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RAPID QUENCHING OF MELTS IN THE SYSTEM ZrO2-SiO2-Al2O3
M. Yoshimura, M. Kaneko, S. Sōmiya
To cite this version:
M. Yoshimura, M. Kaneko, S. Sōmiya. RAPID QUENCHING OF MELTS IN THE SYS- TEM ZrO2-SiO2-Al2O3. Journal de Physique Colloques, 1986, 47 (C1), pp.C1-473-C1-477.
�10.1051/jphyscol:1986171�. �jpa-00225602�
RAPID QUENCHING OF MELTS IN THE SYSTEM Zr0,-Si0,-A1,0,
M. YOSHIMURA, M. KANEKO and S. S ~ M I Y A
Laboratory for Advanced Ceramics, Research Laboratory of Engineering Materials, and Department of Materials Science, Tokyo Institute of Technology, 4259, Nagatsuta, Midori, Yokohama 227, Japan
RdsumiS - Le domaine d e f o r m a t i o n d e phase amorphe d a n s l e systsme Zr02-Si02- A1203 a S t 6 ddterming p a r trempe r a p i d e de miSlanges fondus e n u t i l i s a n t un
f o u r B a r c e t u n systsme B r o u l e a u x . Le r e c u i t de l a phase amorphe au-dessus de 970 OC c o n d u i t 3 une c r i s t a l l i s a t i o n p r i n c i p a l e m e n t d e Zr02 t G t r a g o n a l e , a v e c d e s g r a i n s de 2 10 nm, e t / o u d e m u l l i t e , a v e c d e s g r a i n s d e 2 B 5 pm.
A b s t r a c t - The f o r m a t i o n r e g i o n o f amorphous p h a s e s h a s been d e t e r m i n e d by t h e r a p i d quenching o f m e l t s i n t h e system Zr02-Si02-A1203 u s i n g arc-imaging f u r n a c e s and t w i n - r o l l e r s . Re-heating of t h e amorphous p h a s e b r o u g h t a b o u t t h e c r y s t a l l i z a t i o n mainly o f t-Zr02,210 nm i n s i z e , a n d / o r m u l l i t e , u p t o 2
-
5 y m i n s i z e above 970°C.I- INTRODUCTION
I n t h e r e c e n t y e a r s , n o b l e p r o c e s s e s have been developed t o p r e p a r e advanced
m a t e r i a l s . Rapid quenching of m e l t s i s i n t e r e s t i n g a s a new t e c h n i q u e f o r p r o v i d i n g amorphous o r m e t a s t a b l e p h a s e s . We have a p p l i e d t h i s t e c h n i q u e t o t h e samples i n t h e system Zr02-Si02-A1203 which i s i m p o r t a n t i n t h e s c i e n c e and t h e t e c h n o l o g y of a l k a l i - r e s i s t e n t g l a s s , r e f r a c t o r y and advanced c e r a m i c s , b e c a u s e t h i s system c o n t a i n s corundum ( a - A l Z 0 3 ) , Z i r c o n i a ( Z r 0 2 ) , Z i r c o n (ZrSi04) and M u l l i t e (3A1203' 2Si02 a s r e p r e s e n t a t i v e c o m p o s i t i o n ) . T h i s p a p e r d e a l s w i t h t h e f o r m a t i o n of amorphous p h a s e s by r a p i d quenching of m e l t s and t h e c r y s t a l l i z a t i o n from t h e amorphous p h a s e s upon r e - h e a t i n g .
