Le Yuan

Compared to the well-studied LaAlO3/SrTiO3 heterostructure (HS), the regulation mechanism of ferroelectric on the interfacial properties of LaInO3/BaSnO3 HS remains relatively unexplored. Here, we investigate the interfacial properties of the LaInO3/BaSnO3 HS models with the BaTiO3 ferroelectric film on different positions and with different ferroelectric polarization directions and intensities using first-principles density functional theory calculations. Our results reveal that the BaTiO3 film deposited on the top of LaInO3/BaSnO3 HS can significantly improve the interfacial electron density of the HS. Moreover, the ferroelectric polarization (electric field) direction and intensity of the upper BaTiO3 film play an important role in optimizing the interfacial electronic property of LaInO3/BaSnO3 HS. When the direction of the electric field in the BaTiO3 film is the same as that in the LaInO3 film, it provides an extra force to drive the electron transfer from the surface to the (LaO)+/(SnO2)0 interface. The largest interfacial charge density is 1.56 × 1014 cm−2 in BaTiO3(−0.005)/LaInO3/BaSnO3 HS. When the direction of the electric field in the BaTiO3 film is opposite to that in the LaInO3 film, the force from the LaInO3 film is counteracted by the BaTiO3 film, resulting in less electron transfer to the (LaO)+/(SnO2)0 interface. The interfacial charge density in BaTiO3(+0.005)/LaInO3/BaSnO3 HS is approximately one-tenth of that in BaTiO3(−0.005)/LaInO3/BaSnO3 HS. These findings provide new insights into ferroelectric-dependent interfacial phenomena and offer valuable guidance for designing functional perovskite oxide interfaces.

To reduce the lightness and enhance the thermal resistance of Al-pigmented low-emissivity coatings, CuCr₂O₄ pigment was introduced into the coating system via ball milling. The results revealed that both ball milling time and Al: CuCr₂O₄ mass ratio significantly affect the optical and infrared properties of the coatings. When the milling time reached 9 h, the pigment attained an optimal flake morphology, leading to the best infrared performance of the composite coating. Additionally, the CuCr₂O₄ content effectively suppressed the lightness of Al-pigmented coatings. Compared to Al-pigmented low-emissivity coatings, the composite coating with an Al:CuCr₂O₄ ratio of 10:2 exhibited a reduction in L* value from 90 to 65. Meanwhile, it retained a low average infrared emissivity of 0.42 in the 3–5 μm and 8–14 μm ranges. Moreover, the incorporation of CuCr₂O₄ significantly improved the Al-pigmented coating’s thermal resistance from 500 °C to 600 °C. The composite coating maintained a Grade 1 adhesion rating with heat treatment of 600 °C due to a self-healing effect_. These composite coatings with low emissivity, low lightness, and high-temperature resistance are highly suitable for high-temperature and infrared stealth applications.

Perovskite oxide interfaces exhibit functional properties that are absent in their bulk counterparts. Compared to the well-studied LaAlO3/SrTiO3 (001) interface, the LaAlO3/SrTiO3 (110) interface remains relatively unexplored. Here, we investigate the interfacial properties of n-type LaAlO3/SrTiO3 (110) heterostructures, including cleavage energy, two-dimensional electron gas (2DEG) formation, and the effects of biaxial strain, using first-principles density functional theory calculations. Our results reveal that the (110) interface has a higher cleavage energy than the (001) interface, indicating stronger interfacial bonding interactions. In addition, we find that a critical LaAlO3 thickness of five unit cells is required to induce 2DEG formation in the (110) heterostructure, compared to four unit cells in the (001) system. Notably, biaxial strain in the (110) heterostructure induces behavior opposite to that observed in the (001) system. Compressive strain reduces the polarization strength in the LaAlO3 film, lowering the critical thickness required for 2DEG formation, whereas tensile strain enhances polarization, increasing the critical thickness for 2DEG formation. This contrasting strain response in the (110) and (001) heterostructures can be explained by their distinct crystallographic orientations at the interface. These findings provide new insights into strain-dependent interfacial phenomena and offer valuable guidance for designing functional perovskite oxide interfaces.

In this study, we used desert soil from Gansu, China, as a sample to propose a method for designing hyperspectral stealth coatings against desert soil backgrounds within the spectral range of 400–2500 nm, and the corresponding coating was prepared. Firstly, the correlation between the composition and typical spectral detected characteristics of the desert soil was systematically analyzed. It was found that the color and the spectrum of the desert soil in the range of 400–1000 nm were influenced by different types of iron oxides. The main spectral characteristic and reflection intensity at 1000–2500 nm were impacted by quartz and montmorillonite. Subsequently, the design method for hyperspectral stealth coatings was developed by analyzing the differences in spectral and structural characteristics between the coatings and the soil. The prepared coating exhibited similar color and spectral shape to the soil in the range of 400–1000 nm, with comparable spectral features around 1414 nm, 1915 nm, 2212 nm, 2250 nm, and 2346 nm. The correlation coefficient and the spectral cosine angle between the reflectance spectra of the coating and the soil within the 400–2500 nm wavelength were calculated to be 0.989 and only 0.05 radians, respectively. The effectiveness of the coating in achieving excellent camouflage against the desert soil background was confirmed through the analysis of multispectral images and thermal infrared temperature. This study holds significant importance for the application of hyperspectral stealth techniques in desert soil scenarios.

In order to enhance the hyperspectral camouflage efficacy of stealth coatings against a natural vegetative backdrop, LiCl, known for its significant hygroscopic properties, was incorporated into green Mg–Al layered double hydroxide (Mg–Al LDHs) material. Micron-sized composite microspheres were subsequently synthesized via the spray-drying granulation technique. The structure, morphology, and chemical composition of these microspheres were thoroughly characterized by X-ray diffraction, scanning electron microscopy, laser particle size analysis, nitrogen adsorption–desorption isotherms, and Fourier-transform infrared spectroscopy. The effect of LiCl content on the moisture absorption capacity and near-infrared reflectance spectra of the microspheres was systematically evaluated. We found that incorporating an optimal amount of LiCl into the internal pores of the Mg–Al LDHs microspheres did not compromise their smooth surface morphology and uniform particulate distribution. Notably, when the LiCl content was 10%, the maximum saturation moisture uptake ratio of the coating increased to 0.75 g/g. This hygroscopicity significantly enhanced the absorption and scattering of near-infrared radiation by the coating while concurrently improving its ability to modulate the shape and reflectance of both the visible and near-infrared spectral curves. Spectral congruence between the synthetic coating and natural green foliage was quantified at 97.41%. Moreover, this performance was maintained over 10 cycles of programmed drying and re-humidification, and the coating consistently demonstrated stable hygroscopic properties and sustained over 95% spectral congruence. These optimized artificial coatings were found to effectively confuse hyperspectral classification algorithms, thus blending seamlessly into a natural foliage backdrop. This study provides a new method for regulating VIS and NIR spectral (visible–near infrared spectrum) features, which will be critical for applications in advanced hyperspectral camouflage materials.