Study On The Thermal Expansion Properties Of CL-20 And Its Desensitization Technology

High energy density and low sensitivity of explosives are the pursuing goals of energetic materials in recent years, but there is an essential contradiction existed between the characterizations of energy and safety, while the higher the energy, the lower the safety. With the development of weapons, improving the safety and environmental adaptability of explosives has become the focus of modern weapons development. CL-20 is one of explosives with highest energy density but its high sensitivity leads to the limited applications of CL-20.LLM-105 is one kind of explosive with high energy and low sensitivity and thus can be used to reduce the sensitivity of CL-20 that also assures the high energy of CL-20. The works of this paper are listed below:(a) The α- 、 β- 、 ε- and γ-CL-20 crystals are prepared by the solvent/non-solvent method. The situ XRD technology and Rietveld refinement are applied to study the thermal expansion properties of CL-20 with four polymorphism. The results show that the coefficients of thermal expansion(CTEs) of anhydrous α-CL-20 areαa=2.80×10-5°C-1, αb=5.26×10-5°C-1, αc=7.23×10-5°C-1andαV=15.39×10-5°C-1, respectively. The CTEs of β-CL-20 areαa=5.35×10-5°C-1, αb=1.48×10-5°C-1, αc=6.61×10-5°C-1,αV=13.50×10-5°C-1, respectively. The CTEs of ε-CL-20 areαa=4.95×10-5°C-1, αb=4.91×10-5°C-1, αc=4.40×10-5°C-1,αV=11.80×10-5°C-1, αβ=1.43×10-5°C-1, respectively. The CTEs ofγ-CL-20 are αa=8.72×10-5°C-1, αb=7.51×10-5°C-1, αc=6.38×10-5°C-1,αV=11.80×10-5°C-1, αβ=3.70×10-5°C-1, respectively. The four kinds of CL-20 crystals exhibit linear thermal expansion behaviors while the expansions of α- 、 β- and γ-CL-20 are anisotropic and ε-CL-20 shows approximately isotropic expansion. The different thermal expansion behaviors of CL-20 are caused by the different crystal packing. In addition, the α-CL-20 crystals with different water contents exhibit different thermal expansion behaviors. The α-CL-20·1/2H2 O andα-CL-20·1/4H2 O exhibit the irreversible expansion while anhydrousα-CL-20 exhibits the opposite reversible linear expansion. Those differences are concerned to the hydrogen interactions between water and CL- 20 molecules.(b) The rectangular micro-rod 、 hole shape and tabular LLM-105 crystals are obtained from the recrystallization of LLM-105 by solvent/non-solvent method with [Bmim]BF4 and [Bmim]CF3SO3 ionic liquids as solvents. The morphology and size of crystals are controlled by changing the crystallization conditions. The recrystallized LLM-105 with three different morphologies have same diffraction peak positions with the raw materials, but the crystal habits have changed and present different facets. The relative regular structured rectangular micro-rod crystal exhibits the best thermal stability with the exothermic peak temperature of 353°C and initial decomposition temperature of 323.6°C which have improved by 10°C and 40°C than that of the raw materials,respectively.(c)The CL-20 crystals are successfully filled into the tubular LLM-105 crystals by solvent/non-solvent recrystallization method and the tubular CL-20/LLM-105 composite energetic materials are obtained.The CL-20 crystals are mixed with the recrystallized LLM-105 crystals with different morphologies to study the desensitization effect of the obtained LLM-105. The sensitivity test shows the sensitivity of CL-20 decreases slightly after the mixing with LLM-105 while the plate-like LLM-105 crystal exhibits the most obvious desensitization effect to CL-20.