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1.
Piezoceramic compositions [Pb(Ni1/3Sb2/3)]0.02-[Pb(Zr1−yTiy)]0.98O3 with y = 0.46-0.50 were synthesized by solid state route to study the effect of Zr/Ti ratio on crystal structure, microstructure, piezoelectric and dielectric properties. Calcination was performed at 1060 °C. The specimens were sintered at 1280 °C for 1 h. X-ray diffraction studies indicate the co-existence of tetragonal and rhombohedral perovskite phases in these compositions. Microstructural analysis showed the dense and uniform microstructure for [Pb(Ni1/3Sb2/3)]0.02-[Pb(Zr0.52Ti0.48)]0.98O3. This composition was resulted in optimum values of properties viz. charge constant (d33 = 301 × 10−12 C/N), voltage constant (g33 = 33.7 × 10−3 V m/N), product of piezoelectric charge constant and voltage constant (d33 × g33 = 10.12 × 10−12 C V m/N2) and coupling factor (kp = 0.63). Results indicated that this material composition could be suitable for power harvesting and sensor applications.  相似文献   

2.
Porous PZT-5H single crystals are grown by the solid state crystal growth (SSCG) method. The microstructure, phase structure and dielectric/piezoelectric properties are investigated for [001]-oriented porous PZT-5H single crystal. Evolution of phase structure with temperature is researched using in-situ temperature-dependent X-ray diffraction. The effect of pores on performance parameters is simulated using COMSOL Multiphysics® software. Ultrahigh piezoelectric coefficient d33 of up to about 1700 pC/N and effective piezoelectric coefficient d33* of up to about 3700 pm/V at 5 kV/cm are obtained. Moreover, the effective piezoelectric coefficient d33* is stable around 1900 pm/V under 3 kV/cm and 5 kV/cm in the temperature range of 70–160 °C. Importantly, the sample possess an extremely large figure of merit g33*d33 (111 × 10−12 m2/N), which is related to the presence of pores in the single crystal. This work expands the scope of PZT based single crystal and highlights their significant application possibilities in piezoelectric energy harvester, and actuator at high temperature.  相似文献   

3.
The mixed oxide SiO2/ZrO2 obtained by the sol-gel processing method adsorbs Sb(V) from acid solution, forming a new phase on the matrix surface designated as SiO2/ZrO2/Sb2O5. The amount of Zr(IV) in the matrix was 8.1 wt.%, corresponding to 0.89 mmol g−1, and the amount of Sb(V) incorporated in the matrix was 6.3 wt.% (0.52 mmol g−1). This material presented a specific surface area, SBET=590 m2 g−1. The immobilized Sb2O5 is a good cation exchanger and adsorbs methylene blue (MB) cationic dye with an average surface density δ=1.1×10−11 mol cm−2 (about 0.07 molecule nm−2). The dye is strongly entrapped in the pores of the matrix and it is not leached off in KCl solutions as concentrated as 1.0 M. A carbon paste of the SiO2/ZrO2/Sb2O5/MB material showed a reversible redox pair with midpoint potential Em=−0.1 V versus SCE. This midpoint potential is not affected by solution pH change between 2 and 7. The immobilized dye mediated NADH catalytic oxidation at ca. 50 mV.  相似文献   

4.
Process modeling and design concepts were implemented to aid in the manufacturing of heat-enhanced transdermal drug-delivery systems. The simulated prototype consists of a corticosterone-loaded polymer patch applied to the skin and connected to a heating device in which an exothermic reaction occurs. To achieve a desired transdermal flux of 1.2 × 10−5 mg/cm2 h, this contribution focuses on the influences of the (1) initial reaction rate (−rA0), (2) mass of filler material in the device (m), (3) initial concentration (C0) of medicament in the patch and (4) overall heat transfer coefficient (U). A regression technique yielded the following results: −rA0 = 3.000 × 10−2 kg/m3 s, m = 1.251 × 10−8 kg, U = 6.124 × 10 J/m2 K s and C0 = 1.966 × 10−1 kg/m3. When m was fixed at 12.5 g, the optimum design required the following specifications: rA0 = 2.765 × 10−2 kg/m3 s, U = 1.402 × 103 J/m2 K s and C0 = 1.941 × 10−1 kg/m3. The priority (Si) of the input factors (i) in reaching the target delivery rate is: SC0>SrA0>Sm>SU.  相似文献   

