Hello,

FYI, I used white rice husk ash as a silica source for my aerogel. For supercritical drying, I add 6 litre of absolute ethanol for 1.5 litre of ethanol-soaked alcogel in the drying chamber. The temperature and final pressure of the drying process is around 275 degree C and 1400 psi. I have done this several times, and the results are WHITE aerogel powder (attached image). Although the powder is white, it still shows some basic properties of aerogel such as low density, hydrophobic .. however, I just want to know if there any method to change the color of my aerogel powder?

 

Thanks in advance.

The best you could hope to do would be to make the gel from something with a lower refractive index- i.e. nearer to the index of air.

Silica already has a fairly low refractive index so that might be difficult.

 

How do you get the rice husk ash to form a gel?

Oh, thanks for the tips. I will use that as keyword for my further research.

 

I burn the rice husk in a furnace at 600 deg C to get the white ash. I have custome made furnace for that purpose here in my lab. Then I make Na2O3Si solution by mixing water, NaOH and the ash. I used sulphuric acid to make a gel from the sodium silicate solution.