Layered Potassium Titanium Niobate/Reduced Graphene Oxide Nanocomposite as a Potassium‑Ion Battery Anode

With graphite currently leading as the most viable anode for potassium-ion batteries(KIBs),other materials have been left relatively underexamined.Transition metal oxides are among these,with many positive attributes such as synthetic maturity,longterm cycling stability and fast redox kinetics.Therefore,to address this research deficiency we report herein a layered potassium titanium niobate KTiNbO5(KTNO)and its rGO nanocomposite(KTNO/rGO)synthesised via solvothermal methods as a high-performance anode for KIBs.Through effective distribution across the electrically conductive rGO,the electrochemical performance of the KTNO nanoparticles was enhanced.The potassium storage performance of the KTNO/rGO was demonstrated by its first charge capacity of 128.1 mAh g^(−1) and reversible capacity of 97.5 mAh g^(−1) after 500 cycles at 20 mA g^(−1),retaining 76.1%of the initial capacity,with an exceptional rate performance of 54.2 mAh g^(−1)at 1 A g^(−1).Furthermore,to investigate the attributes of KTNO in-situ XRD was performed,indicating a low-strain material.Ex-situ X-ray photoelectron spectra further investigated the mechanism of charge storage,with the titanium showing greater redox reversibility than the niobium.This work suggests this lowstrain nature is a highly advantageous property and well worth regarding KTNO as a promising anode for future high-performance KIBs.

Nanocomposite superstructure of zinc oxide mesocrystal/reduced graphene oxide with effective photoconductivity

Metal oxide mesocrystals are the alignment of metal oxide nanoparticles building blocks into the ordered superstructure,which have potentially tunable optical,electronic,and electrical properties suitable for practical applications.Herein,we report an effective method for synthesizing mesocrystal zinc oxide nanorods(ZnONRs).The crystal,surface,and internal structures of the zinc oxide mesocrystals were fully characterized.Mesocrystal zinc oxide nanorods/reduced graphene oxide(ZnONRs/rGO)nanocomposite superstructure were synthesized also using the hydrothermal method.The crystal,surface,chemical,and internal structures of the ZnONRs/rGO nanocomposite superstructure were also fully characterized.The optical absorption coefficient,bandgap energy,band structure,and electrical conductivity of the ZnONRs/rGO nanocomposite superstructure were investigated to understand its optoelectronic and electrical properties.Finally,the photoconductivity of the ZnONRs/rGO nanocomposite superstructure was explored to find the possibilities of using this nanocomposite superstructure for ultraviolet(UV)photodetection applications.Finally,we concluded that the ZnONRs/rGO nanocomposite superstructure has high UV sensitivity and is suitable for UV detector applications.

Synergism of Zinc Oxide/Organoclay-Loaded Poly(lactic acid) Hybrid Nanocomposite Plasticized by Triacetin for Sustainable Active Food Packaging

The synergistic effect of organoclay(OC)and zinc oxide(ZnO)nanoparticles on the crucial properties of poly(lactic acid)(PLA)nanocompositefilms was systematically investigated herein.After their incorporation into PLA via the solvent casting technique,the water vapor barrier property of the PLA/OC/ZnOfilm improved by a maximum of 86%compared to the neat PLAfilm without the deterioration of Young’s modulus or the tensile strength.Moreover,thefilm’s self-antibacterial activity against foodborne pathogens,including gram-negative(Escherichia coli,E.coli)and gram-positive(Staphylococcus aureus,S.aureus)bacteria,was enhanced by a max-imum of approximately 98–99%compared to the neat PLAfilm.Furthermore,SEM images revealed the homo-geneous dispersion of both nano-fillers in the PLA matrix.However,the thermal stability of thefilm decreased slightly after the addition of the OC and ZnO.Thefilm exhibited notable light barrier properties in the UV-Vis range.Moreover,the incorporation of a suitable biodegradable plasticizer significantly decreased the Tg and notably enhanced theflexibility of the nanocompositefilm by increasing the elongation at break approxi-mately 1.5-fold compared to that of the neat PLAfilm.This contributes to its feasibility as an active food packa-ging material.

