BET Surface Area Pore Size Analysis Testing Services
Accredited BET surface area pore size analysis testing from Infinita Lab, performed to the exact standard requirements - accurate, reproducible results with full documentation for compliance, R&D, and quality control programs.
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- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
What Is BET Surface Area Pore Size Analysis?
Gas adsorption analysis using the BET (Brunauer-Emmett-Teller) and BJH (Barrett-Joyner-Halenda) methods is the standard approach for measuring specific surface area and pore size distribution of solid, porous materials. The technique works by measuring the amount of nitrogen gas that adsorbs onto and desorbs from a material surface under cryogenic conditions and in vacuum, and then applying established theoretical models to extract surface area and pore structure data from the resulting isotherms.
BET analysis gives the total specific surface area of the material in m²/g. In contrast, BJH analysis uses the desorption branch of the isotherm to derive pore size distribution – including average pore diameter, total pore volume, and the distribution of pore sizes across the mesopore range (2–50 nm). Together, these two analyses give a comprehensive picture of a material’s accessible surface and internal pore architecture.
This is one of the most widely used characterisation techniques across materials science, chemical engineering, and industrial R&D. For porous materials – catalysts, adsorbents, membranes, ceramics, carbons, and pharmaceutical excipients – surface area and pore structure are as fundamental to understanding performance as chemical composition.
Applications and Benefits of BET Surface Area Pore Size Analysis Testing
Scope
Gas adsorption BET/BJH analysis covers the measurement of specific surface area and pore size distribution of solid porous and non-porous materials using nitrogen physisorption at 77 K. Full adsorption and desorption isotherms are collected across a defined relative pressure range, and the data are analyzed using the BET and BJH theoretical frameworks.
The measurement covers:
- BET surface area – multipoint analysis across the P/P₀ range of 0.05–0.30; reported in m²/g, encompassing both external surface area and internal pore wall area accessible to nitrogen
- BJH pore size distribution – derived from the desorption isotherm using Kelvin equation-based analysis; reports pore volume (cm³/g), average pore diameter (nm), and differential pore volume distribution across the mesopore range (2–50 nm)
- Total pore volume – measured from the quantity of nitrogen adsorbed at P/P₀ ≈ 0.99, representing total accessible pore space
- t-plot analysis – separates micropore area from total BET surface area; relevant for microporous materials such as zeolites and activated carbons
- Isotherm type classification – IUPAC isotherm classification (Types I–VI) provides qualitative information on pore geometry (cylindrical, slit-shaped, inkbottle) and material porosity type
Applications
- Catalyst characterisation – surface area and pore size directly govern catalyst activity, selectivity, and mass transfer; BET/BJH is standard practice for characterising fresh, used, and regenerated catalysts across refining, petrochemical, and fine chemical industries
- Activated carbons and adsorbents – pore structure determines adsorption capacity for gases, liquids, and contaminants; BET surface area and BJH pore distribution are key specifications for activated carbon used in water treatment, air purification, and energy storage
- Ceramic and refractory powders – surface area measurement for process control in sintering, coating, and powder compaction; higher surface area powders sinter at lower temperatures and require different binder loading
- Battery and energy materials – electrode materials (cathodes, anodes, separators) and solid electrolytes in lithium-ion and next-generation batteries where interfacial surface area affects rate capability and cycle life
- Metal-organic frameworks (MOFs) and zeolites – extremely high surface area materials (500–7000 m²/g) where BET surface area is a primary performance specification
- Membrane and filtration media – characterisation of porous polymer, ceramic, and carbon membranes for gas separation, ultrafiltration, and nanofiltration applications
Benefits
- Gives both surface area and pore structure in one measurement run – a single nitrogen adsorption/desorption isotherm yields BET surface area, BJH pore size distribution, total pore volume, and average pore diameter without additional sample preparation
- Relevant across a wide range of materials and surface areas – from dense powders at 0.1 m²/g to high-surface-area carbons and MOFs at thousands of m²/g; krypton adsorption extends the method further for very low surface area sintered materials
- Pore size distribution identifies both mesopore volume and geometry – BJH output shows not just average pore size but how pore volume is distributed, which matters for selectivity in separation and catalysis
- Non-destructive and requires small sample quantities – typically 0.05 to 1 g of material depending on surface area; sample is recovered after outgassing in most cases
- Widely accepted across industries and regulatory frameworks – BET surface area data generated per ASTM or ISO methods is accepted in pharmaceutical filings, catalyst specifications, and materials procurement standards worldwide
Gas Adsorption for Surface Area (BET) and Pore Size Analysis (BJH) Test Process
Sample Preparation
The sample is weighed and degassed under vacuum or inert gas to remove moisture and contaminants.
