bluuebunny/crossref_metadata_2025_split huggingface dataset:
50 Years Of Piezoelectric Transformers. Trends In The Technology
Authors: Vázquez Carazo Alfredo 
Published: April 2011

ABSTRACTThe initial concept of a piezoelectric transformer (PT) was proposed by C.A. Rosen, K. Fish, and H.C. Rothenberg and is described in the U.S. Patent 2,830,274, applied for in 1954. Fifty years later, this technology has become one of the most promising alternatives for replacing the magnetic transformers in a wide range of applications. Piezoelectric transformers convert electrical energy into electrical energy by using acoustic energy. These devices are typically manufactured using piezoelectric ceramic materials that vibrate in resonance. With appropriate designs it is possible to step-up and step-down the voltage between the input and output of the piezoelectric transformer, without making use of wires or any magnetic materials.This technology did not reach commercial success until early the 90s. During this period, several companies, mainly in Japan, decided to introduce PTs for applications requiring small size, high step-up voltages, and low electromagnetic interference (EMI) signature. These PTs were developed based on optimizations of the initial Rosen concept, and thus typically referred to as “Rosen-type PTs”. Today's, PTs are used for backlighting LCD displays in notebook computers, PDAs, and other handheld devices. The PT yearly sales estimate was about over 20 millions in 2000 and industry sources report that production of piezoelectric transformers in Japan is growing steadily at a rate of 10% annually. The reliability achieved in LCD applications and the advances in the related technologies (materials, driving circuitry, housing and manufacturing) have currently spurred enormous interest and confidence in expanding this technology to other fields of application. This, consequently, is expanding the business opportunities for PTs.
Optical Constants of Vanadium Dioxide Films and Design of a Solar Energy Control Window
Authors: Tazawa Masato , Asada Hideo , Xu Gang , Jin Ping , Yoshimura Kazuki 
Published: April 2011

ABSTRACTWe determined the optical constants of a vanadium dioxide (VO2) thermochromic film deposited on glass substrate by ellipsometry in wavelength range from 380 nm to 1700 nm. The optical constants were employed to design the optimal stacked thin film structure for smart windows which control the solar radiation and heat transmission from the viewpoint of high luminous transmission.
Piezoresistive Properties of Ceramic Strain Sensors with Controlled Nanoporosity
Authors: Gregory Otto J. , You Tao 
Published: April 2011

ABSTRACTA ceramic strain gage based on reactively sputtered indium tin oxide thin films is being developed to monitor the structural integrity of components employed in aerospace propulsion systems that operate at temperatures in excess of 1500°C. When relatively thick indium-tin-oxide (ITO) strain gages were prepared by reactive sputtering in oxygen:argon atmospheres and annealed in nitrogen, an extremely stable piezoresistive response was observed at temperatures as high as 1530°C. SEM and AFM of these sensor surfaces after high temperature exposure revealed a partially sintered microstructure with interconnected nanoporosity. Specifically, the microstructure consisted of a contiguous network of uniform sized ITO particles with well-defined necks between individual particles. When these microstructures were compared to those of relatively thin ITO sensors sputtered in nitrogen:argon:oxygen atmospheres, i.e. ITO films prepared in a nitrogen rich plasma, the average pore size and particle size was estimated to be an order of magnitude smaller than those associate with thick ITO sensors. In the nitrogen sputtered films, enhanced electrical conduction along the surfaces of the contiguous ITO particles resulted in a very stable and large piezoresistive response with a gage factor of 11.4 and a drift rate of 0.0001%/hour at 1560°C. The improved performance realized when the ITO films were processed in nitrogen may be extended to other ITO based sensors including gas sensors and the advantages of films processed in this manner will be discussed.
Simulations of High-Strain Electrostrictive Chlorinated Terpolymers
Authors: Kavarnos George J. , Ramotowski Thomas 
Published: April 2011

ABSTRACTChlorinated 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.
Effect of piezoelectric vibration on electrical properties of YSZ film prepared by MOCVD
Authors: Masumoto Hiroshi , Goto Takashi 
Published: April 2011

