Purify Argon gas by feeding it through heated titanium chips

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Discussion Overview

The discussion centers on the purification of argon gas by passing it over heated titanium chips prior to a heat treatment process. Participants explore the implications of temperature on the effectiveness of titanium getters and the nature of the reactions involved, including thermodynamic and kinetic considerations.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that the titanium getters should be at a higher temperature than the parts being heat treated to favor kinetics, but notes that more oxygen will be removed if the temperature is not too high.
  • Another participant questions whether the reaction involved is typically exothermic or endothermic.
  • A different participant asserts that the reaction should be exothermic.
  • It is mentioned that titanium getters typically operate around 600°C, and that reactions between metals and oxygen become less favorable with increasing temperature, which affects the minimum achievable oxygen potential of the getter.
  • One participant expresses interest in understanding why reactions are less favorable at higher temperatures despite improved kinetics.
  • A clarification is made that while kinetics generally increase with temperature, the thermodynamic driving force may not always follow the same trend, particularly for reactions between oxides and metals.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between temperature, reaction favorability, and kinetics, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

There are limitations regarding the stability of condensed phases at different temperature ranges, as well as the specific reaction constants for titanium and oxygen interactions, which are not fully explored in the discussion.

lou_skywalker
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If a titanium heat treatment process is to be performed in argon that has been passed over heated Ti chips prior to entering the furnace, should the gettering Ti (the ones used for purifying the argon) be at a higher or lower temperature that the parts being heat treated?

I know that a higher temperature is desired since the kinetics are more favorable but more oxygen will be removed if the temperature is not too high.
 
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is this type of reaction usually exo or endothermic?
 
It should be exothermic
 
Titanium getters typically operate around 600C.

Reactions between metals and oxygen tend to get less favorable with increasing temperature, resulting in a minimum oxygen potential your getter can achieve that increases with temperature (i.e., you can achieve lower oxygen potentials at lower getter temperatures). Take a look at the reaction constants for:

Ti + O2(g) = TiO2(rut.)
Ti + O2(g) = TiO2(ana.)
2Ti + O2(g) = 2TiO

The K values will be the reciprocal of the minimum achievable oxygen partial pressures. Be sure to use condensed phases that are stable in the temperature range you are examining. I don't know the range of stable temp. values for rutile, anatase, and TiO off-hand.
 
alright I will look into that...do you know why reactions are less favorable when you increase the temperature? Because it seems like at higher temperatures the kinetics are more favorable for reactions to occur.
 
I only said reactions between oxides and metals tend to get less favorable with increasing temperature.

Kinetics almost always increase with temperature, but not always the thermodynamic driving force.
 

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