Flexible and lead-free piezoelectric nanocomposites were synthesized with BaTiO3 nanowires (filler) and poly(vinylidene fluoride) (PVDF) (matrix), and the piezoelectric performances of the composites were systematically studied by varying the aspect ratio (AR) and volume fraction of the nanowire and poling time. BaTiO3 nanowires with AR of 18 were synthesized and incorporated into PVDF to improve the piezoelectric performance of the composites. It was found that high AR significantly increased the dielectric constant up to 64, which is over 800% improvement compared to those from the composites containing spheroid shape BaTiO3 nanoparticles. In addition, the dielectric constant and piezoelectric coefficient were also enhanced by increasing the concentration of BaTiO3 nanowires. The piezoelectric coefficient with 50-vol% BaTiO3 nanowires embedded in PVDF displayed 61 pC/N, which is much higher than nanocomposites with spheroid shape BaTiO3 nanoparticles as well as comparable to, if not better, other nanoparticle-filled polymer composites. Our results suggest that it is possible to fabricate nanocomposites with proper mechanical and piezoelectric properties by utilizing proper AR fillers. 相似文献
BaTiO3/bismaleimide/epoxy/glass fiber reinforced composites were prepared using E-glass fiber (E-GF) and silane coated E-glass fiber (SC-EGF) separately as reinforcement. BaTiO3 nanoparticles were prepared by hydrothermal method. Results show that the addition of BaTiO3 nanoparticles has significant effects on the mechanical and dielectric properties of the composite. Both E-GF and SC-EGF reinforced BaTiO3/bismaleimide/epoxy composites with 2 wt percentages of BaTiO3 nanoparticles showed improved tensile strength, flexural strength and dielectric constant and those with 3% showed high dielectric strength indicating this composition is more adaptable for high voltage insulating applications. Dielectric constants and dielectric loss of the fabricated nanocomposites have been obtained at higher frequencies (in GHz) by using Vector Network Analyser at room temperature and was found to be highest for the BMI-Epoxy nanocomposite with 1% weight nanofiller. 相似文献
Summary: This study examines the use of a PMMA‐mediated assembly of BaTiO3 nanoparticles directly onto Cu electrodes under an electric field. The compatibility of the interface between BaTiO3 nanoparticles and PMMA in a mixed organic solvent system enables the homogeneous dispersion of nanoparticles in a solid polymer matrix. This results in the effective packing of particles, which is desirable from the point of view of achieving a high dielectric constant in the composite. In this study, three‐phase Al/BaTiO3/PMMA nanocomposite films from stable colloidal suspensions containing aluminium nitrate salts were also designed using an electrodeposition process. The simultaneous formation of Al metallic inclusions in the BaTiO3 nanoparticles in the PMMA matrix significantly improved the dielectric constant of nanocomposite films.
HRTEM micrographs of BaTiO3 (240 nm)/PMMA and magnified view of BaTiO3 (50 nm)/PMMA/Al(NO3)3 · 9H2O composite particles in each suspension, and FESEM micrograph of electrodeposited three‐phase nanocomposite film. 相似文献
Novel three-phase composites were prepared by embedding graphite nanosheets (GNs) and BaTiO3 nanoparticles into syndiotactic polystyrene (sPS) matrix via a solution blending and flocculation method. The dependences of electric and dielectric properties of the resultant sPS/BaTiO3-GNs composites on volume fractions of GNs (fGNs) and frequency were investigated. The percolation theory was employed to explain the electric and dielectric behavior of sPS/BaTiO3-GNs composite. It was found that the sPS/BaTiO3-GNs composite showed an obvious insulator-conductor transition with a much low percolation threshold of fGNs = 1.44 vol%. The dielectric permittivity of sPS/BaTiO3-GNs composite reached as high as 51.8 at 100 Hz at percolation threshold, which was about 18 and 7 times higher than that of pure sPS and sPS/BaTiO3 composite, respectively. 相似文献
