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Effect of Na 2 O on the High‐Temperature Thermal Conductivity and Structure of Na 2 O–B 2 O 3 Melts
Author(s) -
Park Sewoong,
Sohn Il
Publication year - 2016
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.14013
Subject(s) - raman spectroscopy , x ray photoelectron spectroscopy , analytical chemistry (journal) , fourier transform infrared spectroscopy , thermal conductivity , conductivity , boron , thermal analysis , oxygen , chemistry , infrared spectroscopy , materials science , thermal , nuclear magnetic resonance , chemical engineering , physics , chromatography , composite material , organic chemistry , meteorology , optics , engineering
The effect of Na 2 O and temperature on the thermal conductivity of the Na 2 O–B 2 O 3 binary system has been measured using the hot‐wire method to examine the relationship between the thermal conductivity and structure in high‐temperature melts. The thermal conductivity of the binary melt is measured from 1173 to 1473 K in the fully liquid state. The thermal conductivity slightly increases with Na 2 O content up to 20 wt%. Above 20 wt% Na 2 O, the thermal conductivity decreases with increasing Na 2 O. The network structure of molten glass was analyzed using Fourier transform infrared (FTIR), Raman spectroscopy, and XPS. The FTIR analysis shows that 3‐D complex borate structures, such as tri‐, tetra‐, and pentaborate are made by [BO 4 ] tetrahedral units interconnected with 2‐D structure boroxol rings in the low Na 2 O region. Above 20 wt% Na 2 O content, nonbridged oxygen in [BO 2 O − ] units and diborate groups increase with increase in Na 2 O. The same tendency is shown by the Raman spectroscopy and XPS analyses. The Raman analysis shows that boroxol rings disappeared with large [BO 4 ] groups, such as tri‐, tetra‐, and pentaborate structures, which increase at low Na 2 O content. Isolated diborate groups and nonbridged oxygen in [BO 2 O − ] units increase at high Na 2 O content. It can be inferred that single structure units, such as isolated diborate groups, interfere with conduction. The XPS analysis results show that free oxygen produced by the interconnection of Na 2 O in the borate structure does not cause significant changes to O 2− in the low Na 2 O region, but increases the O o and decreases the O − . Above 20 wt% Na 2 O, O − slightly increases and O o shows a decreasing trend.