ASTM B821 – Standard Guide for Liquid Dispersion of Metal Powders and Related Compounds for Particle Size Analysis
Significance and Use
4.1 The method of powder dispersion in a liquid has a significant effect on the results of a particle size distribution analysis. The analysis will show a too-coarse, unstable, or nonrepeatable distribution if the powder has not been dispersed adequately. It is therefore important that parties wishing to compare their analyses use the same dispersion technique.
4.2 This guide provides ways of deriving dispersion techniques for a range of metal powders and compounds. It should be used by all parties performing liquid-dispersed particle size analysis of all of the materials covered by this guide (see 1.1, 1.2, and 4.1).
4.3 Table 1 provides some dispersion procedures that have been found useful and consistent for the particular materials listed there. These are only suggested dispersion procedures; the procedures and dispersion checks of 7.1.2 – 7.1.4, or the more detailed method development procedures of Guide E3340, should still be used to verify adequate dispersion for each particular material and particle size range.
(A)Stated ultrasonic power and duration times are given as an indication only. Specific conditions should be sought for the particular system in question during the method development phase.
(B)Tween 21, chemically known as polyoxyethylene6 sorbitan monolaurate, is manufactured by Croda International PLC, and is available from various chemical suppliers.
(C)Three to five drops Tween 21 in 30 to 50 mL water.
4.4 This guide should be used in the preparation of powders for use in Test Methods B761 and B822 and other procedures that analyze metal powder particle size distributions in liquid-dispersed systems.
1.1 This guide covers the dispersion in liquids of metal powders and related compounds for subsequent use in particle size analysis instruments. This guide describes a general procedure for achieving and determining dispersion; it also lists procedures that have been found useful for certain materials.
1.2 This guide does not include specific procedures for dry dispersion of particulate materials. It only indicates when liquid dispersion is not appropriate and dry dispersion must be utilized (see 220.127.116.11). For guidance on development of methods of dry dispersion, see Guide E3340.
1.3 This guide is limited to metal powders and related metal compounds. However, the general procedure described herein may be used, with caution as to its significance, for other particulate materials, such as ceramics, pigments, minerals, etc.
1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.