Synergistic effects of Si₃N₄ and CNT on densification and properties of TiC ceramics

A novel TiC-based material was fabricated by introducing Si₃N₄ and carbon nanotubes (CNTs) additives to enhance the thermal conductivity, flexural strength, and hardness of TiC. Spark plasma sintering route was used to produce four different specimens of TiC, TiC-5 wt% CNTs, TiC-5 wt% Si₃N₄, and TiC-5 wt% CNTs-5 wt% Si₃N₄. Though the individual impact of both additives on the relative density of TiC was detrimental, the co-addition of them resulted in a near fully dense composite. According to the results, some carbon left the crystalline structure of TiC, deposited at the grain boundaries as graphite flakes. However, the presence of CNTs in the microstructure stopped the formation of such flakes. The incorporated Si₃N₄ was completely used up over the SPS process, assisting in the in-situ generation of SiC. Additionally, the co-addition of Si₃N₄ and CNTs led to a decline in the mean grain size of the TiC matrix by almost 30%. Apart from this effect, the presence of both these additives provided a wider range of particle size and morphology, leading to a denser microstructure. However, the role of the added CNTs in promoting some chemical reactions in lower temperatures in the ternary system should not be overlooked. Finally, the ceramic co-reinforced with both additives presented the highest values of thermal conductivity (19.2 W/mK), hardness (3213 HV_{0.1 kg}), and flexural strength (530 MPa).