喷雾干燥法制备亚微米鞣酸铁/硝胺炸药复合微球及其催化性能

为了研究鞣酸铁催化剂对固体推进剂中常见组分热分解性能的影响,采用超声喷雾干燥法制得三种亚微米复合微球(鞣酸铁(Ta-Fe)/六硝基六氮杂异伍兹烷(CL-20)、鞣酸铁/黑索今(RDX)、鞣酸铁/奥克托今(HMX))。利用扫描电镜(SEM)和粒度分析等方法分别对复合微球的形貌、粒度和组分进行表征。采用差示扫描量热法(DSC)研究复合微球中鞣酸铁对CL-20、RDX、HMX热分解的催化过程及动力学参数的影响。结果表明,鞣酸铁分布均匀,样品均呈球状颗粒,且流散性好,粒度为500~1000 nm;鞣酸铁能有效促进CL-20、RDX、HMX的热分解,使得CL-20、RDX、HMX的热分解峰温分别提前了17.2,8.2,11.5℃,其中鞣酸铁对CL-20的热分解催化效果最佳,Ta-Fe/CL-20复合微球的活化能与原料CL-20相比降低了9.6 kJ·mol……-1。     

Cu/Al复合材料的制备及其对RDX热分解性能的影响

为了改善铝粉的表面氧化,提高其对含能材料热分解的催化作用,以电爆炸铝粉和二水合氯化铜(CuCl_2·2H_2O)为原料,利用置换反应法,实现了纳米铜粒子在铝粉表面的快速沉积,制备了包覆均匀的Cu/Al复合材料。利用扫描电镜(SEM)、透射电镜(TEM)、X?射线粉末衍射(XRD)、电子能谱(EDS)等对其结构和形貌进行了表征。在不同的升温速率下测试了Cu/Al复合材料与黑索今(RDX)(质量比1∶5)混合物的DSC曲线。计算了该混合物热分解反应的动力学参数。结果表明,电爆炸铝粉表面的氧化层通过氟化铵的刻蚀作用被剥离,复合材料含有单质铝和单质铜晶相,无氧化铜及氧化铝晶相,纳米级铜颗粒均匀包覆在铝粉表面,复合材料粒径为200～500 nm。加入Cu/Al复合材料后,RDX的初始分解温度和分解峰温分别降低8.51℃和26.43℃,分解热提高296 J·g~(-1),热分解活化能降低19.19 kJ·mol~(-1),表明Cu/Al复合材料可促进RDX的热分解行为。     

Confocal Scanning Laser Microscopic Study of the RDX Defect Structure in Deformed Polymer‐Bonded Explosives

The influence of an explosion‐driven deformation on the defect structure in RDX crystals embedded in a polymer‐bonded explosive was investigated by means of confocal scanning laser microscopy. The images were compared to the defect structure in the as‐received RDX grades, embedded in an epoxy resin. In this way it is possible to qualitatively analyze the changes in defect structure of the RDX crystals that were induced by the explosion‐driven deformation. For the first time, these data therefore provide experimental confirmation of how shock waves mechanically interact with energetic crystals – a topic that, up to now, was only explored by means of simulations.     

Theoretical Study of Mechanism and Kinetics of the Reaction of NO2 with s‐Triazine

The decomposition of nitramines explosives have been of great interest for a long time. However, theoretical investigations have concentrated mainly on unimolecular decomposition whereas bimolecular reactions have received only little attention. In this paper, the bimolecular reaction between NO₂ with s‐triazine (TAZ), which is an initial product during the decomposition process of hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) is investigated. The structures and potential energy surface (PES) are explored at B3LYP/6‐31G(d,p) and B3P86/6‐31G(d,p) levels, and the energies are refined using the CCSD(T)/cc‐pVTZ methods. The mechanism of the reaction is analyzed. Quantum chemistry calculations reveal that the title reactions possess small barriers that can be similar to, or smaller than that of initial decomposition reactions of RDX, which suggests that bimolecular reactions are also of great importance, and should be further investigated. Moreover, the kinetics were investigated to verify the proposed mechanism of the reaction.     

NH_3和ClO_3对RDX初始热裂解的影响

用B3LYP/6-31G(d)方法,优化得到RDX及其与高氯酸铵(AP)裂解产物NH3、ClO3形成复合物的稳定构型,计算了RDX及各复合物的N-NO2键解离能.结果表明,复合物中RDX构型变化不是很大,但其CS对称性遭到破坏.RDX与NH3、ClO3结合后其N-NO2键解离能与RDX相比变化不大, NH3、ClO3的存在不影响RDX硝基裂解A位优先于E位的顺序.但一旦复合物裂解,生成的NO2极易与NH3发生反应,放出大量热,从而可引发RDX的后续裂解反应.     

