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Sample records for stabilized ferroelectric liquid

  1. Solitary wave propagation in surface stabilized ferroelectric liquid crystal cells

    OpenAIRE

    VIJ, JAGDISH; SONG, JANG-KUN

    2008-01-01

    PUBLISHED Solitary wave propagation in surface stabilized ferroelectric liquid crystal cells controlled by surface anchoring of the alignment layers is investigated for different conditions of alignment on the two opposite surfaces. We show that the critical field Ec, where the speed of the solitary wave becomes zero, is finite for asymmetric alignment on two surfaces. We also show that the polar anchoring energy difference (Deltawp) between the alignment layers can be calculated by measur...

  2. A Review of Polymer-Stabilized Ferroelectric Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Ingo Dierking

    2014-05-01

    Full Text Available The polymer stabilized state of ferroelectric liquid crystals (FLC is reviewed; and the effect of a dispersed polymer network in an FLC outlined and discussed. All fundamental material aspects are demonstrated; such as director tilt angle; spontaneous polarization; response time and viscosity; as well as the dielectric modes. It was found that the data can largely be explained by assuming an elastic interaction between the polymer network strands and the liquid crystal molecules. The elastic interaction parameter was determined; and increases linearly with increasing polymer concentration.

  3. A Review of Polymer-Stabilized Ferroelectric Liquid Crystals.

    Science.gov (United States)

    Dierking, Ingo

    2014-05-06

    The polymer stabilized state of ferroelectric liquid crystals (FLC) is reviewed; and the effect of a dispersed polymer network in an FLC outlined and discussed. All fundamental material aspects are demonstrated; such as director tilt angle; spontaneous polarization; response time and viscosity; as well as the dielectric modes. It was found that the data can largely be explained by assuming an elastic interaction between the polymer network strands and the liquid crystal molecules. The elastic interaction parameter was determined; and increases linearly with increasing polymer concentration.

  4. Spontaneous Ferroelectric Order in a Bent-Core Smectic Liquid Crystal of Fluid Orthorhombic Layers

    Energy Technology Data Exchange (ETDEWEB)

    R Reddy; C Zhu; R Shao; E Korblova; T Gong; Y Shen; M Glaser; J Maclennan; D Walba; N Clark

    2011-12-31

    Macroscopic polarization density, characteristic of ferroelectric phases, is stabilized by dipolar intermolecular interactions. These are weakened as materials become more fluid and of higher symmetry, limiting ferroelectricity to crystals and to smectic liquid crystal stackings of fluid layers. We report the SmAP{sub F}, the smectic of fluid polar orthorhombic layers that order into a three-dimensional ferroelectric state, the highest-symmetry layered ferroelectric possible and the highest-symmetry ferroelectric material found to date. Its bent-core molecular design employs a single flexible tail that stabilizes layers with untilted molecules and in-plane polar ordering, evident in monolayer-thick freely suspended films. Electro-optic response reveals the three-dimensional orthorhombic ferroelectric structure, stabilized by silane molecular terminations that promote parallel alignment of the molecular dipoles in adjacent layers.

  5. Guest–host interaction in ferroelectric liquid crystal–nanoparticle ...

    Indian Academy of Sciences (India)

    Ferroelectric Cu-doped ZnO (Cu–ZnO) nanoparticles have been added to the pure ferroelectric liquid crystal (FLC) Felix 17/100. The nanoparticles are bigger in size as compared to FLC molecules; therefore, they distort the existing geometry of FLC matrix and set up an antiparallel correlation with the dipole moments of the ...

  6. Ferroelectric Nanoparticles in Liquid Crystals: Recent Progress and Current Challenges.

    Science.gov (United States)

    Garbovskiy, Yuriy; Glushchenko, Anatoliy

    2017-11-01

    The dispersion of ferroelectric nanomaterials in liquid crystals has recently emerged as a promising way for the design of advanced and tunable electro-optical materials. The goal of this paper is a broad overview of the current technology, basic physical properties, and applications of ferroelectric nanoparticle/liquid crystal colloids. By compiling a great variety of experimental data and discussing it in the framework of existing theoretical models, both scientific and technological challenges of this rapidly developing field of liquid crystal nanoscience are identified. They can be broadly categorized into the following groups: (i) the control of the size, shape, and the ferroelectricity of nanoparticles; (ii) the production of a stable and aggregate-free dispersion of relatively small (~10 nm) ferroelectric nanoparticles in liquid crystals; (iii) the selection of liquid crystal materials the most suitable for the dispersion of nanoparticles; (iv) the choice of appropriate experimental procedures and control measurements to characterize liquid crystals doped with ferroelectric nanoparticles; and (v) the development and/or modification of theoretical and computational models to account for the complexity of the system under study. Possible ways to overcome the identified challenges along with future research directions are also discussed.

  7. Ferroelectric Nanoparticles in Liquid Crystals: Recent Progress and Current Challenges

    Directory of Open Access Journals (Sweden)

    Yuriy Garbovskiy

    2017-11-01

    Full Text Available The dispersion of ferroelectric nanomaterials in liquid crystals has recently emerged as a promising way for the design of advanced and tunable electro-optical materials. The goal of this paper is a broad overview of the current technology, basic physical properties, and applications of ferroelectric nanoparticle/liquid crystal colloids. By compiling a great variety of experimental data and discussing it in the framework of existing theoretical models, both scientific and technological challenges of this rapidly developing field of liquid crystal nanoscience are identified. They can be broadly categorized into the following groups: (i the control of the size, shape, and the ferroelectricity of nanoparticles; (ii the production of a stable and aggregate-free dispersion of relatively small (~10 nm ferroelectric nanoparticles in liquid crystals; (iii the selection of liquid crystal materials the most suitable for the dispersion of nanoparticles; (iv the choice of appropriate experimental procedures and control measurements to characterize liquid crystals doped with ferroelectric nanoparticles; and (v the development and/or modification of theoretical and computational models to account for the complexity of the system under study. Possible ways to overcome the identified challenges along with future research directions are also discussed.

  8. Stabilization of the NOP ferroelectric phase in potassium nitrate–barium titanate ferroelectric composites

    Directory of Open Access Journals (Sweden)

    Olga A. Alekseeva

    2017-10-01

    Full Text Available The study of temperature evolution of KNO3 (NOP structure in ferroelectric (1−xKNO3 + (xBaTiO3 composites with BaTiO3 concentrations х = 0.25, 0.50 and 0.53 has been carried out on cooling with the use of the neutron diffraction technique. It was shown that, on cooling, the phase transition temperature (Tc from the high-temperature paraelectric phase into the ferroelectric one did not depend on barium titanate concentration and practically coincided with Tc for pure NOP. Moreover, it was found that the admixture of BaTiO3 essentially enlarged the temperature range of NOP ferroelectric phase stability in the composites with BaTiO3 concentrations x = 0.25 and 0.50. The suppression of the ferroelectric phase was observed for the composite with x = 0.53.

  9. Ferroelectricity, SSFLC, bistability and all that

    OpenAIRE

    Dahl, Ingolf

    2002-01-01

    In the book "Ferroelectric and Antiferroelectric Liquid Crystals" by S. T. Lagerwall, the concept "polar liquid crystals" is proposed for the concept earlier known as "ferroelectric liquid crystals", reserving the word "ferroelectric liquid crystals" for the case of "surface stabilization". Thus Lagerwall in this way, by redefinition, becomes the coinventor of "ferroelectric liquid crystals". The trouble is that a closer look on the invention reveals a state of bad logic and a total confusion...

  10. Bidimensional distortion in ferroelectric liquid crystals with strong ...

    Indian Academy of Sciences (India)

    2015-11-27

    Nov 27, 2015 ... In the last decade, it has been experimentally found that in certain conditions a periodic domain pattern arises in ferroelectric liquid crystals (FLC) in bookshelf geometry. Such a periodic texture appears after switching-off an external electric field, even in strong anchoring conditions. It has a static character ...

  11. A colloid of ferroelectric nanoparticles in a cholesteric liquid crystal

    Science.gov (United States)

    Kurochkin, O.; Buchnev, O.; Iljin, A.; Park, S. K.; Kwon, S. B.; Grabar, O.; Reznikov, Yu

    2009-02-01

    The introduction of a minor quantity of ferroelectric nanoparticles into a cholesteric mixture causes a 45% decrease of the driving voltage with both the optical cell quality and the director field in the cell remaining undisturbed. The drop of the driving voltage results from a more than twofold increase of the effective dielectric anisotropy of the nematic matrix, which is the basic component of the cholesteric compound. The results reported clearly show how promising the ferroelectric liquid crystalline (LC) nanocolloids are for various applications. In particular, they offer a unique way for an effective tuning of the dielectric, optical and electro-optic properties of LC materials in a non-synthetic way that is a new direction for the development of advanced anisotropic meso-materials. We suggest that the strong impact of ferroelectric nanoparticles on the properties of the studied chiral nematics is due to the particle's permanent polarization, which produces a giant electric field around it.

  12. Soft memory in a ferroelectric nanoparticle-doped liquid crystal

    Science.gov (United States)

    Basu, Rajratan

    2014-02-01

    A small quantity of BaTiO3 ferroelectric nanoparticles (FNP) was doped in a liquid crystal (LC), and the LC + FNP hybrid was found to exhibit a nonvolatile electromechanical memory effect in the isotropic phase. The permanent dipole moment of the FNPs causes the LC molecule to form short-range pseudonematic domains surrounding the FNPs. The FNP-induced short-range orders become more prominent in the isotropic phase when the global nematic order is absent. These short-range domains, being anisotropic in nature, interact with an external electric field, exhibiting a Fréedericksz-type transition. When the field is turned off, these domains stay oriented, showing a hysteresis effect due to the absence of any long-range order and restoring forces in the isotropic phase. The hysteresis graph for this memory effect shows a significant pretransitional behavior on approaching the nematic phase from the isotropic phase.

  13. Dynamic mechanism of the ferroelectric to antiferroelectric phase transition in chiral smectic liquid crystals

    OpenAIRE

    VIJ, JAGDISH; Fukuda, Atsuo; SONG, JANG-KUN

    2008-01-01

    PUBLISHED We report on the observation of V-shaped switching in a ferroelectric liquid crystal cell over a wide range of temperatures. Results of the optical transmittance in the visible region give us the helical pitch for various temperatures of the ferroelectric liquid crystalline compound used. We show that the helical pitch, in addition to the spontaneous polarization (PS) and thickness of the alignment layer of the cell, is an important factor in giving V-shaped switching. A longer o...

  14. A comparison between size dependent paraelectric and ferroelectric BaTiO3 nanoparticle doped nematic and ferroelectric liquid crystals

    Science.gov (United States)

    Al-Zangana, S.; Turner, M.; Dierking, I.

    2017-02-01

    The electro-optic and dielectric properties of barium titanate, BaTiO3, and nanoparticle (NP) doped nematic and ferroelectric liquid crystal materials were examined with respect to different size and concentrations of the NPs. Smaller size paraelectric NPs (≈80 nm) are compared to larger, ferroelectric NPs (≈240 nm). It is found that for concentrations larger than 0.5 vol. %, the ferroelectric NPs exhibit an increasing effect on the electro-optic response of the nematic liquid crystal, which is demonstrated by the enhancement of the dielectric anisotropy. This could be induced by the coupling of the electrical dipole moments in the spherical NPs with the LC director field. The electro-optical properties of the SmC* phase, such as the tilt angle Θ, switching time τ s , and spontaneous polarisation P s , are found to be independent of the concentration and size of the NPs. The rotational viscosity η calculated from response times, polarization reversal current, and dielectric properties is comparable for all three methods employed and practically independent of particle concentration and size. The relaxation frequency f R of the Goldstone mode is higher in the ferroelectric NPs suspensions of 2.0 vol. % as compared to the smaller paraelectric NPs.

  15. High-optical-quality ferroelectric film wet-processed from a ferroelectric columnar liquid crystal as observed by non-linear-optical microscopy.

    Science.gov (United States)

    Araoka, Fumito; Masuko, Shiori; Kogure, Akinori; Miyajima, Daigo; Aida, Takuzo; Takezoe, Hideo

    2013-08-07

    The self-organization of ferroelectric columnar liquid crystals (FCLCs) is demonstrated. Columnar order is spontaneously formed in thin films made by the wet-process due to its liquid crystallinity. Electric-field application results in high optical quality and uniform spontaneous polarization. Such good processability and controllability of the wet-processed FCLC films provide us with potential organic ferroelectric materials for device applications. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Ferroelectric domain formation in discotic liquid crystals: Monte Carlo study on the influence of boundary conditions

    Science.gov (United States)

    Bose, Tushar Kanti; Saha, Jayashree

    2015-10-01

    The realization of a spontaneous macroscopic ferroelectric order in fluids of anisotropic mesogens is a topic of both fundamental and technological interest. Recently we demonstrated that a system of dipolar achiral disklike ellipsoids can exhibit long-searched ferroelectric liquid crystalline phases of dipolar origin. In the present work, extensive off-lattice Monte Carlo simulations are used to investigate the phase behavior of the system under the influences of the electrostatic boundary conditions that restrict any global polarization. We find that the system develops strongly ferroelectric slablike domains periodically arranged in an antiferroelectric fashion. Exploring the phase behavior at different dipole strengths, we find existence of the ferroelectric nematic and ferroelectric columnar order inside the domains. For higher dipole strengths, a biaxial phase is also obtained with a similar periodic array of ferroelectric slabs of antiparallel polarizations. We have studied the depolarizing effects by using both the Ewald summation and the spherical cutoff techniques. We present and compare the results of the two different approaches of considering the depolarizing effects in this anisotropic system. It is explicitly shown that the domain size increases with the system size as a result of considering a longer range of dipolar interactions. The system exhibits pronounced system size effects for stronger dipolar interactions. The results provide strong evidence to the novel understanding that the dipolar interactions are indeed sufficient to produce long-range ferroelectric order in anisotropic fluids.

  17. Market liquidity and financial stability.

    OpenAIRE

    Crockett, A.

    2008-01-01

    Stability in financial institutions and in financial markets are closely intertwined. Banks and other financial institutions need liquid markets through which to conduct risk management. And markets need the back-up liquidity lines provided by financial institutions. Market liquidity depends not only on objective, exogenous factors, but also on endogenous market dynamics. Central banks responsible for systemic stability need to consider how far their traditional responsibility for the health ...

  18. Ferroelectric BaTiO3 and LiNbO3 Nanoparticles Dispersed in Ferroelectric Liquid Crystal Mixtures: Electrooptic and Dielectric (Postprint)

    Science.gov (United States)

    2016-10-14

    very high spontaneous polarization (Ps). The electrooptic and dielectric parameters were documented . The dipoles of ferroelectric nanoparticles and those... gestions for applying FLCs in fast moving devices have been described, but even for FLCs there is a need for improving relevant properties. For instance...nanoparticles dispersed in both Nematic and Ferroelectric Liquid Crystals. Fascinat- ing results were documented in [5]. Nano dopants used are from

  19. Stabilization of ferroelectric properties in Hafnia and Zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Kersch, Alfred [Univ. of Applied Sciences Munich (Germany). Modeling and Simulation Lab

    2016-11-01

    Experiments by our collaborators show that not only earth alkaline metals but also lanthanides and boron group metals are capable of inducing ferroelectric behavior in Hafnia. These dopants are known to form more complex defect structures due to their 3-valent nature. This requires further simulation. In some cases computationally more expensive density functionals will be required.

  20. Effects of graphene on electro-optic switching and spontaneous polarization of a ferroelectric liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Basu, Rajratan, E-mail: basu@usna.edu [Department of Physics, Soft-matter and Nanomaterials Laboratory, The United States Naval Academy, Annapolis, Maryland 21402 (United States)

    2014-09-15

    A small quantity of graphene flakes was doped in a ferroelectric liquid crystal (FLC), and the field-induced ferroelectric electro-optic switching was found to be significantly faster in the FLC + graphene hybrid than that of the pure FLC. Further studies revealed that the suspended graphene flakes enhanced the FLC's spontaneous polarization by improving smectic-C ordering resulting from the π–π electron stacking, and reduced rotation viscosity by trapping some of the free ions of the FLC media. These effects coherently impacted the FLC-switching phenomenon, enabling the FLC molecules to switch faster on reversing an external electric field.

  1. Increased lateral dipole moment in the core region of potential ferroelectric liquid crystal molecules

    Science.gov (United States)

    Tiemann, Bruce G.

    2000-10-01

    Visual displays, unlike audio systems, fall far short of human limits: orders of magnitude in information content separate what can be seen from what can be displayed. One technology employed for next-generation high-performance displays uses ferroelectric liquid crystals (FLCs), whose switching speed depends in part on the ferroelectric polarization of the active material, which itself arises from the lateral dipole moment of the constituent molecules. Several series of molecules based on the 2,3-dinitrophenyl moiety, which has a high lateral dipole moment, was conceived and prepared. Most of the new molecules did not exhibit any liquid crystal phases, but those that did had high polarization as expected. One such molecule, 2,3-Dinitro-4-(R)-(2-octyloxy)phenyl 4'-decyloxy-4-biphenylcarboxylate, had a polarization density of over 500 nC/cm2. Compounds with other core geometries, including phenyls, phenyl benzoates, biphenyls, and terphenyls, were prepared but failed to exhibit liquid crystal phases.

  2. Binary mixtures of hydrogen-bonded ferroelectric liquid crystals. Thermal span enhancement in smectic X* phase

    Energy Technology Data Exchange (ETDEWEB)

    Sangameswari, Gopal; Prabu, Nataraj Pongali Sathya; Madhu Mohan, Mathukumalli Lakshmi Narayana [Bannari Amman Institute of Technology, Sathyamangalam (India). Liquid Crystal Research Laboratory (LCRL)

    2015-07-01

    Thermotropic hydrogen-bonded ferroelectric binary liquid crystal mixtures comprising of N-carbamyl-l-glutamic acid (CGA) and p-n-alkyloxy benzoic acids (BAO) are investigated. Variation in the molar proportion of X and Y (where X=CGA+5BAO and Y=CGA+9BAO, CGA+10BAO, CGA+11BAO, and CGA+12BAO) comprising of four series yielded 36 binary mixtures. Optical and thermal properties of these mixtures are meticulously studied in the present article. In addition to the traditional phases, a novel smectic ordering namely smectic X* is observed in all the four series. The aim of the investigation is to obtain abundance occurrence of smectic X* with a large thermal span, and hence, the proportions of the binary mixtures are so chosen that the prelude task is accomplished. Optical tilt angle in smectic X* and smectic C* phases is experimentally determined, and a theoretical fit is performed. Phase diagrams of the four series are constructed from the data obtained from the differential scanning calorimetry and correlated with the phases recorded by the polarising optical microscope studies. Thermal stability factor and thermal equilibrium are also premeditated.

  3. Discriminator Stabilized Superconductor/Ferroelectric Thin Film Local Oscillator

    Science.gov (United States)

    Romanofsky, Robert R. (Inventor); Miranda, Felix A. (Inventor)

    2000-01-01

    A tunable local oscillator with a tunable circuit that includes a resonator and a transistor as an active element for oscillation. Tuning of the circuit is achieved with an externally applied dc bias across coupled lines on the resonator. Preferably the resonator is a high temperature superconductor microstrip ring resonator with integral coupled lines formed over a thin film ferroelectric material. A directional coupler samples the output of the oscillator which is fed into a diplexer for determining whether the oscillator is performing at a desired frequency. The high-pass and lowpass outputs of the diplexer are connected to diodes respectively for inputting the sampled signals into a differential operational amplifier. The amplifier compares the sampled signals and emits an output signal if there is a difference between the resonant and crossover frequencies. Based on the sampled signal, a bias supplied to the ring resonator is either increased or decreased for raising or lowering the resonant frequency by decreasing or increasing, respectively, the dielectric constant of the ferroelectric.

  4. Electrically controlled phases of partially polarized light and orientational Kerr effect in liquid crystal ferroelectrics

    Directory of Open Access Journals (Sweden)

    Kiselev Alexei D.

    2017-01-01

    Full Text Available We study the electro-optic properties of subwavelength-pitch deformed-helix ferroelectric liquid crystals illuminated with partially polarized light. In an experimental setup based on the Mach-Zehnder interferometer, it is found that the interference pattern crucially depends on the degree of polarization of the incident light. We evaluate the electric field dependence of both the Pancharatnam relative phase and the geometric phase for the general case of nonunitarily evolving mixed polarization states.

  5. Speckle noise suppression using a helix-free ferroelectric liquid crystal cell

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, A L; Andreeva, T B; Kompanets, I N [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Zalyapin, N V [National Research Nuclear University ' ' MEPhI' ' (Russian Federation)

    2014-12-31

    We have studied the method for suppressing speckle noise in patterns produced by a laser based on a fast-response electro-optical cell with a ferroelectric liquid crystal (FLC) in which helicoid is absent, i.e., compensated for. The character of smectic layer deformation in an electric field is considered along with the mechanism of spatially inhomogeneous phase modulation of a laser beam passing through the cell which is accompanied by the destruction of phase relations in the beam. Advantages of a helix-free FLC cell are pointed out as compared to helical crystal cells studied previously. (liquid crystal devices)

  6. Analog distorted helix ferroelectric liquid-crystal-on-silicon spatial light modulator

    Science.gov (United States)

    McKnight, Douglas J.; Johnson, Kristina M.; Follett, Mark A.

    1995-03-01

    We report what are to our knowledge the first results from a liquid-crystal-on-silicon spatial light modulator that uses the distorted helix ferroelectric mode to perform analog light modulation. The spatial light modulator is an electronically addressed analog 128 \\times 128 pixel device with which we have demonstrated 16 gray levels and contrast ratios of 33:1 in the zeroth diffracted order and 6:1 when imaged. The liquid-crystal switching speed in this device is \\approximately 235 mu s, which when added to the data load time of 100 mu s gives a maximum frame rate of \\approximately 3 kHz.

  7. Optical switching of a metal-clad waveguide with a ferroelectric liquid crystal.

    Science.gov (United States)

    Mitsuishi, M; Ito, S; Yamamoto, M; Fischer, T; Knoll, W

    1997-12-10

    Optical switching based on waveguide optics with a ferroelectric liquid crystal (FLC) is reported. The FLC cell was prepared as a prism coupler on which the liquid-crystal layer was sandwiched between two gold cladding layers. The role of the gold layer was examined, and the optimum thickness of the top gold layer for obtaining high contrast was determined by use of the Fresnel equation. Various optical modulations of reflectivity were predicted on the basis of theoretical calculation, taking into account the molecular reorientation of the FLC, and examined at an appropriate angle of incidence and rotational angle of the FLC cell with respect to the plane of incidence.

  8. Supramolecular ferroelectrics.

    Science.gov (United States)

    Tayi, Alok S; Kaeser, Adrien; Matsumoto, Michio; Aida, Takuzo; Stupp, Samuel I

    2015-04-01

    Supramolecular chemistry uses non-covalent interactions to coax molecules into forming ordered assemblies. The construction of ordered materials with these reversible bonds has led to dramatic innovations in organic electronics, polymer science and biomaterials. Here, we review how supramolecular strategies can advance the burgeoning field of organic ferroelectricity. Ferroelectrics - materials with a spontaneous and electrically reversible polarization - are touted for use in non-volatile computer memories, sensors and optics. Historically, this physical phenomenon has been studied in inorganic materials, although some organic examples are known and strong interest exists to extend the search for ferroelectric molecular systems. Other undiscovered applications outside this regime could also emerge. We describe the key features necessary for molecular and supramolecular dipoles in organic ferroelectrics and their incorporation into ordered systems, such as porous frameworks and liquid crystals. The goal of this Review is to motivate the development of innovative supramolecular ferroelectrics that exceed the performance and usefulness of known systems.

  9. Effects of ferroelectric nanoparticles on ion-transport in a liquid crystal

    Science.gov (United States)

    Garvey, Alfred; Basu, Rajratan

    2015-03-01

    A small quantity of BaTiO3 ferroelectric nanoparticles (FNPs) of 50 nm diameter was doped in a nematic liquid crystal (LC), and the free ion concentration was found to be significantly reduced in the LC +FNP hybrid compared to that of the pure LC. The strong electric fields, due to the permanent dipole moment of the FNPs, trapped some mobile ions, reducing the free ion concentration in the LC media. The reduction of free ions was found to have coherent impacts on the LC's conductivity, rotational viscosity, and electric field-induced nematic switching.

  10. Pressure dependence of the electro-optic response function in partially exposed polymer dispersed ferroelectric liquid crystals

    Science.gov (United States)

    Parmar, D. S.; Holmes, H. K.

    1993-01-01

    Ferroelectric liquid crystals in a new configuration, termed partially exposed polymer dispersed ferroelectric liquid crystal (PEPDFLC), respond to external pressures and demonstrate pressure-induced electro-optic switching response. When the PEPDFLC thin film is sandwiched between two transparent conducting electrodes, one a glass plate and the other a flexible sheet such as polyvenylidene fluoride, the switching characteristics of the thin film are a function of the pressure applied to the flexible transparent electrode and the bias voltage across the electrodes. Response time measurements reveal a linear dependence of the change in electric field with external pressure.

  11. Snapshot Mueller matrix polarimetry by wavelength polarization coding and application to the study of switching dynamics in a ferroelectric liquid crystal cell.

    Directory of Open Access Journals (Sweden)

    Le Jeune B.

    2010-06-01

    Full Text Available This paper describes a snapshot Mueller matrix polarimeter by wavelength polarization coding. This device is aimed at encoding polarization states in the spectral domain through use of a broadband source and high-order retarders. This allows one to measure a full Mueller matrix from a single spectrum whose acquisition time only depends on the detection system aperture. The theoretical fundamentals of this technique are developed prior to validation by experiments. The setup calibration is described as well as optimization and stabilization procedures. Then, it is used to study, by time-resolved Mueller matrix polarimetry, the switching dynamics in a ferroelectric liquid crystal cell.

  12. Stabilization of ferroelectric phase in tungsten capped Hf0.8Zr0.2O2

    Science.gov (United States)

    Karbasian, Golnaz; dos Reis, Roberto; Yadav, Ajay K.; Tan, Ava J.; Hu, Chenming; Salahuddin, Sayeef

    2017-07-01

    We report on the stabilization of the ferroelectric phase in Hf0.8Zr0.2O2 with a tungsten capping layer. Ferroelectricity is obtained in both metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) capacitors with highly-doped Si serving as the bottom electrode in the MIS structure. Ferroelectricity is confirmed from both the electrical polarization-voltage (P-V) measurement and X-Ray Diffraction analysis that shows the presence of an orthorhombic phase. High-resolution Transmission Electron Microscopy and Energy Dispersive X-ray spectroscopy show minimal diffusion of W into the underlying Hf0.8Zr0.2O2 after the crystallization anneal. This is in contrast to significant Ti and N diffusion observed in ferroelectric HfxZr1-xO2 commonly capped with TiN.

  13. Light amplification by photorefractive ferroelectric liquid crystal blends containing quarter-thiophene photoconductive chiral dopant

    Science.gov (United States)

    Sasaki, T.; Hara, T.; Yamamoto, Y.; Naka, Y.; Le, K. V.

    2017-05-01

    The photorefractive effect is a phenomenon that forms a rewritable hologram in a material. This phenomenon can be utilized in devices including 3D displays, optical tomography, novelty filters, phase conjugate wave generators, and optical amplification. Ferroelectric liquid crystal blends composed of a smectic liquid crystalline mixture, a photoconductive chiral dopant, and an electron trap reagent exhibit significant photorefractivity together with rapid responses. As such, they allow the dynamic amplification of moving optical signals. The photoconductive chiral dopants used in the previous study are ter-thiphene derivatives so that the photorefractive effect was examined at 488 nm. In the present work, chiral dopants possessing quarter-thiphene chromophore were synthesized and the photorefractive effect of the FLC blends at longer wavelength was demonstrated.

  14. Formulation of a room temperature ferroelectric liquid crystal mixture with sub-millisecond switching time

    Science.gov (United States)

    Debnath, A.; Sinha, D.; Mandal, P. K.; Dabrowski, R.

    2015-06-01

    Ferroelectric liquid crystal (FLC) based display devices show faster response compared to nematic LC based devices. Since pure FLC compounds are high temperature LCs and do not possess optimum parameters necessary for display devices, a room temperature FLC mixture has been formulated, first time by any Indian group. The mixture is prepared by doping an appropriate chiral compound in a four-component LC based achiral host mixture. Resulting mixture was characterized using optical polarizing microscopy, frequency domain dielectric spectroscopy and electro-optic methods. It shows very wide range ferroelectric SmC* phase followed by paraelectric SmA* phase (Crbook shelf geometry alignment in display devices. Dielectric spectroscopy study reveals Goldstone (in kHz region) and soft mode (in hundred kHz region) relaxations in SmC* and SmA* phases respectively. The mixture possesses moderate tilt angle (34.5° - 13°), low viscosity (0.9 - 0.05 N.s.m-2) and moderately high spontaneous polarization (112 - 36 nC.cm-2) which decrease with temperature. These result in very fast switching, slowest response time being 475 µs at ambient temperature.

  15. Liquidity Constraints and Fiscal Stabilization Policy

    DEFF Research Database (Denmark)

    Kristoffersen, Mark Strøm

    It is often claimed that the presence of liquidity constrained households enhances the need for and the effects of fi…scal stabilization policies. This paper studies this in a model of a small open economy with liquidity constrained households. The results show that the consequences of liquidity...

  16. Electromechanical memory effect in a ferroelectric nanoparticle-suspended liquid crystal

    Science.gov (United States)

    Basu, Rajratan

    2014-03-01

    A small quantity of BaTiO3 ferroelectric nanoparticles (FNP) was doped in a liquid crystal (LC), and the LC +FNP hybrid was found to exhibit an electromechanical memory effect in the isotropic phase. The permanent dipole moment of the FNPs causes the LC molecule to form short-range order surrounding the FNPs. This FNP-induced short-range order becomes more prominent in the isotropic phase when the global nematic order is absent. These short-range domains, being anisotropic in nature, interact with the external electric field. When the field goes off, these domains stay oriented due to the absence of the long range order in the isotropic phase, showing a hysteresis effect. The area under the hysteresis graph shows a significant pretransitional behavior on approaching the nematic phase from the isotropic phase.

  17. Exploring nanoscale fluctuations and ferroelectric phase stabilization in S doped PbTe thermoelectrics

    Science.gov (United States)

    Knox, Kevin; Bozin, Emil; Malliakas, Christos; Kanatzidis, Mercouri; Billinge, Simon

    2013-03-01

    PbTe is one of the most important commercial thermoelectric materials for applications above room temperature. A paraelectric phase of fluctuating ferroelectric-like Pb structural dipoles emerges in PbTe at elevated temperatures, although it adopts an average rock-salt structure at all temperatures. These intrinsic nanoscale fluctuations are believed to improve the thermoelectric properties of PbTe by limiting the lattice thermal conductivity. Additionally, alloying and chemical substitution in PbTe appreciably improve the thermoelectric figure of merit, as is the case in PbTe1-xSx. However, the exact mechanism for this enhancement is not well understood. It has been shown that PbTe1-xSx exhibits a peak in resistivity at a doping dependent temperature. By analogy with Ge doped PbTe, this anomalous resistivity may be the signature of a ferroelectric phase stabilization. In this talk, we explore this possibility by characterizing the average and the local structure of PbTe1-xSx as a function of temperature and doping using a neutron based atomic pair distribution function (PDF) approach.

  18. Novel biphenyl-substituted 1,2,4-oxadiazole ferroelectric liquid crystals: synthesis and characterization

    Directory of Open Access Journals (Sweden)

    Mahabaleshwara Subrao

    2015-02-01

    Full Text Available Two novel series of unsymmetrically substituted 1,2,4-oxadiazole viz., R.Ox.C*Cn compounds are synthesized and characterized. An optically active, (S-(+-methyl 3-hydroxy-2-methylpropionate is used to introduce a chiral center in the molecule. A biphenyl moiety prepared by Suzuki coupling reaction is directly attached to the oxadiazole core at C-5 position. Investigations for the phase behavior revealed that the series with a benzyl group on one end of the oxadiazole core exhibits an 1D orthogonal smectic-A phase while the second series with dodecyl flexible end chain shows orthogonal smectic-A and tilted chiral smectic-C (SmC* phases over a wide range of temperatures. The smectic-C phase exhibits ferroelectric (FE polarization switching. The mesomorphic thermal stabilities of these compounds are discussed in the domain of the symmetry and the flexibility of the alkyloxy end chain length attached to the chiral center.

  19. Stabilization of supported liquid membranes

    NARCIS (Netherlands)

    Kemperman, Antonius Josephus Bernardus

    1995-01-01

    Membrane processes provide a relatively new and economically attractive separation technique. One type of membrane processes, i.e. the use of facilitated transport in liquid membranes, is particularly attractive. Compared to other membrane processes, liquid membranes show high selectivities, high

  20. Ferroelectric and structural characterization of alkali niobate piezoceramics derived from a citrate liquid precursor

    Energy Technology Data Exchange (ETDEWEB)

    Kakimoto, Kenichi; Nguyen, Lien Thikim; Hayakawa, Yusuke; Shinkai, Yuya; Kagomiya, Isao [Nagoya Institute of Technology, Nagoya (Japan)

    2011-09-15

    Preparation of alkali-niobate ceramic powders of KNbO{sub 3}, (Na,K)NbO{sub 3}, and (Li,Na,K)NbO{sub 3} has been carried out by using a citrate-based liquid precursor route that was a newly developed innovative wet powder processing technique. The derived powders showed a well-sinterable property, and the sintered ceramics demonstrated excellent ferroelectric property. Orthorhombic KNbO{sub 3} showed a remanent polarization (P{sub r}) of 23.3 {mu}C/cm{sup 2} and a coercive field (E{sub c}) of 7.8 kV/cm, and (Na,K)NbO{sub 3} showed a Pr of 31.4 {mu}C/cm{sup 2} and a E{sub c} of 17.3 kV/cm. On the other hand, tetragonal (Li,Na,K)NbO{sub 3} demonstrated a Pr of 19.0 {mu}C/cm{sup 2} and a E{sub c} of 13.6 kV/cm. The citrate liquid precursor route demonstrated a good potential for the synthesis of fine powders suitable for lead-free alkali-niobate ceramics.

  1. Dynamic behaviour of a ferro-electric liquid crystal by means of nuclear magnetic resonance and dielectric spectroscopy

    Science.gov (United States)

    Domenici, Valentina; Marini, Alberto; Menicagli, Rita; Veracini, Carlo Alberto; Bubnov, Aleksej M.; Glogarova, Milada

    2007-05-01

    The field of ferroelectric liquid crystals (FLCs) is one of the most fascinating aspects of the Science of Materials for their interesting electro-optic applications. Among different chemical and physical properties those related to the molecular dynamics are very stimulating due to the relationship between molecular motions and macroscopic response to external fields, such as electric and magnetic ones. In this work, the molecular dynamics of a ferroelectric smectogen, namely the (S)-2-methylbutyl-[4'-(4"-heptyloxyphenyl)-benzoyl-4-oxy-(S)-2-((S)-2')-benzoyl)-propionyl)]-propionate (ZLL 7/*) has been investigated by means of 2H NMR and dielectric relaxation techniques. The first method allows us to get information on the molecular motions in the fast motion regime, in particular the diffusion reorientational motions of the whole molecule, as well as of the internal motions affecting the phenyl and biphenyl fragments. The second technique, which covers the slow motion regime, has been used to detect collective motions and fluctuation modes. This study allows us to have a complete idea of molecular motions in the different smectic phases formed by the ZLL 7/* mesogens, in particular the paraelectric smectic A (SmA), the ferroelectric smectic C* (SmC*), the antiferroelectric smectic C* A (SmC* A) and the re-entrant ferroelectric smectic C* (SmC* r) phases. This last phase has been investigated for the first time in this work, from the point of view of the dynamic behaviour. All results will be discussed in the framework of the molecular dynamics of ferroelectric liquid crystals, reported in the literature so far.

  2. Temperature-induced sign reversal of biaxiality observed by conoscopy in some ferroelectric Sm- C* liquid crystals

    OpenAIRE

    Fukuda, Atsuo; VIJ, JAGDISH KUMAR

    2007-01-01

    PUBLISHED Article number 011709 We have studied various ferroelectric liquid crystals to find the average molecular direction of the shortest axis in the perfectly unwound state by using tilted conoscopic measurements. We find that there exist two types of temperature dependencies of the biaxiality. Some materials exhibit increasing biaxiality while others show decreasing biaxiality with increasing temperature. The former shows a temperature-induced sign reversal of biaxiality. Three di...

  3. Phase diagram of polar states in doped ferroelectric systems

    Science.gov (United States)

    Wang, Dong; Ke, Xiaoqin; Wang, Yunzhi; Gao, Jinghui; Wang, Yu; Zhang, Lixue; Yang, Sen; Ren, Xiaobing

    2012-08-01

    We report a complete phase diagram that describes the relationships among all polar states in doped ferroelectrics, including the paraelectric (polar liquid), ferroelectric (polar crystal), relaxor (polar glass), and precursory states (partially frozen nanopolar domains). We employ a model that considers a randomly distributed local polarization field associated with point defects, which breaks the symmetry of the Landau free energy with respect to polarization. In the meantime, the model also takes into account the effect of point defects on the overall stability of the ferroelectric phase. Based on this model, the phase field simulations reproduce all the polar states and important characteristics associated with ferroelectric-glass (relaxor) transition observed in experiments, including rugged free energy, wide relaxation time, nanosized ferroelectric domain structure, “diffuse” transition, temperature dependence of third-order dielectric susceptibility, nonergodicity, frequency dependence of dielectric loss, and domain switching.

  4. Synthetic strategy of porous ZnO and CdS nanostructures doped ferroelectric liquid crystal and its optical behavior

    Science.gov (United States)

    Pal, Kaushik; Maiti, Uday Narayan; Majumder, Tapas Pal; Debnath, Subhas Chandra; Bennis, Noureddine; Otón, Jose Manuel

    2013-03-01

    A simple and scalable chemical approach has been proposed for the generation of 1-dimensional nanostructures of two most important inorganic materials such as zinc oxide and cadmium sulfide. By controlling the growth habit of the nanostructures with manipulated reaction conditions, the diameter and uniformity of the nanowires/nanorods were tailored. We studied extensively optical behavior and structural growth of CdS NWs and ZnO NRs doped ferroelectric liquid crystal Felix-017/100. Due to doping band gap has been changed and several blue shifts occurred in photoluminescence spectra because of nanoconfinement effect and mobility of charges.

  5. Effect of Viscosity on Liquid Curtain Stability

    Science.gov (United States)

    Mohammad Karim, Alireza; Suszynski, Wieslaw; Francis, Lorraine; Carvalho, Marcio; Dow Chemical Company Collaboration; PUC Rio Collaboration; University of Minnesota, Twin Cities Collaboration

    2016-11-01

    The effect of viscosity on the stability of Newtonian liquid curtains was explored by high-speed visualization. Glycerol/water solutions with viscosity ranging from 19.1 to 210 mPa.s were used as coating liquids. The experimental set-up used a slide die delivery and steel tube edge guides. The velocity along curtain at different positions was measured by tracking small particles at different flow conditions. The measurements revealed that away from edge guides, velocity is well described by free fall effect. However, close to edge guides, liquid moves slower, revealing formation of a viscous boundary layer. The size of boundary layer and velocity near edge guides are strong function of viscosity. The critical condition was determined by examining flow rate below which curtain broke. Curtain failure was initiated by growth of a hole within liquid curtain, close to edge guides. Visualization results showed that the hole forms in a circular shape then becomes elliptical as it grows faster in vertical direction compared to horizontal direction. As viscosity rises, minimum flow rate for destabilization of curtain increased, indicating connection between interaction with edge guides and curtain stability. We would like to acknowledge the financial support from the Dow Chemical Company.

  6. Ferroelectric liquid crystals from bent-core molecules with vinyl end groups

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Soon Sik; Kim, Tae Sung; Lee, Chong Kwang [Gyeongsang National Univ., Jinju (Korea, Republic of); Shin, Sung Tae; Oh, Lee Tack [Korea Univ., Seochang (Korea, Republic of); Choi, E Joon; Kim, Sea Yun [Kumho National University of technology, Gumi (Korea, Republic of); Chien, Liang Chy [Kent State Univ., Kent (United States)

    2003-03-01

    New banana-shaped achiral compounds, 1, 3-phenylene bis (4-(4-(alkenyloxy)phenyliminomethyl)benzoate)s were synthesized by varying the length of alkenyl group; their ferroelectric properties are described. The smectic mesophase, including a switchable chiral smecitc C(Sm C)phase,were characterized by differential scanning calorimetry, polarizing optical microscopy and triangular wave method. The presence of vinyl groups at the terminals of linear side wings in the banana-shaped achiral molecules containing Schiff's base mesogen induced a decrease in melting temperature and formation of the switchable Sm C phase in the melt. The smecitc phases having the octenyloxy group such as (CH{sub 2}){sub 6}CH=CH{sub 2} showed ferroelectric switching , and their values of spontaneous polarization on reversal of an applied electric field were 120 nC/cm{sup 2} (X=H) and 225 nC/cm{sup 2} (X=F), respectively. We could obtain ferroelectric phases by controlling the number of carbon atom in alkenyloxy chain of a bent-core molecule.

  7. Exfoliation of graphene oxide and its application in improving the electro-optical response of ferroelectric liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Veeresh [CSIR-National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110012 (India); Department of Physics, Indian Institute of Technology, New Delhi 110016 (India); Kumar, Ajay [Department of Physics, Deshbandhu College, University of Delhi, Delhi 110019 (India); Bhandari, Shruti; Biradar, A. M.; Pasricha, Renu, E-mail: renup@ncbs.res.in, E-mail: renu1505@gmail.com [CSIR-National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110012 (India); Reddy, G. B. [Department of Physics, Indian Institute of Technology, New Delhi 110016 (India)

    2015-09-21

    Near complete exfoliation and reduction of lyophilized graphene oxide (GO) has been carried out at temperature as low as 400 °C. The structural characterizations of the reduced GO have been performed using X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy techniques. The morphological studies were carried out using scanning electron microscopy. The synthesized GO finds an application in improving the switching performance of a liquid crystal (LC) mixture by remarkably modifying the physical properties, such as spontaneous polarization and rotational viscosity of the ferroelectric LC (FLC) material which in turn resulted into faster response of the FLC. The present study explores the possibility of low temperature thermal reduction of GO along with its application in improving the properties of LC based display systems.

  8. The effect of barium titanate admixture on the stability of potassium nitrate ferroelectric phase in (1–xKNO3 + (xBaTiO3 composites

    Directory of Open Access Journals (Sweden)

    Olga A. Alekseeva

    2015-10-01

    Full Text Available The study of temperature evolution of the KNO3 structure in ferroelectric (1 – xKNO3 + (xBaTiO3 composites at х = 0.25 and 0.50 has been carried out on cooling and on heating using X-ray diffraction. It was shown that on cooling the phase transition temperature (Tc from the high-temperature paraelectric phase into the ferroelectric one did not depend on barium titanate concentration and practically coincided with Tc for the pure KNO3. Simultaneously the admixture of BaTiO3 essentially enlarged the temperature interval of the KNO3 ferroelectric phase stability in these composites. Structure refinement did not confirm the suppression of the ferroelectric phase of potassium nitrate proposed previously for (0.5KNO3 + (0.5BaTiO3 sample on the basis of dielectric spectroscopy data. The transition from the ferroelectric phase into the low-temperature paraelectric α-phase was not observed in this composite on cooling down to 348 K.

  9. The impact of charge compensated and uncompensated strontium defects on the stabilization of the ferroelectric phase in HfO2

    Science.gov (United States)

    Materlik, Robin; Künneth, Christopher; Mikolajick, Thomas; Kersch, Alfred

    2017-08-01

    Different dopants with their specific dopant concentration can be utilized to produce ferroelectric HfO2 thin films. In this work, it is explored for Sr in a comprehensive first-principles study. Density functional calculations reveal structure, formation energy, and total energy of the Sr related defects in HfO2. We found the charge compensated defect with an associated oxygen vacancy SrHfVO to strongly favour the non-ferroelectric, tetragonal P42/mnc phase energetically. In contrast, the uncompensated defect without oxygen vacancy SrHf favours the ferroelectric, orthorhombic Pca21 phase. According to the formation energy, the uncompensated defect can form easily under oxygen rich conditions in the production process. Low oxygen partial pressure existing over the lifetime promotes the loss of oxygen leading to VO, and thus, the destabilization of the ferroelectric, orthorhombic Pca21 phase is accompanied by an increase of the leakage current. This study attempts to fundamentally explain the stabilization of the ferroelectric, orthorhombic Pca21 phase by doping.

  10. Stabilization of Highly Polar BiFeO_{3}-like Structure: A New Interface Design Route for Enhanced Ferroelectricity in Artificial Perovskite Superlattices

    Directory of Open Access Journals (Sweden)

    Hongwei Wang

    2016-03-01

    Full Text Available In ABO_{3} perovskites, oxygen octahedron rotations are common structural distortions that can promote large ferroelectricity in BiFeO_{3} with an R3c structure [1] but suppress ferroelectricity in CaTiO_{3} with a Pbnm symmetry [2]. For many CaTiO_{3}-like perovskites, the BiFeO_{3} structure is a metastable phase. Here, we report the stabilization of the highly polar BiFeO_{3}-like phase of CaTiO_{3} in a BaTiO_{3}/CaTiO_{3} superlattice grown on a SrTiO_{3} substrate. The stabilization is realized by a reconstruction of oxygen octahedron rotations at the interface from the pattern of nonpolar bulk CaTiO_{3} to a different pattern that is characteristic of a BiFeO_{3} phase. The reconstruction is interpreted through a combination of amplitude-contrast sub-0.1-nm high-resolution transmission electron microscopy and first-principles theories of the structure, energetics, and polarization of the superlattice and its constituents. We further predict a number of new artificial ferroelectric materials demonstrating that nonpolar perovskites can be turned into ferroelectrics via this interface mechanism. Therefore, a large number of perovskites with the CaTiO_{3} structure type, which include many magnetic representatives, are now good candidates as novel highly polar multiferroic materials [3].

  11. Temperature independent low voltage polymer stabilized blue phase liquid crystals

    Science.gov (United States)

    Kemiklioglu, E.; Hwang, J. Y.; Chien, L.-C.

    2012-03-01

    Blue phases are types of liquid crystal phase which can appear in a narrow temperature range between a chiral nematic phase and isotropic liquid phase. Blue Phase (BP) liquid crystals have been known to exist in a small temperature range. Recently, broadening the temperature range of a BP liquid crystal has occurred by using a mixture of nematic bimesogenic liquid crystals or by polymerizing a small amount of monomer in a BP to stabilize the cubic lattice against temperature variation. In this study, we report a low switching voltage polymer stabilized blue phase (PSBP) liquid crystal device. We showed the stabilization of blue phases over a temperature range of 30.4 °C including room temperature. We observed the temperature independent of Bragg wavelength. Furthermore, the polymer effect on the electo-optic properties of a self assembled nanostructured blue phase liquid crystal composites have been investigated. As well as the ratio between two monomers, the overall monomers concentration is controlled.

  12. Nanomechanics of Ferroelectric Thin Films and Heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yulan; Hu, Shenyang Y.; Chen , L.Q.

    2016-08-31

    The focus of this chapter is to provide basic concepts of how external strains/stresses altering ferroelectric property of a material and how to evaluate quantitatively the effect of strains/stresses on phase stability, domain structure, and material ferroelectric properties using the phase-field method. The chapter starts from a brief introduction of ferroelectrics and the Landau-Devinshire description of ferroelectric transitions and ferroelectric phases in a homogeneous ferroelectric single crystal. Due to the fact that ferroelectric transitions involve crystal structure change and domain formation, strains and stresses can be produced inside of the material if a ferroelectric transition occurs and it is confined. These strains and stresses affect in turn the domain structure and material ferroelectric properties. Therefore, ferroelectrics and strains/stresses are coupled to each other. The ferroelectric-mechanical coupling can be used to engineer the material ferroelectric properties by designing the phase and structure. The followed section elucidates calculations of the strains/stresses and elastic energy in a thin film containing a single domain, twinned domains to complicated multidomains constrained by its underlying substrate. Furthermore, a phase field model for predicting ferroelectric stable phases and domain structure in a thin film is presented. Examples of using substrate constraint and temperature to obtain interested ferroelectric domain structures in BaTiO3 films are demonstrated b phase field simulations.

  13. Pico-ampere current sensitivity and CdSe quantum dots assembly assisted charge transport in ferroelectric liquid crystal

    Science.gov (United States)

    Pratap Singh, Dharmendra; Boussoualem, Yahia; Duponchel, Benoit; Sahraoui, Abdelhak Hadj; Kumar, Sandeep; Manohar, Rajiv; Daoudi, Abdelylah

    2017-08-01

    Octadecylamine capped CdSe quantum dots (QDs) dispersed 4-(1-methyl-heptyloxy)-benzoic acid 4‧-octyloxy-biphenyl-4-yl ester ferroelectric liquid crystal (FLC) were deposited over gold coated quartz substrate using dip-coating. The topographical investigation discloses that the homogeneously dispersed QDs adopt face-on to edge-on assembly in FLC matrix owing to their concentration. Current-voltage (I-V) measurement was performed using conductive atomic force microscopy (CAFM) which yields ohmic to critical diode like I-V curves depending upon the concentration of QDs in FLC. The recorded pico-ampere (pA) current sensitivity in FLC-QDs composites is attributed to micro-second drift time of electron due to weak electronic coupling between the π-electrons on the FLC and s-electrons on the metal surface. The observed pico-ampere sensitivity is the least current sensitivity recorded so far. For FLC-QDs composites, almost 24% faster electro-optic response was observed in comparison to pure FLC. The pico-ampere current sensitivity can be utilized in touch screen displays whereas the change in polarization for low applied electric field ameliorates the increased electrical susceptibility counteracting the internal electric field and its use in electronic data storage and faster electro-optical devices.

  14. Synthesis and Characterization of Ferroelectric Liquid Crystalline Organosiloxanes Containing 4-(4-undecanyloxy bi-phenyl-1-carboxyloxyphenyl (2S,3S-2-chloro-3-methylvalerate and 4-(4-undecanyloxybenzoyloxybiphenyl (2S,3S-2-chloro-3-methylvalerate

    Directory of Open Access Journals (Sweden)

    Chih-Hung Lin

    2013-10-01

    Full Text Available A series of new organosiloxane ferroelectric liquid crystalline (FLC materials have been synthesized, and their mesomorphic and physical properties have been characterized. Four new disiloxanes and trisiloxanes, containing biphenyl 4-hydroxybenzoate and phenyl 4-hydroxybiphenylcarboxylate as mesogenic units and eleven methylene unit as spacers and (2S,3S-2-chloro-3-methylvalerate unit as chiral end groups. The molecule, using three phenyl ring as a mesogenic unit, formulates much wider liquid crystalline phase temperature ranges than that of a two phenyl ring unit. The phenyl arrangement differences of mesogenic unit result in the greater differences of the liquid crystal phase formation. The siloxane molecule induction is helpful to the more regular smectic phase formation and smectic phase stabilization, such as chiral SC (SC* and SB phases. The siloxane molecule is helpful to reduce the phase transition temperature and broaden the liquid crystal temperature range of the SC* phase and, simultaneously, it will not induce chain crystallization phenomenon and dilute the Ps value. The synthesis and characterization of the new FLCs materials, which exhibit a room temperature SC* phase and higher spontaneous polarization are presented.

  15. Electrohydrodynamic stability of a plasma-liquid interface

    Science.gov (United States)

    Holgate, J. T.; Coppins, M.; Allen, J. E.

    2018-01-01

    Many plasma applications involve the plasma coming into contact with a liquid surface. Previous analyses of the stability of such liquid surfaces have neglected the presence of the sheath region between the bulk plasma and the liquid. Large electric fields, typically in excess of several MV m-1, and strong ion flows are present in this region. This paper considers a linear perturbation analysis of a liquid-sheath interface in order to find the marginal condition for instability. This condition shows that molten metal surfaces in tokamak edge plasmas are stable against the electric field, if a normal sheath is formed, due to the impact of ions on the surface. The stabilization of the liquid surface by ion bombardment is encouraging for the ongoing development of plasma-liquid technologies.

  16. Multi-responsive ionic liquid emulsions stabilized by microgels

    NARCIS (Netherlands)

    Monteillet, H.; Workamp, M.; Li, X.; Schuur, Boelo; Kleijn, J.M.; Leermakers, F.; Sprakel, J.

    2014-01-01

    We present a complete toolbox to use responsive ionic liquid (IL) emulsions for extraction purposes. IL emulsions stabilized by responsive microgels are shown to allow rapid extraction and reversible breaking and re-emulsification. Moreover, by using a paramagnetic ionic liquid, droplets can be

  17. Role of asphaltenes in stabilizing thin liquid emulsion films.

    Science.gov (United States)

    Tchoukov, Plamen; Yang, Fan; Xu, Zhenghe; Dabros, Tadeusz; Czarnecki, Jan; Sjöblom, Johan

    2014-03-25

    Drainage kinetics, thickness, and stability of water-in-oil thin liquid emulsion films obtained from asphaltenes, heavy oil (bitumen), and deasphalted heavy oil (maltenes) diluted in toluene are studied. The results show that asphaltenes stabilize thin organic liquid films at much lower concentrations than maltenes and bitumen. The drainage of thin organic liquid films containing asphaltenes is significantly slower than the drainage of the films containing maltenes and bitumen. The films stabilized by asphaltenes are much thicker (40-90 nm) than those stabilized by maltenes (∼10 nm). Such significant variation in the film properties points to different stabilization mechanisms of thin organic liquid films. Apparent aging effects, including gradual increase of film thickness, rigidity of oil/water interface, and formation of submicrometer size aggregates, were observed for thin organic liquid films containing asphaltenes. No aging effects were observed for films containing maltenes and bitumen in toluene. The increasing stability and lower drainage dynamics of asphaltene-containing thin liquid films are attributed to specific ability of asphaltenes to self-assemble and form 3D network in the film. The characteristic length of stable films is well beyond the size of single asphaltene molecules, nanoaggregates, or even clusters of nanoaggregates reported in the literature. Buildup of such 3D structure modifies the rheological properties of the liquid film to be non-Newtonian with yield stress (gel like). Formation of such network structure appears to be responsible for the slower drainage of thin asphaltenes in toluene liquid films. The yield stress of liquid film as small as ∼10(-2) Pa is sufficient to stop the drainage before the film reaches the critical thickness at which film rupture occurs.

  18. Eigenvalues define conditions of stability in liquid-liquid miscible ...

    African Journals Online (AJOL)

    A miscible displacement process is primarily governed by both convective flow and hydrodynamic dispersion. The proper classification of stability condition in the miscible displacement process is a major requirement for a successful field application of this enhanced crude oil recovery mechanism. This paper derives ...

  19. Liquid marble and water droplet interactions and stability.

    Science.gov (United States)

    Ueno, Kazuyuki; Bournival, Ghislain; Wanless, Erica J; Nakayama, Saori; Giakoumatos, Emma C; Nakamura, Yoshinobu; Fujii, Syuji

    2015-10-21

    The interactions between two individual water droplets were investigated in air using a combination of coalescence rig and high speed video camera. This combination allows the visualization of droplet coalescence dynamics with millisecond resolution which provides information on droplet stability. Bare water droplets coalesced rapidly upon contact, while droplet stability was achieved by coating the droplets with polystyrene particles carrying pH-responsive poly[2-(diethylamino)ethyl methacrylate] hairs (PDEA-PS particles) to form liquid marbles. The asymmetric interaction of a water droplet (pH 3 or 10) armoured with the PDEA-PS particles (liquid marble) with a bare droplet at pH 3 exhibited intermediate stability with coalescence observed following an induction time. The induction time was longer for the pH 10 liquid marble, where the PDEA-PS particles have a hydrophobic surface, than in the case of a pH 3 liquid marble, where the PDEA-PS particles have a hydrophilic surface. Furthermore, film formation of PDEA-PS particles on the liquid marble surface with toluene vapour confirmed capsule formation which prevented coalescence with the neighbouring water droplet instead wetting the capsule upon contact within 3 milliseconds. This study illuminates the stability of individual particle-stabilized droplets and has potential impact on processes and formulations which involve their interaction.

  20. Stability of liquid-nitrogen-jet laser-plasma targets

    Science.gov (United States)

    Fogelqvist, E.; Kördel, M.; Selin, M.; Hertz, H. M.

    2015-11-01

    Microscopic jets of cryogenic substances such as liquid nitrogen are important regenerative high-density targets for high-repetition rate, high-brightness laser-plasma soft x-ray sources. When operated in vacuum such liquid jets exhibit several non-classical instabilities that negatively influence the x-ray source's spatial and temporal stability, yield, and brightness, parameters that all are important for applications such as water-window microscopy. In the present paper, we investigate liquid-nitrogen jets with a flash-illumination imaging system that allows for a quantitative stability analysis with high spatial and temporal resolution. Direct and indirect consequences of evaporation are identified as the key reasons for the observed instabilities. Operating the jets in an approximately 100 mbar ambient atmosphere counteracts the effects of evaporation and produces highly stable liquid nitrogen jets. For operation in vacuum, which is necessary for the laser plasmas, we improve the stability by introducing an external radiative heating element. The method significantly extends the distance from the nozzle that can be used for liquid-jet laser plasmas, which is of importance for high-average-power applications. Finally, we show that laser-plasma operation with the heating-element-stabilized jet shows improved short-term and long-term temporal stability in its water-window x-ray emission.

  1. Stability analysis of the pulmonary liquid bilayer.

    Science.gov (United States)

    Halpern, David; Grotberg, James

    2010-11-01

    The lung consists of liquid-lined compliant airways that convey air to and from the alveoli where gas exchange takes place. Because the airways are coated with a bilayer consisting of a mucus layer on top of a periciliary fluid layer, a surface tension instability can generate flows within the bilayer and induce the formation of liquid plugs that block the passage of air. This is a problem for example with premature neonates whose lungs do not produce sufficient quantities of surfactant and suffer from respiratory distress syndrome. To study this instability a system of coupled nonlinear evolution equations are derived using lubrication theory for the thicknesses of the two liquid layers which are assumed to be Newtonian. A normal mode analysis is used to investigate the initial growth of the disturbances, and reveals how the grow rate is affected by the ratio of viscosities λ, film thicknesses η and surface tensions δ of the two layers which can change by disease. Numerical solutions of the evolution equations show that there is a critical bilayer thickness ɛc above which closure occurs, and that a more viscous and thicker layer compared to the periciliary layer closes more slowly. However, ɛcis weakly dependent on λ, η and δ. We also examine the potential impact of wall shear stress and normal stress on cell damage. This work is funded by NIH HL85156.

  2. Liquidity and Stability of Agriculture in the Czech Republic

    Directory of Open Access Journals (Sweden)

    Lánský J.

    2017-09-01

    Full Text Available This article is based on empirical research and 2007–2012 statistical data from joint stock companies which were active in the agriculture sector of the Czech Republic. It deals with the wider aspects of liquidity and stability using suitable liquidity indicators and a vertical financial analysis over a sufficient period of time providing valid results for assessing liquidity and stability of agriculture in relation to cyclic fluctuations. The vertical financial analysis was performed to determine the liquidity structure at current assets and short term debts. Then convenient indicators of current ratio, quick ratio, and cash ratio were applied and interpreted in relation to cyclical deviations and agriculture specifics. From the viewpoint of liquidity measured using the current ratio, agriculture in the Czech Republic is stable and the current ratio values bear witness to solid liquidity, whereby the short-term assets exceed the short-term external funds. Research is to show whether the agriculture sector is liquid and whether the liquidity indicators provide the basis for solvency in the given field.

  3. Stability of erythrocyte suspensions layered on stationary and flowing liquids

    Science.gov (United States)

    Omenyi, S. N.; Rhodes, P. H.; Snyder, R. S.

    1982-01-01

    The apparent stability of erythrocyte suspensions layered on stationary and flowing Ficoll solutions was studied considering the effects of particle concentration, type and size, and the different flow rates of the particle suspensions and chamber liquid. The data from the flowing system were empirically fitted and, when extrapolated to zero chamber liquid flow rate, gave values comparable to the data from the stationary system, thus confirming the validity of the data and our approach to obtain that data.

  4. Discrete microfluidics transfer across capillaries using liquid bridge stability

    Science.gov (United States)

    Kok Keung Lye, Jonathan; Wah Ng, Tuck; Yeong Liang Ling, William

    2011-11-01

    Discrete microfluidics offers distinct advantages over continuous microfluidics since the need for flow presents significant problems. Here, we demonstrate a method of achieving the gentle transfer of liquid samples between two capillaries with the use of air actuation which limits flow and is amenable to automation. Since the stability of liquid bridges is in operation, there is a relationship established between the gap distance and the liquid volume, thereby resulting in three physical response types that were identified. Only one of these allows for efficient liquid transfer. We advance a model for the optimal gap distance and show that it is in good agreement with the experimental data. During the process of liquid transfer, favorable mixing is also achieved.

  5. Synthesis and stability of liquid molecular DT

    Energy Technology Data Exchange (ETDEWEB)

    Souers, P.C.; Fearon, E.M.; Garza, R.G.; Friffith, C.M.; Mayhugh, S.R.; Mapoles, E.R.; Tsugawa, R.T.; Sater, J.D.; Collins, G.W.; Gaines, J.R.

    1988-05-01

    Regular equimolar deuterium-tritium is a mixture of 25 mol% T/sub 2/-50% DT-25% D/sub 2/. We have synthesized molecular DT of greater purity by the reaction LiT + CH/sub 3/OD ..-->.. DT + LiOCH/sub 3/, run at 243/degree/K. With both the alcohol and reactor-to-cryostat transfer lines at room temperature, we obtain 88 mol% DT purity. By cooling the alcohol and holding the transfer lines at 80/degree/K, the yield rose to 95% DT. The DT disproportionated to D/sub 2/ and T/sub 2/ with a 1e time constant of about 100 h in the liquid at 20.5/degree/K. Nuclear magnetic resonance data showed that the eventual T/sub 2/-DT-D/sub 2/ equilibrium is probably a /open quotes/hot-atom/close quotes/ one. 15 refs., 4 figs., 1 tab.

  6. Ferroelectric devices

    CERN Document Server

    Uchino, Kenji

    2009-01-01

    Updating its bestselling predecessor, Ferroelectric Devices, Second Edition assesses the last decade of developments-and setbacks-in the commercialization of ferroelectricity. Field pioneer and esteemed author Uchino provides insight into why this relatively nascent and interdisciplinary process has failed so far without a systematic accumulation of fundamental knowledge regarding materials and device development.Filling the informational void, this collection of information reviews state-of-the-art research and development trends reflecting nano and optical technologies, environmental regulat

  7. Shear Strength of Stabilized Kaolin Soil Using Liquid Polymer

    Science.gov (United States)

    Azhar, A. T. S.; Fazlina, M. I. S.; Nizam, Z. M.; Fairus, Y. M.; Hakimi, M. N. A.; Riduan, Y.; Faizal, P.

    2017-08-01

    The purpose of this research is to investigate the suitability of polymer in soil stabilization by examining its strength to withstand compressive strength. Throughout this research study, manufactured polymer was used as a chemical liquid soil stabilizer. The liquid polymer was diluted using a proposed dilution factor of 1 : 3 (1 part polymer: 3 parts distilled water) to preserve the workability of the polymer in kaolin mixture. A mold with a diameter of 50 mm and a height of 100 mm was prepared. Kaolin soil was mixed with different percentages of polymer from 10%, 15%, 20%, 25%, 30% and 35% of the mass of the kaolin clay sample. Kaolin mixtures were tested after a curing period of 3 days, 7 days, 14 days and 28 days respectively. The physical properties were determined by conducting a moisture content test and Atterberg limit test which comprise of liquid limit, plastic limit and shrinkage limit. Meanwhile, the mechanical properties of the soil shear strength were identified through an unconfined compressive strength (UCS) test. Stabilized kaolin soil showed the highest compressive strength value when it was mixed with 35% of polymer compared to other percentages that marked an increment in strength which are 45.72% (3 days), 67.57% (7 days), 81.73% (14 days) and 77.84% (28 days). Hence, the most effective percentage of liquid polymer which should be used to increase the strength of kaolin soil is 35%.

  8. Stability of triglyceride liquid films on hydrophilic and hydrophobic glasses.

    Science.gov (United States)

    Vazquez, Rosa; Nogueira, Rui; Orfão, Marta; Mata, José Luís; Saramago, Benilde

    2006-07-01

    Wetting and dewetting of solid surfaces by oily fluids were investigated in terms of the stability of the liquid film formed between an air bubble and the solid surface. With the objective of understanding how molecules with low polarity but relatively complex molecular structure behave at the solid/liquid interface, three liquid triglycerides with different chain length and saturation were chosen, namely, tributyrin, tricaprylin, and triolein. Tributyrin and tricaprylin exist in milkfat while triolein is present in vegetable oils. The stability of the liquid films may be inferred from the shape of the disjoining pressure isotherms, which represent the dependence of the disjoining pressure on the film thickness. Disjoining pressure isotherms for films of the three triglycerides on hydrophilic and hydrophobic glasses were obtained using a recently developed apparatus, based on the interferometric technique. The experimental curves are compared with the theoretical predictions of London-Hamaker. The deviations between theory and experiment are interpreted in terms of a structural component of the disjoining pressure. All triglycerides form metastable films on both hydrophilic and hydrophobic glasses which means that for disjoining pressures higher than a critical value, pi(c), a wetting transition occurs and the film ruptures. The mechanisms for film rupture are discussed and a correlation between film stability and the apolar (Lifshitz-van der Waals) and the polar components of the spreading coefficient is proposed.

  9. The radiation stability of organic ionic liquids in biphasic systems

    Energy Technology Data Exchange (ETDEWEB)

    Howett, S.E.; Noel, J.J.; Wren, J.C., E-mail: jjnoel@uwo.ca [Univ. of Westen Ontario. London, Ontario (Canada)

    2013-07-01

    The influence of γ-radiation on the stability of biphasic water/ionic liquid (IL) and gas/IL systems was studied. The behaviours of two phosphonium-based ionic liquids with the same cation and differing anions were compared. Exposure to γ-radiation did not significantly impact IL-stability, but it did speed up processes that occurred even in the absence of radiation. The two most significant effects of irradiation were the promotion of faster emulsion layer formation and the precipitation of a fine white solid. Precipitate formation could be deleterious,whereas emulsion layer formation could be either beneficial or detrimental, in an IL-based separations process. (author)

  10. Stability of spin-driven ferroelectricity in the thin-film limit: Coupling of magnetic and electric order in multiferroic TbMnO3 films

    Energy Technology Data Exchange (ETDEWEB)

    Becher, Carsten [ETH Zurich, Switzerland; Voigt, Jörg [JCNS and JARA-FIT; Schierle, Enrico [Helmholtz-Zentrum Berlin; Weschke, Eugen [Helmholtz-Zentrum Berlin; Fiebig, Manfred [ETH Zurich, Switzerland; Brückel, Thomas [JCNS and JARA-FIT

    2013-01-01

    We demonstrate spin-spiral-induced ferroelectricity in epitaxial TbMnO3 films grown on YAlO3 substrates down to a film thickness of 6nm. The ferroelectric polarization is identified by optical second-harmonic generation. Using x-ray resonant magnetic scattering we directly prove the existence of a noncollinear magnetic structure in the ferroelectric phase and thus bulk-like multiferroicity. The electric-field-induced reversal of the magnetic domains along with the reversal of the ferroelectric polarization evidences the rigid coupling of magnetic and ferroelectric order and hence a giant magnetoelectric effect in the films.