11-EXPERIMENTAL
S t a r t i n g m a t e r i a l s were h i g h p u r i t y Z i r c o n i a (Zr02: 99.9%, Soekawa Chemical Co. L t d . Tokyo, J a p a n ) , S i l i c a (Si02: Guaranteed r e a g e n t , Kanto Chemical I n c . , Tokyo, Japan) and Alumina (a-A1203: 99.9%, I w a t a n i Chemical I n d u s t r y Co. L t d . , Tokyo, Japan) powders. The r e q u i r e d p r o p o r t i o n s were weighed and mixed t h o r o u g h l y i n a n a g a t e m o r t a r u s i n g e t h a n o l f o r 2 h o u r s . The m i x t u r e s were m e l t e d on t h e water-cooled copper p l a t e w i t h a xenon arc-imaging f u r n a c e /I/ (UF-10001, USHIO I n c . , Tokyo, Japan) a p p l y i n g from 6 t o 8 kw power i n a i r . The m o l t e n samples became s p h e r i c a l g l o b u l e s w i t h t h e d i a m e t e r of = 2 mm by s u r f a c e t e n s i o n i n a few seconds on
r a d i a t i o n . According t o measurement o f weight l o s s a f t e r m e l t i n g , t h e c o m p o s i t i o n a l change by e v a p o r a t i o n was n e g l i g i b l e i n t h i s p r o c e d u r e .
For r a p i d quenching, t h e b r o b u l e was m o l t e n a g a i n on a g r a p h i t e s t a g e and t h e n dropped i n a s t e e l t w i n - r o l l e r 30 mm i n d i a m e t e r a s shown i n F i g . 1 ( a ) / 2 / . Another t e c h n i q u e used a n o t h e r arc-imaging f u r n a c e / 3 , 4 / (SC-5D, Nichiden Machinary I n c . , S h i g a , Japan) f o r f l o a t i n g - z o n e c r y s t a l growth, where m o l t e n d r o p l e t 3 - 4 mm i n d i a m e t e r a t t h e end o f a s i n t e r e d b a r specimen ( 4 x 4 x 40 mm3 ) f a l l e d i n t o a s t e e l t w i n - r o l l e r 50 mm i n d i a m e t e r a s shown i n F i g . 1 ( b ) . The c o o l i n g r a t e of t h e molten samples quenched by t h e t w i n - r o l l e r s r o t a t i n g a t = 4000 rpm were e s t i m a t e d t o b e 105 K/sec b a s e d upon t h e r e l a t i o n by Ota e t a l . / 4 / between t h e c r i t i c a l c o o l i n g r a t e and t h e composition of t h e samples f o r g l a s s f o r m a t i o n i n t h e system Li20-Si02.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1986171
JOURNAL DE PHYSIQUE
The r a p i d l y quenched samples were s t u d i e d w i t h TG-DTA (Thermoflex, Rigaku E l e c t r i c I n c . , Tokyo, Japan) upto llOO°C a t 10°C/min i n a i r , o r re-heated a t 1200°C f o r v a r i o u s hours f o r c r y s t a l l i z a t i o n . The p r o d u c t s were examined by an X-ray d i f f r a c t o m e t e r (RU-200, Rigaku E l e c t r i c I n c . , Tokyo, Japan) o p t i c a l microscope
(Vanox, Olympus, Tokyo, Japan), SEM (T-200, JEOL, Tokyo, Japan) and TEM (H-700, H i t a c h i , Tokyo, J a p a n ) . The phase a n a l y s i s , l a t t i c e parameter and c r y s t a l l i t e -
Emitter
r o l l e r
Motor , Sample pan
'.
'.----'
,(a) Fig. 1
Schematic i l l u s t r a t i o n of r a p i d quenching of m e l t s u s i n g arc-imaging f u r n a c e and t w i n - r o l l e r
( a ) w i t h multi-purpose 1 0 kw Xe arc-imaging f u r n a c e / I , 21.
(b) w i t h arc-imaging f l o a t i n g - z o n e f u r n a c e 13, 4 1 . s i z e d e t e r m i n a t i o n were c a r r i e d o u t by
step-scanning technique u s i n g Cr2O3 a s an i n t e r n a l s t a n d a r d . C a l i b r a t i o n c u r v e s had been determined p r e v i o u s l y by adding known amounts of Cr2O3 t o each phase.
