Study Of Energetic Material RDX At High Temperature And Pressure By Raman Spectroscopy

Energetic materials are widely used in military science and are important energy sources in aerospace,deep well blasting and industrial fields.In recent years,great progress has been made in the field of energetic materials.However,more stringent application environments,such as various extreme conditions in space science and technology,have put forward higher requirements for the heat resistance and energy density of energetic materials.Therefore,the improvement of thermal stability,compatibility,energy density,detonation and mechanical properties is an important goal to improve the properties of energetic materials.As a typical energetic material,RDX has been widely used in the equipment of armed explosives due to its high stability and strong explosive power.Under the action of external stimulation,the microstructure and chemical reaction kinetics of RDX will change,which will also affect the physical characteristics and macro response characteristics of explosives,and further affect the detonation performance and safety performance of armed explosives.Therefore,it is very important to study the influence of external stimulation on the performance of RDX for the progress of missile and solid rocket propellant.In this thesis,the changes of molecular structure,chemical bond and crystal morphology of RDX were studied by spontaneous Raman scattering technique under extreme conditions of high temperature and high pressure.At the same time,this technology is used to conduct an in-depth discussion on the changes of vibration modes such as the C-H bond and C-N bond of the energetic material RDX molecule.The following research results have been obtained:1.The molecular structure evolution behavior ofα-RDX under extreme high temperature conditions was studied by using a confocal Raman spectrometer and a variable temperature system.It is found that when the temperature rises to 463K,the characteristic peaks of C-H equatorial tensile vibration mode at 3077cm^-1 and 3068cm^-1 merge into a new peak at 3073cm^-1.3002cm^-1 and 2950cm^-1 belonging to C-H equatorial tensile vibration mode and C-H axial tensile vibration mode are combined into a single peak at 2987cm^-1.1595cm^-1 and 1573cm^-1 belong to the axial tensile vibration mode of NO2,while 1542cm^-1 belongs to the equatorial tensile vibration mode of NO2.The three Raman peaks gradually merge into one peak,which corresponds to the characteristic peak of the 1572cm^-1 band inβ-RDX.In addition,the bending vibration in the C-H plane,the bending vibration in the C-H plane and the axial tensile vibration mode of N-NO2 in the Raman spectrum all have red shift phenomenon,and it can be confirmed that the transformation fromα-RDX toβ-RDX occurs.At the same time,the fluorescence intensity of RDX in Raman spectra is weakened,and the thermal decomposition phenomenon is also accompanied byα-RDX in the phase transition process.In addition,β-RDX is dynamically stable and does not have reversible behavior during cooling process.This study provides an experimental basis for further exploring the effect of high temperature on the phase transition behavior and thermal decomposition of RDX.2.The structural evolution ofα-RDX under high pressure at normal temperature and atmospheric pressure was studied by means of high pressure apparatus and confocal Raman spectroscopy.At about 6GPa,the double peaks of C-H tensile vibration mode at 3068cm^-1 and 3077cm^-1 are merged.The torsional vibration band at 353cm^-1 has double splitting.At the same time,the C-N tensile vibration mode at 856cm^-1 gradually starts to widen unevenly.The Raman strength of the axial tensile vibration mode at2949cm^-1 in the C-H tensile vibration mode region is greatly reduced,accompanied by a low energy acromial peak.These obvious changes in Raman vibration modes prove that the phase transition fromα-RDX toγ-RDX has occurred.In the pressure range of17.4-18.5GPa,the twin peaks of Raman ring torsion at 488cm^-1,467cm^-1 and 440cm^-1merge into one peak.The ring stretching vibration at 886cm^-1 shows a large frequency shift.A new vibration mode appears at 775cm^-1,862cm^-1 and 988cm^-1.The unimodal split at 3075cm^-1 is bimodal.These changes indicate that the structural phase transition fromγ-RDX toδ-RDX occurs at this pressure.Theδ-RDX phase changes toγ-RDX and then toα-RDX in the depressurization process,which proves that the high pressure phase transformation behavior of RDX is reversible below 20GPa.This study provides a reference for exploring the mechanism of phase transition of RDX under high pressure.