摘要
分子钙钛矿含能材料作为一种新概念单质含能材料,可通过改变其离子组分而调控性能,为设计适用不同领域的实用火炸药提供新途径。氯酸铵具有强氧化性而常用作氧化剂,但其高吸湿性极大限制其应用范围。研究通过混合氯酸钠、氨水和三乙烯二胺(dabco)后进行酸化,获得了新的分子钙钛矿含能材料(H2dabco)(NH4)(ClO3)3(简称DAC‑4)。X射线单晶衍射分析表明,DAC‑4具有ABX3型钙钛矿结构,属于立方Pmm空间群,晶体学密度为1.86 g·c
图文摘要
关键词
在过去几十年里涌现了许多新型含能材料,比如富氮有机含能分子、五氮离子盐、含能共晶以及含能配位化合物
基于其独特的氧燃一体结构和多样可选的离子组分,分子钙钛矿含能材料具有性能可调的特点。比如,在DAP‑4基础上,通过改变A位组分或是以铵根衍生离子作为B位组分,可获得一系列具有高耐热性能的无金属分子钙钛矿含能材
试剂:三乙烯二胺(99%,上海麦克林生化科技股份有限公司);氯酸钠(99%,上海麦克林生化科技股份有限公司);氨水(25%,上海麦克林生化科技股份有限公司);盐酸(36%,广州牌)。
仪器:X射线粉末衍射仪,日本Rigaku Smartlab 3 kw;X射线单晶衍射仪,德国Bruker D8 VENTURE;差热分析仪,捷克OZM 552‑EX;BAM摩擦感度仪,捷克OZM FSKM10。
DAC‑4单晶的合成:将1 mmol的三乙烯二胺(112 mg)、75 μL的氨水和10 mmol的氯酸钠(1 g)溶解于10 mL的去离子水中,在冰水浴的条件下搅拌溶解后缓慢滴入2 mL稀盐酸,随后于室温下静置一段时间,溶液中有透明块状晶体析出,得到可用于单晶X射线衍射分析的DAC‑4单晶样品。
DAC‑4粉末的合成:将1 mmol的三乙烯二胺(112 mg)、75 μL的氨水和10 mmol的氯酸钠(1 g)溶解于10 mL的去离子水中,在冰水浴的条件下搅拌溶解后缓慢滴入1 mL稀盐酸,随后加入20 mL冰乙醇(0 ℃),析出大量DAC‑4白色粉末,产率80%。
安全注意:稀盐酸的加入必须在低温中缓慢进行,避免氯酸快速分解造成危险。
单晶X射线衍射实验:采用Bruker D8 VENTURE衍射仪收集晶体的衍射强度,使用石墨单色化的Mo Kα辐射(λ=0.71073 Å)。采用SHELXS程序使用直接方法解析结构,并使用SHELXL全矩阵最小二乘法进行结构精修。所有非氢原子都采用各向异性原子位移参数。所有氢原子通过几何方式生成,并考虑可能存在的氢键。
热分解性能:采用OZM 552‑EX差热分析仪采集化合物热分解信息,使用5 mg石英砂作为参比。称取5 mg样品在空气氛围、升温速率10 ℃·mi
BAM摩擦感度测试:采用OZM FSKM10摩擦感度仪对化合物进行摩擦感度测试,记下在6次试验中没有发生响应的最低负荷。
吸湿性实验:通过重量增加法研究了DAC‑4的吸湿性。取100 mg的样品,经过干燥至恒定重量,然后分别置于相对湿度为43%、67%、86%和100%的25 ℃恒温室中试样每隔一段时间称重一次。
通过单晶X射线衍射分析,对DAC‑4的晶体结构进行了详细的研究。晶体数据及结构精修参数见
parameters | results |
---|---|
formula | C6H18Cl3N3O9 |
formula weight | 382.64 |
temperature / K | 80(2) |
crystal system | cubic |
space group | Pmm |
a / Å | 6.9863(1) |
V / | 340.99(2) |
Z | 1 |
Dc / (g·c | 1.863 |
R1 [I > 2σ(I) | 0.0873 |
wR2 [I > 2σ(I) | 0.2547 |
R1 (all data) | 0.0949 |
wR2 (all data) | 0.2665 |
GOF | 1.053 |
CCDC No. | 2360784 |

