Sintering process and high temperature stability investigation for nano-scale CaB6 materials

Calcium hexaboride (CaB6) polycrystalline was prepared from its nano-scale powders using vacuum hot-pressing method under 1750 °C, 32 MPa for 5 min. SEM, FESEM and AFM were employed to observe morphology and compared with its bulk material sintered under 1550 °C. Observations showed the structure of the nano-scale CaB6 bulk has the regions with high and low compactness degree due to CaB6 nanometer powder aggregations. The hardness, bending strength and fractural toughness were 79.7 HRA, 198.7 MPa and 3.73 MPa m1/2, respectively, better than those of CaB6 micron-polycrystalline sintered under the same sintering parameters. DSC and TG were tested to investigate high temperature stability. Only one exothermic peak (1117.2 °C) appeared in nano-polycrystalline which began at 1080 °C and area was −167.7 J/g, showing its stability is much better than CaB6 nano-micron composite polycrystalline and micron-polycrystalline.