Damping behavior and acoustic performance of polyurethane/lead zirconate titanate ceramic composites

0–3 Type PU-based lead zirconate titanate ceramic (PZT) composites are prepared by in situ polymerization method, this PU/PZT composite material has excellent sound absorption property at low frequencies because of damping property and piezoelectric property. The dispersion of PZT particles in PU matrix, dielectric loss tangent (tan δ), dynamic storage modulus (E′), dynamic loss modulus (E″), and the acoustic absorption coefficient (α) of PU/PZT composites are studied by scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and two-microphone impedance tube, respectively. The results indicate that the modified PZT particles dispersed well in PU matrix with the content of 30 wt%; the tan δ, E′ and E″ are 0.62, 3.75 GPa and 6.05 GPa, respectively, when the composite with 30 wt% of polarizing PZT; the acoustic absorption coefficient is found to increase with an increase of PZT content, and the average acoustic absorption coefficient is 0.32 at low frequencies from 125 to 500 Hz.     

Electrical properties of lead zirconate titanate thick films prepared by hybrid sol–gel method with multiple infiltration steps

High-quality ferroelectric thick films are required for various piezoelectric applications including high-frequency transducers and microelectromechanical systems. In this work, we report the fabrication of dense crack-free lead zirconate titanate (PZT) thick films on Pt-coated Si substrates using commercial PZT powder dispersed in a sol–gel precursor solution without viscous additives. Preannealed films were infiltrated with the same solution and heat treated at 500 °C. Dielectric and ferroelectric properties of the films are found to be strongly dependent on the number of infiltration steps reaching sufficiently high values: dielectric constant ∼2270 and remanent polarization ∼35 μC cm⁻². Moderate coercive field of 60 kV cm⁻¹ and low dielectric loss ∼0.04 are observed in these films. Effective longitudinal piezoelectric coefficient d₃₃ also depends on the number of infiltrations demonstrating remanent value of ∼80 pm V⁻¹ for eight infiltration steps. The results show the suitability of hybrid sol–gel method for the fabrication of PZT thick films for dielectric and piezoelectric applications.     

Design and fabrication of functionally graded PZT/Pt piezoelectric bimorph actuator

A laminated piezoelectric bimorph actuator with a graded compositional distribution of PZT and Pt was fabricated, and its deflection characteristics were evaluated. Using experimentally determined compositional dependency of elastic and piezoelectric properties in the PZT/Pt composites, the modified classical lamination theory and the finite element method were applied to find the optimum compositional profile that will give a larger deflection and smaller stress, simultaneously. The miniature bimorph-type graded actuator that consists of a composite internal-electrode (PZT/30 vol% Pt) and three piezoelectric layers of different compositions (PZT/0–20 vol% Pt) were fabricated by powder stacking and sintering. The deflection of the actuator was measured using electric strain gages mounted on the top and bottom surfaces of the actuator. The deflection was found to strongly depend on the composition distribution profile. Under an applied electric field of 100 V m⁻¹, the actuator with an optimum composition profile exhibited a curvature of up to 0.03 m⁻¹, which is a satisfactory performance for this kind of actuators. The stress generated on actuation was estimated to be as low as 0.4 MPa, which is much smaller than those of conventional directly bonded actuators and will assure a long actuation life.     

Carbon black reinforced C8 ether linked bismaleimide toughened electrically conducting epoxy nanocomposites

The present work deals with the toughening of brittle epoxy matrix with C8 ether linked bismaleimide (C8 e-BMI) and then study the reinforcing effect of carbon black (CB) in enhancing the conducting properties of insulating epoxy matrix. The Fourier transform infrared spectroscopy (FTIR) and Raman analysis indicate the formation of strong covalent bonds between CB and C8 e-BMI/epoxy matrix. The X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) analysis indicate the event of phase separation in 5 wt% CB loaded epoxy C8 e-BMI nanocomposites. The impact strength increased up to 5 wt% of CB loading with particle pull and crack deflection to be driving mechanism for enhancing the toughness of the nanocomposite and beyond 5 wt% the impact strength started to decrease due to aggregation of CB. The dynamic mechanical analysis (DMA) also indicates the toughness of the nanocomposites was improved with 5 wt% of CB loading due to the phase segregation between epoxy and C8 e-BMI in the presence of CB. The electrical conductivity was also increased with 5 wt% of CB due to classical conduction by ohmic chain contact.     

