六硝基六氮杂异伍兹烷(HNIW,CL-20)具有α-、β-、γ-、ε-等多种晶型,常压下,在不同溶剂系统中,晶型之间会相互转化.采用溶剂/反溶剂法,研究了正庚烷以不同速度加入到HNIW的乙酸乙酯饱和溶液中HNIW的结晶过程,采用红外光谱仪和扫描电子显微镜研究了结晶过程中HNIW的晶型和形貌.结果显示:当正庚烷的加料速度大于100 mL·s-1时,HNIW的结晶机理主要受动力学控制,先是亚稳相β-HNIW晶核的形成和生长,随后由亚稳相β-HNIW向稳定相ε-HNIW转变,最终全部变为ε-HNIW.当正庚烷的加料速度小于20 mL·s-1时,HNIW的结晶机理主要受热力学控制,不存在相转移,只有ε-HNIW的成核和随后生长.在结晶过程中如有水存在,则会生成水合α-HNIW.因此,制备ε-HNIW的溶剂一般采用非极性或极性小的溶剂,而不用极性大的溶剂.%2 ,4,6,8,10,12-Hexanitrohexaazaisowurtzitane( HNIW,or CL-20) exists in four crystalline polymorphs(α-,β-,γ- and ε-) which can be transited in different solvents at ambient conditions. In this work, the ε-HNIW crystallization process in a saturated HNIW solution in ethyl acetate being added to n-heptane with different addition rates. Crystal polymorph and morphology of HNIW were studied by Fourier transform infrare spectroscopy( FTIR) and scanning electron microscope( SEM) ,respectively. It is revealed that crystallization mechanism of ε-HNIW is kinetic-controlled when n-heptane addition rate is above 100 mL ? S-1 and the crystallization process of HNIW is that metastable phase β-HNIW nucleus firstly formed and growed; then,β→ε phase transition occurred and stable phase ε-HNIW increased; at last,β-HNIW disappeared and ε-HNIW attained completely. When n-heptane addition rate is below 20 mL ? S-1, crystallization mechanism of ε-HNIW is thermodynamic-controlled and only ε-HNIW nucleus formed and growed without phase transition in the whole crystallization process. The hydrate α-HNIW will be formed if water existed in HNIW solution. So,the non-solvents used for preparation of ε-HNIW should be non-polar or poor-polar solvents, not solvents with high values of dipole moment.
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