1.1 These test methods use air permeability to determine an envelope-specific surface area and its associated average equivalent spherical diameter (from 0.2 to 75 m) of powders. Two test methods are described: one method for inorganic materials (Method 1) and another method for organic materials (Method 2). The values obtained are not intended to be absolute but are generally useful on a relative basis for control purposes. 1.2 Units-With the exception of the values for density and the mass used to determine density, for which the use of the gram per cubic centimetre (g/cm3) and gram (g) units is the longstanding industry practice and the units for pressure, cm H2O, also long-standing practice, the values in SI units are to be regarded as the standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
A new instrument has emerged for estimating the particle size of powders using air permeability. This is now the only commercially available instrument that uses this technique. These new standard test methods are, therefore, being written to specify procedures for the use of the new instrument. These test methods will be used for control of particle size in powder processing and in specifications of particle size for powder materials. The refractory metals industry, in particular, depends on this type of measurement.
Keywordsair permeability; average particle size; envelope-specific surface area; particle size; permeability; porosity; powder; specific surface
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top