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We introduce the first multifunctional material that simultaneously exhibits enhanced mechanical strength and embedded energy harvesting functionality.

Here, a simple zinc oxide (ZnO) nanoparticle sizing is reported for aramid fibers that simultaneously provides interfacial reinforcement and UV absorption to develop improved fiber-reinforced composites. Through a one-step nanoparticle deposition, the modified aramid fiber showed an increase in interfacial shear strength of 18.9% with the addition of ZnO nanoparticles when tested by single-fiber pullout. The aramid fibers were then treated with a hydrolysis process common to aramid fibers to oxidize the surface and elucidate the importance of oxygen functional groups at the interface. These oxidized fibers proved to further enhance the interface between the fiber surface and nanoparticle, leading to a 33.3% increase relative to the bare fiber. Additionally, due to the absorption properties of ZnO, the retainment of mechanical properties of coated fibers was determined after exposure to an artificial UV light source. After 24 h of exposure, fibers coated with ZnO nanoparticles retained 25% more tensile strength and 21% more modulus than uncoated bare fibers. This work shows that ZnO nanoparticles may serve as a novel, yet simple, multifunctional fiber sizing with which to increase the interfacial strength of aramid fiber composites and improve the resistance to UV irradiation, enabling stronger and more-durable structural fiber composites.

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We developed an operationally simple electrolytic design for the surface treatment of short carbon fibers. Using X-ray photoelectron spectroscopy (XPS), we demonstrated that the electrochemical surface treatment of discontinuous fibers is highly reproducible, uniform, and tunable. Specifically, total amounts of surface oxygen and nitrogen contents (0 to 17 atomic %) as well as surface oxygen-to-nitrogen ratio (1:0 to 1:2) vary significantly over the ranges of each processing parameter: applied voltage (1.5–21 V), location of carbon fiber (i.e., anode, cathode, or mixed mode), initial temperature (3–70.5 °C), and ammonium bicarbonate concentration (0.005–0.75 M). Optimized processing conditions afforded carbon fibers that have similar surface compositions (86.3 ± 1.1 at. % C, 8.9 ± 0.8 at. % O, 4.7 ± 0.6 at. % N) as those of commercially available continuous fibers. In addition, these fibers retain their mechanical properties (tensile strength and tensile modulus) and exhibit no detectable surface damage based on single fiber tensile tests and scanning electron microscopy (SEM). We also performed a number of control experiments to develop a proposed mechanism for the surface functionalization of the carbon fiber. These mechanistic studies demonstrated that water splitting contributes significantly to the oxidation of carbon fibers and that other species in the chemical equilibria of ammonium bicarbonate (and not just its individual ions) play a significant role in functionalizing carbon fiber surfaces.

Ring-opening metathesis polymerization (ROMP) produced homopolymers and copolymers of 5-ethylidene-2norbornene (ENB) and 5-methanol-2-norbornene (NBOH), and this provided a platform to explore the influence of monomer polarity and noncovalent interactions on the mechanical and high velocity impact performance. The tensile yield, mode-I fracture, and high velocity impact behavior displayed a strong dependence on the hydroxyl-containing NBOH content when compounding effects (such as degree of undercooling and polymer topology) are considered. Specifically, the high velocity impact performance systematically increased with increasing hydroxyl groups and tracked well with the increase in yield stress, implying the failure mechanism was yield stress dominated. Positron annihilation lifetime spectroscopy (PALS) data revealed a decrease in the pore volume with increasing NBOH content, giving insight into the increases in density and the positive deviation of the glass transition temperature (T g ) from a simple rule-of-mixtures average. Collectively, these data illustrate a strong correlation between the noncovalent interactions on the nanoscale and macroscopic properties, demonstrating that polarity and noncovalent interactions are a critical design parameter in formulating polymer materials for protection applications.

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Two-dimensional (2D) ferroelectric films have vast applications due to their dielectric, ferroelectric, and piezoelectric properties that meet the requirements of sensors, nonvolatile ferroelectric random access memory (NVFeRAM) devices, and micro-electromechanical systems (MEMS). However, the small surface area of these 2D ferroelectric films has limited their ability to achieve higher memory storage density in NVFeRAM devices and more sensitive sensors and transducer. Thus, conformally deposited ferroelectric films have been actively studied for these applications in order to create three-dimensional (3D) structures, which lead to a larger surface area. Most of the current methods developed for the conformal deposition of ferroelectric films, such as metal-organic chemical vapor deposition (MOCVD) and plasma-enhanced vapor deposition (PECVD), are limited by high temperatures and unstable and toxic organic precursors. In this paper, an innovative fabrication method for barium titanate (BaTiO3) textured films with 3D architectures is introduced to alleviate these issues. This fabrication method is based on converting conformally grown rutile TiO2 nanowire arrays into BaTiO3 textured films using a simple two-step hydrothermal process which allows for thickness-controlled growth of conformal films on patterned silicon wafers coated with fluorine-doped tin oxide (FTO). Moreover, the processing parameters have been optimized to achieve a high piezoelectric coupling coefficient of 100 pm/V. This high piezoelectric response along with high relative dielectric constant (εr = 1600) of the conformally grown textured BaTiO3 films demonstrates their potential application in sensors, NVFeRAM, and MEMS.