전이금속으로 개질된 Red Mud 촉매상에서 휘발성유기화합물 제거

김민기,김상채 한국환경기술학회 2020 한국환경기술학회지 Vol.21 No.2

Red mud(RM), a byproduct of alumina production, was incorporated with a transition metal, which was used as a catalyst for oxidation of volatile organic compounds (VOCs). RM was treated with hydrochloric acid and ammonia and then calcined at 400 ℃(CRM). Cu, Mn, Co, Ni, and Zn were used as the transition metals for the modified CRM catalyst. The physical and chemical properties of each catalyst were investigated by BET, SEM, XRD, TPR and FTIR analysis. The transition metals improved the reaction activity of CRM. The order of activation of each catalyst according to transition metals was Cu/CRM > Mn/CRM> Co/CRM > Ni/CRM ≥ Zn/CRM > CRM. The activity order of the catalysts was associated with the mobility of the lattice oxygen of the catalyst. In addition, the catalytic activity with respect to the VOC molecule (benzene, toluene, and xylene) was related to the ionization potential energy of the aromatic compound.

Electronic Structure Change of NiS2−xSex in the Metal-Insulator Transition Probed by X-ray Absorption Spectroscopy

정진원,박경자,조은진,노한진,김성백,김형도 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.1

The electronic structure change of NiS2−xSe x as a function of Se concentration x has been studied by Ni L-edge X-ray absorption spectroscopy (XAS). The XAS spectra show distinct features in Ni L3 edge, indicating whether the system is insulating or metallic. These features can be semi-quantitatively explained within the framework of the configurational interaction cluster model (CICM). In the S-rich region, relatively large charge-transfer energy (Δ ~ 5 eV) from ligand p to Ni 3d states and a little small p-d hybridization strength (V pdσ ~ 1.1 eV) can reproduce the experimental spectra in the CICM calculation, and vice versa in the Se-rich region. Our analysis result is consistent with the Zaanen-Sawatzky-Allen scheme that the systems in S-rich side (x ≤ 0.5) are a charge transfer insulator. However, it also requires that the Δ value must change abruptly in spite of the small change of x near x = 0.5. As a possible microscopic origin, we propose a percolation scenario where a long range connection of Ni[(S,Se)2]6 octahedra with Se-Se dimers plays a key role to gap closure.

전이 금속 화합물에서 전산모사를 이용한 반쪽 금속 반강자성체 설계

이관우 한국자기학회 2022 韓國磁氣學會誌 Vol.32 No.4

Over the past 25 years, mostly based on the first principles calculations, the compensated half-metals (CHMs) (or half-metallic antiferromagnet) have been investigated as a promising candidate for spintronics applications. Since a few CHMs were successfully observed several years ago, interest in CHMs has very stimulated. In this paper, we will address representative candidates for CHMs focused on our previous research for beginners in this area. Besides, we will briefly discuss the unconventional characters, anticipated so far, and points to be noted in its research. This is expected to provide a useful strategy for beginners on how to design and synthesize CHMs.

2차원 코발트 벌집격자 화합물에서의 키타에프 자성

김흥식 한국자기학회 2022 韓國磁氣學會誌 Vol.32 No.6

Study on realization of Kitaev magnetism in two-dimensional honeycomb lattices is one of the cutting-edge research topics in condensed matter physics and quantum magnetism researches. In this paper I will briefly review recent theoretical and experimental ongoing progresses to engineer Kitaev magnetism in cobalt-based transition metal compounds.

Thermodynamic stability of in situ W–ZrC and W–Zr(CN) composites

Kim, Jae-Hee,Zhe, Gao,Lim, Jaehyuk,Park, Choongkwon,Kang, Shinhoo Elsevier 2015 JOURNAL OF ALLOYS AND COMPOUNDS Vol.647 No.-

<P><B>Abstract</B></P> <P>Powders of W–ZrC and W–Zr(CN) were carbothermally synthesized in situ from milled mixtures of graphite, WO<SUB>3</SUB> and ZrO<SUB>2</SUB>. The thermal stability of Zr(CN) in a W matrix was simulated and compared with that of ZrC in W in terms of free energy change and carbide coarsening. Carbon and nitrogen had high mutual affinity in Zr(CN) of B1 crystal structure, which led their activity curves to exhibit strong negative deviation from ideal mixing behavior. Zr(CN) was more stable than ZrC up to 2075 K; however, a microstructural study showed that it became less stable than ZrC at around 1975 K. This result is attributed to the decreasing thermodynamic stability of ZrN with increasing temperature. Other transition metal carbonitrides containing group 4–6 elements are expected to show similar coarsening behaviors at high temperatures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Zr(CN) phase formed due to the high affinity between C and N in ZrC. </LI> <LI> A complete reversal of the slope is found in the formation energy curves. </LI> <LI> The growth of the carbonitride is due to the nitrogen, reducing the stability. </LI> <LI> Solid solutions containing group 4 elements would show similar growth behavior. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A Significant Reduction of Hysteresis in MnFe(P,Si) Compounds

