The use of small angle neutron scattering with contrast matching and variable adsorbate partial pressures in the study of porosity in activated carbons

Mileeva, Zhanna, Ross, Keith, Wilkinson, David, King, Steven, Ryan, Tony and Sharrock, Harry 2012, 'The use of small angle neutron scattering with contrast matching and variable adsorbate partial pressures in the study of porosity in activated carbons' , Carbon, 50 , pp. 5062-5075.

PDF - Accepted Version
Download (696kB) | Preview


The porosity of a typical activated carbon is investigated with small angle neutron scattering (SANS), using the contrast matching technique, by changing the hydrogen/deuterium content of the absorbed liquid (toluene) to extract the carbon density at different scattering vector (Q) values and by measuring the p/p0 dependence of the SANS, using fully deuterated toluene. The contrast matching data shows that the apparent density is Q-dependent, either because of pores opening near the carbon surface during the activation processor or changes in D-toluene density in nanoscale pores. For each p/p0 value, evaluation of the Porod Invariant yields the fraction of empty pores. Hence, comparison with the adsorption isotherm shows that the fully dry powder undergoes densification when liquid is added. An algebraic function is developed to fit the SANS signal at each p/p0 value hence yielding the effective Kelvin radii of the liquid surfaces as a function of p/p0. These values, when compared with the Kelvin Equation, show that the resultant surface tension value is accurate for the larger pores but tends to increase for small (nanoscale) pores. The resultant pore size distribution is less model-dependent than for the traditional methods of analyzing the adsorption isotherms.

