A straightforward preparation and characterization of novel poly(vinyl alcohol)/organoclay/silver tricomponent nanocomposite films

In the present investigation, novel poly(vinyl alcohol)/organoclay/silver (PVA/OMMT/Ag) tricomponent nanocomposite (NC) films with different compositions were prepared by solution intercalation method under ultrasonic irradiation process. The NC films were obtained by mixing a colloidal solution consisting of Ag nanoparticles (NPs) (3, 5, 7 and 9 wt%) with a water solution of PVA and OMMT (10 wt%) via solution casting method. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis (TGA) were utilized to characterize the morphology and properties of the PVA/OMMT/Ag NC films. TGA confirmed that the heat stability of the nanocomposite was improved. The enhancement in the thermal properties of the hybrid materials was due to strong hydrogen bonding between OH groups of PVA, free acid functionalized groups of OMMT, and the Ag NPs. SEM and TEM results also showed that the OMMT and Ag NPs were dispersed homogeneously in the PVA matrix on nanoscale.     

Reinforcement of structural,thermal and electrical properties and antibacterial activity of PVA/SA blend filled with hybrid nanoparticles (Ag and TiO2 NPs): Nanodielectric for energy storage and food packaging industries‏

In this work, silver nanoparticles (Ag NPs) were prepared using a plant extract which is a cost-effective and environmentally friendly method. The sol-gel method was used to synthesize titanium dioxide nanoparticles (TiO₂ NPs). A solid polymer nanocomposite samples have been prepared via the well-known solution cast way. The present samples were examined using various analytical measurements. The XRD patterns showed a decrease in the degree of crystallinity of the PVA/SA blend due to the addition of the hybrid nanoparticles (Ag and TiO₂ NPs). It was evident by the ATR-FTIR measurement that there is an interaction between the functional groups of the polymeric matrix and the hybrid nanoparticles. XPS confirmed that Ag NPs were loaded onto the surfaces of the PVA/SA/TiO₂ organic-inorganic nanocomposite samples. The TGA curves of the doped samples showed an improvement in their thermal stability compared to the pure sample. From the AC conductivity and electrical modulus, the dynamic ions activity and the kind of relaxation process of the nanocomposites samples were examined. The highest conductivity was log −6.066 S/cm for the polymeric sample doped with 1.60% Ag@TiO₂ NPs, as showed by the AC conductivity measurement. A wide dispersion is observed in the dielectric constant spectra at low frequency. It was also evident from the data that the antibacterial activity of the pristine PVA/SA matrix was growing due to the inclusion of the hybrid nanoparticles to the polymeric matrix. Therefore, the obtained results indicate the applicability of these samples and their potential for use in the semiconductor industry, portable electrochemical batteries and energy storage industry, due to the remarkable improvement in the structural, thermal and electrical properties. Also, the good antibacterial activity of these films provides new samples as effective biomaterials and has the potential to be used in the food packaging industry.     

Improved Photocatalytic Activity Using Ternary Au-ZnO/rGO Nanocomposite

In the present study, ternary Au-ZnO/rGO nanocomposite was prepared using a modified polyol protocol. The ternary structure was attained by deposition of both gold nanoparticles (AuNPs) and ZnO NPs on the rGO surface. No surfactants or ligands are used in this chemical process. On the other hand, 1,3-propanediol was used as solvent, reducing agent and surfactant to ensure the formation of NPs and inhibit particles accumulation. The XRD data confirm the successful formation of the three materials and the high crystallinity of the as-prepared sample. Moreover, the XPS measurements confirmed the high purity of the nanocomposite. TEM images show the formation of ternary Au/ZnO/rGO nanostructure. However, Au and ZnO NPs exhibited spherical shape with an average size of 20 nm and homogeneously distribution onto the rGO surface. The ternary Au-ZnO/rGO nanocomposite exhibited optical response in both UV and visible region due to the plasmonic properties of AuNPs. The BET data revealed an increase of the surface area of Au-ZnO/rGO nanocomposite compared to bare ZnO and hybrid Au-ZnO NPs which render it a promising system for high photocatalytic activity. The preliminary photodegradation measurements against MB molecules prove the high performance of the ternary Au-ZnO/rGO nanocomposite to decompose pollutant molecules compared to bare ZnO. The observed photocatalytic activity enhancement could be attributed to the apport given by both plasmonic properties of AuNPs and the high surface area of rGO.

