Cryoscopic studies in fluoride-oxide-silica systems: Part I. systems containing Li + , Na + and K +
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HIDEAKI SUITO is Lecturer, Research Institute of Tohoku University, Sendal, Japan. D. R. GASKELLis Associate Professor of Metallurgy, Laboratory for Research on the Structure of Matter, University of Pennsylvania,Philadelphia, PA 19174. Manuscript submitted May 6, 1976. METALLURGICAL TRANSACTIONSB
a n i o n s . T h e s e o b s e r v a t i o n s p a r a l l e l t h o s e of the effect of f l u o r i d e s on s l a g v i s c o s i t y . S i m p l e s o l u t i o n of f l u o r i d e to p r o d u c e f r e e F - ions in s o l u t i o n and i n t e r a c t i o n b e t w e e n the f l u o r i d e and the s i l i c a t e ions to f o r m f l u o r o s i l i c a t e i o n s would be expected to have s i g n i f i c a n t l y d i f f e r e n t effects on the m u t u a l s o l u b i l i t i e s , and hence p h a s e r e l a t i o n s h i p s , in f l u o r i d e - s i l i c a t e s y s t e m s . However, although phase r e l a t i o n s i n f l u o r i d e - o x i d e s y s t e m s have b e e n studied f a i r l y e x t e n s i v e l y , 5 c o r r e s p o n d i n g data for f l u o r i d e s i l i c a t e s y s t e m s a p p e a r to be l i m i t e d to the s y s t e m s CaF2-CaO-SiO2 (Refs. 6 to 9) and NaF-Na20-SiO2.10'11 C o n s e q u e n t l y , the p r e s e n t i n v e s t i g a t i o n is c o n c e r n e d with study of the f l u o r i d e l i q u i d u s b e h a v i o r a s a f u n c t i o n of cation type and m e t a l o x i d e / s i l i c a r a t i o in a l k a l i , a l k a l i n e e a r t h and lead f l u o r o s i l i c a t e s y s t e m s c o n t a i n i n g one and two types of cation. The r e s u l t s of i n v e s t i g a t i o n of the a l k a l i s y s t e m s a r e p r e s e n t e d in the p r e s e n t p a p e r and t h o s e of the a l k a l i n e e a r t h and lead s y s t e m s a r e r e p o r t e d i n P a r t II. EXPERIMENTAL Materials C o m m e r c i a l AR grade N a F and KF w e r e m e l t e d i n g r a p h i t e c r u c i b l e s which, p r e v i o u s l y , had b e e n deg a s s e d for 8 h at 1500~ in v a c u u m . The m e l t s w e r e cooled u n d e r d r y a r g o n at r a t e s b e t w e e n 0.2 and 0.8~ p e r m i n and, a f t e r s o l i d i f i c a t i o n , only p i e c e s which, on cleavage, p r o d u c e d c l e a r c r y s t a l l i n e f a c e s , w e r e s e l e c t e d for s u b s e q u e n t u s e . C o m m e r c i a l AR g r a d e L i F was d r i e d by h e a t i n g to 400~ u n d e r v a c u u m for 5 h. Sodium, l i t h i u m and p o t a s s i u m s i l i c a t e s of M 2 0 / SiO2 m o l a r r a t i o s 1.5, 1 and 0.5 w e r e p r e p a r e d by m i x i n g s t o i c h i o m e t r i c a m o u n t s of AR grade a l k a l i c a r b o n a t e and s i l i c a and h e a t i n g i n a p l a t i n u m c r u c i b l e for 7 to 10 h, (until the e v o l u t i o n of gas b u b b l e s f r o m the m e l t ceased) in the r a n g e 1200 to 1300~ Prior to t h e i r b e i n g used, the s o l i d i f i e d s i l i c a t e s w e r e s t o r e d in a d e s i c c a t o r . VOLUME 7B, DECEMBER 1976
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