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Titolo:
Low-temperature specific heats of porous silica xerogels of low densities
Autore:
DAngelo, G; Tripodo, G; Bartolotta, A; Carini, G; Fontana, A; Montagna, M; Rossi, F; Ferrari, M; Terki, F;
Indirizzi:
Univ Messina, Dipartimento Fis, I-98166 Messina, Italy Univ Messina Messina Italy I-98166 artimento Fis, I-98166 Messina, Italy Univ Messina, INFM, I-98166 Messina, Italy Univ Messina Messina Italy I-98166 Messina, INFM, I-98166 Messina, Italy CNR, Ist Tecn Spettroscop, I-98122 Messina, Italy CNR Messina Italy I-98122 , Ist Tecn Spettroscop, I-98122 Messina, Italy Univ Trent, Dipartimento Fis, I-38050 Povo, Trento, Italy Univ Trent PovoTrento Italy I-38050 nto Fis, I-38050 Povo, Trento, Italy Univ Trent, INFM, I-38050 Povo, Trento, Italy Univ Trent Povo Trento Italy I-38050 t, INFM, I-38050 Povo, Trento, Italy CNR, Ctr Fis Stati Aggregati, I-38050 Povo, Trento, Italy CNR Povo TrentoItaly I-38050 tati Aggregati, I-38050 Povo, Trento, Italy Univ Montpellier 2, Lab Verres, UMR 5587, F-34095 Montpellier, France UnivMontpellier 2 Montpellier France F-34095 -34095 Montpellier, France
Titolo Testata:
JOURNAL OF NON-CRYSTALLINE SOLIDS
fascicolo: 1-3, volume: 280, anno: 2001,
pagine: 222 - 227
SICI:
0022-3093(200102)280:1-3<222:LSHOPS>2.0.ZU;2-M
Fonte:
ISI
Lingua:
ENG
Soggetto:
THERMAL-CONDUCTIVITY; AEROGELS; GLASSES; EXCESS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
22
Recensione:
Indirizzi per estratti:
Indirizzo: D'Angelo, G Univ Messina, Dipartimento Fis, I-98166 Messina, Italy Univ Messina Messina Italy I-98166 s, I-98166 Messina, Italy
Citazione:
G. D'Angelo et al., "Low-temperature specific heats of porous silica xerogels of low densities", J NON-CRYST, 280(1-3), 2001, pp. 222-227

Abstract

Low-temperature specific heat measurements have been performed in porous silica xerogels with densities varying from 670 to 1730 kg m(-3) to study the low-energy vibrational dynamics. The specific heat, C-p, shows a bump in the temperature range above 4 K, when reported in a plot of C-p/T-3 againstthe temperature, T. The bump is almost independent of the sample density and is close to the boson peak observed in melt-quenched amorphous silica (a-SiO2). At temperatures <4 K, an additional contribution to that predicted by the Debye theory is observed. It follows an approximately linear temperature dependence (C-exc = a T (1+nu), nu being equal to about 0.25). In the xerogel with the largest density, specific heat of about a factor 5 larger than that of a-SiO2 is measured, which increases with decreasing sample density. By comparison with the corresponding properties of a-SiO2, we conclude that the disorder introduced by the presence of pores does not measurablyaffect the excess density of vibrational states in a frequency range of the boson peak (BP), but increases the density of the two-level systems (TLS). (C) 2001 Elsevier Science B.V. All rights reserved.

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Documento generato il 24/10/20 alle ore 11:37:51