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ASAP 2000 Accelerated Surface Area and Porosimetry System
The ASAP 2000 Accelerated Surface Area and Porosimetry Analyzers
use gas sorption techniques to generate high-quality data for
research and quality control applications. All ASAP 2010 Analyzers
utilize the principle of physical adsorption to obtain information
about the surface area and porosity of a solid material.
Analysis Technique
The basics of the analytical technique are simple; a sample
contained in an evacuated sample tube is cooled (typically)
to cryogenic temperature, then is exposed to analysis gas at
a series of precisely controlled pressures. With each incremental
pressure increase, the number of gas molecules adsorbed on the
surface increases. The pressure at which adsorption equilibrium
occurs is measured and the universal gas law is applied to determine
the quantity of gas adsorbed.
As adsorption proceeds, the thickness of the adsorbed film increases.
Any micropores in the surface are quickly filled, then the free
surface becomes completely covered, and finally larger pores
are filled. The process may continue to the point of bulk condensation
of the analysis gas. Then, the desorption process may begin
in which pressure systematically is reduced resulting in liberation
of the adsorbed molecules. As with the adsorption process, the
changing quantity of gas on the solid surface is quantified.
These two sets of data describe the adsorption and desorption
isotherms. Analysis of the isotherms yields information about
the surface characteristics of the material. |
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