Piezoelectric and pyroelectric properties of (Bi0.5Na0.5)0.94Ba0.06TiO3/P(VDF-TrFE) 0–3 composites

Bismuth sodium barium titanate [(Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ or BNBT] ceramic powder have been incorporated into a polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE) 70/30 mol%] copolymer matrix to form 0–3 composites. With the composition near the MPB region, BNBT has relatively high piezoelectric and dielectric properties. P(VDF-TrFE) ferroelectric copolymer films can be poled to give piezoelectric and pyroelectric performance without prior mechanical stretching. The composites were prepared using solvent casting to disperse the ceramic powder homogeneously in the copolymer matrix. Composites with BNBT volume fraction ϕ ranging from 0.05 to 0.30 were fabricated using a hot-press method. The piezoelectric and pyroelectric coefficients of the composites were studied as a function of ϕ under different poling conditions. As BNBT has a low relative permittivity, so it is relatively easy to pole the BNBT ceramic inclusion. Hence, the BNBT 0–3 composites were found to have better pyroelectric properties than that of the lead zirconate titante PZT/P(VDF-TrFE) 0–3 composites.     

Application feasibility of Pb(Zr,Ti)O3 ceramics fabricated from sol–gel derived powders using titanium and zirconium alkoxides

It is believed that what may be termed the ‘Nanoscaled Century’ will lead to a new industrial revolution, particularly in terms of sol–gel methods of assembly for nanostructure devices. A propyl alcohol (1-Pro) based sol–gel chemical has been developed to replace 2-methoxyethanol (MOE), 1,1,1-tris(hydroxymethyl)ethane (THOME) for the fabrication of PbZr_0.53Ti_0.47O₃ (PZT) piezoelectric ceramics. This chemical is prepared from sol–gel derived powders that are near to the morphotropic phase boundary (MPB). The pyrochlore phase was still apparent when calcining at 900 °C with a shorter calcining time, such as 30 min. However, it disappeared for longer calcining times, for example 3 h or more. From the results of the analysis, PZT ceramics calcinations at 900 °C for 4 h, and sintering at 1100 °C for 2 h could reach a pyrochlore-free crystal phase with relative density of approximately 7.9 g/cm³—close to 98% of the theoretical value. The P–E hysteresis loop, measured by the Sawyer–Tower circuit, revealed that the remanent polarization (P_r) and coercive field (E_c) were 8.54 μC/cm² and 15.6 kV/cm, respectively. The vibration modes of the PZT ceramics were between 150 and 1.5 MHz. Morevoer, under such processing conditions the PZT piezoceramics had uniform grain size distribution less than 1 μm and zero temperature coefficient of resonant frequency (TCF). In summary, the PZT ceramics derived from the sol–gel method were confirmed to possess excellent piezoelectric properties. Furthermore, the processing temperatures were scaled down by 100–200 °C, compared to conventional oxide reaction. Finally, from an energy-saving viewpoint, this experiment can potentially make a very positive contribution.     

