Preparation,Characterization and Photothermal Study of PVA/Ti_(2)O_(3) Composite Films

In this work,flexible photothermal PVA/Ti_(2)O_(3) composite films with different amount(0 wt%,5 wt%,10 wt%,15 wt%)of Ti_(2)O_(3) particles modified by steric acid were prepared by a simple solution casting method.The microstructures,XRD patterns,FTIR spectra,UV-Vis-NIR spectra thermo-conductivity,thermo-stability and photothermal effects of these composite films were all characterized.These results indicated that Ti_(2)O_(3) particles were well dispersed throughout the polyvinyl alcohol(PVA)matrix in the PVA/Ti_(2)O_(3) composite films.And Ti_(2)O_(3) particles could also effectively improve the photothermal properties of the composite films which exhibited high light absorption and generated a high temperature(about 57.4℃for film with 15 wt%Ti_(2)O_(3) amount)on the surface when it was irradiated by a simulated sunlight source(1 kW/m^(2)).

Preparation and Characterization of Cellulose Nanofibril-Waterborne Polyurethane Composite Films

To improve the performance of polyurethane films,small amounts of cellulose nanofibrils(CNF)were physically blended with a waterborne polyurethane(WPU)emulsion,and then CNF/WPU composite films were prepared by cast-coating and drying.The particle size of the emulsions and the chemical structure,micromorphology,thermal stability,mechanical properties,and water resistance of the composite films were characterized using a Malvern laser particle size analyzer,Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),thermogravimetric analysis(TGA),an electronic strength machine,water contact angle analysis(WCA),and water absorption tests,respectively.The results showed that at a low CNF content of 0.3 wt%,the particle size of the WPU emulsion and chemical structure of the film did not change significantly.In addition,the tensile strength of the composite film increased by up to 108%compared to the neat WPU film,and the thermal stability and water resistance were slightly improved.The addition of CNF greatly enhanced the tensile strength while maintaining the other original properties of the WPU film,which may greatly improve the service life and tear resistance of commercial coatings in the future.

Preparation and Properties of Vegetable-Oil-Based Thioether Polyol and Ethyl Cellulose Supramolecular Composite Films

Ethyl cellulose(EC),an important biomass-based material,has excellent film-forming properties.Nevertheless,the high interchain hydrogen bond interaction leads to a high glass transition temperature of EC,which makes it too brittle to be used widely.The hydroxyl group on EC can form a supramolecular system in the form of a non-covalent bond with an effective plasticizer.In this study,an important vegetable-oil-based derivative named dimer fatty acid was used to prepare a novel special plasticizer for EC.Dimer-fatty-acid-based thioether polyol(DATP)was synthesized and used to modify ethyl cellulose films.The supramolecular composite films of DATP and ethyl cellulose were designed using the newly-formed van der Waals force.The thermal stability,morphology,hydrophilicity,and mechanical properties of the composite films were all tested.Pure EC is fragile,and the addition of DATP makes the ethyl cellulose films more flexible.The elongation at the break of EC supramolecular films increased and the tensile strength decreased with the increasing DATP content.The elongation at the break of EC/DATP(60/40)and EC/DATP(50/50)was up to 40.3%and 43.4%,respectively.Noticeably,the thermal initial degradation temperature of the film with 10%DATP is higher than that of pure EC,which may be attributed to the formation of a better supramolecular system in this composite film.The application of bio-based material(EC)is environmentally friendly,and the novel DATP can be used as a special and effective plasticizer to prepare flexible EC films,making it more widely used in energy,chemical industry,materials,agriculture,medicine,and other fields.

Ni nanocomposite films formed by Ni nanowires embedded in Ni matrix using electrodeposition

Ni nanocomposite films formed by Ni nanowires embedded in Ni matrix(Ni nanowire/Ni composite films)were fabricated by electrodeposition combined with supersonic stirring in a conventional Watts'bath containing Ni nanowires with diameter about 30 nm.The deposition temperature-dependent microstructure,crystal orientation,lattice constant and corrosion behavior of the Ni nanowire/Ni composite films were investigated by field emission scanning electron microscope,X-ray diffraction and potentiodynamic polarization tests,respectively.And the possible mechanism was discussed.It is found that to some extent,the deposition temperature has an impact on the microstructure,crystal orientation,lattice constant and corrosion property of the Ni nanowire/Ni composite films.The Ni nanowire/Ni composite films prepared at 50℃exhibit a novel inter-twisted-nanowire microstructure and have the best corrosion resistance.

