Mechanical properties and machinability of AlN-hBN ceramics prepared by spark plasma sintering

Abstract

AlN-hBN ceramic composites with 3 mass% CaF2 were fabricated by spark plasma sintering at 1800°C for 10 min. The effects of hBN content on mechanical properties, microstructure, and machinability of AlN-hBN composites were investigated. With increasing hBN content, relative density, flexural strength, and Young's modulus decreased, whereas fracture toughness increased slightly. Vickers' indentation cracks are largely deflected near hBN platelets, implying a weak interfacial bond between the AlN and the hBN. The fracture surfaces of AlN-hBN composites showed a higher tendency of intergranular fracture than monolithic AlN. During end-milling processes, the cutting resistance decreased with hBN content, demonstrating the machinability of AlN ceramic can be improved significantly by the addition of hBN.

Pulverization of Y2O3 nanoparticles by using nanocomposite particles prepared by mechanical treatment

“…Table 3 also lists relative density of the sintered bodies fired at 1500 • C for 2 h. The relative density of the sintered body produced from the mechanically treated Y 2 O 3 nanoparticles was 97.5%, whereas the relative densities of the sintered bodies made from as-received and ball-milled Y 2 O 3 nanoparticles were 82 and 83.8%, respectively. Because Ca compounds have been reported as a sintering aids in some cases [29,30], the Y 2 O 3 sintered body was fabricated by adding 0.13 wt % of CaCl 2 to the as-received powder, which is the same chemical composition as the mechanically treated Y 2 O 3 nanoparticles estimated by XRF analysis. As a result, the relative density of sintered body was 88.0% in the sample prepared from the powder mixture of the Y 2 O 3 nanoparticles and CaCl 2 .…”

High Frequency Dielectric Properties and Thermal Conductivity of AlN-BN Composites by Spark Plasma Sintering

“…Since h-BN has a plate-like structure, which is similar to graphite, the introduction of BN will facilitate the crack deflection and propagation along the interface of two phases to improve the fracture toughness and consequently the machinability [1,2]. Beside this, Jin et al [3] have synthesized a new AlN / h-nano BN ceramic composite in which the nano-sized BN was encompassing the AlN grain other than retaining a plate-like structure.…”

“…Hot pressing and spark plasma sintering are the widely used methods to sinter the AlN-BN composites. However, high sintering temperature (1700 -2000 °C) is still needed to achieve the final density of the composites [2][3][4][5][6][7][8][9][10][11]. Proper sintering additives may be useful to reduce the sintering temperature and to remove the oxygen atoms from grain boundaries which can enhance the thermal conductivity of the samples.…”