## 3 Results and Discussion
### Characterization and Properties of Hybrid Foams ss-CRMFoams@PCMs
#### 3.2.1. Leaching Tests and Thermal Properties
paraffins was determined. The results in this case indicated that the sample immersed in octadecane showed no leakage onto the filter paper (Figure 7d-right), while a small quantity of RT18 HC bleached from the porous matrix (Figure 7d-left). Against this background, the paraffin was effectively entrapped into the porous matrices, displaying an efficient material for thermal energy storage and EMI shielding applications. Figure 8 shows the mid-IR spectra of ss-CRMFoam@RT18, ss-CRMFoam@OD, and that of CRMFoam-2.5. The infrared spectrum of CRMFoam-2.5 exhibited several bands, which can be attributed to vibrations of metal-oxygen bonds of crystalline phases of gehlenite, tricalcium aluminate and CaTiO\({}_{3}\) perovskite. Specifically, the absorption band at 560 cm\({}^{-1}\) can be assigned to Ti-O stretching and the band at 435 cm\({}^{-1}\) to the Ti-O-Ti bending vibrations, respectively [61, 62]. Furthermore, absorption bands centered at 1017 cm\({}^{-1}\), 975 cm\({}^{-1}\) could be assigned to the asymmetric stretching vibrations of Si-O-Si and Si-O-Al groups of gehlenite (Ca\({}_{2}\)Al[AlSiO\({}_{7}\)]) [63]. The absorption peaks observed in the frequency range 920-800 cm\({}^{-1}\) and below 500 cm\({}^{-1}\) can be attributed to AlO\({}_{4}\) tetrahedral and AlO\({}_{6}\) octahedral groups of tricalcium aluminate (3 CaO Al\({}_{2}\)O\({}_{3}\) or C\({}_{3}\)A) [64, 65]. On the other hand, the absorption maximum near 650 cm\({}^{-1}\) could be assigned to oxidized iron carbide phases, whereas the broad absorption is around at 3450 cm\({}^{-1}\) and the weak band at 1630 cm\({}^{-1}\), due to vibrations of adsorbed water molecules on KBr or the sample. Figure 8: FT-IR spectra of CRMFoam-2.5 and ss-CRMFoam-2.5@OD, ss-CRMFoam-2.5@RT18 hybrids. Figure 7: Leaching tests of the produced hybrids. (**a**) ss-CRMFoam-2.5@PCMs before the remain at 30 \({}^{\circ}\)C for 8 h and (**b**) after the leaching test, (**c**) ss-CRMFoam-2.5@PCMs before the remain at 80 \({}^{\circ}\)C for 72 h and (**d**) after the leaching test (OD: Octadecane, RT18: RT18 HC). The incorporation of PCMs into the open cell structure of CRMFoam-2.5 dramatically changed its infrared spectrum. More specifically, the spectra of ss-CRMFoam@RT18, ss-CRMFoam were dominated by the very strong C-H absorption bands of organic PCMs (octadecane and RTH18 HC), which absorbs near 2900 cm\({}^{-1}\), 1460 cm\({}^{-1}\) and 720 cm\({}^{-1}\). Peaks observed at 2957 cm\({}^{-1}\) and at 2870 cm\({}^{-1}\) were attributed to the asymmetric and symmetric stretching vibrations of methyl (CH\({}_{3}\)) functional groups, whereas these at 2926 cm\({}^{-1}\) and 2851 cm\({}^{-1}\) were attributed to the asymmetric and symmetric stretching vibrations of methylene (CH\({}_{2}\)) groups, respectively [66]. In addition, the absorption peak centered at 1471 cm\({}^{-1}\) was attributed to the deformation vibration of methyl and methylene groups, and the peak at 720 cm\({}^{-1}\) to rocking vibration of methylene groups as well. The absorption bands of CRMFoam-2.5 were not observed, since they are covered by the strong absorption peaks of PCMs. On the other hand, the non-existence of any features in the infrared spectra of ss-CRMFoam@RT18 and ss-CRMFoam@OD samples, indicated that PCMs are physically stable into the porous of the CRMFoams and no chemical bonds between PCMs and foam matrices were formed. The phase transition properties of PCMs, n-octadecane, and RT18 HC were studied using their DSC thermographs. Figure 9 shows the melting-freezing temperatures (T\({}_{\text{m}}\), T\({}_{\text{s}}\)) and the corresponding enthalpies (\(\Delta\)H\({}_{\text{m}}\), \(\Delta\)H\({}_{\text{s}}\)) for the two PCMs. As shown in that figure, the pure n-octadecane melts at 20.7 \({}^{\circ}\)C and freezes at 28.9 \({}^{\circ}\)C, while RTH18 HC melts at 22.2 \({}^{\circ}\)C and freezes at 11.5 \({}^{\circ}\)C. Both the exothermic and endothermic peaks of two PCMs, were asymmetric, implying the existence of more than one crystalline phase.