- Catalycity
Catalycity is a macroscopic parameter to describe surface
catalysis (heterogeneous catalysis). It is usually called a material property, due to its strong dependence on the surface material. This naming is not fully justified, since the catalycity not only dependent on the material but also on its environment.Catalysis
Gases like
Nitrogen ,Oxygen or mixtures of the likeAir consists at low temperatures of molecules. At elevated temperatures they dissociate, i.e. they break apart into single atoms.
Atoms tends to recombine in the gas phase.This process can be accelerated with the help of a
catalyst . The catalyst provides an alternative reaction path, which is in general faster than the original.Such and reaction path could be:adsorption :
reaction at the surface:desorption :Definition
Catalyctiy relates the number of reacting atoms to the number of atoms that hit a surface. Therefore, a catalycity of one means that all impinging particles do recombine.
Usage
The parameter catalycity is mainly used in hypersonics, i.e. the science high speed and high temperature flow. These kind of flows occur for instance in
Atmospheric reentry .Limitations
In mixtures of gases where interactions between the different species occurs, the parameter catalycity is not appropriate.
Determination
The determination of catalycity is usually done in
Plasma (physics) wind tunnels like arc-jets orinductively coupled plasma generators.
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