Nepheline structural and chemical dependence on melt composition

José Marcial; Jarrod Crum; Owen Neill; John McCloy

doi:10.2138/am-2016-5370

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Research Article| February 01, 2016

Nepheline structural and chemical dependence on melt composition

José Marcial;

José Marcial

1

School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164, U.S.A.

2

Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164, U.S.A.

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Jarrod Crum;

Jarrod Crum

3

Pacific Northwest National Laboratory, Richland, Washington 99352, U.S.A.

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Owen Neill;

Owen Neill

4

Peter Hooper GeoAnalytical Laboratory, School of the Environment, Washington State University, Pullman, Washington 99164, U.S.A.

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John McCloy

John McCloy *

1

School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164, U.S.A.

2

Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164, U.S.A.

*

E-mail: [email protected]

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Author and Article Information

José Marcial

1

School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164, U.S.A.

2

Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164, U.S.A.

Jarrod Crum

3

Pacific Northwest National Laboratory, Richland, Washington 99352, U.S.A.

Owen Neill

4

Peter Hooper GeoAnalytical Laboratory, School of the Environment, Washington State University, Pullman, Washington 99164, U.S.A.

John McCloy *

1

School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164, U.S.A.

2

Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164, U.S.A.

*

E-mail: [email protected]

Publisher: Mineralogical Society of America

Received: 02 Apr 2015

Accepted: 12 Aug 2015

First Online: 03 Mar 2017

Online ISSN: 1945-3027

Print ISSN: 0003-004X

American Mineralogist (2016) 101 (2): 266–276.

https://doi.org/10.2138/am-2016-5370

Abstract

Nepheline crystallizes upon slow-cooling in some melts concentrated in Na₂O and Al₂O₃, which can result in a residual glass phase of low chemical durability. Nepheline can incorporate many components often found in high-level waste radioactive borosilicate glass, including glass network ions (e.g., Si, Al, Fe), alkali metals (e.g., Cs, K, Na, and possibly Li), alkaline-earth metals (e.g., Ba, Sr, Ca, Mg), and transition metals (e.g., Mn, and possibly Cr, Zn, Ni). When crystallized from melts of different compositions, nepheline composition varies as a function of starting melt composition. Five simulated high-level nuclear waste borosilicate glasses shown to crystallize large fractions of nepheline on slow-cooling were selected for study. These starting melt compositions contained a range of Al₂O₃, B₂O₃, CaO, Na₂O, K₂O, Fe₂O₃, and SiO₂ concentrations. Compositional analyses of nepheline crystals in glass by electron probe micro-analysis (EPMA) indicate that nepheline is generally rich in silica, whereas boron is unlikely to be present in any significant concentration, if at all, in nepheline. Also, several models are presented for calculating the fraction of vacancies in the nepheline structure.