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1.
This study presents a new type of composite consisting of piezoelectric poly(γ-benzyl-α, l -glutamate) (PBLG) polymer fibers, which contain a large dipole moment, and the elastomer polydimethylsiloxane (PDMS) as the matrix material. PBLG microfibers were fabricated and polarized using the electrospinning method and cast in PDMS to form a unidirectional continuous-fiber composite. The PBLG/PDMS composite was characterized based on various aspects such as crystalline structure, mechanical properties, piezoelectricity, and electromechanical response. The piezoelectric charge constants in the transverse and longitudinal modes were measured to be 10.2 and 54 pC/N, respectively, which are the largest piezoelectric coefficients of biocompatible polymers up to date. The thin PBLG/PDMS composite film can produce up to 200 mV peak-to-peak under sinusoidal actuation and exhibit ultra-sensitivity up to 615 mV N−1. These results show the great potential of the highly flexible piezoelectric polymer fiber-based composite for use in a variety of applications such as energy harvesting devices, biomechanical self-powered structures, and force sensors. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48884.  相似文献   

2.
This paper presents for the first time that poly(l ‐lactic acid) (PLLA) nanofibers can show the piezoelectricity along the fiber direction (d33) by using an electrospinning method. First, the electrospun fiber bundles are characterized by scanning electron microscope, X‐ray, and piezoelectric coefficient measurements. The data show that the supercritical CO2 treatment can greatly enhance the piezoelectricity of electrospun PLLA fibers, which can be resulting from the increased crystallinity of the fibers. Later, it is found that the electrospun PLLA fiber can generate a current of 8 pA and a voltage of 20 mV by a simple push–release process. Further, a single PLLA fiber‐based blood pulse sensor is also fabricated and tested and shows around a 2 pA output for blood pulse. Due to easy fabrication and relatively simple structure, this device enables a broad range of promising future applications in the medical sensor area.

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3.
Lead zirconate titanate (PbZr1 ? xTixO3, PZT)/epoxy composites with one‐ dimensional epoxy in PZT matrix (called 3‐1 type piezocomposites) have been fabricated by tert‐butyl alcohol (TBA)‐based directional freeze casting of PZT matrix and afterward infiltration of epoxy. The composites with PZT volume fraction ranging from 0.36 to 0.69 were obtained by adjusting initial solid loading in freeze‐casting slurry. The effect of poling voltage on piezoelectric properties of the composites was studied for various volume fraction of PZT phase. With the increasing of PZT volume fraction, relative permittivity (εr) increased linearly and piezoelectric coefficient (d33 and d31) increased step by step. The resultant composites with 0.57 PZT volume fraction possessed the highest hydrostatic piezoelectric strain coefficient (dh) value (184 pC/N), voltage coefficient (gh) value (13.6 × 10?3 V/m Pa), and hydrostatic figure of merit (HFOM) value (2168 × 10?15 Pa?1).  相似文献   

4.
In this work, we fabricated the (1‐x)BiFeO3xBaTiO3+y‰ mol CuO ceramics by the modified thermal quenching technique. The pure perovskite phase was formed and a morphotropic phase boundary (MPB) was observed in the ceramics with = 0.30‐0.33. The addition of CuO can significantly enhance the density of the BiFeO3‐BaTiO3 material. Importantly, an enhanced piezoelectric constant (d33=165 pC/N), a large electric‐field‐induced strain (?S = 0.54%: peak to peak strain) and a large piezoelectric actuator constant (d33*=449 pm/V) together with a high Curie temperature (TC) of 503°C were observed in the ceramics with = 0.30 and = 5. As a result, the enhanced piezoelectricity and large electric‐field‐induced strain could significantly stimulate further researches in BFO‐based ceramics.  相似文献   

5.
Four poly(γ‐benzyl‐L ‐glutamate) (PBLG) derivatives bearing at one end specific groups were synthesized by ring‐opening polymerization of the corresponding γ‐benzyl‐L ‐glutamate N‐carboxyanhydride using different amine‐terminated initiators. These moieties were chosen to introduce, on demand, specific functionalities in nanoparticles of pharmaceutical interest. The PBLG and PBLG derivatives were characterized by 1H NMR, viscosimetry, Fourier transform infrared spectroscopy and differential scanning calorimetry. Nanoparticles smaller than 100 nm in diameter could be easily prepared from these PBLG derivatives by slight modification of a known nanoprecipitation technique. Copyright © 2006 Society of Chemical Industry  相似文献   