Effect of magnetic fields on the abnormal electroresistance behavior in epitaxial thin films of La0.8Ca0.2MnO3

We report an unusual electroresistance (ER) behavior induced by a current and its response to magnetic fields in La_0.8Ca_0.2MnO₃ epitaxial thin films. These thin films were fabricated on SrTiO₃ (1 0 0) substrate using pulsed laser deposition (PLD) technique. It is found that the electric resistivity in these films is significantly enhanced by applying a dc current over a threshold value. Simultaneously, an abnormal electroresistance behavior appears in the temperature range from 10 to 300 K. The enhanced resistance turns out to be very sensitive to a weak current. Even a very small dc current can remarkably depress the high resistance, showing an unusual colossal ER effect. The ER reaches ∼1175% at temperatures lower than ∼50 K, and ∼705% at 300 K for a current changing from 0.72 to 10.5 μA. The influence of magnetic fields on the transport was also studied. The I–V curves can be strongly influenced by a low magnetic field even at room temperature. The deduced magnetoresistance (MR) reaches 120% at 300 K upon applying a magnetic field of 0.25 T. An interesting phenomenon is that the observed MR is current dependent.     

Effect of trace HA on microstructure,mechanical properties and corrosion behavior of Mg-2Zn-0.5Sr alloy

Effect of the addition of trace HA particles into Mg-2Zn-0.5Sr on microstructure, mechanical properties, and bio-corrosion behavior was investigated in comparison with pure Mg. Microstructures of the Mg-2Zn-0.5Sr-xHA composites(x = 0, 0.1 and 0.3 wt%) were characterized by optical microscopy(OM),scanning electron microscopy(SEM) equipped with energy dispersion spectroscopy(EDS) and X-ray diffraction(XRD). Results of tensile tests at room temperature show that yield strength(YS) of Mg-2Zn-0.5Sr/HA composites increases significantly, but the ultimate tensile strength(UTS) and elongation decrease with the addition of HA particles from 0 up to 0.3 wt%. Bio-corrosion behavior was investigated by immersion tests and electrochemical tests. Electrochemical tests show that corrosion potential(Ecorr)of Mg-2Zn-0.5Sr/HA composites significantly shifts toward nobler direction from-1724 to-1660 m VSCE and the corrosion current density decreases from 479.8 to 280.8 μA cm~(-2) with the addition of HA particles. Immersion tests show that average corrosion rate of Mg-2Zn-0.5Sr/HA composites decreases from11.7 to 9.1 mm/year with the addition of HA particles from 0 wt% up to 0.3 wt%. Both microstructure and mechanical properties can be attributed to grain refinement and mechanical bonding of HA particles with second phases and α-Mg matrix. Bio-corrosion behavior can be attributed to grain refinement and the formation of a stable and dense CaHPO_4 protective film due to the adsorption of Ca~(2+)on HA particles. Our analysis shows that the Mg-2Zn-0.5Sr/0.3HA with good strength and corrosion resistance can be a good material candidate for biomedical applications.     

RF magnetron sputtering ferroelectric PbZr0.52Ti0.48O3 thin films with (001) preferred orientation on colossal magneto-resistive layers

Deposition by RF magnetron sputtering of PbZr_0.52Ti_0.48O₃ (PZT) ferroelectric thin films on two types of colossal magneto-resistive (CMR) oxide electrodes, La_0.67Sr_0.33MnO₃ (LSMO) and La_0.67Ca_0.33MnO₃ (LCMO), is demonstrated in this work. The multiferroic heterostructure is grown on a STO substrate, which causes a 〈001〉 preferred orientation to develop. Ferroelectric, retention of polarisation and local piezoelectric properties were measured for assessing the success of the integration from the ferroelectric point of view. Remnant polarisation P_r and coercive field E_c were found to be ∼ 40 μC/cm² and ∼ 100 kV/cm, respectively. Films presented good retention of polarisation and piezoresponse loops. These results show that ferroelectric layers with good functionality can be grown on CMR oxide films, and open the possibility of designing a piezoelectrically driven spin valve memory cell device based on this heterostructure.     

