Ultrafine red phosphorus confined in reasonably designed pitch-based carbon matrix built of well-interconnected carbon nanosheets for high-performance lithium and potassium storage

Red phosphorus has been well-recognized as promising anode materials for lithium-ion batteries(LIBs)and potassium-ion batteries(PIBs)due to its extremely high theoretical capacity and low cost.However,the huge volume change and poor electric conductivity severely limit its further practical application.Herein,the nanoscale ultrafine red phosphorus has been successfully confined in a three-dimensional pitch-based porous carbon skeleton composed of well-interconnected carbon nanosheets through the vaporization-condensation method.Except for the traditional requirement of high electric conductivity and stable mechanical stability,the micropores and small mesopores in the porous carbon matrix centered at 1 to 3 nm and the abundant amount of oxygen-containing functional groups are also beneficial for the high loading and dispersion of red phosphorus.As anode for LIBs,the composite exhibits high reversible discharge capacities of 968 mAh g^(-1),excellent rate capabilities of 593 mAh g^(-1)at 2 A g^(-1),and long cycle performance of 557 mAh g^(-1)at 2 A g^(-1).More impressively,as the anode for PIBs,the composite presents a high reversible capacity of 661 mAh g^(-1)and a stable capacity of 312 mAh g^(-1)at 0.5 A g^(-1)for 500 cycles with a capacity retention up to 84.3%.This work not only sheds light on the structure design of carbon hosts with specific pore structure but also open an avenue for high value-added utilization of coal tar pitch.

Dynamic modeling of hydrostatic guideway considering compressibility and inertia effect

Hydrostatic guideways are used as an alter- native to contact bearings due to high stiffness and high damping in heavy machine tools. To improve the dynamic characteristic of bearing structure, the dynamic modeling of the hydrostatic guidway should be accurately known. This paper presents a ＂mass-spring-Maxwell＂ model considering the effects of inertia, squeeze, compressibility and static bearing. To determine the dynamic model coefficients, numerical simulation of different cases between displacement and dynamic force of oil film are performed with fluent code. Simulation results show that hydrostatic guidway can be taken as a linear system when it is subjected to a small oscillation amplitude. Based on a dynamic model and numerical simulation, every dynamic model＇s parameters are calculated by the Levenberg- Marquardt algorithm. Identification results show that ＂mass-spring-damper＂ model is the most appropriate dynamic model of the hydrostatic guidway. This paper provides a reference and preparation for the analysis of the dynamic model of the similar hydrostatic bearings.