A flexible CNT@nickel silicate composite film for high-performance sodium storage

Due to the sufficient ion diffusion channels provided by the large interlayer spacing, layered silicates are widely considered as potential anode materials for lithium ion and sodium ion batteries. However, due to the poor electronic conductivity, the application of layered silicates for electrochemical energy storage has been greatly limited. Carbon nanotube(CNT) film has excellent electrical conductivity and a unique interconnected network, making it an ideal matrix for composite electrochemical material. We herein report a CNT@nickel silicate composite film(CNT@NiSiO) fabricated by a SiO2-mediated hydrothermal conversion process, for sodium storage with excellent electrochemical properties. The obtained composite possesses a cladding structure with homogeneous nanosheets as the outermost and CNT film as the inner network matrix, providing abundant ion diffusion channels, high electronic conductivity, and good mechanical flexibility. Due to these merits, this material possesses an excellent electrochemical performance for sodium storage, including a high specific capacity up to 390 mAh g-1 at 50 mA g-1, good rate performance up to 205 mAh g-1 at 500 mA g-1, and excellent cycling stability. On this basis, this work would bring a promising material for various energy storage devices and other emerging applications.

A Soy Protein-Based Composite Film with a Hierarchical Structure Inspired by Nacre

Soy protein-based composite film is a potential replacement for petroleum-based film with multipurpose applica-tions and cleaner production.It is difficult to improve both the tensile strength and toughness of a protein-based film without sacrificing its elongation.In this study,inspired by the hierarchical structure of nacre,a facile yet delicate strategy was developed to fabricate a novel bio-based film with excellent toughness and high strength.Triglycidylamine(TGA)crosslinked soy protein(SPI)as hard phase and thermoplastic polyurethane elastomer(TPU)as soft phase comprise an alternative lay-up hierarchical structure.The interface of these two phases is enhanced using triglycidylamine(TGA)surface-modified TPU(MTPU).The tensile strength of SPI/MTPU/TGA films increases by 392%to 7.78 MPa and their toughness increases by 391%to 8.50 MJ/m^(3) compared to soy protein/glycerol film.The proposed hierarchical structure can also be extended to other high-performance materials and polymers.

Preparation and Characterization of Co_(3)O_(4)/Graphene/Cellulose Nanofiber Composite Films

Nanocellulose has served as an eye-catching nanomaterial for constructing advanced functional devices with renewability,light weight,flexibility,and environmental friendliness.In this study,Co_(3)O_(4)/graphene/cellulose nanofiber(CNF)flexible composite films,in which the CNF acted as a spacer for the graphene,were prepared via a facile and scalable vacuum filtration method.The effects of the CNF on the microstructure,hydrophilicity,thermal stability,tensile strength,surface resistance,and electrochemical performance of the Co_(3)O_(4)/graphene/CNF composite films were systematically investigated.The results showed that the synergistic interaction of the CNF and graphene substantially improved the overall properties of the Co_(3)O_(4)/graphene/CNF composite films,particularly their hydrophilicity and tensile strength.Meanwhile,Co_(3)O_(4)/graphene/CNF composite films with a CNF content of 4%appeared to have the optimal electrochemical performance,with an area specific capacitance of 56 mF/cm^(2) and prominent capacitance retention of 95.6%at a current density of 1 A/g after 1000 cycles.This work demonstrated that the prepared Co_(3)O_(4)/graphene/CNF flexible composite films have great application potential in the field of flexible energy storage devices.

Electrochemistry and Electrocatalysis with Hemoglobin in DHP-PDDA Surfactant-Polymer Multibilayer Composite Films

Polyionic complex DHP-PDDA was prepared by reacting anionic surfactant dihexadecyl phosphate (DHP) with polycationic poly(diallyldimethyl ammonium) (PDDA). Thin films made from DHP-PDDA with incorporated hemoglobin (Hb) on pyrolytic graphite (PG) electrodes were characterized by electrochemistry and other techniques.

Accurate determination of anisotropic thermal conductivity for ultrathin composite film

Highly anisotropic thermal conductive materials are of significance in thermal management applications. However,accurate determination of ultrathin composite thermal properties is a daunting task due to the tiny thermal conductance,severely hindering the further exploration of novel efficient thermal management materials, especially for size-confined environments. In this work, by utilizing a hybrid measuring method, we demonstrate an accurate determination of thermal properties for montmorillonite/reduced graphene oxide(MMT/r GO) composite film with a thickness range from 0.2 μm to2 μm. The in-plane thermal conductivity measurement is realized by one-dimensional(1D) steady-state heat conduction approach while the cross-plane one is achieved via a modified 3ω method. As-measured thermal conductivity results are cross-checked with different methods and known materials, revealing the high measurement accuracy. A high anisotropic ratio of 60.5, independent of composite thickness, is observed in our measurements, further ensuring the negligible measurement error. Notably, our work develops an effective approach to the determination of ultrathin composite thermal conductivity, which may promote the development of ultrathin composites for potential thermal-related applications.

