Making Cobalt Blue by Sintering Alumina & Cobalt monoxide ?

  • Thread starter Panthera Leo
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In summary, cobalt blue, also known as cobalt(II) aluminate, is a chemical compound made by sintering a mixture of finely ground cobalt oxide and alumina at 1200°C. This temperature was determined experimentally to produce the best results. The fine grinding of the mixture increases the surface area, which is necessary for the sintering process to take place effectively. This allows for the reaction to occur on the surface of the particles, resulting in a more uniform and complete reaction.
  • #1
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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  • #2


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.
 
  • #3


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

1. How does sintering alumina and cobalt monoxide create cobalt blue?

Sintering is a process in which powdered materials are heated to high temperatures, causing them to fuse together and form a solid material. When alumina and cobalt monoxide are sintered together, the cobalt atoms become embedded in the alumina crystal structure, creating the unique blue color.

2. What is the chemical formula for cobalt blue?

The chemical formula for cobalt blue is CoAl2O4, also known as cobalt aluminate.

3. What temperature is needed for sintering alumina and cobalt monoxide?

The temperature needed for sintering can vary, but generally it ranges from 1500-1700°C. The exact temperature will depend on the specific materials being used and the desired properties of the final product.

4. What are the main applications of cobalt blue?

Cobalt blue is primarily used as a pigment in ceramics, glass, and paint. It is also used in the production of batteries, electronics, and jewelry.

5. Are there any safety precautions to consider when working with cobalt blue?

Cobalt blue is generally considered to be safe to handle, but it is important to take precautions to avoid inhaling or ingesting the powder. When handling cobalt blue, it is recommended to wear a dust mask and gloves, and to work in a well-ventilated area. It is also important to wash your hands thoroughly after handling the powder.

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