In this study, the influence of different carbon fillers on the tribological and manufacturing properties of the thermoplastic polyamide PA6 is presented. The following materials were used as carbon additives: glassy carbon (GC), carbon obtained from the pyrolysis of polymer wastes (BC), and graphene oxide (GO). Fillers were introduced into the PA6 matrix by mechanical stirring in alcohol to settle carbon particles onto the granule surface. Samples were made by injection molding from the produced granules. The microstructure, hardness, and melt flow index (MFI) of the prepared materials were determined. Also, the degree of crystallinity of the samples was examined by Differential Scanning Calorimetry (DSC) and X-ray Diffraction (XRD). The melting point (Tm) was examined using DSC, the results from which allowed the correct heat treatment of PA6 to increase the crystallinity of the obtained material to be selected. The dry sliding tribological behavior of the composites was evaluated via pin-on-block tests against cast iron counterparts. The tests were performed at room temperature, with a sliding speed 0.1 m/s, a sliding distance of 250 m, and a normal force of 40 N. The obtained results revealed that the introduction of GO into the PA6 matrix provides favorable wear behavior, such as the formation of debris that acts as rollers that give a decrease in wear and a lower coefficient of friction. The coefficient of friction in samples with graphene oxide was nearly two times lower than with other samples. However, the ease of manufacture of this material was drastically reduced compared to GC or BC fillers. Microstructural investigations of wear tracks revealed poor adhesion between the polymer matrix and micrograins of carbon fillers (GC and BC), and therefore their influence on tribological properties was less compared to graphene oxide.

Aluminium-based hybrid composites are a new class of advanced materials with the potential of satisfying the demands in engineering applications. This paper describes the effects of carbon addition on the formation and properties of AMC with SiC nanoparticles reinforcement. The composites were produced via mechanical alloying followed by hot pressing. Three forms of carbon, graphite (GR), multiwalled carbon nanotubes (CNTs), and, for the first time, glassy carbon (GC), were used for the hybrid composites manufacturing and compared with tribological properties of Al-SiC composite without carbon addition. GC and CNTs enhanced formation of Al-SiC composite particles and resulted in a homogeneous distribution of reinforcing particles. On the other hand, GR addition altered mechanochemical alloying and did not lead to a proper distribution of nanoparticulate SiC reinforcement. Hot pressing technique led to the reaction between Al and carbon as well as SiC particles and caused the formation of Al₄C₃ and γ-Al₂O₃. The subsistence of carbon particles in the composites altered the predominant wear mechanisms since the wear reduction and the stabilization of the friction coefficient were observed. GC with simultaneous γ-Al₂O₃ formation in the hybrid Al-SiC(n)-C composites turned out to be the most effective additive in terms of their tribological behaviour.

In this study, we present a new composite material that was developed using the pressure infiltration method. In this composite, carbon reinforcement in the form of an open-celled rectangular foam (C_of) was applied, and pure magnesium with two commercial magnesium cast alloys (AZ31, RZ5) was used as the matrix. We examined the microstructure (LM, SEM + EDS) of composites as well as the density, porosity, hardness, compressive strength, flexural strength and tribological properties in dry conditions. It was revealed that the chemical composition of the matrix had a significant impact on the macrostructure, microstructure and properties of the composite. The matrix with rare elements (RZ5) induced poor infiltration of C_of and physicochemical degradation of the reinforcement, while pure magnesium ensured good infiltration, a stable friction coefficient and low wear. For the AZ31 alloy, the effects of infiltration were good; however, an increase in the tribological properties was not observed. Compared with the as-cast matrix materials, the presence of carbon foam in both pure Mg and AZ31 alloy induced an increase in compressive strength and stiffness as well as a decrease in flexural strength. Furthermore, SEM examination of the fractured and wear surfaces microstructure showed structural effects’ dependence on the matrix composition.

This paper presents the information about manufacturing processes of hybrid composites with aluminum alloy matrix containing glassy carbon as a solid lubricant. Two methods have been described: the method based on mixing glassy carbon and ceramic particles with a liquid metal matrix; and the precursor method. In the precursor method, carbon is introduced into a composite with the application of liquid precursor and porous ceramic foams. It is then followed by precursor pyrolysis where, as the result, glassy carbon is obtained. Ceramic foams help liquid precursor penetrate the ceramic spheroid pores by forming a thin film of glassy carbon on their walls. Composites produced by the both methods feature good tribological properties. Sliding friction coefficient in air of the new obtained by mixing method composite against cast iron (μ = 0.08 − 0.17 at wearing in and 0.12 after wearing in by reciprocating sliding and 0.14 − 0.17 by rotating sliding) is much lower than in the case of composite containing only ceramic foam as a reinforcing phase (μ = 0.28 − 0.36 by reciprocating sliding and 0.28 − 0.40 by rotating).

This article sought to determine the response of a carbon foam material derived from polyurethane foam when subjected to a quasi-static compression load. The effects of the foam pore densities and additives (solvents) on the compression strength, compressive modulus, and surface morphology of the carbon foam were investigated. In this study, three different carbon foam pore densities (20, 40, and 60 ppi) and three solvents for the phenol–formaldehyde resins that coated the polymer foam (acetone, ethanol, and methanol) were used. Carbon foams were derived from polyurethane foams by carbonization. Quasi-static compression testing was carried out using a universal testing machine. The compressive strength, compressive modulus, and relative density of these different carbon foams were computed and compared. Two-way ANOVA analyses were performed to compare the significance of solvents and pore density. These results showed that pore density and solvents significantly affected the compressive strength, compressive modulus, and surface morphology of the fabricated polyurethane-derived carbon foam. Finally, the maximum compressive strength and maximum compressive modulus were observed in carbon foam (60 ppi) with 40% methanol as the solvent. Conversely, a minimum compressive strength was observed for a 20 ppi carbon foam with a 20% acetone solvent, and a minimum compressive modulus was observed for a 20 ppi foam with 40% methanol. Lastly, the chemical composition of the polyurethane foams was investigated, and these results indicated that the polyurethane-derived carbon foam had 96% carbon atoms after carbonization.

The magnesium matrix composite reinforced with 3 vol. % of short carbon fibers (Csf), fabricated, under industrial conditions, by the stir casting method, was applied to obtain composite bars by two extrusion methods: the novel method of cold severe plastic deformation with a forward-backward rotating die (KoBo) and conventional extrusion at 400 °C. The effect of Mg(α) grain refining, as well as fibers behavior and phenomenon at the fiber-matrix interface, was examined by optical microscopy, scanning electron microscopy with energy dispersive spectroscopy and scanning-transmission electron microscopy methods. The Mg(α) grain quantitative characteristics revealed a decrease of the equivalent diameter from 219 ± 76 μm (as-cast) to 24 ± 10 μm and 0.89 ± 0.35 μm (the hot-extruded and KoBo-processed, respectively). In addition, due to the KoBo application, except for the Csf orientation that was parallel to the extrusion direction, an effect of fibers fragmentation on the length of few Csf diameters was detected. No significant changes in the Csf-matrix interface (besides those between new carbon surfaces) formed by fibers fragmentation, and the matrix created by extrusion were detected. A comparison of the mechanical properties of the Mg-Csf composite showed that the KoBo method ensured a spectacular increase in strength and plasticity.