I11 - RESULTS AND DISCUSSION
111. 1 Amorphous Formation i n t h e System The r a p i d quenching using t h e t w i n - r o l l e r s r e s u l t e d i n t h e formation of amorphous m a t e r i a l s a s shown i n F i g . 2, 121. The p r o d u c t s w i t h wide compositional r e g i o n were t r a n s p a r e n t f l a k e s w i t h few t e n s p m
i n t h i c k n e s s and showed no c r y s t a l l i n i t y under X-ray d i f f r a c t i o n (Fig. 3 ) . Si02- r i c h compositions gave almost t r a n s p a r e n t p r o d u c t s b u t t-Zr02 phase p a r t i a l l y c r y s t a l l i z e d a t t h e t h i c k e r rims of t h e f l a k e s . T h i s s u g g e s t s t h a t SiO2-rich m e l t s have h i g h v i s c o s i t y which reduces
t h e c o o l i n g r a t e owing t o i n c r e a s i n g t h e t h i c k n e s s of t h e sample between r o l l e r s . I n t h e ZrO2-rich samples, t-Zr02 phase mainly c r y s t a l l i z e d a l l over t h e f l a k e s . A1203-rich samples produced a s l i g h t amount of a-A1203 phase a s w e l l a s Zr02 phase under X-ray d i f f r a c t i o n . M u l l i t e phase was observed, only f o r compositions of m u l l i t e and 60 w t % A1203 - 40 w t % Si02 i n t h e samples s t u d i e d .
Si02 Am:amorphous Mu :mullite
A :U-AI,O~ ZrO, ppt.
Fig. 2
Formation r e g i o n of amorphous phase by r a p i d quenching of m e l t s u s i n g a r c - imaging f u r n a c e and t w i n - r o l l e r .
=-present work, 0 : A m o n l y , 0 : A m +
tr. c r y s t a l l i n e phase, @:Am +crysta- l l i n e p h a s e ( s ) i n d i c a t e d .
. . . . . . . . . Amorphous r e g i o n by flame f u s i o n (Thorne, 1965)
-.-.- Amorphous r e g i o n by h y d r o l y s i s of a l k o x i d e s (Makishima e t a l . , 1980)
161 r e s u l t s . He a l s o r a p i d l y quenched t h e m e l t s u s i n g a flame s p h e r u l i z a t i o n technique where a d i s p e r s i o n of samples was i n j e c t e d i n t o an oxy-hydrogen flame s p r a y i n g i n d i s t i l l e d water. The amorphous r e g i o n o b t a i n e d from r a p i d l y quenched m e l t s e x t e n d s toward A1203 s i d e r a t h e r t h a n Zr02 s i d e . The l i q u i d u s s u r f a c e of A1203
i s lower temperature t h a n Zr02 s i d e i n t h e system Zr02-Si02-A1203 171. S a r j e a n t and Roy /81 d e s c r i b e d t h a t c r i t i c a l quenching r a t e below which d e t e c t a b l e c r y s t a l l i n e
Fig. 3
X-ray d i r r a c t i o n p a t t e r n s of v a r i o u s samples r a p i d l y quenched.
30S30A40Z means 30 w t % SiO2-30 wt% Al2O3- 40 wt% Zr02 a s a s t a r t i n g composition.
Fig. 4
C r y s t a l l i t e s i z e of t-Zr02 p r e c i p i t a t e d f n t h e r a p i d l y quenched samples.
111. 2 C r y s t a l l i z a t i o n from t h e Amorphous Phase by Heating
Re-heating of t h e amorphous phases brought about c r y s t a l l i z a t i o n . According t o DTA, a small endother- mic peak was observed a t =92OoC corresponding t o
g l a s s - t r a n s i t i o n temperature, and an extreme exother-
1
mic peak a t 950'- 1000°C of c r y s t a l l i z a t i o n a s shown 8 z i n Fig. 5. The s t a r t i n g temperature of c r y s t a l l i - W
phases a r e o b t a i n e d from melt were p r o p o r t i o n a l t o a square of t h e m e l t i n g tempera- t u r e . T h e r e f o r e i n t h e system Zr02-Si02-Al203, amorphous m a t e r i a l s tended t o form i n t h e high A1203 compositions r a t h e r t h a n i n t h e h i g h ZrO2 compositions seen i n t h e c a s e of Makishima.
