I've been synthesizing bulk hBN powder from boric acid and urea precursors in a tube furnace. However, when I mass the finished powder into water with a stir bar (so I can run reactions with the material), the pH shoots up as the material seems to fall apart in the water. Why is that? How can I synthesize a water-stable boron nitride? (not hydrophilic, just stable)
Synthesis approach:
I've been using a high molar ratio of urea: boric acid for precursors, so I've been doing 30:1 (though I've also tried lower). I add ~150 mg boric acid and ~4.5g urea to a beaker with 20 mL DI H2O + 20 mL methanol (based on:
Article A Template-free Solvent-mediated Synthesis of High Surface A...
), then leave it in a 65C oven overnight to evaporate and recrystallize. In the morning, I grind it to a fine powder using a mortar and pestle, then load the powder into a quartz boat and load that into the quartz tube. I attach the N2 gas line and I run the gas for 30 min, then turn on the instrument. I heat up at 5C/min until 1200C, the max for my furnace, holding at 1200C for a few hours. When it's cool, I use vacuum filtration to wash with water and ethanol, then dry in a 65C oven. I then grind this into a fine white powder and try my reactions.
I think you should check out are there some nanoparticles in your solution. What are the physical methods did you use to prove quality of your product?
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