In order to improve the mechanical properties of polypyrrole, composites were made by electropolymerizing polypyrrole in a polyurethane matrix. Polypyrrole/polyurethane (PPY/PU) composite films containing CLO_4^-, BF_...In order to improve the mechanical properties of polypyrrole, composites were made by electropolymerizing polypyrrole in a polyurethane matrix. Polypyrrole/polyurethane (PPY/PU) composite films containing CLO_4^-, BF_4^- or CH_3-C_6H_4-SO_3^- counter ions were made in a variety of solvent systems and characterized by SEM, electronic conductivity, FTIR, and mechanical properties. Composite films showing much greater fiexibility than pure polypyrrole were obtained, but their electronic conductivities were substantially lower. Measured eonductivities ranged from 0.001 to 8 S/cm, tensile strengths from 44 to 592 psi, and elongation to failure from 3 to 70%.展开更多
A novel method for preparing conductive carbon black fllled polymer composites with low percolation threshold from polyurethane emulsion are reported in this paper. The experimental results indicate that with a rise i...A novel method for preparing conductive carbon black fllled polymer composites with low percolation threshold from polyurethane emulsion are reported in this paper. The experimental results indicate that with a rise in carbon black concentration the insulator-conductor transition in the emulsion blended composites occurs at 0.8-1.4vol%. In contrast, the solution blended composites exhibit drastic increase in conductivity at conducting filler fraction as high as 12.3-13.3vol%. It is demonstrated that the composites microstructure rather than chemical structure of the matrix polymer predominantly determines the electrical conduction performance of the composites.展开更多
A series of divinylphenyl-acryloyl chloride copolymers(PDVB-co-PACl)is synthesized via atom transfer radical polymerization employing tert-butyl acrylate and divinylbenzene as monomers.PDVB-co-PACl is utilized to graf...A series of divinylphenyl-acryloyl chloride copolymers(PDVB-co-PACl)is synthesized via atom transfer radical polymerization employing tert-butyl acrylate and divinylbenzene as monomers.PDVB-co-PACl is utilized to graft on the surface of spherical aluminum nitride(AlN)to prepare functionalized AlN(AlN@PDVB-co-PACl).Polymethylhydrosiloxane(PMHS)is then used as the matrix to prepare thermally conductive AlN@PDVB-co-PACl/PMHS composites with AlN@PDVB-co-PACl as fillers through blending and curing.The grafting of PDVB-co-PACl synchronously enhances the hydrolysis resistance of AlN and its interfacial compatibility with PMHS matrix.When the molecular weight of PDVB-co-PACl is 5100 g mol^(-1)and the grafting density is 0.8 wt%,the composites containing 75 wt%of AlN@PDVB-co-PACl exhibit the optimal comprehensive performance.The thermal conductivity(λ)of the composite is 1.14 W m^(-1)K^(-1),which enhances by 20%and 420%compared to theλof simply physically blended AlN/PMHS composite and pure PMHS,respectively.Meanwhile,AlN@PDVB-co-PACl/PMHS composites display remarkable hydrothermal aging resistance by retaining 99.1%of itsλafter soaking in 90°C deionized water for 80 h,whereas theλof the blended AlN/PMHS composites decreases sharply to 93.7%.展开更多
Glass fibers(GFs)/epoxy laminated composites always present weak interlaminar shear strength(ILSS)and low cross-plane thermal conductivity coefficient(λ⊥).In this work,silica-sol,synthesized from tetraethyl orthosil...Glass fibers(GFs)/epoxy laminated composites always present weak interlaminar shear strength(ILSS)and low cross-plane thermal conductivity coefficient(λ⊥).In this work,silica-sol,synthesized from tetraethyl orthosilicate(TEOS)and KH-560 via sol-gel method,was employed to functionalize the surface of GFs(Si-GFs).Together with a spherical boron nitride(BNN-30),the thermally conductive BNN-30/Si-GFs/epoxy laminated composites were then fabricated.Results demonstrate that Si-sol is beneficial to the improvement of mechanical properties for epoxy laminated composites(especially for ILSS).The BNN-30/Si-GFs/epoxy laminated composites with 15 wt%BNN-30 fillers display the optimal comprehensive properties.In-planeλ(λ//)andλ⊥reach the maximum of 2.37 and 1.07 W.m-1.K-1,146.9%and 132.6%higher than those of SiGFs/epoxy laminated composites(λ//=0.96 W.m-1.K-1 andλ⊥=0.46 W.m-1K-1),respectively,and also about 10.8 and 4.9 times those of pure epoxy resin(λ//=λ⊥,0.22 W.m-1.K-1).And the heat-resistance index(THRI),dielectric constant(ε),dielectric loss(tanδ),breakdown strength(E0),surface resistivity(ρs)as well as volume resistivity(ρv)are 197.3℃,4.95,0.0046,22.3 kV.mm-1,1.8×1014Ω,and 2.1×1014Ω.cm,respectively.展开更多
Rapid development of energy,electrical and electronic technologies has put forward higher requirements for the thermal conductivities of polymers and their composites.However,the thermal conductivity coefficient(λ)va...Rapid development of energy,electrical and electronic technologies has put forward higher requirements for the thermal conductivities of polymers and their composites.However,the thermal conductivity coefficient(λ)values of prepared thermally conductive polymer composites are still difficult to achieve expectations,which has become the bottleneck in the fields of thermally conductive polymer composites.Aimed at that,based on the accumulation of the previous research works by related researchers and our research group,this paper proposes three possible directions for breaking through the bottlenecks:(1)preparing and synthesizing intrinsically thermally conductive polymers,(2)reducing the interfacial thermal resistance in thermally conductive polymer composites,and(3)establishing suitable thermal conduction models and studying inner thermal conduction mechanism to guide experimental optimization.Also,the future development trends of the three above-mentioned directions are foreseen,hoping to provide certain basis and guidance for the preparation,researches and development of thermally conductive polymers and their composites.展开更多
A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes＇ law. Acrylonitrile- butadiene-styren...A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes＇ law. Acrylonitrile- butadiene-styrene/Cu （ABS/Cu） gradient polymeric composites were prepared successfully using this technique. The gradient structures, electrically conductive performance and mechanical properties of the ABS/Cu composites were investigated. Optical microscope observation shows that the gradient distribution of Cu particles in ABS matrix was formed along their thickness-direction. The electrically conductive testing results indicate that the order of magnitude of surface resistivity was kept in 10^15 Ω at ABS rich side, while that declined to 10^5 Ω at Cu particles rich side, and the percolation threshold was in the range of 2.82 vo1%- 4.74 vol% Cu content at Cu particles rich side. Mechanical test shows that the tensile strength reduced insignificantly as the content of Cu increases owing to the gradient distribution.展开更多