ABSTRACTTo 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.
PZT-Driven Micromagnetic Optical Devices
Authors: Takagi H. , Park J. H. , Mizoguchi M. , Nishimura K. , Uchida H. , Lebedev M. , Akedo J. , Inoue M. 
Published: April 2011

ABSTRACTA magneto-optic spatial light modulator (MOSLM) driven by electric field is presented. Using finite element method simulation, the parameters of the MOSLM are decided including the 1 μm piezoelectric lead zirconate titanate (PZT)-based layer, the 200 nm bottom electrode, and the 8V electrical applied voltage. A flat surface magneto-optical bismuth-substituted iron garnet (Bi:YIG) based film having an array-pixels structure was created by a site-selected epitaxial method on a SGGG-based substrate. In order to avoid high temperature annealing process which may damage the Bi:YIG film, the PZT film was deposited by the aerosol deposition method (ADM) on the Bi:YIG film. By stress field induced by the PZT film to the Bi:YIG film with an external magnetic field, the pixels of the device were successfully switched.
Phase Stability of Single Crystalline Co-Ni-Ga Shape Memory Alloy
Authors: Schlagel Deborah L. , Lograsso Thomas A. , Pecharsky Alexandra. O. 
Published: April 2011

ABSTRACTSingle crystals of Co48Ni22Ga30 have been synthesized using a modified Bridgman method. The ability to solidify and retain single phase B2 austenite was found to depend not only on the starting composition and growth rate, but also the ability to maintain sufficiently high cooling rates to avoid the precipitation of a Co-rich FCC phase during post-solidification cooling. DSC measurements on the single crystal found the Ms, Mf, As, and Af to be 35.7°C, -1.8°C, 34.1°C and 72.2°C, respectively. On subsequent heating the B2 phase was found to partially decompose into the Co-rich phase at temperatures exceeding 380°C. Decomposition of the single phase B2 phase was tracked by microstructural observation, DSC, powder diffraction and low temperature heat capacity measurement. Restoration of the crystal to single phase B2 austenite required annealing of the crystal at temperatures above 1125°C followed by rapid cooling.
High Transition Temperature Shape Memory Alloys for Micro-actuator Systems
Authors: Baldwin Elizabeth , Rabiei Afsaneh 
Published: April 2011

ABSTRACTA new generation of thin film shape memory alloy (SMA) for MEMS micro-actuator has been developed, in which film structure and chemistry are optimized, for enhanced higher transition temperature, higher strain recovery rate as well as reduced actuation time by improving the heat transfer rates. Thin film TiPdNi was produced using Ion Beam Assisted Deposition (IBAD) technique both by in-situ heat treating during deposition and followed by post processing heat treatment. Films deposited on unheated substrates were found to be highly amorphous with minimal B2 austenite crystallization, while films deposited on heated substrates produced a highly crystallized twinned B19 martensitic structure through the bulk of the film. For films deposited on heated substrates, a 70 nm thick transition layer was found to exist between the bulk film and silicon substrate. Severe delamination and oxidation as a result of post heat treatment on IBAD deposited samples made in-situ heat treatment most suitable for processing thin film SMAs for MEMS applications. The desire to introduce this innovative technology to the field of SMA micro-actuators is based on two primary advantages of IBAD process over existing technology used to apply thin film SMAs. First, the chemical composition and grain size of the applied coating can be precisely controlled over a wide range of values. Second, the SMA can be deposited as thin films ≤ 2 μm thick with smaller grain size, much denser than films applied using sputter deposition technology. The effects of various processing parameters, and post processing heat treatment, on properties of the thin film SMA were studied.
Ionic Polymer-Metal Composites as Smart Materials under Subzero Temperature Conditions
Authors: Paquette Jason W. , Kim Kwang J. 
Published: April 2011

ABSTRACTThis 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.
Hybrid Actuation in Coupled Ionic / Conducting Polymer Devices
Authors: Bennett Matthew D. , Leo Donald J. 
Published: April 2011