6.
A thermoplastic hydrogel based on a pentablock copolymer composed of poly(γ‐benzyl L ‐glutamate) (PBLG) and poloxamer was synthesized by polymerization of BLG N‐carboxyanhydride, which was initiated by diamine‐terminated groups located at the ends of poly(ethylene oxide) (PEO) chains of the poloxamer, to attain a new pH‐ and temperature‐sensitive hydrogel for drug delivery systems. Circular dichroism measurements in solution and IR measurements in the solid state revealed that the polypeptide block existed in the α‐helical conformation, as in the PBLG homopolymer. The intensity of the wide‐angle X‐ray diffraction patterns of the polymers depended on the poloxamer content in the copolymer and showed basically similar reflections to the PBLG homopolymer. The melting temperature (Tm) of the poloxamer in the copolymer was reduced with an increase of the PBLG block in comparison with the Tm of the poloxamer, which is indicative of a thermoplastic property. The water contents of the copolymers were dependent on the poloxamer content in the copolymers, for example, those for the GPG‐2 (48.7 mol % poloxamer) and GPG‐1 (57.5 mol % poloxamer) copolymers were 31 and 41 wt %, respectively, indicating characteristics of a polymeric hydrogel. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2649–2656, 2003  相似文献   

7.
Ferroelectric phase coexistence was constructed in (1?x)BaTiO3xCaSnO3 lead‐free ceramics, and its relationship with the piezoelectricity of the materials was investigated to ascertain potential factors for strong piezoelectric response. It is found that the addition of CaSnO3 caused a series of phase transitions in the (1?x)BaTiO3xCaSnO3 ceramics, and a ferroelectric coexistence of rhombohedral, orthorhombic, and tetragonal phases is formed at = 0.08, where the ceramics exhibit the lowest energy barrier and consequently facilitate the polarization rotation and extension, resulting in the optimal piezoelectricity of d33 and kp values of 550 pC/N and 0.60, respectively. Our study provides an intuitive insight to understand the origin of high piezoelectricity in the ceramics with the coexistence of multiferroelectric phases.  相似文献   

8.
Electrospinning of a poly(ε‐caprolactone) (PCL)/lactic acid (LA) blend was investigated to fabricate electrospun PCL fibers with improved biodegradability and biocompatibility for biomedical applications. Simple blending of PCL solution with various amounts of LA was used for electrospinning, and the physicochemical properties of the as‐fabricated mat were evaluated using various techniques. Scanning electron microscopy showed that fiber diameter decreased with increasing amount of LA. Fourier transform infrared spectroscopy and thermogravimetric analysis also revealed that LA was successfully incorporated in PCL fibers. The presence of LA can accelerate the biodegradation of PCL fibers and enhance the hydrophilicity of a membrane. The adhesion, viability and proliferation properties of osteoblast cells on the PCL/LA composite fibers were analyzed using in vitro cell compatibility tests which showed that LA can increase the cell compatibility of PCL fibers. Additionally, subsequent conversion of LA into calcium lactate by neutralization with calcium base can provide Ca2+ ions on the fiber surface to promote the nucleation of CaPO4 particles. © 2013 Society of Chemical Industry  相似文献   

9.
This work investigated the effect of MnO2 addition on the phase structure, microstructure, and electrical properties of AgSbO3‐modified (Li,K,Na)(Nb,Ta)O3 (abbreviated as LKNNT‐AS) lead‐free piezoelectric ceramics with an optimized composition endowed with a state of two‐phase coexistence. A small amount (0.1 wt%) of MnO2 can significantly further enhance the piezoelectric property of LKNNT‐AS ceramics, whose piezoelectric constant d33 and converse piezoelectric coefficient d33* as well as planar electromechanical coupling factor kp reach 363 pC/N, 543 pm/V, and 0.49, respectively. The temperature stability of piezoelectricity in MnO2‐modified LKNNT‐AS samples also improved, which is associated with the more uniform and better thermally stable ferroelectric domains that were revealed by piezoresponse force microscopy.  相似文献   

