Dissolution and recrystallization of perovskite induced by N-methyl-2-pyrrolidone in a closed steam annealing method

High quality perovskite films with large columnar grains are greatly desired for efficient perovskite solar cells. Here, low volatility N-methyl-2-pyrrolidone(NMP) was added in MAI/IPA solution in a two-step spin-coating method, which promoted the conversion of lead iodide to perovskite. The perovskite films were annealed by a closed-steam annealing method to prolong the recrystallization process of perovskite films assisted by the residual NMP. It leaded to high quality CH_3NH_3PbI_3 perovskite films with large columnar grains due to its enhancement of the Oswald ripening. The large grain perovskite film leaded to efficient carrier transformation and injection, and low recombination. The photovoltaic performance of the perovskite solar cells was improved significantly.

Polarizable Additive with Intermediate Chelation Strength for Stable Aqueous Zinc‑Ion Batteries

Aqueous zinc-ion batteries are promising due to inherent safety,low cost,low toxicity,and high volumetric capacity.However,issues of dendrites and side reactions between zinc metal anode and the electrolyte need to be solved for extended storage and cycle life.Here,we proposed that an electrolyte additive with an intermediate chelation strength of zinc ion—strong enough to exclude water molecules from the zinc metal-electrolyte interface and not too strong to cause a significant energy barrier for zinc ion dissociation—can benefit the electrochemical stability by suppressing hydrogen evolution reaction,overpotential growth,and den-drite formation.Penta-sodium diethylene-triaminepentaacetic acid salt was selected for such a purpose.It has a suitable chelating ability in aqueous solutions to adjust solvation sheath and can be readily polarized under electrical loading conditions to further improve the passivation.Zn||Zn symmetric cells can be stably operated over 3500 h at 1 mA cm^(-2).Zn||NH4V4O10 full cells with the additive show great cycling stability with 84.6%capacity retention after 500 cycles at 1 A g^(-1).Since the additive not only reduces H2 evolution and corrosion but also modifies Zn2+diffusion and deposition,highlyreversible Zn electrodes can be achieved as verified by the experimental results.Our work offers a practical approach to the logical design of reliable electrolytes for high-performance aqueous batteries.

Controllable fabrication and multifunctional applications of graphene/ceramic composites

Graphene with excellent comprehensive properties has been considered as a promising filler to reinforce ceramics.While numerous studies have been devoted to the improvement of mechanical and electrical properties,incorporating graphene to ceramics also offers new opportunities for endowing ceramics with versatility.In this review,the recent development of graphene/ceramic bulk composites is summarized with the focus on the construction of well-designed architecture and the realization of multifunctional applications.The processing technologies of the composites are systematically summarized towards homogeneous dispersion and even ordered orientation of graphene sheets in the ceramic matrix.The improvement of composites in mechanical,electrical,electromagnetic,and thermal performances is discussed.The novel multifunctional applications brought by smart integration of graphene in ceramics are also addressed,including microwave absorption,electromagnetic interference shielding,ballistic armors,self-monitor damage sensors,and energy storage and conversion.

Novel Synthesis of Sol-gel Derived Nanosized Mullite Powder

Using hydrous aluminum chloride （AlCl3·6H2O） and silicon ethoxide （Si （OC2H5）4） as raw materials, a kind of nano-sized mullite powder was synthesized with the sol-gel process at the medium calcination temperature. The microstructures of the alumina-silica binary aerogel and calcined nano-sized materials were investigated by means of thermogravimetry-differential thermal analysis （TG-DTA）, scanning electron microscopy （SEM） and X-ray diffractometer （XRD）. The results show that the mullitization of Al2O3-SiO2 in gel starts from about 1 000℃ and its formation ofmullite takes place in the range of 1 100℃-1 250 ℃. The size of the nano-sized mullite powder calcined at 1 250 ℃ is measured to be about 30 nm.

