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BET Specific Surface Area & Pore Size Analyzer BELSORP MINI X

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BET specific surface areas from 0.01 m2/g ~ (N2) and pore size distribution from 0.7 ~ 500 nm (option: 0.35 ~ 500 nm by molecular probe method).

Simultaneous Measurement of Multiple Samples

Up to 4 specimens can be measured simultaneously, enabling the measurement times for multiple samples to be shortened significantly.

  • battery materials
  • catalysts
  • zeolite
  • ceramics
  • carbon
  • electronic components
  • fuel cells
  • Toner particles
  • cement
  • medicine / pharmaceuticals
  • silica
  • MOF / PCP
  • pigments
  • cosmetics

    ... and many more!

BET Specific Surface Area & Pore Size Analyzer BELSORP MINI X Operation Software

Gas Adsorption Measurements of Porous & Non-porous Materials: MOFs, Zeolites, Carbons, and More Evaluation Software BELMASTER

A sorption isotherm is defined as the relationship between the adsorbed amount onto an adsorbent and the equilibrium pressure of the adsorptive gas – commonly related to the saturation vapor pressure – at constant temperature. The gas sorption isotherm (e.g. nitrogen) delivers information about the specific surface area, pore size distribution and pore volume of measured material. In the following graph some exemplary sorption isotherms are shown.

The following measurements are conducted using our patented, Advanced Free Space Measurement (AFSMTM). This method allows for high reproducibility by using a reference cell to follow the changes in the free space volume. Our instrument measures the initial free space of the sample cell and reference cell. Since the change of the free space is equal in both cells (same environmental conditions), the change can be continuously followed by the pressure change of the reference cell.

In a product test, a certified reference material CRM-170 (nonporous alpha alumina; certified value of nitrogen BET specific surface area SSA: 1.05 ± 0.05 m2/g) is used to check the accuracy of measurement in low total surface area (TSA) measurements. Although the TSA is reduced from approx. 2 m2 to lower than 0.4 m2, the determined BET specific surface areas SSA stay almost identical.

Advantages of Patented AFSM Technique

  • LN2 level maintenance is less important
  • Improves reproducibility both in surface area and in pore volume
  • Enables adsorption isotherm of low surface area material without using krypton gas (down to 0.1 m2 in total surface area)

The Quick BET Mode can be used to maximize the sample throughput for BET specific surface area measurements. In this mode it is possible to measure three BET adsorption points of four samples in approx. 15 minutes (sample density required). Further, the Quick BET Mode offers two types of free space measurements: Firstly, the free space input option gives you the biggest opportunity to save time. Once the free space is determined for the sample cell, the free space measurement file (dvd file) can be reused for future quick BET measurements. Secondly, the free space can be determined with the actual measurement. A comparison of the obtained BET surface area from full-isotherm measurement (standard mode) and Quick BET Mode is given in the following graphs and table:

Analysis of Pore Size Distribution via NLDFT & GCMC Method

The classical pore size distributions (PSD) are calculated by INNES method (slit shape) and BJH, DH, CI methods (cylinder shape), which evaluate mesopores based on the capillary condensation theory. HK (slit), SF (cylinder), and CY (cage) methods can also be used to evaluate micropores based on the adsorption potential theory. The DA method, as well as the DR method, are also commonly used for pore volume evaluation and pore structure evaluation. The new PSD and capacity evaluation methods, NLDFT and GCMC (optional for BELSORP MINI X), are used for wide range analyses (from micro- to meso and macropores) and more accurate methods, specified in ISO15901-2.

Theory Interaction Surface and Gas Adsorbate Applicable Pore Size Range
BJH, CI, DH,
INNES method
Kelvin equation
(Surface tension and contact angle)
Bulk liquid density > 2 nm
Meso and macropore
HK, SF, CY method Lennard-Jones potential
(Interaction and repulsion force)
Bulk liquid density 0.4 - 2 nm
Micropore
NLDFT, GCMC Statistical thermodynamic model 0.35 - 500 nm
Whole pore range

*1 BELSORP MINI X is equipped with 1000 torr pressure transducers; isotherm starts from ~p/p0 of 1x10-4
*2 Option: 0.35 nm possible by molecular probe method

In recent years, attention has been focused on pore structure evaluation methods using computer simulations, such as the novel pore distribution analysis NLDFT (Non-localized Density Functional Theory) and GCMC (Grand Canonical Monte Carlo) method, which can analyze micropores to meso- and macropores using a unified theory. Pore size distributions obtained from the same adsorption isotherm are different between classical and novel PSD analyses, and even in between novel methods because the filling pressure obtained from each theory is different. Microtrac provides evaluation methods which cover a wide range of pore sizes and various adsorbates, such as N2 (77.4 K), Ar (87.3 K), and CO2 (298 K). It uses NLDFT / GCMC kernels of slit, cylinder, and cage pore models with carbon and metal oxide surface atoms, resulting in the most appropriate description of porous materials.

The BELMASTER software allows easy comparison between experimental and simulated isotherms, with the simulated isotherm serving as a basis for the PSD calculation.

In the following part an example for pore size distribution calculation by BJH method is given:

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