Wearable and stretchable strain sensors have potential values in the fields of human motion and health monitoring,flexible electronics,and soft robotic skin.The wearable and stretchable strain sensors can be directly ...Wearable and stretchable strain sensors have potential values in the fields of human motion and health monitoring,flexible electronics,and soft robotic skin.The wearable and stretchable strain sensors can be directly attached to human skin,providing visualized detection for human motions and personal healthcare.Conductive polymer composites(CPC)composed of conductive fillers and flexible polymers have the advantages of high stretchability,good flexibility,superior durability,which can be used to prepare flexible strain sensors with large working strain and outstanding sensitivity.This review has put forward a comprehensive summary on the fabrication methods,advanced mechanisms and strain sensing abilities of CPC strain sensors reported in recent years,especially the sensors with superior performance.Finally,the structural design,bionic function,integration technology and further application of CPC strain sensors are prospected.展开更多
Current-voltage electrical behavior of in situ microfibrillar carbon black （CB）/poly（ethylene terephthalate） （PET）/polyethylene （PE） （m-CB/PET/PE） composites with various CB concentrations at ambient tempera...Current-voltage electrical behavior of in situ microfibrillar carbon black （CB）/poly（ethylene terephthalate） （PET）/polyethylene （PE） （m-CB/PET/PE） composites with various CB concentrations at ambient temperatures was studied under a direct-current electric field. The current-voltage （l-V） curves exhibited nonlinearity beyond a critical value of voltage. The dynamic random resistor network （DRRN） model was adopted to semi-qualitatively explain the nonlinear conduction behavior of m-CB/PET/PE composites. Macroscopic nonlinearity originated from the interfacial interactions between CB/PET micro fibrils and additional conduction channels. Combined with the special conductive networks, an illustration was proposed to interpret the nonlinear 1-V characteristics by a field emission or tunneling mechanism between CB particles in the CB/PET micro fibers intersections.展开更多
A novel method for preparing conductive polyethylene （PE） composites has been developed. In the method, the powder of low melting point metal alloy （LMPA） is filled into the PE matrix by using twin screw extruder ...A novel method for preparing conductive polyethylene （PE） composites has been developed. In the method, the powder of low melting point metal alloy （LMPA） is filled into the PE matrix by using twin screw extruder at a temperature below the melting point of the LMPA, and followed by a die drawing process at a temperature around the melting point of the metal alloy. It has been found that die drawing process, repeating the die drawing process and adding nano-fillers, such as montmorillonite （MMT） and multi-wall carbon nanotubes （MWCNTs）, all help reduce the metal particle size in the PE matrix, thus improve the conductivity of the composite. The conductivity improvement is attributed to an increased number of the smaller metal particles. Therefore, conductive composites of polymer/metal alloy/nano-filler with high conductivity are possible to be prepared by using the new method.展开更多
To simultaneously endow thermal conductivity,high glass transition temperature(Tg)and healing capability to glass fiber/epoxy(GFREP)composite,dynamic crosslinked epoxy resin bearing reversibleβ-hydroxyl ester bonds w...To simultaneously endow thermal conductivity,high glass transition temperature(Tg)and healing capability to glass fiber/epoxy(GFREP)composite,dynamic crosslinked epoxy resin bearing reversibleβ-hydroxyl ester bonds was reinforced with boron nitride nanosheets modified glass fiber cloth(GFC@BNNSs).The in-plane heat conduction paths were constructed by electrostatic self-assembly of polyacrylic acid treated GFC and polyethyleneimine decorated BNNSs.Then,the GFC@BNNSs were impregnated with the mixture of lower concentration(3-glycidyloxypropyl)trimethoxysilane grafted BN micron sheets,3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate and hexahydro-4-methylphthalic anhydride,which accounted for establishing the through-plane heat transport pathways and avoiding serious deterioration of mechanical performances.The resultant GFREP composite containing less boron nitride particles(17.6 wt%)exhibited superior in-plane(3.29 W·m^(-1)·K^(-1))and through-plane(1.16 W·m^(-1)·K^(-1))thermal conductivities,as well as high Tg of 204℃(Tg of the unfilled epoxy=177℃).The reversible transesterification reaction enabled closure of interlaminar cracks within the composite,achieving decent healing efficiencies estimated by means of tensile strength(71.2%),electrical breakdown strength(83.6%)and thermal conductivity(69.1%).The present work overcame the disadvantages of conventional thermally conductive composites,and provided an efficient approach to prolong the life span of thermally conductive GFREP laminate for high-temperature resistant integrated circuit application.展开更多
Highly conductive polymer composites(CPCs) with excellent mechanical flexibility are ideal materials for designing excellent electromagnetic interference(EMI) shielding materials,which can be used for the electromagne...Highly conductive polymer composites(CPCs) with excellent mechanical flexibility are ideal materials for designing excellent electromagnetic interference(EMI) shielding materials,which can be used for the electromagnetic interference protection of flexible electronic devices.It is extremely urgent to fabricate ultra-strong EMI shielding CPCs with efficient conductive networks.In this paper,a novel silver-plated polylactide short fiber(Ag@PL ASF,AAF) was fabricated and was integrated with carbon nanotubes(CNT) to construct a multi-scale conductive network in polydimethylsiloxane(PDMS) matrix.The multi-scale conductive network endowed the flexible PDMS/AAF/CNT composite with excellent electrical conductivity of 440 S m-1and ultra-strong EMI shielding effectiveness(EMI SE) of up to 113 dB,containing only 5.0 vol% of AAF and 3.0 vol% of CNT(11.1wt% conductive filler content).Due to its excellent flexibility,the composite still showed 94% and 90% retention rates of EMI SE even after subjected to a simulated aging strategy(60℃ for 7 days) and 10,000 bending-releasing cycles.This strategy provides an important guidance for designing excellent EMI shielding materials to protect the workspace,environment and sensitive circuits against radiation for flexible electronic devices.展开更多
