Structural evolution of HMX during processing operations

ABSTRACTThe impact of processing operations such as chemical synthesis conditions, milling, coating and pressing operations on the crystallographic structure of HMX has been studied using X-ray diffraction and Rietveld analysis. Strong differences in grain morphology and X-ray patterns were first observed after synthesis on two different setups with different washing methods. Diffraction pattern refinements were tentatively performed on the basis of known structures and assuming preferential orientations. The impossibility of achieving satisfactory agreement, even considering the orientation of several planes, could be attributed to the presence of polymorphism or hydrates. The possible new polymorphs or hydrates were metastable since milling led to the stable ß-HMX polymorph. No such transformation occurred during the coating operation, but an increase in structural defects was observed. Finally, the pressing step did not induce any transformation but surprisingly led to a decrease in structural defects, probably due to isotropic deformation of the crystallographic cell and the repairing effect of the associated thermal treatment.Keywords: Crystallographyenergetic materialsHMXProcessing operationsX-Ray diffraction AcknowledgmentsThe authors wish to thank Dr Jean-François Willart for useful discussions.Disclosure statementNo potential conflict of interest was reported by the author(s).Supplementary materialSupplemental data for this article can be accessed online at https://doi.org/10.1080/07370652.2023.2267558