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Composite thin film is highly desirable for the dielectric applications. In order to develop composite thin film, a nanocomposite, in which nanosized CaCuTiO (CCTO) particles are used as filler and P(VDF-TrFE) 55/45 mol% copolymer is used as polymer matrix, is investigated. The contents of CCTO in the nanocomposites range from 0% to 50 vol%. The dielectric property of these nanocomposites was characterized at frequencies ranging from 100 Hz to 1 MHz and at temperatures ranging from 200 K to 370 K. A dielectric constant of 62 with a loss of 0.05 was obtained in nanocomposite with 50 vol% CCTO at room temperature at 1 kHz. At the phase transition temperature (∼340 K) of the copolymer, a dielectric constant of 150 with a loss less than 0.1 was obtained in this nanocomposite. It is found that the dielectric loss of the nanocomposites is dominated by the polymer which has a relaxation process. Comparing to composites made using microsized CCTO, the nanocomposites exhibit a much lower dielectric loss and a lower dielectric constant. This indicates that the nanosized CCTO particles have a lower dielectric constant than the microsized CCTO particles. [ABSTRACT FROM AUTHOR]

The micromachining of complex three-dimensional microstructures (bulk micromachining) on metals can be applied to fabricate many novel devices for micro electromechanical system (MEMS), which will greatly benefit the development of MEMS. In this paper, a new electrochemical micromachining method named the confined etchant layer technique (CELT) was explored on the micromachining of the titanium alloy. Micro-scale trapezoidal slots were replicated on titanium alloy by using a mold with the corresponding negative microstructures (trapezoidal teeth). The machining resolution reached 0.503 μm. The electrochemical mechanisms involved in the process are analyzed and the parameters that influenced the machining resolution are discussed. [ABSTRACT FROM AUTHOR]

We experimentally investigate the interfacial morphologies of Rosensweig instability on an extremely thin layer of ferrofluid droplets under a constant perpendicular magnetic field. Striking patterns consisting of numerous subscale droplets that developed from Rosensweig instability are observed. For a dry plate, on which surface tension dominates, the breaking pattern of subscale droplets can be characterized by a dimensionless magnetic Bond number Bom. In general, a more pronounced instability, which is evident by a greater number of breaking subscale droplets N, arises with a higher Bom. For a magnetic Bond number that is larger than a critical value, we identify a new mode of interfacial breakup pattern, where the central droplet is torn apart with major mass loss. In addition, we found that the volume fractions of breaking subscale droplets are strongly affected by the height variation of the initial fluid surface and appear unevenly distributed with dominance of a central droplet. On the other hand, for a prewetted plate, a nearly flat fluid surface is achieved due to a smaller contact angle, which then leads to virtually evenly distributed subscale droplets. A global size for all breaking subscale droplets is observed regardless of their initial diameters. The number of breaking subscale droplets (N) and the diameter of the initial droplet (D) can be approximated by a quadratic proportionality of N∼D2. [ABSTRACT FROM AUTHOR]

The relaxor ferroelectric polymers, i.e., the poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] based terpolymers and high energy electron irradiated copolymers, provide unique opportunity to investigate the ferroelectric relaxor behavior in polymeric materials. Experimental evidence shows that there is fundamental difference in the microstructures between the relaxor terpolymer and relaxor irradiated copolymer even though both exhibit similar macroscopic ferroelectric relaxor response. [ABSTRACT FROM AUTHOR]

