High Pressure Studies On Organic Azide 4-azide Benzoic Acid And Diphenylphosphoryl Azide

The development of energy drives the progress of The Times and is closely related to the production and life of each of us.Along with the development of science and technology,the research on energy-containing materials is getting deeper and deeper.The single bond state polymerization nitrogen is a contain material has the highest energy density,and azide is a ideal system of compound high energy density materials single nitrogen bond state polymerization under high pressure,at the same time,the high pressure study of azide contains rich physical problems such as the structural phase transition,the change in the ionic interactions and bonding change and so on.Therefore the study of high pressure of azide contains both scientific problems,but has application background,has become the hot topics in the study of high pressure.The three nitrogen atoms in the azide molecule are connected to each other in the form of a linear resonance structure,N=N,with a bond of 418 kilojoules per mole.Azide divided into two categories,organic and inorganic azide,the azide group in organic azide and inorganic azide has a big difference in the structure,under the condition of atmospheric pressure,most of the azide root present a linear structure and azide base is more present a curved structure.According to the results of previous studies,azide under the condition of high pressure can make the azide root bending or deformation make it into a zigzag or with benzene ring structure similar to N₆ molecular clusters,prompting adjacent azide root occur electron orbital hybridization to form aggregation of nitrogen.Therefore,compared with inorganic azide,organic azide with bent structure is more likely to form single bond polymerization nitrogen in relatively low pressure conditions.In addition,in the high pressure study of NaN₃,it was found that the azide was decomposed intonon-molecular nitrogen with a similar amorphous structure under the condition of 120 GPa,and converted into polymerization nitrogen when the temperature reached 3300K.This shows that the decomposition of azide is an important intermediate process of nitrogen polymerization,therefore,it is possible to reduce the decomposition pressure point of the azide root to facilitate the occurrence of nitrogen polymerization.Compared with inorganic azide,the decomposition pressure point of azide matrix in organic azide is lower,so research on organic azide under high pressure for us to explore new type of high energy density materials is of great significance.We use 4-azide benzoic acid and diphenylphosphoryl azide as the research object,using diamond anvil high-pressure test technology,combining the in-situ synchrotron radiation X-ray diffraction and high pressure Raman scattering experiment and other test methods,discusses the behavior of this two sample under the condition of high pressure and the change law,concrete content as follows:We carried out high pressure study on 4-azobenzoic acid.We carried out the high pressure Raman scattering and high-pressure synchrotron radiation X-ray diffraction experiment,respectively?In the process,the atmospheric Raman spectra of 4-azide benzoic acid were identified,the experiment proves the azide 4-azide in benzoic acid at atmospheric condition is non-linear.The changes of the Raman spectra within the range of 2.9-4.4 GPa shows 4-azide benzoic acid phase change happened in this pressure range,it is the reason that the benzene ring occures deformation under pressure lead to the change of the molecular organic groups.From the experiments of 4-azide benzoic acid in in-situ high-pressure synchrotron radiation X-ray diffraction we found that when the pressure reached 2.8 GPa,the occurrence of two diffraction peak disappear at the same time shows a new diffraction peaks,which confirmed the conclusion in the high pressure Raman spectra that the sample occurs phase change at 2.9-4.4 GPa,continue to pressure to11.0 GPa,the second phase transformation occurs.When the pressure is greater than11.0 GPa,4-azide benzoic acid gradually shift to amorphous phase structure,when the stress reaches 31 GPa,the sample mainly achieves the amorphous satate,this moment,azide matrix completely decomposition,Compared to inorganic azide,the pressure point of azide group in 4-azide benzoic acid relative low,so it is more likely to occur polymerization.After press relief,the diffraction spectrum does not return to the state of normal pressure,indicating that the phase change in the experiment is irreversible.We carried out high pressure study on diphenylphosphoryl azide.We carried out the high pressure Raman scattering on diphenylphosphoryl azide,it is liquid at normal temperature and pressure.From the conclusion of the high pressure Raman spectra,there is never a new peak appears within the highest pressure range of the experiment neither external mold vibration nor internal model of vibration,so we can conclude that diphenylphosphoryl azide does not transform into a crystalline phase with an ordered molecular orientation in the experimental pressure range.After 7.9 GPa,the majority of Raman peak of diphenylphosphoryl azide was widen and disappear,but there is no new Raman peaks appear in the experimental pressure range,so we guess at 7.9 GPa,the organic groups in diphenylphosphoryl azide gradually decompose,and then we guess diphenylphosphoryl azide might occur nitrogen polymerization under lower pressure point than inorganic azide.