Graphene oxide (GO) incorporation in natural fiber composites has recently defined a novel class of materials with enhanced properties for applications, including ballistic armors. In the present work, the performance of a 0.5 vol % GO-incorporated epoxy matrix composite reinforced with 30 vol % fabric made of ramie fibers was investigated by stand-alone ballistic tests against the threat of a 0.22 lead projectile. Composite characterization was also performed by Fourier-transform infrared spectroscopy, thermal analysis and X-ray diffraction. Ballistic tests disclosed an absorbed energy of 130 J, which is higher than those reported for other natural fabrics epoxy composite, 74–97 J, as well as plain Kevlar (synthetic aramid fabric), 100 J, with the same thickness. This is attributed to the improved adhesion between the ramie fabric and the composite matrix due to the GO—incorporated epoxy. The onset of thermal degradation above 300 °C indicates a relatively higher working temperature as compared to common natural fiber polymer composites. DSC peaks show a low amount of heat absorbed or release due to glass transition endothermic (113–121 °C) and volatile release exothermic (~132 °C) events. The 1030 cm⁻¹ prominent FTIR band, associated with GO bands between epoxy chains and graphene oxide groups, suggested an effective distribution of GO throughout the composite matrix. As expected, XRD of the 30 vol % ramie fabric-reinforced GO-incorporated epoxy matrix composite confirmed the displacement of the (0 0 1) peak of GO by 8° due to intercalation of epoxy chains into the spacing between GO layers. By improving the adhesion to the ramie fabric and enhancing the thermal stability of the epoxy matrix, as well as by superior absorption energy from projectile penetration, the GO may contribute to the composite effective ballistic performance.

The constant concern about environmental issues has led to the growth of researches about eco-friendly materials. Among them, the natural lignocellulosic fibers have already presented their potential in place of petroleum-based synthetics. However, a relevant number of studies still have to deal with their disadvantages, such as the weak bond on the matrices for a composite performance and limited thermal performance. Thus, the present study analyzes a combination of alkaline treatment and graphene oxide coating in hemp fibers, an NLF applied in several products but with few investigations in engineering applications. The hemp fibers were thermally characterized with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The GO-coating was evidenced by the Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Changes in crystallinity were presented by X-ray diffraction (XRD). It was observed an increase of about 4% to 11% of the crystallinity after the alkaline treatment. The thermal stability rose about 13°C in the 10 wt% NaOH-treated and GO-coated fibers, and a change of about 3.5°C was detected for the glass transition temperature. The GO-coating effect was also evidenced by changes in Raman spectra and FTIR curves and was visually detected in the scanning electron microscope (SEM).

This review aims to present the mechanisms of protein interactions with titanium dental implant surfaces. Methods: the analyses were based on searches of scientific articles available in English and Portuguese in PubMed (MEDLINE), Bireme (LILACS), Scielo, Web of Science and Google Scholar. Results: titanium dental implant treatments success rates (95-98%) are mainly due to the biocompatibility of titanium oxide on the implant surface, surgical techniques adopted, good implants manufacturing processes and biomechanical knowledge of the systems. Studies in past decades has empirically developed implant surfaces with significant changes in morphologies, roughness, wettability, surface energy, chemical composition, and chemical groups density or deposited molecules. These changes promoted better protein adsorption, osteoblast adhesion, and changes in the mechanisms involved in osseointegration. Thus, the time to put the implant in function has been reduced and the success rates have increased. In the osseointegration process, at the nanoscale, there is no contact between the bone and the implant surface, but there is the formation of a protein anchorage between the periosteum and the implant with an interface formed by proteins. In all the reactions between the body and the implant surface, the activities of fibronectin and integrin are essential, since they are responsible for transmitting information to the cell for its differentiation, adhesion and mobility. Conclusion: thus, the analyses of protein-implant interactions are indispensable for a better understanding of the performance of osseointegrated dental implants.

Neste trabalho foram preparadas dispersões aquosas de óxido de grafeno (GO) e óxido de grafeno reduzido (rGO), em diferentes tempos de oxidação, com o objetivo de verificar a influência do tempo de oxidação em relação às características das folhas (flakes) finais. As dispersões de GO foram preparadas pelo método de Hummers modificado utilizando os seguintes tempos de oxidação: 4 h; 1 dia; 3 dias; 7 dias e 10 dias. Em seguida, as dispersões de GO foram submetidas ao tratamento de redução com ácido ascórbico, obtendo-se o rGO. As caracterizações das amostras foram realizadas por meio das análises de espectroscopia Raman, espectroscopia de fotoelétrons excitados por raios X (XPS), microscopia eletrônica de varredura (MEV) e difração de raios X (DRX). A espectroscopia Raman mostrou a variação da relação de intensidade entre as bandas D e G (I_D/I_G) à medida que o tempo de oxidação foi aumentado. A análise de XPS exibiu a alteração dos percentuais de carbono (C) e oxigênio (O). Através de análise no MEV foi correlacionada a morfologia dos flakes com o aumento do tempo de oxidação. E por fim, com o auxílio de DRX, foi verificada a variação da distância interplanar.