High-hardness TaN compacts with a diameter and height of 6 mm were synthesized through the phase transformation of CoSn-type into WC-type TaN under experimental conditions of high temperature and high pressure . The Vickers hardness of WC-type TaN compacts obtained at the pressure of 5 GPa and the temperature of 1873 K is found to be ~21.5 ± 1.5 GPa with a load of 3 Kg, which is comparable to that of the pure tungsten carbide compact (~20 GPa) and higher than those of ultrahigh temperature ceramics ZrB 2 and HfB 2 under the same load. The high hardness of WC-type TaN compacts presented in this work is attributed to the deviatoric strain and well-bonded nanograins . The synthesized WC-type TaN compacts also possess a high oxidation temperature (1072 K). These results suggest that the WC-type TaN with high hardness and high thermal stability holds great promise for industrial applications.
The Vickers hardness of the bulk TaB and nano-TaC ceramics sintered at high pressure and high temperature were measured by using a diamond indentation method. Our tests gave a maximum Vickers hardness of 13.9 GPa for TaB, and 19.2 GPa for nano-TaC ceramics under a load of 29.4 N. The hardness of nano-TaC-5 wt% Co composites was also measured under the same load for comparison, which was found to be much lower than that of TaB and nano-TaC. The relative densities calculated by the Archimedes method are 13.5 g/cm 3 for TaB and 13.6 g/cm 3 for nano-TaC. The averaged fracture toughness is 6.8 ± 0.3 MPa m 1/2 for TaB and 5.0 ± 0.2 MPa m 1/2 for nano-TaC. Our results show that the hardness of the TaB may not be as high as previous reports.
In this work, a stereolithography-based method of 3D printing was successfully used to fabricate a complex-shaped triangular zirconia cutting tool with a tool withdrawal groove and a honeycomb ceramic component. The sintered bodies displayed significant shrinkage after sintering, with the maximum shrinkage being 35.26%. The XRD pattern indicated that the crystalline phase of the parts was the t-ZrO 2 phase, while SEM characterization revealed that the sintered bodies were composed of densely packed submicron-grade grains, without any discernible pores. The density of the parts was measured as 97.14% via Archimedes’ water displacement method, which is consistent with the results of SEM characterization. Additionally, the measured Vickers hardness and fracture toughness of the fabricated parts were 13.0597 GPa and 6.0380 MPa m 1/2 , respectively. These values are close to the structural properties of common zirconia ceramics prepared by conventional approaches. Hence, a novel DLP-stereolithography-based 3D printing process for the fabrication of complex and dense zirconia ceramic parts has been proposed in this work.
危险品化学品经营许可证（带存储）