Electroactive polymers (EAPs) can behave as actuators, changing their shape in response to electrical stimulation. EAPs that are controlled by external electric fields -- referred to here as field-type EAPs -- include ferroelectric polymers, electrostrictive polymers, dielectric elastomers and liquid crystal polymers[1-6]. Field-type EAPs can exhibit fast response speeds, low hysteresis[1-8] and strain levels far above those of traditional piezoelectric materials[4-6,910], with elastic energy densities even higher than those of piezoceramics[4,5,9-11]. However, these polymers also require a high field (>70 V μm[SUP-1]) to generate such high elastic energy densities (>0.1 J cm[SUP-3]; refs 4, 5, 9, 10). Here we report a new class of all-organic field-type EAP composites, which can exhibit high elastic energy densities induced by an electric field of only 13 V μm[SUP-1]. The composites are fabricated from an organic filler material possessing very high dielectric constant dispersed in an electrostrictive polymer matrix. The composites can exhibit high net dielectric constants while retaining the flexibility of the matrix. These all-organic actuators could find applications as artificial muscles, 'smart skins' for drag reduction, and in microfluidic systems for drug delivery[1-3,12]. [ABSTRACT FROM AUTHOR]

In poly(vinylidene fluoride-trifluoroethylene) copolymer spin cast films, it has been observed that the polarization switching time increases as the film thickness is reduced. We will show that this change with thickness can be divided into two thickness regimes, those above a critical thickness and below this critical thickness. For films above the critical thickness, the change is in the switching behavior is mainly due to interface effect. While for films below the critical thickness, there is an additional and very large increase of the switching time with reduced film thickness, which is caused by a large drop of the crystallinity in this thickness range. It has been observed that this critical thickness, below which the crystallization in the polymer films is strongly hindered, depends on the film annealing conditions and is directly related to the thermodynamic stable crystallite thickness. [ABSTRACT FROM AUTHOR]

This paper presents experimental results showing that in a certain composition range and under a proper electron-irradiation treatment, a normal ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer can be converted into a material exhibiting many typical features of relaxor ferroelectrics, suggesting that this is a new class of relaxor ferroelectric material. Furthermore, the irradiated copolymer can generate giant electrostriction (approx. 5%) with a high elastic energy density. The X-ray diffraction results obtained from the irradiated copolymer under electric field, indicate that the observed polarization and strain responses are mainly due to the local phase transformation from a non-polar phase to a polar phase. [ABSTRACT FROM AUTHOR]

The dielectric behaviour of the solid-solution ceramics 0.87(Pb1-xLax/2Kx/2)(Zn1/3Nb2/3)O3-0.8PbTiO3-0.05BaTiO3 with x=0.08 and 0.12, was measured and analysed in a broad temperature range and at frequencies from 100 Hz to 100 kHz. It was found that the relation between the temperature and the dielectric constant can be well expressed by an exponential function exp(alpha- beta * T ) at temperatures much higher than the temperature T of m the dielectric constant maximum and that there is a super-exponential relation ] exp\[alpha + ( T / beta ) 1+ delta at temperatures much lower than T . This indicates that the 1 1 m glassy behaviour of the materials is different from that of general glasses. The freezing temperature of the polar regions in these materials is distributed over a broad temperature range, which results in dielectric dispersion of the materials at low temperatures. This demonstrates that both the distribution of the freezing temperatures and the process by which the polar regions are produced are associated with the degree of dielectric relaxation of the materials. Therefore, at least two factors, such as delta and beta , are needed to describe the dielectric relaxation of the materials completely. The relation between the logarithm of the frequency and the dielectric constant at low temperatures can be expressed as a linear function for these materials. The frequency dependence of T for the materials \[-m- ] is analysed using the Vogel-Fulcher relationship omega = omega exp T /( T T ) and \[- ] 0 0 m f a new relationship omega = omega0 exp ( To / Tm ) p] . We confirm that the new fit is much 0 0 m better than the Vogel-Fulcher fit. [ABSTRACT FROM AUTHOR]

Provides information on a study showing that dielectric measures allow for an in-depth investigation of dipole-degradation processes in a typical side-chain photonic polymer. Methodology used to conduct the study; Results of the study; Information on thermal degradation; Indepth look at the lifetime of photonic devices.

