Some years ago I started making my own thermal paste...through a little experimentation I found Barium Chromate and pure silicon thermal grease the best combination, this has been my first choice for about 11 years.
Just recently Diamond thermal paste has become commercially available and I gave one of several a try, it outperformed both Silver and Barium based pastes.
I found this old article as a kick of point and it has motivated me to my tinker table again, Just ordered some "Synthetic" Diamond dust (synthetic outperforms Natural by a sizeable margin) from a lapidary supplier (ebay ....could be sugar for all I know!) and am going to mix a potion myself. if the figures work out I can make it 25x cheaper then buying it over the counter......... I'll keep you informed as to my findings as long as I don't blow myself up .
Some light reading.....Aussie Allan
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[Jared Bouck] over at InventGeek writes about his experience making his own thermal paste. Diamonds can be up to five times as thermally conductive as silver, the primary ingredient in most popular thermal compounds. He combines 60,000 mesh diamond dust he ordered off eBay with non-conductive silicon grease using a special mixer he constructed to keep down the dust. After some experimentation he achieved a max load temperature of 38 degrees Celsius versus a leading silver paste’s temperature of 57c on the same system.