WorldWideScience

Sample records for structure phase transformations

  1. Neutron scattering at structural phase transformations

    International Nuclear Information System (INIS)

    Plakida, N.M.

    1982-01-01

    The specific fractures of neutron scattering cross sections on crystal lattices at structural phase transformations are considered in the lecture. The analysis of the elastic and inelastic scattering is carried out at different transformations (ordering type, displacement type incommensurable transformations). The experimental study on some transitions are given as an example, namely, transformation at the Brillouin zone edge in cubic perovskite. RbCaF 3 transformation in a quasiunidimensional ferroelectrics CsH 2 PO 4 and CsD 2 PO 4 , phase transformation into an incommensurable phase in diphenyl

  2. Phase and structural transformations in magnetorheological suspensions

    Science.gov (United States)

    Iskakova, L. Yu.; Romanchuk, A. P.; Zubarev, A. Yu.

    2006-07-01

    Particle condensation in magnetorheological suspensions (MRS) under external magnetic field is studied theoretically. It is shown that the bulk condensation of particles into dense phases is preceded by the formation of fairly long chain aggregates. Phase transition occurs as a condensation of such chains due to their magnetic interaction. In thin layers of MRS, placed into the normal magnetic field, scenario of the phase transition differs essentially from that in infinite volumes of these systems. Equilibrium state of the system after the phase transition corresponds to the formation of ensemble of discrete domains of the dense phase rather than to separation into two massive phases as it takes place in infinite media.

  3. Structural-phase transformations in bentonite after acid treatment

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2003-01-01

    Full Text Available The methods of X-ray diffraction, Fourier transform infra-red spectroscopy (FTIR, X-ray microanalysis, electron microscopy, BET and cation exchange capacity (CEC were used for investigation of the structural-phase transformations in bentonite under the influence of hydrochloric acid and temperature treatment (100-800ºC. It is established that in HCl medium during temperature treatment, dehydration and dehydroxilation of montmorillonite occur. The presence of gypsum and barium chloride results in an intercalation of interlayer space of montmorillonite by Ca and Ba ions Temperature treatment of intercalated montmorillonite leads to the formation of pores.

  4. Nanocrystalline Fe-Pt alloys. Phase transformations, structure and magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Lyubina, J.V.

    2006-12-21

    This work has been devoted to the study of phase transformations involving chemical ordering and magnetic properties evolution in bulk Fe-Pt alloys composed of nanometersized grains. Nanocrystalline Fe{sub 100-x}Pt{sub x} (x=40-60) alloys have been prepared by mechanical ball milling of elemental Fe and Pt powders at liquid nitrogen temperature. The as-milled Fe-Pt alloys consist of {proportional_to} 100 {mu}m sized particles constituted by randomly oriented grains having an average size in the range of 10-40 nm. Depending on the milling time, three major microstructure types have been obtained: samples with a multilayer-type structure of Fe and Pt with a thickness of 20-300 nm and a very thin (several nanometers) A1 layer at their interfaces (2 h milled), an intermediate structure, consisting of finer lamellae of Fe and Pt (below approximately 100 nm) with the A1 layer thickness reaching several tens of nanometers (4 h milled) and alloys containing a homogeneous A1 phase (7 h milled). Subsequent heat treatment at elevated temperatures is required for the formation of the L1{sub 0} FePt phase. The ordering develops via so-called combined solid state reactions. It is accompanied by grain growth and thermally assisted removal of defects introduced by milling and proceeds rapidly at moderate temperatures by nucleation and growth of the ordered phases with a high degree of the long-range order. In a two-particle interaction model elaborated in the present work, the existence of hysteresis in recoil loops has been shown to arise from insufficient coupling between the low- and the high-anisotropy particles. The model reveals the main features of magnetisation reversal processes observed experimentally in exchange-coupled systems. Neutron diffraction has been used for the investigation of the magnetic structure of ordered and partially ordered nanocrystalline Fe-Pt alloys. (orig.)

  5. Phase transformation and diffusion

    CERN Document Server

    Kale, G B; Dey, G K

    2008-01-01

    Given that the basic purpose of all research in materials science and technology is to tailor the properties of materials to suit specific applications, phase transformations are the natural key to the fine-tuning of the structural, mechanical and corrosion properties. A basic understanding of the kinetics and mechanisms of phase transformation is therefore of vital importance. Apart from a few cases involving crystallographic martensitic transformations, all phase transformations are mediated by diffusion. Thus, proper control and understanding of the process of diffusion during nucleation, g

  6. Synchrotron radiation : characteristics and application in structural studies and phase transformations of materials

    International Nuclear Information System (INIS)

    Craievich, A.F.

    1984-01-01

    The main characteristics of the synchrotron radiation for studying atomic structure and phase transformations in materials are presented. Some specific applications in alloys, glass and solids are described. (E.G.) [pt

  7. Lattice instabilities and structural phase transformations in La2CuO4 superconductors and insulators

    International Nuclear Information System (INIS)

    Axe, J.D.

    1991-01-01

    Soft-mode structural phase transformations, common in many perovskite-based materials, are also found in La 2 CuO 4 and structurally related oxides. The resulting phase behavior is rather complex, but is a natural consequence of the degeneracy of the soft phonon order parameters. This paper reviews the structural and lattice-dynamical results and their interpretation based upon mean-field statistical mechanical models

  8. Non-isothermal kinetics of phase transformations in magnetron sputtered alumina films with metastable structure

    International Nuclear Information System (INIS)

    Zuzjaková, Š.; Zeman, P.; Kos, Š.

    2013-01-01

    Highlights: • Non-isothermal kinetics of phase transformations in alumina films was investigated. • The structure of alumina films affects kinetics of the transformation processes. • Kinetic triplets of all transformation processes were determined. • The KAS, FWO, FR and IKP methods for determination of E a and A were used. • The Málek method for determination of the kinetic model was used. - Abstract: The paper reports on non-isothermal kinetics of transformation processes in magnetron sputtered alumina thin films with an amorphous and γ-phase structure leading ultimately to the formation of the thermodynamically stable α-Al 2 O 3 phase. Phase transformation sequences in the alumina films were investigated using differential scanning calorimetry (DSC) at four different heating rates (10, 20, 30, 40 °C/min). Three isoconversional methods (Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO) and Friedman (FR) method) as well as the invariant kinetic parameters (IKP) method were used to determine the activation energies for transformation processes. Moreover, the pre-exponential factors were determined using the IKP method. The kinetic models of the transformation processes were determined using the Málek method. It was found that the as-deposited structure of alumina films affects kinetics of the transformation processes. The film with the amorphous as-deposited structure heated at 40 °C/min transforms to the crystalline γ phase at a temperature of ∼930 °C (E a,IKP = 463 ± 10 kJ/mol) and subsequently to the crystalline α phase at a temperature of ∼1200 °C (E a,IKP = 589 ± 10 kJ/mol). The film with the crystalline γ-phase structure heated at 40 °C/min is thermally stable up to ∼1100 °C and transforms to the crystalline α phase (E a,IKP = 511 ± 16 kJ/mol) at a temperature of ∼1195 °C. The empirical two-parameter Šesták–Berggren kinetic model was found to be the most adequate one to describe all transformation processes

  9. Pressure-induced structural phase transformation and superconducting properties of titanium mononitride

    Science.gov (United States)

    Li, Qian; Guo, Yanan; Zhang, Miao; Ge, Xinlei

    2018-03-01

    In this work, we have systematically performed the first-principles structure search on titanium mononitride (TiN) within Crystal Structure AnaLYsis by Particle Swarm Optimization (CALYPSO) methodology at high pressures. Here, we have confirmed a phase transition from cubic rock-salt (fcc) phase to CsCl (bcc) phase of TiN at ∼348 GPa. Further simulations reveal that the bcc phase is dynamically stable, and could be synthesized experimentally in principle. The calculated elastic anisotropy decreases with the phase transformation from fcc to bcc structure under high pressures, and the material changes from ductile to brittle simultaneously. Moreover, we found that both structures are superconductive with the superconducting critical temperature of 2-12 K.

  10. Electronic structure and phase stability during martensitic transformation in Al-doped ZrCu intermetallics

    International Nuclear Information System (INIS)

    Qiu Feng; Shen Ping; Liu Tao; Lin Qiaoli; Jiang Qichuan

    2010-01-01

    Martensitic transformation, phase stability and electronic structure of Al-doped ZrCu intermetallics were investigated by experiments and first-principles calculations using the pseudopotentials plane wave method. The formation energy calculations indicate that the stability of the ZrCu phase increases with the increasing Al content. Al plays a decisive role in controlling the formation and microstructures of the martensite phases in Zr-Cu-Al alloys. The total energy difference between ZrCu (B2) austenite and ZrCu martensite plays an important role in the martensitic transformation. The phase stability is dependent on its electronic structure. The densities of states (DOS) of the intermetallics were discussed in detail.

  11. Design optimization of shape memory alloy active structures using the R-phase transformation

    NARCIS (Netherlands)

    Langelaar, M.; Van Keulen, F.

    2007-01-01

    This article illustrates the opportunities that combining computational modeling and systematic design optimization techniques offer to facilitate the design process of shape memory alloy (SMA) structures. Focus is on shape memory behavior due to the R-phase transformation in Ni-Ti, for which a

  12. First principles calculations of the ground state properties and structural phase transformation in YN

    CERN Document Server

    Mancera, L; Takeuchi, N

    2003-01-01

    We have studied the structural and electronic properties of YN in rock salt (sodium chloride), caesium chloride, zinc blende and wurtzite structures using first-principles total energy calculations. Rock salt is the calculated ground state structure with a = 4.93 A, B sub 0 = 157 GPa. The experimental lattice constant is a = 4.877 A. There is an additional local minimum in the wurtzite structure with total energy 0.28 eV/unit cell higher. At high pressure (approx 138 GPa), our calculations predict a phase transformation from a NaCl to a CsCl structure.

  13. Diffusionless phase transformations

    International Nuclear Information System (INIS)

    Vejman, K.M.

    1987-01-01

    Diffusionless phase transformations in metals and alloys in the process of which atomic displacements occur at the distances lower than interatomic ones and relative correspondence of neighbour atoms is preserved, are considered. Special attention is paid to the mechanism of martensitic transformations. Phenomenologic crystallographical theory of martensitic transformations are presented. Two types of martensitic transformations different from the energy viewpoint are pointed out - thermoelastic and non-thermoelastic ones - which are characterized by transformation hysteresis and ways of martensite - initial phase reverse transformation realization. Mechanical effect in the martensitic transformations have been analyzed. The problem of diffusionless formation of ω-phases and the effect of impurities and vacancies on the process are briefly discussed. The role of charge density waves in phase transformations of the second type (transition of initial phase into noncommensurate one) and of the first type (transition of noncommensurate phase into commensurate one) is considered

  14. Solid phase transformations

    CERN Document Server

    Čermák, J

    2008-01-01

    This special-topic book, devoted to ""Solid Phase Transformations"" , covers a broad range of phenomena which are of importance in a number of technological processes. Most commercial alloys undergo thermal treatment after casting, with the aim of imparting desired compositions and/or optimal morphologies to the component phases. In spite of the fact that the topic has lain at the center of physical metallurgy for a long time, there are numerous aspects which are wide open to potential investigative breakthroughs. Materials with new structures also stimulate research in the field, as well as n

  15. Structure and Phase Transformation in the Giant Magnetostriction Laves-Phase SmFe2

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaonan; Lin, Kun; Gao, Qilong; Zhu, He; Li, Qiang; Cao, Yili; Liu, Zhanning; You, Li; Chen, Jun; Ren, Yang [Argonne National Laboratory, X-Ray Science Division, Argonne, Illinois 60439, United States; Huang, Rongjin [Key Laboratory; Lapidus, Saul H. [Argonne National Laboratory, X-Ray Science Division, Argonne, Illinois 60439, United States; Xing, Xianran

    2017-10-13

    As one class of the most important intermetallic compounds, the binary Laves-phase is well-known for their abundant magnetic properties. Samarium-iron alloy system, SmFe2, is a prototypical Laves compound that shows strong negative magnetostriction but relatively weak magnetocrystalline anisotropy. SmFe2 has been identified as a cubic Fd$ \\overline{3}\\ $m structure at room temperature, however, the cubic symmetry does not match the spontaneous magnetization along the [111]cubic direction. Here we studied the crystal structure of SmFe2 by high-resolution synchrotron X-ray powder diffraction and X-ray total scattering methods. SmFe2 is found to adopt a centrosymmetric trigonal R$ \\overline{3}\\ $m structure at room temperature, which transforms to an orthorhombic Imma structure at 200 K. This transition is in agreement with the changes of easy magnetization direction from [111]cubic to [110]cubic direction, and is further evidenced by the inflexion of thermal expansion behavior, the sharp decline of the magnetic susceptibility in the FC-ZFC curve, and the anomaly in the specific heat capacity measurement. The revised structure and phase transformation of SmFe2 could be useful to understand the magnetostriction and related physical properties of other RM2-type pseudo-cubic Laves-phase intermetallic compounds.

  16. Constitutive Model Of Graded Micro-Structure Obtained Via Strain Induced Phase Transformation

    CERN Document Server

    Ortwein, Rafał

    The literature review has been divided into three main sub-chapters. The first one is concentrated on the general information about stainless steels and their applications. It is important to perform a general overview and get an idea where the results of the present thesis could be applied. Description of all the brands of stainless steels, their microstructures and properties are important, as similar characteristics can be found in the newly created functionally graded structures. The second sub-chapter is an overview of the most important constitutive models and the experimental results for materials that undergo plastic strain induced phase transformation. Finally, the last one is devoted to functionally graded microstructures obtained via strain induced martensitic transformation – the subject of particular importance for the present thesis. As a general note, the literature review is organized mainly in a chronological order. In some cases similar publications or publications of the same Authors were...

  17. Solid–solid transformations via nanoscale intermediate interfacial phase: Multiple structures, scale and mechanics effects

    International Nuclear Information System (INIS)

    Levitas, Valery I.; Momeni, Kasra

    2014-01-01

    Solid–solid (SS) phase transformations via nanometer-size intermediate melts (IMs) within the SS interface, hundreds of degrees below melting temperature, were predicted thermodynamically and are consistent with experiments for various materials. A necessary condition for the appearance of IMs, using a sharp interface approach, was that the ratio of the energies of SS and solid–melt (SM) interfaces, k E , were >2. Here, an advanced phase-field approach coupled with mechanics is developed that reveals various new scale and interaction effects and phenomena. Various types of IM are found: (i) continuous and reversible premelting and melting; (ii) jump-like barrierless transformation to IMs, which can be kept at much lower temperature even for k E E E E =1. The theory developed here can be tailored for diffusive phase transformations, formation of intergranular and interfacial phases, and surface-induced phase transformations

  18. Local structure and phase transformation in Zr and Ti based bcc solutions

    International Nuclear Information System (INIS)

    Chang, A.L.J.

    1975-01-01

    High resolution direct lattice imaging and dark field electron microscopy were used to examine the omega phase transformation in Zr--Nb alloys. Direct lattice imaging demonstrates the existence of three subvariants within each omega variant. The kinematic intensity sum, which is evaluated based on the combination of certain atomic arrangements, was carried out to include both untransformed beta phase and the omega phase. An ordered sequence of subvariants was found to be responsible for the diffraction effects in high Nb content alloys. However, the existence of such an ordered sequence among omega subvariants could not be checked out because of the small size of the omega regions. Omega domains of different variant do not interweave. Isolated particles with diameters of 3 to 5 A also are present away from the domains. As the Nb content is increased the omega domains decrease in size while the isolated particles (3 to 5 A) are present over the entire range studied, from 8 to 30 wt percent Nb. It is suggested that fluctuations in structure occur between the beta and omega phases. The isolated particles, also changing with time, are believed to be images of single or small groups of displaced atoms. (Diss. Abstr. Int., B)

  19. Structure evolution of graphene oxide during thermally driven phase transformation: is the oxygen content really preserved?

    Directory of Open Access Journals (Sweden)

    Pengzhan Sun

    Full Text Available A mild annealing procedure was recently proposed for the scalable enhancement of graphene oxide (GO properties with the oxygen content preserved, which was demonstrated to be attributed to the thermally driven phase separation. In this work, the structure evolution of GO with mild annealing is closely investigated. It reveals that in addition to phase separation, the transformation of oxygen functionalities also occurs, which leads to the slight reduction of GO membranes and furthers the enhancement of GO properties. These results are further supported by the density functional theory based calculations. The results also show that the amount of chemically bonded oxygen atoms on graphene decreases gradually and we propose that the strongly physisorbed oxygen species constrained in the holes and vacancies on GO lattice might be responsible for the preserved oxygen content during the mild annealing procedure. The present experimental results and calculations indicate that both the diffusion and transformation of oxygen functional groups might play important roles in the scalable enhancement of GO properties.

  20. Pressure-induced structural phase transformation in cobalt(II) dicyanamide

    Energy Technology Data Exchange (ETDEWEB)

    Yakovenko, Andrey A.; Chapman, Karena W.; Halder, Gregory J.

    2015-05-26

    In situsynchrotron powder diffraction has been used to probe the pressure-dependent structural properties of the magnetic molecular framework material Co(dca)2[dca = dicyanamide or N(CN)2-]. An orthorhombic (Pmnn) to monoclinic (P21/n) transformation to a high-pressure phase, namely γ-Co(dca)2, occurs at 1.1 GPa. Structural determination of γ-Co(dca)2shows that the rutile-like topology of the pristine material is retained at high pressures, with the lower symmetry allowing a progression of volume-reducing structural distortions. γ-Co(dca)2was stable at the maximum pressure measured of 4.2 GPa. Both phases were soft, with bulk moduli (B0) for α-Co(dca)2and γ-Co(dca)2of 13.15 (18) and 9.0 (6) GPa, respectively. Modest uniaxial negative linear compressibility (K) of the order of -4 TPa-1was observed over the entire measured pressure range.

  1. Magnetic field effect on Gd2(MoO4)3 domain structure formation in the phase transformation range

    International Nuclear Information System (INIS)

    Flerova, S.A.; Tsinman, I.L.

    1987-01-01

    The behaviour of ferroelastic-ferroelectric domain structure of gadolinium molybdate crystal (GMO)during its formation in the magnetic field in the vicinity of phase transformation is studied.It is shown that the formation of domain structure in the presence of a temperature gradient occurs in the field of mechanical stresses whose mainly stretching effect is concentrated near phase boundaries.The magnetic field intensifies summary mechanical stresses where a domain structure in a ferroelectric phase is formed due to interaction with the elements of inhomogeneous and differently oriented currents near phase boundaries

  2. Effect of grain structure on phase transformation events in Inconel 718

    International Nuclear Information System (INIS)

    Dahotre, N.B.; McCay, M.H.; McCay, T.D.; Hubbard, C.R.; Porter, W.D.; Cavin, O.B.

    1993-01-01

    Nickel base superalloys generally obtain their maximum strength from γ'[Ni 3 (Al,Ti)] and γ double-prime[Ni 3 (Al,Ti,Nb)] age hardening precipitates. During welding the γ' precipitation is very rapid and can lead to strain age cracking, which limits weldability. Thus, the weldable superalloys are limited in their Al and Ti content and hence in their ultimate strength. One method of increasing the ultimate strength of a superalloy, while avoiding strain age cracking, is the addition of Nb. This produces Ni 3 Nb(δ), and when used in conjunction with a limited amount of γ', results in an increase in strength without strain age cracking problems. The γ double-prime does not lead to strain age cracking because its transformation kinetics are too slow for formation during ordinary welding practice. This combination of γ' and γ double-prime strengthening is incorporated into the Inconel 718 alloys. The research reported herein was undertaken to determine the time-temperature response of Inconel 718 in the as-cast, wrought and wrought-grain-grown states, using differential thermal analysis (DTA). It is essential to locate the temperature regime of each phase transformation event and to study the transformation sequence in order to tailor sound laser welding techniques for Inconel 718. In the present research, a DTA technique was employed to study both the phase transformation events and the phase transformation sequence as a function of the pre-existing condition of the alloy

  3. Structure and phase transformation behavior of electroless Ni-P alloys containing tin and tungsten

    International Nuclear Information System (INIS)

    Balaraju, J.N.; Jahan, S. Millath; Jain, Anjana; Rajam, K.S.

    2007-01-01

    Autocatalytic ternary Ni-Sn-P, Ni-W-P and quaternary Ni-W-Sn-P films were prepared using alkaline citrate-based baths and compared with binary Ni-P coatings. Energy dispersive analysis of X-ray (EDAX) showed that binary Ni-P deposit contained 11.3 wt.% of phosphorus. Codeposition of tungsten in Ni-P matrix resulted in ternary Ni-W-P with 5 wt.% P and 7.8 wt.% of tungsten. Incorporation of tin led to ternary Ni-Sn-P deposit containing 0.4 wt.% Sn and 10.3 wt.% P. Presence of both sodium tungstate and sodium stannate in the basic bath had resulted in quaternary coating with 6.9 wt.% W, traces of Sn and 6.4 wt.% P. X-ray diffraction patterns of all the deposits revealed a single, broad peak which showed the nanocrystalline nature of the deposits. For the first time in related literature, the presence of a metastable phase Ni 12 P 5 in ternary deposits is reported in the present study. Metallographic cross-sections of all the deposits revealed the banded/lamellar structure. Scanning electron microscopy (SEM) studies of the deposits showed smooth nodules for ternary deposits, but coarse and well-defined nodules for quaternary deposits. DSC studies of phase transformation behavior of the ternary Ni-Sn-P deposit revealed a single sharp exothermic peak at 365 o C. However, ternary Ni-W-P and quaternary Ni-W-Sn-P deposits exhibited a low temperature peak at 300 o C, a split type high temperature peak at 405 and 440 o C and a very high temperature peak at 550 o C. Higher activation energy values were obtained for W-based alloy deposits. Presence of W and Sn has helped to retain high microhardness values even at higher temperatures indicating an improved thermal stability

  4. Devil’s Vortex Phase Structure as Frequency Plane Mask for Image Encryption Using the Fractional Mellin Transform

    Directory of Open Access Journals (Sweden)

    Sunanda Vashisth

    2014-01-01

    Full Text Available A frequency plane phase mask based on Devil’s vortex structure has been used for image encryption using the fractional Mellin transform. The phase key for decryption is obtained by an iterative phase retrieval algorithm. The proposed scheme has been validated for grayscale secret target images, by numerical simulation. The efficacy of the scheme has been evaluated by computing mean-squared-error between the secret target image and the decrypted image. Sensitivity analysis of the decryption process to variations in various encryption parameters has been carried out. The proposed encryption scheme has been seen to exhibit reasonable robustness against occlusion attack.

  5. Order-disorder phase transformations and magnetic structure of (Ni1-xCox)Mn alloys

    International Nuclear Information System (INIS)

    Dorofeev, Yu.A.; Men'shikov, A.Z.; Teplykh, A.E.

    2000-01-01

    By means of neutron diffraction one investigated into structure and magnetic states in (Ni 1-x Co x )Mn hardened and annealed alloys. The order-disorder phase transition from the ordered tetragonal phase to the disordered cubic one was shown to occur in the hardened alloys at x ≅ 0.3 and in the annealed ones at x ≅ 0.7. Θ-NiMn magnetic structure when cobalt substituted for nickel was determined to way in such a way that manganese magnetic moments was reoriented from direction in the tetragonal phase to direction in the cubic one and the local magnetic moment in manganese atoms was reduced from 3.8 μ B up to 1.4μ B . There is no magnetic moment in nickel and cobalt atoms both in tetragonal and in cubic phases [ru

  6. Ti α - ω phase transformation and metastable structure, revealed by the solid-state nudged elastic band method

    Science.gov (United States)

    Zarkevich, Nikolai; Johnson, Duane D.

    Titanium is on of the four most utilized structural metals, and, hence, its structural changes and potential metastable phases under stress are of considerable importance. Using DFT+U combined with the generalized solid-state nudged elastic band (SS-NEB) method, we consider the pressure-driven transformation between Ti α and ω phases, and find an intermediate metastable body-centered orthorhombic (bco) structure of lower density. We verify its stability, assess the phonons and electronic structure, and compare computational results to experiment. Interestingly, standard density functional theory (DFT) yields the ω phase as the Ti ground state, in contradiction to the observed α phase at low pressure and temperature. We correct this by proper consideration of the strongly correlated d-electrons, and utilize DFT+U method in the SS-NEB to obtain the relevant transformation pathway and structures. We use methods developed with support by the U.S. Department of Energy (DE-FG02-03ER46026 and DE-AC02-07CH11358). Ames Laboratory is operated for the DOE by Iowa State University under Contract DE-AC02-07CH11358.

  7. Structural transformations in amorphous ↔ crystalline phase change of Ga-Sb alloys

    International Nuclear Information System (INIS)

    Edwards, T. G.; Sen, S.; Hung, I.; Gan, Z.; Kalkan, B.; Raoux, S.

    2013-01-01

    Ga-Sb alloys with compositions ranging between ∼12 and 50 at. % Ga are promising materials for phase change random access memory applications. The short-range structures of two such alloys with compositions Ga 14 Sb 86 and Ga 46 Sb 54 are investigated, in their amorphous and crystalline states, using 71 Ga and 121 Sb nuclear magnetic resonance spectroscopy and synchrotron x-ray diffraction. The Ga and Sb atoms are fourfold coordinated in the as-deposited amorphous Ga 46 Sb 54 with nearly 40% of the constituent atoms being involved in Ga-Ga and Sb-Sb homopolar bonding. This necessitates extensive bond switching and elimination of homopolar bonds during crystallization. On the other hand, Ga and Sb atoms are all threefold coordinated in the as-deposited amorphous Ga 14 Sb 86 . Crystallization of this material involves phase separation of GaSb domains in Sb matrix and a concomitant increase in the Ga coordination number from 3 to 4. Results from crystallization kinetics experiments suggest that the melt-quenching results in the elimination of structural “defects” such as the homopolar bonds and threefold coordinated Ga atoms in the amorphous phases of these alloys, thereby rendering them structurally more similar to the corresponding crystalline states compared to the as-deposited amorphous phases

  8. Structural and phase transformations in zinc and brass wires under heating with high-density current pulse

    Energy Technology Data Exchange (ETDEWEB)

    Pervikov, A. V. [Laboratory of Physical Chemistry of Ultrafine Materials, Institute of Strength Physics and Materials Science, 2/4, pr. Akademicheskii, 634021 Tomsk, Russia and Department of High Voltage Electrophysics and High Current Electronics, Tomsk Polytechnic University, 30 Lenin Avenue, 634050 Tomsk (Russian Federation)

    2016-06-15

    The work is focused on revealing the mechanism of structure and phase transformations in the metal wires under heating with a high-density current pulse (the electric explosion of wires, EEWs). It has been demonstrated on the example of brass and zinc wires that the transition of a current pulse with the density of j ≈ 3.3 × 10{sup 7} A/cm{sup 2} results in homogeneous heating of the crystalline structure of the metal/alloy. It has been determined that under heating with a pulse of high-density current pulse, the electric resistance of the liquid phases of zinc and brass decreases as the temperature increases. The results obtained allow for a conclusion that the presence of the particles of the condensed phase in the expanding products of EEW is the result of overheating instabilities in the liquid metal.

  9. Structural and phase transformations in the low-temperature annealed amorphous “finemet”-type microwires

    Energy Technology Data Exchange (ETDEWEB)

    Tcherdyntsev, V.V., E-mail: vvch08@yandex.ru [National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation); Aleev, A.A. [SSC RF Institute for Theoretical and Experimental Physics, Moscow 117218 (Russian Federation); Churyukanova, M.N.; Kaloshkin, S.D. [National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation); Medvedeva, E.V. [Institute of Electrophysics, Ural Branch, Russian Academy of Sciences, Yekaterinburg 620016 (Russian Federation); Korchuganova, O.A. [SSC RF Institute for Theoretical and Experimental Physics, Moscow 117218 (Russian Federation); Zhukova, V. [Dpto. de Fns. Mater., UPV/EHU, San Sebastian 20018 (Spain); Zhukov, A.P. [Dpto. de Fns. Mater., UPV/EHU, San Sebastian 20018 (Spain); IKERBASQUE, Basque Foundation for Science, 48011 Bilbao (Spain)

    2014-02-15

    Highlights: • Structure and magnetic properties evolution at heating of amorphous microwires was studied. • Relaxation processes in the amorphous phase correlate with an increase in Curie temperature. • Curie temperature change can not be stabilized by a prolonged exposure at pre-crystallization temperatures. • Tomographic atom probe microscopy supports the formation of α-Fe phase precipitations enriched in Si. -- Abstract: Finemet-type glass-coated microwires with amorphous and nanocrystalline structure have been investigated. The relaxation and crystallization processes at heating of amorphous alloy have been studied by DSC method. We observed that the relaxation processes in the amorphous phase correlate with an increasing of the Curie temperature. Additionally a prolonged exposure of the samples below the crystallization temperatures does not stabilize the Curie temperature change. An investigation by the tomographic atom probe microscopy supports the formation of precipitations, probably α-Fe phase, as a result of low-temperature annealing (400 °C, 5 min). We found that the observed nano-sized areas were enriched in silicon.

