• Title/Summary/Keyword: Transition metals

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A Study on the Properties of Transition Metal Nitride Coating Materials for the Recovery of Tungsten and Rare Metals (텅스텐 및 희유금속 회수를 위한 초경합금 전이금속질화물 코팅소재 특성연구)

  • Kim, Jiwoo;Kim, Myungjae;Kim, Hyokyeong;Park, Sohyun;Seo, Minkyeong;Kim, Jiwoong
    • Resources Recycling
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    • v.31 no.1
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    • pp.46-55
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    • 2022
  • The recycling of coated cemented carbide scraps is becoming increasingly significant for the recovery of rare metals. However, coatings consisting of Group IV and V transition metal nitrides are one of the challenging factors in obtaining high-purity materials. We investigated the structural, elastic, and mechanical properties of Group IV and V transition-metal nitrides (TiN, VN, ZrN, NbN, HfN, and TaN) using first-principle calculations. Convergence tests were performed to obtain reliable calculated results. The equilibrium structures of the nitrides were in good agreement with those of a previous study, indicating the reliability of the data. Group IV transition metal nitrides show a higher covalent bonding nature. Thus, they exhibit a higher degree of brittleness than that of Group V transition metal nitrides. In contrast, Group V transition metal nitrides show weaker resistance to shear loading and more ductile behavior than Group IV transition metal nitrides because of the metallic bonds characterized by valence electron concentration. The results of the crystal orbital Hamilton population analysis showed good agreement with the shear resistance tendencies of all transition metal nitrides.

Electrical Behaviour of Some Phthalimide Derivatives and Their Complexes with Transition Metals

  • Mohamed Gamal Abd Ei Wahed;Kamel Ei Manakhly;Hamdy Hammad;Atiat Barakat
    • Bulletin of the Korean Chemical Society
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    • v.17 no.3
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    • pp.285-288
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    • 1996
  • The electrical conductivity of some phthalimide derivatives and their complexes with Co(II), Ni(II), Cu(II), or Zn(II) has been measured in the temperature range 290-435 K. Both the structure of phthalimide molecule and its complexes played an effective role in the conduction process. Conductometric titration and IR spectra were used to characterize the structure of studied samples.

Development and Application of Group IV Transition Metal Oxide Precursors

  • Kim, Da Hye;Park, Bo Keun;Jeone, Dong Ju;Kim, Chang Gyoun;Son, Seung Uk;Chung, Taek-Mo
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.303.2-303.2
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    • 2014
  • The oxides of group IV transition metals such as titanium, zirconium, hafnium have many important current and future application, including protective coatings, sensors and dielectric layers in thin film electroluminescent (TFEL) devices. Recently, group IV transition metal oxide films have been intensively investigated as replacements for SiO2. Due to high permittivities (k~14-25) compared with SiO2 (k~3.9), large band-gaps, large band offsets and high thermodynamic stability on silicon. Herein, we report the synthesis of new group IV transition metal complexes as useful precursors to deposit their oxide thin films using chemical vapor deposition technique. The complexes were characterized by FT-IR, 1H NMR, 13C NMR and thermogravimetric analysis (TGA). Newly synthesised compounds show high volatility and thermal stability, so we are trying to deposit metal oxide thin films using the complexes by Atomic Layer Deposition (ALD).

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Theoretical Investigation of Triple Bonding between Transition Metal and Main Group Elements in (η5-C5H5)(CO)2M≡ER (M = Cr, Mo, W; E = Si, Ge, Sn, Pb; R = Terphenyl Groups)

  • Takagi, Nozomi;Yamazaki, Kentaro;Nagase, Shigeru
    • Bulletin of the Korean Chemical Society
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    • v.24 no.6
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    • pp.832-836
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    • 2003
  • To extend the knowledge of triple bonding between group 6 transition metal and heavier group 14 elements, the structural and bonding aspects of ($η^5-C_5H_5$)$(CO)_2$M≡ER (M = Cr, Mo, W; E = Si, Ge, Sn, Pb) are investigated by hybrid density functional calculations at the B3PW91 level. Substituent effects are also investigated with R = H, Me, $SiH_3$, Ph, $C_6H_3-2,6-Ph_2$, $C_6H_3-2,6-(C_6H_2-2,4,6-Me_3)_2$, and $C_6H_3-2,6-(C_6H_2-2,4,6- iPr_3)_2$.

Rates and Mechanism of Adsorption of Transition Metal Ions on Polystyrene Resins Supported Diethylenetriamine (디에틸렌트리아민을 지지시킨 폴리스틸렌수지에 대한 전이금속이온의 흡착속도와 메카니즘)

  • Kim, Sun-Deuk;Shin, Yun-Yeol;Kim, Chang-Su
    • Analytical Science and Technology
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    • v.12 no.6
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    • pp.465-471
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    • 1999
  • Chloromethylated polystyrene resins supported diethylenetriamine of linear and claw types have been prepared by the reaction of diethylenetriamine with chloromethylated polystyrene. The kinetics of adsorption of transition metal ions on polystyrene resins were measured by the limited-bath technique. This paper reports the results of the diffusion coefficients, entropies of activation, and free energies of activation. The ratedetermining step of the adsorption of transition metals on the resins is a process of diffusion through the particles.

