Abstract: It has been found that the rate constant of thermal decomposition for various crystals of bis(trinitroethyl-N-nitro) ethane (BTNE) is quite different and, in effect, this difference in reactivity depends upon the process of recrystallization of the crystals. In this paper the crystal properties of BTNE have been investigated with such techniques as differential scanning calorimetry (DSC), X-ray powder diffraction and electronic scanning microscope (SEM). Each crystal modification shows a characteristic X-ray diffraction diagram and the transformation of one modification into another causes an endothermic peak on the curve of DSC. However, the DSC curves show that before the appearence of exothermic peak of de-composition the endothermic peak was not found for all samples of BTNE. The results of X-ray diffraction study of BTNE show an identical diffraction diagram. It demonstrates that the crystal modifications of the samples of BTNE are same.
The pictures taken with SEM for crystals of BTNE show fairly different crystal form and surface dislocations. In Fig.2, 3, 4, three typical SEM pictures of BTNE are illustrated. Fig.2 is a picture of BT-5. At a magnification of 6000X the crystal size of BT-5 is quite small, the crystal form is rectangular and rather tidy, and the surface of crystals is rather smooth. Fig.3 is a picture of BT-6. On the surface of crystal BT-6 many streak-form dislocations exist. There are distinct differences when compared with the surface of BT-5. Fig.4 is a picture of BT-3. The crystals of BT-3 look like brokendecaying pieces of wooden logs and on the end of crystal appear a lot of dislocations. Comparing the crystal form and dislocation with the corresponding curves of DSC, it has been seen that the crystals of BTNE having a smooth surface decompose slowly; on the contrry, crystals with rough surfaces dislocation decompose more quickly. In Table 1 the comparison of crystal properties with rate constant of thermal decomposition (at 120 ℃) is demonstrated.
It appears that the factors influencing the reactivity of various crystals of BTNE are the existence and degree of surface dislocation. From a view of solid reaction, the reaction of thermal decomposition for crystalline BTNE begins on the inter- or intrasurfaces. Reaction centres appear more readily at the places of surface dislocations. This means that crystals with more disloctions decompose quite easily and will demonstrate high rate constant of reaction. With a control over the recry-stllizing operation one can prepare BTNE crystals possessing various reactivities. Such peculiarities of crystalline BTNE as here descri bed seem to be worthy of further study.