Characteristics of the binary faceted eutectic: benzoic acid - salicylic acid system

• Published in: Crystal research and technology (1979) 2009-03, Vol.44 (3), p.258-268
• Main Authors: Sharma, B. L., Tandon, S., Gupta, S.
• Format: Article
• Language: English
• Subjects: anisotropic growth; anisotropic properties; mechanical alloying
• ISSN: 0232-1300; 1521-4079
• DOI: 10.1002/crat.200800034

The consistent symmetry relations computed from the heterogeneous nucleation data of the non‐ideal benzoic acid – salicylic acid eutectic system verifies the validity of nucleation theory. The kinetics of crystal growth from the molten state of the system follows the dislocation mechanism. Anomalous behaviour of both viscosity and activation energy for the eutectic melt confirms the essence of specific interactions animating molecular clusters rich in predominating eutectic phase. Micromorphology of the system obeys the Hunt‐Jackson model. The plot between a mechanical property and variable anisotropic growth velocity for the eutectic composite evidentially complies with the Weibull probability distribution curve. The curve is perused with two cut‐off points corresponding to a lower strength limit in the slow and fast growth regions and an upper strength limit in the moderate growth region. The latter aspect reveals the theoretical strength of the eutectic crystallites. The strength‐growth relationship explicated thereby is linear, optimum and linear respectively in the slow, moderate and fast growth regions of solidification. The moderate anisotropic growth (∼2.96 X 10‐7m3s‐1) is of greater interest by virtue of its attribute to unifying and organizing the crystallites parallel to each other in the growth direction. The eutectic composite material obtained by this process attains remarkable superiority in the mechanical properties over its isotropic growth in an ice bath (∼273 K), and its constituent phases. The co‐relation between excess thermodynamic functions indeed predicting the liquidus character and the microstructural parameters inevitably structuring the morphology is presented. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)