The Ni@C composites were successfully synthesized by thermal decomposition of a Ni-based metal organic framework (Ni-MOF). By varying the pyrolysis temperature, Ni@C composites with different morphology and microstructure can be easily synthesized. Benefiting from the synergistic effect between the Ni core and carbon shell, the composite possess good impedance matching and excellent microwave absorption performance. Interestingly, the strongest absorption of the Ni@C composite reaches −55.7 dB corresponding to 6.0 GHz absorption bandwidth (<−10 dB) at a thickness of 1.85 mm. The results demonstrate that Ni@C composites may be promising microwave absorption materials because of their strong absorption, being lightweight, thin thickness and large absorption bandwidth.

No abstract

No abstract

Two-dimensional (2D) materials with the atomically thin thickness have attracted great interest in the post-Moore's Law era because of their tremendous potential to continue transistor downscaling and offered advances in device performance at the atomic limit. However, the metal−semiconductor contact is the bottleneck in field-effect transistors (FETs) integrating 2D semiconductors as channel materials. A robust and tunable doping method at the source and drain region of 2D transistors to minimize the contact resistance is highly sought after. Here we report a stable carrier doping method via the mild covalent grafting of maleimides on the surface of 2D transition metal dichalcogenides. The chemisorbed interaction contributes to the efficient carrier doping without degrading the high-performance carrier transport. Density functional theory results further illustrate that the molecular functionalization leads to the mild hybridization and the negligible impact on the conduction bands of monolayer MoS 2 , avoiding the random scattering from the dopants. Differently from reported molecular treatments, our strategy displays high thermal stability (above 300 °C) and it is compatible with micro/nano processing technology. The contact resistance of MoS 2 FETs can be greatly reduced by ∼12 times after molecular functionalization. The Schottky barrier of 44 meV is achieved on monolayer MoS 2 FETs, demonstrating efficient charge injection between metal and 2D semiconductor. The mild covalent functionalization of molecules on 2D semiconductors represents a powerful strategy to perform the carrier doping and the device optimization.

Bayberry-like, needle array-like and urchin-like NiCo2O4 hierarchical structures were synthesized by simple hydrothermal reactions.