44007

Desiccant adhesion [Texas] 

February 14, 2007

Hi
I am adhering desiccant to a alumina fin. I am first anodizing the fin. After gamma alumina 5 micron is blended with water and phospheric acid. Also some pre-calcinated alumina in part is combine and some porous alumina , both in small concentration.
The porous alumina binds alittle the slurry giving it thickness and the pre-calcinated alumina gives it sand structure ,increasing the physical surface geometry but also has an unconvinient diminished factor to the adhesion characteristic.

Once the fin is dipped , it is calcinated to change the particles to gamma and remove any loquid content creating pores. A second coat is applied after to thicken the desiccant , to provide adsorbtion capacity in thickness.

One of the problem I am encontering is the result of surface tension. Do to the fact that the combine slurry requires a certain proportion of acid to result in a acceptable adhesion , it also creates a skin effect stopping the surface part of the desiccant to capture moisture in air effectively.

Now , I have already maximized the physical or mechanical aspect as much as I could also I added pre-calcinated allumina to increse the surface geometry to my advantage. But I am still missing some effectiveness. Any sugestions and I do not know much about buffers but would that be an option to help my statistics.
Also the phospheric acid is always playing tricks on me. I have read it was cause by it's hydrogen cation not using all of it. Any idea why?

Best Regards,

Gerry Landry
- TX