5.
The pyroelectric effect, which is useful for temperature sensing, was observed in cement-based materials. The use of short steel fibers (8 μm diameter), together with polyvinyl alcohol (PVA), as admixtures greatly enhances the effect, thereby attaining pyroelectric coefficient 6×10−8 C/m2 K (10 kHz). However, due to the high value (2500) of the relative dielectric constant, the pyroelectric voltage is lower than those of plain cement paste or carbon fiber (15 μm diameter) cement paste. Carbon fiber cement paste and plain cement paste are comparable in the pyroelectric voltage, though the pyroelectric coefficient is higher for carbon fiber cement paste than plain cement paste. The pyroelectric effect in cement-based materials is attributed to the increase in mobility of the ions as the temperature increases.  相似文献   

6.
Fly ash (FA) is widely used as a supplementary cementitious material in the production of Portland cement concrete. The effect of addition of carbon nanotubes (CNTs) and FA on the properties of barium calcium stannate titanate (BCTS) ceramic–Portland FA cement composites was investigated. These composites have potential for use as sensors and transducers in the monitoring of structural health in concrete structures containing FA. CNTs were found to have filled the pores of the composites. All composites showed good compatibility with the concrete mix. The dielectric constant and electrical conductivity of composites were in the range 200–257 and 1.04 × 10–6 to 1.66 × 10−6 S/m, respectively. The presence of FA in composites increased the piezoelectric voltage coefficient (g33). Adding CNTs increased the piezoelectric charge coefficient (d33), thickness electromechanical coupling coefficient (Kt), and also g33 but decreased mechanical quality factor (Qm), which is related to good for the receiving sensor and transducer application. CNTs can improve the properties of these composites and composite with FA content at 10 vol.%, and CNTs at 1 vol.% exhibited the highest compressive strength and piezoelectric values (d33 = 44 pC/N, g33 = 20.21×10–3 V m/N, and Kt = 18.9%), along with higher g33 values, than pure BCTS ceramic.  相似文献   

7.
A 50 nm samarium film capped with a 7 nm palladium overlayer switched from a metallic to semiconducting state during ex-situ hydrogen loading via electrochemical means at room temperature. The transition is accompanied by a change in transmittance measured during hydrogen loading and the associated optical appearance. The monitoring of working electrode (WE) potential, the transmittance and chi potential difference (Δχ) has been used to identify the phases present during hydrogen loading. Deloading of hydrogen has been studied in open circuit potential condition. Glancing angle X-ray diffraction (GAXRD) studies show that the rhombohedral structure of metallic samarium film (a0=8.989 Å) changes to hexagonal structure of the SmH3−δ film with average lattice parameters of a=3.775 Å and c=6.743 Å. A direct optical band gap of 2.9 eV has been obtained for SmH3−δ film and 2.0 eV for SmH2 ± ε film from reflectance and transmittance data. Removal of hydrogen from SmH3−δ leads to the formation of localized states within the band whose signature is clearly seen in transmittance and Tauc’s plot curves of SmH2 ± ε film. The Hall coefficient RH measured as a function of hydrogen concentration, changes from a metal-like value −14.23×10-10 m3/C to −1001.1×10−10 m3/C for SmH3−δ films. On unloading hydrogen, the value of RH changes to −3.56×10−10 m3/C at the dihydride composition.  相似文献   

