【作者】 宋小兰；

【导师】 李凤生；

【作者基本信息】 南京理工大学 ， 材料学， 2008， 博士

【摘要】 含能材料的感度研究是一个既传统又富有挑战性的课题,长期以来受到了国内外同行学者的广泛重视。总体来说,影响含能材料感度的因素大致可归纳为内外两种。其中,内因是指含能材料自身分子结构所决定的化学性质,如猛炸药TATB的分子结构中存在三个C-NO₂、三个C-NH₂和一个苯环等不活泼基团,导致它的感度非常低,有“木头炸药”之称。而硝胺类炸药如RDX、HMX和HNIW等,由于其分子结构中含有强致爆基团N-NO₂,导致其感度显著高于TATB。这种分子结构对炸药感度的影响通常是难以改变的。然而,除上述内因外,含能材料的粒度/粒度分布、表面形貌、晶型以及装药密度等外因对感度也会产生显著的影响,更重要的是这种影响在一定程度上是可以控制和调整的。因此,一直以来国内外学者均试图通过调节含能材料的粒度分布和表面形貌来改善和提高武器弹药系统的安全性能。这些研究取得了丰硕的成果,同时也存在很多分歧,特别是缺乏具有系统性和规律性的研究结果。事实上,由含能材料的粒度分布和表面形貌的不同所导致的感度变化只是一种外在的表现形式,而实质原因则是在于含能颗粒群中颗粒尺寸结构及表面形貌的复杂和不均匀（不规则）程度的差异会使得它们的热传导性能发生改变,从而在宏观上体现出感度的不同。本研究旨在结合分形理论和热点学说,采用分形维数来定量地表征含能颗粒群中颗粒的尺寸结构以及表面形貌的复杂和不均匀（不规则）程度,试建立具有分形特征含能颗粒群的热传导模型,并运用该模型结合实验详细研究微纳米含能材料的分形特征对其感度的影响,初步实现将含能颗粒群的分形维数作为衡量其热传导性能以至感度的一个重要依据。首先,研究了含能颗粒群的粒度分布和表面形貌的分形特征,并结合分形理论和热点学说,试建立了具有分形特征含能颗粒群的热传导模型。采用粒度分形维数（D）表征含能颗粒群中颗粒尺寸结构、粒度分布范围、细颗粒所占比例、颗粒尺寸的复杂和不均匀程度等,采用表面分形维数（D_s）表征含能颗粒群中颗粒的表面粗糙度、颗粒比表面积、以及表面形貌的复杂和不规则程度等,并讨论了D和D_s的取值范围和物理意义。在此基础上,试建立了简单分形（只含D）含能颗粒群的热传导模型和混合分形（含D和D_s）含能颗粒群的热传导模型,详细讨论了D和D_s的变化会对含能颗粒群的热传导性能以及感度产生怎样的影响。然后,通过含能颗粒群的粒度累积分布曲线计算出D值,典型的含能单颗粒的表面形貌SEM照片计算出D_s值,根据D值和D_s值作为定性地衡量含能颗粒群热传导性能的变化情况及其感度大小的一个重要依据。其次,从微米级炸药的机械感度和热分解特性等方面入手,系统地研究了炸药的粒度分布和表面形貌的分形特征对其感度的影响规律。采用机械球磨法、溶剂/非溶剂法、物理筛分法以及气流粉碎法等制备了不同粒度/粒度分布和形貌的微米级（HMX、RDX、HNIW和AP）炸药,考察了它们的机械感度和热分解特性等。研究结果表明,对于同类炸药,相同或相似形貌炸药的感度随粒度的变化遵循一定的规律,然而,不同形貌的同类炸药之间其感度随粒度的变化规律却各不相同。以HMX为例,随着粒度(d₅₀)的减小,球形HMX的撞击感度降低、而摩擦感度升高,针形HMX的撞击和摩擦感度均降低,无规则多面状HMX的撞击和摩擦感度均变化不大,球形HMX的热分解速率降低。同样,球形和短棒及片状RDX的感度随粒度也遵循各自不同的变化规律。结合分形分析的研究发现,炸药的撞击感度与粒度分形维数有关,即D值越大,含能颗粒群的热传导性能越好,不易产生热点引发爆炸。并且,炸药的摩擦感度与表面分形维数有关,即D_s值越大,含能颗粒间以及颗粒与周围介质间的摩擦系数增大,摩擦生热量增多,易产生热点引发爆炸。此外,炸药的热分解特性与粒度分形维数和表面分形维数均有关,即D值和D_s值均很大的含能颗粒群的热传导性能好,不易形成热点引发爆炸。第三,在微米炸药的研究基础上,为进一步考察纳米级含能材料的感度性质,分别制备了纳米及纳米复合炸药并进行了机械感度和热分解特性的研究。结合溶胶-凝胶法和超临界GAS法制备了纳米（HNIW/Fe₂O₃、RDX/Fe₂O₃、HMX/Fe₂O₃、AP/Fe₂O₃和ADN/Fe₂O₃）复合炸药,并首次利用酸蚀法祛除其中的惰性骨架（Fe₂O₃）,成功地制备了纳米硝胺（HNIW、RDX和HMX）炸药。研究发现,前驱体Fe（NO₃）₃·9H₂O的摩尔浓度为0.297 mol·L_乙醇^-1内,HNIW浓度为0.438 mol·L_乙酸乙酯^-1内,环氧丙烷用量为8.334mL·g_硝酸铁^-1时,是制备纳米HNIW/Fe₂O₃复合炸药的最佳工艺条件。酸蚀法所获得的纳米HNIW为α晶型和ε晶型的混晶体,以α晶型为主,粒子尺寸约50nm～100nm。此外,纳米RDX中多数粒子尺寸约100nm,纳米HMX是β晶型和α晶型的混晶体,以β晶型为主,大部分粒子尺寸约100nm。感度实验结果表明,纳米复合炸药随其中炸药含量的减少,其撞击感度和摩擦感度以及放热量均呈显著降低的趋势,且放热峰有一定提前（除纳米复合AP/Fe₂O₃的摩擦感度升高外）。另外,纳米硝胺炸药的撞击感度略有降低,但摩擦感度却大幅升高,且放热峰提前。最后,尝试将分形含能颗粒群的热传导理论拓展至混合型含能颗粒群的感度研究中,初步探讨了Si粉的分形特征对微纳米硅/铅丹延期药的热反应特性和机械感度的影响。研究结果表明,在微米硅/铅丹延期药体系中,随着超细Si粉含量的增大,延期药的低温反应提前并增强,总放热量增大,而摩擦感度却普遍升高,这是由于超细Si粉具有较高的表面分形维数（D_s）所致;在纳米硅/铅丹延期药体系中,随着纳米Si粉粒度的减小,延期药的高低温反应均提前,表观活化能（E_a^-）也呈降低的趋势。更多还原

【Abstract】 The subject for investigating the sensitivities of energetic materials always challenges the peer researchers who want to improve their safety.In the mass,two kinds of factors influence the sensitivities of energetic materials.One is inherent properties depending on chemical structure,and the other attributes to external physical configuration,such as particle size,size distribution,morphology,crystal,charge density etc.For example,TATB is well known as“wood explosive”because of containing the low-active bases as C-NO2,C-NH2 and phenyl in its molecular structure,which may result in quite low sensitivity.However,nitroamine explosives with exploding