Epoxy-based nano-composites can be ideal electromagnetic interference(EMI)-shielding materials owing to their lightness,chemical inertness,and mechanical durability.However,poor conductivity and brittleness of the epo...Epoxy-based nano-composites can be ideal electromagnetic interference(EMI)-shielding materials owing to their lightness,chemical inertness,and mechanical durability.However,poor conductivity and brittleness of the epoxy resin are challenges for fast-growing portable and flexible EMI-shielding applications,such as smart wristband,medical cloth,aerospace,and military equipment.In this study,we explored hybrid nanofillers of single-walled carbon nanotubes(SWCNT)/reduced graphene oxide(rGO)as conductive inks and polyester fabrics(PFs)as a substrate for flexible EMI-shielding composites.The highest electrical conductivity and fracture toughness of the SWCNT/rGO/PF/epoxy composites were 30.2 S m^(−1)and 38.5 MPa m^(1/2),which are~270 and 65%enhancement over those of the composites without SWCNTs,respectively.Excellent mechanical durability was demonstrated by stable electrical conductivity retention during 1000 cycles of bending test.An EMI-shielding effectiveness of~41 dB in the X-band frequency of 8.2-12.4 GHz with a thickness of 0.6 mm was obtained with an EM absorption-dominant behavior over a 0.7 absorption coefficient.These results are attributed to the hierarchical architecture of the macroscale PF skeleton and nanoscale SWCNT/rGO networks,leading to superior EMI-shielding performance.We believe that this approach provides highly flexible and robust EMI-shielding composites for next-generation wearable electronic devices.展开更多
Thick electrodes can increase incorporation of active electrode materials by diminishing the proportion of inactive constituents,improving the overall energy density of batteries.However,thick electrodes fabricated us...Thick electrodes can increase incorporation of active electrode materials by diminishing the proportion of inactive constituents,improving the overall energy density of batteries.However,thick electrodes fabricated using the conventional slurry casting approach frequently exhibit an exacerbated accumulation of carbon additives and binders on their surfaces,invariably leading to compromised electrochemical properties.In this study,we introduce a designed conductive agent/binder composite synthesized from carbon nanotube and polytetrafluoroethylene.This agent/binder composite facilitates production of dry-process-prepared ultra-thick electrodes endowed with a three-dimensional and uniformly distributed percolative architecture,ensuring superior electronic conductivity and remarkable mechanical resilience.Using this approach,ultra-thick LiCoO_(2)(LCO) electrodes demonstrated superior cycling performance and rate capabilities,registering an impressive loading capacity of up to 101.4 mg/cm^(2),signifying a 242% increase in battery energy density.In another analytical endeavor,time-of-flight secondary ion mass spectroscopy was used to clarify the distribution of cathode electrolyte interphase(CEI) in cycled LCO electrodes.The results provide unprecedented evidence explaining the intricate correlation between CEI generation and carbon distribution,highlighting the intrinsic advantages of the proposed dry-process approach in fine-tu ning the CEI,with excellent cycling performance in batteries equipped with ultra-thick electrodes.展开更多
All-solid-state lithium batteries(ASSLBs) employing sulfide electrolyte and lithium(Li) anode have received increasing attention due to the intrinsic safety and high energy density.However,the thick electrolyte layer ...All-solid-state lithium batteries(ASSLBs) employing sulfide electrolyte and lithium(Li) anode have received increasing attention due to the intrinsic safety and high energy density.However,the thick electrolyte layer and lithium dendrites formed at the electrolyte/Li anode interface hinder the realization of high-performance ASSLBs.Herein,a novel membrane consisting of Li_(6)PS_(5) Cl(LPSCl),poly(ethylene oxide)(PEO) and Li-salt(LiTFSI) was prepared as sulfide-based composite solid electrolyte(LPSCl-PEO3-LiTFSI)(LPSCl:PEO=97:3 wt/wt;EO:Li=8:1 mol/mol),which delivers high ionic conductivity(1.1 × 10^(-3) S cm^(-1)) and wide electrochemical window(4.9 V vs.Li^(+)/Li) at 25 ℃.In addition,an ex-situ artificial solid electrolyte interphase(SEI) film enriched with LiF and Li3 N was designed as a protective layer on Li anode(Li(SEI)) to suppress the growth of lithium dendrites.Benefiting from the synergy of sulfide-based composite solid electrolyte and ex-situ artificial SEI,cells of S-CNTs/LPSCI-PEO3-LiTFSI/Li(SEI) and Al_(2)O_(3)@LiNi_(0.5)Co_(0.3)Mn_(0.2)O_(2)/LPSCl-PEO3-LiTFSI/Li(SEI) are assembled and both exhibit high initial discharge capacity of 1221.1 mAh g^(-1)(135.8 mAh g^(-1)) and enhanced cycling stability with 81.6% capacity retention over 200 cycles at 0.05 C(89.2% over 100 cycles at 0.1 C).This work provides a new insight into the synergy of composite solid electrolyte and artificial SEI for achieving high-performance ASSLBs.展开更多
Developing an effective method for improving the reproducibility of positive temperature coefficient(PTC)effect is of great significance for large-scale application of polymer based PTC composites,owing to its contrib...Developing an effective method for improving the reproducibility of positive temperature coefficient(PTC)effect is of great significance for large-scale application of polymer based PTC composites,owing to its contribution to the security and reliability.Herein,we developed a carbon black(CB)/high density polyethylene(HDPE)/poly(vinylidene fluoride)(PVDF)composite with outstanding PTC reproducibility,by incorporating 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([OMIm][NTf2])into the composite.After multiple repeated temperature cycles,the PTC performance of as-prepared material keeps almost unchanged and the varition of resistance at room temperature is less than 7%.Our studies revealed that[OMIm][NTf2]contributes to the improvement of PTC reproducibility in two ways:(i)it acts as an efficient plasticizer for refining the co-continuous phase morphology of HDPE/PVDE blends;(ii)it inhibits the crystallization of PVDF through the dilution effect,leading to more overlaps of the volume shrinkage process of HDPE and PVDF melt which results in the decrease of interface gap between HDPE and PVDF.This study demonstrated that ionic liquids as the multifunctional agents have great potential for improving the reproducibility in the application of the binary polymer based PTC composites.展开更多
