High temperature and high pressure synthesis method
Direct transformation method:
Taking hexagonal boron nitride (HBN) as raw material, under the action of high temperature (1500-2200°C), high pressure (5-9 GPa) and catalyst, the phase transformation of hexagonal boron nitride occurs directly to produce cubic boron nitride micropowder. For example, the Chinese invention patent No. CN110670137B uses HBN as the raw material and the mixture of Li3BN2, Li3N and NH4Cl as the catalyst, and obtains cubic boron nitride crystals through high temperature and high pressure treatment.
Sintering method:
Cubic boron nitride single crystal powder is sintered under high temperature and high pressure to form polycrystalline cubic boron nitride, and then cubic boron nitride micropowder is obtained through crushing, grinding and other processes. This method can prepare the micropowder with high purity and stable performance.
Chemical vapor deposition method (CVD)
Using gaseous boron source and nitrogen source, under the conditions of high temperature and catalyst, chemical reaction occurs on the substrate surface, generating cubic boron nitride and deposited on the substrate, and by controlling the reaction conditions and process parameters, we can obtain cubic boron nitride micropowders with different particle sizes and properties. The method can be carried out at lower temperature and pressure, can prepare high quality cubic boron nitride micropowder, and can grow on different substrate materials, suitable for the preparation of thin film or coating cubic boron nitride micropowder.
Explosive method
The instantaneous high temperature and pressure generated by the explosion of explosives is used to synthesize cubic boron nitride micropowder. Mix hexagonal boron nitride with explosives, detonate the explosives in a closed container, and the resulting high temperature and high pressure transforms hexagonal boron nitride into cubic boron nitride. This method can synthesize a large amount of cubic boron nitride micropowder in a short period of time, but the impurity content of the product is relatively high, which requires subsequent purification treatment.
Mechanical crushing method
First synthesize larger particles of cubic boron nitride single crystal through high temperature and high pressure, and then use mechanical crushing methods, such as jaw crusher, ball mill, air flow mill, etc., to crush large particles of cubic boron nitride into micropowder. The process of this method is relatively simple, but the energy consumption is high, the output is low, and impurities may be introduced in the crushing process.
Sol-gel method
Organic or inorganic compounds containing boron and nitrogen are dissolved in a solvent to form a homogeneous sol, and then the boron and nitrogen in the sol are reacted through the processes of gelation, drying, and high-temperature heat treatment to generate cubic boron nitride micropowder. This method can precisely control the composition and particle size of the micropowder, and the prepared micropowder has high purity and uniformity, but the process is more complicated and the cost is higher.
