Advanced Materials Research Vols. 391-392

Abstract: A series of yttrium-doped lithium trivanadates LiV_3-yY_yO₈ (y=0, 0.01, 0.03, 0.05, 0.1 and 0.2) were synthesized by a solid-state reaction. X-ray diffraction (XRD) tests show that a proper amount of yttrium doping in LiV₃O₈ can modify its structure. Charge-discharge tests show that doped samples with a proper amount of yttrium display good cycling stability compared with undoped sample. The cyclic voltammetry (CV) tests indicate that the proper amount of yttrium doping in LiV₃O₈ can stabilize its original structure. Yttrium doping is a convenient and effective method for improving the electrochemical performances of LiV₃O₈.

Abstract: Dibenzyl sulfoxide [C6H5CH2)2SO, DBzSO] has been studied using density functional theory (DFT) methods with a particular emphasis on the theoretical 1H-NMR spectra of the methylene protons. The 1H-NMR chemical shifts of the methylene protons of DBzSO can be divided into two main types. Four possible structures of DBzSO were considered and the total energies were calculated for both a vacuum and in CDCl3 solvent. The change of length of S-O and S-C bonds in solvent was more obvious than that of the C(CH2)-C(C6H5) bonds; The S-O bond was longer and S-C bond was shorter in CDCl3. The essence effect of solvent on the properties of dibenzyl sulfoxide should come from the change of the geometrical structure. The change of shift Δx, [shift (solvent) - shift (vacuum)] showed that the effect of solvent on methylene protons of dibenzyl sulfoxide was apparent. Except of the other H of the rings, the two ortho H which were near S-O bond appeared more sensitivity on the solvent. The optimized structures in CDCl3 were in good agreement with the experimental data. The NMR peaks of methylene protons should be split more apparently in actual circumstance and the complex split of CH2 1HNMR peaks should be explained in some degree.

Abstract: Mixed-ligand Pt(II) complexes containing pyrazine (C₄N₂H₄, pz) and dibenzyl sulfoxide [C₆H₅CH₂)₂SO, DBzSO] ligands have been studied using density functional theory (DFT) methods with a particular emphasis on the theoretical ¹H-NMR spectra of the methylene protons. The DFT optimization calculations on Pt(DBzSO)Cl₂(pz) and {Pt(DBzSO)Cl₂}₂(pz) predicted the structure parameters, vibrational frequency and ¹H-NMR spectra. Different structures of DBzSO will affect the bond lengths and angles in the complexes, except for the pz ligands. The [shift_{(Pt(II)complex)}-shift_(sulfoxide)] values of trans-Pt(DBzSO)(pz)Cl₂ were smaller than those for cis-Pt(DBzSO)(pz)Cl₂ and the calculation results appear to be reasonable. The ¹H-NMR spectra of the methylene protons of cis- and trans-{Pt(DBzSO)Cl₂}₂(pz) indicate that these two structures have high symmetry.

Abstract: Electrochemical sensors for the sensitive detection of H₂O₂ are for the first time described using carbon nanotubes/poly(styrene-co-N-isopropylacrylamide) nanoparticles (CNT/pS-co-NIPAm) modified glassy carbon electrode (GCE). The fabricated GCE is characterized using scan electron microscopy (SEM) and cyclic voltammetry (CV). The CNT/pS-co-NIPAm modified electrode has larger specific surface area and excellent electrocatalytic activity. The peak current of H₂O₂ obviously improves at modified GCE compared to bare electrode. The proposed electrode provides a promising avenue to develop novel electrochemical sensors.

Abstract: A novel electrochemical strategy was proposed for detection of 2,4-Dichlorophenol (2,4-DCP) at fabricated carbon fiber microelectrode (CFME). The resultant CFME was characterized using scan electron microscopy (SEM) and cyclic voltammetry (CV). Upon addition of surfactant TritonX-100 in analytical system, the electrochemical signal of 2,4-DCP was obviously increased. Under the optimized conditions, the resulted CFME showed wide linear range for 2,4-DCP from 3.0×10^-8 to 1.8×10^-6 M with the detection limit of 1.0×10^-8 M (S/N = 3). The proposed method is simple, low-cost and convenient and will be a promising alternative for CFME fabrication.

Abstract: A simple and cost-effective method based on the reduction of AgNO₃ by H₂O₂ (5 vol.%) in 2.5–5 vol.% NH₃•H₂O aqueous solutions at room temperature and under atmospheric pressure was developed for the synthesis of Ag submicron crystallites. X-ray diffraction patterns demonstrated that the resultant products were pure cubic phase Ag powders. Field emission scanning electronic microscopy images showed that the Ag powders synthesized in 2.5 and 5 vol.% NH₃•H₂O aqueous solutions comprised submicron crystallites with the sizes of about 355–580 and 200–650 nm, respectively. Besides, the possible formation mechanism of Ag powders in the present system was also proposed.

Abstract: Based on the irreversible thermodynamics theory, the kinetic of BaSiO₃ solid-solid reaction has been constituted and then the equations were applied to BaSiO₃ solid synthesis reaction. The calculation results showed that the reaction was under control of reaction at 1207K.

Abstract: In this preparation, FCCU main fractionator and corresponding absorption-stabilization system are systemically simulated on the basis of industrial data. Through analysis, a heat exchanging column is added to improve the flowsheet before rich gas cooler to make good use of heat of the compressed rich gas. To decrease LPG lost along with dry gas, a dry gas compression-expansion refrigeration circle is proposed to offer refrigeration capacity in place of the cooling water for the absorber pumparounds. Compared with the regular scheme, energy consumption and C3+ components in dry gas is reduced respectively by 17.18% and 7.16% and LPG yield is increased by 0.41% simultaneously.

Abstract: The pyrolysis of 1-hexene at 873 K was investigated. Primary products include C1-C4 paraffins, C2-C4 olefins, butadiene, pentadiene, cyclopentane, cyclopentene, coke and hydrogen. A chain reaction mechanism was developed to interpret the distribution of products, and the quantitative analysis on the selectivity patterns of radical reactions was presented.

Abstract: Porous asymmetric PVDF membranes were prepared by the phase inversion process induced by a nonsolvent. The effect of pore-forming hydrophilic additives on the membrane morphology and transport properties was investigated. It was found that membranes prepared with hydrophilic polymer additives can offer higher pure water flux, higher porosity and lower pepsin rejection. PEG 10 000 can be used as a good pore forming additive to prepare PVDF membrane with higher pure water flux and relatively high pepsin rejection.