An investigation of density determination methods for porous materials, small samples and particulates

Three new density measurement techniques have been devised and evaluated for the measurement of non-standard objects, namely porous material samples, small solid samples, powders and particulates. Hydrostatic weighing has traditionally been used to determine the density of solid artefacts. This method is not, however, suitable for porous objects since they will adsorb water making weighing in water unstable and possibly detrimental to the material samples. A method, weighing the artefacts in inert gas, has been developed for this application. The density determination of small solid artefacts cannot be achieved by conventional hydrostatic weighing techniques due to limits on the accuracy with which the weight-in-water can be determined. A density gradient column method for such measurements, delivering very low uncertainties, has been developed and evaluated. A liquid pyknometry method has also been investigated as an alternative to traditional helium and mercury pyknometry. The technique offers improved accuracy and a precise determination of thermal coefficient of the sample under test.

► Measurement of the density of porous materials to a relative uncertainty of better than 1 in 104.
► Density gradient measurements with a target uncertainty of better than 1 in 106.
► Liquid pyknometry used to measure density and thermal coefficient of powders.