  10. Structural and phase transformations in the low-temperature annealed amorphous “finemet”-type microwires

    International Nuclear Information System (INIS)

    Tcherdyntsev, V.V.; Aleev, A.A.; Churyukanova, M.N.; Kaloshkin, S.D.; Medvedeva, E.V.; Korchuganova, O.A.; Zhukova, V.; Zhukov, A.P.

    2014-01-01

    Highlights: • Structure and magnetic properties evolution at heating of amorphous microwires was studied. • Relaxation processes in the amorphous phase correlate with an increase in Curie temperature. • Curie temperature change can not be stabilized by a prolonged exposure at pre-crystallization temperatures. • Tomographic atom probe microscopy supports the formation of α-Fe phase precipitations enriched in Si. -- Abstract: Finemet-type glass-coated microwires with amorphous and nanocrystalline structure have been investigated. The relaxation and crystallization processes at heating of amorphous alloy have been studied by DSC method. We observed that the relaxation processes in the amorphous phase correlate with an increasing of the Curie temperature. Additionally a prolonged exposure of the samples below the crystallization temperatures does not stabilize the Curie temperature change. An investigation by the tomographic atom probe microscopy supports the formation of precipitations, probably α-Fe phase, as a result of low-temperature annealing (400 °C, 5 min). We found that the observed nano-sized areas were enriched in silicon

  11. High pressure phase transformations revisited

    Science.gov (United States)

    Levitas, Valery I.

    2018-04-01

    High pressure phase transformations play an important role in the search for new materials and material synthesis, as well as in geophysics. However, they are poorly characterized, and phase transformation pressure and pressure hysteresis vary drastically in experiments of different researchers, with different pressure transmitting media, and with different material suppliers. Here we review the current state, challenges in studying phase transformations under high pressure, and the possible ways in overcoming the challenges. This field is critically compared with fields of phase transformations under normal pressure in steels and shape memory alloys, as well as plastic deformation of materials. The main reason for the above mentioned discrepancy is the lack of understanding that there is a fundamental difference between pressure-induced transformations under hydrostatic conditions, stress-induced transformations under nonhydrostatic conditions below yield, and strain-induced transformations during plastic flow. Each of these types of transformations has different mechanisms and requires a completely different thermodynamic and kinetic description and experimental characterization. In comparison with other fields the following challenges are indicated for high pressure phase transformation: (a) initial and evolving microstructure is not included in characterization of transformations; (b) continuum theory is poorly developed; (c) heterogeneous stress and strain fields in experiments are not determined, which leads to confusing material transformational properties with a system behavior. Some ways to advance the field of high pressure phase transformations are suggested. The key points are: (a) to take into account plastic deformations and microstructure evolution during transformations; (b) to formulate phase transformation criteria and kinetic equations in terms of stress and plastic strain tensors (instead of pressure alone); (c) to develop multiscale continuum

  12. Correlation of Bulk Dielectric and Piezoelectric Properties to the Local Scale Phase Transformations, Domain Morphology, and Crystal Structure Modified

    Energy Technology Data Exchange (ETDEWEB)

    Priya, Shashank [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Viehland, Dwight [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

    2014-12-14

    Three year program entitled “Correlation of bulk dielectric and piezoelectric properties to the local scale phase transformations, domain morphology, and crystal structure in modified lead-free grain-textured ceramics and single crystals” was supported by the Department of Energy. This was a joint research program between D. Viehland and S. Priya at Virginia Tech. Single crystal and textured ceramics have been synthesized and characterized. Our goals have been (i) to conduct investigations of lead-free piezoelectric systems to establish the local structural and domain morphologies that result in enhanced properties, and (ii) to synthesize polycrystalline and grain oriented ceramics for understanding the role of composition, microstructure, and anisotropy

  13. Image encryption based on fractal-structured phase mask in fractional Fourier transform domain

    Science.gov (United States)

    Zhao, Meng-Dan; Gao, Xu-Zhen; Pan, Yue; Zhang, Guan-Lin; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian

    2018-04-01

    We present an optical encryption approach based on the combination of fractal Fresnel lens (FFL) and fractional Fourier transform (FrFT). Our encryption approach is in fact a four-fold encryption scheme, including the random phase encoding produced by the Gerchberg–Saxton algorithm, a FFL, and two FrFTs. A FFL is composed of a Sierpinski carpet fractal plate and a Fresnel zone plate. In our encryption approach, the security is enhanced due to the more expandable key spaces and the use of FFL overcomes the alignment problem of the optical axis in optical system. Only using the perfectly matched parameters of the FFL and the FrFT, the plaintext can be recovered well. We present an image encryption algorithm that from the ciphertext we can get two original images by the FrFT with two different phase distribution keys, obtained by performing 100 iterations between the two plaintext and ciphertext, respectively. We test the sensitivity of our approach to various parameters such as the wavelength of light, the focal length of FFL, and the fractional orders of FrFT. Our approach can resist various attacks.

  14. Structural investigations on the tetragonal to cubic phase transformations in zirconia induced by progressive yttrium additions

    Science.gov (United States)

    Vasanthavel, S.; Kannan, S.

    2018-01-01

    Yttria stabilized zirconia (YSZ) is inevitable in many industrial applications. Yttrium additions in ZrO2 system induces either tetragonal (t-ZrO2) or cubic (c-ZrO2) phase stabilization that predominantly depends on the yttrium content. Here, the structural changes in ZrO2 system upon a wide range of yttrium additions are investigated. Powder synthesis is carried out through citrate-nitrate assisted sol-gel technique and analytical techniques involving XRD, Raman spectra and structural analysis through Rietveld refinement were utilized to investigate the structural changes in ZrO2 upon progressive yttrium additions. The critical limit of yttrium content to retain unique t-ZrO2, mixtures of t-ZrO2 and c-ZrO2 and discrete c-ZrO2 is determined.

  15. Crystal structures and phase transformation of deuterated lithium imide, Li2ND

    International Nuclear Information System (INIS)

    Balogh, Michael P.; Jones, Camille Y.; Herbst, J.F.; Hector, Louis G.; Kundrat, Matthew

    2006-01-01

    We have investigated the crystal structure of deuterated lithium imide, Li 2 ND, by means of neutron and X-ray diffraction. An order-disorder transition occurs near 360K. Below that temperature Li 2 ND can be described to the same level of accuracy as a disordered cubic (Fd3-bar m) structure with partially occupied Li 32e sites or as a fully occupied orthorhombic (Ima2 or Imm2) structure. The high temperature phase is best characterized as disordered cubic (Fm3-bar m) with D atoms randomized over the 192l sites. Density functional theory calculations complement and support the diffraction analyses. We compare our findings in detail with previous studies

  16. Phase transformations in metallic glasses

    DEFF Research Database (Denmark)

    Jiang, Jianzhong

    2003-01-01

    Recent development of grain-size effect on phase transformations induced by pressure is reported. A thermodynamic theory is presented and three components: the ratio of volume collapses, the surface energy differences, and the internal energy differences, governing the change of transition pressure...... in nanocrystals were uncovered. They can be used to explain the results reported in the literature and to identify the main factor to the change of the transition pressure in nanocrystals. We demonstrated that the grain-size effect on the structural stability in nanocrystals with respect to transition pressure...

  17. Surface modification induced phase transformation and structure variation on the rapidly solidified recast layer of titanium

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Ming-Hung [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Haung, Chiung-Fang [School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Division of Family and Operative Dentistry, Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan (China); Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 110, Taiwan (China); Shyu, Shih-Shiun [Department of Dentistry, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei City 231, Taiwan (China); Chou, Yen-Ru [Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 110, Taiwan (China); Graduate Institute of Biomedical Materials and Tissue Engineering, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Lin, Ming-Hong [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); Peng, Pei-Wen, E-mail: apon@tmu.edu.tw [School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); and others

    2015-08-15

    In this study, neodymium-doped yttrium orthovanadate (Nd:YVO{sub 4}) as a laser source with different scanning speeds was used on biomedical Ti surface. The microstructural and biological properties of laser-modified samples were investigated by means of optical microscope, electron microscope, X-ray diffraction, surface roughness instrument, contact angle and cell cytotoxicity assay. After laser modification, the rough volcano-like recast layer with micro-/nanoporous structure and wave-like recast layer with nanoporous structure were generated on the surfaces of laser-modified samples, respectively. It was also found out that, an α → (α + rutile-TiO{sub 2}) phase transition occurred on the recast layers of laser-modified samples. The Ti surface becomes hydrophilic at a high speed laser scanning. Moreover, the cell cytotoxicity assay demonstrated that laser-modified samples did not influence the cell adhesion and proliferation behaviors of osteoblast (MG-63) cell. The laser with 50 mm/s scanning speed induced formation of rough volcano-like recast layer accompanied with micro-/nanoporous structure, which can promote cell adhesion and proliferation of MG-63 cell on Ti surface. The results indicated that the laser treatment was a potential technology to enhance the biocompatibility for titanium. - Highlights: • Laser induced the formation of recast layer with micro-/nanoporous structure on Ti. • An α → (α + rutile-TiO{sub 2}) phase transition was observed within the recast layer. • The Ti surface becomes hydrophilic at a high speed laser scanning. • Laser-modified samples exhibit good biocompatibility to osteoblast (MG-63) cell.

  18. Structure and phase transformations in WC-Co hard alloys irradiated with a low-flux electron beam

    International Nuclear Information System (INIS)

    Petrenko, P.V.; Grabovskij, Yu.E.; Gritskevich, A.L.; Kulish, N.P.; Mel'nikova, N.A.

    2003-01-01

    The structure and phase composition in electron irradiated WC-Co hard alloys have been studied by X-ray diffraction analysis and electron microscopy methods. It is shown that the dose dependences of WC and Co lattice parameters are significantly different for the initial alloys and the electrolytically etched alloys, from the surface of which either cobalt or tungsten carbide was removed. Microstress level, size and volume of primary grains of WC were decreased under irradiation. It is assumed, the radiation-stimulated ordering-disordering transformation processes in tungsten carbide take place, and WC particles redistribution in Co matrix occurs [ru

  19. Structure in the 3D Galaxy Distribution. III. Fourier Transforming the Universe: Phase and Power Spectra

    Science.gov (United States)

    Scargle, Jeffrey D.; Way, M. J.; Gazis, P. G.

    2017-01-01

    We demonstrate the effectiveness of a relatively straightforward analysis of the complex 3D Fourier transform of galaxy coordinates derived from redshift surveys. Numerical demonstrations of this approach are carried out on a volume-limited sample of the Sloan Digital Sky Survey redshift survey. The direct unbinned transform yields a complex 3D data cube quite similar to that from the Fast Fourier Transform of finely binned galaxy positions. In both cases, deconvolution of the sampling window function yields estimates of the true transform. Simple power spectrum estimates from these transforms are roughly consistent with those using more elaborate methods. The complex Fourier transform characterizes spatial distributional properties beyond the power spectrum in a manner different from (and we argue is more easily interpreted than) the conventional multipoint hierarchy. We identify some threads of modern large-scale inference methodology that will presumably yield detections in new wider and deeper surveys.

  20. Phase transformations in engineering materials

    International Nuclear Information System (INIS)

    Bourke, M.A.M.; Lawson, A.C.; Dunand, D.C.

    1996-01-01

    Phase transformations in engineering materials are inevitably related to mechanical behavior and are often precursors to residual stress and distortion. Neutron scattering in general is a valuable tool for studying their effects, and pulsed neutrons are of special value, because of the inherently comprehensive crystallographic coverage they provide in each measurement. At the Manuel Lujan neutron scattering center several different research programs have addressed the relationships between phase transformation/mechanical behavior and residual strains. Three disparate examples are presented; (1) stress induced transformation in a NiTi shape memory alloy, (2) cryogenically induced transformation in a quenched 5180 steel, and (3) time resolved evolution of strain induced martensite in 304 stainless steel. In each case a brief description of the principle result will be discussed in the context of using neutrons for the measurement

  1. Characterizing the Structure and Phase Transformation of Poly(ethylene Oxide)-Urea Complexes Using Terahertz Time-Domain Spectroscopy.

    Science.gov (United States)

    Ye, Hai-Mu; Li, Han; Yao, Shu-Fang

    2017-11-01

    Terahertz time-domain spectroscopy (THz-TDS) was employed to characterize the structure and α→β phase transformation of poly(ethylene oxide) (PEO)-urea complexes. While the THz responses of α- and β-form complexes are both originated from hydrogen bonding interactions, they possess different THz absorption bands. The α-form PEO-urea complex shows two bands at 1.12 and 1.24 THz, which are vibration modes due to the hydrogen bonding among urea and between PEO and urea, respectively; the β-form PEO-urea complex shows a band at 1.48 THz, which is a vibration mode due to the hydrogen bonding among urea. A polarized THz-TDS study demonstrates that the urea-urea hydrogen bonding direction rotates 90° during the β→α transformation process. This study reveals the great potential of THz-TDS for investigating polymer-small molecule complexes.

  2. Phase and structural transformations in a low-carbon steel that occur upon the collapse of a cylindrical shell

    Science.gov (United States)

    Kheifets, A. E.; Zel'dovich, V. I.; Frolova, N. Yu.; Dolgikh, S. M.; Gaan, K. V.; Shorokhov, E. V.

    2017-07-01

    An experiment has been performed on the collapse of a thick-walled shell (tube) made of steel 20 (Fe-0.2 wt % C) to a continuous cylinder under the action of explosion. The changes of the microstructure of the cylinder have been investigated that arise under the effect of two factors, i.e., a shock wave, which causes the initial pulse to the collapse, and high-strain-rate deformation upon the subsequent inertial convergence of the shell walls. Changes in the time-dependent temperature distribution in the cylinder have been calculated. As a result of the deformation, the new structure has been obtained in steel 20 due to barothermic quenching that consists of fine crystals of the α phase, which arise during the quenching at the place of free ferrite, and of regions of the retained initial pearlite. It has been shown that the uncommon order of the occurrence of the α → γ transformation is explained by the different degree of heating of the structural constituents of the steel (free ferrite; and pearlite). The conclusion has been drawn that the high-strain-rate deformation that occurs in this experiment can be used as the method that makes it possible not only to differently deform but also to differently heat the different structural components of multiphase materials.

  3. Thermal activation analysis of the structural and phase transformations in the Zr-Cu-Nb amorphous alloy

    Directory of Open Access Journals (Sweden)

    Fedotova N.L.

    2011-05-01

    Full Text Available In the present work, the procedure of the estimation of the thermal activation parameters from the data of dilatometric measurements and the results of its application to the Zr-Cu-Nb amorphous alloy discussed. The determination of the thermal activation parameters of the processes occurring in materials under known temperature-force conditions can be useful for the identification of the structural mechanisms of phase transformations and the evolution of defect structure. We used the data of dilatometric measurements for evaluating the effective activation energy. This method exhibits some advantages over the conventional one due to the design features of dilatometers. First, it ensures the precise measurement of strains; second, the assigned temperature regime is very precisely maintained both at the stage of heating and upon isothermal holding; third, it ensures a high-speed continuous record of the experimental data. The developed method of evaluating the effective activation energy from the results of dilatometric experiments provides statistically reliable results. The data of the photometric analysis of structure images are in accordance with the results of dilatometric experiments

  4. Effect of Phase Transformations on Seismic Velocities

    Science.gov (United States)

    Weidner, D. J.; Li, L.; Whitaker, M.; Triplett, R.

    2017-12-01

    The radial velocity structure of the Earth consists of smooth variations of velocities with depth punctuated by abrupt changes of velocity, which are typically due to multivariant phase transformations, where high - low pressure phases can coexist. In this mixed phase region, both the effective shear and bulk moduli will be significantly reduced by the dynamic interaction of the propagating wave and the phase transition if the period of the wave is long enough relative to the kinetic time so that some of the transition can take place. In this presentation, we will give examples from both laboratory studies of phases transitions of Earth minerals and the calculated velocity profile based on our models. We focus on understanding the time limiting factor of the phase transformation in order to extrapolate laboratory results to Earth observations. Both the olivine to ringwoodite transition and KLB-1 partial melting are explored. We find that when the transformation requires diffusion, the kinetics are often slowed down considerably and as a result the diffusivity of atoms become the limiting factor of characteristic time. Specifically Fe-Mg exchange rate in the olivine-ringwoodite phase transition becomes the limiting factor that seismic waves are likely to sample. On the other hand, partial melting is an extremely fast phase transformation at seismic wave periods. We present evidence that ultrasonic waves, with a period of a few tens of nanoseconds, are slowed by the reduction of the effective elastic moduli in this case.

  5. Structural phase transformations in KYF4:Er3+ nanoparticles synthesized by hydrothermal method for upconversion applications

    Science.gov (United States)

    Yamini, S.; Priya, P. Sakthi; Gunaseelan, M.; Senthilselvan, J.

    2017-05-01

    KYF4:10%Er3+ upconversion nanoparticles was synthesized by hydrothermal method with potassium hydroxides (KOH) as precursor. Prepared samples were calcined at 600 °C using double crucible method. XRD patterns of as prepared KYF4 and KYF4:Er3+ samples confirm the tetragonal structure, which is well matched with the standard data. Surface morphology is recorded for 600 °C calcined samples using High resolution scanning electron microscopy (HRSEM) shows spheroidal shape with particle sizes of ˜80 nm. From UV-Visible and EDX spectroscopy presence of Er3+ in KYF4:10%Er3+ is confirmed. The prepared KYF4:10%Er3+ can be used to improve efficiency of solar cells, display devices and fiber optical telecommunication applications.

  6. Atomic Migration Induced Crystal Structure Transformation and Core-Centered Phase Transition in Single Crystal Ge2Sb2Te5Nanowires.

    Science.gov (United States)

    Lee, Jun-Young; Kim, Jeong-Hyeon; Jeon, Deok-Jin; Han, Jaehyun; Yeo, Jong-Souk

    2016-10-12

    A phase change nanowire holds a promise for nonvolatile memory applications, but its transition mechanism has remained unclear due to the analytical difficulties at atomic resolution. Here we obtain a deeper understanding on the phase transition of a single crystalline Ge 2 Sb 2 Te 5 nanowire (GST NW) using atomic scale imaging, diffraction, and chemical analysis. Our cross-sectional analysis has shown that the as-grown hexagonal close-packed structure of the single crystal GST NW transforms to a metastable face-centered cubic structure due to the atomic migration to the pre-existing vacancy layers in the hcp structure going through iterative electrical switching. We call this crystal structure transformation "metastabilization", which is also confirmed by the increase of set-resistance during the switching operation. For the set to reset transition between crystalline and amorphous phases, high-resolution imaging indicates that the longitudinal center of the nanowire mainly undergoes phase transition. According to the atomic scale analysis of the GST NW after repeated electrical switching, partial crystallites are distributed around the core-centered amorphous region of the nanowire where atomic migration is mainly induced, thus potentially leading to low power electrical switching. These results provide a novel understanding of phase change nanowires, and can be applied to enhance the design of nanowire phase change memory devices for improved electrical performance.

  7. Low-temperature phase transformation in rubidium and cesium superoxides

    International Nuclear Information System (INIS)

    Alikhanov, R.A.; Toshich, B.S.; Smirnov, L.S.

    1980-01-01

    Crystal structures of rubidium and cesium superoxides which are two interpenetrating lattices of metal ions and oxygen molecule ions reveal a number of phase transformations with temperature decrease. Crystal-phase transformations in CsO 2 are 1-2, 2-3 and low temperature one 3-4 at 378, 190 and 10 K. Low temperature transition is considered as the instability of lattice quadrupoles of oxygen molecule ions to phase transformation of the order-disorder type. Calculated temperatures of low temperature phase transformations in PbO 2 and CsO 2 agree with experimental calculations satisfactory [ru

  8. Pressure Induced Phase Transformations in Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Reimanis, Ivar [Colorado School of Mines, Golden, CO (United States); Cioabanu, Cristian [Colorado School of Mines, Golden, CO (United States)

    2017-10-15

    The study of materials with unusual properties offers new insight into structure-property relations as well as promise for the design of novel composites. In this spirit, the PIs seek to (1) understand fundamental mechanical phenomena in ceramics that exhibit pressure-induced phase transitions, negative coefficient of thermal expansion (CTE), and negative compressibility, and (2) explore the effect of these phenomena on the mechanical behavior of composites designed with such ceramics. The broad and long-term goal is to learn how to utilize these unusual behaviors to obtain desired mechanical responses. While the results are expected to be widely applicable to many ceramics, most of the present focus is on silicates, as they exhibit remarkable diversity in structure and properties. Eucryptite, a lithium aluminum silicate (LiAlSiO4), is specifically targeted because it exhibits a pressure-induced phase transition at a sufficiently low pressure to be accessible during conventional materials processing. Thus, composites with eucryptite may be designed to exhibit a novel type of transformation toughening. The PIs have performed a combination of activities that encompass synthesis and processing to control structures, atomistic modeling to predict and understand structures, and characterization to study mechanical behavior. Several materials behavior discoveries were made. It was discovered that small amounts of Zn (as small as 0.1 percent by mol) reverse the sign of the coefficient of thermal expansion of beta-eucryptite from negative to slightly positive. The presence of Zn also significantly mitigates microcracking that occurs during thermal cycling of eucryptite. It is hypothesized that Zn disrupts the Li ordering in beta-eucryptite, thereby altering the thermal expansion behavior. A nanoindentation technique developed to characterize incipient plasticity was applied to examine the initial stages of the pressure induced phase transformation from beta to

  9. Synthesis of Mn3O4 nanoparticles via a facile gel formation route and study of their phase and structural transformation with distinct surface morphology upon heat treatment

    Directory of Open Access Journals (Sweden)

    A.K.M. Atique Ullah

    2017-11-01

    Full Text Available Mn3O4 nanoparticles (NPs were synthesized from the reduction of KMnO4 with glycerol at 80 °C in aqueous media via a gel formation route. In order to investigate the thermal stability and phase transformation, Mn3O4 NPs were subjected to heat treatment from 200 °C to 700 °C. The formation of different MnOx species observed by X-ray diffraction (XRD measurements showed temperature dependent phase transformation occurring during the heat treatment process. XRD patterns showed that Mn3O4 NPs were formed at a temperature of 80 °C and two new phases Mn5O8 and Mn2O3 were appeared at 350 °C and 700 °C respectively. The three different oxides having their distinct surface morphologies viz., spherical, rod and cube shape respectively, were observed. Detailed morphological and structural investigations using Field Emission Scanning Electron Microscopy (FESEM, XRD, Thermo Gravimetric Analysis (TGA and Differential Scanning Calorimetry (DSC revealed the temperature dependent phases, crystal structures, lattice constants, particle sizes and surface morphologies of the MnOx species.

  10. Phase transformations in the Cu.6 Pd.4 alloy

    International Nuclear Information System (INIS)

    Imakuma, K.

    1977-01-01

    Order-disorder and structural transformations in the Cu-Pd 60-40% (Cu. 6 Pd. 4 ) alloy by means of a temperature and time dependent treatment are studied. The structural transformations by x-rays diffraction are also studied, where the bcc, fcc and tetragonal phases were observed. A qualitative analyze of the resistivity kinetics are made [pt

  11. Study of effect of chromium on titanium dioxide phase transformation ...

    Indian Academy of Sciences (India)

    Administrator

    Electronic Supplementary Material. Study of effect of chromium on titanium dioxide phase transformation by A Bellifa (pp 669–677). Figure S1. Structural schemes of anatase to rutile transition. Figure S2. Analysis ATG-ATD for different samples.

  12. Shear-driven phase transformation in silicon nanowires

    Science.gov (United States)

    Vincent, L.; Djomani, D.; Fakfakh, M.; Renard, C.; Belier, B.; Bouchier, D.; Patriarche, G.

    2018-03-01

    We report on an unprecedented formation of allotrope heterostructured Si nanowires by plastic deformation based on applied radial compressive stresses inside a surrounding matrix. Si nanowires with a standard diamond structure (3C) undergo a phase transformation toward the hexagonal 2H-allotrope. The transformation is thermally activated above 500 °C and is clearly driven by a shear–stress relief occurring in parallel shear bands lying on {115} planes. We have studied the influence of temperature and axial orientation of nanowires. The observations are consistent with a martensitic phase transformation, but the finding leads to clear evidence of a different mechanism of deformation-induced phase transformation in Si nanowires with respect to their bulk counterpart. Our process provides a route to study shear-driven phase transformation at the nanoscale in Si.

  13. Reflectance changes during shock-induced phase transformations in metals.

    Science.gov (United States)

    Stevens, G D; Turley, W D; Veeser, L R; Jensen, B J; Rigg, P A

    2010-06-01

    In performing shock wave experiments to study the characteristics of metals at high pressures, wave profiles (i.e., velocity measurements of the surface of the sample) are an established and useful way to study phase transformations. For example, a sudden change in the velocity or its slope can occur when the phase transformation induces a large volume change leading to a change in particle velocity. Allowing the shock to release into a transparent window that is in contact with the sample surface allows the study of conditions away from the shock Hugoniot. However, in cases where the wave profile is not definitive, an additional phase-transformation diagnostic is often useful. Changes in the electronic structure of the atoms in the crystal offer opportunities to develop new phase-change diagnostics. We have studied optical reflectance changes for several shock-induced phase transformations to see whether reflectance changes might be a generally applicable phase-transformation diagnostic. Shocks were produced by direct contact with explosives or with impacts from guns. Optical wavelengths for the reflectance measurements ranged from 355 to 700 nm. We studied samples of tin, iron, gallium, and cerium as each passed through a phase transformation during shock loading and, if observable, a reversion upon unloading. In addition to metals with complicated phase diagrams, we also measured dynamic, pressure-induced changes in the reflectivity of aluminum. For rapid solid-solid phase changes in tin and iron, we saw small changes in the surface scattering characteristics, perhaps from voids or rough areas frozen into the surface of the sample as it transformed to a new crystal structure. For melt in gallium and cerium, we saw changes in the wavelength dependence of the reflectance, and we surmise that these changes may result from changes in the crystal electronic structure. It appears that reflectance measurements can be a significant part of a larger suite of diagnostics

  14. Grain nucleation and growth during phase transformations

    DEFF Research Database (Denmark)

    Offerman, S.E.; Dijk, N.H. van; Sietsma, J.

    2002-01-01

    The mechanical properties of polycrystalline materials are largely determined by the kinetics of the phase transformations during the production process. Progress in x-ray diffraction instrumentation at synchrotron sources has created an opportunity to study the transformation kinetics at the level...

  15. Percolating hierarchical defect structures drive phase transformation in Ce1−xGdxO2−x/2: a total scattering study

    Directory of Open Access Journals (Sweden)

    Marco Scavini

    2015-09-01

    Full Text Available A new hierarchical approach is presented for elucidating the structural disorder in Ce1−xGdxO2−x/2 solid solutions on different scale lengths. The primary goal of this investigation is to shed light on the relations between the short-range and the average structure of these materials via an analysis of disorder on the mesocopic scale. Real-space (pair distribution function and reciprocal-space (Rietveld refinement and microstructure probing analysis of X-ray powder diffraction data and electron spin resonance (ESR investigations were carried out following this approach. On the local scale, Gd- and Ce-rich droplets (i.e. small regions a few ångströms wide form, exhibiting either a distorted fluorite (CeO2 or a C-type (Gd2O3 structure in the whole compositional range. These droplets can then form C-type nanodomains which, for Gd concentrations xGd ≤ 0.25, are embedded in the fluorite matrix. At the site percolation threshold pC for a cubic lattice (xGd = pC ≃ 0.311, C-type nanodomains percolate inside each crystallite and a structural phase transformation is observed. When this occurs, the peak-to-peak ESR line width ΔHpp shows a step-like behaviour, which can be associated with the increase in Gd–Gd dipolar interactions. A general crystallographic rationale is presented to explain the fluorite-to-C-type phase transformation. The approach shown here could be adopted more generally in the analysis of disorder in other highly doped materials.

  16. Kinetics of solid state phase transformations: Measurement and ...

    Indian Academy of Sciences (India)

    Administrator

    in the realm of metals and alloys. While thermody- namics classifies phase changes in terms of the nature of .... structural change in uranium. 9. It is interesting to note that the temperature interval of the two phase ... diagram for the α → β transformation in uranium is shown. The dotted lines represent various heating rates,.

  17. Soliton bubbles and phase transformations

    International Nuclear Information System (INIS)

    Masperi, L.

