The objective of this paper is to investigate effective magneto-mechanical behavior of composites containing aligned ferromagnetic particles. The effective magneto-elastic properties and the overall magnetostriction of the composites are derived by considering the pair-wise interaction between ferromagnetic particles. For the composites with soft elastomer matrix, the microstructural configuration rapidly changes with the magnetic and mechanical loads so that the local magnetic and elastic fields are fully coupled. This model accounts for the coupled magneto-elastic interaction and pair-wise interaction between particles. The results show that the Young's modulus along the particle-chain direction is reduced and the shear modulus is increased under the applied magnetic field. Predictions from the proposed model are compared with available experimental data and other models.

The authors have showed that rapid-solidified (RS) melt-spun fiber/ribbon/foil type samples have very often strongly textured fine columnar grains, and those can have very high performance of the metallic actuator/sensor properties. However, as for the applications of these sample materials in smart material systems, the developed rapid-solidified samples are thought to be inevitably too small force to move the machines and structures in the engineering field. In this paper, we propose one novel material processing technique that can produce the bulk type solid-state actuator/sensor materials by combing the rapid-solidified fiber/ribbon and short time spark plasma sintering/joining (SPS) method. The produced samples, both 1) the disk-type sample from stacked layers of RS-ribbons and 2)the sintered compact from ball-milled RS-fibers of shape memory Ti50Ni40Cu10 (NITINOL) alloy, showed clear thermoelastic phase transformation by DSC evaluation as well as shape recovery. The same approach was also tried for making bulky magnetostrictive FeGa(Galfenol) alloy systems from stacked FeGa ribbons. Laminated FeGa ribbons maintained large magnetostriction of about 100–200ppm under increasing stressed condition as much as in the case of the strongly textured ribbon sample.

Vanadium dioxide (VO2) thin films were fabricated by e-beam evaporation of vanadium thin films followed by thermal oxidation in oxygen ambient. The properties of the VO2 films were investigated for thermo-optical switching applications. Synthesized VO2 film displays a phase transition at 65 – 68 °C. It exhibits an abrupt change in optical reflectivity over the phase transition temperature range. Results for VO2 on a highly reflective metal layer are strongly dependent on the VO2 thickness. The optical switching has a major hysteresis of about 15 °C between the heating and cooling branches. The evolution of the surface morphology with the oxidation time was studied with a SEM. The VO2 film was patterned on microplatforms by metal lift-off technique. We conclude that the evaporation followed by oxidation is an effective method to produce active VO2 film for thermo-optical switching devices.

Gas sensors based on organically hybridized SnO2 films are demonstrated. Upon exposure to CO gas, the electrical resistance of the hybrid sensor with amino groups in the organic components increases (R-increasing response), whereas other reducing gases such as H2 and CH4 gases cause the decreasing in the sensor resistance. For the n-type semiconductors like SnO2, the R-increasing response cannot be explained by the ordinary combustion mechanism. The appearance of the anomalous R-increasing response to CO gas can be controlled by the functional groups of the organic component. The hybrid sensor with hydroxy groups also exhibits the R-increasing response to CO gas, whereas it is not observed for the sensor with alkyl groups. The hybridization can improve gas selectivity of the SnO2 semiconducting gas sensors.

To improve electric properties of ion-conductors at low temperatures, ion-conducting/piezoelectric multifunctional film was prepared. Yttria-stabilized zirconia (YSZ) film as an ion-conducting film was deposited on a MgO substrate by metal-organic chemical vapor deposition (MOCVD). The significant [100] preferred orientation of cubic-YSZ single-phase film c ontaining 8 mol%Y2O3 was obtained at a deposition temperature of 973 K. The film consisted of fine grains of about 400 nm in diameter and had a columnar structure. It was capable of ionic conduction, as shown by the fact that a semicircle and a spike appeared at high and low frequencies, respectively, in the complex impedance measurement. The obtained YSZ thin film was placed on a multilayer piezoelectric actuator composed of seven sheets of a PZT (lead zirconate titanate) system. The effect of piezoelectric vibration on the electric properties of the ion-conducting film was investigated. The impedance value of the YSZ thin film decreased with increasing amplitude of piezoelectric vibration. The electrical conductivity of the YSZ thin film at 353 K, with an applied vibration frequency of 115 kHz and a voltage of 40 V, was about 2×10-4 Sm-1. The value of this conductivity was 103 times greater than that without vibration. Vibration by the actuator was thus suggested to improve the ionic conduction of the YSZ thin film.

