Ingestion and accumulation of sea salt and other impurities is a major challenge for high speed vessels, turbine engines, and other air breathing systems. The performance and reliability of filters are anticipated to be improved significantly after the rate of performance degradation is reduced via enhanced filtration media and well-designed filtration approaches. This study proposes to apply anionic surfactant to disperse the nanofibers thoroughly and employ cationic surfactant to flocculate the dispersed nanofibers into numerous small groups of nanofiber flocs. Using the wet-lay procedure in the lab, the novel porous microfiber media was then fabricated with small groups of nanofiber flocs together with activated carbon and polyester fibers. The unique nanofiber filter media was then evaluated for filtration performance using face velocity, pressure drop, and filtration efficiency parameters. Due to nanoflocced fiber inclusion, an anomalous region in the filtration efficiency versus pressure drop regime was observed where wall slip occurring at the nanostructured surface provided an unusually high level of filtration efficiency near the most penetrating particle size (MPPS) region of 0.1-0.4 μm with a concomitant reduction in the normally encountered levels of pressure drop. This anomalous increase in the filtration efficiency versus pressure drop is a novel phenomenon and it is highly beneficial to aerosol filtration. The enhanced filtration reveals that the quality factor near the MPPS region increases significantly due to the inclusion of nanofiber flocs. The unique porous filtration media is expected to increase the dirt holding capacity and prolong the lifecycle of the turbine air filter systems.

With the development of new classes of high-speed vessels like LCAC, which are expected to ingest high amounts of salt particulates, it is of vital importance to develop a new class of filtration media which can meet this requirement. A microfibrous filter media embedded with nanofibers was thus developed using a nanofiber flocked suspension with a microfibrous support created using traditional wet-lay papermaking methods. While the pressure drop is normally used as the conventional parameter to predict service-life of the filter media, it does not give a proper indication of filter service life. Therefore, a novel thermal impedance technique was applied in this work to characterize the filtration media using thermal parameters via a heat pulse excitation signal. The transient response for the phase lag of temperature was observed because heat transfer occurs during the air flow across the filtration media. The related thermal parameters were obtained through a thermal equivalent circuit model and a nonlinear least-squares fitting algorithm. The thermal impedance method can be used as a filter media diagnostic tool to obtain useful parameters which can be utilized to regenerate filter media and assist to define the operational lifetime of the filter. This can help protect the power systems and reduce the maintenance, operation, and replacement costs. The improved air quality that can be obtained using this advanced filtration technology will enable enhanced protection of engine turbines and other onboard air-breathing systems.

Lignin is one of the most common naturally occurring macromolecules. It is associated with cellulose and hemicelluloses in terrestrial plants, providing mechanical stiffness and contributing to moisture control and defense toward insects and fungi. Lignin is typically a polymer of three different cinnamyl alcohols, para‐coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol, which varies with the plant species. Solubilized lignin from the kraft pulping process is mainly concentrated and burned as part of the liquor recovery cycle in the kraft pulping. Given its aromatic nature, other uses of lignin include the development of platform chemicals, polymers, and fuels. This work uses lignin to develop carbon fibers to act as supercapacitors. Lignin microfibers were produced using an electrospinning process, carbonized under an inert atmosphere, and activated to increase surface area and improve capacitance. The activation process is shown to improve the specific capacitance of the material. In addition to activation, nanocrystals were grown on the surface of the carbon microfibers as these nanocrystals have been shown to improve the specific capacitance. When both surface modifications are performed to the lignin‐based carbon fiber, it improves the specific capacitance retention regarding scan rate increase during cyclic voltammetry. The specific capacitance for the carbon fiber, activated carbon fiber, Ni(OH)2 carbon fiber, and Ni(OH)2 activated carbon fiber at 10 mV/s are 189, 206, 10, and 103 F/g.