This study was pertained to the effects of Ti coating on diamond surfaces and Si addition into Al matrix on the thermal conductivity（TC） and the coefficient of thermal expansion（CTE） of diamond/Al composites by pr...This study was pertained to the effects of Ti coating on diamond surfaces and Si addition into Al matrix on the thermal conductivity（TC） and the coefficient of thermal expansion（CTE） of diamond/Al composites by pressure infiltration.The fracture surfaces,interface microstructures by metal electro-etching and interfacial thermal conductance of the composites prepared by two methods were compared.The results reveal that Ti coating on diamond surfaces and only12.2 wt% Si addition into Al matrix could both improve the interfacial bonding and increase the TCs of the composites.But the Ti coating layer introduces more interfacial thermal barrier at the diamond/Al interface compared to adding 12.2 wt% Si into Al matrix.The diamond/Al composite with 12.2 wt% Si addition exhibits maximum TC of 534 W·m^-1·K^-1and a very low CTE of 8.9×10^-6K^-1,while the coating Ti-diamond/Al composite has a TC of 514 W·m^-1·K^-1 and a CTE of 11.0×10^-6K^-1.展开更多
To extend the application of carbon nanotubes （CNTs） and explore novel aluminum matrix composites,CNTs were coated by molybdenum layers using metal organic chemical vapor deposition,and then Mo-coated CNT （Mo-CNT）...To extend the application of carbon nanotubes （CNTs） and explore novel aluminum matrix composites,CNTs were coated by molybdenum layers using metal organic chemical vapor deposition,and then Mo-coated CNT （Mo-CNT）/Al composites were prepared by the combination processes of powder mixing and spark plasma sintering.The influences of powder mixing and Mo-CNT content on the mechanical properties and electrical conductivity of the composites were investigated.The results show that magnetic stirring is better than mechanical milling for mixing the Mo-CNTs and Al powders.The electrical conductivity of the composites decreases with increasing Mo-CNT content.When the Mo-CNT content is 0.5wt%,the tensile strength and hardness of Mo-CNT/Al reach their maximum values.The tensile strength of 0.5wt% Mo-CNT/Al increases by 29.9%,while the electrical conductivity only decreases by 7.1%,relative to sintered pure Al.The phase analysis of Mo-CNT/Al composites reveals that there is no formation of Al carbide in the composites.展开更多
Influence of cryogenic thermal cycling treatment （from -120 ℃ to 120 ℃ at 1.3 × 10^-3 Pa） on the thermo- physical properties including thermal conductivity （TC）, thermal diffusivity （TD）, specific heat ...Influence of cryogenic thermal cycling treatment （from -120 ℃ to 120 ℃ at 1.3 × 10^-3 Pa） on the thermo- physical properties including thermal conductivity （TC）, thermal diffusivity （TD）, specific heat （SH） and coefficient of thermal expansion （CTE） ranging from room temperature to 1900 ℃ of carbon/carbon （C/C） composites in x-y and z directions were studied. Test results showed that fiber/matrix interracial debonding, fiber pull-out and microcracks occurred after the cryogenic thermal treatment and they increased significantly with the cycle number increasing, while cycled more than 30 times, the space ofmicrodefects reduced obviously due to the accumulation of cyclic thermal stress. TC, TD, SH and CTE of the cryogenic thermal cycling treated C/C composites were first decreased and then increased in both directions （x-y and z directions） with the increase of thermal cycles. A model regarding the heat conduction in cryogenic thermal cycling treated C/C composites was proposed.展开更多
Flexible conductive films were fabricated from a low-temperature-cured, highly conductive composite of silver nanowires （as conducting filler） and polyvinyl alcohol （PVA, as binder）. Sheet resistance of 0.12 Ω/sq...Flexible conductive films were fabricated from a low-temperature-cured, highly conductive composite of silver nanowires （as conducting filler） and polyvinyl alcohol （PVA, as binder）. Sheet resistance of 0.12 Ω/sq, conductivity of 2.63 ×10^4 S/cm, and contact resistance of 1.0Ω/cm^2 were measured in the films, along with excellent resistance to scratch- ing and good flexibility, making them suitable electrical contact materials for flexible optoelectronic devices. Effects of curing temperature, curing duration, film thickness, and nanowire length on the film＇s electrical properties were studied. Due to the abundance of hydroxyl groups on its molecular chains, the addition of PVA improves the film＇s flexibility and resistance to scratching. Increased nanowire density and nanowire length benefit film conductance. Monte Carlo simulation was used to further explore the impact of these two parameters on the conductivity. It was observed that longer nanowires produce a higher length-ratio of conducting routes in the networks, giving better film conductivity.展开更多
Vinylester （bismethacryloxy derivative with glass-carbon hybrid fibers （CF-GF） weight fraction of a bisphenol-A type EP resin, VE） composites of 50%, were prepared by the compress molding method. The distribution ...Vinylester （bismethacryloxy derivative with glass-carbon hybrid fibers （CF-GF） weight fraction of a bisphenol-A type EP resin, VE） composites of 50%, were prepared by the compress molding method. The distribution of carbon fiber in the hybrids was observed by stereomicroscope. The electrical resistance behavior of the composites filled with different carbon fiber （CF） weight contents （0.5% to 20%） was studied. The experimental results show that the electrical resistance behaviors of CF-GF/VE composites are different with those of CF/VE composites because carbon fibers＇ conducting networks are broken by the glass fibers in the CF-GF/VE composites. The carbon fibers distribute uniformly in the networks of glass fibers （GF） like single silk and form the semi-continuous conducting networks. Composite filled with GF-CF hybrid has a higher percolation threshold than that filled with pure CF. At that time, the resistivity of CF-GF/VE composites varies little with the temperature increasing. The temperature coefficient of resistivity in GF-CF/VE composite is less than 317 ppm and the variation of the resistivity after ten thermal cycles from 20℃ to 240 ℃is less than 1.96%.展开更多
文摘In order to improve the mechanical properties of polypyrrole, composites were made by electropolymerizing polypyrrole in a polyurethane matrix. Polypyrrole/polyurethane (PPY/PU) composite films containing CLO_4^-, BF_4^- or CH_3-C_6H_4-SO_3^- counter ions were made in a variety of solvent systems and characterized by SEM, electronic conductivity, FTIR, and mechanical properties. Composite films showing much greater fiexibility than pure polypyrrole were obtained, but their electronic conductivities were substantially lower. Measured eonductivities ranged from 0.001 to 8 S/cm, tensile strengths from 44 to 592 psi, and elongation to failure from 3 to 70%.
