Electrically insulating polymer dielectrics with high energy densities and excellent thermal conductivities are showing tremendous potential for dielectric energy storage. However, the practical application of polymer dielectrics often requires mutually exclusive multifunctional properties such as high dielectric constants, high breakdown strengths, and high thermal conductivities. The rational assembly of 2D nanofillers of boron nitride nanosheets (BNNS) and reduced graphene oxide (rGO) into a wellaligned micro-sandwich structure in polyimide (PI) composites is reported. The alternating stacking of rGO and BNNS synergistically exploits the large difference in their electrical conductivities to yield a high dielectric constant with a moderate breakdown strength. Moreover, the distinctively separated rGO and BNNS layers give rise to higher thermal conductivities of composites than those containing mixed fillers because of reduced phonon scattering at the interfaces between two identical fillers, as verified by molecular dynamics simulations. Consequently, the micro-sandwich nanocomposite prevails over the PI film with a simultaneously high dielectric constant of ≈579, a high energy density (43-fold higher than PI) and an excellent thermal conductivity (11-fold higher than PI) at a low hybrid filler content of only 2.5 vol%. The multifunctional nanocomposites developed in this work are promising for flexible dielectrics with excellent heat dissipation.

This paper investigates a quaternion-based finite time attitude synchronization and stabilization problem for satellite formation flying. Sufficient conditions are presented for finite time boundness and stability of this distributed consensus problem. More specifically, a nonlinear control law based on a finite time control technique is developed such that the attitude of the rigid spacecraft will coordinate and converge to the attitude of the leader, while the angular velocity will converge to zero in finite time. The associated stability proof is constructive and accomplished by adding a power integrator term in the Lyapunov function. Furthermore, to reduce the heavy communication burden, a modified control law is then designed by introducing a finite time sliding-mode estimator such that only one satellite has to communicate with the leader. Simulation results are presented to demonstrate the effectiveness of the designed scheme, especially the potential advantages derived through the inclusion of the continuous finite time control method, such as the fast convergent rate and the alleviation of chattering.

No abstract

Low surface energy materials resist adhesion due to their chemical inertness and non-wetting properties. Herein, we report the creation of a transparent ionogel adhesive that uses ion−dipole interactions to achieve a higher bonding performance to polytetrafluoroethylene (PTFE) relative to most commercial glues. The ionogel adhesive is composed of a poly(hexafluorobutyl acrylate-co-methyl methacrylate) random copolymer and a hydrophobic ionic liquid. The prepared ionogel can adhere to various hydrophobic substrates, such as PTFE, polypropylene, and polyethylene, as well as hydrophilic glass, ceramics, and steel. The design strategy and adhesion behavior are well interpreted using the density functional theory calculations and molecular dynamics simulations. The straightforward ultravioletcuring method, high optical clarity, versatile adhesion ability, and reversible adhesion capabilities make this high-performance adhesive a promising product for commercialization.