Synthesis and Characterization of Reduced Vanadates

최식영 안동대학교 기초과학연구소 1997 基礎科學 硏究論文集 Vol.8 No.1

New ternary vanadium oxides were synthesized by various methods and investigated their physical properties by measuring resistivity and magnetic susceptibility as a function of temperature. Reduced ternary vanadates, M1V2O3 (M=Sr, Ca), which have a Ruddlesden-Popper structure were synthesized by hydrogen reduction of M_(3)V_(2)O_(5) and reaction of corresponding oxides in the evacuated silica tubes. The temperature dependent resistivity and magnetic susceptibility data for the Sr_(3)V_(2)O_(7) compound show metallic and paramagnetic behavior, respectively. These results suggest that the reduced vanadate contains unpaired electrons.

몰리브덴(V)와 시트릭액시드계 착물합성과 그 성질

최식영,이재덕 安東大學 1989 安東大學 論文集 Vol.11 No.1

A new series of dioxo-di-μ-oxo-dimolybdate(v), ◁화학식 삽입▷(원문을 참조하세요), has been prepared by reaction of pyridinum oxoisothiooyantomolybdate(v) with citric acid derivatives containing amine carboxyl groups. The properties and possible molecular structure of these complexes were discussed by elemental analysis, spectroscopic studies and magnetic susceptibility measurements. The infrared spectra of these complexes all show two strong Mo=O2 stretching bands in the 900~980cm-1, MoO2Mo very prominent strectching bands at around 410~425 and 735~750cm^(-1) to symmetrical and asymmetrical O-bridge stretching, a coordinated coo^(-) asymmetrical band in the 1585~1640cm^(-1). Also, d-d transition of molybdenyl complexes corresponding to ^(2)B_(2)-^(2)B_(1) occured in the 24,800~28,000cm^(-1) region, charge transfer transition corresponding to ligand-to-molybdenum in the 32,500~33,800, 42,000 ~47,500cm^(-1) region. The complexes synthesized were yellow or orange and diamagnetic.

몰리브덴(V)와 1,2-Diaminopropane-N,N,N´,N´-tetraacetic acid계 착물 합성과 그 성질

최식영 安東大學 1988 安東大學 論文集 Vol.10 No.1

A new series of dioxo-di-μ-oxo-dimolybdate (V), ◁화학식 삽입▷(원문을 참조하세요), has been prepared by reaction of pyridinum oxoisothiocyanato mdolybdate (V) with 1, 2-Diaminopropane-N, N, N`, N`-tetracetate derivatives containing amine carboxyl groups. The properties and possible molecular structure of these complexes were discussed by elemental analysis, spectroscopic studies and magnetic susceptibility measurements. The infrared spectra of these complexes all show two strong Mo=Ot stretching modes in the 900~980cm^(-1), MoO_(2)Mo very prominent stretching bands at around 410~425 and 735~750cm^(-1) to symmetrical and asymmetrical O-bridge stretching, a coordinated coo-asymmetrical band in the 1585~1640cm^(-1). The complexes were yellow and diamagnetic.

몰리브덴 (V)와 니트리로아세트산계 착물 합성과 그 성질

최식영 安東大學 1987 安東大學 論文集 Vol.9 No.1

A new series of dioxo-di-μ-oxo-dimolybdate (V), ◁화확식 삽입▷(원문을 참조하세요), has been prepared by reaction of pyridinum oxoisothiocyantomolybdate (V) with nitrilotriacetic acid deivatives containing amine carboxyl groups. The properties and possible molecular structure of these complexes were discussed by elemental analysis, spectroscopic studies and magnetic susceptibility measurements. The infrared spectra of these complexes all show two strong Mo=Ot stretching modes in the 900~980cm^(-1), MoO2 Mo very prominent stretching bands at around 410~425 and 735~750cm^(-1) to symmetrical and antisymmetrical O-bridge stretching, a coordinated COO- antisym-metrical band in the 1585~1640cm^(-1). Also, d-d transition of molybdenyl complexes corresponding to ^(2)B_(2)→^(2)B_(1) occured in the 24,800~28,000cm-1 region, charge transfer transition corresponding to ligand-to-molybdenum in the 32,500~33, 800, 42,000~475,00cm^(-1) region. The complexes synthesized were yellow and diamagnetic.