Polyester moulding compounds of natural fibres and wollastonite

Combination of natural fibres and wollastonite whiskers has been attempted as an alternative to glass fibre reinforcement in polyester dough moulding compounds. Natural fibres (sisal) and wollastonite were surface-modified with polyester compatible neo pentyl (diallyl) oxy, tri (dioctyl) pyro-phosphato titanate and gamma-methacryloxy propyl trimethoxy silane coupling agents, respectively. Reinforcing effect of wollastonite to a level of ∼50 wt% in an unsaturated polyester resin reveals a positive indication because of its favourable physico-mechanical properties and microstructural features. The optimization of short sisal and glass fibres in wollastonite/polyester system was carried out to formulate a doughy compound. It was found that ∼11 wt% sisal fibres in wollastonite/polyester and ∼3 to 5 wt% glass fibres in sisal/wollastonite/polyester give the optimum results. The high loss area observed at α and β transitions in dynamic mechanical analyser (DMA) traces supported the elastic behaviour of sisal/wollastonite/polyester moulding compared to corresponding wollastonite/polyester system. Based on these findings, a dough composition has been formulated and its suitability was assessed vis-à-vis to glass fibre–dough moulding compounds. It is observed that polyester dough moulding compound prepared from sisal/wollastonite reinforcement gives satisfactory results.     

PVDF/PZT/CB高分子复合材料的介电耗能机制

应用压电导电原理,研制了一种新型减振复合材料,通过对PVDF／PZT／CB复合体系的导电性能和动态介电性能的测试分析,探讨了该复合材料的介电耗能微观机制,认为该复合材料可通过界面极化和漏电电流两种介电耗能机制来达到减振目的。     

Effect of expanded graphite and modified graphite flakes on the physical and thermo-mechanical properties of styrene butadiene rubber/polybutadiene rubber (SBR/BR) blends

The aim of the present research work is to develop expanded graphite (EG) and isocyanate modified graphite nanoplatelets (i-MG) filled SBR/BR blends, which can substitute natural rubber (NR) in some application areas. The present study investigated the effect of i-MG on the physical, mechanical and thermo-mechanical properties of polybutadiene rubber (BR), styrene butadiene rubber (SBR) and SBR/BR blends in the presence of carbon black (CB). Graphite sheets were modified to enhance its dispersion in the rubber matrices, which resulting in an improvement in the overall physical and mechanical properties of the rubber vulcanizates. Compounds based on 50:50 of BR and SBR with ∼3 wt% nanofillers with CB were fabricated by melt mixing. The morphology of the filled rubber blends was investigated by wide angle X-ray diffraction (WAXD) and high resolution transmission electron microscopic (HR-TEM) analyses. The intercalated and delaminated structures of the nanofiller loaded rubber blends were observed. Scanning electron microscopic (SEM) analysis of the cryo-fractured surfaces of the rubber compounds showed more rough and tortuous pathway of the fractured surfaces compared to the fractured surfaces of the only CB loaded rubber composites. Filled rubber compounds exhibit increase in the ΔS (torque difference) value, reduced scorch and cure time compared to their respective controls. Dynamic mechanical thermal analysis (DMTA) of the filled rubber compounds shows an increase in the storage modulus compared to the controls. Isocyanate modified graphite nanoplatelets (i-MG) containing rubber compounds in the presence of CB showed an increase in the mechanical, dynamic mechanical, hardness, abrasion resistance and thermal properties compared to the alone CB filled rubber vulcanizates.     

Structural and pyroelectric properties of sol–gel derived multiferroic BFO thin films

Multiferroic BFO/PZT multilayer films were fabricated by spin-coating method on the (1 1 1)Pt/Ti/SiO₂/Si substrate alternately using PZT(30/70), PZT(70/30) and BFO alkoxide solutions. The structural and ferroelectric properties were investigated for uncooled infrared detector applications. The coating and heating procedure was repeated six times to form BFO/PZT multilayer films. All films showed the typical XRD patterns of the perovskite polycrystalline structure without presence of the second phase such as Bi₂Fe₄O₃. The thickness of BFO/PZT multilayer film was about 200–220 nm. The ferroelectric properties such as dielectric constant, remnant polarization and pyroelectric coefficient were superior to those of single composition BFO film, and those values for BFO/PZT(70/30) multilayer film were 288, 15.7 μC/cm² and 9.1 × 10^?9 C/cm² K at room temperature, respectively. Leakage current density of the BFO/PZT(30/70) multilayer film was 3.3 × 10^?9 A/cm² at 150 kV/cm. The figures of merit, F_V for the voltage responsivity and F_D for the specific detectivity, of the BFO/PZT(70/30) multilayer film were 6.17 × 10^?11 Ccm/J and 6.45 × 10^?9 Ccm/J, respectively.     

