Thermosalient materials: example of N’-2-propylidene-4-hydroxybenzohydrazide

Popović, Dean (2014) Thermosalient materials: example of N’-2-propylidene-4-hydroxybenzohydrazide. Diploma thesis, Faculty of Science > Department of Physics.

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Abstract

Thermosalient materials, or colloquially commonly called “jumping crystals”, are promising materials for conversion of thermal (or light) energy into mechanical work on the nanoscale. These materials, when heated or cooled, undergo a sudden and sharp polymorphic single crystal to single crystal phase transition. During this transition the crystals experience a change in their shape, as well as in the size of the unit-cell, and this change is so large that it causes them to jump up to a height that is several times bigger than their size. This phenomenon usually happens in several microseconds. It was reported that N’-2-propylidene-4-hydroxybenzohydrazide behaved similarly as the jumping crystals. It was found that this system exhibited three polymorphic modifications (I, II and III), all having the same polar space group Pna21, with the phase transitions I to II and III to II reported as topotactic (single crystal to single crystal). It was also reported that during the irreversible phase transition from I to II, the periodicity along the polar axis underwent a strong compression (approximately 15%); single crystals of the phase I were violently disintegrated into single crystal fragments of the phase II (with jumping), while in the reversible phase transition III to II the periodicity along the polar axis expanded (approximately 14%) and no movement of crystals was observed. Our measurements showed a somewhat different behaviour. During the irreversible phase transition from I to II some of the crystals did indeed disintegrate into smaller fragments, but a large number remained intact and showed a typical jumping crystal behaviour – jumping all around over large distances (several cm). This is typical for other thermosalient materials. Also, during the reversible phase transition II to III (both ways), crystals exhibited the jumping behaviour, but somewhat weaker than during the phase transition I to II. This is in contrast to the statements reported previously and the new model for the thermosalient effect in this system has to be proposed.

Item Type: Thesis (Diploma thesis)
Keywords: thermosalient materials, jumping crystals, thermosalient effect
Supervisor: Skoko, Željko
Date: 15 July 2014
Subjects: NATURAL SCIENCES > Physics
Divisions: Faculty of Science > Department of Physics
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 02 Sep 2014 13:08
Last Modified: 06 Sep 2016 15:28
URI: http://digre.pmf.unizg.hr/id/eprint/2588

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