TiO2-Loaded WO3 Composite Films for Enhancement of Photocurrent Density

Titanium dioxide(TiO_2) loaded tungsten trioxide(WO_3) composite films are prepared by an E-beam vapor system. Associated with the existence of a heterojunction at the interface of TiO_2 and WO_3, the prepared TiO_2-WO_3 composite film shows enhanced photocurrent density; four times than the pure WO_3 film illuminated under xenon lamp, and higher incident-photon-to-current conversion efficiency. By varying the initial TiO_2 film thickness, such composite structures could be optimized to obtain the highest photocurrent density. We believe that thin TiO_2 films improve the light response and increase the surface roughness of WO_3 films. Furthermore,the existence of the heterojunction results in the efficient charge carriers' separation, transfer process, and a lower recombination of electron-hole pairs, which is beneficial for the enhancement of photocurrent density.

Thermally conductive polyvinyl alcohol composite films via introducing hetero-structured MXene@silver fillers

Ag nanoparticles were in-situ grown on the surface of MXene nanosheets to prepare thermally conductive hetero-structured MXene@Ag fillers.With polyvinyl alcohol(PVA)as the polymer matrix,thermally conductive MXene@Ag/PVA composite films were fabricated by the processes of solution blending,pouring,evaporative self-assembly.With the same mass fraction,MXene@Ag-III(MXene/Ag,2:1,w/w)presents more significant improvement in thermal conductivity coefficient(λ)than MXene@Ag,single MXene,Ag,simply blending MXene/Ag.MXene@Ag-III/PVA composite films show dual functions of excellent thermal conductivity and electromagnetic interference(EMI)shielding.When the mass fraction of MXene@Ag-III is 60 wt.%,the in-planeλ(λ_(∥)),through-planeλ(λ_(⊥)),EMI shielding effectiveness(EMI SE)are 3.72 and 0.41 W/(m∙K),32 dB,which are increased by 3.1,1.3,105.7 times than those of pure PVA film(0.91 and 0.18 W/(m∙K),0.3 dB),respectively.The 60 wt.%MXene@Ag-III/PVA composite film also has satisfying mechanical and thermal properties,with Young’s modulus,glass transition temperature,heat resistance index of 3.8 GPa,58.5 and 175.3℃,respectively.

Flexible,robust,sandwich structure polyimide composite film with alternative MXene and Ag NWs layers for electromagnetic interference shielding

The design and fabrication of electromagnetic interference shielding films with a novel structure to eliminate undesirable electromagnetic pollution is an important research direction.However,it is still a challenge to combine and organize nanofillers in different dimensions into the structured network in polymer-based electromagnetic interference(EMI)shielding composites.In this work,a sandwich struc-ture polyimide(PI)composite film with alternative 2D-MXene network and 1D-Silver nanowires(Ag NWs)network was prepared through the“electrospinning-immersion-hot pressing”method.With the increase of Ag NWs content,the EMI shielding effectiveness(SE)gradually increases while maintaining good flexibility and mechanical robustness.The EMI SE and the tensile strength of 150μm thick sand-wich composite film can reach up to 79.54 dB and 39.82 MPa,respectively.The prepared flexible and robust PI composite film with a sandwich structure has high EMI SE with less metal content,which can provide guidelines for the development of high-performance EMI polymeric films with potentials in wearable devices and equipment.

Organic Memristor Based on High Planar Cyanostilbene/Polymer Composite Films

Organic memristors with low power consumption,fast write/erasure speed,and complementary metal-oxide-semiconductor(CMOS)compatibility have attracted tremendous attention to mimic biological synapses to realize neuromorphic computation in recent years.In this paper,organic resistive switching memory(ORSM)based on(Z)-3-(naphthalen-2-yl)-2-(4-nitrophenyl)acrylonitrile(NNA)and polymer poly(N-vinylcarbazole)(PVK)composite film was prepared by spin-coating method.Device performance based on NNA:PVK composite films with different mass fractions of NNA were systematically investigated.The ORSM based on PVK:40%(mass fraction)NNA composite film exhibited non-volatile and bipolar memory properties with a switching ratio(Ion/Ioff)of 24.1,endurance of 68 times and retention time of 104 s,a“SET”voltage(Vset)of−0.55 V and a“RESET”voltage(Vreset)of 2.35 V.The resistive switching was ascribed to the filling and vacant process of the charge traps induced by NNA and the inherent traps in PVK bulk.The holes trapping and de-trapping process occurred when the device was applied with a negative or positive bias,which caused the transforming of the conductive way of charges,that is the resistive behaviors in the macroscopic.This study provides a promising platform for the fabrication of ORSM with high performance.

