The results of studying the thermal conductivity of hot-pressed AlB
12
–AlN ceramic composites with different AlN concentrations were presented. The thermal conductivity coefficient was measured for ...composite specimens at room temperature and approximated for AlB
12
.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The correlations between structures and mechanical characteristics of α-AlB12-, AlB12C2-, B4C-based lightweight ceramics and composites synthesized or sintered by hot pressing (at 30 MPa) and ...SiC-based ceramics obtained by reactive sintering are compared. The effect of C, TiC and SiC additions on the properties of the resultant composites and the particularities of the ceramics destruction under shock loading are discussed. Ballistic tests performed on 10 mm thick plates fabricated from the developed ceramics (2.63 g/cm3 density; 78 wt% B4C and 22 wt% SiC composition according to X-ray diffraction analysis; B3.64CSi0.01 and SiC1.07 stoichiometry according to SEM microprobe X-ray analysis), showed that the material could withstand a 10 m distance shot using a bullet with initial kinetic energy of 3.7 kJ.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The structure, mechanical characteristics, and high-temperature stability in vacuum and air of ZrB
2
and HfB
2
-based materials sintered at a high quasi-hydrostatic pressure (4.1 GPa) under hot ...pressing (at a pressure of 30 MPa) with and without SiC and Si
3
N
4
additives have been studied. It has been shown that short-term sintering (4 min) under high pressure conditions and at a comparatively low temperature (1800°C) essentially improves the mechanical properties of these materials as compared to the similar materials synthesized by the other method (hot pressing and spark-plasma sintering). In the case of sintering at a high pressure (4.1 GPa), the addition of 20 wt % SiC to ZrB
2
and 30 wt % SiC to HfB
2
leads to a decrease in the specific gravity of ZrB
2
and HfB
2
and increases their hardness by 17 and 46% and fracture toughness by 40 and 21%, respectively. When SiC is added, there occurs the formation of solid solutions through the mutual diffusion of C and Si into the ZrB
2
or HfB
2
matrix phases and the slight diffusion of Zr and Hf into SiC-enriched areas. The improvement of the mechanical properties of ZrB
2
and HfB
2
sintered at a high pressure without additives is explained by the formation of stronger bonds between the sintered material grains. The addition of SiC to ZrB
2
slightly decreases the Young modulus, but increases the damping ability of the synthesized materials. The simultaneous addition of SiC and Si
3
N
4
to ZrB
2
leads to an increase in the hardness to a smaller extent, but results in a further increase in fracture toughness. The melting temperature in vacuum of sintered ZrB
2
and HfB
2
has proven to be much higher as compared to the materials with SiC additives. The composite material synthesized from a HfB
2
–30 wt % SiC mixture has a density ρ = 6.21 g/cm
3
, a microhardness
H
V
(9.8 N) = 38.1 ± 1.4 GPa,
H
V
(49 N) = 27.7 ± 0.24 GPa,
H
V
(98 N) = 26.3 ± 2.03 GPa, and a fracture toughness
K
І
с
(9.8 N) = 8.2 ± 0.2 MPa m
0.5
,
K
І
с
(49 N) = 6.8 ± 0.6 MPa m
0.5
,
K
І
с
(98 N) = 6.4 ± 0.11 MPa m
0.5
, which are much higher than the similar characteristics of HfB
2
sintered under the same conditions, but without the additives.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The structural characteristics and the results of a comprehensive study of the mechanical properties of the B
4
C and AlB
12
ceramic specimens and composites prepared from the B
4
C + 5–25 wt % SiC ...and AlB
12
+ 10–20 wt % TiC mixtures by hot pressing under a pressure of 30 MPa in the temperature range of 1950–2200°C by ultrasound, static, and dynamic methods are presented. The level of achieved mechanical characteristics of the developed composite materials makes them promising for manufacturing armor protection components and other products subjected to substantial dynamic loads. It is shown that one can use disk specimens made of brittle materials with a diameter of 5–15 mm to determine the strength under dynamic loads. The methods developed in the Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine are used for studying the synthesized ceramic materials.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The structures and mechanical properties of materials based on α-AlB12 without additives and with additions of carbon and titanium carbide sintered under high (2 GPa) pressure and by hot pressing (30 ...MPa) in the contact with hexagonal BN. The light materials were obtained having high hardness, fracture toughness, ultimate strengths at bending,
R
bm
, and compression. The addition of 17 wt % C to α-AlB
12
and sintering at 30 MPa makes possible to achieve fracture toughness
K
I
c
(49 N) = 5.9 ± 1.4 MPa·m
0.5
, hardness
H
V
(49 N) = 23.6 ± 2.8 GPa, bending
R
bm
= 310 MPa and compression
R
cs
= 423 MPa strengths and specific weight was γ = 2.7 g/cm
3
. The addition of 20 wt % TiC to α-AlB
12
and sintering at 30 MPa resulted in the formation of AlB1
2
C
2
and TiB
2
, increase of the hardness
H
V
(49 N) = 28.9 ± 1.9 GPa,
R
bm
= 633 MPa,
R
cs
= 640 MPa and γ = 3.2 g/cm
3
, the
K
I
c
(49 N) = 5.2 ± 1.5 MPa·m
0.5
.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The results are presented on the investigation of the structure and mechanical properties of hot-pressed materials based on AlB
12
C
2
powders of sizes 50–150 nm. It is shown that the consolidated ...materials having mechanical properties comparable with boron carbide may be produced at essentially lower (by 270–300°C) sintering temperatures. It has been established that the heating rate at compressing affects the stoichiometry of the impurity phase containing Al, B, O, which define the difference in mechanical properties of the materials (a decrease of the heating rate results in the insignifical decrease of the material hardness and increase of the fracture toughness).
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We would like to inform you that a sad mistake was made in one of our articles in “Journal of Superhaed Materials”, 2017, vol. 39, no. 5, pp. 299–307. The article is “Structure and Properties of ...Superhard Materials Based on Aluminum Dodecaboride α-AlB
12
” by T. A. Prikhna, P. P. Barvitskyi, M. B. Karpets, V. B. Muratov, V. B. Sverdun, P. Khaber, V. V. Kartuzov, V. E. Moshchil’, S. N. Dub, M. G. Loshak, L. I. Aleksandrova,V. V. Kovylyaev, V. V. Garbuz, and A. A. Marchenko.
Thus, the author’s name P. Khaber should be replaced by R. Haber.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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