     

Effect of oxygen functional groups of reduced graphene oxide on the mechanical and thermal properties of polypropylene nanocomposites

Reduced graphene oxide (rGO) with various surface structures was prepared by reducing graphene oxide (GO) with hydrazine hydrate (N₂H₄), sodium borohydride (NaBH₄) and l ‐ascorbic acid, respectively. The resulting rGO were used to fabricate rGO/polypropylene (PP) nanocomposites by a melt‐blending method. The surface structure of rGO as well as multifunctional properties of rGO/PP nanocomposites were thoroughly investigated. It was shown that rGO with highest C/O ratio could be obtained by reducing GO with N₂H₄. The crystallization behaviors, tensile strength, thermal conductivity and thermal stability of rGO/PP nanocomposites were significantly improved with the increase of C/O ratio of rGO. For example, with only 1 phr (parts per hundred PP) rGO reduced by N₂H₄, the degree of crystallinity, tensile strength, maximum heat decomposition temperature and thermal conductivity of PP nanocomposite were increased by 6.2%, 20.5%, 48.0 °C and 54.5%, respectively, compared with those of pure PP. Moreover, the thermal degradation kinetics indicated that the decomposition activation energy of rGO/PP nanocomposites could be enhanced by adding rGO with higher C/O ratio. © 2018 Society of Chemical Industry     

Green synthesis and synergistic catalytic effect ofAg/reduced graphene oxide nanocomposite

A nanocomposite of silver nanoparticles and reduced graphene oxide (Ag/rGO) has been developed as a catalyst for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with sodium borohydride, owing to the larger specific surface area and synergistic effect of rGO. A facile and rapid microwave-assisted green route has been used for the uniform deposition of Ag nanoparticles and the reduction of graphene oxide simultaneously with l-arginine as the reducing agent. The resulting Ag/rGO nanocomposite contained about 51 wt% of Ag, and the Ag nanoparticles deposited on the surface of rGO had a mean diameter of 8.6 ± 3.5 nm. Also, the Ag/rGO nanocomposite exhibited excellent catalytic activity and stability toward the reduction of 4-NP to 4-AP with sodium borohydride. The reduction reaction obeyed the pseudo-first-order kinetics. The rate constants increased not only with the increase of temperature and catalyst amount but also with the increase of initial 4-NP concentration, revealing that the support rGO could enhance the catalytic activity via a synergistic effect. A mechanism for the catalytic reduction of 4-NP with NaBH₄ by Ag/rGO nanocomposite via both the liquid-phase and solid-phase routes has been suggested.     

Simultaneous reduction and surface functionalization of graphene oxide for enhancing flame retardancy and thermal conductivity of mesogenic epoxy composites

Graphene oxide (GO ) is reduced and surface functionalized by 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide simultaneously. This functional reduced graphene oxide (F‐rGO ) with better thermal stability can be used as a nano‐filler to improve the flame retardancy, mechanical properties and thermal conductivity of mesogenic epoxy (EO ). Due to the presence of an oriented structure, EO is an intrinsic highly thermal conductive polymer compared with common polymer. After being filled with F‐rGO , the ordered domains in the EO matrix are connected by F‐rGO . As a result, the thermal conductivity coefficient of F‐rGO /EO composite is increased by 30.8% compared with pure EO . The dynamic mechanical analysis results indicate that E ' of F‐rGO /EO is 26.7% higher than that of EO . Because of the stable structure of F‐rGO , F‐rGO /EO is self‐extinguishing. The total heat release of F‐rGO /EO ‐15 is 24.1 kJ g^?1, which is 5.6 kJ g^?1 lower than that of EO . © 2016 Society of Chemical Industry     

