Dear Sanjay,

Archimedes Measurements of Porosity

The Archimedes method for determining the density (and hence the porosity) of a material is a classic method that has been used previously for determining the density of materials made via additive manufacturing. While it is relatively simple to perform with commercial instrumentation, samples with surface breaking pores or cracks that allow for water-infiltration may result in erroneous measurements.

For the Archimedes measurements, the measured cylinder density is given by

ρ  = (Ma/Ma-Mw) ρw   (1)

where Ma is the measured mass of the cylinder (average of three independent measurements) measured in air, Mw is the measured mass of the cylinder (average of three independent measurements) measured in water, and ρW is the density of water, which we assume to be 1.0 g/cm3 . While in reality the density of water changes with temperature, it varies by only 2 parts per thousand over the range 15 °C to 25 °C [23]. As such we treat this variation as negligible, especially relative to the other uncertainties in our measurements. For these measurements, we used a commercially available Mettler AT201 measurement system with distilled water, to minimize the presence of air bubbles in the water, at room temperature (roughly 22 °C). The water was in thermal equilibrium with the laboratory air. This system allows for precise mass measurements of small samples in both water and air. Three measurement trials were performed for each cylinder both in air and in water. Some care was taken to ensure that air bubbles were not present on the samples under test, although smaller ones could have been missed. The scale was re-zeroed before each measurement, and the enclosure was shut around the scale to prevent air currents from affecting the measurement. Each measurement result was recorded after the scale had reached equilibrium. 

http://nvlpubs.nist.gov/nistpubs/jres/119/jres.119.019.pdf

Alternatives

Total porosities of the sintered specimens can be determined by Archimedes’ principle,using highly volatile xylol (CH3C6H4CH3) with a density of 0.861 g/cm3and a Sartorius precision balance (model CP2245-OCE) equipped with a density determination kit. Fractions of open and closed porosity can be determined by weight measurements prior to and after dipping the samples in xylol for 36 h. Pore size distribution of alloy samples sintered at highest and lowest temperatures can be determined using Quantachrome mercury porosimetry (0-50 psi, at 140◦).

https://www.google.ps/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwit1MKtyu7LAhUMSRoKHcV2C1MQIAgcMAA&url=http%3A%2F%2Fwebcache.googleusercontent.com%2Fsearch%3Fq%3Dcache%3Aok_zlAhDpDAJ%3Adergipark.ulakbim.gov.tr%2Ftbtkengineering%2Farticle%2Fdownload%2F5000022870%2F5000023107%2B%26cd%3D1%26hl%3Den%26ct%3Dclnk%26gl%3Dps&usg=AFQjCNGlmIs55E5F1JBS3oQaBgWqT2YU4A&sig2=8mqOt0D7YBE92cIhx6GI2g&bvm=bv.118443451,d.d2s

http://www.gkn.com/hoeganaes/media/Tech%20Library/125.%20Effect%20of%20Density%20on%20the%20Microstructure%20and%20Mechanical%20Behavior%20of%20Powder%20Metallurgy%20Fe-Mo-Ni%20Steels.pdf

Hoping this will be helpful,

Rafik

Porosity can be calculated from density measurements. For ceramic materials, it's advice able to determine the relative density of the material by employing the popular Archimedes principle to determine the experimental density while rietveld analysis from xrd data of the ceramic materials is analysed as the theoretical density hence, relative density = experimental density/theoretical density. Porosity = 1- relative density. 

Hope the information is useful.

Easiest way to calculate the porosity is to find it from XRD data.

Porosity = 1 - (bulk density / x-ray density)

Hello

   You can calculate the porosity percentage through Image analysis software according to ASTM E2109 Standard. You should take images (optical microscopy) at various positions of the sample. Further ,sample must be polished.

Best regards

Amine

Make a small solid sample (non porous) of the same material composition.You may skip this if you know the density of the non porous material.  This will give you the weight of the solid. Weigh(1) the porous sample on balance having accuracy of  0.1  micrograms. Soak the porous material in water for half hour in a flask, if possible apply partial vacuum to the flask. This ensures that the entrapped air is removed from the sample. Take soaked sample weight in air (2) . (2) has to be more than (1) as all pores are now filled with water (assuming that the internal pores are connected to the surface pores) From (2) - (1) you will get weight of water absorbed  . Note the water temperature, find density of water at that temperature and then calculate the volume of water (porous volume).

Dear All,

I have measured density of my PM samples using archimedes principal but how to relate these to porosity.

Dear Sanjay,

Porosity = Particle density - Bulk density/Particle density - Fluid density

Rafik