The thermal expansions of three kinds of α-CL-20 crystals have been investigated in the temperature range from 30 to 130 °C by means of various-temperature X-ray powder diffraction (XRD) together with Rietveld refinement. The crystals were characterized by SEM, XRD, FTIR, and DSC/TG. The results show that the three samples contain 1/2, 1/4 mol, and none structural water, respectively. The α-CL-20 crystals all perform linear and anisotropic thermal expansion, while some differences exist. The unit-cell axes increase linearly with increasing temperature except for the a-axis. The expansion along the a-axis switches from positive to negative thermal expansion at 90 °C for α-CL-20·1/2H2O. The a-axis exhibits positive thermal expansion (PTE) with thermal irresilience for α-CL-20·1/4H2O while PTE with thermal resilience for the anhydrous α-CL-20. The differences are caused by the structural water. The removal of structural water leads to the collapse of a-axis, further results in structural changes of the unit cell. Different water contents can cause different degree of structural changes, leading to the difference of thermal expansion behaviors.

The thermal expansion of nitroguanidine (NQ) crystal was investigated by means of in situ powder X-ray diffraction method and in situ FTIR spectra method. Results show that the average thermal expansion coefficients of the a-, b-, c-axis at 30-160 ℃ for NQ are 12.9×10-6℃-1, -10.1×10-6℃-1 and 145.5×10-6℃-1, respectively, revealing that the thermal expansion of NQ is obviously anisotropic and thermal expansion along the b -axis is negative. The anisotropic thermal expansion of NQ is caused by the anisotropic intermolecular interaction. The intermolecular hydrogen bond decreases with the increase of temperature, and the intermolecular distance increases, and the space hindrance of the molecules along the b axis is reduced, which leads to a negative expansion along the b axis.

The thermal expansion behaviors of α-CL-20 · 1/2H2O, anhydrous α-, β-, ε-, and γ-CL-20 crystals have been investigated by means of variable-temperature X-ray powder diffraction (XRD) together with Rietveld refinement. The results show that hexanitrohexaazaisowurtane (CL-20) with four polymorphs exhibits linear thermal expansion. The ε phase performs approximately isotropic expansion in the temperature range of 30 to 130°C, but α, β, and γ phases exhibit anisotropic expansion in the temperature ranges of 30 to 130°C, 30 to 120°C, and 30 to 180°C, respectively. The different expansion behaviors are due to the different structures of the four polymorphs. The different thermal expansion behaviors of α-CL-20 · 1/2H2O and anhydrous α are revealed in this work. The a-axis expansion of α-CL-20 · 1/2H2O exhibits a switch from positive thermal expansion (PTE) to negative thermal expansion (NTE) at 90°C, whereas the a-axis of anhydrous α is resilient to PTE. The cause is the loss of the structural water. Moreover, it is easily found that the b-axis of the γ phase shows a constriction that may be attributed to the distortion of the six-membered ring.

The temperature-dependent thermal expansion of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) was investigated by using powder X-ray diffraction (PXRD) together with Rietveld refinement to estimate the dimension at a crystal lattice level. In the temperature range of 30–200°C, the coefficient of thermal expansion (CTE) of LLM-105 is temperature dependent, which is different from other explosives, such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 2,2′,4,4′,6,6′-hexanitrostilbene (HNS) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), with constant CTEs. The results of temperature-dependent infrared (IR) spectra indicated that the intermolecular hydrogen bond network relaxes with increasing temperature, which results in temperature-dependent thermal expansion. In this work, more accurate CTEs for LLM-105 crystals are obtained and the effects of the hydrogen bond network on the thermal expansion are further clarified. These results are beneficial to the design of materials with structural peculiarities and as-expected thermal expansion to satisfy different application requirements.

采用原位X-射线粉末衍射(原位XRD)技术对端羟基聚丁二烯(HTPB)基粘结体系中ε-六硝基六氮杂异伍兹烷(ε-CL-20)的晶型转变行为进行了研究,探讨了HTPB、甲苯二异氰酸酯(TDI)、葵二酸二辛酯(DOS)、二月桂酸二丁基锡(T-12)、高氯酸铵(AP)、Al等添加剂对CL-20晶型转变的影响.结果表明,添加剂能够引起ε-CL-20在热刺激作用下的晶型转变的起始温度发生变化,HTPB和TDI能在一定程度上包覆CL-20晶体,T-12作为胶黏的催化剂与HTPB及TDI联用时能加速包覆,都对ε→γ晶型转变有抑制作用.而DOS与CL-20混合后却促使ε→γ的晶型转变.AP、Al与CL-20属于固固混合,对ε-CL-20晶体的晶型转变影响不明显.另外,将粘结体系ε-CL-20在70℃下持续加热60 h后,发现ε-CL-20晶型未发生转变.