  11. Stability of thin emulsion film between two oil phases with a viscoelastic liquid-liquid interface.

    Science.gov (United States)

    Narsimhan, Ganesan

    2009-02-15

    The viscoelastic properties of adsorbed protein layer in food emulsions and foams are important in providing stability to such systems. Linear stability analysis for a protein stabilized aqueous film sandwiched between two semi-infinite oil phases with a viscoelastic liquid-liquid interface is presented. The interfacial dilatational and shear viscoelastic properties are described by Maxwell models. The aqueous film is found to be more stable for smaller values of dilatational (shear) relaxation times and larger values of interfacial dilatational (shear) viscosities. The asymptotic values of maximum growth coefficient for very large and very small values of interfacial dilatational (shear) viscosities were found to be independent of relaxation times and correspond to those for immobile and fully mobile liquid-liquid interfaces respectively. The aqueous film is shown to be more stable for larger viscosities of the oil phase with the maximum growth coefficient approaching zero as the ratio of viscosities of oil and aqueous phases approach very large values and an asymptotic value corresponding to that for a foam film for very small viscosity ratios.

  12. Stability of Adderall in extemporaneously compounded oral liquids.

    Science.gov (United States)

    Justice, J; Kupiec, T C; Matthews, P; Cardona, P

    2001-08-01

    The short-term stability of Adderall in three extemporaneously compounded oral liquids was studied. Three suspensions of Adderall 1 mg/mL were prepared from commercially available 10-mg Adderall tablets with Ora-Sweet, Ora-Plus, and a 1:1 mixture of Ora-Sweet and Ora-Plus. Each suspension was stored in the dark in a stability chamber at 25 degrees C and 60% relative humidity for 30 days. The stability of the active drug (a mixture of levoamphetamine and dextroamphetamine salts) in each of the three vehicles was determined immediately after preparation and at 10, 20, and 30 days by using gas chromatography-mass spectrometry (GCMS). No significant changes in concentrations of either amphetamine isomer occurred during the 30-day study period. Visual inspection of samples revealed no changes in color or odor. Extemporaneously compounded liquid oral formulations of Adderall 1 mg/mL in Ora-Sweet, Ora-Plus, or a 1:1 mixture of Ora-Sweet and Ora-Plus were stable for at least 30 days at 25 degrees C and 60% relative humidity.

  13. Stability of rifabutin in two extemporaneously compounded oral liquids.

    Science.gov (United States)

    Haslam, J L; Egodage, K L; Chen, Y; Rajewski, R A; Stella, V

    1999-02-15

    The stability of rifabutin 20 mg/mL in two oral liquids was studied. Powder from 100 150-mg rifabutin capsules was placed in a glass mortar. Cherry syrup (pH 2.9) or a 1:1 mixture of Ora-Sweet and Ora-Plus (Paddock Laboratories) was added to produce 750 mL of each formulation, which was then stored in 2-oz plastic prescription bottles. Three bottles of each formulation were stored at 4, 25, 30, and 40 degrees C. At 0, 1, 2, 4, 8, and 12 weeks, the bottles were collected and allowed to remain at room temperature for one hour; samples of about 1 mL were collected from each bottle, weighed, and assayed for rifabutin content by high-performance liquid chromatography. The rifabutin liquids prepared with cherry syrup and stored at 4, 25, and 30 degrees C lost a mean of 10% of the initial drug concentration by 12 weeks. There was a mean loss of < 5% of the initial rifabutin concentration in all the liquids prepared with Ora-Sweet and Ora-Plus. The liquid prepared with cherry syrup, upon standing, showed a tendency for some of the ingredients to float. The suspension prepared with Ora-Sweet and Ora-Plus had a tendency to retain bubbles after it was shaken, but the ingredients did not settle upon standing. Rifabutin 20 mg/mL in two extemporaneously compounded oral liquids prepared from capsules and sweetened vehicles was stable for at least 12 weeks at 4, 25, 30, and 40 degrees C with the exception of rifabutin in cherry syrup, which was stable for only 8 weeks at 40 degrees C.

  14. Electromagnetically Sustained Liquid Metal Flow for Feedback Stabilization Studies

    Science.gov (United States)

    Mirhoseini, Seyyed Mohammad; Volpe, Francesco

    2015-11-01

    Liquid metal walls in fusion reactors, whether nearly static or rapidly flowing, will be subject to instabilities that will make them locally bulge, thus entering in contact with the plasma, or deplete, hence exposing the underlying solid substrate. To prevent this, research has begun at Columbia University to create liquid metal flows and demonstrate their stabilization by electromagnetic forces, adjusted in feedback with thickness measurements. Here we present initial results regarding the sustainment of a flow of Galinstan (a gallium, indium, tin alloy) by a special pump consisting of a ferromagnetic rotor, with permanent magnets mounted on it. The magnetic field is partly ``frozen'' in the liquid metal surrounding the rotor. Therefore, as the field rotates, the liquid metal rotates as well, although with a slip factor. This solution was preferred to conventional pumps, which would enter in electrical contact with the metal flow. The pump, 3D-printed at Columbia, allows to adjust the flow-velocity from few mm/s to several cm/s.

  15. Multitemperature stability and degradation characteristics of pergolide mesylate oral liquid.

    Science.gov (United States)

    Shank, Brandon R; Ofner, Clyde M

    2010-12-01

    The stability of pergolide mesylate in an oral aqueous liquid was studied. Stability and solubility data were used to determine the degradation characteristics of the drug in this formulation. Samples were stored in the dark at 35°C, 45°C, and 60°C. At 1, 2, 4, 8, 12, and 16 weeks, samples were removed and stored in a -80°C freezer for high performance liquid chromatography (HPLC) assay at a later date. The initial drug concentration of 0.30 mg/mL was determined by assay after storage at -80°C. A solubility of 6.9 mg/mL was found for pergolide mesylate in the oral liquid at room temperature with a relative standard deviation (RSD) of 4.0%. The degradation process is considered first-order at 25°C and 35°C. At higher temperatures (45°C and 60°C), a color change and curvature at the latter time points in degradation profiles are ascribed to the presence of methylcellulose. The activation energy calculated for degradation of pergolide mesylate in the oral liquid was 21.3 kcal/mol. The time to reach 90% potency (t90) values were calculated to be 43 days and 3 days, respectively, for storage at 25°C and 35°C. Drug concentrations up to ~6 mg/mL can be maintained as a solution at room temperature with this formulation.

  16. Hydrodynamic Stability of Liquid-Propellant Combustion: Landau's Problem Revisited

    Science.gov (United States)

    Margolis, S. B.

    2001-01-01

    Hydrodynamic, or Landau, instability in combustion is typically associated with the onset of wrinkling of a flame surface, corresponding to the formation of steady cellular structures as the stability threshold is crossed. As its name suggests, it stems from hydrodynamic effects connected with thermal expansion across the reaction region. In the context of liquid-propellant combustion, the classical models that originally predicted this phenomenon have been extended to include the important effects that arise from a dynamic dependence of the burning rate on the local pressure and temperature fields. Thus, the onset of Landau instability has now been shown to occur for sufficiently small negative values of the pressure sensitivity of the burning rate, significantly generalizing previous classical results for this problem that assumed a constant normal burning rate. It has also been shown that the onset of instability occurs for decreasing values of the disturbance wave number as the gravitational-acceleration parameter decreases. Consequently, in an appropriate weak-gravity limit, Landau instability becomes a long-wave phenomena associated with the formation of large cells on the liquid-propellant surface. Additionally, a pulsating form of hydrodynamic instability has been shown to occur as well, corresponding to the onset of temporal oscillations in the location of the liquid/gas interface. This instability occurs for sufficiently large negative values of the pressure sensitivity, and is enhanced by increasing values of the burning-rate temperature sensitivity. It is further shown that for sufficiently small values of this parameter, there exists a stable range of pressure sensitivities for steady, planar burning such that the classical cellular form of hydrodynamic instability and the more recent pulsating form of hydrodynamic instability can each occur as the corresponding stability threshold is crossed. For larger thermal sensitivities, however, the pulsating

  17. Polymer Ferroelectric Memory for Flexible Electronics

    KAUST Repository

    Khan, Mohd Adnan

    2013-11-01

    With the projected growth of the flexible and plastic electronics industry, there is renewed interest in the research community to develop high performance all-polymeric memory which will be an essential component of any electronic circuit. Some of the efforts in polymer memories are based on different mechanisms such as filamentary conduction, charge trapping effects, dipole alignment, and reduction-oxidation to name a few. Among these the leading candidate are those based on the mechanism of ferroelectricity. Polymer ferroelectric memory can be used in niche applications like smart cards, RFID tags, sensors etc. This dissertation will focus on novel material and device engineering to fabricate high performance low temperature polymeric ferroelectric memory for flexible electronics. We address and find solutions to some fundamental problems affecting all polymer ferroelectric memory like high coercive fields, fatigue and thermal stability issues, poor breakdown strength and poor p-type hole mobilities. Some of the strategies adopted in this dissertation are: Use of different flexible substrates, electrode engineering to improve charge injection and fatigue properties of ferroelectric polymers, large area ink jet printing of ferroelectric memory devices, use of polymer blends to improve insulating properties of ferroelectric polymers and use of oxide semiconductors to fabricate high mobility p-type ferroelectric memory. During the course of this dissertation we have fabricated: the first all-polymer ferroelectric capacitors with solvent modified highly conducting polymeric poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) [PEDOT:PSS] electrodes on plastic substrates with performance as good as devices with metallic Platinum-Gold electrodes on silicon substrates; the first all-polymer high performance ferroelectric memory on banknotes for security applications; novel ferroelectric capacitors based on blends of ferroelectric poly(vinylidene fluoride

  18. Stabilizing blue phase liquid crystals with linearly polarized UV light

    Science.gov (United States)

    Xu, Daming; Yuan, Jiamin; Schadt, Martin; Yan, Jing; Wu, Shin-Tson

    2015-03-01

    Polymer-stabilized blue-phase liquid crystal (PS-BPLC) has become an increasingly important technology trend for information display and photonic applications. BPLC exhibits several attractive features, such as reasonably wide temperature range, submillisecond gray-to-gray response time, no need for alignment layer, optically isotropic voltageoff state, and large cell gap tolerance when an in-plane switching (IPS) cell is employed. However, some bottlenecks such as high operation voltage, relatively low transmittance, and noticeable hysteresis and prolonged response time at high field region for IPS mode, still remain to be overcome before widespread application of BPLC can be realized. To reduce operation voltage, both new BPLC materials and new device structures have been investigated. In this paper, we demonstrate the stabilization a photopolymer-embedded blue phase liquid crystal precursor using a linearly polarized UV light for first time. When the UV polarization axis is perpendicular to the stripe electrodes of an IPS cell, anisotropic polymer networks are formed through the linear photo-polymerization process and the electrostriction effect is suppressed. As a result, the measured hysteresis is dramatically reduced from 6.95% to 0.36% and the response time shortened by ~2X compared to unpolarized UV exposure. To induce larger anisotropy in polymer networks for mitigating the electrostriction effect, high-intensity linearly polarized UV exposure is preferred. It is foreseeable this method will guide future BPLC device and material development as well as manufacturing process. The dawn of BPLCD is near.

  19. Stability of cavitation structures in a thin liquid layer.

    Science.gov (United States)

    Wu, Pengfei; Bai, Lixin; Lin, Weijun; Yan, Jiuchun

    2017-09-01

    The inception and evolution of acoustic cavitation structures in thin liquid layers under different conditions and perturbations are investigated experimentally with high speed photography. The stability and characterization of cavitation structures are quantified by image analysis methods. It is found that cavitation structures (shape of bubble cloud and number of bubbles) are stable under unaltered experimental conditions, and the cavitation bubble cloud will return to the original structure and remain stable even in the face of large perturbations. When the experimental conditions are altered (for example, acoustic intensity, cavitation nuclei, boundary), the cavitation structures will vary correspondingly. Further analysis implies that the stability of cavitation structures is closely related to the number of bubbles in the cavitation bubble cloud. There are two mechanisms acting simultaneously in the cavitation bubble cloud evolution, one "bubble production" and the other "bubble disappearance". We propose that the two mechanisms acting together constitute the most likely explanation for the stability of cavitation structures and their transformation. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Liquid Self-Balancing Device Effects on Flexible Rotor Stability

    Directory of Open Access Journals (Sweden)

    Leonardo Urbiola-Soto

    2013-01-01

    Full Text Available Nearly a century ago, the liquid self-balancing device was first introduced by M. LeBlanc for passive balancing of turbine rotors. Although of common use in many types or rotating machines nowadays, little information is available on the unbalance response and stability characteristics of this device. Experimental fluid flow visualization evidences that radial and traverse circulatory waves arise due to the interaction of the fluid backward rotation and the baffle boards within the self-balancer annular cavity. The otherwise destabilizing force induced by trapped fluids in hollow rotors, becomes a stabilizing mechanism when the cavity is equipped with adequate baffle boards. Further experiments using Particle Image Velocimetry (PIV enable to assess the active fluid mass fraction to be one-third of the total fluid mass. An analytical model is introduced to study the effects of the active fluid mass fraction on a flexible rotor supported by flexible supports excited by bwo different destabilizing mechanisms; rotor internal friction damping and aerodynamic cross-coupling. It is found that the fluid radial and traverse forces contribute to the balancing action and to improve the rotor stability, respectively.

  1. Orientational order parameters of a de Vries-type ferroelectric liquid crystal obtained by polarized Raman spectroscopy and x-ray diffraction.

    Science.gov (United States)

    Sanchez-Castillo, A; Osipov, M A; Jagiella, S; Nguyen, Z H; Kašpar, M; Hamplovă, V; Maclennan, J; Giesselmann, F

    2012-06-01

    The orientational order parameters (P{2}) and (P{4}) of the ferroelectric, de Vries-type liquid crystal 9HL have been determined in the SmA and SmC phases by means of polarized Raman spectroscopy, and in the SmA phase using x-ray diffraction. Quantum density functional theory predicts Raman spectra for 9HL that are in good agreement with the observations and indicates that the strong Raman band probed in the experiment corresponds to the uniaxial, coupled vibration of the three phenyl rings along the molecular long axis. The magnitudes of the orientational order parameters obtained in the Raman and x-ray experiments differ dramatically from each other, a discrepancy that is resolved by considering that the two techniques probe the orientational distributions of different molecular axes. We have developed a systematic procedure in which we calculate the angle between these axes and rescale the orientational order parameters obtained from x-ray scattering with results that are then in good agreement with the Raman data. At least in the case of 9HL, the results obtained by both techniques support a "sugar loaf" orientational distribution in the SmA phase with no qualitative difference to conventional smectics A. The role of individual molecular fragments in promoting de Vries-type behavior is considered.

  2. Emulsion liquid membrane for textile dye removal: Stability study

    Science.gov (United States)

    Kusumastuti, Adhi; Syamwil, Rodia; Anis, Samsudin

    2017-03-01

    Although textile dyes is basically available in very low concentration; it should be removed due to the toxicity to human body and environment. Among the existing methods, emulsion liquid membrane (ELM) is a promising method by providing high interfacial area and the ability to remove a very low concentration of the solute. The optimal emulsions were produced using commercially supplied homogeniser. The drop size was measured by the aid of microscope and image J software. Initially, methylene blue in simulated wastewater was extracted using a stirrer. Methylene blue concentration was determined using spectrophotometer. The research obtained optimal emulsion at surfactant concentration of 4 wt. %, kerosene as diluent, emulsification time of 30 min, emulsification speed of 2000 rpm. The lowest membrane breakage and the longest stability time were about 0.11% and 150 min, respectively.

  3. Liquid Crystal Formation from Sunflower Oil: Long Term Stability Studies.

    Science.gov (United States)

    da Rocha-Filho, Pedro Alves; Maruno, Mônica; Ferrari, Márcio; Topan, José Fernando

    2016-06-09

    The Brazilian biodiversity offers a multiplicity of raw materials with great potential in cosmetics industry applications. Some vegetable oils and fatty esters increase skin hydration by occlusivity, keeping the skin hydrated and with a shiny appearance. Sunflower (Helianthus annus L.) oil is widely employed in cosmetic emulsions in the form of soaps, creams, moisturizers and skin cleansers due to the presence of polyphenols and its high vitamin E content. Liquid crystals are systems with many applications in both pharmaceutical and cosmetic formulations and are easily detected by microscopy under polarized light due to their birefringence properties. The aim of this research was to develop emulsions from natural sunflower oil for topical uses. Sunflower oil (75.0% w/w) was combined with liquid vaseline (25.0% w/w) employing a natural self-emulsifying base (SEB) derivative. The high temperature of the emulsification process did not influence the antioxidant properties of sunflower oil. Fatty esters were added to cosmetic formulations and extended stability tests were performed to characterize the emulsions. Fatty esters like cetyl palmitate and cetyl ester increase the formation of anisotropic structures. O/W emulsions showed acidic pH values and pseudoplastic behavior. The presence of a lamellar phase was observed after a period of 90 days under different storage conditions.

  4. Liquid Crystal Formation from Sunflower Oil: Long Term Stability Studies

    Directory of Open Access Journals (Sweden)

    Pedro Alves da Rocha-Filho

    2016-06-01

    Full Text Available The Brazilian biodiversity offers a multiplicity of raw materials with great potential in cosmetics industry applications. Some vegetable oils and fatty esters increase skin hydration by occlusivity, keeping the skin hydrated and with a shiny appearance. Sunflower (Helianthus annus L. oil is widely employed in cosmetic emulsions in the form of soaps, creams, moisturizers and skin cleansers due to the presence of polyphenols and its high vitamin E content. Liquid crystals are systems with many applications in both pharmaceutical and cosmetic formulations and are easily detected by microscopy under polarized light due to their birefringence properties. The aim of this research was to develop emulsions from natural sunflower oil for topical uses. Sunflower oil (75.0% w/w was combined with liquid vaseline (25.0% w/w employing a natural self-emulsifying base (SEB derivative. The high temperature of the emulsification process did not influence the antioxidant properties of sunflower oil. Fatty esters were added to cosmetic formulations and extended stability tests were performed to characterize the emulsions. Fatty esters like cetyl palmitate and cetyl ester increase the formation of anisotropic structures. O/W emulsions showed acidic pH values and pseudoplastic behavior. The presence of a lamellar phase was observed after a period of 90 days under different storage conditions.

  5. Signal Processing Methods for Liquid Rocket Engine Combustion Spontaneous Stability and Rough Combustion Assessments

    Science.gov (United States)

    Kenny, R. Jeremy; Casiano, Matthew; Fischbach, Sean; Hulka, James R.

    2012-01-01

    Liquid rocket engine combustion stability assessments are traditionally broken into three categories: dynamic stability, spontaneous stability, and rough combustion. This work focuses on comparing the spontaneous stability and rough combustion assessments for several liquid engine programs. The techniques used are those developed at Marshall Space Flight Center (MSFC) for the J-2X Workhorse Gas Generator program. Stability assessment data from the Integrated Powerhead Demonstrator (IPD), FASTRAC, and Common Extensible Cryogenic Engine (CECE) programs are compared against previously processed J-2X Gas Generator data. Prior metrics for spontaneous stability assessments are updated based on the compilation of all data sets.

  6. Storage stability of sterilized liquid extracts from pomegranate peel.

    Science.gov (United States)

    Qu, Wenjuan; Breksa Iii, Andrew P; Pan, Zhongli; Ma, Haile; McHugh, Tara H

    2012-07-01

    Pomegranate marc, a byproduct of commercial juice production, has shown promise as a starting material for the recovery of health promoting phenolic compounds. The stability of aqueous extracts prepared from pomegranate marc was evaluated in preparation to directly using these extracts as nutraceuticals or food additives. The liquid extracts were produced under extraction conditions of 25 °C, water to peel ratio of 50 : 1 (w/w) for 2 min, and then sterilized at 121 °C for 10 s. Storage conditions tested included 3 different pH values (3.5, 5.0, and 7.0) and 2 packaging methods (no light and exposure to light). The extracts were evaluated for industrial (pH, total soluble solid content, and clarity), color, spectral, and antioxidant characteristics over a period of 180 d. The results showed that both pH value and packaging method significantly influenced the industrial and color characteristics of the extracts. The high pH had a negative effect on spectral and antioxidant characteristics. Therefore, the recommended storage conditions are low pH and with dark packaging to maintain the high storage stability. After 180 d of storage, extracts stored at low pH (3.5) in dark packaging still retained 67% and 58% of their total soluble phenolic concentration and antioxidant activity, compared with 61% and 43% for high pH (7.0) samples, and were composed of high concentrations of punicalagins A and B, gallic, and ellagic acids. The present research developed an effective recovery of phenolic compounds from pomegranate marc to be used as nutraceuticals or food additives. The aqueous extract product has good quality characteristics with high industrial and color stability, and total phenolic content and antioxidant activity, when stored at pH 3.5 in dark packaging for up to 180 d. The evaluation results of storage stability reported here are important for commercialization. © 2012 Institute of Food Technologists®

  7. The Impact of Sloshing Liquids on Ship Stability for Various Dimensions of Partly Filled Tanks

    Directory of Open Access Journals (Sweden)

    Przemyslaw Krata

    2013-12-01

    Full Text Available Liquid sloshing phenomenon taking place in partly filled ships’ tanks directly affects the stability of a vessel. However, only static calculations are carried out onboard ships nowadays and static transfer of liquid weight is taken into account in the course of routine stability calculation. The paper is focused on a dynamic heeling moment due to liquid sloshing in tanks onboard ships. A number of numerical simulations of liquid sloshing taking place in a moving tank is carried out. The wide range of ship’s tanks is taken into account. The conducted CFD simulations are experimentally verified. Finally, the method of an assessment of the liquid sloshing impact on ship transverse stability is worked out. The key point of the method is a dynamic coefficient describing relation of the researched dynamic heeling moment and the quasi-static one in terms of dynamic stability of a vessel which is related to the weather criterion of ship stability assessment.

  8. Performance and Stability Analyses of Rocket Combustion Devices Using Liquid Oxygen/Liquid Methane Propellants

    Science.gov (United States)

    Hulka, James R.; Jones, G. W.

    2010-01-01

    Liquid rocket engines using oxygen and methane propellants are being considered by the National Aeronautics and Space Administration (NASA) for in-space vehicles. This propellant combination has not been previously used in flight-qualified engine systems, so limited test data and analysis results are available at this stage of early development. NASA has funded several hardware-oriented programs with oxygen and methane propellants over the past several years with the Propulsion and Cryogenic Advanced Development (PCAD) project, under the Exploration Technology Development Program. As part of this effort, NASA Marshall Space Flight Center has conducted combustion, performance, and combustion stability analyses of several of the configurations on these programs. This paper summarizes these analyses. Test and analysis results of impinging and coaxial element injectors using liquid oxygen and liquid methane propellants are included. Several cases with gaseous methane are included for reference. Several different thrust chamber configurations have been modeled, including thrust chambers with multi-element like-on-like and swirl coax element injectors tested at NASA MSFC, and a unielement chamber with shear and swirl coax injectors tested at The Pennsylvania State University. Configurations were modeled with two one-dimensional liquid rocket combustion analysis codes, the Rocket Combustor Interaction Design and Analysis (ROCCID), and the Coaxial Injector Combustion Model (CICM). Significant effort was applied to show how these codes can be used to model combustion and performance with oxygen/methane propellants a priori, and what anchoring or calibrating features need to be applied or developed in the future. This paper describes the test hardware configurations, presents the results of all the analyses, and compares the results from the two analytical methods.

  9. Ferroelectricity in spiral magnets

    NARCIS (Netherlands)

    Mostovoy, M

    2006-01-01

    It was recently observed that the ferroelectrics showing the strongest sensitivity to an applied magnetic field are spiral magnets. We present a phenomenological theory of inhomogeneous ferroelectric magnets, which describes their thermodynamics and magnetic field behavior, e.g., dielectric

  10. Ferroelectric ultrathin perovskite films

    Science.gov (United States)

    Rappe, Andrew M; Kolpak, Alexie Michelle

    2013-12-10

    Disclosed herein are perovskite ferroelectric thin-film. Also disclosed are methods of controlling the properties of ferroelectric thin films. These films can be used in a variety materials and devices, such as catalysts and storage media, respectively.

  11. Effect of bias in ferroelectric-antiferroelectric relaxation

    Science.gov (United States)

    Geday, M. A.; Medialdea, D. P.; Cerrolaza, B.; Bennis, N.; Quintana, X.; Otón, J. M.

    2009-06-01

    The ferroelectric-antiferroelectric transition in greyscale generation of antiferroelectric liquid crystal displays (AFLC) is a heterogeneous process. The process has been described as the growth of finger-like domains [1]. We have previously studied the ferroelectric-antiferroelectric phase transition, relaxation that follows the data pulse in surface stabilized asymmetric antiferroelectric liquid crystal displays using biasless video frequency waveforms [2]. This relaxation involves an intensity decay of the light transmitted by a pixel and depends on several parameters such as surface stabilization, rotational viscosity of the AFLC, magnitude of the data pulse, and bias voltage. The usual multiplexed driving of AFLC displays leads to long-term stabilisation of the grey levels induced by the data pulses within the selection time. However, depending on the bias level, alternative greyscale mechanisms may be obtained by allowing the grey levels to decay during the frametime. These greyscales may be advantageous in some instances since they improve the dynamic response of the AFLC device and reduce the reset time of the waveform. In this study we extend the previous work to include the effect of bias. We present the measured data, in terms of growth pattern and speed and present an extension of the previously model on order to explain the results.

  12. Combustion Stability Analyses of Coaxial Element Injectors with Liquid Oxygen/Liquid Methane Propellants

    Science.gov (United States)

    Hulka, J. R.

    2010-01-01

    Liquid rocket engines using oxygen and methane propellants are being considered by the National Aeronautics and Space Administration (NASA) for in-space vehicles. This propellant combination has not been previously used in a flight-qualified engine system, so limited test data and analysis results are available at this stage of early development. NASA has funded several hardware-oriented activities with oxygen and methane propellants over the past several years with the Propulsion and Cryogenic Advanced Development (PCAD) project, under the Exploration Technology Development Program. As part of this effort, the NASA Marshall Space Flight Center has conducted combustion stability analyses of several of the configurations. This paper presents test data and analyses of combustion stability from the recent PCAD-funded test programs at the NASA MSFC. These test programs used swirl coaxial element injectors with liquid oxygen and liquid methane propellants. Oxygen was injected conventionally in the center of the coaxial element, and swirl was provided by tangential entry slots. Injectors with 28-element and 40-element patterns were tested with several configurations of combustion chambers, including ablative and calorimeter spool sections, and several configurations of fuel injection design. Low frequency combustion instability (chug) occurred with both injectors, and high-frequency combustion instability occurred at the first tangential (1T) transverse mode with the 40-element injector. In most tests, a transition between high-amplitude chug with gaseous methane flow and low-amplitude chug with liquid methane flow was readily observed. Chug analyses of both conditions were conducted using techniques from Wenzel and Szuch and from the Rocket Combustor Interactive Design and Analysis (ROCCID) code. The 1T mode instability occurred in several tests and was apparent by high-frequency pressure measurements as well as dramatic increases in calorimeter-measured heat flux

  13. Linear Stability Analysis of Free Surface Liquid Metal Flow

    Science.gov (United States)

    Giannakis, D.; Rosner, R.; Fischer, P.; Ji, H.; Burin, M.; McMurtry, K.

    2006-10-01

    We study the linear stability of the flow of a liquid metal on a planar surface in the presence of an external magnetic field. The objective is to account for the behavior encountered in a free surface MHD experiment at Princeton, but the model has a range of astrophysical and industrial applications (see companion poster). This class of free surface flow exhibits two mechanisms of linear instability. In the so-called `soft' instability, a downstream propagating surface wave of large wavelength becomes mildly unstable. The second, `hard', instability is of the critical layer type and takes place at shorter wavelengths. Solving the eigenvalue problem posed by the coupled Orr-Sommerfeld and induction equations via a spectral method, we find that in the regime of relevance to the Princeton experiment (Reynolds number, magnetic Reynolds number and Hartmann number up to 10 ^ 5 , 10 ^ - 1 , and 10 ^ 3 , respectively) MHD effects suppress both types of instability. The soft instability is efficiently suppressed via resistive dissipation if the background magnetic field is normal to the basic flow. In contrast, the hard instability is strongly suppressed irrespective of the details of the background magnetic field configuration, even at moderate Hartmann numbers.

  14. Combustion Stability Characteristics of the Project Morpheus Liquid Oxygen / Liquid Methane Main Engine

    Science.gov (United States)

    Melcher, John C.; Morehead, Robert L.

    2014-01-01

    The project Morpheus liquid oxygen (LOX) / liquid methane (LCH4) main engine is a Johnson Space Center (JSC) designed 5,000 lbf-thrust, 4:1 throttling, pressure-fed cryogenic engine using an impinging element injector design. The engine met or exceeded all performance requirements without experiencing any in- ight failures, but the engine exhibited acoustic-coupled combustion instabilities during sea-level ground-based testing. First tangential (1T), rst radial (1R), 1T1R, and higher order modes were triggered by conditions during the Morpheus vehicle derived low chamber pressure startup sequence. The instability was never observed to initiate during mainstage, even at low power levels. Ground-interaction acoustics aggravated the instability in vehicle tests. Analysis of more than 200 hot re tests on the Morpheus vehicle and Stennis Space Center (SSC) test stand showed a relationship between ignition stability and injector/chamber pressure. The instability had the distinct characteristic of initiating at high relative injection pressure drop at low chamber pressure during the start sequence. Data analysis suggests that the two-phase density during engine start results in a high injection velocity, possibly triggering the instabilities predicted by the Hewitt stability curves. Engine ignition instability was successfully mitigated via a higher-chamber pressure start sequence (e.g., 50% power level vs 30%) and operational propellant start temperature limits that maintained \\cold LOX" and \\warm methane" at the engine inlet. The main engine successfully demonstrated 4:1 throttling without chugging during mainstage, but chug instabilities were observed during some engine shutdown sequences at low injector pressure drop, especially during vehicle landing.

  15. H-Bond stabilized columnar discotic liquid crystals

    NARCIS (Netherlands)

    Paraschiv, I.

    2007-01-01

    Since 1977, more than 2300 publications on discotic (disk-like) liquid crystalline materials have appeared. Discotic liquid crystals, which usually consist of polyaromatic molecules surrounded by long peripheral alkyl tails, can form liquid crystalline mesophases in a wide temperature range. Within

  16. On the radiation stability of crown ethers in ionic liquids.

    Energy Technology Data Exchange (ETDEWEB)

    Shkrob, I.; Marin, T.; Dietz, M. (Chemical Sciences and Engineering Division); (Benedictine Univ.); (Univ. of Wisconsin at Milwaukee)

    2011-04-14

    Crown ethers (CEs) are macrocyclic ionophores used for the separation of strontium-90 from acidic nuclear waste streams. Room temperature ionic liquids (ILs) are presently being considered as replacements for traditional molecular solvents employed in such separations. It is desirable that the extraction efficacy obtained with such solvents should not deteriorate in the strong radiation fields generated by decaying radionuclides. This deterioration will depend on the extent of radiation damage to both the IL solvent and the CE solute. While radiation damage to ILs has been extensively studied, the issue of the radiation stability of crown ethers, particularly in an IL matrix, has not been adequately addressed. With this in mind, we have employed electron paramagnetic resonance (EPR) spectroscopy to study the formation of CE-related radicals in the radiolysis of selected CEs in ILs incorporating aromatic (imidazolium and pyridinium) cations. The crown ethers have been found to yield primarily hydrogen loss radicals, H atoms, and the formyl radical. In the low-dose regime, the relative yield of these radicals increases linearly with the mole fraction of the solute, suggesting negligible transfer of the excitation energy from the solvent to the solute; that is, the solvent has a 'radioprotective' effect. The damage to the CE in the loading region of practical interest is relatively low. Under such conditions, the main chemical pathway leading to decreased extraction performance is protonation of the macrocycle. At high radiation doses, sufficient to increase the acidity of the IL solvent significantly, such proton complexes compete with the solvent cations as electron traps. In this regime, the CEs will rapidly degrade as the result of H abstraction from the CE ring by the released H atoms. Thus, the radiation dose to which a CE/IL system is exposed must be maintained at a level sufficiently low to avoid this regime.

  17. Stabilizing liquid drops of arbitrary shape by the interfacial jamming of nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Russell, Thomas P.; Cui, Mengmeng; Emrick, Todd

    2018-01-30

    A stabilized assembly including a first liquid phase of non-spherical droplets in a second liquid phase, wherein the second liquid phase is immiscible with the first phase, and nanoparticle surfactants assembled at an interface of the non-spherical droplets and the second phase is disclosed. The nanoparticle surfactants include nanoparticles and end-functionalized polymers that can interact through ligand type interactions, and the first phase is stabilized by a disordered, jammed layer of nanoparticle surfactants. A method of preparing a stabilized assembly is also disclosed.

  18. Slippery liquid-infused porous surfaces having improved stability

    Energy Technology Data Exchange (ETDEWEB)

    Aizenberg, Joanna; Vogel, Nicolas

    2017-04-25

    Methods and articles disclosed herein relate to liquid repellant surfaces having selective wetting and transport properties. An article having a repellant surface includes a substrate comprising surface features with re-entrant curvature and an immobilized layer of lubricating liquid wetting over the surface features. The surface features with re-entrant curvature can be designed to provide high repellency even after failure or removal of the immobilized layer of lubricating liquid under certain operating conditions.

  19. Composition driven structural instability in perovskite ferroelectrics

    Directory of Open Access Journals (Sweden)

    Chao Xu

    2017-04-01

    Full Text Available Ferroelectric solid solutions usually exhibit enhanced functional properties at the morphotropic phase boundary separating two ferroelectric phases with different orientations of polarization. The underlying mechanism is generally associated with polarization rotational instability and the flattened free energy profile. In this work we show that the polarization extensional instability can also be induced at the morphotropic phase boundary beyond the reported polar-nonpolar phase boundary. The piezoelectricity enhanced by this mechanism exhibits excellent thermal stability, which helps to develop high performance piezoelectric materials with good temperature stability.

  20. Foam-film-stabilized liquid bridge networks in evaporative lithography and wet granular matter

    KAUST Repository

    Vakarelski, Ivan Uriev

    2013-04-23

    Evaporative lithography using latex particle templates is a novel approach for the self-assembly of suspension-dispersed nanoparticles into ordered microwire networks. The phenomenon that drives the self-assembly process is the propagation of a network of interconnected liquid bridges between the template particles and the underlying substrate. With the aid of video microscopy, we demonstrate that these liquid bridges are in fact the border zone between the underlying substrate and foam films vertical to the substrate, which are formed during the evaporation of the liquid from the suspension. The stability of the foam films and thus the liquid bridge network stability are due to the presence of a small amount of surfactant in the evaporating solution. We show that the same type of foam-film-stabilized liquid bridge network can also propagate in 3D clusters of spherical particles, which has important implications for the understanding of wet granular matter. © 2013 American Chemical Society.

  1. Broadband Liquid Dampers to Stabilize Flexible Spacecraft Structures

    NARCIS (Netherlands)

    Kuiper, J.M.

    2012-01-01

    Mass-spring and liquid dampers enable structural vibration control to attenuate single, coupled lateral and torsional vibrations in diverse structures. Out of these, the passively tuned liquid damper (TLD) class is wanted due to its broad applicability, extreme reliability, robustness, long life

  2. Silica nanoparticle stabilization of liquid crystalline lipid dispersions: impact on enzymatic digestion and drug solubilization.

    Science.gov (United States)

    Bhatt, Achal B; Barnes, Timothy J; Prestidge, Clive A

    2015-01-01

    The high internal surface area and drug solubilizing capacity of liquid crystal lipids makes them promising oral drug delivery systems. Pluronic F127 is typically used to disperse highly viscous cubic liquid crystal lipids into cubosomes; however, such copolymers alter the internal structure and provide little control over enzymatic digestion. This study aimed to use hydrophilic silica nanoparticles to stabilize glyceryl monooleate (GMO) cubosomes prepared by ultrasonication. We investigate the influence of silica nanoparticles size and concentration on the physical (colloidal) and chemical (enzymatic digestion) stability, as well as in vitro solubilization of cinnarizine as a poorly soluble model drug. Silica stabilized nanostructured liquid crystal dispersions (120 nm to150 nm in diameter and zeta potentials of-30 mV to -60 mV) were successfully prepared with excellent long-term stability (Silica stabilized GMO cubosomes demonstrated reduced enzymatic digestion compared to pluronic F127 stabilized cubosomes. This reduced digestion was attributed to a combination of adsorbed silica nanoparticles acting as a physical barrier and excess dispersed silica adsorbing/scavenging the lipase enzyme. Under simulated intestinal digestion conditions, silica stabilized GMO cubosomes showed a greater solubilization capacity for cinnarizine, which precipitated in non-crystalline form, in comparison to pure drug suspensions or pluronic F127 stabilized GMO cubosomes. Silica nanoparticle stabilized GMO liquid crystal dispersions are a promising oral delivery vehicle.

  3. Competition, liquidity and stability: international evidence at the bank and systemic levels

    OpenAIRE

    Nguyen, Thi Ngoc My

    2017-01-01

    This thesis investigates the impact of market power on bank liquidity; the association between competition and systemic liquidity; and whether the associations between liquidity and stability at both bank- and systemic- levels are affected by competition. The first research question is explored in the context of 101 countries over 1996-2013 while the second and the third, which require listed banks, use a smaller sample of 32 nations during 2001-2013. The Panel Least Squares and the system Ge...

  4. From antiferroelectricity to ferroelectricity in smectic mesophases ...

    Indian Academy of Sciences (India)

    This contribution gives an overview of ferroelectric switching liquid crystalline phases formed by bent-core molecules. First a description of some general principles behind the mesophase formation within bent-core systems will be given, followed by a short review of the mesophase structures formed by such molecules.

  5. The Colloidal Stability of Magnetic Nanoparticles in Ionic Liquids

    Science.gov (United States)

    2015-08-03

    NOTES 14. ABSTRACT During the reporting period the development of the ionic liquid ferrofluid (ILFF) based on EMIM-NTf2 was continued. The...nitrate (EAN) miscible ferrofluid based on the high-boiling-point solvent sulfolane. As part of this collaboration we have also been investigating new... ferrofluids based on other high-boiling solvents. 15. SUBJECT TERMS Electric Propulsion, Ionic liquids 16. SECURITY CLASSIFICATION

  6. The stability of liquid-filled matrix ionization chamber electronic portal imaging devices for dosimetry purposes

    NARCIS (Netherlands)

    Louwe, R. J. W.; Tielenburg, R.; van Ingen, K. M.; Mijnheer, B. J.; van Herk, M. B.

    2004-01-01

    This study was performed to determine the stability of liquid-filled matrix ionization chamber (LiFi-type) electronic portal imaging devices (EPID) for dosimetric purposes. The short- and long-term stability of the response was investigated, as well as the importance of factors influencing the

  7. Combustion stability with baffles, absorbers and velocity sensitive combustion. [liquid propellant rocket combustors

    Science.gov (United States)

    Mitchell, C. E.

    1980-01-01

    Analytical and computational techniques were developed to predict the stability behavior of liquid propellant rocket combustors using damping devices such as acoustic liners, slot absorbers, and injector face baffles. Models were developed to determine the frequency and decay rate of combustor oscillations, the spatial and temporal pressure waveforms, and the stability limits in terms of combustion response model parameters.

  8. Stabilization of Bend Alignment Using Optical Polymerization of UV Curable Liquid Crystalline Monomers

    Science.gov (United States)

    Asakawa, Youichi; Yokota, Kouji; Nanaumi, Makoto; Takatuka, Naoki; Takahashi, Taiju; Saito, Susumu

    2006-07-01

    Director profiles and electrooptical properties in polymer-stabilized π cells used in optically compensated bend (OCB) liquid crystal displays (LCDs) are theoretically investigated by introducing an additional term which expresses the effect of polymer stabilization on the free energy density. The conditions required to stabilize the bend alignment definitively have been theoretically clarified and experimentally confirmed. As a result, the bend alignment is successfully stabilized even if the twist state is more stable than the bend state before the application of polymer-stabilization treatment.

  9. Interfacial Rheology of Sterically Stabilized Colloids at Liquid Interfaces and Its Effect on the Stability of Pickering Emulsions.

    Science.gov (United States)

    Hooghten, Rob Van; Blair, Victoria E; Vananroye, Anja; Schofield, Andrew B; Vermant, Jan; Thijssen, Job H J

    2017-05-02

    Particle-laden interfaces can be used to stabilize a variety of high-interface systems, from foams over emulsions to polymer blends. The relation between the particle interactions, the structure and rheology of the interface, and the stability of the system remains unclear. In the present work, we experimentally investigate how micron-sized, near-hard-sphere-like particles affect the mechanical properties of liquid interfaces. In particular, by comparing dried and undried samples, we investigate the effect of aggregation state on the properties of the particle-laden liquid interface and its relation to the stability of the corresponding Pickering emulsions. Partially aggregated suspensions give rise to a soft-solid-like response under shear, whereas for stable PMMA particulate layers a liquid-like behavior is observed. For interfacial creep-recovery measurements, we present an empirical method to correct for the combined effect of the subphase drag and the compliance of the double-wall ring geometry, which makes a significant contribution to the apparent elasticity of weak interfaces. We further demonstrate that both undried and dried PMMA particles can stabilize emulsions for months, dispelling the notion that particle aggregation, in bulk or at the interface, is required to create stable Pickering emulsions. Our results indicate that shear rheology is a sensitive probe of colloidal interactions but is not necessarily a predictor of the stability of interfaces, e.g., in quiescent Pickering emulsions, as in the latter the response to dilatational deformations can be of prime importance.

  10. The effects of liquidity risk and credit risk on bank stability: Evidence from the MENA region

    Directory of Open Access Journals (Sweden)

    Ameni Ghenimi

    2017-12-01

    Full Text Available The global financial crisis has induced a series of failures of most conventional banks. This study investigates the main sources of banking fragility. We use a sample of 49 banks operating in the MENA region over the period 2006–2013 to analyze the relationship between credit risk and liquidity risk and its impact on bank stability. Our results show that credit risk and liquidity risk do not have an economically meaningful reciprocal contemporaneous or time-lagged relationship. However, both risks separately influence bank stability and their interaction contributes to bank instability. These findings provide bank managers with more understanding of bank risk and serve as an underpinning for recent regulatory efforts aimed at strengthening the joint risk management of liquidity and credit risks. Keywords: Credit risk, Liquidity risk, Bank stability, MENA region, JEL Classification: F3, G21, O16, 053

  11. Stability analysis of whirling composite shells partially filled with two liquid phases

    Energy Technology Data Exchange (ETDEWEB)

    Sahebnasagh, Mohammad [Department of Mechanical Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Nikkhah-Bahrami, Mansour; Firouz-Abadi, Roohollah [Department of Aerospace Engineering, Sharif University, Tehran (Iran, Islamic Republic of)

    2017-05-15

    In this paper, the stability of whirling composite cylindrical shells partially filled with two liquid phases is studied. Using the first-order shear shell theory, the structural dynamics of the shell is modeled and based on the Navier-Stokes equations for ideal liquid, a 2D model is developed for liquid motion at each section of the cylinder. In steady state condition, liquids are supposed to locate according to mass density. In this study, the thick shells are investigated. Using boundary conditions between liquids, the model of coupled fluid-structure system is obtained. This coupled fluid-structure model is employed to determine the critical speed of the system. The effects of the main variables on the stability of the shell are studied and the results are investigated.

  12. Citral stability in oil-in-water emulsions with solid or liquid octadecane.

    Science.gov (United States)

    Mei, Longyuan; Choi, Seung Jun; Alamed, Jean; Henson, Lulu; Popplewell, Michael; McClements, D Julian; Decker, Eric A

    2010-01-13

    Citral stability in oil-in-water emulsions at pH 3.0 with solid or liquid octadecane was determined. Citral degradation was faster in anionic sodium dodecyl sulfate (SDS)-stabilized emulsions than non-ionic polyoxyethylene (23) lauryl ether (Brij)-stabilized emulsions. Crystallization of octadecane in both Brij- and SDS-stabilized emulsion droplets resulted in faster degradation of citral. Crystallization of octadecane in emulsion droplets increased citral partitioning into the aqueous phase, with 41-53% of the total citral in the aqueous phase when octadecane was solid compared to 18-25% when octadecane was liquid. This research suggests that factors that increase partitioning of citral out of the droplets of oil-in-water emulsions increase citral degradation rates. These results suggest that the stability of citral could be increased in oil-in-water emulsions by technologies that decrease its partitioning and exposure to acidic aqueous phases.

  13. Stabilization of liquid low-level and mixed wastes: a treatability study

    Energy Technology Data Exchange (ETDEWEB)

    Carson, S.; Cheng, Yu-Cheng; Yellowhorse, L.; Peterson, P.

    1996-02-01

    A treatability study has been conducted on liquid low-level and mixed wastes using the stabilization agents Aquaset, Aquaset II, Aquaset II-H, Petroset, Petroset-H, and Petroset and Petroset II. A total of 40 different waste types with activities ranging from 10{sup {minus}14} to 10{sup {minus}4} curies/ml have been stabilized. Reported data for each waste include its chemical and radiological composition and the optimum composition or range of compositions (weight of agent/volume of waste) for each stabilization agent used. All wastes were successfully stabilized with one or more of the stabilization agents and all final waste forms passed the Paint Filter Liquids Test (EPA Method 9095).

  14. Synthesis and characterization of ferroelectric liquid crystal dimers containing thioester and carboxylate linking groups in the inner side of the molecule

    Science.gov (United States)

    Senthil, S.; Kamalraj, V. R.; Wu, S. L.

    2008-08-01

    A homologous series of chiral unsymmetrical liquid crystal dimers possessing carboxyl and carbothiol linkages nearer to the chiral center were synthesized using ( S)-2-(6-methoxynapthyl-2) propionic acid as chiral starting material. All the dimers were characterized by usual spectral techniques, thermal methods and electro-optical studies. Structural effects on the mesomorphic and physicochemical properties were investigated in terms of variation of achiral chain length at both terminals and compared with our previous investigations that contain both carboxylate and both carbothiloate linkages. The microscopic investigation reveals that these dimeric compounds exhibit only SmC ∗ and SmA ∗ mesophases. The liquid crystalline behaviour of the dimers was further confirmed by DSC analysis. It was observed that the SmC ∗ phase range is increased significantly with increase in the achiral chain length. Whereas SmA ∗ phase range decreases with increase in achiral chain length. When comparing the mesomorphic behaviour of LC dimers containing -COO- and -COS- linkages, the present compounds do not exhibit metastable states but increased SmA ∗ and SmC ∗ mesophase stability. The spontaneous polarization ( Ps) and tilt angle values were also measured and a largest of 40.8 nCcm -2 and 44.5 deg were obtained, respectively.

  15. Signal Processing Methods for Liquid Rocket Engine Combustion Stability Assessments

    Science.gov (United States)

    Kenny, R. Jeremy; Lee, Erik; Hulka, James R.; Casiano, Matthew

    2011-01-01

    The J2X Gas Generator engine design specifications include dynamic, spontaneous, and broadband combustion stability requirements. These requirements are verified empirically based high frequency chamber pressure measurements and analyses. Dynamic stability is determined with the dynamic pressure response due to an artificial perturbation of the combustion chamber pressure (bomb testing), and spontaneous and broadband stability are determined from the dynamic pressure responses during steady operation starting at specified power levels. J2X Workhorse Gas Generator testing included bomb tests with multiple hardware configurations and operating conditions, including a configuration used explicitly for engine verification test series. This work covers signal processing techniques developed at Marshall Space Flight Center (MSFC) to help assess engine design stability requirements. Dynamic stability assessments were performed following both the CPIA 655 guidelines and a MSFC in-house developed statistical-based approach. The statistical approach was developed to better verify when the dynamic pressure amplitudes corresponding to a particular frequency returned back to pre-bomb characteristics. This was accomplished by first determining the statistical characteristics of the pre-bomb dynamic levels. The pre-bomb statistical characterization provided 95% coverage bounds; these bounds were used as a quantitative measure to determine when the post-bomb signal returned to pre-bomb conditions. The time for post-bomb levels to acceptably return to pre-bomb levels was compared to the dominant frequency-dependent time recommended by CPIA 655. Results for multiple test configurations, including stable and unstable configurations, were reviewed. Spontaneous stability was assessed using two processes: 1) characterization of the ratio of the peak response amplitudes to the excited chamber acoustic mode amplitudes and 2) characterization of the variability of the peak response

  16. Improving oxidative stability of liquid fish oil supplements for pets

    DEFF Research Database (Denmark)

    Thomsen, Birgitte Raagaard; Griinari, Mikko; Jacobsen, Charlotte

    2017-01-01

    of vegetable oil inclusion, the omega-3 EPA and DHA content of the blends is at least 21% of total fatty acids for both fish and tuna oil based blends. In this study we wanted to examine, whether we could reduce the level of vegetable oil inclusion without compromising oxidative stability. This study...

  17. Techniques for Liquid Rocket Combustion Spontaneous Stability and Rough Combustion Assessments

    Science.gov (United States)

    Kenny, R. J.; Giacomoni, C.; Casiano, M. J.; Fischbach, S. R.

    2016-01-01

    This work presents techniques for liquid rocket engine combustion stability assessments with respect to spontaneous stability and rough combustion. Techniques covering empirical parameter extraction, which were established in prior works, are applied for three additional programs: the F-1 Gas Generator (F1GG) component test program, the RS-84 preburner component test program, and the Marshall Integrated Test Rig (MITR) program. Stability assessment parameters from these programs are compared against prior established spontaneous stability metrics and updates are identified. Also, a procedure for comparing measured with predicted mode shapes is presented, based on an extension of the Modal Assurance Criterion (MAC).

  18. Solubilizing and stabilizing proteins in anhydrous lonic liquids through formation of protein-polymer surfactant nanoconstructs

    OpenAIRE

    Brogan, AP; Hallett, JP

    2016-01-01

    Nonaqueous biocatalysis is rapidly becoming a desirable tool for chemical and fuel synthesis in both the laboratory and industry. Similarly, ionic liquids are increasingly popular anhydrous reaction media for a number of industrial processes. Consequently, the use of enzymes in ionic liquids as efficient, environment-friendly, commercial biocatalysts is highly attractive. However, issues surrounding the poor solubility and low stability of enzymes in truly anhydrous media remain a significant...

  19. Ionic liquid-stabilized non-spherical gold nanofluids synthesized using a one-step method

    OpenAIRE

    Zhang, Hao; Cui, Hua; Yao, Shiwei; Zhang, Kelong; Tao, Haikun; Meng, Haibo

    2012-01-01

    Ionic liquid (IL)-stabilized non-spherical gold nanofluids have been synthesized by a one-step method in aqueous solution. The whole reaction proceeded in room temperature. In the presence of amino-functionalized ionic liquids, gold nanofluids with long-wave surface plasmon resonance (SPR) absorption (>600 nm) could be obtained by adopting tannic acid as the reductant. The specific SPR absorption was related to the non-spherical gold nanoparticles including gold triangle, decahedra, and icosa...

  20. Liquid permeation and chemical stability of anodic alumina membranes

    Directory of Open Access Journals (Sweden)

    Dmitrii I. Petukhov

    2017-03-01

    Full Text Available A study on the chemical stability of anodic alumina membranes and their performance in long-term water and organic solvent permeation experiments is reported. Anodic alumina possesses high stability for both protonic and aprotonic organic solvents. However, serious degradation of the membrane occurs in pure water, leading to a drastic decrease of permeance (over 20% of the initial value after the passing of 0.250 m3/m2 of pure water. The drying of the membrane induces further permeance drop-off. The rate of membrane degradation strongly depends on the pH of the penetrant solution and increases in basic media. According to 27Al NMR and thermogravimetry results, the degradation of the membranes is associated with the dissolution of water-soluble [Al13O4(OH24(H2O12]7+ polyhydroxocomplexes and their further redeposition in the form of [Al(OH4]−, resulting in channels blocking. This process intensifies in basic pH due to the high positive charge of the anodic alumina surface. An approach for improving anodic aluminum oxide stability towards dissolution in water by carbon CVD coating of the membrane walls is suggested.

  1. Ferroelectricity at the nanoscale basics and applications

    CERN Document Server

    Fridkin, Vladimir

    2014-01-01

    This book examines a wide range of ferroelectric materials. It explains the theoretical background of ultrathin ferroelectric films,  presents applications of ferroelectric materials, and displays the mechanism of switching of nanosized ferroelectric films.

  2. Large Energy Storage Density and High Thermal Stability in a Highly Textured (111)-Oriented Pb0.8Ba0.2ZrO3 Relaxor Thin Film with the Coexistence of Antiferroelectric and Ferroelectric Phases.

    Science.gov (United States)

    Peng, Biaolin; Zhang, Qi; Li, Xing; Sun, Tieyu; Fan, Huiqing; Ke, Shanming; Ye, Mao; Wang, Yu; Lu, Wei; Niu, Hanben; Zeng, Xierong; Huang, Haitao

    2015-06-24

    A highly textured (111)-oriented Pb0.8Ba0.2ZrO3 (PBZ) relaxor thin film with the coexistence of antiferroelectric (AFE) and ferroelectric (FE) phases was prepared on a Pt/TiOx/SiO2/Si(100) substrate by using a sol-gel method. A large recoverable energy storage density of 40.18 J/cm(3) along with an efficiency of 64.1% was achieved at room temperature. Over a wide temperature range of 250 K (from room temperature to 523 K), the variation of the energy density is within 5%, indicating a high thermal stability. The high energy storage performance was endowed by a large dielectric breakdown strength, great relaxor dispersion, highly textured orientation, and the coexistence of FE and AFE phases. The PBZ thin film is believed to be an attractive material for applications in energy storage systems over a wide temperature range.

  3. Influence of heat transfer on high pressure flame structure and stabilization in liquid rocket engines

    OpenAIRE

    Mari, Raphaël

    2015-01-01

    This research work deals with the problem of the flame stabilization in the context of high pressure liquid rocket engines. Flame stabilization in a rocket engine is a critical feature. An instability can lead to important damages of the engine or the destruction of the launcher and the satellite. The engines (Vulcain 2 and Vinci) of the Ariane 5, and the future Ariane 6, use the hydrogen/oxygen propellants. One characteristic of this couple is its high specific impulse. The launcher performa...

  4. Experimental investigation of the stability of a moving radial liquid sheet

    Science.gov (United States)

    Paramati, Manjula; Tirumkudulu, Mahesh

    2013-11-01

    Experiments were conducted to understand the stability of moving radial liquid sheets formed by the head-on impingement of two co-linear water jets using laser induced fluorescence technique (LIF). Acoustic sinusoidal fluctuations were introduced at the jet impingement point and we measured the displacement of the center line of the liquid sheet (sinuous mode) and the thickness variation (varicose mode) of the disturbed liquid sheet. Our experiments show that the sinuous disturbances grow as they are convected outward in the radial direction even in the smooth regime (We accounts for the inertia of the liquid phase and the surface tension force in a radial liquid sheet while neglecting the inertial effects due to the surrounding gas phase. The authors acknowledge the financial assistance from Indo-French Center for Pro- motion of Advanced Research and also Indian institute of technology Bombay.

  5. Polymer stabilized liquid crystals: Topology-mediated electro-optical behavior and applications

    Science.gov (United States)

    Weng, Libo

    There has been a wide range of liquid crystal polymer composites that vary in polymer concentration from as little as 3 wt.% (polymer stabilized liquid crystal) to as high as 60 wt.% (polymer dispersed liquid crystals). In this dissertation, an approach of surface polymerization based on a low reactive monomer concentration about 1 wt.% is studied in various liquid crystal operation modes. The first part of dissertation describes the development of a vertical alignment (VA) mode with surface polymer stabilization, and the effects of structure-performance relationship of reactive monomers (RMs) and polymerization conditions on the electro-optical behaviors of the liquid crystal device has been explored. The polymer topography plays an important role in modifying and enhancing the electro-optical performance of stabilized liquid crystal alignment. The enabling surface-pinned polymer stabilized vertical alignment (PSVA) approach has led to the development of high-performance and fast-switching displays with controllable pretilt angle, increase in surface anchoring energy, high optical contrast and fast response time. The second part of the dissertation explores a PSVA mode with in-plane switching (IPS) and its application for high-efficiency and fast-switching phase gratings. The diffraction patterns and the electro-optical behaviors including diffraction efficiency and response time are characterized. The diffraction grating mechanism and performance have been validated by computer simulation. Finally, the advantages of surface polymerization approach such as good optical contrast and fast response time have been applied to the fringe-field switching (FFS) system. The concentration of reactive monomer on the electro-optical behavior of the FFS cells is optimized. The outstanding electro-optical results and mechanism of increase in surface anchoring strength are corroborated by the director field simulation. The density and topology of nanoscale polymer protrusions

  6. Ferroelectricity in spiral magnets.

    Science.gov (United States)

    Mostovoy, Maxim

    2006-02-17

    It was recently observed that the ferroelectrics showing the strongest sensitivity to an applied magnetic field are spiral magnets. We present a phenomenological theory of inhomogeneous ferroelectric magnets, which describes their thermodynamics and magnetic field behavior, e.g., dielectric susceptibility anomalies at magnetic transitions and sudden flops of electric polarization in an applied magnetic field. We show that electric polarization can also be induced at domain walls and that magnetic vortices carry electric charge.

  7. Stability and kinetic studies of supported ionic liquid phase catalysts for hydroformylation of propene

    DEFF Research Database (Denmark)

    Riisager, Anders; Fehrmann, Rasmus; Haumann, Marco

    2005-01-01

    Supported ionic liquid phase (SILP) catalysts have been studied with regard to their long-term stability in the continuous gas-phase hydroformylation of propene. Kinetic data have been acquired by variation of temperature, pressure, syngas composition, substrate concentration, and residence time...

  8. Stabilization of thin liquid films by repulsive van der waals force

    KAUST Repository

    Li, Erqiang

    2014-05-13

    Using high-speed video recording of bubble rise experiments, we study the stability of thin liquid films trapped between a rising bubble and a surfactant-free liquid-liquid meniscus interface. Using different combinations of nonpolar oils and water that are all immiscible, we investigate the extent to which film stability can be predicted by attractive and repulsive van der Waals (vdW) interactions that are indicated by the relative magnitude of the refractive indices of the liquid combinations, for example, water (refractive index, n = 1.33), perfluorohexane (n = 1.23), and tetradecane (n = 1.43). We show that, when the film-forming phase was oil (perfluorohexane or tetradecane), the stability of the film could always be predicted from the sign of the vdW interaction, with a repulsive vdW force resulting in a stable film and an attractive vdW force resulting in film rupture. However, if aqueous electrolyte is the film-forming bulk phase between the rising air bubble and the upper oil phase, the film always ruptured, even when a repulsive vdW interaction was predicted. We interpret these results as supporting the hypothesis that a short-ranged hydrophobic attraction determines the stability of the thin water film formed between an air phase and a nonpolar oil phase. © 2014 American Chemical Society.

  9. Stability, Deactivation, and Regeneration of Chloroaluminate Ionic Liquid as Catalyst for Industrial C4 Alkylation

    Directory of Open Access Journals (Sweden)

    Xiang Li

    2017-12-01

    Full Text Available Alkylation of isobutane and 2-butene was carried out in a continuous unit using triethylamine hydrochloride (Et3NHCl-aluminum chloride (AlCl3 ionic liquid (IL as catalyst. The effects of impurities such as water, methanol, and diethyl ether on the stability of the catalytic properties and deactivation of the ionic liquid were studied in the continuous alkylation. In the Et3NHCl-2AlCl3 ionic liquid, only one half of the aluminum chloride could act as the active site. With a molar ratio of 1:1, the active aluminum chloride in the ionic liquid was deactivated by water by reaction or by diethyl ether through complexation while the complexation of aluminum chloride with two molecular proportions of methanol inactivated the active aluminum chloride in the ionic liquid. The deactivation of chloroaluminate ionic liquid was observed when the active aluminum chloride, i.e., one half of the total aluminum chloride in the ionic liquid, was consumed completely. The regeneration of the deactivated ionic liquid was also investigated and the catalytic activity could be recovered by means of replenishment with fresh aluminum chloride.

  10. Stability of an unsupported multi-layer surfactant laden liquid curtain under gravity

    Science.gov (United States)

    Henry, Dominic; Uddin, Jamal; Marston, Jeremy; Thoroddsen, Sigurdur

    2014-11-01

    The industrial process of curtain coating has long been an important method in coating applications, by which a thin liquid curtain is formed to impinge upon a moving substrate, the highly lucrative advantage being able to coat multiple layers simultaneously. We investigate the linear stability of an unsupported two-layer liquid curtain, which has insoluble surfactants in both liquids. We formulate the governing equations, simplified by making a thin film approximation, from which we obtain equations describing the steady state profiles. We then examine the response of the curtain to small perturbations about this steady state to identify conditions under which the curtain is unstable, finding the addition of surfactants stabilizes the curtain. Our results are then compared to experimental data, showing a favourable trend and therefore extending the work of Brown. D.H. would like to thank EPSRC for their financial support and KAUST for funding the experimental work.

  11. Surface modification and characterization for dispersion stability of inorganic nanometer-scaled particles in liquid media

    Science.gov (United States)

    Kamiya, Hidehiro; Iijima, Motoyuki

    2010-01-01

    Inorganic nanoparticles are indispensable for science and technology as materials, pigments and cosmetics products. Improving the dispersion stability of nanoparticles in various liquids is essential for those applications. In this review, we discuss why it is difficult to control the stability of nanoparticles in liquids. We also overview the role of surface interaction between nanoparticles in their dispersion and characterization, e.g. by colloid probe atomic force microscopy (CP-AFM). Two types of surface modification concepts, post-synthesis and in situ modification, were investigated in many previous studies. Here, we focus on post-synthesis modification using adsorption of various kinds of polymer dispersants and surfactants on the particle surface, as well as surface chemical reactions of silane coupling agents. We discuss CP-AFM as a technique to analyze the surface interaction between nanoparticles and the effect of surface modification on the nanoparticle dispersion in liquids. PMID:27877345

  12. Surface modification and characterization for dispersion stability of inorganic nanometer-scaled particles in liquid media

    Directory of Open Access Journals (Sweden)

    Hidehiro Kamiya and Motoyuki Iijima

    2010-01-01

    Full Text Available Inorganic nanoparticles are indispensable for science and technology as materials, pigments and cosmetics products. Improving the dispersion stability of nanoparticles in various liquids is essential for those applications. In this review, we discuss why it is difficult to control the stability of nanoparticles in liquids. We also overview the role of surface interaction between nanoparticles in their dispersion and characterization, e.g. by colloid probe atomic force microscopy (CP-AFM. Two types of surface modification concepts, post-synthesis and in situ modification, were investigated in many previous studies. Here, we focus on post-synthesis modification using adsorption of various kinds of polymer dispersants and surfactants on the particle surface, as well as surface chemical reactions of silane coupling agents. We discuss CP-AFM as a technique to analyze the surface interaction between nanoparticles and the effect of surface modification on the nanoparticle dispersion in liquids.

  13. Electrochemical Stability Window of Imidazolium-Based Ionic Liquids as Electrolytes for Lithium Batteries.

    Science.gov (United States)

    Kazemiabnavi, Saeed; Zhang, Zhengcheng; Thornton, Katsuyo; Banerjee, Soumik

    2016-06-30

    This paper presents the computational assessment of the electrochemical stability of a series of alkyl methylimidazolium-based ionic liquids for their use as lithium battery electrolytes. The oxidation and reduction potentials of the constituent cation and anion of each ionic liquid with respect to a Li(+)/Li reference electrode were calculated using density functional theory following the method of thermodynamic cycles, and the electrochemical stability windows (ESW)s of these ionic liquids were obtained. The effect of varying the length of alkyl side chains of the methylimidazolium-based cations on the redox potentials and ESWs was investigated. The results show that the limits of the ESWs of these methylimidazolium-based ionic liquids are defined by the oxidation potential of the anions and the reduction potential of alkyl-methylimidazolium cations. Moreover, ionic liquids with [PF6](-) anion have a wider ESW. In addition to characterizing structure-function relationships, the accuracy of the computational approach was assessed through comparisons of the data against experimental measurements of ESWs. The potentials calculated by the thermodynamic cycle method are in good agreement with the experimental data while the HOMO/LUMO method overestimates the redox potentials. This work demonstrates that these approaches can provide guidance in selecting ionic liquid electrolytes when designing high-voltage rechargeable batteries.

  14. The stability of the dome of a liquid bubble rising in a dense liquid

    Science.gov (United States)

    Kanygin, R. I.; Kascheev, A. D.; Kudryavtsev, A. Yu; Meshkov, E. E.; Novikova, I. A.

    2018-02-01

    The results of experiments researching the stability of the dome of a large water bubble rising in a salt solution are presented. The experiments demonstrate the suppression of the Rayleigh–Taylor instability on the dome of the rising bubble with the Atwood number being A ≪ 1. The intensive development of the Kelvin–Helmholtz instability on the lateral surface of the bubble is observed as it rises. The stability of the dome of the rising bubble is explained by the action of an accelerated shear flow of water over the bubble surface. The results of computational modeling of the problem by the STAR-CCM + program are presented.

  15. An optical image stabilization using a droplet manipulation on a liquid crystal and polymer composite film

    Science.gov (United States)

    Wang, Yu-Jen; Chang, Chia-Ming; Tsou, Yu-Shih; Chen, Ming-Syuan; Chen, Hung-Shan; Lin, Yi-Hsin

    2015-09-01

    Motion blur is one of the major factors decreasing the image quality of a hand-held optical imaging system while the system is under shakes or vibrations during exposure. Optical image stabilization (OIS) is a technique to reduce such a blurring. The basic principle of OIS is to stabilize the recorded image in a camera by varying the optical path to the sensor under vibrations during exposure. In this paper, we demonstrate optical image stabilization (OIS) for an imaging system using a droplet manipulation on a liquid crystal and polymer composite film (LCPCF) that reduces the motion blur. The mechanism is based on manipulation of position of the liquid lens on LCPCF by means of electrically adjusting orientations of liquid crystals. The change of the position of the liquid lens compensates the deviation of light when the image system is under a handshake vibration. Therefore, the imaging system forms a clear image with a droplet on different position to overcome handshake vibration. The concept in this paper can also be extended to design other optical components for modulating the direction of light.

