSCMS, while Mn (II) species II with g = 5.1 and 3.2 observed in dehydrated Mn-AlSCMS. Both species I and II are considered to be non-framework Mn(II).

금속 이온이 교환된 석탄 비산재 유래 합성 제올라이트 물질의 암모니아 흡착성능 평가 (Evaluation of Ammonia Adsorption Capacity Using Various Metal Ion-Exchanged Zeolitic Materials Synthesized from Coal Fly Ash )

  • 박종원;곽주영;이창한
    • 한국환경과학회지
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    • 제32권5호
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    • pp.343-353
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    • 2023
  • A zeolite material (ZCH) was synthesized from coal fly ash in an HD thermal power plant using a fusion/hydrothermal method. ZCH with high crystallinity could be synthesized at the NaOH/CFA ratio of 0.9. Ion-exchanged ZCH adsorbents for ammonia removal were prepared by ion-exchanging various cation (Cu2+, Co2+, Fe3+, and Mn2+) on the ZCH. They were used to evaluate the ammonia adsorption breakthrough curves and adsorption capacities. The ammonia adsorption capacities of the ZCH and ion-exchanged ZCHs were high in the order of Mn-ZCH > Cu-ZCH ≅ Co-ZCH > Fe-ZCH > ZCH according to NH3-TPD measurements. Mn-ZCH ion-exchanged with Mn has more Brønsted acid sites than other adsorbents. The ion-exchanged Cu2+, Co2+, Fe3+, or Mn2+ ions uniformly distributed on the surface or in the pores of the ZCH, and the number of acidic sites increased on the alumina sites to form the crystal structure of zeolite material. Therefore, when the ion-exchanged ZCH was used, the adsorption capacity for ammonia gas increased.

침전-증발법에 의해 제조된 리튬이온 2차 전지용 LiMn2O4 양극재료의 특성 (Characteristics of LiMn2O4 Cathode Material Prepared by Precipitation-Evaporation Method for Li-ion Secondary Battery)

  • 김국태;윤덕기;심영재
    • 한국재료학회지
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    • 제12권9호
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    • pp.712-717
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    • 2002
  • New wet chemical method so called precipitation-evaporation method was suggested for preparing spinel structure lithium manganese oxide ($LiMn_2$$O_4$) for Li ion secondary battery. Using precipitation-evaporation method, $LiMn_2$$O_4$ cathode materials suitable for Li ion secondary batteries can be synthesized. Single spinel phase $LiMn_2$$O_4$ powder was synthesized at lower temperature compared to that of prepared by solid-state method. $LiMn_2$$O_4$ powder prepared by precipitation-evaporation method showed uniform, small size and well defined crystallinity particles. Li ion secondary battery using $LiMn_2$$O_4$ as cathode materials prepared by precipitation-evaporation method and calcined at $800^{\circ}C$ showed discharge capacity of 106.03mAh/g and discharge capacity of 95.60mAh/g at 10th cycle. Although Li ion secondary battery showed somewhat smaller initial capacity but good cyclic ability. It is suggested that electro-chemical properties can be improved by controlling particle characteristics by particle morphology modification during calcination and optimizing Li ion secondary battery assembly conditions.

전이금속 치환 리튬이온 이차전지 정극 Li($Mn_{1-\delta}$$M_{\delta}$)$_2$$O_4$의 전기적 특성 (Electrical Characteristics of Cathode Li($Mn_{1-\delta}$$M_{\delta}$)$_2$$O_4$ Substituted by Transition Metals in Li-Ion Secondary Batteries)

  • 박재홍;김정식;유광수
    • 한국세라믹학회지
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    • 제37권5호
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    • pp.466-472
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    • 2000
  • As cathode materials of LiMn2O4-based lithium-ion secondary batteries, Li(Mn1-$\delta$M$\delta$)2O4 (M=Ni and Co, $\delta$=0, 0.05, 0.1 and 0.2) materials which Co and Ni are substituted for Mn, were syntehsized by the solid state reaction at 80$0^{\circ}C$ for 48 hours. No second phases were formed in Li(Mn1-$\delta$M$\delta$)2O4 system with substitution of Co. However, substitution of Ni caued to form a second phase of NiO when its composition exceeded over 0.2 of $\delta$ in Li(Mn1-$\delta$M$\delta$)2O4. As the results of charging-discharging test, the maximum capacity of Li(Mn1-$\delta$M$\delta$)2O4 appeared in $\delta$=0.1 for both Co and Ni. Also, Li(Mn1-$\delta$M$\delta$)2O4 electrode showed higher capacity and better cycle performance than LiMn2O4.

