Lu Xu,Ranran Si,Qi Ni,Jiaan Chen,Jiale Zhang,Qing-Qing Ni
Simultaneously achieving excellent shielding effectiveness (SE) and high absorption rate of flexible electromagnetic interference (EMI) shielding materials has become a growing demand for the new generation of highly integrated electronic devices. This study constructed a double-layer polydimethylsiloxane (PDMS) EMI shielding composite film, with the upper layer using Ni-plated carbon fiber (Ni@CF) as the high absorption loss part and the lower layer using Ag-plated graphene fiber (Ag@GF) as the reflection attenuation part. Due to the synergistic magnetic/dielectric loss effect in the upper layer, high electrical conductivity in the lower layer, and the shielding mechanism of “absorption-reflection-reabsorption” induced by the double-layer structure, this composite film achieves efficient EMI shielding performance and high absorption characteristics in the X-band. The EMI SE values of the 2 mm thick film containing 0.03 wt% Ni@CF and 1.2 wt% Ag@GF reach 33.7 dB, while shielding effectiveness of reflection ( SE R ) and absorption ( SE A ) is 0.8 dB and 32.9 dB, respectively. This result means that the composite film only reflects 17.2 % of the microwaves while shielding 99.9 % and absorbs nearly 82.7 %, exhibiting a significant absorption-dominated shielding mechanism. This flexible and efficient shielding film with a high absorption rate suits portable and wearable intelligent electronic products to reduce secondary electromagnetic pollution.
The fuel cell type gas sensor has attracted wide attention due to its advantages of operating at room temperature, low power consumption and good stability. In this study, a new sensitive electrode material Au-Ni/CF was developed for the detection of NO 2 . Through XRD , SEM and TEM characterization, it has been demonstrated that the electrode material exhibits improved crystallinity after being sintered at high temperatures. This leads to a reduction in charge transfer impedance. Additionally, XPS testing and TEM characterization have confirmed that high temperature sintering results in the reduction of more metal elements, leading to an increase in the electrochemical surface area and effectively improving sensor sensitivity. Furthermore, adjusting the mass ratio of gold to nickel can alter the surface lattice arrangement and electronic structure of the electrode material, subsequently impacting its resistance and catalytic ability towards NO 2 , ultimately enhancing sensor sensitivity. The sensitivity of the sensor using Au 5 Ni 2 /CF as the electrode material for detecting 0.05–10 ppm NO 2 was found to be 47.88 nA/ppm with response and recovery times of 35 s and 25 s respectively when exposed to 2 ppm NO 2 . Furthermore, it exhibited good selectivity and stability, indicating promising potential for application in room temperature atmospheric environment monitoring.
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