Catalytic synthesis of nanodiamond based on CDC principle: influence of different catalysts on types and sizes.

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.

Fe-catalytic synthesis of nanodiamond during the chlorination of vanadium carbide at ambient pressure: influence of the Fe-introduction mode.

The development of technical strategies for synthesizing nanodiamond (ND) under moderate conditions is still an attractive and challenging issue. Herein, an attempt has been made to investigate the effect of the Fe-introduction mode on the catalytic synthesis of ND during the chlorination of vanadium carbide (VC) at ambient pressure. The results show that when Fe powder as a catalyst is adhered on the surface of the VC particle, the resultant carbide-derived carbon (CDC) by chlorinating VC at 800 °C behaves as a remarkably higher structural ordering. However, as the Fe powder is enclosed within the interior of VC particles, the structural ordering of the CDC obtained at the same chlorination temperature becomes greatly lower, and more interestingly, ND structures can be observed in the prepared CDC. This suggests that the catalytic synthesis of ND during VC chlorination at ambient pressure is heavily dependent upon the Fe-introduction mode.

Chemically exfoliated highly conductive layer-tunable graphene by simply controlling the exfoliating temperature.

The development of effective strategies for the massive production of layer-number tunable graphene is of great importance to satisfy the requirements in versatile applications such as energy storage, thermal management, photocatalysis. However, how to prepare the layer-tunable graphene by a simple and efficient way is still a great challenge. Herein, an attempt has been made to exfoliate graphite into layer-tunable graphene by simply soaking the graphite in a binary-component solution composed of H2SO4 and (NH4)2S2O8. In this one-step method, we demonstrate that the layer-number for the as-prepared graphene can be significantly reduced by increasing the exfoliating temperature. An average thickness of ∼20, ∼10, and ∼3 atomic layers can be obtained for the graphene samples exfoliated at the temperature of 30 °C, 60 °C, and 90 °C, respectively. Meanwhile, higher exfoliating temperature not only facilitates the higher efficiency in the exfoliation of graphite, but also achieves a superior conductivity for the prepared graphene. We have demonstrated for the first time that controlling in a sole factor of temperature can effectively tune the layer-number of graphene by a one-step chemical exfoliation method, which will find its great potential in the practical application where the designated property of graphene is required.