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Electrophoretic deposition of Al2O3/ZrO2 layer with controllable thickness in ethanol medium
Chun-mei YANG, Xian-chun CHEN, Xiao-ming LIAO, Zhong-bing HUANG, Ya-dong YAO, Guang-fu YIN
Front Chem Chin. 2011, 6 (2): 76-83.
https://doi.org/10.1007/s11458-011-0240-y
ZrO2 toughened Al2O3 (Al2O3/ZrO2) ceramic layers with required thickness were prepared by electrophoretic deposition (EPD) method using ethanol suspensions with stabilizing agent of polyethyleneimine (PEI) under constant-voltage mode in this paper. The deposition of Al2O3/ZrO2 ceramic powders occurred on the titanium alloy cathode. A stable suspension with 1wt% PEI in ethanol at pH 5 was prepared in terms of the zeta potential and sedimentation of the suspension. The effects of the suspension concentration, applied voltage, deposition time and processing method of titanium alloy cathode on the coating thickness and morphology were investigated. The deposition layers on titanium alloys with smooth surfaces and thickness of 0.35–1.2 mm could be obtained by adjusting the aforementioned parameters. In addition, after being sintered at 1500°C for 3 h in air atmosphere, ZrO2 toughened Al2O3 ceramic layers became smooth and dense.
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Bioassay studies of cobalt (II) complexes of modified diamine
Saeed-UR-REHMAN, Muhammad IKRAM, Sadia REHMAN, Shah NAWAZ
Front Chem Chin. 2011, 6 (2): 98-104.
https://doi.org/10.1007/s11458-011-0232-y
Coordination compounds of modified diamine, the basic unit of which are ethylenediamine, with that of Co (II) are prepared. The modified diamines are ethylenediaceticacid (EDDA) and N,N,N,N-tetaraethylene-1,2-diamine (TEEDA). These diamines are characterized through 1H-NMR, 13C-NMR, elemental analysis and IR techniques. Cobalt (II) complexes of these two ligands were prepared and characterized by physical measurements including elemental analysis, IR, UV-Visible, magnetic susceptibilities and conductance measurements. Antibacterial activities are also carried out in order to investigate the biological activity upon complexation. They were screened against four pathogenic bacteria like BoldItalic and BoldItalic. The results showed significant enhancement in activities.
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The kinetics study of the reduction of Fast Green dye with cetylpyridinum chloride as cationic surfactant
Muhammad SULTAN, Hajira TAHIR, Khalid AHMED, Qazi JAHANZEB
Front Chem Chin. 2011, 6 (2): 105-112.
https://doi.org/10.1007/s11458-011-0233-x
The kinetics of the reaction of Fast Green dye (FG) with cetylpyridinum chloride was studied in alkaline medium by UV-Visible spectrophotometer. Reduction of Fast Green dye was carried out by varying the fast green dye concentration, cetylpyridinum chloride concentration and concentration of sodium hydroxide. In the present study the reduction of dye was carried out in order to reduce the color content. The interaction of dye was carried out with reducing analyte (cetylpyridinum chloride). The rate of the reaction was determined by varying the above parameters at different temperatures. It was observed that the reduction followed pseudo first-order kinetics with respect to dye, surfactant, OH- ion concentration according to the following reaction pathway.![]() ![]() The mechanism for the photo bleaching of the dye has been?proposed and well confirmed by the data simulation procedure. The activation parameters of the reaction like entropy of activation (ΔBoldItalic) and free energy of activation (ΔBoldItalic) showed the extremely solvated states of transient complex which was less disorderly arranged than the oxidized form of dye, whereas BoldItalicBoldItalic values reflects a high amount of energy required for the reduction of dye with cetylpyridinum chloride.
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Applying density functional theory on tautomerism in 3,4-dihydropyrimidin-2(1H)-ones
Asadollah FARHADI, Mohammad Ali TAKASSI
Front Chem Chin. 2011, 6 (2): 142-146.
https://doi.org/10.1007/s11458-011-0237-6
In the present study, the density functional theory (DFT) and Gibbs free energy calculations were performed to investigate the stability and tautomerism of C4-substituted-3,4-dihydropyrimidin-2(1BoldItalic)-ones. Three different forms are possible for the ethyl 3,4-dihydropyrimidinones (ethyl 4-aryl-6-methyl-3,4-dihydropyrimidin-2(1BoldItalic)-one-5-carboxylates, ethyl 4-aryl-2-hydroxy-6-methyl-1,4-dihydropyrimidine-5-carboxylates and ethyl 4-aryl-2-hydroxy-6-methyl-3,4-dihydropyrimidine-5-carboxylates) forms that the most stable form is ethyl 4-aryl-6-methyl-3,4-dihydropyrimidin-2(1BoldItalic)-one-5-carboxylates (keto-form). The obtained data showed that the substitution on the C4-substitut position can be effective on the equilibrium constant (BoldItaliceq).
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Synthesis and characterization of organomodified Na-MMT using cation and anion surfactants
K. R. Vishnu MAHESH, H. N. Narasimha MURTHY, B. E. KUMARASWAMY, N. RAGHAVENDRA, R. SRIDHAR, M. KRISHNA, Niranjan PATTAR, Ratna PAL, B. S. Sherigara
Front Chem Chin. 2011, 6 (2): 153-158.
https://doi.org/10.1007/s11458-011-0239-4
The Sodium Montmorillonite (Na-MMT) is not susceptible to polymer due to its organophilic character and low basal spacing. The primary objective of this study was to improve Na-MMT platelets separation by organically modifying it with cation and anion exchanges using Cetyl trimethyl ammonium bromide (CTAB) and Sodium dodecyl sulfate (SDS) respectively. Basal spacing, presence of functional groups, Zeta-potential with particle size analysis and thermal stability of the Organomodified Na-MMT (OMMT) were characterized using XRD, FTIR, zeta-potential analyzer and TGA respectively. The basal spacing of CTAB modified OMMT increased to 19.5 ? from 11.0 ? which corresponds to the basal spacing of Na-MMT. The SDS modified OMMT did not show any increase in the basal spacing. FTIR spectra of CTAB modified Na-MMT illustrated the attachment of CTAB functional groups to Na-MMT, while the same was absent in the case of SDS modified Na-MMT. The zeta-potential of Na-MMT shifted from -24.88 mV to 15.66 mV in the case of CTAB modified Na-MMT and 12.49 mV for SDS modified Na-MMT, indicating a greater surface potential of the modified nanoclay. The TGA showed greater weight loss for CTAB modified Na-MMT than that for Na-MMT, indicating the effective Na+ ion exchange with alkyl amines.
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