10.
Bi5Ti3FeO15 (BTF) has recently attracted considerable interest as a typical multiferroic oxide, wherein ferroelectric and magnetic orders coexist. The ferroelectric order of BTF implies its piezoelectricity, because a ferroelectric must be a piezoelectric. However, no extensive studies have been carried out on the piezoelectric properties of BTF. Considering its high ferroelectric-paraelectric phase transition temperature (Tc ~ 761°C), it is necessary to analyze the piezoelectricity and thermal stabilities of BTF, a promising high-temperature piezoelectric material. In this study, lightly manganese-modified BTF polycrystalline oxides are fabricated by substituting manganese ions into Fe3+ sites via the conventional solid-state reaction method. X-ray diffraction and Raman spectroscopy analyses reveal that the resultant manganese-modified BTF has an Aurivillius-type structure with m = 4, and that the substitutions of Fe by Mn lead to a distortion of BO6. The temperature-dependent dielectric properties and direct-current (DC) resistivity measurements indicate that the Mn ions can significantly reduce the dielectric loss tanδ and increase the DC resistivity. The piezoelectricity of BTF is confirmed by piezoelectric constant d33 measurements; it exhibits a piezoelectric constant d33 of 7 pC/N. Remarkably, BTF with 4 mol% of Mn (BTF-4Mn) exhibits a large d33 of 23 pC/N, three times that of unmodified BTF, whereas the Curie temperature Tc is almost unchanged, ~765°C. The increased piezoelectric performance can be attributed to the crystal lattice distortion, decreased dielectric loss tanδ, and increased DC resistivity. Additionally, BTF-4Mn exhibits good thermal stabilities of the electromechanical coupling characteristics, which demonstrates that manganese-modified BTF oxides are promising materials for the use in high-temperature piezoelectric sensors.  相似文献   

11.
This study synthesizes thermally sensitive block copolymers poly(N‐isopropylacrylamide)‐b‐poly(4‐methyl‐ε‐caprolactone) (PNIPA‐b‐PMCL) and poly(N‐isopropylacrylamide)‐b‐poly(4‐phenyl‐ε‐caprolactone) (PNIPA‐b‐PBCL) by ring‐opening polymerization of 4‐methyl‐ε‐caprolactone (MCL) or 4‐phenyl‐ε‐caprolactone (BCL) initiated from hydroxy‐terminated poly(N‐isopropylacrylamide) (PNIPA) as the macroinitiator in the presence of SnOct2 as the catalyst. This research prepares a PNIPA bearing a single terminal hydroxyl group by telomerization using 2‐hydroxyethanethiol (ME) as a chain‐transfer agent. These copolymers are characterized by differential scanning calorimetry (DSC), 1H‐NMR, FTIR, and gel permeation chromatography (GPC). The thermal properties (Tg) of diblock copolymers depend on polymer compositions. Incorporating larger amount of MCL or BCL into the macromolecular backbone decreases Tg. Their solutions show transparent below a lower critical solution temperature (LCST) and opaque above the LCST. LCST values for the PNIPA‐b‐PMCL aqueous solution were observed to shift to lower temperature than that for PNIPA homopolymers. This work investigates their micellar characteristics in the aqueous phase by fluorescence spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The block copolymers formed micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range of 0.29–2.74 mg L?1, depending on polymer compositions, which dramatically affect micelle shape. Drug entrapment efficiency and drug loading content of micelles depend on block polymer compositions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

12.
Piezoelectric ceramics with large energy density coefficient d33·g33 value have been found suitable for piezoelectric energy harvesting applications. In this study, the phase structures and piezoelectric properties of xPb(Zr0.5Ti0.5)O3?yPb(Zn1/3Nb2/3)O3?(1?x?y)Pb(Ni1/3Nb2/3)O3 (xPZT?yPZN?(1?x?y)PNN) ceramic were investigated with systematically varying PZN and PNN components. The ternary phase diagram of PZT?PZN?PNN system was illustrated and the composition region of morphotropic phase boundary (MPB) was determined. Piezoelectric and dielectric measurements verify that the materials in MPB region all present large d33 and d33·g33 values. In particular, very high d33·g33 coefficients of 20162.2 × 10?15 m2/N and 21026.3 × 10?15 m2/N are observed from samples 0.75PZT?0.15PZN?0.1PNN and 0.8PZT?0.05PZN?0.15PNN with compositions located on the rhombohedral phase side near MPB because the dielectric coefficient ε33T0 decreases faster than the d33 coefficient at this side.  相似文献   

