ASTM B430-97 pdf free.Standard Test Method for Particle Size Distribution of Refractory Metal Powders and Related Compounds by Turbidimetry.
Fill the sedimentation cell to the proper height (seeNote 3).Adjustment of the final liquid level may be done byusing an eye-dropper filled with sedimentation medium.Close the cell and redisperse the powder in thesedimentation medium by holding it at the top and the bottomand turning it upside down and shaking it for approximately 5 to 10 s to remove any powder that has settled to the bottom.Then give the cell 1 ito 2-min second shake (not quite asvigorous as described in 10.3.2) ending with a gentle end-over-end complete 360° facewise rotation that allows the air bubblecontained in the cell to “wipe”both faces for approximately 10s to rehomogenize the contents.Continue this facewise rotationuntil the cell is placed in the instrument. During this time,visually check the contents of the cell for uniformity ofdispersion and recheck the liquid level.Proceed immediately to step 11.1.The 5-min handshake dispersion procedure is asfollows:Fill the sedimentation cell with sedimentation medium to approximately 1 to 2 mm below the graduated line thatsignifies a 25-mm height of fall.Transfer the weighed sample into the sedimentationcell. Close the cell with a cover and, holding it at the top andbottom between the forefingers and the thumb，shake vigor-ously for 4/2 to 4/4 min. Shake the cell by moving it in an arcof 12 to 15 in. (305 to 380 mm) in length, back and forthapproximately one cycle per second. The sedimentation me-dium movement is distinctly heard as the cell is shaken. Afterthe vigorous shake, remove the cover from the cell and adjustthe liquid level to the graduated line using an eye dropper filledwith sedimentation medium.
10.3.3 Continue by performing steps listed in 10.2.5 and10.2.6 except to eliminate 1 / to 2-min second shake.
During the last 2 to 10 s of the gentle shake, start thechart paper motor，recheck the reference light transmissionvalue (see 7.3), adjusting the instrument accordingly, and movethe cell carriage to block completely the light transmission.The reading of the millivolt recorder or microammeter changesfrom 100 to 0 % transmission. As soon as the transmission is0 %,cautiously drop (Note 12) the cell into the carriage, andthen immediately position in the light path. Exercise care toposition the cell vertically (top to bottom) in the carriage beforemoving it into the light path and that the cell carriage isrecentered before starting the run. As the powder settles,record the light transmissionvalues either manually at the appropriate times determined in8.1,or continuously through the use of the potentiometer andmillivolt recorder. If a recorder is used,read the light trans-mission for the appropriate times from the graph paper aftersedimentation is complete.ASTM B430 pdf download.