Staff

Abstract:
In this study, we investigate the thermal reduction of graphene oxide using high-temperature annealing in various gas atmospheres: Argon, 10% CO in Argon, and 10% CH4 in Argon. Graphene oxide was synthesized, chemically pre-reduced, and dried before undergoing reduction in these controlled atmospheres. To evaluate the impact of different gases on the reduction process, we conducted a series of characterizations, including combustion analysis for C/O ratio, Raman spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller surface area measurements, and electrical conductivity testing. The results demonstrated that the presence of methane during annealing notably increased the reduction rate and induced other changes in the material properties, whereas the use of CO had no significant impact on the final material.

Abstract:
The production and verification of microwave absorbers are a subject of high priority. These are due to the fast development of telecommunication technologies and the need to reduce electromagnetic pollution. Such materials are implementable in multiple industries, including military, medical, and laboratory equipment. One should remember that the desired material should exhibit a high total shielding effectiveness SE T and controllable performance properties. In this work, an ultrathin graphene oxide paper is fabricated and verified as a wide-range, controllable microwave absorber. Stepwise (100 ∘ C – 200 ∘C – 300 ∘C) thermally reduced G-Flake graphene oxide paper of 4.95 μm thickness revealed the conductivity of 1.86 S/cm. A mild level of reduction was proven with combustion elemental analysis, resulting in a 22.4 oxygen percentage (50.9 % before the reduction). Raman spectroscopy suggested the limitation of Stone-Wales defects after heat treatment. Microwave absorption was measured in the W-band frequency region, and the SET/t parameter reached 606 dB/mm for a c.a. 5-μm-thick individual reduced paper sheet. The controlled increase in conductivity resulted in conduction losses, and the occurrence of pores enabled scattering, while the absorption remained the primary shielding mechanism.

Abstract:
The purpose of this study is to present a novel method for producing mechanically strong epoxy composite laminates of different compositions, reinforced with basalt fabric and reduced graphene oxide flakes. The laminates are prepared with basalt fabric, which is subjected to low-temperature plasma treatment. This approach is aimed to enhance the adhesion of fabric to resin filled with reduced graphene oxide flakes. Physical properties, adhesion, and mechanical properties of the obtained materials are determined. Based on the experiments, it is found that the tensile strength is improved by 6–21% after using reduced graphene oxide filler, 9–23% after plasma treatment, and up to 27% using the combination of plasma and reduced graphene. It is found that the highest improvement of tensile strength is obtained for epoxy composite with 0.5 wt% graphene-based filler and 3 min basalt fiber plasma treatment with 25 W plasma power.