  16. Doping a dipole into an incipient ferroelectric: Route to relaxor ferroelectrics

    Science.gov (United States)

    Chaudhary, N. Vijay Prakash; Sarkar, Sagar; Sharma, Neetika; Kundu, Asish K.; Menon, Krishnakumar S. R.; Das, A.; Mahadevan, Priya; Venimadhav, A.

    2017-07-01

    Ti O2 in the rutile phase is known to be an incipient ferroelectric. Considering Nb-Cr codoping we examine if ferroelectricity can be induced at the low doping limit in T i(1 -x )(Nb0.5Cr0.5 ) xO2 (x =0.05 % , 1%, 5%, and 10%). A relaxor behavior is found in the temperature range 20-120 K which obeys the Vogel-Fulcher relation while pyrocurrent measurements confirm switching of the electric polarization. The spontaneous net polarization is doping dependent with a maximum at 1% and for doping concentrations above 5% is found to be paraelectric. Ab initio density functional theory based calculations suggest that the Nb-Cr pair behaves like a dipole and polarizes the neighboring Ti O6 octahedra, stabilizing a ferroelectric ground state akin to magnetic impurities in dilute magnetic semiconductors. At larger doping concentrations one finds that Nb-Cr clusters result in a vanishing polarization.

  17. Solubilizing and Stabilizing Proteins in Anhydrous Ionic Liquids through Formation of Protein-Polymer Surfactant Nanoconstructs.

    Science.gov (United States)

    Brogan, Alex P S; Hallett, Jason P

    2016-04-06

    Nonaqueous biocatalysis is rapidly becoming a desirable tool for chemical and fuel synthesis in both the laboratory and industry. Similarly, ionic liquids are increasingly popular anhydrous reaction media for a number of industrial processes. Consequently, the use of enzymes in ionic liquids as efficient, environment-friendly, commercial biocatalysts is highly attractive. However, issues surrounding the poor solubility and low stability of enzymes in truly anhydrous media remain a significant challenge. Here, we demonstrate for the first time that engineering the surface of a protein to yield protein-polymer surfactant nanoconstructs allows for dissolution of dry protein into dry ionic liquids. Using myoglobin as a model protein, we show that this method can deliver protein molecules with near native structure into both hydrophilic and hydrophobic anhydrous ionic liquids. Remarkably, using temperature-dependent synchrotron radiation circular dichroism spectroscopy to measure half-denaturation temperatures, our results show that protein stability increases by 55 °C in the ionic liquid as compared to aqueous solution, pushing the solution thermal denaturation beyond the boiling point of water. Therefore, the work presented herein could provide a platform for the realization of biocatalysis at high temperatures or in anhydrous solvent systems.

  18. Dimensional t-factor variation and increase of stability of the ferroelectric state in (Na0.5Bi0.5)TiO3-based solid solutions

    Science.gov (United States)

    Ishchuk, V. M.; Kuzenko, D. V.; Sobolev, V. L.

    The influence of the B-site ion substitutions in (1‑x)(Bi1/2Na1/2)TiO3-xBaTiO3 system of solid solutions on the relative stability of the antiferroelectric (AFE) and ferroelectric (FE) phases has been studied. The ions of zirconium, tin, and (In0.5Nb0.5), (Fe0.5Nb0.5), (Al0.5V0.5) ion complexes have been used as substituting elements. An increase in the concentration of the substituting ion results in a near linear variation in the size of the crystal lattice cell. Along with the cell size variation, a change in the relative stability of the AFE and FE phases takes place according to the changes of the tolerance factor of the solid solution. An increase in the tolerance factor leads to the increase in the temperature of the FE-AFE phase transition, and vice versa. Obtained results indicate the way for raising the temperature of the FE-AFE phase transition in (Bi1/2Na1/2)TiO3-based solid solutions.

  19. Field-effect transistor memories based on ferroelectric polymers

    Science.gov (United States)

    Zhang, Yujia; Wang, Haiyang; Zhang, Lei; Chen, Xiaomeng; Guo, Yu; Sun, Huabin; Li, Yun

    2017-11-01

    Field-effect transistors based on ferroelectrics have attracted intensive interests, because of their non-volatile data retention, rewritability, and non-destructive read-out. In particular, polymeric materials that possess ferroelectric properties are promising for the fabrications of memory devices with high performance, low cost, and large-area manufacturing, by virtue of their good solubility, low-temperature processability, and good chemical stability. In this review, we discuss the material characteristics of ferroelectric polymers, providing an update on the current development of ferroelectric field-effect transistors (Fe-FETs) in non-volatile memory applications. Program supported partially by the NSFC (Nos. 61574074, 61774080), NSFJS (No. BK20170075), and the Open Partnership Joint Projects of NSFC–JSPS Bilateral Joint Research Projects (No. 61511140098).

  20. Ferroelectrics principles, structure and applications

    CERN Document Server

    Merchant, Serena

    2014-01-01

    Ferroelectric physics is a theory on ferroelectric phase transition for explaining various related phenomena, which is different from dielectric physics. Ferroelectric materials are important functional materials for various applications such as NVRAMs, high energy density capacitors, actuators, MEMs, sonar sensors, microphones and scanning electron microscopes (SEM). This book investigates the dielectric, ferroelectric and energy storage properties of barium zirconate-titanate/barium calcium-titanate (BZT-BCT) based ceramic for high energy density capacitors. It also compares the energy storage capabilities of ceramic powders with polymer-ceramic nanocomposites; and discusses dielectric properties of ferroelectricity in composition distributions.

  1. Review of Potential Candidate Stabilization Technologies for Liquid and Solid Secondary Waste Streams

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, Eric M.; Mattigod, Shas V.; Westsik, Joseph H.; Serne, R. Jeffrey; Icenhower, Jonathan P.; Scheele, Randall D.; Um, Wooyong; Qafoku, Nikolla

    2010-01-30

    Pacific Northwest National Laboratory has initiated a waste form testing program to support the long-term durability evaluation of a waste form for secondary wastes generated from the treatment and immobilization of Hanford radioactive tank wastes. The purpose of the work discussed in this report is to identify candidate stabilization technologies and getters that have the potential to successfully treat the secondary waste stream liquid effluent, mainly from off-gas scrubbers and spent solids, produced by the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Down-selection to the most promising stabilization processes/waste forms is needed to support the design of a solidification treatment unit (STU) to be added to the Effluent Treatment Facility (ETF). To support key decision processes, an initial screening of the secondary liquid waste forms must be completed by February 2010.

  2. Standard Test Method for Preparing Aircraft Cleaning Compounds, Liquid Type, Water Base, for Storage Stability Testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2002-01-01

    1.1 This test method covers the determination of the stability in storage, of liquid, water-base chemical cleaning compounds, used to clean the exterior surfaces of aircraft. 1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  3. Study of the fission process of deformed Na clusters in liquid-drop stabilized jellium model

    Directory of Open Access Journals (Sweden)

    M Payami

    2008-07-01

    Full Text Available   In this work, using the liquid drop model in the context of the stabilized jellium model, we have studied the fission of charged Na clusters. In this study we have assumed a deformed non-spherical shape for the cluster. The ground state energies, critical sizes, fission barrier height, and the evaporation energies have been calculated. The results show a better agreement to the experimental results compared to our earlier work.

  4. CONCERNS OF CONTEMPORARY DISINFECTION: CHLORINE OR STABILIZED LIQUID SOLUTION OF CHLORINE DIOXIDE

    OpenAIRE

    Abdulah Gagić; Selma Selimović; Suad Jukić; Ajla Ališah; Aida Kustura

    2014-01-01

    It is common that experts use routine procedures for disinfection. Every part of the disinfection procedure is routinely done: preparation of the disinfection media, selection of the type of disinfection, protective measures, effect control and environmental issues. This article offers a new insight into the use of stabilized liquid chlorine dioxide as a qualitative alternative disinfectant for wider application by comparing it to the most frequently used chlorine and its compounds. When used...

  5. The stability of motion of satellites with cavities partially filled with liquid

    Science.gov (United States)

    Nayfeh, A. H.; Meirovitch, L.

    1975-01-01

    The stability and time dependent motion of a spinning satellite, simulated by a rigid body with a cavity partially filled with liquid is examined. The problem formulation, consisting of the boundary-value problem for the liquid and moment equations for the entire system is presented. Because of large Reynold's numbers involved, viscosity effects are negligible everywhere except for a thin boundary layer near the wetted surface. Using a boundary-layer analysis, the effect of the boundary layer is replaced by modified boundary conditions for the liquid. The solution of the differential equations for the inviscid problem is solved in closed form. A semi-analytical numerical solution of the inviscid equations subject to the viscous boundary condition has proved unsucessful.

  6. Surface-screening mechanisms in ferroelectric thin films and their effect on polarization dynamics and domain structures.

    Science.gov (United States)

    Kalinin, Sergei V; Kim, Yunseok; Fong, Dillon D; Morozovska, Anna N

    2018-03-01

    For over 70 years, ferroelectric materials have been one of the central research topics for condensed matter physics and material science, an interest driven both by fundamental science and applications. However, ferroelectric surfaces, the key component of ferroelectric films and nanostructures, still present a significant theoretical and even conceptual challenge. Indeed, stability of ferroelectric phase per se necessitates screening of polarization charge. At surfaces, this can lead to coupling between ferroelectric and semiconducting properties of material, or with surface (electro) chemistry, going well beyond classical models applicable for ferroelectric interfaces. In this review, we summarize recent studies of surface-screening phenomena in ferroelectrics. We provide a brief overview of the historical understanding of the physics of ferroelectric surfaces, and existing theoretical models that both introduce screening mechanisms and explore the relationship between screening and relevant aspects of ferroelectric functionalities starting from phase stability itself. Given that the majority of ferroelectrics exist in multiple-domain states, we focus on local studies of screening phenomena using scanning probe microscopy techniques. We discuss recent studies of static and dynamic phenomena on ferroelectric surfaces, as well as phenomena observed under lateral transport, light, chemical, and pressure stimuli. We also note that the need for ionic screening renders polarization switching a coupled physical-electrochemical process and discuss the non-trivial phenomena such as chaotic behavior during domain switching that stem from this.

  7. Stability and break-up of thin liquid films on patterned and structured surfaces.

    Science.gov (United States)

    Ajaev, Vladimir S; Gatapova, Elizaveta Ya; Kabov, Oleg A

    2016-02-01

    Solid surfaces with chemical patterning or topographical structure have attracted attention due to many potential applications such as manufacture of flexible electronics, microfluidic devices, microscale cooling systems, as well as development of self-cleaning, antifogging, and antimicrobial surfaces. In many configurations involving patterned or structured surfaces, liquid films are in contact with such solid surfaces and the issue of film stability becomes important. Studies of stability in this context have been largely focused on specific applications and often not connected to each other. The purpose of the present review is to provide a unified view of the topic of stability and rupture of liquid films on patterned and structured surfaces, with particular focus on common mathematical methods, such as lubrication approximation for the liquid flow, bifurcation analysis, and Floquet theory, which can be used for a wide variety of problems. The physical mechanisms of the instability discussed include disjoining pressure, thermocapillarity, and classical hydrodynamic instability of gravity-driven flows. Motion of a contact line formed after the film rupture is also discussed, with emphasis on how the receding contact angle is expected to depend on the small-scale properties of the substrate.

  8. Stability of an unsupported multi-layer surfactant laden liquid curtain under gravity

    KAUST Repository

    Henry, D.

    2015-11-07

    The industrial process of curtain coating has long been an important method in coating applications, by which a thin liquid curtain is formed to impinge upon a moving substrate, due to its highly lucrative advantage of being able to coat multiple layers simultaneously. We investigate the linear stability of an unsupported two-layer liquid curtain, which has insoluble surfactants in both liquids, which are widely used in industry to increase the stability of the curtain. We formulate the governing equations, simplified by making a thin film approximation, from which we obtain equations describing the steady-state profiles. We then examine the response of the curtain to small perturbations about this steady state to identify conditions under which the curtain is unstable, finding the addition of surfactants stabilizes the curtain. Our results are then compared to experimental data, showing a favourable trend and thereby extending the works of Brown (J Fluid Mech 10:297–305, 1960) and Dyson et al. (J Eng Math 64:237–250, 2009).

  9. Ionic Liquid Confined in Mesoporous Polymer Membrane with Improved Stability for CO2/N2 Separation

    Directory of Open Access Journals (Sweden)

    Ming Tan

    2017-09-01

    Full Text Available Supported ionic liquid membranes (SILMs have a promising prospect of application in flue gas separation, owing to its high permeability and selectivity of CO2. However, existing SILMs have the disadvantage of poor stability due to the loss of ionic liquid from the large pores of the macroporous support. In this study, a novel SILM with high stability was developed by confining ionic liquid in a mesoporous polymer membrane. First, a mesoporous polymer membrane derived from a soluble, low-molecular-weight phenolic resin precursor was deposited on a porous Al2O3 support, and then 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4] was immobilized inside mesopores of phenolic resin, forming the SILM under vacuum. Effects of trans-membrane pressure difference on the SILM separation performance were investigated by measuring the permeances of CO2 and N2. The SILM exhibits a high ideal CO2/N2 selectivity of 40, and an actual selectivity of approximately 25 in a mixed gas (50% CO2 and 50% N2 at a trans-membrane pressure difference of 2.5 bar. Compared to [emim][BF4] supported by polyethersulfone membrane with a pore size of around 0.45 μm, the [emim][BF4] confined in a mesoporous polymer membrane exhibits an improved stability, and its separation performance remained stable for 40 h under a trans-membrane pressure difference of 1.5 bar in a mixed gas before the measurement was intentionally stopped.

  10. Stability and magnetorheological behaviour of magnetic fluids based on ionic liquids

    Science.gov (United States)

    Rodríguez-Arco, Laura; López-López, Modesto T.; Durán, Juan D. G.; Zubarev, Andrey; Chirikov, Dmitrij

    2011-11-01

    This paper reports the preparation of magnetic fluids consisting of magnetite nanoparticles dispersed in an ionic liquid. Different additives were used in order to stabilize the fluids. Colloidal stability was checked by magnetic sedimentation, centrifugation and direct observation. The results of these tests showed that a true ferrofluid was only obtained when the nanoparticles were coated with a layer of surfactant compatible with the ionic liquid. These experiments also showed that stability could not be reached just by electrostatic repulsion. The conclusions of the stability tests were confirmed by calculations of the interparticle energies of interaction. The rheological behaviour of the magnetic fluids upon magnetic field application was also investigated. The experimental magnetoviscous response was fitted by a microstructural model. The model considered that the fluids consisted of two populations of particles, one with a magnetic core diameter of 9 nm, and another with a larger diameter. Upon field application chain-like structures are supposed to be induced. According to estimations particles of 9 nm are too small to aggregate upon field application. The results of the calculations showed that the intensity of the magnetoviscous response depends on the concentration and size of the large particles, and on the thickness of the surfactant layers.

  11. Colloidal stability of bare and polymer-grafted silica nanoparticles in ionic liquids.

    Science.gov (United States)

    Ueno, Kazuhide; Inaba, Aya; Kondoh, Masashi; Watanabe, Masayoshi

    2008-05-20

    The colloidal stability of bare and poly(methyl methacrylate) (PMMA)-grafted silica nanoparticles was studied in 1-alkyl-3-methylimidazolium ([C(n)mim])-based ionic liquids (ILs) with different anionic structures. The theoretical estimation of the colloidal interaction between monodispersed bare silica particles by using the Derjaguin-Landau-Verwey-Overbeek theory indicates that bare silica particles cannot be stabilized and they rapidly form aggregates in all the ILs used in this study. The instability of bare silica particles was experimentally confirmed by dynamic light scattering measurement and in situ transmission electron microscopy observations by utilizing the negligible vapor pressure of ILs. This evidence suggests that electrostatic stabilization is inefficient in ILs because of the high ionic atmosphere and the resulting surface-charge screening. The PMMA-grafted silica particles exhibited long-term colloidal stability in [C(4)mim][PF(6)] and [C(n)mim][NTf(2)], which are compatible with the grafted PMMA. On the other hand, the PMMA-grafted particles could not be stabilized in [C 4mim][BF 4] due to the poor solubility of the grafted PMMA in the IL. Effective steric stabilization is important for obtaining stable colloidal particles in ILs.

  12. Domains in Ferroelectric Nanostructures

    Science.gov (United States)

    Gregg, Marty

    2010-03-01

    Ferroelectric materials have great potential in influencing the future of small scale electronics. At a basic level, this is because ferroelectric surfaces are charged, and so interact strongly with charge-carrying metals and semiconductors - the building blocks for all electronic systems. Since the electrical polarity of the ferroelectric can be reversed, surfaces can both attract and repel charges in nearby materials, and can thereby exert complete control over both charge distribution and movement. It should be no surprise, therefore, that microelectronics industries have already looked very seriously at harnessing ferroelectric materials in a variety of applications, from solid state memory chips (FeRAMs) to field effect transistors (FeFETs). In all such applications, switching the direction of the polarity of the ferroelectric is a key aspect of functional behavior. The mechanism for switching involves the field-induced nucleation and growth of domains. Domain coarsening, through domain wall propagation, eventually causes the entire ferroelectric to switch its polar direction. It is thus the existence and behavior of domains that determine the switching response, and ultimately the performance of the ferroelectric device. A major issue, associated with the integration of ferroelectrics into microelectronic devices, has been that the fundamental properties associated with ferroelectrics, when in bulk form, appear to change quite dramatically and unpredictably when at the nanoscale: new modes of behaviour, and different functional characteristics from those seen in bulk appear. For domains, in particular, the proximity of surfaces and boundaries have a dramatic effect: surface tension and depolarizing fields both serve to increase the equilibrium density of domains, such that minor changes in scale or morphology can have major ramifications for domain redistribution. Given the importance of domains in dictating the overall switching characteristics of a device

  13. Linear morphological stability analysis of the solid-liquid interface in rapid solidification of a binary system.

    Science.gov (United States)

    Galenko, P K; Danilov, D A

    2004-05-01

    The interface stability against small perturbations of the planar solid-liquid interface is considered analytically in linear approximation. Following the analytical procedure of Trivedi and Kurz [Acta Metall. 34, 1663 (1986)

  14. Ferroelectric and dielectric characterization studies on relaxor- and ferroelectric-like strontium-barium niobates

    Directory of Open Access Journals (Sweden)

    K. Matyjasek

    2013-01-01

    Full Text Available Ferroelectric domain structure evolution induced by an external electric field was investigated by means of nematic liquid crystal (NLC method in two strontium-barium niobate single crystals of nominal composition: Sr0.70Ba0.30Nb2O6 (SBN:70 - relaxor and Sr0.26Ba0.74Nb2O6 (SBN:26 - ferroelectric. Our results provide evidence that the broad phase transition and frequency dispersion that are exhibited in SBN:70 crystal have a strong link to the configuration of ferroelectric microdomains. The large leakage current revealed in SBN:26 may compensate internal charges acting as pinning centers for domain walls, which gives rise to a less restricted domain growth similar to that observed in classical ferroelectrics. Microscale studies of a switching process in conjunction with electrical measurements allowed us to establish a relationship between local properties of the domain dynamics and macroscopic response i.e., polarization hysteresis loop and dielectric properties.

  15. A thermally robust and thickness independent ferroelectric phase in laminated hafnium zirconium oxide

    Directory of Open Access Journals (Sweden)

    S. Riedel

    2016-09-01

    Full Text Available Ferroelectric properties in hafnium oxide based thin films have recovered the scaling potential for ferroelectric memories due to their ultra-thin-film- and CMOS-compatibility. However, the variety of physical phenomena connected to ferroelectricity allows a wider range of applications for these materials than ferroelectric memory. Especially mixed HfxZr1-xO2 thin films exhibit a broad compositional range of ferroelectric phase stability and provide the possibility to tailor material properties for multiple applications. Here it is shown that the limited thermal stability and thick-film capability of HfxZr1-xO2 can be overcome by a laminated approach using alumina interlayers.

  16. Laboratory Study of MHD Effects on Stability of Free-surface Liquid Metal Flow

    Science.gov (United States)

    Burin, M. J.; Ji, H.; McMurtry, K.; Peterson, L.; Giannakis, D.; Rosner, R.; Fischer, P.

    2006-10-01

    The dynamics of free-surface MHD shear flows is potentially important to both astrophysics (e.g. in the mixing of dense plasma accreted upon neutron star surfaces) and fusion reactors (e.g. in liquid metal ‘first walls’). To date however few relevant experiments exist. In order to study the fundamental physics of such flows, a small-scale laboratory experiment is being built using a liquid gallium alloy flowing in an open- channel geometry. The flow dimensions are nominally 10cm wide, 1cm deep, and 70cm long under an imposed magnetic field up to 7kG, leading to maximum Hartman number of 2000 and maximum Reynolds number of 4x10^5. Two basic physics issues will ultimately be addressed: (1) How do MHD effects modify the stability of the free surface? For example, is the flow more stable (through the suppression of cross-field motions), or less stable (through the introduction of new boundary layers)? We also investigate whether internal shear layers and imposed electric currents can control the surface stability. (2) How do MHD effects modify free-surface convection driven by a vertical and/or horizontal temperature gradient? We discuss aspects of both of these issues, along with detailed descriptions of the experimental device. Pertinent theoretical stability analyses and initial hydrodynamic results are presented in companion posters. This work is supported by DoE under contract #DE-AC02-76-CH03073.

  17. Stabilizing effect of elasticity on the inertial instability of submerged viscoelastic liquid jets

    Science.gov (United States)

    Keshavarz, Bavand; McKinley, Gareth

    2017-11-01

    The stability of submerged Newtonian and viscoelastic liquid jets is studied experimentally using flow visualization. Precise control of the amplitude and frequency of the imposed linear perturbations is achieved through a piezoelectric actuator attached to the nozzle. By illuminating the jet with a strobe light driven at a frequency slightly less than the frequency of the perturbation we slow down the apparent motion by large factors ( 100 , 000) and capture the phenomena with high temporal and spatial resolution. Newtonian liquid jets become unstable at moderate Reynolds numbers (Rej 150) and sinuous or varicose patterns emerge and grow in amplitude. As the jet moves downstream, the varicose waves gradually pile up in the sinuous ones due to the difference in their corresponding wave speeds, leading to a unique chevron-like morphology. Experiments with model viscoelastic polymer solutions show that this inertial instability is fully stabilized sufficiently large levels of elasticity. We compare our experimental results with the theoretical predictions of an elastic Rayleigh equation for an axisymmetric jet and show that the presence of streamline tension is indeed the stabilizing effect for inertioelastic jets.

  18. Evolution of liquid holdup profile in a standing protein stabilized foam.

    Science.gov (United States)

    Wang, Zebin; Narsimhan, Ganesan

    2004-12-01

    Evolution of liquid holdup profile in a standing foam formed by whipping and stabilized by sodium caseinate in the presence of xanthan gum when subjected to 16 and 29g centrifugal force fields was measured using magnetic resonance imaging for different pH, ionic strength, protein and xanthan gum concentrations. Drainage resulted in the formation of a separate liquid layer at the bottom at longer times. Foam drainage was slowest at pH 7, lower ionic strength, higher protein and gum concentrations. Foam was found to be most stable at pH 5.1 near the isoelectric point of protein, lower ionic strength and higher protein and xanthan gum concentrations. A predicted equilibrium liquid holdup profile based on a previous model (G. Narsimhan, J. Food Eng. 14 (1991) 139) agreed well with experimental values at sufficiently long times. A proposed model for velocity of drainage of a power law fluid in a Plateau border for two different simplified geometries was incorporated in a previously developed model for foam drainage (G. Narsimhan, J. Food Eng. 14 (1991) 139) to predict the evolution of liquid holdup profiles. The model predictions for simplified circular geometry of Plateau border compared well with the experimental data of liquid holdup profiles at small times. At longer times, however, the predicted liquid holdup profile was larger than the observed, this discrepancy being due to coarsening of bubble size and decrease in foam height not accounted for in the model. A Newtonian model for foam drainage under predicted drainage rates did not agree with the experimental data.

  19. The stability of liquid-filled matrix ionization chamber electronic portal imaging devices for dosimetry purposes.

    Science.gov (United States)

    Louwe, R J W; Tielenburg, R; van Ingen, K M; Mijnheer, B J; van Herk, M B

    2004-04-01

    This study was performed to determine the stability of liquid-filled matrix ionization chamber (LiFi-type) electronic portal imaging devices (EPID) for dosimetric purposes. The short- and long-term stability of the response was investigated, as well as the importance of factors influencing the response (e.g., temperature fluctuations, radiation damage, and the performance of the electronic hardware). It was shown that testing the performance of the electronic hardware as well as the short-term stability of the imagers may reveal the cause of a poor long-term stability of the imager response. In addition, the short-term stability was measured to verify the validity of the fitted dose-response curve immediately after beam startup. The long-term stability of these imagers could be considerably improved by correcting for room temperature fluctuations and gradual changes in response due to radiation damage. As a result, the reproducibility was better than 1% (1 SD) over a period of two years. The results of this study were used to formulate recommendations for a quality control program for portal dosimetry. The effect of such a program was assessed by comparing the results of portal dosimetry and in vivo dosimetry using diodes during the treatment of 31 prostate patients. The improvement of the results for portal dosimetry was consistent with the deviations observed with the reproducibility tests in that particular period. After a correction for the variation in response of the imager, the average difference between the measured and prescribed dose during the treatment of prostate patients was -0.7%+/-1.5% (1 SD), and -0.6%+/-1.1% (1 SD) for EPID and diode in vivo dosimetry, respectively. It can be concluded that a high stability of the response can be achieved for this type of EPID by applying a rigorous quality control program.

  20. Molecular ferroelectrics: where electronics meet biology.

    Science.gov (United States)

    Li, Jiangyu; Liu, Yuanming; Zhang, Yanhang; Cai, Hong-Ling; Xiong, Ren-Gen

    2013-12-28

    In the last several years, we have witnessed significant advances in molecular ferroelectrics, with the ferroelectric properties of molecular crystals approaching those of barium titanate. In addition, ferroelectricity has been observed in biological systems, filling an important missing link in bioelectric phenomena. In this perspective, we will present short historical notes on ferroelectrics, followed by an overview of the fundamentals of ferroelectricity. The latest developments in molecular ferroelectrics and biological ferroelectricity will then be highlighted, and their implications and potential applications will be discussed. We close by noting molecular ferroelectric as an exciting frontier between electronics and biology, and a number of challenges ahead are also described.

  1. Ferroelectric materials and their applications

    CERN Document Server

    Xu, Y

    2013-01-01

    This book presents the basic physical properties, structure, fabrication methods and applications of ferroelectric materials. These are widely used in various devices, such as piezoelectric/electrostrictive transducers and actuators, pyroelectric infrared detectors, optical integrated circuits, optical data storage, display devices, etc. The ferroelectric materials described in this book include a relatively complete list of practical and promising ferroelectric single crystals, bulk ceramics and thin films. Included are perovskite-type, lithium niobate, tungsten-bronze-type, water-soluable

  2. Ionic liquid-stabilized non-spherical gold nanofluids synthesized using a one-step method.

    Science.gov (United States)

    Zhang, Hao; Cui, Hua; Yao, Shiwei; Zhang, Kelong; Tao, Haikun; Meng, Haibo

    2012-10-23

    Ionic liquid (IL)-stabilized non-spherical gold nanofluids have been synthesized by a one-step method in aqueous solution. The whole reaction proceeded in room temperature. In the presence of amino-functionalized ionic liquids, gold nanofluids with long-wave surface plasmon resonance (SPR) absorption (>600 nm) could be obtained by adopting tannic acid as the reductant. The specific SPR absorption was related to the non-spherical gold nanoparticles including gold triangle, decahedra, and icosahedra nanocrystals. All the nanocrystals were observed by transmission electron microscopy. It was deduced that the formation of non-spherical gold nanofluids was related to the hydroxyls in tannic acid while IL acted as the synthesis template.

  3. Quantum electrodynamics in 2 + 1 dimensions, confinement, and the stability of U(1) spin liquids.

    Science.gov (United States)

    Nogueira, Flavio S; Kleinert, Hagen

    2005-10-21

    Compact quantum electrodynamics in 2 + 1 dimensions often arises as an effective theory for a Mott insulator, with the Dirac fermions representing the low-energy spinons. An important and controversial issue in this context is whether a deconfinement transition takes place. We perform a renormalization group analysis to show that deconfinement occurs when N > Nc = 36/pi3 approximately to 1.161, where N is the number of fermion replica. For N Nc-. Our results imply the stability of a spin liquid at the physical value N = 2 for Mott insulators.

  4. Comprehensive Insights into the Thermal Stability, Biodegradability, and Combustion Chemistry of Pyrrolidinium-Based Ionic Liquids.

    Science.gov (United States)

    Eshetu, Gebrekidan Gebresilassie; Jeong, Sangsik; Pandard, Pascal; Lecocq, Amandine; Marlair, Guy; Passerini, Stefano

    2017-08-10

    The use of ionic liquids (ILs) as advanced electrolyte components in electrochemical energy-storage devices is one of the most appealing and emerging options. However, although ILs are hailed as safer and eco-friendly electrolytes, to overcome the limitations imposed by the highly volatile/combustible carbonate-based electrolytes, full-scale and precise appraisal of their overall safety levels under abuse conditions still needs to be fully addressed. With the aim of providing this level of information on the thermal and chemical stabilities, as well as actual fire hazards, herein, a detailed investigation of the short- and long-term thermal stabilities, biodegradability, and combustion behavior of various pyrrolidinium-based ILs, with different alkyl chain lengths, counteranions, and cations, as well as the effect of doping with lithium salts, is described. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Improving Heterogeneous Catalyst Stability for Liquid-phase Biomass Conversion and Reforming.

    Science.gov (United States)

    Héroguel, Florent; Rozmysłowicz, Bartosz; Luterbacher, Jeremy S

    2015-01-01

    Biomass is a possible renewable alternative to fossil carbon sources. Today, many bio-resources can be converted to direct substitutes or suitable alternatives to fossil-based fuels and chemicals. However, catalyst deactivation under the harsh, often liquid-phase reaction conditions required for biomass treatment is a major obstacle to developing processes that can compete with the petrochemical industry. This review presents recently developed strategies to limit reversible and irreversible catalyst deactivation such as metal sintering and leaching, metal poisoning and support collapse. Methods aiming to increase catalyst lifetime include passivation of low-stability atoms by overcoating, creation of microenvironments hostile to poisons, improvement of metal stability, or reduction of deactivation by process engineering.

  6. Stability analysis of liquid filled spacecraft system with flexible attachment by using the energy–Casimir method

    Directory of Open Access Journals (Sweden)

    Yulong Yan

    2016-03-01

    Full Text Available The stability of partly liquid filled spacecraft with flexible attachment was investigated in this paper. Liquid sloshing dynamics was simplified as the spring–mass model, and flexible attachment was modeled as the linear shearing beam. The dynamic equations and Hamiltonian of the coupled spacecraft system were given by analyzing the rigid body, liquid fuel, and flexible appendage. Nonlinear stability conditions of the coupled spacecraft system were derived by computing the variation of Casimir function which was added to the Hamiltonian. The stable region of the parameter space was given and validated by numerical computation. Related results suggest that the change of inertia matrix, the length of flexible attachment, spacecraft spinning rate, and filled ratio of liquid fuel tank have strong influence on the stability of the spacecraft system.

  7. Ferroelectricity the fundamentals collection

    CERN Document Server

    Jimenez, Basilio

    2008-01-01

    This indispensable collection of seminal papers on ferroelectricity provides an overview over almost a hundred years of basic and applied research. Containing historic contributions from renowned authors, this book presents developments in an area of science that is still rapidly growing. Although primarily aimed at scientists and academics involved in research, this will also be of use to students as well as newcomers to the field.

  8. Stabilization of enzymes in ionic liquids via modification of enzyme charge.

    Science.gov (United States)

    Nordwald, Erik M; Kaar, Joel L

    2013-09-01

    Due to the propensity of ionic liquids (ILs) to inactivate enzymes, the development of strategies to improve enzyme utility in these solvents is critical to fully exploit ILs for biocatalysis. We have developed a strategy to broadly improve enzyme utility in ILs based on elucidating the effect of charge modifications on the function of enzymes in IL environments. Results of stability studies in aqueous-IL mixtures indicated a clear connection between the ratio of enzyme-containing positive-to-negative sites and enzyme stability in ILs. Stability studies of the effect of [BMIM][Cl] and [EMIM][EtSO4 ] on chymotrypsin specifically found an optimum ratio of positively-charged amine-to-negatively-charged acid groups (0.39). At this ratio, the half-life of chymotrypsin was increased 1.6- and 4.3-fold relative to wild-type chymotrypsin in [BMIM][Cl] and [EMIM][EtSO4 ], respectively. The half-lives of lipase and papain were similarly increased as much as 4.0 and 2.4-fold, respectively, in [BMIM][Cl] by modifying the ratio of positive-to-negative sites of each enzyme. More generally, the results of stability studies found that modifications that reduce the ratio of enzyme-containing positive-to-negative sites improve enzyme stability in ILs. Understanding the impact of charge modification on enzyme stability in ILs may ultimately be exploited to rationally engineer enzymes for improved function in IL environments. Copyright © 2013 Wiley Periodicals, Inc.

  9. Aging effect evolution during ferroelectric-ferroelectric phase transition: A mechanism study

    Directory of Open Access Journals (Sweden)

    Zuyong Feng

    2013-06-01

    Full Text Available Aging can significantly modify the dielectric, piezoelectric, and ferroelectric performance of ferroelectrics. However, little attention has been paid to the aging effect during ferroelectric-ferroelectric phase transitions that is essentially correlated with real applications. In this letter, the authors report the aging effect evolution between two ferroelectric phases in an acceptor-doped piezoceramics. The results show that aging-induced double hysteresis loops were exhibited in different ferroelectric phases, but disappeared during ferroelectric-ferroelectric phase transitions, suggesting the mechanism that the intrinsic restoring force for the reversible switching of domains caused by the alignment of defect dipoles was weakened due to ferroelectric dipole reorientation.

  10. Phosphomolybdic acid-responsive Pickering emulsions stabilized by ionic liquid functionalized Janus nanosheets.

    Science.gov (United States)

    Meng, Qing Bo; Yang, Peng; Feng, Tianyang; Ji, Xuyang; Zhang, Qian; Liu, Daliang; Wu, Shuyao; Liang, Fuxin; Zheng, Zhaoliang; Song, Xi-Ming

    2017-12-01

    A type of ionic liquid functionalized high-aspect-ratio Janus SiO2 nanosheets (IL-Janus nanosheets), which possesses a side terminated by imidazolin salt groups and the opposite side terminated by phenyl groups, was prepared and its emulsification performance was investigated. The surface wettability of ionic liquid functionalized side could be tailored via simple anion exchanging, giving the amphiphilic or totally hydrophobic Janus nanosheets. The influence of several parameters including surface wettability, particle concentration, oil composition, oil-water ratio as well as initial location of the nanosheets on the stability, morphology and type of the Pickering emulsions (O/W or W/O) stabilized by the amphiphilic IL-Janus nanosheets was evaluated. The research results revealed that average emulsion droplets size was decreased with increase of nanosheets concentration below a concentration value but had almost no change beyond the concentration; catastrophic phase inversion phenomenon occurred by varying volume fraction of water phase in the oil-water systems, and transitional phase inversion could be achieved by in-situ exchanging Cl(-) anion of the IL-Janus nanosheets with phosphomolybdate H2PMo12O40(-). The responsiveness of Pickering emulsions towards phosphomolybdic acid is resulted from irreversible anion exchanging of Cl(-) by H2PMo12O40(-) and the variation of surface wettability of the nanosheets. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Electric field stabilization of viscous liquid layers coating the underside of a surface

    Science.gov (United States)

    Anderson, Thomas G.; Cimpeanu, Radu; Papageorgiou, Demetrios T.; Petropoulos, Peter G.

    2017-05-01

    We investigate the electrostatic stabilization of a viscous thin film wetting the underside of a horizontal surface in the presence of an electric field applied parallel to the surface. The model includes the effect of bounding solid dielectric regions above and below the liquid-air system that are typically found in experiments. The competition between gravitational forces, surface tension, and the nonlocal effect of the applied electric field is captured analytically in the form of a nonlinear evolution equation. A semispectral solution strategy is employed to resolve the dynamics of the resulting partial differential equation. Furthermore, we conduct direct numerical simulations (DNS) of the Navier-Stokes equations using the volume-of-fluid methodology and assess the accuracy of the obtained solutions in the long-wave (thin-film) regime when varying the electric field strength from zero up to the point when complete stabilization occurs. We employ DNS to examine the limitations of the asymptotically derived behavior as the liquid layer thickness increases and find excellent agreement even beyond the regime of strict applicability of the asymptotic solution. Finally, the asymptotic and computational approaches are utilized to identify robust and efficient active control mechanisms allowing the manipulation of the fluid interface in light of engineering applications at small scales, such as mixing.

  12. Collagen films with stabilized liquid crystalline phases and concerns on osteoblast behaviors

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Minjian; Ding, Shan; Min, Xiang; Jiao, Yanpeng, E-mail: tjiaoyp@jnu.edu.cn; Li, Lihua; Li, Hong; Zhou, Changren, E-mail: tcrz9@jnu.edu.cn

    2016-01-01

    To duplicate collagen's in vivo liquid crystalline (LC) phase and investigate the relationship between the morphology of LC collagen and osteoblast behavior, a self-assembly method was introduced for preparing collagen films with a stabilized LC phase. The LC texture and topological structure of the films before and after stabilization were observed with polarizing optical microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The relationship between the collagen films and osteoblast behavior was studied with the 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide method, proliferation index detection, alkaline phosphatase measurements, osteocalcin assay, inverted microscopy, SEM observation, AFM observation, and cytoskeleton fluorescence staining. The results showed that the LC collagen film had continuously twisting orientations in the cholesteric phase with a typical series of arced patterns. The collagen fibers assembled in a well-organized orientation in the LC film. Compared to the non-LC film, the LC collagen film can promote cell proliferation, and increase ALP and osteocalcin expression, revealing a contact guide effect on osteoblasts. - Highlights: • Collagen film with liquid crystalline (LC) phase was observed by POM, SEM and AFM. • The effect of LC collagen film on osteoblasts behaviors was studied in detail. • LC collagen film promoted osteoblast proliferation and osteogenesis activity.

  13. Stability analysis of inclined stratified two-phase gas-liquid flow

    Energy Technology Data Exchange (ETDEWEB)

    Salhi, Yacine, E-mail: yasalhi@ulb.ac.b [Laboratoire de Mecanique des Fluides Theorique et Appliquee, Faculte de Physique, U.S.T.H.B. El-Alia B.P. 32 16111. Alger (Algeria); Service Aero-Thermo-Mecanique Faculte des Sciences Appliquees Universite Libre de Bruxelles CP165, avenue F.D. Roosevelt 50, 1050 Bruxelles, Belgique (Belgium); Si-Ahmed, El-Khider [Laboratoire de Mecanique des Fluides Theorique et Appliquee, Faculte de Physique, U.S.T.H.B. El-Alia B.P. 32 16111. Alger (Algeria); GEPEA, Universite de Nantes, CNRS, UMR6144, CRTT-BP 406, 44602 Saint-Nazaire (France); Legrand, Jack [GEPEA, Universite de Nantes, CNRS, UMR6144, CRTT-BP 406, 44602 Saint-Nazaire (France); Degrez, Gerard [Service Aero-Thermo-Mecanique Faculte des Sciences Appliquees Universite Libre de Bruxelles CP165, avenue F.D. Roosevelt 50, 1050 Bruxelles, Belgique (Belgium)

    2010-05-15

    The present investigation involves the modeling of gas-liquid interface in a two-phase stratified flow through a horizontal or nearly-horizontal circular duct. The most complete and fundamental model used for these calculations is known as the one-dimensional two-fluid model. It is the most accurate of the two-phase models since it considers each phase independently and links both phases with six conservation equations. The mass and momentum balance equations are written in dimensionless form. The dimensionless mass and momentum balance equations are combined with the method of characteristics and an explicit method to simulate the flow. At first, the linear stability of the flow is investigated by disturbing the liquid flow with a small perturbation. An improved version of the one-dimensional two-fluid model for horizontal flows is developed as a set of non-linear hyperbolic governing equations. The importance of this research lies in obtaining a model that accounts for the effects of flow and geometrical conditions (such as liquid viscosity, surface tension). It is shown that, for positive values of the slope angle (upward inclination), the slug flow becomes more probable, whereas negative values of the slope angle (downward inclination) induce a more stable stratified flow.

  14. Supported liquid membrane stability in chiral resolution by chemically and physically modified membranes

    Energy Technology Data Exchange (ETDEWEB)

    Molinari, R.; Argurio, P. [Arcavata di Rende Univ. of Calabria, Arcavata di Rende, CS (Italy). Dept. of Chemical and Materials Engineering

    2001-04-01

    In the present work some stability studies on Supported Liquid Membranes (SLMs) to be used for chiral separations were realized. In particular, primary aim was to determine how a modification of the support surface influences the SLM stability. First, the procedure for support modification was optimised, making a screening of various compounds (sulphuric acid, nitric acid, chromic acid, sodium dodecyl sulphate (SDS), glycerol, oleic alcohol, propylene glycol (PPG), bovine serum albumin (BSA)) and testing their performance by means of contact angle measurements. Next, a second screening was realized by permeation tests in a stirred cell. Finally, to compare the stability of modified with unmodified support in a process of interest for chemical and/or biochemical industries, some permeation tests for resolution of DNB-DL-Leucine were realized in a re-circulation system. Results showed a better surface hydrophilization of chemically modified support and better stability of the sulphonated support. However, in operating conditions a little high stability of the unmodified support was obtained. [Italian] Nel presente lavoro sono stati realizzati degli studi di stabilita' di Membrane Liquide Supportate (SLMs) da impiegare in separazioni chirali. In particolare, obiettivo principale e' stato quello di determinare l'influenza che una modifica della superficie del supporto ha sulla stabilita' della SLM. Cosi', in un primo momento, e' stata ottimizzata le procedura di modifica del supporto, facendo una selezione tra vari composti (acido solforico, acido nitrico, acido cromico, sodio dodecil solfato (SDS), glicerolo, alcool oleico, glicole propilenico (PPG), siero di albumina bovina (BSA)) basata su misure dell'angolo di contatto. Successivamente, e' stata realizzata una seconda selezione mediante prove di permeazione in una cella agitata. Infine, con lo scopo di confrontare la stabilita' della SLM con supporto modificato rispetto

  15. Theoretical study of ferroelectric nanoparticles using phase reconstructed electron microscopy

    DEFF Research Database (Denmark)

    Phatak, C.; Petford-Long, A. K.; Beleggia, Marco

    2014-01-01

    Ferroelectric nanostructures are important for a variety of applications in electronic and electro-optical devices, including nonvolatile memories and thin-film capacitors. These applications involve stability and switching of polarization using external stimuli, such as electric fields. We present...... a theoretical model describing how the shape of a nanoparticle affects its polarization in the absence of screening charges, and quantify the electron-optical phase shift for detecting ferroelectric signals with phase-sensitive techniques in a transmission electron microscope. We provide an example phase shift...

  16. Stability-Indicating Assay for the Determination of Pentobarbital Sodium in Liquid Formulations

    Directory of Open Access Journals (Sweden)

    Myriam Ajemni

    2015-01-01

    Full Text Available A stability-indicating assay by reversed-phase high performance liquid chromatography (RP-HPLC method was developed for the determination of pentobarbital sodium in oral formulations: a drug used for infant sedation in computed tomography (CT or magnetic resonance imaging (MRI scan. The chromatographic separation was achieved on a reversed-phase C18 column, using isocratic elution and a detector set at 214 nm. The optimized mobile phase consisted of a 0.01 M potassium buffer pH 3 and methanol (40 : 60, v/v. The flow rate was 1.0 mL/min and the run time of analysis was 5 min. The linearity of the method was demonstrated in the range of 5 to 250 μg/mL pentobarbital sodium solution (r2 = 0.999. The limit of detection and limit of quantification were 2.10 and 3.97 μg/mL, respectively. The intraday and interday precisions were less than 2.1%. Accuracy of the method ranged from 99.2 to 101.3%. Stability studies indicate that the drug is stable to sunlight and in aqueous solution. Accelerated pentobarbital sodium breakdown by strong alkaline, acidic, or oxidative stress produced noninterfering peaks. This method allows accurate and reliable determination of pentobarbital sodium for drug stability assay in pharmaceutical studies.

  17. Effect of Maillard Conjugates on the Physical Stability of Zein Nanoparticles Prepared by Liquid Antisolvent Coprecipitation.

    Science.gov (United States)

    Davidov-Pardo, Gabriel; Joye, Iris J; Espinal-Ruiz, Mauricio; McClements, David Julian

    2015-09-30

    Protein nanoparticles are often not very stable in a complex food matrix because they are primarily stabilized by electrostatic repulsion. In this study, we envisaged the stabilization of zein nanoparticles through Maillard conjugation reactions with polysaccharides of different molecular mass. Zein nanoparticles (0.5% w/v) containing resveratrol (0.025% w/v grape skin extract) were produced by liquid antisolvent precipitation and coated with Maillard conjugates (MC) of sodium caseinate and different molecular mass carbohydrates during particle production. Zein nanoparticles coated with conjugated polysaccharides of 2.8, 37, and 150 kDa had diameters of 198 ± 5, 176 ± 6, and 180 ± 3 nm, respectively. The encapsulation efficiency (∼83%) was not affected by conjugation, but the conjugates significantly improved particle stability against changes in pH (2.0-9.0), CaCl2 addition (up to 100 mM), and heat treatment (30-90 °C, 30 min). Zein nanoparticles coated by MC may therefore be suitable delivery systems for hydrophobic bioactive molecules in a wide range of commercial products.

  18. Atomistic Simulation and Electronic Structure of Lithium Doped Ionic Liquids: Structure, Transport, and Electrochemical Stability

    Science.gov (United States)

    Haskins, Justin B.; Bauschlicher, Charles W.; Lawson, John W.

    2015-01-01

    Zero-temperature density functional theory (DFT), density functional theory molecular dynamics (DFT-MD), and classical molecular dynamics using polarizable force fields (PFF-MD) are employed to evaluate the influence of Lithium ion on the structure, transport, and electrochemical stability of three potential ionic liquid electrolytes: N--methyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([pyr14][TFSI]), N--methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide ([pyr13][FSI]), and 1-ethyl-3--methylimidazolium boron tetrafluoride ([EMIM][BF4]). We characterize the Lithium ion solvation shell through zero-temperature DFT simulations of [Li(Anion)sub n](exp n-1) -clusters, DFT-MD simulations of isolated lithium ions in small ionic liquid systems, and PFF-MD simulations with high Li-doping levels in large ionic liquid systems. At low levels of Li-salt doping, highly stable solvation shells having 2-3 anions are seen in both [pyr14][TFSI] and [pyr13][FSI], while solvation shells with 4 anions dominate in [EMIM][BF sub 4]. At higher levels of doping, we find the formation of complex Li-network structures that increase the frequency of 4 anion-coordinated solvation shells. A comparison of computational and experimental Raman spectra for a wide range of [Li(Anion) sub n](exp n -1) - clusters shows that our proposed structures are consistent with experiment. We estimate the ion diffusion coefficients and quantify both size and simulation time effects. We find estimates of lithium ion diffusion are a reasonable order of magnitude and can be corrected for simulation time effects. Simulation size, on the other hand, is also important, with diffusion coefficients from long PFF-MD simulations of small cells having 20-40% error compared to large-cell values. Finally, we compute the electrochemical window using differences in electronic energy levels of both isolated cation/anion pairs and small ionic liquid systems with Li-salt doping. The single pair and liquid

  19. Effect of an eccentric rotation on the equilibrium shapes and stability of liquid bridges in a lateral gravity field

    Science.gov (United States)

    Laverón-Simavilla, Ana; Lapuerta, Victoria; Rodríguez, Angel; Perales, Jose Manuel

    A cylindrical liquid bridge supported between two circular-shaped disks in isorotation is considered. The combined effect of a lateral gravity field and an offset between the rotation axis and the axis of the supporting disks (eccentricity) on the stability of the liquid bridge is here studied. In a previous work a numerical method used to determine the stability limit for different values of eccentricity was validated by comparing with analytical results at small eccentricity. In this work we use an extension of that algorithm applied to liquid bridges in a lateral gravitational field rotating around an eccentric axis to study the combined effect of rotation, eccentricity and lateral gravity. The analysis shows that the combined effect of lateral gravity and eccentricity can narrow or broaden the stability region depending on the angle between the gravity direction and the eccentric axis displacement.

  20. Static negative capacitance of a ferroelectric nano-domain nucleus

    Science.gov (United States)

    Sluka, Tomas; Mokry, Pavel; Setter, Nava

    2017-10-01

    Miniaturization of conventional field effect transistors (FETs) approaches the fundamental limits beyond which opening and closing the transistor channel require higher gate voltage swing and cause higher power dissipation and heating. This problem could be eliminated by placing a ferroelectric layer between the FET gate electrode and the channel, which effectively amplifies the gate voltage. The original idea of using a bulk ferroelectric negative capacitor suffers however from irreversible multi-domain ferroelectric switching, which does not allow us to stabilize static negative capacitance, while a recent reversible solution with super-lattices may be difficult to integrate onto FET. Here, we introduce a solution which provides static negative capacitance from a nano-domain nucleus. Phase-field simulations confirm the robustness of this concept, the conveniently achievable small effective negative capacitance and the potentially high compatibility of such a negative nano-capacitor with FET technology.

  1. On the persistence of polar domains in ultrathin ferroelectric capacitors

    Science.gov (United States)

    Zubko, Pavlo; Lu, Haidong; Bark, Chung-Wung; Martí, Xavi; Santiso, José; Eom, Chang-Beom; Catalan, Gustau; Gruverman, Alexei

    2017-07-01

    The instability of ferroelectric ordering in ultra-thin films is one of the most important fundamental issues pertaining realization of a number of electronic devices with enhanced functionality, such as ferroelectric and multiferroic tunnel junctions or ferroelectric field effect transistors. In this paper, we investigate the polarization state of archetypal ultrathin (several nanometres) ferroelectric heterostructures: epitaxial single-crystalline BaTiO3 films sandwiched between the most habitual perovskite electrodes, SrRuO3, on top of the most used perovskite substrate, SrTiO3. We use a combination of piezoresponse force microscopy, dielectric measurements and structural characterization to provide conclusive evidence for the ferroelectric nature of the relaxed polarization state in ultrathin BaTiO3 capacitors. We show that even the high screening efficiency of SrRuO3 electrodes is still insufficient to stabilize polarization in SrRuO3/BaTiO3/SrRuO3 heterostructures at room temperature. We identify the key role of domain wall motion in determining the macroscopic electrical properties of ultrathin capacitors and discuss their dielectric response in the light of the recent interest in negative capacitance behaviour.

  2. Effect of the physicochemical properties of binary ionic liquids on lipase activity and stability.

    Science.gov (United States)

    Yao, Peipei; Yu, Xinxin; Huang, Xirong

    2015-01-01

    In the present study, the lipase-catalyzed hydrolysis of p-nitrophenyl butyrate is used as a model reaction to determine the activity and stability of Candida rugosa lipase in binary ionic liquids (ILs). The binary ILs consist of hydrophobic 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6) and a small amount of hydrophilic 1-butyl-3-methylimidazolium nitrate ([Bmim]NO3) or 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim]CF3SO3) or 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4). The activity and the stability of lipase are first correlated with the physicochemical properties of the binary ILs. In the three binary IL systems, both the hydrophilicity and the polarity of the systems increase with the increase of the content of hydrophilic ILs (HILs). At a fixed concentration of HIL, they vary in a descending order of [Bmim]PF6/[Bmim]NO3>[Bmim]PF6/[Bmim]CF3SO3>[Bmim]PF6/[Bmim]BF4. This order is in contrast with the order of the lipase conformation stability, i.e., the higher the polarity of ILs, the more unstable the lipase conformation. However, both the activity and the stability of lipase depend on the type and the content of the HIL in binary ILs, showing a complex dependency. Analysis shows that the catalytic performance of lipase in the binary ILs is affected not only by the direct influence of the ILs on lipase conformation, but also through their indirect influence on the physicochemical properties of water. The present study helps to explore binary IL mixtures suitable for lipase-based biocatalysis. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Liquid Marbles Stabilized by Fluorine-Bearing Cyclomatrix Polyphosphazene Particles and Their Application as High-Efficiency Miniature Reactors.

    Science.gov (United States)

    Wei, Wei; Lu, Rongjie; Ye, Weitao; Sun, Jianhua; Zhu, Ye; Luo, Jing; Liu, Xiaoya

    2016-02-23

    Increasing attention has been paid to fabricate multifunctional stabilizers of liquid marbles for expanding their application. Here, a kind of hydrophobic cyclomatrix polyphosphazene particles (PZAF) were facilely prepared using a one-step precipitation polycondensation of hexachlorocyclotriphosphazene and 4,4'-(hexafluoroisopropylidene)diphenol, and their ability to stabilize liquid marbles was first investigated. The Ag nanoparticle-decorated PZAF particles (Ag/PZAF) were then fabricated by an in situ reduction of silver nitrate onto PZAF particles and used to construct catalytic liquid marbles. The results revealed that the reduction of methylene blue (MB) in aqueous solution by sodium borohydride could be highly efficiently catalyzed in the catalytic liquid marbles, even with a large volume. An excellent cycle use performance of the catalytic liquid marbles without losing catalytic efficiency was also present. The high catalytic activity is mainly attributed to the uniform immobilization of Ag nanoparticles onto PZAF particles and the adsorption behavior of PZAF particles toward MB, which may play an effect on allowing high catalytic surface area and effective accelerating the mass transfer of MB to the Ag catalytic active sites, respectively. Therefore, the combination of Ag nanoparticles with PZAF particles has been demonstrated clearly to be a facile and effective strategy to obtain the functional stabilizer for preparing the catalytic liquid marbles as promising miniature reactors used in heterogeneous catalytic reactions.

  4. Partial transient liquid phase diffusion bonding of Zircaloy-4 to stabilized austenitic stainless steel 321

    Energy Technology Data Exchange (ETDEWEB)

    Atabaki, M. Mazar, E-mail: m.mazaratabaki@gmail.com [Department of Materials Engineering, Faculty of Mechanical Engineering, University Technology Malaysia, 81310 (Malaysia); Hanzaei, A. Talebi [Department of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran (Iran, Islamic Republic of)

    2010-10-15

    An innovative method was applied for bonding Zircaloy-4 to stabilized austenitic stainless steel 321 using an active titanium interlayer. Specimens were joined by a partial transient liquid phase diffusion bonding method in a vacuum furnace at different temperatures under 1 MPa dynamic pressure of contact. The influence of different bonding temperatures on the microstructure, microindentation hardness, joint strength and interlayer thickness has been studied. The diffusion of Fe, Cr, Ni and Zr has been investigated by scanning electron microscopy and energy dispersive spectroscopy elemental analyses. Results showed that control of the heating and cooling rate and 20 min soaking at 1223 K produces a perfect joint. However, solid-state diffusion of the melting point depressant elements into the joint metal causes the solid/liquid interface to advance until the joint is solidified. The tensile strength of all the bonded specimens was found around 480-670 MPa. Energy dispersive spectroscopy studies indicated that the melting occurred along the interface of the bonded specimens as a result of the transfer of atoms between the interlayer and the matrix during bonding. This technique provides a reliable method of bonding zirconium alloy to stainless steel.

  5. Significant improvements in stability and reproducibility of atomic-scale atomic force microscopy in liquid.

    Science.gov (United States)

    Akrami, S M R; Nakayachi, H; Watanabe-Nakayama, T; Asakawa, H; Fukuma, T

    2014-11-14

    Recent advancement of dynamic-mode atomic force microscopy (AFM) for liquid-environment applications enabled atomic-scale studies on various interfacial phenomena. However, instabilities and poor reproducibility of the measurements often prevent systematic studies. To solve this problem, we have investigated the effect of various tip treatment methods for atomic-scale imaging and force measurements in liquid. The tested methods include Si coating, Ar plasma, Ar sputtering and UV/O₃ cleaning. We found that all the methods provide significant improvements in both the imaging and force measurements in spite of the tip transfer through the air. Among the methods, we found that the Si coating provides the best stability and reproducibility in the measurements. To understand the origin of the fouling resistance of the cleaned tip surface and the difference between the cleaning methods, we have investigated the tip surface properties by x-ray photoelectron spectroscopy and contact angle measurements. The results show that the contaminations adsorbed on the tip during the tip transfer through the air should desorb from the surface when it is immersed in aqueous solution due to the enhanced hydrophilicity by the tip treatments. The tip surface prepared by the Si coating is oxidized when it is immersed in aqueous solution. This creates local spots where stable hydration structures are formed. For the other methods, there is no active mechanism to create such local hydration sites. Thus, the hydration structure formed under the tip apex is not necessarily stable. These results reveal the desirable tip properties for atomic-scale AFM measurements in liquid, which should serve as a guideline for further improvements of the tip treatment methods.

  6. Computation of liquid-liquid equilibria and phase stabilities: implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols

    Directory of Open Access Journals (Sweden)

    A. Zuend

    2010-08-01

    Full Text Available Semivolatile organic and inorganic aerosol species partition between the gas and aerosol particle phases to maintain thermodynamic equilibrium. Liquid-liquid phase separation into an organic-rich and an aqueous electrolyte phase can occur in the aerosol as a result of the salting-out effect. Such liquid-liquid equilibria (LLE affect the gas/particle partitioning of the different semivolatile compounds and might significantly alter both particle mass and composition as compared to a one-phase particle. We present a new liquid-liquid equilibrium and gas/particle partitioning model, using as a basis the group-contribution model AIOMFAC (Zuend et al., 2008. This model allows the reliable computation of the liquid-liquid coexistence curve (binodal, corresponding tie-lines, the limit of stability/metastability (spinodal, and further thermodynamic properties of multicomponent systems. Calculations for ternary and multicomponent alcohol/polyol-water-salt mixtures suggest that LLE are a prevalent feature of organic-inorganic aerosol systems. A six-component polyol-water-ammonium sulphate system is used to simulate effects of relative humidity (RH and the presence of liquid-liquid phase separation on the gas/particle partitioning. RH, salt concentration, and hydrophilicity (water-solubility are identified as key features in defining the region of a miscibility gap and govern the extent to which compound partitioning is affected by changes in RH. The model predicts that liquid-liquid phase separation can lead to either an increase or decrease in total particulate mass, depending on the overall composition of a system and the particle water content, which is related to the hydrophilicity of the different organic and inorganic compounds. Neglecting non-ideality and liquid-liquid phase separations by assuming an ideal mixture leads to an overestimation of the total particulate mass by up to 30% for the composition and RH range considered in the six

  7. Computation of liquid-liquid equilibria and phase stabilities: implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols

    Science.gov (United States)

    Zuend, A.; Marcolli, C.; Peter, T.; Seinfeld, J. H.

    2010-08-01

    Semivolatile organic and inorganic aerosol species partition between the gas and aerosol particle phases to maintain thermodynamic equilibrium. Liquid-liquid phase separation into an organic-rich and an aqueous electrolyte phase can occur in the aerosol as a result of the salting-out effect. Such liquid-liquid equilibria (LLE) affect the gas/particle partitioning of the different semivolatile compounds and might significantly alter both particle mass and composition as compared to a one-phase particle. We present a new liquid-liquid equilibrium and gas/particle partitioning model, using as a basis the group-contribution model AIOMFAC (Zuend et al., 2008). This model allows the reliable computation of the liquid-liquid coexistence curve (binodal), corresponding tie-lines, the limit of stability/metastability (spinodal), and further thermodynamic properties of multicomponent systems. Calculations for ternary and multicomponent alcohol/polyol-water-salt mixtures suggest that LLE are a prevalent feature of organic-inorganic aerosol systems. A six-component polyol-water-ammonium sulphate system is used to simulate effects of relative humidity (RH) and the presence of liquid-liquid phase separation on the gas/particle partitioning. RH, salt concentration, and hydrophilicity (water-solubility) are identified as key features in defining the region of a miscibility gap and govern the extent to which compound partitioning is affected by changes in RH. The model predicts that liquid-liquid phase separation can lead to either an increase or decrease in total particulate mass, depending on the overall composition of a system and the particle water content, which is related to the hydrophilicity of the different organic and inorganic compounds. Neglecting non-ideality and liquid-liquid phase separations by assuming an ideal mixture leads to an overestimation of the total particulate mass by up to 30% for the composition and RH range considered in the six-component system

  8. Effect of UV absorption anisotropy on hybrid aligned polymer stabilized liquid crystal cell

    Science.gov (United States)

    Yamaguchi, R.; Inoue, K.; Takasu, T.

    2016-09-01

    We have proposed a hybrid alignment nematic (HAN) liquid crystal cell using a polymer stabilized (PS) technology. The cell shows a reverse mode scattering property. The PS-HAN cell is transparent at any viewing angle in the off-state and has an asymmetrical scattering property at incident angles in the on-state. Applying the cell to a smart glass, it cell can selectively scatter a midday sunlight with a function of window blinds. In this study, two polymerization processes, an irradiation with UV light from planar and vertical aligned sides of the cell have been investigated. UV penetration depth has also been estimated from planar and vertical aligned sides of the cell. LC materials with different UV absorption spectra were prepared. A driving voltage, an optical property and a polymer morphology were measured in PS-HAN cells. The UV intensity profile have an effect on polymer density and particle size, which changed the driving voltage and the light scattering property in the PS-HAN cell. The study on the UV penetration in the polymer stabilized technology can improve their performance.

  9. Stabilization of glycoprotein liquid formulation using arginine: a study with lactoferrin as a model protein.

    Science.gov (United States)

    Kim, Hyun-Jung; Shin, Chang Hoon; Kim, Chan-Wha

    2009-01-01

    The formulation of new biotherapeutics without human serum albumin (HSA) could decrease the potential risk of blood-transmitted diseases and those caused by infectious viruses and other pathogens. In the present study, arginine was examined as a potential alternative to HAS, and bovine lactoferrin (bLf) was used as a representative model glycoprotein since bLf has potential immunomodulatory and antiviral activity. The optimal formulation for the mixture was determined to be 10 mM arginine, 15% (w/v) trehalose, and 0.02% (v/v) Tween 80, using a statistical analysis program, Minitab. Analyses were performed using reverse-phase high-performance liquid chromatography (HPLC) and SDS-PAGE. The blf HSA-free formulations lost only 12-20% of blf compared with 46% for control (without additives) after 28 d of storage. Based on long-term stability studies, the HSA-free formulation developed in this study had a stronger effect on the stability of bLf (1.4-fold) than HSA formulation under various storage conditions over 6 months.

  10. [Application of denaturing high performance liquid chromatography for detection of alpha-hemoglobin-stabilizing protein gene].

    Science.gov (United States)

    Wang, Zhipeng

    2011-04-01

    An assay method for alpha-hemoglobin-stabilizing protein (AHSP) gene was established based on denaturing high performance liquid chromatography (DHPLC). The AHSP gene sequences are divided into six fragments. Because of one or two common single nucleotide polymorphism (SNPs) in the first, second, fourth and sixth fragments, all samples should be analyzed individually when the fragments were detected. The third and fifth fragments were detected by DHPLC technique combined with DNA pooling for no common SNP in the fragments. The six common SNPs in AHSP gene can be genotyped accurately by the established method. After analyzing AHSP gene of 40 samples by DHPLC detection and gene sequencing, it was found that the results of the two methods were completely consistent. After AHSP gene of 365 samples being analyzed by DHPLC, two rare SNPs (11,810 G > A and 12,802 C > T)were found. Two missense mutations (AHSP D29V and AHSP V56G) were also found. AHSP D29V mutation is a novel mutation. AHSP V56G is a rare mutation. It demonstrated that this method is suitable for the detection of alpha-hemoglobin-stabilizing protein gene.

  11. Stability-indicating high-performance liquid chromatographic assay method and photostability of carprofen.

    Science.gov (United States)

    Wu, A B; Chen, C Y; Chu, S D; Tsai, Y C; Chen, F A

    2001-01-01

    A rapid, sensitive, and accurate stability-indicating high-performance liquid chromatographic assay method for determining the degradation of carprofen (CPF) is developed and validated under acidic, basic, or photo-irradiated conditions. The analysis is monitored with a Cosmosil 5C18-AR column using a mobile phase of CH3CN-H2O-AcOH (50:49:1, v/v/v) at 260 nm. The developed method satisfies the system suitability criteria, peak integrity, and resolution among the parent drug and its degradation products. The results indicate that the established assay method shows good selectivity and specificity suitable for stability measurements of CPF. CPF is found to be more sensitive to exposure to light and in acidic conditions, but it is stable in a basic medium. The kinetic study of the photodegradation of CPF follows an apparent first-order reaction in a variety of solvents. The solvent effects on the rates of degradation are in the decreasing order of chloroform > dichloromethane > methanol > ethanol > 2-propanol, which is irrelevant to the dielectric constant epsilon. However, the hydrogen-donating ability of the solvents is essential to the photochemical decomposition of CPF. A plot of log k versus the Kirkwood function exhibits a linear relationship in aqueous ethanolic solutions, which implies that degradation proceeds via an ionic mechanism.

  12. Nanoparticles Doped, Photorefractive Liquid Crystals

    National Research Council Canada - National Science Library

    Kaczmarek, Malgosia

    2005-01-01

    ...: The main objectives of this exploratory, short project will concern the study of the quality of liquid crystal cells with diluted suspensions of ferroelectric nanoparticles and their photorefractive properties...

  13. Effect of vertical quasiperiodic vibrations on the stability of the free surface of an inviscid liquid layer

    Directory of Open Access Journals (Sweden)

    Belhaq M.

    2012-07-01

    Full Text Available The aim of the present paper is to examine the effect of the vertical quasiperiodic oscillations on the stability of the free surface of an ideal horizontal liquid layer. The quasiperiodic motion considered here is characterized by two incommensurate frequencies ω1 and ω2. The governing system of equations is reduced to a quasiperiodic Mathieu equation. In this situation, using the harmonic balance method developed by Rand et al. [10, 11] and Hill’s determinants, we determine the marginal stability curves. We show that the quasiperiodic excitation produces a stabilizing or a estabilizing effect and is strongly depending on the ratio of the frequencies.