1Dead Volume Calibration
The sample tube is transferred to the instrument, and helium is used to measure dead volume.
2Isotherm Measurement
Nitrogen adsorption and desorption data are collected at 77 K across selected pressure points.
3BET/BJH Analysis
BET is used to calculate surface area, while BJH analysis provides pore size distribution, pore volume, and average pore diameter.
4Gas Adsorption for Surface Area (BET) and Pore Size Analysis (BJH) Technical Specifications
| Parameter | Details |
|---|---|
| Analysis Method | BET (surface area) and BJH (pore size distribution) by nitrogen physisorption |
| Adsorptive Gas | Nitrogen (N₂) at 77 K; Krypton (Kr) for very low surface area materials |
| BET Analysis Range | P/P₀ = 0.05–0.30 (multipoint, minimum 3 points) |
| BJH Pore Size Range | Mesopores: 2–50 nm; analysis from the desorption branch |
| Total Pore Volume | Measured at P/P₀ ≈ 0.99 |
| Additional Analyses | t-plot (micropore area), single-point BET, isotherm type classification |
| Applicable Standards | ASTM C1274, ASTM D3663, ASTM D6556, ISO 9277, ISO 15901-2 |
| Reported Units | Surface area: m²/g; Pore volume: cm³/g; Pore diameter: nm |
| Sample Quantity | Typically 0.05–1 g depending on material surface area |
| Outgassing | Vacuum or inert gas flow; temperature and duration recorded per sample |
- Automated volumetric gas adsorption analyser (Micromeritics ASAP, Quantachrome Autosorb, or equivalent)
- Vacuum degassing station with programmable temperature control
- Liquid nitrogen Dewar for cryogenic analysis
- Analytical balance for pre- and post-outgassing mass
- High-purity nitrogen and helium gas supplies
- Krypton gas supply (for low surface area measurements)
Equipment and Instrumentation Used for Testing
What You Receive: Test Report, Data, and Certification
- BET surface area – specific surface area in m²/g with BET plot, C constant, and R² value of the linear fit
- BJH pore size distribution – differential pore volume plot (dV/d log D vs. pore diameter), average pore diameter, and cumulative pore volume
- Total pore volume – total accessible pore space in cm³/g measured at P/P₀ ≈ 0.99
- Full adsorption-desorption isotherm – raw isotherm data tabulated and plotted, with IUPAC isotherm type noted
- t-plot analysis (where applicable) – external surface area and micropore volume separated from total BET surface area
- Outgassing conditions – temperature, duration, and method- were recorded alongside results
- Sample mass and identification records – pre- and post-outgassing mass, sample description, and lot or batch information
BET Surface Area Pore Size Analysis FAQs
The technique encompasses external area and pore area evaluations to determine the total specific surface area in m2/g.
The BJH analysis method, also known as Barrett-Joyner-Halenda, is used to study the pore size distribution of porous materials like zeolites, activated carbons, MXene, and metal-organic frameworks, including micropores and mesopores.
The pore size range for the nitrogen adsorption method is 2–50 nm [4]. For samples with pore sizes less than 30 nm, gas adsorption is commonly used; for the sample with pore sizes less than 100 μm, mercury intrusion is used.
The BJH (Barrett, Joyner, and Halenda) method complements BET by calculating pore size distributions from experimental isotherms.
Activated carbon is used to remove odors, tastes, colors, or even poisons in liquid or gas form.
BJH stands for Barrett–Joyner–Halenda, a method used to determine pore size distribution and pore volume in porous materials. It analyzes gas adsorption–desorption data, commonly using nitrogen, to estimate pore characteristics, particularly in mesoporous materials.
In a laboratory, a prepared porous material sample is analyzed using a gas adsorption analyzer, typically with nitrogen at cryogenic temperature. The instrument records adsorption and desorption at different pressures, and BJH calculations use the resulting data to estimate pore size distribution and pore volume.
BJH analysis measures the pore structure of porous materials by interpreting gas adsorption–desorption data. The sample is exposed to controlled gas pressures, and the amount of gas adsorbed or released is recorded. Software then calculates pore size distribution and pore volume to support material characterization and quality assessment.
Why Choose Infinita Lab for BET Surface Area Pore Size Analysis Testing
When your BET Surface Area Pore Size Analysis results have to hold up - for compliance, a customer audit, or an engineering decision - accuracy and an unbiased third-party report matter more than price. Infinita Lab routes your BET surface area pore size analysis testing to ISO/IEC 17025-accredited U.S. partner labs with hands-on method experience, so you get defensible data, transparent reporting, and turnaround times built around your project deadline - not ours.
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