Some phase transformation phenomena in solids and liquids
Some phase transformation phenomena in solids and liquids
The frequency spectrum of the polarised light scattered from.. o-terphenyl, dl-camphene and a solution of pyridine-water ( 2 moles of pyridine in 8 moles of water) was investigated. This spectrum was analysed at high resolution,using a piezoelectric scanned Fabry-Perot interferometer. The results of this analysis allowed the direct measurements of the acoustical parameters below and above a 'critical'- tempera ture of the systems: the glass formation temperature in o-terphenyl; the transition temperature from the plastic crystalline phase to the liquid,in dl-camphene and the 'closeness to phase senaration',in the 2pyridine/8water solution.The results were related to the actual nature of the structural changes undergone by the systems, as the 'critical' temperature is approached.The frequency spectrum of the depolarised light scattered by dl-camphene, dl-bornyl chloride,dl-borneol,dl-camphor,liquid pyridine and some pyridine water solutions was also investigated, using the same technique. The entire observed spectrum was found to be fitted by a single Lorentzian plus a broad background. The origin of this spectrum was attributed to molecular reorientation of the permanently anisotropic molecules of the systems. The temperature dependence of the relaxation times for this reorientation in the plastic crystalline solids was found-to obey an Arrhenius law. On this basis,the activation energies associated with the molecular reorientational process were deduced. The relationship between these energies reflects the effect of the intermolecular interactions in the reorientation, being: NH (dl-borneol) > AH (dl-camphor) > AH.(dl-bornyl'chloride) >4H (dl-camphene)'. For pure pyridine. and pyridine-water solutions,the temperature dependence of the reorientation relaxation times still obeys an Arrhenius law. Their concentration dependence follows the concentration dependence of the viscosity,as predicted 'by the Debye relation.The comparison between the relaxation times obtained by dielectric and light scattering measurements showed, that in the systems studied the molecules reorient performing angled jumps. A marked change in the hypersonic parameters was observed for the system 2pyridine/8water,around 70°C,i.e.,in the' closeness to phase separation'. However,noanomalous change was detected in the reorientation of the pyridine molecule for the system,at the same temperatures.
University of Southampton
Amorim da costa, Antonio Marinho
1976
Amorim da costa, Antonio Marinho
Amorim da costa, Antonio Marinho
(1976)
Some phase transformation phenomena in solids and liquids.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The frequency spectrum of the polarised light scattered from.. o-terphenyl, dl-camphene and a solution of pyridine-water ( 2 moles of pyridine in 8 moles of water) was investigated. This spectrum was analysed at high resolution,using a piezoelectric scanned Fabry-Perot interferometer. The results of this analysis allowed the direct measurements of the acoustical parameters below and above a 'critical'- tempera ture of the systems: the glass formation temperature in o-terphenyl; the transition temperature from the plastic crystalline phase to the liquid,in dl-camphene and the 'closeness to phase senaration',in the 2pyridine/8water solution.The results were related to the actual nature of the structural changes undergone by the systems, as the 'critical' temperature is approached.The frequency spectrum of the depolarised light scattered by dl-camphene, dl-bornyl chloride,dl-borneol,dl-camphor,liquid pyridine and some pyridine water solutions was also investigated, using the same technique. The entire observed spectrum was found to be fitted by a single Lorentzian plus a broad background. The origin of this spectrum was attributed to molecular reorientation of the permanently anisotropic molecules of the systems. The temperature dependence of the relaxation times for this reorientation in the plastic crystalline solids was found-to obey an Arrhenius law. On this basis,the activation energies associated with the molecular reorientational process were deduced. The relationship between these energies reflects the effect of the intermolecular interactions in the reorientation, being: NH (dl-borneol) > AH (dl-camphor) > AH.(dl-bornyl'chloride) >4H (dl-camphene)'. For pure pyridine. and pyridine-water solutions,the temperature dependence of the reorientation relaxation times still obeys an Arrhenius law. Their concentration dependence follows the concentration dependence of the viscosity,as predicted 'by the Debye relation.The comparison between the relaxation times obtained by dielectric and light scattering measurements showed, that in the systems studied the molecules reorient performing angled jumps. A marked change in the hypersonic parameters was observed for the system 2pyridine/8water,around 70°C,i.e.,in the' closeness to phase separation'. However,noanomalous change was detected in the reorientation of the pyridine molecule for the system,at the same temperatures.
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Published date: 1976
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Local EPrints ID: 458339
URI: http://eprints.soton.ac.uk/id/eprint/458339
PURE UUID: 531212c2-ac50-451a-a4e8-c9f8429e1846
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Date deposited: 04 Jul 2022 16:46
Last modified: 04 Jul 2022 16:46
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Author:
Antonio Marinho Amorim da costa
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