- Email: [email protected]
Microstructure of patint films
VACUUM Classitied A b s t r a c t s
I
O
O
--
General Science and Engineering Contd.
--
I
AbstractNo.
and References
The Electron Microscope in Biology See A b s t r a c t No. : 6 5 / I I
122/1
The Medical Research Council Linear Accelerator a n d Cyclotron United Kingdom. D e t a i l s are g i v e n on t h e i n s t a l l a t i o n a n d p e r f o r m a n c e of t h e 8 MeV t r a v e l l i n g - w a v e linear accelerator n o w in use at H a m m e r s m i t h Hospital, L o n d o n . T h e t r e a t m e n t r o o m houMng t h e accelerator h a s concrete walls 4 - 6 feet t h i c k a n d is accessible via a n indirect corridor w i t h concrete walIs. T h e p a t i e n t is o b s e r v e d b y t h e o p e r a t o r at t h e control desk t h r o u g h a periscope. T h e t e c h n i c a l details of t h e accelerator h a v e been g i v e n p r e v i o u s l y (see Nature I7G (1953) 297). T h e 3 - m e t r e accelerating t u b e is s u s p e n d e d f r o m t h e ceiling a n d t h e electron b e a m passes into a n X - r a y h e a d where a n e l e c t r o m a g n e t deflects it t h r o u g h 90 ° before s t r i k i n g t h e gold t r a n s m i s s i o n t a r g e t . T h e X - r a y b e a m c a n be collimated to a m a x i m u m d i a m e t e r of 26 cm. at a d i s t a n c e of 1 m e t r e f r o m t h e t a r g e t b y m e a n s of t u n g s t e n - c o p p e r alloy blocks c o n t a i n i n g a conical hole. A n a d j u s t a b l e d i a p h r a g m s y s t e m consisting of 4 t h r e e - i n c h t h i c k t u n g s t e n - c o p p e r alloy blocks facilitates t h e p r o v i s i o n of a t r e a t m e n t field v a r y i n g f r o m 4 to 20 cm. square. T h e n o r m a l t a r g e t - s k i n d i s t a n c e is 1 m e t r e . P o i n t e r s on t h e X - r a y h e a d indicate t h e p o i n t s of e n t r y a n d e x i t of t h e b e a m on t h e p a t i e n t ' s skin. B y r o t a t i o n of t h e X - r a y head, vertical d i s p l a c e m e n t of t h e floor (up to 5 ft.) a n d h o r i z o n t a l m o v e m e n t of t h e t r e a t m e n t conch, t h e p o s i t i o n a n d angle of t h e b e a m on t h e p a t i e n t c a n be a d j u s t e d . T h e h i g h i n t e n s i t y of t h e o u t p u t of t h e accelerator e q u a l l i n g 100-200 r a d / m i n . (1 r a d = 100 erg/g.) reduces t h e t r e a t m e n t t i m e per p a t i e n t to t w o m i n u t e s . T h e 8 MeV m a c h i n e gives g r e a t e r p e n e t r a t i o n t h a n t h e 2 ~{eV m a c h i n e (the so-cMled cobalt unit) a n d t h e c o n v e n t i o n a l 200 k V X - r a y s . B o t h s u p e r v o l t a g e r a d i a t i o n m a c h i n e s (8 MeV a n d 2 MeV) s h o w a b u i l d - u p of i n t e n s i t y at 2.0 cm. a n d 0.5 cm. d e p t h below t h e skin respectively. T h i s is d u e to t h e fact t h a t t h e s e c o n d a r y electrons, w h i c h are e s s e n t i a l l y responsible for t h e ionisation, are m a i n l y projected in t h e direction of t h e i n c i d e n t b e a m a n d h a v e a r a n g e increasing w i t h t h e voltage. As far as is k n o w n high e n e r g y X - r a y s h a v e no biological effects different from low e n e r g y r a y s b u t s k i n r e a c t i o n is reduced a n d bone a b s o r b s less t h a n soft tissue, lowering t h e risk of bone necrosis. A 4 5 - i n c h cyclotron is u n d e r c o n s t r u c t i o n in t h e s a m e building. T h e p u r p o s e is to facilitate i n v e s t i g a t i o n s into t h e effects of n e u t r o n s on living a n d i n e r t m a t t e r . I t will also be e m p l o y e d for t h e p r o d u c t i o n of r a d i o a c t i v e isotopes w h i c h h a v e to be used i m m e d i a t e l y t h e y b e c o m e available b e c a u s e of t h e i r s h o r t life. Sommaire : Des d6tails c o m p l e t s s o n t d o n n e s s u r l'acc616rateur r 6 c e m m e n t install6 k l ' H o s p i t a l d ' H a m m e r s m i t h , Londres, p o u r la th6rapie ~ r a y o n s X. Q u e l q u e s r e n s e i g n e m e n t s s o n t aussi d o n n 6 s s u r u n c y c l o t r o n q u e l'on constrnit'dans la m S m e localit6.