High dielectric constant is highly desirable in capacitors and memory devices. In this work, oleic acid (OA)‐capped BaTiO3 nanocrystals were synthesized by a two‐phase approach. Polyimide (PI)/BaTiO3‐nanocrystal composite thin films with high dielectric constant have been successfully fabricated. The morphologies and dielectric properties of the hybrid films were exploited. The results showed that BaTiO3 nanocrystals can be uniformly dispersed in the PI thin films owing to the surface modification of OA‐capped BaTiO3 nanocrystals. It was found that the dielectric constant of composite film varies with the volume fraction of BaTiO3 nanocrystals and sintering temperatures and reaches a maximum value of 44.1, which is around 13 times higher than that of pristine PI thin film (3.2). These results demonstrated that PI/BaTiO3‐nanocrystal composite films have considerable application potential in microelectronic fields. 相似文献
A new water-soluble precursor of BaTiO3 was prepared from citratoperoxotitanate and barium citrate as the Ti and Ba sources, respectively. The water-soluble precursor was easily solved in water to form a stable solution, which produced BaTiO3 by heat-treatment at 500 °C and above. A water-based dip-coating technique demonstrated a potential application as the coating solution of BaTiO3. Transparent BaTiO3 films were formed on the quartz-glass substrates with an increment of typically 9 nm per coating with 0.05 mol dm?3 solution. The transmittance of the 180 nm-thick film attained almost 90 % at the maximum and the overall transmittance was above 60 % over the visible region. The polycrystalline film was composed of BaTiO3 grains smaller than 200 nm. Although the film was an insulator, it was not suited for the dielectric application because of the structural problems due to the relatively low density and the thinness of the BaTiO3 layer. The BaTiO3 pellet obtained from the water soluble precursor by condensation, pyrolysis and sintering showed the good dielectric properties with εr = 3,500 and tan δ = 0.027 with a sintering temperature of 1,375 °C. 相似文献
Composites of high density polyethylene, HDPE, filled with submicrometric particles of BaTiO3, BT, have been prepared. Uniform dispersion of the particles was achieved by high energy ball milling and subsequent hot pressing. Using SEM, FTIR, TGA-DTA and stress-strain tests, studies of the structural, morphological and mechanical features of the composites have been carried out. Frequency response analysis, dielectric strength and resistivity measurements were also performed to evaluate the final electrical properties as a function of the processing and the amount of BaTiO3 particles. From the analysis of the microscopic structure, it can be deduced that any change in the properties of the materials must be solely ascribed to the presence of the BT particles. A balance between an enhancement of space charge polarization with the presence of BT and the existence of permanent dipoles associated to them might explain an initial increase in the dielectric losses with the BT content, and its later decrease at higher BT content. The observed decrease in resistivity and breakdown voltage when increasing the amount of BaTiO3 can be explained by the lower resistivity of BT particles at room temperature and the growing accumulation of space charge. 相似文献
Triphase polyimide nanocomposite films were fabricated using barium titanate (BaTiO3) with high dielectric constant and silver (Ag) with high conductivity as fillers. In situ method was utilized to obtain the homogeneous dispersion of nanoparticles. The in situ polymerization of polyimide precursor-poly(amic acid) was performed in the presence of BaTiO3 particles. Silver compound 1,1,1-trifluoro-2,4-pentadionato silver(I) was added into the BaTiO3 containing poly(amic acid) solution to achieve silver nanoparticles via in situ self metallization technique. The thermally induced reduction converted silver (I) to metallic silver with concomitant imidization of poly(amic acid) to polyimide. Both BaTiO3 and silver nanoparticles were uniformly dispersed in the polyimide substrate. The dependence of dielectric behavior on the BaTiO3 and Ag contents was studied. The incorporation of small amount of silver nanoparticles greatly increased dielectric constant of composite films. 相似文献
