纳米碳粉掺杂对激光烧蚀GAP的推进性能影响

实验以含能聚合物聚叠氮缩水甘油醚(Glycidyl azide polymer,GAP）作为激光烧蚀微推力器的靶材。通过对不同浓度纳米碳粉掺杂和靶材厚度下激光烧蚀GAP的比冲、冲量耦合系数和能量转化效率测量，结合靶材喷射羽流图像，分析了纳米碳粉掺杂提高激光烧蚀聚合物靶材推进性能的机理，给出纳米碳粉掺杂的适用方式。实验结果表明：透射式下，掺杂纳米碳粉之后，聚合物对激光的吸收大幅增强，但激光烧蚀推进性能不随掺杂浓度增加而显著提升；纳米碳粉吸收激光能量形成温度极高的局部热区促进聚合物中化学能的释放，是推进性能提升的主要原因；掺杂纳米碳粉之后的GAP烧蚀深度降低，表现出面吸收特性；随着靶材厚度的增加，未完全烧蚀的工质质量增加，使得靶材的利用率大大降低，导致聚合物推进性能下降。实验中掺杂3%纳米碳粉、厚度为54 μm的GAP靶材最优能量转化效率超过250%，适合作为透射式激光烧蚀微推力器的靶材。

Effects of Nano Carbon Dopants on Laser Ablation Propulsion Performance of GAP

The energetic polymer polyazide glycidyl ether (GAP) is used as the target of a laser ablation micro thruster in the experiment. The specific impulse, momentum coupling coefficient and ablation efficiency of the laser ablated GAP with different concentrations of carbon nanoparticles doping and target thicknesses are measured and the plumes are observed. The mechanism of the carbon nanoparticles doping to improve the propelling performance of the laser ablative polymer target is analyzed and the suitable method of the carbon nanoparticles doping is investigated. Experimental results show that the laser absorption of the polymer is greatly enhanced after doped with the carbon nanoparticles, but the laser ablation propelling performance does not increase obviously with the increase of the doping concentration. The high temperature local hotspots formed by the carbon nanoparticles after absorbing laser energy promote the release of the chemical energy in the polymer, which is the main reason for the improvement of the propulsion performance. The ablation depth of GAP decreases after doping the carbon nanoparticles, which shows the surface absorption characteristic similar to the metal target. With the increase of the target thicknesses, the mass of the incomplete ablative materials increases, and the utilization ratio of the target material is greatly reduced, which leads to the degradation of the polymer propulsion performance. The optimal ablation efficiency of GAP with 3% carbon concentrations in 54 μm exceeds 250%, which is suitable for a laser ablation micro-thruster.