I am melting Zn based solution in furnace, the solution is in Ceramics crucibles but after heating at 900 C the obtained powder is dark grey colour (Not white) is sticking hardly to crucible (so hard that applying a lot of pressure is insufficient to remove, can only be removed with strong driller like rotating instrument).
I am worried that is it because of any reaction with ZnO?
Thanks.
Of course, ZnO reacts with Al2O3 and SiO2 at 900°C. Zinc aluminate (ZnAl2O4) and zinc silicates (ZnO.nSiO2) are formed accordingly.
Thank you very much Dr Vadim Verlotski
So, then which crucible is advisable to use?
Thanks
Hi Ali,
If you want to melt metallic zinc, do it in a graphite crucible under a protective gas atmosphere at 430-450°C. I did not understand why you warmed zinc at 900°C in air. To get ZnO powder? That's weird.
Thank you!
I am trying to fabricate ZnO tetrapod powder bu using Flame Transport method.
Reference: Versatile Fabrication of Complex Shaped Metal Oxide Nano-Microstructures and Their Interconnected Networks for Multifunctional Applications .
Thanks
Using graphite crucible, under inert atmosphere, or platinum crucible in air will be helpful. However, I am wondering why you are heating the zinc near to its boiling point? what is the role of the polymer and alcohol?
Imad Disher thank you
Please read my above comment.
Thanks
Graphite crucible is also good while using in air?
The oxygen will react with the graphite and your crucible will corrode.
@ qaiser ali khan
I read the article regarding the zinc oxide tetrapod, I think you need to use high quality zirconia or alpha alumina crucible (that have smooth nonporous surface ) along with high heating rate.
Imad Disher Thank you very much.
Yes now i am confused , which one should i buy . I am trying to read about ZnO reaction with Zirconia or alpha Alumina crucible.
Really thanks alot to letting me know about all these problems.
Thanks
The smooth nonporous surface has low surface area which will, in addition to the fast heating rate and short soaking time of 30 min, reduce the reaction between your sample and the crucible.
Buy one piece from each for primary experiments.
Fused quartz crucibles/petri dishes are relatively cheap, and maybe you can use them.
1) Firstly, Since you are trying to convert a Zn based solution into powder, I would suggest a fused quartz petri dish, because it will have a large area, and the solution can react well to the surrounding oxygen.
2) Secondly don't take a large amount of solution in the petri dish, good to have just around 2 to 3 mm height of the solution in the petri dish. This will effectively allow all the solution to get heat treated well.
3) Thirdly, I don't know what is your solution, ( if it is metallo-organic, organo metallic) in nature, definitely during heat treatment, different kinds of gases will evolve. Hence don't do the heating experiment in a closed furnace. Do it in a tube furnace, with flowing oxygen, this carry away any of the evolved gases. Select the fused quartz petri dish of an appropriate diameter, so that it goes into your tube furnace.
4) Finally ZnO does stick and will stick to fused quartz also. Let it stick a little bit. But primarily you should first see a white powder formation. This is important for the reaction to proceed to completion in forming a single phase oxide of ZnO.
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Presently you are seeing a dark grey colored powder, which is not a good indication, it is happening either due to a bad reaction, or even due to a huge deficiency of oxygen in the formed powder.
There are many vapors in the literature trying to evaporate Zn metal vapors to form ZnO nano structures by vapor transport method.
The formation of ZnO all depends on what your so called Zn based solution is comprised of chemically, and accordingly the right level(temperature) and kind of heating (rate of heating) should be implemented.
Also check whether ZnO melts, sublimes, and whether it undergoes evaporation, because some oxides like PbO can evaporate.
K. Sreenivas
Thanks all , unfortunately worked in Quartz glass as suggested but didn't work and again stick alot. The problem is i can not really use the crucibles again .
Part Fibre Toxicol. 2018; 15: 8.
Published online 2018 Feb 12. doi: 10.1186/s12989-018-0246-4
Perhaps of some interest for those interested at this topic: https://www.researchgate.net/post/Is_there_a_recommended_procedure_for_removing_ZnO_from_graphite
https://www.researchgate.net/post/What_is_best_way_to_remove_ZnO_layer_from_Sapphire_substrate
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