The instrument is used for determining the surface area, the pore size distribution, and the surface activity of solids, in both physisorption and chemisorption modes.

In physisorption mode, an adsorption isotherm is measured. It represents the number of molecules that are adsorbed on a solid with respect to the system's pressure. The type and range of porosity can be directly read from the shape of the adsorption isotherm.​

Chemisorption is mainly used to quantify the amount of surface-active sites, which are available to catalyse chemical reactions. With temperature programmed methods in reduction, oxidation or desorption modes, the reduction readiness can be determined and activation energies can be calculated.​

This is a fully automated, three-station instrument capable of high-performance physisorption (mesopore and micropore) and chemisorption. It analyses with superior accuracy, resolution, and data reduction.

While the atoms in the bulk of a solid are bound on all sides, the atoms on the surface of a solid are incompletely bound. These atoms are more reactive (van der Walls forces of interactions) and can attract gas, vapour or liquid molecules to satisfy the imbalance of atomic forces. Surface area helps determine things like how solids burn, dissolve, and react with other materials. Samples need to be pretreated by applying some combination of heat, vacuum, and flowing gas to remove adsorbed contaminants acquired from atmospheric exposure. This is typically typically water and carbon dioxide.

The solid is then cooled, under a vacuum, usually to cryogenic temperature (77 k, -195 oC). An adsorptive such as nitrogen is dosed to the solid in controlled increments. After each dose of adsorptive, the pressure is allowed to equilibrate, and the quantity adsorbed is calculated. The quantity adsorbed at each pressure and temperature defines an adsorption isotherm, from which the quantity of gas required to form a monolayer over the external surface of the solid is determined. With the area covered by each adsorbed gas molecule known, the surface area can be calculated.

By extending this process so that the gas is allowed to condense in the pores, the sample’s fine pore structure can be evaluated. As pressure increases, the gas condenses first in the pores with the smallest dimensions. The pressure is increased until saturation is reached, at which time all pores are filled with liquid. The adsorptive gas pressure is then reduced incrementally, evaporating the condensed gas from the system. Evaluation of the adsorption and desorption branches of these isotherms and the hysteresis between them reveals information about the size, volume, and area.

Visit our surface area and porosity library if you are interested in pore size distributions and BET surface area. ​

It does this by varying the vapour concentration surrounding the sample and measuring the change in mass which this produces. The DVS Intrinsic equipment measures water vapour adsorption isotherms only.

DVS rapidly measures uptake and loss of moisture or organic vapours by flowing a carrier gas at a specified relative humidity or partial pressure over a sample, which can weigh between 1mg and 4g, suspended from the weighing mechanism of an ultra-sensitive recording microbalance.

This particular microbalance, the Surface Measurement Systems Ultrabalance, is used as it is capable of measuring changes in sample mass lower than 1 part in 10 million. This may take from minutes to days to complete, depending upon the sample size and material.