ASTM B430-97
(Test Method)Standard Test Method for Particle Size Distribution of Refractory Metal Powders and Related Compounds by Turbidimetry
Standard Test Method for Particle Size Distribution of Refractory Metal Powders and Related Compounds by Turbidimetry
SCOPE
1.1 This test method covers the determination of particle size distribution of refractory metal powders with a turbidimeter (1). Experience has shown that this test method is satisfactory for the analysis of elemental tungsten, molybdenum, rhenium, tantalum metal powders, and tungsten carbide powders. Other refractory metal powders, for example, elemental metals, carbides, and nitrides, may be analyzed using this test method with caution as to significance until actual satisfactory experience is developed. The procedure covers the determination of particle size distribution of the powder in two conditions:
1.1.1 As the powder is supplied (as-supplied), and
1.1.2 After the powder has been de-agglomerated by rod milling (laboratory milled) according to Practice B859.
1.2 Where dual units are given, inch-pound 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: B 430 – 97
Standard Test Method for
Particle Size Distribution of Refractory Metal Powders and
Related Compounds by Turbidimetry
This standard is issued under the fixed designation B 430; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope E 691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 This test method covers the determination of particle
size distribution of refractory metal powders with a turbidime-
3. Summary of Test Method
ter (1). Experience has shown that this test method is
3.1 A uniform dispersion of the powder in a liquid medium
satisfactory for the analysis of elemental tungsten, molybde-
is allowed to settle in a glass cell. A beam of light is passed
num, rhenium, tantalum metal powders, and tungsten carbide
through the cell at a level having a known vertical distance
powders. Other refractory metal powders, for example, el-
from the liquid level. The intensity of the light beam is
emental metals, carbides, and nitrides, may be analyzed using
determined using a photo cell. This intensity increases with
this test method with caution as to significance until actual
time as sedimentation of the dispersion takes place.
satisfactory experience is developed. The procedure covers the
3.2 The times at which all particles of a given size have
determination of particle size distribution of the powder in two
settled below the level of the transmitted light beam are
conditions:
calculated from Stokes’ law for the series of sizes chosen for
1.1.1 As the powder is supplied (as-supplied), and
the particle size analysis.
1.1.2 After the powder has been de-agglomerated by rod
3.3 The intensity of the light beam at these times is
milling (laboratory milled) according to Practice B 859.
measured as percent of the light transmitted through the cell
1.2 Where dual units are given, inch-pound units are to be
with the clear liquid medium. The size distribution in the
regarded as standard.
powder can be calculated from these relative intensities using
1.3 This standard does not purport to address all of the
the Lambert-Beer law in the modified form (also see Refs 2, 3,
safety concerns, if any, associated with its use. It is the
4).
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- DW 5 d ~log I 2 log I ! (1)
1–2 m d1 d2
bility of regulatory limitations prior to use.
where I and I are the intensities measured at the times
d1 d2
when all particles having diameters larger than d and d
1 2
2. Referenced Documents
respectively have settled below the level of the light beam, d
m
2.1 ASTM Standards:
is the arithmetic mean of particle sizes d and d , and DW
1 2 1-2
B 330 Test Method for Average Particle Size of Powders of
refers to the relative weight for the particle size range between
Refractory Metals and Their Compounds by the Fisher
d and d . Values of DW are determined for each of the particle
1 2
Sub-Sieve Sizer
size ranges chosen. The sum of these values is (DW. The
B 821 Guide for Liquid Dispersion of Metal Powders and
weight percent of particles in the size range from d to d can
1 2
Related Compounds for Particle Size Analysis
then be calculated as:
B 859 Practice for De-Agglomeration of Refractory Metal
Weight, % 5 ~DW /(DW! 3 100 (2)
Powders and Their Compounds Prior to Particle Size
Analysis
4. Significance and Use
E 456 Terminology Relating to Quality and Statistics
4.1 Knowledge of the particle size distribution of refractory
metal powders is useful in predicting powder-processing be-
This test method is under the jurisdiction of ASTM Committee B09 on Metal
havior, and ultimate performance of powder metallurgy parts.
Powders and Metal Powder Products and is the direct responsibility of Subcom-
Particle size distribution is closely related to the flowability,
mittee B09.03 on Refractory Metal Powders.
compressibility, and die-filling characteristics of a powder, as
Current edition approved Sept. 10, 1997. Published February 1998. Originally
published as B 430 – 65 T. Last previous edition B 430 – 95. well as to the final structure and properties of the finished parts.
The boldface numbers in parenthesis refer to the references listed at the end of
However, the degree of correlation between the results of this
this test method.
test method and the quality of powders in use has not been fully
Annual Book of ASTM Standards, Vol 02.05.
determined quantitatively.
