TNAZ-TNT低共熔物的微结构

Microstructure of TNAZ-TNT Eutectic

以1,3,3-三硝基氮杂环丁烷(TNAZ)-2,4,6-三硝基甲苯(TNT)低共熔物为研究对象,采用差示扫描量热仪(DSC)、扫描电镜(SEM)、X射线衍射(XRD)、傅里叶红外光谱(FT-IR)、小角X射线散射(SAXS)结合分子动力学模拟对其微结构进行研究。结果表明,TNAZ-TNT低共熔物仅有一个熔融峰,其熔点远低于原料,且具有更高的熔化焓ΔH_(fus)和熔化熵ΔS fus;TNAZ和TNT具有相似的无量纲熔化熵(ΔS^(0)_(fus))值,易发生非小面化结晶,得到规则的微结构(微米阵列的层层堆积);低共熔物的X射线衍射峰(XRPD)以及傅里叶红外光谱(FT-IR)与原料基本重合,但部分峰发生了微小位移,说明低共熔物中晶格体积的变化以及组分分子间弱氢键的形成;小角X射线散射(SAXS)和分子动力学模拟结果证实,TNAZ-TNT低共熔物中存在粗糙的相界面,界面厚度约为5A;TNAZ和TNT分子间发生了C-H…O氢键作用,氢键键长在2.306~2.775A。

The microstructure of 1,3,3-trinitroazetidine(TNAZ)-2,4,6-trinitrotoluene(TNT)eutectic was investigated by differential scanning calorimetry(DSC),scanning electron microscope(SEM),X-ray diffraction(XRD),Fourier transform infrared spectrum(FT-IR),small-angle X-ray scattering(SAXS)combined with molecular dynamics simulations.The results show that the TNAZ-TNT eutectic has only one melting peak and a substantially lower melting point than the raw materials.The eutectic has high fusion enthalpyΔH_(fus) and fusion entropyΔS fus.Since TNAZ and TNT have similar dimensionless fusion entropy values(ΔS^(0)_(fus)),the solidification in the binary mixture is non-faceted and results in a regular microstructure(layer-layer assembly of micron array).The X-ray powder diffraction(XRPD)and Fourier transform infrared spectrum(FT-IR)peaks of this eutectic are almost identical to those of the raw materials,but some peaks shift,indicating the change of lattice volume and the formation of weak intermolecular hydrogen bonds.Small-angle X-ray scattering(SAXS)and molecular dynamics simulation suggest a rough phase interface in the TNAZ-TNT eutectic with a width of around 5.C-H…O hydrogen-bonding interactions occur between TNAZ and TNT molecules with hydrogen bond lengths ranging from 2.306A to 2.775A.