Aerodynamic levitation technique for containerless high temperature studies on liquid and solid samples
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Aerodynamic Levitation Technique for Containerless High Temperature Studies on Liquid and Solid Samples DAVID A. WINBORNE, PAUL C. NORDINE, DANIEL E. ROSNER, AND NEIL F . MARLEY C h e m i c a l r e a c t i o n s b e t w e e n g a s e s and liquids a r e i m p o r t a n t in s t e e l m a k i n g , 1 the c o m b u s t i o n of m e t a l s 2 and p r o p e l l a n t s , 3 c a t a l y s i s 4 and o t h e r a r e a s of applied c h e m i s t r y . However, the study of g a s / l i q u i d h e t e r o geneous r e a c t i o n k i n e t i c s has b e e n plagued by gasphase diffusion l i m i t a t i o n s and the effects of cont a m i n a t i o n f r o m the s u p p o r t m a t e r i a l . R e p o r t e d l e v i tation t e c h n i q u e s which would avoid c o n t a m i n a t i o n of the s a m p l e include a c o u s t i c , ~ l a s e r , s and e l e c t r o m a g n e t i c levitation, 7 a s well as a e r o d y n a m i c l e v i t a tion in a hot p l a s m a jet s or in a wind t u n n e l v e l o c i t y m i n i m u m . 9 However, each has r e s t r i c t i o n s in a l l o w able p r e s s u r e and s a m p l e size, s t a b i l i t y p r o b l e m s , or a coupling b e t w e e n heating l e v e l and l e v i t a t i o n f o r c e which m a k e s it i m p r a c t i c a l for k i n e t i c s t u d i e s . T h i s note d e s c r i b e s a new a e r o d y n a m i c l e v i t a t i o n method, a p p l i c a b l e to both solids and liquids, which c i r c u m v e n t s the p r o b l e m s of l e v i t a t i o n i n s t a b i l i t y and i n d e p e n d e n t t e m p e r a t u r e c o n t r o l . The method was developed to study g a s / l i q u i d r e a c t i o n r a t e s u n d e r cond i t i o n s f r e e f r o m m a j o r gas phase diffusion l i m i t a tions and has been applied to m e a s u r e i n t r i n s i c F, F z / AI(/) g a s i f i c a t i o n k i n e t i c s . i ~ H e r e we p r e s e n t a des c r i p t i o n of the a p p a r a t u s , along with r e s u l t s p e r t a i n i n g to d e s i g n of s u c c e s s f u l a e r o d y n a m i c l e v i t a tion e x p e r i m e n t s . Specific r e s u l t s with l e v i t a t e d liquid a l u m i n u m and u r a n i u m s a m p l e s a r e given, i n cluding m e a s u r e m e n t s of convective heat and m a s s t r a n s f e r r a t e s . O t h e r p o t e n t i a l a p p l i c a t i o n s of the a e r o d y n a m i c l e v i t a t i o n flow r e a c t o r (ALFR) a r e d i s cussed briefly. The flow r e a c t o r a p p a r a t u s is i l l u s t r a t e d in Fig. 1. The s a m p l e s a r e l e v i t a t e d by a m e t e r e d a r g o n / f l u o r i n e m i x t u r e that flows upward in the A1203 tube (Coors type AD-998 a l u m i n a ) and through a teflon o r b o r o n n i t r i d e n o z z l e . A t o m i c f l u o r i n e m a y be g e n e r a t e d by the 100W, 2450 MHz m i c r o w a v e d i s c h a r g e , i n which case the teflon n o z z l e is n e c e s s a r y b e c a u s e a t o m i c f l u o r i n e r e a c t s with BN. is R e a c t o r p r e s s u r e i
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