123/1
Article by C. A. P. Wood & G. R. Newbery ~¥ature 173, 6.2.1954 233-235
An Evaporated Carbon Replica Technique for Use with the Electron Microscope and its Application to the Study of Photographic Grains See A b s t r a c t No. : 6 9 / I I
~24/i
Microstructure of Paint Films United States. T h e d a t a so far m a d e available b y research on t h e p h y s i c a l properties of p a i n t a n d p a i n t c o n s t i t u e n t s h a v e o n l y in p a r t assisted practical problems. I t a p p e a r s t h a t t h e reproducibility of t h e a p p e a r a n c e of p a i n t films for i n s t a n c e , c a n o n l y be fully explored b y o b t a i n i n g m o r e k n o w l e d g e of film s t r u c t u r e . A s u i t a b l e m e a n s of i n v e s t i g a t i n g film s t r u c t u r e is t h e microscope a n d it is t h e object of t h i s article to r e p o r t on t h e u s e s of t h e electron microscope t e c h n i q u e in o b t a i n i n g q u a l i t a t i v e i n f o r m a t i o n (a) on t h e s t r u c t u r e of t h e resinous b i n d e r w h i c h h a s m i c r o m o l e c u l a r dimensions, (b) t h e a r r a n g e m e n t of p i g m e n t in t h e film i.e. a s t u d y of t h e e x t e n t of flocculation, s e d i m e n t a t i o n etc. a n d (c) t h e s t r u c t u r e of b o t h air a n d a d h e s i o n interfaces of t h e films. T h e i n s t r u m e n t used in t h i s s t u d y w a s a n E M U - 2 R C A electron microscope. T h e t r a n s m i s s i o n t e c h n i q u e was used. One difficulty is p r e s e n t e d b y t h e fact t h a t direct v i e w i n g of t h e film s p e c i m e n ill t h e i n s t r u m e n t is o n l y useful for film t h i c k n e s s e s u p to 0.2 m i c r o n w h e r e a s t h e n o r m a l p a i n t film h a s a t h i c k n e s s of 25 m i c r o n or over. T h i s h a s been overcome b y t h e d e v e l o p m e n t of two replica t e c h n i q u e s w h i c h h a v e p r o v e d s a t i s f a c t o r y to s o m e e x t e n t . F i r s t is t h e so-called silver silica t e c h n i q u e , T h e p a i n t s p e c i m e n is coated w i t h a silver film b y v a c u u m e v a p o r a t i o n . S u b s e q u e n t l y a coat of p o l y v i n y l alcohol is applied to t h e silver surface a n d allowed to dry, T h e c o m p o s i t e film is t h e n s t r i p p e d f r o m t h e s p e c i m e n and t h e n e g a t i v e of t h e replica v a c u u m coated w i t h silica. F i n a l l y t h e p o l y v i n y l alcohol a n d silver c o a t i n g is dissolved b y acid t r e a t m e n t l e a v i n g t h e t r a n s p a r e n t a n d clean silica replica w h i c h is s u i t a b l y s h a d o w e d w i t h c h r o m i u m in v a c u u m . T h e second m e t h o d is t h e polyvinyl-silica t e c h n i q u e . I n t h i s case t h e p o l y v i n y l alcohol is applied to t h e first film n e g a t i v e directly b y m e a n s of a dilute a q u e o u s solution, dried, s t r i p p e d f r o m t h e s p e c i m e n a n d v a c u u m coated w i t h silica. F i n a l l y t h e p o l y v i n y l alcohol film is dissolved a w a y in w a t e r a n d t h e