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Porosity and Surface Area

The interaction of a solid with its surroundings is through the available surface area for adsorption of gas or vapour molecules. This also allows probing of materials’ surfaces including irregularities and pores. One of the most successful methods is based on the BET method for gas adsorption onto a solid surface. The adsorption method of Brunauer, Emmett and Teller (BET) is based on the physical adsorption of a vapour or gas onto the surface of a solid. Such data can be used to analyse the porosity of the materials being studied. Surface Measurement Systems have pioneered the use of both the Dynamic Vapor Sorption (DVS) and the Inverse Gas Chromatography (IGC) methods for determining the surface area and porosity of solid state materials.

The Dynamic Vapour Sorption (DVS) or the Inverse Gas Chromatography Surface Energy Analyser (IGC SEA) can be used for the determination of BET surface areas. Both instruments can carry out experiments at room conditions and need very small sample amount (typically a few milligrams for the DVS). This compares to the traditional nitrogen BET method, which requires very low experimental temperatures and sample sizes of typically 1 gram. An added advantage of the DVS and IGC is that some samples may change their morphology at very low temperatures, so when tested on these instruments at room temperatures this ceases to be a problem.

Application Note 18: Measuring BET Surface Areas using Organic Probe Molecules
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Application Note 225: Isotherm Measurements for BET Surface Area Calculations using Inverse Gas Chromatography
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Finite concentration Inverse Gas Chromatography (IGC) is a useful tool for the investigation of surface and pore properties. The Surface Energy Analyzer (SEA), an instrument based in the principles of IGC, together with thermal desorption data from Dynamic Vapor Sorption (DVS), provide the possibility to separate micropore adsorption from surface adsorption and mesopore adsorption. This allows the calculation of BET values with physical relevance for highly microporous materials and the consideration of molecular sieve effects.

pdficon_small Application Note 215: A Sorption Study on Microporous Materials by Finite Dilution Inverse Gas Chromatography

Surface energy is an important property in numerous industrial application and processes. It shows a strong dependency on various macroscopic properties and relates to many crucial interfacial phenomena, i.e. adhesion and wetting behaviors. Nanomaterials can be energetically inhomogeneous, exhibiting various surface sites, such as structural defects or specific functional groups. Therefore, a surface energetic heterogeneity profile can provide more comprehensive information on the nature and population of these surface sites.

Application Note 226: Surface Energetic Heterogeneity of Carbon-based Nanomaterials
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Many common materials contain pores and pore networks which can greatly impact material behaviour. Nature is full of examples where pores are an integral part of living organisms and inert materials. Also recently, man-made porous materials have been synthesised. These include Metal Organic Frameworks (MOFs), Covalent Organic Frameworks (COFs) and zeolites. They are very good candidates for absorbents, catalysts and separation processes.

Application Note 51: Gas Capture and Vapour Separation by Microporous Materials
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Application Note 54: Detecting and Modelling Porosity in Natural and Engineered Materials
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Application Note 215: Characterisation of Microporous Materials by Finite Concentration Inverse Gas Chromatography | Request a copy

Application Note 504: Water Vapor Induced Mesoporous Structure Collapse Observed by GenRH with Mcell and FT-IR
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