Thermally Conductive Polyimide/Boron Nitride Composite Films with Improved Interfacial Compatibility Based on Modified Fillers by Polyimide Brushes

Polyimide-based composite films with high thermal conductivity,good mechanical property and electrical insulating performance are urgently needed in the electronics and microelectronics fields.As one of the key technical challenges to be solved,interfacial compatibility between filler and matrix plays an important role for composite film.Herein,boron nitride was modified by grafting polyimide brushes via a twostep method,and a series of thermally conductive polyimide/boron nitride composite films were prepared.Both characterization and performance results proved that the interfacial interaction and compatibility was greatly enhanced,resulting in a significant reduction in defects and interfacial thermal resistance.The interphase width of transition zone between two phases was also efficiently enlarged due to polyimide brushes grafted on filler surface.As a result,composite films based on polyimide-grafted boron nitride exhibited significantly improved properties compared with those based on pristine filler.Tensile strength can reach up to 80 MPa even if the filler content is as high as 50 wt%.The out-of-plane and in-plane thermal conductivity of composite film increased to 0.841 and 0.850 W·m^(-1)·K^(-1),respectively.In addition,thermal and dielectric properties of composite films were also enhanced to some extent.The above results indicate that surface modification by chemically grafting polymer brushes is an effective method to improve two-phase interfacial compatibility so as to prepare composite film with enhanced properties.

Microstructure and properties of honeycomb composite films containing Eu and Sn

Honeycomb composite films were prepared by breath figure method via a straightforward,one-step process by doping complex containing Eu or Sn into polystyrene-b-poly(acrylic acid) solution.Several key influencing factors,such as the concentration of the block polymer solution,the relative humidity of the environment and the amount of complexes,were investigated to control micropore size and tune film surface properties.The characteristics of the composite films were studied by scanning electron microscopy(SEM),atomic force microscopy(AFM),X-ray diffraction(XRD),ultraviolet and emission spectra.Results indicate that composite films containing Eu have excellent optical performance,and micro-patterned bowl-like SnO_(2) microparticles could be fabricated from composite films containing Sn after being calcined at 600℃ for 5 h.This general approach for the fabrication of honeycomb composite films opens a convenient and effective route to the functional modification of honeycomb films and offers new prospects for the application in miniaturized sensors,micro-reactor and catalysis.

Thickness dependency of nonlinear optical properties in ITO/Sn composite films

In this study,a batch of indium tin oxide(ITO)/Sn composites with different ratios was obtained based on the principle of thermal evaporation by an electron beam.The crystalline structure,surface shape,and optical characterization of the films were researched using an X-ray diffractometer,an atomic force microscope,a UV-Vis-NIR dual-beam spectrophotometer,and an open-hole Z-scan system.By varying the relative thickness ratio of the ITO/Sn bilayer film,tunable nonlinear optical properties were achieved.The nonlinear saturation absorption coefficientβmaximum of the ITO/Sn composites is−10.5×10^(−7)cm/W,approximately 21 and 1.72 times more enhanced compared to monolayer ITO and Sn,respectively.Moreover,the improvement of the sample nonlinear performance was verified using finite-difference in temporal domain simulations.

Preparation and release of curcumin/silk fibroin/sodium alginate film

The aim of this study was to prepare silk fibroin/sodium alginate composite film containing curcumin by casting method.Orthogonal test was used to optimize the formulation according to the values of tensile strength and elongation at break.The release of curcumin in the optimal film was studied in order to explore its application as wound dressing.The results showed that the optimum composition of curcumin/silk fibroin/sodium alginate composite film was as follows:Silk fibroin(70 mg/mL)2.7 g,sodium alginate(24 mg/mL)0.84 g,span 40(5.0 mg/mL)0.4 g,glycerol(3.75%,V/V)3 mL,curcumin(0.2 mg/mL)0.016 g.The optimum film showed the tensile strength and the elongation at break was(0.628±0.032)MPa and(0.794±0.046)%,respectively.

