How to determine the specific surface area of ​​materials - Database & Sql Blog Articles

Probe orientation needle with a head diameter of 6.0 and length of 2980, used for precise surface analysis

1206 side full-color LED lighting system for enhanced visibility during measurements

The specific surface area is not directly measured but calculated based on the adsorption isotherm data. This process involves selecting an appropriate theoretical model that best fits the sample's characteristics. As a result, the determination of specific surface area is more of an analytical process than a simple measurement. Different analysts may interpret the same set of data differently, leading to variations in the final results. It’s important to remember that when we talk about "measuring" surface area, we are actually performing a detailed analysis.

Is the BET method the most accurate for surface area calculation? How many different methods exist for determining specific surface area?

The BET method is one of the widely used theories in surface area analysis. It was developed based on Langmuir’s monolayer adsorption theory but extended to account for multilayer adsorption. While Langmuir’s theory is suitable for samples with only micropores, BET is more versatile and applicable to a broader range of materials. However, it is not always the best choice for every type of sample.

The BET theory, first introduced in 1938, stands for the Brunauer-Emmett-Teller method. It is considered the standard for surface area analysis in many industries. Despite its popularity, there are cases where other models provide more accurate results. For instance, when analyzing microporous materials using a method designed for mesoporous materials, the BET value may not be reliable. International standards such as ISO 9277:2010 and IUPAC guidelines specify the conditions under which BET should be applied and how results should be interpreted.

Several theoretical models are used to calculate specific surface area, including Langmuir, BET, BJH, DR, and NLDFT. Each model has its own assumptions and is best suited for certain types of materials. For example, the NLDFT (Non-Local Density Functional Theory) is known for providing highly accurate results, especially for microporous and mesoporous materials. Studies have shown that NLDFT closely approximates the true surface area, making it a preferred choice in advanced research and industrial applications.