During a synthesis of CuO-doped TiO2 catalytic coating through sol gel process, the gel formed when i was mixing my solutions to get a sol.
I am not quite sure what i can do to delay the formation of the gel but here are some rough ideas:
1) reduce the amount of acid (as far as i know the acid acts as a catalyst and reduce the gelation time)
2) simply apply the sol onto the support after the addition of about 35% of solution B and let the gel form under heat treatment
Can anyone explain what the exact roles of acetic acid (apart from being a catalyst) and ethanol (apart from being a non aqueous solvent) are? Could the solutions mentioned above theoretically work?
The process is described below:
I was using tetrabutyl orthotitanate and Copper (ii) nitrate pentahydrate as my main reagents. for simplicity i shall name the solutions for the creation the sol solution A and solution B.
Solution A is made up of 30 ml pure Ethanol (>99,5%), 10 ml tetrabutyl orthotitanate and 0,7g of Cu(NO3)2. Solution B is made up of 4 ml 2N acetic acid, 4 ml distilled water and 10 ml pure ethanol.
While i expected the mixture to stay fluid after the addition of solution B to solution A dropwise (under vigorous stirring) , the gelation happened after i added about 40% of my solution B. This should not happen because the sol is intended to be applied onto the surface of a support and a gel should form on the surface under heat treatment.
Put a permanent magnet with high enough magnetic intensity near the beaker containing the solution mixture. wishes
Dear Yu Han Tai
My suggestion is you have to mix Titanium precursor first for about 30 min to get TiO2 sol, then you can pour your copper salt solution, the key issue is pH due to the difference in the electronagtivety of the adopted atoms, my advise is to obtain colorless TiO2 sol by selection of suitable pH. Greeting
Hi,
As you know, sol-gel process involves a series of hydrolysis and condensation reactions. Both hydrolysis and condensation are pH sensitive. You can refer to the following publication to gain more information on this:
A.-M. Siouffi, Silica gel-based monoliths prepared by the sol–gel method: facts and figures, doi:https://doi.org/10.1016/S0021-9673(03)00510-7
Another useful source would be the book of Sol-gel Science by Brinker & Scherer
Good luck.
dearest Yu Han Tai
in sol-gel most important key for product issue is pH coz this will lead to difference in the electronegative of the atoms adopted ,,,,, sure you have here to mix the precursore that you are use for at least 30 to 45 min under constant temperature reach to 35 c then with selection of the pH suitable you will get what you was looking for it >>>>> My suggestion is you have to mix Titanium precursor first for about 30 min to get TiO2 sol, then you can pour your copper salt solution, the key issue is pH due to the difference in the electronagtivety of the adopted atoms, my advise is to obtain colorless TiO2 sol by selection of suitable pH. Greeting
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