  14. Radiation stability of diglycolamide functionalized calix[4]arenes in ionic liquid: Solvent extraction, EPR and GC–MS studies

    NARCIS (Netherlands)

    Sengupta, A; Mohapatra, P.K.; Patil, A.B.; Kadam, R.M.; Verboom, Willem

    2016-01-01

    Ionic liquid-based solvent systems containing diglycolamide-functionalized calix[4]arenes (C4DGAs) are efficient for actinide ion extraction from nitric acid feeds. Therefore, the radiolytic stability of three C4DGAs (wide-rim, narrow-rim and both side DGA-functionalized calix[4]arenes) and TODGA

  15. Effect of SHI irradiation on NBT-BT ceramics: Transformation of relaxor ferroelectric to ferroelectric nature

    Energy Technology Data Exchange (ETDEWEB)

    Shanmuga Sundari, S. [Crystal Growth Centre, Anna University, Chennai 600 025 (India); Kumar, Binay [Crystal Lab, Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Asokan, K. [Inter University Accelerator Centre, New Delhi 110 067 (India); Dhanasekaran, R., E-mail: rdcgc@yahoo.com [Crystal Growth Centre, Anna University, Chennai 600 025 (India)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer The NBT-BT ceramics at MPB were synthesized by conventional solid state reaction method. Black-Right-Pointing-Pointer The prepared ceramics were irradiated with 120 MeV Au{sup 9+} ions at different fluencies. Black-Right-Pointing-Pointer The grain size is increased after irradiation due to the increase of local lattice temperature. Black-Right-Pointing-Pointer As the fluence increases the relaxor nature of the material is transformed to the ferroelectric nature. - Abstract: The lead free NBT-BT ceramics prepared by conventional solid state reaction method were irradiated with 120 MeV Au{sup 9+} ions with different fluences. The structural, dielectric and piezoelectric studies were carried out before and after irradiation. The agglomeration and increase of grain size are observed in SEM analysis after the irradiation. The diffuse phase transition disappeared after high fluence of irradiation and the material becomes ferroelectric in nature. The piezoelectric properties were decreased due to the reduced stability of the ferroelectric domains after the irradiation.

  16. Ferroelectric infrared detector and method

    Science.gov (United States)

    Lashley, Jason Charles; Opeil, Cyril P.; Smith, James Lawrence

    2010-03-30

    An apparatus and method are provided for sensing infrared radiation. The apparatus includes a sensor element that is positioned in a magnetic field during operation to ensure a .lamda. shaped relationship between specific heat and temperature adjacent the Curie temperature of the ferroelectric material comprising the sensor element. The apparatus is operated by inducing a magnetic field on the ferroelectric material to reduce surface charge on the element during its operation.

  17. TOPICAL REVIEW: Surface modification and characterization for dispersion stability of inorganic nanometer-scaled particles in liquid media

    Science.gov (United States)

    Kamiya, Hidehiro; Iijima, Motoyuki

    2010-08-01

    Inorganic nanoparticles are indispensable for science and technology as materials, pigments and cosmetics products. Improving the dispersion stability of nanoparticles in various liquids is essential for those applications. In this review, we discuss why it is difficult to control the stability of nanoparticles in liquids. We also overview the role of surface interaction between nanoparticles in their dispersion and characterization, e.g. by colloid probe atomic force microscopy (CP-AFM). Two types of surface modification concepts, post-synthesis and in situ modification, were investigated in many previous studies. Here, we focus on post-synthesis modification using adsorption of various kinds of polymer dispersants and surfactants on the particle surface, as well as surface chemical reactions of silane coupling agents. We discuss CP-AFM as a technique to analyze the surface interaction between nanoparticles and the effect of surface modification on the nanoparticle dispersion in liquids.

  18. Programmable ferroelectric tunnel memristor

    Directory of Open Access Journals (Sweden)

    Andy eQuindeau

    2014-02-01

    Full Text Available We report an analogously programmable memristor based on genuine electronic resistive switching combining ferroelectric switching and electron tunneling. The tunnel current through an 8 unit cell thick epitaxial Pb(Zr[0.2]Ti[0.8]O[3] film sandwiched between La[0.7]Sr[0.3]MnO[3] and cobalt electrodes obeys the Kolmogorov-Avrami-Ishibashi model for bidimensional growth with a characteristic switching time in the order of 10^-7 seconds. The analytical description of switching kinetics allows us to develop a characteristic transfer function that has only one parameter viz. the characteristic switching time and fully predicts the resistive states of this type of memristor.

  19. Accelerated Metastable Solid-liquid Interdiffusion Bonding with High Thermal Stability and Power Handling

    Science.gov (United States)

    Huang, Ting-Chia; Smet, Vanessa; Kawamoto, Satomi; Pulugurtha, Markondeya R.; Tummala, Rao R.

    2018-01-01

    Emerging high-performance systems are driving the need for advanced packaging solutions such as 3-D integrated circuits (ICs) and 2.5-D system integration with increasing performance and reliability requirements for off-chip interconnections. Solid-liquid interdiffusion (SLID) bonding resulting in all-intermetallic joints has been proposed to extend the applicability of solders, but faces fundamental and manufacturing challenges hindering its wide adoption. This paper introduces a Cu-Sn SLID interconnection technology, aiming at stabilization of the microstructure in the Cu6Sn5 metastable phase rather than the usual stable Cu3Sn phase. This enables formation of a void-free interface yielding higher mechanical strength than standard SLID bonding, as well as significantly reducing the transition time. The metastable SLID technology retains the benefits of standard SLID with superior I/O pitch scalability, thermal stability and current handling capability, while advancing assembly manufacturability. In the proposed concept, the interfacial reaction is controlled by introducing Ni(P) diffusion barrier layers, designed to effectively isolate the metastable Cu6Sn5 phase preventing any further transformation. Theoretical diffusion and kinetic models were applied to design the Ni-Cu-Sn interconnection stack to achieve the targeted joint composition. A daisy chain test vehicle was used to demonstrate this technology as a first proof of concept. Full transition to Cu6Sn5 was successfully achieved within a minute at 260°C as confirmed by scanning electron microscope (SEM) and x-ray energy dispersive spectroscopy (XEDS) analysis. The joint composition was stable through 10× reflow, with outstanding bond strength averaging 90 MPa. The metastable SLID interconnections also showed excellent electromigration performance, surviving 500 h of current stressing at 105 A/cm2 at 150°C.

  20. Accelerated Metastable Solid-liquid Interdiffusion Bonding with High Thermal Stability and Power Handling

    Science.gov (United States)

    Huang, Ting-Chia; Smet, Vanessa; Kawamoto, Satomi; Pulugurtha, Markondeya R.; Tummala, Rao R.

    2017-09-01

    Emerging high-performance systems are driving the need for advanced packaging solutions such as 3-D integrated circuits (ICs) and 2.5-D system integration with increasing performance and reliability requirements for off-chip interconnections. Solid-liquid interdiffusion (SLID) bonding resulting in all-intermetallic joints has been proposed to extend the applicability of solders, but faces fundamental and manufacturing challenges hindering its wide adoption. This paper introduces a Cu-Sn SLID interconnection technology, aiming at stabilization of the microstructure in the Cu6Sn5 metastable phase rather than the usual stable Cu3Sn phase. This enables formation of a void-free interface yielding higher mechanical strength than standard SLID bonding, as well as significantly reducing the transition time. The metastable SLID technology retains the benefits of standard SLID with superior I/O pitch scalability, thermal stability and current handling capability, while advancing assembly manufacturability. In the proposed concept, the interfacial reaction is controlled by introducing Ni(P) diffusion barrier layers, designed to effectively isolate the metastable Cu6Sn5 phase preventing any further transformation. Theoretical diffusion and kinetic models were applied to design the Ni-Cu-Sn interconnection stack to achieve the targeted joint composition. A daisy chain test vehicle was used to demonstrate this technology as a first proof of concept. Full transition to Cu6Sn5 was successfully achieved within a minute at 260°C as confirmed by scanning electron microscope (SEM) and x-ray energy dispersive spectroscopy (XEDS) analysis. The joint composition was stable through 10× reflow, with outstanding bond strength averaging 90 MPa. The metastable SLID interconnections also showed excellent electromigration performance, surviving 500 h of current stressing at 105 A/cm2 at 150°C.

  1. Synthesis of ferroelectric nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Roervik, Per Martin

    2008-12-15

    The increasing miniaturization of electric and mechanical components makes the synthesis and assembly of nanoscale structures an important step in modern technology. Functional materials, such as the ferroelectric perovskites, are vital to the integration and utility value of nanotechnology in the future. In the present work, chemical methods to synthesize one-dimensional (1D) nanostructures of ferroelectric perovskites have been studied. To successfully and controllably make 1D nanostructures by chemical methods it is very important to understand the growth mechanism of these nanostructures, in order to design the structures for use in various applications. For the integration of 1D nanostructures into devices it is also very important to be able to make arrays and large-area designed structures from the building blocks that single nanostructures constitute. As functional materials, it is of course also vital to study the properties of the nanostructures. The characterization of properties of single nanostructures is challenging, but essential to the use of such structures. The aim of this work has been to synthesize high quality single-crystalline 1D nanostructures of ferroelectric perovskites with emphasis on PbTiO3 , to make arrays or hierarchical nanostructures of 1D nanostructures on substrates, to understand the growth mechanisms of the 1D nanostructures, and to investigate the ferroelectric and piezoelectric properties of the 1D nanostructures. In Paper I, a molten salt synthesis route, previously reported to yield BaTiO3 , PbTiO3 and Na2Ti6O13 nanorods, was re-examined in order to elucidate the role of volatile chlorides. A precursor mixture containing barium (or lead) and titanium was annealed in the presence of NaCl at 760 degrees Celsius or 820 degrees Celsius. The main products were respectively isometric nanocrystalline BaTiO3 and PbTiO3. Nanorods were also detected, but electron diffraction revealed that the composition of the nanorods was

  2. A stability-indicating high performance liquid chromatography method to determine apocynin in nanoparticles

    Directory of Open Access Journals (Sweden)

    Juliana Kovalczuk de Oliveira

    2017-04-01

    Full Text Available In this study, we developed and validated a fast, specific, sensitive, precise and stability-indicating high performance liquid chromatography (HPLC method to determine the drug apocynin in bovine serum albumin (BSA nanoparticles. Chromatographic analyses were performed on an RP C18 column and using a photodiode array detector at a wavelength of 276 nm. Mobile phase consisted of a mixture of acetonitrile and 1% acetic acid (60:40, v/v, and it was eluted isocratically at a flow rate of 0.8 mL/min. The retention time of apocynin chromatographic peak was 1.65 min. The method was linear, precise, accurate and specific in the range of 5–100 μg/mL. The intra- and inter-day precisions presented relative standard deviation (RSD values lower than 2%. The method was robust regarding changes in mobile phase proportion, but not for flow rate. Limits of detection and quantitation were 78 ng/mL and 238 ng/mL, respectively. Apocynin was exposed to acid and alkali hydrolysis, oxidation and visible light. The drug suffered mild degradation under acid and oxidation conditions and great degradation under alkali conditions. Light exposure did not degrade the drug. The method was successfully applied to determine the encapsulation efficiency of apocynin in BSA nanoparticles.

  3. Amphenicols stability in medicated feed – development and validation of liquid chromatography method

    Directory of Open Access Journals (Sweden)

    Pietro Wojciech Jerzy

    2014-12-01

    Full Text Available A liquid chromatography-ultraviolet detection method for the determination of florfenicol (FF and thiamphenicol (TAP in feeds is presented. The method comprises the extraction of analytes from the matrix with a mixture of methanol and acetonitrile, drying of the extract, and its dissolution in phosphate buffer. The analysis was performed with a gradient programme of the mobile phase composed of acetonitrile and buffer (pH = 7.3 on a Zorbax Eclipse Plus C18 (150 × 4.6 mm, 5 μm analytical column with UV (λ = 220 nm detection. The analytical procedure has been successfully adopted and validated for quantitative determination of florfenicol and thiamphenicol in feed samples. Sensitivity, specificity, linearity, repeatability, and intralaboratory reproducibility were included in the validation. The mean recovery of amphenicols was 93.5% within the working range of 50-4000 mg/kg. Simultaneous determination of chloramphenicol, which is banned in the feed, was also included within the same procedure of FF and TAP stability studies. Storing the medicated feed at room temperature for up to one month decreased concentration in the investigated drugs even by 45%. These findings are relevant to successful provision of therapy to animals.

  4. Polarisation Dynamics in Ferroelectric Materials

    Science.gov (United States)

    Buchacher, Till

    Ferroelectric materials have established themselves as indispensable in key applications such as piezoelectric transducers and energy storage devices. While the use of ferroelectrics in these fields dates back more than 50 years, little progress has been made to extend applications of ferroelectrics into new fields. To a large extend the observed slow progress is not caused by a lack of potential applications, but to by the inherent complexity associated with a structural phase transition, combined with strong coupling of polarisation, strain and temperature, and the strong modification of the phenomena by material defects. This thesis takes a look at prospective applications in energy storage for pulse power applications, solid state cooling and non-volatile random access memory and identifies key issues that need to be resolved. The thesis delivers time-domain based approaches to determine ferroelectric switching behaviour of bulk materials and thin films down to sub-ns time scales. The approach permitted study of how information written to a ferroelectric memory decays as a result of multiple non-destructive read operations. Furthermore simultaneous direct measurements of temperature and ferroelectric switching established a direct link between the retarded switching phenomenon observed in ferroelectrics and temperature changes brought by the electrocaloric effect. By comparison with analytical models and numerical simulation a large localised temperature change on the scale of individual domains is postulated. It implies a much larger coupling between switching and local temperature than has been previously considered. In extension of the model the frequency dependence of polarisation fatigue under bipolar conditions is explained by the occurrence of large temperature gradients in the material.

  5. Phase diagrams of ferroelectric nanocrystals strained by an elastic matrix.

    Science.gov (United States)

    Nikitchenko, Andrei; Azovtsev, Andrei V; Pertsev, Nikolay A

    2017-11-20

    Ferroelectric crystallites embedded into a dielectric matrix experience temperature-dependent elastic strains caused by differences in the thermal expansion of the crystallites and the matrix. Owing to the electrostriction, these lattice strains may affect polarization states of ferroelectric inclusions significantly, making them different from those of a stress-free bulk crystal. Here, using a nonlinear thermodynamic theory, we study the mechanical effect of elastic matrix on the phase states of embedded single-domain ferroelectric nanocrystals. Their equilibrium polarization states are determined by minimizing a special thermodynamic potential that describes the energetics of an ellipsoidal ferroelectric inclusion surrounded by a linear elastic medium. To demonstrate stability ranges of such states for a given material combination, we introduce an original phase diagram, where the inclusion's shape anisotropy and temperature are used as two parameters. The "shape-temperature" phase diagrams are calculated numerically for PbTiO3 and BaTiO3 nanocrystals embedded into representative dielectric matrices generating tensile (silica glass) or compressive (potassium silicate glass) thermal stresses inside ferroelectric inclusions. The developed phase maps demonstrate that the joint effect of thermal stresses and matrix-induced elastic clamping of ferroelectric inclusions gives rise to several important features in the polarization behavior of PbTiO3 and BaTiO3 nanocrystals. In particular, the Curie temperature displays a nonmonotonic variation with the ellipsoid's aspect ratio, being minimal for spherical inclusions. Furthermore, the diagrams show that the polarization orientation with respect to the ellipsoid's symmetry axis is controlled by the shape anisotropy and the sign of thermal stresses. Under certain conditions, the mechanical inclusion-matrix interaction qualitatively alters the evolution of ferroelectric states on cooling, inducing a structural transition in

  6. Linear stability of buoyant thermocapillary convection for a high-Prandtl number fluid in a laterally heated liquid bridge

    Science.gov (United States)

    Motegi, K.; Kudo, M.; Ueno, I.

    2017-04-01

    The buoyancy effect on the stability of axisymmetric buoyant-thermocapillary flow is investigated in a laterally heated high-Prandtl-number liquid bridge using linear stability analysis. Target geometry is the so-called full-zone (FZ) model in which the liquid is sustained between the coaxial cylindrical disks of the same diameter. The disks are maintained at the same temperature, and the mid part of the liquid bridge is heated, resulting in a non-uniform temperature distribution over the free surface. In that model, axisymmetric basic flow exhibits reflection symmetry around the midplane, and two identical toroidal vortices are formed in the upper and lower halves in zero-gravity conditions. However, the buoyancy breaks this symmetry in gravity conditions. There are two different types of perturbation in the FZ model, the symmetric and antisymmetric modes around the mid plane of the liquid bridge. When increasing the Rayleigh number Ra, the buoyancy strongly stabilizes the basic flow for the antisymmetric oscillatory mode and has a weak destabilizing effect on the symmetric oscillatory mode. Therefore, when Ra exceeds a certain threshold value, the most dangerous mode switches from the antisymmetric oscillatory mode, the most dangerous mode under zero-gravity conditions, to the symmetric oscillatory mode. The neutral stability curve of the symmetric oscillatory mode folds with increasing Ra, wherein the critical Reynolds number suddenly drops. We reveal that such an abrupt change in the neutral curve is caused by the transition of the instability source from the vortex in the upper half of the liquid bridge to the one in the lower half by increasing the buoyancy effect. With a further increase in the Ra, the most dangerous mode switches from the symmetric oscillatory mode to the antisymmetric steady mode.

  7. Liquid Salt as Green Solvent: A Novel Eco-Friendly Technique to Enhance Solubility and Stability of Poorly Soluble Drugs

    Science.gov (United States)

    Patel, Anant A.

    As a result of tremendous efforts in past few decades, various techniques have been developed in order to resolve solubility issues associated with class II and IV drugs, However, majority of these techniques offer benefits associated with certain drawbacks; majorly including low drug loading, physical instability on storage and excessive use of environmentally challenging organic solvents. Hence, current effort was to develop an eco-friendly technique using liquid salt as green solvent, which can offer improvement in dissolution while maintaining long term stability. The liquid salt formulations (LSF) of poorly soluble model drugs ibuprofen, gemfibrozil and indomethacin were developed using 1-Ethyl-3-methylimidazolium ethyl sulfate (EMIM ES) as a non-toxic and environmentally friendly alternate to organic solvents. Liquid medications containing clear solutions of drug, EMIM ES and polysorbate 20, were adsorbed onto porous carrier Neusilin US2 to form free flowing powder. The LSF demonstrated greater rate and extent of dissolution compared to crystalline drugs. The dissolution data revealed that more than 80% drug release from LSF within 20 mins compared to less than 18% release from pure drugs. As high as 70% w/w liquid loading was achieved while maintaining good flowability and compressibility. In addition, the LSF samples exposed to high temperature and high humidity i.e. 40°C/80% RH for 8 weeks, demonstrated excellent physical stability without any signs of precipitation or crystallization. As most desirable form of administration is tablet, the developed liquid salt formulations were transformed into tablets using design of experiment approach by Design Expert Software. The tablet formulation composition and critical parameter were optimized using Box-Behnken Design. This innovative liquid salt formulation technique offered improvement in dissolution rate and extent as well as contributed to excellent physical stability on storage. Moreover, this formulation

  8. The effect of confinement on the stability of field induced states and on supercooling in antiferro-ferroelectric phase transitions in chiral smectic liquid crystals

    OpenAIRE

    VIJ, JAGDISH

    2009-01-01

    PUBLISHED We investigate both the supercooling and the hysteresis phenomena of the phase transitions between the smectic C* and the smectic C *Aphases driven by temperature and electric field, respectively. These two phenomena show similar characteristics for the dependence of transmittance on both the cell thickness and the applied field. The mechanisms for large supercooling and large hysteresis in thin cells are shown to correspond to the suppression of the propagation of solitary wave ...

  9. Practical Methodology for the Inclusion of Nonlinear Slosh Damping in the Stability Analysis of Liquid-Propelled Space Vehicles

    Science.gov (United States)

    Ottander, John A.; Hall, Robert A.; Powers, J. F.

    2018-01-01

    A method is presented that allows for the prediction of the magnitude of limit cycles due to adverse control-slosh interaction in liquid propelled space vehicles using non-linear slosh damping. Such a method is an alternative to the industry practice of assuming linear damping and relying on: mechanical slosh baffles to achieve desired stability margins; accepting minimal slosh stability margins; or time domain non-linear analysis to accept time periods of poor stability. Sinusoidal input describing functional analysis is used to develop a relationship between the non-linear slosh damping and an equivalent linear damping at a given slosh amplitude. In addition, a more accurate analytical prediction of the danger zone for slosh mass locations in a vehicle under proportional and derivative attitude control is presented. This method is used in the control-slosh stability analysis of the NASA Space Launch System.

  10. Anisotropic conductance at improper ferroelectric domain walls.

    Science.gov (United States)

    Meier, D; Seidel, J; Cano, A; Delaney, K; Kumagai, Y; Mostovoy, M; Spaldin, N A; Ramesh, R; Fiebig, M

    2012-02-26

    Transition metal oxides hold great potential for the development of new device paradigms because of the field-tunable functionalities driven by their strong electronic correlations, combined with their earth abundance and environmental friendliness. Recently, the interfaces between transition-metal oxides have revealed striking phenomena, such as insulator-metal transitions, magnetism, magnetoresistance and superconductivity. Such oxide interfaces are usually produced by sophisticated layer-by-layer growth techniques, which can yield high-quality, epitaxial interfaces with almost monolayer control of atomic positions. The resulting interfaces, however, are fixed in space by the arrangement of the atoms. Here we demonstrate a route to overcoming this geometric limitation. We show that the electrical conductance at the interfacial ferroelectric domain walls in hexagonal ErMnO(3) is a continuous function of the domain wall orientation, with a range of an order of magnitude. We explain the observed behaviour using first-principles density functional and phenomenological theories, and relate it to the unexpected stability of head-to-head and tail-to-tail domain walls in ErMnO(3) and related hexagonal manganites. As the domain wall orientation in ferroelectrics is tunable using modest external electric fields, our finding opens a degree of freedom that is not accessible to spatially fixed interfaces.

  11. Polar Superhelices in Ferroelectric Chiral Nanosprings

    Science.gov (United States)

    Shimada, Takahiro; Lich, Le Van; Nagano, Koyo; Wang, Jian-Shan; Wang, Jie; Kitamura, Takayuki

    2016-10-01

    Topological objects of nontrivial spin or dipolar field textures, such as skyrmions, merons, and vortices, interacting with applied external fields in ferroic materials are of great scientific interest as an intriguing playground of unique physical phenomena and novel technological paradigms. The quest for new topological configurations of such swirling field textures has primarily been done for magnets with Dzyaloshinskii-Moriya interactions, while the absence of such intrinsic chiral interactions among electric dipoles left ferroelectrics aside in this quest. Here, we demonstrate that a helical polarization coiled into another helix, namely a polar superhelix, can be extrinsically stabilized in ferroelectric nanosprings. The interplay between dipolar interactions confined in the chiral geometry and the complex strain field of mixed bending and twisting induces the superhelical configuration of electric polarization. The geometrical structure of the polar superhelix gives rise to electric chiralities at two different length scales and the coexistence of three order parameters, i.e., polarization, toroidization, and hypertoroidization, both of which can be manipulated by homogeneous electric and/or mechanical fields. Our work therefore provides a new geometrical configuration of swirling dipolar fields, which offers the possibility of multiple order-parameters, and electromechanically controllable dipolar chiralities and associated electro-optical responses.

  12. Ionic liquids and ionic liquid acids with high temperature stability for fuel cell and other high temperature applications, method of making and cell employing same

    Science.gov (United States)

    Angell, C Austen [Mesa, AZ; Xu, Wu [Broadview Heights, OH; Belieres, Jean-Philippe [Chandler, AZ; Yoshizawa, Masahiro [Tokyo, JP

    2011-01-11

    Disclosed are developments in high temperature fuel cells including ionic liquids with high temperature stability and the storage of inorganic acids as di-anion salts of low volatility. The formation of ionically conducting liquids of this type having conductivities of unprecedented magnitude for non-aqueous systems is described. The stability of the di-anion configuration is shown to play a role in the high performance of the non-corrosive proton-transfer ionic liquids as high temperature fuel cell electrolytes. Performance of simple H.sub.2(g) electrolyte/O.sub.2(g) fuel cells with the new electrolytes is described. Superior performance both at ambient temperature and temperatures up to and above 200.degree. C. are achieved. Both neutral proton transfer salts and the acid salts with HSO.sup.-.sub.4 anions, give good results, the bisulphate case being particularly good at low temperatures and very high temperatures. The performance of all electrolytes is improved by the addition of a small amount of involatile base of pK.sub.a value intermediate between those of the acid and base that make the bulk electrolyte. The preferred case is the imidazole-doped ethylammonium hydrogensulfate which yields behavior superior in all respects to that of the industry standard phosphoric acid electrolyte.

  13. Ferroelectric or non-ferroelectric: Why so many materials exhibit "ferroelectricity" on the nanoscale

    Science.gov (United States)

    Vasudevan, Rama K.; Balke, Nina; Maksymovych, Peter; Jesse, Stephen; Kalinin, Sergei V.

    2017-06-01

    Ferroelectric materials have remained one of the major focal points of condensed matter physics and materials science for over 50 years. In the last 20 years, the development of voltage-modulated scanning probe microscopy techniques, exemplified by Piezoresponse force microscopy (PFM) and associated time- and voltage spectroscopies, opened a pathway to explore these materials on a single-digit nanometer level. Consequently, domain structures and walls and polarization dynamics can now be imaged in real space. More generally, PFM has allowed studying electromechanical coupling in a broad variety of materials ranging from ionics to biological systems. It can also be anticipated that the recent Nobel prize ["The Nobel Prize in Chemistry 2016," http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2016/ (Nobel Media, 2016)] in molecular electromechanical machines will result in rapid growth in interest in PFM as a method to probe their behavior on single device and device assembly levels. However, the broad introduction of PFM also resulted in a growing number of reports on the nearly ubiquitous presence of ferroelectric-like phenomena including remnant polar states and electromechanical hysteresis loops in materials which are non-ferroelectric in the bulk or in cases where size effects are expected to suppress ferroelectricity. While in certain cases plausible physical mechanisms can be suggested, there is remarkable similarity in observed behaviors, irrespective of the materials system. In this review, we summarize the basic principles of PFM, briefly discuss the features of ferroelectric surfaces salient to PFM imaging and spectroscopy, and summarize existing reports on ferroelectric-like responses in non-classical ferroelectric materials. We further discuss possible mechanisms behind observed behaviors and possible experimental strategies for their identification.

  14. Shape and stability in liquid threads and jets : a link to droplet formation

    NARCIS (Netherlands)

    Heugten, van W.G.N.

    2015-01-01

    This thesis explores relevant fluid dynamic processes for the formation of uniformly sized droplets in microfluidic systems. Growing droplets made from a bulk source have often liquid threads or jets in between to supply liquid to the droplet. Liquid threads and jets are however known to be instable

  15. Ferroelectric Properties of Large Area Evaporated Vinylidene Fluoride Thin Films

    Science.gov (United States)

    Foreman, Keith; Poddar, Shashi; Workman, Adam; Callori, Sara; Ducharme, Stephen; Adenwalla, Shireen

    Organic electronics provide advantages in price, processing, and functionality. Poly(vinylidene fluoride) (PVDF) is a popular organic ferroelectric used a in wide variety of applications. The VDF oligomer features a higher surface charge density than PVDF and its copolymers and oligomer thin films can be deposited in vacuum, allowing for deposition on a metallic thin film without breaking vacuum. Despite these advantages, there has been little work towards employing the VDF oligomer in devices. Here, we report on stable and tunable ferroelectric behavior of large area VDF oligomer thin films and the interface with Co thin films. Pyroelectric measurements are used to identify the operating temperature of VDF oligomer-based devices and probe the stability of the ferroelectric polarization states over long periods of time. Using capacitance-voltage, current-voltage, and x-ray diffraction measurements, the remanent polarization and crystalline phase are reported, and the effects of annealing are clarified. X-ray photoelectron spectroscopy is used to characterize the VDF/Co interface. Finally, piezoresponse force microscopy is used to demonstrate large area ferroelectric domain writing VDF oligomer thin films. This work sets the stage for VDF oligomer based organic electronics. Supported by NSF ECCS-1101256 and MRSEC DMR-1420645.

  16. Direct measurement of electric-field-induced birefringence in a polymer-stabilized blue-phase liquid crystal composite.

    Science.gov (United States)

    Yan, Jin; Jiao, Meizi; Rao, Linghui; Wu, Shin-Tson

    2010-05-24

    We demonstrate a method to directly measure the electric-field-induced birefringence of a polymer-stabilized blue-phase liquid crystal (PS-BPLC) composite. The induced birefringence follows the extended Kerr effect well and is approximately 3X the ordinary refractive index change. The measured data are validated by comparing the simulated and measured voltage-dependent transmittance with an in-plane switching cell. The impact of these results to the material optimization of emerging BPLC displays is discussed.

  17. A Review on Current Status of Stability and Knowledge on Liquid Electrolyte-Based Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Frédéric Sauvage

    2014-01-01

    Full Text Available The purpose of this review is to gather the current background in materials development and provide the reader with an accurate image of today’s knowledge regarding the stability of dye-sensitized solar cells. This contribution highlights the literature from the 1970s to the present day on nanostructured TiO2, dye, Pt counter electrode, and liquid electrolyte for which this review is focused on.

  18. Mechanism of electrically induced photonic band gap broadening in polymer stabilized cholesteric liquid crystals with negative dielectric anisotropies.

    Science.gov (United States)

    Nemati, Hossein; Liu, Shiyi; Zola, Rafael S; Tondiglia, Vincent P; Lee, Kyung Min; White, Timothy; Bunning, Timothy; Yang, Deng-Ke

    2015-02-14

    We experimentally observed that the photonic band gap (reflection band) of polymer stabilized cholesteric liquid crystals with negative dielectric anisotropies can be greatly broadened under DC electric fields. We explored the underlying mechanism. We found that the dispersed polymer network moved when DC voltages were applied across the liquid crystal cell. The motion of the polymer network stretched the helical pitch of the liquid crystal on one side of the cell and compressed the helical pitch on the other side of the cell. We proposed a phenomenological theory to explain the motion of the polymer network and the effect of the polymer network on the helical pitch, and this theoretical prediction agreed well with the experimental results.

  19. Surface rheological properties of liquid-liquid interfaces stabilized by protein fibrillar aggregates and protein-polysaccharide complexes

    NARCIS (Netherlands)

    Humblet-Hua, K.N.P.; Linden, van der E.; Sagis, L.M.C.

    2013-01-01

    In this study we have investigated the surface rheological properties of oil-water interfaces stabilized by fibrils from lysozyme (long and semi-flexible and short and rigid ones), fibrils from ovalbumin (short and semi-flexible), lysozyme-pectin complexes, or ovalbumin-pectin complexes. We have

  20. Water-in-water emulsions stabilized by non-amphiphilic interactions: polymer-dispersed lyotropic liquid crystals.

    Science.gov (United States)

    Simon, Karen A; Sejwal, Preeti; Gerecht, Ryan B; Luk, Yan-Yeung

    2007-01-30

    Emulsion systems involving surfactants are mainly driven by the separation of the hydrophobic interactions of the aliphatic chains from the hydrophilic interactions of amphiphilic molecules in water. In this study, we report an emulsion system that does not include amphiphilic molecules but molecules with functional groups that are completely solvated in water. These functional groups give rise to molecular interactions including hydrogen bonding, pi stacking, and salt bridging and are segregated into a dispersion of droplets forming a water-in-water emulsion. This water-in-water emulsion consists of dispersing droplets of a water-solvated biocompatible liquid crystal--disodium cromoglycate (DSCG)--in a continuous aqueous solution containing specific classes of water-soluble polymers. Whereas aqueous solutions of polyols support the formation of emulsions of spherical droplets consisting of lyotropic liquid crystal DSCG with long-term stability (for at least 30 days), aqueous solutions of polyamides afford droplets of DSCG in the shape of prolate ellipsoids that are stable for only 2 days. The DSCG liquid crystal in spherical droplets assumes a radial configuration in which the optical axis of the liquid crystal aligns perpendicular to the surface of the droplets but assumes a tangential configuration in prolate ellipsoids in which the optical axis of the liquid crystal aligns parallel to the surface of the droplet. Other classes of water-soluble polymers including polyethers, polycations, and polyanions do not afford a stable emulsion of DSCG droplets. Both the occurrence and the stability of this unique emulsion system can be rationalized on the basis of the functional groups of the polymer. The different configurations of the liquid crystal (DSCG) droplets were also found to correlate with the strength of the hydrogen bonding that can be formed by the functional groups on the polymer.

  1. Ferroelectric control of spin polarization.

    Science.gov (United States)

    Garcia, V; Bibes, M; Bocher, L; Valencia, S; Kronast, F; Crassous, A; Moya, X; Enouz-Vedrenne, S; Gloter, A; Imhoff, D; Deranlot, C; Mathur, N D; Fusil, S; Bouzehouane, K; Barthélémy, A

    2010-02-26

    A current drawback of spintronics is the large power that is usually required for magnetic writing, in contrast with nanoelectronics, which relies on "zero-current," gate-controlled operations. Efforts have been made to control the spin-relaxation rate, the Curie temperature, or the magnetic anisotropy with a gate voltage, but these effects are usually small and volatile. We used ferroelectric tunnel junctions with ferromagnetic electrodes to demonstrate local, large, and nonvolatile control of carrier spin polarization by electrically switching ferroelectric polarization. Our results represent a giant type of interfacial magnetoelectric coupling and suggest a low-power approach for spin-based information control.

  2. Recent patents on perovskite ferroelectric nanostructures.

    Science.gov (United States)

    Zhu, Xinhua

    2009-01-01

    Ferroelectric oxide materials with a perovskite structure have promising applications in electronic devices such as random access memories, sensors, actuators, infrared detectors, and so on. Recent advances in science and technology of ferroelectrics have resulted in the feature sizes of ferroelectric-based electronic devices entering into nanoscale dimensions. At nanoscale perovskite ferroelectric materials exhibit a pronounced size effect manifesting itself in a significant deviation of the properties of low-dimensional structures from the bulk and film counterparts. One-dimensional perovskite ferroelectric nanotube/nanowire systems, offer fundamental scientific opportunities for investigating the intrinsic size effects in ferroelectrics. In the past several years, much progress has been made both in fabrication and physical property testing of perovskite ferroelectric nanostructures. In the first part of this paper, the recent patents and literatures for fabricating ferroelectric nanowires, nanorods, nanotubes, and nanorings with promising features, are reviewed. The second part deals with the recent advances on the physical property testing of perovskite ferroelectric nanostructures. The third part summarizes the recently patents and literatures about the microstructural characterizations of perovskite ferroelectric nanostructures, to improve their crystalline quality, morphology and uniformity. Finally, we conclude this review with personal perspectives towards the potential future developments of perovskite ferroelectric nanostructures.

  3. Swirl-Stabilized Injector Flow and Combustion Dynamics for Liquid Propellants at Supercritical Conditions

    National Research Council Canada - National Science Library

    Yang, Vigor

    2007-01-01

    An integrated modeling and simulation program has been conducted to substantially improve the fundamental knowledge of supercritical combustion of liquid propellants under conditions representative...

  4. Graded ferroelectrics, transpacitors and transponents

    CERN Document Server

    Mantese, Joseph V

    2005-01-01

    The text details the experimental and theoretical aspects of newly emerging ferroelectric devices, and their extensions to other ferroic systems such as: ferromagnetics, ferroelastics, piezoelectrics, etc. The theory and experimental results pertaining to non-homogeneous active ferroic devices and structures are presented.

  5. Strain gradients in epitaxial ferroelectrics

    NARCIS (Netherlands)

    Catalan, G; Noheda, Beatriz; McAneney, J; Sinnamon, LJ; Gregg, JM

    2005-01-01

    X-ray analysis of ferroelectric thin layers of Ba1/2Sr1/2TiO3 with different thicknesses reveals the presence of strain gradients across the films and allows us to propose a functional form for the internal strain profile. We use this to calculate the influence of strain gradient, through

  6. Stability of the liquid particles separation in the apparatus of oil and gas systems

    Science.gov (United States)

    Vasilevsky, M. V.; Zyatikov, P. N.; Burykin, A. Y.; Deeva, V. S.

    2015-11-01

    The article considers the methods of associated gas purification from liquid particles. The sintering of liquid particles occurs during the separation process and the trapped droplets can be removed as a liquid stream, i.e. there is no need for unloading units. The droplet size depends on the energy input during their fragmentation. The efficiency of drops separation depends on the flow rate and the intensification of droplets coalescence, film formation and liquid flow to the receiver. The dispersion of the liquid particles is the main drawback of the existing purification methods, i.e. lack of sustainability of particle separation. The comparison of the separation system methods and the devices with flow control elements is carried out. The estimation of gas purification efficiency is conducted. It is concluded that the efficiency of associated gas purification gives the possibility to use it in turbine generators, heating furnaces, etc. It significantly reduces the proportion of gas being flared.

  7. Laterally azo-bridged h-shaped ferroelectric dimesogens for second-order nonlinear optics: ferroelectricity and second harmonic generation.

    Science.gov (United States)

    Zhang, Yongqiang; Martinez-Perdiguero, Josu; Baumeister, Ute; Walker, Christopher; Etxebarria, Jesus; Prehm, Marko; Ortega, Josu; Tschierske, Carsten; O'Callaghan, Michael J; Harant, Adam; Handschy, Mark

    2009-12-30

    Two classes of laterally azo-bridged H-shaped ferroelectric liquid crystals (FLCs), incorporating azobenzene and disperse red 1 (DR-1) chromophores along the FLC polar axes, were synthesized and characterized by polarized light microscopy, differential scanning calorimetry, 2D X-ray diffraction analysis, and electro-optical investigations. They represent the first H-shaped FLC materials exhibiting the ground-state, thermodynamically stable enantiotropic SmC* phase, i.e., ground-state ferroelectricity. Second harmonic generation measurements of one compound incorporating a DR-1 chromophore at the incident wavelength of 1064 nm give a nonlinear coefficient of d(22) = 17 pm/V, the largest nonlinear optics coefficient reported to date for calamitic FLCs. This value enables viable applications of FLCs in nonlinear optics.

  8. An efficient liquid chromatography-high resolution mass spectrometry approach for the optimization of the metabolic stability of therapeutic peptides.

    Science.gov (United States)

    Esposito, Simone; Mele, Riccardo; Ingenito, Raffaele; Bianchi, Elisabetta; Bonelli, Fabio; Monteagudo, Edith; Orsatti, Laura

    2017-04-01

    In drug discovery, there is increasing interest in peptides as therapeutic agents due to several appealing characteristics that are typical of this class of compounds, including high target affinity, excellent selectivity, and low toxicity. However, peptides usually present also some challenging ADME (absorption, distribution, metabolism, and excretion) issues such as limited metabolic stability, poor oral bioavailability, and short half-lives. In this context, early preclinical in vitro studies such as plasma metabolic stability assays are crucial to improve developability of a peptidic drug. In order to speed up the optimization of peptide metabolic stability, a strategy was developed for the integrated semi-quantitative determination of metabolic stability of peptides and qualitative identification/structural elucidation of their metabolites in preclinical plasma metabolic stability studies using liquid chromatography-high-resolution Orbitrap™ mass spectrometry (LC-HRMS). Sample preparation was based on protein precipitation: experimental conditions were optimized after evaluating and comparing different organic solvents in order to obtain an adequate extraction of the parent peptides and their metabolites and to minimize matrix effect. Peptides and their metabolites were analyzed by reverse-phase liquid chromatography: a template gradient (total run time, 6 min) was created to allow retention and good peak shape for peptides of different polarity and isoelectric points. Three LC columns were selected to be systematically evaluated for each series of peptides. Targeted and untargeted HRMS data were simultaneously acquired in positive full scan + data-dependent MS/MS acquisition mode, and then processed to calculate plasma half-life and to identify the major cleavage sites, this latter by using the software Biopharma Finder™. Finally, as an example of the application of this workflow, a study that shows the plasma stability improvement of a series of

  9. Retention of intermediate polarization states in ferroelectric materials enabling memories for multi-bit data storage

    Science.gov (United States)

    Zhao, Dong; Katsouras, Ilias; Asadi, Kamal; Groen, Wilhelm A.; Blom, Paul W. M.; de Leeuw, Dago M.

    2016-06-01

    A homogeneous ferroelectric single crystal exhibits only two remanent polarization states that are stable over time, whereas intermediate, or unsaturated, polarization states are thermodynamically instable. Commonly used ferroelectric materials however, are inhomogeneous polycrystalline thin films or ceramics. To investigate the stability of intermediate polarization states, formed upon incomplete, or partial, switching, we have systematically studied their retention in capacitors comprising two classic ferroelectric materials, viz. random copolymer of vinylidene fluoride with trifluoroethylene, P(VDF-TrFE), and Pb(Zr,Ti)O3. Each experiment started from a discharged and electrically depolarized ferroelectric capacitor. Voltage pulses were applied to set the given polarization states. The retention was measured as a function of time at various temperatures. The intermediate polarization states are stable over time, up to the Curie temperature. We argue that the remarkable stability originates from the coexistence of effectively independent domains, with different values of polarization and coercive field. A domain growth model is derived quantitatively describing deterministic switching between the intermediate polarization states. We show that by using well-defined voltage pulses, the polarization can be set to any arbitrary value, allowing arithmetic programming. The feasibility of arithmetic programming along with the inherent stability of intermediate polarization states makes ferroelectric materials ideal candidates for multibit data storage.

  10. Fibrous Support Stabilizes Nitrification Performance of a Membrane-Aerated Biofilm: The Effect of Liquid Flow Perturbation

    DEFF Research Database (Denmark)

    Terada, Akihiko; Ito, J; Matsumoto, S

    2009-01-01

    Nitrification stability and biofilm robustness were examined by comparing a fibrous support membrane-aerated biofilm reactor (FS-MABR), where a woven fibrous support was surrounded on a silicone tube, with an MABR. The overall mass transfer coefficient of oxygen for the FS-MABR, assuming no bound......Nitrification stability and biofilm robustness were examined by comparing a fibrous support membrane-aerated biofilm reactor (FS-MABR), where a woven fibrous support was surrounded on a silicone tube, with an MABR. The overall mass transfer coefficient of oxygen for the FS-MABR, assuming...... liquid flow rate condition was 49% and 75% in the FS-MABR and MABR, exhibiting robust biofilms grown on the fibrous support. The FS-MABR provided more stable nitrification performance than the MABR irrespective of a high liquid flow rate. Both reactors have deteriorated ammonium (NH4+-N) removal without...... a high liquid flow rate condition to eliminate excessive biomass, indicating that regular maintenance is essential to eliminate excessive biofilm from a MABR for nitrification, which potentially acts as a NH4+ diffusion barrier....

  11. The Effect of Interfacial Properties and Liquid Flow on the Stability of Powder Islands

    OpenAIRE

    Ong Xin Yi; Taylor Spencer E.; Ramaioli Marco

    2017-01-01

    This study aims at understanding the interplay between the interfacial properties of the powder grains and the characteristics of the liquid flow used to disperse them, in order to obtain an effective dispersion of a powder in a liquid, avoiding air entrainment. The dispersion of grain “rafts” and powder islands “stacks” was investigated both on a static and on a moving air-liquid interface. Powder wicking prevents the formation of a powder island when the grain contact angle is below a criti...

  12. Evaluation of local anesthetic effects of Lidocaine-Ibuprofen ionic liquid stabilized silver nanoparticles in Male Swiss mice.

    Science.gov (United States)

    Jiang, Qiliang; Yu, Shashuang; Li, Xingwang; Ma, Chuangen; Li, Aixiang

    2018-01-01

    A simple approach for the synthesis of Lidocaine-Ibuprofen ionic liquid stabilized silver nanoparticles (IL-AgNPs) was reported in this work. The shape, size and surface morphology of the Lidocaine-Ibuprofen ionic liquid stabilized AgNPs were characterized by using spectroscopic and microscopic techniques such as Ultraviolet-visible spectroscopy (UV-Visible), X-ray diffraction (XRD) analysis, Selected area electron diffraction (SAED), Transmission electron microscopy (TEM). TEM analysis showed the formation of 20-30nm size of IL-AgNPs with very clear lattice fringes. SAED pattern confirmed the highly crystalline nature of fabricated IL stabilized AgNPs. EDS results confirmed the formation of nanosilver. The fabricated IL-AgNPs were studied for their local anesthetic effect in rats. The results of local anesthetic effect showed that the time for onset of action by IL-AgNPs is 10min, which is significantly higher than that for EMLA. Further, tactile test results confirmed the stronger and faster local anesthetic effect of IL-AgNPs when compared to that of EMLA. Copyright © 2017. Published by Elsevier B.V.

  13. Significant improvements in stability and reproducibility of atomic-scale atomic force microscopy in liquid

    OpenAIRE

    Akrami, S.M.R.; Nakayachi, H.; Watanabe-Nakayama, Takahiro; Asakawa, Hitoshi; Fukuma, Takeshi

    2014-01-01

    Recent advancement of dynamic-mode atomic force microscopy (AFM) for liquid-environment applications enabled atomic-scale studies on various interfacial phenomena. However, instabilities and poor reproducibility of the measurements often prevent systematic studies. To solve this problem, we have investigated the effect of various tip treatment methods for atomic-scale imaging and force measurements in liquid. The tested methods include Si coating, Ar plasma, Ar sputtering and UV/O3 cleaning. ...

  14. Practical Methodology for the Inclusion of Nonlinear Slosh Damping in the Stability Analysis of Liquid-propelled Space Vehicles

    Science.gov (United States)

    Ottander, John A.; Hall, Robert A., Jr.; Powers, Joseph F.

    2017-01-01

    One of the challenges of developing flight control systems for liquid-propelled space vehicles is ensuring stability and performance in the presence of parasitic minimally damped slosh dynamics in the liquid propellants. This can be especially difficult when the fundamental frequencies of the slosh motions are in proximity to the frequency used for vehicle control. The challenge is partially alleviated since the energy dissipation and effective damping in the slosh modes increases with amplitude. However, traditional launch vehicle control design methodology is performed with linearized systems using a fixed slosh damping corresponding to a slosh motion amplitude based on heritage values. This papers presents a method for performing the control design and analysis using damping at slosh amplitudes chosen based on the resulting limit cycle amplitude of the vehicle thrust vector system due to a control-slosh interaction under degraded phase and gain margin conditions.

  15. Investigation into the temporal stability of aqueous standard solutions of psilocin and psilocybin using high performance liquid chromatography.

    Science.gov (United States)

    Anastos, N; Barnett, N W; Pfeffer, F M; Lewis, S W

    2006-01-01

    This paper reports an investigation into the temporal stability of aqueous solutions of psilocin and psilocybin reference drug standards over a period of fourteen days. This study was performed using high performance liquid chromatography utilising a (95:5% v/v) methanol: 10 mM ammonium formate, pH 3.5 mobile phase and absorption detection at 269 nm. It was found that the exclusion of light significantly prolonged the useful life of standards, with aqueous solutions of both psilocin and psilocybin being stable over a period of seven days.

  16. Weak ferromagnetism and nanodimensional ferroelectric domain structure stabilized in the polar phase of Bi{sub 1−x}Nd{sub x}FeO{sub 3} multiferroics via Ti doping

    Energy Technology Data Exchange (ETDEWEB)

    Khomchenko, V. A., E-mail: uladzimir@fis.uc.pt; Paixão, J. A. [CEMDRX/Department of Physics, University of Coimbra, P-3004-516 Coimbra (Portugal); Pereira, L. C. J. [Unidade de Ciências Químicas e Radiofarmacêuticas, IST/CTN, Instituto Superior Técnico, Universidade Técnica de Lisboa/CFMCUL, P-2686-953 Sacavém (Portugal)

    2014-04-28

    Crystal structure, microstructure, local ferroelectric, and magnetic properties of the Bi{sub 0.9}Nd{sub 0.1}Fe{sub 1−x}Ti{sub x}O{sub 3} samples have been investigated at room temperature to reveal the effect of Ti{sup 4+} doping on the multiferroic behavior of the lanthanide-modified compound representing a polar (space group R3c) antiferromagnetic phase of the Bi{sub 1−x}Ln{sub x}FeO{sub 3} perovskites. Ti doping results in a gradual suppression of the rhombohedral distortions, however, symmetry of the crystal structure remains the same in the entire concentration range allowing the single-phase perovskites to be obtained (x ≤ 0.08). The doping tends to reduce existing lone-pair cation-driven polar displacements, thus giving rise to a decrease of the ferroelectric polarization in the Bi{sub 0.9}Nd{sub 0.1}Fe{sub 1−x}Ti{sub x}O{sub 3} (x→0.08) series. A drastic (from ∼10 μm for x = 0 to ∼1 μm for 0.02 ≤ x ≤ 0.08) decrease of the average grain size induced by the doping is accompanied by the formation of a ferroelectric domain structure with the average domain width of ∼40 nm. Finally, the doping was shown to induce an antiferromagnetic to weak ferromagnetic transformation. The maximum remanent magnetization observed in the Bi{sub 0.9}Nd{sub 0.1}Fe{sub 1−x}Ti{sub x}O{sub 3} series at x ∼ 0.05 coincides with the locked magnetization releasing upon the magnetic field-induced suppression of the magnetic cycloid in pure BiFeO{sub 3}.

  17. Probing the ionic dielectric constant contribution in the ferroelectric phase of the Fabre salts

    Science.gov (United States)

    de Souza, Mariano; Squillante, Lucas; Sônego, Cesar; Menegasso, Paulo; Foury-Leylekian, Pascale; Pouget, Jean-Paul

    2018-01-01

    In strongly correlated organic materials it has been pointed out that charge ordering could also achieve electronic ferroelectricity at the same critical temperature Tco. A prototype of such phenomenon are the quasi-one-dimensional (TMTTF)2X Fabre salts. However, the stabilization of a long-range ferroelectric ground state below Tco requires the break of inversion symmetry, which should be accompanied by a lattice deformation. In this paper we investigate the role of the monovalent counteranion X in such mechanism. For this purpose, we measured the quasistatic dielectric constant along the c*-axis direction, where layers formed by donors and anions alternate. Our findings show that the ionic charge contribution is three orders of magnitude lower than the intrastack electronic response. The c* dielectric constant (εc*') probes directly the charge response of the monovalent anion X , since the anion mobility in the structure should help to stabilize the ferroelectric ground state. Furthermore, our εc*' measurements show that the dielectric response is thermally broaden below Tco if the ferroelectric transition occurs in the temperature range where the anion movement begin to freeze in their methyl groups cavity. In the extreme case of the PF6-H12 salt, where Tco occurs at the freezing point, a relaxor-type ferroelectricity is observed. Also, because of the slow kinetics of the anion sublattice, global hysteresis effects and reduction of the charge response upon successive cycling are observed. In this context, we propose that anions control the order-disorder or relaxation character of the ferroelectric transition of the Fabre salts. Yet, our results show that x-ray irradiation damages change the well-defined ferroelectric response of the AsF6 pristine salt into a relaxor.

  18. The Structure of Ferroelectric DCsDA

    DEFF Research Database (Denmark)

    Dietrich, O. W.; Cowley, R. A.; Shapiro, S. M.

    1974-01-01

    Neutron scattering measurements on DCsDA (CsD2AsO4) have failed to show ferroelectric critical scattering above Tc, but have provided evidence for a complex structure in the ferroelectric phase with periodicities of approximately 30, 15, 10 and 5 lattice spacings.......Neutron scattering measurements on DCsDA (CsD2AsO4) have failed to show ferroelectric critical scattering above Tc, but have provided evidence for a complex structure in the ferroelectric phase with periodicities of approximately 30, 15, 10 and 5 lattice spacings....

  19. Sclerosant foam structure and stability is strongly influenced by liquid air fraction.

    Science.gov (United States)

    Cameron, E; Chen, T; Connor, D E; Behnia, M; Parsi, K

    2013-10-01

    To determine the effects of sclerosant foam preparation and composition on foam structure, the time course of liquid drainage, and foam coarsening. Sodium tetradecyl sulphate (STS) and polidocanol (POL) foams were investigated in a range of concentrations (0.5-3%) and liquid-plus-air fractions (LAF; 1 + 2 to 1 + 8). Foam was injected into a vein simulation model (polyvinyl chloride tubing, inner diameter 3 mm, constant pressure 5-7 mmHg) filled with saline or blood. Liquid drainage, bubble count, and diameter were measured and documented by serial photography. Liquid drainage was faster in the vertical position than the horizontal one. In all variations, very small bubbles (diameter foams (foams (>250 μm) and by 7.5 minutes macro-foams (>500 μm) were formed. Following injection, the upper regions of foam coarsened faster as liquid drained to the bottom of the vessel. Wet preparations produced significantly smaller bubbles. Low concentration POL foam produced significantly higher bubble counts and coarsened slower than STS. Foam structure is strongly influenced by the LAF. Despite the initial formation of micro-bubbles in the syringe, mini- and macro-bubbles are formed in target vessels with time post-injection. Copyright © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

  20. Beyond-use date determination of buprenorphine buccal solution using a stability-indicating high-performance liquid chromatographic assay.

    Science.gov (United States)

    Kirk, Loren Madden; Brown, Stacy D

    2015-12-01

    The objectives of this study included developing and validating a stability-indicating high-performance liquid chromatographic (HPLC) method with ultraviolet (UV) detection for the determination of buprenorphine in a buccal solution for veterinary use, and applying that method to determine the stability of a 3 mg/ml buprenorphine preparation in room temperature and refrigerated storage conditions. This preparation, intended for buccal administration in feline patients, plays an important role in pain management in cats. A stability-indicating HPLC method was developed and validated for system suitability, accuracy, repeatability, intermediate precision, specificity, linearity and robustness based on US Pharmacopeia (USP) General Chapter . The method was then applied to the study of potency changes over 90 days in a buccal buprenorphine solution stored at two temperatures. All HPLC-UV method data met acceptable criteria for the quantification of buprenorphine in a buccal solution formulation. The buprenorphine concentrations found in each stability sample remained within the 90-110% of label claim throughout the 90 days of study. All stability test bottles of the buprenorphine buccal solution retained their original appearance. For the room temperature bottles, some white particulate matter was noted in the threads of the container bottles starting at day 21. The pH of the preparations during the course of the study was in the range of 3.57-4.06 and 4.01-4.16 for the room temperature and refrigerated samples, respectively. Pharmacists have compounded a concentrated 3 mg/ml buccal solution to use easily in the home care or outpatient setting for treatment of feline pain. Prior to this investigation, pharmacists empirically assigned beyond-use dates to this formulation based on standards in USP General Chapter Pharmaceutical Compounding - Nonsterile Preparations. This study of a 3 mg/ml buprenorphine buccal solution indicates stability through 90 days. © ISFM and

  1. Ferroelectric Stirling-Cycle Refrigerator

    Science.gov (United States)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    1999-01-01

    A Stirling-cycle refrigerator has a three-pump configuration and pumping sequence, in which one pump serves as a compressor. one pump serves as an expander, and one pump serves as a displacer. The pumps are ferroelectrically actuated diaphragm pumps which are coordinated by synchronizing the ferroelectric-actuator voltages in such a way that the net effect of the displacer is to reduce the deleterious effect of dead space; that is, to circulate a greater fraction of the working fluid through the heat exchangers than would be possible by use of the compressor and expander alone. In addition. the displacer can be controlled separately to make the flow of working fluid in the heat exchangers turbulent (to increase the rate of transfer of heat at the cost of greater resistance to flow) or laminar (to decrease the resistance to flow at the cost of a lower heat-transfer rate).

  2. Transparent Ferroelectric Capacitors on Glass

    Directory of Open Access Journals (Sweden)

    Daniele Sette

    2017-10-01

    Full Text Available We deposited transparent ferroelectric lead zirconate titanate thin films on fused silica and contacted them via Al-doped zinc oxide (AZO transparent electrodes with an interdigitated electrode (IDE design. These layers, together with a TiO2 buffer layer on the fused silica substrate, are highly transparent (>60% in the visible optical range. Fully crystallized Pb(Zr0.52Ti0.48O3 (PZT films are dielectrically functional and exhibit a typical ferroelectric polarization loop with a remanent polarization of 15 μC/cm2. The permittivity value of 650, obtained with IDE AZO electrodes is equivalent to the one measured with Pt electrodes patterned with the same design, which proves the high quality of the developed transparent structures.

  3. Percolation Magnetism in Ferroelectric Nanoparticles.

    Science.gov (United States)

    Golovina, Iryna S; Lemishko, Serhii V; Morozovska, Anna N

    2017-12-01

    Nanoparticles of potassium tantalate (KTaO3) and potassium niobate (KNbO3) were synthesized by oxidation of metallic tantalum in molten potassium nitrate with the addition of potassium hydroxide. Magnetization curves obtained on these ferroelectric nanoparticles exhibit a weak ferromagnetism, while these compounds are nonmagnetic in a bulk. The experimental data are used as a start point for theoretical calculations. We consider a microscopic mechanism that leads to the emerging of a ferromagnetic ordering in ferroelectric nanoparticles. Our approach is based on the percolation of magnetic polarons assuming the dominant role of the oxygen vacancies. It describes the formation of surface magnetic polarons, in which an exchange interaction between electrons trapped in oxygen vacancies is mediated by magnetic impurity Fe3+ ions. The dependences of percolation radius on concentration of the oxygen vacancies and magnetic defects are determined in the framework of percolation theory.

  4. Review on polymer-stabilized short-pitch cholesteric liquid crystal displays

    Science.gov (United States)

    Tan, Guanjun; Lee, Yun-Han; Gou, Fangwang; Chen, Haiwei; Huang, Yuge; Lan, Yi-Fen; Tsai, Cheng-Yeh; Wu, Shin-Tson

    2017-12-01

    Submillisecond response times and low operation voltage are critical to next generation liquid crystal display and photonic devices. In this paper, we review the recent progress of three fast-response short-pitch cholesteric liquid crystal modes: blue phase (BP), uniform standing helix (USH), and uniform lying helix (ULH). This review starts with a brief introduction of device structures and working principles, and then highlights two competing electro-optical effects: dielectric effect and flexoelectric effect. Next, we compare their electro-optical behaviors, response time, temperature dependence, and contrast ratio. Based on our established simulation model, we are able to optimize the phase compensation scheme for improving the viewing angle and gamma shift of USH and ULH modes. Finally, we analyze some major challenges, which remain to be overcome before the widespread applications of these liquid crystal devices can be realized.

  5. SOUND ATTENUATION IN FERROELECTRIC SOLIDS

    OpenAIRE

    Naithani, U.; Semwal, B.

    1981-01-01

    An expression for the sound-attenuation constant in doped displacive ferroelectrics, in the presence of an external electric field, is obtained by using the double-time thermal- Green's -functions technique. The mass and force constant changes between the impurity and the host lattice atoms are taken into account in the Silverman Hamiltonian augmented with higher -order anharmonic and electric-moment terms. The defect-dependent, electric- field-dependent, and anharmonic contributions to the a...

  6. Proceedings of the 6. international conference on stability and handling of liquid fuels. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    Giles, H.N. [ed.] [Deputy Assistant Secretary for Strategic Petroleum Reserve, Washington, DC (United States). Operations and Readiness Office

    1998-12-01

    Volume 1 of these proceedings contain 29 papers related to aviation fuels and long term and strategic storage. Studies investigated fuel contamination, separation processes, measurement techniques, thermal stability, compatibility with fuel system materials, oxidation reactions, and degradation during storage.

  7. Local ferroelectricity in thermoelectric SnTe above room temperature driven by competing phonon instabilities and soft resonant bonding

    Directory of Open Access Journals (Sweden)

    Leena Aggarwal

    2016-06-01

    Full Text Available We report direct observation of local ferroelectric ordering above room temperature in rocksalt SnTe, which is a topological crystalline insulator and a good thermoelectric material. Although SnTe is known to stabilize in a ferroelectric ground state (rhombohedral phase below ∼100 K, at high temperatures it was not expected to show any ferroelectric ordering forbidden by its globally centro-symmetric crystal structure (Fm-3m. Here, we show that SnTe exhibits local ferroelectric ordering that is robust above room temperature through direct imaging of ferroelectric domains by piezoresponse force microscopy and measurement of local polarization switching using switching spectroscopy. Using first-principles theoretical analysis, we show how the local ferroelectricity arises from soft bonding and competing phonon instabilities at intermediate wavelengths, which induce local Sn-off centering in the otherwise cetrosymmetric SnTe crystal structure. The results make SnTe an important member of the family of new multi-functional materials namely the ferroelectric-thermoelectrics.

  8. Feasibility study of Using Liquid Gel in Stabilizing Doogh by Hydrocolloids of Psyllium Husk and Guar Gum

    Directory of Open Access Journals (Sweden)

    Tayebeh Tavakoli Vardanjani

    2014-04-01

    Full Text Available Liquid gel technology is a method that applies in stabilizing of suspension and dispersion of solid particles in beverages. Doogh which is an Iranian traditional and functional drink has allocated a unique position among consumers. Precipitation of hydrocolloids in Doogh has been always one of the most important challenge in producing this drink. Base of this fact, this study deals with using liquid gel technology (Guar gum and Hydrocolloids of  Psyllium Husk .Different hydrocolloids concentration (0.01, 0.03, 0.05 %w/w in Doogh heated to be hydrated at 80 ˚C resulting in producing Gel. Their flow behavior, particle distribution and microstructure analyzed, phase separation also evaluated by measuring volume of separated phases .Guar remarkably effected on Doogh flow behavior and caused to a high apparent viscosity in low shear rates, changing microstructure therefore changing particles size as well. It also subtracted the volume of separated phase .Xanthan and Psyllium increased stability of Doogh by increasing more repulsive force between particles, however larger particles precipitated. Samples containing Guar Gum indicated more yield stress.

  9. Development of cellulase-nanoconjugates with enhanced ionic liquid and thermal stability for in situ lignocellulose saccharification.

    Science.gov (United States)

    Grewal, Jasneet; Ahmad, Razi; Khare, S K

    2017-10-01

    The present work aimed to improve catalytic efficiency of Trichoderma reesei cellulase for enhanced saccharification. The cellulase was immobilized on two nanomatrices i.e. magnetic and silica nanoparticles with immobilization efficiency of 85% and 76% respectively. The nanobioconjugates exhibited increase in Vmax, temperature optimum, pH and thermal stability as compared with free enzyme. These could be efficiently reused for five repeated cycles and were stable in 1-ethyl-3-methylimidazoliumacetate [EMIM][Ac], an ionic liquid. Ionic liquids (IL) are used as green solvents to dissolve lignocellulosic biomass and facilitate better saccharification. The cellulase immobilized on magnetic nanoparticles was used for in situ saccharification of [EMIM][Ac] pretreated sugarcane bagasse and wheat straw for two cycles. The structural deconstruction and decrease in biomass crystallinity was confirmed by SEM, XRD and FTIR. The high hydrolysis yields (∼89%) obtained in this one-pot process coupled with IL stability and recycled use of immobilized cellulase, potentiates its usefulness in biorefineries. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Critical fluctuations in liquid He/sup 3/: Stabilization of the Anderson-Morel phase

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, A.I.

    1979-05-20

    The equations for the renormalized group, which describe the superfluid phase transitions in liquid He/sup 3/, are derived and solved (on the computer). It is shown that the interaction of the critical fluctuations of the order parameter increases the region corresponding to phase A in the phase diagram of He/sup 3/.

  11. Pharmaceutically active ionic liquids with solids handling, enhanced thermal stability, and fast release

    DEFF Research Database (Denmark)

    Bica, Katharina; Rodríguez, Héctor; Gurau, Gabriela

    2012-01-01

    Pharmaceutically active compounds in ionic liquid form immobilized onto mesoporous silica are stable, easily handled solids, with fast and complete release from the carrier material when placed into an aqueous environment. Depending on specific ion-surface interactions, they may also exhibit...

  12. On the existence and stability of liquid water on the surface of mars today.

    Science.gov (United States)

    Kuznetz, L H; Gan, D C

    2002-01-01

    The recent discovery of high concentrations of hydrogen just below the surface of Mars' polar regions by Mars Odyssey has enlivened the debate about past or present life on Mars. The prevailing assumption prior to the discovery was that the liquid water essential for its existence is absent. That assumption was based largely on the calculation of heat and mass transfer coefficients or theoretical climate models. This research uses an experimental approach to determine the feasibility of liquid water under martian conditions, setting the stage for a more empirical approach to the question of life on Mars. Experiments were conducted in three parts: Liquid water's existence was confirmed by droplets observed under martian conditions in part 1; the evolution of frost melting on the surface of various rocks under martian conditions was observed in part 2; and the evaporation rate of water in Petri dishes under Mars-like conditions was determined and compared with the theoretical predictions of various investigators in part 3. The results led to the conclusion that liquid water can be stable for extended periods of time on the martian surface under present-day conditions.

  13. On the existence and stability of liquid water on the surface of mars today

    Science.gov (United States)

    Kuznetz, L. H.; Gan, D. C.

    2002-01-01

    The recent discovery of high concentrations of hydrogen just below the surface of Mars' polar regions by Mars Odyssey has enlivened the debate about past or present life on Mars. The prevailing assumption prior to the discovery was that the liquid water essential for its existence is absent. That assumption was based largely on the calculation of heat and mass transfer coefficients or theoretical climate models. This research uses an experimental approach to determine the feasibility of liquid water under martian conditions, setting the stage for a more empirical approach to the question of life on Mars. Experiments were conducted in three parts: Liquid water's existence was confirmed by droplets observed under martian conditions in part 1; the evolution of frost melting on the surface of various rocks under martian conditions was observed in part 2; and the evaporation rate of water in Petri dishes under Mars-like conditions was determined and compared with the theoretical predictions of various investigators in part 3. The results led to the conclusion that liquid water can be stable for extended periods of time on the martian surface under present-day conditions.

  14. Liquid chromatographic analysis of nitration of diphenylamine stabilizer in explosives. [PBX-9404

    Energy Technology Data Exchange (ETDEWEB)

    MacDougall, C.S.

    1975-12-01

    A high speed liquid chromatographic method was developed for the quantitative analysis of nitrated diphenylamines in PBX-9404. The procedure included extraction of the nitrated diphenylamines into methylene chloride, followed by chromatographic separation and examination of the various species. The method requires a 10-g sample of high explosive in order to provide a sample of nitro DPA suitably concentrated for chromatographic analysis. (auth)

  15. Innovative methods to stabilize liquid membranes for removal of radionuclides from groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Lokhandwala, K. [Membrane Technology and Research, Inc., Menlo Park, CA (United States)

    1997-10-01

    In this Phase I Small Business Innovation Research program, Membrane Technology Research, Inc., is developing a stable liquid membrane for extracting uranium and other radionuclides from groundwater. The improved membrane can also be applied to separation of other metal ions from aqueous streams in industrial operations.

  16. Extraction and stability of selected proteins in ionic liquid based aqueous two phase systems

    NARCIS (Netherlands)

    Desai, R.K.; Streefland, M.; Wijffels, R.H.; Eppink, M.H.M.

    2014-01-01

    Ionic liquid-based aqueous two-phase extraction of a plant protein, Rubisco (Ribulose-1,5-biphosphate carboxylase oxygenase), using Iolilyte 221 PG and sodium potassium phosphate buffer, was investigated as a new alternative extraction method and compared with a conventional PEG-based two-phase

  17. The influence of protruding filamentous bacteria on floc stability and solid-liquid separation in the activated sludge process.

