Hello everyone, I am actually carrying out my research in the synthesis of Black TiO2 by sol gel method. Took TTIP in Diethylene Glycol as precursor and later did hydrolysis leading to formation of gel. The gel was eventually dried (250 deg C) and calcined (300 deg C) to get powders. However, the particles were very coarse and immediately settled when washed with water. I am comparing my particles with the amorphous TiO2 which is very fine indeed and forms a milky suspension in water which takes very long to settle in water. But my particles are not that great even after crushing them. How to get such fine particles which are truly in the nano size range? what are the parameters that affect the final particle size after calcination?
You have asked this question before (and I have replied):
https://www.researchgate.net/post/Are_the_nanoparticles_formed_by_sol_gel_method_indeed_in_the_nano_size_range
Why do you ask it again? Are you not happy with the answers?
The problem is that you have dried your sample and ended up with a fused mass of sub- and post-micron aggregates and agglomerates. To preserve particles in the < 100 nm size range you'll need to keep the particles in suspension and never dry. 'Nanopowder' is an oxymoron. As TiO2 is dense (~ 4.2 g/cm3) then carry out a Stokes' Law sedimentation test (as in Table 1 ASTM E2490-09(15)) to see what size will remain in suspension (> 24 hours to settle 1 cm). It's likely to be < 50 nm. At these sizes your colloidal suspension will appear as clear as water and only a density determination or shining a laser pen through will indicate the presence of particles. Open in IE ONLY:
Dispersion and nanotechnology http://tinyurl.com/hpywsge
Dear Rajaraman Ts,
when does the formation of very coarse particles form ?
I agree with Prof. @Alan F Rawle. You need to disperse the powder. Also, if you want to make black TiO2 you can anneal it under reducing gas such as H2. If you anneal it in air you will get TiO2.
Dear Raja
While preparing particles via sol-gel method particle size is very critical parameter. Use surfactants they may hinder forming coarse grains while evoporation of gel.... Try this. I got good fine particle in my trial.
Best
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