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BET SURFACE AREA ANALYSIS |
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MCA Services applies the BET method to the calculation of surface area from gas adsorption data in the lower range of the adsorption isotherm. This method derives accurate and reliable data both theoretically and practically. The technique may be operated as a single point BET measurement (one adsorption pressure) or more accurately as a multipoint BET measurement. SC6T Test: SC7T Test: Single Point BET Surface Area (Volumetric Technique) The majority of samples are analysed using the Micromeritics TriStar instrument, a state-of-the-art gas adsorption unit, and may be further combined to form part of the standard report generated through the collection of full gas adsorption isotherm data (see the SC3 test). Nitrogen gas is applied to this technique, which is essentially volumetric in nature. Analysis may be undertaken either as a single point BET area or a multipoint BET area measurement. The single point surface area (SC7T) test applies one adsorption pressure, typically either P/Po = 0.15 or 0.25 depending on the nature of the sample. The more accurate multipoint surface area analysis (SC6T test) uses one of the standard MCA Services pressure ranges, again these are selected according to the nature of the sample and can be tailored accordingly.
Standard BET Surface area plot SC13 Test: SC7Q Test: Single Point BET Surface Area (Flow Technique) For particularly low surface areas (typically lower than approximately 0.1 m2g) a flowing gas technique is available. Single point surface area (SC7Q test) and multipoint surface area (SC13 test) analyses are available options, with the multipoint technique typically applying 4 adsorption pressures. In common with our SC6 and SC7T tests, nitrogen gas is also applied to these techniques. SC12 Test: SC14 Test: MCA Services are able to offer further extensions to the standard surface area analyses, thus covering the most specialised samples by offering comprehensive surface area testing capabilities. Through the application of alternative adsorbate gases, such as krypton, argon and carbon dioxide, very low surface area samples or specialist materials may be successfully analysed. In our SC12 test, Kr gas is applied to the flow measurement technique, whilst the SC14 test is conducted using the volumetric technique. As with our standard testing, these methods also employ the BET area method. For such analysis please call the analytical team at MCA services for further details. In order to obtain the most accurate results it is normally necessary to degas samples prior to testing and MCA Services can accommodate a wide range of conditions for this purpose. Furthermore, these may be combined to suit the individual requirements of our clients. Degassing temperatures up to 200˚C under vacuum and 400˚C under flowing nitrogen or helium gas can be applied. Such activities are usually conducted at MCA Services immediately prior to analysis as part of the testing itself. Results are generally emailed as PDF files to speed up transmission to the client and include the BET area plot together with tabulated data and the calculated surface area of the sample. In addition, we offer assistance with interpretation of results at no extra charge. Please contact the staff at MCA Services, who will be happy to advise and discuss the options available. Surface area, or specific surface area, is a critical factor influencing the operation and behaviour of many materials. It is often applicable to such issues as the determination of stability and the efficiency of most materials, including catalysts and pharmaceuticals. The measurement of surface area also provides a critical measurement for quality control of many materials. Our applications page provides more details of the potential uses of the technique.
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