THE ROLE OF SODIUM NICKELATE IN THE METASTABLE RECRYSTALLIZATION OF DIAMOND

Diamond has been observed to recrystallize from an Ni-NaOH-C system at atmospheric pressure. The basic procedure of the experiment involves the dissolution of diamond carbon and nickel in hot NaOH melt (at abou t 850 degrees C) and fast cooling of the system to room temperature. I n this paper the physicochemical studies done to understand the mechan ism of the metastable recrystallization of diamond are reported. The v arious observations and analyses proved that the product of the Ni-NaO H reaction, NaNiO2, plays a critical role in the diamond recrystalliza tion. Evidence points towards a process in which a co-crystallization of carbon (in the form of diamond) and NaNiO2 (as thin, small platelet s) takes place. The crystallization of NaNiO2 in the form of platelets while cooling is thought to create favourable conditions locally for the growth of diamond crystallites.