Well, now I could only try to explain with the images on the poster, as seen in Figure 2, XRD and Raman allowed us to identify the phase that is being talked about, now in Figure 3. It can be seen this phase is stable up to 350 ° C. However, there are more results where this phase has been subjected to more than 200 hours at a temperature of 250 ° C without significant changes in its properties such as solar absorption, for reasons of space they could not be put on the poster.
And answering the question that if the experiments can stabilize the phase we are talking about, I will answer that a temperature of 400 ° C was used and the oxygen was not controlled, it was not allowed to oxidize completely, and how it is known that the way to stabilize a phase is by decreasing the enthalpy or increasing the entropy, the deposition time was controlled to increase the entropy in this way, the time in which the vanadium precursor was deposited allowed the appearance of other phases that can be observed in the same XRD and refinement, thus different phases of the vanadium compound that are joined in this way increase the entropy which decreases the Gibbs free energy and stabilizes the phase. We would like to be able to share more about these issues, you could write to us at these addresses, darwin.hincapie@cinvestav.edu.mx
Yes, there are measurements of sheet resistance, if the Figure is observed, two identified phases appear, the increase in temperature changes phase irreversibly to VO2-B, however this phase that appears after 400 ° C changes color and it is observed in Figure 4 how the lattice behaves and how this behavior is reversible, the measurements for all cases vary precisely due to the variation in temperature, however in this poster we wanted to show the possibility of being used as a solar absorber due to because the VO2-B phase presents high absorbance values.
We would like to be able to share more about these issues, you could write to us at these addresses, darwin.hincapie@cinvestav.edu.mx
Yes, it is expected to design nanoparticles for this material and increase the absorption power through localized plasmonic resonance and then use it as a spectrally selective solar absorber, this in terms of the VO2-B phase. For the phase that appears at 400 °C, there are many interests due to the reversible behavior that occurs.
I'll leave a video on my channel, so you can observe the thermochromic behavior.
Comments
However, there are more results where this phase has been subjected to more than 200 hours at a temperature of 250 ° C without significant changes in its properties such as solar absorption, for reasons of space they could not be put on the poster.
And answering the question that if the experiments can stabilize the phase we are talking about, I will answer that a temperature of 400 ° C was used and the oxygen was not controlled, it was not allowed to oxidize completely, and how it is known that the way to stabilize a phase is by decreasing the enthalpy or increasing the entropy, the deposition time was controlled to increase the entropy in this way, the time in which the vanadium precursor was deposited allowed the appearance of other phases that can be observed in the same XRD and refinement, thus different phases of the vanadium compound that are joined in this way increase the entropy which decreases the Gibbs free energy and stabilizes the phase.
We would like to be able to share more about these issues, you could write to us at these addresses, darwin.hincapie@cinvestav.edu.mx
We would like to be able to share more about these issues, you could write to us at these addresses, darwin.hincapie@cinvestav.edu.mx
For the phase that appears at 400 °C, there are many interests due to the reversible behavior that occurs.
I'll leave a video on my channel, so you can observe the thermochromic behavior.
https://www.youtube.com/watch?v=a7ODB0zzI8k&feature=youtu.be