- Email: [email protected]
Kinetics of N2 desorption from the surfaces of iron-nitrogen solid solutions
Classified abstracts 1920-2104 Classified
abstracts
1920-1928
on this page
Editor’s note The label immediately following the fit/e of each ifem denotes country or origin of publication, and that at the end of each abstract indicates country of origin of work (where known).
I. General-vacuum
science
and engineering
10. VACUUM SCIENCE AND TECHNOLOGY 10 1920. Vacuum conditions and their attainment in the laboratory. (Netherlands) The velocity distribution, mean free path, diffusion of gases, absorbtion, desorption, and diffusion are discussed. Reference is made to obtaining very low pressures by means of materials of high absorptivity such as carbon (physical absorption) and by the use of getters (chemical absorption). Various pumping systems are described. A survey of a few pressure-measuring devices follows, including methods of measuring total and partial pressures. Various methods of leak detection are discussed. J H Makklk, Rep ESRO-TM-B, Nov I966 (European Space Technology Center, Noordwijk, Netherlands).
14. KINETIC THEORY OF GASES 14 : 21 1921. Applications of an approximation to molecular flow in cylindrical tubes. (USA) A simple approximation is developed for the molecular flow of gas through a cylindrical tube. The pressure distribution along the well of the tube is derived and is shown to be a good approximation to the short-tube formula of Clausing. Using these results, the problem of measuring the speed of a pump at the end of a tube is examined. If the pressure gauge is located a distance of one tube radius from the pump, then the intrinsic speed is directly measured in the plane of the gauge. To determine the capture coefficient of an open-ended tube whose inner surface has a uniform sticking coefficient, a differential equation is employed which reproduces the Monte Carlo results of Smith and Lewin with an error of less than 5 per cent. For tubes of infinite length the capture coefficient is given by k=2 ((&/(I &*), where e is the sticking coefficient of the inner tube surface. The calculation is repeated for tubes which have the exit end closed by a surface of the same sticking factor. J C Hebner, J Vat Sci Technol, 4 (4), July-Aug 1967, 179-185. 14 1922. Studies of thermal transpiration for the development of a thermal pump. (USA) Preliminary thermal transpiration data with helium and a porcelain membrane at temperatures below 250°C are reported. The graphed results indicate flow rates, the ratio of gas circulated to gas in the system, and the pressure ratio to temperature ratio versus mean pore diameter to mean free path ratio. M AItman and E HopfInger, Rep NASA-CR-83320; INDEC-SR-11, March 1967, (Pennsylvania &iv, Philadelphia). 14 1923. Propagation of correlations In a Boltztnann gas. (USA) New results are obtained on the propagation of correlations in a Boltzmann gas on the scale of the mean free path and the collisional time scale. E A Frieman and R Goldman, J Math Phys, 7 (12), 1966, 2153-2170. 14 1924. Density distribution of a molecular flux from a short cylindrical tube. (Canada) The radial density distribution of the molecular flux emerging from a short cylindrical tube, which connects two low density gas chambers, is calculated both in the exit plane of the tube and just downstream of that plane. The calculations are based on the kinetic theory of gases.
It is assumed that the upstream density is low enough so that the distribution function in the upstream chamber is Maxwellian with zero average velocity. The molecules emerge into a near-vacuum which is maintained in the downstream chamber. Computations have been made for the tube length-to-diameter ratios 0.25,0.50, 0.75 and 1.00 using the IBM 7040 electronic digital computer facility. Satisfactory agreement was found between the experimental and the calculated results. J H de Leeuw and E 0 Gadamer, Rep UTIXS-TN-103, Feb 1967 (Toronto University, Inst Aerospace Studies). I4 1925. Velocity distribution function of gas molecules near a solid wall In an inhomogeneously heated gas. (USSR) An equation is derived for determining the distribution function of gas molecules over velocities in the vicinity of a solid wall in the case of an inhomogeneously heated gas with the temperature gradient tangential to the wall. Yu I Yalarnov et al, Dokl Akad Nuuk SSSR, 175 (3), 21st July 1967, 549-552 (in Russian). 14 1926. Variation principles for equations of kinetic theory of a gas. (USSR) The paper deals with applying variation principles to the basic equations of the kinetic theory of gases, such as the Boltzmann and Bogolyubov equations. A M Kogan, Dokl Akad Nauk SSSR, 175 (4), 1st Aug 1967, 785-788 (in Russian). 14 1927. Kinetic theory of molecular radiometric force and radiometer. (Germany) The equation for the molecular radiometric force and moment on a body with convex surface enclosed by an arbitrary closed system in the Knudsen regime has been presented based on the revisrd theory of thermal transpiration established recently by Wu (1965). Two exact solutions of the molecular vane radiometers in a cylindrical tube and rectangular duct have been obtained in closed forms and calculated through numerical computation. These solutions reduce to the classical theory developed by Knudsen in the limit of infinitely large containers. Wu Y, Ann Phys, 19 (3-l), 1967, 144-153.
16. GASES AND SOLIDS 16 :30 Surface and volume diffusion in thin films of the system Ag-Se. See abstract number 2019. 16 :30 Caesium deposition on stainless steel. See abstract number 2041. I6 192% Kinetics of Ne desorption from the surfaces of iron-nitrogen solid solutions. (USA) The kinetics of nitrogen desorption from iron surfaces was studied between 400” and 550°C. The nitrogen desorbed isothermally into the gas phase was made available to the surface by diffusion from within the iron at the desorption temperature. The method of rate measurement involved the collection and volumetric measurement of gas samples at low pressures from specimens only a few square centimeters in area. Specimens were prepared by nitrogenizing zonerefined iron with NH,-H, mixtures having a range of N, fugacity between 10 and 3000 atm. The surfaces were then cleaned by ion bombardment in a bakeable high vacuum system. The kinetics of 669
abstracts
1920-1928
on this page
Editor’s note The label immediately following the fit/e of each ifem denotes country or origin of publication, and that at the end of each abstract indicates country of origin of work (where known).
