Graphene has shown great potential in microwave absorption(MA) owing to its high surface area, low density,tunable electrical conductivity and good chemical stability.To fully realize graphenes& MA ability, the mi...Graphene has shown great potential in microwave absorption(MA) owing to its high surface area, low density,tunable electrical conductivity and good chemical stability.To fully realize graphenes& MA ability, the microstructure of graphene should be carefully addressed. Here we prepared graphene microflowers(Gmfs) with highly porous structure for high-performance MA filler material. The efficient absorption bandwidth(reflection loss B-10 dB) reaches 5.59 GHz and the minimum reflection loss is up to -42.9 dB, showing significant increment compared with stacked graphene. Such performance is higher than most graphene-based materials in the literature. Besides, the low filling content(10 wt%) and low density(40–50 mg cm^(-3))are beneficial for the practical applications. Without compounding with magnetic materials or conductive polymers,Gmfs show outstanding MA performance with the aid of rational microstructure design. Furthermore, Gmfs exhibit advantages in facile processibility and large-scale production compared with other porous graphene materials including aerogels and foams.展开更多
The performance of reinforced rubber compounds depends on the filler composition while the reinforcement and dissipation mechanisms still remain unclear. Herein linear and nonlinear dynamic rheological responses of ca...The performance of reinforced rubber compounds depends on the filler composition while the reinforcement and dissipation mechanisms still remain unclear. Herein linear and nonlinear dynamic rheological responses of carbon black/silica hybrid filler filling nature rubber compounds are investigated. The rheological contributions of dynamically retarded bulk phase and filler network are revealed to be crucial at high and low frequencies, respectively, and the bulk phase is shown to be of vital importance for the occurrence of nonlinear Payne effect at mediate frequencies. A framework for simultaneously solving reinforcement and dissipation varying with filler composition and content is suggested, providing a new perspective in understanding the filling effect for manufacturing high-performance rubber materials.展开更多
Detection of Cu(Ⅱ) is very important in disease diagnose, biological system detection and environmental monitoring. Previously, we found that the product TPE-CS prepared by attaching the chromophores of tetrapheny...Detection of Cu(Ⅱ) is very important in disease diagnose, biological system detection and environmental monitoring. Previously, we found that the product TPE-CS prepared by attaching the chromophores of tetraphenylethylene(TPE) to the chitosan(CS) chains showed excellent fluorescent properties. In this study, we tried to use TPE-CS for detecting Cu(Ⅱ) because of the stable complexation of CS with heavy metals and the luminosity mechanism of the Restriction of Intramolecular Rotations(RIR) for aggregation-induced emission(AIE)-active materials. The fluorescence intensity changed when TPE-CS was contacted with different metal ions, to be specific, no change for Na;, slightly increase for Hg;, Pb;, Zn;, Cd;, Fe;, Fe;due to the RIR caused by the complexation between CS and metal ions. However, for Cu;, an obvious fluorescence decrease was observed because of the Photoinduced-Electron-Transfer(PET). Moreover, we found that the quenched FL intensity of TPE-CS was proportional to the concentration of Cu(Ⅱ) in the range of 5 μmol/L to 100 μmol/L, which provided a new way to quantitatively detect Cu(Ⅱ) . Besides, TPE-CS has excellent water-solubility as well as absorbability(the percentage of removal, R = 84%), which is an excellent detection probe and remover for Cu(Ⅱ) .展开更多
Polysulfone (PSF) membranes have gained great attention in the fields of ultrafiltration, microfiltration, and thin film composite membranes for nanofiltration or reverse osmosis. For the first time, it is proposed ...Polysulfone (PSF) membranes have gained great attention in the fields of ultrafiltration, microfiltration, and thin film composite membranes for nanofiltration or reverse osmosis. For the first time, it is proposed to fabricate PSF membranes via thermally induced phase separation (TIPS) process using diphenyl sulfone (DPSO2) and polyethylene glycol (PEG) as mixed diluent. DPSO2 is chosen as a crystallizable diluent, while PEG is considered in terms of molecular weight (Mw) and dosage. We systematically investigate the interactions between PSF, DPSO2 and PEG based on the simulation calculations and solubility parameter theory. It is inferred that DPSO2 has an excellent compatibility with PSF, and the addition of PEG results in the ternary system thermodynamically less stable and then facilitates its liquid-liquid (L-L) phase separation. SEM images indicate that cellular-like pores are obvious throughout the membrane when the PEG content in the mixed diluent is 25 wt%-35 wt%. We can facilely manipulate the pore size, water flux and mechanical properties of PSF membranes with the dosage of PEG-200, the Mw of PEG or the cooling rate. The successful application of TIPS can provide a new approach for structure manipulation and performance enhancement of PSF membranes.展开更多
