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385. Tension stresses in glass coatings and in glass-metal seals in the annealing range
314
46.
Abstracts
Glass Blowing, Glass-to-metal and Ceramic-to-metal Sealing Techniques
46 384. Fundamentals of Glass-to-Metal Bonding : IV, Wettability of Gold and Platinum by Molten Sodium Disilicate. United States. Further studies were made on the effect of the nature of the atmosphere on the wetting of gold and platinum by sodium disilicate at 1000 “C. The gases were oxygen, nitrogen, carbon dioxide, helium, argon, water vapor, carbon monoxide, hydrogen, and several mixtures of some of these gases. Data reported were obtained in the pressure range 1O-5 Torr to approximately 1 Torr. A special experimental apparatus was constructed for this purpose. In this pressure range the results showed that the wetting of gold was unaffected by these atmospheres. The platinum-sodium disilicate contact angle, on the other hand, depended on the nature and pressure of the gas. This angle was affected most by atmospheres of water vapor, carbon monoxide, hydrogen, and oxygen. Water vapor was found to be easily displaced from the metal by oxygen. The results were interpreted on the basis of selective adsorption of the gases at the various metal interfaces and of absorption of oxygen and hydrogen by platinum. (Author) M. L. Volpe, R. M. Fulrath, and J. A. Pask, J. Amer. Sot., 42, 102-106, Feb. 1959.
Ceram.
46 385. Tension Stresses in Glass Coatings and in Glass-Metal Seals in the Annealing Range. United States. The strength of glass coatings applied to metals was found to decrease with time at temperatures in the lower annealing range. This decrease is caused by the well-known decrease in volume which glasses undergo at these temperatures. Glasses applied to a metal surface are constrained in directions parallel to the surface, and the decrease in volume thus produces tension strains in these directions. In this temperature range, the production of tension stress due to density increase is partly offset by stress release due to viscous flow. These effects, calculated from measurements of density variation and of stress release in the glass used for coating, were found to indicate variations in glass strength which agreed approximately with values measured by a cross-bending test. Significant tension stresses of similar origin were observed to appear in glass-metal seals during baking in the lower annealing range. (Author) This investigation was carried out on strips of 430 metal (AISI430), a glass-sealing alloy containing 16 to 18 % Cr, 1% Mn, 0.75 % Si, 0.5 % Ni, and balance iron. Heavy-gauge strip was coated on one side with thin coatings of glass and then subjected to a bending test, both at room temperature and at 425°C. The smallest tension stress which produced cracks in the glass was observed. In addition to Pittsburgh Plate Glass Company glass No. 5533, used commonly for face plates of TV bulbs, two experimental high-alumina glasses were tested. The reader who is concerned with these effects, which have great practical importance. will find a more recent paper by L. F. Oldfield of great interest. He discusses ‘ The eke&s of heat treatments on the thermal expansions of some borosilicate glasses and iron-nickelcobalt alloys and their significance in the behaviour of glass to metal seals.’ (Glastech. Ber., 32K, V, 1959, V/16-V/25.) W. H. K.
J. C. Tul,nbull, J. Amer. Ceram. Sot., 41, 372-376,
47.
Outgassing
Sept. 1958.
Data, Vapour Pressure Data, Gettering Data 47
386. Carbon Elements. United States.
as an Indicator
of Gas
Content
of Metallic
Tube
It is shown in this experimental investigation that the gas evolution from anode materials used in the construction of electron tubes is a nearly linear function of the carbon content of these materials. It is thus desirable to keep
384-388 the carbon content as low as possible, 0.01 or 0.005 per cent being practical values. The main benefit derived from more rigorous outgassing treatment in a reducing atmosphere, such as dry or wet hydrogen, is reflected in greater stability of the tube during life. Prolonged firing of metal parts made from sheet stock results in excessive softening of the material and deterioration of its surface finish. Carbonized anodes cannot be fired for long periods at high temperatures because carbon is then dissolved in the base metal, nickel or steel. Wet hydrogen cannot be used for the firing of carbonized parts as the carbon is lost by reaction with water vapor. It is thus recommended to fire the metal stock in heavier gauges and then roll to final siz: and carbonize. Tests have shown that this finishing treatment, rolling or carbonizing, has no adverse effect on the gas content. Graphs are presented which show the beneficial effect of prolonged firing in wet hydrogen (1 h at 1000 “C) for plain and nickel-plated steel, both in terms of lower carbon content and lower gas pressure during life. Values for emission from oxidecoated cathodes and transconductance of the tubes made from components so treated were uniformly higher on 500 h life tests when compared with control lots without such specially prepared materials. Gas evolution was measured by the method described in Abstract No. 387. W. H. K. D. R. Kerstetter,
Sylvania
Technol.,
12, 26-29,
Apr. 1959.