Large grain polycrystalline silicon films as a sensing material for infrared bolometers have been proposed and investigated. Using a seed selection through ion channeling technique, we have successfully increased the average grain size of polysilicon films up to 1670Å. The achieved TCR value at 20°C and grain boundary defect density of the film are found to be as high as -2.46%/K for a resistivity of 30Ωcm and to be about 1.752×1012/cm2, respectively. From the measurement of noise characteristics of the film, the value of k, 1/f noise parameter, is calculated to be 1.35×10-9. As a result, the estimated detectivity is found to be 5.6×108cmHz1/2/W.

BiFeO3-PbTiO3 (BF-PT) crystalline solutions have been modified by La3+, Ga3+ and Ba2+ substituent. The modified BF-PT had morphotropic phase boundary (MPB), at which the ferroelectric rhombohedral phase transferred to the tetragonal symmetry. The piezoelectric properties at the MPB were strongly depended on different substituents. The modified BF-PT system showed the insulation resistivity up to 1012 ω·cm at room temperature. Lanthanum played a critical role making BF-PT softer to be poled to the piezoelectric state. Ga provided BF-PT additional polarization and breakdown strength with La substituent. In the system with La3+, Ga3+ and Ba3+ simultaneously, addition of Ba enhanced dielectric and piezoelectric activity. It was flexible to tailor BF-PT by using different substituents. In the vicinity of MPB, the Curie temperature Tc was above 385°C of BF-PT for La <10 at%, whereas the d33 constant was as high as 295 pC/N for one with La of 20 at%. The modified BF-PT revealed comparable performances to conventional Pb(Zr,Ti)O3 (PZT) ceramics, but in significantly lead reduced forms.

Field-structured magnetic particle composites are an important new class of materials that have great potential as both sensors and actuators. These materials are synthesized by suspending magnetic particles in a polymeric resin and subjecting these to magnetic fields while the resin polymerizes. If a simple uniaxial magnetic field is used, the particles will form chains, yielding composites whose magnetic susceptibility is enhanced along a single direction. A biaxial magnetic field, comprised of two orthogonal ac fields, forms particle sheets, yielding composites whose magnetic susceptibility is enhanced along two principal directions. A balanced triaxial magnetic field can be used to enhance the susceptibility in all directions, and biased heterodyned triaxial magnetic fields are especially effective for producing composites with a greatly enhanced susceptibility along a single axis. Magnetostriction is quadratic in the susceptibility, so increasing the composite susceptibility is important to developing actuators that function well at modest fields. To investigate magnetostriction in these field-structured composites we have constructed a sensitive, constant-stress apparatus capable of 1 ppm strain resolution. The sample geometry is designed to minimize demagnetizing field effects. We have demonstrated field-structured composites with nearly 10,000 ppm strain, and have shown that at large magnetic fields a structural phase transition occurs within the composite. These experimental results are compared to microscopic, self-consistent field simulations of magnetostriction in these complex, disordered materials.

A coarse-grained model of soft elasticity of nematic elastomers is presented, in which fine-scale spatial oscillations are carefully accounted for in the definition of an effective energy density, and then averaged out from the kinematics. Algorithmically, this amounts to taking a suitable convex envelope of the original free-energy of the system. The resulting finite element simulations of stretching experiments on thin sheets of nematic elastomers enable us to resolve simultaneously the macroscopic mechanical response (e.g., deformed shape, stress-strain curves) and the underlying microscopic mechanisms (e.g., evolution of domain structures, local reorientation of the nematic director).

Several ternary Fe-Pt-Pd alloys with the compositions of Fe-(25-x) at% Pt-x at% Pd and Fe-y at% Pt-(30-y) at% Pd were investigated to study their phase transformations in order to develop ductile ferromagnetic shape memory alloys appearing around room temperature. Alloys were prepared by vacuum floating induction melting, followed by hot rolling at 1000°C and homogenization at 900° C. Homogenized alloys were heat treated at 650°C for various periods of time in vacuum for atomic ordering in encapsulated quartz tubes, and quenched into iced water. It was found that in general the transformation temperatures changes with heat treatment time. In the case of Fe-23at.%Pt-2at.%Pd, Ms temperature increased and the difference between Ms and Mf increased with increasing heat treatment time, which was different from Fe3Pt where a degree of order becomes one. As heat treatment time increased, there was a tendency in that a strong first-order transformation in the disordered state was replaced by a weak first-order transformation. The Curie temperature of the alloys rose drastically with the addition of Pd, along with the transformation temperatures. Fe-23at.%Pt-2at.%Pd showed good shape memory effect after 8 hours of heat treatment at 650°C. This alloy showed much better shape recovery than any other binary Fe-Pt and Fe-Pd shape memory alloys.

