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Long‐Term Heat Treatment of Phase Separating Sodium Borosilicate Glass
Author(s) -
Sander Stephan A. H.,
Weiss Michael,
Denecke Reinhard,
Enke Dirk,
Roggendorf Hans
Publication year - 2019
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201900187
Subject(s) - materials science , microstructure , ostwald ripening , borosilicate glass , scanning electron microscope , porosity , kinetics , activation energy , chemical engineering , analytical chemistry (journal) , mineralogy , composite material , chemistry , nanotechnology , chromatography , physics , quantum mechanics , engineering
The kinetics of spinodal decomposition of glasses with a composition of (in mol%) 8 Na 2 O, 26 B 2 O 3 , and 66 SiO 2 , are investigated as a function of time (up to 64 d) and temperature (between 630 and 750 °C) of heat after leaching in diluted HCl and NaOH solution to generate porosity. The glasses as well as porous materials are analyzed by dilatometry, mercury intrusion porosimetry, nitrogen sorption, X‐ray diffraction, X‐ray fluorescence spectroscopy, helium pycnometry, and scanning electron microscopy (SEM). The development of microstructure parameters like pore sizes are evaluated to characterize the kinetics of microstructure formation. Two different growth stages are identified via their size growth kinetics and the analysis of the obtained microstructures. In both stages the pore sizes follow size time laws d p ∝ t β with an exponent β of 0.33 or 0.5. Both processes are running parallel in the second stage. This lead to the conclusion that the dominating mechanism of microstructure formation in the first identified stage is Ostwald ripening. This process is followed by a new stage which is concluded to be diffusion limited with a calculated activation energy of 220 ± 10 kJ mol −1 . The observed size time laws do not limit the pore sizes.