In perovskites, the relaxor behavior occurs dominantly in lead based compositions. The study of the BaTiO3-KNbO3 binary diagram provided previously evidence for new free from lead ferroelectric relaxor properties but unfortunately at low temperature. The present dielectric studies of ceramics with composition inside the BaTiO3-KNbO3-CaTiO3 showed some of them to be ferroelectric relaxor at temperature close to 300K. Such a favourable effect is due to the Ca2+-Ba2+ cationic substitution. These new compositions are of interest for applications (dielectric for capacitors, actuators) in the way of environmental protection. 相似文献
The glasses within composition as: (80 − x)V2O5/20Bi2O3/xBaTiO3 with x = 2.5, 5, 7.5 and 10 mol% have been prepared. The glass transition (Tg) increases with increasing BaTiO3 content. Synthesized glasses ceramic containing BaTi4O9, Ba3TiV4O15 nanoparticles of the order of 25–35 nm and 30–46 nm, respectively were estimated using XRD. The dielectric properties over wide ranges of frequencies and temperatures were investigated as a function of BaTiO3 content by impedance spectroscopy measurements. The hopping frequency, ωh, dielectric constant, ε′, activation energies for the DC conduction, Eσ, the relaxation process, Ec, and stretched exponential parameter β of the glasses samples have been estimated. The, ωh,β, decrease from 51.63 to 0.31 × 106 (s−1), 0.84 to 0.79 with increasing BaTiO3 respectively. Otherwise, the Eσ, increase from 0.279 to 0.306 eV with increasing BaTiO3. The value of dielectric constant equal 9.5·103 for the 2.5BaTiO3/77.5V2O5/20Bi2O3 glasses-ceramic at 330 K for 1 KHz which is ten times larger than that of same glasses composition. Finally the relaxation properties of the investigated glasses are presented in the electric modulus formalism, where the relaxation time and the respective activation energy were determined. 相似文献
The cerium doped barium titanate (BaTiO3:Ce)/poly methyl methacrylate(PMMA) polymer nano-composites (PNC) were successfully fabricated via solvent evaporation method with microwaves (2.4 GHz) heating. The X-ray diffraction measurements confirm the formation of barium titanate (BT) with crystallite size ranges from 55 to 62 nm. Differential scanning calorimetry study shows that the glass transition temperature (Tg) directly affected by microwaves heat treatment and particle size of filler. The broadband dielectric spectroscopy was employed to investigate the frequency and temperature dependence of the dielectric properties of the nanocomposites in a frequency range from 75 kHz to 5 MHz and temperature range 80–400 K. The introduction of different BT fillers in PMMA enhance the dielectric constant of PNCs drastically and give a smooth response in frequency range mentioned above. The loss factor of the composite can be suppressed by using cerium doped barium titanate filler rather than pure barium titanate filler. 相似文献
A series of Ba1-xSrxMyTi1-yO3 (M = Zr, Sn, 0⩽x⩽0.4, 0⩽y⩽0.3) solid solutions were synthesized with the soft chemical method below 100 °C. XRD pattern and
cell parameters-composition figures of the prepared powder demonstrate that they are completely miscible solid solutions based
on BaTiO3. Furthermore, TEM shows that they have a shape of uniform, substantially spherical particles with an average particle size
of 70 nm in diameter. The sintered ceramics of the powder doped with Sr2+and Zr4+ or Sn4+ have dielectric constant eight times higher and dielectric loss thirty per cent lower than those of pure BaTiO3 phase at room temperature. 相似文献
Summary: The development of a novel technique for the preparation of homogeneous BaTiO3/polyvinylidene fluoride (BT/PVDF) nanocomposites without obvious agglomeration of BaTiO3 particles was reported in this communication. The morphology, structure, and frequency dependence of the dielectric properties of the nanocomposites were characterized. All results show that the dielectric properties of the nanocomposites in this study are desirable, and the process for preparing the nanocomposites has potential applications in the electronic industry.
