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Atoms in solids

Xem 1-20 trên 44 kết quả Atoms in solids
  • In 1 the Zn 2+ cation is tetracoordinated with 2 nitrogen atoms from 2 imidazoles and 2 oxygen atoms from the 2 carboxyl groups in 5-chlorhydroxybenzoate. In 2 the coordination polyhedrons of Cu 2+ center can be described as distorted square pyramidal geometry sharing common edges, with an oxygen atom on the top of the pyramid. The hydrogen bonds and π − π interactions between the 2 ligands contribute to the presence of the infinite one-dimensional chain in the structure.

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  • The charge and size of molecules chemically attached to nanoparticles (NPs) play an important role in their interaction behavior in suspensions. Gold nanoparticles (AuNPs) were modified systematically with peptides and the modification was verified with surface-enhanced Raman scattering (SERS). The behavior of the modified AuNPs in suspension and at the liquid–solid interface was monitored using small angle X-ray scattering (SAXS), UV/Vis spectroscopy and dynamic light scattering (DLS) in suspension, and atomic force microscopy (AFM) at the solid– liquid interface.

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  • The synthesis and characterization of ethylenediaminetetraacetic acid immobilized activated carbon cloth was performed in the present work. It was used for preconcentration-separation of lead(II), cobalt(II), and nickel(II) at trace levels as an adsorbent. Factors including pH, concentration and volume of eluent, sample and eluent flow rates, sample volume, and effect of coexisting ions on the solid phase extraction of analytes were examined. The preconcentration factor was 50.

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  • The metal complexes are retained on resin at pH 6.0 and eluted with 1.0 mol L −1 HCl in acetone in both methods. After the optimum conditions were determined, the methods were applied to seawater, stream water, rice, lentil, tea, tobacco, bulgur, chickpea, wheat, red pepper, black pepper, peppermint, and dried eggplant samples in order to determine the levels of copper and cadmium.

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  • A new chromium(III) ion-imprinted polymer (IIP) was prepared from a Cr(III)-nicotinate complex (template), acrylamide (functional monomer), and ethylene glycol dimethacrylate (cross-linking agent) using 2,2’-azobisisobutyronitrile as the radical initiator. IIP was characterised and used as a selective sorbent for the solid-phase extraction of Cr(III) ions. The conditions for dynamic separation of Cr(III) on IIP were optimised.

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  • A novel preconcentration method for Pb and Zn ions using a column packed with Schiff base modified silica gel is described. The method was based on the sorption of analytes on N,N’-bis(4-methoxysalicylidene)-1,3-propanediamine modified silica gel and elution with HNO3 prior to flame atomic absorption analysis. The parameters pH, flow rate, sample volume, eluent volume, and concentration were optimized using a central composite design.

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  • A new method based on the combination of carrier element-free coprecipitation and flame atomic absorption spectrometric determination has been investigated for simultaneous separation and preconcentration of Pb(II) and Cu(II) ions in some environmental solid and liquid samples. The 2-{3-(4-methylbenzyl)-4-[2-(1H-indol-3-yl)ethyl]-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N’-(phenylmethylene) acetohydrazide (MITA) was utilized as an organic coprecipitating agent without using a carrier element for coprecipitation of the analyte ions.

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  • Intramolecular reorganization energy (RE) of molecules derived from the diketopyrrolopyrrole (DPP) unit has been studied using B3LYP/6-31G(d,p) theory. It was found that the replacement of the oxygen atoms with sulfur in the DPP unit led to a smaller RE for both the hole and electron transfer processes. One disadvantage of the sulfur replacement is the twist of the conjugated backbone, which might impair the π − π interactions in the solid state. The RE calculated from the adiabatic potential energy surfaces and that derived from the normal mode analysis agreed well for both systems.

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  • A new sensitive and accurate solid-phase extraction method for preconcentration of trace amounts of cadmium and lead in various environmental samples prior to flame atomic absorption spectrometry determination has been developed. The proposed method is based on the utilization of multiwalled carbon nanotubes in combination with 5-benzyl-4-[-chlororbenzylidene amine]-4H-1,2,4-triazole-3-thiol (BCBATT) as a solid-phase sorbent with the aid of ultrasonication. The effect of the preconcentration parameters was investigated.

