Search results for "Nitrogen adsorption"
showing 5 items of 5 documents
Pore structural characteristics of mesostructured materials prepared under different conditions
2002
This paper presents an overview of the pore structural properties of different mesostructured materials prepared at room temperature, namely MCM-41, MCM-48 and MMS. The stability towards water vapour of some samples is inferred by XRD and nitrogen adsorption after and prior to water adsorption. It is shown that MMS materials are more stable than MCM-41. A new method for the stabilisation of MCM-41 using tetraethoxysilane (TEOS) in hexane as silicification agent is proposed and it is shown to be effective in stabilising the pore structure and to increase significantly the surface hydrophobicity.
Factors Controlling the Energy of Nitrogen Monolayer Coverage onHigh Surface Area Catalyst Oxide Carriers
2011
Factors affecting the strength of nitrogen physisorption at monolayer coverage on different catalytic oxide carriers (e.g., ZnO, MgO, Al2O3, ZrO2, TiO2, and SiO2) have been addressed. Isotherm elaboration by the two-parameter BET equation provides C-constant values (80–200) inversely related to the polarizing power (PP) of the oxide adsorbent irrespective of the surface area exposure. The energy of monolayer formation depends on the extent of charge-delocalization characterizing the surface cation-oxygen bond, which determines the acid–base character of the oxide and strength of van der Waals interactions with adsorbate molecules. Density functional theory (DFT) calculations on MgO and TiO2…
Comments on surface structure analysis by water and nitrogen adsorption
2004
Specific surface area and pore size distribution are determined usually from adsorption isotherms at low temperatures using nitrogen or noble gases. These are not absolute parameters and the measuring methods are fraught with serious difficulties. General problems of sorption measurements and recent developments are discussed. To obtain information for practical purposes these measurements need to be supplemented by investigations of the sorbate/sorbent system used in practice. Results of the measurement of nitrogen and water vapour adsorption on different materials are compared.
Method of Discrimination of Surface Fractality
1993
Abstract A simple method for the discrimination of surface fractality is proposed. This method is based on the comparison of the nitrogen adsorption isotherm on a given sample with the "standard" isotherm on a smooth surface. The proposed comparative method makes it possible to determine the lower limit of the scale range of surface fractality. A thermodynamic method is recommended as a complement to fractal analysis in the scale range of about 10-1000 A. The results of the investigation of surface roughness are presented with examples of typical samples of silica gels, porous glasses, apatite, and coal.
Nitrogen Adsorption on Graphene Sponges Synthesized by Annealing a Mixture of Nickel and Carbon Powders
2017
The present research has been supported by the National Research Programme for 2014–2017 “Multifunctional Materials and Composites, Photonics and Nanotechnologies”.