Quantitative law of diffusion induced fracture

Through dimension analysis, an almost analytical model for the maximum diffusion induced stress（DIS）and critical temperature（or concentration） difference at which cracks begin to initiate in the diffusion process is developed. It interestingly predicts that the spacing of diffusioninduced cracks is constant, independent of the thickness of specimen and the temperature difference. These conclusions are validated by our thermal shock experiments on alumina plates. Furthermore, the proposed model can interpret observed hierarchical crack patterns for high temperature jump cases, and a three-stage relation between the residual strength and the temperature difference. The prediction for crack spacing can guide the biomimetic thermal-shockfailure proof design, in which the hard platelets smaller than the predicted diffusion induced by constant crack-spacing are embedded in a soft matrix, and, therefore, no fracture will happen. This may guide the design of the thermal protection system and the lithium ion battery. Finally we present the maximum normalized DISes for various geometry and boundary conditions by single-variable curves for the stressindependent diffusion process and two-variable contour plots for the stress-dependent diffusion process, which can provideengineers and materialists a simple and easy way to quickly evaluate the reliability of related materials and devices.

Effects of silver-doping on properties of Cu(In,Ga)Se_(2) films prepared by Cu In Ga precursors

The AgCuInGa alloy precursors with different Ag concentrations are fabricated by sputtering an Ag target and a CuInGa target.The precursors are selenized in the H_(2)Se-containing atmosphere to prepare(Ag,Cu)(In,Ga)Se_(2)(ACIGS)absorbers.The beneficial effects of Ag doping are demonstrated and their mechanism is explained.It is found that Ag doping significantly improves the films crystallinity.This is believed to be due to the lower melting point of chalcopyrite phase obtained by the Ag doping.This leads to a higher migration ability of the atoms that in turn promotes grain boundary migration and improves the film crystallinity.The Ga enrichment at the interface between the absorber and the back electrode is also alleviated during the selenization annealing.It is found that Ag doping within a specific range can passivate the band tail and improve the quality of the films.Therefore,carrier recombination is reduced and carrier transport is improved.The negative effects of excessive Ag are also demonstrated and their origin is revealed.Because the atomic size of Ag is different from that of Cu,for the Ag/(Ag+Cu)ratio(AAC)≥0.030,lattice distortion is aggravated,and significant micro-strain appears.The atomic radius of Ag is close to those of In and Ga,so that the continued increase in AAC will give rise to the Ag;or Ag;defects.Both the structural and compositional defects degrade the quality of the absorbers and the device performance.An excellent absorber can be obtained at AAC of 0.015.

Electrospinning of ceramic nanofibers:Fabrication,assembly and applications

This paper provides a brief review of current research activities that focus on the synthesis and controlled assembly of inorganic nano-bers by electrospinning,their electrical,optical and magnetic properties,as well as their applications in various areas including sensors,catalysts,batteries,filters and separators.We begin with a brief introduction to electrospinning technology and a brief method to produce ceramic nanofibers from electrospinning.We then discuss approaches to the controlled assembly and patterning of electrospun ceramic nanofibers.We continue with a highlight of some recent applications enabled by electrospun ceramic nano-bers,with a focus on the physical properties of functional ceramic nanofibers as well as their applications in energy and environmental technologies.In the end,we conclude this review with some perspectives on the future directions and implications for this new class of functional nanomaterials.It is expected that this review paper can help the readers quickly become acquainted with the basic principles and particularly the experimental procedure for preparing and assembly of 1D ceramic nanofiber and its arrays.

Controllable preparation and microwave absorption properties of shape anisotropic Fe_(3)O_(4) nanobelts

To substantially prevent electromagnetic threatens,microwave absorbing materials(MAMs)are required to eliminate surplus electromagnetic waves.As a typical MAM,Fe_(3)O_(4) particles with complex permittivity and permeability have been widely applied due to the coexistence of magnetic loss and dielectric loss.However,the necessary high mass fraction significantly limited its applications,thus Fe_(3)O_(4) nanostructures have been extensively investigated to overcome this problem.In this work,uniform Fe_(3)O_(4) nanobelts were prepared by electrospinning and two-step thermal treatment.By controlling the composition and viscosity of the electrospinning precursor solution,Fe_(3)O_(4) nanobelts with tunable lateral sizes(200 nme1 mm)were obtained.The samples with low content(only 16.7 wt%)Fe_(3)O_(4) exhibited wide maximum effective absorbing bandwidths(EAB)over 3 GHz,and Fe_(3)O_(4) nanobelts with smaller lateral sizes showed a maximum EAB of 4.93 GHz.Meanwhile,Fe_(3)O_(4) nanobelts with smaller lateral sizes presented superior reflection loss properties,the lowest reflection loss reached-53.93 dB at 10.10 GHz,while the maximum EAB was up to 2.98 GHz.The excellent microwave reflection loss of Fe_(3)O_(4) nanobelts was contributed to the enhanced synergistic effect of magnetic loss,dielectric loss,and impedance matching,originated from the hierarchically cross-linked networks and shape anisotropies.This study could broaden the practical applications of magnetic absorbers,and provided an approach for the development of shape anisotropic magnetic materials.

