Spark Plasma Sintering Of ZrB2 Research Articles

Fabrication of (Zr,Ti)B2–ZrN–BN composites through reactive spark plasma sintering of ZrB2 and TiN

Mechanical properties and sintering behavior of additive-free and TiN-doped ZrB2 ceramics were studied. Reactive spark plasma sintering method was applied for manufacturing of ceramics at 1850 °C for 6 min under 40 MPa. The impact of TiN addition on the microstructure evaluation, densification, and mechanical feathers was investigated. A porous monolithic ZrB2 with a relative density of 76.5 % was manufactured, while the introduction of 5 wt% TiN resulted in enhancement of relative density to 93.1 %. The formation of (Zr,Ti)B2 solid solution and in-situ h-BN and ZrN phases was proven by microstructural assessments and X-ray diffractometry. Minimizing the grain growth and improving the densification, as the results of TiN addition, led to enhancement in mechanical properties. The values of bending strength, fracture toughness, and Vickers hardness boosted from 187.6 MPa, 1.9 MPa.m½, and 10.1 GPa for additive-free ZrB2 to 606.5 MPa, 4.5 MPa.m½, and 18.8 GPa for (Zr,Ti)B2–ZrN–BN composite.

Densification mechanism of spark plasma sintered ZrB2 and ZrB2-SiC ceramic composites

Sintering mechanisms are investigated by determining activation energy of densification (in the temperature range of 1650 °C to 1950 °C) during spark plasma sintering of ZrB2 and SiC-reinforced ZrB2 ceramic composite. The fractured surfaces of sintered composites reveal completely dense microstructures above 1800 °C, whereas porous microstructure prevailed in ZrB2 even after sintering at 1950 °C. Activation energy of 80 ± 16 kJ/mol is obtained for ZrB2 with grain boundary diffusion as governing diffusion mechanism in the temperature range of 1650 to 1950 °C. On the other hand, dominant densification mechanism of grain boundary diffusion (activation energy of 89 ± 19 kJ/mol) estimated in the range of 1650 to 1800 °C changed to lattice diffusion (activation energy of 601 ± 10 kJ/mol) with the addition of 20 vol% SiC in ZrB2. The change of prominent densification mechanism in ZrB2 with SiC, in addition to its impact on the mechanical performance with systemic increase of sintering temperature, is unravelled here.

Densification, mechanical and tribological properties of ZrB2 by SPS: Effect of pulsed current

The influence of direct current pulse on–off patterns on spark plasma sintering of ZrB2 on densification, mechanical and tribological properties has been investigated systematically. The experimental data showed that the maximum relative density (98.65%) is achieved at 50ms pulse on (ton) and 5ms pulse off (toff) time conditions. The maximal Vickers hardness, fracture toughness (DCM) at 1kgf load, wear volume and wear rate at 10N load of the ZrB2 sample (ton=50ms and toff=5ms pulse conditions) were 16.64GPa, 4.69MPa√m, 4.05×104μm3 and 1.01×10−3mm3/N·m, respectively. The electric current delivered during SPS processes in different ‘on–off’ pulse patterns plays a vital role in consolidation and desired structural properties.

Erratum to: “Spark Plasma Sintering of ZrB2- and HfB2-Based Ultra High Temperature Ceramics Prepared by SHS”

Erratum to: “Spark Plasma Sintering of ZrB2- and HfB2-Based Ultra High Temperature Ceramics Prepared by SHS”

Spark plasma sintering of ZrB2- and HfB2-based Ultra High Temperature Ceramics prepared by SHS

The combination of the SHS technique and the Spark Plasma Sintering (SPS) technology was adopted in this work for the fabrication of fully dense MB2-SiC and MB2-MC-SiC (M = Zr, Hf) Ultra High Temperature Ceramics (UHTCs). Specifically, Zr or Hf, B4C, Si, and (for the cases of ternary systems) graphite powders were first reacted by SHS to successfully form the desired composites. The resulting powders were then subjected to consolidation by SPS. In particular, by setting a dwell temperature level of 1800°C, a mechanical pressure of 20 MPa, and a non-isothermal heating time of 10 min, products with relative densities ≥98.5% were obtained for the all systems investigated within 30 min of total processing time. The characteristics of the resulting dense UHTCs, i.e. hardness, fracture toughness, and oxidation resistance, are similar to, and in some cases superior than, those related to analogous products synthesized by alternative, less rapid, methods.