Sticking coefficients of atoms on solid surfaces at low temperatures

1979 ◽  
Vol 20 (2) ◽  
pp. 813-814 ◽  
Author(s):  
Frank O. Goodman ◽  
Nicolás García
Keyword(s):  
Low Temperatures ◽  
Solid Surfaces ◽  
Sticking Coefficients

Friction on Ice

1988 ◽  
Vol 61 (1) ◽  
pp. 14-35 ◽  
Author(s):  
Asahiro Ahagon ◽  
Toshio Kobayashi ◽  
Makoto Mlsawa
Keyword(s):  
Melting Point ◽  
Energy Loss ◽  
Solubility Parameter ◽  
Low Temperatures ◽  
Fluid Layer ◽  
Frictional Resistance ◽  
High Viscosity ◽  
Polymer Chains ◽  
Solid Surfaces ◽  
Ice Surface

Abstract The friction on ice is strongly dependent on temperature. At sufficiently low temperatures, the frictional resistance on ice is high comparable to those on wet or even dry solid surfaces. As temperature rises and approaches the melting point of ice, however, friction rapidly decreases. Differing from the friction of a rubber on ordinary dry or wet solid surfaces the energy loss processes in the rubber do not seem to be the direct source of the frictional resistance on ice. Although frictional melting of ice could occur at high sliding speeds, an ice surface is inherently lubricated with a persistent mobile fluid layer at relatively high temperatures, near the melting point of ice. When a rubber slides on an ice surface, the fluid layer is sheared and undergoes drag flow. The energy loss process necessary for the frictional resistance takes place primarily in the fluid layer, and not in the rubber. The frictional resistance on ice is primarily determined by the viscosity and the thickness of the lubricating fluid layer. What is required of a rubber for better traction under such a condition is that the rubber surface follows the topography of the ice surface as closely as possible, so that more patches of ice surface can be sheared. Therefore, the rubber has to be sufficiently soft to show high friction on ice. Further improvement of the friction could be obtained by making it more resilient. Thus, a rubber with high friction on ice must be compounded so that the polymer chains maintain a high level of mobility at moderately low temperatures. This can be achieved by using polymers with low glass-transition-temperatures. An increased softener loading level helps to improve friction, but to a limited extent. In order to take maximum advantage of softeners, the choice of softener system is important. A relation common to all the mixed softener systems, except the ones containing high-viscosity softeners, was found to exist between the friction on ice and the solubility parameter of the softener mixture in the rubber. The friction on ice was maximized by selecting a softener system with a solubility parameter near that of the polymers in the rubber. The solubility parameter dependence of the friction was consistent with those of softness and resilience.

scholarly journals A study of catalytic actions at solid surfaces. X. -The interaction of carbon monoxide and hydrogen as conditioned by nickel at relatively low temperatures. -A practical synthesis of methane

1923 ◽  
Vol 103 (720) ◽  
pp. 25-34 ◽  
Keyword(s):  
Carbon Monoxide ◽  
Low Temperatures ◽  
Solid Surfaces ◽  
The Other ◽  
Theoretical Interest ◽  
Primary Object ◽  
Pure Methane ◽  
Practical Synthesis ◽  
The One ◽  
Water Gas

The investigation described in this communication had for its primary object the production of formaldehyde or methyl alcohol. In this aim we have been so far unsuccessful, but our results have led to the discovery of an action, Apart from theoretical interest the method would appear to have important technical possibilities, either as a means of producing pure methane is formed from water-gas than by other methods. In order to make clear the course of the action about to be described it will be well briefly to enumerate some of the known interactions of carbon monoxide and hydrogen on the one hand, and of the former gas and steam on the other.

Interpretation of irradiation-induced changes in electron diffractograms and images of extinction contours at low temperatures

1984 ◽  
Vol 42 ◽  
pp. 268-269
Author(s):  
E. Knapek ◽  
H. Formanek ◽  
G. Lefranc ◽  
I. Dietrich
Keyword(s):  
Low Temperatures ◽  
Carbon Films ◽  
Organic Crystals ◽  
Wide Spread ◽  
Lens System ◽  
Preparation Conditions ◽  
Thin Carbon ◽  
Electron Diffractograms ◽  
Diffraction Patterns ◽  
Induced Changes

A few years ago results on cryoprotection of L-valine were reported, where the values of the critical fluence De i.e, the electron exposure which decreases the intensity of the diffraction reflections by a factor e, amounted to the order of 2000 + 1000 e/nm2. In the meantime a discrepancy arose, since several groups published De values between 100 e/nm2 and 1200 e/nm2 /1 - 4/. This disagreement and particularly the wide spread of the results induced us to investigate more thoroughly the behaviour of organic crystals at very low temperatures during electron irradiation.For this purpose large L-valine crystals with homogenuous thickness were deposited on holey carbon films, thin carbon films or Au-coated holey carbon films. These specimens were cooled down to nearly liquid helium temperature in an electron microscope with a superconducting lens system and irradiated with 200 keU-electrons. The progress of radiation damage under different preparation conditions has been observed with series of electron diffraction patterns and direct images of extinction contours.

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