ABSTRACTIonic polymer membrane actuators represent a relatively new and exciting entry into the field of smart materials. Several key limitations of these transducers have prevented them from experiencing widespread use, however. For example, the bandwidth of these devices is limited at very low frequencies by characteristic relaxation and at high frequencies by the low elastic modulus of the polymer. In this paper, an overview of the initial results of work with hybrid ionic / conducting polymer actuators is presented. These hybrid actuators are devices that combine the electromechanical coupling of ionic polymer actuators and conducting polymer actuators into one coupled device. Initial results show that these hybrid devices have the potential to offer marked advantages over traditional ionic polymer membrane transducers, including increased stress and strain generation and higher actuation bandwidth. Details of the preparation of these devices and performance metrics are presented and comparisons to baseline materials are made.
In-Situ Characterisation of Photo-actuating and Photo-rheological Polymers
Authors: Sabey Chris J. , Moniruzzaman M. , Fernando Gerard F. , Badcock Rodney A. , Winter Darren , Akhavan Jackie , Kronfli Esam , Bandara A. 
Published: April 2011

ABSTRACTThis paper reports on the design and validation of three in-situ measurement techniques for characterisation of photo-rheological and photo-actuation phenomena. Results from these in-situ techniques are presented and used to investigate isomerisation and recovery effects in azobenzene and spiropyran polymer systems with and without flexible spacer groups.A new in-situ technique for the measurement of photo-viscosity effects in polymer solutions has been developed using a cone and plate rheometer. The new technique permits simultaneous irradiation of the photo-responsive polymer solutions and continuous measurement of its viscosity in a controlled environment. An additional benefit of the technique is the greatly reduced sample volume compared to traditional capillary viscometers.Techniques for the in-situ measurement of the photo-actuation effect in polymer systems are discussed, including image analysis and interferometric methods. The effects of environmental factors such as temperature are considered and steps taken to minimise them. The resulting measurement techniques provide an accurate means of measuring the effect of irradiation on the photo-actuating polymers in solution and as solids.A range of polymers with photo-responsive azobenzene and spiropyran groups in the polymer side chains have been synthesised and evaluated using these three techniques. The photoviscosity and photo-actuation effects under irradiation have been measured in a variety of solvents. The effect of incorporating a flexible spacer group in the side chain of the azobenzene polymers is examined and its effect on the photo-rheology mechanism is discussed.
Preparation and Properties of the Novel Nanocrystal and Polymer Composite Films for Electro-Optic Applications
Authors: Ren Quan , Xu Dong , Chow Yuktak , Chan Hauping , Chu Paklim 
Published: April 2011

ABSTRACTNovel 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.
Novel Actuating System Based on a Composite of Single-Walled Carbon Nanotubes and an Ionomeric Polymer
Authors: Levitsky Igor A. , Kanelos Peter T. , Euler William B. 
Published: April 2011

ABSTRACTWe report the fabrication and characterization of a novel composite material based on single walled carbon nanotubes (SWNT)s and the ionomeric polymer Nafion. SWNTs were airbrushed from a chloroform suspension onto both sides of a Nafion membrane (180 μm) and the electromechanical properties of the composite material were explored. The outer layers of carbon nanotubes acted as electrodes in order to pass electrical current through the system while the mechanical response was monitored. Under this design, the mechanical response could be characterized, with respect to the electrical signal, as a function of: voltage, waveform (AC vs. DC), and frequency (AC). Data was also compiled to gauge the effect of size and thickness of each individual layer of the system. The reference samples (graphite-Nafion and sputtered gold-Nafion) did not exhibit mechanical actuation at the same conditions. An analytical model for current decay was considered that is in agreement with the experimental data. Bi-exponential decay with a long time component was found for bias, which is above the actuating threshold. That was explained in terms of increasing of the water dielectric constant and polymer-SWNT interface area. The possible mechanisms of the actuation in this novel composite are discussed.
Production of high quality single-walled carbon nanotubes in a nano-agglomerated fluidized bed reactor
Authors: Wang Qixiang , Ning Guoqing , Wei Fei , Luo Guohua 
Published: April 2011

