ASTM B761-98

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: B 761 – 98
Standard Test Method for
Particle Size Distribution of Metal Powders and Related
Compounds by X-Ray Monitoring of Gravity Sedimentation
This standard is issued under the fixed designation B 761; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope Powders and Their Compounds Prior to Particle Size
Analysis
1.1 This test method covers the determination of particle
size distributions of metal powders. Experience has shown that
3. Summary of Test Method
this test method is satisfactory for the analysis of elemental
3.1 A carefully dispersed homogeneous suspension of the
tungsten, tungsten carbide, molybdenum, and tantalum pow-
powder is permitted to settle in a cell scanned by a collimated
ders, all with an as-supplied Fisher number of 6 μm or less, as
X-ray beam of constant intensity. The net X-ray signal is
determined by Test Method B 330. Other metal powders (for
inversely proportional to the sample concentration in the
example, elemental metals, carbides, and nitrides) may be
dispersing medium, and the particle diameter is related to the
analyzed using this test method with caution as to significance
position of the X-ray beam relative to the top of the cell.
until actual satisfactory experience is developed (see 7.2). The
Cumulative mass percent versus equivalent spherical diameter
procedure covers the determination of particle size distribution
are recorded to yield a particle size distribution curve.
of the powder in the following two conditions:
1.1.1 As the powder is supplied (as-supplied), and
4. Significance and Use
1.1.2 After the powder has been deagglomerated by rod
4.1 This test method is useful to both suppliers and users of
milling as described in Practice B 859.
powders, as outlined in 1.1 and 1.2, in determining particle size
1.2 This test method is applicable to particles of uniform
distribution for product specifications, manufacturing control,
density and composition having a particle size distribution
development, and research.
range of 0.1 to 100 μm. However, with tungsten, molybdenum,
4.2 Users should be aware that sample concentrations used
tantalum, and tungsten carbide powders, analyses are limited to
in this test method may not be what is considered ideal by some
a particle size distribution range of 0.1 to 30 μm.
authorities, and that the range of this test method extends into
1.3 This standard does not purport to address all of the
the region where Brownian movement could be a factor in
safety concerns, if any, associated with its use. It is the
conventional sedimentation. Within the range of this test
responsibility of the user of this standard to establish appro-
method, neither the sample concentration nor Brownian move-
priate safety and health practices and determine the applica-
ment are believed to be significant.
bility of regulatory limitations prior to use. Specific hazard
4.3 Reported particle size measurement is a function of both
information is given in Section 7.
the actual particle dimension and shape factor as well as the
2. Referenced Documents particular physical or chemical properties being measured.
Caution is required when comparing data from instruments
2.1 ASTM Standards:
operating on different physical or chemical parameters or with
B 330 Test Method for Average Particle Size of Powders of
different particle size measurement ranges. Sample acquisition,
Refractory Metals and Their Compounds by the Fisher
2 handling, and preparation can also affect reported particle size
Sub-Sieve Sizer
results.
B 821 Guide for Liquid Dispersion of Metal Powders and
Related Compounds for Particle Size Analysis
5. Apparatus
B 859 Practice for De-agglomeration of Refractory Metal
5.1 Gravitational sedimentation particle size analyzer utiliz-
ing X-ray extinction to determine particle concentration.
This test method is under the jurisdiction of ASTM Committee B-9 on Metal
6. Reagents and Materials
Powders and Metal Powder Productsand is the direct responsibility of Subcommit-
tee B09.03on Refractory Metal Powders.
6.1 Purity of Reagents—Reagent grade chemicals shall be
Current edition approved March 10, 1998. Published May 1998. Originally
used in all tests. Unless otherwise indicated, it is intended that
published as B 761 – 86. Last previous edition B 761 – 97.
all reagents conform to the specifications of the Committee on
Annual Book of ASTM Standards, Vol 02.05.
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NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
B 761
TABLE 1 Suggested Approximate Starting Weights for Tungsten
Analytical Reagents of the American Chemical Society where
3 or Tungsten Carbide
such specifications are available. Other grades may be used,
Nominal Fisher Number According
provided it is first ascertained that the reagent is of sufficiently A
Weight , g per 25 mL of
to B 330 of As-Supplied Powder,
Dispersing Medium
high purity to permit its use without lessening the accuracy of
μm
the determination.
1 0.21
6.2 Dispersing Medium—Dissolve 0.10 g of sodium hex-
2 0.23
ametaphosphate [(NaPO ) ] in 1000 mL of distilled or deion- 3 0.26
3 6
4 0.28
ized water.
5 0.30
6.3 Cleaning Solution—Dissolve 0.5 g of Alconox detergent
6 0.33
or equivalent in 1000 mL of distilled or deionized wat
...