Dual-asymmetric poly(vinylidene fluoride) (PVDF) separators have been fabricated by thermally induced phase separation with dimethyl sulfone (DMSO2) and glycerol as mixed diluents. The separators have a porous b...Dual-asymmetric poly(vinylidene fluoride) (PVDF) separators have been fabricated by thermally induced phase separation with dimethyl sulfone (DMSO2) and glycerol as mixed diluents. The separators have a porous bulk with large interconnected pores (-1.0 μm) and two surfaces with small pores (-30 nm). This dual-asymmetric porous structure endows the separators with higher electrolyte uptake amount and rapider uptake rate, as well as better electrolyte retention ability than the commercialized Celgard 2400. The separators even maintain their dimensional stability up to 160 ℃, at which temperature the surface pores close up, leading to a dramatic decrease of air permeability. The electrolyte filled separators also show high ion conductivity (1.72 mS.cm-1) at room temperature. Lithium iron phosphate (LiFePO4)/lithium (Li) cells using these separators display superior discharge capacity and better rate performance as compared with those from the commercialized ones. The results provide new insight into the design and development of separators for high-performance lithium ion batteries with enhanced safety.展开更多
Flexible wearable electronics, when combined with outstanding thermoelectric properties, are promising candidates for future energy harvesting systems. Graphene and its macroscopic assemblies (e.g., graphene-based fi...Flexible wearable electronics, when combined with outstanding thermoelectric properties, are promising candidates for future energy harvesting systems. Graphene and its macroscopic assemblies (e.g., graphene-based fibers and films) have thus been the subject of numerous studies because of their extraordinary electrical and mechanical properties. However, these assemblies have not been considered suitable for thermoelectric applications owing to their high intrinsic thermal conductivity. In this study, bromine doping is demonstrated to be an effective method for significantly enhancing the thermoelectric properties of graphene fibers. Doping enhances phonon scattering due to the increased defects and thus decreases the thermal conductivity, while the electrical conductivity and Seebeck coefficient are increased by the Fermi level downshift. As a result, the maximum figure of merit is 2.76 ~ 10~, which is approximately four orders of magnitude larger than that of the undoped fibers throughout the temperature range. Moreover, the room temperature power factor is shown to increase up to 624 btW.m-l.K-2, which is higher than that of any other material solely composed of carbon nanotubes and graphene. The enhanced thermoelectric properties indicate the promising potential for graphene fibers in wearable energy harvesting systems.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 21325417 and 51533008)National Key R&D Program of China (No. 2016YFA0200200)Fundamental Research Funds for the Central Universities (2017XZZX008-06)
文摘Graphene has shown great potential in microwave absorption(MA) owing to its high surface area, low density,tunable electrical conductivity and good chemical stability.To fully realize graphenes& MA ability, the microstructure of graphene should be carefully addressed. Here we prepared graphene microflowers(Gmfs) with highly porous structure for high-performance MA filler material. The efficient absorption bandwidth(reflection loss B-10 dB) reaches 5.59 GHz and the minimum reflection loss is up to -42.9 dB, showing significant increment compared with stacked graphene. Such performance is higher than most graphene-based materials in the literature. Besides, the low filling content(10 wt%) and low density(40–50 mg cm^(-3))are beneficial for the practical applications. Without compounding with magnetic materials or conductive polymers,Gmfs show outstanding MA performance with the aid of rational microstructure design. Furthermore, Gmfs exhibit advantages in facile processibility and large-scale production compared with other porous graphene materials including aerogels and foams.
基金financially supported by the National Natural Science Foundation of China(Nos.51573157,51333004 and51373149)the Natural Science Foundation of Zhejiang Province(No.R14E030003)+2 种基金the Major Projects of Science and Technology Plan of Guizhou Province(No.(2013)6016)the Open Project Foundation in Shanghai Aerospace System Engineering Institutethe SAST Innovation Fund(No.yy-F08052015100029)
文摘The performance of reinforced rubber compounds depends on the filler composition while the reinforcement and dissipation mechanisms still remain unclear. Herein linear and nonlinear dynamic rheological responses of carbon black/silica hybrid filler filling nature rubber compounds are investigated. The rheological contributions of dynamically retarded bulk phase and filler network are revealed to be crucial at high and low frequencies, respectively, and the bulk phase is shown to be of vital importance for the occurrence of nonlinear Payne effect at mediate frequencies. A framework for simultaneously solving reinforcement and dissipation varying with filler composition and content is suggested, providing a new perspective in understanding the filling effect for manufacturing high-performance rubber materials.
基金This work was supported by the National Natural Science Foundation of China (Nos. 51406236, 51576105, 51327001, 51336009, 51636002, 21325417 and 51533008), the Science Foundation of China University of Petroleum, Beijing (Nos. 2462013YJRC027, and 2462015YQ0402), the Science Fund for Creative Research Groups (No. 51321002), and Tsinghua University Initiative Scientific Research Program.