Photocatalytic ozonation-based degradation of phenol by ZnO—TiO_(2)nanocomposites in spinning disk reactor

Spinning disk reactor(SDR)has emerged as a novel process intensification photocatalytic reactor,and it has higher mass transfer efficiency and photon utilization for the degradation of toxic organic pollutants by advanced oxidation processes(AOPs).In this study,ZnO—TiO_(2)nanocomposites were prepared by solgel method,and coated on the disk of SDR by impregnation-pull-drying-calcination method.The performance of catalyst was characterized by X-ray diffraction,scanning electron microscope,X-ray photoelectron spectroscopy,photoluminescence and ultraviolet—visible diffuse reflectance spectroscopy.Photocatalytic ozonation in SDR was used to remove phenol,and various factors on degradation effect were studied in detail.The results showed that the rate of degradation and mineralization reached 100%and 83.4%under UV light irradiation after 50 min,compared with photocatalysis and ozonation,the removal rate increased by 69.3%and 34.7%,and mineralization rate increased by 56.7%and 62.9%,which indicated that the coupling of photocatalysis and ozonation had a synergistic effect.The radical capture experiments demonstrated that the active species such as photogenerated holes(h^(+)),hydroxyl radicals(·OH),superoxide radical(·O_(2)-)were responsible for phenol degradation,and·OH played a leading role in the degradation process,while h+and·O_(2)^(-)played a non-leading role.

Advanced Nanocomposite Arabic Gum Polyacrylic Acid Hydrogels for Flexible Supercapacitors

In this work,the fabrication and characterization of the nanocomposite hydrogel,as a solid electrode in electro-chemical cell and gel electrolyte material using Indium titanium oxide/polyethylene terephthalate(ITO/PET)flex-ible substrate for double-layer supercapacitors have been reported.The nanocomposite hydrogel composed of Arabic gum(AG),Acrylic acid(AA),reduced graphene oxide(RGO),and silver nanoparticles(AgNPs)was fab-ricated via a physical cross-linked polymerization reaction,in which the ascorbic acid was used as a reducing agent to generate AgNPs and to convert Graphene oxide(GO)to RGO during the polymerization reaction.The morphology and structural characteristics of nanocomposite hydrogel were investigated using atomic force microscopy(AFM),scanning electron microscope(SEM),Fourier transfer infrared(FTIR),and X-rayfluores-cence(XRF).Additionally,the effect of RGO and AgNPs on hydrogel stability was assessed through Thermogra-vimetric analysis(TGA)and differential scanning calorimetry(DSC),while its mechanical properties were studied using the nanoindentation test.Electrochemical impedance spectroscopy(EIS),and cyclic voltammetry(CV)were also conducted to study the electrochemical properties of the prepared hydrogel.The effects of AgNPs,RGO,and water content were all considered in the study of supercapacitor performance.The microstructural tests showed that the nanocomposite hydrogel has a relatively high swelling rate,which has a crucial effect on the capa-citance.Furthermore,the effects of increasing AgNP concentration and water content in the hydrogel matrix showed a significant improvement in its electrochemical performance,compared with that for Arabic gum poly acrylic acid(AGPAA)hydrogel itself,were the specific capacitance exhibited a significant enhancement,convert-ing from a low value to a substantially higher capacitance value.Moreover,when the nanocomposite hydrogel was used as the working electrode in an electrochemical cell with a hydrochloric acid(HCl)electrolyte solution,it exhibited good electrode performance.Additionally,using(ITO/PET)as aflexible substrate for nanocomposite hydrogel shows an improvement in their suitability for supercapacitor applications.Therefore,it is suggested that the fabricated hydrogel supercapacitor has potential applications in thefield of renewable and clean energy harvesting.

