Anodic Oxidation Of Uo2 Part Ii Electrochemical And X Ray Photoelectron Spectroscopic Studies In Alkaline Solutions

Author : S. Sunder
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (141 download)

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Download or read book Anodic dissolution of uo2 in slightly alkaline sodium perchlorate solutions written by S. Sunder and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The anodic dissolution of uo2 has been studied in aqueous sodium perchlorate solutions at ph approximately 9.5. under potentiostatic conditions two distinct regions of oxidation/dissolution behaviour were observed. in the potential (e) range 0.100 v approximately e approximately 0.350 v (vs. sce) currents decayed continuously with time due to the formation of oxidized surface films which gradually blocked further oxidation of the electrode. steady-state currents were not achieved even after 24 hours. on the basis of anodic and cathodic charges (q sub(a), q sub(c) respectively) obtained by integration of the anodic current-time plots (q sub(a)) and cathodic potential scans to reduce accumulated oxidized surface films (q sub(c)), it was shown that approximately 90% of the anodic oxidation current went to produce these films. for e approximately 0.350 v, steady-state currrents were obtained and measurements of q sub(a) and q sub(c) showed the majority of the current went to produce soluble species. the film blocking anodic dissolution appeared to be either uo sub(2.67) or, more probably, uo3 middle dot 2h2o located primarily at grain boundaries. it is proposed that, at the higher potentials, rapid oxidation and dissolution followed by the hydrolysis of dissolved uranyl species leads to the development of acidic conditions in the grain boundaries. at these lower ph values the uo3 middle dot 2h2o is soluble and therefore does not accumulate. alternatively, if this oxide has been formed by prior oxidation at a lower potential, the formation of protons on oxidizing at e > approximately 0.350v causes its redissolution, allowing the current to rise to a steady-state value. on the basis of tafel slopes, an attempt was made to demonstrate that the observed behaviour was consistent with dissolution under acidic conditions. this analysis was only partially successful.