Densification and microstructure of Al2O3-cBN composites prepared by spark plasma sintering

Field‐Assisted Sintering Technology/Spark Plasma Sintering: Mechanisms, Materials, and Technology Developments

“…[206] A wide range of cBN or diamondbased composite materials with ceramic or hard metal matrix has been successfully produced by FAST/SPS. [207][208][209][210][211][212][213][214] Pure carbon nanotubes (CNT) can be densified with FAST/SPS without decomposition up to a density of 1.29 g cm -3 . The remaining pores are all below 6 nm.…”

Densification, phase transformation and hardness of mullite-cubic BN composites prepared by spark plasma sintering

“…No shrinkage of monolithic BN was observed at 1600°C for 600 s. We reported that the starting and finishing temperatures of shrinkage of Al2O3-BN composites containing 10 vol% cBN were 150°C and 100°C, respectively, higher than those of monolithic Al2O3. 17) On the other hand, the shrinkage of the mullite-10 vol% cBN composites was almost the same behavior as that of the monolithic mullite. The shrinkage of β SiAlON-10 vol% cBN composites finished at 150°C lower than that of monolithic β -SiAlON.…”

“…In the case of Al2O3-cBN composites, the phase transformation of cBN started at 1400°C. 17) The phase transformation temperature of the mullite-cBN composites was more than 200°C higher than that of Al2O3-cBN composites. In monolithic BN, the phase transformation temperature was 1650°C, 19) and therefore the mullite-BN composites had almost the same phase transformation temperature as that of monolithic BN.…”

“…In the case of Al2O3-cBN composites, the density of the Al2O3-10 vol% cBN composite drastically decreased to 85%. 17) In the case of β SiAlON-10-30 vol% cBN composites, on the other hand, the density was higher than that of monolithic β -SiAlON.…”

“…The flake-like texture was characteristic of the phase transformation of cBN both in Al2O3-cBN and β SiAlON-cBN composites. 17),18) Figure 5 shows the Vickers hardness of monolithic mullite and mullite-BN composites originally containing 10-40 vol% cBN sintered at 1500-1700°C for 600 s. The Vickers hardness of the mullite-20 vol% cBN composite sintered at 1500°C had the highest value of 16 GPa. The increase in the hardness was caused by high-hardness cBN particles dispersed in the mullite matrix without the phase transformation to hBN.…”