• Journal of the Korean Magnetic Resonance Society
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• v.9 no.2
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• pp.138-154
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• 2005

Vanadium-incorporated aluminophosphate molecular sieve $VO^{2+}-SAPO-5$ was studied by electron spin resonance (ESR) and electron spin echo modulation (ESEM) spectroscopies to determine the vanadium structure and interaction with various adsorbate molecules. It was found that the main species at low concentration of vanadium is a monomeric vanadium units in square pyramidal or distorted octahedral coordination, both in oxidation state (IV) for the calcined hydrated material and in oxidation state (V) for the calcined material. After calcinations in $O_2$ and exposure to moisture, only species A is observed with reduced intensities. It is suggested as a $VO(H_2O)_3^{2+}$ complex coordinated to two framework oxygen bonded aluminum. When calcined, hydrated $VO^{2+}-}SAPO-5$ is dehydrated at elevated temperature, a species loses its water ligands and transforms to $VO^{2+}$ ions coordinated to two framework oxygens (species B). Species B reduces its intensity, significantly after treatment with $O_2\;at\;600^{\circ}C$ for 5 h, thus suggesting oxidation of $V^{4+}\;to\;V^{5+}$. When dehydrated $VO^{2+}-SAPO-5$ contacts with $D_2O$ at room temperature, the EPR signal of species A is observed. Thus species assumed as a $VO^{2+}(O_f)_2(D_2O)_3$, by considering two framework oxygens. Adsorption of deuterated ethanol, propanol on dehydrated $VO^{2+}_{-}SAPO-5$ result in another new vanadium species E and F, respectively, which are identified as a $VO^{2+}-(CH_3CH_2OD)_3,\;VO^{2+}-(CH_3CH_2CH_2OD)_2$ complex. When deuterated benzene is adsorbed on dehydrated $VO^{2+}-SAPO-5$, another new vanadium species G, identified as a $VO^{2+}-(C_6D_6)$ is observed. Possible coordination geometries of these various complexes are discussed.

• Journal of the Korean Chemical Society
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• v.32 no.3
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• pp.179-185
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• 1988

The reaction of VO_2\;^+$ with benzyl alcohol in perchloric acid and aqueous dimethylformamide leads to the formation of $VO^{2+}$ and benzaldehyde. The products, $VO^{2+}$ and benzaldehyde, are identified by infrared spectroscopy and gas chromatography. Kinetic studies on the reaction of VO_2\;^+$ with benzyl alcohol have been carried out using visible spectroscopy. The empirical rate equation can be expressed as $-d[VO_2\;^+]/dt=2\{\\{k_O+k_H[HClO_4]\}\[VO_2\;^+][C_6H_5CH_2OH]$ The rate determining step for the reaction is the process for the formation of $VO^{2+}$ and $C_6H_5CHOH$. The activation parameters are ${\Delta}H^{\neq}=13.32{\pm}1.73\;kcalmol^{-1}$ and ${\Delta}S^{\neq}=-31.02{\pm}0.09\;calmol^{-1}K^{-1}$ for the oxidation of benzyl alcohol in aqueous dimethylformamide.

• Applied Chemistry for Engineering
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• v.24 no.6
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• pp.611-615
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• 2013

Vanadium oxide ($VO_2$) and tungsten-doped vanadium oxide (W-$VO_2$) powder, well known as thermochromic materials, were prepared from vanadium pentoxide ($V_2O_5$) and oxalic acid dihydrate by hydrothermal and calcination process. The crystal structure and thermochromic property of samples were analyzed using FE-SEM, XRD, XPS, DSC, and UV-Vis-NIR spectroscopy. With increasing the doping amount of W, the phase transition temperature of W-$VO_2$ sample decreased from $70^{\circ}C$ to $42^{\circ}C$. When heating W-$VO_2$ sample above the phase transition temperature, the UV-Vis-NIR spectrum was not changed in the visible range and shifted towards a low transparency in the full name (NIR) region.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.74-80
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• 2017

