This is the sample at 350C, we've been trying to synthesize g-C3N4 (graphitic carbon nitride) for over a month to no avail in a tubular furnace.

Our constraints which we cannot change:

-Use of mini-tubular furnace

-The putting of urea in quartz boats

-The apparatus uses a borosilicate glass tube with an N2 inlet, and an outlet to a tube dipped in water to avoid any gases flowing back

We have tried putting aluminum foil and without, tried synthesizing at 350C,400C,450C,500C,550C. With holding times and without for calcination, with multiple ramping rates (5C/min 10C/min). However, it was to no avail. Samples ranged from charcoal black to gray to dark brown. May an expert please be of assistance to us and guide us, as the topic and experiment is extremely vital.