Fabrication And Application Of Carbon Nanotubes Composite Energetic Materials

Carbon nanotube is a novel nano-material.Its unique physical structure and excellent chemical properties have attracted the attention of scientists in many fields,and it also showed a considerable value in the field of energetic materials.Carbon nanotube than graphite has higher mechanical strength,more excellent electrical conductivity and thermal conductivity,and higher chemical and biological activity.So the carbon nanotube as reductant,with an oxidant filled in the 1D cavity,can obtain a new nano composite energetic material with excellent performance.Two kinds of carbon nanotubes(CNTs)were filled with nitrate oxidant in this dissertation.One is sealed with end cap at both ends,and the other is aligned carbon nanotube with opened ends.The aligned carbon nanotubes were fabricated by chemical vapor deposition(CVD)method with porous anodic alumina oxide(AAO)template.A novel nano composite energetic material was formed by using the capillary action to fill the hollow cavities of the carbon nanotubes with nitrate oxidant.The structure and the thermodynamic performance of the nano composite energetic materials were characterized.The results show that carbon nanotubes can be filled with various nitrate oxidants by capillary action.The carbon nanotubes prepared by AAO template method exhibit uniform diameter,and they are straight without winding.The wall structure damage in the end-opening process can be avoided due to the opened ends of the aligned carbon nanotubes,and the reduction of filling rate influenced by opening rate can also be avoided.The thermodynamic properties of 4 aligned carbon nanotubes reagent KNO3+CNTs,KNO3@CNTs,AgNO3+CNTs and AgNO3@CNTs('+' expresses tube external composite,'@'expresses tube internal composite)were investigated.The results show that the reaction energy barrier decreases due to the oxidant filling inside the carbon nanotubes.The activation energy of KNO3@CNTs is 36 kJ·mol-1 less than that of KNO3+CNTs,while the activation energy of AgNO3@CNTs is only 2 kJ·mol-1 less than that of AgNO3+CNTs.The optimized molecular geometry and electronic structure of isolated potassium nitrate,carbon nanotubes and their composite models were simulated by the first principles method,and the thermodynamic parameters were obtained by frequency analysis.The results show that the diameter of carbon nanotube has great influence on the stability of the internal composite model,and the charge transfer decreases obviously with the increase of the diameter.The tube diameter has little effect on the stability of the external composite model,and the charge transfer increases slightly with the increase of the diameter.The charge density of the simulation system corresponds to the charge transfer.The system of maximum charge density overlap and maximum charge transfer is KNO3@CNT(5,5).The system of minimum charge density overlap and minimum charge transfer is KNO3@CNT(7,7).The diameter and the composite mode have little influence on the density of state(DOS),and the systems are still metallic.For CNT(5,5)the external composite system is more stable than the internal composite system.For CNT(6,6)and CNT(7,7)the internal composite system is more stable than the external composite system.The Gibbs free energy(?G)of filling KNO3 into CNT(5,5)is greater than 0,indicating that the preparation process can not happen autonomously.The other preparation processes can happen autonomously(?G<0).The KNO3@CNTs initiator was developed by integrating KNO3@CNTs nanoenergetic materials with a Cu thin-film bridge.The electro-explosion performances,including the voltage and current properties,the electro-explosion time,the electro-explosion phenomenon,the explosive sensitivity,and the temperature distribution of the Cu microbridge and the KNO3@CNTs initiator under capacitor discharge were investigated.The results show that the Cu thin-film bridge and the KNO3@CNTs initiator conduct different electro-explosion behaviors.Compared with the Cu thin-film bridge,the KNO3@CNTs initiator possesses longer electro-explosion time under the same charging voltage.The electro-explosion time of both the Cu thin-film bridge and the KNO3@CNTs initiator exponentially decreases with increasing the charging voltage.The peak temperature of the KNO3@CNTs initiator is obviously higher than that of Cu thin-film bridge under the same charging voltage,and the peak temperatures of both the Cu thin-film bridge and the KNO3@CNTs initiator increase with the increase of voltage.The 99.9%initiation energy of Cu thin-film bridge and the KNO3@CNTs initiator is 1.78J and 0.62J respectively,and the 0.1%initiation energy of Cu thin-film bridge and the KNO3@CNTs initiator is 0.082J and 0.098J respectively.The initiation energy of the KNO3@CNTs initiator is narrower,indicating that the initiation input energy can be lowered by the introduction of KNO3@CNTs composite materials and it is more secure for the initiator during transportation,storage and use process,reducing the possibility of the accidental initiation.Based on the high absorption of light,the laser ignition experiments of the aligned carbon nanotubes composite energetic materials were tested.The ignition performances of 4 agents(KN03+CNTs?KN03@CNTs?AgN03+CNTs ? AgN03@CNTs)under 3 laser mode were investigated,including laser ignition process,laser ignition delay time and laser ignition energy.The results show that for the carbon nanotubes composite energetic materials,the influence factor of laser ignition reaction rate include the laser response characteristics,the reactivity and the thermal conductivity of the composite materials.Under the continuous-wave of the semiconductor laser,the laser ignition delay time and laser ignition energy of KNO3@CNTs are less than that of KNO3+CNTs due to the effect of activation energy is lager than that of thermal conductivity,while the laser ignition delay time and laser ignition energy of AgNO3@CNTs are more than that of AgNO3+CNTs due to the effect of thermal conductivity is lager than that of activation energy.Under the single pulse of the semiconductor laser,the KNO3@CNTs and AgNO3@CNTs can not be ignited,and the ignition energy of AgNO3+CNTs is less than that of KNO3+CNTs due to the activation energy of AgNO3+CNTs is much less than that of KNO3+CNTs.Under the single pulse of Nd:YAG laser,the combustion processes are rapid and violent due to the laser power is high.The high density energy is sufficient for the 4 agents to react instantaneously,so the thermal conductivity of the agent will greatly affect their combustion rate.For both the KNO3 and AgNO3 composite materials,the combustion time of internal composite materials is less than that of external composite materials.