摘要
通过蒸汽扩散法成功合成了3种环糊精金属有机框架(CD‑MOF)材料,并采用单晶X‑射线衍射对其单晶结构进行解析。作为潜在的消焰剂,相比传统的硝酸钾热分解温度(722.0 ℃),3种CD‑MOF更低(250.9 ℃;261.0 ℃;290.3 ℃),更容易释放钾离子,且在硝化纤维素(NC)中显示出良好的物理分散性和化学相容性。此外,添加CD‑MOF的NC在热分解时产生的易燃和有害气体(CO、NO、NO2和N2O)更少。添加γ‑CD‑MOF的单基药在燃烧时表现出最小的火焰面积(119.6 mm²),而添加β‑CD‑MOF的单基药显示出更低的火焰面积标准偏差(8.4 mm²),表明其消焰效能更稳定。相比之下,添加KNO₃的单基药火焰面积最大(392.7 mm²)。
图文摘要
关键词
在现代信息化战争中,中小口径武器射击时产生的膛口二次焰不仅降低士兵隐蔽能力和突击效果,还严重干扰视野清晰度和武器光电制导功能,限制了武器性能提升,已成为国内外的技术难
金属有机框架(MOF)作为一类比表面积高、孔径可调、化学稳定的多孔材料,融合了有机和无机材料的优势与特点,已经在火药领域的燃烧催化方面展现出巨大前
为进一步拓展环糊精金属有机框架在发射药中的应用,对比分析不同环糊精结构对NC热分解的具体效应,本研究以氢氧化钾为溶液,采用甲醇蒸汽扩散
试剂:环糊精(α‑CD、β‑CD和γ‑CD,98%),东京化学工业公司(TCI,日本);氢氧化钾(KOH,98%),无水甲醇(MeOH,99.8%),无水乙醇(EtOH,99.7%),Sigma‑Aldrich(美国);丙酮(99.5%),中国国药化学试剂有限公司。硝酸钾(KNO3,98.5%),上海泰坦科技有限公司(中国)。上述所有试剂均为分析级,无需进一步纯化即可使用。硝化纤维素(氮含量:13.15%)由泸州北方化学工业公司提供。实验所用去离子水通过Millipore系统净化所得。
仪器:美国BRUKER公司D8 Quest型单晶X射线衍射仪(XRD,Mo Kα辐射,λ=0.71073 Å);美国BRUKER公司D8 Focus型粉末X射线衍射仪(Cu‑Kα辐射,测试范围从3°~40°);日本HITACHI公司SU8010型扫描电子显微镜(SEM);德国蔡司公司Sigma 300型扫描电子显微镜(SEM);英国牛津公司Xplore 50型EDS能谱仪;德国Netzsch公司STA 2500型热重分析仪(TG);德国Netzsch公司DSC 204 F1 Phoenix型差示扫描量热法仪(DSC);德国Netzsch公司STA‑2500‑IS50型TG‑FTIR联用仪;德国PCO公司PCO. dimax HS型高速摄像机。
依照文献报道方法合成CD‑MO
NC/消焰剂复合材料的制备:将消焰剂(α‑CD‑MOF,β‑CD‑MOF,γ‑CD‑MOF,KNO3)和NC制以0.05∶1和1∶1的质量比在室温下机械均匀混合,以获得物理复合材料NC/α‑CD‑MOF,NC/β‑CD‑MOF,NC/γ‑CD‑MOF,NC/KNO3,分别用于TG‑FTIR热分解测试,以及DSC相容性测试。
NC基发射药的制备:α‑CD‑MOF、β‑CD‑MOF、γ‑CD‑MOF和KNO3作为消焰剂,其平均粒径为0.15 mm,添加比例为1.6%,研究使用丙酮和乙醇按质量比1∶1比例混合的溶液,将这些混合物用捏合机捏合2 h,NC与混合液的比例为10∶7。捏好的药团通过油压机挤出成管状发射药。最后,将NC基发射药在室温下晾干1 d,然后在45 ℃的烘箱中干燥,直至挥发物质减少到1%,制备得到的含消焰剂的NC基发射药,标记为NC@α‑CD‑MOF、NC@β‑CD‑MOF、NC@γ‑CD‑MOF和NC@KNO3。不添加任何消焰剂的NC基发射药作为空白对照。不添加任何消焰剂的NC基发射药作为空白对照。
单晶X射线衍射采用美国BRUKER公司的Bruker D8 Quest型衍射仪,波长为0.71073 Å。数据处理和晶体索引通过Bruker的APEX3软件进行,使用差向量法确定晶体的晶胞参数并整合。单晶结构的解析通过SHELXL‑2014软件进行。
