ASTM E2980-20

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Designation: E2980 − 15 E2980 − 20
Standard Test Methods for
Estimating Average Particle Size of Powders Using Air
Permeability
This standard is issued under the fixed designation E2980; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
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 μm) of powders. Two test methods are described: One test method for inorganic materials (Test
Method 1), and another test method for organic materials (Test 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/cm ) and gram (g) units is the longstanding industry practice; and the units for pressure, cm H O—also O –
also long-standing practice; the values in SI units are to be regarded as 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
B330 Test Methods for Estimating Average Particle Size of Metal Powders and Related Compounds Using Air Permeability
B859 Practice for De-Agglomeration of Refractory Metal Powders and Their Compounds Prior to Particle Size Analysis
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E1638 Terminology Relating to Sieves, Sieving Methods, and Screening Media
E2589 Terminology Relating to Nonsieving Methods of Powder Characterization
2.2 ISO Documents:
ISO 10070 Metallic Powders: Determinations of Envelope-Specific Surface Area from Measurements of the Permeability to Air
of a Powder Bed Under Steady-State Flow Conditions
3. Terminology
3.1 Definitions—Many terms used in this test method are defined in Terminologies E1638 and E2589.
These test methods are under the jurisdiction of ASTM Committee E29 on Particle and Spray Characterization and is the direct responsibility of Subcommittee E29.02
on Non-Sieving Methods.
Current edition approved Dec. 1, 2015Oct. 1, 2020. Published January 2016October 2020. Originally approved in 2014. Last previous edition approved in 20142015 as
E2980 – 14.15. DOI: 10.1520/E2980-15.10.1520/E2980-20.
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*A Summary of Changes section appears at the end of this standard
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3.2 Definitions of Terms Specific to This Standard:
3.2.1 air permeability, n—measurement of air pressure drop across a packed bed of powder.
3.2.2 average particle size, n—for the purposes of these test methods only, an estimate of the equivalent average spherical particle
diameter, calculated from the measured envelope-specific surface area, assuming that all the powder particles are spherical and that
all are exactly the same size.
3.2.3 de-agglomeration, n—process used to break up agglomerates of particles.
3.2.4 envelope-specific surface area, n—specific surface area of a powder as determined by gas permeametry in accordance with
ISO 10070.
3.2.5 MIC Sub-Sieve AutoSizer (MIC SAS), n—a commercially available permeability instrument for measuring envelope-specific
surface area and estimating average particle size from 0.2 to 75 μm.
3.2.6 porosity of a bed of powder, n—ratio of the volume of the void space in the powder bed to that of the overall volume of the
powder bed.
4. Significance and Use
4.1 These test methods provide procedures for determining the envelope-specific surface area of powders, from which is
calculated an “average” particle diameter, assuming the particles are monosize, smooth surface, nonporous, spherical particles. For
this reason, values obtained by these test methods will be reported as an average particle size. The degree of correlation between
the results of these test methods and the quality of powders in use will vary with each particular application and has not been fully
determined.
4.2 These test methods are generally applicable to all powders, including metals (see Test Methods B330 for specific metal powder
requirements), ceramics, and organic materials, for particles having diameters between 0.2 and 75 μm. They should not be used
for powders composed of particles whose shape is too far from equiaxed -– that is, flakes or fibers. In these cases, it is permissible
to use the test methods described only by agreement between the parties concerned. These test methods shall not be used for
mixtures of different powders, nor for powders containing binders or lubricants. When the powder contains agglomerates, the
measured surface area may be affected by the degree of agglomeration. Methods of de-agglomeration such as that specified in
Practice B859 may be used if agreed upon between the parties concerned.
4.3 When an “average” particle size of powders is determined by these methods, it should be clearly kept in mind that this average
size is derived from the determination of the specific surface area of the powder using a relationship that is true only for powders
of uniform size and spherical shape. Thus, the results of these methods are only estimates of average particle size.
4.4 Reported particle size measurement is a function of both the actual dimension and shape factor as well as the particular
physical or chemical properties of the particle being measured. Caution is required when comparing data from instruments
operating on different physical or chemical parameters or with different particle size measurement ranges. Sample acquisition,
handling, and preparation can also affect reported particle size results.
5. Apparatus
5.1 MIC Sub-Sieve AutoSizer (MIC SAS), consisting of an air pump, a calibrated gas mass flow controller, a precision-bore sample
tube, a sample tube retaining collar, a spacer tool, a gas flow metering valve, two precision pressure transducers (inlet and outlet),
a stepper motor controlled ballscrew-mounted piston, and computer hardware and software for instrument control and calculation
and reporting of results. Included is accessory equipment consisting of a plug manipulator (extraction rod), two porous plugs, and
a supply of paper disks. See schematic diagram in Fig. 1.
The sole source of supply of the MIC Sub-Sieve AutoSizer (MIC SAS) (latest version called MIC SAS II) known to the committee is Micromeritics Instrument
Corporation, Particulate Systems, 4356 Communications Drive, Norcross, GA 30093-2901, USA. If you are aware of alternative suppliers, please provide this information
to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.
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FIG. 1 Schematic Diagram of the MIC Sub-Sieve AutoSizer (MIC SAS)
NOTE 1—When homing the piston, adjust the sample packing assembly (1) as described in the manufacturer’s directions, with the plugs and paper disks
stacked together and placed on the fixed anvil spigot, or (2) using a specially designed baseline (homing) gauge instead of the plugs and paper disks. This
baseline gauge shall have a height of 20.30 6 0.10 mm. Check all plug heights when new plugs are purchased and periodically thereafter to make sure
all are equal in height.
5.2 Powder funnel, stainless steel, with spout outside diameter slightly smaller than the sample tube inside diameter.
5.3 The manufacturer provides instructions which should be followed. Particular attention should be given to proper maintenance
of the instrument with special reference to the instructions on (1) “homing” the piston when turning on from an unpowered state,
(2) setting the pressure and periodic checking of the pressure, (3) condition of O-rings on the piston and sample spigot, and (4)
the sample packing assembly (plugs and paper disks).
5.4 Balance, having a capacity of at least 50 g and a sensitivity of 0.001 g.
6. Standardization of Apparatus
6.1 Before proceeding with standardization of the MIC SAS instrument, the following items shall be checked:
6.1.1 The sample tube and plugs shall not be worn to the point where results are affected.
6.1.2 Inspect the O-ring seals for tears and abrasion marks. The O-ring seals shall not be worn to the point where the sample tube
moves easily by hand or the pressure reading varies as the sample tube is moved.
6.1.3 The drying agent shall be in proper condition.
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6.2 Whenever the instrument is turned on from an unpowered state, the piston shall be “homed” according to the manufacturer’s
instructions. See Note 1 above.
6.3 Before running the initial sample, the pressure shall be set to 50.0 (+0.1, –0.5) cm H O,
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