文摘A novel method for preparing conductive carbon black fllled polymer composites with low percolation threshold from polyurethane emulsion are reported in this paper. The experimental results indicate that with a rise in carbon black concentration the insulator-conductor transition in the emulsion blended composites occurs at 0.8-1.4vol%. In contrast, the solution blended composites exhibit drastic increase in conductivity at conducting filler fraction as high as 12.3-13.3vol%. It is demonstrated that the composites microstructure rather than chemical structure of the matrix polymer predominantly determines the electrical conduction performance of the composites.
基金support from the National Natural Science Foundation of China(52473083 and 52403112)the Technological Base Scientific Research Projects(Highly Thermal conductivity Nonmetal Materials),the Natural Science Basic Research Program of Shaanxi(2024JC-TBZC-04)+4 种基金the Shaanxi Province Key Research and Development Plan Project(2023-YBGY-461)the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57),the Natural Science Foundation of Chongqing,China(2023NSCQ-MSX2547)the Fundamental Research Funds for the Central Universities(D5000240077 and D5000240067)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX2024094)the Analytical&Testing Center of Northwestern Polytechnical University for FT-IR,XRD and TEM tests performed in this work.
文摘A series of divinylphenyl-acryloyl chloride copolymers(PDVB-co-PACl)is synthesized via atom transfer radical polymerization employing tert-butyl acrylate and divinylbenzene as monomers.PDVB-co-PACl is utilized to graft on the surface of spherical aluminum nitride(AlN)to prepare functionalized AlN(AlN@PDVB-co-PACl).Polymethylhydrosiloxane(PMHS)is then used as the matrix to prepare thermally conductive AlN@PDVB-co-PACl/PMHS composites with AlN@PDVB-co-PACl as fillers through blending and curing.The grafting of PDVB-co-PACl synchronously enhances the hydrolysis resistance of AlN and its interfacial compatibility with PMHS matrix.When the molecular weight of PDVB-co-PACl is 5100 g mol^(-1)and the grafting density is 0.8 wt%,the composites containing 75 wt%of AlN@PDVB-co-PACl exhibit the optimal comprehensive performance.The thermal conductivity(λ)of the composite is 1.14 W m^(-1)K^(-1),which enhances by 20%and 420%compared to theλof simply physically blended AlN/PMHS composite and pure PMHS,respectively.Meanwhile,AlN@PDVB-co-PACl/PMHS composites display remarkable hydrothermal aging resistance by retaining 99.1%of itsλafter soaking in 90°C deionized water for 80 h,whereas theλof the blended AlN/PMHS composites decreases sharply to 93.7%.
基金financially supported by the National Natural Science Foundation of China(Nos.51973173 and 51773169)Natural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province of China(No.20191C-11)+1 种基金Funuaneilal Resealuh Funds fur te Centual Univel sities(No.310201911py010)and Fund Project of Basic and Applied Basic Research in Guangdong Province of China(No.2019B1515120093).
文摘Glass fibers(GFs)/epoxy laminated composites always present weak interlaminar shear strength(ILSS)and low cross-plane thermal conductivity coefficient(λ⊥).In this work,silica-sol,synthesized from tetraethyl orthosilicate(TEOS)and KH-560 via sol-gel method,was employed to functionalize the surface of GFs(Si-GFs).Together with a spherical boron nitride(BNN-30),the thermally conductive BNN-30/Si-GFs/epoxy laminated composites were then fabricated.Results demonstrate that Si-sol is beneficial to the improvement of mechanical properties for epoxy laminated composites(especially for ILSS).The BNN-30/Si-GFs/epoxy laminated composites with 15 wt%BNN-30 fillers display the optimal comprehensive properties.In-planeλ(λ//)andλ⊥reach the maximum of 2.37 and 1.07 W.m-1.K-1,146.9%and 132.6%higher than those of SiGFs/epoxy laminated composites(λ//=0.96 W.m-1.K-1 andλ⊥=0.46 W.m-1K-1),respectively,and also about 10.8 and 4.9 times those of pure epoxy resin(λ//=λ⊥,0.22 W.m-1.K-1).And the heat-resistance index(THRI),dielectric constant(ε),dielectric loss(tanδ),breakdown strength(E0),surface resistivity(ρs)as well as volume resistivity(ρv)are 197.3℃,4.95,0.0046,22.3 kV.mm-1,1.8×1014Ω,and 2.1×1014Ω.cm,respectively.
基金National Natural Science Foundation of China(51773169 and 51973173)Guangdong Basic and Applied Basic Research Foundation(2019B1515120093)+2 种基金Technological Base Scientific Research ProjectsNatural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province(2019JC-11)Polymer Electromagnetic Functional Materials Innovation Team of Shaanxi Sanqin Scholars.
文摘Rapid development of energy,electrical and electronic technologies has put forward higher requirements for the thermal conductivities of polymers and their composites.However,the thermal conductivity coefficient(λ)values of prepared thermally conductive polymer composites are still difficult to achieve expectations,which has become the bottleneck in the fields of thermally conductive polymer composites.Aimed at that,based on the accumulation of the previous research works by related researchers and our research group,this paper proposes three possible directions for breaking through the bottlenecks:(1)preparing and synthesizing intrinsically thermally conductive polymers,(2)reducing the interfacial thermal resistance in thermally conductive polymer composites,and(3)establishing suitable thermal conduction models and studying inner thermal conduction mechanism to guide experimental optimization.Also,the future development trends of the three above-mentioned directions are foreseen,hoping to provide certain basis and guidance for the preparation,researches and development of thermally conductive polymers and their composites.