    1989-01-01

    It is shown that no topological classical solutions in form of bubbles of a real scalar field theory with Lagrangian of quartet and sextet self interactions in 1+1 dimensions are responsible to discontinue transitions in the quantum problem between phases with degenerated and disordered excited level. (M.C.K.)

  18. Path Dependency of High Pressure Phase Transformations

    Science.gov (United States)

    Cerreta, Ellen

    2017-06-01

    At high pressures titanium and zirconium are known to undergo a phase transformation from the hexagonal close packed (HCP), alpha-phase to the simple-hexagonal, omega-phase. Under conditions of shock loading, the high-pressure omega-phase can be retained upon release. It has been shown that temperature, peak shock stress, and texture can influence the transformation. Moreover, under these same loading conditions, plastic processes of slip and twinning are also affected by similar differences in the loading path. To understand this path dependency, in-situ velocimetry measurements along with post-mortem metallographic and neutron diffraction characterization of soft recovered specimens have been utilized to qualitatively understand the kinetics of transformation, quantify volume fraction of retained omega-phase and characterize the shocked alpha and omega-phases. Together the work described here can be utilized to map the non-equilibrium phase diagram for these metals and lend insight into the partitioning of plastic processes between phases during high pressure transformation. In collaboration with: Frank Addesssio, Curt Bronkhorst, Donald Brown, David Jones, Turab Lookman, Benjamin Morrow, Carl Trujillo, Los Alamos National Lab.; Juan Pablo Escobedo-Diaz, University of New South Wales; Paulo Rigg, Washington State University.

  19. Complexion-mediated martensitic phase transformation in Titanium

    Science.gov (United States)

    Zhang, J.; Tasan, C. C.; Lai, M. J.; Dippel, A.-C.; Raabe, D.

    2017-02-01

    The most efficient way to tune microstructures and mechanical properties of metallic alloys lies in designing and using athermal phase transformations. Examples are shape memory alloys and high strength steels, which together stand for 1,500 million tons annual production. In these materials, martensite formation and mechanical twinning are tuned via composition adjustment for realizing complex microstructures and beneficial mechanical properties. Here we report a new phase transformation that has the potential to widen the application window of Ti alloys, the most important structural material in aerospace design, by nanostructuring them via complexion-mediated transformation. This is a reversible martensitic transformation mechanism that leads to a final nanolaminate structure of α'' (orthorhombic) martensite bounded with planar complexions of athermal ω (a-ω, hexagonal). Both phases are crystallographically related to the parent β (BCC) matrix. As expected from a planar complexion, the a-ω is stable only at the hetero-interface.

  20. On the akaganeite crystal structure, phase transformations and possible role in post-excavational corrosion of iron artefacts

    DEFF Research Database (Denmark)

    Ståhl, Kenny; Nielsen, Kurt; Jiang, Jianzhong

    2003-01-01

    The crystal structure of akaganeite and the akaganeite to hematite transition has been studied by means of conventional and synchrotron X-ray and neutron powder diffraction. The chemical formula of akaganeite can be written as FeO0.833(OH)(1.167)Cl-0.167. The crystal structure does not contain fr...

  1. Phase Transformations During Cooling of Automotive Steels

    Science.gov (United States)

    Padgett, Matthew C.

    This thesis explores the effect of cooling rate on the microstructure and phases in advanced high strength steels (AHSS). In the manufacturing of automobiles, the primary joining mechanism for steel is resistance spot welding (RSW), a process that produces a high heat input and rapid cooling in the welded metal. The effect of RSW on the microstructure of these material systems is critical to understanding their mechanical properties. A dual phase steel, DP-600, and a transformation induced plasticity bainitic-ferritic steel, TBF-1180, were studied to assess the changes to their microstructure that take place in controlled cooling environments and in uncontrolled cooling environments, i.e. resistance spot welding. Continuous cooling transformation (CCT) diagrams were developed using strip specimens of DP-600 and TBF-1180 to determine the phase transformations that occur as a function of cooling rate. The resulting phases were determined using a thermal-mechanical simulator and dilatometry, combined with light optical microscopy and hardness measurements. The resulting phases were compared with RSW specimens where cooling rate was controlled by varying the welding time for two-plate welds. Comparisons were drawn between experimental welds of DP-600 and simulations performed using a commercial welding software. The type and quantity of phases present after RSW were examined using a variety of techniques, including light optical microscopy using several etchants, hardness measurements, and x-ray diffraction (XRD).

  2. Effect of thermal treatment on the nano-structure and phase transformation of metakaolin-based geopolymers.

    Science.gov (United States)

    Kim, Yongsung; Kang, Seunggu

    2014-11-01

    Enhancement of the mechanical strength of metakaolin-based geopolymers activated with NaOH was attempted by calcining metakaolin at a higher temperature than that commonly reported. Increasing the calcination temperature from 750 degrees C to 1150 degrees C promoted the recrystallization of mullite. Two type of zeolite of sodium aluminum silicate hydrates were found in the geopolymers made of metakaolin calcined at 750 degrees C-1050 degrees C. The h-zeolite [Na6(AlSiO4)6 x H2O] was not found in the geopolymer made of metakaolin calcined above 900 degrees C, while Z-zeolite [Na2O x Al2O3 x SiO2 x H2O] remained in specimens calcined at up to 1050 degrees C, All zeolite disappeared above 1150 degrees C. The pozzolanic reaction generates very small particles of 10-30 nm on the surface of metakaolin grains of 0.2-0.6 μm, rendering the matrix denser by binding the grains. The maximum compressive strength was revealed with the geopolymer made of metakaolin calcined at 1050 degrees C. The reason for the increased strength of the geopolymer obtained using higher calcination temperature is thought to be the combined effects of matrix hardening by geopolymeric reaction and reinforcement by mullite crystal phases.

  3. Modelling of phase transformations in substitutional alloys

    Czech Academy of Sciences Publication Activity Database

    Svoboda, Jiří; Vala, J.; Gamsjäger, E.; Fischer, F. D.

    237-240, - (2005), s. 647-652 ISSN 1012-0386. [DIMAT 2004 /6./. Krakow, 18.07.2004-23.07.2004] R&D Projects: GA AV ČR(CZ) 1QS200410502 Institutional research plan: CEZ:AV0Z20410507 Keywords : phase transformations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.483, year: 2005

  4. Orbital momentum and topological phase transformation

    Czech Academy of Sciences Publication Activity Database

    Středa, Pavel; Kučera, Jan

    2015-01-01

    Roč. 92, č. 23 (2015), "235152-1"-"235152-6" ISSN 1098-0121 R&D Projects: GA ČR GA15-13436S Institutional support: RVO:68378271 Keywords : orbital momentum * anomalous Hall effect * topological phase transformation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  5. Phase transformations, stability, and materials interactions

    International Nuclear Information System (INIS)

    Morris, J.W. Jr.; Brewer, L.; Cost, J.R.; Shewmon, P.

    1977-07-01

    The proceedings of the Materials Sciences Workshop on Phase Transformations, Stability, and Materials Interactions are divided into sections according to the following topics: (I) workshop scope and priorities; (II) study group reports--ERDA mission needs; (III) study group reports--technical area research priorities

  6. Phase and structural transformations in VVER-440 RPV base metal after long-term operation and recovery annealing

    Science.gov (United States)

    Kuleshova, E. A.; Gurovich, B. A.; Maltsev, D. A.; Frolov, A. S.; Bukina, Z. V.; Fedotova, S. V.; Saltykov, M. A.; Krikun, E. V.; Erak, D. Yu; Zhurko, D. A.; Safonov, D. V.; Zhuchkov, G. M.

    2018-04-01

    This study was carried out to evaluate the possibility of 1st generation VVER-440 reactors lifetime extension by recovery re-annealing with the respect to base metal (BM). Comprehensive studies of the structure and properties of BM templates (samples cut from the inner surface of the shells in beltline region) of operating VVER-440 reactor (after primary standard recovery annealing 475 °C/150 h and subsequent long-term re-irradiation within reactor pressure vessel (RPV)) were conducted. These templates were also subjected to laboratory re-annealing 475 °C/150 h. TEM, SEM and APT studies of BM after laboratory re-annealing revealed significant recovery of radiation-induced hardening elements (Cu-rich precipitates and dislocation loops). Simultaneously a process of strong phosphorus accumulation at grain boundaries occurs since annealing temperature corresponds to the maximum reversible temper brittleness development. The latter is not observed for VVER-440 weld metal (WM). Comparative assessment of the properties return level for the beltline BM templates after recovery re-annealing 475 °C/150 h showed that it does not reach the one typical for beltline WM after the same annealing.

  7. Morphological variations in cadmium sulfide nanocrystals without phase transformation.

    Science.gov (United States)

    Dhage, Sanjay R; Colorado, Henry A; Hahn, Thomas

    2011-06-14

    A very novel phenomenon of morphological variations of cadmium sulfide (CdS) nanorods under the transmission electron microscopy (TEM) beam was observed without structural phase transformation. Environmentally stable and highly crystalline CdS nanorods have been obtained via a chemical bath method. The energy of the TEM beam is believed to have a significant influence on CdS nanorods and may melt and transform them into smaller nanowires. Morphological variations without structural phase transformation are confirmed by recording selected area electron diffraction at various stages. The prepared CdS nanorods have been characterized by X-ray powder diffraction, TEM, UV-Vis spectroscopy, and photoluminescence spectroscopy. The importance of this phenomenon is vital for the potential application for CdS such as smart materials.

  8. Morphological variations in cadmium sulfide nanocrystals without phase transformation

    Directory of Open Access Journals (Sweden)

    Colorado Henry

    2011-01-01

    Full Text Available Abstract A very novel phenomenon of morphological variations of cadmium sulfide (CdS nanorods under the transmission electron microscopy (TEM beam was observed without structural phase transformation. Environmentally stable and highly crystalline CdS nanorods have been obtained via a chemical bath method. The energy of the TEM beam is believed to have a significant influence on CdS nanorods and may melt and transform them into smaller nanowires. Morphological variations without structural phase transformation are confirmed by recording selected area electron diffraction at various stages. The prepared CdS nanorods have been characterized by X-ray powder diffraction, TEM, UV-Vis spectroscopy, and photoluminescence spectroscopy. The importance of this phenomenon is vital for the potential application for CdS such as smart materials.

  9. Simulation of phase structures

    International Nuclear Information System (INIS)

    Lawson, J.

    1995-01-01

    This memo outlines a procedure developed by the author to extract information from phase measurements and produce a simulated phase structure for use in modeling optical systems, including characteristic optics for the Beamlet and NIF laser systems. The report includes an IDL program listing

  10. The use of Fourier reverse transforms in crystallographic phase refinement

    Energy Technology Data Exchange (ETDEWEB)

    Ringrose, Sharon [Iowa State Univ., Ames, IA (United States)

    1997-10-08

    Often a crystallographer obtains an electron density map which shows only part of the structure. In such cases, the phasing of the trial model is poor enough that the electron density map may show peaks in some of the atomic positions, but other atomic positions are not visible. There may also be extraneous peaks present which are not due to atomic positions. A method for determination of crystal structures that have resisted solution through normal crystallographic methods has been developed. PHASER is a series of FORTRAN programs which aids in the structure solution of poorly phased electron density maps by refining the crystallographic phases. It facilitates the refinement of such poorly phased electron density maps for difficult structures which might otherwise not be solvable. The trial model, which serves as the starting point for the phase refinement, may be acquired by several routes such as direct methods or Patterson methods. Modifications are made to the reverse transform process based on several assumptions. First, the starting electron density map is modified based on the fact that physically the electron density map must be non-negative at all points. In practice a small positive cutoff is used. A reverse Fourier transform is computed based on the modified electron density map. Secondly, the authors assume that a better electron density map will result by using the observed magnitudes of the structure factors combined with the phases calculated in the reverse transform. After convergence has been reached, more atomic positions and less extraneous peaks are observed in the refined electron density map. The starting model need not be very large to achieve success with PHASER; successful phase refinement has been achieved with a starting model that consists of only 5% of the total scattering power of the full molecule. The second part of the thesis discusses three crystal structure determinations.

  11. Phase Transformations in Cast Duplex Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yoon-Jun [Iowa State Univ., Ames, IA (United States)

    2004-01-01

    Duplex stainless steels (DSS) constitute both ferrite and austenite as a matrix. Such a microstructure confers a high corrosion resistance with favorable mechanical properties. However, intermetallic phases such as σ and χ can also form during casting or high-temperature processing and can degrade the properties of the DSS. This research was initiated to develop time-temperature-transformation (TTT) and continuous-cooling-transformation (CCT) diagrams of two types of cast duplex stainless steels, CD3MN (Fe-22Cr-5Ni-Mo-N) and CD3MWCuN (Fe-25Cr-7Ni-Mo-W-Cu-N), in order to understand the time and temperature ranges for intermetallic phase formation. The alloys were heat treated isothermally or under controlled cooling conditions and then characterized using conventional metallographic methods that included tint etching, and also using electron microscopy (SEM, TEM) and wavelength dispersive spectroscopy (WDS). The kinetics of intermetallic-phase (σ + χ) formation were analyzed using the Johnson-Mehl-Avrami (MA) equation in the case of isothermal transformations and a modified form of this equation in the case of continuous cooling transformations. The rate of intermetallic-phase formation was found to be much faster in CD3MWCuN than CD3MN due mainly to differences in the major alloying contents such as Cr, Ni and Mo. To examine in more detail the effects of these elements of the phase stabilities; a series of eight steel castings was designed with the Cr, Ni and Mo contents systematically varied with respect to the nominal composition of CD3MN. The effects of varying the contents of alloying additions on the formation of intermetallic phases were also studied computationally using the commercial thermodynamic software package, Thermo-Calc. In general, σ was stabilized with increasing Cr addition and χ by increasing Mo addition. However, a delicate balance among Ni and other minor elements such as N and Si also exists. Phase equilibria in DSS can be affected by

  12. Phase transformations in cast duplex stainless steels

    Science.gov (United States)

    Kim, Yoon-Jun

    Duplex stainless steels (DSS) constitute both ferrite and austenite as a matrix. Such a microstructure confers a high corrosion resistance with favorable mechanical properties. However, intermetallic phases such as sigma (sigma) and chi (chi) can also form during casting or high-temperature processing and can degrade the properties of the DSS. This research was initiated to develop time-temperature-transformation (TTT) and continuous-cooling-transformation (CCT) diagrams of two types of cast duplex stainless steels, CD3MN (Fe-22Cr-5Ni-Mo-N) and CD3MWCuN (Fe-25Cr-7Ni-Mo-W-Cu-N), in order to understand the time and temperature ranges for intermetallic phase formation. The alloys were heat treated isothermally or under controlled cooling conditions and then characterized using conventional metallographic methods that included tint etching, and also using electron microscopy (SEM, TEM) and wavelength dispersive spectroscopy (WDS). The kinetics of intermetallic-phase (sigma + chi) formation were analyzed using the Johnson-Mehl-Avrami (JMA) equation in the case of isothermal transformations and a modified form of this equation in the case of continuous cooling transformations. The rate of intermetallic-phase formation was found to be much faster in CD3MWCuN than CD3MN due mainly to differences in the major alloying contents such as Cr, Ni and Mo. To examine in more detail the effects of these elements of the phase stabilities, a series of eight steel castings was designed with the Cr, Ni and Mo contents systematically varied with respect to the nominal composition of CD3MN. The effects of varying the contents of alloying additions on the formation of intermetallic phases were also studied computationally using the commercial thermodynamic software package, Thermo-Calc. In general, a was stabilized with increasing Cr addition and chi by increasing Mo addition. However, a delicate balance among Ni and other minor elements such as N and Si also exists. Phase equilibria in

  13. Stacking faults and phase transformations in silicon nitride

    Science.gov (United States)

    Milhet, X.; Demenet, J.-L.; Rabier, J.

    1998-11-01

    From observations of extended dislocation nodes in β silicon nitride, possible stacking fault structures in the basal plane of this compound have been investigated. It has been found that stacking fault structure is locally analogous to α silicon nitride. A phase transformation α to β or β to α can also be achieved by cooperative shear of partial dislocations with 1/3<~ngle1bar{1}00rangle Burgers vectors.

  14. The lattice correspondence and diffusional-displacive phase transformations

    International Nuclear Information System (INIS)

    Nie, J.F.; Muddle, B.C.

    1999-01-01

    When a coherent interface is maintained between parent and product phases in a solid state phase transformation, then it is always possible to define a lattice correspondence across this interface and describe the structural change by a homogeneous lattice deformation, S T . For certain transformations, this strain is an invariant plane strain, with the invariant plane defining the planar, coherent interface between parent and product. This group includes the familiar martensitic face-centred cubic to close-packed hexagonal transformation in, for example, cobalt-based alloys, but it is demonstrated here that it also contains transformations giving rise to a broad range of plate-shaped, diffusional precipitation products. For many such transformation products, the transformation strain has a significant shear component and the accommodation of shear strain energy is potentially an important, and often overlooked, factor in both the nucleation and growth of such products. More commonly S T is not an invariant plane strain and, if a planar interface is to be preserved between parent and product, it is necessary to combine S T with a lattice invariant strain to allow a partially-coherent interface that is macroscopically invariant. It is demonstrated that there are diffusional transformation products which also have the geometric and crystallographic features of both of the common forms of partially-coherent martensitic products

  15. Role of valence electrons in phase transformation kinetics of thallium and its dilute alloys

    Science.gov (United States)

    Ahmed, R.; Ahmed, S.

    1991-01-01

    The kinetics of the phase transformation of thallium and its dilute alloys were investigated using XRD and calorimetry. Pure thallium exhibits a beta(bcc) to alpha(hcp) phase transformation on cooling at 508 K. With alloying additions, the crystal structure for each phase does not change, although the size of the unit cell increases. The enthalpy and the temperature of phase transformation of each alloy have been determined. The chemical free energy change associated with the phase transformation of each alloy was calculated. The valence electrons make an outstanding contribution to the chemical free energy change required for the phase change.

  16. Elementary excitations and phase transformations in solids

    International Nuclear Information System (INIS)

    Cowley, R.A.

    1985-01-01

    Neutron scattering is and will continue to be a uniquely powerful tool for the study of elementary excitations and phase transformations in solids. The paper examines a few recent experiments on molecular crystals, superionic materials, paramagnetic scattering and phase transitions to see what experimental features made these experiments possible, and hence to make suggestions about future needs. It is concluded that new instruments will extend the scope of neutron scattering studies to new excitations, that there is a need for higher resolution, particularly for phase transition studies, and that it will be important to use intensity information, discrimination against unwanted inelastic processes and polarization analysis to reliably measure the excitations in new materials. (author)

  17. Phase transformations in Mo-doped FINEMETs

    Energy Technology Data Exchange (ETDEWEB)

    Silveyra, Josefina M., E-mail: jsilveyra@fi.uba.a [Lab. de Solidos Amorfos, INTECIN, FIUBA-CONICET, Paseo Colon 850, (C1063ACV) Buenos Aires (Argentina); Illekova, Emilia; Svec, Peter; Janickovic, Dusan [Institute of Physics SAS, Dubravska cesta 9, 845 11 Bratislava (Slovakia); Rosales-Rivera, Andres [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Manizales (Colombia); Cremaschi, Victoria J. [Lab. de Solidos Amorfos, INTECIN, FIUBA-CONICET, Paseo Colon 850, (C1063ACV) Buenos Aires (Argentina)

    2010-06-15

    In this paper, the phase transformations occurring during the crystallization process of FINEMETs in which Nb has been gradually replaced by Mo have been studied by a variety of techniques including DSC, DTA, TGA, XRD and TEM. The thermal stability of the alloy was deteriorated as a consequence of Mo's smaller atomic size. The gradual replacement of Nb by Mo reduced the onset temperature of Fe-Si and of the borides. The Curie temperature of the amorphous phase slightly decreased from 594 K for x=0 to 587 K for x=3. The borides compounds Fe{sub 2}B and Fe{sub 23}B{sub 6} as well as the (Nb,Mo){sub 5}Si{sub 3} phase were found to precipitate in the second and third crystallization.

  18. Anomalous compression behavior of germanium during phase transformation

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Xiaozhi [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); Tan, Dayong [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); Guangzhou Institute of Geochemistry, Chinese Academic of Sciences, Guangzhou 510640 (China); Ren, Xiangting [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); Yang, Wenge, E-mail: yangwg@hpstar.ac.cn, E-mail: duanweihe@scu.edu.cn [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); He, Duanwei, E-mail: yangwg@hpstar.ac.cn, E-mail: duanweihe@scu.edu.cn [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Institute of Fluid Physics and National Key Laboratory of Shockwave and Detonation Physic, China Academy of Engineering Physics, Mianyang 621900 (China); Mao, Ho-Kwang [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 (United States)

    2015-04-27

    In this article, we present the abnormal compression and plastic behavior of germanium during the pressure-induced cubic diamond to β-tin structure transition. Between 8.6 GPa and 13.8 GPa, in which pressure range both phases are co-existing, first softening and followed by hardening for both phases were observed via synchrotron x-ray diffraction and Raman spectroscopy. These unusual behaviors can be interpreted as the volume misfit between different phases. Following Eshelby, the strain energy density reaches the maximum in the middle of the transition zone, where the switch happens from softening to hardening. Insight into these mechanical properties during phase transformation is relevant for the understanding of plasticity and compressibility of crystal materials when different phases coexist during a phase transition.

  19. Crystal structure of Cs3H(SeO4)2 (T=295 K) and its changes in phase transformations

    International Nuclear Information System (INIS)

    Merinov, B.V.; Bolotina, N.B.; Baranov, A.I.; Shuvalov, L.A.

    1988-01-01

    Crystal structure of Cs 3 H(SeO 4 ) 2 3 phase at T=295 K is decoded by X-ray diffraction data. Monoclinic cell parameters are improved: a=10.903(3), b=6.390(8), c=8.452(2)A, β=112.46(1) deg, V=544 A 3 , Z=2, sp. gr. C2/m. Structural peculiarities of 3↔2↔1 phase transitions in Cs 3 H(SeO 4 ) 2 and proton conductivity mechanism in superionic phase are considered

  20. Isomorphic phase transformation in shocked cerium using molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Dupont, Virginie [Los Alamos National Laboratory; Germann, Timothy C [Los Alamos National Laboratory; Chen, Shao - Ping [Los Alamos National Laboratory

    2010-08-12

    Cerium (Ce) undergoes a significant ({approx}16%) volume collapse associated with an isomorphic fcc-fcc phase transformation when subject to compressive loading. We present here a new Embedded Atom Method (EAM) potential for Cerium that models two minima for the two fcc phases. We show results from its use in Molecular Dynamics (MD) simulations of Ce samples subjected to shocks with pressures ranging from 0.5 to 25 GPa. A split wave structure is observed, with an elastic precursor followed by a plastic wave. The plastic wave causes the expected fcc-fcc phase transformation. Comparisons to experiments and MD simulations on Cesium (Cs) indicate that three waves could be observed. The construction of the EAM potential may be the source of the difference.

  1. Peculiarities of structural transformations in zirconia nanocrystals

    Science.gov (United States)

    Vasilevskaya, A.; Almjasheva, O. V.; Gusarov, V. V.

    2016-07-01

    The transitions of metastable tetragonal phase as well as high-temperature tetragonal phase into the low-temperature monoclinic phase upon heating and cooling were thoroughly studied in zirconia nanoparticles. High-temperature X-ray diffraction, thermal analysis and Raman spectroscopy were used to provide the systematic approach to the investigation of zirconia nanoparticles thermal behavior. A phase transformation sequence in the ZrO2-H2O system was determined, and the mechanisms of tetragonal-to-monoclinic transition upon heating and cooling were suggested. Here, the phenomenon was found and described, which was determined as "self-powdering" of nanoparticles occurring during structural transition. This phenomenon was observed by in situ investigation of the evolution of crystalline nanoparticles from amorphous zirconium hydroxide during thermal treatment in air. The tetragonal-to-monoclinic phase transition, induced by cooling from the temperature of equilibrium of tetragonal zirconia (i.e., above 1170 °C), is accompanied by a significant crystallite size decrease (with corresponding 3-4 times decrease of crystallite volume). The experimental results facilitate applications of zirconia nanoparticles to obtain high-performance nanopowders for nanoceramics.

  2. Phase Transformations during the Reaction Heat Treatment

    CERN Document Server

    Scheuerlein, C; Thilly, L; Buta, F; Peng, X; Gregory, E; Parrell, J A; Pong, I; Bordini, B; Cantoni, M

    2009-01-01

    The evolution of Nb containing phases during the diffusion heat treatment of three different high critical current Nb3Sn strand types is compared, based on synchrotron X-ray diffraction results that have been obtained at the ID15 beam line of the European Synchrotron Radiation Facility (ESRF). In all strands studied, Nb3Sn formation is preceded by the formation of a Cu-Nb-Sn ternary phase, NbSn2 and Nb6Sn5. As compared to the PIT and Tube Type strand, the amount of these phases formed in the RRP strand is relatively small. In the RRP strand subelements with a fine filament structure Nb3Sn grows more quickly, thereby preventing to a large extent the formation of the other higher tin phases.

  3. Relationships between molecular structure and kinetic and thermodynamic controls in lipid systems. Part II: Phase behavior and transformation paths of SSS, PSS and PPS saturated triacylglycerols--effect of chain length mismatch.

    Science.gov (United States)

    Bouzidi, Laziz; Narine, Suresh S

    2012-01-01

    The kinetic phase behavior and phase transformation paths of purified tristearoylglycerol (SSS), 3-palmitoyl-1,2-distearoyl-sn-glycerol (PSS) and 1,2-dipalmitoyl-3-stearoyl-sn-glycerol (PPS) were investigated in terms of polymorphism, crystallization and melting. The details of the phase transformation paths were obtained using the heating cycles of two sets of experiments: (a) cooling rate was varied and heating rate fixed and (b) cooling rate was fixed and heating rate varied. Kinetic effects were manifest in all measured properties, underscoring the complexity of the phase transformation paths for each TAG, and the intricate thermodynamics-molecular relationships. For the first time, XRD data obtained for SSS, PSS and PPS TAGs, cooled at rates higher than 0.5°C/min, suggested the formation of a transient structure similar to the so-called α(2)-phase which has been observed in mixed saturated-unsaturated TAGs quenched from the melt. The more stable phases (β' in PSS and PPS, and β in SSS) were only observed for cooling rates lower than 1.0°C/min. The kinetic and thermodynamic differences observed in the crystallization, structure and melting of SSS, PSS and PPS are proposed to be mainly due to the disturbances introduced at the "terrace" level via methyl-end group interactions, i.e., the missing of two or four CH(2) groups compared to SSS. The symmetrical SSS with a relatively flat "terrace" crystallizes preferably in the most stable β-form. Two missing CH(2) groups at the sn-1 position (PSS) introduces enough structural disturbances to promote the relative prevalence and persistence of the β'-phase, and four missing CH(2) groups at the sn-1 and sn-2 positions (PPS) is relatively too large of a disturbance and therefore favors the α-form. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  4. Structured-illumination reflectance imaging coupled with spiral phase transform for bruise detection and three-dimensional geometry reconstruction of apples

    Science.gov (United States)

    Structured-illumination reflectance imaging (SIRI) is a new, promising imaging technique with enhanced, versatile capabilities for quality evaluation of food products. SIRI enables simultaneous acquisition of higher-contrast/resolution and better depth-controlled intensity and phase images for detec...

  5. Design and Implementation of GSM Based Transformer Phase ...

    African Journals Online (AJOL)

    In this work, the design and implementation of a transformer phase monitoring system, which continuously check for blown fuses on each phases of the distribution transformer was carried out. The system promptly reports any transformer with blown J&P fuse via a preprogrammed SMS which will state the location of the ...

  6. Phase transformations in neutron-irradiated Zircaloys

    International Nuclear Information System (INIS)

    Chung, H.M.

    1986-04-01

    Microstructural evolution in Zircaloy-2 and -4 spent-fuel cladding specimens after ∼3 years of irradiation in commercial power reactors has been investigated by TEM and HVEM. Two kinds of precipitates induced by the fast-neutron irradiation in the reactors have been identified, i.e., Zr 3 O and cubic-ZrO 2 particles approximately 2 to 10 nm in size. By means of a weak-beam dark-field ''2-1/2D-microscopy'' technique, the bulk nature of the precipitates and the surficial nature of artifact oxide and hydride phases could be discerned. The Zr(Fe/sub x/,Cr/sub 1-x/) 2 and Zr 2 (Fe/sub x/,Ni/sub 1-x/) intermetallic precipitates normally present in the as-fabricated material virtually dissolved in the spent-fuel cladding specimens after a fast-neutron fluence of ∼4 x 10 21 ncm -2 in the power reactors. The observed radiation-induced phase transformations are compared with predictions based on the currently available understanding of the alloy characteristics. 29 refs

  7. Phase transformations of nanostructured Zr-Y-O coatings under loading

    Science.gov (United States)

    Fedorischeva, M. V.; Kalashnikov, M. P.; Bozhko, I. A.; Mironov, Yu. P.; Sergeev, V. P.