α‑CD‑MOF,β‑CD‑MOF,γ‑CD‑MOF和KNO3的热分解性能测试进行采用德国Netzsch公司STA 2500型热重分析仪(TG)。测试样品量为(0.7±0.02) mg,在N2气氛下(20 mL·mi
相容性测试采用德国Netzsch公司DSC 204 F1 Phoenix型差示扫描量热法仪(DSC)。
NC/α‑CD‑MOF,NC/β‑CD‑MOF,NC/γ‑CD‑MOF,NC/KNO3测试样品量为(0.5±0.02) mg,实验在N2气氛中进行,流量为40.0 mL·mi
热分解气体产物测试采用德国Netzsch公司STA‑2500‑IS50型TG‑FTIR联用仪。TG‑FTIR测试是在将一台STA 2500 Regulus型热重分析仪和一台Thermo Scientific Nicolet iS50型红外光谱仪连接后进行的。测试样品量为(2.0±0.2) mg,实验在N2气氛下(50 mL·mi
将制成的NC@α‑CD‑MOF,NC@β‑CD‑MOF,NC@γ‑CD‑MOF和NC@KNO3发射药横截面切块,厚度约2 mm。取块体样品直接粘到导电胶上,并使用Quorum SC7620溅射镀膜仪喷金45 s,喷金为10 mA;随后使用ZEISS Sigma 300扫描电子显微镜拍摄样品形貌、能谱mapping等测试,形貌拍摄时加速电压为3 kV,能谱mapping拍摄时加速电压为15 kV,探测器为SE2二次电子探测器。
通过单晶X射线衍射(XRD)和粉末X射线衍射(PXRD)对环糊精金属有机框架(CD‑MOF)进行了结构表征。单晶XRD分析(
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a. α‑CD‑MOF
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b. β‑CD‑MOF
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c. γ‑CD‑MOF
图1 α‑CD‑MOF、β‑CD‑MOF、γ‑CD‑MOF的XRD和PXRD测试结果
Fig.1 XRD and PXRD results for α‑CD‑MOF, β‑CD‑MOF, and γ‑CD‑MOF
通过扫描电子显微镜(SEM)对CD‑MOF的形貌进行了观察。具体来说,α‑CD‑MOF(
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图2 α‑CD‑MOF(a),β‑CD‑MOF(b),γ‑CD‑MOF(c),KNO3(d)的扫描电镜图
Fig.2 SEM images of α‑CD‑MOF (a), β‑CD‑MOF (b),γ‑CD‑MOF (c), KNO3 (d)
为研究3种环糊精金属有机框架(CD‑MOF)材料(α‑CD‑MOF,β‑CD‑MOF,γ‑CD‑MOF)作为新型消焰剂的热分解性能,本研究对这些材料与传统消焰剂硝酸钾(KNO3)都进行了热重分析(TG)测试。结果如
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图3 α‑CD‑MOF、β‑CD‑MOF、γ‑CD‑MOF、KNO3的TG曲线图
Fig.3 TG curves of α‑CD‑MOF,β‑CD‑MOF,γ‑CD‑MOF,KNO3
samples | T0 / ℃ | Tp / ℃ | Te / ℃ |
---|---|---|---|
α‑CD‑MOF | 250.9 | 287.4 | 316.1 |
β‑CD‑MOF | 290.3 | 318.5 | 344.2 |
γ‑CD‑MOF | 261.0 | 297.6 | 325.7 |
KNO3 | 722.0 | 775.7 | 800.2 |
Note: T0 is onset extrapolated temperature, Tp is peak temperature, Te is endset extrapolated temperature.
