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Very pure metals
VACUUM Classified A b s t r a c t s
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General Science a n d E n g i n e e r i n g Contd.
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Metal Melting Under V a c u u m . Some Mechanical Problems United tfingdom. D u r i n g the last t e n years the process of v a c u u m melting has o u t g r o w n operations on a l a b o r a t o r y scale. There is n o w s t a n d a r d e q u i p m e n t available for production on an industrial scale w i t h crucible capacities ranging from 20-240 lb. per charge. One installation in Switzerland, is k n o w n to consist of a furnace w i t h a capacity of 450 lb. per charge. Details and illustrations are given of a m o d e r n 60 lb. plant. I t s v a c u u m c h a m b e r is m a d e of stainless steel arid is double-walled to facilitate w a t e r cooling. I t is fitted w i t h a feeder device of the t y p e described in Vol. I I I , A b s t r a c t No. 125/III. The q u a r t z glass inspection w i n d o w in the cover is reinforced w i t h a panel of F y r e x glass. Metal films deposited on the w i n d o w during processing can be r e m o v e d b y a wiper ill the form of a wire brush, operated from outside the chamber. P y r o m e t r i c m e a s u r e m e n t is effected b y m e a n s of a ttlermocouple housed in a q u a r t z tube. A special mechanism, contro!)ed externally, p e r m i t s the insertion of the t h e r m o c o u p l e into the crucible w h e n required and its withdrawal, wLeu not in use, to an area where it c a n n o t suffer mechanical or t h e r m a l damage, during p o u r i n g for instance. Various m e t h o d s of p o u r i n g are mentioned. I n the p l a n t described the c h a m b e r is s t a t i o n a r y and the crucible only is tilted for the purpose. H e a t i n g is effected b y induction and the moulds of cast-iron or steel, have a s m o o t h surface and are pre-heated to a b o u t 300°C immediately prior to use. The progress of a typical tool steel melt is s h o w n in a time-pressure diagram, details of which were discussed ill Vol. h i , A b s t r a c t No. 164/111. The pressure in the chamber, before melting s t a r t s a n d immediately prior to pouring, is 10 ~3 mm. Hg. I t is s t a t e d t h a t the cons u m p t i o n of electrical energy for v a c u u m melting differs little from t h a t required for melting an equivalent charge in the same t y p e of furnace at atmospheric pressure. Sommaire : D6tails d ' u n four ~ induction ~ vide d ' u n e capacit4 de 30 kg e o n v e n a n t p o u r la fusion et la coul6e d'aciers p o u r outil.
Abstraot ~o. and References
54/I
Article by Anon.
Metallurgia Nov. 1953 259-260
Furnace for V a c u u m Distillation of Zinc and Silver Contained in Alloys of Zinc and Silver, Constructed by the Institute Pesquisas Tecnologicas of Sao Paulo See A b s t r a c t No. : 3 2 / I I I
55/I
The Evaporation of Metals and Metalloids in V a c u u m See A b s t r a c t No. : 3 8 / I I I
56/I
Method of Preparing Nickel Powder with a Large Surface Area United States. Fine nickel p o w d e r s are used as chemical, physical or catalytical agents. F o r instance, it is s o m e t i m e s necessary to m e a s u r e the h e a t produced when nickel p o w d e r is wetted w i t h certain liquids. Also, nickel p o w d e r is e m p l o y e d in the h y d r o g e n a t i o n of vegetable oils for the p r o d u c t i o n of shortenings. F o r this and o t h e r applications it is desirable to m a k e nickel p o w d e r s available which have a large specific surface. At present, nickel p o w d e r s obtainable t h r o u g h n o r m a l commercial channels have surface areas not exceeding 1 m2/g. I n isolated instances nickel p o w d e r s w i t h surface areas of 50 me/g. have been produced b u t the processes involved are r a t h e r complex. A m e t h o d for the regular p r o d u c t i o n of large surface nickel powders is described as follows: Nickel oxalate (NiCeO 4. 