Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) nanofibers with diameter of 150~200 nm are prepared via electrospinning and used as dielectric fillers in Poly(vinylidene fluoride) (PVDF)-based composite films. Highly flexible polymer composite films are fabricated with a solution cast method. Enhanced dielectric constants are obtained at low volume fraction of PZT nanofibers. The orientation of PZT nanofibers perpendicular to the external electric field gives rise to improved dielectric breakdown strength. A subsequent uniaxial stretching of the composite films leads to higher crystallinity and breakdown strength of the polymer composites, which is favorable for the polarization of the nanocomposites at higher electric fields. Enhanced ferroelectric properties, i.e., higher saturated and remnant polarization, are obtained in these composite films. High piezoelectric coefficient (d 33 ) of ~ 87.4 pm/V is also achieved for the polymer composite films filled with only 2.4 vol.% of PZT nanofibers. The results show that the PZT/PVDF composite films have potential applications in piezoelectric sensors, and even piezoelectric actuators
Adding fiber can improve the brittleness of plain concrete. Compared with plain concrete, basalt fiber-reinforced concrete has the advantages of strengthening, toughening, and crack resistance. Compared with steel fiber-reinforced concrete, basalt fiber-reinforced concrete has better construction performance. Basalt fiber concrete is a type of inorganic material with environmental protection and high mechanical properties, which has an important mechanical advantage for controlling the deformation of the soft surrounding rock tunnel. Through the indoor model test of mechanical behavior of reinforced concrete and basalt fiber-reinforced concrete lining, the bearing characteristics of basalt fiber-reinforced concrete lining was studied. The results show that, compared with reinforced concrete, the initial crack load of basalt fiber-reinforced concrete is increased by 20%; the toughness of lining structure is enhanced by adding basalt fiber, and the lining can still bear large bending moment and deformation after the initial crack appears; after the initial crack appears, the bearing characteristic curve of reinforced concrete lining rises slowly and converges rapidly; the bearing characteristic curve of basalt fiber-reinforced concrete lining rises slowly, and there is no sign of convergence when it reaches 2 times of initial crack load. For the soft surrounding rock tunnel, it is necessary to seal the rock surface as early as possible, provide support as soon as possible, and have a certain deformation capacity. Basalt fiber-reinforced concrete can better meet these needs.
One novel fluorene-based amphiphilic copolymers has been synthesized by Suzuki
polycondensation (SPC) with monomer 2,7-dibromo-9,9-bis-(3,6-dioxahepyl)fluorene and
9,9-dioctylfluorene-2,7-bis-(trimethyleneboronate). The copolyfluorenes’ molecular structure is
characterized by 1H and 13C NMR as well as elemental analysis. The copolyfluorenes have high
molecular weight and narrow molecular weight distribution, at the same time, are found to have good
solubility and thermal stabilities. The copolyfluorenes exhibit a UV-visible absorption band in the
range of 389-393 nm in both toluene solution and the film state. Upon photo-excitation around the
absorption maximum wavelength, their PL spectra show a maximum peaks around at 415-427 nm.
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