Brunauer-Emmett-Teller (BET) analysis
Brunauer-Emmett-Teller (BET) theory can be used to calculate the specific surface area of solid materials based on gas adsorption measurements. The method is suitable for analyzing a wide range of solid matrices from catalyst powders to monolithic materials.
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What is BET analysis?
While BET technically refers to the theory used in the calculation of specific surface area, the term is often extended to refer to surface area and pore size measurement by gas adsorption more broadly. The analysis is based on the physical adsorption of inert gas, such as nitrogen, on the solid surface of the sample. The measured specific surface area is given in m2/g.
What is BET analysis used for?
BET analysis is mainly used for analyzing the fineness of cement and concrete, the adsorption capability of activated carbon, catalyst characterization, the adsorption performance of gas purifiers, and studying nanomaterials. Nanomaterial identification can be based on measuring the volume-specific surface area (VSSA), which can be determined using BET and He pycnometry.
How is BET surface area determined?
The specific surface area of the BET sample is determined by the physisorption of an inert gas, typically nitrogen, argon, or krypton, on the sample surface. The surface area determination should be carried out at a constant temperature (isothermal). The appropriate temperature depends on the inert gas used (e.g. 77 K for liquid nitrogen). The properties of the sample define the suitable inert gas for the analysis.
The small gas molecules are attracted to the surface of the solid sample and open a porous structure forming a monolayer of adsorbed gas. After the gaseous monolayer of molecules is created, the sample is placed into a non-nitrogen atmosphere and heated. This allows the release of the adsorbed nitrogen gas molecules from the surface of the sample. The released gas molecules can then be quantified and the surface area and porosity calculated.
Sample requirements and preparation
BET is suitable for the characterization of powders and monolithic solids. Usually, around 500 mg to 1 g of sample material is needed to obtain reliable results, but sometimes smaller sample amounts can be used. Sample preconditioning is an essential step before starting a specific surface area measurement. All possible physically bonded surface impurities including moisture must be removed via a degassing step. The degassing step is performed under vacuum conditions and at high temperatures for no less than 16 hours. Before starting the actual BET measurement, the setup should be calibrated by performing a blank run with helium gas. The helium will not typically be adsorbed on the surface of the solid sample.
Need a BET analysis?
Measurlabs offers BET analysis services of high quality with fast results and affordable prices. If you have any questions about your sample or its suitability for the method, our experts are always happy to help. You can contact us through the form below or by emailing us at firstname.lastname@example.org.
Suitable sample matrices
- Pharmaceutical ingredients
- Activated carbon
- Carbon nanotubes
- Other powders and porous materials
Ideal uses of BET analysis
- Assessing the adsorption capability of materials
- Quality control in metallurgy, pharmaceuticals, cement, and concrete industries
- Characterization of catalysts
- Research on powder metallurgy and nanomaterials
- Porous molecular sieve development
- Gas filtration development
Frequently asked questions
BET analysis is mainly used for analyzing the fineness of cement and concrete, the adsorption capability of activated carbon, catalyst characterization, the adsorption performance of gas purifiers, and for studying nanomaterials.
Powders and monolithic solids like cement, concrete, minerals, zeolites, carbon, and pharmaceutical ingredients can be analyzed with BET.
Measurlabs offers a variety of laboratory analyses for product developers and quality managers. We perform some of the analyses in our own lab, but mostly we outsource them to carefully selected partner laboratories. This way we can send each sample to the lab that is best suited for the purpose, and offer high-quality analyses with more than a thousand different methods to our clients.
When you contact us through our contact form or by email, one of our specialists will take ownership of your case and answer your query. You get an offer with all the necessary details about the analysis, and can send your samples to the indicated address. We will then take care of sending your samples to the correct laboratories and write a clear report on the results for you.
Samples are usually delivered to our laboratory via courier. Contact us for further details before sending samples.