Self-cleaning antireflected surfaces based on treated PEO/SiO2 nanocomposite films

In this study, the polyethylene oxide (PEO)/SiO₂ nanoparticles (NPs) nanocomposite films with various SiO₂ NPs concentrations were prepared using an in situ formation of NPs in the polymer matrix for self-cleaning antireflected surface applications. The effect of SiO₂ NPs in PEO/SiO₂ NPs nanocomposite films on the structural, morphological, chemical, thermal, optical, and electrical properties of PEO/SiO₂ NPs nanocomposite films was performed. According to the x-ray diffraction and the differential scanning calorimetry analysis, the crystallinity degree of the nanocomposite films decreases by increasing the SiO₂ NPs concentrations. The bandgap energy of PEO/SiO₂ NPs nanocomposite films decreases from 3.95 to 3.55 eV as the SiO₂ NPs concentration increases up to 10 wt.%. The average electrical conductivity of the PEO/SiO₂ NPs nanocomposite films increases from 5.1 × 10⁻⁷ to 2.0 × 10⁻⁶ S/cm as the SiO₂ NPs concentration increases up to 10 wt.%. The refractive index decreases to 1.64 at 550 nm for the PEO/SiO₂ NPs nanocomposite films with 10 wt.% of SiO₂ NPs, and the water contact angle decreases to around 0° after thermal treatment, which confirms that the PEO/SiO₂ NPs nanocomposite films can be used as self-cleaning antireflected surfaces.     

Realizing load bearing-heat insulation integration of lightweight porosity-controlled SiC(rGO) bulk ceramics via precursor route for hypersonic vehicles

Realizing integration of admirable load bearing and outstanding heat insulation characteristics of porosity-controlled ceramics for hypersonic vehicles is a great challenge. Herein, an ingenious strategy based on re-pyrolysis process of ball-milling-induced fillers/precursors(pore-forming agents) blends is proposed to prepare porous SiC(rGO) bulk polymer-derived ceramics (PDCs) for thermal protection. During re-pyrolysis, dense integrated β-SiC/SiOxCy/C_free(rGO) framework, belonging to SiC(rGO)_p tightly tied by SiC(rGO) from polycarbosilane-vinyltriethoxysilane-graphene oxide (PCS-VTES-GO, PVG), can be formed to maintain brilliant mechanical properties of products. Meanwhile, good interfacial compatibility of nanocomposite structure within the framework also contributes to load capacity. A uniquely uniform distribution of dentinal tubules-like pores, originated from polystyrene (PS) in SiC(rGO) region, could relax stress at crack tips and ensure good thermal insulation. Particularly, lightweight porous SiC(rGO) bulk PDCs with 10 wt% PS content possess low thermal conductivity (0.25 W·m^?1·K^?1), excellent fracture toughness (1.96 MPa·m^1/2), outstanding hardness (3.58 GPa), optimal compressive strength (51.80 MPa) and good flexural strength (33.86 MPa). Their large-sized molding ability and good high-temperature oxidation resistance were significantly demonstrated by further exploration. Such well-balanced high load bearing and good heat insulation integration nature can be used to make thermal insulators with complex shapes in a facile and economical manner.     

