In order to realize the construction of environmentally friendly potassium sodium niobate ceramic coating on metal surface, potassium sodium niobate ceramic coating was prepared by supersonic plasma spraying technology. The morphology, element extension and phase structure of such coating were investigated. The dielectric and ferroelectric properties were also analyzed. The results show that the coating has good quality and tetragonal phase structure. When test frequency ≥ 2 MHz, the dielectric constant is stable at about 300, and also dielectric loss is stable at about 0.05. The coating exhibits good hysteresis loops under different applied electric fields. When the applied electric field is 16 KV/cm, residual polarization value of as-prepared coating reaches 17.02 μC·cm⁻².

High-temperature resistant high-entropy alloys (HEAs) have attracted extensive attention due to their excellent thermodynamic stability and mechanical properties, especially at high temperatures. However, a highly effective method for large-size HEAs is still desirable but challengeable. This research reported a facile yet effective strategy for MoNbTaWTi HEAs via in-situ wire arc additive manufacturing (WAAM). The wire was MoNbTaWTi cable-type welding wire (CTWW) consisting of one center wire and seven twisted peripheral wires. Then, additive manufacturing of MoNbTaWTi high entropy alloys (HEAs) was accomplished, and various analytical techniques studied the microstructures and mechanical properties of the overlaying formed layers. X-ray diffraction showed the overlaying formed layers to contain a single disordered BCC solid solution phase with high-temperature structural stability. In addition, the single-phase BCC structure was maintained from 0 to 1400 °C. The bottom of the overlaying formed layers was made of columnar cellular structure, and the upper part resembled “cauliflower-like” fine dendrite and equiaxed crystal structure. The hardness of the overlaying formed layers averaged 533 HV_0.2 at room temperature. At 1000 °C, the hardness was around 110 HV₁, close to the value of Inconel 718 alloy (125 HV₁). The compressive strength of the overlaying formed alloy layers displayed no sensitivity towards change in temperature from 500 to 1000 °C. As the temperature rose from 500 to 1000 °C, the compressive strength changed from 629 to 602 MPa, equivalent to only a 27 MPa decrease. The latter was much higher than the strength of Inconel 718 alloy at the same temperature (200 MPa).

Thermal control coating is an important means of ensuring that a spacecraft remains operational at high temperatures. Due to limitations regarding preparation technology and material properties, the mechanical properties of the conventional thermal control coatings still need to be improved. To solve this problem, nanostructured alumina coatings (NCs) and conventional alumina coatings (CCs) were prepared using plasma-spraying technology. The microscopic morphology, phase structure, hardness, and thermal control properties (solar absorptance (α_s) and emissivity (ε)) of the nanostructured alumina coatings were investigated and compared with those of conventional alumina coatings. The results show that the NC has a higher hardness value (1168.8 HV) and that its reflectivity exceeds 75% in the wavelength range of 446–1586 nm, while a high degree of emissivity of 0.863–0.87 is still maintained at 300–393 K. Furthermore, the results show that these highly reflective properties are related to the phase composition and internal micromorphology of the NC, whereby the solar absorption of the coating is reduced due to the increase in the alpha phase content (21.4%), the high porosity (5.21%) and the nanoparticles favoring the internal scattering. All these properties can improve the performance of this CC coating with low solar absorptance (α_s) and high emissivity (ε).

The current work aims to compare the effects of systematic A-site substitutions on the electrical properties of potassium sodium niobate (KNN)-based coating. The A-site elements were replaced by Li⁺ to form (K_0.4675Na_0.4675Li_0.065) NbO₃ (KNLN). The pure KNN coating and the Li⁺-doped potassium sodium niobate (KNLN) coating with dense morphology and single perovskite structure were successfully prepared by supersonic plasma spraying, and the phase composition, microscopic morphology and electrical properties of the two coatings were compared and analyzed in detail by XRD, XPS, three-dimensional morphology and SEM on an Agilent 4294A (Santa Clara, CA, USA) and FE-5000 wide-range ferroelectric performance tester. The results show that: as the polarization voltage increases, the pure KNN coating is flatter and fuller, but the leakage current is large. The KNLN coating has a relatively long hysteresis loop and is easily polarized. The domain deflection responds faster to the external electric field, and the resistance of the domain wall motion to the external electric field is small. The dielectric constant of KNLN coating is 375, which is much higher than that of the pure KNN coating with 125, and the dielectric loss is stable at 0.01, which is lower than that of pure KNN coating at 0.1–0.35. This is because Li⁺ doping has successfully constructed a polycrystalline phase boundary in which O-T phases coexist, and has higher dielectric properties, piezoelectric properties and ferroelectric properties. At the same time, due to the high-temperature acceleration process in supersonic plasma spraying, the violent volatilization of the alkaline elements Li⁺, Na⁺ and K⁺ leads to the presence of oxygen vacancies and part of Nb⁴⁺ in the coating, which seriously affects the electrical properties of the coating.

Because the threshing device of a combine harvester determines the harvesting level and threshing separation performance of a combine harvester, the analysis and study of the threshing device of a combine harvester is key to improving its performance. Based on the threshing device of a half-feed combine harvester, the simulation model of a discrete element threshing device is established in this paper. With the threshing drum rotation speed, feed volume, and concave sieve vibration frequency as the variable factors, the BP neural network model and linear regression equation model established for the loss rate and impurity content for two kinds of threshing performance indicators, respectively, and through the discrete element threshing performance test, two kinds of methods of threshing performance prediction are analyzed. The results show that the neural network and linear regression can be used for the threshing performance indicators, however, the BP neural network prediction effect has a better prediction precision, better reliability, and the trained neural network can be used in the general case of the threshing performance indicators. This provides a new idea for improving the threshing performance of a combine harvester.

The ferroelectric domain surface charge dynamics after a cubic-to-tetragonal phase transition on the BaTiO₃ single crystal (001) surface was directly measured through scanning probe microscopy. The captured surface potential distribution shows significant changes: the domain structures formed rapidly, but the surface potential on polarized c domain was unstable and reversed its sign after lengthy lapse; the high broad potential barrier burst at the corrugated a-c domain wall and continued to dissipate thereafter. The generation of polarization charges and the migration of surface screening charges in the surrounding environment take the main responsibility in the experiment. Furthermore, the a -c domain wall suffers large topological defects and polarity variation, resulting in domain wall broadening and stress changes. Thus, the a-c domain wall has excess energy and polarization change is inclined to assemble on it. The potential barrier decay with time after exposing to the surrounding environment also gave proof of the surface screening charge migration at surface. Thus, both domain and domain wall characteristics should be taken into account in ferroelectric application.