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; Sharrock, Harry

Abstract

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.

Citation

Mileeva, Z., Ross, K., Wilkinson, D., King, S., Ryan, T., & Sharrock, H. (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, 5062-5075. https://doi.org/10.1016/j.carbon.2012.06.046

• Journal Article Type: Article
• Publication Date: Jan 1, 2012
• Deposit Date: Jun 27, 2012
• Publicly Available Date: Apr 5, 2016
• Journal: Carbon
• Print ISSN: 0008-6223
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 50
• Pages: 5062-5075
• DOI: https://doi.org/10.1016/j.carbon.2012.06.046
• Keywords: activated carbons;small angle neutron scattering;deuterated toluene;porod invariant
• Publisher URL: http://dx.doi.org/10.1016/j.carbon.2012.06.046
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