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SiO 2 -Na 2 O-B 2 O 3 density: A comparison of experiments, simulations, and theory

Marina Barlet

a , Ali Kerrache b ,Jean-MarcDelaye b , Cindy L. Rountree a, a CEA, IRAMIS, SPCSI, Groupe Complex Systems & Fracture, F91191 Gif-sur-Yvette, France b CEA, DEN, DTCD, SECM, LMPA CEA Marcoule, BP 17171, 30207 Bagnols sur Cèze cedex, France abstractarticle info

Article history:

Received 22 May 2013

Received in revised form 19 September 2013

Available online 23 October 2013

Keywords:

Sodium borosilicate glasses;

Density;

Molecular dynamics;

Glass structureThispaperisdevotedto a comparisonofexperimental,simulation,andtheoreticalresults on thedensity ofSiO

2 B 2 O 3 -Na 2

O glasses. It isfound that theoretical and simulation densities do compare favorably with experimental

values yet simulations give a better estimate of the density of the samples. Furthermore, the structural make-up

(i.e. types of borate and silicate units) of the ternary glasses and the volume of the elementary units have also

been investigated with simulations and compared to theory. These results are found to compare favorably

whenRbR d1 R¼

Na2O½

B

2O3½

;K¼

SiO2½

B

2O3½

and Rd1

¼0:5þ0:25K??

yet variations do exists whenRNR d1 . These varia- tions include more Na ions attaching to the borate network in simulations than theorized.

© 2013 Elsevier B.V. All rights reserved.

1. Introduction

Sodium oxide (Na

2

O), boron trioxide (B

2 O 3 ), and silica (SiO 2 )are the three major components of many industrial important glasses including: BOROFLOAT 33, Schott BK-7 Borosilicate Crown Glass, Corning Pyrex 7740ƒ. The uses of these glasses range from cookware to laboratory glassware to optical glass. Due to the varying applications, many studies have been conducted to understand how the molar mass of each component affects the ternary glass structure. These studies in- clude several spectroscopic techniques such as Raman[1-

3],Infrared

[4],NMR[5,6]ƒ. Moreover, NMR measurements permit quantitative structural information by employing11

BNMR[7-10]and

29

Si NMR

[11]. Subsequent studies suggest that the structural building blocks advantage tothe structural building blockmodels is thatthey are strict- ly based on least-square datats. Understanding the structural makeup of these glasses is by far more to investigate the density of seven ternary glass systems. In addition, molecular dynamics (MD) simulations are used to gather information on the fraction and volume of elementary building blocks and the overall densities of these systems. These results are compared and (compiled inAppendix A). This paper willrst present a review of the structural makeup of the SiO2 -B 2 O 3 -Na 2

O ternary glasses. In developing this section, thecoauthors havescouredthe currentliterature. All ofthe parts of thepic-

ture exist in literature, yet the comprehensive picture we are trying to bring has been alluded to but never realized.Section 3depicts how the fractions of the structural units are used to estimate the densities of glasses in several models. The next two sections detail our experi- mental and simulation procedures. Afterwards is a presentation of the experimental and simulation results and how they compare and con- trast with current theories.

2. Review of structural makeup

In general, ternaryglassstructures arecomplex glasses whosestruc- ture is dependent on its oxides and their relative proportion. Herein so- diumborosilicateternaryglasses arecomposedoftwonetwork formers (SiO2 and B 2 O 3 ) and one network modier (Na 2

O)[15-17]. Pure silica

(amorphousSiO 2 and boron trioxide have short- and mid-range orders. The short range order of silica is a tetrahedron (SiO 4 ) and four bridging oxygen atoms. The mid-range order is the linkingof the tetrahedrons to form predom- inantly 6-membered rings (number of silicon per ring) with some ring size dispersions[18-23].Similarly,B 2 O 3 has a mid-range order of boroxol rings (3 borons per ring)[24-26].B 2 O 3 's short range order is aplanarBO 3/2 group and has no non-bridging oxygen atoms (NBOs). (Borons with 3 bridging oxygen atoms attached to it shall be referred to as B3 henceforth.) Contrary to SiO2 and B 2 O 3 ,Na 2

Oisananti′uorite

crystal structure. Mixing two (i.e. binary glass) or all three components of the glass will lead to variations in the structure of the glasses as reviewed below. Journal of Non-Crystalline Solids 382 (2013) 32-44

Corresponding author.

E-mail address:cindy.rountree@cea.fr(C.L. Rountree).

0022-3093/$-see front matter © 2013 Elsevier B.V. All rights reserved.

Contents lists available atScienceDirect

Journal of Non-Crystalline Solids

journal homepage: www.elsevier.com/ locate/ jnoncrysol

2.1. Binary B

2 O 3 -Na 2

Oglass

The structure of the binary B

2 O 3 -Na 2

O glass has been studied inten-

sively over the past 60 years[10,12,27-30]. The binary B 2 O 3 -Na 2 O structure has 5 well known structural units. The fraction of these units depends on the ratioR=[Na 2 O]/[B 2 O 3 ] where [·]mol%[8,31].As stated above a pure B 2 O 3 glass has a short-range B3 structure and mid-range structure of boroxol rings. Low quantities of Na 2

O(0-20%)

added to the B 2 O 3 glass will predominantly convert B3 to a tetrahedral BO 4 structure (to be referred to as B4, boron with 4 bridging oxygen atoms) with an adjacent sodium ion forming Tetraborate units (chem- ical formula Na 2 O4B 2 O 3 )[8,32]. Additional sodium (20%-33%;

0.25bR0.5) will convert Tetraborate units into a diborate group

(chemical formula Na 2 O2B 2 O 3 )). Less frequently at lowR,Na 2 Ocan also convert B3s to form planar BO 3/2 groups each with 1 NBO (non- bridging oxygen) and 1 Na ion nearby (i.e. 2 Metaborate units, chemical formula (Na 2 OB 2 O 3 ))[12]. However this conversion is rare and frequently ignored. Locally allRb0.5 conversions corre- spond to R l =1 (local conversion ratio implying one Na ion for the borate unit). ForRN0.5, other structural units will come about in- cluding: (1) Metaborate units: a planar BO 3/2 group with 1 NBO and 1 Na ion nearby (chemical formula (Na 2 OB 2 O 3 ) and local R l = 1); (2) Pyroborate unit: a planar BO 3/2 group with 2 NBOs and 2 Na ions nearby (chemical formula 1 2 2Na 2 OB 2 O 3

ðÞand

local R l = 2); (3) orthoborate unit: a planar BO 3/2 group with 3quotesdbs_dbs47.pdfusesText_47

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