Underafkølet Sucrose: Supercooled Sugar

Lisa Anita Roed, Heidi Lundgaard Sørensen, Rasmus Saldern Antonsen & Jon Tofteskov

Studenteropgave: Semesterprojekt

Abstrakt

Abstract: The purpose of this rapport is to investigate the flow-properties of supercooled liquids in the proximity of the glasstransition temperature. Through experiments we have tested the hypothesis that supercooled liquids exhibit flow as a Newtonian liquid, by constructing a fitting model and deploying Poiseuille’s law to the latter. As reference to our results, calorimetric and dielectric measurements were conducted on supercooled sucrose. None of these results proved to be of any use, wherefore we do not have any references to the values of viscosity that were based on our experiments and calculated via Poiseuille’s law. Furthermore it became apparent during the course of the project that sucrose is not a suitable substitute for a supercooled liquid, as the thermo-history of the material has a great influence on the viscosity at a given temperature. This influence was impossible to manipulate to become an advantage, whereas it became the opposite. Based on our results we cannot conclude that supercooled liquids exhibit a Newtonian flow, but on the contrary we do not have data that suggests that the hypothesis is implausible. The analysis of our results taken into account, we do not see any objections to considering supercooled liquids as Newtonian. It is merely important to mention that the field of research in glass and glassforming liquids is an area that is still characterized by lack of research in certain sub-categories, whereas there is no justification for the fact that supercooled liquids should flow Newtonian. Resumé: Denne rapport har til formål at undersøge underafkølede væskers flydeegenskaber nær glasovergangen. Ud fra hypotesen underafkølede væsker flyder newtonsk har vi eksperimentelt undersøgt, om dette er gældende for underafkølet sucrose, ved at opstille en model og anvende Poiseuilles lov på denne. Som reference for vores resultater har vi lavet kalorimetriske og dielektriske målinger på underafkølet sucrose. Ingen af disse målinger gav dog nogle brugbare resultater, hvorfor vi ikke har nogle referencer til de ved hjælp af Poiseuilles lov, beregnede viskositeter fra vores forsøg. Endvidere viste sucrose sig at være en dårlig repræsentant for underafkølede væsker, da dens termiske historie har stor indflydelse på viskositeten ved en given temperatur og vi ikke havde mulighed for at kontrollere denne indflydelse. Af vores forsøgsresultater, kan vi derfor ikke direkte konkludere, at underafkølede væsker flyder newtonsk, men vi har omvendt heller ingen data, der forkaster den opstillede hypotese. Således ser vi intet til hinder for at betragte underafkølede væsker som newtonske. Blot skal nævnes, at dette område indenfor forskning i glas og glasdannende væsker stadig er uafdækket, og at der derfor ikke er belæg for, at underkølede væsker nødvendigvis flyder newtonsk.

UddannelserBasis - Naturvidenskabelig Bacheloruddannelse, (Bachelor uddannelse) Basis
SprogDansk
Udgivelsesdato21 jun. 2007
VejledereKristine Niss

Emneord

  • Poiseuilles lov
  • Sucrose
  • Glas
  • Sukker
  • Underafkølet væske
  • Flydedynamik