• Title/Summary/Keyword: Solid state reaction

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Nano-particles of Mechanochemical Synthesis

  • Urakaev, Farit Kh.
    • Journal of the Speleological Society of Korea
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    • no.71
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    • pp.5-11
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    • 2006
  • A theoretical investigation of the solid phase mechanochemical synthesis of nano sized target product on the basis of dilution of the initial powdered reagent mixture by another product of an exchange reaction is presented. On the basis of the proposed 3 mode particle size distribution in mechanically activated mixture, optimal molar ratios of the components in mixture are calculated, providing the occurrence of impact friction contacts of reagent particles and excluding aggregation of the nanosized particles of the target reaction product. Derivation of kinetic equations for mechanochemical synthesis of nanoscale particles by the final product dilution method in the systems of exchange reactions is submitted. On the basis of obtained equations the necessary times of mechanical activation for complete course of mechanochemical reactions are designed. Kinetics of solid phase mechanosynthesis of nano TlCl by dilution of initial (2NaCl+$Tl_2SO_4$) mixture with the exchange reaction product (diluent,$zNa_2SO_4$, z=z*=11.25) was studied experimentally. Some peculiar features of the reaction mechanism were found. Parameters of the kinetic curve of nano TlCl obtained experimentally were compared with those for the model reaction KBr+TlCl+zKCl=(z+1) KCl+TlBr (z=z1*=13.5), and for the first time the value of mass transfer coefficient in a mechanochemical reactor with mobile milling balls was evaluated. Dynamics of the size change was followed for nanoparticle reaction product as a function of mechanical activation time.

Theory of Nanoparticles Mechanosynthesis

  • Urakaev, Farit Kh.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.07a
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    • pp.405-406
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    • 2005
  • A theoretical investigation of the solid-phase mechanochemical synthesis of nano-sized target product on the basis of dilution of the initial powdered reagent mixture by another product of an exchange reaction is presented. On the basis of the proposed 3-mode particle size distribution in mechanically activated mixture, optimal molar ratios of the components in mixture are calculated, providing the occurrence of impact-friction contacts of reagent particles and excluding aggregation of the nanosized particles of the target reaction product. Derivation of kinetic equations for mechanochemical synthesis of nanoscale particles by the final product dilution method in the systems of exchange reactions is submitted. On the basis of obtained equations the necessary times of mechanical activation for complete course of mechanochemical reactions are designed. Kinetics of solid phase mechanosynthesis of nano-TlCl by dilution of initial (2NaCl + $Tl_2SO_4$) mixture with the exchange reaction product (diluent, $zNa_2SO_4$, $z=z^*=11.25$) was studied experimentally. Some peculiar features of the reaction mechanism were found. Parameters of the kinetic curve of nano-TlCl obtained experimentally were compared with those for the model reaction KBr + TlCl + zKCl = (z + 1) KCl + TlBr ($z=z_l^*=13.5$), and for the first time the value of mass transfer coefficient in a mechanochemical reactor with mobile milling balls was evaluated. Dynamics of the size change was followed for nanoparticle reaction product as a function of mechanical activation time.

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Superconducting Properties and Phase Formation of MgB2 Superconductors Prepared by the Solid State Reaction Method using MgB4 and Mg Powder (MgB4와 Mg 분말을 원료로 사용하여 고상반응법으로 제조한 MgB2 초전도체의 상생성과 초전도 특성)

  • Jeong, Hyeondeok;Kim, Chan-Joong;Jun, Byung-Hyuk;Kim, Seolhyang;Park, Hai-Woong
    • Journal of Powder Materials
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    • v.22 no.5
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    • pp.344-349
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    • 2015
  • $MgB_2$ bulk superconductors are synthesized by the solid state reaction of ($MgB_4$+xMg) precursors with excessive Mg compositions (x=1.0, 1.4, 2.0 and 2.4). The $MgB_4$ precursors are synthesized using (Mg+B) powders. The secondary phases ($MgB_4$ and MgO) present in the synthesized $MgB_4$ are removed by $HNO_3$ leaching. It is found that the formation reaction of $MgB_2$ is accelerated when Mg excessive compositions are used. The magnetization curves of $Mg_1+_xB_2$ samples show that the transition from the normal state to the superconducting state of the Mg excessive samples with x=0.5 and x=0.7 are sharper than that of $MgB_2$. The highest $J_c-B$ curve at 5 K and 20 K is achieved for x=0.5. Further addition of Mg decreases the $J_c$ owing to the formation of more pores in the $MgB_2$ matrix and smaller volume fraction of $MgB_2$.

