Sagar Kanhere

Chemically oxidized pitch-based carbon fibers used as a redox flow batteries (RFBs) electrode materials proved to increase the electrochemical performance of the battery and the fibers perform on par with the commercial electrode materials.

This study explores the fabrication and mechanical characterization of biocomposite hydrogels composed of poly(vinyl alcohol) (PVA) and lignin. Two series of membranes were developed using bulk, unfractionated lignin and its low molecular weight (LMW) and high molecular weight (HMW) fractions. Membranes were cast from 5 wt % and 10 wt % PVA-DMSO solutions, incorporating lignin at concentrations of 20 wt % and 60 wt % relative to the mass of PVA. The hydrogels were formed via one or three freeze-thaw (F/T) cycles, a method known to enhance physical crosslinking, via crystallization, and improve mechanical performance. Mechanical testing was conducted to assess the influence of formulation parameters on properties such as Young’s modulus and ultimate tensile strength (UTS). In general, an increase in the number of F/T cycles resulted in stiffer hydrogels, particularly for those cast from the 5 wt% PVA-DMSO solution. Among all tested compositions, hydrogels containing LMW lignin consistently exhibited superior mechanical properties. Specifically, the highest hydrated Young’s modulus values — approximately 2 MPa and 4 MPa — were observed in 5 wt % and 10 wt % PVA-based hydrogels, respectively, both containing LMW lignin. Similarly, the highest UTS values, reaching up to 400 kPa, were measured in 10 wt % PVA hydrogels with LMW lignin, while most 5 wt % PVA membranes showed UTS values below 100 kPa. The enhanced mechanical performance of hydrogels containing LMW lignin is likely due to its improved dispersion within the PVA matrix and its greater compatibility during network formation under freeze-thaw cycling. This study demonstrates that lignin molecular weight, concentration, and the number of freeze-thaw cycles can be strategically tuned to fabricate hydrogels with a broad range of mechanical properties. This tunability enables modulus matching across a wide spectrum, offering valuable flexibility for applications in biotechnology, particularly in the design of tissue implants where mechanical compatibility with native tissue is critical.

The low-cost and sustainable non-woven carbon fibers produced from petroleum pitch using a melt-blowing process are shown to be an ideal alternative to expensive polyacrylonitrile-based carbon felt electrode material for redox flow batteries.

Corn stover-derived lignin, a sustainable and cheaper precursor, was ALPHA-fractionated and dry-spun using ethanol solvent to produce carbon fibers with improved properties via faster processing.

Metals are being replaced with high-performance and lightweight polymers, but their low thermal conductivity and poor electrostatic dissipative properties are significant problems. For the protection of sensitive electronic circuitry in automotive and aerospace parts, some device housing materials must provide electrostatic discharge and dissipate heat generated at higher rates as electronic circuits are increasingly miniaturized. Micro-texturing on the film surface can greatly enhance the heat dissipation area and was investigated in this study using low-cost graphite nanoplatelet (GNP)-filled LLDPE films. Micro-finned films (30 vol% GNP) having a 51 ± 10% larger heat-dissipation area were successfully produced using a continuous extrusion process. The through-thickness thermal conductivity of 30 vol% GNP-filled LLDPE was measured at 1.3 W/m·K, which represents a 200% improvement over that of pure LLDPE. For a GNP content of 30 vol%, the surface and volume electrical conductivity of the composite films also increased by 8 orders of magnitude (resistivity down from ≈10¹⁵ to 10⁷ Ω·cm) and electrostatic decay time reduced to a below-resolution limit of 0.01 s, at par with military standard requirements. Thus, micro-fin textured GNP-LLDPE offers a unique combination of electrical and thermal transport desired for the protection of electronic encapsulation materials.