Super-toughening polyamide-612 by controlling dispersed phase domain size: Essential work of fracture assessment

A new pathway to super-toughen polyamide-612 (PA-612) by incorporating domains of soft poly(octene-co-ethylene)-g-maleic anhydride (POE-g-MA) via melt blending leading to more than ∼1100% increase in notched Izod impact strength vis-à-vis fracture toughness enhancement is demonstrated. Fourier transform infra red (FTIR) studies showed effective phase interactions between PA-612 and POE-g-MA whereas dynamic mechanical analysis (DMA) revealed a reduction in loss-peak intensity at ∼45 °C with increase in the soft phase fraction. The optimal dependence of fracture-toughness (in plane-stress) on domain-size (D_n) of dispersed-phase in the form of a reduction in resistance to crack initiation indicated by essential work of fracture (w_e) and linear increase in resistance to crack propagation indicated by non-essential work of fracture (βw_p) of the blends ⩾10 wt% of POE-g-MA content is correlated to an increase in domain-size ⩾∼0.3 μm. Fracture surface morphology indicated crazing to be responsible for the transition in fracture behavior, i.e. remarkable toughening of PA-612 at the critical rubber phase domain size range of ∼0.2–0.3 μm.     

Morphology,interfacial and mechanical properties of polylactide/poly(ethylene terephthalate glycol) blends compatibilized by polylactide-g-maleic anhydride

Polylactide/poly(ethylene terephthalate glycol) (PLA/PETG 80/20 wt) blends compatibilized with polylactide-g-maleic anhydride (PLA-g-MAH) were prepared by melt blending and the rheological, morphological and mechanical properties of the blends were studied. PLA/PETG (80/20 wt) blend formed a typical sea-island morphology, while upon compatibilization, the size and size distribution of the dispersed phase decreased significantly and the 3 wt% PLA-g-MAH compatibilized blend exhibited the smallest phase size and the narrowest distribution of the dispersed particles. The interfacial tension between PLA and PETG was determined from the morphological characteristics and the viscoelastic response of PLA/PETG blends via using two emulsion models. A minimum for PLA/PETG blend containing 3 wt% PLA-g-MAH was observed from both Palierne model and G–M model. The elongation-at-break increased by ∼320%, from 6.9% for PLA to 28.7% for the blend containing 3 wt% PLA-g-MAH without significant loss in the tensile modulus and tensile strength.     

Electroresistance and magnetoresistance in La0.9Ba0.1MnO3 thin films

The electroresistance and magnetoresistance effects have been investigated in La_0.9Ba_0.1MnO₃ epitaxial thin films. Tensile strain caused by substrate mismatch makes the Curie temperature T_C of the film at ∼300 K. The influence of an applied dc-current on the resistance in the absence of a magnetic field was studied. Significant change of the peak resistance at different currents was found. The reduction of the peak resistance reaches ∼27% with an electric current density up to 1.3 × 10⁵ A cm⁻². We also studied colossal magnetoresistance (CMR) effect in the films. Applying a magnetic field of 2 T could lead to a magnetoresistance as large as 42%. The reduction of resistance caused by a current density ∼1.3 × 10⁵ A cm⁻² was found to be equivalent to the CMR effect caused by 1.5 T near T_C. The phenomenon that the resistance in CMR manganites could be easily controlled by the electric current should be of high interest for both fundamental research and practical applications.     