Preparation and oxidation behaviour of electrodeposited Ni-CeO_2 nanocomposite coatings

Ni-CeO2 nanocomposite coatings with different CeO2 contents were prepared by codeposition of Ni and CeO2 nanoparticles with an average particle size of 7 nm onto pure Ni surfaces from a nickel sulfate. The CeO2 nanoparticles were dispersed in the electrodeposited nanocrystalline Ni grains （with a size range of 10-30 nm）. The isothermal oxidation behaviours of Ni-CeO2 nanocomposite coatings with two different CeO2 particles contents and the electrodeposited pure Ni coating were comparatively investigated in order to elucidate the effect of CeO2 at different temperatures and also CeO2 contents on the oxidation behaviour of Ni-CeO2 nanocomposite coatings. The results show that the as-codeposited Ni-CeO2 nanocomposite coatings have a superior oxidation resistance compared with the electrodeposited pure Ni coating at 800 °C due to the codeposited CeO2 nanoparticles blocking the outward diffusion of nickel along the grain boundaries. However, the effects of CeO2 particles on the oxidation resistance significantly decrease at 1050 °C and 1150 °C due to the outward-volume diffusion of nickel controlling the oxidation growth mechanism, and the content of CeO2 has little influence on the oxidation.

Oxidation and hot corrosion of electrodeposited Ni-7Cr-4Al nanocomposite

A Ni-7Cr-4Al（mass fraction, %） nanocomposite was fabricated by co-electrodeposition of Ni with Cr（40 nm） and Al（100 nm） nanoparticles from a nickel sulfate bath, and its oxidation at 800 °C in air and hot corrosion under molten 75% Na2SO4 ＋ 25% Na Cl salts（mass fraction） at 750 °C were investigated. For comparison, Ni-11 Cr nanocomposite and Ni-film were also investigated in order to elucidate the effect of Cr nanoparticles. The results indicate that Cr and Al nanoparticles are dispersed in the electrodeposited nanocrystalline Ni grains（in size range of 20-60 nm）. Ni-7Cr-4Al nanocomposite exhibits a dramatically increased oxidation resistance compared with Ni-11 Cr nanocomposite and Ni-film due to the fast formation of alumina scale, which also improves its hot corrosion resistance under molten 75% Na2SO4 ＋ 25% Na Cl salts.

Effect of annealing treatment on cyclic-oxidation of electrodeposited Ni-Al nanocomposite

An electrodeposited Ni-Al nanocomposite having a nanocrystalline Ni matrix dispersing Al nanoparticles was annealed in vacuum at 500 ℃ for different time （3, 5 and 8 h, respectively）. The results show that the annealing treatment leads to the reaction of Ni and Al to form intermetallics and the coarsened Ni grains that are doped with a certain amount of Al atoms diffused from the nanoparticles. Cyclic oxidation in air at 1 000 ℃ indicates that the scale spallation resistance of the annealed Ni-Al nanocomposite increases with the increase of annealing time, due to prevention of the composite intergranular cracking during the cycling, reduction of numerous surface NiO nodules formed on the scale spalled area and prevention of internal oxidation.

Highly dispersed NiMo@rGO nanocomposite catalysts fabricated by a two-step hydrothermal method for hydrogen evolution

Exploring and designing a high-performance non-noble metal catalyst for hydrogen evolution reaction(HER)are crucial for the large-scale application of H2 by water electrolysis.Here,novel catalysts with NiMo nanoparticles decorated on reduced graphene oxide(NiMo@r GO)synthesized by a two-step hydrothermal method were reported.Physical characterization results showed that the prepared NiMo@r GO-1 had an irregular lamellar structure,and the NiMo nanoparticles were uniformly dispersed on the rGO.NiMo@rGO-1 exhibited outstanding HER performance in an alkaline environment and required only 93 and 180 mV overpotential for HER in 1.0 M KOH solution to obtain current densities of-10 and-50 mA·cm^(-2),respectively.Stability tests showed that NiMo@rGO-1 had a certain operating stability for32 h.Under the same condition,the performance of NiMo@rGO-1 can be comparable with that of commercial Pt/C catalysts at high current density.The synergistic effect between NiMo particles and lamellate graphene can remarkably promote charge transfer in electrocatalytic reactions.As a result,NiMo@rGO-1 presented the advantages of high intrinsic activity,large specific surface area,and small electrical impedance.The lamellar graphene played a role in dispersion to prevent the aggregation of nanoparticles.The prepared NiMo@rGO-1 can be used in anion exchange membrane water electrolysis to produce hydrogen.This study provides a simple preparation method for efficient and low-cost water electrolysis to produce hydrogen in the future.

