High performance wide band-gap power device is expected to be operated in high temperature. Electroless Ni-P plating film is widely used to provide suitable surface for device packaging. However, commonly used electroless Ni-P plating (P: 6-12 wt %) causes embrittlement resulting cracking in high temperature. In this study, we introduce a cracking-less, heat-resistant electroless Ni-P plating film and its heat-resistant characteristics in comparison with conventional plating films.
In this work, we assembled thermal cycling equipment by a halogen lamp heater and applied the acoustic emission (AE) technique to real-time monitor and diagnose the health state of die attach structures used in power electronics. The assembled equipment is able to execute a cycling environment with a temperature variation from room temperature to 165 °C. Meanwhile, AE monitoring can be applied at the same time to real-time diagnose the health condition of a die attach structure. A soldered die attach structure was tested by 10000 cycles on this platform. AE signals were acquired during the cycling test, which originated from solder layer cracks that were confirmed by scanning acoustic tomography observations. This platform shows a superior specialty in detecting cracking of solder layer due to the high sensitivity of AE monitoring. Meanwhile, the cumulative AE counts that indicate the degree of cracking can be an important indication for diagnosing the health condition of the die attach structure.
Three-dimensional (3D) Na2Ti6O13 microflowers assembled from directionally arranged and closely interlinked one-dimensional N-doped carbon Na2Ti6O13 nanorods have been successfully prepared by a self-sacrificed template method followed by sintering in argon. In situ high-temperature X-ray powder diffraction (XRD) characterization was conducted to explore the phase transformation and structural evolution. The results indicated that the NaTi3O6(OH)·2H2O precursor was converted into the tunnel Na2Ti6O13 phase and the layered Na2Ti3O7 phase at the different temperatures. At a certain temperature, the tunnel and layered phases have a mutual transformation. The higher temperature was not conductive to the formation of pure phases. The crystal structural evolution has been given based on the synthesis process and in situ high temperature XRD patterns. When served as anode for SIBs, a capacity of ca. 30 mAh g–1 over 6000 continuous cycles was retained at 2000 mA g–1. Moreover, the structural and morphology integrity, reaction mechanism and pseudocapacitance behavior were also investigated.
Software-based redundant execution (SRE) is a popular fault-tolerant design method which makes use of faults occurring randomly. Software-based heterogeneous redundant execution (SHRE) uses heterogeneous redundant software replicas with identical function based on SRE and diversity of software. By voting the results of heterogeneous redundant software replicas, SHRE can resist threats from software vulnerabilities and monoculture. SHRE resisting network attacks was proved to be reliable. The classification method of SHRE was proposed, and the costs analysis method of SHRE was introduced. Finally, the costs calculation process was taken as an example.
The application of concrete containing mineral admixtures was attempted in Northwest China in this study, where the environment has the characteristics of low humidity and large temperature variation. The harsh environment was simulated by using an environmental chamber in the laboratory and four types of concrete were prepared, including ordinary concrete and three kinds of mineral admixture concretes with different contents of fly ash and blast-furnace slag. These concretes were cured in the environmental chamber according to the real curing conditions during construction. The compression strength, fracture properties, SEM images, air-void characteristics, and X-ray diffraction features were researched at the early ages of curing before 28 d. The results showed that the addition of fly ash and slag can improve the compression strength and fracture properties of concrete in the environment of low humidity and large temperature variation. The optimal mixing of mineral admixture was 10% fly ash and 20% slag by replacing the cement in concrete, which can improve the compression strength, initial fracture toughness, unstable fracture toughness, and fracture energy by 23.9%, 25.2%, 45.3%, and 22.6%, respectively, compared to ordinary concrete. Through the analysis of the microstructure of concrete, the addition of fly ash and slag can weaken the negative effects of the harsh environment of low humidity and large temperature variation on concrete microstructure and cement hydration.
The application of sodium titanate anodes of low cost, feasible operating voltage, and nontoxic nature were severely hindered by their inferior cycling stability and poor rate capability. Here, three-dimensional (3D) chestnut-like NaTi3O6(OH)·2H2O@N-doped carbon nanospheres (NTOH@CN) with loose crystal structures were prepared by a self-sacrificed template method. The nanospheres were composed of nanosheets and linked with nanowires, which interweaved to construct a meshwork structure. The growth mechanism of unique 3D NTOH@CN nanospheres was investigated by tracking the synthesis process of different hydrothermal durations. The rate performances of 3D NTOH@CN were superior to that of NaTi3O6(OH)·2H2O irregular spheres assembled from nanosheets (3D NTOH) and NaTi3O6(OH)·2H2O nanosheets (two-dimensional NTOH). Excellent cycling and rate performance were obtained due to their open crystal structure, unique 3D nanosphere morphology with short diffusion paths, N-doped carbon surrounding, and the solid solution reaction. In addition, the reaction mechanism, morphology change, and dynamics research during the sodium insertion/desertion process have been carefully studied. Based on varying ex situ analyses, the irreversible metallic titanium formation and the excellent structural stability of nanosphere morphology have been evidenced. The pseudocapacitive phenomenon was also detected, which effectively enhanced Na+ ion storage capability. The systematical and comprehensive study provide a holograph for the design and synthesis of sodium titanate nanostructures.
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