ABSTRACTSSingle-walled carbon nanotubes (SWNTs) have attracted much attention due to their unique structural, mechanical, chemical, and electrical properties. Catalytic chemical vapor deposition (CCVD) through decomposition of hydrocarbons is one of the most challenging synthesis methods to produce SWNTs in large scale. In this paper, high quality SWNTs prepared in a nano-agglomerated fluidized bed reactor (NAFBR) was reported. The reactor is a vertical quartz tube with the inner diameter of about 50 mm. Catalysts nanoparticles used for the production of SWNTs were prepared with Fe metal nanoparticles carried on the surface of MgO. About 150g catalysts powders were loaded on the gas distribution grid. The reaction temperature was controlled at not less than 1123 K. The carrier gas of argon was used to maintain turbulent fluidization of the catalysts powders in FBR. The hydrogen gas was used to reduce the catalysts and to synergize the growth of SWNTs with methane. The powder products were spherical agglomerates of SWNTs bundles tangling with the catalysts particles. By optimizing the process parameters of CCVD, the products of SWNTs with the diameter about 0.9 ∼ 1.8 nm were prepared, without any multi-walled carbon nanotubes (MWNTs) or amorphous carbon. The microstructure of SWNTs products were characterized by the methods of high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Raman spectra, etc. The NAFBR is a commercially viable (effective and continuous production at a low cost) process for the production of SWNTs.
Electron Spin Resonance Characterization of Defects at Interfaces in Stacks of Ultrathin High-κ Dielectric Layers on Silicon
Authors: Stesmans A. L. , Afanas'ev V.V. 
Published: April 2011

ABSTRACTElectron spin resonance (ESR) analysis of (100)Si/SiOx/ZrO2, (100)Si/Al2O3 and Si/HfO2 structures with nm-thin dielectric layers deposited by different chemical vapor deposition procedures reveals, after hydrogen detachment, the presence of the trivalent Si dangling-bond-type centers Pb0, Pb1 as prominent defects in all entities. This Pb0, Pb1 fingerprint, generally unique for the thermal (100)Si/SiO2 interface, indicates that the as-deposited (100)Si/metal oxides interface is basically Si/SiO2-like. Though sensitive to the deposition process, the Pb0 density is found to be substantially larger than in standard (100)Si/SiO2. As probed by the Pb- type center properties, the Si/dielectric interfaces of all structures are under enhanced (unrelaxed) stress, typical for low temperature Si/SiO2 growth. Standard quality thermal Si/SiO2 properties in terms of Pb signature may be approached by appropriate annealing (≥ 650°C) in vacuum in the case of (100)Si/SiOx/ZrO2. Yet, O2 ambient appears required for Si/Al2O3 and Si/HfO2. It appears that Si/high-κ metal oxide structures with device grade quality interfaces can be realized with sub-nm thin SiOx interlayers. The density of fast interface states closely matches the Pb0 density variations, suggesting the center as the dominant fast interface trap. They may be efficiently passivated in H2 at 400 °C.
On the interface quality of MIS structures fabricated from Atomic Layer Deposition of HfO2, Ta2O5 and Nb2O5−Ta2O5−Nb2O5 dielectric thin films
Authors: Dueñas S. , Castán H. , García H. , Barbolla J. , Kukli K. , Ritala M. , Leskelä M. 
Published: April 2011

ABSTRACTA study of metal-insulator-semiconductor (MIS) structures based on atomic layer deposited HfO2, Ta2O5 and Nb2O5−Ta2O5−Nb2O5 thin films is presented. Our attention was focussed on interface quality and defect density in the dielectric. Interface states as well as defects inside the insulator bulk were measured by using capacitance-voltage (C-V), deep level transient spectroscopy (DLTS) and conductance transient (G-t) techniques. Nb2O5−Ta2O5−Nb2O5 based capacitors exhibit the highest interface state density, whereas the minimum is obtained for HfO2. Conductance transients are not observed in Al/HfO2/SiO2/Si stacks, thus indicating that disordered induced gap states (DIGS) are not present in these structures. We also observed that post-metallization annealing in forming gas diminishes the trap interface density at the expense of increasing DIGS in the Al/HfO2/Si cases.