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Giant magnetostrictive transducers (GMTs) featuring high energy density, fast responses, and large output force are playing an increasingly important role in high-power underwater acoustic detection, acoustic sensors, precision actuation, and other fields. However, the presence of strong magnetic bias, eddy current loss, and hysteresis significantly impact the input and output responses of the transducers, making it difficult to effectively reflect the overall nonlinear characteristics of GMT. Therefore, it is crucial to establish a comprehensive dynamic model that can accurately characterize the dynamic behavior of GMT, including different bias magnetic fields, input frequencies, input amplitudes, and time-domain output characteristic. To this end, a comprehensive dynamic nonlinear model, which thoroughly considers the electric, magnetic, mechanical, and their interactions, particularly under the influence of strong bias magnetic field, is developed. First, a magnetic field model is constructed to incorporate both bias magnetic field and ac driving magnetic field. Second, an enhanced dynamic magnetization model is proposed to depict the dynamic magnetization process of giant magnetostrictive material (GMM) rod and the internal distribution of the effective magnetic field, based on the theory of energy conservation. Lastly, a multidegree of freedom (MDOF) dynamic model, considering the distribution characteristics of the GMM rod, is constructed. In order to validate the developed dynamic model, an experimental prototype is produced. The experimental results illustrate that the proposed model is in excellent agreement with the dynamic characteristics of the GMT.

Supported palladium (Pd) catalysts are widely utilized to reduce the emission of exhaust CH4from lean-burn engines by catalytic combustion. A large amount of water vapor in the exhaust makes hydroxyls accumulate on the catalyst surface at temperatures below 450 °C, leading to severe catalyst deactivation. Tuning palladium chemistry and inhibiting water adsorption are critical to developing active catalysts. Modifying the support surface with inert silicates would both change the palladium–support interaction and decrease water adsorption sites. This study reports an improved Pd/Y2O3–ZrO2catalyst by constructing silicate patches on yttria-stabilized zirconia (Y2O3–ZrO2) support. The silicates hindered electron transfer from Y2O3–ZrO2oxygen vacancies to palladium, which optimized palladium chemistry, especially the reducibility of active PdO species, and thereby boosted CH4conversion under dry conditions. The temperature of 90% methane conversion (T90) over the catalyst decreased from 386 to 309 °C. Moreover, the inert silicates decreased surface oxygen vacancies of Y2O3–ZrO2to improve support hydrophobicity, thereby inhibiting hydroxyl accumulation. The poisoning effect of water on the active sites located on the palladium-silicate interface was alleviated. When reaction gases contained 10 vol % water, the silicate-modified catalyst still showed higher activity with T90of 404 °C, which is lower than T90of 452 °C for unmodified catalyst. This work represents a step forward in preparing high-performance palladium catalysts for low-temperature wet methane combustion.

The effect of aging time of V/Zr-based conversion bath on coating formation and corrosion resistance ability was investigated. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the morphology and composition of the conversion coating. Neutral salt spray (NSS), electrochemical impedance spectroscopy (EIS), and Tafel polarization tests were used to characterize the corrosion resistance of the conversion coating. The results showed that as the aging time of the solution increased, V ions were more completely hydrolyzed and converted to VO3−ions, and the presence of VO3−promoted the formation of the conversion coating. In addition, the vanadium element in the conversion coating tends to exist in the form of V2O5, and the proportion of V2O5increases with the aging time of the conversion bath. The increase in aging time of the conversion bath also has a positive effect on improving the corrosion resistance of V/Zr-coated aluminum alloys.