    Science.gov (United States)

    Burger, Wilhelm; Krysiak-Baltyn, Konrad; Scales, Peter J; Martin, Gregory J O; Stickland, Anthony D; Gras, Sally L

    2017-10-15

    Filamentous bacteria can impact on the physical properties of flocs in the activated sludge process assisting solid-liquid separation or inducing problems when bacteria are overabundant. While filamentous bacteria within the flocs are understood to increase floc tensile strength, the relationship between protruding external filaments, dewatering characteristics and floc stability is unclear. Here, a quantitative methodology was applied to determine the abundance of filamentous bacteria in activated sludge samples from four wastewater treatment plants. An automated image analysis procedure was applied to identify filaments and flocs and calculate the length of the protruding filamentous bacteria (PFB) relative to the floc size. The correlation between PFB and floc behavior was then assessed. Increased filament abundance was found to increase interphase drag on the settling flocs, as quantified by the hindered settling function. Additionally, increased filament abundance was correlated with a lower gel point concentration leading to poorer sludge compactability. The floc strength factor, defined as the relative change in floc size upon shearing, correlated positively with filament abundance. This influence of external protruding filamentous bacteria on floc stability is consistent with the filamentous backbone theory, where filamentous bacteria within flocs increase floc resistance to shear-induced breakup. A qualitative correlation was also observed between protruding and internal filamentous structure. This study confirms that filamentous bacteria are necessary to enhance floc stability but if excessively abundant will adversely affect solid-liquid separation. The tools developed here will allow quantitative analysis of filament abundance, which is an improvement on current qualitative methods and the improved method could be used to assist and optimize the operation of waste water treatment plants. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Development of a generic combustion stability code for liquid propellant rocket engines

    Science.gov (United States)

    Fang, J. J.; Jones, Y. T.

    1987-01-01

    The mathematical framework for a combustion stability analysis code is outlined. The goal for the code is to be general enough in problem treatment so that its validity and accuracy extend over a wide range of problem applications and that it lends the convenience for any future model improvement if necessary. An approach for modeling the combustion dynamics is devised to meet both requirements. An open-loop numerical procedure is also developed to mechanistically model various combustion processes for determining the stability parameters.

  19. Low-Loss Ferroelectric for Accelerator Application

    CERN Document Server

    Kanareykin, Alex; Karmanenko, Sergei F; Nenasheva, Elisaveta; Yakovlev, Vyacheslav P

    2005-01-01

    Ferroelectric ceramics have an electric field-dependent dielectric permittivity that can be altered by applying a bias voltage. Ferroelectrics have unique intrinsic properties that makes them attractive for high-energy accelerator applications: very small response time of ~ 10-11

  20. Ferroelectric phase diagram of PVDF:PMMA

    NARCIS (Netherlands)

    Li, M.; Stingelin, N.; Michels, J.J.; Spijkman, M.-J.; Asadi, K.; Feldman, K.; Blom, P.W.M.; Leeuw, D.M. de

    2012-01-01

    We have investigated the ferroelectric phase diagram of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA). The binary nonequilibrium temperature composition diagram was determined and melting of α- and β-phase PVDF was identified. Ferroelectric β-PVDF:PMMA blend films were made

  1. Ferroelectric Phase Diagram of PVDF : PMMA

    NARCIS (Netherlands)

    Li, Mengyuan; Stingelin, Natalie; Michels, Jasper J.; Spijkman, Mark-Jan; Asadi, Kamal; Feldman, Kirill; Blom, Paul W. M.; de Leeuw, Dago M.

    2012-01-01

    We have investigated the ferroelectric phase diagram of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA). The binary nonequilibrium temperature composition diagram was determined and melting of alpha- and beta-phase PVDF was identified. Ferroelectric beta-PVDF:PMMA blend films

  2. Electrolyte effects on the stability of nematic and lamellar lyotropic liquid crystal phases: colligative and ion-specific aspects.

    Science.gov (United States)

    Dawin, Ute C; Lagerwall, Jan P F; Giesselmann, Frank

    2009-08-20

    We investigated the electrolyte effects on the stability of nematic and lamellar lyotropic liquid crystalline (LLC) phases formed by the simple anionic surfactant cesium pentadecafluorooctanoate (CsPFO) in water. To the lyotropic guest phase, at the constant CsPFO-mass fraction of 0.55, the series of electrolytes LiCl, NaCl, KCl, CsCl, CsI, and Cs(2)SO(4), respectively, was added at concentrations ranging from 0.5 to 2.5 mol %. With increasing electrolyte concentration two substantially different effects were observed. At low concentrations all added electrolytes caused an increase of the thermal stability of the LLC phases, favoring the lamellar phase over the nematic phase. This behavior is, at least qualitatively, understood within the packing parameter model. The extent of the stabilization clearly depends on the chemical nature of the added cation. For a given cation, however, the effect is colligative, i.e., independent of the chemical nature of the added anion. At higher salt concentrations a salting-out-like phase separation was induced. This effect is clearly ion-specific as the salting-out concentration varied for each cation following the order of the Hofmeister series for cations.

  3. Extraction and stability of bovine serum albumin (BSA) using cholinium-based Good’s buffers ionic liquids

    Science.gov (United States)

    Taha, Mohamed; Quental, Maria V.; Correia, Isabel; Freire, Mara G.; Coutinho, João A. P.

    2017-01-01

    Good’s buffers ionic liquids (GB-ILs), composed of cholinium-based cations and Good’s buffers anions, display self-buffering characteristics in the biological pH range, and their polarity and hydrophobicity can be easily tuned by a proper manipulation of their ions chemical structures. In this work, the extraction ability for bovine serum albumin (BSA) of aqueous biphasic systems (ABS) formed by polypropylene glycol 400 (PPG 400) and several GB-ILs was evaluated. ABS formed by PPG 400 and cholinium chloride ([Ch]Cl), GBs, and sucrose were also investigated for comparison purposes. It is shown that BSA preferentially migrates for the GB-IL-rich phase, with extraction efficiencies of 100%, achieved in a single-step. Dynamic light scattering, and circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopies were employed to evaluate the effect of the investigated cholinium-based GB-ILs on the BSA stability, and compared with results obtained for the respective GBs precursors, [Ch]Cl and sucrose, a well-known protein stabilizer. Molecular docking studies were also carried out to investigate on the binding sites of GB-IL ions to BSA. The experimental results confirm that BSA has a higher stability in GB-ILs than in any of the other compounds investigated. PMID:28239260

  4. Non-agglomerated gold-PMMA nanocomposites by in situ-stabilized laser ablation in liquid monomer for optical applications

    Science.gov (United States)

    Schwenke, Andreas; Dalüge, Hauke; Kiyan, Roman; Sajti, C. Laszlo; Chichkov, Boris N.

    2013-05-01

    The main goal in the production of nanocomposites for optical applications is the uniform and non-agglomerated incorporation of nanoparticles into polymer matrices. Therefore, in this work gold nanoparticles have been generated by short-pulsed liquid phase laser ablation in methyl methacrylate (MMA) with or without dissolved poly(methyl methacrylate) (PMMA) followed by polymerization. The polymeric materials were then used in injection molding to form model nanocomposites for further analysis. It has been observed that the steric in situ-stabilization of nanoparticles by dissolved PMMA inhibits particle aggregation in MMA and due to particle quenching results in smaller nanoparticles than that achieved by working in pure MMA. Similar but even more pronounced stability issues have been highlighted on injection molded optical nanocomposites, revealing that the in situ-stabilization of nanoparticles with PMMA not only prevent an agglomeration in the colloidal state but could also prevent changes in particles dispersion along the entire processing chain ending in final 3D polymer samples. Besides the optical study of the characteristic plasmon peak of gold nanoparticles and the nonlinear absorption behavior for femtosecond laser pulses, XRD analysis revealed the appearance of atomic gold in a centrosymmetric Fm3m cubic structure.

  5. The effect of gravity on the stability of an evaporating dichloromethane liquid film

    CERN Document Server

    Narendranath, Aneet; Kolkka, Robert W; Struthers, Allan A; Allen, Jeffrey S

    2013-01-01

    Zero gravity evaporation of a Dicholoromethane (DCM) liquid film is explored. The resulting film dynamics are presented and a criterion for stable films is described based on the long wave theory. It is concluded that films subject to long wave instabilities shows the appearance of the mode of maximum growth rate at rupture, irrespective of the initial condition or domain size conditions. Films stable in Earth's gravity are destabilized in zero gravity.

  6. Effect of domains configuration on crystal structure in ferroelectric ...

    Indian Academy of Sciences (India)

    2017-09-09

    Sep 9, 2017 ... structure in ferroelectric ceramics. Keywords. Electronic ceramics; ferroelectricity; piezoelectricity. 1. Introduction. It is well known that ferroelectric domains and crystal structure control the physical properties of ferroelectrics. [1–5]. Therefore, intensive studies have focused on domain structures and the ...

  7. Ab Initio Simulations and Electronic Structure of Lithium-Doped Ionic Liquids: Structure, Transport, and Electrochemical Stability.

    Science.gov (United States)

    Haskins, Justin B; Bauschlicher, Charles W; Lawson, John W

    2015-11-19

    Density functional theory (DFT), density functional theory molecular dynamics (DFT-MD), and classical molecular dynamics using polarizable force fields (PFF-MD) are employed to evaluate the influence of Li(+) on the structure, transport, and electrochemical stability of three potential ionic liquid electrolytes: N-methyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([pyr14][TFSI]), N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide ([pyr13][FSI]), and 1-ethyl-3-methylimidazolium boron tetrafluoride ([EMIM][BF4]). We characterize the Li(+) solvation shell through DFT computations of [Li(Anion)n]((n-1)-) clusters, DFT-MD simulations of isolated Li(+) in small ionic liquid systems, and PFF-MD simulations with high Li-doping levels in large ionic liquid systems. At low levels of Li-salt doping, highly stable solvation shells having two to three anions are seen in both [pyr14][TFSI] and [pyr13][FSI], whereas solvation shells with four anions dominate in [EMIM][BF4]. At higher levels of doping, we find the formation of complex Li-network structures that increase the frequency of four anion-coordinated solvation shells. A comparison of computational and experimental Raman spectra for a wide range of [Li(Anion)n]((n-1)-) clusters shows that our proposed structures are consistent with experiment. We then compute the ion diffusion coefficients and find measures from small-cell DFT-MD simulations to be the correct order of magnitude, but influenced by small system size and short simulation length. Correcting for these errors with complementary PFF-MD simulations, we find DFT-MD measures to be in close agreement with experiment. Finally, we compute electrochemical windows from DFT computations on isolated ions, interacting cation/anion pairs, and liquid-phase systems with Li-doping. For the molecular-level computations, we generally find the difference between ionization energy and electron affinity from isolated ions and interacting cation/anion pairs to

  8. Synthesis of surfactant-free electrostatically stabilized gold nanoparticles by plasma-induced liquid chemistry

    Science.gov (United States)

    Patel, J.; Němcová, L.; Maguire, P.; Graham, W. G.; Mariotti, D.

    2013-06-01

    Plasma-induced non-equilibrium liquid chemistry is used to synthesize gold nanoparticles (AuNPs) without using any reducing or capping agents. The morphology and optical properties of the synthesized AuNPs are characterized by transmission electron microscopy (TEM) and ultraviolet-visible spectroscopy. Plasma processing parameters affect the particle shape and size and the rate of the AuNP synthesis process. Particles of different shapes (e.g. spherical, triangular, hexagonal, pentagonal, etc) are synthesized in aqueous solutions. In particular, the size of the AuNPs can be tuned from 5 nm to several hundred nanometres by varying the initial gold precursor (HAuCl4) concentration from 2.5 μM to 1 mM. In order to reveal details of the basic plasma-liquid interactions that lead to AuNP synthesis, we have measured the solution pH, conductivity and hydrogen peroxide (H2O2) concentration of the liquid after plasma processing, and conclude that H2O2 plays the role of the reducing agent which converts Au+3 ions to Au0 atoms, leading to nucleation growth of the AuNPs.

  9. Ferroelectric Electron Emission Principles and Technology

    CERN Document Server

    Riege, H

    1997-01-01

    The spontaneous electrical polarization of ferroelectric materials can be changed either by reversal or by phase transition from a ferroelectric into a non-ferroelectric state or vice versa. If spontaneous polarization changes are induced with fast heat, mechanical pressure, laser or electric field pulses on a submicrosecond time scale, strong uncompensated surface charge densities and related polarization fields are generated, which may lead to the intense self-emission of electrons from the negatively charged free surface areas of the ferroelectric sample. Hence, electron guns can be built with extraction-field-free ferroelectric cathodes, which may be easily separated from the high-field regions of post-accelerating gap structures. The intensity, the energy, the temporal and spatial distribution, and the repetitition rate of the emitted electron beams can be controlled within wide limits via the excitation pulses and external focusing and accelerating electromagnetic fields. The technological advantages an...

  10. Proceedings of the 6. international conference on stability and handling of liquid fuels. Volume 2

    Energy Technology Data Exchange (ETDEWEB)

    Giles, H.N. [ed.] [Deputy Assistant Secretary for Strategic Petroleum Reserve, Washington, DC (United States). Operations and Readiness Office

    1998-12-01

    Volume 2 of these proceedings contain 42 papers arranged under the following topical sections: Fuel blending and compatibility; Middle distillates; Microbiology; Alternative fuels; General topics (analytical methods, tank remediation, fuel additives, storage stability); and Poster presentations (analysis methods, oxidation kinetics, health problems).

  11. Insulation effect on thermal stability of Coated Conductors wires in liquid nitrogen

    Science.gov (United States)

    Rubeli, Thomas; Dutoit, Bertrand; Martynova, Irina; Makarevich, Artem; Molodyk, Alexander; Samoilenkov, Sergey

    2017-02-01

    Superconducting wires are not perfectly homogeneous in term of critical current as well as stabilization. In resistive fault current limiter applications this could lead to hot spots if the fault current is only slightly above the nominal current of the device. Increasing stabilization by using thicker silver coating for example may prevent this problem but this method implies longer wire length to maintain the same impedance during a fault. Very efficient cooling in another way to prevent hot spots, this can be achieved in nucleate boiling regime. Optimal insulation can be used to prevent film boiling regime, staying in nucleate boiling regime in a much broader temperature range. In this work a novel technique is used to monitor in real time the temperature of the wire during the quench. Using this method several increasing insulation thicknesses are tested, measuring for each the heat exchange rate to the nitrogen bath. Exchange rate measurements are made in quasistatic regime and during the re-cooling of the wire. SuperOx wires provided with different insulation thicknesses exhibit an excellent stability, far above a bare wire. On the other side, for very thick insulations the stability gain is lost. Re-cooling speeds dependency on insulation thicknesses is measured too.

  12. A scaling method for combustion stability rating of coaxial gas liquid injectors in a subscale chamber

    Energy Technology Data Exchange (ETDEWEB)

    Sohn, Chae Hoon; Kim, Young Jun [Sejong Univ., Seoul (Korea, Republic of); Kim, Young Mog [Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Pikalov, Valery P. [Research Institute of Chemical Machine Building, Sergiev Posad (Russian Federation)

    2012-11-15

    A scaling method to examine combustion stability characteristics of a coaxial injector is devised based on the acoustics and combustion dynamics in a chamber. The method is required for a subscale test of stability rating with a model chamber, which is cost effective compared with an actual full scale test. First, scaling and similarity rules are considered for stability rating and thereby, three conditions of acoustic, hydrodynamic, and flame condition similarities are proposed. That is, for acoustic similarity, the natural or resonant frequencies in the actual chamber should be maintained in the model chamber. And, two parameters of density ratio and velocity ratio are derived for the requirement of hydrodynamic and flame condition similarities between the actual and the model conditions. Next, one example of an actual combustion chamber with high performance is selected and the proposed scaling method is applied to the chamber for understanding of the method. The design operating condition for a model test is presented by mass flow rates of propellants. Stability boundaries can be identified on the coordinate plane of chamber pressure and mixture ratio of fuel and oxidizer by applying the scaling method.

  13. Ferroelectric-Enhanced Polysulfide Trapping for Lithium-Sulfur Battery Improvement.

    Science.gov (United States)

    Xie, Keyu; You, You; Yuan, Kai; Lu, Wei; Zhang, Kun; Xu, Fei; Ye, Mao; Ke, Shanming; Shen, Chao; Zeng, Xierong; Fan, Xiaoli; Wei, Bingqing

    2017-02-01

    A brand new polysulfide entrapping strategy based on the ferroelectric effect has been demonstrated for the first time. By simply adding the nano-ferroelectrics (BaTiO3 nanoparticles) into the cathode, the heteropolar polysulfides can be anchored within the cathode due to the internal electric field originated from the spontaneous polarization BaTiO3 nanoparticles, and thus significantly improving the cycle stability of Li-S batteries. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Preparation of a Thermally Light-Transmittance-Controllable Film from a Coexistent System of Polymer-Dispersed and Polymer-Stabilized Liquid Crystals.

    Science.gov (United States)

    Guo, Shu-Meng; Liang, Xiao; Zhang, Cui-Hong; Chen, Mei; Shen, Chen; Zhang, Lan-Ying; Yuan, Xiao; He, Bao-Feng; Yang, Huai

    2017-01-25

    Polymer-dispersed liquid crystal (PDLC) and polymer-stabilized liquid crystal (PSLC) systems are the two primary distinct systems in the field of liquid crystal (LC) technology, and they are differentiated by their unique microstructures. Here, we present a novel coexistent system of polymer-dispersed and polymer-stabilized liquid crystals (PD&SLCs), which forms a homeotropically aligned polymer network (HAPN) within the LC droplets after a microphase separation between the LC and polymer matrix and combines the advantages of both the PDLC and PSLC systems. Then, we prepare a novel thermally light-transmittance-controllable (TLTC) film from the PD&SLC system, where the transmittance can be reversibly changed through thermal control from a transparent to a light-scattering state. The film also combines the advantageous features of flexibility and a potential for large-scale manufacturing, and it shows significant promise in future applications from smart windows to temperature sensors.

  15. A Study On Dispersion Stability Of Nickel Nanoparticles Synthesized By Wire Explosion In Liquid Media

    Directory of Open Access Journals (Sweden)

    Kim C.K.

    2015-06-01

    Full Text Available In this study, nickel nanoparticles were synthesized in ethanol using portable pulsed wire evaporation, which is a one-step physical method. From transmission electron microscopy images, it was found that the Ni nanoparticles exhibited a spherical shape with an average diameter of 7.3 nm. To prevent aggregation of the nickel nanoparticles, a polymer surfactant was added into the ethanol before the synthesis of nickel nanoparticles, and adsorbed on the freshly synthesized nickel nanoparticles during the wire explosion. The dispersion stability of the prepared nickel nanofluids was investigated by zeta-potential analyzer and Turbiscan optical analyzer. As a result, the optimum concentration of polymer surfactant to be added was suggested for the maximized dispersion stability of the nickel nanofluids.

  16. Stability of a nanofiltration membrane after contact with a low-level liquid radioactive waste

    Directory of Open Access Journals (Sweden)

    Elizabeth Eugenio de Mello Oliveira

    2013-01-01

    Full Text Available This study investigated the treatment of a liquid radioactive waste containing uranium (235U + 238U using nanofiltration membranes. The membranes were immersed in the waste for 24-5000 h, and their transport properties were evaluated before and after the immersion. Surface of the membranes changed after immersion in the waste. The SW5000 h specimen lost its coating layer of polyvinyl alcohol, and its rejection of sulfate ions and uranium decreased by about 35% and 30%, respectively. After immersion in the waste, the polyamide selective layer of the membranes became less thermally stable than that before immersion.

  17. Determination of drug stability in aspirin tablet formulations by high-pressure liquid chromatography.

    Science.gov (United States)

    Taguchi, V Y; Cotton, M L; Yates, C H; Millar, J F

    1981-01-01

    Salicylic acid and aspirin were resolved from the other salicylates in thermally degraded multicomponent tablets and determined quantitatively. The analytical method involved wetting the powdered tablet with acetic acid and diluting with chloroform to extract the drug components. Automated high-pressure liquid chromatographic analyses of filtered extracts were performed on a silica column with a mobile phase of acetic acid in heptane. The method was capable of resolving the major thermally induced transformation products in tablet formulations. It was sensitive to approximately 0.1 mg of salicylic acid/tablet. Good agreement with the compendial method for free salicylic acid was obtained.

  18. Combustion stability analysis of preburners in liquid propellant rocket engines during shutdown

    Science.gov (United States)

    Lim, Kair-Chuan; George, Paul E., II

    1987-01-01

    A linearized one-dimensional lumped-parameter model capable of predicting the occurrence of the low frequency combustion instability (chugging) experienced during preburner shutdown in the Space Shuttle Main Engines is discussed, and predictions are compared with NASA experimental results. Results from a parametric study of parameters including chamber pressure, fuel and oxygen temperatures, and the effective bulk modulus of the liquid oxidizer suggest that chugging is probably affected by conditions at shutdown through the fuel and oxidizer temperatures. It is suggested that chugging is initiated when the fuel, oxidizer, and helium temperature and flow rates pass into an unstable region, and that chugging may be terminated by decaying pressures.

  19. Tunable band gap in epitaxial ferroelectric Ho(Mn,Ga)O{sub 3} films

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Daesu; Noh, Tae Won, E-mail: twnoh@snu.ac.kr [Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742 (Korea, Republic of); Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Choi, Woo Seok [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2016-05-09

    Ferroelectrics have recently attracted attention as a new class of materials for use in optical and photovoltaic devices. We studied the electronic properties in epitaxially stabilized ferroelectric hexagonal Ho(Mn{sub 1−x}Ga{sub x})O{sub 3} (x = 0, 0.33, 0.67, and 1) thin films. Our films exhibited systematic changes in electronic structures, such as bandgap and optical transitions, according to the Ga concentration. In particular, the bandgap increased systematically from 1.4 to 3.2 eV, including the visible light region, with increasing Ga concentration from x = 0 to 1. These systematic changes, attributed to lattice parameter variations in epitaxial Ho(Mn{sub 1−x}Ga{sub x})O{sub 3} films, should prove useful for the design of optoelectronic devices based on ferroelectrics.

  20. NOx Binding and Dissociation: Enhanced Ferroelectric Surface Chemistry by Catalytic Monolayers

    Science.gov (United States)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab

    2013-03-01

    NOx molecules are regulated air pollutants produced during automotive combustion. As part of an effort to design viable catalysts for NOx decomposition operating at higher temperatures that would allow for improved fuel efficiency, we examine NOx chemistry on ferroelectric perovskite surfaces. Changing the direction of ferroelectric polarization can modify surface electronic properties and may lead to switchable surface chemistry. Here, we describe our recent work on potentially enhanced surface chemistry using catalytic RuO2 monolayers on perovskite ferroelectric substrates. In addition to thermodynamic stabilization of the RuO2 layer, we present results on the polarization-dependent binding of NO, O2, N2, and atomic O and N. We present results showing that one key problem with current catalysts, involving the difficulty of releasing dissociation products (especially oxygen), can be ameliorated by this method. Primary support from Toyota Motor Engineering and Manufacturing, North America, Inc.

  1. Intrinsic stability of ferroelectric and piezoelectric properties of epitaxial PbZr0.45Ti0.55O3 thin films on silicon in relation to grain tilt

    Directory of Open Access Journals (Sweden)

    Evert P Houwman, Minh D Nguyen, Matthijn Dekkers and Guus Rijnders

    2013-01-01

    Full Text Available Piezoelectric thin films of PbZr0.45Ti0.55O3 were grown on Si substrates in four different ways, resulting in different crystalline structures, as determined by x-ray analysis. The crystalline structures were different in the spread in tilt angle and the in-plane alignment of the crystal planes between different grains. It is found that the deviations of the ferroelectric polarization loop from that of the ideal rectangular loop (reduction of the remanent polarization with respect to the saturation polarization, dielectric constant of the film, slanting of the loop, coercive field value all scale with the average tilt angle. A model is derived based on the assumption that the tilted grain boundaries between grains affect the film properties locally. This model describes the observed trends. The effective piezoelectric coefficient d33,eff shows also a weak dependence on the average tilt angle for films grown in a single layer, whereas it is strongly reduced for the films deposited in multiple layers. The least affected properties are obtained for the most epitaxial films, i.e. grown on a SrTiO3 epitaxial seed layer, by pulsed laser deposition. These films are intrinsically stable and do not require poling to acquire these stable properties.

  2. Intrinsic stability of ferroelectric and piezoelectric properties of epitaxial PbZr0.45Ti0.55O3 thin films on silicon in relation to grain tilt

    Science.gov (United States)

    Houwman, Evert P.; Nguyen, Minh D.; Dekkers, Matthijn; Rijnders, Guus

    2013-08-01

    Piezoelectric thin films of PbZr0.45Ti0.55O3 were grown on Si substrates in four different ways, resulting in different crystalline structures, as determined by x-ray analysis. The crystalline structures were different in the spread in tilt angle and the in-plane alignment of the crystal planes between different grains. It is found that the deviations of the ferroelectric polarization loop from that of the ideal rectangular loop (reduction of the remanent polarization with respect to the saturation polarization, dielectric constant of the film, slanting of the loop, coercive field value) all scale with the average tilt angle. A model is derived based on the assumption that the tilted grain boundaries between grains affect the film properties locally. This model describes the observed trends. The effective piezoelectric coefficient d33,eff shows also a weak dependence on the average tilt angle for films grown in a single layer, whereas it is strongly reduced for the films deposited in multiple layers. The least affected properties are obtained for the most epitaxial films, i.e. grown on a SrTiO3 epitaxial seed layer, by pulsed laser deposition. These films are intrinsically stable and do not require poling to acquire these stable properties.

  3. Role of the Electrostatic Interactions in the Stabilization of Ionic Liquid Crystals: Insights from Coarse-Grained MD Simulations of an Imidazolium Model.

    Science.gov (United States)

    Saielli, Giacomo; Wang, Yanting

    2016-09-01

    In order to investigate the role of the electrostatic interactions in stabilizing various phases of ionic liquids, especially smectic ionic liquid crystals, we have employed a coarse-grained model of 1-hexadecyl-3-methylimidazolium nitrate, [C16mim][NO3], to perform molecular dynamics simulations with the partial charges artificially rescaled by a factor from 0.7 to 1.2. The simulated systems have been characterized by means of orientational and translational order parameters and by distribution functions. We have found that increasing the total charge of the ions strongly stabilizes the ionic smectic phase by shifting the clearing point (melting into the isotropic liquid phase) to higher temperatures, while a smaller effect is observed on the stability of the crystal phase. Our results highlight the importance of the electrostatic interactions in promoting the formation of ionic liquid crystals through microphase segregation. Moreover, as the total charge of the model is increased, we observe a transformation from a homogeneous to a nanosegregated isotropic structure typical of ionic liquids. Therefore, a connection can be established between the degree of nanosegregation of ILs and the stability of ILC phases. All the above can be understood by the competition among electrostatic interactions between charged groups (cationic head groups and anions), van der Waals interactions between nonpolar cationic tail groups, and thermal fluctuations.

  4. Efficient CO2 capture by tertiary amine-functionalized ionic liquids through Li+-stabilized zwitterionic adduct formation

    Directory of Open Access Journals (Sweden)

    Zhen-Zhen Yang

    2014-08-01

    Full Text Available Highly efficient CO2 absorption was realized through formation of zwitterionic adducts, combining synthetic strategies to ionic liquids (ILs and coordination. The essence of our strategy is to make use of multidentate cation coordination between Li+ and an organic base. Also PEG-functionalized organic bases were employed to enhance the CO2-philicity. The ILs were reacted with CO2 to form the zwitterionic adduct. Coordination effects between various lithium salts and neutral ligands, as well as the CO2 capacity of the chelated ILs obtained were investigated. For example, the CO2 capacity of PEG150MeBu2N increased steadily from 0.10 to 0.66 (mol CO2 absorbed per mol of base through the formation of zwitterionic adducts being stabilized by Li+.

  5. Stabilizing lithium metal using ionic liquids for long-lived batteries

    Science.gov (United States)

    Basile, A.; Bhatt, A. I.; O'Mullane, A. P.

    2016-01-01

    Suppressing dendrite formation at lithium metal anodes during cycling is critical for the implementation of future lithium metal-based battery technology. Here we report that it can be achieved via the facile process of immersing the electrodes in ionic liquid electrolytes for a period of time before battery assembly. This creates a durable and lithium ion-permeable solid–electrolyte interphase that allows safe charge–discharge cycling of commercially applicable Li|electrolyte|LiFePO4 batteries for 1,000 cycles with Coulombic efficiencies >99.5%. The tailored solid–electrolyte interphase is prepared using a variety of electrolytes based on the N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide room temperature ionic liquid containing lithium salts. The formation is both time- and lithium salt-dependant, showing dynamic morphology changes, which when optimized prevent dendrite formation and consumption of electrolyte during cycling. This work illustrates that a simple, effective and industrially applicable lithium metal pretreatment process results in a commercially viable cycle life for a lithium metal battery. PMID:27292652

  6. Influence of virtual surfaces on Frank elastic constants in a polymer-stabilized bent-core nematic liquid crystal.

    Science.gov (United States)

    Madhuri, P Lakshmi; Hiremath, Uma S; Yelamaggad, C V; Madhuri, K Priya; Prasad, S Krishna

    2016-04-01

    Effect of a polymer network on the threshold voltage of the Fréedericksz transition, Frank elastic constants, switching speed, and the rotational viscosity are investigated in a polymer-stabilized bent-core nematic liquid crystal with different polymer concentrations. These polymer networks form virtual surfaces with a finite anchoring energy. The studies bring out several differences in comparison to similar studies with a calamitic liquid crystal as the nematic host. For example, on varying the polymer content the threshold voltage decreases initially, but exhibits a drastic increase above a critical concentration. A similar feature-reaching a minimum before rising-is seen for the bend elastic constant, which gets enhanced by an order of magnitude for a polymer content of 2.5 wt %. In contrast, the splay elastic constant has a monotonic variation although the overall enhancement is comparable to that of the bend elastic constant. The behavior changing at a critical concentration is also seen for the switching time and the associated rotational viscosity. The presence of the polymer also induces a shape change in the thermal dependence of the bend elastic constant. We explain the features observed here on the basis of images obtained from the optical and atomic force microscopy.

  7. Determination of seven sunscreen agents and two ultraviolet stabilizers in skin care products using ultra-performance liquid chromatography.

    Science.gov (United States)

    Gowell, Aimee; Habel, John; Weiss, Caryn; Parkanzky, Paul

    2015-01-01

    Ultraviolet radiation (UVR) is a well-known environmental carcinogen. Protection against UVR exposure has resulted in an increasing number of sunscreen agents being incorporated into a greater variety of cosmetic formulations including moisturizing lotions, color cosmetics, and skin care creams. Meanwhile, global regulation of sun care products is changing. New guidelines for sunscreen efficacy have resulted in a shift in product formulation that requires sunscreen products to provide broad spectrum UV protection. Since not all sunscreen ingredients protect against both UVA and UVB radiation, most sun care products require a combination of sunscreen agents. This article describes a new method for simultaneous separation and quantitation of seven organic sunscreens and two UV stabilizers using ultra-performance liquid chromatography. This method is capable of resolving all nine analytes, and has been validated for selectivity, precision, and accuracy. Because of the use of core-shell column technology, the separation is also achieved at back pressures compatible with conventional high-performance liquid chromatography instrumentation.

  8. Prediction of new ferroelectrics and multiferroics

    Science.gov (United States)

    Xiang, Hongjun

    Ferroelectrics, whose spontaneous electric polarization can be switched electrically, are useful for a range of applications, such as memory or sensing devices. However, relatively few naturally occurring materials are ferroelectric. Available theoretical methods for designing new ferroelectrics are usually restricted to high symmetric systems. We have developed a more general computational approach that can be applied to any system, and have used it to identify previously unrecognised classes of ferroelectrics. With this approach, we show that the R-3c perovskite structure can become ferroelectric by substituting half of the B-site cations. ZnSrO2 with a non-perovskite layered structure can also be ferroelectric through the anion substitution. Moreover, our approach can be used to design new multiferroics as illustrated in the case of fluorine substituted LaMnO3. In addition, we predict that two-dimensional P2O3 adopt two possible stable ferroelectric structures (P2O3-I and P2O3-II) as the lowest energy configurations within a given layer thickness. Their electric polarizations are perpendicular and parallel to the lateral plane, respectively. We propose that P2O3 could be used in a novel nanoscale multiple-state memory device.

  9. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  10. Thermo-mechanical concepts applied to modeling liquid propellant rocket engine stability

    Science.gov (United States)

    Kassoy, David R.; Norris, Adam

    2016-11-01

    The response of a gas to transient, spatially distributed energy addition can be quantified mathematically using thermo-mechanical concepts available in the literature. The modeling demonstrates that the ratio of the energy addition time scale to the acoustic time scale of the affected volume, and the quantity of energy added to that volume during the former determine the whether the responses to heating can be described as occurring at nearly constant volume, fully compressible or nearly constant pressure. Each of these categories is characterized by significantly different mechanical responses. Application to idealized configurations of liquid propellant rocket engines provides an opportunity to identify physical conditions compatible with gasdynamic disturbances that are sources of engine instability. Air Force Office of Scientific Research.

  11. INTERACTIONS OF NATURAL ANTIOXIDANTS WITH RED GRAPE POMACE ANTHOCYANINS IN A LIQUID MODEL MATRIX: STABILITY AND COPIGMENTATION EFFECTS

    Directory of Open Access Journals (Sweden)

    BADHERDINE SIDANI

    2011-03-01

    Full Text Available The purpose of this study was an examination of the stability and colour en-hancement of red grape pomace anthocyanins in a juice model matrix, and the effect of the addition of natural antioxidants. The approach was based on a juice-like liquid medium (10.1 °Bx, pH 3.48, which was used as the model matrix to test the effect of the addition of natural antioxidants (L-cysteine, as-corbic acid, catechin and quercetin on the degradability of anthocyanin pigments, extracted from grape pomace. It was found that treatment of the model solutions at 80 °C induced anthocyanin decomposition, which obeyed first order kinetics. Addition of increasing amounts of antioxidants, including L-cysteine, ascorbic acid, catechin and quercetin, did not provoke a proportional impact, either positive or negative, with regard to anthocyanin stability. The best stabilising effect was seen after addition of ascorbic acid and catechin at con¬centrations of 4 and 2 mg L-1, respectively (P < 0.001. Quercetin, however, was demonstrated a very efficient copigment, inducing an increase in A520 by 63%, at pH 5.6 and a copigment-to-pigment ratio of 10.

  12. Influence of reactive oxygen species on the enzyme stability and activity in the presence of ionic liquids.

    Directory of Open Access Journals (Sweden)

    Pankaj Attri

    Full Text Available In this paper, we have examined the effect of ammonium and imidazolium based ionic liquids (ILs on the stability and activity of proteolytic enzyme α-chymotrypsin (CT in the presence of cold atmospheric pressure plasma jet (APPJ. The present work aims to illustrate the state of art implementing the combined action of ILs and APPJ on the enzyme stability and activity. Our circular dichroism (CD, fluorescence and enzyme activity results of CT have revealed that buffer and all studied ILs {triethylammonium hydrogen sulphate (TEAS from ammonium family and 1-butyl-3-methyl imidazolium chloride ([Bmim][Cl], 1-methylimidazolium chloride ([Mim][Cl] from imidazolium family} are notable to act as protective agents against the deleterious action of the APPJ, except triethylammonium dihydrogen phosphate (TEAP ammonium IL. However, TEAP attenuates strongly the deleterious action of reactive oxygen species (ROS created by APPJ on native structure of CT. Further, TEAP is able to retain the enzymatic activity after APPJ exposure which is absent in all the other systems.This study provides the first combined effect of APPJ and ILs on biomolecules that may generate many theoretical and experimental opportunities. Through this methodology, we can utilise both enzyme and plasma simultaneously without affecting the enzyme structure and activity on the material surface; which can prove to be applicable in various fields.

  13. An insight into structure and stability of DNA in ionic liquids from molecular dynamics simulation and experimental studies.

    Science.gov (United States)

    Jumbri, K; Abdul Rahman, M B; Abdulmalek, E; Ahmad, H; Micaelo, N M

    2014-07-21

    Molecular dynamics simulation and biophysical analysis were employed to reveal the characteristics and the influence of ionic liquids (ILs) on the structural properties of DNA. Both computational and experimental evidence indicate that DNA retains its native B-conformation in ILs. Simulation data show that the hydration shells around the DNA phosphate group were the main criteria for DNA stabilization in this ionic media. Stronger hydration shells reduce the binding ability of ILs' cations to the DNA phosphate group, thus destabilizing the DNA. The simulation results also indicated that the DNA structure maintains its duplex conformation when solvated by ILs at different temperatures up to 373.15 K. The result further suggests that the thermal stability of DNA at high temperatures is related to the solvent thermodynamics, especially entropy and enthalpy of water. All the molecular simulation results were consistent with the experimental findings. The understanding of the properties of IL-DNA could be used as a basis for future development of specific ILs for nucleic acid technology.

  14. Bulk characterization of topological crystalline insulators: Stability under interactions and relations to symmetry enriched U (1) quantum spin liquids

    Science.gov (United States)

    Zou, Liujun

    2018-01-01

    Topological crystalline insulators (TCIs) are nontrivial quantum phases of matter protected by crystalline (and other) symmetries. They are originally predicted by band theories, so an important question is their stability under interactions. In this paper, by directly studying the physical bulk properties of several band-theory-based nontrivial TCIs that are conceptually interesting and/or experimentally feasible, we show they are stable under interactions. These TCIs include (1) a weak topological insulator, (2) a TCI with a mirror symmetry and its time-reversal symmetric generalizations, (3) a doubled topological insulator with a mirror symmetry, and (4) two TCIs with symmetry-enforced-gapless surfaces. We describe two complementary methods that allow us to determine the properties of the magnetic monopoles obtained by coupling these TCIs to a U (1 ) gauge field. These methods involve studying different types of surface states of these TCIs. Applying these methods to our examples, we find all of them have nontrivial monopoles, which proves their stability under interactions. Furthermore, we discuss two levels of relations between these TCIs and symmetry enriched U (1 ) quantum spin liquids (QSLs). First, these TCIs are directly related to U (1 ) QSLs with crystalline symmetries. Second, there is an interesting correspondence between U (1 ) QSLs with crystalline symmetries and U (1 ) QSLs with internal symmetries. In particular, the TCIs with symmetry-enforced-gapless surfaces are related to the "fractional topological paramagnets" introduced in Zou et al. [arXiv:1710.00743].

  15. Ultrafast Photovoltaic Response in Ferroelectric Nanolayers

    Energy Technology Data Exchange (ETDEWEB)

    Daranciang, Dan

    2012-02-15

    We show that light drives large-amplitude structural changes in thin films of the prototypical ferroelectric PbTiO3 via direct coupling to its intrinsic photovoltaic response. Using time-resolved x-ray scattering to visualize atomic displacements on femtosecond timescales, photoinduced changes in the unit-cell tetragonality are observed. These are driven by the motion of photogenerated free charges within the ferroelectric and can be simply explained by a model including both shift and screening currents, associated with the displacement of electrons first antiparallel to and then parallel to the ferroelectric polarization direction.

  16. Static Characteristics of the Ferroelectric Transistor Inverter

    Science.gov (United States)

    Mitchell, Cody; Laws, crystal; MacLeond, Todd C.; Ho, Fat D.

    2010-01-01

    The inverter is one of the most fundamental building blocks of digital logic, and it can be used as the foundation for understanding more complex logic gates and circuits. This paper presents the characteristics of an inverter circuit using a ferroelectric field-effect transistor. The voltage transfer characteristics are analyzed with respect to varying parameters such as supply voltage, input voltage, and load resistance. The effects of the ferroelectric layer between the gate and semiconductor are examined, and comparisons are made between the inverters using ferroelectric transistors and those using traditional MOSFETs.

  17. Chemical segregation and self polarisation in ferroelectrics

    Directory of Open Access Journals (Sweden)

    Bernard E. Watts

    2009-06-01

    Full Text Available Chemical partitioning or segregation is commonly encountered in solid-state syntheses. It is driven by compositional, thermal and electric field gradients. These phenomena can be quite extreme in thin films and lead to notable effects on the electrical properties of ferroelectrics. The segregation in ferroelectric thin films will be illustrated and the mechanisms explained in terms of diffusion processes driven by a potential gradient of the oxygen. The hypothesis can also explain self polarisation and imprint in ferroelectric hysteresis.

  18. Strong ultrasonic microwaves in ferroelectric ceramics.

    Science.gov (United States)

    Arlt, G

    1998-01-01

    It is well known that ferroelectric materials have piezoelectric properties which allow the transformation of electrical signals into mechanical signals and vice versa. The transducer action normally is restricted to frequencies up to the mechanical resonance frequency of the sample. There are, however, two mechanisms which allow transducer action in ferroelectric ceramics at much higher frequencies: one is the normal piezoelectric effect in a ferroelectric ceramic in which the crystallites have periodic domain structures, the other is a domain wall effect in which ferroelastic domain walls in a periodic domain structure are powerful shear wave emitters. Both mechanisms give rise to extensive dielectric losses in ceramics at microwave frequencies.

  19. Computation of liquid-liquid equilibria and phase stabilities: implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols

    National Research Council Canada - National Science Library

    A. Zuend; C. Marcolli; T. Peter; J. H. Seinfeld

    2010-01-01

    .... Such liquid-liquid equilibria (LLE) affect the gas/particle partitioning of the different semivolatile compounds and might significantly alter both particle mass and composition as compared to a one-phase particle...

  20. Rapid, simple and stability-indicating determination of polyhexamethylene biguanide in liquid and gel-like dosage forms by liquid chromatography with diode-array detection

    National Research Council Canada - National Science Library

    Küsters, Markus; Beyer, Sören; Kutscher, Stephan; Schlesinger, Harald; Gerhartz, Michael

    2013-01-01

    A rapid and simple method for the determination of potyhexamethylene biguanide (polyhexanide, PHMB) in liquid and gel-like pharmaceutical formulations by means of high performance liquid chromatography coupled to diode-array detection...

  1. In vitro effects of proteases in human pancreatic juice on stability of liquid and carrier-bound fibrin sealants.

    Science.gov (United States)

    Adelmeijer, J; Porte, R J; Lisman, T

    2013-10-01

    Fibrin sealants are used in pancreatic surgery to prevent leakage of pancreatic fluid and reduce associated complications. The efficacy of this approach is unclear. Fibrin clots were generated in vitro from two commercially available liquid fibrin sealants (Tissucol Duo® and Evicel®) and the carrier-bound fibrin sealant Tachosil®, and exposed to normal saline or human pancreatic fluid. Stability of the sealants was assessed by release of the fibrin and collagen degradation products, D-dimer and hydroxyproline. The effect of protease inhibitors on sealant breakdown was assessed. Clots generated from liquid fibrin sealants degraded rapidly in pancreatic fluid, but not in normal saline. D-dimer release from fibrin clots by pancreatic fluid was approximately 1700 µg/ml after 24 h and less than 20 µg/ml by saline. Pancreatic fluid, but not normal saline, degraded both the fibrin and collagen component of Tachosil®. After 6 h, mean(s.e.m.) D-dimer levels in pancreatic fluid exposed to Tachosil® were 850(183) ng/ml, compared with 60(6) ng/ml in normal saline. The mean(s.e.m.) hydroxyproline concentration in pancreatic fluid was 497(17) µg/ml after a 24-h exposure to Tachosil®, compared with 26(12) µg/ml in normal saline. Protease inhibitors significantly inhibited breakdown of liquid sealants (D-dimer levels less than 50 µg/ml after 24 h) and Tachosil® (D-dimer release 179(12) ng/ml at 6 h; hydroxyproline release 181(29) µg/ml at 24 h). Proteases in pancreatic juice effectively degrade both liquid and carrier-bound fibrin sealants in vitro. The use of these products in pancreatic surgery with the aim of preventing leakage of pancreatic fluid is not supported by this experimental study. © 2013 British Journal of Surgery Society Ltd. Published by John Wiley & Sons Ltd.

  2. Impact of silage additives on aerobic stability and characteristics of high-moisture maize during exposure to air, and on fermented liquid feed

    DEFF Research Database (Denmark)

    Canibe, Nuria; Kristensen, Niels Bastian; Jensen, Bent Borg

    2014-01-01

    Aims To (i) measure the aerobic stability- and describe the characteristics, during aeration, of high-moisture maize (HMM) treated with various additives, and (ii) describe the microbial characteristics of fermented liquid feed (FLF) added HMM. Methods and Results Four treatments were prepared wi...

  3. Ferroelectricity in d0 double perovskite fluoroscandates

    Science.gov (United States)

    Charles, Nenian; Rondinelli, James M.

    2015-08-01

    Ferroelectricity in strain-free and strained double perovskite fluorides, Na3ScF6 and K2NaScF6 , is investigated using first-principles density functional theory. Although the experimental room temperature crystal structures of these fluoroscandates are centrosymmetric, i.e., Na3ScF6 (P 21/n ) and K2NaScF6 (F m 3 ¯m ), lattice dynamical calculations reveal that soft polar instabilities exist in each prototypical cubic phase and that the modes harden as the tolerance factor approaches unity. Thus the double fluoroperovskites bear some similarities to A B O3 perovskite oxides; however, in contrast, these fluorides exhibit large acentric displacements of alkali metal cations (Na, K) rather than polar displacements of the transition metal cations. Biaxial strain investigations of the centrosymmetric and polar Na3ScF6 and K2NaScF6 phases reveal that the paraelectric structures are favored under compressive strain, whereas polar structures with in-plane electric polarizations (˜5 -18 μ C cm-2 ) are realized at sufficiently large tensile strains. The electric polarization and stability of the polar structures for both chemistries are found to be further enhanced and stabilized by a coexisting single octahedral tilt system. Our results suggest that polar double perovskite fluorides may be realized by suppression of octahedral rotations about more than one Cartesian axis; structures exhibiting in- or out-of-phase octahedral rotations about the c axis are more susceptible to polar symmetries.

  4. Local polarization switching in stressed ferroelectric polymers

    Science.gov (United States)

    Cai, Ronggang; Nysten, Bernard; Hu, Zhijun; Jonas, Alain M.

    2017-05-01

    Ferroelectric polymers are used in flexible organic ferroelectric memories, ferroelectric polarization enhanced organic solar cells, and organic multiferroics. Therefore, understanding their polarization switching mechanism under bending is important for the operation of such devices. Here, we study locally by piezoresponse force microscopy (PFM) polarization switching in bent thin films of the ferroelectric polymer poly(vinylidene fluoride-ran-trifluoroethylene). In bent samples, higher probability of domain nucleation, faster domain wall propagation, and lower coercive field are consistently observed by PFM. We ascribe these observations to a decrease of the domain wall pinning energy, resulting from the mechanical energy stored in the sample due to bending in the presence of the compression gradient generated below the PFM tip.

  5. Interface control of bulk ferroelectric polarization

    Energy Technology Data Exchange (ETDEWEB)

    Yu, P [University of California, Berkeley; Luo, Weidong [ORNL; Yi, D. [University of California, Berkeley; Zhang, J.-X. [University of California, Berkeley; Rossell, M.D. [Lawrence Berkeley National Laboratory (LBNL); Yang, C.-H. [Korea Advanced Institute of Science and Technology; You, L. [University of California, Berkeley; Singh-Bhalla, G. B. [University of California, Berkeley & LBNL; Yang, S.Y [University of California, Berkeley; He, Q [University of California, Berkeley; Ramasse, Q. M. [Lawrence Berkeley National Laboratory (LBNL); Erni, R. [Lawrence Berkeley National Laboratory (LBNL); Martin, L. W. [University of Illinois, Urbana-Champaign; Chu, Y. H. [University of California, Berkeley; Pantelides, Sokrates T [ORNL; Pennycook, Stephen J [ORNL; Ramesh, R. [University of California, Berkeley

    2012-01-01

    The control of material interfaces at the atomic level has led to no- vel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we em- ploy a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite un- derlayers extends the generality of this phenomenon.

  6. Ferroelectric symmetry-protected multibit memory cell

    Science.gov (United States)

    Baudry, Laurent; Lukyanchuk, Igor; Vinokur, Valerii M.

    2017-02-01

    The tunability of electrical polarization in ferroelectrics is instrumental to their applications in information-storage devices. The existing ferroelectric memory cells are based on the two-level storage capacity with the standard binary logics. However, the latter have reached its fundamental limitations. Here we propose ferroelectric multibit cells (FMBC) utilizing the ability of multiaxial ferroelectric materials to pin the polarization at a sequence of the multistable states. Employing the catastrophe theory principles we show that these states are symmetry-protected against the information loss and thus realize novel topologically-controlled access memory (TAM). Our findings enable developing a platform for the emergent many-valued non-Boolean information technology and target challenges posed by needs of quantum and neuromorphic computing.

  7. Thermally tunable ferroelectric thin film photonic crystals.

    Energy Technology Data Exchange (ETDEWEB)

    Lin, P. T.; Wessels, B. W.; Imre, A.; Ocola, L. E.; Northwestern Univ.

    2008-01-01

    Thermally tunable PhCs are fabricated from ferroelectric thin films. Photonic band structure and temperature dependent diffraction are calculated by FDTD. 50% intensity modulation is demonstrated experimentally. This device has potential in active ultra-compact optical circuits.

  8. Multifunctional Polycrystalline Ferroelectric Materials Processing and Properties

    CERN Document Server

    Pardo, Lorena

    2011-01-01

    This book presents selected topics on processing and properties of ferroelectric materials that are currently the focus of attention in scientific and technical research. Ferro-piezoelectric ceramics are key materials in devices for many applications, such as automotive, healthcare and non-destructive testing. As they are polycrystalline, non-centrosymmetric materials, their piezoelectricity is induced by the so-called poling process. This is based on the principle of polarization reversal by the action of an electric field that characterizes the ferroelectric materials. This book was born with the aim of increasing the awareness of the multifunctionality of ferroelectric materials among different communities, such as researchers, electronic engineers, end-users and manufacturers, working on and with ferro-piezoelectric ceramic materials and devices which are based on them. The initiative to write this book comes from a well-established group of researchers at the Laboratories of Ferroelectric Materials, Mate...

  9. Spherical monovalent ions at aqueous liquid-vapor interfaces: interfacial stability and induced interface fluctuations.

    Science.gov (United States)

    Ou, Shuching; Hu, Yuan; Patel, Sandeep; Wan, Hongbin

    2013-10-03

    Ion-specific interfacial behaviors of monovalent halides impact processes such as protein denaturation, interfacial stability, and surface tension modulation, and as such, their molecular and thermodynamic underpinnings garner much attention. We use molecular dynamics simulations of monovalent anions in water to explore effects on distant interfaces. We observe long-ranged ion-induced perturbations of the aqueous environment, as suggested by experiment and theory. Surface stable ions, characterized as such by minima in potentials of mean force computed using umbrella sampling MD simulations, induce larger interfacial fluctuations compared to nonsurface active species, conferring more entropy approaching the interface. Smaller anions and cations show no interfacial potential of mean force minima. The difference is traced to hydration shell properties of the anions, and the coupling of these shells with distant solvent. The effects correlate with the positions of the anions in the Hofmeister series (acknowledging variations in force field ability to recapitulate essential underlying physics), suggesting how differences in induced, nonlocal perturbations of interfaces may be related to different specific-ion effects in dilute biophysical and nanomaterial systems.

  10. Forced degradation behavior of epidepride and development of a stability-indicating method based on liquid chromatography–mass spectrometry

    Directory of Open Access Journals (Sweden)

    Wei-Hsi Chen

    2014-06-01

    Full Text Available A reversed-phase high-performance liquid chromatography (HPLC and liquid chromatography-tandem mass spectrometry (LC-MS/MS method was applied to study the forced degradation behavior and stability of epidepride. 123I radioisotope-labeled epidepride, [(--N-{[(2S-1-ethylpyrrolidin-2-yl]methyl}-5-iodo-2,3- dimethoxybenzamide] is a radiotracer with a high affinity for dopamine D2 receptors in the brain and has been used as an imaging agent for single-photon emission computed tomography. HPLC studies were performed using 127I-epidepride (the nonradioactive compound, instead of 123I-epidepride, with an RP-18 column using a mobile phase consisting of methanol, acetonitrile, and ammonium acetate (pH 7.0, 10 mM. The eluent flow rate and the wavelength for HPLC detection were 0.5 mL/min and 210 nm, respectively. The ligand was exposed to acid (1 N HCl and alkaline (1 N NaOH media and was subjected to oxidative decomposition at room temperature using 3% H2O2 and to thermal decomposition at 50°C. After various reaction times (30 minutes, 1 hour, 2 hours, 8 hours, and 24 hours, the substances were investigated by HPLC and LC-MS/MS. Although no decomposition products were observed after the acidic, alkaline, and thermal treatments, >80% of the initial amount of 127I-epidepride was oxidized within 24 hours in the presence of H2O2. Only one major oxidation product with an m/z value of 435 was observed, in addition to the 127I-epidepride species (m/z 419. The product was characterized by LC-MS/MS fragmentation, and the deteriorated type and fragmentation pathways were proposed for epidepride.

  11. Analytical Method Validation of High-Performance Liquid Chromatography and Stability-Indicating Study of Medroxyprogesterone Acetate Intravaginal Sponges

    Directory of Open Access Journals (Sweden)

    Nidal Batrawi

    2017-02-01

    Full Text Available Medroxyprogesterone acetate is widely used in veterinary medicine as intravaginal dosage for the synchronization of breeding cycle in ewes and goats. The main goal of this study was to develop reverse-phase high-performance liquid chromatography method for the quantification of medroxyprogesterone acetate in veterinary vaginal sponges. A single high-performance liquid chromatography/UV isocratic run was used for the analytical assay of the active ingredient medroxyprogesterone. The chromatographic system consisted of a reverse-phase C18 column as the stationary phase and a mixture of 60% acetonitrile and 40% potassium dihydrogen phosphate buffer as the mobile phase; the pH was adjusted to 5.6. The method was validated according to the International Council for Harmonisation (ICH guidelines. Forced degradation studies were also performed to evaluate the stability-indicating properties and specificity of the method. Medroxyprogesterone was eluted at 5.9 minutes. The linearity of the method was confirmed in the range of 0.0576 to 0.1134 mg/mL ( R 2 > 0.999. The limit of quantification was shown to be 3.9 µg/mL. Precision and accuracy ranges were found to be %RSD <0.2 and 98% to 102%, respectively. Medroxyprogesterone capacity factor value of 2.1, tailing factor value of 1.03, and resolution value of 3.9 were obtained in accordance with ICH guidelines. Based on the obtained results, a rapid, precise, accurate, sensitive, and cost-effective analysis procedure was proposed for quantitative determination of medroxyprogesterone in vaginal sponges. This analytical method is the only available method to analyse medroxyprogesterone in veterinary intravaginal dosage form.

  12. Understanding the relationship between biotherapeutic protein stability and solid-liquid interfacial shear in constant region mutants of IgG1 and IgG4.

    Science.gov (United States)

    Tavakoli-Keshe, Roumteen; Phillips, Jonathan J; Turner, Richard; Bracewell, Daniel G

    2014-02-01

    Relative stability of therapeutic antibody candidates is currently evaluated primarily through their response to thermal degradation, yet this technique is not always predictive of stability in manufacture, shipping, and storage. A rotating disk shear device is proposed that produces defined shear conditions at a known solid-liquid interface to measure stability in this environment. Five variants of IgG1 and IgG4 antibodies were created using combinations of two discrete triple amino acid sequence mutations denoted TM and YTE. Antibodies were ranked for stability based on shear device output (protein decay coefficient, PDC), and compared with accelerated thermal stability data and the melting temperature of the CH2 domain (Tm 1) from differential scanning calorimetry to investigate technique complimentarity. Results suggest that the techniques are orthogonal, with thermal methods based on intramolecular interaction and shear device stability based on localized unfolding revealing less stable regions that drive aggregation. Molecular modeling shows the modifications' effects on the antibody structures and indicates a possible role for Fc conformation and Fab-Fc docking in determining suspended protein stability. The data introduce the PDC value as an orthogonal stability indicator, complementary to traditional thermal methods, allowing lead antibody selection based on a more full understanding of process stability. © 2013 The Authors. Journal of Pharmaceutical Sciences published by Wiley Periodicals, Inc. and the American Pharmacists Association.

  13. Development of Polar Order by Liquid-Crystal Self-Assembly of Weakly Bent Molecules.

    Science.gov (United States)

    Alaasar, Mohamed; Prehm, Marko; Poppe, Silvio; Tschierske, Carsten

    2017-04-24

    Organic ferroelectrics are of growing importance for multifunctional materials. Here we provide an understanding of the distinct stages of the development of sterically induced polar order in liquid-crystalline (LC) soft matter. Three series of weakly bent molecules derived from 4-cyanoresorcinol as the bent core unit with laterally fluorinated azobenzene wings have been synthesized, and the effects of the position of fluorine substitution, alkyl-chain length, and temperature on the LC self-assembly and polar order were studied. In the LC phases a paraelectric-ferroelectric transition took place as the size of the polar domains gradually increased, thereby crossing a permittivity maximum, similar to inorganic solid-state ferroelectrics. An increase in polar coherence length simultaneously led to a transition from synpolar to antipolar domain correlation in the high-permittivity paraelectric range. Associated with the emergence of polar order was the development of a tilted organization of the molecules and a growing coherence of tilt. This led to a transition from non-tilted via tilt-randomized uniaxial to long-range-tilted biaxial smectic phases, and to surface-stabilized symmetry breaking with the formation of chiral conglomerates and field-induced tilt. Moreover, there is a remarkably strong effect of the position of fluorination; polar order is favored by peripheral core substitution and is suppressed by inside-directed fluorination. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Directly patternable high refractive index ferroelectric sol–gel resist

    Energy Technology Data Exchange (ETDEWEB)

    Garoli, D., E-mail: denis.garoli@iit.it [Istituto Italiano di Tecnologia, Via Morego 16, 16136 Genova (Italy); Della Giustina, G. [Industrial Engineering Department, University of Padova and INSTM, Via Marzolo 9, 35131 Padova (Italy)

    2015-08-15

    The development of a ferroelectric negative tone sol–gel resist for Ultraviolet (UV) and Electron Beam (EB) lithography is presented. A new system based on Lead Zirconate Titanate (PZT, with formula PbZr{sub 0.52}Ti{sub 0.48}O{sub 3}) was synthesized by sol–gel method. The lithographic performances were investigated and several structures spanning from the micron range down to less than 50 nm have been achieved by UV and EB lithography. The system interaction with UV light and Electron beam was thoroughly characterized by FT-IT spectroscopy. The exposed PZT was annealed at high temperatures in order to study the crystalline phase evolution, the optical constants values and stability of patterned structures. After exposure and annealing, the refractive index of the material can vary from 1.68 up to 2.33 (@400 nm), while the ferroelectric behaviour seems to be maintained after high temperature annealing. These results suggest a possible application of PZT resist not only as ferroelectric but also as nanopatternable high refractive index material. Moreover, direct nanopatterning by means of Focused Ion Beam (FIB) lithography was verified and the potentiality for the preparation of high aspect ratio hollow nanostructures will be presented. - Highlights: • A new formula directly patternable PZT high refractive index resist is presented. • The gel is sensitive to both UV and electron beam exposure. • The refractive index can vary from 1.68 up to 2.33 (@400 nm). • Direct nanopatterning by means of Focused Ion Beam (FIB) lithography was verified. • High aspect ratio hollow nanostructures will be presented.

  15. Ferroelectricity by Bose-Einstein condensation in a quantum magnet.

    Science.gov (United States)

    Kimura, S; Kakihata, K; Sawada, Y; Watanabe, K; Matsumoto, M; Hagiwara, M; Tanaka, H

    2016-09-26

    The Bose-Einstein condensation is a fascinating phenomenon, which results from quantum statistics for identical particles with an integer spin. Surprising properties, such as superfluidity, vortex quantization or Josephson effect, appear owing to the macroscopic quantum coherence, which spontaneously develops in Bose-Einstein condensates. Realization of Bose-Einstein condensation is not restricted in fluids like liquid helium, a superconducting phase of paired electrons in a metal and laser-cooled dilute alkali atoms. Bosonic quasi-particles like exciton-polariton and magnon in solids-state systems can also undergo Bose-Einstein condensation in certain conditions. Here, we report that the quantum coherence in Bose-Einstein condensate of the magnon quasi particles yields spontaneous electric polarization in the quantum magnet TlCuCl 3 , leading to remarkable magnetoelectric effect. Very soft ferroelectricity is realized as a consequence of the O(2) symmetry breaking by magnon Bose-Einstein condensation. The finding of this ferroelectricity will open a new window to explore multi-functionality of quantum magnets.

  16. Photoalignment control: self-focusing effect in hybrid- and homeotropic-aligned dye-doped polymer-stabilized liquid crystals

    Science.gov (United States)

    Wang, J.; Shishido, A.

    2015-09-01

    Nonlinear optics has drawn much attention for its great potential in applications, such as frequency conversion, multiple-photon absorption, self-focusing, and so on. However, such optical nonlinearities are generally observed at very high light intensities. In this study, we designed hybrid-aligned dye-doped polymer-stabilized liquid crystals (PSLC), in which the molecular director orientation gradually changes from homeotropic at one surface to homogeneous at the other. In such film, the threshold intensity required to form self-focusing effect was markedly reduced by a factor of 8.5 compared to that in a conventional homeotropic cell, which enabled the generation of the self-focusing effect using a handheld 1-mW laser pointer. In addition, we investigated the structural effect of dye molecules: azo-dye methyl red (MR, photoisomerizable)-doped PSLC was prepared and its NLO response was evaluated. It turned out that such MR-based LC system was not effective for self-focusing effect compared to oligothiophene-doped systems.

  17. A microencapsulation process of liquid mercury by sulfur polymer stabilization/solidification technology. Part II: Durability of materials

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Delgado, A.; Guerrero, A.; Lopez, F. A.; Perez, C.; Alguacil, F. J.

    2012-11-01

    Under the European LIFE Program a microencapsulation process was developed for liquid mercury using Sulfur Polymer Stabilization/Solidification (SPSS) technology, obtaining a stable concrete-like sulfur matrix that allows the immobilization of mercury for long-term storage. The process description and characterization of the materials obtained were detailed in Part I. The present document, Part II, reports the results of different tests carried out to determine the durability of Hg-S concrete samples with very high mercury content (up to 30 % w/w). Different UNE and RILEM standard test methods were applied, such as capillary water absorption, low pressure water permeability, alkali/acid resistance, salt mist aging, freeze-thaw resistance and fire performance. The samples exhibited no capillarity and their resistance in both alkaline and acid media was very high. They also showed good resistance to very aggressive environments such as spray salt mist, freeze-thaw and dry-wet. The fire hazard of samples at low heat output was negligible. (Author)

  18. The formation of calcium phosphate coatings by pulse laser deposition on the surface of polymeric ferroelectric

    Energy Technology Data Exchange (ETDEWEB)

    Bolbasov, E.N. [Tomsk Polytechnic University, 30 Lenin Avenue, Tomsk 634050 (Russian Federation); Lapin, I.N.; Svetlichnyi, V.A. [Tomsk State University, 36 Lenin Avenue, Tomsk 634050 (Russian Federation); Lenivtseva, Y.D. [Tomsk Polytechnic University, 30 Lenin Avenue, Tomsk 634050 (Russian Federation); Malashicheva, A. [Federal Almazov Medical Research Centre, 2 Akkuratova St., St. Petersburg 197341 (Russian Federation); St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034 (Russian Federation); ITMO University, Institute of translational Medicine, St. Petersburg (Russian Federation); Malashichev, Y. [St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034 (Russian Federation); Golovkin, A.S. [Federal Almazov Medical Research Centre, 2 Akkuratova St., St. Petersburg 197341 (Russian Federation); Anissimov, Y.G. [Griffith University, School of Natural Sciences, Engineering Dr., Southport, QLD 4222 (Australia); Tverdokhlebov, S.I., E-mail: tverd@tpu.ru [Tomsk Polytechnic University, 30 Lenin Avenue, Tomsk 634050 (Russian Federation)

    2015-09-15

    Graphical abstract: - Highlights: • Calcium phosphate coatings were obtained on ferroelectric polymer materials surface by using PLD method. • Obtained coatings have well-developed surface. • Depending on sputtering target composition it is possible to obtain crystalline or amorphous coating. • Formation of coating does not change the crystal structure of the ferroelectric polymer material. - Abstract: This work analyses the properties of calcium phosphate coatings obtained by pulsed laser deposition on the surface of the ferroelectric polymer material. Atomic force and scanning electron microscopy studies demonstrate that, regardless of the type of sputtering target, the calcium phosphate coatings have a multiscale rough surface that is potentially capable of promoting the attachment and proliferation of osteoblasts. This developed surface of the coatings is due to its formation mainly from a liquid phase. The chemical and crystalline composition of the coatings depends on the type of sputtering target used. It was shown that, regardless of the type of sputtering target, the crystalline structure of the ferroelectric polymer material does not change. Cell viability and adhesion studies of mesenchymal stromal cells on the coatings were conducted using flow cytometry and fluorescent microscopy. These studies indicated that the produced coatings are non-toxic.

  19. Absence of ferroelectricity in methylammonium lead iodide perovskite

    Directory of Open Access Journals (Sweden)

    Mohammad Sajedi Alvar

    2017-09-01

    Full Text Available Ferroelectricity has been proposed as one of the potential origins of the observed hysteresis in photocurrent-voltage characteristics of perovskite based solar cells. Measurement of ferroelectric properties on perovskite solar cells is hindered by the presence of (inorganic charge transport layers. Here we fabricate metal-perovskite-metal capacitors and unambiguously show that methylammonium lead iodide is not ferroelectric at room temperature. We propose that the hysteresis originates from the movement of positive ions rather than ferroelectric switching.

  20. Translucency and color stability of resin composite and dental adhesives as modeling liquids – A one-year evaluation

    National Research Council Canada - National Science Library

    José Augusto SEDREZ-PORTO; Eliseu Aldrighi MÜNCHOW; Maximiliano Sérgio CENCI; Tatiana PEREIRA-CENCI

    2017-01-01

    ...; without modeling liquid) or a restorative dental modeling insertion technique (RDMIT) with dental adhesives as modeling liquids (Scotchbond™ Multi-Purpose [SBMP; 3M ESPE] or Adper™ Single Bond 2 [SB; 3M ESPE...

  1. Model for Charge Transport in Ferroelectric Nanocomposite Film

    Directory of Open Access Journals (Sweden)

    Meng H. Lean

    2015-01-01

    Full Text Available This paper describes 3D particle-in-cell simulation of charge injection and transport through nanocomposite film comprised of ferroelectric ceramic nanofillers in an amorphous polymer matrix and/or semicrystalline ferroelectric polymer with varying degrees of crystallinity. The classical electrical double layer model for a monopolar core is extended to represent the nanofiller/nanocrystallite by replacing it with a dipolar core. Charge injection at the electrodes assumes metal-polymer Schottky emission at low to moderate fields and Fowler-Nordheim tunneling at high fields. Injected particles propagate via field-dependent Poole-Frenkel mobility. The simulation algorithm uses a boundary integral equation method for solution of the Poisson equation coupled with a second-order predictor-corrector scheme for robust time integration of the equations of motion. The stability criterion of the explicit algorithm conforms to the Courant-Friedrichs-Levy limit assuring robust and rapid convergence. Simulation results for BaTiO3 nanofiller in amorphous polymer matrix and semicrystalline PVDF with varying degrees of crystallinity indicate that charge transport behavior depends on nanoparticle polarization with antiparallel orientation showing the highest conduction and therefore the lowest level of charge trapping in the interaction zone. Charge attachment to nanofillers and nanocrystallites increases with vol% loading or degree of crystallinity and saturates at 30–40 vol% for the set of simulation parameters.