Two-dimensional (2D) plate-like HMX crystals have been grown first on hydrophilic substrate using an evaporation/solvent nonsolvent crystallization technique. As-grown crystals have been investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), confocal laser scanning microscope (CLSM), and atomic force microscopy (AFM). The results unambiguously indicate that the plate-like crystals with large (011) faces are beta-HMX, and the fluctuations in the smooth area of (011) face are monomolecular or bimolecular HMX, which suggests the mechanism of monomolecular stacking pattern and layer-by-layer growth. Furthermore, the distinct recess consisting of hexagons parallel to each other is observed on the center of the (011) face. The special growth morphology, which is markedly different from that by the classical spiral growth, is attributed mainly to the negative concentration gradient in the constrained condition.

A new energetic cocrystal of TNT/TNB was obtained by evaporating ethanol at room temperature over a period of 3 days. It is found that the donor–acceptor π–π interaction, p–π interaction, and C–H···O hydrogen bond interaction are dominant in the formation of the cocrystal. In this work, physicochemical characteristics of cocrystal have also been studied using several methods: Optical Microscopy, Powder X-ray Diffraction, Single Crystal X-ray Diffraction and differential scanning calorimetry. It is shown that TNT and TNB molecules cocrystallize in a monoclinic system with space group P21/c and cell parameters a = 20.4570(8) Å, b = 6.1222(2) Å, c = 15.1635(6) Å, β = 110.091(4)°, and Z = 4. The cocrystal has a crystal density of 1.640 g cm−3 and H50 (50 % explosion characteristics of drop height) of 112.2 cm, which is higher than that of TNT (100 cm), TNB (77.8 cm) and most of the other explosives. The result shows that co-crystallization may help to improve the performance of TNT and TNB.

Co-crystallization is an effective way to improve performance of the high explosive 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20). A new CL-20/caprolactam (CPL) cocrystal has been prepared by a rapid solvent evaporation method, and the crystal structure investigations show that the cocrystal is formed by strong intermolecular hydrogen bond interaction. The cocrystal can only be prepared with low moisture content of the air, because water in the air has a profound effect on the cocrystal formation, and it can lead to crystal form conversion of CL-20, but not the formation of cocrystal. The CL20/CPL explosive possess very low sensitivity, and may be used as additive in explosives formulation to desensitize other high explosives.

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 pi-stacking interactions are found to be the most prominent. Especially, the interactions between electron-poor g-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.

The spheroidizing of TATB (1,3,5-triamino-2,4,6-trinitrobenzene) can help to control preferred orientation and anisotropic expansion of TATB based PBXs, as well as to improve crystal quality, desensitizing efficiency, packing density, and even explosive energy. In this paper, TATB crystals with different morphology were obtained by high temperature recrystallization from anti-solvents. TATB was dispersed into DMSO and heated to dissolve. Water as an anti-solvent was added to the solution with different conrol parameters. We designed additional experiments to study the particular influence of these parameters. It was shown that the crystal morphology is strongly affected by the stirring rate and the amount of water added. The recrystallized TATB samples have similar thermal stability as starting TATB, but higher densities and purities, which indicates that the quality of TATB crystals was improved. By slowly adding an appropriate amount of water and cooling, regular crystals of TATB were obtained, which proves that water is a good morphology modifier for TATB.

A phase diagram of 1,3,3-trinitroazetidine(TNAZ) and 3-amino-2,4,6-trinitroanisole (ANTA) was draw by origin software and the sensitivity, thermal stability, and detonation performance of the eutectic mixture were tested in order to design a potential TNT replacement for melt-cast explosive. The results show that when the weight percent of 3-methoxy-2,4,6-trinitrobenzenamine is 40%, the mixture has the lowest melting point, 84 ℃. The eutectic mixture has good thermal stability and its friction sensitivity, impact sensitivity, electrostatics sensitivity are comparable to TNT. The working capability of the mixture is 148% equivalent to TNT and 114% equivalent to Comp.B. Furthermore, another advantage of eutectic mixture is that there is no permeability oil at 70 ℃ for 6 h. These results indicate that the eutectic mixture is a potential replacement of TNT for melt-cast explosive.

通过共晶工程法使不同种类的单质炸药在分子层面有序排列,可望解决现有炸药高能与钝感的矛盾,对提高炸药的性能具有重要意义[1-3].苯并三氧化呋咱(BTF)是一种性能优良的炸药,爆轰能量与HMX相当,但感度相对较高,冲击起爆感度和熄爆直径与太安相当[4],使其应用受到一定的限制.通过共晶工程的方法使BTF与安全性能相对较好的单质炸药,如与TNT、TNB等形成共晶,有望在不降低能量的前提下改善其安全性能.

The melt point, crystal shape, structures and interaction of different mole contents of methyl-nitroguanidine and hydrazine nitrate were tested by differential scanning calorimeter(DSC), optical microscope, X-ray diffraction(XRD) and density functional theory respectively. The experimental results show that the lowest melt point is 67.06 ℃, the most stable configuration, the stick crystallization shape which is different from methyl-nitroguanidine and hydrazine nitrate appear at mol ratio of 32, and the structure is uniformity compared with other mol ratio eutectics. Calculation results of quantum chemistry show that the eutectic is not a simply mechanical mixtures, but to be formed by some sort of loose molecular or atomic interaction which can agree well with the result of enthalpy of fusion.

