In this study, a flower-like TiO₂ filled polymethyl methacrylate (PMMA) composite is presented as a positive tribo-material to produce an excellent-performance triboelectric nanogenerator (TENG).

With the development of electronical technology and the construction of the fifth‐generation cellular networks, electronic devices with higher integrated level and power are widely applied. Hence, greater demands are being placed on electronic packaging materials. High‐Pb solder alloys were widely used for low‐ and medium‐temperature soldering for the past decades but have been prohibited due to toxicity. Au‐based solder alloys with proper melting and mechanical properties show great potential to replace high‐Pb solder alloys and are being emphasized recently. But in comparison with Pb‐containing solder alloys, the investigation on novel Au‐based solder alloys is quite insufficient, and their performance and reliability are still unclear. In this paper, the recent research studies on Au‐based solder alloys with low temperature and medium temperature were reviewed and their microstructure, mechanical performance, and reliability were introduced and analyzed. Moreover, the novel processing technologies of Au‐based solder alloys were discussed and compared.

This article addresses the problem of designing intelligent robust tracking controls of robot systems actuated by brushed direct current motors. The structures of both mechanical and electrical dynamics are allowed to be completely unknown and adaptive fuzzy (or neural network) systems are employed to approximate these two uncertainties. Consequently, an adaptive fuzzy-based (or neural network-based) state feedback tracking controller is developed such that the resulting closed-loop system guarantees that all the states and signals are bounded and the tracking error can be made as small as possible. Finally, simulation examples are made to demonstrate the effectiveness and tracking performance.

Adding alloy elements to develop excellent properties in Al alloy/steel welding–brazing joints to realize lightweight vehicle structures has become a feasible task. Here, CMT welding–brazing was used to realize the reliable connection of Al/steel with a Cu coating. Al alloy/steel welding–brazing joints with different thicknesses of Cu coating were designed to study the influence of Cu on microstructure composition, mechanical properties and corrosion resistance. Then, the action rule of the Cu element on the interfacial microstructure evolution was clarified. The results showed that the appropriate Cu coating could effectively inhibit the reaction of Al and Fe and reduce the thickness of interfacial brittle intermetallic compounds (IMCs). Moreover, Cu could react with Al, Fe and Si to promote the formation of the τ₅-Al_7.2(Cu,Fe)_1.8Si phase and control the formation of the brittle θ-Fe(Al,Si)₃ phase, which improved the toughness of IMCs. When the thickness of the Cu coating on the surface of steel was 10 μm, the tensile strength of the Al alloy/steel CMT welding–brazing joint reached a maximum of 138.7 MPa and the corrosion resistance of the joint reached the optimum level. However, when the thickness of the Cu coating increased to 20 μm, the IMCs’ thickness at the interface of the joint reached the minimum, but Cu reacted with Al to form a brittle Al₂Cu phase under the higher Cu content, which deteriorated the tensile strength and corrosion resistance of joints. This work will provide an experimental and theoretical basis for developing good properties in Al/Cu-coating/steel welding joints.

Al alloy/steel composite structures combine the advantage of a lightweight Al alloy and high-strength steel and are widely used in new energy vehicles, solar photovoltaic, and other fields. The main problems with the connection of an Al alloy and steel are poor weld formation and difficulty in controlling the thickness of the intermetallic compounds (IMCs) at the interface of the Al alloy and steel, which deteriorates the mechanical properties and corrosion resistance of the Al alloy/steel joints. Therefore, experiments on Al alloy/steel CMT (cold metal transfer, CMT) welding brazing were conducted by using AlSi5 and AlSi12 flux-cored welding wires as filler metals. The macro morphology, microstructure composition, tensile strength, and corrosion resistance of the Al alloy/steel joints were then analyzed. The mechanism of the Noclock flux on the wettability and spreadability of the Al–Si welding wire to a low-carbon steel surface was discussed and the formation behavior of the IMCs at the interface layer of the Al alloy/steel joints was clarified. The results showed that the NH₄F and NH₄AlF₄ of the Noclock flux induced and accelerated the removal of oxide films on the surface of the Al alloy and Al–Si welding wire at a high temperature. It promoted the wettability and spreadability of the Al–Si welding wire, which resulted in the improvement of the Al alloy/steel joint formation. Under the CMT arc heat source, the Al–Si welding wire melted, and then a chemical metallurgical reaction occurred among the Al, Si, and Fe elements. The τ₅-Al_7.2Fe_1.8Si phase formed preferentially near the Al alloy fusion zone while the θ-Fe (Al, Si)₃ phase formed near the steel side. Actually, the interface reaction layer was composed of a double-layer compound including the τ₅-Al_7.2Fe_1.8Si phase and θ-Fe (Al, Si)₃ phase. Additionally, the IMC thickness of the Al alloy/steel joint with the AlSi12 flux-cored welding wire was 3.01 μm, which was less than that with the AlSi5 flux-cored welding wire, so its tensile strength was less but its corrosion resistance was superior. The main reason for the corrosion resistance of Al alloy/steel joints was the presence of a large amount of Al₂O₃, FeO, and Fe₂O₃ in the passive film.