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Recently, we have successfully achieved the atmospheric pressure catalytic synthesis of nanodiamonds by applying high stress to Ti3C2/Ni composite and then performing chlorine gas etching at atmospheric pressure. In this work, we chose three different catalysts (Fe, Co and Ni), with Ti3C2 as the precursor, aiming to investigate the effect of catalyst type on the synthesis of NDs. The results show that all three catalysts can catalyze the synthesis of NDs and that the crystal type and plasticity of the catalysts may have an important effect on the type and size of the resulting ND. When Fe and Ni were used as catalysts, the percentage of C-type NDs obtained was higher than that of C-type NDs catalyzed by Co (hexagonal close-packed crystal structure) due to its face-centered cubic crystal structure. In contrast, more H-type NDs were catalytically synthesized when Co (hexagonal close-packed crystal structure) was used as the catalyst. In addition, the number of small-size NDs (< 10 nm) catalytically synthesized by Co was significantly more than that catalytically synthesized by Fe and Ni, this may be caused by the poor plasticity of Co with a hexagonal close-packed crystal structure compared to Fe and Ni with a face-centered cubic crystal structure. [ABSTRACT FROM AUTHOR]

Recently, we have successfully realized the catalytic synthesis of nanodiamond (ND) by embedding the Fe catalyst into carbide under high stress, followed by chlorine-etching at atmospheric pressure. In this work, we selected Fe, Co and Ni as the catalyst, and TiC as the precursor, aiming at investigating the influence of the catalyst type on the synthesis of NDs. The results have shown that all the three catalysts can catalyze the synthesis of ND structure, where various types of NDs have been observed. Furthermore, the crystal type and plasticity of the catalyst may have an important influence on the type and size of the resultant ND. In the case of Fe and Ni as the catalyst, both of which have a face centered cubic crystal structure, the types of NDs obtained are mainly C-type and R-type but only a few H-type. However, when the Co with a close-packed hexagonal crystal structure is used as the catalyst, more H-type NDs can be catalytically synthesized. Moreover, more small-sized NDs have been catalytically synthesized by Co, which may be ascribed to the worse plasticity of Co by comparison to Fe and Ni. [ABSTRACT FROM AUTHOR]