Han Gao

A facile one-pot solvothermal synthesis of CoFe2O4/RGO and its excellent catalytic activity on thermal decomposition of ammonium perchlorate

CoFe2O4/RGO hybrids have been successfully fabricated via a facile one-pot solvothermal method, which were characterized by X-ray diffraction (XRD), Raman, Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). During this process, graphene oxide was reduced to graphene (RGO) and CoFe2O4 nanoparticles were deposited on the RGO. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the average size of CoFe2O4/RGO hybrids was 120 nm, which was smaller than that of bare CoFe2O4, implying that RGO could effectively prevent CoFe2O4 nanoparticles from aggregating. To investigate the catalytic activity of the as-synthesized CoFe2O4 particles and CoFe2O4/RGO hybrids, the thermal decomposition of ammonium perchlorate (AP) was characterized by differential thermal analyser (DTA). Both of the two exothermic processes were merged into a sole exothermic process with the addition of bare CoFe2O4 and CoFe2O4/RGO hybrids, though there was no change in the position of the phase transition temperature of AP. Moreover, the catalytic activity of CoFe2O4/RGO hybrids is higher than that of bare CoFe2O4, due to the large surface area and enhanced properties of RGO in the hybrids. The temperature programmed reduction (TPR) measurements showed that the reduction temperature of CoFe2O4/RGO decreased by 55 °C compared with bare CoFe2O4, which further confirmed the higher catalytic activity of CoFe2O4/RGO of than that of CoFe2O4 nanocomposites. Hence, CoFe2O4/RGO hybrids could be a promising additive in modifying the burning behaviour of AP-based composite propellant.

Synthesis and Characterization of a New Co-Crystal Explosive with High Energy and Good Sensitivity

ABSTRACT A new energetic co-crystal consisting of one of the most powerful explosive molecules 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and the military explosive cyclotrimethylenetrinitramine (RDX) was prepared with a simple solvent evaporation method. Scanning electron microscopy (SEM) revealed the morphology of the bar-shaped product, which differed greatly from the morphology of the individual components. Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction spectrum (XRD), and differential scanning calorimetry (DSC) proved the formation of the co-crystal at the molecular level. The result of mechanical sensitivity test indicated the sensitivity was effectively reduced compared to raw CL-20. Finally, a possible crystallization mechanism was discussed.

Facile preparation of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane/glycidylazide polymer energetic nanocomposites with enhanced thermolysis activity and low impact sensitivity

1,3,5,7-tetranitro-1,3,5,7-tetrazocane/glycidylazide polymer (HMX/GAP) nanocomposites were successfully prepared via a facial sol–gel supercritical method. The as-synthesized HMX/GAP nanocomposites were characterized by X-ray diffraction (XRD), Raman, and Fourier-transform infrared spectroscopy (FT-IR), which indicated that HMX were successfully trapped in GAP gel skeleton. Scanning electron microscopy (SEM) images revealed that the GAP gel skeleton possessed nano-porous structure, which made it possible to load HMX particles. The thermal decomposition behaviours of GAP, raw HMX and HMX/GAP nanocomposites were determined by differential thermal analyser (DTA). The results indicated that GAP aerogel could promote the decomposition of HMX and enhance the interaction between GAP and HMX. The kinetic, thermodynamic and thermal stability parameters, such as activation energy (Ea), per-exponent factor (ln A), activation heat (ΔH≠), activation free energy (ΔG≠), activation entropy (ΔS≠), critical temperature of thermal explosion (Tb) and the self-accelerating decomposition temperature (TSADT) were calculated according to DTA analysis. The calculated results implied that HMX/GAP showed much lower activation energy than raw HMX. Similarly, the HMX/GAP presented a much lower Tb and TSADT than raw HMX. According to the impact sensitivity tests, the mechanical sensitivities of HMX/GAP nanocomposites were significantly lower than those of raw HMX.

