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In the present work, the properties of Al2O3nanocomposite prepared via spark-plasma sintering and reinforced with 0.5–2 wt % graphene are studied. Samples with different graphene contents are subjected to measurements of density, microhardness, coefficient of friction of composite–ruby, and frictional wear rate of composite. The fracture and wear track surface are inspected via fractography, and the composite as a whole is examined via X-ray diffraction. The graphene additive is established to increase the microhardness and to decrease the frictional wear rate by two orders of magnitude on account of absence of flaking of grains.

Electrical conductivity (s), relative dielectric permittivity (er) and dissipation factor (D) measured in graphene-alumina composites. Samples obtained by plasma spark sintering (SPS) from a mixture of raw powders: d-alumina (36 nm average particle size) and graphene flakes (3 nm thickness and 2-3 um length). Graphene content in samples was 0, 1 and 2% by weight. The study carried out for frequencies from 50 Hz to 100 kHz. Both c and er were higher for Al2O3-2% graphene: up to 90 uS/m and 19 respectively; while alumina with 1% graphene showed similar values to the pure alumina samples: 50 uS/m to electrical conductivity and 16 to relative permittivity. The dissipation factor was similar in the three materials tested. D increased with the frequency, reaching high values (0.7) at 100 kHz. Composites with 1 and 2% graphene content showed a dissimilar dielectric behavior with the frequency. Alumina reflected a classical behavior of the permittivity dependence with the frequency. Graphene composites also show the same behavior at frequencies above 100 Hz. Below this frequency, the presence of graphene increases the relative permittivity to exceed that from pure alumina. The graphene content leads to rise of relative permittivity, which means easier polarizability.

The ultrasonic dispersion and spark plasma sintering technique have been used to process Al2O3/Graphene nanocomposite (Al2O3/G) with 0-2wt.% graphene. The topography of fracture, microstructure, density, microhardness, Young modulus, electrical and thermal conductivity of Al2O3/G nanocomposite are investigated.