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
B 430
4.2 This test method is suitable for manufacturing control 7. Preparation of Apparatus
and research and development in the production and use of
7.1 Warm up equipment by turning on the light source and
refractory metal-type powders, as indicated in 1.1.
recorder for a minimum of 1 h prior to use.
4.3 Reported particle size measurement is a function of both
7.2 Fill the cell with sedimentation medium to a height
the actual particle dimension and shape factor, as well as the
sufficient to cover the light beam path by at least 10 mm and
particular physical or chemical properties being measured.
place the cell in the turbidimeter (Note 3). If a microammeter
Caution is required when comparing data from instruments
is used to measure light intensity, adjust the light transmission
operating on different physical or chemical parameters or with
to 100 % using the diaphragm. If a millivolt recorder is used,
different particle size measurement ranges. Sample acquisition,
adjust the potentiometer so that the photovoltaic cell output is
handling, and preparation also can affect reported particle size
10 mV or 100 %. In this case, the diaphragm is not adjusted
results.
and is completely open.
5. Apparatus
NOTE 3—For convenience in filling the cell to the proper height,
inscribe a line on each face of the cell at the desired liquid-level height.
5.1 Turbidimeter (5)—The recommended instrument is one
The height of fall is usually 25 mm. To determine the location of the line,
using a cell rectangular in cross section, approximately 50 mm
the center of the light beam path must be established and 25 mm added to
high, 40 mm wide, and 10-mm sedimentation medium thick-
this value.
ness, and having optically parallel faces.
7.3 After the instrument is adjusted to 100 % light transmis-
5.2 Millivolt Recorder, 0 to 10-mV range, 10-in. (254-mm)
sion through the sedimentation cell and medium, move the cell
wide strip chart, 0 to 100 graduations, 120 in./h (50 mm/min)
carriage until light is passing through a reference glass held in
chart speed, or microammeter with 0 to 100 graduations,
another slot of the cell carriage. Read and record the percent of
15-μA full scale, 4.5-mV full scale.
reference light transmission. Having been selected to have
NOTE 1—While a 120-in./h (50-mm/min) chart speed is recommended,
approximately 70 to 95 % of the transmission of the sedimen-
other speeds may be satisfactory.
tation cell and medium, the reference glass will indicate 100 %
5.3 Ultrasonic Cleaning Tank, with tank dimensions ap-
light transmission through the sedimentation cell when the
proximately 5 by 5 by 3 in. (127 by 127 by 76 mm) deep and
recorder reads this value through the reference cell.
1 1 5
an output of 50 W, or approximately 3 ⁄2 by 3 ⁄2 by 2 ⁄8 in. (89
by 89 by 67 mm) deep and an output of 25 W. 8. Calculation of Times at Which Light Intensity is
5.4 Glass Vial, nominal 2-dram, flat-bottom, with a tight-
Measured
fitting cap. The vial shall be approximately 2 in. (51 mm) in
8.1 The times at which the light transmission values should
height with a ⁄8-in. (16-mm) outside diameter and approxi-
be read are calculated from Stokes’ law. A uniform 1-μm
mately a ⁄32-in. (0.8-mm) wall.
interval should be used in making measurements through the
10-μm size and, depending upon the particular powder, either
6. Reagents
1-μm or 5-μm intervals thereafter. The form of Stokes’ law
6.1 Sedimentation Medium:
used is as follows:
6.1.1 Base Medium, distilled or deionized water (see Note
8 2
4).
t 5 ~18 3 10 Nh!/d ~r 2r !g (3)
x m
6.1.2 Use either one of the following as recommended in
where:
Guide B 821:
t = time, s,
6.1.2.1 Daxad (No. 11) —Dissolve 25 mg in 1 L of base
N = viscosity of settling medium at ambient temperature,
medium.
P (Note 4),
6.1.2.2 Sodium Hexametaphosphate—Dissolve 0.1 g in 1 L
h = height of fall, cm (distance from liquid level height
of base medium.
to midpoint of light beam),
NOTE 2—Use water that is pure. Do not store the sedimentation
d = diameter of particle, μm (d , d , et al),
1 2
medium longer than a week, and do not use rubber tubing in any storage
r = theoretical density of the powder being tested (for
x
container. Clean thoroughly all sedimentation medium containers every
tungsten, use 19.3 g/cm ),
week.
r = density of settling medium at ambient temperature
m
(Note 4), and
The recommended instrument is a Cenco Photelometer (not made anymore) of
g = gravitational constant (980 cm/s ).
original or modified designs or any proven equivalent instrument. A schematic
diagram of the Photelometer is shown in the papers referenced at the end of this test
NOTE 4—The viscosity and density values at different temperatures that
method. Copies of detailed drawings of an acceptable instrument are available from
are used for the sedimentation medium in this procedure are the same as
ASTM Headquarters. Order ADJA0430. A fabricated instrument can be secured
for pure water. Some viscosity (from the Handbook of Chemistry and
from WAB Instruments Co., 5171 Hickory Dr., Cleveland, OH 44124.
