Electrotransport of carbon, nitrogen, and oxygen in hafnium metal
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F. A. SCHMIDT,
AND
J. C. SEVER
The e l e c t r o t r a n s p o r t v e l o c i t i e s of car b o n , n i t r o g e n , and oxygen in alpha and b e t a hafnium w e r e d e t e r m i n e d f o r the t e m p e r a t u r e r a n g e of 1650 to 2130~ Diffusion c o e f f i c i e n t s and e f f e c t i v e v a l e n c e s w e r e also obtained f o r e a c h solute. T h e s e data w e r e used to p r e d i c t the d e g r e e of p u r i f i c a t i o n a c h i e v a b l e in a hafnium r o d a f t e r e l e c t r o t r a n s p o r t at 2000~ f o r d i f f e r e n t t i m e s . A c o m p a r i s o n was made b e t w e e n the p r e d i c t e d and e x p e r i m e n t a l l y o b s e r v e d results. T H E m i g r a t i o n of solute a t o m s d u r i n g the p a s s a g e of a high d e n s i t y d i r e c t c u r r e n t t h r o u g h a m e t a l is a s u b j e c t of s o m e i n t e r e s t at the p r e s e n t t i m e . The e a r l i e s t work on the e l e c t r o t r a n s p o r t of i n t e r s t i t i a l s o l u t e s in m e t a l s was that of De B o e r and F a s t t who noted that oxygen is d i s p l a c e d t o w a r d the anode end of a r o d of z i r c o n i u m t h r o u g h which a c u r r e n t was p a s s e d at e l e v a t e d t e m p e r a t u r e s . M o r e r e c e n t l y Schmidt e t a l . 2 m e a s u r e d the e l e c t r o t r a n s p o r t p a r a m e t e r s of carbon, n i t r o g e n , and oxygen in fi z i r c o n i u m . V e r y l i t t l e is known of the b e h a v i o r of t h e s e s o l u t e s in the o t h e r Group IV t r a n s i t i o n m e t a l s . C l a i s s e and Koenig 3 o b s e r v e d that oxygen a l s o m i g r a t e s in t i t a n i u m t o w a r d the anode but F r a n t s e v i c h and K o v e n ' s k i y 4 found c a r bon to m o v e in the opposite d i r e c t i o n . Nothing has b e e n r e p o r t e d on the e l e c t r o t r a n s p o r t of the i n t e r s t i t i a l s o l utes in hafnium. This i n v e s t i g a t i o n was undertaken, t h e r e f o r e , to d e t e r m i n e the e l e c t r i c m o b i l i t y , diffusion c o e f f i c i e n t and e f f e c t i v e v a l e n c e f o r c a r b o n , n i t r o g e n , and oxygen in hafnium m e t a l f o r c o m p a r i s o n with z i r c o n i u m . Of p a r t i c u l a r i n t e r e s t was the high t r a n s f o r m a t i o n t e m p e r a t u r e of hafnium (1735~ which o f f e r e d the p o s s i b i l i t y of d e t e r m i n i n g the e l e c t r o t r a n s p o r t v e l o c i t y and d i r e c tion t h e s e s o l u t e s t r a v e l in two d i f f e r e n t c r y s t a l f o r m s of the s a m e m e t a l . T h e s e p a r a m e t e r s would then be used to d e t e r m i n e the conditions n e c e s s a r y to p u r i f y s m a l l r o d s of hafnium m e t a l by the e l e c t r o t r a n s p o r t method. In p r e v i o u s work, this a p p r o a c h has b e e n quite s u c c e s s f u l in d e c r e a s i n g the i n t e r s t i t i a l i m p u r i t y content of t h o r i u m , s, 6 v a n a d i u m , v, s
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