Enhancing Mechanical and Combustion Performance of Boron/Polymer Composites via Boron Particle Functionalization.
ACS applied materials & interfaces
High-speed air-breathing propulsion systems, such as solid fuel ramjets (SFRJ), are important for space exploration and national security. The development of SFRJ requires high-performance solid fuels with excellent mechanical and combustion properties. One of the current solid fuel candidates is composed of high-energy particles (e.g., boron (B)) and polymeric binder (e.g., hydroxyl-terminated polybutadiene (HTPB)). However, the opposite polarities of the boron surface and HTPB lead to poor B particle dispersion and distribution within HTPB. Herein, we demonstrate that the surface functionalization of B particles with nonpolar oleoyl chloride greatly improves the dispersion and distribution of B particles within HTPB. The improved particle dispersion is quantitatively visualized through X-ray computed tomography imaging, and the particle/matrix interaction is evaluated by dynamic mechanical analysis. The surface-functionalized B particles can be uniformly dispersed up to 40 wt % in HTPB, the highest mass loading reported to date. The surface-functionalized B (40 wt %)/HTPB composite exhibits a 63.3% higher Young's modulus, 87.5% higher tensile strength, 16.2% higher toughness, and 16.8% higher heat of combustion than pristine B (40 wt %)/HTPB. The surface functionalization of B particles provides an effective strategy for improving the efficacy and safety of B/HTPB solid fuels for future high-speed air-breathing vehicles.
View details for DOI 10.1021/acsami.1c06727
View details for PubMedID 34110148
- Dinaphthobenzo[1,2:4,5]dicyclobutadiene: Antiaromatic and Orthogonally Tunable Electronics and Packing ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 2019; 58 (7): 2034–39
Dinaphthobenzo[1,2:4,5]dicyclobutadiene with Strong Antiaromaticity and Orthogonally Tunable Electronics and Packing.
Angewandte Chemie (International ed. in English)
Polycyclic conjugated hydrocarbons containing antiaromatic four-membered cyclobutadienoids are of great fundamental and technical interest. However, their challenging synthesis has hampered the exploration and understanding of such systems. We report herein a modular and efficient synthesis of novel CBD-containing acene analogues, dinaphthobenzo[1,2:4,5]dicyclobutadiene (DNBDCs) with orthogonally tunable electronic properties and molecular packing. Our design also features strong antiaromaticity of CBD units, as revealed by nucleus-independent chemical shift and anisotropy of the induced current density calculations as well as X-ray crystallography. Tuning the size of silyl substituents resulted in the most favorable "brick-layer" packing for triisobutylsilyl-DNBDC and a charge mobility of up to 0.52 cm2 V-1 s-1 in field-effect transistors.
View details for PubMedID 30565363