Abundant Heterointerfaces Research Articles

Yolk–shell structured Co-C/Void/Co9S8 composites with a tunable cavity for ultrabroadband and efficient low-frequency microwave absorption

A yolk–shell structured Co-C/Void/Co9S8 ternary composite composed of a Co nanoparticle-embedded porous carbon core and Co9S8 shell was synthesized by the sulfidation of a Co-based zeolitic imidazolate framework and subsequent pyrolysis. The composition and interior cavity of the Co-C/Void/Co9S8 composite could be precisely modulated by controlling the sulfidation reaction. Due to the abundant heterointerfaces, well-controlled cavity, and magnetic–dielectric synergistic effects, the Co-C/Void/Co9S8 exhibited excellent and tunable microwave-absorbing properties. The optimized Co-C/Void/Co9S8, having a loading of 25 wt.% and thickness only 2.2 mm, displayed an ultrabroad absorption bandwidth of 8.2 GHz at high frequencies. Moreover, the composite could achieve an extremely high reflection loss of–54.02 dB at low frequencies by adjusting its loading to 30 wt.%. This study provides a new insight into promising lightweight microwave-absorbing materials with ultrabroad absorption bandwidths and strong low-frequency absorption.

Atomic Heterointerfaces and Electrical Transportation Properties in Self‐Assembled LaNiO3–NiO Heteroepitaxy

AbstractVertical nanostructure heteroepitaxy opens new opportunities for designing next‐generation electronic devices due to the enthralling multifunction combinations and the abundant heterointerfaces manipulated effects. In this study, self‐assembled heteroepitaxial thin films, vertically aligned metallic LaNiO3 (LNO) and semiconducting NiO with diverse heterointerfaces, are created and systematically investigated by advanced transmission electron microscopy. With the increase of LaNiO3 content, the LaNiO3 phases present as isolated islands encircled by the connected NiO nanoplates and eventually become the continuous matrix with embedded NiO nanopillars. The atomic heterointerface between NiO and LaNiO3 phases is determined to be [NiO2–LaO]LaNiO3–LaO–[NiO]NiO, in which an extra La–O layer is enriched at the heterointerface. Besides, the formation mechanism of the heterointerface and antiphase boundaries observed in LaNiO3 phase is discussed. The electrical transport properties at room temperature can be tuned gradually by changing the volume ratio of constituents. The correlation among the insulator‐to‐metal transition, the carrier types associated with transport behaviors, and the heterostructure evolutions are explored. This study offers a desirable platform to design new multifunctional electronic devices based on the oxide heterojunctions.