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Transition Metal-Catalyzed and -Promoted Reactions via Carbene and Vinylidene Complexes Generated from Alkynes

  • Ohe, Kouichi
    • Bulletin of the Korean Chemical Society
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    • v.28 no.12
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    • pp.2153-2161
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    • 2007
  • The transition metal-induced in situ generation of carbene complexes from alkynes having a carbonyl or imino group as a nucleophilic functionality has been investigated. These reactive carbenoid species are generated with high atom efficiency through a 6-endo-dig cyclization mode based on the electrocyclization of vinylidene complexes or a 5-exo-dig cyclization mode in π-alkyne complexes, and have been found to serve as versatile intermediates in catalytic carbene transfer reactions. Highlighted and reviewed in this account are the generation and preparation of pyranylidene, furylcarbene, pyrrolylcarbene, and vinylcarbene complexes and their application to [3,3]sigmatropic rearrangement of acylcyclopropylvinylidenes, catalytic cyclopropanation reactions, [2,3]sigmatropic rearrangement or condensation reactions via ylides, ring-opening and substitution reactions with heteroaromatic compounds, and catalytic isomerization of oligoynes.

Electronic and Magnetic Structures of Rare-earth Permanent Magnets (희토류 영구자석의 전자기적 구조)

  • 민병일;장영록
    • Journal of the Korean Magnetics Society
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    • v.1 no.1
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    • pp.6-11
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    • 1991
  • In order to investigate electronic and magnetic properties of permanent magnets, we have performed self-consistent electronic structure calculations on compounds of rare-earth and transition metals, such as $SmCo_{5},\;NdB_{6},\;NdFe_{5},\;NdFe_{4}B$. Employing the local density LMTO(linearized muffin tin orbital) band method, we have obtained the ground state parameters, such as band structures, density of states, Stoner parameters, and magnetic moments. We have also investigated interactions between d,f-electrons of Nd, Sm rare-earths and d-electrons of Fe, Co transition metals, and the s,p electrons of boron and explored effects of such interactions on the bonding mechanism and the electronic and magnetic structures in these rare-earth compounds.

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Electronic and magnetic structure calculations of $La_2MnFeO_6$ with double perovskite oxide (이중 페로브스카이트 구조 $La_2MnFeO_6$의 전자구조와 자기구조 계산)

  • 박기택
    • Journal of the Korean Magnetics Society
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    • v.10 no.3
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    • pp.139-142
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    • 2000
  • We present results based on FLAPW local spin density(LSD) calculations of double perovskite structure oxide L $a_2$MnFe $O_{6}$ . The total energy calculations with various spin structures show that this material has a stable ferromagnetic spin configuration. The ionic state of transition metals depend on the spin configuration $_Mn^{4+}$ and F $e^{2+}$ for ferromagnetic structure, M $n^{3+}$ and F $e^{3+}$ for ferrimagnetic structure). It is explained by super exchange interaction between transition metals. The calculated magnetic structure is well matched with recent experimental result.ult.t.

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Epitaxial Overlayers vs Alloy Formation at Aluminum-Transition Metal Interfaces

  • Smith, R.J.
    • Proceedings of the Korean Vacuum Society Conference
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    • 1999.07a
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    • pp.29-29
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    • 1999
  • The synthesis of layered structures on the nanometer scale has become essential for continued improvements in the operation of various electronic and magnetic devices. Abrupt metal-metal interfaces are desired for applications ranging from metallization in semiconductor devices to fabrication of magnetoresistive tunnel junctions for read heads on magnetic disk drives. In particular, characterizing the interface structure between various transition metals (TM) and aluminum is desirable. We have used the techniques of MeV ion backscattering and channeling (HEIS), x-ray photoemission (ZPS), x-ray photoelectron diffraction(XPD), low-energy ion scattering (LEIS), and low-energy electron diffraction(LEED), together with computer simulations using embedded atom potentials, to study solid-solid interface structure for thin films of Ni, Fe, Co, Pd, Ti, and Ag on Al(001), Al(110) and Al(111) surfaces. Considerations of lattice matching, surface energies, or compound formation energies alone do not adequately predict our result, We find that those metals with metallic radii smaller than Al(e.g. Ni, Fe, Co, Pd) tend to form alloys at the TM-Al interface, while those atoms with larger atomic radii(e.g. Ti, Ag) form epitaxial overlayers. Thus we are led to consider models in which the strain energy associated with alloy formation becomes a kinetic barrier to alloying. Furthermore, we observe the formation of metastable fcc Ti up to a critical thickness of 5 monolayers on Al(001) and Al(110). For Ag films we observe arbitrarily thick epitaxial growth exceeding 30 monolayers with some Al alloying at the interface, possible driven by interface strain relief. Typical examples of these interface structures will be discussed.

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