No abstract

The thermal expansions of the group IV-VII transition-metal disilicides and Mn15Si26 have been investigated from room temperature to about 1500 K by x-ray powder-diffraction techniques. The results are discussed in relation to the structure of the compounds. Most of the disilicides studied exhibit a high degree of thermal expansion isotropy, exceptions being ZrSi2, HfSi2, and CrSi2. The observed linear thermal expansion coefficients are normally in the range 8–9×10−6 K−1 (298 K) to 11–15×10−6 K−1 (1300 K). The most extreme expansion was exhibited by CrSi2 with a linear expansion coefficient of 22×10−6 K−1 for the a axis at 1300 K.

The structural transformations of the C 70 in benzene, toluene, and hexane solutions were studied. The X-ray powder diffraction experiments made directly on the C 70 solution samples showed structural transformations of similar types for all the tested solvents. It is shown that C 70 in benzene and hexane solution forms solvated phases at room temperature similar to the toluene solvate described before (Agafonov, V.; Ceolin, R.; Andre, D.; De Bruijn, J.; Gonthier-Vassal, A.; Szwarc, H.; Rodier, N.; Dugue, J.; Toscani, S.; Sizaret, P. Y.; Fabre, C.; Greugny, V.; Rassat, A. Chem. Phys. Lett. 1993, 208, 68). Experiments with C 70 crystallized from benzene solutions performed at room temperature resulted in the formation of the orthorhombic solvated phase, while crystals grown at T > 40°C appeared to be a mixture of the pure C 70 hcp phase and the monoclinic solvate phase.

No abstract

No abstract