13.
To achieve excellent biofunctionality of Bombyx mori silk fibroin (SF), we explored a novel hybridization method to combine the unique properties of SF with poly(ε‐caprolactone) (PCL) electrospun fibers. The hybrid electrospun fibers demonstrate excellent hydrophilicity and biocompatibility that are important to tissue engineering applications. The biomimetic fibrous structure was fabricated by conventional electrospinning of PCL. The individual surfaces of PCL electrospun fibers were coated with silk fibroin protein using a lyophilization technique. The SF coating layers were durable which were further developed by surface modification with fibronectin to improve their biological function. The hybrid electrospun fibers show excellent support for normal human dermal fibroblast (NHDF) cells adhesion and proliferation than neat PCL fibers, while the surface‐modified hybrid electrospun fibers show significantly enhanced proliferation of NHDF cells on their surface. This study indicates the new opportunity of fabrication technique that can construct a biomimetic fibrous structure while the original function as a biomaterial remained existing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41653.  相似文献   

14.
In this article, perovskite‐structured BiFeO3–Bi(Zn1/2Ti1/2)O3–PbTiO3 (BF–BZT–PT) ternary solid solutions were prepared with traditional solid‐state reaction method and demonstrated to exhibit a coexistent phase boundary (CPB) with Curie temperature of TC~700°C in the form of ceramics with microstructure grain size of several micron. It was found that those CPB ceramics fabricated with conventional electroceramic processing are mechanically and electrically robust and can be poled to set a high piezoelectricity for the ceramics prepared with multiple calcinations and sintering temperature around 750°C. A high piezoelectric property of TC = 560°C, d33 = 30 pC/N, ε33T0 = 302, and tanδ = 0.02 was obtained here for the CPB 0.53BF–0.15BZT–0.32PT ceramics with average grain size of about 0.3 μm. Primary experimental investigations found that the enhanced piezoelectric response and reduced ferroelectric Curie temperature are closely associated with the small grain size of microstructure feature, which induces lattice structural changes of increased amount ratio of rhombohedral‐to‐tetragonal phase accompanying with decreased tetragonality in the CPB ceramics. Taking advantage of structural phase boundary feature like the Pb(Zr,Ti)O3 systems, through adjusting composition and microstructure grain size, the CPB BF–BZT–PT ceramics is a potential candidate to exhibit better piezoelectric properties than the commercial K‐15 Aurivillius‐type bismuth titanate ceramics. Our essay is anticipated to excite new designs of high–temperature, high–performance, perovskite‐structured, ferroelectric piezoceramics and extend their application fields of piezoelectric transducers.  相似文献   

15.
The structure and electrical properties of perovskite layer structured (PLS) (1?x)Sr2Nb2O7x(Na0.5Bi0.5)TiO3 (SNO‐NBT) prepared by solid‐state reaction method are investigated. The addition of NBT is beneficial to speed up mass transfer and particle rearrangement during sintering, leading to better sinterability and higher bulk density up to 96.8%. The solid solution limit x in the SNO‐NBT system is below 0.03, over which Ti4+ is preferable to aggregate and results in the generation of secondary phase. After the modification by NBT, all SNO‐NBT ceramics have a Curie temperature Tc up to over 1300°C and piezoelectric constant d33 about 1.0 pC/N. The breakthrough of piezoelectricity can mainly be attributed to rotation and distortion of oxygen octahedron as well as higher poling electric field resulting from the improved bulk density. This study not only demonstrates how to improve piezoelectricity by NBT addition, but also opens up a new direction to design PLS piezoceramics by introducing appropriate second phase.  相似文献   

16.
The 0.72Bi(Fe1?xAlx)O3–0.28BaTiO3 (= 0, 0.01, 0.03, 0.05, and 0.07, abbreviated as BFAx–BT) lead‐free high‐temperature ceramics were prepared by the conventional ceramic processing. Systematic investigation on the microstructures, crystalline structures, dielectric and piezoelectric properties, and high‐temperature stability of piezoelectric properties was carried out. The crystalline structures of BFAx–BT ceramics evolve from rhombohedral structure with x < 0.01 to the coexistence of rhombohedral structure and pseudocubic phases with ≈ 0.01, finally to pseudocubic phases when x > 0.03. Remarkably high‐temperature stability with near‐zero temperature coefficient of piezoelectric properties (TCkp), together with improved piezoelectric properties has been achieved for = 0.01 BFAx–BT ceramics. The BFAx–BT(= 0.01) ceramics simultaneously show the excellent piezoelectric properties of d33 = 151 pC/N, kp = 0.31 and super‐high‐temperature stability of Td = 420°C, TCkp = 1 × 10?4. It is considered that the observed strong piezoelectricity and remarkably high‐temperature stability should be ascribed to the phase coexistence of rhombohedral and pseudocubic phases. The rhombohedral phases have a positive TCkp value and the pseudocubic phases possess a negative TCkp value. Thus, the TCkp value of BFAx–BT ceramics can be tuned by composition of x.  相似文献   