This study focuses on the effects of doping $Zn_2BiVO_6$ and $Co_3O_4$ on the sintering and electrical properties of ZnO; where, ZZ consists of 0.5 mol% $Zn_2BiVO_6$ in ZnO, and ZZCo consists of 1/3 mol% $Co_3O_4$ in ZZ. As ZnO was sintered at about $800^{\circ}C$, the liquid phases, which are composed of $Zn_2BiVO_6$ and $Zn_2BiVO_6$-rich phases, were found to be segregated at the grain boundaries of sintered ZZ and ZZCo, respectively, which demonstrates that $V_o^{\cdot}$(0.33~0.36 eV) are formed as dominant defects according to the analysis of admittance spectroscopy. As $Co_3O_4$ is doped to ZZ, the resistivity of ZnO decreases to ~38%, while donor density ($N_d$), interface state density ($N_t$), and barrier height (${\Phi}_b$) increase twice higher than those of ZZ, according to C-V characteristics. This result harbingers that ZZCo and its derivative compositions will open the gate for ZnO to be applied as more progressive varistors in the future, as well as the advantageous opportunity of manufacturing ZnO chip varistors at lower sintering temperatures below $900^{\circ}C$.

• Journal of the Korean Chemical Society
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• v.56 no.1
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• pp.62-67
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• 2012

A series of homo binuclear complexs of the type $[M_2(L/L^')(NO_3)n].mH_2O$, [where $M=U{O_2}^{2+},\;Th^{4+},\;ZrO^{2+}$] and $[(VO)_2(L/L^')(SO_4)_2]{\cdot}2H_2O$, L=1,5,6,9,12,15,16,20 octaaza-7,813,14-tetraphenyl-2,4,17,19-tetramethyl-1,4,6,8,12,14,16,19-docosaoctene (OTTDO) or L'=10:11;21:22-dibenzo-1,5,6,9,12,15,16,20-octaaza-7,813,14-tetraphenyl-2,4,17,19-tetramethyl-1,4,6,8,12,14,16,19-docosaoctene (DOTTOT), n=4 for $U{O_2}^{2+}$, $ZrO^{2+}$ n=8 for $Th^{4+}$ m=1,2,3 respectively, have been synthesized in template method from ethylenediamine/orthophenylene diamine, benzil monohydrazone and acetyl acetone and characterized on the basis of elemental analysis, thermal analysis, molar conductivity, magnetic moment, electronic, infrared, $^1H$-NMR studies. The results indicate that the VO(IV) ion is penta co-ordinated yielding paramagnetic complexes; $UO_2(VI)$, ZrO(IV) ions are hexa co-ordinated where as Th(IV) ion is octa co-ordinated yielding diamagnetic complexes of above composition. The fungi toxicity of the ZrO(IV) and VO(IV) complexes against some fungal pathogen has been studied.

• The Korean Journal of Ceramics
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• v.2 no.3
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• pp.131-136
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• 1996

The electrical conductivity of polycrystalline TiO2 samples was measured over the temperature range 1000°-1400℃ and from 0.21 to 10-16 atm of oxygen. Based on the excellent fit observed between the theoretically derived relatin σ3=(Aσ+B)Po2-1/2+D'σ2 and the experimental conductivity data, the nonstoichimetric defect structure of TiO2 was rationalized in terms of a defect model involving quasi-free electrons and both singly and doubly ionized oxygen vacancies. The standard enthalpy of formation for the following defect reactions in TiO2. (a) OO={{{{ { 1} over {2 } }}O2(g)+VO+e'; Δ{{{{ { H}`_{o } ^{a } }}=5.15(eV) (b) OO={{{{ { 1} over {2 } }}O2(g)+VO+2e'; Δ{{{{ { H}`_{0 } ^{ a} }}=6.30(eV) (c) VO=VO+e'; Δ{{{{ { H}`_{0 } ^{a } }}=1.15(eV) were determined from the temperature dependence of A and B obtained from the above relation and from the experimental expression between the electron mobility and temperature. The electrical conductivity of TiO2 in air below approximately 950℃ appears, on the basis of this investigation, to be impurity controlled due to the presence of aluminum rather than intrinsic conduction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.136-140
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• 1992

The purpose of this research is to develop the lithium secondary battery. This paper describes the preparation, electrochemical properties of nontstoichiometric(NS)-$V_6O_{13}$ and characteristics of Li/$V_6O_{13}$ secondary battery. NS-$V_6O_{13}$ was prepared by thermal decomposition of $NH_4VO_3$ under Ar stream of 140ml/min~180ml/min flow rate. And then, this NS-$V_6O_{13}$ was used for cathode active material. Cathode sheet was prepared by compressing the composite of NS-$V_6O_{13}$, acetylene black(A.B) and teflon emulsion (T.E). Characteristics of the test cell are summarised as follows. Oxidation capacity of NS-$V_6O_{13}$ was about 20% less than its reduction capacity. A part of NS-$V_6O_{13}$ cathode active material showed irreversible reaction in early charge-discharge cycle. This phenomena seems to be caused by irreversible incoporation/discoporation of lithium cation to/from NS-$V_6O_{13}$ host. Discharge characteristics curve of Li/$V_6O_{13}$ cell showed 4 potential plateaus. Charge-discharge capacity was declined in the beginning of cycling and slowly increased in company with increasing of coulombic efficiency. Energy density per weight of $V_6O_{13}$ cathode material was as high as 522Wh/kg~765Wh/kg.