  2. Simulation studies of nucleation of ferroelectric polarization reversal.

    Energy Technology Data Exchange (ETDEWEB)

    Brennecka, Geoffrey L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Winchester, Benjamin Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-08-01

    Electric field-induced reversal of spontaneous polarization is the defining characteristic of a ferroelectric material, but the process(es) and mechanism(s) associated with the initial nucleation of reverse-polarity domains are poorly understood. This report describes studies carried out using phase field modeling of LiTaO3, a relatively simple prototype ferroelectric material, in order to explore the effects of either mechanical deformation or optically-induced free charges on nucleation and resulting domain configuration during field-induced polarization reversal. Conditions were selected to approximate as closely as feasible those of accompanying experimental work in order to provide not only support for the experimental work but also ensure that additional experimental validation of the simulations could be carried out in the future. Phase field simulations strongly support surface mechanical damage/deformation as effective for dramatically reducing the overall coercive field (Ec) via local field enhancements. Further, optically-nucleated polarization reversal appears to occur via stabilization of latent nuclei via the charge screening effects of free charges.

  3. Nanoscale phenomena in ferroelectric thin films

    Science.gov (United States)

    Ganpule, Chandan S.

    Ferroelectric materials are a subject of intense research as potential candidates for applications in non-volatile ferroelectric random access memories (FeRAM), piezoelectric actuators, infrared detectors, optical switches and as high dielectric constant materials for dynamic random access memories (DRAMs). With current trends in miniaturization, it becomes important that the fundamental aspects of scaling of ferroelectric and piezoelectric properties in these devices be studied thoroughly and their impact on the device reliability assessed. In keeping with this spirit of miniaturization, the dissertation has two broad themes: (a) Scaling of ferroelectric and piezoelectric properties and (b) The key reliability issue of retention loss. The thesis begins with a look at results on scaling studies of focused-ion-beam milled submicron ferroelectric capacitors using a variety of scanning probe characterization tools. The technique of piezoresponse microscopy, which is rapidly becoming an accepted form of domain imaging in ferroelectrics, has been used in this work for another very important application: providing reliable, repeatable and quantitative numbers for the electromechanical properties of submicron structures milled in ferroelectric films. This marriage of FIB and SPM based characterization of electromechanical and electrical properties has proven unbeatable in the last few years to characterize nanostructures qualitatively and quantitatively. The second half of this dissertation focuses on polarization relaxation in FeRAMs. In an attempt to understand the nanoscale origins of back-switching of ferroelectric domains, the time dependent relaxation of remnant polarization in epitaxial lead zirconate titanate (PbZr0.2Ti0.8O 3, PZT) ferroelectric thin films (used as a model system), containing a uniform 2-dimensional grid of 90° domains (c-axis in the plane of the film) has been examined using voltage modulated scanning force microscopy. A novel approach of

  4. Properties and stability of a liquid crystal form of cyclosporine-the first reported naturally occurring peptide that exists as a thermotropic liquid crystal.

    Science.gov (United States)

    Lechuga-Ballesteros, David; Abdul-Fattah, Ahmad; Stevenson, Cynthia L; Bennett, David B

    2003-09-01

    A new solid-state form of cyclosporine produced by spray-drying exhibited characteristics consistent with a liquid crystal. No sharp diffraction peaks were observed by powder X-ray diffraction; however, analysis by both small-angle X-ray diffraction (SAXR) and microscopic under polarized light (PLM) confirmed the existence of two-dimensional ordered liquid crystal. Hot stage microscopy revealed a solid-to-liquid transition, in the range of 118 to 125 degrees C. Moreover, the solid-to-liquid transition showed frequency dependence by dielectric analysis (DEA), and was coincidental with a stepwise heat capacity change measured by differential scanning Calorimetry (DSC). The two-dimensional order was maintained above the solid-to-liquid transition temperature indicated by low-angle diffraction by SAXR and birefringence by PLM. However, birefringence was lost at temperatures above 170 degrees C, indicating the conversion of the liquid crystal into an isotropic liquid. In situ annealing experiments, by DSC, revealed the presence of an endotherm, unexplained by either a phase transition or solvent loss, and it is believed to be the result of a structural rearrangement that has no impact on the macroscopic properties of the material. Spray-dried cyclosporine at room temperature is therefore a frozen thermotropic liquid crystal due to the presence of two-dimensional order and the lack of substantial residual solvent. This is, to our knowledge, the first report of the existence of a thermotropic liquid crystal of a naturally occurring peptide. Copyright 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:1821-1831, 2003

  5. Fatigue mechanism of yttrium-doped hafnium oxide ferroelectric thin films fabricated by pulsed laser deposition.

    Science.gov (United States)

    Huang, Fei; Chen, Xing; Liang, Xiao; Qin, Jun; Zhang, Yan; Huang, Taixing; Wang, Zhuo; Peng, Bo; Zhou, Peiheng; Lu, Haipeng; Zhang, Li; Deng, Longjiang; Liu, Ming; Liu, Qi; Tian, He; Bi, Lei

    2017-02-01

    Owing to their prominent stability and CMOS compatibility, HfO2-based ferroelectric films have attracted great attention as promising candidates for ferroelectric random-access memory applications. A major reliability issue for HfO2 based ferroelectric devices is fatigue. So far, there have been a few studies on the fatigue mechanism of this material. Here, we report a systematic study of the fatigue mechanism of yttrium-doped hafnium oxide (HYO) ferroelectric thin films deposited by pulsed laser deposition. The influence of pulse width, pulse amplitude and temperature on the fatigue behavior of HYO during field cycling is studied. The temperature dependent conduction mechanism is characterized after different fatigue cycles. Domain wall pinning caused by carrier injection at shallow defect centers is found to be the major fatigue mechanism of this material. The fatigued device can fully recover to the fatigue-free state after being heated at 90 °C for 30 min, confirming the shallow trap characteristic of the domain wall pinning defects.

  6. Emerging ferroelectric transistors with nanoscale channel materials: the possibilities, the limitations

    Science.gov (United States)

    Hong, Xia

    2016-03-01

    Combining the nonvolatile, locally switchable polarization field of a ferroelectric thin film with a nanoscale electronic material in a field effect transistor structure offers the opportunity to examine and control a rich variety of mesoscopic phenomena and interface coupling. It is also possible to introduce new phases and functionalities into these hybrid systems through rational design. This paper reviews two rapidly progressing branches in the field of ferroelectric transistors, which employ two distinct classes of nanoscale electronic materials as the conducting channel, the two-dimensional (2D) electron gas graphene and the strongly correlated transition metal oxide thin films. The topics covered include the basic device physics, novel phenomena emerging in the hybrid systems, critical mechanisms that control the magnitude and stability of the field effect modulation and the mobility of the channel material, potential device applications, and the performance limitations of these devices due to the complex interface interactions and challenges in achieving controlled materials properties. Possible future directions for this field are also outlined, including local ferroelectric gate control via nanoscale domain patterning and incorporating other emergent materials in this device concept, such as the simple binary ferroelectrics, layered 2D transition metal dichalcogenides, and the 4d and 5d heavy metal compounds with strong spin-orbit coupling.

  7. Uncooled monolithic ferroelectric IRFPA technology

    Science.gov (United States)

    Belcher, James F.; Hanson, Charles M.; Beratan, Howard R.; Udayakumar, K. R.; Soch, Kevin L.

    1998-10-01

    Once relegated to expensive military platforms, occasionally to civilian platforms, and envisioned for individual soldiers, uncooled thermal imaging affords cost-effective solutions for police cars, commercial surveillance, driving aids, and a variety of other industrial and consumer applications. System prices are continuing to drop, and swelling production volume will soon drive prices substantially lower. The impetus for further development is to improve performance. Hybrid barium strontium titanate (BST) detectors currently in production are relatively inexpensive, but have limited potential for improved performance. The MTF at high frequencies is limited by thermal conduction through the optical coating. Microbolometer arrays in development at Raytheon have recently demonstrated performance superior to hybrid detectors. However, microbolometer technology lacks a mature, low-cost system technology and an abundance of upgradable, deployable system implementations. Thin-film ferroelectric (TFFE) detectors have all the performance potential of microbolometers. They are also compatible with numerous fielded and planned system implementations. Like the resistive microbolometer, the TFFE detector is monolithic; i.e., the detector material is deposited directly on the readout IC rather than being bump bonded to it. Imaging arrays of 240 X 320 pixels have been produced, demonstrating the feasibility of the technology.

  8. Electric-field-driven dynamics of magnetic domain walls in magnetic nanowires patterned on ferroelectric domains

    OpenAIRE

    Wiele, Ben Van de; Leliaert, Jonathan; Franke, Kévin J A; Dijken, Sebastiaan van

    2016-01-01

    Strong coupling of magnetic domain walls onto straight ferroelastic boundaries of a ferroelectric layer enables full and reversible electric-field control of magnetic domain wall motion. In this paper, the dynamics of this new driving mechanism is analyzed using micromagnetic simulations. We show that transverse domain walls with a near-180° spin structure are stabilized in magnetic nanowires and that electric fields can move these walls with high velocities. Above a critical velocity, which ...

  9. INVESTIGATING THE LONG-TERM STABILITY AND KINETICS OF SUPEROXIDE ION IN DIMETHYL SULFOXIDE CONTAINING IONIC LIQUIDS AND THE APPLICATION OF THIOPHENE DESTRUCTION

    OpenAIRE

    Hayyan,M.; Ibrahim, M. H.; Hayyan,A.; M. Ali Hashim

    2017-01-01

    Abstract The long-term stability of superoxide ion (O2•−) with four ionic liquids (ILs), namely 1-(2-methoxyethyl)-1-methylpiperidinium tris(pentafluoroethyl)trifluorophosphate [MOEMPip][TPTP], 1-(3-methoxypropyl)-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide [MOPMPip][TFSI], N-ethyl-N,N-dimethyl-2-methoxyethylammonium bis(trifluoromethylsulfonyl)imide [N112,1O2][TFSI], and ethyl-dimethyl-propylammonium bis(trifluoromethylsulfonyl)imide [EDMPAmm][TFSI], was studied for up...

  10. Switching Characteristics of Ferroelectric Transistor Inverters

    Science.gov (United States)

    Laws, Crystal; Mitchell, Coey; MacLeod, Todd C.; Ho, Fat D.

    2010-01-01

    This paper presents the switching characteristics of an inverter circuit using a ferroelectric field effect transistor, FeFET. The propagation delay time characteristics, phl and plh are presented along with the output voltage rise and fall times, rise and fall. The propagation delay is the time-delay between the V50% transitions of the input and output voltages. The rise and fall times are the times required for the output voltages to transition between the voltage levels V10% and V90%. Comparisons are made between the MOSFET inverter and the ferroelectric transistor inverter.

  11. The Structure of Ferroelectric DCsDA

    DEFF Research Database (Denmark)

    Meyer, G. M.; Dietrich, O. W.; Nelmes, R. J.

    1976-01-01

    In further neutron scattering experiments on the (orthorhombic) ferroelectric phase of DCsDA and CsDA, a study has been made of the scattering arising at wavevectors along the a* direction at positions away from Bragg reflections. It is shown that this most probably arises from Bragg scattering...... in which two different ferroelectric domains are involved. Below Tc each Bragg reflection can split into four separate spots corresponding to the different domain types. Surprisingly in DCsDA a central Bragg spot from the (tetragonal) paraelectric phase persists with decreasing intensity over a 60K...

  12. Ferroelectric domain continuity over grain boundaries

    DEFF Research Database (Denmark)

    Mantri, Sukriti; Oddershede, Jette; Damjanovic, Dragan

    2017-01-01

    Formation and mobility of domain walls in ferroelectric materials is responsible for many of their electrical and mechanical properties. Domain wall continuity across grain boundaries has been observed since the 1950's and is speculated to affect the grain boundary-domain interactions, thereby...... orientation. We have also incorporated the effect of grain boundary ferroelectric polarization charge created when any two domains meet at the grain boundary plane. The probability of domain wall continuity for three specific grain misorientations is studied. Use of this knowledge to optimize processing...

  13. Transitional subphases near the electric-field-induced phase transition to the ferroelectric phase in Se-containing chiral smectic liquid crystals observed by resonant x-ray scattering.

    Science.gov (United States)

    Iida, Atsuo; Takanishi, Yoichi; Fukuda, Atsuo; Vij, Jagdish K

    2016-11-01

    Resonant x-ray scattering experiments revealed transitional subphases near the electric-field-induced phase transition of a Se-containing chiral liquid crystal in a planar aligned cell geometry. In the lower-temperature range (Sm-C_{A}^{*} and three-layer periodicity Sm-C_{γ}^{*} phases), the six-layer periodicity subphase appeared with increasing electric field during the field-induced transition from Sm-C_{γ}^{*} to Sm-C^{*}. In the higher-temperature range [four-layer periodicity antiferroelectric (AF) phase], the peak positions of the three-layer satellites shifted to those of the four-layer satellites and then the satellites corresponding to the five- through seven-layer periodicity appeared in sequence. Near the AF to Sm-C_{α}^{*} phase transition temperature, the layer periodicity increased with applied field. The molecular configurations of the subphases near the field-induced transition are discussed based on the Ising, distorted clock, and perfect clock models.

  14. Metal-Organic Coordination Complexes Serve the Electronic Industry as Low-Value Dielectric Constant Ferroelectric Material

    Science.gov (United States)

    Ahmad, Nazir; Kotru, P. N.

    2017-10-01

    Single crystals of praseodymium tartrate dihydrate possessing excellent ferroelectric, non-linear optical (NLO) properties and exhibiting remarkably flat habit faces are successfully grown by gel technique. The most predominant habit face is identified to be {101}. The dielectric behaviour recorded on {101} planes of single crystals exhibit a dielectric anomaly at 245°C, revealing a ferroelectric transition which is supported by thermal and polarisation versus electric field studies. The optical measurement leads to a band gap of 5.13 eV which is shown to be in good agreement with the studies of high-resolution x-ray diffraction (HRXRD), transport properties and NLO behaviour of the material. Absence of grain boundaries, thermal stability, ferroelectric and NLO behaviour supports the grown single crystal to find its place in microelectronic industry as a multifunctional material.

  15. Static ferroelectric memory transistor having improved data retention

    Science.gov (United States)

    Evans, Jr., Joseph T.; Warren, William L.; Tuttle, Bruce A.

    1996-01-01

    An improved ferroelectric FET structure in which the ferroelectric layer is doped to reduce retention loss. A ferroelectric FET according to the present invention includes a semiconductor layer having first and second contacts thereon, the first and second contacts being separated from one another. The ferroelectric FET also includes a bottom electrode and a ferroelectric layer which is sandwiched between the semiconductor layer and the bottom electrode. The ferroelectric layer is constructed from a perovskite structure of the chemical composition ABO.sub.3 wherein the B site comprises first and second elements and a dopant element that has an oxidation state greater than +4 in sufficient concentration to impede shifts in the resistance measured between the first and second contacts with time. The ferroelectric FET structure preferably comprises Pb in the A-site. The first and second elements are preferably Zr and Ti, respectively. The preferred B-site dopants are Niobium, Tantalum, and Tungsten at concentrations between 1% and 8%.

  16. Ferroelectric Material Application: Modeling Ferroelectric Field Effect Transistor Characteristics from Micro to Nano

    Science.gov (United States)

    MacLeod, Todd, C.; Ho, Fat Duen

    2006-01-01

    All present ferroelectric transistors have been made on the micrometer scale. Existing models of these devices do not take into account effects of nanoscale ferroelectric transistors. Understanding the characteristics of these nanoscale devices is important in developing a strategy for building and using future devices. This paper takes an existing microscale ferroelectric field effect transistor (FFET) model and adds effects that become important at a nanoscale level, including electron velocity saturation and direct tunneling. The new model analyzed FFETs ranging in length from 40,000 nanometers to 4 nanometers and ferroelectric thickness form 200 nanometers to 1 nanometer. The results show that FFETs can operate on the nanoscale but have some undesirable characteristics at very small dimensions.

  17. Flexible ferroelectric element based on van der Waals heteroepitaxy.

    Science.gov (United States)

    Jiang, Jie; Bitla, Yugandhar; Huang, Chun-Wei; Do, Thi Hien; Liu, Heng-Jui; Hsieh, Ying-Hui; Ma, Chun-Hao; Jang, Chi-Yuan; Lai, Yu-Hong; Chiu, Po-Wen; Wu, Wen-Wei; Chen, Yi-Chun; Zhou, Yi-Chun; Chu, Ying-Hao

    2017-06-01

    We present a promising technology for nonvolatile flexible electronic devices: A direct fabrication of epitaxial lead zirconium titanate (PZT) on flexible mica substrate via van der Waals epitaxy. These single-crystalline flexible ferroelectric PZT films not only retain their performance, reliability, and thermal stability comparable to those on rigid counterparts in tests of nonvolatile memory elements but also exhibit remarkable mechanical properties with robust operation in bent states (bending radii down to 2.5 mm) and cycling tests (1000 times). This study marks the technological advancement toward realizing much-awaited flexible yet single-crystalline nonvolatile electronic devices for the design and development of flexible, lightweight, and next-generation smart devices with potential applications in electronics, robotics, automotive, health care, industrial, and military systems.

  18. Giant Electrocaloric Effect in Ferroelectrics with Tailored Polaw-Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Qiming [Pennsylvania State Univ., University Park, PA (United States)

    2015-06-24

    systems with nano- and meso-scale disorders. Through the efforts of this DoE program, we have developed understandings for many questions and materials approaches for many hypotheses listed above. The major accomplishments include: (i) The first one to show that a giant ECE can be obtained in bulk materials of ferroelectric P(VDF-TrFE) copolymer, which has a large ß coefficient and high polarization, near FE-PE transition.[1,3,12] (ii) The first who developed the theoretical analyses on the upper bound of dipolar entropy change in polar-materials and the general approach to maximize the coexisting phases with vanishingly small switching fields among the coexisting phases[10,23] Experimental results confirm these theoretical predictions.[24] (iii) The first to show that the relaxor ferroelectrics, due to built-in defects structures at nano- and meso scale, exhibit a giant ECE over a broad temperature range.[1,3,7,14] (iv) The first to show that a large ECE can be obtained near order-disorder transition in dielectric fluids such as liquid crystals with large dielectric anisotropy. Also the study developed a general approach for developing dielectric fluids to achieve a large electric field induced entropy change.[26] (v) We are starting to explore the multi-field effect (multiferroic effect) in nanocomposites in which there exist large dielectric contrasts between the matrix and nanofilelrs and showed that a significantly enhanced ECE compared with polymer matrix.[36] (vi) By facially tuning the nano- and meso-scale dipolar coupling, we are the first to show that an anomalous ECE can be obtained in a relaxor/normal ferroelectric blend.[39] (vii) Introduced and demonstrated that the internal bias field approach can be effective in enhancing the EC response at low electric field. The result is significant since for practical applications, a low applied field is highly desired. (viii) A high sensitivity ECE characterization system has been developed. This program has made

  19. A microencapsulation process of liquid mercury by sulfur polymer stabilization/solidification technology. Part II: Durability of materials

    Directory of Open Access Journals (Sweden)

    López-Delgado, A.

    2012-02-01

    Full Text Available Under the European LIFE Program a microencapsulation process was developed for liquid mercury using Sulfur Polymer Stabilization/Solidification (SPSS technology, obtaining a stable concrete-like sulfur matrix that allows the immobilization of mercury for long-term storage. The process description and characterization of the materials obtained were detailed in Part I. The present document, Part II, reports the results of different tests carried out to determine the durability of Hg-S concrete samples with very high mercury content (up to 30 % w/w. Different UNE and RILEM standard test methods were applied, such as capillary water absorption, low pressure water permeability, alkali/acid resistance, salt mist aging, freeze-thaw resistance and fire performance. The samples exhibited no capillarity and their resistance in both alkaline and acid media was very high. They also showed good resistance to very aggressive environments such as spray salt mist, freeze-thaw and dry-wet. The fire hazard of samples at low heat output was negligible.

    Dentro del Programa Europeo LIFE, se ha desarrollado un proceso de microencapsulación de mercurio liquido, utilizando la tecnología de estabilización/solidificación con azufre polimérico (SPSS. Como resultado se ha obtenido un material estable tipo concreto que permite la inmovilización de mercurio y su almacenamiento a largo plazo. La descripción del proceso y la caracterización de los materiales obtenidos, denominados concretos Hg-S, se detallan en la Parte I. El presente trabajo, Parte II, incluye los resultados de los diferentes ensayos realizados para determinar la durabilidad de las muestras de concreto Hg-S con un contenido de mercurio de hasta el 30 %. Se han utilizado diferentes métodos de ensayo estándar, UNE y RILEM, para determinar propiedades como la absorción de agua por capilaridad, la permeabilidad de agua a baja presión, la resistencia a álcali y ácido, el comportamiento en

  20. Tunable metallic conductance in ferroelectric nanodomains.

    Science.gov (United States)

    Maksymovych, Peter; Morozovska, Anna N; Yu, Pu; Eliseev, Eugene A; Chu, Ying-Hao; Ramesh, Ramamoorthy; Baddorf, Arthur P; Kalinin, Sergei V

    2012-01-11

    Metallic conductance in charged ferroelectric domain walls was predicted more than 40 years ago as the first example of an electronically active homointerface in a nonconductive material. Despite decades of research on oxide interfaces and ferroic systems, the metal-insulator transition induced solely by polarization charges without any additional chemical modification has consistently eluded the experimental realm. Here we show that a localized insulator-metal transition can be repeatedly induced within an insulating ferroelectric lead-zirconate titanate, merely by switching its polarization at the nanoscale. This surprising effect is traced to tilted boundaries of ferroelectric nanodomains, that act as localized homointerfaces within the perovskite lattice, with inherently tunable carrier density. Metallic conductance is unique to nanodomains, while the conductivity of extended domain walls and domain surfaces is thermally activated. Foreseeing future applications, we demonstrate that a continuum of nonvolatile metallic states across decades of conductance can be encoded in the size of ferroelectric nanodomains using electric field. © 2011 American Chemical Society

  1. Photovoltaics with Ferroelectrics: Current Status and Beyond.

    Science.gov (United States)

    Paillard, Charles; Bai, Xiaofei; Infante, Ingrid C; Guennou, Maël; Geneste, Grégory; Alexe, Marin; Kreisel, Jens; Dkhil, Brahim

    2016-07-01

    Ferroelectrics carry a switchable spontaneous electric polarization. This polarization is usually coupled to strain, making ferroelectrics good piezoelectrics. When coupled to magnetism, they become so-called multiferroic systems, a field that has been widely investigated since 2003. While ferroelectrics are birefringent and non-linear optically transparent materials, the coupling of polarization with optical properties has received, since 2009, renewed attention, triggered notably by low-bandgap ferroelectrics suitable for sunlight spectrum absorption and original photovoltaic effects. Consequently, power conversion efficiencies up to 8.1% were recently achieved and values of 19.5% were predicted, making photoferroelectrics promising photovoltaic alternatives. This article aims at providing an up-to-date review on this emerging and rapidly progressing field by highlighting several important issues and parameters, such as the role of domain walls, ways to tune the bandgap, consequences arising from the polarization switchability, and the role of defects and contact electrodes, as well as the downscaling effects. Beyond photovoltaicity, other polarization-related processes are also described, like light-induced deformation (photostriction) or light-assisted chemical reaction (photostriction). It is hoped that this overview will encourage further avenues to be explored and challenged and, as a byproduct, will inspire other research communities in material science, e.g., so-called hybrid halide perovskites. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Scaling and metastable behavior in uniaxial ferroelectrics

    NARCIS (Netherlands)

    Fernández del Castillo, J.R.; Noheda, B.; Cereceda, N.; Gonzalo, J.A.; Iglesias, T.; Przeslawski, J.

    1998-01-01

    Improved experimental resolution and computer aided data analysis of hysteresis loops at T≈TC in uniaxial ferroelectrics triglycene sulfate (ordinary critical point), and triglycine selenate (quasitricritical point) show that scaling holds in a wide range of scaled fields spanning many orders of

  3. Pyroelectric Ferroelectric and Resistivity Studies on Samarium ...

    African Journals Online (AJOL)

    Barium Strontium Sodium Niobate (Ba1-xSrx)2NaNb5O15 (BSNN) belongs to tungsten bronze ferroelectric morphotrophic phase boundary (MPB) system at x = 0.6, having large spontaneous polarisation, pyroelectric coefficient and low dielectic constant and is expected to be applicable for piezoceramic filter and ...

  4. Multi-bit organic ferroelectric memory

    NARCIS (Netherlands)

    Khikhlovskyi, V.; Gorbunov, A.V.; Breemen, A.J.J.M. vN; Janssen, R.A.J.; Gelinck, G.H.; Kemerink, M.

    2013-01-01

    Storage of multiple bits per element is a promising alternative to miniaturization for increasing the information data density in memories. Here we introduce a multi-bit organic ferroelectric-based non-volatile memory with binary readout from a simple capacitor structure. The functioning of our

  5. Ferroelectrics under the Synchrotron Light: A Review

    Science.gov (United States)

    Fuentes-Cobas, Luis E.; Montero-Cabrera, María E.; Pardo, Lorena; Fuentes-Montero, Luis

    2015-01-01

    Currently, an intensive search for high-performance lead-free ferroelectric materials is taking place. ABO3 perovskites (A = Ba, Bi, Ca, K and Na; B = Fe, Nb, Ti, and Zr) appear as promising candidates. Understanding the structure–function relationship is mandatory, and, in this field, the roles of long- and short-range crystal orders and interactions are decisive. In this review, recent advances in the global and local characterization of ferroelectric materials by synchrotron light diffraction, scattering and absorption are analyzed. Single- and poly-crystal synchrotron diffraction studies allow high-resolution investigations regarding the long-range average position of ions and subtle global symmetry break-downs. Ferroelectric materials, under the action of electric fields, undergo crystal symmetry, crystallite/domain orientation distribution and strain condition transformations. Methodological aspects of monitoring these processes are discussed. Two-dimensional diffraction clarify larger scale ordering: polycrystal texture is measured from the intensities distribution along the Debye rings. Local order is investigated by diffuse scattering (DS) and X-ray absorption fine structure (XAFS) experiments. DS provides information about thermal, chemical and displacive low-dimensional disorders. XAFS investigation of ferroelectrics reveals local B-cation off-centering and oxidation state. This technique has the advantage of being element-selective. Representative reports of the mentioned studies are described. PMID:28787814

  6. Ferroelectrics under the Synchrotron Light: A Review

    Directory of Open Access Journals (Sweden)

    Luis E. Fuentes-Cobas

    2015-12-01

    Full Text Available Currently, an intensive search for high-performance lead-free ferroelectric materials is taking place. ABO3 perovskites (A = Ba, Bi, Ca, K and Na; B = Fe, Nb, Ti, and Zr appear as promising candidates. Understanding the structure–function relationship is mandatory, and, in this field, the roles of long- and short-range crystal orders and interactions are decisive. In this review, recent advances in the global and local characterization of ferroelectric materials by synchrotron light diffraction, scattering and absorption are analyzed. Single- and poly-crystal synchrotron diffraction studies allow high-resolution investigations regarding the long-range average position of ions and subtle global symmetry break-downs. Ferroelectric materials, under the action of electric fields, undergo crystal symmetry, crystallite/domain orientation distribution and strain condition transformations. Methodological aspects of monitoring these processes are discussed. Two-dimensional diffraction clarify larger scale ordering: polycrystal texture is measured from the intensities distribution along the Debye rings. Local order is investigated by diffuse scattering (DS and X-ray absorption fine structure (XAFS experiments. DS provides information about thermal, chemical and displacive low-dimensional disorders. XAFS investigation of ferroelectrics reveals local B-cation off-centering and oxidation state. This technique has the advantage of being element-selective. Representative reports of the mentioned studies are described.

  7. Identifying intrinsic ferroelectricity of thin film with piezoresponse force microscopy

    Directory of Open Access Journals (Sweden)

    Zhao Guan

    2017-09-01

    Full Text Available Piezoresponse force microscopy (PFM is a powerful technique to characterize ferroelectric thin films by measuring the dynamic electromechanical response. The ferroelectricity is commonly demonstrated by the PFM hysteresis loops and a 180o phase difference of PFM images before and after poling. Such ferroelectric-like behaviors, however, recently are also found in many non-ferroelectrics. Consequently, it is still a challenge to identify intrinsic ferroelectricity in various kinds of thin films. Here, using PFM, we systematically studied the electromechanical responses in ferroelectric thin films with fast (BaTiO3 and slow (PVDF switch dynamics, and also in the non-ferroelectric (Al2O3 thin films. It is found that both of the ac voltage (Vac and pulsed dc voltage (Vdc play an important role in the PFM measurement. When the Vac amplitude is higher than a explicit threshold voltage (Vc, collapse of the PFM hysteresis loops is observed for the films with fast switch dynamics. By measuring PFM hysteresis loops at various Vdc frequencies, an explicit Vc could be found in ferroelectric rather than in non-ferroelectric. The existence of an explicit Vc as well as nonvolatile behavior is proposed as an important approach to unambiguously identify intrinsic ferroelectricity in materials regardless of switch dynamics.

  8. Enhanced contrast ratio and viewing angle of polymer-stabilized liquid crystal via refractive index matching between liquid crystal and polymer network.

    Science.gov (United States)

    Lee, Ji-Hoon; Lee, Jung Jin; Lim, Young Jin; Kundu, Sudarshan; Kang, Shin-Woong; Lee, Seung Hee

    2013-11-04

    Long standing electro-optic problems of a polymer-dispersed liquid crystal (PDLC) such as low contrast ratio and transmittances decrease in oblique viewing angle have been challenged with a mixture of dual frequency liquid crystal (DFLC) and reactive mesogen (RM). The DFLC and RM molecules were vertically aligned and then photo-polymerized using a UV light. At scattering state under 50 kHz electric field, DFLC was switched to planar state, giving greater extraordinary refractive index than the normal PDLC cell. Consequently, the scattering intensity and the contrast ratio were increased compared to the conventional PDLC cell. At transparent state under 1 kHz electric field, the extraordinary refractive index of DFLC was simultaneously matched with the refractive index of vertically aligned RM so that the light scattering in oblique viewing angles was minimized, giving rise to high transmittance in all viewing angles.

  9. High-performance ferroelectric memory based on phase-separated films of polymer blends

    KAUST Repository

    Khan, Yasser

    2013-10-29

    High-performance polymer memory is fabricated using blends of ferroelectric poly(vinylidene-fluoride-trifluoroethylene) (P(VDF-TrFE)) and highly insulating poly(p-phenylene oxide) (PPO). The blend films spontaneously phase separate into amorphous PPO nanospheres embedded in a semicrystalline P(VDF-TrFE) matrix. Using low molecular weight PPO with high miscibility in a common solvent, i.e., methyl ethyl ketone, blend films are spin cast with extremely low roughness (Rrms ≈ 4.92 nm) and achieve nanoscale phase seperation (PPO domain size < 200 nm). These blend devices display highly improved ferroelectric and dielectric performance with low dielectric losses (<0.2 up to 1 MHz), enhanced thermal stability (up to ≈353 K), excellent fatigue endurance (80% retention after 106 cycles at 1 KHz) and high dielectric breakdown fields (≈360 MV/m). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Stability of Wavy Films in Gas-Liquid Two-Phase Flows at Normal and Microgravity Conditions

    Science.gov (United States)

    Balakotaiah, V.; Jayawardena, S. S.

    1996-01-01

    For flow rates of technological interest, most gas-liquid flows in pipes are in the annular flow regime, in which, the liquid moves along the pipe wall in a thin, wavy film and the gas flows in the core region. The waves appearing on the liquid film have a profound influence on the transfer rates, and hence on the design of these systems. We have recently proposed and analyzed two boundary layer models that describe the characteristics of laminar wavy films at high Reynolds numbers (300-1200). Comparison of model predictions to 1-g experimental data showed good agreement. The goal of our present work is to understand through a combined program of experimental and modeling studies the characteristics of wavy films in annular two-phase gas-liquid flows under normal as well as microgravity conditions in the developed and entry regions.

  11. THE USE OF STABILIZED LIQUIDE CHLORINE DIOXIDE (ClO2 FOR INTERNAL WATER SUPPLY SYSTEM SANITATION OF FARM WITH LAYING FLOCK AFFECTED BY COLISEPTICEMIA

    Directory of Open Access Journals (Sweden)

    Abdulah Gagić

    2014-03-01

    Full Text Available A successful and harmless method for rehabilitation of hygienic status of water and its supply system using a stabilized liquid chlorine dioxide solution on a farm of the laying hens affected by severe colisepticemia is described. Source of infection was drinking water contaminated by slurry from two pig facilities located above the water tank. The contaminated water caused the emergence of biofilm consisting mainly of coliform bacteria on the interior surfaces of the plastic pipes. Through drinking the contaminated water the infection of the laying flocks occurred. With the aim of improving the flocks’ health status, a programme of sanitary treatment of external and internal water supply system and water was created and implemented. In order to prevent biofilm formation and improve sanitation prescribed was the use of stabilized liquid chlorine dioxide (ClO2 in the 4‰ concentration for so-called night "shock" treatments, and 2‰ concentration for prophylactic daily disinfection of drinking water. With the improvement of the flocks’ health status, the "shock" treatments with ClO2 were repeated in the upcoming months. As an add-on therapy, 40 mg per bird of vitamin C through drinking water for three days was prescribed. The use of non-resorptive antibiotics, AD3E vitamins and amino acid supplements was excluded because they had failed to improve the flocks’ health status in the acute phase. Therefore, the sanitation programme based on the use of stabilized liquid ClO2 in the water supply system of the laying flocks affected by severe colisepticemia resulted in radical decrease of mortality during the next three months. Key words: chlorine dioxide, biofilm, sanitation, disinfection, colisepticemia

  12. The effect of turbulence on the stability of liquid jets and the resulting droplet size distributions. Third quarterly technical report, July 1, 1993--September 30, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Mansour, A.; Chigier, N.

    1993-12-01

    Laminar and turbulent columns of liquids issuing from capillary tubes were studied in order to determine the effects of turbulence on the stability of liquid jets and to establish the influence of liquid turbulence on droplet size distributions after breakup. Two capillary tubes were chosen with diameters D{sub 1}=3.0mm and D{sub 2}=1.2mm; jet Reynolds numbers were 1000--30000, and 400--7200. For water injection into stagnant air, stability curve is bounded by a laminar portion, where a jet radius and {delta}{sub o} initial disturbance amplitude, and a fully developed turbulent portion characterized by high initial disturbance amplitude (ln(a/{delta}{sub o,T}) {approximately} 4.85). In the transition region, ln(a/{delta}{sub o}) is not single valued; it decreases with increasing Reynolds number. In absence of aerodynamic effects, turbulent jets are as stable as laminar jets. For this breakup mode turbulence propagates initial disturbances with amplitudes orders of magnitude larger than laminar jets ({delta}{sub o,T}=28{times}10{sup 6} {delta}{sub o,L}). Growth rates of initial disturbances are same for both laminar and turbulent columns with theoretical Weber values. Droplet size distribution is bi-modal; the number ratio of large (> D/2), to small (< D/2) droplets is 3 and independent of Reynolds number. For laminar flow optimum wavelength ({lambda}{sub opt}) corresponding to fastest growing disturbance is equal to 4.45D, exactly the theoretical Weber value. For turbulent flow conditions, the turbulent column segments. Typically, segments with lengths of one to several wavelengths, detach from the liquid jet. The long ligaments contract under the action of surface tension, resulting in droplet sizes larger than predicted by Rayleigh and Weber. For turbulent flow conditions, {lambda}{sub opt} = 9.2D, about 2 times the optimum Weber wavelength.

  13. Ferroelectric domain wall motion induced by polarized light.

    Science.gov (United States)

    Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F

    2015-03-17

    Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO₃ single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO₃ at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light.

  14. Standard Practice for Preparing Aircraft Cleaning Compounds, Liquid-Type, Temperature-Sensitive, or Solvent-Based, for Storage Stability Testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 This practice covers the determination of the stability in storage of liquid enzyme-based, terpene-based, and solvent-based chemical cleaning compounds used to clean the exterior surfaces of aircraft. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  15. Effects of the vertically switching electric field on the photoelectric properties of polymer-stabilized blue-phase liquid crystal cells using the director model.

    Science.gov (United States)

    Chi, Cheng-Yu; Qiu, Shi-Hao; Lin, Guan-Jhong; Chen, Tien-Jung; Yang, Yin-Jay; Wu, Jin-Jei

    2017-03-20

    This study uses the director model to analyze the optoelectronic properties of polymer-stabilized blue-phase liquid crystal (PS-BPLC). The director model revealed a linear relationship of refractive index change and the cosine squared of the angle between the LCs and the direction of the electric field. Moreover, we employed simulations based on the Kerr effect and compared the results with those of the director model. The simulation results also show high consistency with real circumstances. Consequently, it can be of great help to design BPLC displays that can be applied to adopting better strategies for developing next-generation LCD devices.

  16. Characteristics and controllability of vortices in ferromagnetics, ferroelectrics, and multiferroics

    Science.gov (United States)

    Zheng, Yue; Chen, W. J.

    2017-08-01

    Topological defects in condensed matter are attracting e significant attention due to their important role in phase transition and their fascinating characteristics. Among the various types of matter, ferroics which possess a switchable physical characteristic and form domain structure are ideal systems to form topological defects. In particular, a special class of topological defects—vortices—have been found to commonly exist in ferroics. They often manifest themselves as singular regions where domains merge in large systems, or stabilize as novel order states instead of forming domain structures in small enough systems. Understanding the characteristics and controllability of vortices in ferroics can provide us with deeper insight into the phase transition of condensed matter and also exciting opportunities in designing novel functional devices such as nano-memories, sensors, and transducers based on topological defects. In this review, we summarize the recent experimental and theoretical progress in ferroic vortices, with emphasis on those spin/dipole vortices formed in nanoscale ferromagnetics and ferroelectrics, and those structural domain vortices formed in multiferroic hexagonal manganites. We begin with an overview of this field. The fundamental concepts of ferroic vortices, followed by the theoretical simulation and experimental methods to explore ferroic vortices, are then introduced. The various characteristics of vortices (e.g. formation mechanisms, static/dynamic features, and electronic properties) and their controllability (e.g. by size, geometry, external thermal, electrical, magnetic, or mechanical fields) in ferromagnetics, ferroelectrics, and multiferroics are discussed in detail in individual sections. Finally, we conclude this review with an outlook on this rapidly developing field.

  17. Ferroelectric nanostructure having switchable multi-stable vortex states

    Science.gov (United States)

    Naumov, Ivan I [Fayetteville, AR; Bellaiche, Laurent M [Fayetteville, AR; Prosandeev, Sergey A [Fayetteville, AR; Ponomareva, Inna V [Fayetteville, AR; Kornev, Igor A [Fayetteville, AR

    2009-09-22

    A ferroelectric nanostructure formed as a low dimensional nano-scale ferroelectric material having at least one vortex ring of polarization generating an ordered toroid moment switchable between multi-stable states. A stress-free ferroelectric nanodot under open-circuit-like electrical boundary conditions maintains such a vortex structure for their local dipoles when subject to a transverse inhomogeneous static electric field controlling the direction of the macroscopic toroidal moment. Stress is also capable of controlling the vortex's chirality, because of the electromechanical coupling that exists in ferroelectric nanodots.

  18. Ferroelectric devices, interconnects, and methods of manufacture thereof

    KAUST Repository

    Alshareef, Husam N.

    2013-12-12

    A doped electroconductive organic polymer is used for forming the electrode of a ferroelectric device or an interconnect. An exemplary ferroelectric device is a ferrelectric capacitor comprising: a substrate (101); a first electrode (106) disposed on the substrate; a ferroelectric layer (112) disposed on and in contact with the first electrode; and a second electrode (116) disposed on and in contact with the ferroelectric layer, wherein at least one of the first electrode and the second electrode is an organic electrode comprising a doped electroconductive organic polymer, for example DMSO-doped PEDOT-PSS.

  19. Stability and Degradation of Caffeoylquinic Acids under Different Storage Conditions Studied by High-Performance Liquid Chromatography with Photo Diode Array Detection and High-Performance Liquid Chromatography with Electrospray Ionization Collision-Induced Dissociation Tandem Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Meng Xue

    2016-07-01

    Full Text Available Caffeoylquinic acids (CQAs are main constituents in many herbal medicines with various biological and pharmacological effects. However, CQAs will degrade or isomerize when affected by temperature, pH, light, etc. In this study, high-performance liquid chromatography with photodiode array detection (HPLC-PDA and high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS was utilized to study the stability and degradation of CQAs (three mono-acyl CQAs and four di-acyl CQAs under various ordinary storage conditions (involving different temperatures, solvents, and light irradiation. The results indicated that the stability of CQAs was mainly affected by temperature and light irradiation, while solvents did not affect it in any obvious way under the conditions studied. Mono-acyl CQAs were generally much more stable than di-acyl CQAs under the same conditions. Meanwhile, the chemical structures of 30 degradation products were also characterized by HPLC-MSn, inferring that isomerization, methylation, and hydrolysis were three major degradation pathways. The result provides a meaningful clue for the storage conditions of CQAs standard substances and samples.

  20. Ferroelectric Cathodes in Transverse Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

    2002-07-29

    Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode.

  1. A ferroelectric memory technology for embedded LSI

    CERN Document Server

    Kunio, T

    1999-01-01

    We have developed an FeRAM (Ferroelectric Random Access Memory) embedded smart card LSI by using double metal 0.8- mu m CMOS technology. The smart-card has a 256-byte FeRAM macro and an 8-bit microcontroller. The FeRAM macro has the $9 performance of 10/sup 8/ endurance cycles and is half the size of an EEPROM macro. We have also developed a new CMVP (Capacitor on Meta/Via Stacked Plug) cell for an advanced FeRAM embedded LSI by using 0.25- mu m CMOS technology. $9 The ferroelectric capacitors of this cell are fabricated after the multiple interconnect is formed, and a cell area of 3.2 mu m/sup 2/ is obtained. (8 refs).

  2. Fracture mechanics of piezoelectric and ferroelectric solids

    CERN Document Server

    Fang, Daining

    2013-01-01

    Fracture Mechanics of Piezoelectric and Ferroelectric Solids presents a systematic and comprehensive coverage of the fracture mechanics of piezoelectric/ferroelectric materials, which includes the theoretical analysis, numerical computations and experimental observations. The main emphasis is placed on the mechanics description of various crack problems such static, dynamic and interface fractures as well as the physical explanations for the mechanism of electrically induced fracture. The book is intended for postgraduate students, researchers and engineers in the fields of solid mechanics, applied physics, material science and mechanical engineering. Dr. Daining Fang is a professor at the School of Aerospace, Tsinghua University, China; Dr. Jinxi Liu is a professor at the Department of Engineering Mechanics, Shijiazhuang Railway Institute, China.

  3. Glucose Suppresses Biological Ferroelectricity in Aortic Elastin

    Science.gov (United States)

    Liu, Yuanming; Wang, Yunjie; Chow, Ming-Jay; Chen, Nataly Q.; Ma, Feiyue; Zhang, Yanhang; Li, Jiangyu

    2013-04-01

    Elastin is an intriguing extracellular matrix protein present in all connective tissues of vertebrates, rendering essential elasticity to connective tissues subjected to repeated physiological stresses. Using piezoresponse force microscopy, we show that the polarity of aortic elastin is switchable by an electrical field, which may be associated with the recently discovered biological ferroelectricity in the aorta. More interestingly, it is discovered that the switching in aortic elastin is largely suppressed by glucose treatment, which appears to freeze the internal asymmetric polar structures of elastin, making it much harder to switch, or suppressing the switching completely. Such loss of ferroelectricity could have important physiological and pathological implications from aging to arteriosclerosis that are closely related to glycation of elastin.

  4. Reversible Polarization Rotation in Epitaxial Ferroelectric Bilayers

    DEFF Research Database (Denmark)

    Liu, Guangqing; Zhang, Qi; Huang, Hsin-Hui

    2016-01-01

    Polarization rotation engineering is a promising path to giant dielectric and electromechanical responses in ferroelectric materials and devices. This work demonstrates robust and reversible in- to out-of-plane polarization rotation in ultrathin (nanoscale) epitaxial (001) tetragonal PbZr0.3Ti0.7O3...... (PZT-T)/rhombohedral PbZr0.55Ti0.45O3 (PZT-R) ferroelectric bilayers. An underlying 20 nm thick PZT-R layer reduces the symmetry in a 5 nm thick PZT-T layer by imposing an in-plane tensile strain while simultaneously decoupling the PZT-T layer from the substrate. This prevents clamping and facilitates...

  5. Modelling Ferroelectric Nanoparticles in Nematic Liquid Crystals (FERNANO)

    Science.gov (United States)

    2015-02-26

    DIPARTIMENTO DI CHIMICA FISICA ED INORGANICA VIALE DEL RISORGIMENTO 4 BOLOGNA, 40136 ITALY EOARD GRANT #FA8655-11-1-3046 Report...AND ADDRESS(ES) DIPARTIMENTO DI CHIMICA FISICA ED INORGANICA VIALE DEL RISORGIMENTO 4 BOLOGNA, 40136 ITALY 8. PERFORMING ORGANIZATION

  6. Guest–host interaction in ferroelectric liquid crystal–nanoparticle ...

    Indian Academy of Sciences (India)

    Administrator

    SmA*, N*, Iso at –20, 72, 82 and 95 °C. The nanoparti- cle-doped sample of Felix 017/100 was prepared by the dispersion of nanoparticles (NPs) in 2% wt/wt concentra- tion in the pure FLC and termed as doped-FLC. The NPs, used for present study, are ZnO-doped with 10% of Cu. These NPs are prepared by solvothermal ...

  7. Bidimensional distortion in ferroelectric liquid crystals with strong ...

    Indian Academy of Sciences (India)

    1Dipartimento di Fisica del Politecnico di Torino and Istituto Nazionale di Fisica della Materia. (INFM), C.so Duca degli Abruzzi 24, I-10129 Torino, Italy. 2Joint Laboratory of Orientationally Ordered Media (OOM-Lab), C. Duca degli Abruzzi 24,. I-10129 Torino, Italy. 3FSUE, “NIOPIK”, Organic Intermediates and Dyes Institute, ...

  8. A Rapid, Stability Indicating RP-UPLC Method for Simultaneous Determination of Ambroxol Hydrochloride, Cetirizine Hydrochloride and Antimicrobial Preservatives in Liquid Pharmaceutical Formulation.

    Science.gov (United States)

    Trivedi, Rakshit Kanubhai; Patel, Mukesh C; Jadhav, Sushant B

    2011-01-01

    A stability indicating reversed phase ultra performance liquid chromatography (RP-UPLC) method was developed for simultaneous determination of ambroxol hydrochloride (AMB), cetirizine hydrochloride (CTZ), methylparaben (MP) and propylparaben (PP) in liquid pharmaceutical formulation. The desired chromatographic separation was achieved on an Agilent Eclipse plus C18, 1.8 μm (50 × 2.1 mm) column using gradient elution at 237 nm detector wavelength. The optimized mobile phase consists of a mixture of 0.01 M phosphate buffer and 0.1 % triethylamine as a solvent-A and acetonitrile as a solvent-B. The developed method separates AMB, CTZ, MP and PP in presence of twelve known impurities/degradation products and one unknown degradation product within 3.5 min. Stability indicating capability was established by forced degradation experiments and seperation of known and unknown degradation products. The lower limit of quantification was established for AMB, CTZ, MP and PP. The developed RP-UPLC method was validated according to the International Conference on Harmonization (ICH) guidelines. This validated method is applied for simultaneous estimation of AMB, CTZ, MP and PP in commercially available syrup samples. Further, the method can be extended for estimation of AMB, CTZ, MP, PP and levo-cetirizine (LCTZ) in various commercially available dosage forms.

  9. Ferroelectric-carbon nanotube memory devices

    Science.gov (United States)

    Kumar, Ashok; Shivareddy, Sai G.; Correa, Margarita; Resto, Oscar; Choi, Youngjin; Cole, Matthew T.; Katiyar, Ram S.; Scott, James F.; Amaratunga, Gehan A. J.; Lu, Haidong; Gruverman, Alexei

    2012-04-01

    One-dimensional ferroelectric nanostructures, carbon nanotubes (CNT) and CNT-inorganic oxides have recently been studied due to their potential applications for microelectronics. Here, we report coating of a registered array of aligned multi-wall carbon nanotubes (MWCNT) grown on silicon substrates by functional ferroelectric Pb(Zr,Ti)O3 (PZT) which produces structures suitable for commercial prototype memories. Microstructural analysis reveals the crystalline nature of PZT with small nanocrystals aligned in different directions. First-order Raman modes of MWCNT and PZT/MWCNT/n-Si show the high structural quality of CNT before and after PZT deposition at elevated temperature. PZT exists mostly in the monoclinic Cc/Cm phase, which is the origin of the high piezoelectric response in the system. Low-loss square piezoelectric hysteresis obtained for the 3D bottom-up structure confirms the switchability of the device. Current-voltage mapping of the device by conducting atomic force microscopy (c-AFM) indicates very low transient current. Fabrication and functional properties of these hybrid ferroelectric-carbon nanotubes is the first step towards miniaturization for future nanotechnology sensors, actuators, transducers and memory devices.

  10. Amperometric glucose biosensor with remarkable acid stability based on glucose oxidase entrapped in colloidal gold-modified carbon ionic liquid electrode.

    Science.gov (United States)

    Liu, Xiaoying; Zeng, Xiandong; Mai, Nannan; Liu, Yong; Kong, Bo; Li, Yonghong; Wei, Wanzhi; Luo, Shenglian

    2010-08-15

    A colloidal gold-modified carbon ionic liquid electrode was constructed by mixing colloidal gold-modified graphite powder with a solid room temperature ionic liquid n-octyl-pyridinium hexafluorophosphate (OPPF(6)). Glucose oxidase (GOD) was entrapped in this composite matrix and maintained its bioactivity well and displayed excellent stability. The effect conditions of pH, applied potential and GOD loading were examined. Especially, the glucose oxidase entrapped in this carbon ionic liquid electrode fully retained its activity upon stressing in strongly acidic conditions (pH 2.0) for over one hour. The proposed biosensor responds to glucose linearly over concentration range of 5.0x10(-6) to 1.2x10(-3) and 2.6x10(-3) to 1.3x10(-2) M, and the detection limit is 3.5x10(-6) M. The response time of the biosensor is fast (within 10s), and the life time is over two months. The effects of electroactive interferents, such as ascorbic acid, uric acid, can be significantly reduced by a Nafion film casting on the surface of resulting biosensor. Copyright 2010 Elsevier B.V. All rights reserved.

  11. Effect of dietary vitamin E, fishmeal and wood and liquid smoke on the oxidative stability of bacon during 16 weeks' frozen storage.

    Science.gov (United States)

    Coronado, Stephanie A; Trout, Graham R; Dunshea, Frank R; Shah, Nagendra P

    2002-09-01

    Twelve (Large White×Landrace) gilts were randomly allotted in a 2×2 factorial design with the respective factor being dietary vitamin E (10 or 200 mg/kg feed) and dietary fishmeal (0 or 5%). Bacon was manufactured from the meat obtained from the animals after slaughter using wood smoke only or a combination of liquid and wood smoke. The oxidative stability of the bacon was examined over 16 weeks of frozen storage. Lipid oxidation in the product was measured by means of thiobarbituric acid reactive substances (TBARS) and fluorescence shift. Dietary fishmeal supplementation increased lipid oxidation in bacon, while dietary vitamin E supplementation reduced lipid oxidation in the product. Lipid oxidation in frozen bacon was successfully reduced when bacon was manufactured from pigs fed a diet supplemented with or without 200 mg of α-tocopherol per kilogram of feed and processed with a combination of liquid and wood smoke. It is concluded that bacon processed with a combination of liquid and wood smoke was significantly less (Poxidation than bacon processed with wood smoke only.

  12. Selective Ion Transporting Polymerized Ionic Liquid Membrane Separator for Enhancing Cycle Stability and Durability in Secondary Zinc-Air Battery Systems.

    Science.gov (United States)

    Hwang, Ho Jung; Chi, Won Seok; Kwon, Ohchan; Lee, Jin Goo; Kim, Jong Hak; Shul, Yong-Gun

    2016-10-05

    Rechargeable secondary zinc-air batteries with superior cyclic stability were developed using commercial polypropylene (PP) membrane coated with polymerized ionic liquid as separators. The anionic exchange polymer was synthesized copolymerizing 1-[(4-ethenylphenyl)methyl]-3-butylimidazolium hydroxide (EBIH) and butyl methacrylate (BMA) monomers by free radical polymerization for both functionality and structural integrity. The ionic liquid induced copolymer was coated on a commercially available PP membrane (Celguard 5550). The coat allows anionic transfer through the separator and minimizes the migration of zincate ions to the cathode compartment, which reduces electrolyte conductivity and may deteriorate catalytic activity by the formation of zinc oxide on the surface of the catalyst layer. Energy dispersive X-ray spectroscopy (EDS) data revealed the copolymer-coated separator showed less zinc element in the cathode, indicating lower zinc crossover through the membrane. Ion coupled plasma optical emission spectroscopy (ICP-OES) analysis confirmed over 96% of zincate ion crossover was reduced. In our charge/discharge setup, the constructed cell with the ionic liquid induced copolymer casted separator exhibited drastically improved durability as the battery life increased more than 281% compared to the pure commercial PP membrane. Electrochemical impedance spectroscopy (EIS) during the cycle process elucidated the premature failure of cells due to the zinc crossover for the untreated cell and revealed a substantial importance must be placed in zincate control.

  13. Comparison of polarization switching in ferroelectric TGS and relaxor SBN crystals

    Directory of Open Access Journals (Sweden)

    K. Matyjasek

    2013-01-01

    Full Text Available The comparative experimental analysis of polarization reversal kinetics in conventional homogeneous triglycine sulfate (NH2 CH2 COOH3 ˙ H2SO4; TGS and relaxor strontium barium niobate (Sr0.61Ba0.39Nb2O6; SBN crystals have been performed in a broad range of measurement conditions. The experimental data have been collected from microscopic observation of the domain structure, switching current and D-E hysteresis loop registration. The hysteresis loop and dielectric spectra has a strong link to the configuration of ferroelectric microdomains. The domain structure dynamics was examined by the nematic liquid crystal (NLC method.

  14. Strain-induced improper ferroelectricity in Ruddlesden-Popper perovskite halides

    Science.gov (United States)

    Zhang, Yajun; Sahoo, M. P. K.; Shimada, Takahiro; Kitamura, Takayuki; Wang, Jie

    2017-10-01

    Activating multiple symmetry modes and promoting a strong coupling between different modes by strain are indispensable to stabilize a polar ferroelectric (FE) phase from a nonpolar perovskite. Herein, through first-principles calculations, we propose an undiscovered and general avenue to engineering ferroelectricity in photovoltaic perovskites with a Ruddlesden-Popper (RP) structure. It is demonstrated that an experimentally accessible compressive strain can induce an in-plane polarization in RP perovskite halides thin films, resulting in an unusual paraelectric to FE phase transition. The detailed analysis on structure and energy reveals that the unusual FE phase transition in the perovskite halides stems from the strong coupling between strain and antiferrodistortive (AFD) mode. Further calculations show that the strain-AFD coupling-induced ferroelectricity is not only exhibited by perovskite halides but also observed in perovskite sulfides such as Ba3Zr2S7 . Moreover, it is found that the strained FE thin film possesses a suitable band gap of 1.6 eV for photovoltaic application. These findings not only unfold a general way to engineering nonpolar-to-polar transition, but also open an avenue to design optimal FE semiconductors for solar cell applications.

  15. Extrinsic scaling effects on the dielectric response of ferroelectric thin films

    Science.gov (United States)

    Ihlefeld, Jon F.; Vodnick, Aaron M.; Baker, Shefford P.; Borland, William J.; Maria, Jon-Paul

    2008-04-01

    Scaling effects in polycrystalline ferroelectric thin films were investigated by preparing barium titanate in a manner that maintained constant composition and film thickness while allowing systematically increased grain size and crystalline coherence. The average grain dimensions ranged from 60to110nm, and temperature dependence of permittivity analysis revealed diffuse phase transitions in all cases. Maximum permittivity values ranged from 380 to 2040 for the smallest to largest sizes, respectively. Dielectric hysteresis is evident at room temperature for all materials, indicating stability of the ferroelectric phase. Comparison of permittivity values at high electric fields indicates that the intrinsic dielectric response is identical and microstructural artifacts likely have a minimal influence on film properties across the sample series. Permittivity values, however, are substantially smaller than those reported for bulk material with similar grain dimensions. X-ray line broadening measurements were taken for the grain size series at the Cornell High Energy Synchrotron Source (CHESS), which revealed coherent scattering dimensions substantially smaller than the microscopy-determined grain size. Collectively these data sets suggest that permittivity values are influenced not only by grain size but also by the mosaic structure existing within each grain, and that thin film thermal budgets, which are several hundred degrees lower than used for bulk processing, are responsible for reduced crystalline coherence, and likely the origin of degraded electromechanical response in thin film ferroelectrics.

  16. On the stoichiometry and stability of americium(III) complexes with a hydrophilic SO3-Ph-BTP ligand, studied by liquid-liquid extraction.

    Science.gov (United States)

    Steczek, Łukasz; Rejnis, Magdalena; Narbutt, Jerzy; Charbonnel, Marie-Christine; Moisy, Philippe

    1:1 and 1:2 complexes of americium(III) with a hydrophilic anionic SO 3 -Ph-BTP 4- ligand were detected in acidic aqueous nitrate solutions by a solvent extraction method. The determined conditional stability constants of these complexes, log β 1  = 4.35 ± 0.07 and log β 2  = 7.67 ± 0.06, related to 1 M aqueous solutions, are much lower than the literature values for the analogous curium species, determined by TRLFS in very dilute aqueous solutions. There is also no evidence for the existence of the 1:3 Am 3+ complex similar to the reported curium(III) complex. A hypothesis has been formulated to explain these discrepancies. It suggests the necessity to carefully check the equilibria in each phase of solvent extraction systems containing two competing ligands-lipophilic and hydrophilic.

  17. INVESTIGATING THE LONG-TERM STABILITY AND KINETICS OF SUPEROXIDE ION IN DIMETHYL SULFOXIDE CONTAINING IONIC LIQUIDS AND THE APPLICATION OF THIOPHENE DESTRUCTION

    Directory of Open Access Journals (Sweden)

    M. Hayyan

    Full Text Available Abstract The long-term stability of superoxide ion (O2•− with four ionic liquids (ILs, namely 1-(2-methoxyethyl-1-methylpiperidinium tris(pentafluoroethyltrifluorophosphate [MOEMPip][TPTP], 1-(3-methoxypropyl-1-methylpiperidinium bis(trifluoromethylsulfonylimide [MOPMPip][TFSI], N-ethyl-N,N-dimethyl-2-methoxyethylammonium bis(trifluoromethylsulfonylimide [N112,1O2][TFSI], and ethyl-dimethyl-propylammonium bis(trifluoromethylsulfonylimide [EDMPAmm][TFSI], was studied for up to 24 h using two-second intervals. This was achieved by chemical generation of O2•− by dissolution of potassium superoxide salt in dimethyl sulfoxide and the subsequent addition of the IL. The decrease in the concentration of O2•− after the introduction of the IL was monitored using a UV-vis spectrophotometer. The ammonium-based ILs were found to be more stable than piperidinium-based ILs. To the best of our knowledge, this was the first time that O2•− stability with ILs has been monitored continuously for up to 24 h. This should provide a better insight into the stability and kinetics of O2•− for industrial applications and its role in energy-storage devices. The most appropriate IL as a medium was [EDMPAmm][TFSI], and O2•− generated in this IL was used to destroy nearly 90% of thiophene.

  18. Translucency and color stability of resin composite and dental adhesives as modeling liquids - A one-year evaluation.

    Science.gov (United States)

    Sedrez-Porto, José Augusto; Münchow, Eliseu Aldrighi; Cenci, Maximiliano Sérgio; Pereira-Cenci, Tatiana

    2017-07-03

    The aim of this study is to evaluate the influence of modeling liquids on the translucency and color shade of resin composites (RCs) after one year of storage. RC specimens were prepared using either a conventional insertion technique (control; without modeling liquid) or a restorative dental modeling insertion technique (RDMIT) with dental adhesives as modeling liquids (Scotchbond™ Multi-Purpose [SBMP; 3M ESPE] or Adper™ Single Bond 2 [SB; 3M ESPE]). The initial colors of the specimens were obtained with a digital spectrophotometer and the CIEL*a*b* color system, after which specimens were stored (37°C) in distilled water or red wine for 12 months. Color measurements were reassessed after 6 and 12 months of storage, and scanning electron microscopy was performed after 12 months. Translucency and color change (ΔE*) were calculated and analyzed using ANOVA and Tukey's test (α = 5%). RC samples prepared via RDMIT showed a translucency similar to that of control samples. ΔE* was also less intense for RCs containing SBMP than for RCs containing SB. Specimens stored in wine showed a clear pattern of degradation, especially in the control group, and surface degradation seemed to be less intense for specimens prepared with SBMP and SB than for specimens without. Specimens stored in water did not show clear evidence of surface degradation. RDMIT appears to be an interesting approach to reduce ΔE* in RCs over time without negative effects on the translucency of the material. However, the modeling liquid should feature a hydrophobic composition, similar to that used in the SBMP group, the achieve the best results.

  19. Translucency and color stability of resin composite and dental adhesives as modeling liquids – A one-year evaluation

    Directory of Open Access Journals (Sweden)

    José Augusto SEDREZ-PORTO

    2017-07-01

    Full Text Available Abstract The aim of this study is to evaluate the influence of modeling liquids on the translucency and color shade of resin composites (RCs after one year of storage. RC specimens were prepared using either a conventional insertion technique (control; without modeling liquid or a restorative dental modeling insertion technique (RDMIT with dental adhesives as modeling liquids (Scotchbond™ Multi-Purpose [SBMP; 3M ESPE] or Adper™ Single Bond 2 [SB; 3M ESPE]. The initial colors of the specimens were obtained with a digital spectrophotometer and the CIEL*a*b* color system, after which specimens were stored (37°C in distilled water or red wine for 12 months. Color measurements were reassessed after 6 and 12 months of storage, and scanning electron microscopy was performed after 12 months. Translucency and color change (ΔE* were calculated and analyzed using ANOVA and Tukey’s test (α = 5%. RC samples prepared via RDMIT showed a translucency similar to that of control samples. ΔE* was also less intense for RCs containing SBMP than for RCs containing SB. Specimens stored in wine showed a clear pattern of degradation, especially in the control group, and surface degradation seemed to be less intense for specimens prepared with SBMP and SB than for specimens without. Specimens stored in water did not show clear evidence of surface degradation. RDMIT appears to be an interesting approach to reduce ΔE* in RCs over time without negative effects on the translucency of the material. However, the modeling liquid should feature a hydrophobic composition, similar to that used in the SBMP group, the achieve the best results.

  20. Ferroelectrics: A pathway to switchable surface chemistry and catalysis

    Science.gov (United States)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab; Altman, Eric I.

    2016-08-01

    It has been known for more than six decades that ferroelectricity can affect a material's surface physics and chemistry thereby potentially enhancing its catalytic properties. Ferroelectrics are a class of materials with a switchable electrical polarization that can affect surface stoichiometry and electronic structure and thus adsorption energies and modes; e.g., molecular versus dissociative. Therefore, ferroelectrics may be utilized to achieve switchable surface chemistry whereby surface properties are not fixed but can be dynamically controlled by, for example, applying an external electric field or modulating the temperature. Several important examples of applications of ferroelectric and polar materials in photocatalysis and heterogeneous catalysis are discussed. In photocatalysis, the polarization direction can control band bending at water/ferroelectric and ferroelectric/semiconductor interfaces, thereby facilitating charge separation and transfer to the electrolyte and enhancing photocatalytic activity. For gas-surface interactions, available results suggest that using ferroelectrics to support catalytically active transition metals and oxides is another way to enhance catalytic activity. Finally, the possibility of incorporating ferroelectric switching into the catalytic cycle itself is described. In this scenario, a dynamic collaboration of two polarization states can be used to drive reactions that have been historically challenging to achieve on surfaces with fixed chemical properties (e.g., direct NOx decomposition and the selective partial oxidation of methane). These predictions show that dynamic modulation of the polarization can help overcome some of the fundamental limitations on catalytic activity imposed by the Sabatier principle.

  1. Phase transition in triglycine family of hydrogen bonded ferroelectrics

    Indian Academy of Sciences (India)

    Hydrogen bonded ferroelectric crystals form a subclass of ferroelectrics in which hydrogen bonds play an important role in determining the properties. Triglycine family is one such class which includes triglycine sulphate (TGS), triglycine selenate. (TGSe), triglycine fluoroberyllate (TGFBe), mixed crystals like ...

  2. The operational mechanism of ferroelectric-driven organic resistive switches

    NARCIS (Netherlands)

    Kemerink, M.; Asadi, K.; Blom, P.W.M.; Leeuw, D.M. de

    2012-01-01

    The availability of a reliable memory element is crucial for the fabrication of 'plastic' logic circuits. We use numerical simulations to show that the switching mechanism of ferroelectric-driven organic resistive switches is the stray field of the polarized ferroelectric phase. The stray field

  3. Single Crystal Relaxor Ferroelectrics by Seeded Polycrystal Conversion

    National Research Council Canada - National Science Library

    Harmer, Martin

    2003-01-01

    ...) to ferroelectric materials. Initial work at Lehigh established the feasibility of using the SPC process to grow single crystals of the relaxor-based ferroelectric PbMg(1 /3)Nb(2/3))O(3-) 5mol%PbTiO3 (PMN-3 5PT...

  4. Ferroelectricity in Sodium Nitrite Thin Films | Britwum | Journal of the ...

    African Journals Online (AJOL)

    Investigations have been conducted on the ferroelectric property of thin films of NaNO2. The thin films were prepared with the dip coating technique. The phase transition was investigated by observing the change in the dielectric constant with temperature change. The presence of ferro-electricity was investigated with a ...

  5. Origin of multiple memory states in organic ferroelectric field-effect transistors

    NARCIS (Netherlands)

    Kam, B.; Li, X.; Cristoferi, C.; Smits, E.C.P.; Mityashin, A.; Schols, S.; Genoe, J.; Gelinck, G.H.; Heremans, P.

