Multilayer graphene–paraffin composites with different contents of graphene (0–10 wt.%) were prepared using an ultra-high shear mixer. The aim is to improve the heat transfer in paraffin wax, which will lead to more-efficient thermal buffering in electronic applications. The multi-layer graphenes obtained by supercritical fluid exfoliation of graphite in alcohol were investigated by Raman spectroscopy, scanning electron microscopy and atomic force microscopy. Interesting morphological features were found to be related to the intercalation of paraffins between the multilayer graphene flakes. Thermal properties were also investigated in terms of phase change transition temperatures, latent heat by differential scanning calorimetry and thermal conductivity. It was found that the addition of graphene resulted in a slight decrease in energy storage capacity but a 150% improvement in thermal conductivity at the highest graphene loading level. This phase-change material is then used as a thermal heat sink for an embedded electronic processor. The temperature of the processor during the execution of a pre-defined programme was used as a performance indicator. The use of materials with multilayer graphene contents of more than 5 wt.% was found to reduce the processor operating temperature by up to 20%. This indicates that the use of such composite materials can significantly improve the performance of processors.

This paper presents an experimental approach to maximizing the voltage generated by Na_xCoO₂ and improving the overall efficiency of the p-type thermoelectric leg by doping with Na up to x = 0.88. Two samples with different geometries were tested, each measured with and without an additional magnetic field applied in the direction of the temperature gradient. The properties of sodium cobaltite in response to hydration were explored, at temperatures between 300$\mathrm{a}\mathrm{n}\mathrm{d}$380 K. Water injection boosted the current and power up to 75–100 µW at a temperature of 350–360 K. This power boost can be attributed to an electron-ion fluid flow pattern maintained by the longitudinal thermomagnetic effect and by water molecules forming hydrogen bonds with oxygen atoms in the CoO₂ layers, inside the material. An electronic circuit was designed to boost the voltage to the desired level, for three or more sodium cobaltite samples mounted in parallel, and to store the energy in a supercapacitor. The output voltage and resistivity change of sodium cobaltite samples can be readily used as a humidity and temperature-sensing element in a transducer when paired with an appropriate electronic conditioning scheme.