The Dielectropheretic assembly of electrically functional microwires from nanopartical suspensions is introduced. Meanwhile growth mechanism of the microwires is discussed. The agglomeration is based on the polarizati...The Dielectropheretic assembly of electrically functional microwires from nanopartical suspensions is introduced. Meanwhile growth mechanism of the microwires is discussed. The agglomeration is based on the polarization and mobility of particles caused by alternating electric fields, commonly referred to as dielectrophoresis (DEP). The spatial distributions of the electric potential, field and dieletrophoretic force are analytically calculated in terms of AC electrokinetics. The calculated results show that the electrophoretic force, very strong near the apex of the microwire, drops abruptly with increasing distance. The electrophoretic force near the apex of the microwire agrees well with the fact that the nanoparticles are highly concentrated at the end of the tip and subsequently aggregate to extend the wire in the direction of the field gradient.展开更多
To enhance the piezoelectric performance of piezoelectric polymer thin films in general,hybrid polyvinylidene difluoride(PVDF)and nanosized barium titanate(BaTiO_(3))piezoelectric films were prepared and their piezoel...To enhance the piezoelectric performance of piezoelectric polymer thin films in general,hybrid polyvinylidene difluoride(PVDF)and nanosized barium titanate(BaTiO_(3))piezoelectric films were prepared and their piezoelectric performance examined.The hybrid nanofibers were fabricated via electrospinning at an external voltage of 15 kV.The nonwoven fabrics were collected using a roller collection device,and their morphological structures were analyzed via scanning electron microscopy.The crystal structures of these piezoelectric films were characterized via micro-Raman spectroscopy.β-phase of the composite nanofiber membrane almost increased to twice owing to the addition of BaTiO_(3)nanoparticles.Compared with pure,electrospun PVDF piezoelectric film,the piezoelectric characteristics of the hybrid piezoelectric films were considerably enhanced because of the additional BaTiO_(3)nanoparticles.The maximum instantaneous open-circuit voltage of the hybrid PVDF-BaTiO_(3)nanofibers film can be high up to 80 V.The high-performance hybrid piezoelectric films exhibited notable prospects for applications in wearable electronic textiles.展开更多
Excellent thermal insulating materials are highly demanded in various applications including buildings, aerospace and sport equipment. However, in practical applications,the performance of thermal insulating materials...Excellent thermal insulating materials are highly demanded in various applications including buildings, aerospace and sport equipment. However, in practical applications,the performance of thermal insulating materials usually deteriorates under diverse temperature and humidity conditions.Therefore, it is highly essential to construct a bulk material that exhibits outstanding thermal insulation performance under extremely humid and hot environment. In this work, we have conceived a green and effective strategy to fabricate a superhydrophobic and compressible polyvinylidene fluoride/polyimide(PVDF/PI) nanofiber composite aerogel via electrospinning and freeze-drying technique. Interestingly, the PVDF nanofibers and PI nanofibers function as the hydrophobic fibrous framework and mechanical support skeleton,respectively, forming a robust three-dimensional framework with good mechanical flexibility. The PVDF/PI aerogel possesses outstanding superhydrophobic feature(water contact angle of 152°) and low thermal conductivity(31.0 m W m^(-1)K^(-1))at room temperature. Significantly, even at 100% relative humidity(80℃), the PVDF/PI aerogel still exhibits a low thermal conductivity of only 48.6 m W m^(-1)K^(-1), which outperforms the majority of commercial thermal insulating materials. Therefore, the novel PVDF/PI aerogel is promising as an excellent thermal insulating material for the applications in high-temperature and humid environment.展开更多
基金Funded by the Applied Basic Research Project of the Science and Technology Committee of Chongqing (No. 7327) and Key Teacher Foundation of Chongqing University.
文摘The Dielectropheretic assembly of electrically functional microwires from nanopartical suspensions is introduced. Meanwhile growth mechanism of the microwires is discussed. The agglomeration is based on the polarization and mobility of particles caused by alternating electric fields, commonly referred to as dielectrophoresis (DEP). The spatial distributions of the electric potential, field and dieletrophoretic force are analytically calculated in terms of AC electrokinetics. The calculated results show that the electrophoretic force, very strong near the apex of the microwire, drops abruptly with increasing distance. The electrophoretic force near the apex of the microwire agrees well with the fact that the nanoparticles are highly concentrated at the end of the tip and subsequently aggregate to extend the wire in the direction of the field gradient.
基金The National Natural Science Foundation of China(No.52375563)the Science and Technology on Avionics Integration Laboratory(No.201913069001,20200055069001).
文摘To enhance the piezoelectric performance of piezoelectric polymer thin films in general,hybrid polyvinylidene difluoride(PVDF)and nanosized barium titanate(BaTiO_(3))piezoelectric films were prepared and their piezoelectric performance examined.The hybrid nanofibers were fabricated via electrospinning at an external voltage of 15 kV.The nonwoven fabrics were collected using a roller collection device,and their morphological structures were analyzed via scanning electron microscopy.The crystal structures of these piezoelectric films were characterized via micro-Raman spectroscopy.β-phase of the composite nanofiber membrane almost increased to twice owing to the addition of BaTiO_(3)nanoparticles.Compared with pure,electrospun PVDF piezoelectric film,the piezoelectric characteristics of the hybrid piezoelectric films were considerably enhanced because of the additional BaTiO_(3)nanoparticles.The maximum instantaneous open-circuit voltage of the hybrid PVDF-BaTiO_(3)nanofibers film can be high up to 80 V.The high-performance hybrid piezoelectric films exhibited notable prospects for applications in wearable electronic textiles.
基金the financial support from the National Natural Science Foundation of China (21674019 and 21704014)the Fundamental Research Funds for the Central Universities(2232019A3-03)+3 种基金the Graduate Student Innovation Fund of Donghua University (CUSF-DH-D-2019006)Shanghai Sailing Program(17YF1400200)Shanghai Municipal Education Commission (17CG33)the Ministry of Education of the People’s Republic of China(6141A0202202)。
文摘Excellent thermal insulating materials are highly demanded in various applications including buildings, aerospace and sport equipment. However, in practical applications,the performance of thermal insulating materials usually deteriorates under diverse temperature and humidity conditions.Therefore, it is highly essential to construct a bulk material that exhibits outstanding thermal insulation performance under extremely humid and hot environment. In this work, we have conceived a green and effective strategy to fabricate a superhydrophobic and compressible polyvinylidene fluoride/polyimide(PVDF/PI) nanofiber composite aerogel via electrospinning and freeze-drying technique. Interestingly, the PVDF nanofibers and PI nanofibers function as the hydrophobic fibrous framework and mechanical support skeleton,respectively, forming a robust three-dimensional framework with good mechanical flexibility. The PVDF/PI aerogel possesses outstanding superhydrophobic feature(water contact angle of 152°) and low thermal conductivity(31.0 m W m^(-1)K^(-1))at room temperature. Significantly, even at 100% relative humidity(80℃), the PVDF/PI aerogel still exhibits a low thermal conductivity of only 48.6 m W m^(-1)K^(-1), which outperforms the majority of commercial thermal insulating materials. Therefore, the novel PVDF/PI aerogel is promising as an excellent thermal insulating material for the applications in high-temperature and humid environment.
