The main problem is that transition metal alkoxides tend to react very quickly. I attempted to make a pure zirconia gel, and - after a small amount of literature research - came across a simple recipe that used a much higher acid concentration. I wanted to tweak this method to produce a transition metal sol that would gel within a time scale of a couple of hours. However, I came across a stumbling block: It seems the gels form either very quickly (within seconds) or not at all (they remain sols even after a month or so). Ideally I need a gellation time of a couple of hours so I can obtain deeper information on the reaction during Insitu Xray Scattering Runs. The faster reactions are also of use though - provided the software at the synchrotron beamline can handle it!

Just a slight alteration in precursor ratios can generate a completely different end product. Sometimes the stuff will precipitate, other times I get an opaque or clear gel. 

 

I've chosen Yttria-Zirconia simply because the two elements are next to each other on the periodic table. This give a much better ASAXS resolution - which is beneficial at such an early stage in my PhD. Both nuclei are also strong scatterers in comparison to lighter elements such as Silicon.

 

 Because of the cost of the materials involved, I need to get this right without too much initial wastage in trying things out. Can anyone suggest a good method of making a pure Zirconia Sol that will Gel in a couple of hours? I gather (from Sol-Gel Science, chapter 2, for example) that all transition metals are equally as reactive, so Yttria will generate the same problems. The process appears to be similar in nature to making Titania Gels.

 

I'm using Zirconium n-propoxide as a precursor. I'm also going to be making my own Yttrium Ethoxide by reacting Yttrium Chloride with Potassium Ethoxide (itself from disolving potassium metal in Ethanol)

 

 

If anyone has any suggestions/ recipes than please let me know.

 

 

Regards,

 

 

Twilight

 

 

 

 

However, I'm interested in gathering information on the initial stages of the reaction just as the precursors are mixed and hydrolised. Increasing the ph of a sol that has been left for several months wouldn't be of much use to us in the experiment. Presumably we'd have lost a lot of important information from the sol phase. Though, this could be an interesting thing to do as a comparison. I could, technically, mix the sol 'insiti' and then add drops of ammonia during the experiment to produce the zirconia-yttria gel.

 

Does ammonia solution have any effect in the reaction chemistry?

 

I'll try it out and let you know how it goes.

 

 

Twi

 

 

ps. sorry it's taken so long for me to reply. I've been busy finishing off my first year literature report... Now it's done and dusted, so I can finally get back to the science. :)