There are research on calculating the kinetics of phase transformation or calculating the solid fractions during solidification, using differential scanning calorimetry (DSC).
But I was wondering if it is possible to measure the volume fraction of solid-state phase transformations using this technique.
Yes, it is possible if one knows the enthalpy change for that transformation in pure state. Fraction of the parent phase will proportionally result into the same fraction of that enthalpy change, which DCS measures.
Thanks. As I have understood, Enthalpy of transformation is the area under the peak and is only related to the phase that is forming.
So we can have the Cp of that phase, we can calculate the mass of the phase. right?
But then how to measure the Cp of a pure phase (if it is difficult to have the pure phase)?
Also how do we correlate the phase mass into its total vol.% in the samples? We shall have its density? or is there any easier way?
First two lines of your reply are correct.
Answer to your first question: if you know Cp then it is possible to calculate mass% of phase.
Answer to 2nd question: That is why I emphasized on enthalpy (just the area under the curve during the transformation from a DSC trace) rather than Cp. All you need to have is the numerical value of change in enthalpy for that transformation (when one pure phase is transforming to other pure phase) and your experimental DSC curve (area under the peak).
By the word "fraction", it is always "wt%", to calculate vol% you need density of all the phases.
Hope this helps.
Thanks. I guess I got what you mean. Correct me if I am wrong:
we calculate the enthalpy of formation of the phase using thermodynamics (theoretically) and then measure the energy under the peak from DSC (experimentally) and see how much is the difference in % ...?
A bit confusing though, because if we have a DSC peak for a phase transformation, it shows the enthalpy of formation of that phase; if there is any difference from this value and the theoretical value that we get from thermodynamics, it should be related to errors coming from non-equilibrium conditions...
Am I missing something?
It would be great if you share reference(s) regarding your answer to the 2nd question.
Thanks again
Hello, my opinion is that it is not possible. For this have to be used a X-Ray diffraction for example.
Regards
In a multiphase mixture you also need to do a deconvolution of the peaks to get massfractions.
For calculating phase fraction using DSC, you need to integrate the phase transformation peak by fixing the Ts (transformation start) and Tf (transformation finish) and calculate the area as a function of temperature using origin software or any other. There after divide the area by the mass of sample used for DSC experiment. After getting area perunit mass as function of temperature, divide it by total area of the peak and you will get phase fraction as function of temperature, which you cat fit using KJMA model and any other
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