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8.1 Frequently Asked Questions
What is porosity (percentage of void) of powder bed in a Fisher Scientific Sub Sieve Sizer?
-There are spaces among particles in powder bed, as a result the space 1cm3 of true density particles actually occupies is more than 1cm3. If it is 1.25cm3, then the filling degree is 1/1.25=0.8 and therefore the powder bed porosity is 1-0.80=0.20.
What is porosity (percentage of void) of powder bed?
The true density mentioned above is the density of the material, which makes up the powder. If the sample is a quartz powder, the true density is that of solid quartz and is equal to 2.65gm/cm3. By weighing out a powdered sample equal to 2.65 grams, the solid particles will be one cm3 in actual volume but will occupy more than one cm3 in space, depending upon how much the sample is compacted. This latter volume is generally designated as the apparent volume of the sample, as contrasted to true volume. The apparent density of the packed sample (the weight of one cm3 of packed powder) will obviously be less than the true density of the material from which the powder was ground and will depend on the degree of packing.
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