    2012-01-01

    In this work, we investigate the ferroelectric polarization state in metal-ferroelectric-semiconductor-metal structures and in ferroelectric field-effect transistors (FeFET). Poly(vinylidene fluoride-trifluoroethylene) and pentacene was used as the ferroelectric and semiconductor, respectively. This

  6. Characteristics of Radio-Frequency Circuits Utilizing Ferroelectric Capacitors

    Science.gov (United States)

    Eskridge, Michael; Gui, Xiao; MacLeod, Todd; Ho, Fat D.

    2011-01-01

    Ferroelectric capacitors, most commonly used in memory circuits and variable components, were studied in simple analog radio-frequency circuits such as the RLC resonator and Colpitts oscillator. The goal was to characterize the RF circuits in terms of frequency of oscillation, gain, etc, using ferroelectric capacitors. Frequencies of oscillation of both circuits were measured and studied a more accurate resonant frequency can be obtained using the ferroelectric capacitors. Many experiments were conducted and data collected. A model to simulate the experimental results will be developed. Discrepancies in gain and frequency in these RF circuits when conventional capacitors are replaced with ferroelectric ones were studied. These results will enable circuit designers to anticipate the effects of using ferroelectric components in their radio- frequency applications.

  7. The Modification of Ferroelectric Surfaces for Catalysis

    Science.gov (United States)

    Herdiech, Matthew William

    Ferroelectrics are a class of materials in which a net dipole can be associated with each repeat unit, resulting in a potentially large electric field through the material. The ability to reversibly switch the polarization direction by applying an external electric field distinguishes ferroelectrics from polar orientations of ordinary materials. Recent studies exploring the reactivity of ferroelectric surfaces toward polar molecules have shown that the heats of adsorption for these molecules are polarization dependent, but the surfaces tend to be unreactive. Despite the inertness of ferroelectric surfaces, their use as supports for catalytically active materials could yield novel reactivity. As even metal oxides that are generally considered inert can influence the catalytic properties of supported layers, a ferroelectric support may offer the opportunity to modulate catalytic activity since charge compensation of the polar surfaces might include chemical and electronic reconstructions of the active layer. In this thesis, the fabrication of active layers with polarization dependent properties was investigated by coating ferroelectric substrates with catalytically active oxides that are likely to grow in a layer-by-layer manner. Two systems in particular were explored: chromium oxide on ferroelectric lithium niobate (Cr2O3/LiNbO3), and ruthenium oxide on ferroelectric lead zirconate titanate (RuO2/Pb(Zr0.2Ti0.8)O 3). The chromium oxide and ruthenium oxide films were characterized with X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), and reflection high energy electron diffraction (RHEED). Additionally, the chromium oxide films were characterized with X-ray diffraction (XRD) and X-ray reflectivity (XRR) measurements, and the ruthenium oxide films were characterized with ion scattering spectroscopy (ISS) measurements. The reactivity of the films was investigated using temperature programmed desorption (TPD) measurements. In particular

  8. Structure and switching of in-plane ferroelectric nano-domains in strained PbxSr1-xTiO3 thin films

    Energy Technology Data Exchange (ETDEWEB)

    Matzen, Sylivia [University of Groningen, The Netherlands; Nesterov, Okeksiy [ORNL; Rispens, Gregory [University of Groningen, The Netherlands; Heuver, J. A. [University of Groningen, The Netherlands; Bark, C [University of Wisconsin, Madison; Biegalski, Michael D [ORNL; Christen, Hans M [ORNL; Noheda, Beatriz [University of Groningen, The Netherlands

    2014-01-01

    Nanoscale ferroelectrics, the active elements of a variety of nanoelectronic devices, develop denser and richer domain structures than the bulk counterparts. With shrinking device sizes understanding and controlling domain formation in nanoferroelectrics is being intensely studied. Here we show that a precise control of the epitaxy and the strain allows stabilizing a hierarchical domain architecture in PbxSr1-xTiO3 thin films, showing periodic, purely in-plane polarized, ferroelectric nano-domains that can be switched by a scanning probe.

  9. Performance and stability tests of bare high purity germanium detectors in liquid argon for the GERDA experiment

    Energy Technology Data Exchange (ETDEWEB)

    Barnabe Heider, Marik

    2009-05-27

    GERDA will search for neutrinoless double beta decay of {sup 76}Ge by using a novel approach of bare germanium detectors in liquid argon (LAr). Enriched germanium detectors from the previous Heidelberg-Moscow and IGEX experiments have been reprocessed and will be deployed in GERDA Phase-I. At the center of this thesis project is the study of the performance of bare germanium detectors in cryogenic liquids. Identical detector performance as in vacuum cryostats (2.2 keV FWHM at 1.3 MeV) was achieved in cryogenic liquids with a new low-mass detector assembly and contacts. One major result is the discovery of a radiation induced leakage current (LC) increase when operating bare detectors with standard passivation layers in LAr. Charge collection and build-up on the passivation layer were identified as the origin of the LC increase. It was found that diodes without passivation do not exhibit this feature. Three month-long stable operation in LAr at {proportional_to} 5 pA LC under periodic gamma irradiation demonstrated the suitability of the modi ed detector design. Based on these results, all Phase-I detectors were reprocessed without passivation layer and subsequently successfully characterized in LAr in the GERDA underground Detector Laboratory. The mass loss during the reprocessing was {proportional_to}300 g out of 17.9 kg and the exposure above ground {proportional_to} 5 days. This results in a negligible cosmogenic background increase of {proportional_to} 5.10{sup -4} cts/(keV.kg.y) at {sup 76}Ge Q{sub {beta}}{sub {beta}} for {sup 60}Co and {sup 68}Ge. (orig.)

  10. Inversion of particle-stabilized emulsions of partially miscible liquids by mild drying of modified silica particles.

    Science.gov (United States)

    White, Kathryn A; Schofield, Andrew B; Wormald, Philip; Tavacoli, Joseph W; Binks, Bernard P; Clegg, Paul S

    2011-07-01

    Using a system of modified silica particles and mixtures of water and 2,6-lutidine to form particle-stabilized emulsions, we show that subtle alterations to the hydration of the particle surface can cause major shifts in emulsion structure. We use fluorescence confocal microscopy, solid state nuclear magnetic resonance (NMR) and thermo-gravimetric analysis (TGA) to explore this sensitivity, along with other shifts caused by modifications to the silica surface chemistry. The silica particles are prepared by a variant of the Stöber procedure and are modified by the inclusion of 3-(aminopropyl)triethoxysilane and the dye fluorescein isothiocyanate. Treatment prior to emulsification consists of gently drying the particles under carefully controlled conditions. In mixtures of water and 2,6-lutidine of critical composition, the particles stabilize droplet emulsions and bijels. Decreasing particle hydration yields an inversion of the emulsions from lutidine-in-water (L/W) to water-in-lutidine (W/L), with bijels forming around inversion. So dependent is the emulsion behavior on particle hydration that microscopic differences in drying within a particle sample can cause differences in the wetting behavior of that sample, which helps to stabilize multiple emulsions. The formation of bijels at emulsion inversion is also crucially dependent on the surface modification of the silica. Copyright © 2011 Elsevier Inc. All rights reserved.

  11. Quantum Hall Ferroelectrics and Nematics in Multivalley Systems

    Directory of Open Access Journals (Sweden)

    Inti Sodemann

    2017-12-01

    Full Text Available We study broken symmetry states at integer Landau-level fillings in multivalley quantum Hall systems whose low-energy dispersions are anisotropic. When the Fermi surface of individual pockets lacks twofold rotational symmetry, like in bismuth (111 [Feldman et al. , Observation of a Nematic Quantum Hall Liquid on the Surface of Bismuth, Science 354, 316 (2016SCIEAS0036-807510.1126/science.aag1715] and in Sn_{1-x}Pb_{x}Se (001 [Dziawa et al., Topological Crystalline Insulator States in Pb_{1-x}Sn_{x}Se, Nat. Mater. 11, 1023 (2012NMAACR1476-112210.1038/nmat3449] surfaces, interactions tend to drive the formation of quantum Hall ferroelectric states. We demonstrate that the dipole moment in these states has an intimate relation to the Fermi surface geometry of the parent metal. In quantum Hall nematic states, like those arising in AlAs quantum wells, we demonstrate the existence of unusually robust Skyrmion quasiparticles.

  12. Synthesis and physical properties of new surfactants based on ionic liquids: Improvement of thermal stability and mechanical behaviour of high density polyethylene nanocomposites.

    Science.gov (United States)

    Livi, Sébastien; Duchet-Rumeau, Jannick; Pham, Thi Nhàn; Gérard, Jean-François

    2011-02-15

    Ionic liquids based on alkyltriphenyl phosphonium and dialkyl imidazolium cations with long alkyl chains have been synthesized and used as new surfactants for cationic exchange of layered silicates. The influence of the alkyl chain length and the chemical nature of the conteranion or of the cation on the thermal stability of these new intercalating agents and on imidazolium- (MMT-I) or phosphonium- (MMT-P) modified montmorillonites have been analyzed by thermogravimetric analysis (TGA). Thermoplastic nanocomposites based on these modified montmorillonites with a very low amount of nanofillers (1wt.%) have been processed by melt mixing using a twin screw extruder. The distribution of the clay layers in a high density polyethylene (HDPE) matrix was characterized and finally the mechanical and thermal properties of the corresponding nanocomposites were determined. Copyright © 2010 Elsevier Inc. All rights reserved.

  13. Long-term stability of liquid ionization chambers with regard to their qualification as local reference dosimeters for low dose-rate absorbed dose measurements in water.

    Science.gov (United States)

    Bahar-Gogani, J; Grindborg, J E; Johansson, B E; Wickman, G

    2001-03-01

    The long-term sensitivity and calibration stability of liquid ionization chambers (LICs) has been studied at a local and a secondary standards dosimetry laboratory over a period of 3 years. The chambers were transported several times by mail between the two laboratories for measurements. The LICs used in this work are designed for absorbed dose measurements in the dose rate region of 0.1-100 mGy min(-1) and have a liquid layer thickness of 1 mm and a sensitive volume of 16.2 mm3. The liquids used as sensitive media in the chambers are mixtures of isooctane (C8H18) and tetramethylsilane (Si(CH3)4) in different proportions (about 2 to 1). Operating at a polarizing voltage of 300 V the leakage current of the chambers was stable and never exceeded 3% of the observable current at a dose rate of about 1 mGy min(-1). The volume sensitivity of the chambers was measured to be of the order of 10(-9) C Gy(-1) mm3. No systematic changes in the absorbed dose to water calibration was observed for any of the chambers during the test period (sigma Measurements showed that the LIC response varies by 0.15% per 1% change in applied voltage around 300 V. No significant change could be observed in the LIC sensitivity after a single absorbed dose of 15 kGy. The results indicate that the LIC can be made to serve as a calibration transfer instrument and a reference detector for absorbed dose to water determinations providing good precision and long-term reproducibility.

  14. Dielectric and electro-optical properties of polymer-stabilized liquid crystal. II. Polymer PiBMA dispersed in MBBA

    Science.gov (United States)

    Tripathi, Pankaj Kumar; Pande, Mukti; Singh, Shri

    2016-09-01

    In continuation of our earlier work (Pande et al. in Appl Phys A 122:217-226, 2016), we report the results of dielectric and electro-optical properties of pure MBBA and PSLC (polymer PiBMA dispersed in MBBA) systems. The polymer networks domains formed are found to be anisotropic and are oriented in the direction of electric field for both the planar and homeotropic alignment cells. The dielectric anisotropy, optical anisotropy, response time, threshold voltage, splay elastic constant and rotational viscosity were observed for both the LC and PSLC systems with electric field. The liquid crystal properties are affected significantly with increasing concentration of polymer in pure LC material. It has been observed that the polymer networks interaction plays a major role in changing the properties of PSLC system. The effect of dielectric loss and dielectric permittivity on both pure LC and PSLC systems is also discussed.

  15. Unravelling and controlling hidden imprint fields in ferroelectric capacitors.

    Science.gov (United States)

    Liu, Fanmao; Fina, Ignasi; Bertacco, Riccardo; Fontcuberta, Josep

    2016-04-28

    Ferroelectric materials have a spontaneous polarization that can point along energetically equivalent, opposite directions. However, when ferroelectric layers are sandwiched between different metallic electrodes, asymmetric electrostatic boundary conditions may induce the appearance of an electric field (imprint field, Eimp) that breaks the degeneracy of the polarization directions, favouring one of them. This has dramatic consequences on functionality of ferroelectric-based devices such as ferroelectric memories or photodetectors. Therefore, to cancel out the Eimp, ferroelectric components are commonly built using symmetric contact configuration. Indeed, in this symmetric contact configuration, when measurements are done under time-varying electric fields of relatively low frequency, an archetypical symmetric single-step switching process is observed, indicating Eimp ≈ 0. However, we report here on the discovery that when measurements are performed at high frequency, a well-defined double-step switching is observed, indicating the presence of Eimp. We argue that this frequency dependence originates from short-living head-to-head or tail-to-tail ferroelectric capacitors in the device. We demonstrate that we can modulate Eimp and the life-time of head-to-head or tail-to-tail polarization configurations by adjusting the polarization screening charges by suitable illumination. These findings are of relevance to understand the effects of internal electric fields on pivotal ferroelectric properties, such as memory retention and photoresponse.

  16. X-ray linear dichroism dependence on ferroelectric polarization.

    Science.gov (United States)

    Polisetty, S; Zhou, J; Karthik, J; Damodaran, A R; Chen, D; Scholl, A; Martin, L W; Holcomb, M

    2012-06-20

    X-ray absorption spectroscopy and photoemission electron microscopy are techniques commonly used to determine the magnetic properties of thin films, crystals, and heterostructures. Recently, these methods have been used in the study of magnetoelectrics and multiferroics. The analysis of such materials has been compromised by the presence of multiple order parameters and the lack of information on how to separate these coupled properties. In this work, we shed light on the manifestation of dichroism from ferroelectric polarization and atomic structure using photoemission electron microscopy and x-ray absorption spectroscopy. Linear dichroism arising from the ferroelectric order in the PbZr0:2Ti0:8O3 thin films was studied as a function of incident x-ray polarization and geometry to unambiguously determine the angular dependence of the ferroelectric contribution to the dichroism. These measurements allow us to examine the contribution of surface charges and ferroelectric polarization as potential mechanisms for linear dichroism. The x-ray linear dichroism from ferroelectric order revealed an angular dependence based on the angle between the ferroelectric polarization direction and the x-ray polarization axis, allowing a formula for linear dichroism in ferroelectric samples to be defined.

  17. Stability of nicotinate and dodecyl sulfate in a Lewis acidic ionic liquid for aluminum electroplating and characterization of their degradation products.

    Science.gov (United States)

    Kosmus, Patrick; Steiner, Oliver; Goessler, Walter; Gollas, Bernhard; Fauler, Gisela

    2016-04-01

    Plating bath additives are essential for optimization of the morphology of electroplated layers. The ionic liquid 1-ethyl-3-methylimidazolium (EMIM) chloride plus 1.5 mol equivalents of AlCl3 has great potential for electroplating of aluminum. In this study, the chemical and electrochemical stability of the additives EMIM-nicotinate and sodium dodecyl sulfate and their effect on the stability of EMIM was investigated and analyzed. Nicotinate and its electrochemical decomposition product β-picoline could be detected and we show with a single HPLC-UV-MS method that EMIM is not affected by the decomposition of this additive. An adapted standard HPLC-UV-MS method together with GC-MS and ion chromatography was used to analyze the decomposition products of SDS and possible realkylation products of EMIM. Several volatile medium and short chain-length alkanes as well as sulfate ions have been found as decomposition products of SDS. Alkenium ions formed as intermediates during the decomposition of SDS realkylate EMIM to produce mono- up to pentasubstituted alkyl-imidazoles. A reaction pathway involving Wagner-Meerwein rearrangements and Friedel-Crafts alkylations has been suggested to account for the formation of the detected products. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Controlled Charging of Ferroelastic Domain Walls in Oxide Ferroelectrics.

    Science.gov (United States)

    Wei, Xian-Kui; Sluka, Tomas; Fraygola, Barbara; Feigl, Ludwig; Du, Hongchu; Jin, Lei; Jia, Chun-Lin; Setter, Nava

    2017-02-22

    Conductive domain walls (DWs) in ferroic oxides as device elements are a highly attractive research topic because of their robust and agile response to electric field. Charged DWs possessing metallic-type conductivity hold the highest promises in this aspect. However, their intricate creation, low stability, and interference with nonconductive DWs hinder their investigation and the progress toward future applications. Here, we find that conversion of the nominally neutral ferroelastic 90° DWs into partially charged DWs in Pb(Zr 0.1 Ti 0.9 )O 3 thin films enables easy and robust control over the DW conductivity. By employing transmission electron microscopy, conductive atomic force microscopy and phase-field simulation, our study reveals that charging of the ferroelastic DWs is controlled by mutually coupled DW bending, type of doping, polarization orientation and work-function of the adjacent electrodes. Particularly, the doping outweighs other parameters in controlling the DW conductivity. Understanding the interplay of these key parameters not only allows us to control and optimize conductivity of such ferroelastic DWs in the oxide ferroelectrics but also paves the way for utilization of DW-based nanoelectronic devices in the future.

  19. Elastic recoil detection analysis of ferroelectric films

    Energy Technology Data Exchange (ETDEWEB)

    Stannard, W.B.; Johnston, P.N.; Walker, S.R.; Bubb, I.F. [Royal Melbourne Inst. of Tech., VIC (Australia); Scott, J.F. [New South Wales Univ., Kensington, NSW (Australia); Cohen, D.D.; Dytlewski, N. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia)

    1996-12-31

    There has been considerable progress in developing SrBi{sub 2}Ta{sub 2}O{sub 9} (SBT) and Ba{sub O.7}Sr{sub O.3}TiO{sub 3} (BST) ferroelectric films for use as nonvolatile memory chips and for capacitors in dynamic random access memories (DRAMs). Ferroelectric materials have a very large dielectric constant ( {approx} 1000), approximately one hundred times greater than that of silicon dioxide. Devices made from these materials have been known to experience breakdown after a repeated voltage pulsing. It has been suggested that this is related to stoichiometric changes within the material. To accurately characterise these materials Elastic Recoil Detection Analysis (ERDA) is being developed. This technique employs a high energy heavy ion beam to eject nuclei from the target and uses a time of flight and energy dispersive (ToF-E) detector telescope to detect these nuclei. The recoil nuclei carry both energy and mass information which enables the determination of separate energy spectra for individual elements or for small groups of elements In this work ERDA employing 77 MeV {sup 127}I ions has been used to analyse Strontium Bismuth Tantalate thin films at the heavy ion recoil facility at ANSTO, Lucas Heights. 9 refs., 5 figs.

  20. The AHA Moment: Assessment of the Redox Stability of Ionic Liquids Based on Aromatic Heterocyclic Anions (AHAs) for Nuclear Separations and Electric Energy Storage.

    Science.gov (United States)

    Shkrob, Ilya A; Marin, Timothy W

    2015-11-19

    Because of their extended conjugated bond network, aromatic compounds generally have higher redox stability than less saturated compounds. We conjectured that ionic liquids (ILs) consisting of aromatic heterocyclic anions (AHAs) may exhibit improved radiation and electrochemical stability. Such properties are important in applications of these ILs as diluents in radionuclide separations and electrolytes in the electric energy storage devices. In this study, we systematically examine the redox chemistry of the AHAs. Three classes of these anions have been studied: (i) simple 5-atom ring AHAs, such as the pyrazolide and triazolides, (ii) AHAs containing an adjacent benzene ring, and (iii) AHAs containing electron-withdrawing groups that were introduced to reduce their basicity and interaction with metal ions. It is shown that fragmentation in the reduced and oxidized states of these AHAs does not generally occur, and the two main products, respectively, are the H atom adduct and the imidyl radical. The latter species occurs either as an N σ-radical or as an N π-radical, depending on the length of the N-N bond, and the state that is stabilized in the solid matrix is frequently different from that having the lowest energy in the gas phase. In some instances, the formation of the sandwich π-stack dimer radical anions has been observed. For trifluoromethylated anions, H adduct formation did not occur; instead, there was facile loss of fluoride from their fluorinated groups. The latter can be problematic in nuclear separations, but beneficial in batteries. Overall, our study suggests that AHA-based ILs are viable candidates for use as radiation-exposed diluents and electrolytes.

  1. Structural, dielectric and ferroelectric characterization of PZT thin films

    Directory of Open Access Journals (Sweden)

    Araújo E.B.

    1999-01-01

    Full Text Available In this work ferroelectric thin films of PZT were prepared by the oxide precursor method, deposited on Pt/Si substrate. Films of 0.5 mm average thickness were obtained. Electrical and ferroelectric characterization were carried out in these films. The measured value of the dielectric constant for films was 455. Ferroelectricity was confirmed by Capacitance-Voltage (C-V characteristics and P-E hysteresis loops. Remanent polarization for films presented value around 5.0 µC/cm2 and a coercive field of 88.8 kV/cm.

  2. STABILITY AND VIBRATION OF DRILL STRINGS WITH INTERNAL FLOWS OF LIQUIDS IN THE CHANNELS OF HORIZONTAL BORE-HOLES

    Directory of Open Access Journals (Sweden)

    Andrusenko E.N.

    2015-12-01

    Full Text Available In connection with elaboration of new technologies of hydrocarbons extraction from shales, in the oil and gas industry, the great attention is payed to the problems of drilling inclined and horizontal bore-holes. The peculiarities of these bore-hole drivage consist in essential influence of friction and contact forces on proceeding of drilling processes. In this paper, the problem about bifurcational buckling and small bending vibration of a rotating drill string lying in the channel of a horizontal bore-hole is stated. With allowance made for friction forces and additional constraint reactions, differential equations are deduced, their eigen-value solutions describing stability and vibration of the drill string of finite and infinite lengths are received.

  3. Rayleigh-Benard stability and the validity of quasi-Boussinesq or quasi-anelastic liquid approximations

    CERN Document Server

    Alboussiere, Thierry

    2016-01-01

    The linear stability threshold of the Rayleigh-Benard configuration is analyzed with compressible effects taken into account. It is assumed that the fluid obeys a Newtonian rheology and Fourier's law of thermal transport with constant, uniform (dynamic) viscosity and thermal conductivity in a uniform gravity field. Top and bottom boundaries are maintained at different constant temperatures and we consider here boundary conditions of zero tangential stress and impermeable walls. Under these conditions, and with the Boussinesq approximation, Rayleigh (1916) first obtained analytically the critical value 27pi^4/4 for a dimensionless parameter, now known as the Rayleigh number, at the onset of convection. This manuscript describes the changes of the critical Rayleigh number due to the compressibility of the fluid, measured by the dimensionless dissipation parameter D and due to a finite temperature difference between the hot and cold boundaries, measured by a dimensionless temperature gradient a. Different equati...

  4. Utilizing mechanical loads and flexoelectricity to induce and control complicated evolution of domain patterns in ferroelectric nanofilms

    Science.gov (United States)

    Chen, Weijin; Zheng, Yue; Feng, Xue; Wang, Biao

    2015-06-01

    We have conducted a systematical investigation to reveal the stability and evolution path of various ferroelectric domain patterns in nanofilms subjected to mechanical loads and related flexoelectric field. Within a rigorous framework of flexoelectricity, a phase-field approach has been established for simulating the domain structure of ferroelectric nanofilms. The electromechanical fields of the nanofilms are numerically solved by a fast Fourier transform technique (FFT) based on the combination of Khachaturyan's microscopic elastic theory and Stroh's formalism of anisotropic elasticity. Using this approach, we simulate eight types of domain patterns that can be stabilized in the nanofilms. It is further demonstrated that these domain patterns can be significantly affected by the mechanical loads and related flexoelectric field and exhibit fruitful evolution paths. To adapt the applied mechanical strain and strain gradient, the domain pattern may remain stable, evolve into another polydomain pattern, or become a monodomain state (an effect of domain erasing). The domain fraction, detailed domain morphology, average stresses in the nanofilms, average polarization and temporal evolution characteristics of the domain patterns under various mechanical loads and sources of flexoelectric field have been analyzed. This investigation should provide instructive information for the practical application of ferroelectric nanofilms under complex and changeable mechanical conditions.

  5. Stability Indicating Liquid Chromatographic Method for Estimation of Trihexyphenidyl Hydrochloride and Risperidone in Tablet Formulation: Development and Validation Consideration

    Directory of Open Access Journals (Sweden)

    Patel Bhaumik

    2014-01-01

    Full Text Available This paper describes validated reverse phase high-performance liquid chromatographic (RP-HPLC method for simultaneous estimation of trihexyphenidyl hydrochloride (THP and risperidone (RSP in the pure powder form and in combined tablet dosage form. The HPLC separation was achieved on a core shell C18 (100 mm length × 4.6 mm, 2.6 μm particle size using methanol : ammonium acetate buffer 1% (85 : 15 v/v; pH-6.5 as mobile phase and delivered at flow rate of 0.8 mL/min. The calibration plot showed good linear relationship with r2 = 0.997 ± 0.001 for THP and r2 = 0.998 ± 0.001 for RSP in concentration range of 50–175 μg/mL and 50–175 μg/mL, respectively. LOD and LOQ were found to be 0.40 and 1.29 μg/mL for THP and 1.24 and 3.92 μg/mL for RSP. Assay of THP and RSP was found to be 100.16 ± 0.03% and 99.83 ± 0.02%, respectively. THP and RSP were subjected to different stress conditions (acidic, basic, oxidative, thermal, and photolytic degradation. The degraded product peaks were well resolved from the pure drug peak. The method was successfully validated as per the ICH guidelines. The developed RP-HPLC method was successfully applied for the estimation of THP and RSP in tablet dosage form.

  6. Dimensional scaling of perovskite ferroelectric thin films

    Science.gov (United States)

    Keech, Ryan R.

    Dimensional size reduction has been the cornerstone of the exponential improvement in silicon based logic devices for decades. However, fundamental limits in the device physics were reached ˜2003, halting further reductions in clock speed without significant penalties in power consumption. This has motivated the research into next generation transistors and switching devices to reinstate the scaling laws for clock speed. This dissertation aims to support the scaling of devices that are based on ferroelectricity and piezoelectricity and to provide a roadmap for the corresponding materials performance. First, a scalable growth process to obtain highly {001}-oriented lead magnesium niobate - lead titanate (PMN-PT) thin films was developed, motivated by the high piezoelectric responses observed in bulk single crystals. It was found that deposition of a 2-3 nm thick PbO buffer layer on {111} Pt thin film bottom electrodes, prior to chemical solution deposition of PMN-PT reduces the driving force for Pb diffusion from the PMN-PT to the bottom electrode, and facilitates nucleation of {001}-oriented perovskite grains. Energy dispersive spectroscopy demonstrated that up to 10% of the Pb from a PMN-PT precursor solution may diffuse into the bottom electrode. PMN-PT grains with a mixed {101}/{111} orientation in a matrix of Pb-deficient pyrochlore phase were then promoted near the interface. When this is prevented, phase pure films with {001} orientation with Lotgering factors of 0.98-1.0, can be achieved. The resulting films of only 300 nm in thickness exhibit longitudinal effective d33,f coefficients of ˜90 pm/V and strain values of ˜1% prior to breakdown. 300 nm thick epitaxial and polycrystalline lead magnesium niobate - lead titanate (70PMN-30PT) blanket thin films were studied for the relative contributions to property thickness dependence from interfacial and grain boundary low permittivity layers. Epitaxial PMN-PT films were grown on SrRuO 3 /(001)SrTiO3, while

  7. Periodic arrays of flux-closure domains in ferroelectric thin films with oxide electrodes

    Science.gov (United States)

    Li, S.; Zhu, Y. L.; Wang, Y. J.; Tang, Y. L.; Liu, Y.; Zhang, S. R.; Ma, J. Y.; Ma, X. L.

    2017-07-01

    Flux-closure domain structures in ferroelectric thin films are considered to have potential applications in electronic devices. It is usually believed that these structures are stabilized by the depolarization field and the contact with electrodes tends to screen the depolarization field and may limit their formation. In this work, the influence of oxide electrodes (SrRuO3 and La0.7Sr0.3MnO3) on the formation of flux-closure domains in PbTiO3 thin films deposited on (110)-oriented GdScO3 substrates by pulsed laser deposition was investigated by Cs-corrected transmission electron microscopy. It is found that periodic flux-closure domain arrays can be stabilized in PbTiO3 films when the top and bottom electrodes are symmetric, while a/c domains appear when asymmetric electrodes are applied. The influence of asymmetric electrodes on the domain configuration is proposed to have a connection with their different work functions and conductivity types. These results are expected to shed light on understanding the nature of flux-closure domains in ferroelectrics and open some research possibilities, such as the evolution of these structures under external electric fields.

  8. Hybrid dual gate ferroelectric memory for multilevel information storage

    KAUST Repository

    Khan, Yasser

    2015-01-01

    Here, we report hybrid organic/inorganic ferroelectric memory with multilevel information storage using transparent p-type SnO semiconductor and ferroelectric P(VDF-TrFE) polymer. The dual gate devices include a top ferroelectric field-effect transistor (FeFET) and a bottom thin-film transistor (TFT). The devices are all fabricated at low temperatures (∼200°C), and demonstrate excellent performance with high hole mobility of 2.7 cm2 V-1 s-1, large memory window of ∼18 V, and a low sub-threshold swing ∼-4 V dec-1. The channel conductance of the bottom-TFT and the top-FeFET can be controlled independently by the bottom and top gates, respectively. The results demonstrate multilevel nonvolatile information storage using ferroelectric memory devices with good retention characteristics.

  9. Concurrent transition of ferroelectric and magnetic ordering near room temperature.

    Science.gov (United States)

    Ko, Kyung-Tae; Jung, Min Hwa; He, Qing; Lee, Jin Hong; Woo, Chang Su; Chu, Kanghyun; Seidel, Jan; Jeon, Byung-Gu; Oh, Yoon Seok; Kim, Kee Hoon; Liang, Wen-I; Chen, Hsiang-Jung; Chu, Ying-Hao; Jeong, Yoon Hee; Ramesh, Ramamoorthy; Park, Jae-Hoon; Yang, Chan-Ho

    2011-11-29

    Strong spin-lattice coupling in condensed matter gives rise to intriguing physical phenomena such as colossal magnetoresistance and giant magnetoelectric effects. The phenomenological hallmark of such a strong spin-lattice coupling is the manifestation of a large anomaly in the crystal structure at the magnetic transition temperature. Here we report that the magnetic Néel temperature of the multiferroic compound BiFeO(3) is suppressed to around room temperature by heteroepitaxial misfit strain. Remarkably, the ferroelectric state undergoes a first-order transition to another ferroelectric state simultaneously with the magnetic transition temperature. Our findings provide a unique example of a concurrent magnetic and ferroelectric transition at the same temperature among proper ferroelectrics, taking a step toward room temperature magnetoelectric applications.

  10. Polarization-coupled tunable resistive behavior in oxide ferroelectric heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Gruverman, Alexei [Univ. of Nebraska, Lincoln, NE (United States); Tsymbal, Evgeny Y. [Univ. of Nebraska, Lincoln, NE (United States); Eom, Chang-Beom [Univ. of Wisconsin, Madison, WI (United States)

    2017-05-03

    This research focuses on investigation of the physical mechanism of the electrically and mechanically tunable resistive behavior in oxide ferroelectric heterostructures with engineered interfaces realized via a strong coupling of ferroelectric polarization with tunneling electroresistance and metal-insulator (M-I) transitions. This report describes observation of electrically conductive domain walls in semiconducting ferroelectrics, voltage-free control of resistive switching and demonstration of a new mechanism of electrical control of 2D electron gas (2DEG) at oxide interfaces. The research goals are achieved by creating strong synergy between cutting-edge fabrication of epitaxial single-crystalline complex oxides, nanoscale electrical characterization by scanning probe microscopy and theoretical modeling of the observed phenomena. The concept of the ferroelectric devices with electrically and mechanically tunable nonvolatile resistance represents a new paradigm shift in realization of the next-generation of non-volatile memory devices and low-power logic switches.

  11. Introduction to the special issue on ultrasonics and ferroelectrics.

    Science.gov (United States)

    Saniie, Jafar; Kamba, Stanislav

    2014-08-01

    The sixteen articles in this special section were presented at the 2013 IEEE Ultrasonics, Ferroelectrics, and Frequency Control (UFFC) Symposium that was held in Prague, the Czech Republic, from July 21-25, 2013.

  12. Ferroelectric Rashba semiconductors as a novel class of multifunctional materials

    National Research Council Canada - National Science Library

    Picozzi, Silvia

    2014-01-01

    .... Semiconductor spintronics makes no exception. In this context, we have discovered by means of density-functional simulations that, when a sizeable spin-orbit coupling is combined with ferroelectricity, such as in GeTe, one obtains novel...

  13. Ferroelectric charged domain walls in an applied electric field

    OpenAIRE

    Gureev, M. Y.; Mokry, P.; Tagantsev, A. K.; Setter, N.

    2012-01-01

    The interaction of electric field with charged domain walls in ferroelectrics is theoretically addressed. Ageneral expression for the force acting per unit area of a charged domain wall carrying free charge is derived. It is shown that, in proper ferroelectrics, the free charge carried by the wall is dependent on the size of the adjacent domains. As a result, the mobility of such domain wall (with respect to the applied field) is sensitive to the parameters of the domain pattern containing th...

  14. Direct observations of retention failure in ferroelectric memories.

    Science.gov (United States)

    Gao, Peng; Nelson, Christopher T; Jokisaari, Jacob R; Zhang, Yi; Baek, Seung-Hyub; Bark, Chung Wung; Wang, Enge; Liu, Yuanming; Li, Jiangyu; Eom, Chang-Beom; Pan, Xiaoqing

    2012-02-21

    Nonvolatile ferroelectric random-access memory uses ferroelectric thin films to save a polar state written by an electric field that is retained when the field is removed. After switching, the high energy of the domain walls separating regions of unlike polarization can drive backswitching resulting in a loss of switched domain volume, or in the case of very small domains, complete retention loss. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Strain-induced ferroelectricity in simple rocksalt binary oxides

    OpenAIRE

    Bousquet, Eric; Spaldin, Nicola A.; Ghosez, Philippe

    2009-01-01

    The alkaline earth binary oxides adopt a simple rocksalt structure and form an important family of compounds because of their large presence in the earth's mantle and their potential use in microelectronic devices. In comparison to the class of multifunctional ferroelectric perovskite oxides, however, their practical applications remain limited and the emergence of ferroelectricity and related functional properties in simple binary oxides seems so unlikely that it was never previously conside...

  16. Formation of (111) orientation-controlled ferroelectric orthorhombic HfO{sub 2} thin films from solid phase via annealing

    Energy Technology Data Exchange (ETDEWEB)

    Mimura, Takanori; Katayama, Kiliha [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Shimizu, Takao [Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Uchida, Hiroshi [Department of Materials and Life Sciences, Sophia University, Tokyo 102-8554 (Japan); Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Sakata, Osami [Synchrotron X-ray Station at SPring-8 and Synchrotron X-ray Group, National Institute for Materials Science, Sayo, Hyogo 679-5148 (Japan); Funakubo, Hiroshi, E-mail: funakubo.h.aa@m.titech.ac.jp [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); School of Materials and Chemical Technology, Tokyo Institute of Technology, Yokohama 226-8502 (Japan)

    2016-08-01

    0.07YO{sub 1.5}-0.93HfO{sub 2} (YHO7) films were prepared on various substrates by pulse laser deposition at room temperature and subsequent heat treatment to enable a solid phase reaction. (111)-oriented 10 wt. % Sn-doped In{sub 2}O{sub 3}(ITO)//(111) yttria-stabilized zirconia, (111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si substrates, and (111)ITO/(111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si substrates were employed for film growth. In this study, X-ray diffraction measurements including θ–2θ measurements, reciprocal space mappings, and pole figure measurements were used to study the films. The film on (111)ITO//(111)yttria-stabilized zirconia was an (111)-orientated epitaxial film with ferroelectric orthorhombic phase; the film on (111)ITO/(111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si was an (111)-oriented uniaxial textured film with ferroelectric orthorhombic phase; and no preferred orientation was observed for the film on the (111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si substrate, which does not contain ITO. Polarization–hysteresis measurements confirmed that the films on ITO covered substrates had saturated ferroelectric hysteresis loops. A remanent polarization (P{sub r}) of 9.6 and 10.8 μC/cm{sup 2} and coercive fields (E{sub c}) of 1.9 and 2.0 MV/cm were obtained for the (111)-oriented epitaxial and uniaxial textured YHO7 films, respectively. These results demonstrate that the (111)-oriented ITO bottom electrodes play a key role in controlling the orientation and ferroelectricity of the phase formation of the solid films deposited at room temperature.

  17. Ocean sequestration of carbon dioxide: modeling the deep ocean release of a dense emulsion of liquid Co2-in-water stabilized by pulverized limestone particles.

    Science.gov (United States)

    Golomb, D; Pennell, S; Ryan, D; Barry, E; Swett, P

    2007-07-01

    The release into the deep ocean of an emulsion of liquid carbon dioxide-in-seawater stabilized by fine particles of pulverized limestone (CaCO3) is modeled. The emulsion is denser than seawater, hence, it will sink deeper from the injection point, increasing the sequestration period. Also, the presence of CaCO3 will partially buffer the carbonic acid that results when the emulsion eventually disintegrates. The distance that the plume sinks depends on the density stratification of the ocean, the amount of the released emulsion, and the entrainment factor. When released into the open ocean, a plume containing the CO2 output of a 1000 MW(el) coal-fired power plant will typically sink hundreds of meters below the injection point. When released from a pipe into a valley on the continental shelf, the plume will sink about twice as far because of the limited entrainment of ambient seawater when the plume flows along the valley. A practical system is described involving a static mixer for the in situ creation of the CO2/seawater/pulverized limestone emulsion. The creation of the emulsion requires significant amounts of pulverized limestone, on the order of 0.5 tons per ton of liquid CO2. That increases the cost of ocean sequestration by about $13/ ton of CO2 sequestered. However, the additional cost may be compensated by the savings in transportation costs to greater depth, and because the release of an emulsion will not acidify the seawater around the release point.

  18. Evaluation of cefaclor oral suspensions stability using reversed phase high performance liquid chromatography and antimicrobial diffusion methods.

    Science.gov (United States)

    Tarawneh, Khaled Ahmad; Halasah, Zina Atallah; Khleifat, Ali Mohmad; Batarseh, Mufeed Issa Batarseh Issa Batarseh; Khleifat, Khaled Mohmad; Al-Mustafa, Ahmed Hussein

    2011-07-01

    The effect of temperature stresses on Cefaclor suspensions under different storage conditions for a duration of 14 days was tested. The degradation of Cefaclor was determined on the 2nd, 7th and 14th day after reconstitution using a sensitive and precise Reversed phase High Performance Liquid Chromatographic (RP-HPLC) method. The RSD values for Forticef, Midocef, Ceclor, Cefabac and Cloracef, indicated a good precision of the RP-HPLC method. The limit of detection (LOD) and the limit of quantification (LOQ) were found 0.008 mg/ml and 0.03mg/ml respectively. The antimicrobial effect of Cefaclor suspension was also tested against pathogenic bacteria using the cylinder diffusion method. The RSD values range of the antimicrobial assay for all the Cefaclor compounds were 1.47-3.7%. The LOD and LOQ were 0.2mg/ml and 1mg/ml respectively. During the normal use of Ceclor, Midocef, and Forticef the loss of activity and the degradation were less than 5% on the 14th day of preservation at 4°C. However, the percentage of degradation for Cefabac and Cloracef on the 14th day reached 5 and 6%, respectively. Statistical multiple comparison between the effect of 4°C and 25°C indicated non significant mean differences (P>0.05) for Forticef, Cefabac, Ceclor and Cloraf and significant effect for Midocef (P <0.05). Significant effects were observed between (4oC and 37°C) and (25°C and 37°C) for all except Ceclor. Multiple comparisons between days of storage showed non significant mean difference values at 4°C except Cefabac. However significant results between days were found at 25°C and 37°C except for Midocef between (7th and 14th day). It was found that the pediatric suspensions of Cefaclor in the Jordanian market were stable and contained the amount of active ingredient specified by the United States pharmacopoeias specification (USP) and the British Pharmacopoeias specifications (BP).

  19. Ferroelectric Phase Transitions from First Principles

    CERN Document Server

    Rabe, K M

    1995-01-01

    An effective Hamiltonian for the ferroelectric transition in $PbTiO_3$ is constructed from first-principles density-functional-theory total-energy and linear-response calculations through the use of a localized, symmetrized basis set of ``lattice Wannier functions.'' Preliminary results of Monte Carlo simulations for this system show a first-order cubic-tetragonal transition at 660 K. The involvement of the Pb atom in the lattice instability and the coupling of local distortions to strain are found to be particularly important in producing the behavior characteristic of the $PbTiO_3$ transition. A tentative explanation for the presence of local distortions experimentally observed above $T_c$ is suggested. Further applications of this method to a variety of systems and structures are proposed for first-principles study of finite-temperature structural properties in individual materials.

  20. A response surface methodology study of ferroelectric memory devices

    Science.gov (United States)

    Smith, Kevin C.

    1992-03-01

    Fatigue in ferroelectric memory devices was studied. The application of fatigue pulses to a ferroelectric sample was controlled by the RT-66 Ferroelectric Tester, a variation of the Sawyer-Tower circuit. The RT-66 also controlled data collection following the fatiguing process. Seven variables were evaluated for their potential-affect on fatigue. A sequence of fatigue tests, which varied the settings of these variables, was developed using Response Surface Methodology (RSM) experimental designs. Least-squares regression models were developed once a particular RSM set of design experiments was completed. These models were evaluated using RSM tools, and the analysis of these models allowed the iterative development of new RSM designs. Within the experimental operating region it was determined that aging did not affect fatigue, and that differences in ferroelectric materials and electrode materials were the most important factors in determining fatigue. First-order models failed to fit the data for any of the RSM designs. The final model developed had two pure quadratic terms and three first-order terms. However, this design only involved one type of ferroelectric. Further testing is necessary before the findings of this study can be extended to modeling fatigue in other ferroelectric materials.

  1. Improper ferroelectrics as high-efficiency energy conversion materials

    Energy Technology Data Exchange (ETDEWEB)

    Wakamatsu, Toru; Tanabe, Kenji; Terasaki, Ichiro; Taniguchi, Hiroki [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)

    2017-05-15

    An improper ferroelectric is a certain type of ferroelectrics whose primary order parameter is not polarization but another physical quantity such as magnetization. In contrast to a conventional proper ferroelectrics as represented by Pb(Zr,Ti)O{sub 3} and BaTiO{sub 3}, the improper ferroelectrics has been inconceivable for practical applications thus far. Herein, we illustrate the great potential of improper ferroelectrics for efficient conversion of temperature fluctuation to electric energy, as demonstrated with (Ca{sub 0.84}Sr{sub 0.16}){sub 8}[AlO{sub 2}]{sub 12}(MoO{sub 4}){sub 2} (CSAM-16). The present study has experimentally proven that CSAM-16 achieves an excellent electrothermal coupling factor and high electric field sensitivity for pyroelectric energy conversion that approach a practical level for application to self-powered autonomous electronic devices for rapidly spreading wireless sensor networks. The present results provide a novel approach to developing innovative pyroelectric energy harvesting devices using improper ferroelectrics. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Validated stability indicating liquid chromatographic determination of ebastine in pharmaceuticals after pre column derivatization: Application to tablets and content uniformity testing.

    Science.gov (United States)

    Ibrahim, Fawzia; Sharaf El-Din, Mohie Khaled; Eid, Manal Ibrahim; Wahba, Mary Elias Kamel

    2011-05-09

    An accurate, simple, sensitive and selective reversed phase liquid chromatographic method has been developed for the determination of ebastine in its pharmaceutical preparations. The proposed method depends on the complexation ability of the studied drug with Zn2+ ions. Reversed phase chromatography was conducted using an ODS C18 (150 × 4.6 mm id) stainless steel column at ambient temperature with UV-detection at 260 nm. A mobile phase containing 0.025%w/v Zn2+ in a mixture of (acetonitril/methanol; 1/4) and Britton Robinson buffer (65:35, v/v) adjusted to pH 4.2, has been used for the determination of ebastine at a flow rate of 1 ml/min. The calibration curve was rectilinear over the concentration range of 0.3 - 6.0 μg/ml with a detection limit (LOD) of 0.13 μg/ml, and quantification limit (LOQ) of 0.26 μg/ml. The proposed method was successfully applied for the analysis of ebastine in its dosage forms, the obtained results were favorably compared with those obtained by a comparison method. Furthermore, content uniformity testing of the studied pharmaceutical formulations was also conducted. The composition of the complex as well as its stability constant was also investigated. Moreover, the proposed method was found to be a stability indicating one and was utilized to investigate the kinetics of alkaline and ultraviolet induced degradation of the drug. The first-order rate constant and half life of the degradation products were calculated.

  3. Validated stability indicating liquid chromatographic determination of ebastine in pharmaceuticals after pre column derivatization: Application to tablets and content uniformity testing

    Directory of Open Access Journals (Sweden)

    Eid Manal

    2011-05-01

    Full Text Available Abstract An accurate, simple, sensitive and selective reversed phase liquid chromatographic method has been developed for the determination of ebastine in its pharmaceutical preparations. The proposed method depends on the complexation ability of the studied drug with Zn2+ ions. Reversed phase chromatography was conducted using an ODS C18 (150 × 4.6 mm id stainless steel column at ambient temperature with UV-detection at 260 nm. A mobile phase containing 0.025%w/v Zn2+ in a mixture of (acetonitril/methanol; 1/4 and Britton Robinson buffer (65:35, v/v adjusted to pH 4.2, has been used for the determination of ebastine at a flow rate of 1 ml/min. The calibration curve was rectilinear over the concentration range of 0.3 - 6.0 μg/ml with a detection limit (LOD of 0.13 μg/ml, and quantification limit (LOQ of 0.26 μg/ml. The proposed method was successfully applied for the analysis of ebastine in its dosage forms, the obtained results were favorably compared with those obtained by a comparison method. Furthermore, content uniformity testing of the studied pharmaceutical formulations was also conducted. The composition of the complex as well as its stability constant was also investigated. Moreover, the proposed method was found to be a stability indicating one and was utilized to investigate the kinetics of alkaline and ultraviolet induced degradation of the drug. The first-order rate constant and half life of the degradation products were calculated.

  4. A validated stability indicating high-performance liquid chromatographic method for simultaneous estimation of cefuroxime sodium and sulbactam sodium in injection dosage form

    Directory of Open Access Journals (Sweden)

    Falguni M Patel

    2012-01-01

    Full Text Available Background: A fixed dose combination of cefuroxime sodium (β lactam antibiotic and sulbactam sodium (β Lactamase inhibitor is used in ratio of 2:1 as powder for injection for the treatment of resistant lower respiratory tract and other infections. Aims: A simple, precise, and accurate ion-pair reverse-phase high-performance liquid chromatography (RP-HPLC method was developed and validated for determination of cefuroxime Na(CEF and sulbactam Na(SUL in injection. Materials and Methods: Isocratic RP-HPLC separation was achieved on an ACE C 18 column (150×4.6 mm id, 5 μm particle size using the mobile phase 0.002 M tetrabutylammonium hydroxide sulfate (TBAH in 10 mm potassium di-hydrogen phosphate buffer-acetonitrile (86:14 v/v, pH 3.7 at a flow rate of 1.0 ml/min. Results and Conclusion: The retention time of sulbactam Na and cefuroxime Na were 3.2 min and 10.2 min, respectively. The ion-pairing reagent improved the retention of highly polar sulbactam Na on reverse-phase column. The detection was performed at 210 nm. The method was validated for linearity, precision, accuracy, robustness, solution stability, and specificity. The method was validated for linearity, precision, accuracy, robustness, solution stability, and specificity. The method was linear in the concentration range of 10-100 μg/ml for cefuroxime Na and 5-50 μg/ml for sulbactam Na, with a correlation coefficient of 0.9999 and 0.9998 for the respective drugs. The intraday precision was 0.13-0.21% and 0.48-0.65%, and the interday precision was 0.32-0.81% and 0.60-0.83% for cefuroxime Na and sulbactam Na, respectively. The accuracy (recovery was found to be in the range of 98.76-100.61% and 98.99-100.30% for cefuroxime Na and sulbactam Na, respectively. The drugs were found to degrade under hydrolytic and oxidative conditions. The drugs could be effectively separated from different degradation products, and hence the method can be used for stability analysis.

  5. Evaluation of cannabinoids concentration and stability in standardized preparations of cannabis tea and cannabis oil by ultra-high performance liquid chromatography tandem mass spectrometry.

    Science.gov (United States)

    Pacifici, Roberta; Marchei, Emilia; Salvatore, Francesco; Guandalini, Luca; Busardò, Francesco Paolo; Pichini, Simona

    2017-08-28

    Cannabis has been used since ancient times to relieve neuropathic pain, to lower intraocular pressure, to increase appetite and finally to decrease nausea and vomiting. The combination of the psychoactive cannabis alkaloid Δ9-tetrahydrocannabinol (THC) with the non-psychotropic alkaloids cannabidiol (CBD) and cannabinol (CBN) demonstrated a higher activity than THC alone. The Italian National Institute of Health sought to establish conditions and indications on how to correctly use nationally produced cannabis to guarantee therapeutic continuity in individuals treated with medical cannabis. The evaluation of cannabinoids concentration and stability in standardized preparations of cannabis tea and cannabis oil was conducted using an easy and fast ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) assay. Extraction efficiency of oil was significantly higher than that of water with respect to the different cannabinoids. This was especially observed in the case of the pharmacologically active THC, CBD and their acidic precursors. Fifteen minutes boiling was sufficient to achieve the highest concentrations of cannabinoids in the cannabis tea solutions. At ambient temperature, a significant THC and CBD decrease to 50% or less of the initial concentration was observed over 3 and 7 days, respectively. When refrigerated at 4 °C, similar decreasing profiles were observed for the two compounds. The cannabinoids profile in cannabis oil obtained after pre-heating the flowering tops at 145 °C for 30 min in a static oven resulted in a complete decarboxylation of cannabinoid acids CBDA and THCA-A. Nevertheless, it was apparent that heat not only decarboxylated acidic compounds, but also significantly increased the final concentrations of cannabinoids in oil. The stability of cannabinoids in oil samples was higher than that in tea samples since the maximum decrease (72% of initial concentration) was observed in THC coming from unheated flowering

  6. Improvement of the fatigue and the ferroelectric properties of PZT films through a LSCO seed layer

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Sofia A.S., E-mail: sofiarodrigues@fisica.uminho.pt; Silva, José P.B.; Khodorov, Anatoli; Martín-Sánchez, Javier; Pereira, M.; Gomes, M.J.M.

    2013-11-01

    Highlights: • Pulsed laser deposited PZT thin films. • Seed layer effect on the structural and ferroelectric properties of the PZT films. • The stability of P{sub r} was improved with the introduction of the LSCO layer. -- Abstract: The ability to optimizate the preparation of Lead Zirconate Titanate (PZT) films on platinized Si substrate by pulsed laser deposition was demonstrated. The effect of the modification of the interface film/electrode through the use of a (La,Sr)CoO{sub 3} (LSCO) seed layer on the remnant polarization, fatigue endurance and stress in PZT films was studied. An improvement on the ferroelectric properties was found with the using of the LSCO layer. A remnant polarization (P{sub r}) of 19.8 μC/cm{sup 2} and 4.4 μC/cm{sup 2} for films with and without the LSCO layer were found. In the same way the polarization fatigue decreases significantly after deposition of the LSCO layer between the film and substrate. Atomic force microscopy (AFM) images revealed a different growth process in the films. Current–voltage (I–V) measurements showed that the use of LSCO seed layer improves the leakage current and, on the other hand the conduction mechanisms in the film without LSCO, after the fatigue test, was found to be changed from Schottky to Poole–Frenkel. The trap activation energy (about 0.14 eV) determined from Poole–Frenkel mode agrees well with the energy level of oxygen vacancies. The films stresses were estimated by XRD in order to explain the improvement on the structure and consequentially ferroelectric properties of the films. The model proposed by Dawber and Scott was found to be in agreement with our experimental data, which seems to predict that the oxygen vacancies play an important role on fatigue.

  7. Stress degradation studies of Telmisartan and Metoprolol extended release tablets by a validated stability indicating reverse phase-high performance liquid chromatography method

    Directory of Open Access Journals (Sweden)

    Kabeer Ahmed Shaikh

    2014-01-01

    Full Text Available Background and Aim: A sensitive reverse phase high-performance liquid chromatographic method has been developed for the simultaneous determination of Telimisartan and Metoprolol in tablet dosage form. Materials and Method: The chromatographic separation was achieved on Inertsil ODS 3V, 150 x 4.6 mm, 5μ analytical column. Mobile phase consisting of mobile phase A- 0.05M sodium dihydrogen phosphate buffer pH 3.0 and mobile phase B-Acetonitrile, with gradient program time in min /Mobile phase B% 0/22, 4/45, 6/45,18/22, 20/22. Detector was set at 222nm. Results and Conclusion: The described method shows excellent linearity over a range of 80-2 μg mL−1 for Telmisartan and 100-4 μg mL−1 for Metoprolol. The correlation coefficient for Telmisartan is 0.9998 and Metoprolol is 0.9999. The proposed method was found to be suitable for determination of Telmisartan and Metoprolol in tablet dosage form. Forced degradation of the drug product was conducted in accordance with the ICH guideline. Acidic, basic, hydrolytic, oxidative, thermal and photolytic degradation was used to assess the stability indicating power of the method. The drug product was found to be stable in acid, oxidation, thermal and photolytic stress condition and found degradation in base hydrolysis stress condition.

  8. A new filter that accurately mimics the solar UV-B spectrum using standard UV lamps: the photochemical properties, stabilization and use of the urate anion liquid filter.

    Science.gov (United States)

    Sampath-Wiley, Priya; Jahnke, Leland S

    2011-02-01

    The physiological effects unique to solar ultraviolet (UV)-B exposure (280-315 nm) are difficult to accurately replicate in the laboratory. This study evaluates the effectiveness of the sodium urate anion in a liquid filter that yields a spectrum nearly indistinguishable from the solar UV-B spectrum while filtering the emissions of widely used UV-B lamps. The photochemical properties and stability of this filter are examined and weighed against a typical spectrum of ground-level solar UV-B radiation. To test the effectiveness of this filter, light-saturated photosynthetic oxygen evolution rates were measured following exposure to UV-B filtered either by this urate filter or the widely used cellulose acetate (CA) filter. The ubiquitous marine Chlorophyte alga Dunaliella tertiolecta was tested under identical UV-B flux densities coupled with ecologically realistic fluxes of UV-A and visible radiation for 6 and 12 h exposures. These results indicate that the urate-filtered UV-B radiation yields minor photosynthetic inhibition when compared with exposures lacking in UV-B. This is in agreement with published experiments using solar radiation. In sharp contrast, radiation filtered by CA filters produced large inhibition of photosynthesis. © 2010 Blackwell Publishing Ltd.

  9. Development and validation of a stability-indicating high performance liquid chromatographic (HPLC) method for the determination of related substances of micafungin sodium in drug substances.

    Science.gov (United States)

    Zhu, Shengsheng; Meng, Xiang; Su, Xin; Luo, Yongwei; Sun, Zuyue

    2013-10-24

    An isocratic, sensitive and stability-indicating high performance liquid chromatographic (HPLC) method for separation and determination of the related substances of micafungin sodium was developed. The chromatographic separation was achieved on Agilent Zorbax SB-C18 column (250 × 4.6 mm, 5 μm). Forced degradation study confirmed that the newly developed method was specific and selective to the degradation products. The performance of the method was validated according to the present ICH guidelines for specificity, linearity, accuracy, precision and robustness. Regression analysis showed correlation coefficient value greater than 0.999 for micafungin sodium and its six impurities. Limit of detection of impurities was in the range of 0.006%-0.013% indicating the high sensitivity of the newly developed method. Accuracy of the method was established based on the recovery obtained between 98.2% and 102.0% for all impurities. RSD obtained for the repeatability and intermediate precision experiments, was less than 1.0%. The method was successfully applied to quantify related substances of micafungin sodium in bulk drugs.

  10. Medicinal cannabis: Principal cannabinoids concentration and their stability evaluated by a high performance liquid chromatography coupled to diode array and quadrupole time of flight mass spectrometry method.

    Science.gov (United States)

    Citti, Cinzia; Ciccarella, Giuseppe; Braghiroli, Daniela; Parenti, Carlo; Vandelli, Maria Angela; Cannazza, Giuseppe

    2016-09-05

    In the last few years, there has been a boost in the use of cannabis-based extracts for medicinal purposes, although their preparation procedure has not been standardized but rather decided by the individual pharmacists. The present work describes the development of a simple and rapid high performance liquid chromatography method with UV detection (HPLC-UV) for the qualitative and quantitative determination of the principal cannabinoids (CBD-A, CBD, CBN, THC and THC-A) that could be applied to all cannabis-based medicinal extracts (CMEs) and easily performed by a pharmacist. In order to evaluate the identity and purity of the analytes, a high-resolution mass spectrometry (HPLC-ESI-QTOF) analysis was also carried out. Full method validation has been performed in terms of specificity, selectivity, linearity, recovery, dilution integrity and thermal stability. Moreover, the influence of the solvent (ethyl alcohol and olive oil) was evaluated on cannabinoids degradation rate. An alternative extraction method has then been proposed in order to preserve cannabis monoterpene component in final CMEs. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Stabilization of new forms of the intermetallic phases beta-RENiGe2 (RE = Dy, Ho, Er, Tm, Yb, Lu) in liquid indium.

    Science.gov (United States)

    Salvador, J R; Gour, J R; Bilc, D; Mahanti, S D; Kanatzidis, M G

    2004-02-23

    Flux conditions using liquid indium bypass the thermodynamically stable structure and yield new forms of the phases RENiGe2 (RE = Dy, Er, Yb, Lu). The compounds crystallize in the orthorhombic Immm space group and possess the YIrGe2 structure type. Lattice parameters for ErNiGe2, DyNiGe2, YbNiGe2, and LuNiGe2 are a = 4.114(1) A, b = 8.430(2) A, c = 15.741(5) A; a = 4.1784(9) A, b = 8.865(2) A, c = 15.745(3) A; a = 4.0935(6) A, b = 8.4277(13) A, c = 15.751(2) A, and a = 4.092(1) A, b = 8.418(3) A, c = 15.742(5) A, respectively. These phases represent a new structural arrangement (beta) of the compound type RENiGe2 as another set of compounds with identical stoichiometry are known to adopt the orthorhombic Cmcm CeNiSi2 type structure (alpha). In this paper we report the crystal and electronic band structure of four new members of the YIrGe2 structure type, as well as an investigation of the relative thermodynamic stabilities of the two forms.

  12. Transparent image generator by using vertically aligned polymer-stabilized liquid crystal (VA-PSLC) for see-through display applications

    Science.gov (United States)

    Wang, Mu-Hao; Choi, Wing-Kit; Su, Guo-Dung

    2012-10-01

    We demonstrate the feasibility of using a Vertically-Aligned Polymer-Stabilized Liquid Crystal (VA-PSLC) film, which is also known as LC gel, as a transparent image generator to form a see-through display system. This is achieved, in its simplest form, by projecting a collimated LED light source onto a transparent glass screen, with the image generated by the scattered light from the VA-PSLC. By moving the observer's head slightly away from the incident light specular reflection direction, a clear image can be observed on the transparent glass screen together with the background objects that are behind the screen. From our experimental results, this see-through display system using VA-PSLC transparent image generator can achieve a fast response time (with rise time of ~10 ms and fall time of ~5ms) and an acceptable contrast ratio (< ~100:1). The driving voltage is about 15~20V. Further improvements can be achieved by further optimizing the LC material/monomer parameters, device fabrication process/conditions and the optical system setup. In this system, polarizers are not required so that very high light efficiency can be obtained.

  13. A versatile, stability-indicating and high-throughput ultra-fast liquid chromatography method for the determination of isoflavone aglycones in soybeans, topical formulations, and permeation assays.

    Science.gov (United States)

    Nemitz, Marina C; Yatsu, Francini K J; Bidone, Juliana; Koester, Letícia S; Bassani, Valquiria L; Garcia, Cássia V; Mendez, Andreas S L; von Poser, Gilsane L; Teixeira, Helder F

    2015-03-01

    There is a growing interest in the pharmaceutical field concerning isoflavones topical delivery systems, especially with regard to their skin care properties and antiherpetic activity. In this context, the present work describes an ultra-fast liquid chromatography method (UFLC) for determining daidzein, glycitein, and genistein in different matrices during the development of topical systems containing isoflavone aglycones (IA) obtained from soybeans. The method showed to be specific, precise, accurate, and linear (0.1 to 5 µg mL(-1)) for IA determination in soybean acid extract, IA-rich fraction obtained after the purification process, IA loaded-nanoemulsions, and topical hydrogel, as well as for permeation/retention assays in porcine skin and porcine esophageal mucosa. The matrix effect was determined for all complex matrices, demonstrating low effect during the analysis. The stability indicating UFLC method was verified by submitting IA to acidic, alkaline, oxidative, and thermal stress conditions, and no interference of degradation products was detected during analysis. Mass spectrometry was performed to show the main compounds produced after acid hydrolysis of soybeans, as well as suggest the main degradation products formed after stress conditions. Besides the IA, hydroxymethylfurfural and ethoxymethylfurfural were produced and identified after acid hydrolysis of the soybean extract and well separated by the UFLC method. The method's robustness was confirmed using the Plackett-Burman experimental design. Therefore, the new method affords fast IA analysis during routine processes, extract purification, products development, and bioanalytical assays. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. In situ and real-time atomic force microscopy studies of the stability of oligothiophene langmuir-blodgett monolayers in liquid

    KAUST Repository

    Yin, Naining

    2014-03-20

    Oligothiophene thin films have been considered as promising material for molecular electronics due to their desirable electronic properties and high structural stability under ambient conditions. To ensure performance in devices the functional structures, such as individual ordered domains, must be stable under practical and operational conditions or environments including exposure to various media. This work investigates the structure of oligothiophene Langmuir-Blodgett (LB) films upon exposure to liquid media such as water, ethanol (EtOH), and mixed tetrahydrofuran (THF)/EtOH solutions. The LB films form islands ranging from 500 nm up to 1 μm consisting of densely packed oligothiophene molecules. These islands are surrounded by bare substrate and loosely packed adsorbates. In situ and time-dependent AFM images were acquired to reveal the structural evolution, from which degradation pathways and kinetics are extracted. Degradation of these LB films initiates and propagates from intraisland defect sites, such as cracks and pin holes, whereas the edges of islands remain intact on the surface. The observations appear to be in contrast to the known degradation mechanism among self-assembled monolayers, such as alkanethiols on gold, which initiates and progresses at domain boundaries. Rationale for the observed degradation processes will also be discussed. © 2014 American Chemical Society.

  15. Tunable Microwave Filter Design Using Thin-Film Ferroelectric Varactors

    Science.gov (United States)

    Haridasan, Vrinda

    Military, space, and consumer-based communication markets alike are moving towards multi-functional, multi-mode, and portable transceiver units. Ferroelectric-based tunable filter designs in RF front-ends are a relatively new area of research that provides a potential solution to support wideband and compact transceiver units. This work presents design methodologies developed to optimize a tunable filter design for system-level integration, and to improve the performance of a ferroelectric-based tunable bandpass filter. An investigative approach to find the origins of high insertion loss exhibited by these filters is also undertaken. A system-aware design guideline and figure of merit for ferroelectric-based tunable band- pass filters is developed. The guideline does not constrain the filter bandwidth as long as it falls within the range of the analog bandwidth of a system's analog to digital converter. A figure of merit (FOM) that optimizes filter design for a specific application is presented. It considers the worst-case filter performance parameters and a tuning sensitivity term that captures the relation between frequency tunability and the underlying material tunability. A non-tunable parasitic fringe capacitance associated with ferroelectric-based planar capacitors is confirmed by simulated and measured results. The fringe capacitance is an appreciable proportion of the tunable capacitance at frequencies of X-band and higher. As ferroelectric-based tunable capac- itors form tunable resonators in the filter design, a proportionally higher fringe capacitance reduces the capacitance tunability which in turn reduces the frequency tunability of the filter. Methods to reduce the fringe capacitance can thus increase frequency tunability or indirectly reduce the filter insertion-loss by trading off the increased tunability achieved to lower loss. A new two-pole tunable filter topology with high frequency tunability (> 30%), steep filter skirts, wide stopband

  16. Physical aspects of ferroelectric semiconductors for photovoltaic solar energy conversion

    Science.gov (United States)

    Lopez-Varo, Pilar; Bertoluzzi, Luca; Bisquert, Juan; Alexe, Marin; Coll, Mariona; Huang, Jinsong; Jimenez-Tejada, Juan Antonio; Kirchartz, Thomas; Nechache, Riad; Rosei, Federico; Yuan, Yongbo

    2016-10-01

    Solar energy conversion using semiconductors to fabricate photovoltaic devices relies on efficient light absorption, charge separation of electron-hole pair carriers or excitons, and fast transport and charge extraction to counter recombination processes. Ferroelectric materials are able to host a permanent electrical polarization which provides control over electrical field distribution in bulk and interfacial regions. In this review, we provide a critical overview of the physical principles and mechanisms of solar energy conversion using ferroelectric semiconductors and contact layers, as well as the main achievements reported so far. In a ferroelectric semiconductor film with ideal contacts, the polarization charge would be totally screened by the metal layers and no charge collection field would exist. However, real materials show a depolarization field, smooth termination of polarization, and interfacial energy barriers that do provide the control of interface and bulk electric field by switchable spontaneous polarization. We explore different phenomena as the polarization-modulated Schottky-like barriers at metal/ferroelectric interfaces, depolarization fields, vacancy migration, and the switchable rectifying behavior of ferroelectric thin films. Using a basic physical model of a solar cell, our analysis provides a general picture of the influence of ferroelectric effects on the actual power conversion efficiency of the solar cell device, and we are able to assess whether these effects or their combinations are beneficial or counterproductive. We describe in detail the bulk photovoltaic effect and the contact layers that modify the built-in field and the charge injection and separation in bulk heterojunction organic cells as well as in photocatalytic and water splitting devices. We also review the dominant families of ferroelectric materials that have been most extensively investigated and have provided the best photovoltaic performance.

