The reduction of Al 2 O 3 to aluminum in a plasma
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The r e d u c t i o n of a l u m i n u m oxide to a l u m i n u m in radio f r e q u e n c y g e n e r a t e d p l a s m a s was studied e x p e r i m e n t a l l y . Argon with h y d r o g e n , c a r b o n dioxide, and methane were u s e d a s p l a s m a g a s e s . P r o d u c t was c o l l e c t e d f r o m the r e a c t o r w a l l s a n d / o r c o l d - f i n g e r c o l l e c t o r s . G a s e o u s q u e n c h i n g was also i n v e s t i g a t e d , u s i n g h y d r o g e n , m e t h a n e , and c a r b o n dioxide. Conv e r s i o n s up to 50 pct were d e t e r m i n e d u s i n g wet c h e m i s t r y . O p t i c a l and X - r a y m e t h o d s conf i r m e d the s p e c i e s p r e s e n t d u r i n g and a f t e r r e a c t i o n . The effects of p a r t i c l e s i z e , flow r a t e s , and power input were d e t e r m i n e d . Solutions of e n e r g y , m o m e n t u m , and m a s s b a l a n c e s yield a qualitative e x p l a n a t i o n of the p r o c e s s . V a p o r i z a t i o n r a t e c o n t r o l s . T H E p r i m a r y aim of this r e s e a r c h was to i n v e s t i g a t e the r e d u c t i o n of AltOs to a l u m i n u m in r a d i o f r e q u e n c y g e n e r a t e d , induction coupled p l a s m a s . It was also intended to d e m o n s t r a t e that an i n d u c t i o n - c o u p l e d p l a s m a r e a c t o r i s e s p e c i a l l y s u i t a b l e for such g a s - s o l i d r e a c t i o n s . The c o n v e r s i o n of AltOs to a l u m i n u m in this study was effected in a r g o n , Ar-H2, A r - C O , and Ar-CH4 p l a s m a s . Different quench t e c h n i q u e s and t h r e e r e a c tion v a r i a b l e s were i n v e s t i g a t e d . S e v e r a l i n v e s t i g a t o r s 1-5 have a t t e m p t e d p l a s m a r e d u c t i o n s of m e t a l l i c o x i d e s , c h l o r i d e s , and s u l f i d e s . T h e i r work d e m o n s t r a t e s that the r e d u c t i o n of m e t a l l i c oxides in p l a s m a s is feasible. The extent of the r e d u c tion depends on the oxide p a r t i c l e s i z e , the oxide flow r a t e , and the power input to the p l a s m a . It i s a p p a r e n t that the lack of s u c c e s s with A1203 was due to the use of p a r t i c l e s i z e s and flow r a t e s that were too great. The gaseous a l u m i n u m suboxides a r e of i n t e r e s t s i n c e they a r e expected to o c c u r e i t h e r d u r i n g the d i s s o c i a t i o n of AltOs or by a r e c o m b i n a t i o n of a l u m i num and oxygen a t o m s . It is concluded f r o m an e x a m i n a t i o n of the l i t e r a t u r e 6 that A10 and A120 a r e the only two i m p o r t a n t g a s e o u s oxides of a l u m i n u m . The f o r m e r i s the p r i n c i p a l g a s e o u s suboxide u n d e r n e u t r a l o r oxidizing conditions and the l a t t e r p r e d o m i n a t e s u n d e r r e d u c i n g conditions. T h e r e has b e e n no c o n c l u s i v e evidence that solid s u b o x i d e s can exist at r o o m t e m p e r a t u r e 6 but solid A10 and AlsO
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