An investigation of the interface between graphite and beta/beta″ alumina

✍ Scribed by N.S. Choudhury; M.W. Breiter; E.L. Hall

• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 688 KB
• Volume: 31
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(86)85006-x

✦ Synopsis

The anodic degradation of beta/beta" alumina of different compositions was investigated by voltammetric techniques in cells of the type Cu/Rodar alloy/carbon fibers/graphite layer/solid electrolyte/NaNOI/Pt/Cu at 350°C. The possibility was evaluated if the voltammetric results are useful as a diagnostic tool for the prediction of the failure of beta/beta" alumina electrolytes in sodium sulfurcells . Single voltage sweeps were applied into the anodic and also the cathodic direction at relatively low sweep rates (0.1-100 mV s -v), starting at the open circuirt voltage and extending to different voltages of reversal The anodic current-voltage curves display a continuous rise ofcurrent with voltage up to 4 .5 V, as a Na reference electrode, followed by a gradual decrease afterwards . The anodic current is mainly attributed to the formation of sodium carbonate and carbon monoxide . The oxygen is supplied by the degradation of the solid electrolyte . The cathodic current-voltage curves reveal the intercalation of sodium into the graphite . Structural studies of specimens from the solid electrolyte were carried out by electron microscopy before and after the electrochemical runs . They yielded information on how the anodic degradation proceeds with time .