Unusual types of extended defects in synthetic high pressure–high temperature diamonds

Abstract

Side view of a HPHT diamond with unusual cone-like defects and the high magnification image of the defect.

Defect and Stress Reduction in High-Pressure and High-Temperature Synthetic Diamonds Using Gradient Cooling Technology

“…Previous research has suggested that filiform defects arise due to diamond misorientation during cubic diamond synthesis. 15,16 The conditions conducive to cubic diamond growth are similar to those required for the graphite−diamond transition curve, 24 and the growth process may have experienced a slight interruption before quickly resuming. Thus, the misorientation may have subsequently occurred in cubic diamond; however, filiform defects were also observed in cub-octahedron and octahedron diamonds.…”

“…14 Therefore, Fe-based catalysts alloy are the most promising for synthesizing high-purity diamonds, but filiform defects are often found in larger diamonds synthesized using these materials. 15,16 The origin of filiform defects in diamonds remains unclear, and there have been no reports on methods to eliminate them. Hence, it is crucial to understand the formation mechanism of filiform defects in diamonds and take effective measures to eliminate or reduce their occurrence.…”

“…Fe, Co, Ni, or their alloys are the main catalysts used to obtain high-quality diamonds via HPHT. , Among them, Ni and Co are easily incorporated into diamond lattices via substitution, , but it is much more difficult to incorporate Fe . Therefore, Fe-based catalysts alloy are the most promising for synthesizing high-purity diamonds, but filiform defects are often found in larger diamonds synthesized using these materials. , The origin of filiform defects in diamonds remains unclear, and there have been no reports on methods to eliminate them. Hence, it is crucial to understand the formation mechanism of filiform defects in diamonds and take effective measures to eliminate or reduce their occurrence.…”

The influence of a convection field on the growth of high-quality diamond under high-temperature, high-pressure conditions using catalyst systems with different viscosities

“…The simulated boundary conditions and the material parameters used in the finite element model are shown in Tables 1 and 2. [20][21][22] Diamond crystallization experiments were carried out in a China-type large cubic high-pressure apparatus with sample assembly dimensions of 42 × 42 mm 2 , a pressure of 5.7 GPa, and a temperature range of 1250-1350 °C. Fig.…”

An effective method to improve the growth rate of large single crystal diamonds under HPHT processes: optimized design of the catalyst geometric construction

“…High pressure and high temperature (HPHT) processes make it possible to produce high-quality large single-crystal diamonds, which can be used in a wide variety of industrial and commercial applications such as ultra-precision machining, electronics, optics, quantum processes and jewelry. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The growth of large diamonds by the temperature gradient method (TGM) using HPHT processes occurs in solvent/catalyst environments. Using TGM, the temperature gradient of the catalyst provides the main driving force for diamond growth, while the carbon atoms in the catalyst can be transported to the seed crystal by convection ow.…”