8.
Thick films of niobium doped lead zirconate titanate (PNZT) were prepared from a sol-gel/PZT powder composite slurry. The effects of adding different amounts of sol-gel derived lead germanium oxide (PGO) as sintering aid were examined. Four layers of composite, with intermediate sol infiltrations, were deposited by spinning onto Pt/Ti/SiO2/Si substrates followed by drying and annealing. Addition of PGO enhanced the densification process at a temperature as low as 770 °C. It resulted in an increase in the film properties that depended upon the level of PGO addition. Film properties were assessed by measuring the capacitance and dielectric loss. d33,f and e31,f piezoelectric coefficient measurements were carried out after poling at 10 V/μm for 5 min at 130 °C. A maximum relative permittivity of 500 was observed between 5 and 8 wt.% PGO addition. The maximum in d33,f was found to be about 40 pC/N. Additions between 7 and 10 wt.% PGO led to the maximum e31,f piezoelectric coefficient of about −1.5 C/m2.  相似文献   

9.
An electrochemical method based on potentiometric stripping analysis (PSA) employing a cryptand [2.2.1] (CRY) and carbon nanotube (CNT) modified paste electrode (CRY-CNT-PE) has been proposed for the subnanomolar determination of bismuth. The characterization of the electrode surface has been carried out by means of scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronocoulometry (CC). It was observed that by employing CRY-CNT-PE, a 9-fold enhancement in the PSA signal (dt/dE) was observed as compared to plain carbon paste electrode (PCPE). Under the optimized conditions, dt/dE (s/V) was proportional to the Bi(III) concentration in the range of 5.55 × 10−8 to 9.79 × 10−11 M (r = 0.9990) with the detection limit (S/N = 3) of 3.17 × 10−11 M. The practical analytical utilities of the modified electrode were demonstrated by the determination of bismuth in pharmaceutical formulations, human hair, sea water, urine and blood serum samples. The prepared modified electrode showed several advantages, such as a simple preparation method, high sensitivity, very low detection limits and excellent reproducibility. Moreover, the results obtained for bismuth analysis in commercial and real samples using CRY-CNT-PE and those obtained by atomic absorption spectroscopy (AAS) are in agreement at the 95% confidence level.  相似文献   

10.
Lead-free piezoelectric 0.885(Bi0.5Na0.5)TiO3–0.05(Bi0.5K0.5)TiO3–0.015(Bi0.5Li0.5)TiO3 0.05BaTiO3 ceramics (abbreviated as BNKLBT-1.5) were prepared by a conventional mixed oxide method. The composition has a piezoelectric d33 constant of 154 × 10−12 C/N, an electromechanical coupling coefficient kt of 0.519, a relatively low dissipation factor (tan δ = 1.6%) at 1 kHz. BNKLBT-1.5 multilayered actuators have been fabricated using a roll-casting technique. Each single layer has dimensions of 9.0 mm × 9.0 mm × 0.2 mm. Four multilayer actuators with 5, 10, 15 and 20 layers have been fabricated. Their capacitance and displacement under an a.c. field were measured. The capacitance measured at 1 kHz is 9.64 nF, 14.69 nF, 25.36 nF, 32.59 nF and the displacement measured at 5 kHz is 867 pm/V, 1331 pm/V, 2060 pm/V, 2442 pm/V, respectively.  相似文献   

11.
The bismuth layer-structured ferroelectrics (BLSF) are promising high-temperature piezoelectric materials, in which large piezoelectricity, good thermal stability and high electrical resistivity are desired. Here highly textured CaBi4Ti4O15 BLSF ceramics with orientation factor of 82% have been fabricated by spark plasma sintering technique. The piezoelectric coefficient d33 is significantly enhanced by 250%, from 7.2 pC/N for the texture-less sample to 25.3 pC/N for the textured one, accompanied by a high Curie temperature TC= 788 °C. The variation of d33 is below 5% in the temperature range of 25–500 °C, showing excellent thermal stability. The textured sample exhibits high electrical resistivity ρ = 2.1 × 1011 Ω·cm, an order of magnitude larger than that of the texture-less sample. At the temperature as high as 500 °C, the textured sample still maintains excellent electrical properties of d33 = 24.2 pC/N, tanδ = 9.9% and ρ = 2.7 × 106 Ω·cm, suggesting that the textured CaBi4Ti4O15 ceramics could be a potential candidate for high-temperature piezoelectric sensor or detector applications.  相似文献   

