Tetiana Prikhna

Abstract:

The results of a structural and mechanical properties study of aluminum dodecaboride (a-AlB₁₂, AlB₁₂C₂, a-AlB₁₂-TiB₂-TiC)- and boron carbide (B₄C and B₄C-SiC)-based ceramics, hot pressed at 30 MPa, 1950 - 2240°C, and high pressure (2 GPa) as well as high temperature (1200-1400°C) sintered and synthesized, will be under discussion. The materials can be used as protective armor or constructional ceramics for nuclear power plants, additives to the boron-carbide-based materials, or as solid fuel, abrasives, explosives, etc. [1-5]. The materials were manufactured from a-AlB₁₂, AlB₁₂C₂, C nanopowders and B₄C, SiC, TiC micropowders. The preliminary mixtures of powders were prepared using high speed planetary activator. The a-AlB₁₂ powder with and without carbon additions can be sintered to the dense state of 1200-1400°C, 2 GPa, 1 h, while the hardness of the materials was not high (12.5-17.8 GPa at 49 N-load). The AlB₁₂C₂ nanopowder sintered at 1400°C, 2 GPa, 1 h contained 89 wt.% AlB₁₂C₂ and 11 wt.% of admixture Al₂O₃ (according x-ray diffraction study) and demonstrated hardness HV(49 N-load)=26.6-0.6 GPa, fracture toughness K_1<i>c</i> (49 N)=5.9-0.5 MPa-m0.5, density g=2.73 g/сm³. The materials obtained at 30 MPa, 2240-1950°C had much higher characteristics. γ-AlB₁₂ (94-98 wt.%, p=2.53-2.58 g/cm³) showed HV(49 N)=24.1 GPa; K_1<i>c</i> (49 N)=4.9 MPa-m0.5; bending R_bs=336 MPa and compressive R_cs=378 MPa strengths. Composite 74 wt.% AlB₁₂C₂, 22 wt% TiB₂ , 4 wt% Al₂O₃ (p=3.1 g/сm3) had HV(49N)=37.65-6.74 GPa, K_1<i>c</i>(49 N)=5.2 MPa-m0.5, R_bs = 646 MPa and R_cs =795 MPa. B4C(p=2.52 g/сm3) demonstrated HV(4.9 N)=40 GPa, K_1<i>c</i> (3-point bending)=4.89 MPa-m0,5, R_cs=392 MPa, R_cs=1551 MPa and B₄C-20%SiC (p = 2.67 g/cm³) had HV(49 N)= 35 GPa, K_1<i>c</i>(3-point bending)=5.9 MPa-m0,5, R_bs=474 MPa, R_cs=1878 MPa.