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Chapter 2
Summary Gas-solid interaction
In the chapter Gas-solid interaction we focus on a series of phenomena that occur as a result of the interaction between the chaotically moving gas particles and the surrounding solid surface (e.g. the walls of the enclosure). This interaction, together with the ability of solids to bind and store gas particles, is the major obstacle for obtaining extremely low pressures. On the other hand, gas-solid interactions also form the basis for different pump principles in vacuum technology. Topics to be discussed are: physical adsorption, gas-surface interaction potential (Lennard-Jones), adsorption and desorption rate, residence time, dynamic equilibrium between adsorption and desorption, adsorption models and isotherms (Langmuir, BET), mobile versus localized adsorption, surface migration, porous materials and their ability to capture large quantities of gas, chemisorption, condensation, absorption, diffusion, permeation and outgassing of solid materials.
Some figures in Gas-solid interaction
Contents Gas-solid interaction
2.1 Introduction 63
2.2 Physical adsorption 63
2.3 Why no mirror reflection at a solid surface? 65
2.4 Lennard-Jones potential 67
2.5 Rate of adsorption 71
2.6 Residence time 71
2.7 Rate of desorption 73
2.8 Adsorption-desorption equilibrium 75
2.9 Adsorption isotherms 76
2.9.1 Monolayer (Langmuir) adsorption 76
2.9.2 Multilayer (BET) adsorption 78
2.10 Surface migration; mobile versus localized adsorption 81
2.11 Porous materials; persorption 82
2.12 Chemisorption 85
2.13 Condensation 89
2.14 Absorption, diffusion and permeation 90
2.15 Outgassing 97
exercises