17.
A nickel (Ni) nanoparticle catalyst, supported on 4‐channel α‐Al2O3 hollow fibers, was synthesized by atomic layer deposition (ALD). Highly dispersed Ni nanoparticles were successfully deposited on the outside surfaces and the inside porous structures of hollow fibers. The catalyst was employed to catalyze the dry reforming of methane (DRM) reaction and showed a methane reforming rate of 2040 Lh?1gNi?1 at 800°C. NiAl2O4 spinel was formed when Ni nanoparticles were deposited on alpha‐alumina substrates by ALD, which enhanced the Ni‐support interaction. Different cycles (two, five, and ten) of Al2O3 ALD films were applied on the Ni/hollow fiber catalysts to further improve the interaction between the Ni nanoparticles and the hollow fiber support. Both the catalyst activity and stability were improved with the deposition of Al2O3 ALD films. Among the Al2O3 ALD coated catalysts, the catalyst with five cycles of Al2O3 ALD showed the best performance. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2625–2631, 2018  相似文献   

18.
This study was addressed to the influence of an electric field strength applied at fabrication process and matrix properties, such as the dielectric constant and the Young's modulus, on “pseudo‐1‐3 piezoelectric ceramic/polymer composite” in order to further enhance the piezoelectricity of that. The pseudo‐1‐3 piezoelectric ceramic/polymer composite consists of linearly ordered piezoelectric ceramic particles in polymer material. Silicone gel, silicone rubber, urethane rubber, and poly‐methyl‐methacrylate, which exhibit different dielectric constants and Young's modulus, were used as matrices to evaluate the matrix influence. The piezoelectricity of the pseudo‐1‐3 piezoelectric ceramic/polymer composite was evaluated using the piezoelectric strain constant d33. The d33 is one of the indices of the piezoelectric properties for piezoelectric materials. As a result, it was confirmed that d33 of the pseudo‐1‐3 piezoelectric ceramic/polymer composite increased with the increase of the electric filed strength applied at fabrication process, though, it reached a constant value at a certain strength value. Further it was confirmed that dielectric constant of the matrix had a small influence on d33 of the pseudo‐1‐3 piezoelectric ceramic/polymer composite, however, in case of matrix of lower Young's modulus, d33 was increase. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41817.  相似文献   

19.
Electrospinning process was used to fabricate fine fibers from poly[(R)‐3‐hydroxybutyrate‐co‐(R)‐3‐hydroxyvalerate] embedded with multiwalled carbon nanotubes (MWCNTs). Rotating disc collector was used to provide additional drawing force to stretch and align both the embedded MWCNTs and electrospun fibers themselves. Morphological observation revealed MWCNTs aligned to the fiber axis and protruding from the surface. To understand the electrical properties of the fiber, a single‐composite fiber has been deposited on a substrate, across multiple electrodes. Electrical conductivity of the single‐electrospun fiber with low MWCNT content of 0.2 wt % was calculated to be in a remarkable magnitude of about 2.07 Sm?1. Electrical current flow spanning the fiber length of 1400 μm indicates that the presence of an interconnected network of MWCNTs exists within the fiber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

20.
[001] textured 0.40BiScO3-0.60PbTiO3-0.125 mol%Nb5+ (BS-60PT-0.125Nb) high-temperature piezoelectric ceramics were synthesized using templated grain growth process. A high texture degree F001 of 99% was obtained using 2 vol% BaTiO3 (BT) templates. The piezoelectric charge constant d33 and the unipolar strain under 40 kV cm−1 at room temperature for the textured ceramics are 646 pC N−1 and 0.36%, respectively, which is over two times as those for untextured ceramics (∼243 pC N−1 and 0.17%). The electrostriction Q33 value of the textured sample remarkably increased from 0.034 m4 C−2 to 0.068 m4 C−2 under 30 kV cm−1, showing a twice higher than untextured. Compared with random ceramics, the improvement piezoelectric response of the textured ceramics is primarily attributed to the increase of the dielectric constant εr and electrostriction coefficient Q33 along [001] orientation, which is originating from the anisotropy of piezoelectricity. The BS-60PT-0.125Nb textured ceramics have large piezoelectric response and ultrahigh electrostriction with high temperature stability (high depolarization temperature Td of ∼360°C and high Curie temperature Tc of 421°C), showing great potential for the piezoelectric applications at high temperatures.  相似文献   

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