## 3 Results and Discussion  
The specific heat of the pure carbonate salt eutectic (62 mol % of Li2 CO3 and 38 mol % of K2 CO3) was measured prior to the specific heat measurements of the nanofluids. The specific heat of the pure eutectic was 1.646 [J/g\(\cdot\)K], which exhibits good accordance with the value of 1.6 [J/g\(\cdot\)K] reported by [PERSON] et al. [44]. As shown in Figure 3, the heat-flow curve of the pure eutectic exhibits typical features, such as a linearly increasing specific heat in the solid phase and an almost uniform specific heat in the liquid phase. The specific heat values of the pure salt eutectic measured in this study and the pure salt mixtures obtained from the previous study are presented in Table 1. Additionally, the specific heat of the carbonate salt eutectic-1 wt % GA mixture was measured to examine whether the GA increased the specific heat of the molten salt mixtures. The specific heat of the eutectic-GA mixture was measured to be 1.592 [J/g\(\cdot\)K], which is approximately 3.3% lower than that of the pure eutectic. Thus, the GA is not attributed to the specific heat increase of the molten salt nanofluids. For the nanofluids, the enhancement of the specific heat was calculated using the specific heat values of the pure salt mixtures shown in Table 1.  
Figure 4 shows the variation of the specific heat of the nanofluids with GA of 1 wt % (Group 1) with the changing mole fraction of the two carbonate salts in the base fluid. As observed in Figure 4, the specific heat of the pure salt mixture in the liquid phase drastically increases with the increase of the lithium carbonate around the eutectic composition with the increase of lithium carbonate salt. Regarding the specific heat of the molten salt nanofluids, the increment in the specific heat was measured to be higher in the nanofluids whose composition was far from the eutectic point (62 mol % of Li\({}_{2}\)CO\({}_{3}\)). For instance, the increment of the specific heat for sample 5 (90 mol % of Li\({}_{2}\)CO\({}_{3}\)) was higher than that for sample 4 (80 mol % of Li\({}_{2}\)CO\({}_{3}\)) in both the 0.1 and 1.0 wt % conditions. The enhancement of the specific heat exhibited a similar increment. This feature is clearly indicated by the enhancement graph of Figure 5. The enhancements of the specific heat for the nanofluids with the chemical composition of sample 1 (90:10) were 20.0% and 25.4% for the nanoparticle concentrations of 0.1 and 1.0 wt %, respectively. For the nanofluids with the chemical composition of sample 5 (40:60), the specific heat enhancements were 21.6% and 30.1% for nanoparticle concentrations of 0.1 and 1.0 wt %, respectively. However, the specific heat enhancements for the nanofluids with the chemical compositions of samples 2 and 4 were between 12.2% and 24.8%. The enhancements for salt mixtures 2 and 4 were smaller than those for samples 1 and 5. This distinctive feature is indicated by a V-shaped bar graph with the eutectic composition as the center in Figure 5. According to these results for the specific heat of the molten salt nanofluids, two possible issues are important for understanding the increase of the specific heat of the binary carbonate salt mixtures: the concentration of nanoparticles and the dispersion homogeneity of nanoparticles. Moreover, stability of the enhanced thermal characteristics of the nanofluids has been considered to be a significant issue. For engineering applications, the stability should be examined. In this study, the DSC thermal cycles (specific heat measurements) were repeated 5 times for the same samples to check whether or not the degradation of the specific heat enhanced was arisen. Figure 6 shows the specific heat ratio to the first cycle measurement. In other words, Figure 6 represents the relative change of the specific heat of the molten salt nanofluids to the specific heat measured at the first thermal cycle in DSC.