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Electromagnetic interference (EMI) shielding composites with good flexibility and weatherability properties have attracted increased attention. In this study, we combined the surface modification method of sub-atmospheric pressure glow discharge plasma with in situ atmospheric pressure surface dielectric barrier discharge plasma (APSDBD) reduction to prepare polyethylene terephthalate supported silver (Ag/PET). Due to the prominent surface modification of PET film, mild plasma reduction, and effective control of the silver morphology by polyvinylpyrrolidone (PVP), a 3.32 μm thick silver film with ultralow sliver loading (0.022 wt%) exhibited an EMI shielding efficiency (SE) of 39.45 dB at 0.01 GHz and 31.56 dB at 1.0 GHz (>30 dB in the range of 0.01–1.0 GHz). The SEM results and EMI shielding analysis indicated that the high performance originated from the synergistic effect of the formation of silver nanoparticles (AgNPs) with preferentially oriented cell-like surface morphologies and layer-by-layer-like superimposed microstructures inside, which demonstrated strong microwave reflection properties. Fourier transform infrared spectrometer and x-ray diffractometer showed that the surface structures of the heat-sensitive substrate materials were not destroyed by plasma. Additionally, APSDBD technology for preparing Ag/PET had no special requirements on the thickness, dielectric constant, and conductivity of the substrate, which provides an effective strategy for manufacturing metal or alloy films on surfaces of heat-sensitive materials at a relatively low cost.

The production and consumption of austenitic stainless steel account for about 70% of stainless steel worldwide. The content of chromium (Cr) must be accurately detected and controlled to form a stable austenite structure and obtain strong properties in production. Laser-induced breakdown spectroscopy (LIBS) can be used to detect the Cr content of austenitic stainless steel in a complex production process. However, LIBS signals may be weak and unstable because the experimental signals are seriously affected by noise, self-absorption, the matrix effect, and the instability of the shot-to-shot signal, rendering the quantitative detection results inaccurate and unstable. The spectral-preprocessing methods of baseline correction and denoising can improve the accuracy of quantitative detection of LIBS. An improved segmented Hermite cubic-interpolation method is proposed herein to correct the baseline offset and produce baseline signals that are smooth and convergent (to overcome the Runge phenomenon). Empirical mode decomposition (EMD) based on the wavelet method is proposed to remove LIBS noise; this is done by exploiting the adaptivity of EMD to refine the wavelet-scaling coefficients. Compared with other denoising methods, the proposed method has good denoising evaluation indices and stability and, thus, effectively removes the noise. To verify detection accuracy, the internal standard quantitative method is used to detect the Cr content, and a cyclic-inversion prediction method is designed to verify detection stability. The results show that the correlation coefficient of the calibration curve is improved, the root-mean-square error is reduced, and the average relative error of the predicted Cr content decreases from 10.46% to 3.858%.

Surface thermal lensing (STL) is a high sensitive pump-probe technique for photothermal characterization of weakly absorbing defects in optical materials. Commonly, the frequency modulation is applied in the pump beam, and the STL signal that appears as small modulation on top of an intense background is then detected on the probe beam by lock-in amplification. However, the lock-in detection by filtering the signal in the frequency domain results in low efficiency in the STL, preventing investigations of the large area surfaces. Here it is shown that the multi-channel averaging, which corresponds to temporal integration, is better suited for detection of the STL signal. It is demonstrated that by converting the conventional single-point scanning STL to the line scanning STL and employing suitable width of the time bins and the number of records, the imaging speed of the multi-channel averaging detection can be improved by a factor of 3.7 relative to the lock-in detection at the same signal-to-noise ratio of 6 dB and imaging resolution of 20 μm. Therefore, high-quality photothermal images of weakly absorbing defects can be recorded with higher efficiency and lower laser irradiance, making it possible to investigate large samples.