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This paper introduce the formation of alumina matrix composites reinforced with multilayered graphene, graphene oxide and nickel-phosphorus coated multilayered graphene. The powder metallurgy technique followed by the Spark Plasma Sintering (SPS) method were utilized to fabricate the specimens. The influence of graphene-family material additions on microstructure was investigated, and correlated with measurements of mechanical properties. The emphasis of the research has been placed on the tribological performance conducted with the use of the ball-on-disc method under loads of 10 N and 30 N. Both the wear tracks of composites and the corresponding counterparts were carefully analysed, to evaluate the combined influence of mechanical properties and tribofilm formation on the measured wear rates. All results were compared to pure alumina as a reference specimen.

The effect of graphene-based materials: multilayer graphene (MLG), graphene oxide (GO), and nickel-coated graphene (Gn-Ni-P) addition on the mechanical properties of commercial Al2O3–ZrO2 and Al2O3–Ti(C,N) materials is discussed in this paper. The influence of used reinforcements on relative density, microstructure, hardness, and fracture toughness was investigated. Moreover, the combination of strengthening effects deriving from the addition of graphene-based materials and the presence of zirconia or carbon nitride titanium particles was analysed. In order to determine the wear resistance of the obtained composites, tribology test was conducted. The added reinforcement had an evident effect on hardness of the obtained composites in both series, an almost 150 HV5 increase was observed for the TAZ+0.2 wt%GO composites. Fracture toughness remained unchanged or decreased, which was related to the complexity of the Al2O3 + ZrO2 + Ti (CN) + Graphene Family Nanomaterials system. Moreover, an almost 800% decrease of wear rate for the TACN based composite with a 0.2 wt% addition of GO was noted. Other composites also showed an increase in wear resistance depending on the type of matrix, the type of reinforcements and the load applied during the tribology test.

Polytype instability of SiC epitaxial films was the main focus of attention in the experiment performed since this factor has a decisive influence on graphene growth, which was the second stage of the experiment. Layers deposited in various initial C/Si ratios were analyzed. Our observations indicate that the initial C/Si ratio in epitaxial growth is a crucial parameter determining which polytype will be grown, in particular for cubic (3C) or hexagonal (4H) polytypes. If the initial C/Si ratio was close to its final value, the dominant polytype was 4H. On the other hand, when the initial C/Si ratio was close to zero, 3C became the major polytype in spite of a non favourable growth temperature. The results for graphene growth on an epi-SiC layer and a bulk substrate, in which case the dominant polytype was 4H, are also presented. These results indicate that layers on epitaxial 4H-SiC are thicker, more relaxed and have better quality in comparison with samples on 4H-SiC substrates. Morphology and defects in SiC epilayers were analyzed using Nomarsky optical microscopy, scanning electron microscopy (SEM) and high resolution X-ray diffraction (XRD). Graphene quality was characterized by Raman spectroscopy.