The c r y s t a l l i z a t i o n of t-Zr02 i n t h e amorphous r e g i o n n e a r t h e Si02-ZcO2 j o i n seemed t o b e caused by t h e phase s e p a r a t i o n due t o t h e two-liquid r e g i o n i n t h e
F i g . 5
DTA curve of t h e amorphous phase by r a p i d quenching
of m e l t . Sample : 20 w t % Zr02-80 w t % 3hl2O3.2SiO2 900 'om 11.00
h e a t i n g r a t e : 1O0C/min. ( c )
system Si02-Zr02. The c r y s t a l l i n e phase of t h e quenched samples was mainly m e t a s t a b l e t-ZrOg phase of which c r y s t a l l i t e s i z e became l a r g e r w i t h t h e d i s t a n - c e s from t h e amorphous formation r e g i o n a s i n d i c a t e d i n Fig. 4. Monoclinic Zr02 was observed i n t h e
p r o d u c t s of t h e o u t e r r e g i o n i n t h i s diagram. T h i s i s 2
c o n s i s t e n t w i t h t h e argument /9/ t h a t t-Zr02 can W c r y s t a l l i z e from amorphous phases t h e n t r a n s f o r m i n t o m-Zr02 b u t m-Zr02 cannot c r y s t a l l i z e d i r e c t l y from t h e amorphous phases. T h i s i s f u r t h e r supported by t h e c r y s t a l l i z a t i o n of t h e amorphous phases upon r e h e a t i n g d e s c r i b e d below.
T
+
JOURNAL DE PHYSIQUE
z a t i o n peak i n DTA w i t h h e a t i n g r a t e of IOoc/min was h i g h e r i n t h e samples l o c a t e d i n n e r of t h e amorphous r e g i o n ( F i g . 6 ) . No d i s t i n c t exothermic peak was observed i n t h e samples c r y s t a l l i z e d a l r e a d y during quenching and i n t h e Si02-Zr02 r i c h samples probably due t o slow c r y s t a l l i z a t i o n k i n e t i c s . Figure 7 shows t h e phase assemblages of v a r i o u s samples a f t e r r e h e a t i n g upto l l O O o ~ i n a i r i n d i c a t i n g t h e c r y s t a l l i z a t i o n of t-Zr02 i n Z r O 2 - r i c h r e g i o n , m u l l i t e i n m u l l i t e - r i c h r e g i o n and t-Zr02 + m u l l i t e i n i n t e r m e d i a t e r e g i o n . The phase a n a l y s i s (Table 1 ) demonstrated t h e i n c r e a s e of t-Zr02 and m u l l i t e by t h e c r y s t a l l i z a t i o n . The c o n t e n t of m-Zr02, however remained c o n s t a n t w i t h i n t h e experimental e r r o r s (f 5 wt%) upon r e h e a t i n g .
Formation region of
: t-Zr02 O.:mullite
* : cc-A1203
Fig.7
Fig. 6 C r y s t a l l i z a t i o n of t-Zr02 and/or
Beginning temperature ("C) of t h e c r y s t a l l - m u l l i t e from t h e amorphous phase by i z a t i o n from t h e amorphous phase by DTA r e - h e a t i n g upto l l O O a C w i t h 10°C/min.
w i t h 10°C/min. F i l l e d symbols mean t h e c r y s t a l l i -
z a t i o n b e f o r e r e - h e a t i n g . These r e s u l t s r e v e a l e d t h a t Table 1.
m u l l i t e and t-Zr02 were c r y s t a l l - V a r i a t i o n of phase composition by r e - h e a t i n g i z e d from t h e amorphous phase a t upto 1100°C of r a p i d l y quenched samples.