Solid-State 51V NMR and Infrared Spectroscopic Study of Vanadium Oxide Supported on $ZrO_2-WO_3$

  • 손종락;이만호;도임자;배영일
    • Bulletin of the Korean Chemical Society
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    • v.19 no.8
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    • pp.856-862
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    • 1998
  • Vanadium oxide catalyst supported on ZrO2-WO3 was prepared by adding the Zr(OH)4 powder into a mixed aqueous solution of ammonium metavanadate and ammonium metatungstate followed by drying and calcining at high temperatures. The characterization of prepared catalysts was performed using solid-state 51V NMR and FTIR. In the case of calcination temperature at 773 K, for the samples containing low loading V2O5 below 18 wt % vanadium oxide was in a highly dispersed state, while for samples containing high loading V2O5 equal to or above 18 wt % vanadium oxide was well crystallized due to the V2O5 loading exceeding the formation of monolayer on the surface of ZrO2-WO3. The ZrV2O7 compound was formed through the reaction Of V2O5 and ZrO2 at 873 K and the compound decomposed into V2O5 and ZrO2 at 1073 K, which were confirmed by FTIR and 51V NMR.

Solid-state reaction kinetics for the formation of aluminium titanate ($AL_2TiO_5$) from amorphous $TiO_2$ and $\alpha-AL_2O_3$ (비정질 $TiO_2$$\alpha-AL_2O_3$부터 $AL_2TiO_5$를 합성하기 위한 고체상태 반응속도)

  • Ik Jin Kim;Oh Seong Kweon;Young Shin Ko;Constantin Zografou
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.7 no.2
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    • pp.259-270
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    • 1997
  • Reaction kinetics for the solid-state reaction of $\alpha-Al_2O_3$ with amorphous $TiO_2$ to produce $Al_2TiO_5$ (Tialite) was studied in the temperature range of $1200~1300^{\circ}C$. Rate of kinetic reaction were determined by using $TiO_2$-coated $Al_2O_3$ compact containing 50 mol% $TiO_2$ and heating the reactant mixtures in MgO at definite temperature for various times. Amount of products and unreacted reactants were determined by X-ray diffractometry. Data from the volume fraction and ratio of peak intensities of $\beta-Al_2TiO_5$ indicated that the reaction of $\alpha-Al_2O_3$ with $TiO_2$ to form pseudobrookite starts between 1280 and $1300^{\circ}C$. The activation energy for solid-state reaction was determined by using the Arrhenius equation ; The activation energy was 622.4 kJ/mol.

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Construction of Indole Library for Serotonin Related Drugs and Macrocyclization Using Selenium Chemistry in Solid-Phase Reaction.

  • Mun, Han-Seo;Jeong, Jin-Hyun
    • Proceedings of the PSK Conference
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    • 2003.04a
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    • pp.246.1-246.1
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    • 2003
  • Hetero chain compounds have high possibilities of being good medicinal candidate because of their well-known medicinal activity and relatively low subtitled carbon. By constructing the method of making this compound library, this research has the purpose to create a new medicinal candidate materials based on an easy medicinal search. The first step is to construct an Indole library in a compounding process with the design of a linker connecting a solid-state resin and a substrate. (omitted)

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Electrochemical properties of all solid state Li/LiPON/Sn-substituted LiMn2O4 thin film batteries