为分析CD‑MOF(α‑CD‑MOF, β‑CD‑MOF, γ‑CD‑MOF)和KNO3作为消焰剂对NC热分解的影响,研究进行了热重‑傅立叶变换红外(TG‑FTIR)测试。在NC降解过程中,一旦O─NO2键断裂,就会产生强氧化剂NO2。它聚集在NC的聚合物骨架中,增强了自催化反应,促进剩余的O─NO2键和环内氧桥的断裂,从而释放出CO、NO、NO2、N2O等气
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图4 NC/α‑CD‑MOF、NC/β‑CD‑MOF、NC/γ‑CD‑MOF和NC/KNO3的TG曲线图
Fig.4 TG curves of NC/α‑CD‑MOF, NC/β‑CD‑MOF, NC/γ‑CD‑MOF and NC/KNO3
已有研究表明,降低可燃气体浓度对控制和消除二次火焰是有效
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a. NC/α‑CD‑MOF
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b. NC/β‑CD‑MOF
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c. NC/γ‑CD‑MOF
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d. NC/KNO3
图5 NC/α‑CD‑MOF、NC/β‑CD‑MOF、NC/γ‑CD‑MOF和NC/KNO3的气相分解产物的强度分布
Fig.5 Intensity distribution of gas‑phase decomposition products of NC/α‑CD‑MOF, NC/β‑CD‑MOF, NC/γ‑CD‑MOF and NC/KNO3
samples | CO | NO | NO2 | N2O |
---|---|---|---|---|
NC/α‑CD‑MOF | 0.0116 | 0.0038 | 0.0116 | 0.0103 |
NC/β‑CD‑MOF | 0.0147 | 0.0008 | 0.0072 | 0.0143 |
NC/γ‑CD‑MOF | 0.0276 | 0.0143 | 0.0079 | 0.0165 |
NC/KNO3 | 0.0708 | 0.0423 | 0.0347 | 0.104 |
为研究不同消焰剂对NC基发射药(NC@α‑CD‑MOF、NC@β‑CD‑MOF、NC@γ‑CD‑MOF、NC@KNO3)分散性,研究进行了扫描电子显微镜(SEM)和能谱分析(EDS)测试,结果如
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图 6 不同消焰剂在NC基发射药中的分布情况的SEM和mapping图像: (a) NC@α‑CD‑MOF,(b) NC@β‑CD‑MOF,(c) NC@γ‑CD‑MOF,(d) NC@KNO3
Fig.6 SEM and mapping images showing the distribution of different flame suppressants in NC‑based gun propellants: (a)NC@α‑CD‑MOF,(b)NC@β‑CD‑MOF,(c)NC@γ‑CD‑MOF,(d) NC@KNO3
研究使用DSC在不同升温速率1、2、5、10 K·mi
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a. NC
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b. NC/α‑CD‑MOF
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c. NC/β‑CD‑MOF
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d. NC/γ‑CD‑MOF
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e. NC/KNO3
图7 NC、NC/α‑CD‑MOF、NC/β‑CD‑MOF、NC/γ‑CD‑MOF、NC/KNO3的DSC曲线
Fig.7 DSC curves of NC, NC/α‑CD‑MOF, NC/β‑CD‑MOF, NC/γ‑CD‑MOF, NC/KNO3
为进一步研究不同消焰剂对发射药燃烧特性的影响,使用四视图燃烧室和高速摄影对发射药的火焰形态和燃烧状态进行了评估。每种样品平均测试3次,结果如
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图8 3 MPa下(a)NC@α‑CD‑MOF、(b)NC@β‑CD‑MOF、(c)NC@γ‑CD‑MOF、(d)NC@KNO3的火焰照片
Fig.8 Flame photographs of (a) NC@α‑CD‑MOF, (b) NC@β‑CD‑MOF, (c) NC@γ‑CD‑MOF, and (d) NC@KNO3 at 3 MPa
sample | flame area/m | ||||
---|---|---|---|---|---|
group 1 | group 2 | group 3 | average | standard deviation | |
NC@α‑CD‑MOF | 148.8 | 169.4 | 128.3 | 148.8 | 16.8 |
NC@β‑CD‑MOF | 178.4 | 191.0 | 170.6 | 180.0 | 8.4 |
NC@γ‑CD‑MOF | 128.9 | 92.0 | 131.8 | 119.6 | 18.1 |
NC@KNO3 | 229.3 | 415.8 | 532.9 | 392.7 | 125.0 |
Note: The test position is at the center of a 40 mm long single‑base propellant.
研究通过绿色简易的甲醇蒸汽扩散法成功合成了α‑CD‑MOF、β‑CD‑MOF和γ‑CD‑MOF 3种新型消焰剂,并与传统消焰剂硝酸钾(KNO3)进行了对比。得出结论如下:
(1)相比于KNO3,添加CD‑MOF的NC在热分解过程中释放的可燃、有害气体更少。NC/α‑CD‑MOF在CO、NO、NO2和N2O的释放量方面分别降低了约83.62%、91.02%、66.57%和90.10%,表现出更好的环境友好性和安全性。
(2)在静态燃烧试验中,添加CD‑MOF的NC比添加了KNO3的样品显示出更小的火焰面积,平均面积分别为NC@α‑CD‑MOF 148.8 mm², NC@β‑CD‑MOF 180.0 mm², NC@γ‑CD‑MOF 119.6 mm², NC@KNO3 392.7 mm²。这一效果归因于CD‑MOF较低的分解温度,能够有效释放更多钾离子。此外,加入β‑CD‑MOF后,发射药的火焰区面积标准偏差最低,显示出燃烧稳定性。但在发射装药动态燃烧中,还需要进一步测试和验证消焰效果。
(3)SEM和EDS表征显示,CD‑MOF在NC中的物理分散性明显优于KNO3,且显示出良好的化学相容性。为发射药的配方设计和应用提供了理论依据。
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