Synthesis of novel carbon dots based combustion catalysts and their effects on thermolysis and laser ignition of 1,1′-dihydroxy-5,5′-ditetrazolium dihydroxyammonium salt (TKX-50)

Abstract

The carbon dots (CDs) were prepared by the oxidation etching method. On this basis, the composite materials of CDs and Cu (CDs/Cu) were synthesized by the hydrothermal method. The elemental composition, morphology and structure were analyzed by TEM, SEM, EDS, XRD and XPS. The effects of CDs and CDs/Cu for thermal decomposition of TKX-50 pyrolysis were studied by DSC-FTIR-MS and in-situ solid FTIR. The CDs and CDs/Cu reduced the low-temperature decomposition peak temperature of TKX-50 by 10.1 ℃ and 16.1 ℃ respectively (10 ℃·min−1), and the second decomposition peak almost disappeared. This is because CDs and CDs/Cu can effectively facilitate the thermal decomposition of TKX-50 into NH2OH and 1,1′-ditetrazole diol (BTO). The CDs can promote the direct decomposition of BTO into small molecule gases and stable polymers at the initial pyrolysis stage. And they inhibit the combination of BTO and NH3 into 5,5′-bistetrazole-1,1′-didiolate (ABTOX), which is more difficult to decompose. So, the HCN and N2/CO were increased obviously during pyrolysis while NH3 and H2O content were decreased. On the other hand, the CDs/Cu promotes the decomposition of NH2OH in the first reaction. It manifested as the increase of NH3 and H2O. At the same time, the CDs/Cu facilitates the transition of difficult to decompose ABTOX losing NH3 to BOX to accelerate thermal decomposition reaction, playing a synergistic catalytic effect. Thus, in-situ solid FTIR signal of ABTOX was significantly weakened and the total content of NH3 was raised, especially the significant expansion of NH3 in the second stage. Finally, the influence of the catalysts in ignition characteristics was contrasted and discussed. Under the lower-power density region, the CDs and CDs/Cu decreased the ignition delay time of TKX-50. The CDs/Cu caused the flame propagation velocity of TKX-50 faster. Therefore, the CDs and their composites, as another new lightweight carbon material, are expected to be applied in the catalytic combustion of energetic materials.