Well! the material to be freeze-dried is irradiated with IR radiations before, why?? Also I am confused as to how can ice sublime at atmospheric pressure?? Isn't the triple point of water much lower? is the vaccum around the material created for this reason? ( to lower the pressure I mean) Also stupid it may sound, but why does the phase diagram of H20 show that at atmospheric pressure water will undergo phase transition at a perticular temperature ?? (100°C) when evaporation occurs all the time i.e at all temperatures!! thanks in advance!