Hi
I'm going to put a nanomaterial (Mg(OH)2) with two types of particle size (different particle sizes) which have been synthesized under the same conditions under thermal analysis (DTA-TGA). Are different thermal behavior of nanoparticles with each other?
Dear Sadegh Yousefi:
Than the higher the temperature, that the greater the rate of diffusion of nanoparticles. An approximate dependence of the diffusion coefficient D on temperature in liquids can often be found using Stokes–Einstein equation. D is often used to calculate the hydrodynamic radius of a sphere nanoparticles through the Stokes–Einstein equation.
Best regards.
If yoou are interested in the thermal degradation characteristics, you can expect differences. I am a bit familiar with polymer TGA. In the case of epoxy resins e.g. there is a big difference between the TGA behavior of bulk and powder samples. I did not investigate systematically the particle size dependence but as most decomposition processes are diffusion controlled, a size dependence is expected.
if the nanoparticles are unfunctionalized act as filler and depending on the size, shape and dispersion modify the curing of the material and its thermal degradation . You should realize studies by TEM or Light scattering to determine the dispersion and size of the nanoparticles.
Dear Sadegh Yousefi,
We investigated DSC curve of serpentine and compared it with brucite (Mg(OH)2) and magnesite, all in the same mine. The endothermic or dehydroxylation reaction of the serpentine with 1mm particle size, was occured at 663oC and as the particle size decreased the endothermic peak temperature decreased to a minimum of 641oC, when it was ground to 250 micron. Decreasing particle size below 250 micron did not decrease the endothermic peak temperature any further. The brucite had the similar behavior in endothermic reactions but it is not as large as those noted for the serpentine. Thermal reaction of brucite at 350–450 °C: Mg(OH)2 to MgO+H2O.
Based on above description, we expect that particle size change in nano-scale sizes, don't affect the endothermic or dehydroxylation reaction of the brucite, considerably. However, the effect of this particle size change on sintering and recrystallization, is a different manner that occurs in higher temperatures in your DTA-TGA pattern.
Dear Sadegh Yousefi
Al salamu alikom
Of course, The particles size affect the thermal behavior of nanoparticles. There is a closed relation between the behaviour of the investigated sample and its temperature. Raising the temperature of the sample affect on the crystallite sizes and in turn affect the particle sizes of samples.
Good luck
The particle shape and size are likely to affect the TGA behaviour, and this affect is due the (different) interface interactions between the dispersed nanopartcles and the (polymer) matrix in which they are dispersed. Two different shaped particles will have different surface/interface areas.
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