The structure of molten binary silicate systems CaO-SiO 2 and MgO-SiO 2
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T h e s c h e m a t i c a r r a n g e m e n t of the s a m p l e h o l d e r h e a t e r a s s e m b l y is shown in F i g . 1. T h e s l a g was heated in a s a m p l e h o l d e r (20 • 12 • 4 mm) which was p a r t of the m a i n h e a t e r , and by an a d d i t i o n a l h e a t e r d i r e c t e d to the top s u r f a c e of the s l a g to i n s u r e a u n i form sample t e m p e r a t u r e . The h e a t e r - s a m p l e holder a s s e m b l y was e n c l o s e d u n d e r a p u r i f i e d d r y a r g o n a t m o s p h e r e . The s a m p l e t e m p e r a t u r e was m o n i t o r e d with a W - 5 pct R e / W - 2 6 pct Re t h e r m o c o u p l e which was located at the b o t t o m of the s a m p l e h o l d e r . T h e s a m p l e t e m p e r a t u r e was c a l i b r a t e d by m e a s u r i n g the l a t t i c e p a r a m e t e r of Pt or Me powder packed into the m e s h of the net and by c o m p a r i n g the change in l a t t i c e p a r a m e t e r with the t h e r m a l e x p a n s i o n data of t h e s e e l e m e n t s .2 T h i s c a l i b r a t i o n e r r o r is l e s s than +10~ By u s i n g this m o n i t o r i n g method, the s a m p l e was m a i n t a i n e d within +5~ of the d e s i r e d t e m p e r a t u r e d u r i n g the c o u r s e of the m e a s u r e m e n t s . High p u r i t y SiO2, CaCO3 and MgCO3 (A.R. grade) w e r e p u r c h a s e d f r o m Wakoh C h e m i c a l C o m p a n y . P r i o r to the X - r a y d i f f r a c t i o n m e a s u r e m e n t s , the s a m p l e was p r e m e l t e d in a P t o r Me c r u c i b l e by m e a n s of a high f r e q u e n c y i n d u c t i o n f u r n a c e , then r a p i d l y quenched to r o o m t e m p e r a t u r e . T h i s o p e r a tion was r e p e a t e d a n u m b e r of t i m e s to i n s u r e h o m o geneity of the s a m p l e . F i n a l l y , the s a m p l e was g r o u n d b e f o r e use. Many of t h e s e q u e n c h e d s a m p l e s w e r e in a glassy state. II. ANALYSIS OF INTENSITY P A T T E R N S The method of a n a l y z i n g the m e a s u r e d X - r a y i n t e n s i t y has b e e n d e s c r i b e d in d e t a i l p r e v i o u s l y , 1'3 and c o n s e q u e n t l y only the e s s e n t i a l f e a t u r e s a r e given b e low. A r e d u c e d i n t e r f e r e n c e f u n c t i o n i(Q) is e x p r e s s e d in t e r m s of the c o h e r e n t X - r a y s c a t t e r i n g i n t e n s i t y
Sample ~
Thermocouple
Fig. 1--Schematic diagram of the experimental apparatus for the high temperature furnace. VOLUME 8B, DECEMBER 1977 563
/~e~ (Q), (in e l e c t r o n units), which i s d i r e c t l y o b t a i n a b l e f r o m the e x p e r i m e n t s a s : m
coh
/~
i(q) = lieu (Q) -~__2 f ~ ( Q ) V [ . ~ j f i ( Q ) ] z i=1
Z=I
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[1]
w h e r e fi(Q) i s the a t o m i c s c a t t e r i n g f a c t o r o f / - k i n d of a t o m s , Q = 4~ s i n 0/x, 20 is the angle b e t w e e n the i n c i d e n t and d i f f r a c t e d X - r a y s and X is the wavelength. In o r d e r to e x p r e s s the o b s e r v
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