Current – voltage (IVC) and capacitance – voltage (CVC) of heterostructures (Cd, Zn)Te/ZnCdHgTe are studied for the first time. Thin films ZnxCdyHg1-x-yTe were grown on monocrystalline (111) CdTe and ZnTe substrates by PLE technology. Deposition was carried out on substrates held at temperatures near 290 K. The thickness of investigated films was estimated to be about 5 μm. Electric characteristics of the as-grown structures were examined under T = 77–290 K in the wide range of applied bias. All investigated samples have demonstrated diode-like IVC and CVC under test signal frequency f = 1 kHz. Heterostructures CdTe/ZnCdHgTe have exhibited a room temperature photosensitivity in spectral range 0.50–0.65 μm.

Novel nanocrystals and polymer composite thin films for the applications of electro-optical devices were prepared. We used PbTiO3 nanocrystals as a nonlinear chromophore (guest) in the NLO polymer system. The transparent polymer polyetherketone (PEK-c) was chosen as the polymer host due to its high glass transition temperature. The PbTiO3 nanocrystals were synthesized successfully by the chemical solution decomposition method. The size of the PbTiO3 nanocrystals was estimated to be 30–40 nm. The weight ratio of PbTiO3 nanocrystals to polymer polyetherketone was 15 %. The composite thin films of PbTiO3 / PEK-c were prepared by spin-coating technique. The films were then electrically poled to induce asymmetry in the material by heating the films to a temperature close to their glass transition and applying an electric field. The refractive indices of the un-poled composite PbTiO3 / PEK-c film were found to be 1.55165 for 633 nm and 1.65352 for 414 nm by using the Metricon prism coupling system. In the poled composite PbTiO3 / PEK-c film sample, the TE- and TM-indices differences were found to be 0.02945 for 633 nm and 0.03915 for 414 nm, showing very good optical anisotropy properties. Dielectric constant ε of the film was determined to be 7.32 at room temperature at 100 KHz using an Impedance Analyzer. The electro-optic coefficient, γ33, of poled PbTiO3 / PEK-c composite film was measured to be 18.34 pm/Vat 633 nm under room temperature by the simple transmission technique. The factor F2 = n7 γ2 /ε, figures of merit, was estimated to be 1546. The relaxation time constant was calculated to be 5836 min.

High-resolution domain studies were performed in Pb(Zn1/3Nb2/3)O3-4.5%PbTiO3 (PZN-PT) single crystals via piezoresponse force microscopy (PFM). Irregular domain patterns with the typical sizes of 20–100 nm were observed on the (001)-oriented surfaces of unpoled samples. On the contrary, (111) crystal cuts exhibited normal micron-sized regular domains with the domain boundaries directed along allowed crystallographic planes. The existence of nanodomains in (100)-oriented crystals was tentatively attributed to the relaxor nature of PZN-PT where small polar clusters were predicted to exist upon zero-field cooling. These nanodomains were considered as the nuclei of the opposite polarization state that ease the switching process for this particular crystal cut. Local piezoelectric hysteresis was also performed by PFM on the nanometer scale. Similar switching behavior of (111)- and (100)-oriented PZN-PT crystals suggests that their superior piezoelectric properties can be related to the domain wall motion rather than to the perovskite lattice itself.

Among various electroactive polymer (EAP) actuator materials developed recently, the class of EAPs whose responses are stimulated by external electrical fields (often known as the field type EAPs) is especially attractive due to their high strain level and elastic energy density. However, for most field type EAPs, dielectric constant is low, generally less than 10. Consequently, these polymers usually require high electric fields (>100 V/μm) to generate high elastic energy density which limits their applications. In this paper, we will investigate some avenues to significantly raise the dielectric constant and electromechanical response in field type polymeric materials. By exploiting an all-organic composite approach in which high-dielectric-constant organic particulates were blended with a polymer matrix, a polymeric-like material can reach a dielectric constant higher than 400, which results in a significant reduction of the applied field to generate high strain with high elastic energy density. An all-polymer high-dielectric-constant (K>1,000 @1 kHz) percolative composite material was fabricated by the combination of conductive polyaniline particles (K>105) within a fluoroterpolymer matrix (K>50). These high-K polymer hybrid materials also exhibit high electromechanical responses under low applied fields. In addition, a three-component all-organic composite was designed and prepared to improve the dielectric constant and the electromechanical response, as well as the stability of the composites, in which a high-dielectric-constant organic dielectric phase and an organic conductive phase were embedded into the soft dielectric elastomer matrix.