2H20 ) is heated in a t u b e at 200°C in an oven to eliminate the w a t e r of crystallisation and theI1 h e a t - t r e a t e d at a b o u t 320~C. The t u b e is e x h a u s t e d in order to accelerate the decomposition of the material and to p r e v e n t conversion to the oxide or carbonate. E v e r y 24 hours tile t u b e is closed b y m e a n s of a stopcock, r e m o v e d from the oven, cooled d o w n and the contents weighed to check on the progress of the decomposition. W h e n decomposition is 99-100% complete, the p o w d e r is r e a d y for use. If t h e p o w d e r is to be stored, benzene or an inert gas is introduced into the t u b e w i t h o u t breaking the v a c u u m to p r o t e c t the material f r o m oxidation. W h e n required for use, the nickel benzene m i x t u r e is placed in glass bulbs connected to a v a c u u m s y s t e m to e v a p o r a t e and r e m o v e the benzene. E v a c u a t i o n is continued at 320°C and t h e bulbs are sealed off w h e n the pressure has reached l0 -5 m m . Hg. The t e m p e r a t u r e applied during t r e a t m e n t is i m p o r t a n t . Nickel p o w d e r p r e p a r e d at 400°C h a s a surface area of a b o u t 44 m2/g. The p o w d e r produced b y this m e t h o d is pyrophoric. I n contact w i t h liquids such as benzene it evolves h e a t of the order of 0.1 to 0.2 c a l . / m e. Sommaire : M4thode p o u r la p r 4 p a r a t i o n de p o u d r e de nickel ~ grande surface.
57/I
N. J. DeLollis U.S. Pat. 2,660,523
V a c u u m Dezincing of Desilverised Lead Bullion See A b s t r a c t No. : 3 3 / I I I
58/I
Production of Pure and Deliberately Contaminated Iron and Studies of These Materials See A b s t r a c t N o . : 3 4 / I I I
59/I
January, 195ff
Vacuum VoL I V No. I
96
I
O
©
--
General Science a n d E n g i n e e r i n g Contd.
--
I
Metal Melting Under V a c u u m . Some Mechanical Problems United tfingdom. D u r i n g the last t e n years the process of v a c u u m melting has o u t g r o w n operations on a l a b o r a t o r y scale. There is n o w s t a n d a r d e q u i p m e n t available for production on an industrial scale w i t h crucible capacities ranging from 20-240 lb. per charge. One installation in Switzerland, is k n o w n to consist of a furnace w i t h a capacity of 450 lb. per charge. Details and illustrations are given of a m o d e r n 60 lb. plant. I t s v a c u u m c h a m b e r is m a d e of stainless steel arid is double-walled to facilitate w a t e r cooling. I t is fitted w i t h a feeder device of the t y p e described in Vol. I I I , A b s t r a c t No. 125/III. The q u a r t z glass inspection w i n d o w in the cover is reinforced w i t h a panel of F y r e x glass. Metal films deposited on the w i n d o w during processing can be r e m o v e d b y a wiper ill the form of a wire brush, operated from outside the chamber. P y r o m e t r i c m e a s u r e m e n t is effected b y m e a n s of a ttlermocouple housed in a q u a r t z tube. A special mechanism, contro!)ed externally, p e r m i t s the insertion of the t h e r m o c o u p l e into the crucible w h e n required and its withdrawal, wLeu not in use, to an area where it c a n n o t suffer mechanical or t h e r m a l damage, during p o u r i n g for instance. Various m e t h o d s of p o u r i n g are mentioned. I n the p l a n t described the c h a m b e r is s t a t i o n a r y and the crucible only is tilted for the purpose. H e a t i n g is effected b y induction and the moulds of cast-iron or steel, have a s m o o t h surface and are pre-heated to a b o u t 300°C immediately prior to use. The progress of a typical tool steel melt is s h o w n in a time-pressure diagram, details of which were discussed ill Vol. h i , A b s t r a c t No. 164/111. The pressure in the chamber, before melting s t a r t s a n d immediately prior to pouring, is 10 ~3 mm. Hg. I t is s t a t e d t h a t the cons u m p t i o n of electrical energy for v a c u u m melting differs little from t h a t required for melting an equivalent charge in the same t y p e of furnace at atmospheric pressure. Sommaire : D6tails d ' u n four ~ induction ~ vide d ' u n e capacit4 de 30 kg e o n v e n a n t p o u r la fusion et la coul6e d'aciers p o u r outil.