12.
Fang Ye  Lishi Wang 《Electrochimica acta》2008,53(12):4156-4160
5-[o-(4-Bromine amyloxy)phenyl]-10,15,20-triphenylporphrin (o-BrPETPP) was electropolymerized on a glassy carbon electrode (GCE), and the electrocatalytic properties of the prepared film electrode response to dopamine (DA) oxidation were investigated. A stable o-BrPETPP film was formed on the GCE under ultrasonic irradiation through a potentiodynamic process in 0.1 M H2SO4 between −1.1 V and 2.2 V versus a saturated calomel electrode (SCE) at a scan rate of 0.1 V s−1. The film electrode showed high selectivity for DA in the presence of ascorbic acid (AA) and uric acid (UA), and a 6-fold greater sensitivity to DA than that of the bare GCE. In the 0.05 mol L−1 phosphate buffer (pH 6.0), there was a linear relationship between the oxidation current and the concentration of DA solution in the range of 5 × 10−7 mol L−1 to 3 × 10−5 mol L−1. The electrode had a detection limit of 6.0 × 10−8 mol L−1(S/N = 3) when the differential pulse voltammetric (DPV) method was used. In addition, the charge transfer rate constant k = 0.0703 cm s−1, the transfer coefficient α = 0.709, the electron number involved in the rate determining step nα = 0.952, and the diffusion coefficient Do = 3.54  10−5 cm2 s−1 were determined. The o-BrPETPP film electrode provides high stability, sensitivity, and selectivity for DA oxidation.  相似文献   

13.
A gel polymer electrolyte (GPE) is prepared from polymethylmethacrylate interpenetrating polymer network, benzoyl peroxide, and 1.1 M LiPF6/EC-DEC (1:1 vol.%). The LiCoO2/graphite cells are prepared and their electrochemical properties were evaluated at various current densities and temperatures. The viscosity of the precursor containing 5 vol.% curable mixture is around 4.6 mPa s. The ionic conductivity of the GPE at 20 °C is around 5.8×10−3 S cm−1. The GPE has good electrochemical stability up to 4.8 V vs. Li/Li+. The capacity of the cell at 1.0C rate is 82% of the discharge capacity at 0.2C rate. The capacity of the cell at −10 °C is 86% of the discharge capacity at 20 °C. Discharge capacity of the cell with GPE is stable with charge-discharge cycling.  相似文献   

14.
Electromechanical energy demands on homogenous thick films of piezoceramics with sufficiently large piezoelectric constant and reproducible performance. Single-phase LiTaO3 films deposited by sol-gel processing have been fabricated as cantilevers to investigate the interdependence of dielectric and piezoelectric properties as a function of film thickness. Phase pure LiTaO3 films with varying thickness in the range of 2.07-4.37 µm on stainless steel substrates were obtained after calcination of samples at 650°C. The relative permittivity of optimized spin-coated films peaked at 479.73 (1 kHz), whereas the piezoelectric coefficient (d33 mode) determined by piezoresponse force microscopy was in the range of 21-24 pm/V. The effect of poling was studied through the butterfly and phase curves. A figure of merit (FOM) up to 3.29 (10−18 m2/V2) was determined for cantilever devices, which were able to generate a peak-to-peak voltage of 0.046-0.15 V using a 1 MΩ resistor as an impedance load at a fixed acceleration of 1.5 m/s2. While the power density was in the range of ~4-20 × 10−9 W/m3, which increased with the increasing film thickness. The leakage current density decreased in the range of 4 × 10−5-6 × 10−7 A/m2 in the same direction. As both ferroelectric and piezoelectric properties of LiTaO3 films are dependent on film thickness, an optimal energy conversion efficiency was obtained for a thickness of ~3 µm. Furthermore, these devices were tested up to a temperature of 150°C for voltage generation. Given the need for lead-free piezoelectric materials for environmental applications, these LiTaO3 cantilevers are very promising for vibrational energy harvester (VEH) applications especially due to their cost effectiveness, small size, stability at higher temperatures, and repeatable properties, which makes them suitable for MEMS devices for industrial applications.  相似文献   

