Publications

The feasibility of carbon nanofibers (CNF) to impart transport properties to a flexible and ductile polyethylene matrix for electromagnetic compatibility (EMC) was assessed in contrast to traditional carbon fibers (CF). Raman spectroscopy and electrical resistivity measurements of the bulk of the carbon fillers showed that commercial Pyrograf-III, PR-19 grade CNF were significantly more amorphous with lower transport properties than Thornel P-55 CF. A range of CNF/polyethylene nanocomposites (concentrations 0–40 wt %) were prepared via twin-screw extrusion and their electrical, dielectric, electrostatic dissipation, electromagnetic shielding, and mechanical properties were investigated. Good dispersion was revealed by electron microscopy, demonstrating the dispersibility of CNFs. PR-19 CNF led to superior surface conductivity and electrostatic dissipation at low concentrations. Nevertheless, the microcomposites prepared with P-55 pitch-based CF led to higher electromagnetic shielding (∼11 dB), electrical conductivities (i.e., surface resistivity of 1.4 × 10³ Ω/sq), and relative permittivity (72.2–81.5j) at larger concentrations, displaying an in-plane anisotropic behavior. The microcomposites, though, displayed a stiff (modulus ∼1.4 GPa at 40 wt %), weak (breaking strength of only ∼3 MPa at 40 wt %), and brittle behavior (<3% at 40 wt %), whereas the nanocomposites retained acceptable flexibility (modulus ∼1 GPa), strength (∼10 MPa), and ductility (∼30%) at comparable concentrations. This study points out the feasibility of pristine CNFs for flexible thin-wall materials for EMC applications.

In this work, we comprehensively report on the synthesis of octadecylamine (ODA)-functionalized graphene (G-ODA) and compare its performance to those of graphene nanoplatelets (GNPs) and graphene oxide (GO) as asphalt binder modifiers. An exploration into the mechanisms through which asphalt binder properties are enhanced by each graphene-based material has been conducted, identifying the one that demonstrates superior compatibility with asphalt. The study systematically evaluates the performance of each modifier, analyzing viscosity, rheology, anti-aging properties, morphology, and chemical transformations within asphalt binders. Experimental results indicate that all three graphene-based modifiers enhance the high-temperature performance and aging resistance of the asphalt binder, with GO emerging as the most compatible material, exhibiting superior performance across all investigated responses. The rheological properties results show that GO can improve G*/sin(δ) for the unaged binder by about 120%, followed by G-ODA and GNP. On the contrary, multiple stress creep and recovery (MSCR) results indicate that both GO and GNP efficiently reduce permanent deformation, with reductions in Jnr of about 39% and 34%, respectively while the G-ODA shows a smaller reduction of − 10%. Additionally, GO excels in improving elastic response, showing a substantial increase in percent recovery at 297%, compared to 48.4% with GNP and 28.8% with G-ODA. Fourier-transform infrared spectroscopy (FTIR) analysis establishes the absence of evidence indicating chemical interaction between any of the graphene-based materials and asphalt molecules. This suggests that the improvement is solely attributed to physical interaction, specifically through π-π interaction. On the other hand, AFM phase images indicate that all graphene-based materials can alter the morphology of asphalt binders. They increase the projected surface area of the Peri/Catana phases, which can influence the rheological properties of the binder.

While graphene nanoplatelets (GnPs) have emerged as promising nano-modifiers of asphalt binder in recent years, much is still unknown in terms of the existing correlations between the physical, chemical, and geometric characteristics of this nanofiller and observed asphalt binder properties. In this work, we investigate the important correlation between the geometric characteristics of GnPs and the rheological properties of the GnP-modified asphalt binder at high temperatures. Our results indicate that, in general, incorporating GnPs with large mean particle diameters (> 14 μm) and thicknesses (> 8 nm) enhances the high-temperature performance of the asphalt binder. The results of the multiple stress creep and recovery tests confirm that including GnPs in asphalt binder can decrease its permanent deformation by 33.2% and enhance its elastic recovery by 53.9%. Phase contrast images obtained by atomic force microscopy further indicate that the presence of GnPs with large mean particle diameters alters the morphology of the asphalt binder, leading to improved temperature stability and less susceptibility to permanent deformation.

A cutting-edge method that uses electromagnetic (EM) energy for the melt processing of thermoplastic polymer nanocomposites (TPNCs) is reported. The properties and microstructures of TPNCs produced via the proposed EM-processing method and TPNCs via conventional heat processing are contrasted. The EM-processed TPNCs prepared with EM-susceptible carbon nanotubes (CNTs) exhibited a significant enhancement in transport and mechanical properties, outperforming the conventionally processed TPNCs. Thus, the EM-processed TPNCs demonstrated an ultralow electrical percolation threshold (∼0.09 vol %) and a remarkable increase in volume electrical conductivity of 8 orders of magnitude (i.e., 1.1 × 10^–5 S/m) at only 1.0 wt % CNT loading, compared to their hot-pressed counterparts. This highlights the superior network formation, level of segregation, and structuring enabled by EM processing. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) revealed that EM-processed TPNCs exhibited higher crystallinity (∼9% higher) and a predominantly α crystal phase compared to the hot-pressed TPNCs. Microstructural inspection by electron microscopy disclosed that EM processing led to segregated but interconnected multiscale networks of a thin and well-defined CNT interphase that encompassed from the nanoscale of the CNTs to the macroscopic scale of TPNCs. In contrast, conventional processing developed a more diffused CNT interphase with less interconnectivity. The EM-processed TPNCs developed a statistically higher stiffness (+20%) and in certain cases, even better strength (+10%) than the hot-pressed TPNCs. However, the EM-processed TPNCs displayed significantly lower ductility, owing to their higher crystallinity, more brittle crystal α phase, and the potential formation of microvoids in the bulk of the TPNCs inherent to the unoptimized EM processing. This work provides an understanding of an alternative and unconventional processing method capable of achieving higher structuring in nanocomposites with advanced multifunctional properties.

Although water is essential for life, as per the United Nations, around 2 billion people in this world lack access to safely managed drinking water services at home. Herein we report the development of a two-dimensional (2D) fluorinated graphene oxide (FGO) and polyethylenimine (PEI) based three-dimensional (3D) porous nanoplatform for the effective removal of polyfluoroalkyl substances (PFAS), pharmaceutical toxins, and waterborne pathogens from contaminated water. Experimental data show that the FGO-PEI based nanoplatform has an estimated adsorption capacity (q_m) of ∼219 mg g^–1 for perfluorononanoic acid (PFNA) and can be used for 99% removal of several short- and long-chain PFAS. A comparative PFNA capturing study using different types of nanoplatforms indicates that the q_m value is in the order FGO-PEI > FGO > GO-PEI, which indicates that fluorophilic, electrostatic, and hydrophobic interactions play important roles for the removal of PFAS. Reported data show that the FGO-PEI based nanoplatform has a capability for 100% removal of moxifloxacin antibiotics with an estimated q_m of ∼299 mg g^–1. Furthermore, because the pore size of the nanoplatform is much smaller than the size of pathogens, it has a capability for 100% removal of Salmonella and Escherichia coli from water. Moreover, reported data show around 96% removal of PFAS, pharmaceutical toxins, and pathogens simultaneously from spiked river, lake, and tap water samples using the nanoplatform.