Study On Preparation And Properties Of Butterfly Wing-like Nanocomposites

Micro/nano hierarchical structure is a composite structure in which the structural units on micro-scale are built from the secondary nano-scale structural units.The fabrication of hierarchical micro/nanostructures not only can overcome the shortcomings of easy aggregation and bad diaspora et al of nano materials,but also produce new propreties for the materials.In this thesis,taking butterfly wing scales with fine micro/nano hierarchical structure as the bio-templates,butterfly wing-like TiO₂ and CuO have been prepared to improve their catalytic activity for ammonium chlorate（AP）thermal decomposition.Through the confined crystallization of hexanitrohexaazaisowurtzitane（CL-20）and AP into the 3D scaffold of carbonized butterfly wing scales（CWs）,a nanostructured energetic nanocomposition CWs/CL-20/AP has been obtained to solve the key problems of combustion instability and bad low combustion efficiency of high-energy density compound in micro thrusters.The main research contents are as follows:（1）Butterfly wing-shaped titanium dioxide（BW-TiO₂）nanoparticles and copper oxide/carbonized butterfly wing（CuO/CWs）nanocomposite were prepared by dipping-calcination method using butterfly wing as a template.Its morphology,structure and composition were characterized by SEM,TEM,XRD,XPS and BET.The results show that BW-TiO₂ and CuO/CWs closely resemble the parallel window structure of BW,containing well-connected nano tubular channels and a large number of micro-pores.The addition of5wt%BW-TiO₂ as catalyst for AP thermal decomposition can reduce the high-temperature decomposition peak temperature from 429.1 to 374.1°C,increase the exothermic heat from255 to 1323 J?g^-1,and decrease the active energy from 190 to 130.9 kJ?mol^-1,exhibiting the excellent catalytic activity.The CuO/CWs nanocomposites have excellent catalytic activity for the thermal decomposition of AP,the high-temperature decomposition temperature has been reduced by 88.3°C,the apparent activation energy reduced from 190.0 kJ?mol^-1 to103.1 kJ?mol^-1,and the heat release increased from 255 J?g^-1 to 1841 J?g^-1.（2）CWs with a micro/nano hierarchical structure have been obtained by carbonizing the butterfly wings,and then CL-20 and AP are loaded into the three-dimensional hierarchical porous structure of CWs through a confined crystallization method to obtain a nanostructured CWs/CL-20/AP compositions.Its morphology and structure were characterized by SEM and XRD,and its thermal decomposition performance and micro-scale combustion performance in micro thrusters were studied by DSC-TG and laser-ignition combustion（LIC）.The stable and self-propagating LIC has been achieved due to the hierarchical porous channels,ultrathin freestanding structure,the good thermal conductivity and high light absorption of CWs,as well as the size effect and synergistic reaction of CL-20 and AP nanocrystals.As the high-energy density chemical fuel used in micro thrusters,CWs/CL-20/AP exhibits the small size,high-efficiency,stable and self-sustaining combustion feature due to the enhanced heat and mass transfer as well as a large amount of gaseous products,which effectively compensate the heat and pressure loss during the microcombustion process.The oxygen balance of CWs/CL-20/AP can be conveniently regulated by adjusting the mass ratio of CL-20 and AP.The composition with oxygen balance close to zero has the best LIC and microcombustion performance and the thrust in the micro thruster is around 20 times of AC（active carbon）/CL-20/AP and GO（graphene oxide）/CL-20/AP.