base as N-NO₂ exhibit high sensitive,such as RDX,HMX and HNIW etc.The influence of chemical structure on sensitivity is generally difficult to alter,but the influence depending on external physical configuration may be controlled or adjusted in a large degree.Therefore,researchers inside or aboard devoted themselves to improving the safety of ammunition by adjusting the size distribution and morphology of energetic particles. They have obtained deals of experimental results,among which many discrepancy and faultiness are presented.As an appearance of influence on sensitivity of energetic materials, size distribution and morphology do act on heat conduction properties of energetic particles, and finally lead to the changes of sensitivities.This study intends to combine fractal and hot spots theories together,apply fractal dimensions to characterizing the complexity degree of particle size and morphology of energetic materials quantificationally,and establish the models heat conduction for fractal energetic particles finally.These models will be employed to investigate the influence of fractal particle size and morphology on sensitivities of micron and nanometer energetic materials by means of experimental results.Fractal dimensions（D and D_s）are also applied to assess the sensitivities of energetic materials.Firstly,fractal characteristics of particle size distribution and morphology of energetic materials are investigated,and the models heat conduction of energetic particles have been established by combining fractal and hot spot theories.Particle size fractal dimension“D”is used to characterize the size formation,span of size distribution,proportion of fine particles, and the complex degree of the asymmetric energetic particles.Another morphology fractal dimension“D_s”is employed to describe the coarse degree and proportion of surface,and complex degree of the anomalistic surface morphology of energetic particles,either.The value scope and physical signification of D and D_s are also discussed.After that,two heat conduction models had been established,which one containing D is for simple fractal energetic particles,and the other containing D and D_S is for mixed fractal energetic particles. How D and D_S influence heat conduction along with sensitivity of energetic particles are discussed in detail.The value of D could be calculated with cumulation distribution data,and D_S could be obtained from SEM images of typical particle.Both D and D_S can be a quantitative criterion to estimate heat conduction and sensitivity of energetic materials.Next,influence of fractal particle size and morphology on sensitivity of micrometer explosives is investigated in detail.Micrometer explosives as HMX,RDX,HNIW and AP with different particle size distribution and morphology were prepared by milling,solvent and non-solvent,sieving,and airflow crushing.Their mechanical sensitivities and thermal decomposition are also investigated in detail.The results indicated that sensitivity of explosive with similar morphology changes regularly along with particle size.However,these rules