In situ polymerization of 1,3-dioxolane infiltrating 3D garnet framework with high ionic conductivity and excellent interfacial stability for integrated solid-state Li metal battery

The polymer-ceramic composite electrolyte is considered as one of promising electrolytes for solid-state battery.However,in previous research,ceramic particles are usually dispersed in polymer matrix and could not form continuous Li+conductive channels.The agglomeration of ceramic particles could also lead to low ionic conductivity and poor interfacial electrode/electrolyte contact.In this paper,self-supported porous Li_(6.4)La_(3) Zr_(1.4)Ta_(0.6)O_(12)(LLZTO) electrolyte is synthesized by gelcasting process,which possesses three-dimensional(3D) interconnected pore channels and relatively high strength.The 1,3-dioxolane(DOL) could penetrate into the porous LLZTO framework for its excellent fluidity.The subsequent in situ polymerization process by thermal treatment could completely fill the internal pores and improve the interfacial contact with electrode.The resulting 3D composite electrolyte with dual continuous Li+transport channels in ceramic and polymer components exhibits high ionic conductivity of 2.8 × 10^(-4) S·cm^(-1) at room temperature and low Li/electrolyte interfacial resistance of 94 Ω·cm^(2) at 40 ℃.The corresponding Li/Li symmetric cell delivers stable voltage profiles for over 600 h under 0.1 and 0.2 mA·cm^(-2).The solid-state Li/LiFePO_(4) battery shows superior rate and cycling performance under 0.1 C and 0.2 C.This work guides the preparation of composite electrolyte with dual continuous Li+conductive paths as well as high ceramic ratio and interface modification strategy for solid-state Li metal battery.

Characterization of individual grain boundaries and grains of CaCu_3Ti_4O_(12) ceramic

Microcontact measurement is employed to locally investigate the electric and dielectric properties of individual grains and grain boundaries in CaCu3Ti4O12 ceramic. The measurements give more detail of the impedance spectroscopy, capacitance, and I-V characteristics of the microstructure, and will help with further understanding of the mechanism of the electric and dielectric properties of CaCu3Ti4O12 ceramics.

Grain size refinement of additive manufactured Ce-TZP ceramics by coupled two-step pre-sintering and HIP

Ceria-stabilized tetragonal zirconia polycrystal(Ce-TZP)has exceptional fracture toughness and flaw tolerance due to facile t‒m phase transformation toughening.However,its wider-range applications are limited by its relatively low strength due to its large grain size and low transformation stress,which results in yield-like failure.Here,we combined additive manufacturing(AM),pressureless two-step sintering,and hot isostatic pressing(HIP),and addressed the challenging grain size refinement problem in Ce-TZPs.We successfully produced dense ultrafine-grained Ce-TZP ceramics with an average grain size below 500 nm,a three-point bending strength above 800 MPa,and a single-edge-notch-beam fracture toughness in the range of 11‒12 MPa·m^(1/2).The critical roles of processing design,mixed Ce valences,and under-vs.over-stabilization of tetragonal polymorphs were noted.Our work offers insights and strategies for the future development of stronger and tougher Ce-TZP ceramics that can compete with tetragonal yttria-stabilized zirconia in various applications,including additive manufacturing.

Nanocellulose-Graphene Hybrids: Advanced Functional Materials as Multifunctional Sensing Platform

Naturally derived nanocellulose with unique physiochemical properties and giant potentials as renewable smart nanomaterials opens up endless novel advanced functional materials for multi-sensing applications.However,integrating inorganic functional two-dimensional carbon materials such as graphene has realized hybrid organic-inorganic nanocomposite materials with precisely tailored properties and multi-sensing abilities.Altogether,the affinity,stability,dispersibility,modification,and functionalization are some of the key merits permitting their synergistic interfacial interactions,which exhibited highly advanced multifunctional hybrid nanocomposites with desirable properties.Moreover,the high performance of such hybrids could be achievable through green and straightforward approaches.In this context,the review covered the most advanced nanocellulose-graphene hybrids,focusing on their synthetization,functionalization,fabrication,and multi-sensing applications.These hybrid films exhibited great potentials as a multifunctional sensing platform for numerous mechanical,environmental,and human bio-signals detections,mimicking,and in-situ monitoring.