    2017-12-01

    The deposition of nanostructured Zr-Y-O/Si-Al-N-based coatings was implemented by the pulse magnetron methods. The structural-phase state of the nanostructured coatings was studied with TEM and X-ray analysis. The phase transformation in Zr-Y-O layer was observed with the X-ray diffraction analysis in the "in-situ" mode under loading in conditions of free and constrained volumes. It was found, that there were martensitic phase transformations at certain deformation levels under the conditions of the free volume and martensitic phase transformations in the local regions of the coating layer with the structure fining in constrained volume.

  8. Research on coordinate transformation of the three-phase circuit

    OpenAIRE

    Tian Ming Xing; yan hong; Yuan Dong Sheng

    2013-01-01

    The different three-phase circuit coordinate transformation matrixes are given in relevant literatures , which may cause some difficulties to understand and apply the coordinate transformation. The paper presents a general expression of the coordinate transformation matrixes in three-phase circuit and points out that the coordinate transformation matrixes having different specific expressions are due to existing the parameters which can be selected in the general expression. On this basis, th...

  9. An optical Fourier transform coprocessor with direct phase determination.

    Science.gov (United States)

    Macfaden, Alexander J; Gordon, George S D; Wilkinson, Timothy D

    2017-10-20

    The Fourier transform is a ubiquitous mathematical operation which arises naturally in optics. We propose and demonstrate a practical method to optically evaluate a complex-to-complex discrete Fourier transform. By implementing the Fourier transform optically we can overcome the limiting O(nlogn) complexity of fast Fourier transform algorithms. Efficiently extracting the phase from the well-known optical Fourier transform is challenging. By appropriately decomposing the input and exploiting symmetries of the Fourier transform we are able to determine the phase directly from straightforward intensity measurements, creating an optical Fourier transform with O(n) apparent complexity. Performing larger optical Fourier transforms requires higher resolution spatial light modulators, but the execution time remains unchanged. This method could unlock the potential of the optical Fourier transform to permit 2D complex-to-complex discrete Fourier transforms with a performance that is currently untenable, with applications across information processing and computational physics.

  10. Deformation-induced phase transformation in 4H–SiC nanopillars

    International Nuclear Information System (INIS)

    Chen, Bin; Wang, Jun; Zhu, Yiwei; Liao, Xiaozhou; Lu, Chunsheng; Mai, Yiu-Wing; Ringer, Simon P.; Ke, Fujiu; Shen, Yaogen

    2014-01-01

    The deformation behaviour of single-crystal SiC nanopillars was studied by a combination of in situ deformation transmission electron microscopy and molecular dynamics simulations. An unexpected deformation-induced phase transformation from the 4H hexagonal structure to the 3C face-centred cubic structure was observed in these nanopillars at room temperature. Atomistic simulations revealed that the 4H to 3C phase transformation follows a stick–slip process with initiation and end stresses of 12.1–14.0 and 7.9–9.0 GPa, respectively. The experimentally measured stress of 9–10 GPa for the phase transformation falls within the range of these theoretical upper and lower stresses. The reasons for the phase transformation are discussed. The finding sheds light on the understanding of phase transformation in polytypic materials at low temperature

  11. Phase transformations in lithium aluminates irradiated with neutrons

    International Nuclear Information System (INIS)

    Carrera, L.M.; Delfin L, A.; Urena N, F.; Basurto, R.; Bosch, P.

    2003-01-01

    The lithium aluminate like candidate to be used in the coverings producers of tritium in the fusion nuclear reactors, presents high resistance to the corrosion to the one to be stuck to structural materials as special steels. However, the crystallographic changes that take place in the cover that is continually subjected to irradiation with neutrons, can alter its resistance to the corrosion. In this work the changes of crystalline structure are shown that they present two types of nano structures of lithium aluminates, subjected to an average total dose 7.81 x 10 8 Gy in the fixed irradiation system of capsules of the one TRIGA Mark lll nuclear reactor of the Nuclear Center of Mexico. The studied nano structures presented only phase transformations without formation of amorphous material. (Author)

  12. Physical nature of structural and phase transformations in Cu-Al α solid solutions upon low-temperature irradiation and subsequent annealing

    Science.gov (United States)

    Petrenko, P. V.; Kulish, N. P.; Mel'nikova, N. A.; Grabovskii, Yu. E.

    2013-12-01

    Methods of X-ray diffraction analysis and measurements of residual resistivity have been used to study effects of electron irradiation in the temperature range of 250-330 K on the structural and phase state of the Cu-15 at % Al solid solution. The results obtained are explained by the presence in the Cu-Al alloys of an inhomogeneous short-range order of two types, i.e., low-temperature, α2 type; and high-temperature, γ2 type.

  13. Transmission Network Expansion Planning Considering Phase-Shifter Transformers

    Directory of Open Access Journals (Sweden)

    Celso T. Miasaki

    2012-01-01

    Full Text Available This paper presents a novel mathematical model for the transmission network expansion planning problem. Main idea is to consider phase-shifter (PS transformers as a new element of the transmission system expansion together with other traditional components such as transmission lines and conventional transformers. In this way, PS are added in order to redistribute active power flows in the system and, consequently, to diminish the total investment costs due to new transmission lines. Proposed mathematical model presents the structure of a mixed-integer nonlinear programming (MINLP problem and is based on the standard DC model. In this paper, there is also applied a specialized genetic algorithm aimed at optimizing the allocation of candidate components in the network. Results obtained from computational simulations carried out with IEEE-24 bus system show an outstanding performance of the proposed methodology and model, indicating the technical viability of using these nonconventional devices during the planning process.

  14. In-situ X-ray diffraction studies of the phase transformations and structural states of B2, R and B19′ phases in Ti{sub 49.5}Ni{sub 50.5} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ostapenko, Marina G., E-mail: artifakt@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Meisner, Ludmila L., E-mail: llm@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Lotkov, Aleksandr I., E-mail: lotkov@ispms.tsc.ru; Gudimova, Ekaterina Y., E-mail: egu@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Zakharova, Margarita A., E-mail: tibiboreth@gmail.com [National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    The martensitic transformation, Debye–Waller factor, mean-square atomic displacements and the coefficient of thermal expansion on cooling of the Ti{sub 49.5}Ni{sub 50.5} shape memory alloy were examined using in-situ X-ray diffraction. It was revealed B2→R (T{sub R} ≡ T = 273 ± 10 K) along with B2→B19’ (M{sub s} ≡ T = 273 ± 10 K) transitions occur. It was found that Debye–Waller factor and mean-square displacement of B2 phase undergo significant increase as functions of temperature when phase transition B2→R and B2→B19’ take place. The analysis of the thermal expansion coefficient of the B2 phase indicates that the value of a increases almost linearly while cooling.

  15. Experimental demonstration of conformal phased array antenna via transformation optics.

    Science.gov (United States)

    Lei, Juan; Yang, Juxing; Chen, Xi; Zhang, Zhiya; Fu, Guang; Hao, Yang

    2018-02-28

    Transformation Optics has been proven a versatile technique for designing novel electromagnetic devices and it has much wider applicability in many subject areas related to general wave equations. Among them, quasi-conformal transformation optics (QCTO) can be applied to minimize anisotropy of transformed media and has opened up the possibility to the design of broadband antennas with arbitrary geometries. In this work, a wide-angle scanning conformal phased array based on all-dielectric QCTO lens is designed and experimentally demonstrated. Excited by the same current distribution as such in a conventional planar array, the conformal system in presence of QCTO lens can preserve the same radiation characteristics of a planar array with wide-angle beam-scanning and low side lobe level (SLL). Laplace's equation subject to Dirichlet-Neumann boundary conditions is adopted to construct the mapping between the virtual and physical spaces. The isotropic lens with graded refractive index is realized by all-dielectric holey structure after an effective parameter approximation. The measurements of the fabricated system agree well with the simulated results, which demonstrate its excellent wide-angle beam scanning performance. Such demonstration paves the way to a robust but efficient array synthesis, as well as multi-beam and beam forming realization of conformal arrays via transformation optics.

  16. Study of structural phase transformation and hysteresis behavior of inverse-spinel α-ferrite nanoparticles synthesized by co-precipitation method

    Science.gov (United States)

    Dabagh, Shadab; Chaudhary, Kashif; Haider, Zuhaib; Ali, Jalil

    2018-03-01

    Substitution of cobalt (Co2+) ions in cobalt ferrite (CoFe2O4) with copper (Cu2+) and aluminum (Al3+) ions allows variations in their electric and magnetic properties which can be optimized for specific applications. In this article, synthesis of inverse-spinel Co1-xCuxFe2-xAlxO4 (0.0 ≤ x ≤ 0.8) nanoparticles by substituting Cu2+ and Al3+ ions in CoFe2O4 via co-precipitation method is reported. By controlling copper and aluminum (Cu-Al) substituent ratio, the magnetic moment and coercivity of synthesized cobalt ferrite nanoparticles is optimized. The role of substituents on the structure, particle size, morphology, and magnetic properties of nano-crystalline ferrite is investigated. The Co1-xCuxFe2-xAlxO4 (0.0 ≤ x≤ 0.8) nanoparticles with crystallite size in the range of 23.1-26.5 nm are observed, 26.5 nm for x = 0.0-23.1 nm for x = 0.8. The inverse-spinel structure of synthesized Co1-xCuxFe2-xAlxO4 (0.0 ≤ x ≤ 0.8) nano-particles is confirmed by characteristic vibrational bands at tetrahedral and octahedral sites using Fourier transform infrared spectroscopy. A decreases in coercive field and magnetic moment is observed as Cu-Al contents are increased (x = 0.0-0.8). The positive anisotropy of synthesized particles Co1-xCuxFe2-xAlxO4 (0.0 ≤ x ≤ 0.8) is obtained in the range 1.96 × 105 J/m3 for x = 0.0 to 0.29 × 105 J/m3 for x = 0.8.

  17. Phase Stability and Transformations in Vanadium Oxide Nanocrystals

    Science.gov (United States)

    Bergerud, Amy Jo

    Vanadium oxides are both fascinating and complex, due in part to the many compounds and phases that can be stabilized as well as the phase transformations which occur between them. The metal to insulator transitions (MITs) that take place in vanadium oxides are particularly interesting for both fundamental and applied study as they can be induced by a variety of stimuli ( i.e., temperature, pressure, doping) and utilized in many applications (i.e., smart windows, sensors, phase change memory). Nanocrystals also tend to demonstrate interesting phase behavior, due in part to the enhanced influence of surface energy on material thermodynamics. Vanadium oxide nanocrystals are thus expected to demonstrate very interesting properties in regard to phase stability and phase transformations, although synthesizing vanadium oxides in nanocrystal form remains a challenge. Vanadium sesquioxide (V2O3) is an example of a material that undergoes a MIT. For decades, the low temperature monoclinic phase and high temperature corundum phase were the only known crystal structures of V2O3. However, in 2011, a new metastable polymorph of V2O3 was reported with a cubic, bixbyite crystal structure. In Chapter 2, a colloidal route to bixbyite V2O 3 nanocrystals is presented. In addition to being one of the first reported observations of the bixbyite phase in V2O3, it is also one of the first successful colloidal syntheses of any of the vanadium oxides. The nanocrystals possess a flower-like morphology, the size and shape of which are dependent on synthesis time and temperature, respectively. An aminolysis reaction mechanism is determined from Fourier transform infrared spectroscopy data and the bixbyite crystal structure is confirmed by Rietveld refinement of X-ray diffraction (XRD) data. Phase stability is assessed in both air and inert environments, confirming the metastable nature of the material. Upon heating in an inert atmosphere above 700°C, the nanocrystals irreversibly transform

  18. Mechanisms of diffusional phase transformations in metals and alloys

    CERN Document Server

    Aaronson, Hubert I; Lee, Jong K

    2010-01-01

    Developed by the late metallurgy professor and master experimentalist Hubert I. Aaronson, this collection of lecture notes details the fundamental principles of phase transformations in metals and alloys upon which steel and other metals industries are based. Mechanisms of Diffusional Phase Transformations in Metals and Alloys is devoted to solid-solid phase transformations in which elementary atomic processes are diffusional jumps, and these processes occur in a series of so-called nucleation and growth through interface migration. Instead of relying strictly on a pedagogical approach, it doc

  19. Acoustic emission during low temperature phase transformations in plutonium

    International Nuclear Information System (INIS)

    Khejpl, K.; Karpenter, S.

    1988-01-01

    To study the nature of phase transformations in plutonium and plutonium-gallium alloys (0.3 and 0.57% Ga) the measurement of acoustic emission is conducted. The presence of acoustic emission testifies to martensitic character of transformation, related to sharp local changes in the volume, which cause elastic waves. It is detected that during α reversible β transformations in non-alloyed plutonium acoustic emission is absent, and that testifies to nonmartensitic nature of the transformations. σ reversible α transformation in plutonium-gallium alloys is accompanied by the appearance of acoustic emission, i.e. it is of martensitic origin

  20. Study of structural phase transformation and hysteresis behavior of inverse-spinel α-ferrite nanoparticles synthesized by co-precipitation method

    Directory of Open Access Journals (Sweden)

    Shadab Dabagh

    2018-03-01

    Full Text Available Substitution of cobalt (Co2+ ions in cobalt ferrite (CoFe2O4 with copper (Cu2+ and aluminum (Al3+ ions allows variations in their electric and magnetic properties which can be optimized for specific applications. In this article, synthesis of inverse-spinel Co1−xCuxFe2−xAlxO4 (0.0 ≤ x ≤ 0.8 nanoparticles by substituting Cu2+ and Al3+ ions in CoFe2O4 via co-precipitation method is reported. By controlling copper and aluminum (Cu-Al substituent ratio, the magnetic moment and coercivity of synthesized cobalt ferrite nanoparticles is optimized. The role of substituents on the structure, particle size, morphology, and magnetic properties of nano-crystalline ferrite is investigated. The Co1−xCuxFe2−xAlxO4 (0.0 ≤ x≤ 0.8 nanoparticles with crystallite size in the range of 23.1–26.5 nm are observed, 26.5 nm for x = 0.0–23.1 nm for x = 0.8. The inverse-spinel structure of synthesized Co1−xCuxFe2−xAlxO4 (0.0 ≤ x ≤ 0.8 nano-particles is confirmed by characteristic vibrational bands at tetrahedral and octahedral sites using Fourier transform infrared spectroscopy. A decreases in coercive field and magnetic moment is observed as Cu-Al contents are increased (x = 0.0–0.8. The positive anisotropy of synthesized particles Co1−xCuxFe2−xAlxO4 (0.0 ≤ x ≤ 0.8 is obtained in the range 1.96 × 105 J/m3 for x = 0.0 to 0.29 × 105 J/m3 for x = 0.8. Keywords: Co-precipitation method, XRD, Spinel ferrites, VSM, TEM

  1. Size dependent phase and morphological transformation of alumina nanoparticles

    Science.gov (United States)

    Dommisa, D. B.; Dash, R. K.

    2018-03-01

    The size effect of the alumina nanoparticles on the phase and morphological transition by thermal treatment at various temperatures is investigated by choosing two different sizes alumina nanoparticles. Our experimental results revealed that phase and morphological transformation behavior is significantly different for smaller size alumina nanoparticles than that of larger size. The more stable alpha phase transformation occurs at a higher temperature for smaller size alumina nanoparticles in comparison to that of the larger size alumina nanoparticles. Moreover, the experimental facts also elucidated that the nucleation and growth process at the nanoscale for the phase transition is also size dependent. Our experimental result from the FESEM and TEM analysis also revealed that there is a direct correlation between phase and morphological transition of alumina nanoparticles size which is consistent with the XRD results. Therefore, we believe that our experimental findings can be extended to other complex nanomaterials for understanding the size-dependent phase and morphological transformation at the nanoscale.

  2. The self-healing of defects induced by the hydriding phase transformation in palladium nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ulvestad, A.; Yau, A.

    2017-11-09

    Nanosizing can dramatically alter material properties by enhancing surface thermodynamic contributions, shortening diffusion lengths, and increasing the number of catalytically active sites per unit volume. These mechanisms have been used to explain the improved properties of catalysts, battery materials, plasmonic materials, etc. Here we show that Pd nanoparticles also have the ability to self-heal defects in their crystal structures. Using Bragg coherent diffractive imaging, we image dislocations nucleated deep in a Pd nanoparticle during the forward hydriding phase transformation that heal during the reverse transformation, despite the region surrounding the dislocations remaining in the hydrogen-poor phase. We show that defective Pd nanoparticles exhibit sloped isotherms, indicating that defects act as additional barriers to the phase transformation. Our results resolve the formation and healing of structural defects during phase transformations at the single nanoparticle level and offer an additional perspective as to how and why nanoparticles differ from their bulk counterparts.

  3. Phase transformations in titanium oxycarbide TiC0.545O0.08

    International Nuclear Information System (INIS)

    Tashmetov, M.Yu.; Em, V.T.; Savenko, B.N.; Batdemberel, G.

    2003-01-01

    Phase transformations in titanium oxycarbide TiC 0.545 O 0.08 have been studied by the methods of neutron diffraction and X-ray structure analysis. It was established that the ordered cubic structure δ ' (sp. gr. Fd3m) of the oxycarbide sample is the low-temperature ordered phase existing up to 990 K. The order-disorder phase transition (990 K) results in the formation of an ordered trigonal structure (sp. gr. R3-barm or P3 1 21). The α-Ti-phase is separated at the temperature 1020 K. The order-disorder phase transition was found at T = 1040 K

  4. Diffusion phase transformation and deformation in steels

    Czech Academy of Sciences Publication Activity Database

    Gamsjaeger, E.; Antretter, T.; Schmaranzer, C.; Preis, W.; Chimani, C.; Simha, N. K.; Svoboda, Jiří; Fischer, F. D.

    2002-01-01

    Roč. 25, č. 1 (2002), s. 92-99 ISSN 0927-0256 R&D Projects: GA AV ČR KSK1010104 Institutional research plan: CEZ:AV0Z2041904 Keywords : Transformation kinetics * Fe-C system * steel Subject RIV: BJ - Thermodynamics Impact factor: 0.856, year: 2002

  5. Estimating Transformation Length in Linear- to Minimum-Phase Transformation Using Cepstrums

    DEFF Research Database (Denmark)

    Bysted, Tommy Kristensen

    1997-01-01

    response of the minimum-phase FIR-filter. The transformation length estimation is made using the absolute value of the dominating zero in the linear-phase FIR-filter and the maximum allowed amplitude and phase deviation of the disturbing function. Two examples are given. The first one verifies...

  6. Kinetics of solid state phase transformations: Measurement and ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 122; Issue 1. Kinetics of solid state phase transformations: Measurement and modelling of some basic issues. S Raju E ... are enumerated. A simple and general modelling methodology for understanding the kinetics of non-isothermal transformations is outlined.

  7. A Novel Three Phase to Seven Phase Conversion Technique Using Transformer Winding Connections

    Directory of Open Access Journals (Sweden)

    M. Tabrez

    2017-10-01

    Full Text Available This paper proposes a novel multiphase transformer connection scheme which converts three phase balanced AC input to seven phase balanced AC output. Generalized theory to convert a three phase utility supply into any number of phases is presented. Based on the proposed generalized principle, a three phase to seven phase power converting transformer design is presented with connection scheme, analysis and simulation and experimental results of the proposed three phase to seven phase conversion transformer. The proposed transformer in this paper is analyzed and compared with the connection scheme for seven phase available in the literature. The connection scheme is found to have higher power density, lower core area and lower core requirement as compared to the available connection scheme of the same rating. Impedance mismatching between different phases of the transformer is observed in the three phase to seven phase transformer available in the literature. As this mismatching introduces error in study of per phase equivalent circuit diagrams as well as imbalance in voltage and currents. The present design also addresses the impedance mismatching issue and reduces mismatching in the proposed transformer design. A prototype of the proposed system is developed and waveforms are presented. The proposed design is verified using simulation and validated using experimental approach.

  8. SIMULATION OF CHARACTERISTICS OF DUAL-CORE PHASE SHIFTING TRANSFORMER

    Directory of Open Access Journals (Sweden)

    Kalinin L.P.

    2014-04-01

    Full Text Available The role and importance of phase shifting transformers are increased as a result of the further development of integrated power systems. This gives the rise to new technical solutions which entails the necessity of comparison of new developments with existing. The article consider the technical characteristics of dual-core phase shifting transformer which later will be used as a basis for comparison with other competing options and assess of their technical efficiency.

  9. Urbanization with and without Structural Transformation

    OpenAIRE

    Douglas Gollin; Remi Jedwab; Dietrich Vollrath

    2013-01-01

    We document several new facts regarding urbanization and structural change in developing countries and develop a model that can account for them. Most developing countries follow a standard pattern: urbanization is a by-product of either "push" from agricultural productivity growth or a "pull" from industrial productivity growth. In these countries urbanization occurs with structural transformation and cities are "production cities", with a mix of workers in tradable and non-tradable sectors....

  10. Phase transformation of metastable cubic γ-phase in U-Mo alloys

    International Nuclear Information System (INIS)

    Sinha, V.P.; Hegde, P.V.; Prasad, G.J.; Dey, G.K.; Kamath, H.S.

    2010-01-01

    Over the past decade considerable efforts have been put by many fuel designers to develop low enriched uranium (LEU 235 ) base U-Mo alloy as a potential fuel for core conversion of existing research and test reactors which are running on high enriched uranium (HEU > 85%U 235 ) fuel and also for the upcoming new reactors. U-Mo alloy with minimum 8 wt% molybdenum shows excellent metastability with cubic γ-phase in cast condition. However, it is important to characterize the decomposition behaviour of metastable cubic γ-uranium in its equilibrium products for in reactor fuel performance point of view. The present paper describes the phase transformation behaviour of cubic γ-uranium phase in U-Mo alloys with three different molybdenum compositions (i.e. 8 wt%, 9 wt% and 10 wt%). U-Mo alloys were prepared in an induction melting furnace and characterized by X-ray diffraction (XRD) method for phase determination. Microstructures were developed for samples in as cast condition. The alloys were hot rolled in cubic γ-phase to break the cast structure and then they were aged at 500 o C for 68 h and 240 h, so that metastable cubic γ-uranium will undergo eutectoid decomposition to form equilibrium phases of orthorhombic α-uranium and body centered tetragonal U 2 Mo intermetallic compound. U-Mo alloy samples with different ageing history were then characterized by XRD for phase and development of microstructure.

  11. Phase Transformation of Hydrothermally Synthesized Nanoparticle ...

    African Journals Online (AJOL)

    NJD

    Mild hydrothermal hydrolysis of TiCl4 produces nanorods of the rutile phase of titanium dioxide in high yield, while in the presence of organic ..... Reading, MA, 1969. 39 H.P. Klug and L.E. Alexander, X-ray Diffraction Procedures for. Polycrystalline and Amorphous Materials, 2nd edn. John Wiley & Sons,. New York, 1974.

  12. Phase Transformation of Hydrothermally Synthesized Nanoparticle ...

    African Journals Online (AJOL)

    Mild hydrothermal hydrolysis of TiCl4 produces nanorods of the rutile phase of titanium dioxide in high yield, while in the presence of organic acids (citric, acetic, D-tartaric and benzoic acids) anatase is the only product. The effect of these organic acids on the products of the hydrolysis reaction as well as the reaction kinetics ...

  13. Chemically Induced Phase Transformation in Austenite by Focused Ion Beam

    Science.gov (United States)

    Basa, Adina; Thaulow, Christian; Barnoush, Afrooz

    2014-03-01

    A highly stable austenite phase in a super duplex stainless steel was subjected to a combination of different gallium ion doses at different acceleration voltages. It was shown that contrary to what is expected, an austenite to ferrite phase transformation occurred within the focused ion beam (FIB) milled regions. Chemical analysis of the FIB milled region proved that the gallium implantation preceded the FIB milling. High resolution electron backscatter diffraction analysis also showed that the phase transformation was not followed by the typical shear and plastic deformation expected from the martensitic transformation. On the basis of these observations, it was concluded that the change in the chemical composition of the austenite and the local increase in gallium, which is a ferrite stabilizer, results in the local selective transformation of austenite to ferrite.

  14. Domains and interfaces produced by a cooperative crystal-phase transformation. Application to the hexagonal to monoclinic phase transformation of rare earth sesquioxides. 2

    International Nuclear Information System (INIS)

    Yangui, B.

    1982-01-01

    A general study of domains by crystallographic phase transformation is done in the first part of this study, taking into account the epitaxy between the two structures. Rotation domains are said to be equivalent when they correspond to the same kind of epitaxy; if not they are not equivalent domains. The A (hexagonal) to B (monoclinic) phase transformation of the rare earth sesquioxides is a cooperative one where the c-axis of A becomes the [101-bar] axis of B and the (00.1) plane of A becomes the (201-bar) plane of B. Each crystal seed of the B structure appears by epitaxial growth on the A structure; it is made of two different rotation domains which are not equivalent. Each of them has six equivalent rotation domains so that twelve rotation variants can occur in this phase transformation. All these domains can be related by a rotation about the [101-bar] axis of the B structure. They can sometimes be related by twinning or by a double twinning. In this last case a new rotation domain occurs; this phenomenon is at the origin of the formation of multistar domains which are observed in the same kind of crystallographic phase transformations. (author)

  15. Study of 18-Pulse Rectifier Utilizing Hexagon Connected 3-Phase to 9-Phase Transformer

    Directory of Open Access Journals (Sweden)

    Ahmad Saudi Samosir

    2008-04-01

    Full Text Available The 18-pulse converter, using Y or -connected differential autotransformer, is very interesting since it allows natural high power factor correction. The lowest input current harmonic components are the 17th and 19th. The Transformer is designed to feed three six-pulse bridge rectifiers displaced in phase by 200. This paper present a high power factor three-phase rectifier bases on 3-phase to 9-phase transformer and 18-pulse rectifier. The 9-phase polygon-connected transformer followed by 18-pulse diode rectifiers ensures the fundamental concept of natural power factor correction. Simulation results to verify the proposed concept are shown in this paper.

  16. Continuum mechanics methods in the theory of phase transformations

    Science.gov (United States)

    Grinfel'D, Mikhail A.

    A theory for phase transformations in solids is developed on the basis of the variational principles of thermodynamics. The discussion focuses on the fundamental concepts of the theory, detailed classification of phase transformations at the phenomenological level, and statement of essentially new boundary value problems for continuum mechanics equations. General solutions are illustrated by the equilibrium and stability analysis of specific two-phase systems and solution of problems of practical importance. The methods and results discussed here are relevant to various problems in rigid body mechanics, hydrodynamics, materials science, geomechanics, and other fields.

  17. Modelling of phase transformations occurring in low activation martensitic steels

    International Nuclear Information System (INIS)

    Brachet, J.-C.; Gavard, L.; Boussidan, C.; Lepoittevin, C.; Servant, C.

    1998-01-01

    The main objective of this paper is to summarize modelling of on-heating and on-cooling phase transformations occurring in low activation martensitic (LAM) steels. Calculations of thermodynamic equilibrium phase fractions and kinetic aspects of phase transformations have been performed by using different approaches from experimental data (CCT and TTT diagrams obtained by dilatometry). All the calculated data have been compared to an important and systematic set of experimental data obtained on different LAM steels of the 7.5-11% CrWVT a type. (orig.)

  18. Modelling of phase transformations occurring in low activation martensitic steels

    Science.gov (United States)

    Brachet, J.-C.; Gavard, L.; Boussidan, C.; Lepoittevin, C.; Denis, S.; Servant, C.

    1998-10-01

    The main objective of this paper is to summarize modelling of on-heating and on-cooling phase transformations occurring in Low Activation Martensitic (LAM) steels. Calculations of thermodynamic equilibrium phase fractions and kinetic aspects of phase transformations have been performed by using different approaches from experimental data (CCT and TTT diagrams obtained by dilatometry). All the calculated data have been compared to an important and systematic set of experimental data obtained on different LAM steels of the 7.5-11% CrWVT a type.