Item Type: Article
Uncontrolled Keywords: activated carbons;small angle neutron scattering;deuterated toluene;porod invariant
Themes: Energy
Schools: Schools > School of Computing, Science and Engineering > Salford Innovation Research Centre (SIRC)
Journal or Publication Title: Carbon
Publisher: Elsevier
Refereed: Yes
ISSN: 0008-6223
Funders: University of Salford
Depositing User: Prof D. Keith Ross
Date Deposited: 27 Jun 2012 09:06
Last Modified: 29 Oct 2015 00:10
References: [1] Ross DK. Hydrogen storage: The major technological barrier to the development of hydrogen fuel cell cars. Vacuum 2006; 80: 1084-1089 [2] McNicholas TP, Wang AM, O’Neill K, Anderson RJ, Stadie, NP, Kleinhammes A, et al. H2 storage in microporous carbons from PEEK precursors. J. Phys. Chem. C 2010; 114: 13902-13908. [3] Calo JM, Hall PJ. The application of small angle scattering techniques to porosity characterization in carbons. Carbon 2004; 42: 1299-1304. [4] Li JC, Ross DK, Howe LD, Stefanopoulos KL, Fairclough, JPA, Heenan R, Ibel K. Small angle neutron scattering studies of the fractal-like network formed during desorption and adsorption of water in porous materials. Phys. Rev. B 1994; 49:5911-5917i [5] Bale HD, Schmidt PW. Small-angle X-ray scattering investigation of sub-microscopic porosity with fractal properties. Phys. Rev. Lett. 1984; 53: 596 - 599. [6] Diduszko R, Swiatkowski A, Trznadel BJ. On surface of micropores and fractal dimension of activated carbon determined on the basis of adsorption and SAXS investigations. Carbon 2000; 38:1153-1162. [7] He LL, Chathoth SM, Melnichenko YB, Presser V, McDonough J, Goyotsi Y. Small-angle neutron scattering characterization of the structure of nanoporous carbons for energy-related applications. Microporous and Mesoporous Materials 2012 ; 149 46-54. [8] Mergia K, Stefanopoulos KL, Ordas N, Garcia-Rosales C. A comparative study of the porosity of doped graphites by small angle neutron scattering, nitrogen adsorption and helium pycnometry. Microporous and Mesoporous Materials 2010; 134:141-149. [9] Mascotto S, Wallacher D, Brandt A, Hauss T, Thommes M, Zichler GA, et al. Analysis of microporosity in ordered mesoporous hierarchically structured silica by combining physisorption with in situ small-angle scattering (SAXS and SANS). Langmuir 2009; 25:12670-12681.). [10] Benham MJ, Ross DK. Experimental determination of absorption-desorption isotherms by computer-controlled gravimetric analysis. Z. Physik. Chemie NF 1989;163:S25-32. [11] Broekhoff JCP, de Boer JH. Studies of pore systems in catalysts: XII Pore distributions from the desorption branch of a nitrogen sorption isotherm in the case of cylindrical pores. A. An analysis of the capillary evaporation process. J. Catalysis 1968; 10:368-376. [12] Halsey G, Physical adsorption on non-uniform surfaces. J. Chem. Phys. 1948; 16:931. [13] Dubinin MM, Astakhov VA. Description of adsorption equilibria of vapours on zeolites over wide ranges of temperature and pressure. Adv. Chem. Series 1971; 102:69-&. [14] Heenan RK, King SM, Osborn R, Stanley HB. COLETTE Users Guide. Rutherford Appleton Laboratory Report, RAL-89-128, 1989; King SM, Heenan RK. Using COLETTE. Rutherford Appleton Laboratory Report, RAL-95-005, 1995. [15] Wignall GD, Bates FS. Absolute calibration of small-angle neutron scattering data. J. Appl. Crystallogr. 1987; 20: 28. [16] King SM. In: Pethrick RA, Dawkins JV, editors. Modern techniques for polymer characterisation, New York: John Wiley, 1999; p171. [17] Pfeifer P, Obert M. In Avnir D, editor. The Fractal Approach to Heterogeneous Chemistry, New York: Wiley; 1989; p. 11. [18] Pfeifer P, Ehrburger-Dolle F, Rieker TP, Gonzalez MT, Hoffman WP, Molina-Sabio M, et al. Nearly space-filling fractal networks of carbon nanopores. Phys. Rev. Lettrs. 2002; 88:115502. [19] Bunde A, Halvin S. Fractals and Disordered Systems. Berlin: Springer-Verlag; 1991, p. 229. [20] Mandelbrot BB. The Fractal Geometry of Nature. New York: W.H. Freeman and Company; 1982. [21] Winter R, Gabke A, Czeslik C, Pfeifer P. Power-law fluctuations in phase-separated lipid membranes. Phys. Rev. E 1999; 60:7354-7359. [22] Freltoft T, Kjems JK, Sinha SK. Power law correlations and finite size effects in silica particle aggregates studied by small-angle neutron scattering. Phys. Rev. B 1986; 33: 269 – 275. [23] Porod G. General Theory. In: Glatter O, Kratky O, Editors. Small Angle X-Ray Scattering, London: Academic Press, 1982, p 17-52. [24] Mileeva Z and Ross DK. The effect of the activation process on an activated carbon studied by Small Angle Neutron Scattering. Macroporous and Mesoporous Materials, to be published. [25] Malbrunot P, Vidal D, Vermesse J, Chahine R Bose TK. Adsorbent helium density measurement and its effect on adsorption isotherms at high pressure. Langmuir 1997; 13: 539-544. [26] Neimark NV and Ravikovitch PI. Calibration of pore volume in adsorption experiments and theoretical models. Langmuir 1997; 13: 5148-5160. [27] Higgins JS, Benoit HC. Polymers and Neutron Scattering: Oxford Series on Neutron Scattering in Condensed Matter, 8, Oxford: Oxford University Press, 1997. [28] Jeffrey A, Zwillinger D. Tables of Integrals, Series, and Products, New York: Academic Press, 7th Edition; 2007. [29] Gaines GL, Legrand DG. The surface tension of some deuterated hydrocarbons. Colloids and Surfaces A: Physicochemical and Engineering Aspects 1994; 82 : 299-300. [30] Bering BP, Dubinin MM, Serpinsky VV. Adsorption of argon and nitrogen on NaX zeolite modified by treatment with water. J. Colloid. Interface Sci.1966; 21: 378 [31] Broseta D, Barre L, Viziki O, Shahidzadeh N, Guilbaud JP, Lyonard S. Capillary condensation in a fractal porous medium. Phys. Rev. Lettrs. 2001; 86:5313 – 5316.

Actions (login required)

Edit record (repository staff only) Edit record (repository staff only)


Downloads per month over past year