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Theoretical Calculation of Zero Field Splitting of $Mn^{2+}$ Ion in $LiTaO_3$Crystal

  • Yeom, T.H;Lee, S.H
    • Journal of Magnetics
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    • 제6권3호
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    • pp.77-79
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    • 2001
  • The semi-empirical superposition model has been applied to calculate the zero field splitting parameters of $Mn^{2+}$ion in $LiTaO_3$ single crystal, assuming that $Mn^{2+}$ion occupies one of two possible sites: $Li^{l+} \;or\; Ta^{5+}$ site, respectively. The 2nd-order axial zero field splitting parameters are $958\times10^{-4}cm^{-1}\; at\; Li^{1+}$ site and $193\times 10^{-4}cm^{-1} \;at\; Ta^{5+}$ site for $Mn^{2+}$ions. The 4th-order zero field splitting parameters at $Li^{l+} \;and\; Ta^{5+}$ sites are also determined. These calculated zero field splitting parameters are very important to determine the substitutional sites of doped impurity ions in $LiTaO_3$ crystal.

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이온 치환된 천연 제올라이트를 활용한 암모니아성 질소, Mn, As의 제거 (Removal of Ammonia Nitrogen, Manganese and Arsenic in The Ion Exchanged Natural Zeolite)

  • 이경한;길보민;유철휘;황갑진
    • 멤브레인
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    • 제29권5호
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    • pp.237-245
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    • 2019
  • 암모니아성 질소($NH_4-N$)는 산업 폐수, 농업 및 축산 폐수에 포함되어 있으며 인과 함께 수질의 부영양화를 일으키는 물질로 잘 알려져 있다. 또한 망간(Mn)과 비소(As)는 광산 처리수 등에 포함되어 있으며, 수질 오염의 원인 물질로 알려져 있다. 천연 제올라이트는 수중에서 암모니아성 질소를 제거하는데 사용되고 있지만 낮은 흡착능력을 가진다. 이러한 천연 제올라이트의 낮은 흡착능력을 개선하기 위해 $Na^+$, $Ca^{2+}$, $K^+$, $Mg^{2+}$로 이온 치환을 진행하였다. 암모니아성 질소($NH_4-N$)의 흡착량과 제거율은 $Na^+$로 이온 치환된 제올라이트에서 0.66 mg/g과 89.8%로 가장 높은 값을 보였다. 이온 치환된 제올라이트를 이용하여 Mn과 As의 흡착실험을 진행하였다. $Mg^{2+}$로 이온 치환된 제올라이트에서 Mn과 As의 높은 흡착량과 제거율을 보였다.

카본을 부극으로 사용하는 $LiMnO_2$ 전지의 전기화학적 특성 (Charge/Discharge Characteristics of $LiMnO_2$ Battery using Carbon as Anode Materials)

  • 김은미;임승규;김남인;구할본
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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    • pp.277-278
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    • 2008
  • Orthorhombic $LiMnO_2$(o-$LiMnO_2$) has attracted public attentions as a cathode materials of Lithium ion battery because it has low cost and high theoretical discharge capacity of 285mAh $g^{-1}$. In our study, o-$LiMnO_2$ is synthesized by quenching method. To verify their phase structure, X-ray diffraction is accomplished. Test cells are assembled to check electrochemical characteristics using acquired o-$LiMnO_2$ cathode and carbon anode. Charge/Discharge cycling was carried out for 50cycles. And impedance was measured at 1, 2, 5, 10, 30, 50cycle. During cycle test, the max discharge capacity was recorded 139mAh $g^{-1}$ at 10cycle.

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리튬 이온 이차전지 Cathode용 Li(Mn$_{1-}$$\delta$Nb$\delta$)$_2$O$_4$의 전기적 특성 (Electrical Characteristics of Li(Mn$_{1-}$$\delta$Nb$\delta$)$_2$O$_4$ Cathode Materials for Li-Ion Secondary Batteries)

  • 오용주;유광수
    • 한국세라믹학회지
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    • 제35권9호
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    • pp.995-1001
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    • 1998
  • As a basic study for cathode materials of {{{{ { {LiMn }_{2 }O }_{4 } }}-based lithium-ion secondary batteries Li({{{{ { { { {Mn }_{1-$\delta$ }Nb }_{$\delta$} )}_{2 }O }_{4 } }} ($\delta$=0.05, 0.1, 0.2) materials which Nb is substituted for Mn were synthesized by the solid state reaction at 80$0^{\circ}C$ and 110$0^{\circ}C$ respectively. The second phase {{{{ { LiNbO}_{3 } }} appeared above $\delta$=0.1 As the result of im-pedance analysis as the amount of substituted Nb increased the resistivity of grain boundary increased greatly. Compared to undoped-{{{{ { {LiMn }_{2 }O }_{4 } }} the electrical conductivity of Li({{{{ { { { {Mn }_{1-$\delta$ }Nb }_{$\delta$} )}_{2 }O }_{4 } }} decreased slightly but is charging capacity and potential plateau increased.

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