15.
ZrO2 + 8 wt.% Y2O3 powder of a mean diameter dVS = 38 μm was milled to obtain fine particles having mean size of dVS = 1 μm. The fine powder was used to formulate a suspension with water, ethanol and their mixtures. The zeta potential of obtained suspensions was measured and found out to be in the range from −22 to −2 mV depending on suspension formulation. The suspension was injected through a nozzle into plasma jet and sprayed onto stainless steel substrates. The plasma spray experimental parameters included two variables: (i) spray distance varying from 40 to 60 mm and (ii) torch linear speed varying from 300 to 500 mm/s. The microstructure of obtained coatings was characterized with scanning electron microscope (SEM) and X-ray diffraction (XRD). The coatings had porosity in the range from 10% to 17% and the main crystal phase was tetragonal zirconium oxide. The scratch test enabled to find the critical load in the range of 9-11 N. Finally, thermal diffusivity of the samples at room temperature, determined by thermographic method, was in the range from 2.95 × 10−7 to 3.79 × 10−7 m2/s what corresponds to thermal conductivities of 0.69 W/(mK) and 0.97 W/(mK) respectively.  相似文献   

16.
Barium zirconate titanate (40−60 vol.%; BZT), Portland cement (PC) and polyvinylidene fluoride (0−7 vol.%; PVDF) were used as raw materials to produce 0–3 piezoelectric cement-based composites. The highest piezoelectric charge coefficient (d33∼26-27 pC/N) was found at 50−60 vol.% BZT with 5 vol.% PVDF. Moreover, the composite with 50 vol.% BZT and 5 vol.% PVDF had the highest piezoelectric voltage coefficient (g33 = 16.0 × 10−3 V·m/N). Scanning electron microscopy was used to investigate the morphology of the fracture surface of the composite. When PVDF was used in the composite, it was observed to fill some pores at the interface zone and within the cement phase. The elastic behaviour of PVDF could also be seen in the fracture surface, where it appeared as a stretched material different from both the BZT ceramic and cement, which are brittle materials. In addition, increasing the PVDF content led to increased fracture toughness.  相似文献   

17.
Functionalized polypyrrole film were prepared by incorporation of (Fe(CN)6)4− as doping anion, during the electropolymerization of pyrrole onto a carbon paste electrode (CPE) in aqueous solution by using potentiostatic method. The electrochemical behavior of the (Fe(CN)6)3−/(Fe(CN)6)4− redox couple in polypyrrole was studied by cyclic voltammetry and double step potential chronoamperometry methods. In this study, an obvious surface redox reaction was observed and dependence of this reaction on the solution pH was illustrated. The electrocatalytic ability of polypyrrole/ferrocyanide films modified carbon paste electrode (Ppy/FCNMCPEs) was demonstrated by oxidation of ascorbic acid. It has been found that under optimum condition (pH 7.00), the oxidation of ascorbic acid at the surface of such electrode occurs at a potential about 540 mV less positive than unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α and catalytic reaction rate constant, kh′, were also determined by using various electrochemical approaches.The catalytic oxidation peak current showed a linear dependent on the ascorbic acid concentration and a linear calibration curve was obtained in the range of 4.5×10−4 to 9.62×10−3 M of ascorbic acid with a correlation coefficient of 0.9999. The detection limit (2σ) was determined as 5.82×10−5 M.  相似文献   

