Facile, Large-Scale, and Expeditious Synthesis of Hollow Co and Co@Fe Nanostructures: Application for Electromagnetic Wave Absorption

Hollow metal materials have drawn a lot of attention owing to their excellent performance for wide potential applications. Here we have successfully synthesized hollow Co nanostructure with controllable structures and compositions, including hollow Co nanospheres, hollow Co nanochains, and hollow Co@Fe nanospheres. Uniform Fe nanospheres and nanochains are first synthesized; then, Fe@Co nanospheres are achieved by electroless plating cobalt on iron surfaces. Hollow Co nanostructures are obtained easily by galvanic cell reaction between Co shells and Fe cores in hydrochloric acid at room temperature. Furthermore, hollow Co@Fe nanospheres form after plating iron on the as-synthesized hollow Co nanospheres, which acted as templates. Electromagnetic (EM) wave absorption properties of hollow Co nanostructures are investigated. Hollow Co nanochains, when blended with 40 wt % in paraffin-based filler, exhibit better EM wave absorption (−42.5 dB) than the hollow Co nanospheres (−30.4 dB) with same ratio of filler. On the contrary, because the filler content is 60 wt %, the reflection loss of hollow Co nanochains degrades to −14.0 dB, which is much worse compared with hollow Co nanospheres (−41.7 dB). Moreover, hollow Co@Fe nanospheres (with 60 wt % filler) show excellent EM wave absorption properties with minimum RL of −47.3 dB and effective bandwidth of 4.8 GHz compared with hollow Co nanospheres. The method of electroless plating followed by galvanic cell reaction to synthesize hollow nanostructures is simple, robust, and widely applicable for some metals or composites with various potential

Olivine FePO₄ Cathode Material for Rechargeable Mg-Ion Batteries

In this work, Mg_<i>x</i>FePO₄ is exploited as a cathode material for rechargeable Mg-ion batteries. FePO₄/C prepared via electrochemical delithiation of LiFePO₄/C is directly used as the cathode in aqueous Mg²⁺ electrolyte, and reversible capacity is achieved for the first time. Notably, the capacity (82 mA h/g) is half of the theoretical value (164 mA h/g) and “asymmetric” discharge/charge behavior can be observed. In addition, first-principles calculations show it is the strong Mg-ion interactions between adjacent channels that not only limit the capacity of the cathode but also lead to the difference in rates for Mg-ion intercalation and deintercalation. This work provides experimental and theoretical evidence that reveal the mechanism of Mg-ion intercalation and deintercalation in a FePO₄ host, which gives guidance in designing cathode materials for rechargeable batteries based on multivalent metal ions

Clay loess(Zone III) degree of saturation and matric suction fitting result.

Clay loess(Zone III) degree of saturation and matric suction fitting result.</p

VG model parameters table for each zone.

VG model parameters table for each zone.</p

The data summary of Van Genuchten model parameters on soil-water characteristic curves in Chinese Loess Plateau.

(XLS)</p

The predicted unsaturated permeability coefficient graph in Zone I(Jingbian).

The predicted unsaturated permeability coefficient graph in Zone I(Jingbian).</p

Unsaturated permeability coefficient data source.

Unsaturated permeability coefficient data source.</p

Typical soil-water characteristic curve.

Typical soil-water characteristic curve.</p

The predicted unsaturated permeability coefficient graph in Zone II(Yan’an).

The predicted unsaturated permeability coefficient graph in Zone II(Yan’an).</p

The predicted unsaturated permeability coefficient graph in Zone III(Yangling).

The predicted unsaturated permeability coefficient graph in Zone III(Yangling).</p