Effect of Mechanical Activation and High Pressure High Temperature Treatment on Synthesis of Material Based on Nanostructured Boron Nitride

• Main Authors: Vladimir T. Senyut, Svetlana A. Kovaliova, Igor V. Val’kovich, Viktor I. Zhornik, Wensheng Li, Cheng Bo, Dongqing He, Haimin Zhai
• Format: Article
• Language: English
• Published: National Academy of Sciences of Belarus, State Scientific Institution “The Joint Institute of Mechanical Engineering" 2019-09-01
• Series: Механика машин, механизмов и материалов
• Subjects: nanocrystalline bn; mechanical activation; chemical purification; high pressure high temperature
• Online Access: http://mmmm.by/en/readers-en/archive-room-en?layout=edit&id=1497

In the paper, the study of the influence of mechanical activation (MA) and subsequent high pressure high temperature (HPHT) treatment of the powder of hexagonal boron nitride (hBN) on its structure and phase composition is given. X-ray diffraction and electron microscope studies show that MA leads to the transformation of the BN substructure from crystalline to nanocrystalline and amorphous. At the same time, along with the formation of amorphous nanocrystalline cubic boron nitride (cBN) in BN powders after MA, another high-pressure phase — wurtzite boron nitride wBN is formed. As a result of sintering of the hBN powders after MA under pressure of 2.5 GPa and under temperature in the range of 1000–1300 °C, in addition to the hBN, wBN and cBN phases, the BN phases of rhombic, hexagonal and tetragonal crystallographic systems are formed in the resulting material. The HPHT treatment of the hBN powders after MA under pressure of 7 GPa allows to obtain a material containing a cBN phase with cBN crystallites about 50 nm in size. The addition of aluminum decreases the sintering pressure, but at the same time, due to recrystallization, the grain size of cBN in the obtained material increases by an order of magnitude compared with the original powder.