Regulation mechanism of catalyst structure on diamond crystal morphology under HPHT process*

Abstract

To elucidate the regulation mechanism of catalyst geometry structure to diamond growth, we establish three catalyst modes with different structures. The simulation results show that with the decrease of the protruding height of the catalyst, the low-temperature region gradually moves toward the center of the catalyst, which causes the distribution characteristics of the temperature and convection field in the catalyst to change. The temperature difference in vertical direction of the catalyst decreases gradually and increases in the horizontal direction, while the catalyst convection velocity has the same variation regularity in the corresponding directions. The variation of temperature difference and convection velocity lead the crystal growth rate in different crystal orientations to change, which directly affects the crystal morphology of the synthetic diamond. The simulation results are consistent with the experimental results, which shows the correctness of the theoretical rational analysis. This work is expected to be able to facilitate the understanding of catalyst structure regulation mechanism on diamond morphology and the providing of an important theoretical basis for the controllable growth of special crystal shape diamond under HPHT process.

Two-step high-pressure high-temperature synthesis of nanodiamonds from naphthalene*

“…It has been suggested that diamond nucleation is more likely to occur with carbon nanoparticles containing amorphous carbon as a precursor, [46][47][48][49] and that the quantity of nucleation and granularity of synthesized nanodiamonds decrease with increasing crystallinity of the graphite precursor. [50][51][52][53] Thus, the decreasing average grain size of samples N1-N3 with increasing carbonization time may be attributed to the increase of crystallinity of carbon intermediates, which does not favor the nucleation and growth of nanodiamonds. The average grain size of sample N4 is slightly larger than that of sample N3.…”

Current sensor based on diamond nitrogen-vacancy color center

“…The diamond used in the experiment was purchased from ElementSix with a size of 1.5 mm×1.5 mm×1 mm, nitrogen content is about 10 −4 . Polished surface of diamond (1.5 mm×1.5 mm) is the (100) surface, which is irradiated for 3 h under 10 MeV electron irradiation and then annealed for 2 h under 850 • C. [28][29][30][31][32][33] The NV color center concentration formed is about 10 −6 . The functions of magnetic gathering ring mainly include magnetic gathering and antiinterference, so it is appropriate to use soft magnetic material and it is required to have high permeability, low coercivity low loss, high resistivity and high saturation magnetic induction.…”

Характеризация Электрофизическими Методами Монокристаллического Алмаза, Легированного Бором (Обзор)

“…Объемные кристаллы алмаза успешно выращивают методом HPHT при температурах 1400 ± 50 • C и давлениях порядка 5−6 GPa; в современных установках роста типа Cubic высокое гидростатическое давление обеспечивается шестью цилиндрами сверхвысокого давления [27][28][29]. Россия в лице компании " New Diamond Technology" (NDT) является мировым лидером в этой области [30,31] -в 2020 г. компания сообщила о синтезированных монокристаллах весом более 100 карат.…”