Preparation And Properties Of (Mg_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2O High-Entropy Oxide

One-dimensional nanostructures,such as nanowires,nanobelts,nanofibers,nanorods,have large specific surface area.It has attracted widespread attention because of its exhibit unique electronic properties,mechanical properties,and catalytic properties.Electrospinning technology is a facile and low-cost process.Electrospinning technology has been widely used in the preparation of ceramic nanomaterials.By controlling the diameter,composition and morphology in electrospinning,property of ceramic nanomaterials can be distinctly enhanced.High-entropy oxide(MgCoNiCuZn)O has exhibted exellent insulation,corrosion resistance,low thermal conductivity,anti-ferromagnetic,catalysis,and lithium storage property.In this disteration,(MgCoNiCuZn)O was prepared by electrospinning technology and ultrafast high-temperature sintering(UHS),and its electrical properties were studied.The specific contents are as follows:First,(MgCoNiCuZn)O high-entropy nanowires has been prepared by electrospinning for the first time.Effects of polymers,calcining temperatures and holding times on the phase composition,microstructure and electrochemical property have been invrstigated.(MgCoNiCuZn)O nanowire with single rock salt phase is obtained after calcinating at 850? for 2 minutes,and quenching in air.(MgCoNiCuZn)O nanowire was used as the anode material to assemble lithium-ion batteries to study its electrochemical performance.Lithium-ion battery with(MgCoNiCuZn)O nanowire has better cycle stability and specific capacity.As the calcination temperature increasing,the crystal grains and fiber diameters of(MgCoNiCuZn)O become larger,and the discharge specific capacity and rate performance of the lithium-ion half-cell decreases.The diameter of the nanowire prepared by calcination at 850 ? for 2 min is about 400 nm,and the lithium-ion half-cell has higher discharge specific capacity.At a current density of 200 m A/g,the specific discharge capacity reaches 300 m Ah/g.To reduce the calcination time,the as-spun fiber precursor was prepared by the bovel ultrafast high-temperature sintering method,which can shortens the time for preparing(MgCoNiCuZn)O.Carbon-coated(MgCoNiCuZn)O can be obtained as the current is140A,150A and 160A,and sintered for 4 min.Composite of(MgCoNiCuZn)O and PVDF were prepared by cold sintered process after adding(MgCoNiCuZn)O by the ultrafast high-temperature sintering and conventional process,respectively.The dielectric constant of composite is increased to 17(1 k Hz)after adding 80wt%(MgCoNiCuZn)O nanofiber by conventional process,which is 3 times that of the pure PVDF.Much notable enhancement of dielectric constant about 5.7,7,8 times that of the pure PVDF have been achieved by adding C coated(MgCoNiCuZn)O powder by ultrafast high-temperature sintering process at 140 A,150 A and 160 A,respectively.