Dielectric and Ferroelectric Properties of BaTiO_3 Nanofibers Prepared via Electrospinning

BaTiO3 nanofibers of about 400 nm in diameter were synthesized via electrospinning.The evolution of the morphology and phase composition of the BaTiO3 nanofibers was studied by scanning electron microscopy and X-ray diffraction within the annealing temperature of 750-1050 ℃.Higher annealing temperature led to rougher surface and better crystallization of the BaTiO3 nanofibers.Below 1050 ℃,the BaTiO3 nanofibers maintained its large aspect ratios and could still be regarded as individual nanofiber.The dielectric permittivities of the BaTiO3 nanofibers（εr 820） were calculated with the MG equation by considering the porous bulk specimens as composites of BaTiO3 nanofibers and air.The ferroelectric properties of the BaTiO3nanofibers were measured by using a ferroelectric analyzer coupled with an atomic force microscope.P-E loop measured for the BaTiO3 nanofiber exhibits small hysteresis.

Nest-like multilevel structured graphene oxide-on-polyacrylonitrile membranes for highly efficient filtration of ultrafine particles

Developing filtration media for particulate matter(PM)removal has been proven to be extremely challenging.Here,we report a facile and scalable strategy to fabricate a multi-level structured polyacrylonitrile/graphene oxide(PAN/GO)air filtration membrane to remove ultrafine particles in air by combining multi-jet electrospinning and physical bonding.Our approach allows the thin PAN nanofibers and two-dimensional GO nanosheets to form interpenetrating bonding structures on non-woven fabric and to assemble into stable filtration media.The resultant composite membranes can filtrate 300 nm particles with a high removal efficiency of 98.8%,a low pressure drop of 55 Pa,and a desirable quality factor of 0.34 Pa^(-1).This multi-level PAN/GO filter is expected to have wider applications not only for the ultrafine particle filtration and separation but also for the design of three-dimensional functional structures in the future.

Energy storage properties of 0.87BaTiO3-0.i3Bi(Zn2/3(Nb0.85Ta0.15)1/3)O3 multilayer ceramic capacitors with thin dielectric layers

Multilayer ceramic capacitors(MLCCs)for energy storage applications require a large discharge energy density and high discharge/charge efficiency under high electric fields.Here,0.87BaTiO3--0.13Bi(Zn23(Nbog8sTao.1s)u3)O3(BTBZNT)MLCCs with double active dielectric layers were fabricated,and the effects of inner electrode and sintering method on the energy storage properties of BTBZNT MLCCs were investigated.By using the pure Pt as inner electrode instead of Ago.6Pdo4 aloys,an alternating current(AC)breakdown strength(BDS)enhancement from 1047 to 1500 kV/cm was achieved.By investigating the leakage current behavior of BTBZNT MLCCs,the Pt inner electrode and two-step sintering method(TSS)were confirmed to enhance the Schottky barrier and minimize the leakage current density.With relatively high permitivity,dielectric sublinearity,and ultra-high BDS,the Pt TSS BTBZNT MLCCs exhibited a surprisingly discharge energy density(Udis)of 14.08 J/cm2.Moreover,under an operating electric field of 400 kV/cm,the MLCCs also exhibited thermal stability with Udis variation<±8%over a wide temperature (t) range from-50 to 175℃ and cycling reliability with Uais reduction<0.3%after 3000 charge-discharge cycles.These remarkable performances make Pt TSS BTBZNT MLCCs promising for energy storage applications.

Thermal shock behavior of ZrB2-SiC ceramics with different quenching media

The thermal shock behavior of ZrB2-SiC ceramics was studied with water, air and methyl silicone oil as quenching media, respectively. The temperature of all coolants was room temperature （25℃） and the residual strength of the ceramics after quenching was tested. The strength of the ceramics after water quenching had an obvious drop when the temperature difference, AT, was about 275℃, while the residual strength of the specimens quenched by air and silicone oil only varied a little and even increased slightly when the temperature difference was higher than 800℃. The different thermal conductive coefficient of the coolants and surface heat transfer coefficient resulted in the differences in the thermal shock behavior. The formation of oxidation layer was beneficial for improving the residual strength of the ceramics after quenching.