密封条件对钝化RDX快速烤燃响应特性的影响

为评估传爆药的易损性,设计了密封状态不同的多种烤燃弹结构。用快速烤燃实验方法,研究了壳体密封条件对RDX基传爆药的烤燃响应特性,分析了影响传爆药大火烤燃响应特性的主要因素。结果表明,壳体密封结构是影响钝化RDX烤燃响应的关键因素。相同条件下,随着壳体密封条件的减弱,传爆药快速烤燃响应的剧烈程度增加,认为壳体的密封条件影响传爆药的易损性,壳体采用一定的泄漏方式能够降低传爆药的火烤易损性能。     

溶胶-凝胶法制备RDX/SiO_2薄膜

为有效阻止RDX/SiO2膜的开裂,基于溶胶-凝胶法制膜原理,通过调节SiO2溶胶的摩尔配比和陈化时间,在其凝胶点处加入一定量RDX的N,N-二甲基酰胺(DMF)溶液,同时添加适量黏结剂,手工旋涂并冷冻干燥成膜。结果表明,适当增加水与正硅酸乙酯(TEOS)的摩尔比(r),缩短溶胶恒温陈化时间,缓慢干燥的同时保证环境湿度,加入质量分数3%~5%的氟橡胶(FPM2602)或聚乙烯醇(PVA),均可以增强凝胶骨架的连接作用,在一定程度上减少RDX/SiO2膜的开裂。     

Production and Sensitivity Evaluation of Nanocrystalline RDX‐based Explosive Compositions

The initiation sensitivity of cyclotrimethylenetrinitramine (RDX) was investigated as a function of crystal size. For this study, RDX powders with mean crystal sizes of ca. 200 and 500 nm were prepared by rapid expansion of supercritical solutions (RESS) with carbon dioxide as the solvent. Initiation sensitivity testing to impact, sustained shock, and electrostatic discharge stimuli was performed on uncoated as well as wax‐coated specimens. The test data revealed that in a direct comparison to coarser grades the nanocrystalline RDX‐based samples were substantially less sensitive to shock and impact stimuli. Furthermore, the 500 nm RDX‐based specimens exhibited the lowest sensitivity values, an indication that minima in shock and impact sensitivities with respect to crystal size exist.     

RDX biodegradation column study: influence of ubiquitous electron acceptors on anaerobic biotransformation of RDX

A series of column studies, with aquifer material from the former Nebraska Ordinance Plant (NOP), were performed to explore the phenomenon of electron competition from ubiquitous inorganic electron acceptors (nitrate and sulfate) present in contaminated groundwater. Acetate was used as a source of readily biodegradable carbon in all of the treatment‐column systems. Influent hexahydro‐1, 3, 5‐trinitro‐1, 3, 5‐triazine (RDX) concentrations (1–1.8 mg dm^?3) were completely removed to below detection levels of 20 µg dm^?3 in all treatment‐column systems without any nitroso‐metabolites. In the control‐column system (with no carbon amendment) significant levels (～30% of the inlet molar RDX) of nitroso‐substituted RDX derivates were observed in the effluent stream. The estimated first‐order biodegradation rate coefficient for RDX was highest (0.79 h^?1) in the treatment‐column system where acetate was the only amendment, about 52 times higher than the rate coefficient (0.015 h^?1) obtained in the control‐column system. The presence of sulfate (100 mg dm^?3) in influent groundwater temporarily delayed the onset of RDX biotransformation without any adverse effects on overall RDX biotransformation. Coexistence of low (100 mg dm^?3) nitrate levels in the influent feed water reduced the first‐order biodegradation rate coefficient obtained in the absence of nitrate by about 80% to 0.16 h^?1. These nitrate levels, however, were low to halt the RDX biodegradation probably because the available carbon levels were high enough to exceed the demands for nitrate reduction. High levels of nitrate (500 mg dm^?3) initially halted RDX removal, and significantly reduced the rate of RDX biotransformation by about 98% to 0.02 h^?1, thereby increasing the half‐life from 0.9 h in the absence of nitrate to about 32 h, with noticeable levels of untreated RDX in the effluent stream. Contrary to the expectations, the presence of ammonium in conjunction with acetate resulted in a lower (0.09 h^?1) biodegradation rate coefficient as compared with the one obtained in the absence of ammonium. Copyright © 2003 Society of Chemical Industry