Engineering multicomponent crystals through cocrystallization and doping
Abstract
Crystalline materials are the basis of most solid energetic materials used in defense applications. Workhorse explosives, includingTNT and HMX, and oxidizers key for propulsion, including ammonium perchlorate (AP), are crystalline. The crystalline state achievesthe highest possible density for a material and is therefore advantageous for performance. Stability is also often improved relative to solution/liquid states of matters as is handling and compound purity. The drawback of crystalline materials, compared to polymers or liquid formulations, is that the properties of a crystal are typically considered to be inherent to the crystallized compound.Although crystal polymorphism can introduce some variability in properties such as impact sensitivity, the properties of a crystalline compound are not inherently tunable. This issue is addressed in the proposal through two complementary approaches: cocrystallization and molecular doping.Mixing two crystalline materials generally leads to a physical mixture with properties that can manifest as a simple blend of the two components. In cocrystallization, two compounds combine into a new lattice with properties that do not resemble a blend. This approach has been extensively demonstrated for energetic materials where sensitivity, performance, and hygroscopicity can all be altered. It is the last property that motivates our current work on making a cocrystal of hydroxylammonium nitrate (HAN) that can be handled in ambient conditions. HAN is a very promising replacement for AP if its hygroscopicity can be tamed. Using a database approach, and several model compounds, we will develop a roadmap for HAN cocrystallization. In a second aspect of this project, we will explore molecular doping as a complement to cocrystallization. Because doping incorporates low levels (typically <2%) of a second molecule within the lattice of a host, the host performance can be maintained while perturbing the interaction withoptical stimuli or tuning reaction pathways with designed additives. Molecular doping has barely been studied for energetic materials and this represents a fertile ground for methodology development with broad implications for applications involving crystalline materials.Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 10, 2025
- Source ID
- N000142512207
Entities
People
- Adam J. Matzger
Organizations
- Board of Regents of the University of Michigan
- Office of Naval Research
- United States Navy