Thermal behavior of Et4N10BH4 and (Et4N)2B20H18

The thermal behavior and crystal transformation processes from I to II and from II to I for Et4N10BH4 and from I′ to II′ and from II′ to I′ for (Et4N)2B20H18 are determined by DSC. The results show that their crystal transformation processes are reversible. The values of ΔHcr and ΔScr are 101.0 J g−1 and 38.68 J mol−1 k−1 for Et4N10BH4 and 148.4 J g−1 and 182.7 J mol−1 k−1 for (Et4N)2B20H18, respectively. The apparent activation energy (E) and pre-exponential constant (A) are 213.0 kJ mol−1 and 1017.7 s−1 for Et4N10BH4, and E1=105.4 kJ mol−1, A1=109.1 s−1, E2=180.2 kJ mol−1, A2=1015 s−1 for two exothermic processes of (Et4N)2B20H18, respectively.