In this paper, the microstructure and the shear property of Cu/In–45Cu/Ni solder joints by transient liquid phase were studied, and the intermetallic compounds (IMCs) growth mechanism was investigated. The results showed that the IMCs volume ratio of solder joints was increased firstly and then decreased with increasing bonding time, and the IMCs volume ratio reached its maximum value of 95.8% at 60 min. The Cu interfacial IMC of the solder joint with dense microstructure was Cu2In phase at 60 min, and the Ni interfacial IMC was Ni3In7. The maximum shear strength of solder joints was obtained at 60 min, which is 15.21 MPa. The shear fracture appeared honeycomb structure, and the fracture occurred at the phase interface of Ni3In7/Cu11In9. The thickness of the interfacial IMCs and the white IMCs around the Cu particles (Cu@IMC) was increased continuously with increasing bonding time, and thus, the interconnection of Cu–Ni substrates was realized ultimately.

The excessive use of plastic, especially polystyrene (PS), has caused serious environmental pollution. The efficient utilization of plastics and the conversion of plastics into value-added carbon materials are the concerns of researchers. Herein, we propose novel “pyrolysis–deposition” method to convert one popular plastic substance, PS, into ordered mesoporous carbons (OMCs). During the synthesis process, PS is pyrolyzed into small organic gases under high temperature, which is then adsorbed through capillary adsorption into the mesoporous of SBA-15 in the presence of catalyst. The obtained OMCs have high specific surface area, uniform pore size, and ordered pore structure. The OMCs exhibit specific capacitance of 118 F/g at a current density of 0.2 A/g and electrochemical stability of 87.2% at a current density of 2 A/g after 5000 cycles. The pyrolysis–deposition strategy provides a new idea to convert waste plastics into high-performance carbon materials for electrochemical applications.

The research of high-performance flexible supercapacitors is urgent due to the rapid development of wearable and portable electronics. The key challenge is the preparation of flexible electrodes with high areal capacitance since electrodes are the most important part of supercapacitors. Compared to those conventional electrodes loading with typical flexible substrates such as textile, PET, paper et al, free-standing electrodes have many advantages such as more efficient capacity contribution, solidly embedded active materials and thinner thickness. Herein, we have successfully fabricated a novel sandwich-like structure free-standing MoO3-rGO (reduced graphene oxide) composite film electrode for flexible supercapacitors using simple vacuum filtration method followed by HI reduction process. The obtained MoO3-rGO composite film electrode shows excellent electrochemical performance, whose areal specific capacitance reaches 8972 mF·cm-2 (1.5 mA·cm-2). Here, MoO3 provides pseudocapacitance and rGO provides double-layer capacitance. After cycling for 2000 cycles, the capacity retention is 86.7%, showing good cycle stability. Besides, the as-prepared composite film has good flexibility and will not break easily during following bending, rolling, folding or twisting steps. This study has been approved to be an important step for the high-performance electrode design for free-standing flexible supercapacitors.

For any bounded linear operator A in a Banach space, two generalized condition numbers, k(A) and k(A) are defined in this paper. These condition numbers may be applied to the perturbation analysis for the solution of ill-posed differential equations and bounded linear operator equations in infinite dimensional Banach spaces. Different expressions for the two generalized condition numbers are discussed in this paper and applied to the perturbation analysis of the operator equation.