Equilibrium formation and thermodynamic properties of gaseous silicon monosulfide
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= 12,740 - 19.18 T
AF~1686-2953 K =
640 -- 12.02 T
Sits) + 1/2 S2(g) = SiStg) Sit/) + 1/2 Sztg) = SiStg)
C O M P O U N D S of s i l i c o n and s u l f u r have long b e e n r e c o g n i z e d . Silicon s u l f i d e s , in p a r t i c u l a r s i l i c o n m o n o s u l f i d e , have b e e n r e p o r t e d in the d e s u l f u r i z a tion p r o c e s s e s u s e d in the s t e e l i n d u s t r y . R e c e n t l y e x p e r i m e n t a l e v i d e n c e l-x~ h a s shown that the f o r m a tion of g a s e o u s s i l i c o n m o n o s u l f i d e is m a i n l y r e s p o n s i b l e for the r e l a t i v e l y e a s y r e m o v a l of s u l f u r d u r i n g v a c u u m d e s u l f u r i z a t i o n of f e r r o a l l o y s containing s i l i con and s u l f u r . E x a m i n a t i o n of t h e s e and o t h e r p r o c e s s e s involving s i l i c o n s u l f i d e s h a s been h a m p e r e d by the a b s e n c e of a c c u r a t e t h e r m o d y n a m i c d a t a . T h e s i t u a t i o n is p a r t i c u l a r l y e v i d e n t for s i l i c o n m o n o s u l f i d e . Until v e r y r e c e n t l y no e x p e r i m e n t a l t h e r m o c h e m i c a l p r o p e r t i e s of g a s e o u s s i l i c o n m o n o s u l f i d e have b e e n r e p o r t e d . Only d a t a d e r i v e d f r o m s p e c t r o s c o p i c e x a m i n a t i o n w e r e a v a i l a b l e . F r u e h a n and T u r k d o g a n 1~ u s e d a m a s s s p e c t r o m e t e r - K n u d s e n c e l l technique to i n v e s t i g a t e the r e a c t i o n b e t w e e n s i l i c o n d i s u l f i d e and silicon. SiS2(s) + Sits) = 2 SiStg)
[1]
T h e y w e r e unable to obtain r e p r o d u c i b l e e q u i l i b r i u m p r e s s u r e d a t a a s the i o n i z a t i o n c r o s s - s e c t i o u and m u l t i p l i e r e f f i c i e n c y of the effusing s p e c i e s w e r e not a c c u r a t e l y known. H o w e v e r , they r e p o r t e d a h e a t of r e a c t i o n of 102.2 k c a l / m o l e a t 1100 K f o r the p r o c e s s d e s c r i b e d by Eq. [1]. The p r e s e n t p a p e r r e p o r t s a d e t a i l e q u i l i b r i u m study of f o r m a t i o n of g a s e o u s s i l i c o n m o n o s u i f i d e acco~rd ing to Eq. [1] u s i n g the K n u d s e n e f f u s i o n - g r a v i m e t r i c m e t h o d . The e q u i l i b r i u m SiS p r e s s u r e d a t a was o b t a i n e d in the t e m p e r a t u r e r a n g e 863 to 1161 K. F r o m this e q u i l i b r i u m p r e s s u r e d a t a the e q u i l i b r i u m c o n -
J. J. BYERLEY and W. K. TEO are with the Metallurgical Chemistry Research Laboratory, Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada. Manuscript submitted June 6, 1972. METALLURGICAL TRANSACTIONS
s t a n t s , the s t a n d a r d f r e e e n e r g y change and o t h e r t h e r m o d y n a m i c functions a r e c o m p u t e d . P R E L I M I N A R Y STUDIES ON THE FORMATION AND P R O P E R T I E S O F SILICON MONOSULFIDE L i k e m a n y d i v a l e n t c o m p
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