Dear Asif Ali Haider

The color of the as-prepared xerogel is depending on the type and amount of the residual organic groups in the sample. On heating, these groups may thermally degrade by several processes involving dehydration of the free and structural water, carbonization, decomposition and volatilization at higher temperature, and so the color will changed accordingly.

Best regards

Greetings,

Dear Asif,

The color of the two samples may vary depending on the type and amount of the residual organic groups in the sample, as suggested by Mohammed Hussein j. H. Al'Atia Sir. However, this may be due to several reasons, for eg.

1) The amount of solution mixed in the sample may vary, due to human error and hence may not be identical.

2) Due to the non-uniform heating rate in the oven (maybe due to the position of the sample in the oven, the heating rate is different).

3) The time duration of mixing on the samples is different.

It may not affect the sample after calcination, since at higher temperatures all the organic content will eventually leave the sample. However, the results may vary if you alter the ramping rate of calcination for the two samples. As far as the ramping rate is constant, the samples should give uniform results (if identical entities).

Thanks

Yes, the morphology of the calcined material depends on its heating rate during calcination as said by Dr. Mohammad Yusuf.

I totally agree with Mohammad Yusuf reason(s). A good way to finalize the actual colour, to be sure it is not from human error, will be to carefully synthesize the sample again for the third time, to know if the colour matches any of the two.

All the best!

But some time after calcination, some samples show like carbon is not completely dissolved and appeared the sample black but not whole powder. Especially the yellow-colored sample I showed above. What to do to avoid this. I know if calcination temperature is increased then this problem can be resolved but at the same temperature, I observed this like at 600C above two samples are not giving the same results after calcination.

https://www.researchgate.net/post/Why_the_color_of_same_samples_are_different_using_sol-gel_method,kindly check this link.

https://www.researchgate.net/post/Why_the_color_of_same_samples_are_different_using_sol-gel_method2,this link may be useful.