Microwave-assisted green synthesis of Ag/reduced graphene oxide nanocomposite as a surface-enhanced Raman scattering substrate with high uniformity

A nanocomposite of silver nanoparticles/reduced graphene oxide (Ag/rGO) has been fabricated as a surface-enhanced Raman scattering (SERS) substrate owing to the large surface area and two-dimensional nanosheet structure of rGO. A facile and rapid microwave-assisted green route has been used for the formation of Ag nanoparticles and the reduction of graphene oxide simultaneously with L-arginine as the reducing agent. By increasing the cycle number of microwave irradiation from 1 and 4 to 8, the mean diameters of Ag nanoparticles deposited on the surface of rGO increased from 10.3 ± 4.6 and 21.4 ± 10.5 to 41.1 ± 12.6 nm. The SERS performance of Ag/rGO nanocomposite was examined using the common Raman reporter molecule 4-aminothiophenol (4-ATP). It was found that the Raman intensity of 4-ATP could be significantly enhanced by increasing the size and content of silver nanoparticles deposited on rGO. Although the Raman intensities of D-band and G-band of rGO were also enhanced simultaneously by the deposited Ag nanoparticles which limited the further improvement of SERS detection sensitivity, the detectable concentration of 4-ATP with Ag/rGO nanocomposite as the SERS substrate still could be lowered to be 10⁻¹⁰ M and the enhancement factor could be increased to 1.27 × 10¹⁰. Furthermore, it was also achievable to lower the relative standard deviation (RSD) values of the Raman intensities to below 5%. This revealed that the Ag/rGO nanocomposite obtained in this work could be used as a SERS substrate with high sensitivity and homogeneity.     

Ionic liquid‐modified graphene/poly(vinyl alcohol) composite with enhanced properties

How to preserve the structure integrity of graphene while enhance its dispersion and compatibility in matrix attracts the attention of researchers in graphene/polymer nanocomposite field. In this paper, methacryloxyethyltrimethyl ammonium chloride (DMC), a kind of ionic liquids, was first used to non‐covalently functionalize graphene in the process of graphene oxide (GO) reduction. The as‐modified graphene (DMC‐rGO) was further incorporated into poly(vinyl alcohol) (PVA) matrix by solution casting technique to fabricate DMC‐rGO/PVA composites. The structure and properties of the obtained DMC‐rGO were investigated by X‐ray diffraction analysis (XRD), X‐ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscope (TEM), Atomic force microscopy (AFM), and Raman test. The results showed that graphene could be successfully modified by DMC through ionic–π interaction and the structure integrity of the graphene could be reserved by this non‐covalently approach. Furthermore, after co‐reduction process, some hydroxyl groups were introduced into DMC‐rGO. In virtue of these intrinsic properties of DMC‐rGO, the fabricated DMC‐rGO/PVA composites exhibit considerable enhancements in mechanical properties and remarkable improvements in thermal stability, as well as the enhancement in electrical conductivity at low DMC‐rGO loading. This simple modification approach gives a new opportunity to improve the performances of graphene/polymer composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45006.     

Ag and Si Codoped Phosphate Glasses: Plasmonic Nanocomposites with Enhanced UV Transparency

The use of silicon powder to produce plasmonic Ag nanocomposite phosphate glasses which also exhibit improved transparency in the ultraviolet (UV) is proposed. Ag₂O/Si codoped glasses were prepared in a barium‐phosphate matrix by a simple melt‐quench method in ambient atmosphere. The as‐prepared glasses exhibit enhanced UV transparency, whereby the surface plasmon resonance of Ag nanoparticles (NPs) is manifested for the glasses with higher Ag₂O contents. ³¹P nuclear magnetic resonance spectroscopy is consistent with the formation of P–O–Si bonds, thus suggesting their possible role on the improved UV light transmission. Consequently, a model was presented accounting for the influence of silicon on the polymerization of the phosphate network concomitant with the creation of highly reactive oxygen species. Further exploiting the proposed reactive species, a real‐time spectroscopic study of the plasmonic response of Ag NPs in Ag/Si codoped glass samples was carried out during an in situ thermal processing. The temperature dependence of the Ag particle precipitation was studied in the 400°C–430°C range, from which an Arrhenius‐type plot allowed for estimating the activation energy of the process at 3.42 (±0.38) eV. Ultimately, the vanishing of the luminescence ascribed to Ag⁺ ions was observed in a heat‐treated sample, consistent with the high reactivity acquired by the glass matrix. Silicon thus appears promising for producing UV transparent glasses for high‐performance optics and for the reduction of Ag⁺ ions to produce Ag nanocomposites valuable for photonic (nanoplasmonic) applications.     

