Introduction to Gas Adsorption Test, (BET)
Gas adsorption techniques based on the BET and BJH methods are now widely used to characterize the adsorbent-specific surface area, pore size distribution, and pore volume. These methods, named after their respective developers, Brunauer, Emmett, and Teller for BET, and Barrett, Joyner, and Halenda for BJH, rely on the analysis of gas adsorption and desorption isotherms to provide valuable information about the porous structure of materials. Nitrogen is commonly employed as the adsorbate due to its inert nature, although Argon or Krypton may be used for more sensitive measurements. The experimental protocol outlined in ASTM D5160 is a guideline for conducting gas adsorption studies.
Principle and Methodology of Gas Adsorption Test, BET
The gas adsorption technique begins with removing any impurities from the active sites of the adsorbent through heating and vacuum treatment. Subsequently, the adsorbent is placed in an analytical tube under vacuum and chilled to liquid nitrogen (77 K). Nitrogen gas is then progressively charged onto the solid, then incrementally charged to the solid, starting at low pressures, and the volume of adsorbed gas is measured after each increment. This process continues until saturation pressure is reached and adsorption ceases. An isotherm is plotted, depicting the volume uptake versus relative pressure.
| Service Name | Remarks |
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| BET Analysis | Contact US |
| BJH Analysis | Contact US |
The low-pressure region of the isotherm corresponds to monolayer adsorption, while higher-pressure regions indicate multilayer adsorption. The BET method uses the monolayer segment of the isotherm to determine surface area using the BET equation, which connects adsorbed gas volume to monolayer volume and system pressure. The BJH approach, on the other hand, uses the Kelvin equation to calculate pore volumes and pore size distributions using experimental isotherms, making it especially useful for mesopore and small macropore size ranges.
To calculate the BJH volume of pores and the pore size distribution, Nitrogen pressure is incrementally increased, followed by measuring the adsorbed volume in the multilayer adsorption region. Capillary condensation occurs at higher relative pressures, filling the pores with liquid Nitrogen. The process is reversed by lowering the relative pressure and determining the desorption equilibrium. Hysteresis may occur between the adsorption and desorption curves. The pore size distribution is then computed using the desorption isotherm, providing valuable insights into the material’s porous structure.
What is the difference between BET and BJH methods for surface analysis?
BET
This method is used to measure the surface area of a material by adsorbing gas onto its surface at a low temperature. The BET method is based on a theory developed by scientists Brunauer, Emmett, and Teller in 1938.
BJH
This method is used to study the pore size distribution of a material, including micropores and mesopores. The BJH method uses the adsorption and desorption isotherms obtained from BET analysis
Instrument Used for BET Analysis
The gas adsorption method assesses surface area and pore size distribution for sizes ranging from millimeters to nanometers. Mercury porosimetry measures the millimeter-to-micrometer size range and is also beneficial for surface and internal structure research using electron microscopy. Sample preparation is critical in investigating the internal structure of nanoparticles using electron microscopy.
Instrumentation for BJH Analysis
Adsorbing inert gases onto the sample’s surface at 77 K, the temperature of liquid nitrogen, and gas adsorption analysis determine the surface area and pore size distribution of solid or powdered materials. This approach makes accurate surface area and pore size distribution measurements possible. For gas adsorption, there are three different kinds of instruments: dynamic, chromatographic, and continuous flow.
Common Applications of Gas Adsorption Test
- Design of separation procedures.
- Characterization of Solid Porous Adsorbents
- Characterization and Development of Nanoscale Materials
- Development of improved batteries
- Evaluation of heterogeneous catalysts.
Industrial Applications of Gas Adsorption Test
- Gas purification methods
- Water purification using advanced materials.
- Catalyst and Battery Technology
Benefits of Gas Adsorption Test
- It is a non-destructive test.
- Surface area, pore volume, and distribution data can all be collected from the same experiment.
Drawbacks of Gas Adsorption Test
- Closed pores are not accessible from the material surface and so cannot be examined using this technique.
- Only applicable for physical adsorption.
Techniques Related to Gas Adsorption Test
The Gas Adsorption Test is related to techniques including BET (Brunauer-Emmett-Teller) Analysis, Langmuir Adsorption, Barrett-Joyner-Halenda (BJH) Analysis, and T-Plot Method.
Related
FAQ's
Where can I get the gas adsorption test for surface area and pore size analysis tested?
You can share your gas adsorption test for surface area and pore size analysis testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific gas adsorption test for surface area and pore size analysis test to various testing techniques.
How much do I need to pay for the gas adsorption test for surface area and pore size analysis test?
Please contact us for a detailed quote for your gas adsorption test for surface area and pore size analysis testing needs. Cost incurred to carry out different gas adsorption test for surface area and pore size analysis testing methodology depends on the type of raw material; number of samples, coupons, or specimens; test conditions, turn around time etc. Costs of some ASTM testing methods start from $100 and the final value depends upon the factors listed above. Please contact us for the best and latest prices.
How many samples are required for gas adsorption test for surface area and pore size analysis?
The required number of samples or specimens should comply with the procedure given in the gas adsorption test for surface area and pore size analysis standard. However, the MaTestLab operations team can assist you for your special requirements once you share your testing details with us.
How much discount can I get on the gas adsorption test for surface area and pore size analysis test?
MaTestLab has a vast testing laboratory network, hence we bring you the best testing facilities in a cost-effective way. We offer considerable discounts (15-20%) to our returning customers based on test volume and frequency.
How many days will it take to complete the gas adsorption test for surface area and pore size analysis test?
The turnaround time for gas adsorption test for surface area and pore size analysis test methodology depends upon the test procedure mentioned in the standard test document. However, we at MaTestLab understand your research requirements and hence try to get your test completed within the least possible time.
Where can I get the gas adsorption test for surface area and pore size analysis tested?
You can share your gas adsorption test for surface area and pore size analysis testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific gas adsorption test for surface area and pore size analysis test to various testing techniques.