• Korean Journal of Materials Research
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• v.10 no.12
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• pp.838-844
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• 2000

For the fabrication of titanium diboride($TiB_2$)- based cermet as applications of cutting tools and wear resistant materials, a binder metal with good mechanical properties and sinterability is essential. In this study, SUS316L was chosen for the binder metal to obtain a new $TiB_2$ cermet with superior hardness and toughness.$TiB_2$-SUS316L cermets were densified to relative density of more than 99% by pressureless sintering at temperature above $1650^{\circ}C$ The flexural strength was up to 1290MPa at 10vo1%SUS316L cermet in spite of the formation of $Fe_2$B phase during the sintering. The fracture toughness was obtained up to $6MPam^{1/2}$ with Victors hardness over 18Gpa. These hardness and fracture toughness combinations are better than those of conventional cermet. The high temperature strength remarkably decreased by the plastic deformations of SUS316L binder phase at nearby $800^{\circ}C$ .

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.537-543
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• 2013

In this study, the push-pull structure polymer for organic photo voHaics (OPVs) was synthesized and characterized. The poly{4,8-didodecyloxybenzo[1,2-b;3,4-b]dithiophene-alt-5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]-thiadiazole} (PDBDT-TBTD) was synthesized by Stille coupling reaction using the benzothiadiazole (BTD) derivative as an electron acceptor and benzodithiophene (BDT) derivative as an electron donor. The structure of monomers and polymers was identified by $^1H-NMR$ and GC-MS. The optical, physical and electrochemical properties of the conjugated polymer were identified by GPC, TGA, UV-Vis and cyclic voltammetry. The number average molecular weight ($M_n$) and initial decomposition temperature (5% weight loss temperature, $T_d$) of PDBDT-TBTD were 6200 and $323^{\circ}C$, respectively. The absorption maxima on the film was about 599 nm and the optical band gap was about 1.70 eV. The structure of device was ITO/PEDOT : PSS/PDBDT-TBTD : $PC_{71}BM/BaF_2/Ba/Al$. PDBDT-TBTD and $PC_{71}BM$ were blended with the weight ratio of 1:2 which were then used as an optical active layer. The power conversion efficiency (PCE) of fabricated device was measured by solar simulator and the best PCE was 2.1%.

• Natural Product Sciences
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• v.20 no.4
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• pp.274-280
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• 2014

Six compounds were isolated from the n-BuOH fraction of the aerial parts of Aruncus dioicus var. kamtschaticus including: sambunigrin (1), prunasin (2), aruncide A (3), aruncide C (4), 1-O-caffeoyl-${\beta}$-D-glucopyranose (5), and caffeic acid (6). Their structures were confirmed by comparing the spectral data with those reported in the literature. The isolated compounds (1 - 6) were then examined for their cytotoxic effects towards MCF-7, HL-60, and HeLa cancer cell lines, as well as their DPPH radical scavenging activity. The results indicated that compound 4 possessed the strongest inhibitory effect toward HeLa cell line with $IC_{50}$ value of $5.38{\pm}0.92{\mu}M$. Compound 3 possessed selective cytotoxic activity on HL-60 cells with $IC_{50}$ value of $6.27{\pm}0.17{\mu}M$, compound 5 was found as the best in inhibiting proliferation with $IC_{50}$ value of $2.25{\pm}0.09{\mu}M$, and the other compounds showed significant inhibition with $IC_{50}$ values ranging from 6.10 to $11.27{\mu}M$. Compound 5 also displayed the strongest cytotoxic effect toward MCF-7 cell line ($IC_{50}$ $4.32{\pm}0.15{\mu}M$). Both 5 and 6 demonstrated strong radical scavenging activity ($IC_{50}$ $6.87{\pm}0.03$ and $4.33{\pm}0.22{\mu}M$, respectively). Compounds 1 and 5 were isolated for the first time from this plant.