47 387. Measurements of Gas Evolution or Sorption of Anode Materials Under Simulated Life Conditions. United States. An experimental procedure is described which allows monitoring gas evolution and sorption of electron tube anode materials over prolonged periods of time. A corrugated strip of the material under study is supported by a Kovar wire on a soft-glass header and sealed into a T-9 soft-glass bulb which is sealed on to a trolley exhaust system. A Bayard-Alpert-type ion gauge is attached to the tube containing the sample and both are sealed off after suitable heat treating and pumping. A thermocouple is attached to the sample which is maintained at a temperature of 600 “C during the simulated life test by focusing the beam fr’om a projector lamp with an internal reflector on it while keeping the bulb temperature at 50 “C by forced air cooling. Pressure variation is recorded for a 500 h period for plain steel For a tube not containing a metal and nickel-plated steel. sample, the pressure remains essentially at the 1O-6 Torr level for the first 10 h, increasing slightly thereafter. Plain steel reaches a maximum pressure of lO-4 Torr in about 50 h and then resorbs some of the gas initially released. Nickel-plated steel evolves less gas after some initial bursts in the first few hours and attains a lower pressure after being on test for some 50 h than the one observed initially. W. H. K. C. H. Rehkopf,
Materials
49.
Sylvania
and Processes
Technol.,
of Electron
Miscellaneous
11, 114-116,
Devices.
Oct. 1958. 47 : 27 : 37 : 40 See Abstr. 356.
Materials and Techniques
49 388. Surface Phenomena Associated with Application of Organic Films to Phosphor Screens. United States. The use of aluminized cathode ray tube screens
has become almost universal in the manufacture of television picture tubes and to a lesser extent in the manufacture of instrument and radar tubes. The well-known technique of aluminizing screens involves the production of a temporary organic barrier layer or film upon which the reflecting aluminum coating may be deposited, usually by evaporation in vacuum. The success of the aluminizing process depends largely on the production of this organic film free from variations in thickness and imperfections which would allow the aluminum to penetrate round the phosphor crystals and so cause local undesirable reductions in the light output from the screen. It is also necessary for this layer to be extremely thin (less than 1 1~)and to be composed of a material
46.
Abstracts
Glass Blowing, Glass-to-metal and Ceramic-to-metal Sealing Techniques
46 384. Fundamentals of Glass-to-Metal Bonding : IV, Wettability of Gold and Platinum by Molten Sodium Disilicate. United States. Further studies were made on the effect of the nature of the atmosphere on the wetting of gold and platinum by sodium disilicate at 1000 “C. The gases were oxygen, nitrogen, carbon dioxide, helium, argon, water vapor, carbon monoxide, hydrogen, and several mixtures of some of these gases. Data reported were obtained in the pressure range 1O-5 Torr to approximately 1 Torr. A special experimental apparatus was constructed for this purpose. In this pressure range the results showed that the wetting of gold was unaffected by these atmospheres. The platinum-sodium disilicate contact angle, on the other hand, depended on the nature and pressure of the gas. This angle was affected most by atmospheres of water vapor, carbon monoxide, hydrogen, and oxygen. Water vapor was found to be easily displaced from the metal by oxygen. The results were interpreted on the basis of selective adsorption of the gases at the various metal interfaces and of absorption of oxygen and hydrogen by platinum. (Author) M. L. Volpe, R. M. Fulrath, and J. A. Pask, J. Amer. Sot., 42, 102-106, Feb. 1959.
Ceram.
46 385. Tension Stresses in Glass Coatings and in Glass-Metal Seals in the Annealing Range. United States. The strength of glass coatings applied to metals was found to decrease with time at temperatures in the lower annealing range. This decrease is caused by the well-known decrease in volume which glasses undergo at these temperatures. Glasses applied to a metal surface are constrained in directions parallel to the surface, and the decrease in volume thus produces tension strains in these directions. In this temperature range, the production of tension stress due to density increase is partly offset by stress release due to viscous flow. These effects, calculated from measurements of density variation and of stress release in the glass used for coating, were found to indicate variations in glass strength which agreed approximately with values measured by a cross-bending test. Significant tension stresses of similar origin were observed to appear in glass-metal seals during baking in the lower annealing range. (Author) This investigation was carried out on strips of 430 metal (AISI430), a glass-sealing alloy containing 16 to 18 % Cr, 1% Mn, 0.75 % Si, 0.5 % Ni, and balance iron. Heavy-gauge strip was coated on one side with thin coatings of glass and then subjected to a bending test, both at room temperature and at 425°C. The smallest tension stress which produced cracks in the glass was observed. In addition to Pittsburgh Plate Glass Company glass No. 5533, used commonly for face plates of TV bulbs, two experimental high-alumina glasses were tested. The reader who is concerned with these effects, which have great practical importance. will find a more recent paper by L. F. Oldfield of great interest. He discusses ‘ The eke&s of heat treatments on the thermal expansions of some borosilicate glasses and iron-nickelcobalt alloys and their significance in the behaviour of glass to metal seals.’ (Glastech. Ber., 32K, V, 1959, V/16-V/25.) W. H. K.