  19. Stress-Induced Cubic-to-Hexagonal Phase Transformation in Perovskite Nanothin Films.

    Science.gov (United States)

    Cao, Shi-Gu; Li, Yunsong; Wu, Hong-Hui; Wang, Jie; Huang, Baoling; Zhang, Tong-Yi

    2017-08-09

    The strong coupling between crystal structure and mechanical deformation can stabilize low-symmetry phases from high-symmetry phases or induce novel phase transformation in oxide thin films. Stress-induced structural phase transformation in oxide thin films has drawn more and more attention due to its significant influence on the functionalities of the materials. Here, we discovered experimentally a novel stress-induced cubic-to-hexagonal phase transformation in the perovskite nanothin films of barium titanate (BaTiO 3 ) with a special thermomechanical treatment (TMT), where BaTiO 3 nanothin films under various stresses are annealed at temperature of 575 °C. Both high-resolution transmission electron microscopy and Raman spectroscopy show a higher density of hexagonal phase in the perovskite thin film under higher tensile stress. Both X-ray photoelectron spectroscopy and electron energy loss spectroscopy does not detect any change in the valence state of Ti atoms, thereby excluding the mechanism of oxygen vacancy induced cubic-to-hexagonal (c-to-h) phase transformation. First-principles calculations show that the c-to-h phase transformation can be completed by lattice shear at elevated temperature, which is consistent with the experimental observation. The applied bending plus the residual tensile stress produces shear stress in the nanothin film. The thermal energy at the elevated temperature assists the shear stress to overcome the energy barriers during the c-to-h phase transformation. The stress-induced phase transformation in perovskite nanothin films with TMT provides materials scientists and engineers a novel approach to tailor nano/microstructures and properties of ferroelectric materials.

  20. Frame transforms, star products and quantum mechanics on phase space

    International Nuclear Information System (INIS)

    Aniello, P; Marmo, G; Man'ko, V I

    2008-01-01

    Using the notions of frame transform and of square integrable projective representation of a locally compact group G, we introduce a class of isometries (tight frame transforms) from the space of Hilbert-Schmidt operators in the carrier Hilbert space of the representation into the space of square integrable functions on the direct product group G x G. These transforms have remarkable properties. In particular, their ranges are reproducing kernel Hilbert spaces endowed with a suitable 'star product' which mimics, at the level of functions, the original product of operators. A 'phase space formulation' of quantum mechanics relying on the frame transforms introduced in the present paper, and the link of these maps with both the Wigner transform and the wavelet transform are discussed

  1. Role of Reversible Phase Transformation for Strong Piezoelectric Performance at the Morphotropic Phase Boundary

    Science.gov (United States)

    Liu, Hui; Chen, Jun; Huang, Houbing; Fan, Longlong; Ren, Yang; Pan, Zhao; Deng, Jinxia; Chen, Long-Qing; Xing, Xianran

    2018-01-01

    A functional material with coexisting energetically equivalent phases often exhibits extraordinary properties such as piezoelectricity, ferromagnetism, and ferroelasticity, which is simultaneously accompanied by field-driven reversible phase transformation. The study on the interplay between such phase transformation and the performance is of great importance. Here, we have experimentally revealed the important role of field-driven reversible phase transformation in achieving enhanced electromechanical properties using in situ high-energy synchrotron x-ray diffraction combined with 2D geometry scattering technology, which can establish a comprehensive picture of piezoelectric-related microstructural evolution. High-throughput experiments on various Pb /Bi -based perovskite piezoelectric systems suggest that reversible phase transformation can be triggered by an electric field at the morphotropic phase boundary and the piezoelectric performance is highly related to the tendency of electric-field-driven phase transformation. A strong tendency of phase transformation driven by an electric field generates peak piezoelectric response. Further, phase-field modeling reveals that the polarization alignment and the piezoelectric response can be much enhanced by the electric-field-driven phase transformation. The proposed mechanism will be helpful to design and optimize the new piezoelectrics, ferromagnetics, or other related functional materials.

  2. Phase Transformation of Metastable Austenite in Steel during Nano indentation

    International Nuclear Information System (INIS)

    Ahn, Taehong; Lee, Sung Bo; Han, Heung Nam; Park, Kyungtae

    2013-01-01

    These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite

  3. Phase Transformation of Metastable Austenite in Steel during Nano indentation

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Taehong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Sung Bo; Han, Heung Nam [Seoul National Univ., Seoul (Korea, Republic of); Park, Kyungtae [Hanbat National Univ., Daejeon (Korea, Republic of)

    2013-05-15

    These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite.

  4. Analysis and simulation of phase transformation kinetics of zeolite A from amorphous phases

    Energy Technology Data Exchange (ETDEWEB)

    Marui, Yukiko; Matsuoka, Masakuni; Uchida, Hirohisa; Takiyama, Hiroshi [Tokyo Univ. of Agriculture and Technology, Koganei, Tokyo (Japan)

    2003-05-01

    Experiments on transformation rates of zeolite A from amorphous phases at different feed rates to alter the particle size of the amorphous phases were carried out to analyze the kinetics of the transformation, and were analyzed by performing simulation of the transformation. A clear dependence of the induction time for nucleation of zeolite A crystals on the surface area of the amorphous phase was recognized, indicating that the nucleation of zeolite A was heterogeneous and the nucleation rate was almost proportional to the size of the amorphous particles. From the simulation, the mechanism of the transformation was found to be heterogeneous nucleation of zeolite A crystals on the surface of amorphous particles followed by solution mediated phase transformation, and the transformation kinetics were well reproduced at different feed rates. (author)

  5. Analysis and simulation of phase transformation kinetics of zeolite A from amorphous phases

    CERN Document Server

    Marui, Y; Uchida, H; Takiyama, H

    2003-01-01

    Experiments on transformation rates of zeolite A from amorphous phases at different feed rates to alter the particle size of the amorphous phases were carried out to analyze the kinetics of the transformation, and were analyzed by performing simulation of the transformation. A clear dependence of the induction time for nucleation of zeolite A crystals on the surface area of the amorphous phase was recognized, indicating that the nucleation of zeolite A was heterogeneous and the nucleation rate was almost proportional to the size of the amorphous particles. From the simulation, the mechanism of the transformation was found to be heterogeneous nucleation of zeolite A crystals on the surface of amorphous particles followed by solution mediated phase transformation, and the transformation kinetics were well reproduced at different feed rates. (author)

  6. Domain Wall Evolution in Phase Transforming Oxides

    Science.gov (United States)

    2015-01-14

    Domain wall motion and electric?field?induced strains in NBT ?xBT solid solutions from in situ neutron diffraction,” T.-M. Usher,* J. S. Forrester, E...Morphotropic Phase Boundary of NBT ?BT,” L. M. Denis,* J. Glaum, M. Hoffman, J. Forrester, and J. L. Jones, Electronic Materials and Applications 2013...titanate (PZT) and lead-free compositions Na0.5K0.5NbO3 (NKN) and Na0.5Bi0.5TiO3 ( NBT ). This past year, we reported results on piezoelectric compositions

  7. Effect of phase transformations on microstructures in deep mantle materials

    Science.gov (United States)

    Merkel, Sébastien; Langrand, Christopher; Rosa, Angelika; Hilairet, Nadège

    2017-04-01

    Phase transformations induce microstructural changes in deep Earth materials, including changes in grain size and orientation distribution. The effect of phase transformations on mineral microstructures is usually studied using electron microscopy on quench products from high P/T experiments. The method allows for a precise evaluation of the microscopic mechanisms involved. It is limited, however, to samples that can be quenched to ambient conditions and allows for investigations at a single P/T point for each experiment. In recent years, we extended the use of multigrain crystallography to samples inside diamond anvil cells under mantle P/T conditions. The method allows for monitoring the orientations of hundreds of grains and grain size variations during various physical processes, such as plastic deformation and successions of phase transformations (Rosa et al 2015, Langrand et al 2017). Here, we will show results concerning hydrous Mg2SiO4 during the series of α-β-γ phase transformations up to 40 GPa and 850 °C. Such results are important to understand the descending behaviour of subducted slabs, observations of seismic anisotropy, and polarity changes for seismic waves reflected of deep Earth interfaces. The data is used to asses the effect of the transformation on grain orientation and grain sizes. In particular, we do not observe orientation relationships between the parent α-phase and the daughter β-phase phase, suggesting an incoherent growth. We also observe significant grain size reductions and only little grain growth within the newly formed phases (Rosa et al 2016). These new results are important for understanding the mechanical behavior of subducting slabs, seismic anisotropy in the Earth's mantle, and phase transformation mechanisms in olivine. Now that it is validated, the method can also be applied to other phases that can not be studied using electron microscopy, such as perovskite and post-perovskite. Langrand, Hilairet, Nisr, Roskosz, Rib

  8. Amelogenin Affects Brushite Crystal Morphology and Promotes Its Phase Transformation to Monetite

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Dongni; Ruan, Qichao; Tao, Jinhui; Lo, Jonathan; Nutt, Steven; Moradian-Oldak, Janet

    2016-09-07

    Amelogenin protein is involved in organized apatite crystallization during enamel formation. Brushite (CaHPO4·2H2O), which is one of the precursors for hydroxyapatite in in vitro mineralization, has been used for fabrication of biomaterials for hard tissue repair. In order to explore its potential application in biomimetic material synthesis, we studied the influence of amelogenin on brushite morphology and phase transformation to monetite. Our results show that amelogenin can adsorb onto surface of brushite, leading to the formation of layered structures on the (010) face. Amelogenin promoted the phase transformation of brushite into monetite (CaHPO4) in the dry state, presumably by interacting with crystalline water layers in brushite unit cell. Changes to the crystal morphology by amelogenin continued even after the phase transformation to monetite forming an organized nanotextured structure of nano-sticks resembling the bundle structure in enamel.

  9. Formation, transformation and dissolution of phases formed on surfaces

    International Nuclear Information System (INIS)

    Shoesmith, D.W.

    1983-03-01

    The basic mechanisms of film growth, transformation, and dissolution of phases formed on surfaces are discussed. Film growth can occur via solid-state processes or via substrate (usally metal or alloy) dissolution, followed by local supersaturation and precipitation of an insoluble phase. The phase(s) formed may be metastable and transform to a more stable phase, via either solid-state or dissolution-reprecipitation processes. Film dissolution reactions can also occur via a variety of mechanisms, including: (i) direct chemical dissolution when no oxidation state change occurs; (ii) redox dissolution when the film dissolves via a redox reaction involving a reducing or oxidizing agent in solution; and (iii) autoreduction, where film dissolution is coupled to metal dissolution. Such film-growth and dissolution processes, which often produce complex multilayer films, are common in the nuclear industry. A number of examples are discussed

  10. Phase Transformations in a Uranium-Zirconium Alloy containing 2 weight per cent Zirconium

    Energy Technology Data Exchange (ETDEWEB)

    Lagerberg, G.

    1961-04-15

    The phase transformations in a uranium-zirconium alloy containing 2 weight percent zirconium have been examined metallographically after heat treatments involving isothermal transformation of y and cooling from the -y-range at different rates. Transformations on heating and cooling have also been studied in uranium-zirconium alloys with 0.5, 2 and 5 weight per cent zirconium by means of differential thermal analysis. The results are compatible with the phase diagram given by Howlett and Knapton. On quenching from the {gamma}-range the {gamma} phase transforms martensitically to supersaturated a the M{sub S} temperature being about 490 C. During isothermal transformation of {gamma} in the temperature range 735 to 700 C {beta}-phase is precipitated as Widmanstaetten plates and the equilibrium structure consists of {beta} and {gamma}{sub 1}. Below 700 C {gamma} transforms completely to Widmanstaetten plates which consist of {beta} above 660 C and of a at lower temperatures. Secondary phases, {gamma}{sub 2} above 610 C and {delta} below this temperature, are precipitated from the initially supersaturated Widmanstaetten plates during the isothermal treatments. At and slightly below 700 C the cooperative growth of |3 and {gamma}{sub 2} is observed. The results of isothermal transformation are summarized in a TTTdiagram.

  11. Transmission Network Expansion Planning Considering Phase-Shifter Transformers

    OpenAIRE

    Miasaki, Celso T.; Franco, Edgar M. C.; Romero, Ruben A.

    2012-01-01

    This paper presents a novel mathematical model for the transmission network expansion planning problem. Main idea is to consider phase-shifter (PS) transformers as a new element of the transmission system expansion together with other traditional components such as transmission lines and conventional transformers. In this way, PS are added in order to redistribute active power flows in the system and, consequently, to diminish the total investment costs due to new transmission lines. Proposed...

  12. Displacive phase transformations and generalized stacking faults

    Czech Academy of Sciences Publication Activity Database

    Paidar, Václav; Ostapovets, Andriy; Duparc, O. H.; Khalfallah, O.

    2012-01-01

    Roč. 122, č. 3 (2012), s. 490-492 ISSN 0587-4246. [International Symposium on Physics of Materials, ISPMA /12./. Praha, 04.09.2011-08.09.2011] R&D Projects: GA AV ČR IAA100100920 Institutional research plan: CEZ:AV0Z10100520 Keywords : ab-initio calculations * close-packed structures * generalized stacking faults * homogeneous deformation * lattice deformation * many-body potentials Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.531, year: 2012

  13. Oxygen mobility and structural phase transformation in Bi2Sr2CaCu2O8+δ measured by anelastic spectroscopy

    International Nuclear Information System (INIS)

    Albuquerque de Gimenez, Juliana Maria; Grandini, Carlos Roberto; Santos, Dayse Iara dos

    2004-01-01

    One of the most studied ceramic superconductors for application has been, undoubtedly, Bi 2 Sr 2 CaCu 2 O 8+δ . Although being a multiphasic material, it has proved to have great advantages compared to other ceramic systems. Measurements of the elastic energy loss and modulus (anelastic spectroscopy) as a function of temperature can distinguish among different atomic jumps that occur inside the various phases or at different local ordering. In this paper, mechanical loss spectra of Bi 2 Sr 2 CaCu 2 O 8+δ bar shaped samples, made by a conventional method, have been measured between 80 and 600 K, using a torsion pendulum operating in frequencies below 50 Hz, for samples annealed in vacuum up to 600 K. Possible relaxation mechanisms are proposed to explain the origin of the mechanical-loss peaks observed 300 and 500 K

  14. Phase transformations in intermetallic phases in zirconium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Filippov, V. P., E-mail: vpfilippov@mephi.ru [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation); Kirichenko, V. G. [Kharkiv National Karazin University (Ukraine); Salomasov, V. A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation); Khasanov, A. M. [University of North Carolina – Asheville, Chemistry Department (United States)

    2017-11-15

    Phase change was analyzed in intermetallic compounds of zirconium alloys (Zr – 1.03 at.% Fe; Zr – 0.51 at.% Fe; Zr – 0.51 at.% Fe – M(M = Nb, Sn). Mössbauer spectroscopy on {sup 57}Fe nuclei in backscattering geometry with the registration of the internal conversion electrons and XRD were used. Four types of iron bearing intermetallic compounds with Nb were detected. A relationship was found between the growth process of intermetallic inclusions and segregation of these phases. The growth kinetics of inclusions possibly is not controlled by bulk diffusion, and a lower value of the iron atom’s activation energy of migration can be attributed to the existence of enhanced diffusion paths and interface boundaries.

  15. Martensitic phase transformation in shape-memory alloys

    International Nuclear Information System (INIS)

    Golestaneh, A.A.

    1979-01-01

    Isothermal studies are described of the shape-recovery phenomenon, stress-strain behavior, electrical resistivity and thermo-electric power associated with the martensite-parent phase reaction in the Ni-Ti shape-memory alloys. The energy-balance equation that links the reaction kinetics with the strain energy change during the cooling-deforming and heating cycle is analyzed. The strain range in which the Clausius-Clapeyron equation satisfactorily describes this reaction is determined. A large change in the Young's modulus of the specimen is found to be associated with the M → P reaction. A hysteresis loop in the resistivity-temperature plot is found and related to the anomaly in the athermal resistivity changes during cyclic M → P → M transformation. An explanation for the resistivity anomaly is offered. The M structure is found to be electrically negative relative to the P structure. A thermal emf of greater than or equal to 0.12 mV is found at the M-P interface

  16. Martensitic phase transformation in shape-memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Golestaneh, A A

    1979-01-01

    Isothermal studies are described of the shape-recovery phenomenon, stress-strain behavior, electrical resistivity and thermo-electric power associated with the martensite-parent phase reaction in the Ni-Ti shape-memory alloys. The energy-balance equation that links the reaction kinetics with the strain energy change during the cooling-deforming and heating cycle is analyzed. The strain range in which the Clausius-Clapeyron equation satisfactorily describes this reaction is determined. A large change in the Young's modulus of the specimen is found to be associated with the M ..-->.. P reaction. A hysteresis loop in the resistivity-temperature plot is found and related to the anomaly in the athermal resistivity changes during cyclic M ..-->.. P ..-->.. M transformation. An explanation for the resistivity anomaly is offered. The M structure is found to be electrically negative relative to the P structure. A thermal emf of greater than or equal to 0.12 mV is found at the M-P interface.

  17. AC system stabilization via phase shift transformer with thyristor commutation

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Jose Carlos de; Guimaraes, Geraldo Caixeta; Moraes, Adelio Jose [Uberlandia Univ., MG (Brazil); Abreu, Jose Policarpo G. de [Escola Federal de Engenharia de Itajuba, MG (Brazil); Oliveira, Edimar Jose de [Juiz de Fora Univ., MG (Brazil)

    1994-12-31

    This article aims to present initially the constructive and operative forms of a phase-shift autotransformer which provides both magnitude and phase angle change through thyristor commutation, including a technic to reduce the number of thyristors. Following, it is proposed a control system to make such equipment an efficient AC system stabilizing tool. It is presented some simulation results to show the operation of this transformer in an electrical system. (author) 3 refs., 11 figs., 3 tabs.

  18. Z-transform Zeros in Mixed Phase Deconvolution of Speech

    DEFF Research Database (Denmark)

    Pedersen, Christian Fischer

    2013-01-01

    The present thesis addresses mixed phase deconvolution of speech by z-transform zeros. This includes investigations into stability, accuracy, and time complexity of a numerical bijection between time domain and the domain of z-transform zeros. Z-transform factorization is by no means esoteric, bu...... vectors prior to polynomial expansion achieve persistent estimation accuracies near machine epsilon. The associated time complexity cost is effectively countered by proposing a refined Leja ordering obtained via `1 maximization....... phases of the glottal flow derivative is investigated analytically with regard to model parameters and sequence lengths. It is shown that time domain concatenation and convolution of the phases are tightly related. Therefore, immiscibility remains regardless of considering entire glottal flow derivative...... sequences or individual opening and closing sequences. To counter the computational burden associated with z-transform factorization, an adaptive ZZT estimation method is proposed for time-varying z-transforms. The method bounds estimation drifting as accuracy is the cost of lowered time complexity...

  19. Phase-transformation-induced lubrication of earthquake sliding

    Science.gov (United States)

    Green, Harry W.

    2017-08-01

    Frictional failure is not possible at depth in Earth, hence earthquakes deeper than 30-50 km cannot initiate by overcoming dry friction. Moreover, the frequency distribution of earthquakes with depth is bimodal, suggesting another change of mechanism at about 350 km. Here I suggest that the change at 30-50 km is from overcoming dry friction to reduction of effective stress by dehydration embrittlement and that the change at 350 km is due to desiccation of slabs and initiation by phase-transformation-induced faulting. High-speed friction experiments at low pressure indicate that exceeding dry friction provokes shear heating that leads to endothermic reactions and pronounced weakening. Higher-pressure studies show nanocrystalline gouge accompanying dehydration and the highest pressure experiments initiate by exothermic polymorphic phase transformation. Here I discuss the characteristic nanostructures of experiments on high-speed friction and high-pressure faulting and show that all simulated earthquake systems yield very weak transformation-induced lubrication, most commonly nanometric gouge or melt. I also show that phase-transformation-induced faulting of olivine to spinel can propagate into material previously transformed to spinel, apparently by triggering melting analogous to high-speed friction studies at low pressure. These experiments taken as a whole suggest that earthquakes at all depths slide at low frictional resistance by a self-healing pulse mechanism with rapid strength recovery. This article is part of the themed issue 'Faulting, friction and weakening: from slow to fast motion'.

  20. Understanding Strain‐Induced Phase Transformations in BiFeO3 Thin Films

    Science.gov (United States)

    Beekman, Christianne; Schlepütz, Christian M.; Siemons, Wolter; Yang, Yongsoo; Senabulya, Nancy; Clarke, Roy; Chi, Miaofang

    2015-01-01

    Experiments demonstrate that under large epitaxial strain a coexisting striped phase emerges in BiFeO3 thin films, which comprises a tetragonal‐like (T′) and an intermediate S′ polymorph. It exhibits a relatively large piezoelectric response when switching between the coexisting phase and a uniform T′ phase. This strain‐induced phase transformation is investigated through a synergistic combination of first‐principles theory and experiments. The results show that the S′ phase is energetically very close to the T′ phase, but is structurally similar to the bulk rhombohedral (R) phase. By fully characterizing the intermediate S′ polymorph, it is demonstrated that the flat energy landscape resulting in the absence of an energy barrier between the T′ and S′ phases fosters the above‐mentioned reversible phase transformation. This ability to readily transform between the S′ and T′ polymorphs, which have very different octahedral rotation patterns and c/a ratios, is crucial to the enhanced piezoelectricity in strained BiFeO3 films. Additionally, a blueshift in the band gap when moving from R to S′ to T′ is observed. These results emphasize the importance of strain engineering for tuning electromechanical responses or, creating unique energy harvesting photonic structures, in oxide thin film architectures. PMID:27980962

  1. Misfit dislocations and phase transformations in high-T sub c superconducting films

    CERN Document Server

    Gutkin, M Y

    2002-01-01

    A theoretical model is suggested that describes the effects of misfit stresses on defect structures, phase content and critical transition temperature T sub c in high-T sub c superconducting films. The focus is placed on the exemplary case of YBaCuO films deposited onto LaSrAlO sub 4 substrates. It is theoretically revealed here that misfit stresses are capable of inducing phase transformations controlled by the generation of misfit dislocations in growing cuprate films. These transformations, in the framework of the suggested model, account for experimental data on the influence of the film thickness on phase content and critical temperature T sub c of superconducting cuprate films, reported in the literature. The potential role of stress-assisted phase transformations in suppression of critical current density across grain boundaries in high-T sub c superconductors is briefly discussed.

  2. Numerical model of phase transformation of steel C80U during hardening

    Directory of Open Access Journals (Sweden)

    T. Domański

    2007-12-01

    Full Text Available The article concerns numerical modelling of the phase transformations in solid state hardening of tool steel C80U. The transformations were assumed: initial structure – austenite, austenite – perlite, bainite and austenite – martensite. Model for evaluation of fractions of phases and their kinetics based on continuous heating diagram (CHT and continuous cooling diagram (CCT. The dilatometric tests on the simulator of thermal cycles were performed. The results of dilatometric tests were compared with the results of the test numerical simulations. In this way the derived models for evaluating phase content and kinetics of transformations in heating and cooling processes were verified. The results of numerical simulations confirm correctness of the algorithm that were worked out. In the numerical example the simulated estimation of the phase fraction in the hardened axisimmetrical element was performed.

  3. The Phase-Space Transformer Instrument (PASTIS) and the Phase-Space Transformation on Ultra-Cold Neutrons

    International Nuclear Information System (INIS)

    Henggeler, W.; Boehm, M.

    2003-11-01

    Both reports - part I by Wolfgang Henggeler and part II by Martin Boehm - serve as a comprehensive basis for the realisation of a PST (phase-space transformation) instrument coupled either to cold or ultra-cold neutrons, respectively. This publication accidentally coincides with the 200 th birthday of the Austrian physicist C.A. Doppler who discovered the principle (i.e., the effect denoted later by his name) giving rise to the phase-space transformation described in the present work. (author)

  4. Phase transformation order-disorder in nonstoichiometric titanium carbide

    International Nuclear Information System (INIS)

    Vlasov, V.A.; Karmo, Yu.S.; Kustova, L.V.

    1986-01-01

    Titanium carbide delta-phase is studied using the methods of electric conductivity and differential thermal analysis (DTA). It is shown on the Ti-C system phase diagram that two regions of TiCsub(0.46-0.60) and TiCsub(0.65-1.00) compositions, different in their properties, correspond to delta-phase. Both ordered and disordered phases exist within the TiCsub(0.046-0.60) concentration range, and in equilibrium heating or cooling one phase converts to another at 590 deg C (the first order phase transformation). Samples of the TiCsub(0.65-1.00) composition are characterized by low electric conductivity stability, that is explained by strong titanium carbide electric conductivity sensitivity to defects and impurities

  5. Effect of isochronal annealing on phase transformation studies of ...

    Indian Academy of Sciences (India)

    Abstract. The effect of isochronal annealing on the phase transformation in iron oxide nanoparticles is reported in this work. Iron oxide nanoparticles were successfully synthesized using an ash supported technique followed by annealing for 2 h at various temperatures between 300 and 700◦C. It was observed using X-ray ...

  6. Effect of isochronal annealing on phase transformation studies of ...

    Indian Academy of Sciences (India)

    The effect of isochronal annealing on the phase transformation in iron oxide nanoparticles is reported in this work. Iron oxide nanoparticles were successfully synthesized using an ash supported technique followed by annealing for 2 h at various temperatures between 300 and 700° C. It was observed using X-ray diffraction ...

  7. In-situ High Temperature Phase Transformations in Ceramics

    Science.gov (United States)

    2009-07-28

    dissertations from U.S. & Canadian institutions. 1861-present in ProQuest 29 SciELO : Scientific Electronic Library Online Identifies scientific...literature published in Spain and coverage dates that vary with resource in SciELO 19 High Temperature Phase Transformations in Oxide Ceramics

  8. The Phase Transformations in Hypoeutectoid Steels Mn-Cr-Ni

    Directory of Open Access Journals (Sweden)

    RoŻniata E.

    2015-04-01

    Full Text Available The results of a microstructure and hardness investigations of the hypoeutectoid steels Mn-Cr-Ni, imitating by its chemical composition toughening steels, are presented in the paper. The analysis of the kinetics of phase transformations of undercooled austenite of steels containing different amounts of alloying elements in their chemical composition, constitutes the aim of investigations.

  9. Unsteady detonations driven by first-order phase transformations

    Energy Technology Data Exchange (ETDEWEB)

    Rabie, R.L.; Fickett, W.

    1978-01-01

    Reactive waves supported by the energy released during a phase transformation are examined as elementary detonations. It is found that a class of eigenvalue detonations exist containing the well known Chapman-Jouguet solution as a particular case. In general the set of eigenvalue detonations are unsteady in any single inertial reference frame.

  10. Deconstructing the BRICs : Structural transformation and aggregate productivity growth

    NARCIS (Netherlands)

    de Vries, G.J.; Erumban, Abdul Azeez; Timmer, M.P.; Voskoboynikov, I.; Wu, H.X.

    de Vries, Gaaitzen J., Erumban, Abdul A., Timmer, Marcel P., Voskoboynikov, Ilya-Deconstructing the BRICs: Structural transformation and aggregate productivity growth This paper studies structural transformation and its implications for productivity growth in the BRIC countries (Brazil, Russia,

  11. Age-hardening and related phase transformation in an experimental Ag-Cu-Pd-Au alloy

    International Nuclear Information System (INIS)

    Seol, Hyo-Joung; Lee, Doung-Hun; Lee, Hee-Kyung; Takada, Yukyo; Okuno, Osamu; Kwon, Yong Hoon; Kim, Hyung-Il

    2006-01-01

    The age-hardening behaviour, phase transformation and related microstructural changes of an experimental Ag-Cu-Pd-Au alloy were examined by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and electron probe microanalysis (EPMA). The specimen alloy showed apparent age-hardenability at the aging temperatures of 350 deg. C and 400 deg. C. By aging the solution-treated specimen at 400 deg. C, two phases of the Ag-rich α 1 phase and the Pd-containing Cu-rich α 2 phase were transformed into four phases of the Ag-rich α 1 ' phase, the Cu-rich α 2 ' phase, the CsCl-type CuPd phase and the AuCu(I) ordered phase. Microstructure of the solution-treated specimen consisted of the Ag-rich α 1 matrix, Cu-rich α 2 particle-like structures of various sizes and the lamellar structure of the α 1 and α 2 phases. When the peak hardness was obtained, the very fine lamellar structure consisting of the Ag-rich α 1 ' and Cu-rich α 2 ' phases was newly formed in the matrix. By further aging, the very fine lamellar structure grew and coarsened apparently, and the matrix was covered with the coarsened lamellar structure. The hardness increase was considered to be caused mainly by the diffusion and precipitation of Cu from the Ag-rich α 1 matrix, and the hardness decrease in the latter stage of age-hardening process was caused by the coarsening of the very fine lamellar structure. The CsCl-type CuPd phase and the AuCu(I) ordered phase did not contribute to the hardness increase

  12. Grain Boundary Phase Transformations in Nanostructured Conducting Oxides

    Science.gov (United States)

    Straumal, B. B.; Myatiev, A. A.; Straumal, P. B.; Mazilkin, A. A.

    Nanostructured conducting oxides are very promising for various applications like varistors (doped zinc oxide), electrolytes for the solid oxide fuel cells (SOFC) (ceria, zirconia, yttria), semipermeable membranes, and sensors (perovskite-type oxides). Grain boundary (GB) phases crucially determine the properties of nanograined oxides. GB phase transformations (wetting, prewetting, pseudopartial wetting) proceed in the conducting oxides. Novel GB lines appear in the conventional bulk phase diagrams. They can be used for the tailoring of properties of nanograined conducting oxides, particularly by using the novel synthesis method of liquid ceramics.

