Effect of Full Temperature Field Environment on Bonding Strength of Aluminum Alloy

In this paper, the influence of temperature on the bonding strength of aluminum alloy joints under the full temperature field is studied. Based on the service temperature range of vehicle bonding structures, the failure strength of aluminum alloy joints at different temperature points, namely −40 °C, −20 °C, 0 °C, 25 °C (RT), 40 °C, 60 °C and 80 °C, is tested. The results showed that compared with the failure strength of the adhesive at −40 °C, it decreased by 47.69% and 68.15% at RT and 80°C, respectively; the Young’s modulus of the adhesive decreased by 57.63% and 75.42% at RT and 80°C, respectively; with the increase of temperature, the young’s modulus, tensile strength and failure strain of the adhesive decreased. In addition, the failure strength of aluminum alloy joints varied with temperature. To be specific, the stiffness of joints decreased gradually from 25 °C to 80 °C and increased gradually from −40 °C. Based on the failure strength data of bonded joints at different temperature points, the secondary stress failure criteria of bonded joints at different temperatures were obtained. Then, the surface function of failure criteria under the full temperature field was established to provide reference for failure prediction of bonded structures under different temperatures and stresses.

Estimating the Polytropic Indices of Plasmas with Partial Temperature Tensor Measurements: Application to Solar Wind Protons at ~1 au

We examine the relationships between temperature tensor elements and their connection to the polytropic equation, which describes the relationship between the plasma scalar temperature and density. We investigate the possibility to determine the plasma polytropic index by fitting the fluctuations of temperature either perpendicular or parallel to the magnetic field. Such an application is particularly useful when the full temperature tensor is not available from the observations. We use solar wind proton observations at ~1 au to calculate the correlations between the temperature tensor elements and the scalar temperature. Our analysis also derives the polytropic equation in selected streamlines of solar wind plasma proton observations that exhibit temperature anisotropies related to stream-interaction regions. We compare the polytropic indices derived by fitting fluctuations of the scalar, perpendicular, and parallel temperatures, respectively. We show that the use of the parallel or perpendicular temperature, instead of the scalar temperature, still accurately derives the true, average polytropic index value, but only for a certain level of temperature anisotropy variability within the analyzed streamlines. The use of the perpendicular temperature leads to more accurate calculations, because its correlation with the scalar temperature is less affected by the anisotropy fluctuations.

Intrinsically weak magnetic anisotropy of cerium in potential hard-magnetic intermetallics

Cerium-based intermetallics are currently attracting much interest as a possible alternative to existing high-performance magnets containing scarce heavy rare-earth elements. However, the intrinsic magnetic properties of Ce in these systems are poorly understood due to the difficulty of a quantitative description of the Kondo effect, a many-body phenomenon where conduction electrons screen out the Ce-4f moment. Here, we show that the Ce-4f shell in Ce–Fe intermetallics is partially Kondo screened. The Kondo scale is dramatically enhanced by nitrogen interstitials suppressing the Ce-4f contribution to the magnetic anisotropy, in striking contrast to the effect of nitrogenation in isostructural intermetallics containing other rare-earth elements. We determine the full temperature dependence of the Ce-4f single-ion anisotropy and show that even unscreened Ce-4f moments contribute little to the room-temperature intrinsic magnetic hardness. Our study thus establishes fundamental constraints on the potential of cerium-based permanent magnet intermetallics.

Make It Stereoscopic: Interfacial Design for Full-Temperature Adaptive Flexible Zinc-Air Batteries

Flexible zinc-air batteries (ZABs) have been scrutinized as a type of promising flexible power source for next-generation electronic devices, but the batteries’ temperature adaptability has been a major hurdle due...

Semimetal to semiconductor transition in Bi/TiO2 core/shell nanowires

Full temperature-dependent thermoelectric and structural characterization of individual bismuth-based core/shell nanowires under the influence of strain induced by the shell.

Novel resonant pressure sensor based on piezoresistive detection and symmetrical in-plane mode vibration

In this paper, a novel resonant pressure sensor is developed based on electrostatic excitation and piezoresistive detection. The measured pressure applied to the diaphragm will cause the resonant frequency shift of the resonator. The working mode stress–frequency theory of a double-ended tuning fork with an enhanced coupling beam is proposed, which is compatible with the simulation and experiment. A unique piezoresistive detection method based on small axially deformed beams with a resonant status is proposed, and other adjacent mode outputs are easily shielded. According to the structure design, high-vacuum wafer-level packaging with different doping in the anodic bonding interface is fabricated to ensure the high quality of the resonator. The pressure sensor chip is fabricated by dry/wet etching, high-temperature silicon bonding, ion implantation, and wafer-level anodic bonding. The results show that the fabricated sensor has a measuring sensitivity of ~19 Hz/kPa and a nonlinearity of 0.02% full scale in the pressure range of 0–200 kPa at a full temperature range of −40 to 80 °C. The sensor also shows a good quality factor >25,000, which demonstrates the good vacuum performance. Thus, the feasibility of the design is a commendable solution for high-accuracy pressure measurements.