I. General-vacuum
science
and engineering
10. VACUUM SCIENCE AND TECHNOLOGY 10 1920. Vacuum conditions and their attainment in the laboratory. (Netherlands) The velocity distribution, mean free path, diffusion of gases, absorbtion, desorption, and diffusion are discussed. Reference is made to obtaining very low pressures by means of materials of high absorptivity such as carbon (physical absorption) and by the use of getters (chemical absorption). Various pumping systems are described. A survey of a few pressure-measuring devices follows, including methods of measuring total and partial pressures. Various methods of leak detection are discussed. J H Makklk, Rep ESRO-TM-B, Nov I966 (European Space Technology Center, Noordwijk, Netherlands).
14. KINETIC THEORY OF GASES 14 : 21 1921. Applications of an approximation to molecular flow in cylindrical tubes. (USA) A simple approximation is developed for the molecular flow of gas through a cylindrical tube. The pressure distribution along the well of the tube is derived and is shown to be a good approximation to the short-tube formula of Clausing. Using these results, the problem of measuring the speed of a pump at the end of a tube is examined. If the pressure gauge is located a distance of one tube radius from the pump, then the intrinsic speed is directly measured in the plane of the gauge. To determine the capture coefficient of an open-ended tube whose inner surface has a uniform sticking coefficient, a differential equation is employed which reproduces the Monte Carlo results of Smith and Lewin with an error of less than 5 per cent. For tubes of infinite length the capture coefficient is given by k=2 ((&/(I &*), where e is the sticking coefficient of the inner tube surface. The calculation is repeated for tubes which have the exit end closed by a surface of the same sticking factor. J C Hebner, J Vat Sci Technol, 4 (4), July-Aug 1967, 179-185. 14 1922. Studies of thermal transpiration for the development of a thermal pump. (USA) Preliminary thermal transpiration data with helium and a porcelain membrane at temperatures below 250°C are reported. The graphed results indicate flow rates, the ratio of gas circulated to gas in the system, and the pressure ratio to temperature ratio versus mean pore diameter to mean free path ratio. M AItman and E HopfInger, Rep NASA-CR-83320; INDEC-SR-11, March 1967, (Pennsylvania &iv, Philadelphia). 14 1923. Propagation of correlations In a Boltztnann gas. (USA) New results are obtained on the propagation of correlations in a Boltzmann gas on the scale of the mean free path and the collisional time scale. E A Frieman and R Goldman, J Math Phys, 7 (12), 1966, 2153-2170. 14 1924. Density distribution of a molecular flux from a short cylindrical tube. (Canada) The radial density distribution of the molecular flux emerging from a short cylindrical tube, which connects two low density gas chambers, is calculated both in the exit plane of the tube and just downstream of that plane. The calculations are based on the kinetic theory of gases.
It is assumed that the upstream density is low enough so that the distribution function in the upstream chamber is Maxwellian with zero average velocity. The molecules emerge into a near-vacuum which is maintained in the downstream chamber. Computations have been made for the tube length-to-diameter ratios 0.25,0.50, 0.75 and 1.00 using the IBM 7040 electronic digital computer facility. Satisfactory agreement was found between the experimental and the calculated results. J H de Leeuw and E 0 Gadamer, Rep UTIXS-TN-103, Feb 1967 (Toronto University, Inst Aerospace Studies). I4 1925. Velocity distribution function of gas molecules near a solid wall In an inhomogeneously heated gas. (USSR) An equation is derived for determining the distribution function of gas molecules over velocities in the vicinity of a solid wall in the case of an inhomogeneously heated gas with the temperature gradient tangential to the wall. Yu I Yalarnov et al, Dokl Akad Nuuk SSSR, 175 (3), 21st July 1967, 549-552 (in Russian). 14 1926. Variation principles for equations of kinetic theory of a gas. (USSR) The paper deals with applying variation principles to the basic equations of the kinetic theory of gases, such as the Boltzmann and Bogolyubov equations. A M Kogan, Dokl Akad Nauk SSSR, 175 (4), 1st Aug 1967, 785-788 (in Russian). 14 1927. Kinetic theory of molecular radiometric force and radiometer. (Germany) The equation for the molecular radiometric force and moment on a body with convex surface enclosed by an arbitrary closed system in the Knudsen regime has been presented based on the revisrd theory of thermal transpiration established recently by Wu (1965). Two exact solutions of the molecular vane radiometers in a cylindrical tube and rectangular duct have been obtained in closed forms and calculated through numerical computation. These solutions reduce to the classical theory developed by Knudsen in the limit of infinitely large containers. Wu Y, Ann Phys, 19 (3-l), 1967, 144-153.
16. GASES AND SOLIDS 16 :30 Surface and volume diffusion in thin films of the system Ag-Se. See abstract number 2019. 16 :30 Caesium deposition on stainless steel. See abstract number 2041. I6 192% Kinetics of Ne desorption from the surfaces of iron-nitrogen solid solutions. (USA) The kinetics of nitrogen desorption from iron surfaces was studied between 400” and 550°C. The nitrogen desorbed isothermally into the gas phase was made available to the surface by diffusion from within the iron at the desorption temperature. The method of rate measurement involved the collection and volumetric measurement of gas samples at low pressures from specimens only a few square centimeters in area. Specimens were prepared by nitrogenizing zonerefined iron with NH,-H, mixtures having a range of N, fugacity between 10 and 3000 atm. The surfaces were then cleaned by ion bombardment in a bakeable high vacuum system. The kinetics of 669