326:-1) ≥ 1. Fragility is related to materials bond breaking processes caused by thermal fluctuations. Bond breaking modifies the properties of an amorphous material so that the higher the concentration of broken bonds termed configurons the lower the viscosity. Materials with a higher enthalpy of configuron formation compared with their enthalpy of motion have a higher Doremus fragility ratio, conversely melts with a relatively lower enthalpy of configuron formation have a lower fragility. More recently, the fragility has been quantitatively related to the details of the interatomic or intermolecular potential, and it has been shown that steeper interatomic potentials lead to more fragile liquids.
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The mechanical properties of glass-forming liquids depend primarily on the viscosity. Therefore, the following working points are defined in terms of viscosity. The temperature is indicated for industrial
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at high temperatures (in the liquid state). Amorphous materials are classified accordingly to the deviation from
Arrhenius type behaviour of their viscosities as either strong when Q
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270:. Viscous flow in amorphous materials is characterised by deviations from the Arrhenius-type behaviour: the activation energy of
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M.I. Ojovan, W.E. Lee. Fragility of oxide melts as a thermodynamic parameter. Phys. Chem. Glasses, 46, 7-11 (2005).
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Götze,W (2009): Complex
Dynamics of glass forming liquids. A mode-coupling theory. Oxford: Oxford University Press.
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17:
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Zarzycki,J (1982): Les Verres et l'état vitreux. Paris: Masson. Also available in
English translations.
306:. The fragility of amorphous materials is numerically characterized by the Doremus’ fragility ratio R
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266:. This classification has no direct relation with the common usage of the word "fragility" to mean
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426:"Interatomic repulsion softness directly controls the fragility of supercooled metallic melts"
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the melting point of the concurrent crystalline phase. That melting point is rather called
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on cooling towards a critical temperature Tc, typically located 20% above Tg.
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and collaborators since the 1980s. This theory describes a slowing down of
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The microscopic dynamics at low to moderate viscosities is addressed by a
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Proceedings of the
National Academy of Sciences of the USA
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at low temperatures (in the glassy state) to a low value Q
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J. T. Littleton, J. Am. Ceram. Soc., 18, 239 (1935).
322:-1) < 1, whereas fragile melts are those with (R
396:; it is about 1000..1040 deg C in soda lime glass.
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246:In a widespread classification, due to chemist
424:Krausser, J.; Samwer, K.; Zaccone, A. (2015).
27:Term for fluids with high levels of viscosity
65:are often used interchangeably to designate
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254:if its viscosity approximately obeys an
125:temperature (deg C, in soda lime glass)
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250:, a glass-forming liquid is called
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318:. Strong melts are those with (R
89:Working points in glass processing
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69:that are at the same time highly
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486:Glassforming liquids and melts
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184:softening point (dilatometric)
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274:Q changes from a high value Q
236:Fragile-strong classification
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173:softening point (Littleton)
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379:Zarzycky (1982), p.219,222
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242:Fragility (glass physics)
47:condensed matter physics
30:Not to be confused with
443:10.1073/pnas.1503741112
258:(log η is linear in 1/
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344:structural relaxation
100:is done at about the
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81:, and able to form a
394:liquidus temperature
336:mode-coupling theory
330:Mode-coupling theory
63:glass forming liquid
436:(45): 13762–13767.
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59:supercooled liquid
51:physical chemistry
350:Notes and sources
294:or fragile when Q
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77:), can be or are
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222:strain point
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98:Glassblowing
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53:, the terms
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40:Supercooling
268:brittleness
119:designation
79:supercooled
475:Categories
368:References
162:flow point
152:sink point
36:Subcooling
355:Textbooks
272:viscosity
229:<~500
216:<~500
203:<~500
190:>~500
147:950-1000
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388:This is
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264:fragile
71:viscous
67:liquids
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252:strong
213:10..10
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290:<Q
168:~900
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83:glass
73:(see
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458:PMID
179:600
49:and
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390:not
226:~10
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314:/Q
310:=Q
302:≥Q
298:-Q
286:-Q
176:10
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324:D
320:D
316:L
312:H
308:D
304:L
300:L
296:H
292:L
288:L
284:H
280:L
276:H
260:T
104:.
42:.
20:)
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