IFEG   20353
INSTITUTO DE FISICA ENRIQUE GAVIOLA
Unidad Ejecutora - UE
artículos
Título:
Characterization of solid phases and study of transformation kinetics in m-chlorofluorobenzene by 35Cl nuclear quadrupole resonance
Autor/es:
S. PÉREZ; A.E. WOLFENSON
Revista:
SOLID STATE NUCLEAR MAGNETIC RESONANCE
Editorial:
ACADEMIC PRESS INC ELSEVIER SCIENCE
Referencias:
Año: 2012 vol. 41 p. 68 - 73
ISSN:
0926-2040
Resumen:
Polymorphism is of widespread occurrence in the world of molecular
crystals. In this work we present experimental results showing the
existence of four solid phases in m-chlorofluorobenzene. A glass
structure is achieved by quenching the liquid phase at 77 K. This glassy
state crystallizes in a disordered phase at T∼143 K, which in turn transforms to the high-temperature stable phase (phase I) at T∼153 K.
Depending on the thermal history of the sample, a different ordered
phase (phase III) can be obtained. The disorder is attributed to a
molecular orientational disorder. There is no evidence of molecular
reorientation in any phase. A study of the disorder-order phase
transformation kinetics, using nuclear quadrupole resonance, is
presented. The results are analyzed following Cahn's theory. Nucleation
seems to take place at grain boundaries. Growth rates for different
temperatures have been determined.