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  • The partial substitution of potassium atoms by strontium atoms in initial matrix K3Fe2(PO4)3 with formation of complex phosphates K3−2xSrx Fe2(PO4)3 (x = 0.75, 1.0, and 1.25) was determined using a solid-state reaction method. According to powder X-ray diffraction (XRD) data, the prepared phosphates with x = 1.0 and 1.25 crystallize in a cubic system (space group P213) and belong to langbeinite family compounds, while for the sample with x = 0.75 a mixture of langbeinite-type phase and a minor amount of K3Fe2(PO4)3 was obtained.

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  • 2-Aminothiazole derivatives bear three nucleophilic centers, i.e. endocyclic N, exocyclic NH2 , and S atom in the ring system. In addition to these centers there are π -electrons in the ring system which can also expectedly be involved in some sort of coordination. To the best of our knowledge the solid state coordination chemistry of such ligands has not been fully presented in the literature.

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  • This study is the development of a new solid phase extraction method based on using magnetic multiwalled carbon nanotubes impregnated with 1-(2-pyridylazo)2-naphthol (PAN) for separation, preconcentration, and flame atomic absorption spectrometric determination of Pb(II) and Cu(II). Optimization of the method was done by investigating pH effect, amount of magnetic multiwalled carbon nanotubes impregnated with PAN, eluent type and volume, matrix effects, and volume of the sample. The optimum adsorbent amount was found to be 75 mg and the optimum pH value was found as 5.5.

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  • The simulation finds a large number of vacancy-simplexes, which plays a role of diffusion vehicle for cobalt atom and varies with relaxation degree. A new diffusion mechanism for tracer diffusivity in cobalt amorphous solid is supposed as follows: The elemental atomic movement includes a jump of neighbouring atoms into the vacancy-simplexes and then collective displacement of a large number of atoms.

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  • In this work, O3-NaFe0.5Co0.5O2 layered cathode material was synthesized by solid state reaction at 900 oC followed by a quenching step at 600 oC in argon atmosphere. X-rays diffraction patterns indicated that O3-layered structure could be maintained after a quenching process at 600 oC. The chemical composition and morphology of the synthesized material were analyzed by Atomic Absorption Spectroscopy (AAS) and Scanning Electron Microscopy (SEM).

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  • This paper investigated the Sr doping effect on the microstructure, chemical stability, and conductivity of Ba1 xSrxCe0.65Zr0.25Nd0.1O3 d (0 6 x 6 0.2) electrolyte prepared by sol-gel method. The lattice constants and unit cell volumes were found to decrease as Sr atomic percentage increased in accordance with the Vegard law, confirming the formation of solid solution. Incor- poration of Sr into the composition resulted in smaller grains besides suppressing the formation of secondary phases of SrCeO3. Among the synthesized samples BaCe0.65Zr0.25Nd0.

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  • This work reports the melting of boride precipitates along the grain boundary of a supposedly solid state welding of a polycrystalline superalloy, and discusses its attendant effect on the hot ductility behaviour of the alloy. Nickel-based superalloy used for this study was previously processed by hot extrusion of argon atomized powered followed by forging. The alloy was solution heat treated at 1120°C, aged at 760°C and subsequently air cooled to room temperature.

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  • The temperature is increased from 50 K to 5500 K in order to observe the change of the structure during heating process. Various thermodynamic quantities related to the change of structure are calculated such as the radial distribution functions the Lindemann criterion, the occurrence/growth of liquidlike atoms, the formation of clusters, and the ring statistics. The melting point is defined. The phase transition from solid to liquid states exhibits first order behavior.

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  • (bq) part 1 book "fundamentals of materials science and engineering" has contents: introduction, atomic structure and interatomic bonding, structures of metals and ceramics, imperfections in solids, polymer structures, mechanical properties, deformation and strengthening mechanisms,...and other contents.

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  • (bq) part 1 book "instant notes - inorganic chemistry" has contents: atomic structure, introduction to inorganic substances, structure and bonding in molecules, structure and bonding in solids, chemistry in solution.

    pdf157p bautroibinhyen20 06-03-2017 35 9   Download

  • (bq) part 2 book "general chemistry - the essential concepts" has contents: energy relationships in chemical reactions; the electronic structure of atoms; the periodic table; introduction to organic chemistry; intermolecular forces and liquids and solids; intermolecular forces and liquids and solids; chemical kinetics; chemical kinetics,... and other contents.

    pdf655p bautroibinhyen20 06-03-2017 63 10   Download

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