Glass transition temperature its exploitation and new conception of fragility

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F49777513%3A23640%2F18%3A43954226" target="_blank" >RIV/49777513:23640/18:43954226 - isvavai.cz</a>

Result on the web

<a href="http://dx.doi.org/10.13036/17533562.59.6.053" target="_blank" >http://dx.doi.org/10.13036/17533562.59.6.053</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.13036/17533562.59.6.053" target="_blank" >10.13036/17533562.59.6.053</a>

Result language

angličtina

Original language name

Glass transition temperature its exploitation and new conception of fragility

Original language description

When cooled or pressurised, melts exhibit a tremen-dous reduction in molecular mobility. If the process is performed at a high enough rate, the structural relaxation time of the liquid eventually exceeds the time allowed for equilibration. This brings the system out of equilibrium, and the liquid is operationally defined as a glass – a solid lacking long range order. Despite almost 100 years of research on the liquid/glass changeover, it is not yet clear which molecular mechanisms are fully responsible for such a unique slow down in molecular dynamics.(1–3) The major characteristic of this transformation process is the single minded glass transition tem-perature Tg which is a conceivably distinguishable democratic average (simple arithmetic mean) value of temperatures labelling the glass transformation region (GTR) becoming often the source of disput-able interpretations and various scrutiny. It can be operationally defined via near equilibrium scans, where physical quantities are measured as a function of thermodynamic variables (e.g. temperature, pres-sure) scanning from the glassy to the liquid state and vice versa. Such an obtained Tg denomination can be referred to as pseudo thermodynamic, or thermal resem-bling value which in the case of the most commonly performed experiments via DTA/DSC experiments is a common subject of customary determination. Let us mention that even if computationally appealing for its simplicity, this Tg numerical value always implicates averaging and thus bears certain accidental subjec-tivity. Tg may also incorporate the impact of other inclusive properties, such as for a thin layered sample the Tg value would approach the bulk (standard) value with the reciprocal film thickness dependence. Treatments of experimental effects are not the subject of our contribution(4–9) even though significant. Though not uniquely and specifically definable (just on the previously prepared glass) Tg became one of the e nsuing parameters capable of yielding valuable predictive numbers. Glass forming ability (GFA) and consequent glass stability (GS) of the associated constrained (i.e. frozen-in) state are ac knowledged to hold substantial meaning for all those who are interested in various applications to which glassy materials lend themselves and thus worth reconsideration. When a glassy material turns out to be experimentally accessible upon a suitable melt quenching (critical cooling rate, Rc) from its well dis-tinguishable melting point (Tm) down through GTR, demarcated as shown above by the temperature, Tg, certain data became accessible for material identifica - tion. (10) A liquid with good GFA exhibits a low value of R for the glass formation, which has remained a lon

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

20303 - Thermodynamics

Project

Result was created during the realization of more than one project. More information in the Projects tab.

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2018

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Physics and Chemistry of Glasses-European Journal of Glass Science and Technology Part B

ISSN

1753-3562

e-ISSN

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Volume of the periodical

59

Issue of the periodical within the volume

6

Country of publishing house

GB - UNITED KINGDOM

Number of pages

8

Pages from-to

259-266

UT code for WoS article

000455857500002

EID of the result in the Scopus database

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