Phase Change Material Particles and Their Application in Heat Transfer Fluids - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 452

Fig. 2 a SEM image of the
as-produced paraffin
microcapsules with
melamine-formaldehyde
shell. b TEM image of the
melamine-formaldehyde
shell of a microcapsule [ 28 ]
Figure 2 a shows the SEM image of the as-produced microcapsule comprising
paraffin core and melamine-formaldehyde shell. It can be found that the micro-
capsules are shaped spherically, with their sizes in about 5-15 microns. The
surface of the microcapsules is relatively smooth, with small concaves on the
surface of some particles, which are caused by contraction during the temperature
drop from the experimental temperature to room temperature. Figure 2 b shows the
core-shell structure of a microcapsule particle, in which the melamine-formal-
dehyde shell is uniform in thickness of about 110 nm.
3.3 Phase Change Behavior of Paraffin-Polymer
Microcapsules
Figure 3 shows the cyclic DSC heating and cooling curves for the paraffin-
polymer microcapsules and the bulk paraffin. The latent heat of the microcapsules