Abstraot ~o. and References
54/I
Article by Anon.
Metallurgia Nov. 1953 259-260
Furnace for V a c u u m Distillation of Zinc and Silver Contained in Alloys of Zinc and Silver, Constructed by the Institute Pesquisas Tecnologicas of Sao Paulo See A b s t r a c t No. : 3 2 / I I I
55/I
The Evaporation of Metals and Metalloids in V a c u u m See A b s t r a c t No. : 3 8 / I I I
56/I
Method of Preparing Nickel Powder with a Large Surface Area United States. Fine nickel p o w d e r s are used as chemical, physical or catalytical agents. F o r instance, it is s o m e t i m e s necessary to m e a s u r e the h e a t produced when nickel p o w d e r is wetted w i t h certain liquids. Also, nickel p o w d e r is e m p l o y e d in the h y d r o g e n a t i o n of vegetable oils for the p r o d u c t i o n of shortenings. F o r this and o t h e r applications it is desirable to m a k e nickel p o w d e r s available which have a large specific surface. At present, nickel p o w d e r s obtainable t h r o u g h n o r m a l commercial channels have surface areas not exceeding 1 m2/g. I n isolated instances nickel p o w d e r s w i t h surface areas of 50 me/g. have been produced b u t the processes involved are r a t h e r complex. A m e t h o d for the regular p r o d u c t i o n of large surface nickel powders is described as follows: Nickel oxalate (NiCeO 4. 2H20 ) is heated in a t u b e at 200°C in an oven to eliminate the w a t e r of crystallisation and theI1 h e a t - t r e a t e d at a b o u t 320~C. The t u b e is e x h a u s t e d in order to accelerate the decomposition of the material and to p r e v e n t conversion to the oxide or carbonate. E v e r y 24 hours tile t u b e is closed b y m e a n s of a stopcock, r e m o v e d from the oven, cooled d o w n and the contents weighed to check on the progress of the decomposition. W h e n decomposition is 99-100% complete, the p o w d e r is r e a d y for use. If t h e p o w d e r is to be stored, benzene or an inert gas is introduced into the t u b e w i t h o u t breaking the v a c u u m to p r o t e c t the material f r o m oxidation. W h e n required for use, the nickel benzene m i x t u r e is placed in glass bulbs connected to a v a c u u m s y s t e m to e v a p o r a t e and r e m o v e the benzene. E v a c u a t i o n is continued at 320°C and t h e bulbs are sealed off w h e n the pressure has reached l0 -5 m m . Hg. The t e m p e r a t u r e applied during t r e a t m e n t is i m p o r t a n t . Nickel p o w d e r p r e p a r e d at 400°C h a s a surface area of a b o u t 44 m2/g. The p o w d e r produced b y this m e t h o d is pyrophoric. I n contact w i t h liquids such as benzene it evolves h e a t of the order of 0.1 to 0.2 c a l . / m e. Sommaire : M4thode p o u r la p r 4 p a r a t i o n de p o u d r e de nickel ~ grande surface.
57/I
N. J. DeLollis U.S. Pat. 2,660,523
V a c u u m Dezincing of Desilverised Lead Bullion See A b s t r a c t No. : 3 3 / I I I
58/I
Production of Pure and Deliberately Contaminated Iron and Studies of These Materials See A b s t r a c t N o . : 3 4 / I I I
59/I
January, 195ff
Vacuum VoL I V No. I
96