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Microstructural Design and Conductivity and Ultrasonic Activation in the Ion Exchange of H3O+ and NH4+β"-Aluminas

Published online by Cambridge University Press:  28 February 2011

Patrick S. Nicholson
Patrick S. Nicholson*
Affiliation:
Ceramic Engineering Research GroupMcMaster UniversityHamilton, Ont., CANADA
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Abstract

H3O+- and NH4 + -A12O3 polycrystals have been conductivity-optimised by eliminating metastable grain-boundary phases (NaA1O2 and MgAl2O4) and texturing the microstructure. The grain-boundary conductivity is considerably improved (up to 5x10-5(Ω-cm)-i) from 10–6 (Ω-cm)-l). The dc-field-assisted, H3O+ ion exchange process for K+/Na+-β"-A12O3 in HAC has been accelerated by cyclic switching of the dc field (cycle = 3secs) or injecting ultrasonic energy. The formeroubles the steady-state ion-exchange current to 12 μA by dispersing the HAC/electrolyte, interfacial, H3O+ polarisation layer. The ion-exchange currentefficiency is not improved from 0.15. The ultrasound (23 MHz) markedly shortens the time to complete ion-exchange (400 hrs.vs. > 700 hrs), more than doubles the final ion-exchange current (360 μA.vs. 150 μA) and improves the ion-exchange current efficiency to 0.24. These results are interpreted in terms of ionic “activation ”in the electrolyte. Evidence is presented of a mixed-cation-effect in H3O+-K-β"-AI2O3.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 210: Symposium L – Solid State Ionics II , 1990 , 541
Copyright
Copyright © Materials Research Society 1991

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