scholarly journals Transporting Specimens into Extremely High Vacuum from Atmospheric Pressure.

Shinku ◽  
1994 ◽  
Vol 37 (9) ◽  
pp. 758-762 ◽  
Author(s):  
Kenji ODAKA ◽  
Kazue TAKAHASHI ◽  
Shinjiro UEDA
Keyword(s):  
Atmospheric Pressure ◽  
High Vacuum

scholarly journals The influence of pressure on the boiling points of metals

1910 ◽  
Vol 83 (565) ◽  
pp. 483-491 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
Boiling Point ◽  
High Vacuum ◽  
Similar Type ◽  
Exact Relation ◽  
Reduced Pressure ◽  
Boiling Points ◽  
Experimental Values ◽  
Low Pressures ◽  
Very High

Part I. — Pressures below 760 mm . In a previous communication (‘Proc.’, A, vol. 82, 1909, p. 396) the approximate boiling points of a number of metals were determined at atmospheric pressure. Apart from the question of finding the exact relation between the boiling point and pressure, it is an important criterion of any method for fixing the temperatures of ebullition to demonstrate that the experimental values obtained are dependent on the pressure. It is specially desirable when dealing with substances boiling at temperatures above 2000° to have some evidence that the points indicated are true boiling points. Previous work on the vaporisation of metals at different pressures has been confined to experiments in a very high vacuum except for metals like bismuth, cadmium, and zinc, which boil at relatively low temperatures under atmospheric pressure. The observations were limited to very low pressures on account of the difficulty of obtaining any material capable of withstanding a vacuum at temperatures over 1400° and the consequent necessity for keeping the boiling point below this limit by using very low pressures. Moreover in the case of the majority of the metals, e. g. , copper, tin, ebullition under reduced pressure has never been observed. The difficulties indicated above were avoided by using a similar type of apparatus to that previously described, and arranging the whole furnace inside a vacuum enclosure, thus permitting of the use of graphite crucibles to contain the metal.

Chemical Reactions at the in Vacuo Au/Inp Interface

1986 ◽  
Vol 83 ◽  
Author(s):  
R. Stanley Williams ◽  
C. Thomas Tsai ◽  
Eun-Hee Cirlin
Keyword(s):  
Intermetallic Compound ◽  
Atmospheric Pressure ◽  
High Vacuum ◽  
Thermodynamic System ◽  
External Pressure ◽  
Ultra High Vacuum ◽  
Reaction Products ◽  
Inp Substrate ◽  
Major Reaction ◽  
Closed Thermodynamic System

ABSTRACTThe reaction between a Au film and an Inp substrate occurs much more readily in vacuo than under an external pressure of an inert ga. At atmospheric pressure, the compounds Au2P3 and the γ intermetallic compound (at times designated Au7In3, Au9In4, or Au2In) are formed at 450 °C and remain fairly stable even when annealed at 500°C for hours. Under ultra-high vacuum conditions, phosphorous readily escapes from the film when a sample is annealed at 300°C for 15 minutes, and the major reaction products are the ψ phase (Au3In2) and another intermetallic compound that is probably AuIn. The presence of an inert gas creates a kinetic barrier for the escape of phosphorous from the surface, and thus Au/InP behaves more like a closed thermodynamic system under pressure than in a vacuum.

Low-Cost, Atmospheric-Pressure Scanning Transmission Electron Microscopy

2011 ◽  
Vol 19 (3) ◽  
pp. 16-20
Author(s):  
Niels de Jonge ◽  
Elisabeth A. Ring ◽  
Wilbur C. Bigelow ◽  
Gabriel M. Veith
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atmospheric Pressure ◽  
Low Cost ◽  
High Vacuum ◽  
Nanoscale Systems ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Thin Electron

Solid materials in subambient gaseous environments have been imaged using in situ transmission electron microscopy (TEM), for example to study dynamic effects: carbon nanotube growth, nanoparticle changes during redox reactions, and phase transitions in nanoscale systems. In these studies the vacuum level in the specimen region of the electron microscope was increased to pressures of up to 10 mbar using pump-limiting apertures that separated the specimen region from the rest of the high-vacuum electron column, but it has not been possible to achieve the higher pressures that are desirable for catalysis research. TEM imaging at atmospheric pressure and at elevated temperature was achieved with 0.2-nm resolution by enclosing a gaseous environment several micrometers thick between ultra-thin, electron transparent silicon nitride windows. Although Ångström-level resolution in situ TEM has been demonstrated with aberration-corrected systems, the key difficulty with TEM imaging is its dependence on phase contrast, which requires ultra-thin specimens, limiting the choice of experiments.

