Thermal behavior of Et4N10BH4 and (Et4N)2B20H18

The thermal behavior and crystal transformation processes from I to II and from II to I for Et 4 N 10 BH 4 and from I′ to II′ and from II′ to I′ for (Et 4 N) 2 B 20 H 18 are determined by DSC. The results show that their crystal transformation processes are reversible. The values of Δ H cr and Δ S cr are 101.0 J g −1 and 38.68 J mol −1 k −1 for Et 4 N 10 BH 4 and 148.4 J g −1 and 182.7 J mol −1 k −1 for (Et 4 N) 2 B 20 H 18 , respectively. The apparent activation energy ( E ) and pre-exponential constant ( A ) are 213.0 kJ mol −1 and 10 17.7 s −1 for Et 4 N 10 BH 4 , and E 1 =105.4 kJ mol −1 , A 1 =10 9.1 s −1 , E 2 =180.2 kJ mol −1 , A 2 =10 15 s −1 for two exothermic processes of (Et 4 N) 2 B 20 H 18 , respectively.