Five novel BTF (benzotrifuroxan) cocrystals, possessing a similar density to RDX (1,3,5-trinitrohexahydro-1,3,5-triazine), have been prepared and reported first. Their single-crystal structures are presented and discussed. Interactions between cocrystal formers are discussed with shifts in the IR spectra providing additional support for the presence of various interactions. Hydrogen-bonding and π-stacking interactions are found to be the most prominent. Especially, the interactions between electron-poor π-systems of BTF and electron-rich groups of other cocrystal formers such as nitro groups of TNB exist commonly in all five novel cocrystals. This kind of interaction can be a more potential driving force for energetic cocrystals, since explosives with poor active hydrogen bonds are usually hard to form cocrystals with other explosives for the lack of strong intermolecular interactions. Because of the changes in structure, the physicochemical characteristics including density and melting point together with energetic properties of BTF altered after cocrystallization. All of the densities are between both of the cocrystal formers. Cocrystals of BTF with TNT and TNB have impact sensitivities between those of both cocrystal formers, while the remaining three cocrystals (BTF/TNA, BTF/MATNB, and BTF/TNAZ) all are more sensitive than either cocrystal former. It indicates that a cocrystal with TNT or TNB can reduce the shock sensitivity of BTF; especially, the cocrystal BTF/TNB not only has a lower sensitivity than RDX but also equal energetic properties, which potentially improve the viability of BTF in explosive applications. This paper owns an important consideration in the design of future BTF and other explosive cocrystals, and the result provides some feasibility to improve the application of the high explosive BTF.

Phase behavior of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is investigated by X-ray powder diffraction (XRD). The XRD patterns at elevated temperature show that there is a co-existing temperature range of b-and d-phase during the phase transition process. Additionally, mechanical forces can catalyze the conversion from d-back to b-phase. Based on the diffraction patterns of b-and d-phase at different temperatures, we calculate the coefficients of thermal expansion by Rietveld refinement. For b-HMX, the linear coefficients of thermal expansion of a-axis and b-axis are about 1.37 Â 10 À5 and 1.25 Â 10 À4 8C À1 . A slight decrease in c-axis with temperature is also observed, and the value is about À 0.63 Â 10 À5 8C À1 . The volume coefficient of thermal expansion is about 1.60 Â 10 À4 8C À1 , with a 2.2% change from 30 to 170 8C. For d-HMX, the linear coefficients of thermal expansion of a-axis and c-axis are found to be 5.39 Â 10 À5 and 2.38 Â 10 À5 8C À1 , respectively. The volume coefficient of thermal expansion is about 1.33 Â 10 À4 8C À1 , with a 2.6% change from 30 to 230 8C. The results indicate that b-HMX has a similar volume coefficient of thermal expansion compared with d-HMX, and there is about 10.5% expansion from b-HMX at 30 8C to d-HMX at 230 8C, of which about 7% may be attributed to the reconstructive transition.

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Powerful oxidizer N2O was incorporated into an organic lattice cavity through aeration crystallization, and smart host–guest energetic materials with highly-energetic and low-sensitivity performance were obtained.

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The photogating effect in hybrid structures has manifested itself as a reliable and promising approach for photodetectors with ultrahigh responsivity. A crucial factor of the photogating effect is the built-in potential at the interface, which controls the separation and harvesting of photogenerated carriers. So far, the primary efforts of designing the built-in potential rely on discovering different materials and developing multilayer structures, which may raise problems in the compatibility with the standard semiconductor production line. Here, we report an enhanced photogating effect in a monolayer graphene photodetector based on a structured substrate, where the built-in potential is established by the mechanism of potential fluctuation engineering. We find that the enhancement factor of device responsivity is related to a newly defined parameter, namely, fluctuation period rate (P f). Compared to the device without a nanostructured substrate, the responsivity of the device with an optimized P f is enhanced by 100 times, reaching a responsivity of 240 A/W and a specific detectivity, D*, of 3.4 × 1012 Jones at 1550 nm wavelength and room temperature. Our experimental results are supported by both theoretical analysis and numerical simulation. Since our demonstration of the graphene photodetectors leverages the engineering of structures with monolayer graphene rather than materials with a multilayer complex structure. it should be universal and applicable to other hybrid photodetectors.