Gas sorption is routinely used to characterize the surface area and pore-size distribution of materials. These two important physical properties can greatly influence materials performance characteristics.
Surface generally determined using BET (Brunauer-Emmett-Teller) analysis of nitrogen isotherms at -196°C. For very little surfaces it is possible to analyse with Krypton. Pore-size in the meso and micro range (pore radius between 1-50 nm) are determined using BJH (Barrett-Joyner-Halenda) of DH (Dollimore-Heal) and SF (Saito-Foley) or DA (Dubinin-Astakhov) analysis of nitrogen isotherms at -196°C.
The interaction of materials with water vapour is of interest to a broad spectrum of science and industry. The affects of water can be both harmful and beneficial depending on the material and how it is used. The material properties can change as a function of humidity and temperature and the stability, type, magnitude and the kinetics of interaction are all important in this regard. Water sorption is a general term that encompasses the range of possible interactions for water molecules with surfaces and bulk matter: These include physical adsorption, chemical (hydrogen) bonding and hydroxylation. Water sorption can also induce bulk changes such as hydration and amorphous phase transitions. Materials are broadly classed as hydrophobic or hydrophilic, but detailed measurements of the interaction are required to investigate a given specimen and this generally requires determination of the water sorption isotherm. With the gravimetric method we can analyse the water sorption in mass %. It is also possible to analyse the sorption from organic solvents.