Durability of Sodium Selective Super Ionic Conductors in Sodium and Chloride Containing Aqueous Environments at pH 2-11

Author

Venkata Chennapragada, Boise State UniversityFollow

Publication Date

8-2014

Date of Final Oral Examination (Defense)

6-2-2014

Type of Culminating Activity

Thesis - Boise State University Access Only

Degree Title

Master of Science in Materials Science and Engineering

Department

Materials Science and Engineering

Major Advisor

Darryl P. Butt, Ph.D.

Advisor

Michael F. Hurley, Ph.D.

Advisor

Dmitri A. Tenne, Ph.D.

Abstract

NASICON (Na₃Zr₂Si₂PO₁₂) ceramic specimens were synthesized by dry pressing and sintering Na₂CO₃, ZrP₂O₇, SiO₂, and ZrO₂ powders. The resulting NASICON membranes were exposed to 1M NaCl solutions titrated to pH values between 2 and 11. Accelerated electrochemical exposure testing was performed, which involved exposing thin discs of NASICON to both static and flowing 1M NaCl solutions with either HCl or NaOH solutions to pH 2, 7, or 11, under an applied effective current of 65 mA/cm² to drive ion transport until failure was observed. Three and four electrode testing was performed to observe if any catastrophic failure would occur due to electrochemical exposure under the applied conditions. The three electrode set-up was a static solution set-up with 1M NaCl titrated to different pH for exposure conditions. The specimens were characterized by XRD, SEM, and XPS. At pH 7 and 11, no degradation of NASICON was observed, although current profiles suggest higher pH solutions tend to fail faster than the low pH. At pH 2, it was found that a buildup of Na on the surface and apparent depletion of Si/P from the surface lead to a degradation of the NASICON ceramic specimen.

Recommended Citation

Chennapragada, Venkata, "Durability of Sodium Selective Super Ionic Conductors in Sodium and Chloride Containing Aqueous Environments at pH 2-11" (2014). Boise State University Theses and Dissertations. 869.
https://scholarworks.boisestate.edu/td/869