I have an array of hydroxyapatite powders which exhibit slightly varying compositions. I'm interested in measuring how these small compositional changes affect the mechanics of the powders. More specifically I would like to measure the elastic modulus. Does anyone have recommendations as to the best techniques for obtaining the elastic modulus of a powder?
Powder? May be I do not understand well, but elastic modulus is meaningful concept only in solids. Hence you should scale down to obtain dimensions in which your granules or grains can be considered as continuum… Nanoindentaion or microindetation could be useful, but probably crumbing could be a problem.
We are trying to do bending tests on individual crystals but due to their small size (>1 um) this has been quite difficult to do. We were hoping to use a confined compression system in which we could take into account reorientation and porosity but have had difficulties there as well. This attached publication may help to explain what I'm looking for.
Article On the Elastic Modulus of Powders
Do you want deternine elastic modulus of single grane or a system of granes in whole?
Single grain would be ideal, but even with AFM testing these grains are often too small (30 nm x 30 nm x 2 nm). Therefore we would settle for knowing the modulus of the systems of grains in whole.
Very small grains.
For larger grains it is possible try the following
Produce composite grain in matrix, composite for which there exists formula for computation of effective constants. Measure composite effective constants. Than, inversing the formula, compute constants of grains
I did measure the young modulus of rust powder. For that, we used oedometric test, ultrasonic measurements, micro-macro theories (Hashin Strickman bounds) and Hertz' contact theory... However, please consider first that the stress to strain relationship of a powder is non linear from the very beginning of the curve ! This can be understood by regarding the non linear equations of the Hertz theory.
For more details see our paper : Mechanical properties of an iron oxide formed by corrosion in reinforced concrete structures, available on the web.
Do not hesitate to contact me for further information.
I recently measured the bulk modulus and estimated the Young's modulus of hydroxyapatite from dentine by using a combination of high-pressure and x-ray diffraction. This hydrostatic pressure experiment enabled to derive lattice parameters of the unit cell. I guess that similar experiment can be done on powder.
http://www.sciencedirect.com/science/article/pii/S1751616115001976
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