So in a simple way, the path to create a tile/ceramic (with conventional ceramic processing / solid state reactions) is as follows:
1-Mixing powder
2-Calcining
3-Pressing
4-Sintering
In my case (manganese zinc ferrite) the temperature for both Calcining and Sintering process are relatively the same. I wanted to know if it is possible to exempt the process from Calcining step, and only rely on Sintering process to both (1) Synthesis the crystalline structure, and (2) From the ceramic?
Dear friend Ali Reza Fattahi
It is generally not recommended to skip the calcination step in the conventional ceramic processing/solid-state reaction method, as this step is essential for the synthesis of the desired crystalline structure in the ceramic material. Calcination involves heating the mixture of powders at a high temperature for a specific time, which causes chemical reactions to occur and leads to the formation of the desired crystal structure. Without calcination, the ceramic material may not have the desired structure or properties.
In addition, the calcination step also helps to remove any organic or volatile components from the powder mixture, which can affect the properties of the final ceramic material. Skipping this step may result in a lower quality ceramic material with reduced strength, density, and other desired properties.
Therefore, it is not recommended to skip the calcination step in the ceramic preparation process. While the sintering process can help to form the ceramic material, it cannot replace the calcination step in terms of synthesizing the desired crystal structure.
https://www.researchgate.net/post/What-is-the-difference-between-annealing-sintering-and-calcination#:~:text=Annealing%20%3D%20thermal%20treatment%20to%20remove,(O2%20or%20air)%20atmosphere.
Depends on the raw materials you are using to form your final compound. If carbonates are involved, then calcination will convert the carbonates to oxides during the calcination step. Try to do a TGA analysis of your mixed powder, and see the changes (wright loss) to figure out the different reactions that can occur within you raw powder mixture, and determine the temperature when there is no more weight loss, and the curve is almost stable /constant. This will give you an idea of the calicnation tmperature. Sintering tempering is higher than your calcination temperature, and is purely meant for densification and further grain growth processes. For sintering you normally mix a binder material for achieving good grannulation, and densify your well reacted powder into a densified compact pellet.
K. Sreenivas
Thank you for your answer Prof. Sreenivas
I'm looking to produce ferrite tiles made of Manganese Zinc Ferrite (MZF). All of my precursors are Metal Oxides and the chemical reaction is as follows:
4Fe2O3+2ZnO+2MnO2->2ZnMnFe2O8+O2
Plus, both sintering and calcining temperature for my case tend to lie between 1000-1200 Celsius. [Temperatures vary in some sources but I got a good XRD by calcining at 1050]
As you mentioned, binders like PVA are added before pressing, and during sintering process, they evaporate. So I'm assuming that same goes for O2 molecule and it can easily leave the structure as well!
Now, since during the milling process, molecules are arranged within each other, logically I can not understand why both of aforementioned processes can't happen in Sintering step.
And finally, this project is intended to reach industrial capacity and as you know (1) thermal treatment is very costly & (2) lots of aggregation will occur in calcining step which getting rid of them (in industrial milling) is a big issue.
No, it is not possible to shorten the ceramic preparation path by simply ignoring the calcination step. Calcination is an essential part of the preparation process and is used to remove impurities from the raw material and to convert it into a more stable form. Without calcination, the ceramic product may be of poor quality and may even be dangerous due to the presence of impurities.
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