Reinforcement of Epoxy Resin by Additives of Amine-Functionalized Graphene Nanosheets

Optimizing dielectric constants of epoxy composites infused with Palmyra palm and nano fillers using response surface methodology

The study focuses on Palm fruit Fibers (PF) extracted from the palmyra palm tree (Borassus flabellifer) treated with 5 % alkali solution (NaOH). This treatment eliminates impurities from the fiber surface and enhances bonding with the epoxy matrix. Epoxy composites, reinforced with PF/nanofillers (h-BN, Al2O3 and MWCNT), are developed by using the box Behnken method (BBD) and dielectric constant is investigated under high-frequency and electrical field conditions. Dielectric constants (K) of the nanocomposites are determined using various capacitor terminal setups. The electrical properties of the Epoxy/PF nanocomposite, based on fiber content (Wt. %), fiber mesh size (μm) and nanofillers are evaluated using response surface methodology (RSM). Models, predicting nanocomposite dielectric constants, are established, fitting experimental values closely with R2 nearing 1 and residuals adhering to a normal probability plot. The optimized dielectric constant of 1.05 is achieved at 3 wt% palm fiber content, 150 μm fiber mesh size and 1 wt% nano h-BN.

A First-Principles Study of Anion Doping in LiFePO4 Cathode Materials for Li-Ion Batteries

Doping anions into LiFePO4 can improve the electrochemical performance of lithium-ion batteries. In this study, structures, electronic properties and Li-ion migration of anion (F- , Cl- , and S2- ) doping into LiFePO4 were systematically investigated by means of density functional theory calculations. Anion substitution for oxygen atoms leads to an expansion of the LiFePO4 lattice, significantly facilitating Li-ion diffusion. For Cl- and F- anion doped into LiFePO4 , the energy barrier of Li-ion migration gets lowered to 0.209 eV and 0.283 eV from 0.572 eV. The introduction of anions narrows the forbidden band of LiFePO4 , enhancing its electronic conductivity. This work pays a way towards the rational design of high-performance lithium-ion batteries.

Corrosion Resistance and Thermal Conductivity Enhancement of Reduced Graphene Oxide–BaSO4–Epoxy Composites

The results of studies on the corrosion protectiveness and thermal conductivity of reduced graphene oxide–BaSO4 epoxy composites are reported here. A commercial epoxy resin and reduced graphene oxide (rGO) were blended with a hardening reagent and then mixed with prepared BaSO4–epoxy resin (B–epoxy). The reduced graphene oxide–BaSO4–epoxy composite (rGO–B–epoxy) paste was used to coat the surfaces of Al 7205 alloy and the corrosion and thermal properties were investigated. A corrosion test in a 3.5 wt% synthetic sea water solution showed that the composite coating containing BaSO4 had the best corrosion resistance. Moreover, the rGO–B–epoxy composite showed better protection against corrosion than the epoxy alone. The rGO–B–epoxy composite with 5 wt% BaSO4 had an in-plane coefficient of thermal conductivity of approximately 165.0 W/m K, and the in-plane thermal diffusivity was 71.38 mm2/s. In standard thermal conductivity tests, all three samples had values below 40 W/m K. The rGO–B–epoxy composites showed good surface corrosion protection and in-plane thermal conductivity.

Mechanical Performances of Phenolic Modified Epoxy Resins at Room and High Temperatures

Epoxy is an important resin matrix and has been widely applied in laminated composites as a coating or adhesive material. In this article, the phenolic was applied to modify the mechanical properties of epoxy resin. The phenolic modified epoxy resins with various phenolic content were prepared via a polytetrafluoroethylene mould, and the phenolic modified epoxy-based plain woven laminated composites (PWLCs) were manufactured via vacuum assisted resin transfer method for further study of phenolic modified epoxy resins’ mechanical properties. The compression tests were performed perpendicularly to thickness at 2 mm/min to investigate the mechanical performances of phenolic modified epoxy resins and epoxy-based PWLCs. The results showed that the addition of phenolic into epoxy could improve the mechanical performances of epoxy resins and epoxy-based composites at room temperature, and the phenolic influenced epoxy-based PWLC more than epoxy matrix at room temperature. However, at high temperatures, the addition of phenolic decreased the mechanical performances of epoxy resins and epoxy-based composites, and the adverse effect of phenolic became more serious with the increase of phenolic content at high temperature. In addition, the thermogravimetric analyses were also conducted from 30 °C to 800 °C on phenolic modified epoxy resins and the results showed that the phenolic modified epoxy resin had an earlier loss in weight than unmodified epoxy resin. The earlier loss in weight meant that the addition of phenolic into epoxy resin led to the formation of unstable molecules at high temperature.

Variable-Angle Spectroscopic Ellipsometry of Graphene-Based Films

A review of the authors’ research works on Variable-Angle Spectroscopy (VASE) of graphene-based films is presented. The interaction of graphene oxide (GO) with magnetron-sputtered metals is a promising research area. VASE optical models of GO thin films deposited on magnetron-sputtered titanium (Ti), silver (Ag) and gold (Au) are discussed. Moreover, the optical properties of graphene nanoplatelet (GNPS) films and reduced graphene oxide (RGO) stabilized with Poly(Sodium 4-Styrenesulfonate) (PSS) films, which are less studied graphene-related materials, are shown. Finally, different optical behaviors of chemical vapor deposition (CVD)-grown monolayer, bilayer, and trilayer graphene films on silicon and polyethylene terephthalate (PET) substrates are recapitulated.