Analyzing the Distribution of Microencapsulated Organic Phase Change Materials Embedded in a Metallic Matrix

This work aims to mitigate the overdesign of steady state packaging systems by combining an organic phase change material (o-PCM) and a metallic PCM (m-PCM) to create a passive cooling composite for pulse power applications. The organic constituent, melamine microencapsulated paraffin spheres, is manually mixed into a Field's metal (32.5Bi/51In/16.5Sn wt%) matrix. Four concentrations are synthesized containing organic volumetric fractions (VF) of 21.8%, 40.3%, 50.1%, and 61.2%, with a liquid-solid melting temperature near 60 degrees C. Several tools aid in determining the physical arrangement and thermal properties of the prepared PCM composites. A scanning electron microscope (SEM) shows preliminary o-PCM orientations on the composite surface at various magnifications. For interior o-PCM sphere distribution analysis, still images are taken from time-lapse videos created from a micro-computed tomographic (micro-CT) system. Binarization and pixel counting techniques are able to determine effective internal VFs within 3-5% of the prepared bulk VF. Differential scanning calorimetry is employed to determine the phase change onset temperature, heating peak temperature, and latent heat of the PCM composites. This novel PCM fabrication approach decreases the device package size, limits the associated weight, increases the system performance, and minimizes the composite cost.