  13. Iterative-Transform Phase Retrieval Using Adaptive Diversity

    Science.gov (United States)

    Dean, Bruce H.

    2007-01-01

    A phase-diverse iterative-transform phase-retrieval algorithm enables high spatial-frequency, high-dynamic-range, image-based wavefront sensing. [The terms phase-diverse, phase retrieval, image-based, and wavefront sensing are defined in the first of the two immediately preceding articles, Broadband Phase Retrieval for Image-Based Wavefront Sensing (GSC-14899-1).] As described below, no prior phase-retrieval algorithm has offered both high dynamic range and the capability to recover high spatial-frequency components. Each of the previously developed image-based phase-retrieval techniques can be classified into one of two categories: iterative transform or parametric. Among the modifications of the original iterative-transform approach has been the introduction of a defocus diversity function (also defined in the cited companion article). Modifications of the original parametric approach have included minimizing alternative objective functions as well as implementing a variety of nonlinear optimization methods. The iterative-transform approach offers the advantage of ability to recover low, middle, and high spatial frequencies, but has disadvantage of having a limited dynamic range to one wavelength or less. In contrast, parametric phase retrieval offers the advantage of high dynamic range, but is poorly suited for recovering higher spatial frequency aberrations. The present phase-diverse iterative transform phase-retrieval algorithm offers both the high-spatial-frequency capability of the iterative-transform approach and the high dynamic range of parametric phase-recovery techniques. In implementation, this is a focus-diverse iterative-transform phaseretrieval algorithm that incorporates an adaptive diversity function, which makes it possible to avoid phase unwrapping while preserving high-spatial-frequency recovery. The algorithm includes an inner and an outer loop (see figure). An initial estimate of phase is used to start the algorithm on the inner loop, wherein

  14. Nanoindentation-induced phase transformations in silicon at elevated temperatures

    International Nuclear Information System (INIS)

    Ruffell, S; Bradby, J E; Williams, J S; Munoz-Paniagua, D; Tadayyon, S; Coatsworth, L L; Norton, P R

    2009-01-01

    The nanoindentation-induced phase transformation behavior of silicon at elevated temperatures (25-150 deg. C) has been studied. Nucleation of Si-III/Si-XII on unloading is enhanced with increasing temperature and at the highest temperatures in an amorphous Si matrix, occurs in a continuous fashion without a pop-out event. Interestingly, for slow unloading at the highest temperatures, formation of Si-III/Si-XII in a crystalline Si matrix was not observed. Elevated temperatures enhance the nucleation of Si-III and Si-XII during unloading but the final composition of the phase transformed zone is also dependent on the thermal stability of the phases in their respective matrices.

  15. Aliasless fresnel transform image reconstruction in phase scrambling fourier transform technique by data interpolation

    International Nuclear Information System (INIS)

    Yamada, Yoshifumi; Liu, Na; Ito, Satoshi

    2006-01-01

    The signal in the Fresnel transform technique corresponds to a blurred one of the spin density image. Because the amplitudes of adjacent sampled signals have a high interrelation, the signal amplitude at a point between sampled points can be estimated with a high degree of accuracy even if the sampling is so coarse as to generate aliasing in the reconstructed images. In this report, we describe a new aliasless image reconstruction technique in the phase scrambling Fourier transform (PSFT) imaging technique in which the PSFT signals are converted to Fresnel transform signals by multiplying them by a quadratic phase term and are then interpolated using polynomial expressions to generate fully encoded signals. Numerical simulation using MR images showed that almost completely aliasless images are reconstructed by this technique. Experiments using ultra-low-field PSFT MRI were conducted, and aliasless images were reconstructed from coarsely sampled PSFT signals. (author)

  16. Parallel molecular dynamics simulations of pressure-induced structural transformations in cadmium selenide nanocrystals

    Science.gov (United States)

    Lee, Nicholas Jabari Ouma

    Parallel molecular dynamics (MD) simulations are performed to investigate pressure-induced solid-to-solid structural phase transformations in cadmium selenide (CdSe) nanorods. The effects of the size and shape of nanorods on different aspects of structural phase transformations are studied. Simulations are based on interatomic potentials validated extensively by experiments. Simulations range from 105 to 106 atoms. These simulations are enabled by highly scalable algorithms executed on massively parallel Beowulf computing architectures. Pressure-induced structural transformations are studied using a hydrostatic pressure medium simulated by atoms interacting via Lennard-Jones potential. Four single-crystal CdSe nanorods, each 44A in diameter but varying in length, in the range between 44A and 600A, are studied independently in two sets of simulations. The first simulation is the downstroke simulation, where each rod is embedded in the pressure medium and subjected to increasing pressure during which it undergoes a forward transformation from a 4-fold coordinated wurtzite (WZ) crystal structure to a 6-fold coordinated rocksalt (RS) crystal structure. In the second so-called upstroke simulation, the pressure on the rods is decreased and a reverse transformation from 6-fold RS to a 4-fold coordinated phase is observed. The transformation pressure in the forward transformation depends on the nanorod size, with longer rods transforming at lower pressures close to the bulk transformation pressure. Spatially-resolved structural analyses, including pair-distributions, atomic-coordinations and bond-angle distributions, indicate nucleation begins at the surface of nanorods and spreads inward. The transformation results in a single RS domain, in agreement with experiments. The microscopic mechanism for transformation is observed to be the same as for bulk CdSe. A nanorod size dependency is also found in reverse structural transformations, with longer nanorods transforming more

  17. Color image cryptosystem using Fresnel diffraction and phase modulation in an expanded fractional Fourier transform domain

    Science.gov (United States)

    Chen, Hang; Liu, Zhengjun; Chen, Qi; Blondel, Walter; Varis, Pierre

    2018-05-01

    In this letter, what we believe is a new technique for optical color image encryption by using Fresnel diffraction and a phase modulation in an extended fractional Fourier transform domain is proposed. Different from the RGB component separation based method, the color image is converted into one component by improved Chirikov mapping. The encryption system is addressed with Fresnel diffraction and phase modulation. A pair of lenses is placed into the fractional Fourier transform system for the modulation of beam propagation. The structure parameters of the optical system and parameters in Chirikov mapping serve as extra keys. Some numerical simulations are given to test the validity of the proposed cryptosystem.

  18. Analytical electron microscope study of the omega phase transformation in a zirconium-niobium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zaluzec, N. J.

    1979-01-01

    The study of the as-quenched omega phase morphology shows that the domain size of Zr-15% Nb is on the order of 30 A. No alignment of omega domains along <222>..beta.. directions was observed and samples having undergone thermal cycling in thin foil form, did not develop a long-period structure of alternating ..beta.. and ..omega.. phases below the omega transformation temperature. (FS)

  19. Analytical electron microscope study of the omega phase transformation in a zirconium-niobium alloy

    International Nuclear Information System (INIS)

    Zaluzec, N.J.

    1979-01-01

    The study of the as-quenched omega phase morphology shows that the domain size of Zr-15% Nb is on the order of 30 A. No alignment of omega domains along β directions was observed and samples having undergone thermal cycling in thin foil form, did not develop a long-period structure of alternating β and ω phases below the omega transformation temperature

  20. Phase transformations of a talc ore under heated chlorine atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Orosco, P., E-mail: porosco@unsl.edu.ar [Instituto de Investigaciones en Tecnología Química (INTEQUI-CONICET), Chacabuco y Pedernera, 5700 San Luis (Argentina); Ruiz, M. del C. [Instituto de Investigaciones en Tecnología Química (INTEQUI-CONICET), Chacabuco y Pedernera, 5700 San Luis (Argentina); Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis (Argentina); González, J. [Instituto de Investigaciones en Tecnología Química (INTEQUI-CONICET), Chacabuco y Pedernera, 5700 San Luis (Argentina); Instituto de Ciencias Básicas, Universidad Nacional de Cuyo, Mendoza (Argentina)

    2013-02-20

    Highlights: ► We studied the effect of Cl{sub 2} on minerals present in a talc of ultramafic origin. ► Isothermal and non-isothermal assays were performed in N{sub 2} and Cl{sub 2}–N{sub 2} atmospheres. ► The reagents and the products were analyzed by DTA, XRD, SEM, and EPMA. ► The chlorination produced protoenstatite at 800 °C. ► Calcination of a talc ore in Cl{sub 2} produces more enstatite than thermal treatment in N{sub 2}. - Abstract: The effect of Cl{sub 2} on the phase transformations of the minerals present in a talc (Mg{sub 3}Si{sub 4}O{sub 10}(OH){sub 2}) unpurified with clinochlore (Mg{sub 5}Al{sub 2}Si{sub 3}O{sub 10}(OH){sub 8}), magnesite (MgCO{sub 3}), dolomite (MgCa(CO{sub 3}){sub 2}), hematite (Fe{sub 2}O{sub 3}) and pyrite (FeS{sub 2}) was studied with the purpose of deferricating the mineral and obtaining protoenstatite (MgSiO{sub 3}), which is the basic component of steatite ceramics. Isothermal and non-isothermal assays in N{sub 2} and Cl{sub 2}–N{sub 2} atmospheres were performed using a thermogravimetric device at temperatures between 600 and 980 °C. The reagents and the products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Results obtained showed that the following phenomena were produced in Cl{sub 2}: (a) The transformation of vitreous silica (SiO{sub 2}), from the chlorination reaction of talc, into enstatite (MgSiO{sub 3}) started at about 700 °C, being dolomite the mineral that favored this reaction. At 800 °C, more enstatite was formed as a result of the reaction between vitreous silica not transformed, MgCl{sub 2} and O{sub 2} derived from the chlorination of dolomite and magnesite; then, polymorphic transformation of enstatite into protoenstatite was produced. (b) At about 950 °C, CaCl{sub 2} produced as a result of dolomite chlorination led to the destruction of the protoenstatite

  1. A Phase Transformation with no Change in Space Group Symmetry: Octafluoronaphtalene

    DEFF Research Database (Denmark)

    Pawley, G. S.; Dietrich, O. W.

    1975-01-01

    A solid-state phase transformation in octafluoronaphthalene has been discovered at 266.5K on cooling, and at 15K higher on heating. The symmetry of both phases is found to be the same, namely monoclinic with space group P21/c. The unit cell parameters change by up to 10%, but the integrity...... of a single crystal, which shatters on cooling, is good enough for a single-crystal structure determination. This has been done in both phases to a sufficient accuracy that a mechanism for the transformation can be proposed. Molecules which lie parallel to one another shear to a new parallel position......, the shear movement being equal to one carbon-carbon bond of the naphthalene skeleton. In this process the molecules reorient, but are still related by the same symmetry operations. This transformation, although not unique, is probably the first of its kind to be discovered in molecular systems....

  2. Phase gradients in acceleration structures

    International Nuclear Information System (INIS)

    Decker, F.J.; Jobe, R.K.

    1990-05-01

    In linear accelerators with two or more bunches the beam loading of one bunch will influence the energy and energy spread the following bunches. This can be corrected by quickly changing the phase of a travelling wave structure, so that each bunch recieves a slightly different net phase. At the SLAC Linear Collider (SLC) three bunches, two (e + ,e - ) for the high energy collisions and one (e - -scavenger) for producing positrons should sit at different phases, due to their different tasks. The two e - -bunches are extracted from the damping ring at the same cycle time about 60 ns apart. Fast phase switching of the RF to the bunch length compressor in the Ring-To-Linac (RTL) section can produce the necessary advance of the scavenger bunch (about 6 degree in phase). This allows a low energy spread of this third bunch at the e + -production region at 2/3 of the linac length, while the other bunches are not influenced. The principles and possible other applications of this fast phase switching as using it for multi-bunches, as well as the experimental layout for the actual RTL compressor are presented

  3. Lectures notes on phase transformations in nuclear matter

    CERN Document Server

    López, Jorge A

    2000-01-01

    The atomic nucleus, despite of being one of the smallest objects found in nature, appears to be large enough to experience phase transitions. The book deals with the liquid and gaseous phases of nuclear matter, as well as with the experimental routes to achieve transformation between them.Theoretical models are introduced from the ground up and with increasing complexity to describe nuclear matter from a statistical and thermodynamical point of view. Modern critical phenomena, heavy ion collisions and computational techniques are presented while establishing a linkage to experimental data.The

  4. Plasticity induced by phase transformation in steel: experiment vs modeling

    International Nuclear Information System (INIS)

    Tahimi, Abdeladhim

    2011-01-01

    The objectives of this work are: (i) understand the mechanisms and phenomena involved in the plasticity of steels in the presence of a diffusive or martensitic phase transformation. (ii) develop tools for predicting TRIP, which are able to correctly reproduce the macroscopic deformation for cases of complex loading and could also provide information about local elasto-visco-plastic interactions between product and parent phases. To this purpose, new experimental tests are conducted on 35NCD16 steel for austenite to martensite transformation and on 100C6 steel for austenite to pearlite transformation. The elasto viscoplastic properties of austenite and pearlite of the 100C6 steel are characterized through tension compression and relaxation tests. The parameters of macro-homogeneous and crystal-based constitutive laws could then be identified such as to analyse different models with respect to the experimental TRIP: the analytical models of Leblond (1989) and Taleb and Sidoroff (2003) but also, above all, different numerical models which can be distinguished by the prevailing assumptions concerning the local kinetics and the constitutive laws. An extension of the single-grain model dedicated to martensitic transformations developed during the thesis of S. Meftah (2007) is proposed. It consists in introducing the polycrystalline character of the austenite through a process of homogenization based on a self-consistent scheme by calculating the properties of an Equivalent Homogeneous Medium environment (EHM). (author)

  5. Microstructures and phase transformations in interstitial alloys of tantalum

    International Nuclear Information System (INIS)

    Dahmen, U.

    1979-01-01

    The analysis of microstructures, phases, and possible ordering of interstitial solute atoms is fundamental to an understanding of the properties of metal-interstitial alloys in general. As evidenced by the controversies on phase transformations in the particular system tantalum--carbon, our understanding of this class of alloys is inferior to our knowledge of substitutional metal alloys. An experimental clarification of these controversies in tantalum was made. Using advanced techniques of electron microscopy and ultrahigh vacuum techology, an understanding of the microstructures and phase transformations in dilute interstitial tantalum--carbon alloys is developed. Through a number of control experiments, the role and sources of interstitial contamination in the alloy preparation (and under operating conditions) are revealed. It is demonstrated that all previously published work on the dilute interstitially ordered phase Ta 64 C can be explained consistently in terms of ordering of the interstitial contaminants oxygen and hydrogen, leading to the formation of the phases Ta 12 O and Ta 2 H

  6. Phase transformation of NiTi alloys during vacuum sintering

    Science.gov (United States)

    Wang, Jun; Hu, Kuang

    2017-05-01

    The aim of this study is to ascertain the Phase transformation of NiTi alloys during vacuum sintering. NiTi shape memory alloys (SMA) of atomic ratio 1:1 were prepared through press forming and vacuum sintering with the mixture of Ni and Ti powders. Different samples were prepared by changing the sintering time and the sintering temperature. Phase and porosity of the samples were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that in the process of sintering NiTi2 and Ni3Ti phases are formed firstly and then transform into NiTi phase. The quantity of NiTi2 and Ni3Ti phases gradually decreased but not eliminate completely with increase of sintering time. The porosity of specimen sintering at 900°C decreases slightly with increase of sintering time. With increase of sintering time the porosity of specimen sintering at 1050°C decreased firstly and then increased because of generation rich titanium liquid in the process of sintering.

  7. Phase Transformation of Hot Dipped Aluminium during High Temperature Oxidation

    International Nuclear Information System (INIS)

    Zaifol Samsu; Muhammad Daud; Hishamuddin Husain; Mohd Saari Ripin; Rusni Rejab; Zaiton Selamat; Mohd Shariff Sattar

    2014-01-01

    Low alloy carbon steel was coated by hot-dipping into a molten aluminum bath. Isothermal oxidations were carried out at 750 degree Celsius in static air to study the oxidation behaviour of the hot-dipped aluminide steel. The phase transformation in the aluminide layer during diffusion at 750 degree Celsius in static air was analyzed by SEM-EDX and XRD. After hot-dip treatment, the coating layers consisted of three phases, where Al, thinner layer of FeAl 3 , and thicker layer of Fe 2 Al 5 were detected from external topcoat to the aluminide/ steel substrate. After oxidation, the Fe 2 Al 5 formed during the immersion process completely transformed to Fe 2 Al 5 , FeAl 2 , FeAl and Al-Fe(Al) phases because of the composition gradient and the chemical diffusion by oxidation. After oxidation, there are some voids were found at the coating/ substrate interface due to the rapid inter-diffusion of iron and aluminium during oxidation. The FeAl phase kept growing with increasing exposure time at 750 degree Celsius, while the Fe 2 Al 5 was consumed during oxidation. After 168 hrs oxidation, the Fe 2 Al 5 phase was going disappeared as the aluminum layer was consumed. (author)

  8. Kinetics of the polymorphic phase transformation of Cu6Sn5

    International Nuclear Information System (INIS)

    Zeng, Guang; McDonald, Stuart D.; Read, Jonathan J.; Gu, Qinfen; Nogita, Kazuhiro

    2014-01-01

    Cu 6 Sn 5 is a critical intermetallic compound in soldering and three-dimensional integrated circuit packaging technology and exists in at least five different crystal structures in the solid state, with a polymorphic phase transformation from hexagonal to monoclinic structures occurring on cooling. The kinetics of polymorphic transformations in Sn-rich Cu 6 Sn 5 and Cu-rich Cu 6 Sn 5 is systematically investigated in this study. This includes the generation of continuous cooling transformation diagrams as well as time–temperature transformation diagrams. Techniques used include variable temperature synchrotron powder X-ray diffraction and differential scanning calorimetry. The findings have important implications for the manufacture of solder joints and their in-service performance

  9. Application of phase coherent transform to cloud clutter suppression

    Energy Technology Data Exchange (ETDEWEB)

    Ng, L.C. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    This paper describes a tracking algorithm using frame-to-frame correlation with frequency domain clutter suppression. Clutter suppression was mechanized via a `Phase Coherent Transform` (PCT) approach. This approach was applied to explore the feasibility of tracking a post-boost rocket from a low earth orbit satellite with real cloud background data. Simulation results show that the PCT/correlation tracking algorithm can perform satisfactorily at signal-to-clutter ratio (SCR) as low as 5 or 7 dB.

  10. A TECHNIQUE OF IDENTIFICATION OF THE PHASE-DISPLACEMENT GROUP OF THREE-PHASE TRANSFORMER

    International Nuclear Information System (INIS)

    Aburjania, A.; Begiashvili, V.; Rezan Turan

    2007-01-01

    It is demonstrated that the arbitrary choice of arbitrarily pisitive direction of induced currents and voltages contradicts the energy conservation law and leads to equilibrium equations and standards making no sense from the physical standpoint. Of 12 recognized standard phase-displacement groups of three-phase transformer, only three have real physical bases. The rest are based on a wrong assumption about mutual biasing of primary and secondary currents. They does not rule out the occurrence of emergency situations and, thus, must be eliminated from use. A new method of identification of the phase-displacement of three-phase transformer is proposed. The method is based on well-known physical laws with consideration for the dual character of the inertia of mutual inductance and exhausts for all possible versions of connection of transformer windings. (author)

  11. Structural formation of aluminide phases on titanium alloy during annealing

    International Nuclear Information System (INIS)

    Mamaeva, A.A.; Romankov, S.E.; Sagdoldina, Zh.

    2006-01-01

    Full text: The aluminum layer on the surface of titanium alloy has been formed by thermal deposition. The structural formation of aluminide phases on the surface has been studied. The sequence of structural transformations at the Ti/Al interface is limited by the reaction temperature and time. The sequence of aluminide phase formation is occurred in compliance with Ti-Al equilibrium phase diagram. At the initial stages at the Ti/Al interface the Al3Ti alloy starts forming as a result of interdiffusion, and gradually the whole aluminum films is spent on the formation of this layer. The Al3Ti layer decomposes with the increase of temperature (>600C). At 800C the two-phase (Ti3Al+TiAl) layer is formed on the titanium surface. The TiAl compound is unstable and later on with the increase of the exposure time at 800C gradually transforms into the Ti3Al. The chain of these successive transformations leads to the formation of the continuous homogeneous layer consisting of the Ti3Al compound on the surface. At temperatures exceeding the allotropic transformation temperature (>900C) the Ti3Al compound starts decomposing. All structural changes taking place at the Ti/Al interface are accompanied by considerable changes in micro hardness. The structure of initial substrate influences on kinetics of phase transformation and microstructure development. (author)

  12. Nuclear resonant scattering evidence of the phase co-existence during structural phase transformation in [Fe(H{sub 2}O){sub 6}](ClO{sub 4}){sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Vanko, Gy. [European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble (France); Research Group for Nuclear Techniques in Structural Chemistry, Hungarian Academy of Sciences at Eoetvoes L. University, P.O. Box 32, H-1518 Budapest (Hungary); Bottyan, L. [KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, H-1525 Budapest (Hungary); Deak, L. [KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, H-1525 Budapest (Hungary); Fetzer, Cs. [KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, H-1525 Budapest (Hungary); Juhasz, G. [Department of Nuclear Chemistry, Eoetvoes L. University, P.O. Box 32, H-1518 Budapest (Hungary); Leupold, O. [European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble (France); Institut fuer Experimentalphysik, Universitaet Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany); Molnar, B. [KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, H-1525 Budapest (Hungary); Rueter, H.D. [KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, H-1525 Budapest (Hungary); Szilagyi, E. [KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, H-1525 Budapest (Hungary); Nagy, D.L. [KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, H-1525 Budapest (Hungary)]. E-mail: nagy@rmki.kfki.hu

    2005-09-29

    The phase transition associated with orbital-ground-state inversion of high-spin Fe{sup 2+} in [Fe(H{sub 2}O){sub 6}](ClO{sub 4}){sub 2} was studied with nuclear resonant forward scattering of synchrotron radiation (SR). The sudden change in the {sup 57}Fe{sup 2+} quadrupole interaction results in a change of the quantum-beat frequencies. Quantum-beat patterns taken at the phase transition of [Fe(H{sub 2}O){sub 6}](ClO{sub 4}){sub 2} are in accordance with mainly coherent rather than with incoherent sums of the scattering amplitudes of the high- and low-quadrupole-interaction phases, a fact supporting the real co-existence of the two phases.

  13. Thermally induced phase transformation in multi-phase iron oxide nanoparticles on vacuum annealing

    Science.gov (United States)

    Anupama, A. V.; Keune, W.; Sahoo, B.

    2017-10-01

    The evolution of magnetic phases in multi-phase iron oxide nanoparticles, synthesized via the transferred arc plasma induced gas phase condensation method, was investigated by X-ray diffraction, vibrating sample magnetometry and 57Fe Mössbauer spectroscopy. The particles are proposed to be consisting of three different iron oxide phases: α-Fe2O3, γ-Fe2O3 and Fe3O4. These nanoparticles were exposed to high temperature (∼935 K) under vacuum (10-3 mbar He pressure), and the thermally induced phase transformations were investigated. The Rietveld refinement of the X-ray diffraction data corroborates the least-squares fitting of the transmission Mössbauer spectra in confirming the presence of Fe3O4, γ-Fe2O3 and α-Fe2O3 phases before the thermal treatment, while only Fe3O4 and α-Fe2O3 phases exist after thermal treatment. On thermal annealing in vacuum, conversion from γ-Fe2O3 to Fe3O4 and α-Fe2O3 was observed. Interestingly, we have observed a phase transformation occurring in the temperature range ∼498 K-538 K, which is strikingly lower than the phase transformation temperature of γ-Fe2O3 to α-Fe2O3 (573-623 K) in air. Combining the results of Rietveld refinement of X-ray diffraction patterns and Mössbauer spectroscopy, we have attributed this phase transformation to the phase conversion of a metastable "defected and strained" d-Fe3O4 phase, present in the as-prepared sample, to the α-Fe2O3 phase. Stabilization of the phases by controlling the phase transformations during the use of different iron-oxide nanoparticles is the key factor to select them for a particular application. Our investigation provides insight into the effect of temperature and chemical nature of the environment, which are the primary factors governing the phase stability, suitability and longevity of the iron oxide nanomaterials prepared by the gas-phase condensation method for various applications.

  14. Phase field modeling of tetragonal to monoclinic phase transformation in zirconia

    Science.gov (United States)

    Mamivand, Mahmood

    Zirconia based ceramics are strong, hard, inert, and smooth, with low thermal conductivity and good biocompatibility. Such properties made zirconia ceramics an ideal material for different applications form thermal barrier coatings (TBCs) to biomedicine applications like femoral implants and dental bridges. However, this unusual versatility of excellent properties would be mediated by the metastable tetragonal (or cubic) transformation to the stable monoclinic phase after a certain exposure at service temperatures. This transformation from tetragonal to monoclinic, known as LTD (low temperature degradation) in biomedical application, proceeds by propagation of martensite, which corresponds to transformation twinning. As such, tetragonal to monoclinic transformation is highly sensitive to mechanical and chemomechanical stresses. It is known in fact that this transformation is the source of the fracture toughening in stabilized zirconia as it occurs at the stress concentration regions ahead of the crack tip. This dissertation is an attempt to provide a kinetic-based model for tetragonal to monoclinic transformation in zirconia. We used the phase field technique to capture the temporal and spatial evolution of monoclinic phase. In addition to morphological patterns, we were able to calculate the developed internal stresses during tetragonal to monoclinic transformation. The model was started form the two dimensional single crystal then was expanded to the two dimensional polycrystalline and finally to the three dimensional single crystal. The model is able to predict the most physical properties associated with tetragonal to monoclinic transformation in zirconia including: morphological patterns, transformation toughening, shape memory effect, pseudoelasticity, surface uplift, and variants impingement. The model was benched marked with several experimental works. The good agreements between simulation results and experimental data, make the model a reliable tool for

  15. Phase Transformation Study in Nb-Mo Microalloyed Steels Using Dilatometry and EBSD Quantification

    Science.gov (United States)

    Isasti, Nerea; Jorge-Badiola, Denis; Taheri, Mitra L.; Uranga, Pello

    2013-08-01

    A complete microstructural characterization and phase transformation analysis has been performed for several Nb and Nb-Mo microalloyed low-carbon steels using electron backscattered diffraction (EBSD) and dilatometry tests. Compression thermomechanical schedules were designed resulting in the undeformed and deformed austenite structures before final transformation. The effects of microalloying additions and accumulated deformation were analyzed after CCT diagram development and microstructural quantification. The resulting microstructures ranged from polygonal ferrite and pearlite at slow cooling ranges, to a combination of quasipolygonal ferrite and granular ferrite for intermediate cooling rates, and finally, to bainitic ferrite with martensite for fast cooling rates. The addition of Mo promotes a shift in the CCT diagrams to lower transformation start temperatures. When the amount of Nb is increased, CCT diagrams show little variations for transformations from the undeformed austenite and higher initial transformation temperatures in the transformations from the deformed austenite. This different behavior is due to the effect of niobium on strain accumulation in austenite and its subsequent acceleration of transformation kinetics. This article shows the complex interactions between chemical composition, deformation, and the phases formed, as well as their effect on microstructural unit sizes and homogeneity.

  16. PVA assisted low temperature anatase to rutile phase transformation (ART) and properties of titania nanoparticles

    International Nuclear Information System (INIS)

    Mondal, Shrabani; Madhuri, Rashmi; Sharma, Prashant K.

