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    Enhancement of surface adsorption-desorption rates in microarrays invoking surface charge heterogeneity

    , Article Sensors and Actuators, B: Chemical ; Volume 242 , 2017 , Pages 956-964 ; 09254005 (ISSN) Abdollahzadeh, M ; Saidi, M. S ; Sadeghi, A ; Sharif University of Technology
    Elsevier B.V  2017
    Abstract
    This investigation is devoted to the influences of non-uniform wall characteristics on the surface adsorption-desorption rates in an electrokinetic microarray. Utilizing already explored electroosmotic and electrophoretic velocities, the species transport equations are solved by a finite-volume-based numerical approach. Uniform, sinusoidal, and pulse-like distributions of the zeta potential are considered in the analysis. The developed model is validated by comparing the results with those of two analytical solutions that are derived for limiting conditions. The results reveal that, in some cases, the surface charge heterogeneity can reduce the saturation time by more than 60%. The efficacy... 

    Effect of side by side interactions on the thermodynamic properties of adsorbed CO molecules on the Ni(111) surface: A cluster model study

    , Article Molecular Physics ; Volume 108, Issue 10 , 2010 , Pages 1397-1412 ; 00268976 (ISSN) Shamkhali, A. N ; Parsafar, G ; Sharif University of Technology
    Abstract
    The effect of electrostatic interactions on vibrational frequencies and thermodynamic properties of CO adsorbate on the Ni(111) surface is calculated by taking the first and second nearest-neighbour interactions into account. In order to obtain reasonable results, the cluster model of various surface adsorption sites with CO adsorbate is partially optimized, using Density Functional Theory and also the MP2 method for the hcp site. Comparison between DFT and MP2 results shows that DFT results are more reliable for this system. The stretching and bending frequencies of CO adsorbate are calculated using both Partial Hessian Analysis and Cluster-Adsorbate Coupling methods. Stretching and bending... 

    Removal of chromium from aqueous solution using polyaniline - Poly ethylene glycol composite

    , Article Journal of Hazardous Materials ; Volume 184, Issue 1-3 , December , 2010 , Pages 248-254 ; 03043894 (ISSN) Riahi Samani, M ; Borghei, S. M ; Olad, A ; Chaichi, M. J ; Sharif University of Technology
    2010
    Abstract
    The adsorption of chromium compounds from solutions by a composite of polyaniline/poly ethylene glycol (PANi/PEG) was investigated in this study. Experiments were conducted in batch mode under various operational conditions including agitation time, solution pH, PANi/PEG dose and initial concentration of chromium salts. Results showed that concentration of PEG at synthesizing stage has a significant effect on the capacity of produced composite for removal of chromium. Morphologically, PANi/PEG composite is closely dependent on the concentration of PEG. Maximum removal of hexavalent chromium was experienced when 2. g/L of PEG was used in synthesis of PANi/PEG. Removal of hexavalent chromium... 

    Study of temperature and velocity distribution of rarefied gas flow in micro-nano channels

    , Article Proceedings of the ASME Fluids Engineering Division Summer Conference 2009, FEDSM2009, 2 August 2009 through 6 August 2009, Vail, CO ; Volume 1, Issue PART B , 2009 , Pages 1045-1050 ; 9780791843727 (ISBN) Ghezel Sofloo, H ; Shams, A ; Ebrahimi, R ; Sharif University of Technology
    Abstract
    This paper deals with simulation of transport phenomena in micro and nano pores. The number of cavities and the cavity radius were estimated by using Henry's law for adsorption of Argon onto ZSM-5 and NaX zeolites. This work showed both of zeolites have pores with average size less than 1 nm. Then with using micro- nano channel assumption instead of micro-nano pores, gas flow and heat transfer were investigated. Subsonic nonideal gas flow and heat transfer for different Knudsen number are investigated numerically using the Direct Simulation Monte Carlo method modified with a consistent Boltzamnn algorithm. The collision rate is also modified based on the Enskog theory for dense gas. It is... 

    Enhanced electrochemical hydrogen storage by catalytic Fe-doped multi-walled carbon nanotubes synthesized by thermal chemical vapor deposition

    , Article Journal of Power Sources ; Volume 188, Issue 2 , 2009 , Pages 404-410 ; 03787753 (ISSN) Reyhani, A ; Mortazavi, S.Z ; Moshfegh, A.Z ; Golikand, A.N ; Amiri, M ; Sharif University of Technology
    2009
    Abstract
    Hydrogen storage capacities of raw, oxidized, purified and Fe-doped multi-walled carbon nanotubes (MWCNTs) were studied by electrochemical method. Based on transmission electron microscopy and Raman spectroscopic data, thermal oxidation removed defective graphite shells at the outer walls of MWCNTs. The analysis results indicated that the acid treatment dissolved most of the catalysts and opened some tips of the MWCNTs. Thermal gravimetric analysis and differential scanning calorimetry results illustrated that by oxidation and purification of MWCNTs, the weight loss peak shifts toward a higher temperature. N2 adsorption isotherms of the purified and oxidized MWCNTs showed an increase in N2...