摘要
以氰基硼氢根(CBH)为阴离子、1‑乙烯基咪唑(VIM)为配体,过渡金属Co、Mn、Ni为中心离子制备出3种具有高还原活性的含能配合物,通过X射线单晶衍射仪准确测定其晶体结构,3种含能配合物的分子式分别为Co(VIM)4(CBH)2、Mn(VIM)4(CBH)2、Ni(VIM)4(CBH)2。对3种配合物的热分解性、燃烧热值和机械感度进行了测试。结果表明,3种配合物均具有较高的燃烧热值(26.5~29.1 kJ·
高活性燃料是具有较强还原活性、高热值的可燃材料,作为复合含能材料配方体系的重要组分起着提高输出能量的作用,在火炸药、推进剂及烟火药等领域均有重要应
低蒸气压、无毒无腐蚀的自燃离子液体可以解决传统肼及其衍生物作为自燃燃料的毒性和环境危害等问题,具有作为绿色自燃推进剂的潜力而倍受关
为此,本研究以具有强还原活性的氰基硼氢阴离子为基,1‑乙烯基咪唑为配体,过渡金属Co、Mn、Ni为连接中心,合成了3种高活性金属配合物燃料,表征了它们的分子结构和基本性质。同时,将其与溴酸钠混合,制备出高活性配合物/NaBrO3复合药剂,进行了点火燃烧测试,探讨其作为新型点火药的可行性。
六水合硝酸钴(Co(NO3)2∙6H2O)、硝酸锰水溶液(Mn(NO3)2, 50%),分析纯,上海阿拉丁生化科技股份有限公司。六水合硝酸镍(Ni(NO3)2∙6H2O),分析纯,北京市通广精细化工公司。1‑乙烯基咪唑(C5H6N2),分析纯,上海阿拉丁生化科技股份有限公司。氰基硼氢化钠(NaBH3CN),分析纯,上海韶远试剂有限公司。溴酸钠(NaBrO3),分析纯,上海迈瑞尔化学技术有限公司。
采用配备MoKα辐射(λ=0.71073 Å)的Rigaku AFC‑10/Saturn 724+CCD型衍射仪收集单晶结构数据。3种配合物的晶体结构采用SHELXL‑97程序解析,用全矩阵最小二乘法进行修正,并对所有的非氢原子进行了各向异性精修。采用Rigaku D/Max‑2500PC X射线衍射仪收集粉末衍射(PXRD)数据。采用上海精科天美科学仪器有限公司的CRY‑1P型差示扫描量热(DSC)仪在干燥空气中进行DSC分析, 采用PerkinElmer公司的Pyris‑1热重(TG)分析仪在N2氛围下进行热重(TG)分析,升温速率均为10 ℃·mi
配合物的合成路线如

Scheme 1 Synthetic route of ACCs 1-3
通过光学显微镜观察3种高活性配合物晶体的形貌如

a. ACC‑1

b. ACC‑2

c. ACC‑3
图1 3种配合物的晶体形貌
Fig.1 Crystal morphologies of energetic coordination compounds
对培养的ACCs 1-3晶体进行X射线单晶衍射解析,得到的晶体学数据列于

图2 ACCs 1-3的分子结构
Fig.2 Molecular structures of ACCs 1-3

图3 3种配合物的粉末样品图及其实验与晶体模拟的PXRD图
Fig.3 Powder sample images, experimental and simulated PXRD patterns of ACCs 1-3
在升温速率为10 ℃·mi
Note: 1) Melting point. 2) Decomposition peak temperature. 3) Standard molar enthalpies of combustion. 4) Gravimetric energy density. 5) Volumetric energy density. 6) Impact sensitivity. 7) Friction sensitivity. 8) Ignition delay times.

图4 3种高活性配合物的TG曲线
Fig.4 TG curves of ACCs 1-3
采用氧弹量热仪测定了3种高活性配合物在氧气中燃烧的质量热值,并计算出体积热值。3种高活性配合物均具有较高的热值(26.5~29.1 kJ·
点火延迟时间(Ignition delay times, tid)是指燃料与氧化剂从发生接触到开始燃烧的时间间隔,tid是评估燃料反应活性的一个重要因素。本研究通过滴液实验测定了3种配合物燃料与白烟硝酸(White fuming nitric acid, WFNA)发生自燃反应的点火延迟时间。实验时首先称取30 mg配合物燃料放置于圆底离心管中,然后用滴管向其中滴加WFNA,可观察到样品接触后瞬间发生点火燃烧,且在点火后可以维持稳定燃烧,整个实验过程采用高速摄像记录,得到的点火燃烧过程如

a. ACC‑1

b. A CC‑2

c. ACC‑3
图5 3种高活性配合物与白烟硝酸接触的自燃点火过程
Fig.5 High‑speed camera images selected from the hypergolic ignition tests of ACCs 1-3 with WFNA
对3种复合点火药样品进行X射线粉末衍射、扫描电子显微镜及X射线能量色散谱(SEM‑EDS)分析,结果如

图6 ACC‑3/NaBrO3复合药剂的实验测定衍射图谱与纯ACC‑3及NaBrO3单晶模拟衍射图对比
Fig.6 Comparison of experimental diffraction pattern of ACC‑3/NaBrO3 mixture with simulated diffraction patterns of pure ACC‑3 and NaBrO3 single crystal

图7 (a) ACC‑3/NaBrO3复合药剂的扫描电镜图 (b~h) ACC‑3/NaBrO3混合药剂的能谱分析图
Fig.7 (a) SEM images of ACC‑3/NaBrO3 mixtures (b-h) EDS of ACC‑3/NaBrO3 mixtures
用电热丝点燃置于铜坩埚内的粉状复合药剂(30 mg),通过高速摄像记录高活性配合物/溴酸钠复合点火的燃烧过程,燃烧过程如

a. ACC‑1/NaBrO3

b. ACC‑2/NaBrO3

c. ACC‑3/NaBrO3
图8 高速摄像记录的ACC‑1/NaBrO3,ACC‑2/NaBrO3和ACC‑3/NaBrO3复合点火药的燃烧过程
Fig.8 Combustion processes of ACC‑1/NaBrO3, ACC‑2/NaBrO3 and ACC‑3/NaBrO3 mixtures, as captured by the high‑speed camera
(1)基于氰基硼氢阴离子、1‑乙烯基咪唑与过渡金属离子Co/Mn/Ni制备了3种高活性配合物Co(VIM)4(CBH)2(ACC‑1)、Mn(VIM)4(CBH)2(ACC‑2)和Ni(VIM)4(CBH)2(ACC‑3),获取了它们的单晶结构。
(2)对3种高活性配合物的基础性质进行了表征,氧弹实验表明ACCs 1-3的热值可高达29.1 kJ·
(3)将高活性配合物用作燃料组分,与固体氧化剂混合制备的ACCs 1-3/NaBrO3复合点火药在燃烧过程中放出大量的光和热,燃烧温度较高且能进行稳定的自持燃烧,有潜力成为新型火工药剂。
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