Observations of surface movements of liquid copper and tin
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BRIMACOMBE
AND
F. WEINBERG
THE behavior of interfaces between liquid metals and other fluids can considerably influence the kinetics of metallurgical reactions since most of the reactions occur at interphase boundaries. The retarding effect of surface active agents concentrated at an interface, I or the acceleration of reaction rates due to emulsion formation 2 are well documented. Spontaneous interracial motion--"inter facial turbulence "--is another phenomenon which may cause increases in metallurgical reaction rates, especially of transport controlled reactions. The turbulence may create intense mixing in the interracial regions and an increase in interracial area through ripple formation. Interracial turbulence has been observed recently in amalgam-electrolyte systems 3 and has been reported for the liquid Fe-O system.4 It has also been studied extensively in aqueous-organic systems. 5 Spontaneous interfacial movements may occur when sufficiently large gradients of interracial tension are established locally. Under these conditions the interface moves in the direction of highest interracial tension. Interfacial tension gradients may be created by local changes at the interface of electrical potential or c o n c e n t r a t i o n of a s u r f a c e a c t i v e s o l u t e . P o t e n t i a l f l u c t u a t i o n s w i l l be i m p o r t a n t in s y s t e m s which d i s p l a y e I e c t r o c a p i l l a r y b e h a v i o r such a s a m a l g a m - e l e c t r o l y t e 6 o r iiquid m e t a I - f u s e d s a l t s y s t e m s . V a r i a t i o n s in c o n c e n t r a t i o n of a s u r f a c e a c t i v e s o l u t e at the i n t e r f a c e a r e r e s p o n s i b l e for i n t e r f a c i a l t u r b u l e n c e in m a n y of the a q u e o u s - o r g a n i c s y s t e m s . In the l a t t e r e a s e , the i n t e r r a c i a l m o t i o n is d e s c r i b e d a s the M a r a n g o n i effect .7 It is p o s s i b l e that the M a r a n g o n i e f f e c t c a n a l s o o c c u r in m e t a l l u r g i c a l s y s t e m s s i n c e e l e m e n t s l i k e o x y gen a r e known to be highly s u r f a c e a c t i v e , l o w e r i n g the s u r f a c e t e n s i o n of m a n y liquid m e t a l s . 8'9 To i n v e s t i g a t e t h i s p o s s i b i l i t y , p r e l i m i n a r y e x p e r i m e n t s have b e e n conducted in which the c o n c e n t r a t i o n of oxygen at the s u r f a c e of high p u r i t y liquid m e t a l s was l o c a l l y p e r t u r b e d . A low m o m e n t u m jet of p u r e oxygen w a s blown v e r t i c a l l y f r o m a 0,75 m m ID s t a i n l e s s s t e e l tube onto the s u r f a c e of liquid tin or c o p p e r at 1100~ The tip of the tube was b e t w e e n 3 and 4 r a m . f r o m the l i q u i d s u r f a c e . The m e t a l s , c o n t a i n e d in a 4.5 c m d i a m by 3.5 c m r e c r y s t a l l i z e d a l u m i n a c r u c i b l e , w e r e f i r s t induction m e l t e d u n d e r v a c u u m in a l a r g e c h a m b e r , P r i o r to oxygen blowing, the c h a m
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