Preparation and characterization of RDX/BAMO-THF energetic nanocomposites

ABSTRACT Novel 1,3,5-trinitro-1,3,5-triazine/3,3-bis (azidomethyl) oxetane-tetrahydrofuran copolymer (RDX/BAMO-THF) energetic nanocomposites were successfully prepared by a facile sol–gel freezing–drying method. The as-prepared RDX/BAMO-THF energetic nanocomposites were characterized by Raman and Fourier transform infrared spectroscopy, which revealed that RDX particles were incorporated into BAMO-THF gel matrix. Scanning electron microscopy was used to characterize the morphology and the particle size of the as-obtained samples. The results showed that RDX particles were trapped in the BAMO-THF gel matrix and the particle sizes were in nanoscale. Differential thermal analyzer (DTA) was performed to determine the thermal decomposition behaviors of BAMO-THF, raw RDX and RDX/BAMO-THF nanocomposites. The results indicated that the thermal decomposition process of RDX/BAMO-THF nanocomposites was enhanced compared with that of BAMO-THF and RDX. The kinetic, thermodynamic and thermal stability parameters were calculated according to DTA analysis. The calculated results revealed that RDX/BAMO-THF nanocomposites presented high thermal reactivity. The results of impact sensitivities for RDX/BAMO-THF nanocomposites indicated the sensitivity was effectively reduced compared to raw RDX.

Preparation and characterization of an ultrafine HMX/NQ co-crystal by vacuum freeze drying method

In this paper a new energetic co-crystal consisting of 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) and nitroguanidine (NQ) was prepared using a vacuum freeze drying method. Scanning electron microscopy (SEM) revealed that the particle size was under 500 nm and the morphology was spherical. Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy suggest that hydrogen bonds exist between HMX and NQ molecules. Powder X-ray diffraction spectra (PXRD) indicated the product was different from the single components and their mechanical mixture. Thermal gravimetric analysis and differential scanning calorimetry (TGA/DSC) were employed to characterize the thermal behavior of the co-crystal and then the related thermodynamic parameters were calculated, which indicated that after co-crystallization the molecule of the co-crystal needed more energy to activate. The result of an impact sensitivity test indicated that the sensitivity was effectively reduced compared to neat HMX and the mechanical mixture. The density of the product was found to be 1.80 g cm−3 and the storage performance was also investigated.

Template-assisted synthesis of 3D ordered macroporous structured CuO as catalyst for ammonium perchlorate

Three-dimensionally ordered macroporous (3DOM) CuO is prepared by colloidal crystal templated method. The obtained 3DOM structure with about 230nm pore diameter is composed of small CuO windows. The special structured CuO is used as a catalyst for thermal decomposition of ammonium perchlorate (AP) and its catalytic activity is measured by simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC) techniques. Test results show that thermal decomposition performance is significantly improved after adding 2wt.% 3DOM CuO.

Preparation and characterization of copper-based nanoparticles as catalyst for ammonium perchlorate(AP)

In this study, Cu-based nanoparticles (Copper oxide (CuO), Copper chromite (CuCr2O4), Copper β-resorcylate (β-Cu)) were prepared in large-scale using wet mechanical grinding method and extracted by vacuum freeze-drying technology. The crystal forms were characterized by X-ray diffraction (XRD) and the particle sizes were analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). At the same time, the catalytic performances of the as-obtained Cu-based nanoparticles on the thermal decomposition of ammonium perchlorate (AP) were studied through thermogravimetric analysis/differential scanning calorimetric (TG-DSC) techniques. Results had shown that CuO, CuCr2O4 and β-Cu nanoparticles were showing the same crystal forms as their corresponding raw materials and had fine dispersion states with the fairly uniform sizes of 17 nm, 40 nm and 100 nm, respectively. Inspiringly, the prepared CuO, CuCr2O4 and β-Cu nanoparticles had excellent catalytic performances on the thermal decomposition of AP, exhibiting great decrement of high temperature decomposition peaks by 83.0 °C, 87.9 °C and 98.4 °C, respectively. Furthermore, the synthesis route and formation mechanism of Cu-based nanoparticles were discussed in details. These results are very encouraging and may lead to potential applications of Cu-based nanoparticles in solid propellants.