Investigation of improved dielectric and thermal properties of ternary nanocomposite PMMA/MXene/ZnO fabricated by in-situ bulk polymerization

Electric power system applications demand for high-temperature dielectric materials. The improved performance of polymer nanocomposites requires improvement in their thermal conductivity & stability, dielectric stability and processing technique. However, they often lose their dielectric properties with a rise in temperature. Here, we offer a solution by incorporating electrically conducting material (MXene) and semiconducting inorganic nanoparticles (ZnO NPs) into an insulating PMMA polymer matrix to maintain high dielectric constant, both at the room and high temperature. Therefore, to achieve desirable thermal and dielectric properties is the main objective of the present study based on the homogeneous distribution of the nanofillers by in-situ bulk polymerization assisted by strong sonication in the corresponding polymer. The introduction of MXene and ZnO NPs into the PMMA not only acquires a substantial increment in the dielectric constant, to attain a value 437, with minimum energy loss of 0.36 at 25 Hz, but also improves the thermal conductivity of PMMA up to 14 times by causing the reduction of thermal resistance, which is actually responsible for the poor thermal conductivity of amorphous pure PMMA polymer. More importantly, hybrid PMMA/4:2 wt% MXene:ZnO nanocomposite leads to an excellent thermal stability. Moreover, further characterization of the synthesized nanocomposites by FTIR, SEM and XRD leads to the evaluation of strong interaction of ternary components with PMMA matrix.     

Impact of enhanced interfacial strength on physical,mechanical and tribological properties of copper/reduced graphene oxide composites: Microstructural investigation

Copper/reduced graphene oxide (rGO) composites were prepared to improve the mechanical and tribological properties of copper without adversely affecting its physical properties in any significant manner. No hazardous chemicals were used for reduced graphene oxide production, which maintained the integrity of layers. For better dispersibility of rGO in the copper matrix, electroless deposition of copper was done on the activated and sensitized rGO surfaces. Different amounts of prepared Copper/rGO nanocomposites were then dispersed in bulk copper using ethanol and finally compacted using spark plasma sintering. The coefficient of friction of copper reinforced with 0.5 wt% of nanocomposite reduced by 77.5% compared to neat copper. The flexural strength of copper reinforced with 0.75 wt% of nanocomposite and modulus of 1 wt% of nanocomposite reinforced copper increased by 15.2% and 31.3%, respectively, with different strengthening mechanisms before and after yield point. The increase in hardness and strength of the material along with thin rGO films in the wear track accounted for the sharp decrease in the coefficient of friction for the composites. There was a minimal and gradual decrease in the physical properties (electrical and thermal conductivities) of the composites with an increase in the amount of reinforcement. The two-step composite fabrication process ensured better dispersion of rGO in the copper matrix, which resulted in even properties throughout the composite.     

A multifunctional Ag/TiO2/reduced graphene oxide with optimal surface-enhanced Raman scattering and photocatalysis