silica replica c h r o m i u m s h a d o w e d as before. T h e f o r m e r t e c h h i q u e h a s a n e x c e p t i o n a l l y fine resolution b u t t h e l a t t e r is good e n o u g h for t h e t r a c i n g of s t r u c t u r a l i t e m s w h i c h are no smaller t h a n 0.02 micron, i.e. it is useful for n o r m a l p i g m e n t s t r u c t u r e investigation. B o t h t e c h n i q u e s c a n be applied to t h e air a n d a d h e s i o n interface of t h e film. To strip' t h e l a t t e r f r o m t h e s u b s t r a t e (tin), t h e t i n p l a t e s u p p o r t i n g t h e film w a s dissolved electrolytically b y m a k i n g it t h e c a t h o d e versus a p l a t i n u m anode in 0.25% s o d i u m c a r b o n a t e solution a n d a p p l y i n g a direct c u r r e n t of 1 to 2 A a t a b o u t 40 V. S t r i p p i n g b y t h i s m e t h o d t a k e s a b o u t 1 m i n u t e . T h e s e t e c h n i q u e s were applied in t h e p r e p a r a t i o n of e l e c t r o n - m i c r o g r a p h s to i n v e s t i g a t e t h e causes of lustre a n d gloss v a r i a t i o n s in t h e surfaces of w h i t e e n a m e l s c o n t a i n i n g 17 % t i t a n i u m dioxide b y v o l u m e a n d 3 8 % t i t a n i u m dioxide a l t e r n a t i v e l y . I n t h e f o r m e r e n a m e l t h e crowded p i g m e n t a t i o n s e e m e d to a c c o u n t for t h e surface r o u g h n e s s w h i c h caused diffused s c a t t e r i n g of l i g h t w h e r e a s in t h e case of t h e
125/1
April, 1954
Vacuum Vol. I V No 2
226
VACUUM Cla ssiiied A b s t r a c t s
I --
General
Science
and
Engineering
--
I
Contd.
second enamel with a low pigment concentration the presence of an overlay of clear binder at the air interface could be noticed. H o w e v e r it was found that pigment-volume concentration is not the only contributory factor to lustre variation. The experiments proved the influence of flocculation and sedimentation properties of the pigment. It appears that s m M l flocculates, w h e n wetted by the vehicle, will settle near the adhesion interface at low pigment concentration as long as the time allowed for film formation facilitates settling but the larger flocculates will concentrate near the air interface. This is assumed to be due to the fact that they are not wetted. Fine textural differences in the film surface producing a variation in lustre on films of identical composition appear to be caused by floatation of pigments. In conclusion the authors record observations m a d e during the electrolytical stripping of the paint film from the substrate. Stripping was found to be more difficultin some places than in others and it is suggested that this p h e n o m e n o n m a y be worthwhile following up in Order to explore adhesion properties of paint films more fully. So~nmaire : Des pellicules de peinture ont 6t6 examinees au microscope 61ectronique. O n donne des d6tails sur les diff6rentes techniques de r6plique developp6es pour ces recherches.
17 - -
METALLURGY
--
Abstract No. und References
Article by E. G. Bobalek L. R. Lebras A. S. Powell & W. yon Fischer Indust'r. Engng. Chem.