J. C. Tul,nbull, J. Amer. Ceram. Sot., 41, 372-376,
47.
Outgassing
Sept. 1958.
Data, Vapour Pressure Data, Gettering Data 47
386. Carbon Elements. United States.
as an Indicator
of Gas
Content
of Metallic
Tube
It is shown in this experimental investigation that the gas evolution from anode materials used in the construction of electron tubes is a nearly linear function of the carbon content of these materials. It is thus desirable to keep
384-388 the carbon content as low as possible, 0.01 or 0.005 per cent being practical values. The main benefit derived from more rigorous outgassing treatment in a reducing atmosphere, such as dry or wet hydrogen, is reflected in greater stability of the tube during life. Prolonged firing of metal parts made from sheet stock results in excessive softening of the material and deterioration of its surface finish. Carbonized anodes cannot be fired for long periods at high temperatures because carbon is then dissolved in the base metal, nickel or steel. Wet hydrogen cannot be used for the firing of carbonized parts as the carbon is lost by reaction with water vapor. It is thus recommended to fire the metal stock in heavier gauges and then roll to final siz: and carbonize. Tests have shown that this finishing treatment, rolling or carbonizing, has no adverse effect on the gas content. Graphs are presented which show the beneficial effect of prolonged firing in wet hydrogen (1 h at 1000 “C) for plain and nickel-plated steel, both in terms of lower carbon content and lower gas pressure during life. Values for emission from oxidecoated cathodes and transconductance of the tubes made from components so treated were uniformly higher on 500 h life tests when compared with control lots without such specially prepared materials. Gas evolution was measured by the method described in Abstract No. 387. W. H. K. D. R. Kerstetter,
Sylvania
Technol.,
12, 26-29,
Apr. 1959.
47 387. Measurements of Gas Evolution or Sorption of Anode Materials Under Simulated Life Conditions. United States. An experimental procedure is described which allows monitoring gas evolution and sorption of electron tube anode materials over prolonged periods of time. A corrugated strip of the material under study is supported by a Kovar wire on a soft-glass header and sealed into a T-9 soft-glass bulb which is sealed on to a trolley exhaust system. A Bayard-Alpert-type ion gauge is attached to the tube containing the sample and both are sealed off after suitable heat treating and pumping. A thermocouple is attached to the sample which is maintained at a temperature of 600 “C during the simulated life test by focusing the beam fr’om a projector lamp with an internal reflector on it while keeping the bulb temperature at 50 “C by forced air cooling. Pressure variation is recorded for a 500 h period for plain steel For a tube not containing a metal and nickel-plated steel. sample, the pressure remains essentially at the 1O-6 Torr level for the first 10 h, increasing slightly thereafter. Plain steel reaches a maximum pressure of lO-4 Torr in about 50 h and then resorbs some of the gas initially released. Nickel-plated steel evolves less gas after some initial bursts in the first few hours and attains a lower pressure after being on test for some 50 h than the one observed initially. W. H. K. C. H. Rehkopf,
Materials
49.
Sylvania
and Processes
Technol.,
of Electron
Miscellaneous
11, 114-116,
Devices.
Oct. 1958. 47 : 27 : 37 : 40 See Abstr. 356.
Materials and Techniques
49 388. Surface Phenomena Associated with Application of Organic Films to Phosphor Screens. United States. The use of aluminized cathode ray tube screens
has become almost universal in the manufacture of television picture tubes and to a lesser extent in the manufacture of instrument and radar tubes. The well-known technique of aluminizing screens involves the production of a temporary organic barrier layer or film upon which the reflecting aluminum coating may be deposited, usually by evaporation in vacuum. The success of the aluminizing process depends largely on the production of this organic film free from variations in thickness and imperfections which would allow the aluminum to penetrate round the phosphor crystals and so cause local undesirable reductions in the light output from the screen. It is also necessary for this layer to be extremely thin (less than 1 1~)and to be composed of a material