18.
Cyclic voltammetry, constant current charge/discharge, and electrochemical impedance spectroscopy have been applied to establish the electrochemical characteristics for electric double-layer capacitor (EDLC) consisting of the 1 M (C2H5)3CH3NBF4 electrolyte in acetonitrile and micro/mesoporous carbon electrodes prepared from Mo2C, noted as C(Mo2C). The N2 sorption (total BET specific surface area (SBET ≤ 1855 m2 g−1), micropore area (Smicro ≤ 1823 m2 g−1), total pore volume (Vtot ≤ 1.399 m3 g−1) and pore size distribution (average NLDFT pore width dNLDFT ≥ 0.89 nm) values obtained have been correlated with the electrochemical characteristics for EDLCs (region of ideal polarizability (ΔV = 3.0 V), characteristic time constant (τR = 1.05 s), gravimetric capacitance (Cm ≤ 143 F g−1)) dependent strongly on the C(Mo2C) synthesis temperature. High gravimetric energy (35 Wh kg−1) and gravimetric power (237 kW kg−1) values, normalised to the total active mass of both C(Mo2C) electrodes, synthesised at Tsynt = 800 °C, have been demonstrated at cell voltage 3.0 V and T = 20 °C.  相似文献   

19.
K.M Shaju 《Electrochimica acta》2003,48(18):2691-2703
Li ion kinetics in the O2-phase layered manganese oxides, Li2/3(Co0.15Mn0.85)O2 (O2(Li)) and Li(2/3)+x(Co0.15Mn0.85)O2 (x=1/3 (O2(Li+x))), has been studied by the electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT) at room temperature and the results were correlated with the observed cathodic behaviour. Both compounds show a reversible capacity of ∼180 mA h/g at low current density (∼5 mA/g). EIS studies as a function of cycle number show an increased contribution of resistance associated with surface film formation and bulk contribution which is in agreement with the increased capacity fading observed in O2(Li+x) after 10-15 cycles. The Li ion diffusion coefficient (DLi) vs voltage plots show minima during the first charge cycle coinciding with the irreversible plateau of the voltage vs capacity profiles reflecting the irreversible phase change in both the compounds. The values of DLi (GITT method) observed for the second and subsequent cycles (≤6) in the full voltage range (3.0-4.4 V) are 2×10−11-10×10−11 cm2/s for O2(Li+x) and 0.5×10−10-3.0×10−10 cm2/s for O2(Li). Variation of DLi as a function of cycle number (up to 35) indicates that, in addition to the interface kinetics, changes in the DLi values with cycling also contribute to the capacity fading of the compounds, especially in O2(Li+x).  相似文献   

20.
《Ceramics International》2023,49(1):474-479
Achieving both the large transduction coefficient (the product of piezoelectric charge d33 and voltage coefficients g33) and high Curie temperature is very important to improve the power generation performance and their thermal stability of piezoelectric energy harvesters. It is difficult to improve the transduction coefficient of the commercial PZT based piezoelectric ceramics due to the same variation trend of piezoelectric charge coefficient and dielectric constant with chemical modifications. In this work, Bi2O3 and Fe2O3 co-modified ((Pb1-xBix)((Zr0.53Ti0.47)1-xFex)O3) ceramics were prepared by conventional solid state reaction method, and their dielectric and piezoelectric properties were studied. The piezoelectric charge coefficient d33 increases by Bi and Fe co-modifications due to the enlarged grain size and reduced lattice distortion, while the dielectric constant ε33 deceases mainly owing to the increased micro-pores in grains, leading to the enhancement transduction coefficient d33×g33. The Curie temperature Tc and maximum transduction coefficient d33×g33 are 346 °C and 17169 × 10?15 m2/N, respectively, which are both higher than those of commercial PZT and PZN-PZT based piezoelectric ceramics. This work provides a new way to enhance the transduction coefficient of PZT based ceramics for piezoelectric energy harvesters used in wide temperature range.  相似文献   

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