We report on the application of a static (dc) electric field in the plume region during the pulsed Nd doped yttrium aluminum garnet laser deposition (PLD) of tetrahedral amorphous carbon (ta-C) films in vacuum ambient $(\text{pressure}={10}^{-4}–{10}^{-3}\mathrm{Pa})$ , where the working pressure is exclusively due to ablation vapor. This approach is strikingly different from the plasma- or ion-beam-assisted PLD because the mean free path at this pressure is by far longer than the target to substrate distance. Thus, the electric field interacts with individual ionized species invoking ion acceleration and gas-phase reactions among different ionized species. These phenomena are clearly dependent on the laser wavelength (first, second, or third harmonic, $\lambda =1064$ , 532, and $355\mathrm{nm}$ , respectively) used for the ablation. We found that the application of the electric field causes surface smoothing (the roughness decreases from about $1\text{to}0.4\mathrm{nm}$ ) and faster deposition rate (from about $2\text{to}7\mathrm{nm}∕\min$ ) for the second and third harmonics. In addition, the phenomena are less intense in the case of the first harmonic due to the low concentration of ionized species in the plume. In addition, in the case of PLD using $\lambda =532\mathrm{nm}$ , the electric field improves the film’s density (from $2.60\text{to}2.95\mathrm{g}∕{\mathrm{cm}}^3$ ). The correlations found are discussed in terms of the ablated species and the deposition mechanisms of the ta-C.

We report results concerning the functionalization of graphene-based nanoplatelets for improving the thermal energy storage capacity of commonly used phase change materials (PCMs). The goal of this study was to enhance the low thermal conductivity of the PCMs, while preserving their specific and latent heats. We focused on wax-based PCMs, and we tested several types of graphene nanoparticles (GNPs) at a set of different concentrations. Both the size and shape of the GNPs were found to be important factors affecting the PCM’s thermal properties. These were evaluated using differential scanning calorimetry measurements and a modified enthalpy-based water bath method. We found that a small addition of GNPs (1% weight) with high aspect ratio is sufficient to double the thermal conductivity of several widely used PCMs. Our results suggest a simple and efficient procedure for improving the thermal properties of PCMs used in thermal energy storage applications.