Light dense materials of the AlB12-SiC system

DOI: 10.62564/M4-PB2030

Pavlo Barvitskyi¹, Tetiana Prikhna¹, Anastasiia Lokatkina¹, Valeriy Muratov², Victor Moshchil¹, Myroslav Karpets<sup>3

1</sup>V. Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine
²Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine
³E.O. Paton Institute of Materials' Science and Welding, Ukraine


The work describes the creation hard AlB12C2-based ceramic materials under by hot pressing and by high pressure-high temperature conditions. The high mechanical performance of the materials we obtained are similar to those of boron carbide, which can be explained by the structural features of B4C and AlB12/ AlB12C2 [1], namely the presence of almost identical structural elements - regular icosahedrons of boron atoms. The possibility of modifying the structure and properties by introducing additives became the reason for conducting research. To obtain the material, sintering of a powder mixture of of αAlB12 and SiC was used. Relatively cheap nanopowders (50-150 nm, with a specific surface area of 21-15 m2/g) α-AlB12 synthesized by PhD. V.B. Muratov (IPM NASU) were used in work [2]. The hot pressing at 30 MPa 1800-1970 оC of two compounds from α-AlB12 nanopowder with 15 (I) and 20 (II) wt.% SiC addition can result in formation of ceramic elements having according x-ray an-is 88 wt.% AlB12C2-12 wt.% Al2O3-SiC(additives) and 85.5 wt.% AlB12C2-14.5 wt.% Al2O3-SiC(additives) phases compositions respectively. Both materials turned out to be light (density rI=2.6 and rII=2.36 g/cm3) and quite dense (porosity PI=5 %; PII=8 %). Samples of the first (I) material were demonstrated HV - 23.3 GPa hardness, fracture toughness K1c - 5.0 MPa•m0.5 and samples of the second (II) material showed HV - 25.6 GPa, K1c - 5.7 MPa•m0.5 accordingly. The sintering under high-pressure apparatus at 4,1 GPa generally allows to reduce sintering temperatures. At a reduced temperature to 1700 oC at 4.1 GPa and holding for 8 min, the samples were perfect on the outside, but with a large amount of internal stress. This material had hardness HV - 25.2 GPa and fracture toughness K1c - 4.2 MPa•m0.5 at density rIIІ=2.75 g/cm3 and porosity PIII=5 %. High performance characteristics of the obtained composites can be explained by the formation of solid solutions in the structure.

Keywords
Refractory borides, hot pressing, mechanical characteristics, functional composites

Acknowledgments
Not provided

References
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