Graphene-supported single atomic metals (G-SAMs) have recently attracted considerable research interest for their intriguing catalytic, electronic, and magnetic properties. The development of effective synthetic methodologies toward G-SAMs with monodispersed metal atoms is vital for exploring their fundamental properties and potential applications. A convenient, rapid, and general strategy to synthesize a series of monodispersed atomic transition metals (for example, Co, Ni, Cu) embedded in nitrogen-doped graphene by two-second microwave (MW) heating the mixture of amine-functionalized graphene oxide and metal salts is reported here. The MW heating is able to simultaneously induce the reduction of graphene oxide, the doping of nitrogen, and the incorporation of metal atoms into the graphene lattices in one simple step. The rapid MW process minimizes metal diffusion and aggregation to ensure exclusive single metal atom dispersion in graphene lattices. Electrochemical studies demonstrate that graphene-supported Co atoms can function as highly active electrocatalysts toward the hydrogen evolution reaction. This MW-assisted method provides a rapid and efficient avenue to supported metal atoms for wide ranges of applications.

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This paper reports a novel method to fabricate auxetic warp knitted fabrics on a tricot warp knitting machine based on a special structure design and knitting process. Three auxetic warp knitted structures were successfully developed and all of them were designed to form a reentrant hexagonal geometry to acquire an auxetic effect. To provide the fabrics with reentrant frames, elastomeric yarns and stiff yarns were used to form the elastic underlaps and stiff underlaps, respectively. While the elastic underlaps can keep the reentrant structures stable, the stiff underlaps can support the reentrant structures to keep their reentrant frames. To alleviate the transfer of yarns in the loops under tension, an additional front yarn guide bar was used to feed binding yarns to basic reentrant structures. After knitting, all the fabrics were subjected to a heat setting process to keep their shape and a tensile test to assess their auxetic behavior. The experimental results showed that all the fabrics exhibited an obvious auxetic behavior within a wide range of strain. In particular, the fabrics retained auxetic behavior until breaking when stretched in the wale direction, and the Poisson’s ratio of the fabrics could be as low as –0.5. On the other hand, the fabrics exhibited a large tensile elongation when stretched in the course direction and their Poisson’s ratios changed from negative to positive after the tensile strain exceeded a certain value.

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Auxetic woven fabrics made with special geometrical structures have gained the interest of textile scientists in recent years. This paper reports a study on auxetic woven fabric based on a double-directional parallel in-phase zig-zag foldable geometrical structure. Such a fabric has been already produced and investigated for its negative Poisson's ratio effect in two principal directions (weft and warp directions). However, its negative Poisson's ratio effect in biased tensile directions as well as under repeated tensile loading conditions has not been studied yet. Therefore, in this paper, these two limitations are addressed. The auxetic woven fabric was firstly fabricated, and then subjected not only to tensile tests in different tensile directions, including two principle directions and three biased directions, but also to repeated tensile loading. It was found that both the negative Poisson's ratio effect and the resistance to tensile deformation are dependent upon the tensile direction, and the highest negative Poisson's ratio effect and higher resistance to tensile deformation are obtained in two principal directions.