Effect of water vapor on NH_3–NO/NO_2 SCR performance of fresh and aged MnO_x–NbO_x–CeO_2 catalysts

A MnOx-NbOx-CeO2 catalyst for low temperature selective catalytic reduction（SCR） of NOx with NH3 was prepared by a sol-gel method, and characterized by NH3-NO/NO2 SCR catalytic activity, NO/NH3 oxidation activity, NOx/NH3 TPD, XRD, BET, H2-TPR and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy（DRIFTS）. The results indicate that the Mn Ox-Nb Ox-CeO2 catalyst shows excellent low temperature NH3-SCR activity in the temperature range of 150-300℃. Water vapor inhibits the low temperature activity of the catalyst in standard SCR due to the inhibition of NOx adsorption. As the NO2 content increases in the feed, water vapor does not affect the activity in NO2 SCR. Meanwhile, water vapor significantly enhances the N2 selectivity of the fresh and the aged catalysts due to its inhibition of the decomposition of NH4NO3 into N2O.

Tunnel elasticity enhancement effect of 3D submicron ceramics(A_(l)2O_(3),TiO_(2),ZrO_(2)) fiber on polydimethylsiloxane (PDMS)

Some polymers are flexible,foldable,and wearable.Structural-functional composite is fabricated by adding inorganic fillers with functional properties.Up to date,compared with the polymer matrix,the composite prepared by polymer-inorganic fillers has lower flexibility,higher brittleness,and higher modulus of elasticity.In this paper,three-dimensional (3D) net-shaped submicron α-Al_(2)O_(3),orthorhombic ZrO_(2),and rutile TiO_(2) fiber were fabricated by solution blowing spinning on a large scale.On the contrary,the elastic modulus (E) of the composite prepared by this 3D ceramic fiber was greatly reduced,and the flexibility of the composite was higher than that of the polymer matrix.When the strain was 75%,the E of the 3D net-shaped Al_(2)O_(3) fiber-polydimethylsiloxane(PDMS) composite was 20% lower than that of PDMS.When the strain was 78%,the E of the 3D net-shaped TiO_(2) fiber-PDMS and 3D net-shaped ZrO_(2) fiber-PDMS composites decreased by 20% and 25%,respectively.This abnormal effect,namely the tunnel elastic enhancement effect,has great practical significance.In all-solid-state lithium-ion batteries,the composite inhibits lithium dendrite growth and the 3D inorganic network contributes to lithium ion transport.It is possible to promote the industrial production of low-cost and large-scale flexible solid-state lithium-ion batteries and it can enhance the energy storage density of energy storage materials.This novel idea also has bright prospects in flexible electronic materials.

Flexible and highly-sensitive pressure sensor based on controllably oxidized MXene

Conductive Ti_(3)C_(2)T_(x)MXenes have been widely investigated for the construction of flexible and highly-sensitive pressure sensors.Although the inevitable oxidation of solution-processed MXene has been recognized,the effect of the irreversible oxidation of MXene on its electrical conductivity and sensing properties is yet to be understood.Herein,we construct a highly-sensitive and degradable piezoresistive pressure sensor by coating Ti_(3)C_(2)T_(x)MXene flakes with different degrees of in situ oxidation onto paper substrates using the dipping-drying method.In situ oxidation can tune the intrinsic resistance and expand the interlayer distance of MXene nanosheets.The partially oxidized MXene-based piezoresistive pressure sensor exhibits a high sensitivity of 28.43 kPa^(-1),which is greater than those of pristine MXene,over-oxidized MXene,and state-of-the-art paper-based pressure sensors.Additionally,these sensors exhibit a short response time of 98.3 ms,good durability over 5000 measurement cycles,and a low force detection limit of 0.8 Pa.Moreover,MXene-based sensing elements are easily degraded and environmentally friendly.The MXene-based pressure sensor shows promise for practical applications in tracking body movements,sports coaching,remote health monitoring,and human–computer interactions.