Thermal expansion of explosives have important impact on their applications and investigations on the relationship between thermal expansion and crystal preferred orientation can provide some guide for controlling the shape stability. This paper studied the preferred orientation (F) of 1,3,5-triamino-2,4,6-trinitrobenzene(TATB) crystals using X-ray diffraction and Rietveld refinement, and studied the thermal expansion of die-pressed cylinders with near-spherical, platy and raw materials TATB. Finally, the relationship between the crystals preferred orientation and thermal expansion was investigated. It′s shown that die-pressed TATB cylinders usually take place anisotropic thermal expansion with the coefficient of thermal expansion (CTE) along the diameter about 2 times of that along the radial, and the formula can be pressed as αCTE=(7.08+10.37×F)×10-5K-1. The thermal expansion of TATB cylinders increase with the crystal preferred orientation, and TATB cylinders with different morphological crystals have different preferred orientation. So, we can try to control the preferred orientation by change the crystal morphology, further to restrain the anisotropy of thermal expansion, and finally to improve the shape stability of TATB cylinders.

The origin of irreversible expansion of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) based PBX is still controversial. In this study, the irreversible expansion of TATB cylinder is investigated. No evident variation of the lattice parameters was observed on TATB crystal and the density of TATB powder decreased by only about 0.02% after it suffered from thermal cycling process at the range from -54 degrees C to 74 degrees C, while the density of TATB cylinder decreased by about 1.0%. It is suggested that the density variation of TATB powder has little contribution to the density decrease of TATB cylinder. Therefore, the increasing interspaces between TATB powder originated from the thermal cycling should be responsible to the irreversible expansion of TATB cylinder.

1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is a widely applied insensitive explosive. However, the TATB-based PBXs commonly present anisotropic expansion and deformation, which usually bring some negative effects on the application of TATB. It is predicted that PBXs packed from spherical TATB crystals may have less anisotropic expansion and deformation. In this paper, TATB crystals with different morphology were obtained by means of high temperature non-solvents recrystallization. That means TATB was dispersed into DMSO and heated to a higher temperature to make it dissolv, and then water, as a non-solvent, was added to the solution with other ingredients controlled. It is shown that the crystal morphology is strongly affected by stirring rate and the proportion of water.

The linear coefficient of thermal expansion (CTE) and the theoretical density are important for energetic materials. To obtain the CTE and theoretical density of 2,2′,4,4′,6,6′-hexanitrostilbene (HNS), X-ray powder diffraction (XRD) together with Rietveld refinement was employed to estimate the dimension and density change at a crystal lattice level, in the range of temperature 30–240 °C. The CTE of a-, b-, c-axis and volume were obtained as 7.6719 × 10−5/°C, 6.8044 × 10−5/°C, 1.1192 × 10−5/°C and 16.725 × 10−5/°C, respectively. Also, the possible reasons for the expansion property of HNS have been discussed by comparing its structure with 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Based on the refined lattice parameters, the theoretical densities of HNS at various temperatures were obtained. By extrapolation of linear fitting the theoretical density of HNS at 20 °C was gotten as 1.7453 g/cm3. Furthermore, a good thermal resilience of HNS has also been observed when the temperature returned from 240 to 30 °C.

Coefficient of thermal expansion (CTE) and theoretical density of explosive crystal are significant properties, which affect the performance of explosives largely. X-Ray powder diffraction (XRD) is an important method to measure the CTE and theoretical density of explosives. The methods and principles for measuring the two parameters by XRD were described, and the experimental results of RDX and HMX explosive crystals obtained by density gradient method verified the reliability and accuracy of the method. It is proposed that the application of X-ray diffraction should be strengthened in research of explosive crystal.

To find suitable components for energetic eutectic mixtures,3-amino-2,4,6-trinitroanisole with an overall yield of 76% was synthesized via the sequence methylation-VNS amination of commercial picric acid.And its properties were preliminarily studied by IR,1H NMR and elemental analysis.The mechanism of methylation and VNS amination were discussed.DSC-TG curves show that the endothermic peak temperature is 133.77 ℃ and the exothermic peak temperature is 254.10 ℃.The massloss is about 1.71% at 199.6 ℃.H50 is 82.5 cm and the friction sensitivity is 0%.V50 is 11.42 kV and E50 is 1.99 J.The theoretical detonation velocity is 7.459 km·s-1(ρ=1.709 g·cm-3),and the theoretical detonation pressure is 22.9 GPa(ρ=1.709 g·cm-3).Results show that 3-amino-2,4,6-trinitroanisole is stable to heat.The theoretical detonation velocity and pressure of 3-amino-2,4,6-trinitroanisole are larger than that of TNT.

The present report aims to discuss the crystal state variation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) suffering from thermal cycling process. In this study, in situ X-ray powder diffraction (XRD) was employed to determine thermal expansion and crystal fragmentation, primarily attributed to its crystal state variation. The results showed that the change of crystal volume mainly stemmed from the thermal expansion at the c axis of crystal lattice, and TATB crystal had the same thermal expansion coefficients at a and b axes. It was also demonstrated that crystal fragmentation occurred during this process, and more auto-repair happened in the [002] plane of TATB than other planes. These results will have an implication on the process of TATB-based materials.