Synthesis, properties, and applications of graphene oxide/reduced graphene oxide and their nanocomposites

Thanks to their remarkable mechanical, electrical, thermal, and barrier properties, graphene-based nanocomposites have been a hot area of research in the past decade. Because of their simple top-down synthesis, graphene oxide (GO) and reduced graphene oxide (rGO) have opened new possibilities for gas barrier, membrane separation, and stimuli-response characteristics in nanocomposites. Herein, we review the synthesis techniques most commonly used to produce these graphene derivatives, discuss how synthesis affects their key material properties, and highlight some examples of nanocomposites with unique and impressive properties. We specifically highlight their performances in separation applications, stimuli-responsive materials, anti-corrosion coatings, and energy storage. Finally, we discuss the outlook and remaining challenges in the field of practical industrial-scale production and use of graphene-derivative-based polymer nanocomposites.

Nickel Oxide/Carbon Nanotubes Nanocomposite for Electrochemical Capacitance

A nanocomposite of nickel oxide/carbon nanotubes was prepared through a simple chemical precipitation followed by thermal annealing. The electrochemical capacitance of this electrode material was studied. When the mass fraction of CNTs (carbon nanotubes) in NiO/CNT composites increases, the electrical resistivity of nanocomposites decreases and becomes similar to that of pure CNTs when it reaches 30%. The specific surface area of composites increases with increasing CNT mass fraction and the specific capacitance reaches 160 F/g under 10 mA/g discharge current density at CNT mass fraction of 10%.

Surface Oxidation of Al_2O_3/SiC Nanocomposite: Phase Transformation and Microstructure

The surface oxidation behavior of pressureless sintered Al2O3/SiC nanocomposite was studied from 1000 to 1400 ℃ for more than 10 h in air. Weight gain during the process of heat treatment was measured by TG analysis. Phase transformation and microstructure changes of these specimens due to oxidation were investigated with X-ray diffraction （XRD）, SEM and EDX technology. Thermogravimetric analysis show that the weight gain as a result of oxidation of SiC become significant above 1200 ℃. In the range of 1000 - 1300 ℃, the SiC grits are usually coated with a layer of amorphous silica after oxidation. Above 1300 ℃, the amorphous silica reacted with alumina matrix and formed mullite or crystallized into cristobalite. The rate of oxidation depends on the formation of dense cristobalite film. Large amount of needle-like mullite and alumina crystals are formed on the surface after oxidation at 1400℃.

Polyimide-silver nanocomposite containing phosphine oxide moieties in the main chain:Synthesis and properties

New flame-retardant polyimide-silver nanocomposite containing phosphine oxide moiety in the main chain was synthesized by a convenient ultraviolet irradiation technique.A precursor such as AgNO_3 was used as the source of the silver particles.Polyimide 6 as a source of polymer was synthesized by polycondensation reaction of bis（3-aminophenyl） phenyl phosphine oxide 4 with pyromellitic anhydride 5 in the presence of iso-quinoline as base and in m-cresol solution.The resulting composite film was characterized by FTIR spectroscopy,X-ray diffraction（XRD）,transmission electron microscopy（TEM）,thermogravimetry（TGA） and differential scanning calorimetry（DSC）.The average size of the nanometer Ag particles is about 10 nm.The temperature of 5 and 10%weight loss and also the char yield at 600℃of polyimide-silver nanocomposite 6a were higher than the pure PI 6.