950"-1000°C. The exothermic r e a c t i o n observed i n DTA c o r r e s - ponds t o t h e c r y s t a l l i z a t i o n of m u l l i t e , because no s i g n i f i c a n t peaks were observed i n DTA of t h e samples i n which only t h e c o n t e n t s of t-Zr02 i n c r e a s e d upon r e - h e a t i n g a s i n d i c a t e d i n Fig.
6 . The c r y s t a l l i t e s i z e of t- Zr02 c r y s t a l l i z e d from t h e amor- phous phase was about 10 nm s i m i - l a r t o t h e c r i t i c a l c r y s t a l l i t e s i z e a t t h e boundary of t h e amorphous r e g i o n a s shown i n F i g . 4.
The r e - h e a t i n g of t h e amor- phous phase upto 1100°C y i e l d e d t-Zr02 and m u l l i t e b u t s t i l l l e f t a c o n s i d e r a b l e amounts of
1
t h e amorphous phase a s i n d i c a t e d 1
i n Table 1. The h e a t t r e a t m e n t
a t 1200°C, on t h e o t h e r hand, * Z:ZrOp S:Si02 A:A1203 3.2M:3AI2O3'2SiO2 brought about almost complete
c r y s t a l l i z a t i o n /lo/. For ** The remains are amorphous phases Sample
composition*
302705 OA 35Z40S25A 40260s OA 47223S30A 50Z 5S45A 50Z40SlOA 61Z29SlOA 10240S50A 10Z90(3.2M) 20280(3.2M) 40210S50A 40Z30S30A
Crystal 1 ine phase (wtX) **
before heating m-Zr02
12
-
26
- -
29 19
- - - - -
after heating t-Zr02
11 13
8 10 22 18 33
- - - - -
m-Zr02
- 8 24 - -
24
- 14
- - - -
t-Zr02 19 34 16 40 42 28 39 - - 6 32 3 1
mu1 1 i te
- - -
-
- - -
4 1 64 63
- -
2 S i 0 c o m p o s i t i o n c r y s t a l l i z e d i n t o 83.8 wt% m u l l i t e + +
m-zr8 w i t h i n a h a l f h o u r . The TEM o b s e r v a t i o n r e v e a l e d t h a t t h e p r o d u c t c o n s i s t o f m u E l i t e g r a i n s 3 - 5 p m i n s i z e which c o n t a i n e d t i n y Zr02 c r y s t a l s 1 0 d 2 0 nm i n s i z e , F i g . 8 ( a ) . These m u l l i t e g r a i n s were s i n g l e c r y s t a l s a s i n d i c a t e d i n F i g . 8 ( b ) . The c h a r a c t e r i s t i c r a d i a l a r r a n g e m e n t s of Zr02 c r y s t a l s i n t h e m u l l i t e g r a i n s , F i g . 8 (c), s u g g e s t t h a t t h e s e Zr02 c r y s t a l s were p r e c i p i t a t e d by t h e e x o l u t i o n upon c r y s t a l l i z a t i o n of m u l l i t e from t h e amorphous m a t r i x . These m i c r o s t r u c t u r e s a l s o s u g g e s t t h a t t h e c r y s t a l l i z a t i o n o f m u l l i t e r a t h e r t h a n Zr02 i s dominant upon h e a t i n g o f t h e s e m a t e r i a l s .
According t o t h e l a t t i c e p a r a m e t e r s , t h e c o m p o s i t i o n of m u l l i t e would change from A1203-excess ( 77 wt% A1203 ) toward s t o i c h i o m e t r i c ( 72 wt% A1203 f o r 3A1203.
2Si02 ) by prolonged h e a t t r e a t m e n t a t 1200°C. The d e t a i l s of t h e c r y s t a l l i - z a t i o n p r o c e s s i n t h e s e m a t e r i a l s a r e r e p o r t e d i n a n o t h e r p a p e r 1101.
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