vary along with the morphology of energetic particles.For example,the impact sensitivity of spherical HMX samples falls,and friction sensitivity decreases as the particle size(d₅₀)decrease.Both impact and friction sensitivities of needle HMX samples fall as the particle size decrease.However,the mechanical sensitivities of polyhedral HMX samples change a little.Similarly,the sensitivities of spherical RDX and sheet RDX samples vary at different rules.After fractal analysis,we found that impact sensitivity is related to D.The heat conduction of energetic particles with high D value exhibits too excellent to form hot spots which would cause exploding.Meanwhile,friction sensitivity is related to D_s.The friction coefficient among particles with high D_s value increases,which would yield more heat to form hot spots leading to explode.In addition,thermal decomposition is related to both D and D_s.The heat conduction of energetic particles with high D and D_s become superior,and not easy to form hot spots.Thirdly,in order to investigate the sensitivity of nanoscale energetic materials,several nanometer explosives and composite explosives were prepared,and their mechanical sensitivities and thermal decomposition are also discussed.Combining sol-gel reaction and supercritical GAS method,we had prepared nanometer HNIW/Fe₂O₃,RDX/Fe₂O₃, HMX/Fe₂O₃,AP/Fe₂O₃ and ADN/Fe₂O₃ energetic composites.After etching Fe₂O₃,nanometer HNIW、RDX and HMX powders were prepared,respectively.The results indicated that the optimal technical parameters were located at Fe（NO₃）₃·9H₂O molar concentration of 0.297 mol·L_ethanol^-1,HNIW concentration within 0.438 mol·L_{ethyl acetate}^-1and 1,2-epoxypropane dosage of 8.334mL·g₍Fe(NO_/wZ,-gFe（N0₃）^-1.Nanometer HNIW powders of 50nm tolOOnm contain mainlyαcrystals,and a few e crystals.Meanwhile,nanometer RDX powders are mostly about 100nm,and nanometer HMX powders of l00nm contain mostlyβcrystals and a fewαcrystals.Experimental results indicated that both impact and friction sensitivities of nanometer composite explosives decrease as the content of explosives reduce,and exothermic peak move ahead,except that friction sensitivity of nanometer AP/Fe₂O₃ increases.In addition,the impact sensitivity of nanometer nitroamine explosives falls a bit.However,the friction sensitivity increase largely,and exothermic peak move ahead either.Finally,we tried to develop the model heat conduction of fractal energetic particles into sensitivity study of blending energetic materials.The influence of fractal characteristic of Si powders on thermal reaction and mechanical sensitivities of Si/Pb₃O₄ composites are discussed.The results indicated that for micrometer Si/Pb₃O₄ composites,as the content of superfine Si powders increase,the low temperature reaction moves ahead with added exothermic quantity.Meanwhile,the friction sensitivity increases because of superfine Si powders with high D_s.However,for nanometer Si/Pb₃O₄ composites,as the particle size of nanometer Si reduces,the low and high temperature reactions go ahead,and the activation energy（?）_a decrease either.更多还原