Magnetic Fe_3O_4-Reduced Graphene Oxide Nanocomposites-Based Electrochemical Biosensing

An electrochemical biosensing platform was developed based on glucose oxidase(GOx)/Fe3O4-reduced graphene oxide(Fe3O4-RGO) nanosheets loaded on the magnetic glassy carbon electrode(MGCE).With the advantages of the magnetism, conductivity and biocompatibility of the Fe3O4-RGO nanosheets, the nanocomposites could be facilely adhered to the electrode surface by magnetically controllable assembling and beneficial to achieve the direct redox reactions and electrocatalytic behaviors of GOx immobilized into the nanocomposites. The biosensor exhibited good electrocatalytic activity, high sensitivity and stability. The current response is linear over glucose concentration ranging from 0.05 to 1.5 m M with a low detection limit of0.15 μM. Meanwhile, validation of the applicability of the biosensor was carried out by determining glucose in serum samples. The proposed protocol is simple, inexpensive and convenient, which shows great potential in biosensing application.

Effect of graphene oxide on the corrosion,mechanical and biological properties of Mg-based nanocomposite

This study investigates the effect of graphene oxide(GO)on the mechanical and corrosion behavior,antibacterial performance,and cell response of Mg–Zn–Mn(MZM)nanocomposite.MZM/GO nanocomposites with different amounts of GO(i.e.,0.5 wt%,1.0 wt%,and1.5 wt%)were fabricated by the semi-powder metallurgy method.The influence of GO on the MZM nanocomposite was analyzed through the hardness,compressive,corrosion,antibacterial,and cytotoxicity tests.The experimental results showed that,with the increase in the amount of GO(0.5 wt%and 1.5 wt%),the hardness value,compressive strength,and antibacterial performance of the MZM nanocomposite increased,whereas the cell viability and osteogenesis level decreased after the addition of 1.5 wt%GO.Moreover,the electrochemical examination results showed that the corrosion behavior of the MZM alloy was significantly enhanced after encapsulation in 0.5 wt%GO.In summary,MZM nanocomposites reinforced with GO can be used for implant applications because of their antibacterial performance and mechanical property.

Pt-Containing Ag_2S-Noble Metal Nanocomposites as Highly Active Electrocatalysts for the Oxidation of Formic Acid

Nanocomposites with synergistic effect are of great interest for their enhanced properties in a given application. Herein, we reported the high catalytic activity of Pt-containing Ag2S-noble metal nanocomposites in formic acid oxidation, which is a key reaction in direct formic acid fuel cell. The electrochemical measurements including voltammograms and chronoamperograms are used to characterize the catalytic property of Pt-containing nanocomposites for the oxidation of formic acid. In view of the limited literatures on using nanocomposites consisting of semiconductor and noble metals for catalyzing the reactions of polymer electrolyte membrane-based fuel cells, this study provides a helpful exploration for expanding the application of semiconductor-noble metal nanocomposites.

Enhanced Fenton,photo-Fenton and peroxidase-like activity and stability over Fe_3O_4/g-C_3N_4 nanocomposites