基金Funded by the National Natural Science Foundation of China(No.21274007)the Beijing Natural Science Foundation+1 种基金the Key Scientific Project of Beijing Municipal Education Commission(No.KZ201110011014)the Science and Technology Innovation Platform of Beijing Municipal Education Commission(No.PXM2012-014213-000025)
文摘A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes＇ law. Acrylonitrile- butadiene-styrene/Cu （ABS/Cu） gradient polymeric composites were prepared successfully using this technique. The gradient structures, electrically conductive performance and mechanical properties of the ABS/Cu composites were investigated. Optical microscope observation shows that the gradient distribution of Cu particles in ABS matrix was formed along their thickness-direction. The electrically conductive testing results indicate that the order of magnitude of surface resistivity was kept in 10^15 Ω at ABS rich side, while that declined to 10^5 Ω at Cu particles rich side, and the percolation threshold was in the range of 2.82 vo1%- 4.74 vol% Cu content at Cu particles rich side. Mechanical test shows that the tensile strength reduced insignificantly as the content of Cu increases owing to the gradient distribution.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2021R1A2C1008380)Nano Material Technology Development Program[NRF-2015M3A7B6027970]+1 种基金the Chey Institute for Advanced Studies'International Scholar Exchange Fellowship for the academic year of 2021-2022supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Korea government(MOTIE)(20215710100170).
文摘Wearable and stretchable strain sensors have potential values in the fields of human motion and health monitoring,flexible electronics,and soft robotic skin.The wearable and stretchable strain sensors can be directly attached to human skin,providing visualized detection for human motions and personal healthcare.Conductive polymer composites(CPC)composed of conductive fillers and flexible polymers have the advantages of high stretchability,good flexibility,superior durability,which can be used to prepare flexible strain sensors with large working strain and outstanding sensitivity.This review has put forward a comprehensive summary on the fabrication methods,advanced mechanisms and strain sensing abilities of CPC strain sensors reported in recent years,especially the sensors with superior performance.Finally,the structural design,bionic function,integration technology and further application of CPC strain sensors are prospected.
基金financially supported by the National Science Fund for Distinguished Young Scholars (No. 50925311)National Science Fund of China (Nos. 20976112, 51033004)
文摘Current-voltage electrical behavior of in situ microfibrillar carbon black （CB）/poly（ethylene terephthalate） （PET）/polyethylene （PE） （m-CB/PET/PE） composites with various CB concentrations at ambient temperatures was studied under a direct-current electric field. The current-voltage （l-V） curves exhibited nonlinearity beyond a critical value of voltage. The dynamic random resistor network （DRRN） model was adopted to semi-qualitatively explain the nonlinear conduction behavior of m-CB/PET/PE composites. Macroscopic nonlinearity originated from the interfacial interactions between CB/PET micro fibrils and additional conduction channels. Combined with the special conductive networks, an illustration was proposed to interpret the nonlinear 1-V characteristics by a field emission or tunneling mechanism between CB particles in the CB/PET micro fibers intersections.
文摘A novel method for preparing conductive polyethylene （PE） composites has been developed. In the method, the powder of low melting point metal alloy （LMPA） is filled into the PE matrix by using twin screw extruder at a temperature below the melting point of the LMPA, and followed by a die drawing process at a temperature around the melting point of the metal alloy. It has been found that die drawing process, repeating the die drawing process and adding nano-fillers, such as montmorillonite （MMT） and multi-wall carbon nanotubes （MWCNTs）, all help reduce the metal particle size in the PE matrix, thus improve the conductivity of the composite. The conductivity improvement is attributed to an increased number of the smaller metal particles. Therefore, conductive composites of polymer/metal alloy/nano-filler with high conductivity are possible to be prepared by using the new method.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.52033011,51973237 and 52373095)Natural Science Foundation of Guangdong Province,China(Nos.2019B1515120038 and 2021A1515010417)+2 种基金Science and Technology Planning Project of Guangdong Province(No.2020B010179001)Science and Technology Planning Project of Guangzhou City(No.202201011568)GBRCE for Functional Molecular Engineering,and Fundamental Research Funds for the Central Universities,Sun Yat-sen University(No.23yxqntd002).
文摘To simultaneously endow thermal conductivity,high glass transition temperature(Tg)and healing capability to glass fiber/epoxy(GFREP)composite,dynamic crosslinked epoxy resin bearing reversibleβ-hydroxyl ester bonds was reinforced with boron nitride nanosheets modified glass fiber cloth(GFC@BNNSs).The in-plane heat conduction paths were constructed by electrostatic self-assembly of polyacrylic acid treated GFC and polyethyleneimine decorated BNNSs.Then,the GFC@BNNSs were impregnated with the mixture of lower concentration(3-glycidyloxypropyl)trimethoxysilane grafted BN micron sheets,3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate and hexahydro-4-methylphthalic anhydride,which accounted for establishing the through-plane heat transport pathways and avoiding serious deterioration of mechanical performances.The resultant GFREP composite containing less boron nitride particles(17.6 wt%)exhibited superior in-plane(3.29 W·m^(-1)·K^(-1))and through-plane(1.16 W·m^(-1)·K^(-1))thermal conductivities,as well as high Tg of 204℃(Tg of the unfilled epoxy=177℃).The reversible transesterification reaction enabled closure of interlaminar cracks within the composite,achieving decent healing efficiencies estimated by means of tensile strength(71.2%),electrical breakdown strength(83.6%)and thermal conductivity(69.1%).The present work overcame the disadvantages of conventional thermally conductive composites,and provided an efficient approach to prolong the life span of thermally conductive GFREP laminate for high-temperature resistant integrated circuit application.
基金supported by the National Natural Science Foundation of China(Nos.51973142,52033005,52003169).