46, March 1954 572-577
x7
O
O
A n A p p a r a t u s for the Determination of the Solidus T e m p e r a t u r e s of High-Melting Alloys See A b s t r a c t ~ o . : 8 7 / i i i
126/i
Thermal Diffusivity of Metals at High Temperatures U~ited Stales. T h e t h e r m a l d i f f u s i v i t y (k) a n d c o n d u c t i v i t y (K) of a m a t e r i a l are related b y K = k c 9 where c is t h e specific h e a t a n d p t h e density. ~ n g s t r o e m developed a m e t h o d for t h e d'etermination of k. A semiinfinite rod is fitted with a heat source at one end which emits heat in periodic pulses. At a given distance in the rod the velocity of the propagation of the heat oscillationsand the decrements of the amplitudes of the heat pulses are measured and give a measure of the diffusivity. In the present experiments the periodic changes of the heat emission were Sillusoidalto facilitateaccurate determination of these quantities. The original method requires considerable time for the determinations with the attendant danger of causing errors in the experiment resulting from surface reactions occurring during the experiment due to annealing, for instance. Therefore, the authors modified the original ~ngstroem method so that velocity of propagation of heat and decrement of the amplitude of the sinusoidally changing heat pulses could be measured in one run for a single period. The samples of the materials tested by the authors had a length of 50 cm. and a diameter of ½ inch. The sample heater, a small resistance heater element, was fitted loosely into a hole bored in the rod: A n input of ½ watt to the heater produced a temperature variation of about I°C at a point in the rod about 3.5 crn a w a y from the heater. Details of the electrical circuitry employed are given. To facilitate the measurements, two thermocouples were placed into holes drilled into the rod, at a distance from each other sufficientlylarge to permit the determination of the time the heat pulse required to travel between the two thermocouples. The heat source was a few centimetres a w a y from the nearest thermocouple. It is of importance for the success of such measurements that the ambient temperature is rigidly controlled at a stable value and any variation must not exceed the amplitude of the heat pulse at the thermocouple furthest away from the heater, i.e. in the present experiments it could not be allowed to vary by Inore than {°C. For that reason all measurements were carried out with the sample positioned in a furnace evacuated "to I0 -4 ram. Hg. The furnace was water cooled and its temperature was rigidly controlled manually or automatically. ]Radiation shields were used to prevent heat loss of the sample. Before an experimental run was started the sample was placed into the furnace, the furnace was evacuated and time allowed for temperature equilibrium to be established. Then, the output of each thermocouple, which was amplified and charted in a recorder, was calibrated. Subsequently the heater was switched on emitting sinusoidal heat pulses. After equilibrium conditions had been reached the output of the thermocouple nearest to the heater was recorded for several cycles and subsequently the output of the other thermocouple. The amplitudes recorded on the chart for each thermocouple were converted into voltage amplitudes with the help of the calibration data previously obtained and the ratio of the voltage amplitudes of the two thermocouples represents the amplitude decrement to be determined. F r o m the same record the velocity of the temperature pulse as it passed between the two thermocouples could be found. F r o m both these determinations the diffusivity of the sample under test could be calculated. The author determined thermal diffusivities for copper, nickel and thorium in the temperature range of 30 ° to 500°G by this method. The results are shown in graphs and are in good agreement with values calculated from data already available on c o n d u c t i v i t y , specific h e a t a n d density. Sommaire : U n e m 6 t h o d e d'~_ngstroem modifi6e p o u r le m e s u r e de diffusion Sp6eifique et de c o n d u c t i v i t 6 de la c h a l e u r des m 6 t a u x a ~t6 d6velopp6e. D6s ddtails s o n t d o n n d s s u r le procdd6 e x p e r i m e n t a l qui emploi le vide.
127/I
128/i
Casting Titanium See A b s t r a c t No. : 8 1 / I I I
April, 7954
Article by P. H. Sidles & G. C. Danielson J. Appl. Phys. 25, Jan. 1954 58-66
Vacuum Vol. I V No. 2
227
I
O
O
--
General Science and Engineering Contd.
