Preparation of MXene-based hybrids and their application in neuromorphic devices

The traditional von Neumann computing architecture has relatively-low information processing speed and high power consumption,making it difficult to meet the computing needs of artificial intelligence(AI).Neuromorphic computing systems,with massively parallel computing capability and low power consumption,have been considered as an ideal option for data storage and AI computing in the future.Memristor,as the fourth basic electronic component besides resistance,capacitance and inductance,is one of the most competitive candidates for neuromorphic computing systems benefiting from the simple structure,continuously adjustable conductivity state,ultra-low power consumption,high switching speed and compatibility with existing CMOS technology.The memristors with applying MXene-based hybrids have attracted significant attention in recent years.Here,we introduce the latest progress in the synthesis of MXene-based hybrids and summarize their potential applications in memristor devices and neuromorphological intelligence.We explore the development trend of memristors constructed by combining MXenes with other functional materials and emphatically discuss the potential mechanism of MXenes-based memristor devices.Finally,the future prospects and directions of MXene-based memristors are briefly described.

MXenes and MXene-based composites for energy conversion and storage applications

MXenes have received extensive attention from scholars due to their unique layered structure,significant electrical conductivity,and excellent mechanical properties.In addition to their pristine forms,they could also be incorporated with other components for attaining hybrids and nanocomposites,accompanying with amplified functionalities.It has been widely used in lithium batteries,supercapacitors,electromagnetic shielding,tumor therapy,biosensors,photocatalysis,and other fields,and has shown great application potential in energy conversion and storage.The purpose of this article is to encyclopaedically overview the latest progress in synthesis and characterization of MXenes,while their potential applications in energy conversation such as water splitting and solar cells,as well as in energy storage such as Li-ion batteries,supercapacitors,and hydrogen energy will be comprehensively elaborated.Development opportunities and challenges are summarized.

An overview on transparent ceramics with pyrochlore and fluorite structures

Transparent ceramics have potential applications in various areas,including aerospace,relativistic optics industries,medical cares and defense.Specifically,they can be used as laser gain media,armor windows,IR domes,solid-state phosphors,scintillators and electro-optical components.From crystal structure point of view,transparent ceramic materials should have high crystallographic symmetries(cubic,tetragonal and hexagonal),which have minimal birefringent effect.Currently,transparent ceramics are dominantly based on oxide materials,although there are also nonoxides,such as fluorides and nitrides(oxynitrides).Transparent ceramics with pyrochlore and fluorite structures have attracted much attention in recent years,whereas fluorides are not well described in the open literature.Therefore,this paper is aimed to deliver an overview on the progress of the two categories of transparent ceramics,from material processing and characterization point of view.

Chinese ink-facilitated fabrication of paper-based composites as electrodes for supercapacitors

Commercial Chinese ink was employed to disperse pristine vapor-grown carbon nanofibers(VGCNFs)in aqueous suspensions via horizontal ball milling.The obtained suspension was used to fabricate conductive paper-based composites through filtration-deposition onto filter paper.It was found that the carbon black particles from the Chinese ink helped separate VGCNFs and acted as connection points between the VGCNFs,while the glue reinforced the conduction network.Thus,the VGCNF-ink/paper ternary composite showed sufficiently low sheet resistance.With merely 2.5 mg·cm^(−2)VGCNFs,the sheet resistance could be reduced to 4.5Ω·sq^(−1).As a proof of concept,these paper-based composites were directly used as electrodes of solid-state symmetric electronic double-layer capacitors(EDLCs)and the substrate for the electrodeposition of MnO_(2)to achieve higher electrochemical performances.The EDLCs fabricated with 2.5 mg·cm^(−2)VGCNFs showed a specific capacitance of 224 mF·cm^(−2)at a current density of 1 mA·cm^(−2),which was retained by 86.4%after 10,000 charge-discharge cycles.Moreover,thanks to the high electrical conductivity and the porous structure,the MnO_(2)decorated paper-based composites exhibited dramatically enhanced specific capacitance.It is believed that our finding offers an idea to directly utilize commercial Chinese ink for the fabrication of electrode materials.

Optimization of Ni_(0.95-x)Zn_(x)Co_(0.05)Fe_(1.90)Mn_(0.02)O_(4) ceramics with promising magneto-dielectric properties for VHF antenna miniaturization

Magnetic,dielectric and DC conductive properties of Ni_(0.95-x)Zn_(x)Co_(0.05)Fe_(1.90)Mn_(0.02)O_(4)(with x=0-0.20 at an interval of 0.05)ferrite ceramics were studied,in order to develop magneto-dielectric materials with almost equal values of relative permeability and permittivity,for the miniaturization of HF(3-30 MHz)and VHF(30-90MHz and 100-300 MHz)antennas.The ferrite ceramics were prepared by using the conventional two-step sintering process.The real part of relative permeability is increased almost linearly with increasing concentration of Zn,while that of relative permittivity keeps nearly unchanged.It is found that promising magneto-dielectric materials,with close values of real permeability and permittivity over 30-90 MHz(VHF),can be obtained for the samples at Zn concentrations between x=0.05 and x=0.10.

RELAXOR FERROELECTRIC MATERIALS FOR MICROWAVE TUNABLE APPLICATIONS

With strong dependences of dielectric constant on external applied electric fields,relaxor barium zirconium titanate(BaZr_(x)Ti_(1-x)O_(3)or BZT)and barium stannate titanate(BaS_(n)xTi_(1-x)O_(3)or BTS),in both bulk ceramic and thinfilm forms,are increasingly being recognized as potential candidates of microwave tunable materials for device applications.This paper is aimed to review the recent progress in understanding the dielectric properties(such as tunability,dielectric loss and dielectric constant)of these relaxor materials.However,due to their relatively high dielectric constant and loss tangent,pure Ba(Zr,Ti)O_(3) and Ba(Sn,Ti)O_(3) do not fully satisfy the requirements of practical device applications.Therefore,various strategies have been developed to improve the dielectric properties of these two groups of relaxor materials.In this paper,wefirst discussed the dielectric tunability characteristics of pure Ba(Zr,Ti)O_(3) and Ba(Sn,Ti)O_(3) and then summarized the strategies that have been used,including(i)small amount acceptor or donor doping(such as rare-earth ions and transition metal ions)and(ii)forming composites with low loss and low dielectric constant microwave dielectric materials(such as MgO,MgTiO_(3) and so on).At the same time,the relationship between relaxor behavior and dielectric tunability was also discussed.

Rapid processing of ferrite ceramics with promising magneto-dielectric characteristics

Ferrite ceramics,Ni_(0.88)Zn_(0.07)Co_(0.05)Fe_(1.98)O_(4),with the addition of 4 wt.%Bi_(2)O_(3) as sintering aid,were fabricated by using a simple one-step processing without involving the step of calcination.X-ray diffraction(XRD)results indicated that single phase ferrite ceramics can be achieved after sintering at 1000℃ for 2 h.The samples demonstrated relative densities in the range of 97-99%.Desired magneto-dielectric properties have been approached by adjusting the sintering temperature and sintering time duration.This technique is believed to be applicable to other ceramic materials.