5/5/2023 0 Comments Igetter quality loss![]() M i c r o b a l a n c e in a high v a c u u m r e c e i v e r and heated inĪn induction coil by 1 MHz ac. The e v a p o r a t i o n r a t e has b e e n d e t e r m i n e d in m o s tĬ a s e s from the weight loss of m e t a l d i s k s or cylind e r s, 3 to 8 m m in diam, which were s u s p e n d e d on a Gaseous s u r f a c e b o u n d a r y l a y e r. That the r e d u c t i o n of the e v a p o r a t i o n r a t e is m a i n l yĬaused by the diffusion of m e t a l a t o m s through a Is a r e a s o n a b l e value and it supports the a s s u m p t i o n is in the r a n g e of 10 m e a nįree path length of i n e r t gas a t o m s for v / v o = 0.5. I n s e r t i n g a p p r o p r i a t e t h e o r e t i c a l values for K11 andĮ x p e r i m e n t a l data in Eq. The t h i c k n e s s dD of the diffusion l a y e r obtained by With K and exponent n b e i n g two fitting p a r a m e t e r s. If theĪpproach of F i s c h e r, J a n k e and S t a h l s c h m i d t 2 is followed and dD is used as a p r e s s u r e dependent e x p e r i m e n t a l fitting p a r a m e t e r of the s y s t e m, the followingĮ m p i r i c a l f o r m u l a p r o v i d e s an a p p r o p r i a t e r e p r e s e n tation for e x p e r i m e n t a l c u r v e s : I n e r t gas and m e t a l a t o m s in the gas phase. Point where the m e t a l v a p o r p r e s s u r e is about zero,Īnd K1 a c o n s t a n t c o n t a i n i n g a t o m i s t i c data of the T h r e e p r o c e s s e s a r e r e s p o n s i b l e for m e t a l t r a n s p o r t in the gas phase:ġ) diffusion due to the c o n c e n t r a t i o n g r a d i e n t ,Ģ) t h e r m a l t r a n s p o r t due to the t e m p e r a t u r e g r a d i ent, andģ) t r a n s p o r t in the convection s t r e a m of the i n e r t Is not p r e s e n t l y a v a i l a b l e. Specific g e o m e t r i c a l a r r a n g e m e n t of the device used, ![]() S o l u t i o n of the m i g r a t i o n rate of m e t a l a t o m s in thisĬomplicated s y s t e m, which in addition depends on the A r e l i a b l e q u a n t i t a t i v e t h e o r e t i c a l S u r f a c e, it r e a c h e s a m a x i m u m and then drops again At i n c r e a s i n g d i s t a n c e s f r o m the Steep g r a d i e n t and the v e l o c i t y of gas convection at In the n e a r s u r f a c e r e g i o n the gas t e m p e r a t u r e and the m e t a l v a p o r p r e s s u r e (see F i g. The solid or liquid m e t a l as well as with the cooled Gas a t m o s p h e r e is in contact with the hot s u r f a c e of U n d e r n o r m a l conditions in a v a c u u m v e s s e l the S e m i e m p i r i c a l r u l e for p r a c t i c a l a p p l i c a t i o n s. P e r f o r m e d in our l a b o r a t o r y in o r d e r to obtain a Extended e x p e r i m e n t s i n c l u d i n g 15 m e t a l sĪnd g a s e s such as He, A r, and N2, have t h e r e f o r e b e e n The t h e o r e t i c a l t r e a t m e n t s ~-4 do not p e r m i t q u a n t i t a tive c a l c u l a t i o n of the r e d u c t i o n of e v a p o r a t i o n by ine r t g a s e s. Only for a few m e t a l s and alloys and f u r t h e r m o r e However, q u a n t i t a tive data on the magnitude of this effect a r e a v a i l a b l e M e l t i n g or a n n e a l i n g p r o c e s s e s in v a c u u m can be r e duced by an i n e r t gas p r e s s u r e. Well known that m e t a l l o s s e s o c c u r r i n g d u r i n g If a m e t a l f o r m s volatile oxides s m a l l i m p u r i t i e s of O2 or H20 in the i n e r t gasĬan i n c r e a s e a g a i n the m e t a l l o s s e s. p)-I (p in Pa) is obtained, which s e e m s to be c o r r e c t within a f a c t o r of.F r o m these r e s u l t s and l i t e r a t u r e data the a p p r o x i m a t e f o r m u l a v / v o The r e d u c t i o n of the e v a p o r a t i o n rate of Ti, Z r, V, Nb, Ta, Mo, W, Re, Co, Ni, Pd, Pt, I r ,Ĭu, Ag in A r and in a few r u n s a l s o in He o r N2 has b e e n d e t e r m i n e d as a function of
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