--
I
AbstractNo.
and References
The Electron Microscope in Biology See A b s t r a c t No. : 6 5 / I I
122/1
The Medical Research Council Linear Accelerator a n d Cyclotron United Kingdom. D e t a i l s are g i v e n on t h e i n s t a l l a t i o n a n d p e r f o r m a n c e of t h e 8 MeV t r a v e l l i n g - w a v e linear accelerator n o w in use at H a m m e r s m i t h Hospital, L o n d o n . T h e t r e a t m e n t r o o m houMng t h e accelerator h a s concrete walls 4 - 6 feet t h i c k a n d is accessible via a n indirect corridor w i t h concrete walIs. T h e p a t i e n t is o b s e r v e d b y t h e o p e r a t o r at t h e control desk t h r o u g h a periscope. T h e t e c h n i c a l details of t h e accelerator h a v e been g i v e n p r e v i o u s l y (see Nature I7G (1953) 297). T h e 3 - m e t r e accelerating t u b e is s u s p e n d e d f r o m t h e ceiling a n d t h e electron b e a m passes into a n X - r a y h e a d where a n e l e c t r o m a g n e t deflects it t h r o u g h 90 ° before s t r i k i n g t h e gold t r a n s m i s s i o n t a r g e t . T h e X - r a y b e a m c a n be collimated to a m a x i m u m d i a m e t e r of 26 cm. at a d i s t a n c e of 1 m e t r e f r o m t h e t a r g e t b y m e a n s of t u n g s t e n - c o p p e r alloy blocks c o n t a i n i n g a conical hole. A n a d j u s t a b l e d i a p h r a g m s y s t e m consisting of 4 t h r e e - i n c h t h i c k t u n g s t e n - c o p p e r alloy blocks facilitates t h e p r o v i s i o n of a t r e a t m e n t field v a r y i n g f r o m 4 to 20 cm. square. T h e n o r m a l t a r g e t - s k i n d i s t a n c e is 1 m e t r e . P o i n t e r s on t h e X - r a y h e a d indicate t h e p o i n t s of e n t r y a n d e x i t of t h e b e a m on t h e p a t i e n t ' s skin. B y r o t a t i o n of t h e X - r a y head, vertical d i s p l a c e m e n t of t h e floor (up to 5 ft.) a n d h o r i z o n t a l m o v e m e n t of t h e t r e a t m e n t conch, t h e p o s i t i o n a n d angle of t h e b e a m on t h e p a t i e n t c a n be a d j u s t e d . T h e h i g h i n t e n s i t y of t h e o u t p u t of t h e accelerator e q u a l l i n g 100-200 r a d / m i n . (1 r a d = 100 erg/g.) reduces t h e t r e a t m e n t t i m e per p a t i e n t to t w o m i n u t e s . T h e 8 MeV m a c h i n e gives g r e a t e r p e n e t r a t i o n t h a n t h e 2 ~{eV m a c h i n e (the so-cMled cobalt unit) a n d t h e c o n v e n t i o n a l 200 k V X - r a y s . B o t h s u p e r v o l t a g e r a d i a t i o n m a c h i n e s (8 MeV a n d 2 MeV) s h o w a b u i l d - u p of i n t e n s i t y at 2.0 cm. a n d 0.5 cm. d e p t h below t h e skin respectively. T h i s is d u e to t h e fact t h a t t h e s e c o n d a r y electrons, w h i c h are e s s e n t i a l l y responsible for t h e ionisation, are m a i n l y projected in t h e direction of t h e i n c i d e n t b e a m a n d h a v e a r a n g e increasing w i t h t h e voltage. As far as is k n o w n high e n e r g y X - r a y s h a v e no biological effects different from low e n e r g y r a y s b u t s k i n r e a c t i o n is reduced a n d bone a b s o r b s less t h a n soft tissue, lowering t h e risk of bone necrosis. A 4 5 - i n c h cyclotron is u n d e r c o n s t r u c t i o n in t h e s a m e building. T h e p u r p o s e is to facilitate i n v e s t i g a t i o n s into t h e effects of n e u t r o n s on living a n d i n e r t m a t t e r . I t will also be e m p l o y e d for t h e p r o d u c t i o n of r a d i o a c t i v e isotopes w h i c h h a v e to be used i m m e d i a t e l y t h e y b e c o m e available b e c a u s e of t h e i r s h o r t life. Sommaire : Des d6tails c o m p l e t s s o n t d o n n e s s u r l'acc616rateur r 6 c e m m e n t install6 k l ' H o s p i t a l d ' H a m m e r s m i t h , Londres, p o u r la th6rapie ~ r a y o n s X. Q u e l q u e s r e n s e i g n e m e n t s s o n t aussi d o n n 6 s s u r u n c y c l o t r o n q u e l'on constrnit'dans la m S m e localit6.