    2015-01-01

    Anatase to rutile phase transformation (ART) of titania nanoparticles is observed at very low temperature (180 °C) just by introducing polyvinyl alcohol (PVA) during co-precipitation followed by hydrothermal synthesis. The detailed investigations pertaining to the structural, optical and electrochemical properties of the nanosized titania and titania/PVA nanohybrid has been carried out. The crystallite size and crystal structure is confirmed using X-ray diffraction (XRD). Transmission electron microscopic (TEM) image reveals formation of spherical NPs in both the cases. Identification of functional groups is done using Fourier transform infrared spectroscopy (FTIR). The photoluminescence studies showed that emission slightly shifts towards higher wavelength side with remarkable decrease in intensity for TiO 2 /PVA nanocomposite (rutile samples). The remarkable decrease in PL intensity in TiO 2 /PVA nanocomposite (rutile samples) is explained considering the surface passivation during growth process. Ion transportation is monitored via Cyclic voltammetric (CV) and Electrochemical Impedance Spectroscopy (EIS) measurements. A significant enhancement of peak cathodic current in case of nanocomposite modified electrode is observed. It is assumed that TiO 2 /PVA (rutile) nanoparticles provided the conducting path for the electrons and hence enhanced the electrochemical reaction. - Graphical abstract: Present work reports anatase to rutile phase transformation (ART) of titania nanoparticles at very low temperature (180 °C) just by introducing polyvinyl alcohol (PVA) during co-precipitation followed by hydrothermal synthesis. - Highlights: • Low temperature phase transformation of TiO 2 nanoparticles from anatase to rutile. • Role of PVA in phase transformation. • Synthesis of spherical shaped uniformly distributed PVA capped TiO 2 NPs. • Explained the charge transfer process among anatase to rutile phase transformation via luminescence studies. • Enhanced

  17. Transformers: the changing phases of low-dimensional vanadium oxide bronzes.

    Science.gov (United States)

    Marley, Peter M; Horrocks, Gregory A; Pelcher, Kate E; Banerjee, Sarbajit

    2015-03-28

    In this feature article, we explore the electronic and structural phase transformations of ternary vanadium oxides with the composition MxV2O5 where M is an intercalated cation. The periodic arrays of intercalated cations ordered along quasi-1D tunnels or layered between 2D sheets of the V2O5 framework induce partial reduction of the framework vanadium atoms giving rise to charge ordering patterns that are specific to the metal M and stoichiometry x. This periodic charge ordering makes these materials remarkably versatile platforms for studying electron correlation and underpins the manifestation of phenomena such as colossal metal-insulator transitions, quantized charge corrals, and superconductivity. We describe current mechanistic understanding of these emergent phenomena with a particular emphasis on the benefits derived from scaling these materials to nanostructured dimensions wherein precise ordering of cations can be obtained and phase relationships can be derived that are entirely inaccessible in the bulk. In particular, structural transformations induced by intercalation are dramatically accelerated due to the shorter diffusion path lengths at nanometer-sized dimensions, which cause a dramatic reduction of kinetic barriers to phase transformations and facilitate interconversion between the different frameworks. We conclude by summarizing numerous technological applications that have become feasible due to recent advances in controlling the structural chemistry and both electronic and structural phase transitions in these versatile frameworks.

  18. Phase transformation during silica cluster impact on crystal silicon substrate studied by molecular dynamics simulation

    International Nuclear Information System (INIS)

    Chen Ruling; Luo Jianbin; Guo Dan; Lu Xinchun

    2008-01-01

    The process of a silica cluster impact on a crystal silicon substrate is studied by molecular dynamics simulation. At the impact loading stage, crystal silicon of the impact zone transforms to a locally ordered molten with increasing the local temperature and pressure of the impact zone. And then the transient molten forms amorphous silicon directly as the local temperature and pressure decrease at the impact unloading stage. Moreover, the phase behavior between the locally ordered molten and amorphous silicon exhibits the reversible structural transition. The transient molten contains not only lots of four-fold atom but also many three- and five-fold atoms. And the five-fold atom is similar to the mixture structure of semi-Si-II and semi-bct5-Si. The structure transformation between five- and four-fold atoms is affected by both pressure and temperature. The structure transformation between three- and four-fold atoms is affected mostly by temperature. The direct structure transformation between five- and three-fold atoms is not observed. Finally, these five- and three-fold atoms are also different from the usual five- and three-fold deficient atoms of amorphous silicon. In addition, according to the change of coordination number of atoms the impact process is divided into six stages: elastic, plastic, hysteresis, phase regressive, adhesion and cooling stages

  19. Pressure-induced phase transformations in L-alanine crystals

    DEFF Research Database (Denmark)

    Olsen, J. Staun; Gerward, Leif; Freire, P.T.C.

    2008-01-01

    Raman scattering and synchrotron X-ray diffraction have been used to investigate the high-pressure behavior of L-alanine. This study has confirmed a structural phase transition observed by Raman scattering at 2.3 GPa and identified it as a change from orthorhombic to tetragonal structure. Another...

  20. Phase transformations and thermodynamics of aluminum-based metallic glasses

    Science.gov (United States)

    Gao, Changhua (Michael)

    This thesis examines the thermodynamics and associated kinetics and phase transformations of the glass forming Al-Ni-Gd and Al-Fe-Gd systems. In order to fully understand the unique glass forming ability (GFA) of Al-based metallic glasses, the ternary Al-Fe-Gd and Al-Ni-Gd systems in their Al-rich corners were examined experimentally to assist in a thermodynamic assessment. The solid-state phase equilibria are determined using XRD and TEM-EDS techniques. While this work basically confirms the solid-state equilibria in Al-Fe-Gd reported previously, the ternary phase in Al-Ni-Gd system has been identified to be Al15Ni3Gd2 rather than Al16Ni 3Gd reported in the literature. DTA analysis of 24 alloys in the Al-Fe-Gd system and 42 alloys in the Al-Ni-Gd system have yielded critical temperatures pertaining to the solid-liquid transition. Based on these data and information from the literature, a self-consistent thermodynamic database for these systems has been developed using the CALPHAD technique. Parameters describing the Gibbs free energy for various phases of the Al-Gd, Al-Fe-Gd and Al-Ni-Gd systems are manually optimized in this study. Once constructed, the database is used to calculate driving forces for nucleation of crystalline phases which can qualitatively explain the phase formation sequence during crystallization at low temperatures. It was also confirmed that alloy compositions with the lowest Gibbs free energy difference between the equilibrium state and undercooled liquid state exhibit better GFA than other chemistries. Based on 250°C isothermal devitrification phase transformations of 17 Al-Ni-Gd alloys, a phase formation sequence map is constructed. Fcc-Al nanocrystals are formed first in most of the alloys studied, but eutectic crystallization of a metastable phase and fcc-Al is also observed. Addition of Al or Ni promotes fcc-Al phase formation, while increasing Gd suppresses it. The continuous heating DSC scans revealed that crystallization in Al

  1. Light activated phase transformation of metastable tetragonal nanocrystalline zirconia

    DEFF Research Database (Denmark)

    Nielsen, Mette Skovgaard; Almdal, Kristoffer; van Lelieveld, A

    2012-01-01

    This study searches for small molecules, which can be generated by photoacid generators (PAGs) capable of inducing the tetragonal-to-monoclinic transformation in zirconia nanocrystals. Metastable tetragonal zirconia nanocrystals were exposed in alcohol suspension. X-ray diffraction analysis showed...... that water, HCl, HF, and NH3, all initiate phase transformation of tetragonal zirconia at room temperature, whereas NBu4Cl and NBu4OH do not. 2-(4-Methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine) was the most efficient (monoclinic volume fraction reached 0.57) out of the four tested PAGs....... For dispersion in a dimethacrylate matrix together with zirconia crystals, a monoclinic volume fraction of 0.19 was observed after 2 min of exposure to light, increasing to 0.6 after 30 min....

  2. Landau theory of the displacive phase transformations in gold-cadmium and titanium-nickel alloys

    Energy Technology Data Exchange (ETDEWEB)

    Barsch, G.R. [Pennsylvania State Univ., Philadelphia, PA (United States). Dept. of Physics

    2000-07-01

    On the basis of group theoretical symmetry criteria, the primary and secondary order parameters (OP's) have been identified for the three ferroelastic martensitic transformations that occur in the Au-Cd binary, and in the Ti-Ni-M (M=Fe,Al,Cu) pseudo-binary shape-memory alloys, viz (i) from the cubic {beta}{sub 2} austenite parent phase (B2 structure) to the rhombohedral (R) {zeta}'{sub 2} product phase of P3 symmetry, (ii) from the {beta}{sub 2} to the orthorhombic ({gamma}{sub 2}) product phase of Pmma symmetry (B19 structure), and (iii) fromthe B19 to the monoclinic B19' structure of P2{sub 1}/m symmetry. For all three transformations, the Landau free energy and the relations between the primary OP and the atom shuffle displacements are given for the transition to a single product phase variant. For case (i), the 12 experimentally measured structural (shuffle) parameters of the R phase can be accounted for and fitted by only two theoretical model parameters, giving satisfactory agreement with the (only available) room temperature data for Au{sub .505}Cd{sub .495}; for Ti{sub .4977}Ni{sub .5023} larger discrepancies, but mostly within the relatively large experimental error are found. For the two cases (ii) and (iii), the two shuffle displacements each can be fitted exactly by the two theoretical model parameters required. (orig.)

  3. Program for three-phase power transformer design

    Directory of Open Access Journals (Sweden)

    Olivian Chiver

    2011-12-01

    Full Text Available This paper presents a program developed for designing three-phase power transformers used in power systems. The program was developed in Visual Basic because this programming language allows us to realize a friendly and suggestive interface with minimum effort. The second reason, which is the most important, is to use Visual Basic, because this language is recognized by the used finite elements analysis (FEA software, MagNet produced by Infolytica. This software package is designed for calculation of the magnetic field of electromagnetic devices and machines. The 3D components of the numerical model are carried out using CATIA program, automatically, based on the calculated main geometric data.

  4. A Transformer-less Single Phase Inverter For photovoltaic Systems

    DEFF Research Database (Denmark)

    Mostaan, Ali; Alizadeh, Ebrahim; Qu, Ying

    2017-01-01

    A single phase transformer-less inverter is introduced in this paper. The negative polarities of the input voltage and output terminal have common ground. Therefore, the leakage current problem that is common in PV systems is eliminated naturally. In addition, the proposed inverter has fewer...... components compared with its counterparts and only one switch conducts during the active states which enhance the inverter efficiency. The proposed inverter is analyzed in details and compared with some existing topologies. The performance of the proposed inverter is validated using the simulation results....

  5. Surface modification-induced phase transformation of hexagonal close-packed gold square sheets

    KAUST Repository

    Fan, Zhanxi

    2015-03-13

    Conventionally, the phase transformation of inorganic nanocrystals is realized under extreme conditions (for example, high temperature or high pressure). Here we report the complete phase transformation of Au square sheets (AuSSs) from hexagonal close-packed (hcp) to face-centered cubic (fcc) structures at ambient conditions via surface ligand exchange, resulting in the formation of (100)f-oriented fcc AuSSs. Importantly, the phase transformation can also be realized through the coating of a thin metal film (for example, Ag) on hcp AuSSs. Depending on the surfactants used during the metal coating process, two transformation pathways are observed, leading to the formation of (100)f-oriented fcc Au@Ag core-shell square sheets and (110)h/(101)f-oriented hcp/fcc mixed Au@Ag nanosheets. Furthermore, monochromated electron energy loss spectroscopy reveals the strong surface plasmon resonance absorption of fcc AuSS and Au@Ag square sheet in the infrared region. Our findings may offer a new route for the crystal-phase and shape-controlled synthesis of inorganic nanocrystals. © 2015 Macmillan Publishers Limited. All rights reserved.

  6. Phase Transformations and Phase Equilibria in the Fe-N System at Temperatures below 573 K

    DEFF Research Database (Denmark)

    Malinov, S.; Böttger, A.J.; Mittemeijer, E.J.

    2001-01-01

    The phase transformations of homogeneous Fe-N alloys of nitrogen contents from 10 to 26 at. pct were investigated by means of X-ray diffraction analysis upon aging in the temperature range from 373 to 473 K. It was found that precipitation of alpha double prime-Fe16N2 below 443 K does not only oc...

  7. Modeling of diffusional phase transformation in multi-component systems with stoichiometric phases

    Czech Academy of Sciences Publication Activity Database

    Svoboda, Jiří; Fischer, F. D.; Abart, R.

    2010-01-01

    Roč. 58, č. 8 (2010), s. 2905-2911 ISSN 1359-6454 R&D Projects: GA MŠk(CZ) OC10029 Institutional research plan: CEZ:AV0Z20410507 Keywords : Interdiffusion * Intermetallics * Phase transformation kinetics Subject RIV: BJ - Thermodynamics Impact factor: 3.781, year: 2010

  8. Optical image encryption in Fresnel domain using spiral phase transform

    Science.gov (United States)

    Kumar, Ravi; Bhaduri, Basanta

    2017-09-01

    In this study, we propose a new nonlinear optical image encryption technique using spiral phase transform (SPT). First, the primary image is phase encoded and multiplied with a random amplitude mask (RAM), and using power function, the product is then powered to m. This powered output is Fresnel propagated with distance z 1 and then modulated with a random phase mask (RPM). The modulated image is further Fresnel propagated with distance z 2. Similarly, a security image is also modulated with another RAM and then Fresnel propagated with distance z 3. Next, the two modulated images after Fresnel propagations, are interfered and further Fresnel propagated with distance z 4 to get a complex image. Finally, this complex image is SPT with particular spiral phase function (SPF), to get the final encrypted image for transmission. In the proposed technique, the security keys are Fresnel propagation distances, the security image, RPM, RAMs, power order, m, and order of SPF, q. Numerical simulation results confirm the validity and effectiveness of the proposed technique. The proposed technique is robust against noise and brutal force attacks.

  9. Phase transformations in nickel-aluminum alloys during ion beam mixing

    International Nuclear Information System (INIS)

    Eridon, J.; Rehn, L.; Was, G.

    1986-01-01

    The effect of ion beam mixing of nickel-aluminum alloys with 500 keV krypton ions has been investigated over a range of temperature, composition, ion dose, and post-irradiation thermal treatments. Samples were formed by alternate evaporation of layers of aluminum and nickel. A portion of these samples was subsequently annealed to form intermetallic compounds. Irradiations were performed at both room temperature and 80 0 K using the 2MV ion accelerator at Argonne National Laboratory. Phase transformations were observed during both in situ irradiations in the High Voltage Electron Microscope (HVEM) at Argonne, and also in subsequent analysis of an array of irradiated samples. Electron diffraction indicates the presence of metastable crystalline structures not present in the conventional nickel-aluminum phase diagram. Transformations occur at doses as low as 5 x 10 14 cm -2 and continue to develop as the irradiation progresses up to 2 x 10 16 cm -2 . Layer mixing is followed through Rutherford Backscattering analysis. Samples are also checked with x-rays and Electron Energy Loss Spectroscopy (EELS). A thermodynamic argument is presented to explain the phase transformations in terms of movements on a free energy diagram. This analysis explains the interesting paradox concerning the radiation hardness of the NiAl phase and the amorphous structure of mixed Ni-50% Al layers

  10. Extension of love wave transformation theory to laterally heterogeneous structures

    International Nuclear Information System (INIS)

    Romanelli, F.; Panza, G.F.

    1993-08-01

    By means of the spherical-to-flat transformations for torsional waves, all the flat-transformed components of motion (two for displacement and five for stress) have been derived. This provides the formal basis necessary to treat the propagation of torsional waves in spherical 3-D structures, by using the existing flat-structure computational techniques. (author). 8 refs, 1 fig., 1 tab

  11. Study of phase transformations in Fe-Mn-Cr Alloys

    International Nuclear Information System (INIS)

    Schule, W.; Panzarasa, A.; Lang, E.

    1988-01-01

    Nickel free alloys for fusion reactor applications are examined. Phase changes in fifteen, mainly austenitic iron-manganese-chromium-alloys of different compositions were investigated in the temperature range between -196 0 C and 1000 0 C after different thermo-mechanical treatments. A range of different physical measuring techniques was employed to investigate the structural changes occurring during heating and cooling and after cold-work: electrical resistivity techniques, differential thermal analysis, magnetic response, Vickers hardness and XRD measurement. The phase boundary between the α Fe-phase and the γ-phase of the iron manganese alloy is approximately maintained if chromium is added to the two component materials. Consequently all the alloy materials for contents of manganese smaller than about 30% Mn are not stable below 500 0 C. This concerns also the AMCR alloys. However the α Fe-phase is not formed during slow cooling from 1000 0 C to ambient temperature and is only obtained if nucleation sites are provided and after very long anneals. A cubic α Mn-type-phase is found for alloys with 18% Cr and 15% Mn, with 13% Cr and 25% Mn, with 10% Cr and 30% Mn, and with 10% Cr and 40% Mn. For these reasons the γ-phase field of the iron-chromium-manganese alloys is very small below 600 0 C and much narrower than reported in the literature. 95 figs. 22 refs

  12. Relationship between transport properties and phase transformations in mixed-conducting oxides

    International Nuclear Information System (INIS)

    Deng, Z.Q.; Yang, W.S.; Liu, W.; Chen, C.S.

    2006-01-01

    To elucidate the relationship between transport properties and phase transformations in mixed-conducting oxides, Sr 0.9 Ca 0.1 Co 0.89 Fe 0.11 O 3- δ (SCCFO) and SrCoO 3- δ (SCO) were chosen as the model materials and have been investigated in detail. Oxygen permeation measurements verified that both oxides are well permeable to oxygen at elevated temperatures, e.g., at 900 deg. C during a cooling procedure, oxygen permeation rates as large as 1.5 and 2.0 mL/min/cm 2 could be obtained with disk-shaped SCCFO and SCO membranes of thickness 1.5 mm, respectively. But when cooled to critical temperatures, the oxygen permeability of these kinds of oxides diminished sharply, which could be recovered by increasing the temperature again to certain values. Abrupt changes on electrical conductivity were also observed for both oxides around the same region of temperature as that of oxygen permeability. As indicated by high-temperature X-ray diffraction and thermal analysis, the SCCFO and SCO systems undergo phase transformation between a low-temperature orthorhombic brownmillerite structure (B) or a hexagonal 2H-type structure (H) and a high-temperature cubic perovskite structure (C), respectively. The present results suggest the observed abrupt changes in transport properties versus temperature are attributed to such phase transformation, which may be directly associated with the order-disorder transition of oxygen vacancies. Moreover, compared to the B/C transformation that mainly involves an order-disorder transition on the oxygen sublattice, the H/C one necessarily also involves the cooperative long-range reorganization on the cation sublattice. Therefore it occurs at a higher temperature and absorbs more heat quantity than those of B/C transformation

  13. Structure transformations in ion implanted anodic alumina films

    International Nuclear Information System (INIS)

    Cherenda, N.N.; Uglov, V.V.; Litvinovich, G.V.; Daniluyk, A.L.

    2002-01-01

    The effect of ion implantation on aluminium oxide has been widely studied. The change of mechanical, electrical, optical and chemical properties were investigated. Most studies were performed on a single crystal (a- or c-oriented) α-Al 2 O 3 though polycrystalline α-Al 2 O 3 or amorphous aluminium oxide films were the subject of the investigation too. Porous anodic alumina films were the object of the investigation of this work. An unique structure, low cost, controllability and ease of production allow it application in developing of microelectronic devices. Earlier it was shown that implantation of metal ions in anodic alumina films decreases its surface resistance to tens of Ωm. The aim of this work was the investigation of anodic alumina films structure changes after implantation. The implantation of Ti and Cu ions was carried out using a MEVVA source with an impulse duration of 1 ms. The applied acceleration voltage was 80 kV, the ions current density - 53 μA/cm 2 , the doses -1·10 17 ions/cm 2 and 1.5·10 18 ions/cm 2 . Implantation was carried out into two types of crystalline structure: amorphous and γ-Al 2 O 3 . The latter structure was produced by annealing at 830 deg. C. A variety of techniques were used for phase and element composition investigations: X-ray diffraction analysis, Auger electron spectroscopy, Rutherford backscattering analysis and scanning electron microscopy. It was found that implantation into amorphous film results in the formation of γ-AO 2 O 3 while implantation into γ-Al 2 O 3 film - in the formation of an amorphous structure. Implantation both to amorphous and crystalline AA films also led to the formation of θ-Al 2 O 3 phase inclusions in the film structure. The whole structure of AA films with the thickness of 200 μm undergoes these transformations. Implantation also lead to sputtering of the surface barrier layer thus resulting in the shift of the ions depth profile to the surface at higher doses. Diffusion of Ti

  14. Thermal analysis of high temperature phase transformations of steel

    Directory of Open Access Journals (Sweden)

    K. Gryc

    2013-10-01

    Full Text Available The series of thermal analysis measurements of high temperature phase transformations of real grain oriented electrical steel grade under conditions of two analytical devices (Netzsch STA 449 F3 Jupiter; Setaram SETSYS 18TM were carried out. Two thermo analytical methods were used (DTA and Direct thermal analysis. The different weight of samples was used (200 mg, 23 g. The stability/reproducibility of results obtained by used methodologies was verified. The liquidus and solidus temperatures for close to equilibrium conditions and during cooling (20 °C/min; 80 °C/min were determined. It has been shown that the higher cooling rate lead to lower temperatures for start and end of solidification process of studied steel grade.

  15. Interaction of stress and phase transformations during thermochemical surface engineering

    DEFF Research Database (Denmark)

    Jespersen, Freja Nygaard

    dissolution. The present project is devoted to understanding the mutual interaction of stresses and phase transformations during thermochemical surface engineering by combining numerical modelling with experimental materials science. The modelling was done by combining solid mechanics with thermodynamics...... by chromium atoms, and the effect of composition-induced stress on surface concentration and diffusive flux. The effect of plasticity was also included. Temperature and concentration dependencies of mechanical and diffusion material properties were studied, and the effect of incorporation in the model...... examined. The effect of pre-stressing the sample was also tested, to investigate the effects of a residual stress-state that might be present from processing of the metal specimen. Controlled thermochemical treatment of austenitic stainless steel was investigated experimentally by in-diffusion of nitrogen...

  16. Prediction and measurement of selected phase transformation temperatures of steels

    Directory of Open Access Journals (Sweden)

    Martiník O.

    2017-01-01

    Full Text Available The study deals with precise determination of phase transformation temperatures of steel. A series of experimental measurements were carried out by Differential Thermal Analysis (DTA and Direct Thermal Analysis (TA to obtain temperatures very close to the equilibrium temperatures. There are presented results from the high temperatures region, above 1000°C, with focus on the solidus temperatures (TS, peritectic transition (TP and liquidus (TL of multicomponent steels. The data obtained were verified by statistical evaluation and compared with computational thermodynamic and empirical calculations. The calculations were performed using 15 empirical equations obtained by literature research (10 for TL and 5 for TS, as well as by software InterDendritic Solidification (IDS and Thermo-Calc (2015b, TCFE8; TC. It was verified that both thermo-analytical methods used are set correctly; the results are reproducible, comparable and close to equilibrium state.

  17. Thermodynamics and phase transformations: the selected works of Mats Hillert

    International Nuclear Information System (INIS)

    Agren, J.; Brechet, Y.; Hutchinson, Ch.; Purdy, G.

    2006-01-01

    For over half a century, Mats Hillert has contributed greatly to the science of materials. He is widely known and respected as an innovator and an educator, a scientist with an enormous breadth of interest and depth of insight. In acknowledgment of his many contributions, a conference was held in Stockholm in December 2004 to mark his eightieth birthday. This volume was conceived prior to, and publicly announced during the conference. The difficult choice of twenty-four papers from a publication list of more than three hundred was carried out in consultation with Mats. He also suggested or approved the scientists who would be invited to write a brief introduction to each paper. A brief reading of the topics of the selected papers and their introductions reveals something of their range and depth. Several early selections (for example, those on 'The Role of Interfacial Energy during Solid State Phase Transformations', and 'A Solid-Solution Model for Inhomogeneous Systems') contained seminal material that established Mats as a leading figure in the study of phase transformations in solids. Others established his presence in the areas of solidification and computational thermodynamics. A review of his full publication list shows that he has consistently built upon those early foundational papers, and maintained a dominant position in those fields. Although many of his contributions have been of a theoretical nature, he has always maintained a close contact with experiment, and indeed, he has designed numerous critical experiments. This volume represents a judicious sampling of Mats Hillert's extensive body of work; it is necessarily incomplete, but it is hoped and expected that it will prove useful to students of materials science and engineering at all levels, and that it will inspire the further study and appreciation of his many contributions. (authors)

  18. Revealing Structural Transformations during Crystallization of DNA-Nanoparticle Assemblies

    Science.gov (United States)

    Zhang, Yugang; Lu, Fang; van der Lelie, Daniel; Gang, Oleg

    2013-03-01

    Nanoparticle assembly via sequence-specific DNA recognition emerges as a powerful strategy for the fabrication of nanoparticle (NP)-based crystalline materials. Generally, a delicate thermal annealing is essential for the crystallization of NPs from kinetically trapped disordered states. Due to the complex coupling between interactions, entropic and chain effects in these systems, the crystallization pathway remains an intricate and open question. Herein, we present an experimental study of the crystallization process for DNA-directed nanoparticle assembly systems using synchrotron-based small angle x-ray scattering (SAXS). We demonstrated the effects of two crystallization-dominant factors, namely, temperature and volume fraction, on the structural transformation and order development. By combining a single component and binary systems we uncovered the evolution of global and local particle arrangements, such as correlation length, compositional disorder and coordination number, during the phase transformation. Research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.

  19. Structural and functional group transformations of carbohydrates

    OpenAIRE

    2014-01-01

    D.Sc. (Chemistry) The aim of this study was to develop new methodology for the transformation of unsaturated carbohydrates utilising organometallic compounds. The first half of the study was directed toward developing a general synthesis of complex allyltins and in determining their application to carbon-carbon bond formation. It was decided to utilise carbohydrate substrates in this regard to develop a novel method of producing glycosides...

  20. Phase transformation during mechano-synthesis of nanocrystalline/amorphous Fe–32Mn–6Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Amini, Rasool, E-mail: ramini2002@gmail.com [Department of Materials Science and Engineering, Shiraz University of Technology, 71555-313 Shiraz (Iran, Islamic Republic of); Shamsipoor, Ali [Department of Materials Science and Engineering, Shiraz University of Technology, 71555-313 Shiraz (Iran, Islamic Republic of); Ghaffari, Mohammad [Department of Electrical and Electronics Engineering, UNAM-National Institute of Materials Science and Nanotechnology Bilkent University, Ankara 06800 (Turkey); Alizadeh, Morteza [Department of Materials Science and Engineering, Shiraz University of Technology, 71555-313 Shiraz (Iran, Islamic Republic of); Okyay, Ali Kemal [Department of Electrical and Electronics Engineering, UNAM-National Institute of Materials Science and Nanotechnology Bilkent University, Ankara 06800 (Turkey)

    2013-10-15

    Mechano-synthesis of Fe–32Mn–6Si alloy by mechanical alloying of the elemental powder mixtures was evaluated by running the ball milling process under an inert argon gas atmosphere. In order to characterize the as-milled powders, powder sampling was performed at predetermined intervals from 0.5 to 192 h. X-ray florescence analyzer, X-ray diffraction, scanning electron microscope, and high resolution transmission electron microscope were utilized to investigate the chemical composition, structural evolution, morphological changes, and microstructure of the as-milled powders, respectively. According to the results, the nanocrystalline Fe–Mn–Si alloys were completely synthesized after 48 h of milling. Moreover, the formation of a considerable amount of amorphous phase during the milling process was indicated by quantitative X-ray diffraction analysis as well as high resolution transmission electron microscopy image and its selected area diffraction pattern. It was found that the α-to-γ and subsequently the amorphous-to-crystalline (especially martensite) phase transformation occurred by milling development. - Graphical abstract: Mechano-synthesis of nanocrystalline/amorphous Fe–32Mn–6Si shape memory alloys in the powder form: amorphous phase formation, α-to-γ phase transformation, mechano-crystallization of the amorphous, and martensite phase formation during the process. Highlights: • During MA, the α-to-γ phase transformation and amorphization occurred. • Mechano-crystallization of the amorphous phase occurred at sufficient milling time. • The formation of high amount of ε-martensite was evidenced at high milling times. • The platelet, spherical, and then irregular particle shapes was extended by MA. • By MA, the particles size was increased, then reduced, and afterward re-increased.

  1. Low Temperature Phase Transformations in Copper-Quenched Ti-44.5Al-8Nb-2.5V Alloy

    Directory of Open Access Journals (Sweden)

    Shouzhen Cao

    2017-02-01

    Full Text Available In this study, an easily controlled transformation similar to the β + α → β + α + γ and the analysis of metastable phases in a β solidifying Ti-44.5Al-8Nb-2.5V alloy were investigated. Therefore, a liquid alloy copper-quenching followed by annealing at an application temperature (850 °C has been carried out. Following quenching, a microstructure composed of several supersaturated phases—the basket-weave β0 (βbv phase, the plate-like α2 (αp phase and the stripe-like γ (γs phase—was obtained. In the annealing processes, phase transformations in the prior βbv and αp phases domain corresponded nicely to the β + α → β + α + γ transformation during solidification. Also, in the annealed γs phase, the kinetics of the phase transformations involving the metastable L12 phase was firstly detected by transmission electron microscopy (TEM. The L12 phase had a lattice structure similar to the γ phase, whereas the composition of the phase was similar to the α2 phase. The formation of the γ pre-twin phase with an anti-phase boundary (APB was detected in the γs phase of the matrix. The orientation relationships between the γs and precipitated: γ (γp phase are <101]γs//<114]γp, (10 1 ¯ γs//( 1 ¯ 10γp and (0 1 ¯ 0γs//(22 1 ¯ γp.