基金financially supported by the Key Science Technology Innovation Team of Zhejiang Province(No.2013TD02)the National Natural Science Foundation of China(Nos.21104067,21274127,21374099 and 51473144)
文摘Detection of Cu(Ⅱ) is very important in disease diagnose, biological system detection and environmental monitoring. Previously, we found that the product TPE-CS prepared by attaching the chromophores of tetraphenylethylene(TPE) to the chitosan(CS) chains showed excellent fluorescent properties. In this study, we tried to use TPE-CS for detecting Cu(Ⅱ) because of the stable complexation of CS with heavy metals and the luminosity mechanism of the Restriction of Intramolecular Rotations(RIR) for aggregation-induced emission(AIE)-active materials. The fluorescence intensity changed when TPE-CS was contacted with different metal ions, to be specific, no change for Na;, slightly increase for Hg;, Pb;, Zn;, Cd;, Fe;, Fe;due to the RIR caused by the complexation between CS and metal ions. However, for Cu;, an obvious fluorescence decrease was observed because of the Photoinduced-Electron-Transfer(PET). Moreover, we found that the quenched FL intensity of TPE-CS was proportional to the concentration of Cu(Ⅱ) in the range of 5 μmol/L to 100 μmol/L, which provided a new way to quantitatively detect Cu(Ⅱ) . Besides, TPE-CS has excellent water-solubility as well as absorbability(the percentage of removal, R = 84%), which is an excellent detection probe and remover for Cu(Ⅱ) .
基金supported by the National Natural Science Foundation of China(Nos.21174124 and 21534009)
文摘Polysulfone (PSF) membranes have gained great attention in the fields of ultrafiltration, microfiltration, and thin film composite membranes for nanofiltration or reverse osmosis. For the first time, it is proposed to fabricate PSF membranes via thermally induced phase separation (TIPS) process using diphenyl sulfone (DPSO2) and polyethylene glycol (PEG) as mixed diluent. DPSO2 is chosen as a crystallizable diluent, while PEG is considered in terms of molecular weight (Mw) and dosage. We systematically investigate the interactions between PSF, DPSO2 and PEG based on the simulation calculations and solubility parameter theory. It is inferred that DPSO2 has an excellent compatibility with PSF, and the addition of PEG results in the ternary system thermodynamically less stable and then facilitates its liquid-liquid (L-L) phase separation. SEM images indicate that cellular-like pores are obvious throughout the membrane when the PEG content in the mixed diluent is 25 wt%-35 wt%. We can facilely manipulate the pore size, water flux and mechanical properties of PSF membranes with the dosage of PEG-200, the Mw of PEG or the cooling rate. The successful application of TIPS can provide a new approach for structure manipulation and performance enhancement of PSF membranes.
基金financially supported by the National Natural Science Foundation of China(Nos.21174124 and 21534009)
文摘Dual-asymmetric poly(vinylidene fluoride) (PVDF) separators have been fabricated by thermally induced phase separation with dimethyl sulfone (DMSO2) and glycerol as mixed diluents. The separators have a porous bulk with large interconnected pores (-1.0 μm) and two surfaces with small pores (-30 nm). This dual-asymmetric porous structure endows the separators with higher electrolyte uptake amount and rapider uptake rate, as well as better electrolyte retention ability than the commercialized Celgard 2400. The separators even maintain their dimensional stability up to 160 ℃, at which temperature the surface pores close up, leading to a dramatic decrease of air permeability. The electrolyte filled separators also show high ion conductivity (1.72 mS.cm-1) at room temperature. Lithium iron phosphate (LiFePO4)/lithium (Li) cells using these separators display superior discharge capacity and better rate performance as compared with those from the commercialized ones. The results provide new insight into the design and development of separators for high-performance lithium ion batteries with enhanced safety.
文摘Flexible wearable electronics, when combined with outstanding thermoelectric properties, are promising candidates for future energy harvesting systems. Graphene and its macroscopic assemblies (e.g., graphene-based fibers and films) have thus been the subject of numerous studies because of their extraordinary electrical and mechanical properties. However, these assemblies have not been considered suitable for thermoelectric applications owing to their high intrinsic thermal conductivity. In this study, bromine doping is demonstrated to be an effective method for significantly enhancing the thermoelectric properties of graphene fibers. Doping enhances phonon scattering due to the increased defects and thus decreases the thermal conductivity, while the electrical conductivity and Seebeck coefficient are increased by the Fermi level downshift. As a result, the maximum figure of merit is 2.76 ~ 10~, which is approximately four orders of magnitude larger than that of the undoped fibers throughout the temperature range. Moreover, the room temperature power factor is shown to increase up to 624 btW.m-l.K-2, which is higher than that of any other material solely composed of carbon nanotubes and graphene. The enhanced thermoelectric properties indicate the promising potential for graphene fibers in wearable energy harvesting systems.