Calorimetric Study on Structural Relaxation of Molecular Ground

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A top-loating adiabatic calorimeter has been constructed for the first time. From the test experiments of an empty cell and benzoic acid (standard substance), the precision and accuracy of heat capacity were confirmed to be better that 0.1 % in the temperature region between 12 and 380 K.tri-OMICRON-methyl-beta-cyclodextrin (TMCD), sucrose (SUC), salicin (SAL), phenolphthalein (PP), 1,3,5-tri-alpha-naphthylbenzene (TNB), p-quaterphenyl (p-QP), p-terphenyl (p-TP) and 1,3,5-triphenylbenzene (TPB) were ground with a vibration mill and their abilities of mechanical milling amorphization were investigated by X-ray powder diffraction and differential thermal analysis. It was found that the ability of mechanical milling amorphization is strongly related to the glass forming ability.The heat capacities of the ground amorphous solids (GAS) and liquid-quenched glasses (LQG) of TMCD and TNB were measured with an adiabatic calorimeter in the temperature range between 5 and 380 K.It was found that GAS exhibits larger configurational enthalpy than LQG for both samples, suggesting that the molecular GAS has a structure with large orientational disorder, local strain, and defects.The grinding-time and grinding-temperature dependences of the enthalpy relaxation were investigated using TMCD.It was found that the amorphization process and enthalpy obtaining process are associated with not only the free-energy difference between the liquid and the crystal and the structural relaxation time but also the mechanical properties (e.g.plasticity) of the crystal and the amorphized solid.