We prepared the Fe3O4/g‐C3N4nanoparticles(NPs)through a simple electrostatic self‐assembly method with a3:97weight ratio to investigate their Fenton,photo‐Fenton and oxidative functionalities besides photocatalytic functionality.We observed an improvement of the Fenton and photo‐Fenton activities of the Fe3O4/g‐C3N4nanocomposites.This improvement was attributed to efficient charge transfer between Fe3O4and g‐C3N4at the heterojunctions,inhibition of electron‐hole recombination,a high surface area,and stabilization of Fe3O4against leaching by the hydrophobic g‐C3N4.The obtained NPs showed a higher degradation potential for rhodamine B(RhB)dye than those of Fe3O4and g‐C3N4.As compared to photocatalysis,the efficiency of RhB degradation in the Fenton and photo‐Fenton reactions was increased by20%and90%,respectively.Additionally,the horseradish peroxidase(HRP)activity of the prepared nanomaterials was studied with3,3,5,5‐tetramethylbenzidinedihydrochloride(TMB)as a substrate.Dopamine oxidation was also examined.Results indicate that Fe3O4/g‐C3N4nanocomposites offers more efficient degradation of RhB dye in a photo‐Fenton system compared with regular photocatalytic degradation,which requires a long time.Our study also confirmed that Fe3O4/g‐C3N4nanocomposites can be used as a potential material for mimicking HRP owing to its high affinity for TMB.These findings suggest good potential for applications in biosensing and as a catalyst in oxidation reactions.

Buckling analysis of embedded graphene oxide powder-reinforced nanocomposite shells

In this study,the buckling analysis of a Graphene oxide powder reinforced(GOPR)nanocomposite shell is investigated.The effective material properties of the nanocomposite are estimated through Halpin-Tsai micromechanical scheme.Three distribution types of GOPs are considered,namely uniform,X and O.Also,a first-order shear deformation shell theory is incorporated with the principle of virtual work to derive the governing differential equations of the problem.The governing equations are solved via Galerkin’s method,which is a powerful analytical method for static and dynamic problems.Comparison study is performed to verify the present formulation with those of previous data.New results for the buckling load of GOPR nanocomposite shells are presented regarding for different values of circumferential wave number.Besides,the influences of weight fraction of nanofillers,length and radius to thickness ratios and elastic foundation on the critical buckling loads of GOP-reinforced nanocomposite shells are explored.

Formation mechanism of Al2O3/MoS2 nanocomposite coating by plasma electrolytic oxidation(PEO)

In this study,an Al2O3/MoS2 nanocomposite coating was created on an aluminum 1050 substrate using the plasma electrolytic oxidation method.The zeta potential measurements showed that small MoS2 particles have negative potential and move toward the anode electrode.The nanoparticles of MoS2 were found to have a zeta potential of-25 mV,which prevents suspension in the solution.Thus,to produce an Al2O3/MoS2 nanocomposite,one has to use the microparticles of MoS2.The X-ray diffraction analyses showed that the produced coatings containedα-Al2O3,γ-Al2O3,and MoS2,and that the size of MoS2 particles can be reduced to 30 nm.It was observed that prolonged suspension in the electrolyte results in an enhanced formation of an Al2O3/MoS2 nanocomposite.Using the results,it was hypothesized that the mechanism of the formation of the Al2O3/MoS2 nanocomposite coating on the aluminum 1050 substrate is based on electrical energy discharge.

Electro-conductive Nanocrystalline Cellulose Film Filled with TiO_2-ReducedGraphene Oxide Nanocomposite

Imparting electro-conductive properties to nanocellulose-based products may render them suitable for applications in electronics, optoelectronics, and energy storage devices. In the present work, an electro-conductive nanocrystalline cellulose （NCC） film filled with TiO2-reduced-graphene oxide （TiO2-RGO） was developed. Initially, graphene oxide （GO） was prepared using the modified Hummers method and thereafter photocatalytically reduced using TiO2 as a catalyst. Subsequently, an electro-conductive NCC film was prepared via vacuum filtration with the as-prepared TiO2-RGO nanocomposite as a functional filler. The TiO2-RGO nanocomposite and the NCC/TiO2-RGO film were systematically characterized. The results showed that the obtained TiO2-RGO nanocomposite exhibited reduced oxygen-containing group content and enhanced electro-conductivity as compared with those of GO. Moreover, the NCC flm flled with TiO2-RGO nanocomposite displayed an electro-conductivity of up to 9.3 S/m and improved mechanical properties compared with that of the control. This work could provide a route for producing electro-conductive NCC flms, which may hold signifcant potential as transparent ？exible substrates for future electronic device applications.