123/1
Article by C. A. P. Wood & G. R. Newbery ~¥ature 173, 6.2.1954 233-235
An Evaporated Carbon Replica Technique for Use with the Electron Microscope and its Application to the Study of Photographic Grains See A b s t r a c t No. : 6 9 / I I
~24/i
Microstructure of Paint Films United States. T h e d a t a so far m a d e available b y research on t h e p h y s i c a l properties of p a i n t a n d p a i n t c o n s t i t u e n t s h a v e o n l y in p a r t assisted practical problems. I t a p p e a r s t h a t t h e reproducibility of t h e a p p e a r a n c e of p a i n t films for i n s t a n c e , c a n o n l y be fully explored b y o b t a i n i n g m o r e k n o w l e d g e of film s t r u c t u r e . A s u i t a b l e m e a n s of i n v e s t i g a t i n g film s t r u c t u r e is t h e microscope a n d it is t h e object of t h i s article to r e p o r t on t h e u s e s of t h e electron microscope t e c h n i q u e in o b t a i n i n g q u a l i t a t i v e i n f o r m a t i o n (a) on t h e s t r u c t u r e of t h e resinous b i n d e r w h i c h h a s m i c r o m o l e c u l a r dimensions, (b) t h e a r r a n g e m e n t of p i g m e n t in t h e film i.e. a s t u d y of t h e e x t e n t of flocculation, s e d i m e n t a t i o n etc. a n d (c) t h e s t r u c t u r e of b o t h air a n d a d h e s i o n interfaces of t h e films. T h e i n s t r u m e n t used in t h i s s t u d y w a s a n E M U - 2 R C A electron microscope. T h e t r a n s m i s s i o n t e c h n i q u e was used. One difficulty is p r e s e n t e d b y t h e fact t h a t direct v i e w i n g of t h e film s p e c i m e n ill t h e i n s t r u m e n t is o n l y useful for film t h i c k n e s s e s u p to 0.2 m i c r o n w h e r e a s t h e n o r m a l p a i n t film h a s a t h i c k n e s s of 25 m i c r o n or over. T h i s h a s been overcome b y t h e d e v e l o p m e n t of two replica t e c h n i q u e s w h i c h h a v e p r o v e d s a t i s f a c t o r y to s o m e e x t e n t . F i r s t is t h e so-called silver silica t e c h n i q u e , T h e p a i n t s p e c i m e n is coated w i t h a silver film b y v a c u u m e v a p o r a t i o n . S u b s e q u e n t l y a coat of p o l y v i n y l alcohol is applied to t h e silver surface a n d allowed to dry, T h e c o m p o s i t e film is t h e n s t r i p p e d f r o m t h e s p e c i m e n and t h e n e g a t i v e of t h e replica v a c u u m coated w i t h silica. F i n a l l y t h e p o l y v i n y l alcohol a n d silver c o a t i n g is dissolved b y acid t r e a t m e n t l e a v i n g t h e t r a n s p a r e n t a n d clean silica replica w h i c h is s u i t a b l y s h a d o w e d w i t h c h r o m i u m in v a c u u m . T h e second m e t h o d is t h e polyvinyl-silica t e c h n i q u e . I n t h i s case t h e p o l y v i n y l alcohol is applied to t h e first film n e g a t i v e directly b y m e a n s of a dilute a q u e o u s solution, dried, s t r i p p e d f r o m t h e s p e c i m e n a n d v a c u u m coated w i t h silica. F i n a l l y t h e p o l y v i n y l alcohol film is dissolved a w a y in w a t e r a n d t h e