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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]

Due to the excellent properties of nanodiamonds (NDs), the synthesis of NDs under mild conditions is very attractive but still faces great challenges. In this work, we have developed a new strategy for synthesizing NDs under atmospheric pressure, which is realized by atmospheric chlorine-etching the Ti 3 C 2 /Ni composite, where the Ni catalyst is distributed among the Ti 3 C 2 sheets in a high-stress state. The results have shown that when the prepared Ti 3 C 2 /Ni composite is chlorine-etched under atmospheric pressure, Ni has successfully catalyzed the synthesis of NDs, where various crystalline types of NDs can be observed. The Ni-catalytic synthesis of NDs is heavily dependent upon the pressing pressure, which is used in the preparation of Ti 3 C 2 /Ni composite, and a higher pressing pressure is beneficial to the NDs formation. Furthermore, the pressing pressure has also an important effect on the crystalline type of the catalytically synthesized NDs. This discovery may provide a new strategy for tailoring the type of NDs by the pressing pressure to meet specific application requirements in the future. [Display omitted] • A new strategy for the atmospheric pressure catalytic synthesis of NDs is developed. • This strategy includes high-stress pressing of Ti 3 C 2 /Ni composite followed by atmospheric pressure chlorination. • Catalytic synthesis of NDs by chlorination of Ti 3 C 2 /Ni composite is reported for the first time. • The ND type can be regulated by the pressing pressure used in the preparation of Ti 3 C 2 /Ni composite. [ABSTRACT FROM AUTHOR]

How to synthesize nanodiamonds (NDs) under moderate conditions is still a challenging issue. Recently, we have demonstrated that high-stress embedding the Fe catalyst into VC can lead to the catalytic synthesis of NDs by chlorine-etching VC at atmospheric pressure. Herein, we have further probed into the influence of the carbide type on the Fe-catalytic synthesis of NDs, where four carbides - VC, TiC, NbC and β-SiC are used as the precursor to be chlorine-etched in the presence of Fe catalyst, respectively. It has been discovered that various types of NDs, including C type, H type and R type, can be catalytically synthesized. The type of carbide has a decisive influence on the Fe-catalytic synthesis of NDs. Furthermore, the size and type of NDs synthesized are closely related to the number of carbon atoms contained per unit volume in the carbide. This finding may open a new avenue for tailoring the size and type of NDs to satisfy the specified application requirement. [Display omitted] • Influence of the carbide type on Fe-catalytic synthesis of NDs during chlorine-etching carbide is systematically studied. • The diversity of synthesized NDs is a distinct feature of this method in comparison to those traditional ND synthesis routes. • The size and type of NDs can be tailored by varying the number of carbon atoms contained per unit volume in the carbide. [ABSTRACT FROM AUTHOR]