A multifunctional Ag/TiO₂/reduced graphene oxide (rGO) ternary nanocomposite was prepared by a one-step photochemical reaction with TiO₂ and Ag nanoparticles successively deposited on reduced graphene oxide. The structure, morphology, composition, optical, and photoelectrochemical properties of Ag/TiO₂/rGO were investigated in detail. Meanwhile, the ternary nanocomposite possessed much higher adsorption capacity to organic dyes compared with bare TiO₂ and binary Ag/TiO₂, which would help to its use for surface-enhanced Raman scattering detection and photocatalytic degradation. Due to the charge transfer between rGO and organic dyes and enhanced electromagnetic mechanism of Ag, Ag/TiO₂/rGO nanocomposites as surface-enhanced Raman scattering substrates demonstrated dramatically improved sensitivity and good uniformity. The detection limit of rhodamine 6G (R6G) was as low as 10⁻⁹ mol/L, and the relative standard deviation values of the intensities remained below 5%. Most importantly, the synergistic coupling effect of three components extended the photoresponse range and accelerated separation of the electron-hole pairs, leading to greatly improved photocatalytic activity under simulated sunlight. The maximum rate constant (k, 0.06243 min⁻¹) of Ag/TiO₂/rGO was 50 and four times higher than that of TiO₂ and Ag/TiO₂, respectively.     

Heteroatom-doped reduced graphene oxide/polyaniline nanocomposites with improved n-type thermoelectric performance

Polyaniline (PANI) is a potential candidate for n-type thermoelectric (TE) materials owing to its intrinsic electrical conductivity, low thermal conductivity, and facile synthesis techniques. However, its low Seebeck coefficient and power factor have limited its widespread usage. In this study, nitrogen-doped, and sulfur-nitrogen co-doped reduced graphene oxide (rGO) were used for tuning the TE properties of PANI. Doped rGO and PANI/doped-rGO nanocomposites were prepared via hydrothermal technique and chemical oxidative polymerization respectively and thereafter characterized. The TE properties of the nanocomposites were also studied and an optimized Seebeck coefficient, power factor and zT value of −1.75 mV K⁻¹, 95 μW m⁻¹ K⁻² and 0.06, respectively were reported for the PANI nanocomposite containing 1 wt% sulfur-nitrogen co-doped rGO. These results suggest that PANI/heteroatom-doped rGO can serve as promising candidates for n-type based TE applications.     

Antibacterial activities of novel nanocomposite biofilms of chitosan/phosphoramide/Ag NPs

Novel nanocomposite films of chitosan/phosphoramide/Ag NPs were prepared containing 1–5% of silver nanoparticles. The Ag NPs were synthesized according to the citrate reduction method. The XRD and SEM analysis of Ag NPs, chitosan (CS), phosphoramide (Ph), CS/Ph, CS/Ag NPs films and the nanocomposite films 1–5 containing CS/Ph/1–5% Ag NPs were investigated. The in vitro antibacterial activities were evaluated against four bacteria including two Gram‐positive Staphylococcus aureus (S. aureus), Bacillus cereus (B. cereus) and two Gram‐negative Escherchia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) bacteria. Results revealed greater antibacterial effects of the films against Gram‐positive bacteria. Also, nanocomposite films containing higher percent of Ag NPs showed more antibacterial activities. POLYM. COMPOS. 36:454–466, 2015. © 2014 Society of Plastics Engineers     

Enhanced the dispersibility and permeability of silver nanoparticles over rGO grafted by positively-charged polyethyleneimine toward broad-spectrum sterilization

Silver nanoparticles (Ag NPs) are used as antimicrobial agents due to their high-efficiency, broad-spectrum disinfection activity. However, the agglomeration and stability problems caused by excessive release of silver ions (Ag⁺) have severely restricted their developments. Herein, a novel silver/polyethyleneimine/reduced graphene oxide (Ag/PEI/rGO) antibacterial material featuring good dispersibility and permeability was rationally designed, thus benefiting for the capture of bacteria due to the introducing of highly-cationic PEI modifier and controllable release of biocidal agents (Ag⁺). Compared with Ag/rGO, the Ag/PEI/rGO has excellent stability and shows a more efficient sterilization efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) with 100% germicidal efficiency with low orders of dozens of ppm. In addition, the outstanding biocompatibility of this Ag/PEI/rGO antibacterial material endows it with promising potential in sterilization applications, which is expected to solve the infection problem caused by bacterial biofilm formation.     