scholarly journals Design and Simulation of a Wireless SAW–Pirani Sensor with Extended Range and Sensitivity

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2421 ◽  
Author(s):  
Sofia Toto ◽  
Pascal Nicolay ◽  
Gian Luca Morini ◽  
Michael Rapp ◽  
Jan G. Korvink ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
High Vacuum ◽  
Industrial Processes ◽  
Extended Range ◽  
Vacuum Sensor ◽  
Gas Kinetic Theory ◽  
And Control ◽  
Measurement And Control

Pressure is a critical parameter for a large number of industrial processes. The vacuum industry relies on accurate pressure measurement and control. A new compact wireless vacuum sensor was designed and simulated and is presented in this publication. The sensor combines the Pirani principle and Surface Acoustic Waves, and it extends the vacuum sensed range to between 10−4 Pa and 105 Pa all along a complete wireless operation. A thermal analysis was performed based on gas kinetic theory, aiming to optimize the thermal conductivity and the Knudsen regime of the device. Theoretical analysis and simulation allowed designing the structure of the sensor and its dimensions to ensure the highest sensitivity through the whole sensing range and to build a model that simulates the behavior of the sensor under vacuum. A completely new design and a model simulating the behavior of the sensor from high vacuum to atmospheric pressure were established.

Development of Friction Properties Experimental Device of Mechanical Seal Material in Vacuum Working Condition

2013 ◽  
Vol 572 ◽  
pp. 371-374
Author(s):  
Feng Zhang ◽  
Bao Yu Song ◽  
Jia Peng Sun ◽  
Song Zhang
Keyword(s):  
Atmospheric Pressure ◽  
Working Condition ◽  
Space Exploration ◽  
High Vacuum ◽  
Experimental System ◽  
Mechanical Seal ◽  
Test Rig ◽  
Environment Temperature ◽  
Friction Performance ◽  
Materials Used

Mechanical seal plays a very important role in rotating machinery for space exploration, but it is very difficult to estimate its friction performance by simulative experiment. In this paper, a experimental system for measuring friction properties of mechanical seal materials used in spacecraft is developed. It is able to provide some adjustable parameters in the experiment, such as environment temperature -60°C~60°C, load 100N~300N, rotational speed of 30r/min~110r/min and atmospheric pressure and high vacuum. Friction coefficients of babbitt graphite M120B and hard alloy YG6 are obtained by the test rig and the experimental results testify that the device can conduct simulative experiment effectively.

scholarly journals 592 Water Flux from Lettuce Plants at Reduced Atmospheric Pressure

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 499A-499
Author(s):  
Kenneth A. Corey ◽  
Phil A. Fowler ◽  
Raymond M. Wheeler
Keyword(s):  
Relative Humidity ◽  
Plant Growth ◽  
Vapor Pressure ◽  
Water Loss ◽  
Atmospheric Pressure ◽  
Ambient Pressure ◽  
High Vacuum ◽  
Thermal Control ◽  
Plant Responses ◽  
Reduced Pressure

Reduced atmospheric pressures may be used to minimize mass and engineering requirements for plant growth habitats used in some extraterrestrial applications. A chamber with high vacuum capability and thermal control at Kennedy Space Center was used to measure water loss of lettuce plants at reduced atmospheric pressures. A test stand with three, high-pressure sodium vapor lamps was used to determine short-term plant responses to reduced pressure. Initial experiments with lettuce showed that a pressure of 10 kPa (≈0.1 atm) resulted in a 6.1-fold increase in the rate of water loss compared to water loss at ambient pressure. However, due to low relative humidity, plants wilted after 30 minutes exposure to 10 kPa. A follow-up experiment in which relative humidity was controlled between 70% and 85%, demonstrated that water loss was directly proportional to the vapor pressure gradient, regardless of atmospheric pressure in the pressure range of 10 to 101 kPa. However, the response was curvilinear, suggesting effects on the pathway resistance. Results indicate that plant growth at atmospheric pressures of 5 to 10 kPa should be achievable. Further work will necessitate better relative humidity control and carbon dioxide control in order to separate vapor pressure deficit effects from diffusion effects.

Sign in / Sign up

Export Citation Format

Share Document