Thermophysical Properties of ZrB₂ and ZrB₂–SiC Ceramics

Abstract

Thermophysical properties were investigated for zirconium diboride (ZrB 2 ) and ZrB 2 -30 vol% silicon carbide (SiC) ceramics. Thermal conductivities were calculated from measured thermal diffusivities, heat capacities, and densities. The thermal conductivity of ZrB 2 increased from 56 W (m K) À1 at room temperature to 67 W (m K) À1 at 1675 K, whereas the thermal conductivity of ZrB 2 -SiC decreased from 62 to 56 W (m K) À1 over the same temperature range. Electron and phonon contributions to thermal conductivity were determined using electrical resistivity measurements and were used, along with grain size models, to explain the observed trends. The results are compared with previously reported thermal conductivities for ZrB 2 and ZrB 2 -SiC.

Lattice thermal conductivity of ultra high temperature ceramics ZrB2 and HfB2 from atomistic simulations

“…The reduction of κ tot relative to single crystals comes primarily from the thermal resistance of grain boundaries. Variations of κ tot with grain size can be substantial 8,10 . For ZrB 2 at 300K, κ e was estimated to be 32W/(m · K) using the WF relation, giving 28W/(m · K) for κ ph .…”

“…Thermal conductivity of polycrystalline ZrB 2 and Hf B 2 has been more thoroughly studied [8][9][10] . Room temperature measurements give 60W/(m · K) for ZrB 2 and 104W/(m · K) for Hf B 2 .…”

Toward Oxidation-Resistant ZrB2-SiC Ultra High Temperature Ceramics

“…Hot Pressing Hot pressing is the conventional method for fabricating UHTCs and has been used extensively, [8][9][10]12,16,17,20,22,27,33,35,39,47,48,[50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65] with typical temperatures of~2173 K (1900°C) and applied pressures between 30 and 50 MPa. It allows full densification without the use of sintering aids, although most research employs modest amounts of sintering aids such as silicides, borides, metals (e.g., Ni), or C to reduce processing times and temperatures, thus reducing the costs associated with the production technique.…”

The thermal shock behavior of Zr3[Al(Si)]4C6 and in situ (ZrB2+ZrC)/Zr3[Al(Si)]4C6 composite

“…As a result, Zr 3 [Al(Si)] 4 C 6 matrix composites reinforced by ZrB 2 and ZrC have been developed in our previous work, in which Zr 3 [Al(Si)] 4 C 6 matrix was toughened and strengthened significantly by the in situ incorporation of ZrB 2 and ZrC [13]. Moreover, in consideration of higher thermal conductivity of ZrB 2 and ZrC compared with monolithic Zr 3 [Al(Si)] 4 C 6 [5,14,15], improved thermal shock resistance of (ZrB 2 + ZrC)/Zr 3 [Al(Si)] 4 C 6 composite should also can be expected. So far, however, there are no relevant reports about the thermal shock behavior of monolithic Zr 3 [Al(Si)] 4 C 6 ceramic and Zr 3 [Al(Si)] 4 C 6 matrix composites.…”