Han Qigang

An Effective Solution for the Best Set of Beveling Parameters of the Cubic High-Pressure Tungsten Carbide Anvil

Determining the best set of beveling parameters is an advantageous characteristic of the geometrical conditions for a cubic high-pressure tungsten carbide (WC) anvil, but it is almost impossible to deduce experimentally (much affected by defects in the material). In order to remove the affection of defects in materials, we investigate computational stress analyses in different beveling parameters of WC anvils by the finite element method. The results indicate that the rate of cell pressure transmitting and failure crack in the WC anvil monotonically increases with the bevel angle from 42° to 45°. Furthermore, there are two groups of actual users of beveled anvils, one group preferring 41.5°, which can decrease the rate of failure crack in WC anvil, the other group preferring 42°, which can increase the rate of cell pressure transmitting. This work would give an effective solution to solve the problem of the design of a cubic high-pressure WC anvil experimentally and will greatly help to improve the cubic high-pressure WC anvil type high pressure techniques.

Finite Element Analysis of Convection in Growth Cell for Diamond Growth Using Ni-Based Solvent

Thermal-electrical-fluid coupled finite element analyses are performed in the model of the growth cell in a high- pressure and high-temperature (HPHT) cubic apparatus in which the large diamond crystal can be grown by using Ni-based solvent with temperature gradient method (TGM). The convection in the Ni-based solvent with different thicknesses at 1700–1800K is simulated by finite element method (FEM). The experiments of diamond crystal growth are also carried out by using Ni-based solvent at 5.7GPa and 1700–1800K in a China-type cubic high pressure apparatus (CHPA). The simulation results show that the Rayleigh number in the solvent is enhanced obviously with the increasing solvent thickness. Good quality diamond single crystal cannot be grown if the Rayleigh number in the solvent is too high.