Freezing and melting of water in ordered nanoporous silica materials

Title: Freezing and melting of water in ordered nanoporous silica materials
Author(s): G.H. Findenegg, A. Schreiber
Paper category : conference
Book title: International RILEM Workshop on Frost Resistance of Concrete
Editor(s): M. J. Setzer, R. Auberg and H. - J. Keck
Print-ISBN: 2-912143-30-6
e-ISBN: 2351580370
Publisher: RILEM Publications SARL
Publication year: 2002
Pages: 105 - 114
Total Pages: 10
Nb references: 20
Language: English

Abstract: The freezing and melting of water in MCM-41 type ordered mesoporous silica materials with cylindrical pores of uniform size (3 - 12 nm pore width) was studied by differential scanning calorimetry (DSC). A systematic dependence of the melting point depression ?Tm on the pore radius R was observed which can be represented by a modified Gibbs-Thomson equation, ?Tm(R) = K / (R-t), where t can be taken as the thickness of a surface layer of non-frozen water at the pore wall. The experimental value of K agrees with an estimate of the Gibbs-Thomson constant based on thermodynamic data for the normal melting point of ice. DSC freezing scans on samples with partially filled pores show a peak pattern that depends on the degree of pore filling ?. The individual peaks are ascribed to different states of the liquid in the pore space, viz. pore water in completely filled regions, and water as an adsorbed film at the pore wall. These two states coexist in a pore filling range ?min < ? < 1, but only the film state exists at ? < ?min. In heating scans only one DSC peak is observed, independent of the pore filling.

Online publication: 2010-06-28
Publication type : full_text
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