To overcome the low discharging efficiency of ceramic-polymer composites using ferroelectric polymers as matrix and to take the advantage in fabrication offered by the polar polymer, a polar but non-ferroelectric polymer – poly(methyl methacrylate) (PMMA) – was selected as the matrix in the development of high performance composites for energy storage. Ba 0.5 Sr 0.5 TiO 3 (BST) nanoparticles were selected as the filler. Freestanding and flexible BST-PMMA ceramic-polymer nanocomposites with BST content up to 30 vol.% were fabricated in thickness of about 5 μm using spin-coating process and were systemically studied. Due to the strong interaction between the polar groups of PMMA and the hydroxyl groups on the surface of BST nanoparticles, the suspension of BST nanoparticles in PMMA solution exhibits excellent stability and, hence, the nanocomposite films have excellent microstructure uniformity and compatibility between the BST nanoparticles and PMMA matrix. All the BST-PMMA films exhibit excellent frequency (100 Hz to 1 MHz) and temperature (−90 to 100 °C) stabilities in their dielectric properties with a high energy-storage density of more than 11 J/cm3. Most importantly, an ultra-high discharging efficiency of almost 100% is obtained in all the nanocomposites. Image 1 • Non-ferroelectric polar polymer is introduced as matrix for the nanocomposites used as energy-storage dielectrics. • High energy density with ultrahigh discharging efficiency (~100%) are demonstrated by BST-PMMA nanocomposite films. • The BST-PMMA nanocomposite films exhibit excellent temperature and frequency stabilities of dielectric properties. [ABSTRACT FROM AUTHOR]

The design of a piezoelectric diaphragm as a dual-functional biosensor platform, bending and thickness modes, is reported. The diaphragm using bending mode exhibits a higher sensitivity than the state-of-the-art microcantilevers, while the diaphragm using thickness mode has a much higher sensitivity than the bending mode. It was experimentally found that for the bending mode the diaphragm in liquid exhibits the same Q value as the diaphragm in air, while for the thickness mode the diaphragm in liquid exhibits a much smaller Q value. That is, the bending mode is the better candidate for developing high performance sensor platforms employed in liquid. [ABSTRACT FROM AUTHOR]

Magnetostrictive microcantilever (MSMC) as remote biosensor platform is reported. The mass sensitivity of the MSMCs is simulated and compared with the other microcantilevers. MSMCs with a thickness of 30–35 μm and different lengths and widths were fabricated from the magnetostrictive metal glass coated with a copper layer by sputtering. The resonance behavior of the MSMCs was experimentally determined. It is experimentally found that the MSMCs work well in either air or liquid. For MSMCs operated in air, a Q value of more than 500 was obtained. For MSMCs operated in water, the Q value reaches more than 30. The application of a MSMC as a biosensor platform is demonstrated by in situ detection of the yeast cells in water using the MSMC sensor. [ABSTRACT FROM AUTHOR]

The electromechanical response of poly(vinylidene-fluoride-chlorotrifluoroethylene) [P(VDF-CTFE)] copolymers with 9 mol % (CT9) and 12 mol % CTFE (CT12) is reported. The CT12 (at room temperature) exhibits an electrostrictive strain response of more than 5% and a piezoelectric constant d33 of 140 pC/N at a dc bias of 70 MV/m. It is found that about 70% of crystalline regions in P(VDF-CTFE) is at the nonpolar phase and that the CT9 has a crystallinity about 25% higher than the CT12. The difference in electromechanical performance between the CT9 and CT12 cannot be completely explained using the structure/conformation change alone. It is believed that the contribution of the interfacial layers to the polarization and electrostrictive strain response plays an important role. [ABSTRACT FROM AUTHOR]

Based on the optic and dielectric data acquired under different mechanical and electric conditions and temperature, we show that an orthorhombic phase exists near the morphotropic phase boundary (MPB) (on both the rhombohedral and tetragonal sides of MPB). Because of the proximity of the free energy of this phase to the two other morphotropic phases, i.e., the rhombohedral and tetragonal phases, the experimentally observed phases and phase diagrams near MPB depend crucially on the mechanical and electric conditions as well as the sample history. [ABSTRACT FROM AUTHOR]