BaV₂O_(6-x)N_(x)의 합성과 그 구조

최식영,한선미 安東大學 1996 安東大學 論文集 Vol.18 No.1

Mixed metal oxyntirides with the perovskite and related structrue have previously been reported for the several early transition metal. Most of the known phases are insulators e.g. ATaO_(2)N (A=Ca, Sr, Ba) ATiO_(2)N (A=La, Yb), A_(2)TaO_(3)N (A=Ca, Sr, Ba) and the pyrochlore Ln_(2)Ti_(2)O_(5)_(5)N (Ln=Y, Dy, Sm). Some compositions have been found to be semiconductors with mixed valence cations and a range of nitrogen contents. We have investigated the reaction of ammonia with the compounds BaV_(2)O_(6). Two types of ternary vanadium oxides were synthesized by sample solid state reaction methods and investigated their structure by measuring XRD (X-ray Diffractometer) and EDX (Energy Dispersive X-ray spectroscopy), ESCA (Electron Spectroscopy for Chemical Analysis). Ternary vanadium oxides of the type BaV_(2)O_(6) having tungsten bronze structure were prepared by sample solid state reaction methods. Attempts to preparing the reduced vana-date by employing N^(-3) into the O^(-2) site in the BaV_(2)O_(6) compounds were successful.

Electronic Structure of Superconductivity in Metallic Hydrogn

최식영 안동대학교 기초과학연구소 1992 基礎科學 硏究論文集 Vol.3 No.1

The crystal structure of solid H_(2)(P6_(3)/mmc) is calculated by employing the tight-binding method within the extended Hukel frame work. We examine how the calculated band electronic structures of solid H2 are correspond to this crystal structure and superconducting.

Surface analysis of rayon-based carbon nanofibers and activated carbon fibers

최식영,김연정,임우택,류상훈 한국분석과학회 2007 분석과학 Vol.20 No.4

Carbon nanofibers (CNFs) are non-microporous materials with a high surface area (100~200 m2/g) and high purity. Therefore, the material has a high potential for use as catalyst support. Activated carbonfibers (ACFs) are of increasing concern with regard to the levels of toxic air pollutants emitted from high-technology industry. Rayon-based CNFs and ACFs was subjected to thermal oxidation under a wide varietyof temperature and air conditions to modify the surface properties. Rayon-based CNFs and ACFs were preparedby using thermal chemistry. CNFs were synthesized at temperatures above 600oC in an air atmosphere andgrew with increased temperature and air conditions. After heating at 800oC for 72 hr, carbonized rayon withACFs had 2,662 m2/g (BET) of surface area and 1.41 cm3/g of pore volume. The resulting ACFs had a 99 %surface area in which pore size was 10 nm or less, and a 60 % surface area in which pore size was 2 nm or less.

BaV_(2)O_(6-x)Cl_(x)의 합성과 그 특성

Choi, Sik-Young,Bae, Sung-Hee 안동대학교 기초과학연구소 1996 基礎科學 硏究論文集 Vol.7 No.1

Ternary vanadium oxides of the type BaV_(2)O_(6) having tungsten bronze structure were prepared by solid state reaction methods. Attempts to prepare the reduced vanadate by employing Cl- into the O2- site on the BaV_(2)O_(6) compounds were successful. The BaV_(2)O_(6)-_(x)Cl_(x) has been synthesized by solid state reaction on flowing chlorine atmosphere, but the quantity of chlorine was small(x=0.24). The structure of start material and target material were analyzed by XRD(X-ray Diffractometer), and the quantity of these were analyzed by EDX(Energy Dispersive X-ray spectrometer). The resistivity of BaV_(2)O_(6) is 152㏁,㎝ at room temperature and that of BaV_(2)O_(6)-_(x)Cl_(x) is 1.01㏁,㎝.

