Kroll process beryllium
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T. CAMPBELL,
R. E. MUSSLER,
AND
F. E. BLOCK
H i g h - p u r i t y b e r y l l i u m m e t a l was p r e p a r e d on a l a b o r a t o r y s c a l e by K r o l l p r o c e s s p r o c e d u r e s in which sodium was u s e d as a r e d u c t a n t . C r u d e b e r y l l i u m c h l o r i d e , p u r c h a s e d f r o m c o m m e r cial s o u r c e s , was p u r i f i e d by v a c u u m s u b l i m a t i o n and f u s e d - s a l t s c r u b b i n g . P u r i f i e d b e r y l l i u m c h l o r i d e was v a p o r i z e d and r e a c t e d at a c o n t r o l l e d rate with m o l t e n s o d i u m at t e m p e r a t u r e s r a n g i n g f r o m 650 ~ to 750~ to f o r m b e r y l l i u m sponge. E x c e s s m e t a l r e d u c t a n t and b y p r o d u c t salt were r e m o v e d f r o m the sponge m e t a l by v a c u u m d i s t i l l a t i o n . B e r y l l i u m sponge m e t a l was wet ball m i l l e d to - 2 0 0 o r - 4 0 0 m e s h p o w d e r s . B e r y l l i u m powder m e t a l , s u b s e q u e n t l y c o n s o l i dated by i s o s t a t i d p r e s s i n g , was hot extruded and m a c h i n e d into t e n s i l e s p e c i m e n s for e v a l u a tion of m e c h a n i c a l p r o p e r t i e s . E v a l u a t i o n i n d i c a t e s that the b e r y l l i u m d e s c r i b e d in this study i s of higher purity than c o m p a r a b l e c o m m e r c i a l g r a d e s of m e t a l ; also it i s m o r e ductile but has somewhat lower s t r e n g t h . The o v e r a l l p r o c e s s a p p e a r s to have an e x c e l l e n t potential f r o m an e c o n o m i c standpoint.
k.~URRENTLY, m o s t of the w o r l d ' s b e r y l l i u m is p r o duced e i t h e r by m a g n e s i u m r e d u c t i o n of b e r y l l i u m fluoride o r by f u s e d - s a l t e l e c t r o l y s i s of b e r y l l i u m c h l o r i d e . Those r e a d e r s who a r e i n t e r e s t e d in the c u r r e n t s t a t e of the a r t a r e r e f e r r e d to the book Beryllium by D a r w i n and Buddery. 1 B e c a u s e of the s u c c e s s f u l a p p l i c a t i o n of the Kroll p r o c e s s for the production of z i r c o n i u m and t i t a n i u m , the B u r e a u of Mines i n s t i t u t e d r e s e a r c h involving the a p p l i c a t i o n of K r o l l p r o c e s s p r o c e d u r e s as a method for p r e p a r i n g h i g h - p u r i t y b e r y l l i u m . It was anticipated that b e r y l l i u m m e t a l of c o n s i s t e n t l y high quality could be produced and that the p r o c e d u r e s would offer an e c o n o m i c advantage o v e r c u r r e n t p r a c t i c e . The a u t h o r s d i s c u s s e d the p r e p a r a tion of h i g h - p u r i t y b e r y l l i u m in a p r i o r paper; 2 howe v e r , m a n y m o d i f i c a t i o n s w e r e adopted d u r i n g l a t e r s t u d i e s , and these m o d i f i c a t i o n s , as well as an e v a l u a tion of s o m e of the m e c h a n i c a l p r o p e r t i e s of b e r y l l i u m powder, a r e the s u b j e c t of this paper. Since the e x t r a c t
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