Combining polymers with small amounts of stiff carbon-based nanofillers such as graphene or graphene oxide is expected to yield low-density nanocomposites with exceptional mechanical properties. However, such nanocomposites have remained elusive because of incompatibilities between fillers and polymers that are further compounded by processing difficulties. Here we report a water-based process to obtain highly reinforced nanocomposite films by simple mixing of two liquid crystalline solutions: a colloidal nematic phase comprised of graphene oxide platelets and a nematic phase formed by a rod-like high-performance aramid. Upon drying the resulting hybrid biaxial nematic phase, we obtain robust, structural nanocomposites reinforced with graphene oxide.

The purpose of this research was to investigate the use of Fused Filament Fabrication (FFF) to fabricate structural components from polycarbonate in an on-orbit environment. This included investigating the ability of an FFF printer to function in a simulated on-orbit environment and evaluation of the dimensional accuracy and mechanical properties of components fabricated in a simulated on-orbit environment. A commercially available FFF printer was placed in a vacuum environment of 1000 Pa. Aspects of the on-orbit environment other than the pressure were ignored. Tests were performed in vacuum to determine functionality of the printer. Test components were then fabricated in vacuum with a control group fabricated in a normal atmosphere. Test components were evaluated for dimensional and mass accuracy, quality and presence of defects. Flexural, tensile and compressive testing was carried out according to ASTM D790, D638 and D695 respectively. The FFF process was successfully carried out in a vacuum environment. Dimensional analysis of components showed that there were often significantly different dimensions depending on the environment they were printed however they pose little practical issues. There was no consistent change in the mass or quality of components when fabricated vacuum. Components fabricated in the vacuum environment had 5.4% higher tensile yield strength and 59% higher extension at fracture than components printed in a normal atmosphere indicating increased strength and ductility. Components tested in compression had approximately 11.2% higher ultimate compressive strength when printed in a vacuum environment. No differences were observed during the flexural test. It was found to be possible to use the FFF process in a vacuum environment to fabricate dimensionally accurate, high quality polycarbonate components with a variety of geometries. This is a promising conclusion as it provides a proof of concept that FFF can be used in an on-orbit environment. In the future FFF could be used for maintenance and repair of satellites or to manufacture entire space systems more efficiently than current manufacture on-ground and launch methods.

Amorphous titanium oxide nanoparticles were prepared from titanium isopropoxide. In situ measurements reveal an extraordinary high capacity of 810 mAh/g on the first discharge. Upon cycling at a charge/discharge rate of 33.5 mA/g, this capacity gradually decreases to 200 mAh/g after 50 cycles. The origin of this fading was investigated using X-ray absorption spectroscopy and solid-state nuclear magnetic resonance. These measurements reveal that a large fraction of the total amount of the consumed Li atoms is due to the reaction of H₂ O/OH species adsorbed at the surface to Li₂ O, explaining the irreversible capacity loss. The reversible capacity of the bulk, leading to the Li_0.5 TiO₂ composition, does not explain the relatively large reversible capacity, implying that part of Li₂ O at the TiO₂ surface may be reversible. The high reversible capacity, also at large (dis)charge rates up to 3.35 A/g (10C), makes this amorphous titanium oxide material suitable as a low cost electrode material in a high power battery.