Janus(BNNS/ANF)-(AgNWs/ANF)thermal conductivity composite films with superior electromagnetic interference shielding and Joule heating performances

Highly thermal conductivity materials with excellent electromagnetic interference shielding and Joule heating performances are ideal for thermal management in the next generation of communication industry,artificial intelligence and wearable electronics.In this work,silver nanowires(AgNWs)are prepared using silver nitrate as the silver source and ethylene glycol as the solvent and reducing agent,and boron nitride(BN)is performed to prepare BN nanosheets(BNNS)with the help of isopropyl alcohol and ultrasonication-assisted peeling method,which are compounded with aramid nanofibers(ANF)prepared by chemical dissociation,respectively,and the(BNNS/ANF)-(AgNWs/ANF)thermal conductivity and electromagnetic interference shielding composite films with Janus structures are prepared by the"vacuum-assisted filtration and hot-pressing"method.Janus(BNNS/ANF)-(AgNWs/ANF)composite films exhibit"one side insulating,one side conducting"performance,the surface resistivity of the BNNS/ANF surface is 4.7×10^(13) Ω,while the conductivity of the AgNWs/ANF surface is 5,275 S/cm.And Janus(BNNS/ANF)-(AgNWs/ANF)composite film with thickness of 95 pm has a high in-plane thermal conductivity coefficient of 8.12 W/(m·K)and superior electromagnetic interference shielding effectiveness of 70 dB.The obtained composite film also has excellent tensile strength of 122.9 MPa and tensile modulus and 2.7 GPa.It also has good temperature-voltage response characteristics(high Joule heating temperature at low supply voltage(5 V,215.0℃),fast response time(10 s)),excellent electrical stability and reliability(stable and constant real-time relative resistance under up to 300 cycles and 1,500 s of tensile-bending fatigue work tests).

Multifunctional Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/polyimide)composite films with Janus structure for outstanding electromagnetic interference shielding and superior visual thermal management

Flexible multifunctional polymer-based electromagnetic interference(EMI)shielding composite films have important application values in the fields of 5G communication technology,wearable electronic devices and artificial intelligence.In this work,Fe_(3)O_(4)/polyamic acid(PAA)nanofiber films are prepared by in-situ polymerization and electrospinning technology,and Ti_(3)C_(2)T_(x)nanosheets are deposited on the surface of the Fe_(3)O_(4)/PAA nanofiber films via vacuum-assisted filtration.Then,Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/polyimide(PI))composite films are obtained by thermal imidization.The two sides of the Janus films exhibit completely different properties.The Fe_(3)O_(4)/PI side has excellent hydrophobicity and insulation property,and the Ti_(3)C_(2)T_(x)side has hydrophilicity and terrific conductivity.When the mass fraction of Ti_(3)C_(2)T_(x)is 80 wt.%,the Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/PI)composite film has excellent EMI shielding performances and mechanical properties,with EMI shielding effectiveness,tensile strength and Young’s modulus reaching 66 dB,114.5 MPa and 5.8 GPa,respectively.At the same time,electromagnetic waves show different absorption shielding effectiveness(SEA)when incident from two sides of the Janus films.When the electromagnetic waves are incident from the Fe_(3)O_(4)/PI side,the SEA of the Janus film is 58 dB,much higher than that when the electromagnetic waves are incident from the Ti_(3)C_(2)T_(x)side(39 dB).In addition,the Ti_(3)C_(2)T_(x)side of the Janus Ti_(3)C_(2)T_(x)-(Fe_(3)O_(4)/PI)composite films also has excellent electrothermal and photothermal conversion performances.When the applied voltage is 4 V,the stable surface temperature reaches 108°C;when it is irradiated by simulated sunlight with power density of 200 mW/cm2,the stable surface temperature reaches 95℃.

High photocatalytic activity of Cu2O/TiO2/Pt composite films prepared by magnetron sputtering

Cu_2O/TiO_2/Pt three-layer films were deposited on glass substrates using magnetron sputtering method.The surface morphology and the optical properties of the composite film were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), ultravioletvisible spectroscopy(UV-Vis) and photoluminescence spectroscopy(PL). The photocatalytic activity of the samples was evaluated by the photocatalytic degradation of methyl orange(MO) aqueous solution under visible light irradiation. The results indicate that the Cu_2O/TiO_2/Pt composite films are made up of three layers which are Pt layer,anatase-TiO_2 layer and Cu_2O layer from bottom to top. The surface of the films is even and composed of regular-shaped spherical particles. The photocatalytic activity of the Cu_2O/TiO_2/Pt three-layer film is much higher than that of the Cu_2O/TiO_2 double-layer film. Such enhancement is ascribed to the presence of Pt layer, which further inhibits the photogenerated electron-hole recombination, prolongs the lifetime of the photogenerated carriers, increases the quantum efficiency and hence improves the photocatalytic activity of the film effectively.