铁酸铋/石墨烯纳米复合材料的制备及其对高氯酸铵热分解的催化作用

为了提高纳米复合金属氧化物对高氯酸铵(AP)热分解的催化作用,以Bi(NO₃)₃·5H₂O、Fe(NO₃)₃·9H₂O和GO为前驱体,采用水热法制备了铁酸铋/石墨烯(BiFeO₃/rGO)纳米复合材料;利用XRD、FT-IR、XPS、TGA、SEM和TEM等对所制备样品的结构、粒径及形貌进行了表征;采用差热分析研究了不同添加量的BiFeO₃/rGO纳米复合材料对AP热分解过程的影响,分析了BiFeO₃/rGO对AP热分解的催化机理及其对AP热分解动力学的影响。结果表明,rGO的引入有效阻止了纳米BiFeO₃颗粒的团聚,大大增加了比表面积;当BiFeO₃/rGO纳米复合材料的质量分数为4%时,AP的高温分解峰降低最多,达167℃,表观分解热增加了1631J/g,达2518J/g,表观活化能从172.07kJ/mol降低至128.35kJ/mol,表明所制备的BiFeO₃/rGO纳米复合材料能有效催化AP的热分解。     

Electrical-Triggered Multicolor Reversible Color-Changing Ag Nanoparticles/Reduced Graphene Oxide/Polyurethane Conductive Fibers

Smart color-changing fibers attract much attention owing to their importance as a component of flexible electronics. A facile and scalable method of multicolor reversible electro–thermochromic Ag nanoparticles/reduced graphene oxide/polyurethane conductive fiber (ETC AgNPs/rGO/PU conductive fiber) is fabricated, which contains the polyurethane (PU) as the inner layer, reduced graphene oxide (rGO) with Ag nanoparticles (AgNPs) as the conductive layer, and thermochromic paste as the outermost layer. It possesses excellent electrothermal and color-changing properties and rapidly generates Joule heat at 0.5 V, which makes the fiber surface temperature reach 39.81 °C rapidly. The color switching rate is fast and changes from green to yellow within 2 s. During the process of 250 times on/off voltage, ETC AgNPs/rGO/PU conductive fibers still maintain excellent electrical and thermal properties and color change stability; even in the washing, strong acid, and strong alkali environment, they still have excellent durability. This human subjective adjustable electrical–thermal–color multi-level induced modulation makes it possible to be applied to smart wearable fields such as visual camouflage, personal thermal management, and active information transfer.     

Enhanced mechanical and anisotropic thermal conductive properties of polyimide nanocomposite films reinforced with hexagonal boron nitride nanosheets

To attain thermally conductive but electrically insulating polymer films, in this study, polyimide (PI) nanocomposite films with 1–30 wt% functionalized hexagonal boron nitride nanosheets (BNNSs) were fabricated via solution casting and following imidization. The microstructures, mechanical and thermal conductive properties of PI/BNNS nanocomposite films were examined by taking account of the relative content, anisotropic orientation, and interfacial interaction of BNNS and PI matrix. The scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffractometry data revealed that BNNSs with hydroxy and amino functional groups have specific molecular interactions with PI matrix and they form stacked aggregates in the nanocomposite films with high BNNS loadings of 10–30 wt%. The tensile mechanical strength/modulus, thermal degradation temperatures, and thermal conductivity of the nanocomposite films were found to be significantly enhanced with increasing the BNNS loadings. For the nanocomposite films with 1–30 wt% BNNS loadings, the in-plane thermal conductivity was measured to be 1.82–2.38 W/mK, which were much higher than the out-of-plane values of 0.35–1.14 W/mK. The significant anisotropic thermal conductivity of the nanocomposite films was found to be owing to the synergistic anisotropic orientation effects of both BNNS and PI matrix. It is noticeable that the in-plane and out-of-plane thermal conductivity values of the nanocomposite film with 30 wt% BNNS were ~1.31 and ~3.35 times higher than those of neat PI film, respectively.