B. Huliyageqi,Yao-xiang Geng,Ying-jie Li,O. Tegus 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3

The magnetocaloric effects in Mn1.3Fe0.7−xCoxP0.46Si0.54 compounds (x = 0, 0.025, 0.05 and0.1) were investigated systematically. X-ray diffraction shows that the compounds crystallize in theFe2P-type hexagonal structure with space group P-62m symmetry. Magnetic measurements showthat the paramagnetic-ferromagnetic transition temperatures range from 247 to 298 K. The maximalmagnetic entropy changes in the Mn1.3Fe0.7P0.46Si0.54 compound reaches 8.3 J/kgK for a fieldchange from 0 to 1.5 T. The thermal hysteresis of these compounds is less than 3 K. The maximumadiabatic temperature change is 2.2 K in Mn1.3Fe0.7P0.46Si0.54 and Mn1.3Fe0.65Co0.05P0.46Si0.54compounds for a field change from 0 to 1.48 T, indicating this material system has potential forroom-temperature magnetic refrigeration applications.

Magnetic Resonance Properties of Zn1-xMnxO thin Films grown by Using Molecular Beam Epitaxy

Jan Stehr,Christoph Knies,Detlev M. Hofmann,Wei Xu,Yingxue Zhou,Xinyi Zhang 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1

We present the results of an electron paramagnetic resonance study of Zn1-xMnxO thin lms grown by molecular beam epitaxy on sapphire substrates. The Mn concentrations in the samples vary between x = 0.03 and x = 0.3. In addition to residual Mo3+ ions, the exchange interaction of the Mn2+ ions is studied. Our results show dominantly antiferromagnetic coupling of the ions. We present the results of an electron paramagnetic resonance study of Zn1-xMnxO thin lms grown by molecular beam epitaxy on sapphire substrates. The Mn concentrations in the samples vary between x = 0.03 and x = 0.3. In addition to residual Mo3+ ions, the exchange interaction of the Mn2+ ions is studied. Our results show dominantly antiferromagnetic coupling of the ions.

Influences of Co-substitution on Magnetic Properties of Tetragonal D0<SUB>22-</SUB>Mn₃Ga

Thi Quynh Anh Nguyen,Thi H. Ho,S. C. Hong,S. H. Rhim 한국자기학회 2019 한국자기학회 학술연구발표회 논문개요집 Vol.29 No.2

[60]Fullerene–Metal Cluster Complexes: Understanding Novel η¹ and η^2[6:5] Bonding Modes of Metallofullerenes

Han, Young-Kyu,Kim, Kyoung Hoon,Kim, Jong Chan,Park, Bo Keun,Park, Joon T. WILEY-VCH Verlag 2010 European journal of inorganic chemistry Vol.2010 No.10

<P>We performed extensive density functional calculations on various metallofullerene complexes and their polyanions to gain insight into novel η<SUP>1</SUP> and η<SUP>2[6:5]</SUP> metal (M)–C<SUB>60</SUB> bonding modes. For L<SUB>n</SUB>MC<SUB>60</SUB> (L = ligand), the η<SUP>1</SUP> mode is calculated to be the most stable, followed by η<SUP>2[6:5]</SUP> and η<SUP>2[6:6]</SUP> for –3 anions, in contrast to η<SUP>2[6:6]</SUP> >> η<SUP>2[6:5]</SUP> ≈ η<SUP>1</SUP> for neutral cases. This observation is responsible for the transformation from η<SUP>2[6:6]</SUP> to η<SUP>1</SUP> for L<SUB>n</SUB>M<SUB>3</SUB>C<SUB>60</SUB>, such as [Os<SUB>3</SUB>(CO)<SUB>9</SUB>C<SUB>60</SUB>], upon successive electron reductions. Our energy partitioning analysis (EPA) indicates that the π-type character of η<SUP>2[6:6]</SUP> is much larger than that of η<SUP>2[6:5]</SUP>. An electron addition decreases the π-type interaction of both the η<SUP>2[6:6]</SUP> and η<SUP>2[6:5]</SUP> modes by about 35 %, whereas it has little effect on σ-type interactions. Because of the large proportion of π-character in η<SUP>2[6:6]</SUP> coordination, the stability of η<SUP>2[6:6]</SUP> coordination decreases steeply as electron reductions continue. On the basis of the EPA results, we could explain why the reaction of [Os<SUB>3</SUB>(CO)<SUB>8</SUB>(CNR)(μ<SUB>3</SUB>-η<SUP>2[6:6]</SUP>,η<SUP>2[6:6]</SUP>,η<SUP>2[6:6]</SUP>-C<SUB>60</SUB>)] (R = CH<SUB>2</SUB>Ph) with CNR (4e donor) produces [Os<SUB>3</SUB>(CO)<SUB>8</SUB>(CNR)(μ<SUB>3</SUB>-CNR)(μ<SUB>3</SUB>-η<SUP>1</SUP>,η<SUP>2[6:5]</SUP>,η<SUP>1</SUP>-C<SUB>60</SUB>)]. The η<SUP>1</SUP> and η<SUP>2[6:5]</SUP> bonding modes of M–C<SUB>60</SUB> are crucial to fully understand the bonding nature of M–C<SUB>60</SUB> bonds in exohedral metallofullerene complexes.</P> <B>Graphic Abstract</B> <P>The reaction of [Os<SUB>3</SUB>(CO)<SUB>8</SUB>(CNR)(μ<SUB>3</SUB>-η<SUP>2[6:6]</SUP>,η<SUP>2[6:6]</SUP>,η<SUP>2[6:6]</SUP>-C<SUB>60</SUB>)] (R = CH<SUB>2</SUB>Ph) with CNR (4e donor) produces [Os<SUB>3</SUB>(CO)<SUB>8</SUB>(CNR)(μ<SUB>3</SUB>-CNR)(μ<SUB>3</SUB>-η<SUP>1</SUP>,η<SUP>2[6:5]</SUP>,η<SUP>1</SUP>-C<SUB>60</SUB>)]. DFT calculations clearly show that the η<SUP>1</SUP> and η<SUP>2[6:5]</SUP>modes are preferable to η<SUP>2[6:6]</SUP> for electron-rich environments. Electron additions were found to significantly decrease π-type interactions, whereas they had little effect on σ-type interactions. <img src='wiley_img_2010/14341948-2010-2010-10-EJIC200901188-fig000.gif' alt='wiley_img_2010/14341948-2010-2010-10-EJIC200901188-fig000'> </P>

