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New superhard B 12-nC3Me n boride♣

Z. ZAKHARIEV1,* , M. BESHKOVA2, V. BLASKOV1, I. STAMBOLOVA1, C. PERCHEMLIEV1

Affiliation

  1. Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, bl11 Acad. G Bonchev St., 1113 Sofia, Bulgaria
  2. Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia, Bulgaria

Abstract

The aim of this paper is to study the microhardness of boride composite materials B l2C 3+MexIV-VI B y sintered without pressing, and to elucidate the reasons for the drastic increase of the hardness of B 12C 3 (50 - 77 GPa). This increase, as compared with HP-high pressure- B 12C 3 (29-34 GPa) was established. XRD data show that the lattice parameter c of B 12 C 3 decreases significantly from 12.12 to 12.02 Å after sintering of the composite materials B 12 C3 +MexB y. The dissolution of the transition metal into the crystal lattice of B 12C 3 led to the formation of new superhard ternary borides with formulae B 12- nC 3Me n. The hardness of the new ternary borides exceeded considerably that of pure B 12 C3 , and was equal to the hardness of cubic-BN and some synthetic diamonds of the type "CB" or "Carbonado ACPK"..

Keywords

Composite materials, Powder metallurgy, Mechanical properties, Hardness.

Submitted at: Nov. 5, 2008
Accepted at: Oct. 3, 2009

Citation

Z. ZAKHARIEV, M. BESHKOVA, V. BLASKOV, I. STAMBOLOVA, C. PERCHEMLIEV, New superhard B 12-nC3Me n boride♣, Journal of Optoelectronics and Advanced Materials Vol. 11, Iss. 10, pp. 1533-1536 (2009)