An experimental investigation was carried out to study the crack initiation and growth in a single-edge notched NiTi shape memory alloy sheet under tension. It is observed that a crack initiated at the tip of a V-shape notch before the peak axial load was reached and it grew steadily across the width of the NiTi sheet until final fracture. In-plane crack-tip deformation fields at various stages of the crack growth were measured based on an image correlation technique and the crack-tip opening displacement (CTOD) and crack-tip opening angle (CTOA) were subsequently determined. The fracture surface of the NiTi sheet was dimpled based on scanning electron microscopy examinations.

Chlorinated poly(vinylidene fluoride/trifluoroethylene) terpolymers are remarkable examples of high strain electrostrictive materials. These polymers are synthesized by copolymerizing vinylidene fluoride and trifluoroethylene with small levels of a third chlorinated monomer. The electromechanical responses of these materials are believed to originate from the chlorine atom, which, by its presence in the polymer chains and by virtue of its large van der Waals radius, destroys the long-range crystalline polar macro-domains and transforms the polymer from a normal to a high-strain relaxor ferroelectric. To exploit the strain properties of the terpolymer, it is desirable to understand the structural implications resulting from the presence of the chlorinated monomer. To this end, computations have been performed on model superlattices of terpolymers using quantum-mechanical based force fields. The focus has been on determining the energetics and kinetics of crystallization of the various polymorphs that have been identified by x-ray diffraction and fourier transform infrared spectroscopy. The chlorinated monomer is shown to act as a defect that can be incorporated into the lamellar structures of annealed terpolymer without a high cost in energy. The degree of incorporation of the chlorinated monomer into the crystal lattice is controlled by annealing conditions and ultimately determines the ferroelectric behavior of the terpolymers.

Composite structures are presented that allow a wide design space for strains in response to an applied stimulus to be accessed. The basic principle of operation is described and examples of how it can be used to obtain a range of behaviours are given. Experiments were conducted to assess the basic behaviour of building blocks for such composites and it is shown that the results agree reasonable with simple predictions made by considering bending and stretching of the beams in the structures.

Rapid-solidification method was applied to make Fe-15at%Ga and Fe-17at%Ga ribbons of 100 μm thickness. These ribbons have large magnetostriction of 270 ppm, where the coercive force exhibits a maximum value. The phenomenon is related to special metallic texture, that is, the ribbon has strongly [001]-oriented textured fine columnar microstructure with grain size of 2∼5 μm. The ribbon has little-hysteresis loop of magnetostriction and a good ductility (i.e., full bending is possible). Rapid-solidified Fe-Ga alloy has a promising possibility as a new magnetic-induced sensor/actuator material.

This paper presents a description of Ionic Polymer-Metal Composites (IPMCs) as an attractive solution for cold operation actuators. This is because of their capability for actuation with relatively low voltages (1 to 5 V), durability and capability of operating within the subzero regime T < 0 °C. The building block material of IPMCs experiences phase changes within the base polymeric material that results in an alteration of the performance of the material in terms of actuator performance. An experimental apparatus is constructed in order to have a controlled temperature environment in which to analyze the material. The overall temperature within the reservoir, the temperature on the IPMC surface electrodes, the conductivity of the membrane and the blocking force were all measured. The phase changes inherent at these low temperatures are investigated further by means of Differential Scanning Calorimeter to obtain the phase change temperatures and characteristics. The results are presented and interpreted to show that there is definite promise for these low temperature polymeric actuators to operate in practical applications.

Highly branched photoluminescent polyphenylenes (PP) containing 1,3,5-triphenylbenzene (TPB) fragments were prepared via combination of cyclocondensation of acetylaromatic compounds and Ni0-catalyzed dehalogenation. Defect free PP with star-like fragments were synthesized using Ni0-catalyzed polymerization of aromatic bromides obtained by modification of 1,3,5-tri(p-bromophenyl)benzene. The molecular weights of the polymers were 6700, 8600, and 15300 Da. The maximum photoluminescence in solution (quantum yield of 96%) was obtained for the highly branched polymer with star-like TPB fragments, bearing no Br or acetyl groups. The PP of this kind show also very bright fluorescence in a solid state under UV irradiation at 360 nm so they can be considered as promising materials for OLED applications.