文摘Highly conductive polymer composites(CPCs) with excellent mechanical flexibility are ideal materials for designing excellent electromagnetic interference(EMI) shielding materials,which can be used for the electromagnetic interference protection of flexible electronic devices.It is extremely urgent to fabricate ultra-strong EMI shielding CPCs with efficient conductive networks.In this paper,a novel silver-plated polylactide short fiber(Ag@PL ASF,AAF) was fabricated and was integrated with carbon nanotubes(CNT) to construct a multi-scale conductive network in polydimethylsiloxane(PDMS) matrix.The multi-scale conductive network endowed the flexible PDMS/AAF/CNT composite with excellent electrical conductivity of 440 S m-1and ultra-strong EMI shielding effectiveness(EMI SE) of up to 113 dB,containing only 5.0 vol% of AAF and 3.0 vol% of CNT(11.1wt% conductive filler content).Due to its excellent flexibility,the composite still showed 94% and 90% retention rates of EMI SE even after subjected to a simulated aging strategy(60℃ for 7 days) and 10,000 bending-releasing cycles.This strategy provides an important guidance for designing excellent EMI shielding materials to protect the workspace,environment and sensitive circuits against radiation for flexible electronic devices.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2022M3J7A1062940).
文摘Epoxy-based nano-composites can be ideal electromagnetic interference(EMI)-shielding materials owing to their lightness,chemical inertness,and mechanical durability.However,poor conductivity and brittleness of the epoxy resin are challenges for fast-growing portable and flexible EMI-shielding applications,such as smart wristband,medical cloth,aerospace,and military equipment.In this study,we explored hybrid nanofillers of single-walled carbon nanotubes(SWCNT)/reduced graphene oxide(rGO)as conductive inks and polyester fabrics(PFs)as a substrate for flexible EMI-shielding composites.The highest electrical conductivity and fracture toughness of the SWCNT/rGO/PF/epoxy composites were 30.2 S m^(−1)and 38.5 MPa m^(1/2),which are~270 and 65%enhancement over those of the composites without SWCNTs,respectively.Excellent mechanical durability was demonstrated by stable electrical conductivity retention during 1000 cycles of bending test.An EMI-shielding effectiveness of~41 dB in the X-band frequency of 8.2-12.4 GHz with a thickness of 0.6 mm was obtained with an EM absorption-dominant behavior over a 0.7 absorption coefficient.These results are attributed to the hierarchical architecture of the macroscale PF skeleton and nanoscale SWCNT/rGO networks,leading to superior EMI-shielding performance.We believe that this approach provides highly flexible and robust EMI-shielding composites for next-generation wearable electronic devices.
基金supported by the National Key Research and Development Program of China,China(2019YFA0705102)the National Natural Science Foundation of China,China(22179144,22005332)。
文摘Thick electrodes can increase incorporation of active electrode materials by diminishing the proportion of inactive constituents,improving the overall energy density of batteries.However,thick electrodes fabricated using the conventional slurry casting approach frequently exhibit an exacerbated accumulation of carbon additives and binders on their surfaces,invariably leading to compromised electrochemical properties.In this study,we introduce a designed conductive agent/binder composite synthesized from carbon nanotube and polytetrafluoroethylene.This agent/binder composite facilitates production of dry-process-prepared ultra-thick electrodes endowed with a three-dimensional and uniformly distributed percolative architecture,ensuring superior electronic conductivity and remarkable mechanical resilience.Using this approach,ultra-thick LiCoO_(2)(LCO) electrodes demonstrated superior cycling performance and rate capabilities,registering an impressive loading capacity of up to 101.4 mg/cm^(2),signifying a 242% increase in battery energy density.In another analytical endeavor,time-of-flight secondary ion mass spectroscopy was used to clarify the distribution of cathode electrolyte interphase(CEI) in cycled LCO electrodes.The results provide unprecedented evidence explaining the intricate correlation between CEI generation and carbon distribution,highlighting the intrinsic advantages of the proposed dry-process approach in fine-tu ning the CEI,with excellent cycling performance in batteries equipped with ultra-thick electrodes.
基金supported by the National Natural Science Foundation of China(51872027)the Fundamental Research Funds for the Central Universities(FRF-TP-20-014A2)。
文摘All-solid-state lithium batteries(ASSLBs) employing sulfide electrolyte and lithium(Li) anode have received increasing attention due to the intrinsic safety and high energy density.However,the thick electrolyte layer and lithium dendrites formed at the electrolyte/Li anode interface hinder the realization of high-performance ASSLBs.Herein,a novel membrane consisting of Li_(6)PS_(5) Cl(LPSCl),poly(ethylene oxide)(PEO) and Li-salt(LiTFSI) was prepared as sulfide-based composite solid electrolyte(LPSCl-PEO3-LiTFSI)(LPSCl:PEO=97:3 wt/wt;EO:Li=8:1 mol/mol),which delivers high ionic conductivity(1.1 × 10^(-3) S cm^(-1)) and wide electrochemical window(4.9 V vs.Li^(+)/Li) at 25 ℃.In addition,an ex-situ artificial solid electrolyte interphase(SEI) film enriched with LiF and Li3 N was designed as a protective layer on Li anode(Li(SEI)) to suppress the growth of lithium dendrites.Benefiting from the synergy of sulfide-based composite solid electrolyte and ex-situ artificial SEI,cells of S-CNTs/LPSCI-PEO3-LiTFSI/Li(SEI) and Al_(2)O_(3)@LiNi_(0.5)Co_(0.3)Mn_(0.2)O_(2)/LPSCl-PEO3-LiTFSI/Li(SEI) are assembled and both exhibit high initial discharge capacity of 1221.1 mAh g^(-1)(135.8 mAh g^(-1)) and enhanced cycling stability with 81.6% capacity retention over 200 cycles at 0.05 C(89.2% over 100 cycles at 0.1 C).This work provides a new insight into the synergy of composite solid electrolyte and artificial SEI for achieving high-performance ASSLBs.
基金financially supported by the National Natural Science Foundation of China(Nos.51803103 and 21873059)Taishan Mountain Scholar Foundation(Nos.TS20081120 and tshw20110510)。
文摘Developing an effective method for improving the reproducibility of positive temperature coefficient(PTC)effect is of great significance for large-scale application of polymer based PTC composites,owing to its contribution to the security and reliability.Herein,we developed a carbon black(CB)/high density polyethylene(HDPE)/poly(vinylidene fluoride)(PVDF)composite with outstanding PTC reproducibility,by incorporating 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([OMIm][NTf2])into the composite.After multiple repeated temperature cycles,the PTC performance of as-prepared material keeps almost unchanged and the varition of resistance at room temperature is less than 7%.Our studies revealed that[OMIm][NTf2]contributes to the improvement of PTC reproducibility in two ways:(i)it acts as an efficient plasticizer for refining the co-continuous phase morphology of HDPE/PVDE blends;(ii)it inhibits the crystallization of PVDF through the dilution effect,leading to more overlaps of the volume shrinkage process of HDPE and PVDF melt which results in the decrease of interface gap between HDPE and PVDF.This study demonstrated that ionic liquids as the multifunctional agents have great potential for improving the reproducibility in the application of the binary polymer based PTC composites.
