The determination of the specific surface area provides an important parameter for characterizing the properties of finely divided, dispersed solid and porous substances, such as for material development, production processes, quality control and application technology.
The specific surface area is the total surface area (outer and inner) of a solid with reference to one gram of material which is accessible to gases. The inner surface area of porous substances incorporates all walls of cracks, interstices, pores and hollow spaces.
Among the wide range of methods for determining the specific surface area of disperse or porous solids, low-temperature gas adsorption as used in the AREAMAT plays a particular role.
The Measuring Principle
The measuring method of the AREAMAT, standardized in DIN 66132, is based on the use of differential pressure measurement to determine the quantity of nitrogen gas adsorbed on the surface of the sample and evaluation according to a simplified BET equation.
This BET single-point method provides the advantage of short measuring times in conjunction with a wide measuring range. The method enables the determination of specific surface areas in the range from about 0.1 to 1000 m2/g. In addition to all powdered substances, pieces of material can also be investigated due the large neck diameter of the adsorption vessel of 18 mm. The automatic change of the bath vessels simplifies the handling as well as the automatic cryogenic bath immersion.
The Application
Examples of powdered and porous materials for which the knowledge of the specific surface area plays a big role in the evaluation of the product and quality control are:
Adsorbent materials, catalysts, fillers, carbon graphite powder, pigments, paint, varnish, cement, lime, plaster, powdered metal, ceramic materials, fibers, sediments, fertilizers, polymers, resins, cosmetics and pharmaceutical products.
The Benefits
• BET single-point method according to DIN 66132, low temperature nitrogen adsorption,
wide measuring range
• Equilibrium method; no influence of transport processes and thermodiffusion;
measurement of all pores accessible to the adsorbate
• Differential method; no influence of the total volume; no vacuum required
• Fully automated procedure; short measurement times; automatic endpoint detection and analysis, display of the differential pressure during measurement
• Wide-necked (diameter 18 mm) glass vessels, also suitable for pieces and course grained material
• Automatic change of water bath and cryogenic bath, automatic level regulation
• Simple operation using an external PC with MS Windows interface, data storage
• External sample preparation independent of the measuring unit
