| dc.contributor.author | Bessonette, Paul William Rupert. | en_US |
| dc.date.accessioned | 2014-10-21T12:37:55Z | |
| dc.date.available | 1998 | |
| dc.date.issued | 1998 | en_US |
| dc.identifier.other | AAINQ36570 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55582 | |
| dc.description | In many solids, the substitution of deuterium for hydrogen causes a change in the polymorphic phase transition temperature. In more extreme cases, however, the deuterated form of a compound undergoes a low-temperature phase transition which is completely absent in the hydrogenated form. These are called deuterium-induced phase transitions. The research work presented in this thesis was focused on the study of a specific example of a deuterium-induced phase transition. A low-temperature phase transition occurs in sodium deuteroxide (NaOD) at a temperature of 153 K which has no analogue in the hydrogenated form, sodium hydroxide (NaOH), at atmospheric pressure. | en_US |
| dc.description | To explain the anomalous low-temperature behaviour of NaOH, residual entropy or frozen-in disorder for NaOH was postulated. This postulate was tested extensively, by studying NaOH using the techniques of adiabatic calorimetry and dielectric relaxation to see if NaOH exhibited any evidence indicating a glassy phase transition, which would be associated with frozen-in disorder. | en_US |
| dc.description | An apparatus was designed and constructed to perform dielectric relaxation measurements on powdered solid samples as a function of temperature and electric field frequency. This apparatus was automated and tested by using it to measure some common ionic salts. No evidence for a glassy phase transition was found in NaOH from the dielectric experiments. Furthermore, calorimetric experiments did not show evidence of unusual relaxation effects that could be attributed to glassy phase behaviour. Therefore, it was concluded that residual entropy does not exist in NaOH. | en_US |
| dc.description | The dielectric measurements of NaOH did reveal a broad anomaly at T ∼ 170 K which was interpreted as a prelude, at atmospheric pressure, to a phase transition which would occur in NaOH at higher pressures. Some of the NaOH dielectric results provided evidence for the possible observation of this high-pressure phase in metastable form. | en_US |
| dc.description | Structural differences between the alkali-metal hydroxides and their corresponding deuterated forms allow the deuterated compounds the potential to form stronger (i.e., shorter) hydrogen bonds due to shorter oxygen-to-oxygen distances in the solid structure. It seems that the slight structural differences between NaOH and NaOD are sufficient to allow a phase transition to occur in NaOD that cannot occur for NaOH. | en_US |
| dc.description | A comparison of the heat capacities of NaOH and NaOD revealed that NaOH has an anomalously high heat capacity at low temperatures. This indicates that NaOH has exclusive access to energy levels that are not available to NaOD. These levels are likely due to quantum-mechanical tunnelling of the hydrogen atoms in NaOH. Tunnelling would help to prevent a phase transition in NaOH, and the entropy removal due to the thermal depopulation of tunnelling levels would also allow it to have zero entropy at a temperature of absolute zero, in accordance with the third law of thermodynamics. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1998. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Chemistry, Inorganic. | en_US |
| dc.subject | Chemistry, Physical. | en_US |
| dc.title | Low-temperature hydrogen-atom ordering in NaOH in relation to the deuterium-induced phase transition in NaOD. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
