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Two-dimensional code marking and coloration mechanism on titanium alloy surfaces via laser gas nitriding

In this study, a nanosecond laser marking machine was employed to nitride the surface of a Ti-6Al-4V alloy in a nitrogen-rich environment. Consequently, a crack-free and uniform nitriding layer was successfully achieved. Furthermore, a 2D code with enhanced contrast was imprinted on the sample, and subsequently, a durability test was conducted to assess its performance. The impacts of laser power (ranging from 9 to 11 W), scanning speed (17 to 23 mm/s), and line spacing (20 to 40 µm) on the surface morphology, thickness, and color alteration of the nitride layer were systematically investigated through experimental analysis. Utilizing a spectrophotometer, scanning electron microscope, optical microscope, energy dispersive spectroscopy instrument, and other advanced equipment, we further delved into the underlying mechanism of surface color change during laser gas nitriding of a Ti-6Al-4V alloy. Results indicate that an increase in laser power and a decrease in line spacing and scanning speed lead to the generation of higher energy densities on the material surface, intensifying ablation and causing the formation of more molten material. Consequently, this results in the development of more complex surface structures, thicker nitride layers, and lower reflectance. The surface microstructure of the nitride layer exhibits similarities and variations, and the thickness of the nitride layer differs, leading to distinct light absorption and reflection properties on its surface. Consequently, the nitride-layer surfaces prepared under varying laser parameters exhibit diverse contrasts.

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Identifying the geographical origin and processing technology of Moyao () on the basis of near-infrared spectroscopy combined with chemometrics.

To evaluate the quality of Moyao (Myrrh) in the identification of the geographical origin and processing of the products. Raw Moyao (Myrrh) and two kinds of Moyao (Myrrh) processed with vinegar from three countries were identified using near-infrared (NIR) spectroscopy combined with chemometric techniques. Principal component analysis (PCA) was used to reduce the dimensionality of the data and visualize the clustering of samples from different categories. A classical chemometric algorithm (PLS-DA) and two machine learning algorithms [K-nearest neighbor (KNN) and support vector machine] were used to conduct a classification analysis of the near-infrared spectra of the Moyao (Myrrh) samples, and their discriminative performance was evaluated. Based on the accuracy, precision, recall rate, and F1 value in each model, the results showed that the classical chemometric algorithm and the machine learning algorithm obtained positive results. In all of the chemometric analyses, the NIR spectrum of Moyao (Myrrh) preprocessed by standard normal variation or Multivariate scattering correction combined with KNN achieved the highest accuracy in identifying the geographical origins, and the accuracy of identifying the processing technology established by the KNN method after first-order derivative pretreatment was the best. The best accuracy of geographical origin discrimination and processing technology discrimination were 0.9853 and 0.9706 respectively. NIR spectroscopy combined with chemometric technology can be an important tool for tracking the origin and processing technology of Moyao (Myrrh) and can also provide a reference for evaluations of its quality and the clinical use.

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Stearate‐Modified Montmorillonite and Polylactic Acid Synergistically Enhanced the Microcellular of Thermoplastic Polyurethane Elastomer Foam and Improved Its Dimensional Stability

Thermoplastic polyurethane (TPU) elastomer is a commonly used material for foam preparation. However, its application is hindered by significant shrinkage behavior. To reduce the foam shrinkage, polylactic acid (PLA) and calcium stearate‐modified montmorillonite (MMT‐St) are incorporated into the polyurethane matrix. The TPU/PLA/MMT‐St composite foams are formed using an intermittent supercritical carbon‐dioxide‐foaming process. The addition of PLA inhibits the relaxation of TPU chain segments, while the introduction of calcium stearate (GaSt2) improves the dispersion of MMT within the matrix, increases the nucleation sites of cell growth, and improves cell structure. The cell diameter decreases from 10 to 4 μm, while the cell density increased from 4.1 × 1012 to 15.8 × 1012 cell cm−3. In addition, the cell distribution range narrows from 4–19 to 2–6 μm. Incorporating MMT‐St increases the crystallinity and thermal stability of TPU/PLA, mitigates chain relaxation at room temperature, and enhances foam dimensional stability. As a result, this leads to a decrease in shrinkage rate from 27.5% to 5%. As both matrices of the material are thermoplastic, this composite foam possesses recyclability with enhanced material utilization.

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Dual-Step Redox Engineering of 2D CoNi-Alloy Embedded B, N-Doped Carbon Layers Toward Tunable Electromagnetic Wave Absorption and Light-Weight Infrared Stealth Heat Insulation Devices.

2D layered metallic graphite composites are promising electromagnetic wave absorption materials (EWAMs) for their combined properties of abundant interlayer free spaces, rich metallic polarized sites, and high conductivity, but the controllable synthesis remains rather challenging. Herein, a dual-step redox engineering strategy is developed by employing cobalt boron imidazolate framework (Co-BIF) to construct 2D CoNi-alloy embedded B, N-doped carbon layers (2D-CNC) as a promising EWAM. In the first step, a chemical etching oxidation process on Co-BIF is used to obtain an optimized 2D-CoNi-layered double hydroxide (2D-CoNi-LDH) intermediate and in the second, high-temperature calcination reduction is implemented to modify graphitization of the degree of the 2D-CNC. The obtained sample delivers superior reflection loss (RLmin) of -60.1dB and wide effective absorption bandwidth (EAB) of 6.24GHz. The synergy mechanisms of interfacial/dipole polarization and magnetic coupling are in-depth evidenced by the hologram and Lorentz electron microscopy, revealing its significant contribution on multireflection and impedance matching. Further theoretical evaluation by COMSOL simulation in different fields based on the dynamic loss process toward the test ring reveals the in situ EW attenuation process. This work presents a strategy to develop multifunctional light-weight infrared stealthy aerogel with superior pressure-resistant, anti-corrosion, and heat-insulating properties for future applications.

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Electropolymerization of 1,5-diaminonaphthalene in water-in-reline electrolyte as supercapacitor electrode material

Developing novel conducting polymers as electrode materials with improved charge storage capacity and cycling stability is important for energy storage devices. Here, 1,5-diaminonaphthalene is for the first time electropolymerized from a water-in-reline (reline: a deep eutectic solvent composed of choline chloride and urea with a molar ratio 0.5) solution with perchloric acid at 323 K. The morphology of the poly(1,5-diaminonaphthalene) deposited on carbon cloth (PDAN/CC) changes from granular to dense with extended electropolymerization duration. The electrochemical charge storage performance of the PDAN/CC is investigated, and the PDAN/CC-10 exhibits the specific capacity of 57.89 mAh g−1 at the current density of 1 A g−1 using the three-electrode test in 1 M H2SO4. Ex-situ characterizations reveal the mechanism of charge storage of PDAN/CC, where the charge is stored by the amino/imino redox processes, together with (de)intercalation of the electrolyte anion. A solid-state supercapacitor using two PDAN/CC-10 and polyvinylalcohol (PVA)-H2SO4 gel is constructed, and its specific energy reaches 5.2 Wh kg−1 at the power density of 312.6 W kg−1 (0.5 A g−1). After 3000 repetitive charge-discharge cycles at 5 A g−1, 64.1 % of the initial specific capacity is maintained, which is probably caused by the degradation and dissolution of PDAN along with the repetitive charging and discharging.

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