Thermal,mechanical and electrical properties of polyurethane/(3-aminopropyl) triethoxysilane functionalized graphene/epoxy resin interpenetrating shape memory polymer composites

Functionalized graphene (FG) was successfully synthesized by treating graphene oxide with (3-aminopropyl) triethoxysilane (KH-550) and then reduced by hydrazine hydrate. Subsequently, significant reinforcement of polyurethane/epoxy resin (PU/EP) composites in situ synthesized on the FG is prepared. Morphologic study shows that, due to the formation of chemical bonding, the FG was dispersed well in the PU/EP matrix and the mechanical performance is improved. Meanwhile, the thermal degradation temperature was enhanced almost 50 °C higher than that of PU/EP. The conductivity of PU/FG/EP nanocomposites was 82.713 × 10⁻⁶ S/m at 2.0 wt% loadings. The resulting composites exhibited 96% shape fixity, 94% shape recovery, enhanced shape recovery force to realize thermo-electric dual-responsive property. Comparing with the results in literature, the composites used in this study have shown a progress between electrical conductivity and shape memory property.     

Heating aging behavior of Al–8.35Zn–2.5Mg–2.25Cu alloy

In the present work, the influence of heating aging treatment (HAT) on the microstructure and mechanical properties of Al–Zn–Mg–Cu alloy was investigated. When the final aging temperature (FAT) was lower than 180 °C, the hardness increased with the decreasing of heating rate, however, in the case of the FAT was higher than 180 °C, the variation of hardness was opposite. The electrical conductivity of Al–Zn–Mg–Cu alloy increased with the decrease of heating rate regardless of FAT. The tensile strength, yield strength and conductivity of the Al alloy after (100–180 °C, 20 °C/h) HAT increased by 1.6%, 4.5% and 14.1% than that after T6 treatment, respectively. The precipitates sequence of HAT was coincident with that of isothermal aging, which is SSS → GP zone → η′ → η. With the increase of FAT and the decrease of heating rate, the fine precipitates became larger and the continuous η phase at grain boundary grew to be individual large precipitates. The HAT time was decreased about 80% than that for T6 treatment, indicating HAT could improve the mechanical properties, corrosion resistance and production efficiency with less energy consumption.     

Interdigital transducer generated surface acoustic waves suitable for powder transport

Recently, in the electronics and pharmaceutical industries, miniature devices that can transport a tiny amount of dry powder with a particle size of 100 μm or less are desired. We therefore focused on a surface acoustic wave (SAW) device, and we experimentally studied an interdigital transducer (IDT) that generates the SAW. As a result, it was found that an IDT with a 2-mm pitch size at a 90° inclination angle, against the perpendicular direction of a piezoelectric wafer (127.8° y-rotated x-propagating LiNbO₃) orientation flat, had a high efficiency of copper powder (about 100-μm particle size) transport. Then, to investigate the availability of a SAW actuator with this highly efficient IDT, we fabricated a miniature feeder (13-mm height × 18-mm width × 78-mm length) mounted with a hopper on the SAW actuator and carried out a powder supply experiment. As a result, it was found that, when 1 W of electric power was applied to the IDT of the feeder, the powder supply capability of the feeder was about 18 mg/s. From this fact, it was experimentally shown that a SAW actuator with a highly efficient IDT has a great potential to control dry powder with superior accuracy.     

Synergy of fiber length and content on free vibration and damping behavior of natural fiber reinforced polyester composite beams

This work addresses the results of experimental investigation carried out on free vibration characteristics of short sisal fiber (SFPC) and short banana fiber (BFPC) polyester composites. Influence of fiber length and weight percentage on mechanical properties and free vibration characteristics are analyzed. Composite beam specimen is fabricated with random fiber orientations at17 MPa compression using compression molding machine. Natural frequencies and associated modal damping values of the composite laminates were obtained by carrying out the experimental modal analysis. It is found that an increase in fiber content increases the mechanical and damping properties. For SFPC, 3 mm fiber length and 50 wt% fiber content yielded better properties, whereas for BFPC, 4 mm fiber length and 50 wt% fiber content was the best combination. Scanning electron microscopy was performed to study the interfacial mechanism.