Synthesis and Single-crystal Structure of Fully Dehydrated Fully Ca2+-exchanged Zeolite Y (FAU), |Ca35.5|[Si121Al71O384]-FAU

서성만,최식영,서정민,Ki Jin Jung,허남호,임우택 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.8

The single-crystal structure of |Ca35.5|[Si121Al71O384]-FAU, Ca35.5Si121Al71O384 per unit cell, a = 24.9020(10) Å, dehydrated at 673 K and 2 × 10-6 Torr, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd 3m at 294 K. The large single crystals of zeolite Y (Si/Al = 1.70) were synthesized up to diameters of 200 μm and Ca2+-exchanged zeolite Y were prepared by ion exchange in a batch method of 0.05 M aqueous Ca(NO3)2 for 4 hrs at 294 K. The structure was refined using all intensities to the final error indices (using only the 971 reflections for which Fo > 4σ(Fo)) R1 = 0.038 (based on F) and R2 = 0.172 (based on F2). About 35.5 Ca2+ ions per unit cell are found at an unusually large number of crystallographically distinct positions, four. Nearly filling site I (at the centers of the double 6-rings), 14.5 octahedrally coordinated Ca2+ ions (Ca-O = 2.4194(24) Å and O-Ca-O = 87.00(8) and 93.00(8)o) are found per unit cell. One Ca2+ ions per unit cell is located at site II’ in the sodalite cavity and extends 0.50 Å into the sodalite cavity from its 3-oxygen plane (Ca-O = 2.324(13) Å and O-Ca-O = 115.5(10)o). The remaining twenty Ca2+ ions are found at two nonequivalent sites II (in the supercages) with occupancies of 10 and 10 ions, respectively. Each of these Ca2+ ions coordinates to three framework oxygens, either at 2.283(3) or 2.333(5) Å, respectively, and extends either 0.24 or 0.54 Å, respectively, into the supercage from the three oxygens to which it is bound. In this crystal, site I is the most populated; sites II’ and II are only sparsely occupied. Ca2+ appears to fit the octahedral site I best. No cations are found at sites III or III’, which are clearly less favorable for Ca2+ ions in dehydrated zeolite Y.

Synthesis and Crystal Structure of Ag4Br4 Nanoclusters in the Sodalite Cavities of Fully K+-Exchanged Zeolite A (LTA)

임우택,최식영,김복조,김창민,In Su Lee,김석한,허남호 대한화학회 2005 Bulletin of the Korean Chemical Society Vol.26 No.7

Ag4Br4 nanoclusters have been synthesized in about 75% of the sodalite cavities of fully K+-exchanged zeolite A (LTA). An additional KBr molecule is retained in each large cavity as part of a near square-planar K4Br3+ cation. A single crystal of Ag12-A, prepared by the dynamic ion-exchange of Na12-A with aqueous 0.05 M AgNO3 and washed with CH3OH, was placed in a stream of flowing 0.05 M KBr in CH3OH for two days. The crystal structure of the product (K9(K4Br)Si12Al12O48•0.75Ag4Br4, a = 12.186(1) Å) was determined at 294 K by single-crystal X-ray diffraction in the space group Pm m. It was refined with all measured reflections to the final error index R1 = 0.080 for the 99 reflections for which Fo > 4(Fo). The thirteen K+ ions per unit cell are found at three crystallographically distinct positions: eight K+ ions in the large cavity fill the six-ring site, three K+ ions fill the eight-rings, and two K+ ions are opposite four-rings in the large cavity. One bromide ion per unit cell lies opposite a four-ring in the large cavity, held there by two eight-ring and two six-ring K+ ions (K4Br3+). Three Ag+ and three Br ions per unit cell are found on 3-fold axes in the sodalite unit, indicating the formation of nano-sized Ag4Br4 clusters (interpenetrating tetrahedra; symmetry Td; diameter ca. 7.9 Å) in 75% of the sodalite units. Each cluster (Ag-Br = 2.93(3) Å) is held in place by the coordination of its four Ag+ ions to the zeolite framework (each Ag+ cation is 2.52(3) A from three six-ring oxygens) and by the coordination of its four Br ions to K+ ions through six-rings (Br-K = 3.00(4) A).