silica replica c h r o m i u m s h a d o w e d as before. T h e f o r m e r t e c h h i q u e h a s a n e x c e p t i o n a l l y fine resolution b u t t h e l a t t e r is good e n o u g h for t h e t r a c i n g of s t r u c t u r a l i t e m s w h i c h are no smaller t h a n 0.02 micron, i.e. it is useful for n o r m a l p i g m e n t s t r u c t u r e investigation. B o t h t e c h n i q u e s c a n be applied to t h e air a n d a d h e s i o n interface of t h e film. To strip' t h e l a t t e r f r o m t h e s u b s t r a t e (tin), t h e t i n p l a t e s u p p o r t i n g t h e film w a s dissolved electrolytically b y m a k i n g it t h e c a t h o d e versus a p l a t i n u m anode in 0.25% s o d i u m c a r b o n a t e solution a n d a p p l y i n g a direct c u r r e n t of 1 to 2 A a t a b o u t 40 V. S t r i p p i n g b y t h i s m e t h o d t a k e s a b o u t 1 m i n u t e . T h e s e t e c h n i q u e s were applied in t h e p r e p a r a t i o n of e l e c t r o n - m i c r o g r a p h s to i n v e s t i g a t e t h e causes of lustre a n d gloss v a r i a t i o n s in t h e surfaces of w h i t e e n a m e l s c o n t a i n i n g 17 % t i t a n i u m dioxide b y v o l u m e a n d 3 8 % t i t a n i u m dioxide a l t e r n a t i v e l y . I n t h e f o r m e r e n a m e l t h e crowded p i g m e n t a t i o n s e e m e d to a c c o u n t for t h e surface r o u g h n e s s w h i c h caused diffused s c a t t e r i n g of l i g h t w h e r e a s in t h e case of t h e
125/1
April, 1954
Vacuum Vol. I V No 2
226
VACUUM Cla ssiiied A b s t r a c t s
I --
General
Science
and
Engineering
--
I
Contd.
second enamel with a low pigment concentration the presence of an overlay of clear binder at the air interface could be noticed. H o w e v e r it was found that pigment-volume concentration is not the only contributory factor to lustre variation. The experiments proved the influence of flocculation and sedimentation properties of the pigment. It appears that s m M l flocculates, w h e n wetted by the vehicle, will settle near the adhesion interface at low pigment concentration as long as the time allowed for film formation facilitates settling but the larger flocculates will concentrate near the air interface. This is assumed to be due to the fact that they are not wetted. Fine textural differences in the film surface producing a variation in lustre on films of identical composition appear to be caused by floatation of pigments. In conclusion the authors record observations m a d e during the electrolytical stripping of the paint film from the substrate. Stripping was found to be more difficultin some places than in others and it is suggested that this p h e n o m e n o n m a y be worthwhile following up in Order to explore adhesion properties of paint films more fully. So~nmaire : Des pellicules de peinture ont 6t6 examinees au microscope 61ectronique. O n donne des d6tails sur les diff6rentes techniques de r6plique developp6es pour ces recherches.
17 - -
METALLURGY
--
Abstract No. und References
Article by E. G. Bobalek L. R. Lebras A. S. Powell & W. yon Fischer Indust'r. Engng. Chem.
