Making Cobalt Blue by Sintering Alumina & Cobalt monoxide ?

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SUMMARY

The synthesis of Cobalt Blue, or Cobalt(II) Aluminate (CoAl2O4), requires sintering a stoichiometric mixture of finely ground Cobalt(II) oxide (CoO) and alumina (Al2O3) at a temperature of 1200°C. Lower temperatures, such as 900°C or 1000°C, may yield minimal amounts of the compound, as optimal results have been experimentally determined at 1200°C. The requirement for fine grinding is crucial to increase the surface area, facilitating better contact during the sintering process, which enhances the reaction efficiency.

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  • Cobalt(II) oxide (CoO) and alumina (Al2O3) properties
  • Sintering process fundamentals
  • Temperature effects on chemical reactions
  • Surface area and its impact on reaction kinetics
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Chemists, materials scientists, and anyone involved in the synthesis of inorganic compounds, particularly those interested in the production of Cobalt Blue pigments.

Panthera Leo
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Making Cobalt Blue by Sintering Alumina & Cobalt monoxide...??

Hi,

This is what is written in wikipedia about Cobalt Blue [Cobalt(II) Aluminate] :

"Chemically, cobalt blue is a cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl2O4. The compound is made by sintering the stoichiometric mixture of finely ground CoO and Al2O3 (alumina) at 1200°C"

Source: http://en.wikipedia.org/wiki/Cobalt%28II%29_aluminate"

My questions are:

Does this mean Cobalt(II) aluminate can't be made at 900 or 1000C ? Why 1200?
&
why does it have to be "finely ground" ? (just to increase surface area, in order to increase contact zone? )

Thanks in advance :)
 
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Panthera Leo said:
Does this mean Cobalt(II) aluminate can't be made at 900 or 1000C ?

Either can't or it will be made in minute amounts.

Why 1200?

These things are determined experimentally. Apparently this was tried and gave best results.

why does it have to be "finely ground" ? (just to increase surface area, in order to increase contact zone? )

Isn't it how sintering works? Reaction takes place in a thin layer on the grain surface. You want the grains to be so small after reaction "surface zone" occupies whole volume.
 


Many Thanks Borek, You are very informative as usual :)
& Sorry for my late reply, I was away.