I have 2 questions sent by PM from Rajaraman Ts. As RG is not a free consultancy service I will post these questions below for others to answer:
Respected Sir,
This is Rajaraman from India having TiO2 nanoparticles as my research area. I had posted some questions regarding my final product being in nano range. You had twice given me very helpful answers. But I still had some doubt regarding the same and it would be great if you could help me out.
1)
Actually, in one of the replies you had mentioned that I should not dry my product as drying fuses them together as agglomerates. So, instead I should just keep them in suspension. My query is that the method which I am using for the synthesis is sol-gel method where in a certain step I get gel formation after hydrolysis. Almost all literature states that drying and calcination steps are necessary to aid in the formation of TiO2 from Ti-OH. So, how can I not dry and keep them in suspension when drying and calcination steps seem inevitable. I mean, is there some method where I keep convert the gel into nano TiO2 suspension without drying and calcination?
2)
And another query which I had is that in the gel itself there is lot of unreacted alcohol (DEG) which I had used as solvent initially. I have to use that solvent in excess. Can you suggest me some technique where I can remove the extra solvent from the gel through some washing or something. Because the same alcohol gets carried over until the final calcination step where I am getting carbon residues in my powder because of it. So, in order to get purer TiO2, it seems logical to eliminate DEG in between somewhere.
Thank you so much sir for your earlier replies and looking forward for the same here as well.
Regards,
Rajaraman
Hello sir,
This is Rajaraman from India. I am currently working on the synthesis of black TiO2 as part of my research area. I had posted a couple of questions related to preparing fine particles in the nano range and your replies gave me deeper insights for which I am very thankful. However, I had some query related to the same and wanted to clarify with you.
1) In the reply to my question on how to synthesize very fine powders, you had told to eliminate the calcination step which actually causes removal of moisture and agglomeration due to which the particles are not fine. You had also suggested me that I should keep the particles in the dispersion itself and skip the calcination step to get finer particles But the method of Sol Gel which I have taken up for the synthesis of nanoparticles , inherently has calcination step. I need to dry and calcine my gel to get the powders. So , I was wondering is there still a way where I can skip the calcination step and obtain particles in the dispersion form directly from the gel? Is there some kind of washing that I can do for the gel where the I get my TiO2 particles in dispersion form? Or can I give my final product a very long and hard crushing till it seems to be very fine? Because ultimately my application of the product demands it to be dispersed in water. So, I need finer particles for larger surface area and higher stability without stirring.
Thanks for your earlier replies sir. Hope for the same as this would be very beneficial to me.
Regards,
Rajaraman
Point is the author wants to synthesize black/reduced titania.
-- So instead of struggling to get nano size TiO2 without any agglomerates, why not directly purchase Anatase TiO2 ( commercially available) or Degussa P25 ( If you need mixture of Anatase and Rutile phase). In this manner, one can save time and directly go for synthesis of reduced titania. You can follow below protocol for synthesizing reduced titania, although there are many in literature.
1. Materials Today 20(9):507-515, DOI: 10.1016/j.mattod.2017.09.005
-- Skipping calcination part might not help because it would lead to amorphous Titania which isn't catalytically active. So calcination is necessary. You can try calcining your sample at milder temperature ( 300 - 400 C) for couple of hours. In this manner one can prevent formation of agglomerates and crystallize TiO2 into Anatase phase.
But still I suggest purchasing titania, which is of high quality and time saving.
Good luck!
I suggest the calcinated process between 400-800 degrees is best process to change the phase of TiO2 from anatase to rutile..............
From my opinion purchased powder always have the disadvantage of aggregation.
But why not use a basic procedure like the ones published by Anpo et al. So, he can decide if he want to have Rutil or anatas (at moderate temperatures) and the particles are very small. Reduction using UV-light source and a hole scavenger (e.g. an organic acid = Photo-Kolbe) shouldn’t be a problem (he might compare to the Photo-reactor experiments within our studies).
https://www.researchgate.net/scientific-contributions/78609501_Masakazu_Anpo
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