Employment of SnO₂:F@Ni₃Sn₂/Ni nanoclusters composites as an anode material for lithium-ion batteries

Kim, Min Kyu,Kim, A-Young,Woo, Jae Young,Lim, Jong Choo,Jeon, Bup Ju,Lee, Joong Kee Elsevier 2016 JOURNAL OF ALLOYS AND COMPOUNDS Vol.680 No.-

<P><B>Abstract</B></P> <P>Surface modification of SnO<SUB>2</SUB>:F particles which obtained from a large-scale electron cyclotron resonance-metal organic chemical vapor deposition system was carried out by two consecutive processes: electroless plating processing and annealing. First, Ni film on the SnO<SUB>2</SUB>:F and Ni nanoclusters were observed after Ni electroless plating; the film on the SnO<SUB>2</SUB>:F was then converted to Ni<SUB>3</SUB>Sn<SUB>2</SUB> after annealing at 800 °C under an argon atmosphere. A Ni<SUB>3</SUB>Sn<SUB>2</SUB> bimetallic structure formed instead of NiO during the annealing process because of the presence of carbon impurities in SnO<SUB>2</SUB>:F. The surface-modified Ni<SUB>3</SUB>Sn<SUB>2</SUB>-covered SnO<SUB>2</SUB>:F with Ni nanoclusters (SnO<SUB>2</SUB>:F@Ni<SUB>3</SUB>Sn<SUB>2</SUB>/Ni-nc) was employed as an anode material for lithium-ion batteries. The inactive Ni in Ni<SUB>3</SUB>Sn<SUB>2</SUB> acts as a buffer matrix against the Sn active material during the charge-discharge reactions, enhancing the electrochemical performance. The Ni nanoclusters in SnO<SUB>2</SUB>:F@Ni<SUB>3</SUB>Sn<SUB>2</SUB>/Ni-nc perform dual functions: they not only improve the conductivity as the contacting media, but also increase the initial columbic efficiency by the decomposition of Li<SUB>2</SUB>O—an electrochemically irreversible material. An outstanding reversible capacity of 600.69 mA h g<SUP>−1</SUP> and a coulombic efficiency of 99.23% for SnO<SUB>2</SUB>:F@Ni<SUB>3</SUB>Sn<SUB>2</SUB>/Ni-nc were observed at the 350<SUP>th</SUP> cycle under 200 mA g<SUP>−1</SUP> in the our experimental range.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Employment of SnO<SUB>2</SUB>:F/Ni<SUB>3</SUB>Sn<SUB>2</SUB>/Ni nanoclusters composite as anode material for LIBs. </LI> <LI> Electroless plating and annealing were used for preparation of SnO<SUB>2</SUB>:F/Ni<SUB>3</SUB>Sn<SUB>2</SUB>/Ni-nc. </LI> <LI> Electrochemical stability was attributed to the Ni<SUB>3</SUB>Sn<SUB>2</SUB> intermetallic structure. </LI> <LI> Ni nanoclusters enhance coulombic efficiency and improve conductivity as well. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The Ni<SUB>3</SUB>Sn<SUB>2</SUB> coated SnO<SUB>2</SUB>:F with Ni nanoclusters (SnO<SUB>2</SUB>:F@Ni<SUB>3</SUB>Sn<SUB>2</SUB>/Ni-nc) was successfully prepared by sequence process, such as simple electroless plating and annealing. The novel SnO<SUB>2</SUB>:F@Ni<SUB>3</SUB>Sn<SUB>2</SUB>/Ni-nc exhibited more excellent electrochemical performances. The excellent electrochemical performance of SnO<SUB>2</SUB>:F@Ni<SUB>3</SUB>Sn<SUB>2</SUB>/Ni-nc can be attributed to a synergy effect of stability of Ni-Sn intermetallic structure and the presence of Ni nanoclusters.</P> <P>[DISPLAY OMISSION]</P>