Nitrogen Solubility in Liquid Ni-V, Ni-Ta, Ni-Cr-V, and Ni-Cr-Ta Alloys

Qian, Kun; Chen, Bo; Shu, Lei; Liu, Kui

doi:10.3390/met9111184

Cited by 8 publications

(1 citation statement)

References 42 publications

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“…Titanium is the most effective additive to alloys that can increase the solubility of nitrogen in Fe and Ni melts 5 , 6 . However, a paradoxical situation is observed: the introduction of Ti into the growth system must increase the solubility of nitrogen in the Fe–Ni melt, but as a result the amount of nitrogen in diamond decreases.…”

Section: Introductionmentioning

confidence: 99%

The composition of the fluid phase in inclusions in synthetic HPHT diamonds grown in system Fe–Ni–Ti–C

Сонин

Томиленко

Жимулев

et al. 2022

Sci Rep

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Diamonds grown by high pressure high temperature process (HPHT) are usually characterized by yellow color and high contents of nitrogen. Introduction of Ti decreases nitrogen content in diamond. Understanding the formation of nitrogen-poor diamond is very important not for the progress of HPHT process only, but because these diamond varieties represent the rare natural stones, although their crystallization conditions have not been clarified yet. Here we studied the composition of fluid phase in synthetic diamonds. The experiments were performed using a high-pressure apparatus BARS at pressures 5.5–6.0 GPa and temperatures 1350–1400 °C. It was found that introduction of metallic Ti leads to concentration of nitrogen mainly as nitrogenated hydrocarbons. The hypothesis that elucidates the formation of low-nitrogen diamond in Fe–Ni is proposed: the presence of Ti leads to an increase of hydrogen fugacity in the metal melt which drastically reduces the nitrogen solubility. As a result, nitrogen concentrates in the form of complex hydrocarbon compounds, while diamond grows colorless and characterized by very low nitrogen content. It is suggested that the proposed mechanism acts the same way in the presence of other metals which are strong reducing agents.

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Section: Introductionmentioning

confidence: 99%