图1 DAC‑4的晶体结构晶胞单元(其中12个处于棱心的氯酸根,除一个显示了无序及原子细节外,其余11个氯酸根由较大的透明绿色球体简化表示,8个顶点处的球体为无序的铵根,体心处是三乙烯二铵阳离子。无序部分虚化表示,为方便观察,H原子已省略)
Fig.1 The cell structure of DAC‑4(Among the 12 chlorate ions at the edge centers, except for one that shows disorder and atomic details, the remaining 11 chlorate ions are represented by large transparent green spheres. The spheres at the 8 vertices stand for disordered ammonium ions, and the triethylenediammonium cation is located at the body center.. The disordered regions are shown as partially faded for clarity, and all hydrogen (H) atoms are omitted for convenience of observation)
为研究化合物DAC‑4的热分解性能,在空气氛围、升温速率10 ℃·mi

图2 DAC‑4的DTA曲线
Fig.2 DTA of compound DAC‑4
compounds | Td / ℃ | Tp / ℃ |
---|---|---|
DAP‑ | 344 | 361 |
DAP‑ | 364 | 377 |
DAP‑ | 352 | 369 |
DAP‑ | 365 | 383 |
DAC‑4 | 100 | 106 |
Note: Td is onset decomposition temperature. Tp is peak decomposition temperature.
采用Materials Studio分子模拟软件中的DMol3模块,选择PBE‑GGA基组,根据Monkhorst‑Pack方案选择K点集合以保证倒易晶格的精确布里渊区采样,对DAC‑4及其分解产物进行结构优化计算得到0 K下化合物的总能量。在设定的分解反应式下,用产物的能量之和减去反应物的能量得到反应的能量差ΔEdet。通过Louisa J. Hope‑Weeks根据已有经典有机含能材料的ΔEdet和爆热ΔHdet拟合的经验线性方程(1
(1) |
在得到化合物的爆热之后,爆速和爆压可以通过Kamlet‑Jacob′s方程组进行预
(2) |
(3) |
(4) |
式中,ρ为化合物的密度,g·c
计算结果列于
compound | ρ / g·c | D / km· | p / GPa | ΔHf / kJ·mo | Q / kJ· | OB / % | FS / N |
---|---|---|---|---|---|---|---|
RD | 1.80 | 8.80 | 34.9 | 70.30 | 5.74 | -21.6 | 120 |
DAP‑ | 1.87 | 8.81 | 35.2 |
-483.96/+278. | 10.38 | -27.9 | 36 |
DAC‑4 | 1.86 | 8.43 | 32.6 | -390.22 | 4.91 | -43 | 36 |
DAN‑ | 1.68 | 7.57 | 23.4 | -339.13 | 5.43 | -49.5 | >360 |
TN | 1.65 | 6.90 | 20.0 | -59.3 | 4.36 | -74 | 360 |
Note: ρ is the crystal density at 298 K. D is the calculated detonation velocity. p is the calculated detonation pressure. ΔHf is the calculated molar enthalpy of formation in solid state. Q is the heat of detonation. OB is the oxygen balance based on CO2. FS is the friction sensitivity.
通过重量增加法研究了DAC‑4的吸湿性。取100 mg(m0)的样品,经过干燥至恒定重量,然后分别置于相对湿度为43%、67%、86%和100%的恒温室中。试样每隔一段时间称重一次(m1
(5) |
作为对比,在相同条件下,测试了氯酸铵的吸湿性,结果如

a. 43%

b. 67%

c. 86%

d. 100%
图3 DAC‑4与NH4ClO3分别于不同湿度下的重量变化曲线
Fig.3 Weight variation curves of DAC‑4 and NH4ClO3 at different relative humidities
我们通过混合dabco、氯酸钠和氨水,继而酸化后,以多种离子在水溶液中的高效自组装,获得了分子钙钛矿含能晶体的新成员DAC‑4,并研究了它的晶体结构、热稳定性、理论爆轰性能和吸湿性。DAC‑4结晶于立方晶系空间群,阴阳离子之间通过库伦作用力和氢键相互作用形成稳定的ABX3钙钛矿结构;这种在分子水平上将氧化性和还原性离子组分交替紧密堆积的方式使得DAC‑4具有优秀的理论爆轰性能(爆热、爆速和爆压分别是4.91 kJ·
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