TEM micrograph of dry BT/PVDF mixtures with nanosized BT particles. 相似文献
A series of Ba1-xSrxMyTi1-yO3 (M = Zr, Sn, 0?x?0.4, 0?y?0.3) solid solutions were synthesized with the soft chemical method below 100 °C. XRD pattern and cell parameters-composition figures of the prepared powder demonstrate that they are completely miscible solid solutions based on BaTiO3. Furthermore, TEM shows that they have a shape of uniform, substantially spherical particles with an average particle size of 70 nm in diameter. The sintered ceramics of the powder doped with Sr2+and Zr4+ or Sn4+ have dielectric constant eight times higher and dielectric loss thirty per cent lower than those of pure BaTiO3 phase at room temperature. 相似文献
Bi(Mg0.5Hf0.5)O3–modified BiFeO3–BaTiO3 ternary solid solutions of (0.725-x)BiFeO3-0.275BaTiO3-xBi(Mg0.5Hf0.5)O3 (0 < x ≤ 0.05, abbreviated as BFO-BTO-xBMHO) were prepared for lead-free piezoelectrics. The addition of BMHO delivers a rhombohedral (R3c, denoted as R-phase) to tetragonal (P4mm, denoted as T-phase) phase transition at x = 0.05, giving the coexistence of R- and T-phase in intermediate compositions: R-phase dominated in x = 0.01–0.02 and T-phase dominated in x = 0.03–0.04. The increment of BMHO tunes the grain size, lowers the ferroelectric transition temperature (TC) and dielectric loss (tanδ), and drives a gradually ferroelectric to relaxor transition. The morphotropic phase boundary between the R-and T-phases, together with the homogeneous morphology, results in the best performance for x = 0.04 case with piezoelectric d33 of 130 pC/N, Kp of 0.286, Qm of 58.993, electrostrain Smax of 0.18%, and TC of 428 °C, showing potential applications for lead-free piezoelectric ceramics at considerably high temperature. 相似文献
BaTiO3:(5 %)Eu3+ nanoparticles and BaTiO3:(5 %)Eu3+@SiO2 composites were synthesized by the solvothermal method. The effects on the structure, morphology and luminescent properties were studied using samples with different molar ratios of BaTiO3:(5 %)Eu3+@SiO2: 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, 08:92, 6.5:93.5, 05:95, and 1.5:98.5. When the amount of silica in the composites was increased, the orange emission of Eu3+ increased, too; this was observed by exciting the charge transfer band centered at 283 nm. Furthermore, an increase in the intensity of the emission was obtained under excitation at 394 nm as a consequence of the improvement in the crystallinity of the samples. The presence of silica and the degree of crystallinity of the samples were determined through the Fourier transform infrared spectra and X-ray diffraction patterns. All of the results suggest that our ceramic material could be a good candidate for biomedical applications such as biolabeling, since the luminescence of BaTiO3:(5 %)Eu3+@SiO2 composites have an emission intensity higher than that of nanoparticles composed solely of BaTiO3:Eu3+. This work demonstrates that BaTiO3:Eu3+@SiO2 composites have an emission intensity higher than that of nanoparticles composed solely of BaTiO3:Eu3+. 相似文献
Thermoplastic polyurethane composites with an excellent dielectric constant and high thermal conductivity were obtained using CNT@BaTiO3 as a filler through a low-speed melt extrusion method. Before preparing the hybrid filler for the composite, the filler particles were surface modified to ensure that the outer surfaces could facilitate the reaction among particles to form the hybrid and ensure complete dispersion in the thermoplastic polyurethane matrix. After confirming the proper surface treatment of the filler particles using infrared spectroscopy, thermal degradation analysis and field emission scanning electron microscopy, they were used to prepare the composite materials at a processing temperature of 200 °C. The thermal stability, thermomechanical properties, mechanical properties, thermal conductivity, and dielectric properties of the composites were investigated. Compared to the neat thermoplastic polyurethane matrix, the prepared composite exhibited a higher thermal stability, approximately 300% higher storage modulus, higher tensile strength and elongation at break values, approximately three times higher thermal conductivity (improved from 0.19 W/(m.K) to 0.38 W/(m.K), and approximately five times larger dielectric constant at high frequencies (at 1 MHz a dielectric constant of 19.2 was obtained). 相似文献