基金financially supported by the National Natural Science Foundation of China (No.51274040)the Fundamental Research Funds for the Central Universities (No.FRF-TP-10-003B)
文摘This study was pertained to the effects of Ti coating on diamond surfaces and Si addition into Al matrix on the thermal conductivity（TC） and the coefficient of thermal expansion（CTE） of diamond/Al composites by pressure infiltration.The fracture surfaces,interface microstructures by metal electro-etching and interfacial thermal conductance of the composites prepared by two methods were compared.The results reveal that Ti coating on diamond surfaces and only12.2 wt% Si addition into Al matrix could both improve the interfacial bonding and increase the TCs of the composites.But the Ti coating layer introduces more interfacial thermal barrier at the diamond/Al interface compared to adding 12.2 wt% Si into Al matrix.The diamond/Al composite with 12.2 wt% Si addition exhibits maximum TC of 534 W·m^-1·K^-1and a very low CTE of 8.9×10^-6K^-1,while the coating Ti-diamond/Al composite has a TC of 514 W·m^-1·K^-1 and a CTE of 11.0×10^-6K^-1.
基金supported by the National High-Tech Research and Development Program of China (No.2009AA03Z116)the National Natural Science Foundation of China (No.50971020)
文摘To extend the application of carbon nanotubes （CNTs） and explore novel aluminum matrix composites,CNTs were coated by molybdenum layers using metal organic chemical vapor deposition,and then Mo-coated CNT （Mo-CNT）/Al composites were prepared by the combination processes of powder mixing and spark plasma sintering.The influences of powder mixing and Mo-CNT content on the mechanical properties and electrical conductivity of the composites were investigated.The results show that magnetic stirring is better than mechanical milling for mixing the Mo-CNTs and Al powders.The electrical conductivity of the composites decreases with increasing Mo-CNT content.When the Mo-CNT content is 0.5wt%,the tensile strength and hardness of Mo-CNT/Al reach their maximum values.The tensile strength of 0.5wt% Mo-CNT/Al increases by 29.9%,while the electrical conductivity only decreases by 7.1%,relative to sintered pure Al.The phase analysis of Mo-CNT/Al composites reveals that there is no formation of Al carbide in the composites.
基金supported by the Research Fund of the State Key Laboratory of Solidification Processing (NWPU) of China (No. 105QP-2014)the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2015JM5247)
文摘Influence of cryogenic thermal cycling treatment （from -120 ℃ to 120 ℃ at 1.3 × 10^-3 Pa） on the thermo- physical properties including thermal conductivity （TC）, thermal diffusivity （TD）, specific heat （SH） and coefficient of thermal expansion （CTE） ranging from room temperature to 1900 ℃ of carbon/carbon （C/C） composites in x-y and z directions were studied. Test results showed that fiber/matrix interracial debonding, fiber pull-out and microcracks occurred after the cryogenic thermal treatment and they increased significantly with the cycle number increasing, while cycled more than 30 times, the space ofmicrodefects reduced obviously due to the accumulation of cyclic thermal stress. TC, TD, SH and CTE of the cryogenic thermal cycling treated C/C composites were first decreased and then increased in both directions （x-y and z directions） with the increase of thermal cycles. A model regarding the heat conduction in cryogenic thermal cycling treated C/C composites was proposed.
基金Project supported by the National Natural Science Foundation of China(Grant No.61306080)the Natural Science Foundation of Hunan Province,China(Grant No.2015JJ3143)the Scientific and Technological Project of Hunan Provincial Development and Reform Commission,China
文摘Flexible conductive films were fabricated from a low-temperature-cured, highly conductive composite of silver nanowires （as conducting filler） and polyvinyl alcohol （PVA, as binder）. Sheet resistance of 0.12 Ω/sq, conductivity of 2.63 ×10^4 S/cm, and contact resistance of 1.0Ω/cm^2 were measured in the films, along with excellent resistance to scratch- ing and good flexibility, making them suitable electrical contact materials for flexible optoelectronic devices. Effects of curing temperature, curing duration, film thickness, and nanowire length on the film＇s electrical properties were studied. Due to the abundance of hydroxyl groups on its molecular chains, the addition of PVA improves the film＇s flexibility and resistance to scratching. Increased nanowire density and nanowire length benefit film conductance. Monte Carlo simulation was used to further explore the impact of these two parameters on the conductivity. It was observed that longer nanowires produce a higher length-ratio of conducting routes in the networks, giving better film conductivity.
基金Funded by the Natural Science Foundation of Hubei Province (No.2007ABA028)
文摘Vinylester （bismethacryloxy derivative with glass-carbon hybrid fibers （CF-GF） weight fraction of a bisphenol-A type EP resin, VE） composites of 50%, were prepared by the compress molding method. The distribution of carbon fiber in the hybrids was observed by stereomicroscope. The electrical resistance behavior of the composites filled with different carbon fiber （CF） weight contents （0.5% to 20%） was studied. The experimental results show that the electrical resistance behaviors of CF-GF/VE composites are different with those of CF/VE composites because carbon fibers＇ conducting networks are broken by the glass fibers in the CF-GF/VE composites. The carbon fibers distribute uniformly in the networks of glass fibers （GF） like single silk and form the semi-continuous conducting networks. Composite filled with GF-CF hybrid has a higher percolation threshold than that filled with pure CF. At that time, the resistivity of CF-GF/VE composites varies little with the temperature increasing. The temperature coefficient of resistivity in GF-CF/VE composite is less than 317 ppm and the variation of the resistivity after ten thermal cycles from 20℃ to 240 ℃is less than 1.96%.
