六方B2CN的合成及其热膨胀性能

In this paper, an amorphous B2CN precursor was prepared by mechanical alloying using B, graphite, and hexagonal BN powder as raw materials. The amorphous B2CN precursor was crystallized under high pressure and high temperature (5.5GPa ,900-1500 ℃). The crystal structure and thermal expansion properties of B2CN compound were measured. The results show that the amorphous B2CN precursor was transformed to hexagonal crystal under high pressure and temperature. With the synthesis temperature increased, the intensity of diffraction peaks of the hexagonal B2CN phase gradually increased, and the peak width gradually decreases. A well crystallized B2CN crystal was obtained under 5.5GPa and 1500 ℃ condition. At 20 to 500 ℃ temperature range the hexagonal B2CN crystal along a-axis direction shows negative thermal expansion properties, its thermal expansion coefficient is -3.461×10-6 K-1, at 500 ~ 1200 ℃ temperature range shows zero expansion properties. From room temperature to 1200 ℃ the thermal expansion coefficient is 3.768 × 10-6 K-1 along c-axis direction.