Eigenschaften und Wertung von elektrolytisch hergestellten Arten MnO2

The surface areas of natural ores, electrolytic, chemical, and synthetic hydrous MnO2 samples were determined by both low-temperature nitrogen gas adsorption and water vapor adsorption at 25~ using the B.E.T. adsorption isotherm relationship. These various types of manganese dioxides have distinctly different surface areas as determined by the two methods. The water content retained at ll0~ and corrected total water content were found to be surface area dependent. The synthetic hydrous MnO 2 samples occupy a unique position due to their high water content.

Section: Resultssupporting

confidence: 60%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Investigation of Manganese Dioxides

Amlie¹,

Tvarusko²

1964

“…The water content depends not only on the origin and type of MnO2 (29) but also on the parameters of the preparations, for example, for electrolytic ~-MnO2, on the electrode material (30) and temperature of electrodeposition (27,31). Gattow (32) describes the difficulty of reproducing the water content.…”

mentioning

confidence: 99%

Investigation of Manganese Dioxides

Tvarusko¹

1964

The water content of natural ores, electrolytic, chemical, and synthetic hydrous MnO2 samples, equilibrated in an atmosphere of 75% relative humidity, was determined at 110°, 235°, and 400°C. Total water varied from 1% for a highly crystalline β‐MnO2 to 20% for synthetic hydrous MnO2 . The pH of the MnO2 samples increased with increasing temperature, except for natural ores and their derivatives which showed a decrease in pH at 235°C. The degree of resorption of water vapor was dependent on the drying temperature and decreased with increasing temperature.

“…In recent literature, however, it is found that pyrolytic MnO2 contains various amounts of hydrogen (16)(17)(18)(19) so that the MnO2 can act as the proton donor.…”

Section: The System T a / T A 2 O J E V A P O R A T E D Pt E X Hmentioning

confidence: 99%

The Mechanism of Electrolytic Rectification

Middelhoek

1964

g r a p h i c p l a t e s w e r e p l a c e d w i t h i n 1-3 m m of the s p e c i m e n to r e c o r d the image. A n g l e s of incidence of 10~~ w e r e used, and these g a v e s u b s t r a t e cont r i b u t i o n s to the i m a g e of less t h a n 2%. E x p o s u r e times of 30 min w e r e used.Cliffe and F a r r (2) f o u n d m a r k e d differences in the t o p o g r a p h y of deposits f o r m e d a b o v e and b e l o w a critical e l e c t r o l y t e t e m p e r a t u r e r a n g e of 94~176In o r d e r to c o m p a r e these deposit structures, p l a ting was c a r r i e d out at 10 m a / c m e for 30 m i n ( g i v i n g a 6~ thick d e p o s i t ) at 25 ~ and at 99~ E L E C T R O L Y T I C R E C T I F I C A T I O N 379F i g u r e 2 is a B e r g -B a r r e t t i m a g e of the substrate, and the l i n e a r s t r i a t i o n s u b s t r u c t u r e is seen as light and d a r k bands. T h e c i r c u l a r a r e a c o r r e s p o n d s to a p o r o s i t y hole f o r m e d in freezing the metal. This f e a t u r e p r o v e d useful as a location m a r k .In the i m a g e f r o m the deposit f o r m e d at 25~ (Fig. 3), the hole m a y be seen, b u t t h e r e is no e v idence of the s t r i a t i o n s u b s t r u c t u r e . In contrast, the s t r i a t i o n s t r u c t u r e has c l e a r l y b e e n r e p r o d u c e d in the deposit f o r m e d at 99~ (Fig. 4).It a p p e a r s t h e r e f o r e t h a t deposits f o r m e d a b o v e 98~ are e p i t a x i a l w i t h the substrate. W h i l e L a u e spots w e r e still o b t a i n a b l e f r o m the d e p o s i t f o r m e d at 25~ the deposit no l o n g e r c o n f o r m e d so closely to the s t r u c t u r e of the s u b s t r a t e . AcknowledgmentsThe a u t h o r s t h a n k P r o f e s s o r E. C. Rollason for his i n t e r e s t and for the p r o v i s i o n of l a b o r a t o r y facilities. T h a n k s are also due to Messrs. J o s e p h L u c a s Ltd. for g e n e r o u s financial assistance.Manuscript received Oct. 21, 1963. A n y discussion of this paper will appear in a Discussion Section to be published in the December 1964 215, 483 (1959). 2. D. R. Cliffe and J. P. G. Farr, This Journal, 111, 299 (1964). 3. R. Brownsword and J. P. G. Farr, Nature, 195, 373 (1962). The Mechanism of Electrolytic RectificationA. Middelhoek N. V. Philips Gloeilampen3~abrieken, Zwolle, The NetherlandsIt has b e e n k n o w n for a long t i m e t h a t the s y s t e m m e t a l / m e t a l o x i d e / e l e c t r o l y t e , w h e r e the m e t a l is Ta, A1, etc. ( s o -c a l l e d v a l v e m e t a l s ) , e x h i b i t s r e c t ification. W h e n the m e t a l is a n o d i c a l l y polarized, t h e r e is a " s m a l l " c u r r e n t , the l e a k a g e c u r r e n t ; w h e n the m e t a l is c a t h o d i c a l l y polarized, a " h i g h " c u r r e n t flows, the f o r w a r d current.V a r i o u s theories, as m e n t i o n e d in S c h m i d t ' s a r t i c l e (1), h a v e b e e n p r o p o s e d to e x p l a i n the p h e n o m e n o n of...