46, March 1954 572-577
x7
O
O
A n A p p a r a t u s for the Determination of the Solidus T e m p e r a t u r e s of High-Melting Alloys See A b s t r a c t ~ o . : 8 7 / i i i
126/i
Thermal Diffusivity of Metals at High Temperatures U~ited Stales. T h e t h e r m a l d i f f u s i v i t y (k) a n d c o n d u c t i v i t y (K) of a m a t e r i a l are related b y K = k c 9 where c is t h e specific h e a t a n d p t h e density. ~ n g s t r o e m developed a m e t h o d for t h e d'etermination of k. A semiinfinite rod is fitted with a heat source at one end which emits heat in periodic pulses. At a given distance in the rod the velocity of the propagation of the heat oscillationsand the decrements of the amplitudes of the heat pulses are measured and give a measure of the diffusivity. In the present experiments the periodic changes of the heat emission were Sillusoidalto facilitateaccurate determination of these quantities. The original method requires considerable time for the determinations with the attendant danger of causing errors in the experiment resulting from surface reactions occurring during the experiment due to annealing, for instance. Therefore, the authors modified the original ~ngstroem method so that velocity of propagation of heat and decrement of the amplitude of the sinusoidally changing heat pulses could be measured in one run for a single period. The samples of the materials tested by the authors had a length of 50 cm. and a diameter of ½ inch. The sample heater, a small resistance heater element, was fitted loosely into a hole bored in the rod: A n input of ½ watt to the heater produced a temperature variation of about I°C at a point in the rod about 3.5 crn a w a y from the heater. Details of the electrical circuitry employed are given. To facilitate the measurements, two thermocouples were placed into holes drilled into the rod, at a distance from each other sufficientlylarge to permit the determination of the time the heat pulse required to travel between the two thermocouples. The heat source was a few centimetres a w a y from the nearest thermocouple. It is of importance for the success of such measurements that the ambient temperature is rigidly controlled at a stable value and any variation must not exceed the amplitude of the heat pulse at the thermocouple furthest away from the heater, i.e. in the present experiments it could not be allowed to vary by Inore than {°C. For that reason all measurements were carried out with the sample positioned in a furnace evacuated "to I0 -4 ram. Hg. The furnace was water cooled and its temperature was rigidly controlled manually or automatically. ]Radiation shields were used to prevent heat loss of the sample. Before an experimental run was started the sample was placed into the furnace, the furnace was evacuated and time allowed for temperature equilibrium to be established. Then, the output of each thermocouple, which was amplified and charted in a recorder, was calibrated. Subsequently the heater was switched on emitting sinusoidal heat pulses. After equilibrium conditions had been reached the output of the thermocouple nearest to the heater was recorded for several cycles and subsequently the output of the other thermocouple. The amplitudes recorded on the chart for each thermocouple were converted into voltage amplitudes with the help of the calibration data previously obtained and the ratio of the voltage amplitudes of the two thermocouples represents the amplitude decrement to be determined. F r o m the same record the velocity of the temperature pulse as it passed between the two thermocouples could be found. F r o m both these determinations the diffusivity of the sample under test could be calculated. The author determined thermal diffusivities for copper, nickel and thorium in the temperature range of 30 ° to 500°G by this method. The results are shown in graphs and are in good agreement with values calculated from data already available on c o n d u c t i v i t y , specific h e a t a n d density. Sommaire : U n e m 6 t h o d e d'~_ngstroem modifi6e p o u r le m e s u r e de diffusion Sp6eifique et de c o n d u c t i v i t 6 de la c h a l e u r des m 6 t a u x a ~t6 d6velopp6e. D6s ddtails s o n t d o n n d s s u r le procdd6 e x p e r i m e n t a l qui emploi le vide.
127/I
128/i
Casting Titanium See A b s t r a c t No. : 8 1 / I I I
April, 7954
Article by P. H. Sidles & G. C. Danielson J. Appl. Phys. 25, Jan. 1954 58-66
Vacuum Vol. I V No. 2
227