The Preparation And Performance Research Of Ultra-fine Potassium Nitrate Powder

Potassium nitrate（KNO₃） is the most common energetic material that is widely used as an oxidizer in ignition charge, showing excellent mechanical, thermal stability and compatibility. Recent studies have shown that the decrease of the particle size of KNO₃ can enhance the combustion rate of ignition compositions and detonation properties of explosives. In this paper, the superfine potassium nitrate （KNO₃） was prepared through an air-jet mill. Due to big specific surface area and easy moisture absorption, the anti-caking of superfine KNO₃ should be studied. The main results are shown as follows:Firstly, KNO₃ was ground with a GQF-1 flat air-jet mill and crushing process for superfine KNO₃ was investigated as follows:crushing times, air pressure, feeding speed etc could affect the superfine KNO₃. These parameters were determined by experiments finding. SEM and particles size measurement revealed that raw KNO₃ was irregular with a size of 180 μm and the superfine KNO₃ obtained from the jet mill was similarly spherical with a size of about 2.5 μm, which indicated that the GQF-1 air-jet mill had a good grinding result.Secondly, the superfine KNO₃ was modified with octadecane amine means of coating in liquid-phase and gas phase, respectively. And the two methods were compared to each other. The results show that the moisture absorption of superfine KNO₃ modified with 1% and 1.5% of octadecane amine means of coating in liquid-phase was decreased by 5.65% and 6.70% than superfine KNO₃, respectively. The moisture absorption of superfine KNO₃ modified with 1% and 1.5% of octadecane amine means of coating in gas phase was decreased by 5.30% and 6.36% than superfine KNO₃, respectively, which indicated that the method of coating in liquid-phase was better than gas phase.Thirdly, the superfine KNO₃/Boron composites were fabricated by an improved solvent-nonsolvent method. The thermo-analytical behaviors and mechanical sensitivity of superfine KNO₃/Boron composites were characterized. The results show that the apparent activation of superfine KNO₃/B composites was increased by 428.54 KJ/mol and 133.91 KJ/mol and the critical ignition temperature of superfine KNO₃/B composites was decreased by 37.8℃ and 26.0℃, respectively, compared with simply mixed raw KNO₃+B and simply mixed superfine KNO₃+B. In addition, the impact and friction sensitivity of superfine KNO₃/B composites were reduced by 206.07% and 20%, respectively. Results demonstrate that superfine KNO₃/B composites are more insensitive to impact and friction stimuli and more stable during safe processing, handling and storage.