A noncrystalline Pt-Sb phase and its equilibration kinetics
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f o r m e d by splat cooling in the P t - S i and P t - S b s y s t e m s , and with the k i n e t i c s of the d e c o m p o s i t i o n of a n o n c r y s t a l l i n e phase p r e s e n t in s p l a t cooled Pto.66Sbo.34 alloy. X - r a y d i f f r a c t i o n , e l e c t r o n diffraction, and t r a n s m i s s i o n m i c r o s c o p y t e c h n i q u e s w e r e e m ployed. E X P E R I M E N T A L METHODS P r e p a r a t i o n of Alloys and Rapid Quenching The a l l o y s were p r e p a r e d by m e l t i n g high p u r i t y c o n s t i t u e n t m e t a l s in an i n e r t gas, n o n c o n s u m a b l e e l e c t r o d e a r c m e l t i n g f u r n a c e . The homogeneous alloy buttons, weighing about 10 g, were cut into p i e c e s of 40 to 90 rag, each of which was u s e d as a c h a r g e for a splat-cooling experiment. The technique u s e d for s p l a t cooling is d e s c r i b e d in detail in Refs. 1 to 3; a v e r t i c a l r e s i s t a n c e - h e a t e d a l u m i n a c r u c i b l e with a hole of about 1 m m diam at the bottom was used, through which the m o l t e n charge was expelled in the form of fine d r o p l e t s by a shock wave. The e j e c t e d d r o p l e t s were i m p a c t e d a g a i n s t a cold s u b s t r a t e in the form of thin f i l m s . The quenched f i l m s were between ~ 0.1 and 10 ~ thick and had u n d e r gone cooling r a t e s of 106 to 109~ p e r sec. 1~'18 Alloys were splat cooled to - 1 9 0 ~ and 20~ After quenching t o - 190~ no s i g n i f i c a n t i m p r o v e m e n t in the r e l a t i v e a m o u n t of the m e t a s t a b l e phase over the yield obtained at 20~ was noticed. S t r u c t u r e and D e c o m p o s i t i o n Studies
A Hitachi H u - l l e l e c t r o n m i c r o s c o p e with hot stage was u s e d for the e l e c t r o n t r a n s m i s s i o n and diffraction s t u d i e s . B e c a u s e of e l e c t r o n b e a m heating and low heat t r a n s f e r within the i r r e g u l a r thin film, it was not p o s s i b l e to m a i n t a i n a d e s i r e d c o n s t a n t t e m p e r a t u r e in the hot stage of the m i c r o s c o p e . Before heating, the s t r u c t u r e and diffraction p a t t e r n of a s u i t a b l e thin a r e a were photographed. The s p e c i m e n was then heated P K. SRIVASTAVA,formerly Research Assistant, Department of slowly and was continuously o b s e r v e d ; o c c a s i o n a l l y its Metallurgy and Materials Science, Massachusetts Institute of Technology, s t r u c t u r e and diffraction p a t t e r n were photographed. Cambridge, Mass., is now with Carbon and Metals Division, Union CarX - r a y d i f f r a c t i o n p a t t e r n s were taken on a Ge-XRD5 bide India, Ltd., Calcutta, India. B. C. GIESSEN, formerly Research d i f f r a c t o m e t e r with CuK~ r a d i a t i o n . F o r the X - r a y Associate, Department of Metallurgy and Materials Science, M.I.T., is study of the s t r u c t u r a l changes taking place upon a n now Associate Professor of Chemistry, Northeastern University, n e a l i n g
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