Physics, 65th Edition, CRC Press, 1984) and density (from Metrological
The 69800-Q1, Model S, Type G, Speedomax W, or XL630 Series recorder as
Handbook 145, NIST, 1990) values are given as follows:
made by the Leeds and Northrup Co., have been found satisfactory.
Temperature, Viscosity, Density,
Ultrasonic tank Model Nos. 2 or 12 as made by Bransonic Instrument Co.,
°C °F cP g/cm
Stamford, CT, have been found satisfactory.
Two-dram Titeseal vials, as made by Chemical Rubber Co., Cleveland, OH,
18 64.4 1.0530 0.9986
have been found satisfactory.
19 66.2 1.0270 0.9984
Daxad No. 11 powder as made by the W. R. Grace and Co., Polymers and
20 68.0 1.0020 0.9982
Chemicals Div., 62 Whittemore Ave., Cambridge, MA 02140, has been found
21 69.8 0.9779 0.9980
satisfactory.
B 430
10.2 The 5-min ultrasonic treatment dispersion procedure is
22 71.6 0.9548 0.9978
23 73.4 0.9325 0.9975
as follows:
24 75.2 0.9111 0.9973
10.2.1 Fill the vial with 2 mL of sedimentation medium or
25 77.0 0.8904 0.9970
to a height of approximately ⁄4in. (7.0 mm). Add weighed
26 78.8 0.8705 0.9968
27 80.6 0.8513 0.9965
amount of powder and cap the vial. Place into the ultrasonic
28 82.4 0.8327 0.9962
tank, handholding the vial for 5 min.
29 84.2 0.8148 0.9959
30 86.0 0.7975 0.9956
NOTE 8—Depth of the liquid in the tank should be 1 ⁄2 to 2 in.
(approximately 40 to 50 mm) from the bottom. Liquid in the tank is
9. Conditioning (or De-agglomeration) of the Powder
distilled or deionized water, room temperature, with a small amount of
Prior to Analysis
detergent. A 1-min warm-up of the ultrasonic tank is recommended prior
9.1 For as-supplied particle size distribution determinations,
to vial immersion.
NOTE 9—If any of the powder sample is on the walls of the vial, the
this step is not needed.
liquid may be swirled before and during the ultrasonic treatment to rinse
9.2 For laboratory-milled particle size distribution determi-
the powder down into the bottom. The vial need not be held in a stationary
nations, follow the procedure specified in Practice B 859.
position nor perpendicular to the bottom. Depth of immersion and location
NOTE 5—Since milled powder has a greater tendency than as-supplied of the vial are generally at the center portion of the tank, but may vary.
powder to pick up moisture and oxidize, the analysis procedure should be Where cavitation within the vial is noticeable, as evidenced by rapid
initiated immediately after milling is completed. This is particularly agitation of the powder dispersion, the bottom of the vial could even be at
important if the powder is to be dispersed using the 5-min hand-shake the surface of the tank liquid. Agitation within the vial should be
procedure (see Section 8) where a difference can be seen between noticeable. Where agitation is not evident within the vial, the vial should
be moved until agitation is evident. The vial generally is immersed to a
determinations made in succession on powders having significant amounts
depth where powder dispersion is at or below tank liquid level with the
of 1-μm size powder. This difference, related to the size of the powder, is
vial bottom not closer than ⁄2 in. (about 10 mm) to the bottom of the tank.
greater for fine powders. For all practical purposes, however, two runs can
Immersion is generally not within 1 in. (about 25 mm) from any tank wall.
be made in succession on each milled powder. If more than two runs on
During ultrasonic treatment, a slight tingling feeling at the fingertips,
the same milled powder are desired using the 5-min shake procedure,
where they touch the vial, might be present. Also, while vial and contents
provisions may be taken to lessen (elimination is not possible) the effect
are slightly warmed during treatment, no temperature correction need be
of humidity on the milled powder such as immediate splitting of the
made because of the subsequent dilution in the sedimentation cell.
sample and storage under dry nitrogen or in a desiccator. If the 5-min
ultrasonic procedure is used to disperse the powder for analysis, the milled
10.2.2 Wipe dry or rinse the outside of the vial immediately
powder may be stored for several days without any effect being seen in the
after ultrasonic treatment to prevent ultrasonic tank liquid
distribution results.
contamination in the sedimentation cell.
10.2.3 Quantitatively transfer the powder dispersion into an
10. Dispersion
empty sedimentation cell. Thoroughly rinse the vial, making
10.1 The powder, either as supplied, or laboratory milled in
sure that all the powder is in the cell.
accordance with 9.2, may be dispersed in the sedimentation
medium either by a 5-min ultra
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