Spark plasma sintering of TaC–HfC UHTC via disilicides sintering aids

Microstructure, mechanical properties and oxidation behavior of TaC- and HfC-based materials containing short SiC fiber

“…TaC Young's modulus value of 550 GPa was measured by Lopez-de-la-Torre et al [23]. For hot pressed HfC-based composites with 15 vol% MoSi 2 , hardness up to 19 GPa was obtained [14], and mechanical strength of 450-465 MPa and Young's modulus of 415-434 GPa for pressureless composites with 5-10 vol% of the same sintering additive were measured [16]. There are no recent reports on thermal properties like linear CTE up to 1300 1C in Ar, thermal conductivity up to 1900 1C in Ar.…”

“…Hot pressing, spark plasma sintering and pressureless sintering have been often associated to the use of additives to improve densification and mitigate the severe sintering temperatures [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Small amounts of metals such as Fe, Mn, Co, and Ni, lower the temperature needed for densification [5][6][7]; alternative sintering additives such as B, C, and B 4 C, remove surface oxides on the starting particles enabling densification at 1900-2300 1C [8,9].…”

“…TaC and HfC þ 5 vol% MoSi 2 with relative densities above 90% have been obtained starting from synthesized ultrafine powders [10]. Recently, spark plasma sintering was also used to consolidate Ta 0.8 Hf 0.2 C using MoSi 2 and TaSi 2 as sintering aids at 1650 1C under 30 MPa [19].…”

Nano-(Ta, Zr)C Precipitates at Multigrain Conjunctions in TaC Ceramic with 10 mol% ZrC and 5 mol% Cu as Sintering Aid

“…Because TaC ceramics are extremely hard to densify [2], sintering aids such as C [3][4][5][6], Si [7,8], B 4 C [9,10], SiC [11,12], TaSi 2 [13,14], MoSi 2 [13,15], TaB 2 [9,10,16], and Si 3 N 4 [17] were used to increase densification. In a previous work, TaC ceramics were hot pressed with ZrC plus Cu as sintering aids [18].…”

Effect of carbon fiber crystallite size on the formation of hafnium carbide coating and the mechanism of the reaction of hafnium with carbon fibers

“…In particular, HfC, which possesses one of the highest melting points (3890 °C), excellent phase stability, as well as good thermomechanical and thermochemical properties, is therefore the most attractive candidate for application as a thermal protection barrier, withstanding high temperatures exceeding 2000 °C in severely oxidizing atmospheres [3][4][5]. HfC is often introduced into C/C composites to enhance oxidation and ablation performance, which can efficiently prolong the lifetime of C/C composites in severely ablative environments [6,7].…”