Specific surface area
Total accessible surface per gram, from a multipoint BET fit.
Useful forCatalysts, adsorbents, battery powdersSurface, Particle & Porosity
BET
Brunauer–Emmett–Teller Surface Area Analysis
BET measures the specific surface area of powders and porous solids from nitrogen adsorption at 77 K. It is the standard way to compare catalysts, adsorbents and battery materials.
4 test optionsN₂ adsorption at 77 KSurface area in m²/gTypical turnaround 4–6 working days
BET measurement principleIllustrative
01 / Overview
What is BET?
BET analysis cools a degassed sample in liquid nitrogen and doses it with nitrogen gas in small steps. The amount adsorbed at each pressure gives an isotherm, and the BET equation converts the monolayer capacity into a specific surface area.
Because gas molecules reach every open pore and crack, BET reports the full accessible surface rather than the outer particle size. Recording desorption as well gives total pore volume and a mesopore size distribution from the same run.
02 / How it works
How it works
- 01
Sample is degassed
The powder is heated under vacuum or gas flow to clear moisture and adsorbed gases from its pores.
- 02
Cooled to 77 K
The sample tube is lowered into liquid nitrogen so gas can adsorb on its surface.
- 03
Gas is dosed step by step
Known doses of nitrogen are admitted and the pressure is logged as the surface takes up gas.
- 04
Surface area is calculated
The BET equation is fitted to the low-pressure data for surface area; the full curve gives pore data.
03 / What it measures
What it measures
Total pore volume
Pore volume from the gas taken up close to saturation pressure.
Useful forPorous supports, silicas, activated carbonsPore size distribution (BJH)
Share of pore volume in each mesopore size range.
Useful forMesoporous materials, catalyst supportsAdsorption–desorption isotherm
The full curve; its hysteresis loop hints at pore shape.
Useful forComparing porous structuresMicropore area (t-plot)
Estimate how much of the surface lies in micropores.
Useful forZeolites, microporous carbons04 / Test options
Choose the BET options you need
4 options · none added yet
05 / Sample requirements
Sample requirements
- Accepted forms
- Dry powders, granules, pellets or small solid pieces
- Quantity
- Typically 0.2–1 g; up to 2–3 g for low-surface-area materials
- Piece size
- Must fit a sample tube with a ~9 mm neck; say if pieces may be crushed
- Thermal stability
- State the highest temperature the sample tolerates during degassing
- Dry, free-flowing powder or small pieces
- State the maximum safe degassing temperature
- Send extra material for low-surface-area samples
- Sealed, labelled containers
- No liquids, slurries or wet pastes
- No samples that melt or decompose below ~100 °C without discussing first
Hazardous or air-sensitive samples: mention it in your request, and attach the MSDS if you have one.
06 / Results & turnaround
Results & turnaround
What you receive
- BET surface area (m²/g) with C constant and fit range
- Adsorption–desorption isotherm plot
- Pore volume and BJH pore size distribution, if ordered
- Raw data files
- Report PDF
Turnaround & pricing
Typically 4–6 working days after samples reach the lab.
Price confirmed in your quotation, depending on user type, options and number of samples.
07 / Limitations
When BET isn't the right fit
Narrow micropores below ~0.7 nm
Particle size of powders or dispersions
Surface chemistry or composition
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