  17. Physical aspects of ferroelectric semiconductors for photovoltaic solar energy conversion

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Varo, Pilar [Departamento de Electrónica y Tecnología de Computadores, CITIC-UGR, Universidad de Granada, 18071 Granada (Spain); Bertoluzzi, Luca [Institute of Advanced Materials (INAM), Universitat Jaume I, 12006 Castelló (Spain); Bisquert, Juan, E-mail: bisquert@uji.es [Institute of Advanced Materials (INAM), Universitat Jaume I, 12006 Castelló (Spain); Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Alexe, Marin [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Coll, Mariona [Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193, Bellaterra, Catalonia (Spain); Huang, Jinsong [Department of Mechanical and Materials Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588-0656 (United States); Jimenez-Tejada, Juan Antonio [Departamento de Electrónica y Tecnología de Computadores, CITIC-UGR, Universidad de Granada, 18071 Granada (Spain); Kirchartz, Thomas [IEK5-Photovoltaik, Forschungszentrum Jülich, 52425 Jülich (Germany); Faculty of Engineering and CENIDE, University of Duisburg–Essen, Carl-Benz-Str. 199, 47057 Duisburg (Germany); Nechache, Riad; Rosei, Federico [INRS—Center Énergie, Matériaux et Télécommunications, Boulevard Lionel-Boulet, Varennes, Québec, J3X 1S2 (Canada); Yuan, Yongbo [Department of Mechanical and Materials Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588-0656 (United States)

    2016-10-07

    Solar energy conversion using semiconductors to fabricate photovoltaic devices relies on efficient light absorption, charge separation of electron–hole pair carriers or excitons, and fast transport and charge extraction to counter recombination processes. Ferroelectric materials are able to host a permanent electrical polarization which provides control over electrical field distribution in bulk and interfacial regions. In this review, we provide a critical overview of the physical principles and mechanisms of solar energy conversion using ferroelectric semiconductors and contact layers, as well as the main achievements reported so far. In a ferroelectric semiconductor film with ideal contacts, the polarization charge would be totally screened by the metal layers and no charge collection field would exist. However, real materials show a depolarization field, smooth termination of polarization, and interfacial energy barriers that do provide the control of interface and bulk electric field by switchable spontaneous polarization. We explore different phenomena as the polarization-modulated Schottky-like barriers at metal/ferroelectric interfaces, depolarization fields, vacancy migration, and the switchable rectifying behavior of ferroelectric thin films. Using a basic physical model of a solar cell, our analysis provides a general picture of the influence of ferroelectric effects on the actual power conversion efficiency of the solar cell device, and we are able to assess whether these effects or their combinations are beneficial or counterproductive. We describe in detail the bulk photovoltaic effect and the contact layers that modify the built-in field and the charge injection and separation in bulk heterojunction organic cells as well as in photocatalytic and water splitting devices. We also review the dominant families of ferroelectric materials that have been most extensively investigated and have provided the best photovoltaic performance.

  18. A novel readout integrated circuit for ferroelectric FPA detector

    Science.gov (United States)

    Bai, Piji; Li, Lihua; Ji, Yulong; Zhang, Jia; Li, Min; Liang, Yan; Hu, Yanbo; Li, Songying

    2017-11-01

    Uncooled infrared detectors haves some advantages such as low cost light weight low power consumption, and superior reliability, compared with cryogenically cooled ones Ferroelectric uncooled focal plane array(FPA) are being developed for its AC response and its high reliability As a key part of the ferroelectric assembly the ROIC determines the performance of the assembly. A top-down design model for uncooled ferroelectric readout integrated circuit(ROIC) has been developed. Based on the optical thermal and electrical properties of the ferroelectric detector the RTIA readout integrated circuit is designed. The noise bandwidth of RTIA readout circuit has been developed and analyzed. A novel high gain amplifier, a high pass filter and a low pass filter circuits are designed on the ROIC. In order to improve the ferroelectric FPA package performance and decrease of package cost a temperature sensor is designed on the ROIC chip At last the novel RTIA ROIC is implemented on 0.6μm 2P3M CMOS silicon techniques. According to the experimental chip test results the temporal root mean square(RMS)noise voltage is about 1.4mV the sensitivity of the on chip temperature sensor is 0.6 mV/K from -40°C to 60°C the linearity performance of the ROIC chip is better than 99% Based on the 320×240 RTIA ROIC, a 320×240 infrared ferroelectric FPA is fabricated and tested. Test results shows that the 320×240 RTIA ROIC meets the demand of infrared ferroelectric FPA.

  19. Electron emission from ferroelectric thin films enhanced by the presence of 90 degree ferroelectric domains.

    Science.gov (United States)

    Suchaneck, Gunnar; Vidyarthi, Vinay S; Gerlach, Gerald; Solnyshkin, Alexander V; Kislova, Inna L

    2007-12-01

    In this work, a ferroelectric domain-enhanced electron emission mechanism is proposed. The polarization distribution near 90 degrees domain walls is calculated by solving a set of second order differential equations, including the Poisson's one and equations derived from an expansion of the free energy Phi(P) in power series of the polarization according to the Devonshire-Landau-Ginzburg theory. Domain walls intersecting the emitting surface cause sufficient electric fields and lower the potential barrier for electron emission. This induces centers of enhanced electron emission. Relaxing domain walls were found to excite trapped excess electrons in front of the wall.

  20. Observation of coexistence of ferroelectric and antiferroelectric phases in Sc substituted BiFeO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Durga Rao, T.; Asthana, Saket, E-mail: asthanas@iith.ac.in; Niranjan, Manish K.

    2015-09-05

    Highlights: • Coexisting ferro- and antiferroelectric phases in Sc substituted compounds. • Structural studies (XRD and Raman) supports the incorporation of Sc at B-site. • Presence of non-centrosymmetric monoclinic phase correlates with AFE ordering. • Grain resistance and activation energies increase with the Sc-content. • Electrical relaxations are originated due to oxygen vacancy movements. - Abstract: Polycrystalline BiFe{sub 1−x}Sc{sub x}O{sub 3} (x = 0, 0.05, 0.10 and 0.15) compounds were prepared using solid state reaction route. The X-ray diffraction patterns showed that Sc substitution stabilized the crystal structure in rhombohedral structure with R3c space group along with nominal percentage of monoclinic structure with Cm space group. Raman and FTIR measurements revealed that the substituent replaced Fe-ions and caused structural distortions. Co-existence of ferroelectric and antiferroelectric phases were observed in Sc substituted BiFeO{sub 3} and antiferroelectric phase is found to be evolved at the expense of ferroelectric phase with the Sc content. The electric field driven effects indicated that antiferroelectric phase was suppressed and ferroelectric phase was enriched. Frequency dependence of dielectric constant (ε{sub r}) and dielectric loss tangent (tan δ) at different temperatures were investigated. Further, grain resistances and grain boundary resistances were increased with the Sc content. Activation energies estimated from dielectric, impedance and modulus data indicated that these relaxations originated presumably due to the oxygen vacancy movements.

  1. Magneto-electric coupling in antiferromagnet/ferroelectric Mn{sub 2}Au/BaTiO{sub 3} interface

    Energy Technology Data Exchange (ETDEWEB)

    Plekhanov, Evgeny [King' s College London, Theory and Simulation of Condensed Matter (TSCM), The Strand, London WC2R 2LS (United Kingdom); Stroppa, Alessandro [Consiglio Nazionale delle Ricerche, Istituto SPIN, UOS CNR-SPIN L' Aquila, I-67100 L' Aquila (Italy); Picozzi, Silvia [Consiglio Nazionale delle Ricerche, Istituto SPIN, UOS L' Aquila, Sede di lavoro CNR-SPIN c/o University “G. D' Annunzio,” 66100 Chieti (Italy)

    2016-08-21

    Within the crucial issue of the electric field control of magnetism, the use of antiferromagnets (AFMs) coupled to ferroelectrics is much less explored than the ferromagnets counterpart, although the first choice might lead to better performances and larger stability with respect to external perturbations (such as magnetic fields). Here, we explore the possibility to control the magnetic anisotropy of a Mn{sub 2}Au layer by reversing the ferroelectric polarization of BaTiO{sub 3} in Mn{sub 2}Au/BaTiO{sub 3} interfaces. By means of a thorough exploration of many possible geometry configurations, we identify the two most stable, corresponding to compressive and tensile strain at the interface. The first appears to be easy-axis, while the second—easy-plane—with a large induced moment on the interface Ti atom. The reversal of ferroelectric polarization changes the anisotropy by approximately 50%, thus paving the way to the control of AFM properties with an electric field.

  2. Model of two-dimensional electron gas formation at ferroelectric interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Aguado-Puente, P.; Bristowe, N. C.; Yin, B.; Shirasawa, R.; Ghosez, Philippe; Littlewood, P. B.; Artacho, Emilio

    2015-07-01

    The formation of a two-dimensional electron gas at oxide interfaces as a consequence of polar discontinuities has generated an enormous amount of activity due to the variety of interesting effects it gives rise to. Here, we study under what circumstances similar processes can also take place underneath ferroelectric thin films. We use a simple Landau model to demonstrate that in the absence of extrinsic screening mechanisms, a monodomain phase can be stabilized in ferroelectric films by means of an electronic reconstruction. Unlike in the LaAlO3/SrTiO3 heterostructure, the emergence with thickness of the free charge at the interface is discontinuous. This prediction is confirmed by performing first-principles simulations of free-standing slabs of PbTiO3. The model is also used to predict the response of the system to an applied electric field, demonstrating that the two-dimensional electron gas can be switched on and off discontinuously and in a nonvolatile fashion. Furthermore, the reversal of the polarization can be used to switch between a two-dimensional electron gas and a two-dimensional hole gas, which should, in principle, have very different transport properties. We discuss the possible formation of polarization domains and how such configuration competes with the spontaneous accumulation of free charge at the interfaces.

  3. Silicon-doped hafnium oxide anti-ferroelectric thin films for energy storage

    Science.gov (United States)

    Ali, Faizan; Liu, Xiaohua; Zhou, Dayu; Yang, Xirui; Xu, Jin; Schenk, Tony; Müller, Johannes; Schroeder, Uwe; Cao, Fei; Dong, Xianlin

    2017-10-01

    Motivated by the development of ultracompact electronic devices as miniaturized energy autonomous systems, great research efforts have been expended in recent years to develop various types of nano-structural energy storage components. The electrostatic capacitors characterized by high power density are competitive; however, their implementation in practical devices is limited by the low intrinsic energy storage density (ESD) of linear dielectrics like Al2O3. In this work, a detailed experimental investigation of energy storage properties is presented for 10 nm thick silicon-doped hafnium oxide anti-ferroelectric thin films. Owing to high field induced polarization and slim double hysteresis, an extremely large ESD value of 61.2 J/cm3 is achieved at 4.5 MV/cm with a high efficiency of ˜65%. In addition, the ESD and the efficiency exhibit robust thermal stability in 210-400 K temperature range and an excellent endurance up to 109 times of charge/discharge cycling at a very high electric field of 4.0 MV/cm. The superior energy storage performance together with mature technology of integration into 3-D arrays suggests great promise for this recently discovered anti-ferroelectric material to replace the currently adopted Al2O3 in fabrication of nano-structural supercapacitors.

  4. On the ferroelectric and magnetoelectric mechanisms in low Fe3+ doped TbMnO3

    Science.gov (United States)

    Vilarinho, R.; Queirós, E.; Passos, D. J.; Mota, D. A.; Tavares, P. B.; Mihalik, M., Jr.; Zentkova, M.; Mihalik, M.; Almeida, A.; Moreira, J. Agostinho

    2017-10-01

    This work addresses the effect of substituting Mn3+ by Fe3+ at the octahedral site of TbMnO3 on the magnetic phase sequence, ferroelectric and magnetoelectric properties, keeping the Fe3+ concentration below 5%. The temperature dependence of the specific heat, dielectric permittivity and electric polarization was studied as a function of Fe3+ concentration and applied magnetic field. From the experimental results a strong decrease of the electric polarization with increasing Fe3+ substitution is observed, vanishing above a concentration of 4%. However, within this range, a significant increase of the magnetic sensitivity of the electric polarization is obtained by increasing Fe3+ concentration. For Fe3+ concentration above 4%, a non-polar phase emerges, whose spin structure prevents ferroelectricity according to the Dzyaloshinskii-Moriya model. The experimental results here reported reveal the crucial effect of B-site substitution on the magnetic phase sequence, as well as, on the polar and magnetoelectric properties, evidencing the important role played by the eg electrons on the stabilization of the magnetic structures that are suitable for the emergence of electric polarization.

  5. Highly mobile ferroelastic domain walls in compositionally graded ferroelectric thin films.

    Science.gov (United States)

    Agar, J C; Damodaran, A R; Okatan, M B; Kacher, J; Gammer, C; Vasudevan, R K; Pandya, S; Dedon, L R; Mangalam, R V K; Velarde, G A; Jesse, S; Balke, N; Minor, A M; Kalinin, S V; Martin, L W

    2016-05-01

    Domains and domain walls are critical in determining the response of ferroelectrics, and the ability to controllably create, annihilate, or move domains is essential to enable a range of next-generation devices. Whereas electric-field control has been demonstrated for ferroelectric 180° domain walls, similar control of ferroelastic domains has not been achieved. Here, using controlled composition and strain gradients, we demonstrate deterministic control of ferroelastic domains that are rendered highly mobile in a controlled and reversible manner. Through a combination of thin-film growth, transmission-electron-microscopy-based nanobeam diffraction and nanoscale band-excitation switching spectroscopy, we show that strain gradients in compositionally graded PbZr1-xTixO3 heterostructures stabilize needle-like ferroelastic domains that terminate inside the film. These needle-like domains are highly labile in the out-of-plane direction under applied electric fields, producing a locally enhanced piezoresponse. This work demonstrates the efficacy of novel modes of epitaxy in providing new modalities of domain engineering and potential for as-yet-unrealized nanoscale functional devices.

  6. Why is the electrocaloric effect so small in ferroelectrics?

    Directory of Open Access Journals (Sweden)

    G. G. Guzmán-Verri

    2016-06-01

    Full Text Available Ferroelectrics are attractive candidate materials for environmentally friendly solid state refrigeration free of greenhouse gases. Their thermal response upon variations of external electric fields is largest in the vicinity of their phase transitions, which may occur near room temperature. The magnitude of the effect, however, is too small for useful cooling applications even when they are driven close to dielectric breakdown. Insight from microscopic theory is therefore needed to characterize materials and provide guiding principles to search for new ones with enhanced electrocaloric performance. Here, we derive from well-known microscopic models of ferroelectricity meaningful figures of merit for a wide class of ferroelectric materials. Such figures of merit provide insight into the relation between the strength of the effect and the characteristic interactions of ferroelectrics such as dipolar forces. We find that the long range nature of these interactions results in a small effect. A strategy is proposed to make it larger by shortening the correlation lengths of fluctuations of polarization. In addition, we bring into question other widely used but empirical figures of merit and facilitate understanding of the recently observed secondary broad peak in the electrocalorics of relaxor ferroelectrics.

  7. The direct magnetoelectric effect in ferroelectric-ferromagnetic epitaxial heterostructures.

    Science.gov (United States)

    Fina, I; Dix, N; Rebled, J M; Gemeiner, P; Martí, X; Peiró, F; Dkhil, B; Sánchez, F; Fàbrega, L; Fontcuberta, J

    2013-09-07

    Ferroelectric (FE) and ferromagnetic (FM) materials engineered in horizontal heterostructures allow interface-mediated magnetoelectric coupling. The so-called converse magnetoelectric effect (CME) has been already demonstrated by electric-field poling of the ferroelectric layers and subsequent modification of the magnetic state of adjacent ferromagnetic layers by strain effects and/or free-carrier density tuning. Here we focus on the direct magnetoelectric effect (DME) where the dielectric state of a ferroelectric thin film is modified by a magnetic field. Ferroelectric BaTiO3 (BTO) and ferromagnetic CoFe2O4 (CFO) oxide thin films have been used to create epitaxial FE/FM and FM/FE heterostructures on SrTiO3(001) substrates buffered with metallic SrRuO3. It will be shown that large ferroelectric polarization and DME can be obtained by appropriate selection of the stacking order of the FE and FM films and their relative thicknesses. The dielectric permittivity, at the structural transitions of BTO, is strongly modified (up to 36%) when measurements are performed under a magnetic field. Due to the insulating nature of the ferromagnetic layer and the concomitant absence of the electric-field effect, the observed DME effect solely results from the magnetostrictive response of CFO elastically coupled to the BTO layer. These findings show that appropriate architecture and materials selection allow overcoming substrate-induced clamping in multiferroic multi-layered films.

  8. Performing spectroscopic and specific heat studies of improper ferroelectrics

    Science.gov (United States)

    Coleman, L. B.

    1982-01-01

    The results of infrared measurements on Ni-Br, Cu-Cl, and Fe-I boracite improper ferroelectrics and far infrared measurements of Ni-Br boracite are presented. The boracites have the general formula X3B7O3Y, where X = divalent metal and Y = halogen. They undergo a first order phase transition from a high temperature paraelectric phase with cubic symmetry to a ferroelectric phase with orthorhombic symmetry. The boracites are "improper ferroelectrics" since the spontaneous polarization is not the primary order parameter in the cubic-orthorhombic phase transition. Current understanding of these materials is that the primary order parameter is associated with a doubly degenerate zone-boundary phonon in the cubic phase. The degenerate critical modes become homogeneous and split into the A sub 1 and A sub 2 modes in the orthorhombic phase, doubling the volume of the primitive cell. An harmonic coupling between the softing A sub 1 and a low frequency A sub 1 optic mode induces a spontaneous polarization as a secondary effect in the ferroelectric phase. This secondary non-critical nature of the ferroelectric mode earns these materials the "improper" title and is responsible for their unique properties and high figure of merit in detector use.

  9. Evaluation of Ferroelectric Domain Behaviors Using Acoustic Emission Method

    Science.gov (United States)

    Aburatani, Hideaki

    2010-09-01

    Two kinds of acoustic emission (AE) signals are used to evaluate the ferroelectric domain behaviors in tetragonal lead zirconate titanate (PZT) ceramics: AE related to the ferroelectric domain and vibro acoustic emission (vibro-AE) caused by sample vibration. The signal level of vibro-AE caused by the sample vibration is suppressed using an external resistor, and the vibro-AE and AE related to the ferroelectric domain are observed simultaneously. It is shown that the vibro-AE measured as an AE signal Vrms reflects the piezoelectricity of the sample. The Kaiser effect in terms of electrical loading is found to be valid for ferroelectric PZT ceramics. From the vibro-AE measurement, it is shown that domain clamping occurs at critical fields at which the vibro-AE signal vanishes. It is also shown that domain-related AE takes place above the coercive field Ec and after domain clamping occurs. From these obtained AE activities, conflicts among ferroelectric domains in the sequence of domain reorientation from the clamped state to the aligned domain state and the resulting stress relaxations are considered to be the origin of AE.

  10. Enhanced photocatalytic efficiency of C3N4/BiFeO3heterojunctions: the synergistic effects of band alignment and ferroelectricity.

    Science.gov (United States)

    Deng, Xian-Zhu; Song, Chuang; Tong, Yin-Lin; Yuan, Guoliang; Gao, Feng; Liu, Dan-Qing; Zhang, Shan-Tao

    2018-01-31

    As one of the most promising photocatalysts, graphitic carbon nitride (g-C 3 N 4 ) shows a visible light response and great chemical stability. However, its relatively low photocatalytic efficiency is a major obstacle to actual applications. Here an effective and feasible method to dramatically increase the visible light photocatalytic efficiency by forming C 3 N 4 /BiFeO 3 ferroelectric heterojunctions is reported, wherein the band alignment and piezo-/ferroelectricity have synergistic positive effects in accelerating the separation of the photogenerated carriers. At the optimum composition of 10 wt% BiFeO 3 , the heterojunction shows 1.4 times improved photocatalytic efficiency than that of the pure C 3 N 4 . Most importantly, mechanical pressing and electrical poling can also improve the photocatalytic efficiencies by 1.3 times and 1.8 times, respectively. The optimized photocatalytic efficiency is even comparable with that of some noble metal based compounds. These results not only prove the improved photocatalytic activity of the C 3 N 4 -ferroelectric heterojunctions, but also provide a new approach for designing high-performance photocatalysts by taking advantage of ferroelectricity.

  11. Stability evaluation and sensitive determination of antiviral drug, valacyclovir and its metabolite acyclovir in human plasma by a rapid liquid chromatography-tandem mass spectrometry method.

    Science.gov (United States)

    Yadav, Manish; Upadhyay, Vivek; Singhal, Puran; Goswami, Sailendra; Shrivastav, Pranav S

    2009-03-15

    A simple, sensitive and high throughput liquid chromatography/positive-ion electrospray ionization mass spectrometry (LC-ESI-MS/MS) method has been developed for the simultaneous determination of valacyclovir and acyclovir in human plasma using fluconazole as internal standard (IS). The method involved solid phase extraction of the analytes and IS from 0.5 mL human plasma with no reconstitution and drying steps (direct injection of eluate). The chromatographic separation was achieved on a Gemini C18 analytical column using isocratic mobile phase, consisting of 0.1% formic acid and methanol (30:70 v/v), at a flow-rate of 0.8 mL/min. The precursor-->product ion transition for valacyclovir (m/z 325.2-->152.2), acyclovir (m/z 226.2-->152.2) and IS (m/z 307.1-->220.3) were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) mode. The method was validated over the concentration range 5.0-1075 ng/mL and 47.6-10225 ng/mL for valacyclovir and acyclovir respectively. The mean recovery of valacyclovir (92.2%), acyclovir (84.2%) and IS (103.7%) from spiked plasma samples was consistent and reproducible. The bench top stability of valacyclovir and acyclovir was extensively evaluated in buffered and unbuffered plasma. It was successfully applied to a bioequivalence study in 41 healthy human subjects after oral administration of 1000 mg valacyclovir tablet formulation under fasting condition.

  12. Stability-indicating reversed-phase liquid chromatographic method for simultaneous determination of atorvastatin and ezetimibe from their combination drug products.

    Science.gov (United States)

    Chaudhari, Bharat G; Patel, Natvarlal M; Shah, Paresh B; Patel, Laxman J; Patel, Vipul P

    2007-01-01

    A simple, precise, and rapid stability-indicating reversed-phase column liquid chromatographic (RP-LC) method has been developed and subsequently validated for simultaneous estimation of atorvastatin (ATV) and ezetimibe (EZE) from their combination drug product. The proposed RP-LC method utilizes a LiChrospher 100 C18, 5 microm, 250 x 4.0 mm id column at ambient temperature; the optimum mobile phase consists of acetonitrile-water-methanol (45 + 40 + 15, v/v/v) with apparent pH adjusted to 4.0 +/- 0.1; mobile phase flow rate of 1.0 mL/min; and UV detection at 250 nm. ATV, EZE, and their combination drug product were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. There were no other coeluting, interfering peaks from excipients, impurities, or degradation products due to variable stress conditions, and the method is specific for the estimation of ATV and EZE in the presence of degradation products. The response was linear over the concentration range of 1-80 microg/mL for ATV and EZE. The mean recoveries were 99.27 and 98.5% for ATV and EZE, respectively. The intermediate precision data were obtained under different experimental conditions, and the calculated value of the coefficient of variation was found to be less than the critical value. The proposed method can be useful in the quality control of bulk manufacturing and pharmaceutical dosage forms.

  13. Diglycolamide-functionalized calix[4]arenes showing unusual complexation of actinide ions in room temperature ionic liquids: role of ligand structure, radiolytic stability, emission spectroscopy, and thermodynamic studies.

    Science.gov (United States)

    Mohapatra, Prasanta K; Sengupta, Arijit; Iqbal, Mudassir; Huskens, Jurriaan; Verboom, Willem

    2013-03-04

    Diglycolamide-functionalized calix[4]arenes (C4DGAs) with varying structural modifications were evaluated for actinide complexation from their extraction behavior toward actinide ions such as UO2(2+), Pu(4+), PuO2(2+), and Am(3+) in the room temperature ionic liquid (RTIL) 1-n-octyl-3-methylimidazolium bis(trifluoromethane)sulfonamide (C8mimNTf2). The formation constants were calculated for Am(3+) which showed a significant role of ligand structure, nature of substituents, and spacer length. Although the alkyl substituents on the amidic nitrogen increase the extraction efficiency of americium at lower acidity because of the inductive effect of the alkyl groups, at higher acidity the steric crowding around the ligating site determines the extraction efficiency. All C4DGAs formed 1:1 complexes with Am(3+) while for the analogous Eu(3+) complexes no inner sphere water molecules were detected and the asymmetry of the metal ligand complex differed from one another as proved by time-resolved laser induced fluorescence spectroscopy (TRLIFS). Thermodynamic studies indicated that the extraction process, predominant by the Am(3+)-C4DGA complexation reaction, is exothermic. The unique role of the medium on Am(3+) complexation with the C4DGA molecules with varying spacer length, L-IV and L-V, was noticed for the first time with a reversal in the trend observed in the RTIL compared to that seen in a nonpolar molecular diluent like n-dodecane. Various factors leading to a more preorganized structure were responsible for favorable metal ion complexation. The solvent systems show promise to be employed for nuclear waste remediation, and sustainability options were evaluated from radiolytic stability as well as stripping studies.

  14. Optically addressed ferroelectric memory with nondestructive readout.

    Science.gov (United States)

    Thakoor, S; Thakoor, A P

    1995-06-10

    We present a review of the emerging optically addressed ferroelectric memory with nondestructive readout as a nonvolatile memory technology, identify its high-impact applications, and project on some novel device designs and architectures that will enable its realization. Based on the high-speed bidirectional polarization-dependent photoresponse, simulation of a readout circuit for a 16-kbit VLSI ferromemory chip yields read-access times of ~20 ns and read-cycle times of ~30 ns (~34 ns and ~44 ns, respectively, within a framework of a radiation-hard environment), easily surpassing those of the conventional electrical destructive readout. Extension of the simulation for a 64-kbit memory shows that the read-access and -cycle times are only marginally increased to ~21 ns and ~31 ns, respectively (~38 ns and ~48 ns, with a radiation-hard readout circuitry). Commercial realization of the optical nondestructive readout, however, would require a reduction in the incident (optical) power by roughly an order of magnitude for the readout or an enhancement in the delivered power-to-size ratio of semiconductor lasers for compact implementation. We present a new two-capacitor memory-cell configuration that provides an enhanced bipolar optoelectronic response from the edges of the capacitor at incident power as low as ~ 2 mW/µm(2). A novel device design based on lead zirconate titanate with the c axis parallel to the substrate is suggested to reduce the requirement of incident optical power further by orders of magnitude.

  15. Wave-mixing solitons in ferroelectric crystals

    Science.gov (United States)

    Bugaychuk, S.; Kovacs, L.; Mandula, G.; Polgar, K.; Rupp, R. A.

    Although the sine-Gordon equation was originally obtained for the description of four-wave mixing in transmission geometry, it describes self-diffraction of the wave from shifted gratings as well. The sine-Gordon equation governs soliton propagation. The photoinduced amplitude of the refractive-index grating exhibits also a soliton shape in the crystal volume. The origin of this effect is the change of the contrast of light due to energy transfer between coupled waves during their propagation, which occurs in bulk crystals with strong photorefractive gain. The theoretical description shows the possibility to control the soliton properties by changing the input intensity ratio and/or input phase difference of the wave. The effect can lead to diffraction efficiency management, auto-oscillations and bistability of the output waves due to wave-mixing in ferroelectrics. Results on the first experimental observation of non-uniform distribution of the grating amplitude profile and its changes versus input intensity ratio are presented.

  16. Advances in monolithic ferroelectric uncooled IRFPA technology

    Science.gov (United States)

    Hanson, Charles M.; Beratan, Howard R.; Belcher, James F.; Udayakumar, K. R.; Soch, Kevin L.

    1998-07-01

    The success of uncooled IR imaging at Raytheon has awakened a new view of the potential of thermal imaging. Once relegated to only expensive military platforms, occasionally to civilian platforms, and envisioned for individual soldiers, thermal imaging is now affordable for police cars, commercial surveillance, driving aids, and a variety of other industrial and consumer applications. System prices are as low as $8000, and swelling production volume will soon drive prices substantially lower. The impetus for further development is performance. The hybrid barium strontium titanate (BST) detectors currently in production have limited potential for improved sensitivity, and their MTF is suppressed at high frequencies. Microbolometer arrays in development at Raytheon have demonstrated performance superior to hybrid detectors. However, microbolometer technology lacks a mature, low-cost system technology and an abundance of deployable system implementations. Thin-film ferroelectric (TFFE) detectors have all the performance potential of microbolometers, and arguably more. They are also compatible with numerous fielded and planned system implementations. Like a microbolometer, the TFFE detector is monolithic; i.e., the detector material is deposited directly on the readout IC rather than being bump bonded to it. Initial imaging arrays of 240 X 320 pixels have been produced, demonstrating the feasibility of the technology.

  17. Hybrid liquid crystals: Enhanced electro-optic and nonlinear response for manipulating beams (Conference Presentation)

    Science.gov (United States)

    Kaczmarek, Malgosia; D'Alessandro, Giampaolo; Proctor, Matthew B.

    2016-09-01

    The manipulation and processing of light beams can be efficiently accomplished through devices based on soft matter placed in a hybrid "symbiosis" with other organic or inorganic, photoresponsive materials. The performance of such smart modulating systems often relies on a subtle balance between individual properties of each component, together with the varying interaction between organic and inorganic elements. Some promising demonstrations in the visible as well as in the THz regimes include liquid crystals integrated with plasmonic or ferroelectric nanoparticles, photoconductive or photosensitive polymers as well as metamaterials. They offer adaptive, flexible and tailor-made solutions for applications in displays and optoelectronics, switching, steering and modulating electromagnetic waves. Hybrid configurations that include multiple photoresponsive layers, sandwiched with liquid crystals, led to stronger modulation and steering of light beams in the visible. Such effects can also be observed in the other regions of spectrum, as inorganic nanoparticles dispersed in liquid crystals modify the magnitude of the material refractive indices measured in THz. The development of such hybrid materials has to be accompanied by comprehensive characterisation of their uniformity, stability and optical quality across the whole surface of the device, capable of determining their optical, electrical and physical parameters.

  18. Electrical characterisation of ferroelectric field effect transistors based on ferroelectric HfO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yurchuk, Ekaterina

    2015-02-06

    Ferroelectric field effect transistor (FeFET) memories based on a new type of ferroelectric material (silicon doped hafnium oxide) were studied within the scope of the present work. Utilisation of silicon doped hafnium oxide (Si:HfO{sub 2}) thin films instead of conventional perovskite ferroelectrics as a functional layer in FeFETs provides compatibility to the CMOS process as well as improved device scalability. The influence of different process parameters on the properties of Si:HfO{sub 2} thin films was analysed in order to gain better insight into the occurrence of ferroelectricity in this system. A subsequent examination of the potential of this material as well as its possible limitations with the respect to the application in non-volatile memories followed. The Si:HfO{sub 2}-based ferroelectric transistors that were fully integrated into the state-of-the-art high-k metal gate CMOS technology were studied in this work for the first time. The memory performance of these devices scaled down to 28 nm gate length was investigated. Special attention was paid to the charge trapping phenomenon shown to significantly affect the device behaviour.

  19. Controlling the spin-torque efficiency with ferroelectric barriers

    KAUST Repository

    Useinov, A.

    2015-02-11

    Nonequilibrium spin-dependent transport in magnetic tunnel junctions comprising a ferroelectric barrier is theoretically investigated. The exact solutions of the free electron Schrödinger equation for electron tunneling in the presence of interfacial screening are obtained by combining Bessel and Airy functions. We demonstrate that the spin transfer torque efficiency, and more generally the bias dependence of tunneling magneto- and electroresistance, can be controlled by switching the ferroelectric polarization of the barrier. In particular, the critical voltage at which the in-plane torque changes sign can be strongly enhanced or reduced depending on the direction of the ferroelectric polarization of the barrier. This effect provides a supplementary way to electrically control the current-driven dynamic states of the magnetization and related magnetic noise in spin transfer devices.

  20. Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

    Science.gov (United States)

    Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

    2013-01-01

    Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics. PMID:23884324

  1. Polarization control at spin-driven ferroelectric domain walls.

    Science.gov (United States)

    Leo, Naëmi; Bergman, Anders; Cano, Andres; Poudel, Narayan; Lorenz, Bernd; Fiebig, Manfred; Meier, Dennis

    2015-04-14

    Unusual electronic states arise at ferroelectric domain walls due to the local symmetry reduction, strain gradients and electrostatics. This particularly applies to improper ferroelectrics, where the polarization is induced by a structural or magnetic order parameter. Because of the subordinate nature of the polarization, the rigid mechanical and electrostatic boundary conditions that constrain domain walls in proper ferroics are lifted. Here we show that spin-driven ferroelectricity promotes the emergence of charged domain walls. This provides new degrees of flexibility for controlling domain-wall charges in a deterministic and reversible process. We create and position a domain wall by an electric field in Mn0.95Co0.05WO4. With a magnetic field we then rotate the polarization and convert neutral into charged domain walls, while its magnetic properties peg the wall to its location. Using atomistic Landau-Lifshitz-Gilbert simulations we quantify the polarization changes across the two wall types and highlight their general occurrence.

  2. Quantum tunnelling and charge accumulation in organic ferroelectric memory diodes

    Science.gov (United States)

    Ghittorelli, Matteo; Lenz, Thomas; Sharifi Dehsari, Hamed; Zhao, Dong; Asadi, Kamal; Blom, Paul W. M.; Kovács-Vajna, Zsolt M.; de Leeuw, Dago M.; Torricelli, Fabrizio

    2017-06-01

    Non-volatile memories--providing the information storage functionality--are crucial circuit components. Solution-processed organic ferroelectric memory diodes are the non-volatile memory candidate for flexible electronics, as witnessed by the industrial demonstration of a 1 kbit reconfigurable memory fabricated on a plastic foil. Further progress, however, is limited owing to the lack of understanding of the device physics, which is required for the technological implementation of high-density arrays. Here we show that ferroelectric diodes operate as vertical field-effect transistors at the pinch-off. The tunnelling injection and charge accumulation are the fundamental mechanisms governing the device operation. Surprisingly, thermionic emission can be disregarded and the on-state current is not space charge limited. The proposed model explains and unifies a wide range of experiments, provides important design rules for the implementation of organic ferroelectric memory diodes and predicts an ultimate theoretical array density of up to 1012 bit cm-2.

  3. Modeling of PZT Ferroelectric Ceramic Depolarization Driven by Shock Stress

    Science.gov (United States)

    Lan, Chao-Hui; Peng, Yu-Fei; Long, Ji-Dong; Wang, Qiang; Wang, Wen-Dou

    2011-08-01

    Shock-induced phase transition of ferroelectric ceramic PZT 95/5 causes elastic stiffening and depolarization, releasing stored electrostatic energy into the load circuit. We develop a model to describe the response of the PZT ferroelectric ceramic and implement it into simulation codes. The model is based on the phenomenological theory of phase transition dynamics and takes into account the effects of the self-generated intensive electrical field and stress. Connected with the discharge model and external circuit, the whole transient process of PZT ceramic depoling can be investigated. The results show the finite transition velocity of the ferroelectric phase and the double wave structure caused by phase transition. Simulated currents are compared with the results from experiments with shock pressures varying from 0.4 to 2.8 GPa.

  4. Fast Ferroelectric L-Band Tuner for Superconducting Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Jay L. Hirshfield

    2011-03-01

    Analysis and modeling is presented for a fast microwave tuner to operate at 700 MHz which incorporates ferroelectric elements whose dielectric permittivity can be rapidly altered by application of an external voltage. This tuner could be used to correct unavoidable fluctuations in the resonant frequency of superconducting cavities in accelerator structures, thereby greatly reducing the RF power needed to drive the cavities. A planar test version of the tuner has been tested at low levels of RF power, but at 1300 MHz to minimize the physical size of the test structure. This test version comprises one-third of the final version. The tests show performance in good agreement with simulations, but with losses in the ferroelectric elements that are too large for practical use, and with issues in bonding of ferroelectric elements to the metal walls of the tuner structure.

  5. Heterogeneous Ferroelectric Solid Solutions Phases and Domain States

    CERN Document Server

    Topolov, Vitaly

    2012-01-01

    The book deals with perovskite-type ferroelectric solid solutions for modern materials science and applications, solving problems of complicated heterophase/domain structures near the morphotropic phase boundary and applications to various systems with morphotropic phases. In this book domain state–interface diagrams are presented for the interpretation of heterophase states in perovskite-type ferroelectric solid solutions. It allows to describe the stress relief in the presence of polydomain phases, the behavior of unit-cell parameters of coexisting phases and the effect of external electric fields. The novelty of the book consists in (i) the first systematization of data about heterophase states and their evolution in ferroelectric solid solutions (ii) the general interpretation of heterophase and domain structures at changing temperature, composition or electric field (iii) the complete analysis of interconnection domain structures, unit-cell parameters changes, heterophase structures and stress relief.

  6. Electrochemical ferroelectric switching: Origin of polarization reversal in ultrathin films

    Science.gov (United States)

    Bristowe, N. C.; Stengel, Massimiliano; Littlewood, P. B.; Pruneda, J. M.; Artacho, Emilio

    2012-01-01

    Against expectations, robust switchable ferroelectricity has been recently observed in ultrathin (1 nm) ferroelectric films exposed to air [V. Garcia , Nature (London)NATUAS0028-083610.1038/nature08128 460, 81 (2009)]. Based on first-principles calculations, we show that the system does not polarize unless charged defects or adsorbates form at the surface. We propose electrochemical processes as the most likely origin of this charge. The ferroelectric polarization of the film adapts to the external ionic charge generated on its surface by redox processes when poling the film. This, in turn, alters the band alignment at the bottom electrode interface, explaining the observed tunneling electroresistance. Our conclusions are supported by energetics calculated for varied electrochemical scenarios.

  7. An Apparatus of increased precision for the Measurement of Electro-Optical parameters of Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Vishal Singh Chandel

    2012-11-01

    Full Text Available The ferroelectric liquid crystals (FLCs are demanding high attention now a day, because of their potential applications in many electro-optical devices, particularly in displays. The suitable applications of FLCs in devices are decided by their electro-optical properties like tilt angle, birefringence and spontaneous polarization. In this paper  we are presenting a new apparatus for highly accurate measurement of electro-optical parameters of FLCs. The accuracy of the apparatus is the best among the currently available equipments in the market. The accuracy and performance of the apparatus has been confirmed by performing the experiments on standard ferroelectric liquid crystals.

  8. Fatigue and retention in ferroelectric Y-Ba-Cu-O/Pb-Zr-Ti-O/Y-Ba-Cu-O heterostructures

    Science.gov (United States)

    Ramesh, R.; Chan, W. K.; Wilkens, B.; Gilchrist, H.; Sands, T.; Tarascon, J. M.; Keramidas, V. G.; Fork, D. K.; Lee, J.; Safari, A.

    1992-09-01

    Fatigue and retention characteristics of ferroelectric lead zirconate titanate thin films grown with Y-Ba-Cu-O(YBCO) thin-film top and bottom electrodes are found to be far superior to those obtained with conventional Pt top electrodes. The heterostructures reported here have been grown in situ by pulsed laser deposition on yttria-stabilized ZrO2 buffer [100] Si and on [001] LaAlO3. Both the a- and c-axis orientations of the YBCO lattice have been used as electrodes. They were prepared using suitable changes in growth conditions.

  9. Enhancement of the saturation mobility in a ferroelectric-gated field-effect transistor by the surface planarization of ferroelectric film

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo Young, E-mail: semigumi@kaist.ac.kr [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Jeon, Gwang-Jae; Kang, In-Ku; Shim, Hyun Bin; Lee, Hee Chul [Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2015-09-30

    Ferroelectricity refers to the property of a dielectric material to undergo spontaneous polarization which originates from the crystalline phase. Hence, ferroelectric materials have a certain degree of surface roughness when they are formed as a thin film. A high degree of surface roughness may cause unintended phenomena when the ferroelectric material is used in electronic devices. Specifically, the quality of subsequently deposited film could be affected by the rough surface. The present study reports that the surface roughness of ferroelectric polymer film can be reduced by a double-spin-coating method of a solution, with control of the solubility of the solution. At an identical thickness of 350 nm, double-spin-coated ferroelectric film has a root-mean-square roughness of only 3 nm, while for single-spin-coated ferroelectric film this value is approximately 16 nm. A ferroelectric-gated field-effect transistor was fabricated using the proposed double-spin-coating method, showing a maximum saturation mobility as much as seven-fold than that of a transistor fabricated with single-spin-coated ferroelectric film. The enhanced saturation mobility could be explained by the Poole–Frenkel conduction mechanism. The proposed method to reduce the surface roughness of ferroelectric film would be useful for high performance organic electronic devices, including crystalline-phase dielectric film. - Highlights: • Single and double-layer solution-processed polymer ferroelectric films were obtained. • Adjusting the solvent solubility allows making double-layer ferroelectric (DF) films. • The DF film has a smoother surface than single-layer ferroelectric (SF) film. • DF-gated transistor has faster saturation mobility than SF-based transistor. • Solvent solubility adjustment led to higher performance organic devices.

  10. Ferroelectric-antiferroelectric mixed systems. Equation of state, thermodynamic functions

    Directory of Open Access Journals (Sweden)

    N.A.Korynevskii

    2006-01-01

    Full Text Available The problem of equation of state for ferroelectric-antiferroelectric mixed systems in the whole region of a concentration change (0≤n≤1 is discussed. The main peculiarity of the presented model turns out to be the possibility for the site dipole momentum to be oriented ferroelectrically in z-direction and antiferroelectrically in x-direction. Such a situation takes place in mixed compounds of KDP type. The different phases (ferro-, antiferro-, paraelectric, dipole glass and some combinations of them have been found and analyzed.

  11. Engineering ferroelectric tunnel junctions through potential profile shaping

    Energy Technology Data Exchange (ETDEWEB)

    Boyn, S.; Garcia, V., E-mail: vincent.garcia@thalesgroup.com; Fusil, S.; Carrétéro, C.; Garcia, K.; Collin, S.; Deranlot, C.; Bibes, M.; Barthélémy, A. [Unité Mixte de Physique CNRS/Thales, 1 Av. Fresnel, 91767 Palaiseau, France and Université Paris-Sud, 91405 Orsay (France); Xavier, S. [Thales Research and Technology, 1 Av. Fresnel, 91767 Palaiseau (France)

    2015-06-01

    We explore the influence of the top electrode materials (W, Co, Ni, Ir) on the electronic band profile in ferroelectric tunnel junctions based on super-tetragonal BiFeO{sub 3}. Large variations of the transport properties are observed at room temperature. In particular, the analysis of current vs. voltage curves by a direct tunneling model indicates that the metal/ferroelectric interfacial barrier height increases with the top-electrode work function. While larger metal work functions result in larger OFF/ON ratios, they also produce a large internal electric field which results in large and potentially destructive switching voltages.

  12. Voltage tunability of thermal conductivity in ferroelectric materials

    Science.gov (United States)

    Ihlefeld, Jon; Hopkins, Patrick Edward

    2016-02-09

    A method to control thermal energy transport uses mobile coherent interfaces in nanoscale ferroelectric films to scatter phonons. The thermal conductivity can be actively tuned, simply by applying an electrical potential across the ferroelectric material and thereby altering the density of these coherent boundaries to directly impact thermal transport at room temperature and above. The invention eliminates the necessity of using moving components or poor efficiency methods to control heat transfer, enabling a means of thermal energy control at the micro- and nano-scales.

  13. Switching properties of self-assembled ferroelectric memory cells

    Science.gov (United States)

    Alexe, M.; Gruverman, A.; Harnagea, C.; Zakharov, N. D.; Pignolet, A.; Hesse, D.; Scott, J. F.

    1999-08-01

    In this letter, we report on the switching properties of an ordered system of Bi4Ti3O12 ferroelectric memory cells of an average lateral size of 0.18 μm formed via a self-assembling process. The ferroelectricity of these cells has been measured microscopically and it has been demonstrated that an individual cell of 0.18 μm size is switching. Switching of single nanoelectrode cells was achieved via scanning force microscopy working in piezoresponse mode.

  14. Ferroelectric emission studies for electron emission lithography applications.

    Science.gov (United States)

    Yoo, In K; Ryu, Sang O; Suchicital, Carlos T A; Lee, June K; Kim, Byong M; Chung, Chee W

    2003-10-01

    Ferroelectric switching emission, dielectric switching emission, and pyroelectric emission were studied by patterning images on electron resist for electron emission lithography applications. It was observed that the pyroelectric emission is most acceptable for a high throughput 1:1 electron projection lithography application. A 1:1 electron projection lithography was demonstrated by patterning images with line widths of 30 microm and using pyroelectric emission. A degradation of the pyroelectric emission property of the material was observed during repeated heating cycles below the phase-transition temperature of the ferroelectric material. Annealing excursions above the phase transition temperature prevented the degradation of the pyroelectric emitter.

  15. Liquids and liquid mixtures

    CERN Document Server

    Rowlinson, J S; Baldwin, J E; Buckingham, A D; Danishefsky, S

    2013-01-01

    Liquids and Liquid Mixtures, Third Edition explores the equilibrium properties of liquids and liquid mixtures and relates them to the properties of the constituent molecules using the methods of statistical thermodynamics. Topics covered include the critical state, fluid mixtures at high pressures, and the statistical thermodynamics of fluids and mixtures. This book consists of eight chapters and begins with an overview of the liquid state and the thermodynamic properties of liquids and liquid mixtures, including vapor pressure and heat capacities. The discussion then turns to the thermodynami

  16. Graphene separation and stretching induced by piezoelectric effect of ferroelectric domains: impact on the conductance of graphene channel

    OpenAIRE

    Morozovska, Anna N.; Kurchak, Anatolii I.; Strikha, Maksym V.

    2017-01-01

    P-N junctions in graphene on ferroelectric have been actively studied, but the impact of piezoelectric effect in ferroelectric substrate with ferroelectric domain walls (FDWs) on graphene characteristics was not considered. Due to the piezo-effect ferroelectric domain stripes with opposite spontaneous polarizations elongate or contract depending on the polarity of voltage applied to the substrate. We show that the alternating piezoelectric displacement of the ferroelectric domain surfaces can...

  17. Transport Phenomena in Liquid Foams and Liquid Marble Colloids

    OpenAIRE

    Attia, Joseph

    2016-01-01

    Liquid foams consist of randomly packed bubbles separated by a thin liquid fluid. They can be found in various industrial applications including separation processes, oil recovery, water treatment, food, and material processings. They are also being considered as coolant in heat exchangers systems for heat transfer enhancement compared with single-phase air. Similarly, liquid marbles, a phase inversion of liquid foams, consisting of a liquid core stabilized by closely packed solid hydrophobic...

  18. Ferroelectric switching of poly(vinylidene difluoride-trifluoroethylene) in metal-ferroelectric-semiconductor non-volatile memories with an amorphous oxide semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Gelinck, G. H., E-mail: Gerwin.Gelinck@tno.nl [Holst Centre/TNO, High Tech Campus 31, 5656 AE Eindhoven (Netherlands); Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Breemen, A. J. J. M. van; Cobb, B. [Holst Centre/TNO, High Tech Campus 31, 5656 AE Eindhoven (Netherlands)

    2015-03-02

    Ferroelectric polarization switching of poly(vinylidene difluoride-trifluoroethylene) is investigated in different thin-film device structures, ranging from simple capacitors to dual-gate thin-film transistors (TFT). Indium gallium zinc oxide, a high mobility amorphous oxide material, is used as semiconductor. We find that the ferroelectric can be polarized in both directions in the metal-ferroelectric-semiconductor (MFS) structure and in the dual-gate TFT under certain biasing conditions, but not in the single-gate thin-film transistors. These results disprove the common belief that MFS structures serve as a good model system for ferroelectric polarization switching in thin-film transistors.

  19. Investigation on crystalline perfection, mechanical, piezoelectric and ferroelectric properties of L-tartaric acid single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Murugan, G. Senthil, E-mail: nanosen@gmail.com; Ramasamy, P., E-mail: nanosen@gmail.com [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam, Tamilnadu - 603110 (India)

    2014-04-24

    Polar organic nonlinear optical material, L-tartaric acid single crystals have been grown from slow evaporation solution growth technique. Single crystal X-ray diffraction study indicates that the grown crystal crystallized in monoclinic system with space group P2{sub 1}. Crystalline perfection of the crystal has been evaluated by high resolution X-ray diffraction technique and it reveals that the crystal quality is good and free from structural grain boundaries. Mechanical stability of the crystal has been analyzed by Vickers microhardness measurement and it exhibits reverse indentation size effect. Piezoelectric d{sub 33} co-efficient for the crystal has been examined and its value is 47 pC/N. The ferroelectric behaviour of the crystal was analyzed by polarization-electric field hysteresis loop measurement.

  20. Antiferroelectric and ferroelectric orderings in frustrated chiral tilted smectics and a continuous change from anticlinic SmCA* to synclinic SmC*

    Science.gov (United States)

    Sandhya, K. L.; Chandani-Perera, A. D. L.; Fukuda, Atsuo; Vij, J. K.; Ishikawa, Ken

    2010-06-01

    In a frustrated binary-mixture system of ferroelectric and antiferroelectric liquid crystals, where the border line between SmCA* and SmC* in the temperature-concentration phase diagram runs almost parallel to the ordinate temperature axis, we have found a continuous change between them close to the critical concentration. The continuity has been confirmed as an intrinsic property in the bulk by observing almost perfect bell-shaped Bragg reflection bands due to the helicoidal director structure. The temperature variation of peak wavelength of the half-pitch band and, in particular, the characteristic disappearance of the full-pitch band apparently within the SmC* temperature region have been simulated with a change in the ratio of ferroelectric and antiferroelectric orderings. The observed continuous change has been described by the entropy effect in the 1D Ising model with the synclinic and anticlinic orderings as spins.

  1. Static negative capacitance of a ferroelectric nano-domain nucleus.

    Czech Academy of Sciences Publication Activity Database

    Sluka, T.; Mokrý, Pavel; Setter, N.

    2017-01-01

    Roč. 111, č. 15 (2017), č. článku 152902. ISSN 0003-6951 R&D Projects: GA ČR(CZ) GA14-32228S Institutional support: RVO:61389021 Keywords : Ferroelectric materials * Capacitors * Bipolar transistors * Electrodes * Dielectrics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.411, year: 2016

  2. Physics of organic ferroelectric field-effect transistors

    NARCIS (Netherlands)

    Brondijk, J.J.; Asadi, K.; Blom, P.W.M.; Leeuw, D.M. de

    2012-01-01

    Most of the envisaged applications of organic electronics require a nonvolatile memory that can be programmed, erased, and read electrically. Ferroelectric field-effect transistors (FeFET) are especially suitable due to the nondestructive read-out and low power consumption. Here, an analytical model

  3. Effect of domains configuration on crystal structure in ferroelectric ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 40; Issue 6. Effect of domains configuration on crystal structure in ferroelectric ceramics as revealed by XRD and dielectric spectrum. JIWEN XU WEIDONG ZENG QINGNING LI LING YANG CHANGRONG ZHOU. Volume 40 Issue 6 October 2017 pp 1159-1163 ...

  4. A comparative study regarding effects of interfacial ferroelectric ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 37; Issue 2. A comparative study regarding effects of interfacial ferroelectric Bi4Ti3O12 (BTO) layer on electrical characteristics of Au/-Si structures. M Yildirim M Gökçen. Electronic Supplementary Material Volume 37 Issue 2 April 2014 pp 257-262 ...

  5. Dielectric properties of KDP-type ferroelectric crystals in the ...

    Indian Academy of Sciences (India)

    Considering external electric field as well as third- and fourth-order phonon anharmonic interaction terms in the pseudospin-lattice coupled mode (PLCM) model Hamiltonian for KDP-type ferroelectrics, expressions for field-dependent shift, width, renormalized soft mode frequency, Curie temperature, dielectric constant and ...

  6. Effects of Bi doping on dielectric and ferroelectric properties of ...

    Indian Academy of Sciences (India)

    Effects of Bi doping on structure, dielectric and ferroelectric properties of PLBZT were investigated. Bi doping is useful in crystallization of PLBZT films and promoting grain growth. When the Bi-doping content is not more than 0.4, an obvious improvement in dielectric properties and leakage current of PLBZT was confirmed ...

  7. Artificial design for new ferroelectrics using nanosheet-architectonics concept.

    Science.gov (United States)

    Kim, Yoon-Hyun; Dong, Lei; Osada, Minoru; Li, Bao-Wen; Ebina, Yasuo; Sasaki, Takayoshi

    2015-06-19

    Control over the emergence of ferroelectric order remains a fundamental challenge for the rational design of artificial materials with novel properties. Here we report a new strategy for artificial design of layered perovskite ferroelectrics by using oxide nanosheets (high-k dielectric Ca2Nb3O10 and insulating Ti0.87O2) as a building block. We approached the preparation of superlattice films by a layer-by-layer assembly involving Langmuir-Blodgett deposition. The artificially fabricated (Ti0.87O2/Ca2Nb3O10)2(Ti0.87O2) superlattices are structurally unique, which is not feasible to create in the bulk form. By such an artificial structuring, we found that (Ti0.87O2/Ca2Nb3O10)2(Ti0.87O2) superlattices possess a new form of interface coupling, which gives rise to ferroelectricity with a good fatigue-free characteristic. Considering the flexibility of self-assembled nanosheet interfaces, this technique provides a route to synthesize a new kind of layered ferroelectric oxides.

  8. Ferroelectric displacements in multiferroic Y(Mn,Ga)O-3

    NARCIS (Netherlands)

    Adem, U.; Nugroho, A. A.; Meetsma, A.; Palstra, T. T. M.

    We have studied the effects of substitution of Mn3+ by Ga3+ on the crystal structure of YMnO3. Y(Mn,Ga)O-3 is a magnetoferroelectric in which the ferroelectric displacements from the YO7 polyhedra are associated with buckling and tilting of the MnO5 bipyramids. The differences in ionic radius and

  9. Domain walls and ferroelectric reversal in corundum derivatives

    Science.gov (United States)

    Ye, Meng; Vanderbilt, David

    2017-01-01

    Domain walls are the topological defects that mediate polarization reversal in ferroelectrics, and they may exhibit quite different geometric and electronic structures compared to the bulk. Therefore, a detailed atomic-scale understanding of the static and dynamic properties of domain walls is of pressing interest. In this work, we use first-principles methods to study the structures of 180∘ domain walls, both in their relaxed state and along the ferroelectric reversal pathway, in ferroelectrics belonging to the family of corundum derivatives. Our calculations predict their orientation, formation energy, and migration energy and also identify important couplings between polarization, magnetization, and chirality at the domain walls. Finally, we point out a strong empirical correlation between the height of the domain-wall-mediated polarization reversal barrier and the local bonding environment of the mobile A cations as measured by bond-valence sums. Our results thus provide both theoretical and empirical guidance for future searches for ferroelectric candidates in materials of the corundum derivative family.

  10. Effect of microstructure on irradiated ferroelectric thin films

    Science.gov (United States)

    Brewer, Steven J.; Zhou, Hanhan; Williams, Samuel C.; Rudy, Ryan Q.; Rivas, Manuel; Polcawich, Ronald G.; Cress, Cory D.; Glaser, Evan R.; Paisley, Elizabeth A.; Ihlefeld, Jon F.; Jones, Jacob L.; Bassiri-Gharb, Nazanin

    2017-06-01

    This work investigates the role of microstructure on radiation-induced changes to the functional response of ferroelectric thin films. Chemical solution-deposited lead zirconate titanate thin films with columnar and equiaxed grain morphologies are exposed to a range of gamma radiation doses up to 10 Mrad and the resulting trends in functional response degradation are quantified using a previously developed phenomenological model. The observed trends of global degradation as well as local rates of defect saturation suggest strong coupling between ferroelectric thin film microstructure and material radiation hardness. Radiation-induced degradation of domain wall motion is thought to be the major contributor to the reduction in ferroelectric response. Lower rates of defect saturation are noted in samples with columnar grains, due to increased grain boundary density offering more sites to act as defect sinks, thus reducing the interaction of defects with functional material volume within the grain interior. Response trends for measurements at low electric field show substantial degradation of polarization and piezoelectric properties (up to 80% reduction in remanent piezoelectric response), while such effects are largely diminished at increased electric fields, indicating that the defects created/activated are primarily of low pinning energy. The correlation of film microstructure to radiation-induced changes to the functional response of ferroelectric thin films can be leveraged to tune and tailor the eventual properties of devices relying on these materials.

  11. Structural visualization of polarization fatigue in epitaxial ferroelectric oxide devices.

    Science.gov (United States)

    Do, Dal-Hyun; Evans, Paul G; Isaacs, Eric D; Kim, Dong Min; Eom, Chang Beom; Dufresne, Eric M

    2004-06-01

    Ferroelectric oxides, such as Pb(Zr,Ti)O(3), are useful for electronic and photonic devices because of their ability to retain two stable polarization states, which can form the basis for memory and logic circuitry. Requirements for long-term operation of practical devices such as non-volatile RAM (random access memory) include consistent polarization switching over many (more than 10(12)) cycles of the applied electric field, which represents a major challenge. As switching is largely controlled by the motion and pinning of domain walls, it is necessary to develop suitable tools that can directly probe the ferroelectric domain structures in operating devices-thin-film structures with electrical contacts. A recently developed synchrotron X-ray microdiffraction technique complements existing microscopic probes, and allows us to visualize directly the evolution of polarization domains in ferroelectric devices, through metal or oxide electrodes, and with submicrometre spatial resolution. The images reveal two regimes of fatigue, depending on the magnitude of the electric field pulses driving the device: a low-field regime in which fatigue can be reversed with higher electric field pulses, and a regime at very high electric fields in which there is a non-reversible crystallographic relaxation of the epitaxial ferroelectric film.

  12. Strain incompatibility and residual strains in ferroelectric single crystals.

    Science.gov (United States)

    Pramanick, A; Jones, J L; Tutuncu, G; Ghosh, D; Stoica, A D; An, K

    2012-01-01

    Residual strains in ferroelectrics are known to adversely affect the material properties by aggravating crack growth and fatigue degradation. The primary cause for residual strains is strain incompatibility between different microstructural entities. For example, it was shown in polycrystalline ferroelectrics that residual strains are caused due to incompatibility between the electric-field-induced strains in grains with different crystallographic orientations. However, similar characterization of cause-effect in multidomain ferroelectric single crystals is lacking. In this article, we report on the development of plastic residual strains in [111]-oriented domain engineered BaTiO(3) single crystals. These internal strains are created due to strain incompatibility across 90° domain walls between the differently oriented domains. The average residual strains over a large crystal volume measured by in situ neutron diffraction is comparable to previous X-ray measurements of localized strains near domain boundaries, but are an order of magnitude lower than electric-field-induced residual strains in polycrystalline ferroelectrics.

  13. Formation of charged ferroelectric domain walls with controlled periodicity.

    Science.gov (United States)

    Bednyakov, Petr S; Sluka, Tomas; Tagantsev, Alexander K; Damjanovic, Dragan; Setter, Nava

    2015-10-30

    Charged domain walls in proper ferroelectrics were shown recently to possess metallic-like conductivity. Unlike conventional heterointerfaces, these walls can be displaced inside a dielectric by an electric field, which is of interest for future electronic circuitry. In addition, theory predicts that charged domain walls may influence the electromechanical response of ferroelectrics, with strong enhancement upon increased charged domain wall density. The existence of charged domain walls in proper ferroelectrics is disfavoured by their high formation energy and methods of their preparation in predefined patterns are unknown. Here we develop the theoretical background for the formation of charged domain walls in proper ferroelectrics using energy considerations and outline favourable conditions for their engineering. We experimentally demonstrate, in BaTiO3 single crystals the controlled build-up of high density charged domain wall patterns, down to a spacing of 7 μm with a predominant mixed electronic and ionic screening scenario, hinting to a possible exploitation of charged domain walls in agile electronics and sensing devices.

  14. Flexible NAND-Like Organic Ferroelectric Memory Array

    NARCIS (Netherlands)

    Kam, B.; Ke, T.H.; Chasin, A.; Tyagi, M.; Cristoferi, C.; Tempelaars, K.; Breemen, A.J.J.M. van; Myny, K.; Schols, S.; Genoe, J.; Gelinck, G.H.; Heremans, P.

    2014-01-01

    We present a memory array of organic ferroelectric field-effect transistors (OFeFETs) on flexible substrates. The OFeFETs are connected serially, similar to the NAND architecture of flash memory, which offers the highest memory density of transistor memories. We demonstrate a reliable addressing

  15. Tunable tunneling electroresistance in ferroelectric tunnel junctions by mechanical loads.

    Science.gov (United States)

    Luo, Xin; Wang, Biao; Zheng, Yue

    2011-03-22

    Combining nonequilibrium Green function's approach with density functional theory, effects of the applied mechanical loads on polarization, electrostatic potential, and tunneling conductance of a ferroelectric tunneling junction (FTJ) have been investigated. Using the first principle calculations, we show that compressive strains can induce and enhance the polarization in ferroelectric tunnel barriers, and practically achieve ferroelectricity in two unit cell thickness under a -2.2% compressive strain. More importantly, mechanical strains can significantly change the effective electrostatic potential in FTJ and thus control its tunneling conductance, which is defined as giant piezoelectric resistance (GPR) effect. Our calculations indicate that GPR effect is particularly significant near the paraelectric/ferroelectric phase transition, and increases exponentially with the barrier thickness. Furthermore, it is also found that defects of oxygen vacancies and nitrogen doping have little impact on GPR ratio of strained FTJ. Because of its high-sensitivity to external mechanical loads, FTJ with GPR effect should be adequate for applications in agile mechanical sensors, transducers, and other multifunctional devices.

  16. Persistence of strong and switchable ferroelectricity despite vacancies

    Science.gov (United States)

    Raeliarijaona, Aldo; Fu, Huaxiang

    2017-01-01

    Vacancies play a pivotal role in affecting ferroelectric polarization and switching properties, and there is a possibility that ferroelectricity may be utterly eliminated when defects render the system metallic. However, sufficient quantitative understandings of the subject have been lacking for decades due to the fact that vacancies in ferroelectrics are often charged and polarization in charged systems is not translationally invariant. Here we perform first-principles studies to investigate the influence of vacancies on ferroelectric polarization and polarization switching in prototypical BaTiO3 of tetragonal symmetry. We demonstrate using the modern theory of polarization that, in contrast to common wisdom, defective BaTiO3 with a large concentration of vacancies (or , or ) possesses a strong nonzero electric polarization. Breaking of Ti-O bonds is found to have little effect on the magnitude of polarization, which is striking. Furthermore, a previously unrecognized microscopic mechanism, which is particularly important when vacancies are present, is proposed for polarization switching. The mechanism immediately reveals that (i) the switching barrier in the presence of is small with ΔE = 8.3 meV per bulk formula cell, and the polarization is thus switchable even when vacancies exist; (ii) The local environment of vacancy is surprisingly insignificant in polarization switching. These results provide profound new knowledge and will stimulate more theoretical and experimental interest on defect physics in FEs.

  17. Phase transition properties of a cylindrical ferroelectric nanowire

    Indian Academy of Sciences (India)

    In the present paper, we apply the mean-field theory to investigate the phase transition properties of a cylindrical ferroelectric nanowire by taking into account two different exchange interactions and two different transverse field parameters in the. TIM. The effects of various parameters on the phase diagrams are given, and ...

  18. Conformal growth method of ferroelectric materials for multifunctional composites

    Science.gov (United States)

    Bowland, Christopher Charles

    Multifunctional composites are the next generation of composites and aim to simultaneously meet multiple performance objectives to create system-level performance enhancements. Current fiber-reinforced composites have offered improved efficiency and performance through weight reduction and increased strength. However, these composites satisfy singular performance objectives. Therefore, the concept of multifunctional composites was developed as an approach to create components in a system that serve multiple functions. These composites aim to reduce the required components in a system by integrating unifunctional components together thus reducing the weight and complexity of the system as a whole. This work offers an approach to create multifunctional composites through the development of a structural, multifunctional fiber. This is achieved by synthesizing a ferroelectric material on the surface of carbon fiber. In this work, a two-step hydrothermal reaction is developed for synthesizing a conformal film of barium titanate (BaTiO3) on the surface of carbon fiber. A fundamental understanding of this hydrothermal process is performed on planar substrates leading to the development of processing parameters that result in epitaxial-type growth of highly-aligned BaTiO3 nanowires. This work establishes the hydrothermal reaction as a powerful synthesis technique for generating nanostructured BaTiO3 on carbon fiber creating a novel, multifunctional fiber. A reaction optimization process leads to the development of parameters that stabilize tetragonal phase BaTiO3 without the need for subsequent heat treatments. The application potential of these fibers is illustrated with both single fibers and woven fabrics. Single fiber cantilever beams are fabricated and subjected to vibrations to determine its voltage output with the ultimate goal of producing an air flow sensor. Carbon fiber reinforced composite integration is carried out by scaling up the hydrothermal reaction to

  19. Are Ionic Liquids Chemically Stable?

    Science.gov (United States)

    Wang, Binshen; Qin, Li; Mu, Tiancheng; Xue, Zhimin; Gao, Guohua

    2017-05-24

    Ionic liquids have attracted a great deal of interest in recent years, illustrated by their applications in a variety of areas involved with chemistry, physics, biology, and engineering. Usually, the stabilities of ionic liquids are highlighted as one of their outstanding advantages. However, are ionic liquids really stable in all cases? This review covers the chemical stabilities of ionic liquids. It focuses on the reactivity of the most popular imidazolium ionic liquids at structural positions, including C2 position, N1 and N3 positions, and C4 and C5 positions, and decomposition on the imidazolium ring. Additionally, we discuss decomposition of quaternary ammonium and phosphonium ionic liquids and hydrolysis and nucleophilic reactions of anions of ionic liquids. The review aims to arouse caution on potential decomposition of ionic liquids and provides a guide for better utilization of ionic liquids.

  20. Nonlinear dielectric response in ferroelectric thin films

    Directory of Open Access Journals (Sweden)

    Lente, M. H.

    2004-08-01

    Full Text Available Electrical permittivity dependence on electric external bias field was investigated in PZT thin films. The results revealed the existence of two mechanisms contributing to the electrical permittivity. The first one was related to the domain reorientation, which was responsible for a strong no linear dielectric behavior, acting only during the poling process. The second mechanism was associated with the domain wall vibrations, which presented a reasonable linear electrical behavior with the applied bias field, contributing always to the permittivity independently of the poling state of the sample. The results also indicated that the gradual reduction of the permittivity with the increase of the bias field strength may be related to the gradual bending of the domain walls. It is believed that the domain wall bending induces a hardening and/or a thinning of the walls, thus reducing the electrical permittivity. A reinterpretation of the model proposed in the literature to explain the dielectric characteristics of ferroelectric materials at high electric field regime is proposed.

    Se ha estudiado la dependencia de la permitividad eléctrica con un campo bias externo en láminas delgadas de PZT. Los resultados revelaron la existencia de dos mecanismos que contribuyen a la permitividad eléctrica. El primero está relacionado con la reorientación de dominios, actúa sólo durante el proceso de polarización y es responsable de un comportamiento dieléctrico fuertemente no lineal. El segundo mecanismo se asocia a las vibraciones de las paredes de dominio, presentando un comportamiento eléctrico razonablemente lineal con el campo bias aplicado, contribuyendo siempre a la permitividad independientemente del estado de polarización de la muestra. Los resultados indicaron también que la reducción gradual de la permitividad con el aumento de la fuerza del campo bias podría estar relacionada con el “bending” gradual de las paredes de dominio