  • Kong, Woo-Yeon;Yim, Hae-Na;Yoon, Seok-Jin;Nahm, Sahn;Choi, Ji-Won
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.409-409
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    • 2011
  • All solid-state thin film lithium batteries have many applications in miniaturized devices because of lightweight, long-life, low self-discharge and high energy density. The research of cathode materials for thin film lithium batteries that provide high energy density at fast discharge rates is important to meet the demands for high-power applications. Among cathode materials, lithium manganese oxide materials as spinel-based compounds have been reported to possess specific advantages of high electrochemical potential, high abundant, low cost, and low toxicity. However, the lithium manganese oxide has problem of capacity fade which caused by dissolution of Mn ions during intercalation reaction and phase instability. For this problem, many studies on effect of various transition metals have been reported. In the preliminary study, the Sn-substituted LiMn2O4 thin films prepared by pulsed laser deposition have shown the improvement in discharge capacity and cycleability. In this study, the thin films of LiMn2O4 and LiSn0.0125Mn1.975O4 prepared by RF magnetron sputtering were studied with effect of deposition parameters on the phase, surface morphology and electrochemical property. And, all solid-state thin film batteries comprised of a lithium anode, lithium phosphorus oxy-nitride (LiPON) solid electrolyte and LiMn2O4-based cathode were fabricated, and the electrochemical property was investigated.

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Field-induced Resistive Switching in Ge25Se75 Based ReRAM

  • Kim, Jang-Han;Nam, Gi-Hyeon;Jeong, Hong-Bae
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.413-414
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    • 2012
  • Programmable Metallization Cell (PMC) memory, which utilizes electrochemical control of nanoscale quantities of metal in thin films of solid electrolyte, shows great promise as a future solid state memory. The technology utilizes the electrochemical formation and removal of metallic pathways in thin films of solid electrolyte. Key attributes are low voltage and current operation, excellent scalability, and a simple fabrication sequence. In this study, we investigated the nature of thin films formed by photo doping of Ag+ ions into chalcogenide materials for use in solid electrolyte of programmable metallization cell devices. We measured the I-V characteristics by field-effect of the device. The results imply that a Ag-rich phase separates owing to the reaction of Ag with free atoms from chalcogenide materials.

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A Study on the Rheological Properties of Branched Polypropylene/silicate Composites (분지형 폴리프로필렌/실리케이트 복합체의 유변학적 특성 연구)

  • Dahal, Prashanta;Yoon, Kyung Hwa;Kim, Youn Cheol
    • Applied Chemistry for Engineering
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    • v.22 no.6
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    • pp.679-684
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    • 2011
  • Branched polypropylenes (LCB-PP) with a long chain branch were prepared by the solid-state and molt-state reaction. Divinylbenzene (DVB), 1,4-benzenediol (RES), and furfuryl sulphide (FS) were used as branching agents of fabricate LCB-PP/silicate composites. Chemical structures, thermal properties, and rheological properties of the LCB-PP were determined by FT-IR, DSC, TGA, and dynamic rheometer (ARES). The chemical structure of the LCB-PP was confirmed by the existence of =C-H stretching peak of the branching agent at $3100cm^{-1}$. From DSC and TGA results, the melting reaction was more effective than the solid state reaction in the manufacture of LCB-PP, which was additionally certified by rheological properties. Based on rheological properties, FS was the best for branching efficiency of PP. Compared to PP, LCB-PPs indicated an increase of complex viscosity in the low frequency and shear thinning tendency, and G'-G" plot represented an increase in elasticity and the heterogeneousness in a melt state. Rheological properties of LCB-PP/silicate composites were observed with the silicate content. When 5 wt% silicate was added in LCB-PP, distinct changes in the shear thinning and the slope of G'-G" plots were observed.

Eutectic Ceramic Composites by Melt-Solidification

  • Goto, Takashi;Tu, Rong
    • Journal of the Korean Ceramic Society
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    • v.56 no.4
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    • pp.331-339
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    • 2019
  • While high-temperature ceramic composites consisting of carbides, borides, and nitrides, the so-called ultra-high-temperature ceramics (UHTCs), have been commonly produced through solid-state sintering, melt-solidification is an alternative method for their manufacture. As many UHTCs are binary or ternary eutectic systems, they can be melted and solidified at a relatively low temperature via a eutectic reaction. The microstructure of the eutectic composites is typically rod-like or lamellar, as determined by the volume fraction of the second phase. Directional solidification can help fabricate more sophisticated UHTCs with highly aligned textures. This review describes the fabrication of UHTCs through the eutectic reaction and explains their mechanical properties. The use of melt-solidification has been limited to small specimens; however, the recently developed laser technology can melt large-sized UHTCs, suggesting their potential for practical applications. An example of laser melt-solidification of a eutectic ceramic composite is demonstrated.