Transient liquid phase sintering of tantalum carbide ceramics by using silicon as the sintering aid and its effects on microstructure and mechanical properties

TaC–NbC formed by spark plasma sintering with the addition of sintering additives

“…%) of B 4 C to TaC and hot pressing at 2100°C. Zhong et al 22) showed a hardness of 13.2 GPa when adding 0.78 wt. % Si to TaC and sintering by SPS at 1700°C.…”

“…While other researchers have seen the formation of TaSi 2 as a result of the addition of Si in the TaC system, this was only seen when adding concentrations greater than 37 vol.%. 14), 22) 3.3 Densification process and sintering mechanisms Figure 5 shows the SPS process outputs of temperature, chamber pressure, and ram pressure as well as the calculated relative instantaneous density of the TaCNbC sample with the addition of 5 vol % B 4 C as the sintering additive. The densification process can be split up into 6 stages (marked on figure) based on the slope of the densification curve with the most significant densification occurring in stages 35.…”

“…Stage 2 did not contain significant densification; however the increase in the chamber pressure could be an indication of a reaction between surface oxides and the silicon which would result in the release of SiO or CO gas. 22) Stages 3 and 4, taking place between 1287 and 1725°C, brings the beginning of significant densification. The densification mechanism attributed to these stages is particle rearrangement by creep flow up to 1413°C (melting point of Si) and then wetting of the TaCNbC particles and the formation of TaSi 2 and SiC.…”

Microstructure and Mechanical Properties of Nanofiller Reinforced Tantalum-Niobium Carbide Formed by Spark Plasma Sintering

“…could not be discerned on the XRD plots [76]. This overlap of SiC has been previously reported when adding Si or SiC to TaC composites but only at concentrations greater than 37 vol.% [39,69].…”

“…Again, stage I densification is a result of the increase of mechanical ram pressure which results in greater powder packing and the release of trapped air. Stage II did not contain significant densification; however the increase in the chamber pressure could be an indication of a reaction between surface oxides and the silicon which would result in the release of SiO or CO gas [69]. Stages III and IV, taking place between 1287°C and 1725°C, brings the beginning of significant densification.…”