  2. Nanoalloying and phase transformations during thermal treatment of physical mixtures of Pd and Cu nanoparticles

    Directory of Open Access Journals (Sweden)

    Vineetha Mukundan

    2014-03-01

    Full Text Available Nanoscale alloying and phase transformations in physical mixtures of Pd and Cu ultrafine nanoparticles are investigated in real time with in situ synchrotron-based x-ray diffraction complemented by ex situ high-resolution transmission electron microscopy. The combination of metal–support interaction and reactive/non-reactive environment was found to determine the thermal evolution and ultimate structure of this binary system. At 300 °C, the nanoparticles supported on silica and carbon black intermix to form a chemically ordered CsCl-type (B2 alloy phase. The B2 phase transforms into a disordered fcc alloy at higher temperature (> 450 °C. The alloy nanoparticles supported on silica and carbon black are homogeneous in volume, but evidence was found of Pd surface enrichment. In sharp contrast, when supported on alumina, the two metals segregated at 300 °C to produce almost pure fcc Cu and Pd phases. Upon further annealing of the mixture on alumina above 600 °C, the two metals interdiffused, forming two distinct disordered alloys of compositions 30% and 90% Pd. The annealing atmosphere also plays a major role in the structural evolution of these bimetallic nanoparticles. The nanoparticles annealed in forming gas are larger than the nanoparticles annealing in helium due to reduction of the surface oxides that promotes coalescence and sintering.

  3. Promoting structural transformation: Strategic diversification vs laissez-faire approach

    NARCIS (Netherlands)

    Freire Junior, Clovis

    2017-01-01

    Economic development is associated with structural transformation and the increase of complexity of production and exports. This paper examines whether strategic diversification is required to increase economic complexity or whether market incentives would be sufficient to drive this process of

  4. Co removal and phase transformations during high power diode laser irradiation of cemented carbide

    Energy Technology Data Exchange (ETDEWEB)

    Barletta, M., E-mail: barletta@ing.uniroma2.it [Dipartimento di Ingegneria Meccanica, Universita degli Studi di Roma Tor Vergata, Via del Politecnico, 1 - 00133 Roma (Italy); Rubino, G. [Dipartimento di Ingegneria Meccanica, Universita degli Studi di Roma Tor Vergata, Via del Politecnico, 1 - 00133 Roma (Italy); Gisario, A. [Dipartimento di Meccanica ed Aeronautica, Universita degli Studi di Roma La Sapienza, Via Eudossiana, 18 - 00184 Roma (Italy)

    2011-02-15

    The use of a continuous wave-high power diode laser for removing surface Co-binder from Co-cemented tungsten carbide (WC-Co (5.8 wt%.)) hardmetal slabs was investigated. Combined scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analyses were performed in order to study the phase transformations and micro-structural modifications of the WC-Co substrates occurring during and after laser irradiation. The micro-structure of the WC-Co progressively transforms as energy density increased, exhibiting stronger removal of Co and WC grain growth. At very high energy density, local melting of the WC grains with the formation of big agglomerates of interlaced grains is observed, and the crystalline structure of the irradiated substrate shows the presence of a brittle ternary eutectic phase of W, Co and C (often referred to as the {eta}-phase). The latter can be detrimental to the mechanical properties of WC-Co. Therefore, the proper adjustment of the laser processing parameters plays a crucial role in surface treatments of WC-Co substrates prior to post-processing like diamond deposition.

  5. Temperature induced reversible polymorphic phase transformations in a bis-hydrazone compound

    Science.gov (United States)

    Jayant, Vikrant; Das, Dinabandhu

    2018-03-01

    Two reversible polymorphic phase transformation of 2,3-butanedione, 2,3- bis[4,4‧-bis(diethylamino)benzophenone hydrazone] (DEBH) have been identified in DSC experiment. Topotactic phase transformation of three polymorphs has been observed in variable temperature Single Crystal X-ray Diffraction experiment. The reversible phase transformation of bulk material has been confirmed by Powder X-ray diffraction study.

  6. Phase transformation in Mg—Sb3Te thin films

    International Nuclear Information System (INIS)

    Li Jun-Jian; Chen Yi-Min; Nie Qiu-Hua; Lü Ye-Gang; Wang Guo-Xiang; Shen Xiang; Dai Shi-Xun; Xu Tie-Feng

    2014-01-01

    Mg-doped Sb 3 Te films are proposed to improve the performance of phase-change memory (PCM). We prepare Mg-doped Sb 3 Te films and investigate their crystallization behaviors, structural, optical and electrical properties. We find that Mg-doping can increase the crystallization temperature, enhance the activation energy, and improve the 10-year data retention of Sb 3 Te. Especially Mg 25.19 (Sb 3 Te)74.81 shows higher T c (∼ 190 °C) and larger E a (∼ 3.49 eV), which results in a better data retention maintaining for 10 yr at ∼ 112 °C. Moreover R a /R c value is also improved. These excellent properties make Mg—Sb—Te material a promising candidate for the phase-change memory (PCM). (special topic — international conference on nanoscience and technology, china 2013)

  7. Synthesizing lattice structures in phase space

    International Nuclear Information System (INIS)

    Guo, Lingzhen; Marthaler, Michael

    2016-01-01

    In one dimensional systems, it is possible to create periodic structures in phase space through driving, which is called phase space crystals (Guo et al 2013 Phys. Rev. Lett. 111 205303). This is possible even if for particles trapped in a potential without periodicity. In this paper we discuss ultracold atoms in a driven optical lattice, which is a realization of such a phase space crystals. The corresponding lattice structure in phase space is complex and contains rich physics. A phase space lattice differs fundamentally from a lattice in real space, because its coordinate system, i.e., phase space, has a noncommutative geometry, which naturally provides an artificial gauge (magnetic) field. We study the behavior of the quasienergy band structure and investigate the dissipative dynamics. Synthesizing lattice structures in phase space provides a new platform to simulate the condensed matter phenomena and study the intriguing phenomena of driven systems far away from equilibrium. (paper)

  8. Deployable Composite Structures, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA is seeking innovative structure technologies that will advance expandable modules for orbital and surface based habitats. These secondary structures must...

  9. Crystal structure transformation of TiO 2 in presence of Fe 2 O 3 and ...

    Indian Academy of Sciences (India)

    ... Lecture Workshops · Refresher Courses · Symposia · Live Streaming. Home; Journals; Bulletin of Materials Science; Volume 25; Issue 4. Crystal structure transformation of TiO2 in presence of Fe2O3 and NiO in air atmosphere. S Riyas V Ahmed Yasir P N Mohan Das. Phase Transitions Volume 25 Issue 4 August 2002 pp ...

  10. Pressure-induced structural transformations in the molybdate Sc-2(MoO4)(3)

    DEFF Research Database (Denmark)

    Paraguassu, W.; Maczka, M.; Filho, A. G. Sonza

    2004-01-01

    High pressure Raman scattering and x-ray diffraction studies of the molybdate Sc-2(MoO4)(3) are presented. A sequence of changing symmetry effects is observed through two structural phase transitions ending up with an amorphous state. The observed two structural phase transformations are reversible....... The crystal to amorphous transition is irreversible. Our results point out that the amorphization process in Sc-2(MoO4)(3) may be due to a kinetic hindrance of a phase transition rather than due to chemical decomposition effects as have been proposed to occur for some molybdates and tungstates....

  11. Phase transformations of (Ca, Ti)-partially stabilized zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Hon Yungshon; Shen Pouyan (Inst. of Materials Science and Engineering, Nation Sun Yat-Sen Univ., Kaohsiung (Taiwan))

    1991-01-20

    The results of phase transformation and microstructural investigation of the ZrO{sub 2}-rich corner of the CaO-TiO{sub 2}-ZrO{sub 2} system are reported. Samples of Ca-PSZ powder (where PSZ is partially stabilized zirconia) containing 10.8 mol.% CaO, had added to them 0-14 mol.% TiO{sub 2} (designated specimens 0T to 14T). The samples were sintered at 1600deg C for 6 h and studied by X-ray diffraction and electron microscopy. Saturation of TiO{sub 2} in the cubic (c) zirconia was reached at a total TiO{sub 2} addition of about 4 mol.% at 1600deg C, whereas the solubility limit in tetragonal (t) zirconia was not reached in the composition range studied. The t-zirconia precipitates remained tweed in the cubic matrix for specimens 2T and 4T, but became lenticular with the (101) habit plane for specimens having a larger TiO{sub 2} content (e.g. 8T). The amount of t-zirconia increased with increasing TiO{sub 2} content at 1600deg C. The addition of TiO{sub 2} also enhanced the eutectoid decomposition of Ca-PSZ to form the PHI{sub 1}-phase (CaZr{sub 4}O{sub 9}). Calzirtite (Ca{sub 2}Zr{sub 5}Ti{sub 2}O{sub 16}) was precipitated from the shell of the zirconia grains in specimen 8T. (orig.).

  12. Derivation of transformation equations for the parameters that characterize a plane acoustic wave without using phase invariance and Lorentz-Einstein transformation

    OpenAIRE

    Rothenstein, Bernhard

    2005-01-01

    We show that the transformation equations for the parameters that characterize a plane acoustic wave: period, (frequency), wave vector, wave length and phase velocity can be derived without using phase invariance and Lorentz-Einstein transformation

  13. Small interfering ribonucleic acid induces liquid-to-ripple phase transformation in a phospholipid membrane

    Energy Technology Data Exchange (ETDEWEB)

    Choubey, Amit; Nomura, Ken-ichi; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya [Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States)

    2014-09-15

    Small interfering ribonucleic acid (siRNA) molecules play a pivotal role in silencing gene expression via the RNA interference mechanism. A key limitation to the widespread implementation of siRNA therapeutics is the difficulty of delivering siRNA-based drugs to cells. Here, we examine changes in the structure and dynamics of a dipalmitoylphosphatidylcholine bilayer in the presence of a siRNA molecule and mechanical barriers to siRNA transfection in the bilayer. Our all-atom molecular dynamics simulation shows that siRNA induces a liquid crystalline-to-ripple phase transformation in the bilayer. The ripple phase consists of a major region of non-interdigitated and a minor region of interdigitated lipid molecules with an intervening kink. In the ripple phase, hydrocarbon chains of lipid molecules have large compressive stresses, which present a considerable barrier to siRNA transfection.

  14. Low-temperature structural transformation and magnetic properties of GaMo4S8-type defect spinel compounds

    International Nuclear Information System (INIS)

    Shamraj, V.F.; Lejtus, G.M.

    1987-01-01

    Crystal structure and physical properties of GaMo 4 S 8 and GaM x Mo 4 S 8 (M=C, Si, Ge) phases, referring to magnetic semiconductors were investiagted at room and low temperatures. All investigated compounds in the range T p =30-45 K experience phase transformations. Theoretical group analysis of possible symmetry changes, supposing that observed crystal-phase transformation is the first-kind transformation, close to the second-kind one, is carried out. It is shown, that crystal-phase transformation is syfficient in forming magnetic properties of ''defect spinel'' type structural phases (Curie temperature T M ≅ 20 K). Superexchange interactions between magnetic moments, localized on molybdenum ions, are responsible for magnetic order

  15. Optimisation of Transmission Systems by use of Phase Shifting Transformers

    Energy Technology Data Exchange (ETDEWEB)

    Verboomen, J.

    2008-10-13

    In this thesis, transmission grids with PSTs (Phase Shifting Transformers) are investigated. In particular, the following goals are put forward: (a) The analysis and quantification of the impact of a PST on a meshed grid. This includes the development of models for the device; (b) The development of methods to obtain optimal coordination of several PSTs in a meshed grid. An objective function should be formulated, and an optimisation method must be adopted to solve the problem; and (c) The investigation of different strategies to use a PST. Chapter 2 gives a short overview of active power flow controlling devices. In chapter 3, a first step towards optimal PST coordination is taken. In chapter 4, metaheuristic optimisation methods are discussed. Chapter 5 introduces DC load flow approximations, leading to analytically closed equations that describe the relation between PST settings and active power flows. In chapter 6, some applications of the methods that are developed in earlier chapters are presented. Chapter 7 contains the conclusions of this thesis, as well as recommendations for future work.

  16. Analysis of reconstructed interference fields in digital holographic interferometry using the polynomial phase transform

    International Nuclear Information System (INIS)

    Gorthi, Sai Siva; Rastogi, Pramod

    2009-01-01

    A noisy wrapped phase map is the end-output of commonly employed phase estimation methods in digital holographic interferometry. Hence filtering and unwrapping are necessary to obtain continuous phase distributions. This paper introduces a new approach for phase estimation in digital holographic interferometry using the polynomial phase transform. The proposed approach directly provides an accurate estimation of the unwrapped phase distribution from a noisy reconstructed interference field, thereby bypassing cumbersome and error-prone filtering and 2D phase unwrapping procedures

  17. Ion transport and phase transformation in thin film intercalation electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Wunde, Fabian; Nowak, Susann; Muerter, Juliane; Hadjixenophontos, Efi; Berkemeier, Frank; Schmitz, Guido [Stuttgart Univ. (Germany). Inst. fuer Materialwissenschaft

    2017-11-15

    Thin film battery electrodes of the olivine structure LiFePO{sub 4} and the spinel phase LiMn{sub 2}O{sub 4} are deposited through ion-beam sputtering. The intercalation kinetics is studied by cyclo-voltammetry using variation of the cycling rate over 4 to 5 orders of magnitude. The well-defined layer geometry allows a detailed quantitative analysis. It is shown that LiFePO{sub 4} clearly undergoes phase separation during intercalation, although the material is nano-confined and very high charging rates are applied. We present a modified Randles-Sevcik evaluation adapted to phase-separating systems. Both the charging current and the overpotential depend on the film thickness in a systematic way. The analysis yields evidence that the grain boundaries are important short circuit paths for fast transport. They increase the electrochemical active area with increasing layer thickness. Evidence is obtained that the grain boundaries in LiFePO{sub 4} have the character of an ion-conductor of vanishing electronic conductivity.

  18. Investigating the phase transformations in starch during gelatinisation

    International Nuclear Information System (INIS)

    Tan, I.; Sopade, P.A.; Halley, P.J.

    2003-01-01

    Full text: Starch, a natural polymer of amylose and amylopectin, continues to be a prime material for biodegradable plastic applications as well as many food and non-food uses. Raw starch exists as semicrystalline granules with complex internal supramolecular packing and can be hierarchically organised on four length scales: molecular scale (∼ Angstroms), lamellar structure (∼90 Angstroms); growth rings (∼ 0.1 μm) and the whole granule morphology (∼μm). Starch can be converted into thermoplastic material (TPS) through destructurisation in the presence of plasticisers under specific extrusion conditions. During the transformation of granular starch into TPS, the complex granular supramolecular structure gives rise to the characteristic endothermic first order transition known as gelatinization. Despite advances in research on starch gelatinisation, the precise structural change and transitions involved are still a matter of debate. Moreover, structural variables such as botanical origins, amylose/amylopectin ratio, macromolecular sizes, etc, have been known to influence the physicochemical properties of starch and the transitions it undergoes.While understanding the linkage between structural characteristics and gelatinisation behaviour will provide fundamental knowledge that is critical for the development of next-generation starch biodegradable plastics, this has proved difficult mainly due to poor knowledge of the exact mechanism involved in gelatinisation. This is further complicated by the sketchy idea on the role of structure and organisation of the starch granule. Studies in our laboratory on four types of maize starches with different amylose/amylopectin ratio revealed that although there is a general trend on the variation of gelatinisation parameters with plasticisers concentration, the extent of the variation are different for different types of starch. It was also found that these differences are not a directly related to the variation in

  19. Structural transformations in MoO{sub x} thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Camacho-Lopez, M.A.; Haro-Poniatowski, E. [Departamento de Fisica, Laboratorio de Optica Cuantica, Universidad Autonoma Metropolitana Iztapalapa, Apdo. Postal 55-534, 09340, Mexico D. F. (Mexico); Escobar-Alarcon, L. [Departamento de Fisica, Instituto Nacional de Investigaciones Nucleares, Apdo. Postal 18-1027, 11801, Mexico D. F. (Mexico)

    2004-01-01

    In this work, laser-induced crystallization in MoO{sub x} thin films (1.8{<=}x{<=}2.1) is reported. This transformation involves a MoO{sub x} oxidation and subsequently a crystallization process from amorphous MoO{sub 3} to crystalline {alpha}MoO{sub 3}. For comparison purposes crystallization is induced thermally, in an oven, as well. The crystallization kinetics is monitored by Raman spectroscopy; a threshold in the energy density necessary to induce the phase transformation is determined in the case of photo-crystallization. This threshold depends on the type of substrate on which the film is deposited. For the thin films deposited on glass substrates, the structural transformation is from amorphous MoO{sub x} to the thermodynamically stable {alpha}MoO{sub 3} crystalline phase. For the thin films deposited on Si(100) the structural transformation is from amorphous MoO{sub x} to a mixture of {alpha}MoO{sub 3} and the thermodynamically unstable {beta}MoO{sub 3} crystalline phases. The structural transformations are also characterized by scanning electron microscopy and light-transmission experiments. (orig.)

  20. Structural Nervous System, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — GTL's SNS technology aids in the operation of new or existing structural health monitoring (SHM) systems by integrating data and power pathways into the structure....

  1. The influence of peak shock stress on the high pressure phase transformation in Zr

    International Nuclear Information System (INIS)

    Cerreta, E K; Addessio, F L; Bronkhorst, C A; Brown, D W; Escobedo, J P; Fensin, S J; Gray, G T III; Lookman, T; Rigg, P A; Trujillo, C P

    2014-01-01

    At high pressures zirconium is known to undergo a phase transformation from the hexagonal close packed (HCP) alpha phase to the simple hexagonal omega phase. Under conditions of shock loading, a significant volume fraction of high-pressure omega phase is retained upon release. However, the hysteresis in this transformation is not well represented by equilibrium phase diagrams and the multi-phase plasticity under shock conditions is not well understood. For these reasons, the influence of peak shock stress and temperature on the retention of omega phase in Zr has been explored. VISAR and PDV measurements along with post-mortem metallographic and neutron diffraction characterization of soft recovered specimens have been utilized to quantify the volume fraction of retained omega phase and qualitatively understand the kinetics of this transformation. In turn, soft recovered specimens with varying volume fractions of retained omega phase have been utilized to understand the contribution of omega and alpha phases to strength in shock loaded Zr.

  2. Strain-induced phase transformation behavior of stabilized zirconia ceramics studied via nanoindentation.

    Science.gov (United States)

    Liu, Erqiang; Xiao, Gesheng; Jia, Wufei; Shu, Xuefeng; Yang, Xuexia; Wang, Yulei

    2017-11-01

    To study the tetragonal-to-monoclinic (T-M) phase transformation behavior under different strain rates and indentation depths, nanoindentation tests were performed on stabilized zirconia ceramics with Continuous Stiffness Measurements. The results indicate decreased phase transformation velocities at both lower and higher strain rates, but increased velocity under medium strain rate during loading. The phase transformation process is sensitive to Ṗ/P but the final volume fractions are almost identical (45%). Furthermore, most of the phase transformation is completed during a short initial time followed by slight linear increase of the M-phase volume fraction with holding time. The phase transformation continuously slowed with increasing indentation depth when indented with a constant strain rate. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Structural transformations in liquid metallic glassformers

    International Nuclear Information System (INIS)

    Son, L.; Ryltcev, R.; Sidorov, V.; Sordelet, D.

    2007-01-01

    The statistics and thermodynamics of quasi-chemical bonds in glass forming liquid alloys have been described by method used in polymer statistics. It is shown that this bonging results in structural anomalies of two types. The first corresponds to relaxation of metastable globular state, which takes place at lower temperature, while the second one represents the drastic change of mean length of quasi-polymers

  4. Russian Population Ethnic Structure: Trends and Transformations

    Directory of Open Access Journals (Sweden)

    Safronov S.

    2015-08-01

    Full Text Available Based on the census data from 1989, 2002 and 2010, the article analyzes the evolution of the ethnic structure of the population of the post-Soviet Russia from the territorial perspective. The stability of the ethnic structure of the “Russian mega nucleus” and indigenization of the national regions are considered in view of the differences in migration trends during the two inter-census periods and the socioeconomic situation in the regions. The urbanization rate of major ethnic groups is an indirect indicator of the prospects of traditional “primordial” ethnic identities in different ethnic groups. Special attention is paid to new trends — an increase in the number of people refraining from answering the question about their ethnic identity or giving an unclear answer. Alongside serious census errors, this phenomenon can be a result of growing complexity of the ethnic identity structures and the processes of modernization, which occur at different rates in Russian and national regions. Based on the 2010 census data, the article analyses the differences in polyethnicity between the rural and urban population, which are accounted for by the historical background, particularities of regional development, settlement features, and migration processes of the past two decades.

  5. Features of order-disorder phase transformation in nonstoichiometric transition metals carbides

    International Nuclear Information System (INIS)

    Emel'yanov, A.N.

    1996-01-01

    Measurements of temperature and electric conductivity of nonstoichiometric transition metals carbides TiC χ and NbC χ in the area of order-disorder phase transformation are carried out. There are certain peculiarities on the temperature and electric conductivity curves of the carbides, connected with the carbon sublattice disordering. On the basis of the anomalies observed on the curves of the temperature conductivity of nonstoichiometric carbides of transition metals above the temperature of the order-disorder transition the existence of the second structural transition is supposed

  6. THREE-PHASE TRANSFORMER PARAMETERS CALCULATION CONSIDERING THE CORE SATURATION FOR THE MATLAB-SIMULINK TRANSFORMER MODEL

    Directory of Open Access Journals (Sweden)

    I. V. Novash

    2015-01-01

    Full Text Available This article describes the parameters calculation for the three-phase two-winding power transformer model taken from the SimPowerSystems library, which is the part of the MatLab- Simulink environment. Presented methodology is based on the power transformer nameplate data usage. Particular attention is paid to the power transformer magnetization curve para- meters  calculation.  The  methodology  of  the  three-phase  two-winding  power  transformer model parameters calculation considering the magnetization curve nonlinearity isn’t presented in Russian-and English-language sources. Power transformers demo models described in the SimPowerSystems user’s guide have already calculated parameters, but without reference to the sources of their determination. A power transformer is a nonlinear element of the power system, that’s why for its performance analysis in different modes of operation is necessary to have the magnetization curve parameters.The process analysis during no-load energizing of the power transformer is of special interest. This regime is accompanied by the inrush current on the supply side of the power transformer, which is several times larger than the transformer rated current. Sharp rising of the magnetizing current is explained by the magnetic core saturation. Therefore, magnetiza- tion characteristic accounting during transformer no-load energizing modeling is a mandatory requirement. Article authors attempt to put all calculating formulas in a more convenient form and validate the power transformer nonlinear magnetization characteristics parameters calcu- lation. Inrush current oscillograms obtained during the simulation experiment confirmed the adequacy of the calculated model parameters.

  7. A flow-through hydrothermal cell for in situ neutron diffraction studies of phase transformations

    International Nuclear Information System (INIS)

    O'Neill, Brian; Tenailleau, Christophe; Nogthai, Yung; Studer, Andrew; Brugger, Joel; Pring, Allan

    2006-01-01

    A flow-through hydrothermal cell for the in situ neutron diffraction study of crystallisation and phase transitions has been developed. It can be used for kinetic studies on materials that exhibit structural transformations under hydrothermal conditions. It is specifically designed for use on the medium-resolution powder diffractometer (MRPD) at ANSTO, Lucas Heights, Sydney. But it is planned to adapt the design for the Polaris beamline at ISIS and the new high-intensity powder diffractometer (Wombat) at the new Australian reactor Opal. The cell will operate in a flow-through mode over the temperature range from 25-300 deg. C and up to pressures of 100 bar. The first results of a successful transformation of pentlandite (Fe,Ni) 9 S 8 to violarite (Fe,Ni) 3 S 4 under mild conditions (pH∼4) at 120 deg. C and 3 bar using in situ neutron diffraction measurements are presented

  8. Symmetry structure and phase transitions

    Indian Academy of Sciences (India)

    Spontaneous symmetry breaking is one of the most important concepts of all unified gauge theories. The idea that ... stable configurations of gauge and Higgs fields in the form of domain walls, cosmic strings and monopoles on the ..... pressure to balance the surface tension and the pressure of the hadron phase. The quark.

  9. Phase transformation upon cooling path in Ca2SiO4: Possible geological implication

    Science.gov (United States)

    Chang, Yun-Ting; Kung, Jennifer; Hsu, Han

    2016-04-01

    At the contact metamorphism zone two different Ca2SiO4 phases can be found; calcio-olivine (γ phase) and larnite (β phase). In-situ experiments illustrated the existence of five various polymorphs in Ca2SiO4, i.e., α, α'H, α'L, β and γ. The path of phase transformation and the transformation temperatures are shown as follows. γ → α'L(700° C) → α'H(1100° C) → α (1450° C) α'L → β (680° C) → γ (500° C) Experiments showed that the phase transitions at lower temperature is not reversible and seemed to be complicated; β phase is only stable from 500° C to 680° C upon cooling. To understand the possible mechanism of the β phase being metastable at room temperature, atmosphere condition, we were motivated to investigate the route of phase transition in Ca2SiO4 in different thermal process. Powder samples were synthesized by the solid-state reaction. Pure reagent oxides CaCO3 and SiO2 were mixed in 2:1 stoichiometric mole. Two control factors were designated in the experiments; the sintering temperature of starting materials and the cooling path. The sintering temperature was set within the range of stable phase field of α'L phase (˜900° C) and α'H phase (1300° C). The cooling process was designed in three different routes: 1) the quenched procedure from sintering temperature with rate of 900° C/min and 1300° C/min, 2) the furnace cooling procedure, 3) set a slow cooling rate (0.265 ° C/min). The products were examined for the crystal structure by X-ray powder diffraction. First-principle calculation was also applied to investigate the thermodynamic properties of α'H, β and γ phases. A major finding in this study showed that the γ phase presented in the final product when the sintering temperature was set at the stable field of α'H phase; on the other hand, the β phase would present when the sintering temperature was set within the field of α'L phase. It was noted that the existing phase in the product would be modified by the

  10. Phase analysis of amplitude binary mask structures

    Science.gov (United States)

    Puthankovilakam, Krishnaparvathy; Scharf, Toralf; Herzig, Hans Peter; Vogler, Uwe; Bramati, Arianna; Voelkel, Reinhard

    2016-03-01

    Shaping of light behind masks using different techniques is the milestone of the printing industry. The aerial image distribution or the intensity distribution at the printing distances defines the resolution of the structure after printing. Contrast and phase are the two parameters that play a major role in shaping of light to get the desired intensity pattern. Here, in contrast to many other contributions that focus on intensity, we discuss the phase evolution for different structures. The amplitude or intensity characteristics of the structures in a binary mask at different proximity gaps have been analyzed extensively for many industrial applications. But the phase evolution from the binary mask having OPC structures is not considered so far. The mask we consider here is the normal amplitude binary mask but having high resolution Optical Proximity Correction (OPC) structures for corners. The corner structures represent a two dimensional problem which is difficult to handle with simple rules of phase masks design and therefore of particular interest. The evolution of light from small amplitude structures might lead to high contrast by creating sharp phase changes or phase singularities which are points of zero intensity. We show the phase modulation at different proximity gaps and can visualize the shaping of light according to the phase changes. The analysis is done with an instrument called High Resolution Interference Microscopy (HRIM), a Mach-Zehnder interferometer that gives access to three-dimensional phase and amplitude images. The current paper emphasizes on the phase measurement of different optical proximity correction structures, and especially on corners of a binary mask.

  11. Insight into the Effects of Reinforcement Shape on Achieving Continuous Martensite Transformation in Phase Transforming Matrix Composites

    Science.gov (United States)

    Zhang, Xudong; Ren, Junqiang; Wang, Xiaofei; Zong, Hongxiang; Cui, Lishan; Ding, Xiangdong

    2017-12-01

    A continuous martensite transformation is indispensable for achieving large linear superelasticity and low modulus in phase transforming metal-based composites. However, determining how to accurately condition the residual martensite in a shape memory alloy matrix though the reinforcement shape to achieve continuous martensite transformation has been a challenge. Here, we take the finite element method to perform a comparative study of the effects of nanoinclusion shape on the interaction and martensite phase transformation in this new composite. Two typical samples are compared: one reinforced by metallic nanowires and the other by nanoparticles. We find that the residual martensite within the shape memory alloy matrix after a pretreatment can be tailored by the reinforcement shape. In particular, our results show that the shape memory alloy matrix can retain enough residual martensite phases to achieve continuous martensite transformation in the subsequent loading when the aspect ratio of nanoreinforcement is larger than 20. In contrast, the composites reinforced with spherical or low aspect ratio reinforcement show a typical nonlinear superelasticity as a result of a low stress transfer-induced discontinuous martensite transformation within the shape memory alloy matrix.

  12. Thermal stability and phase transformation of metastable phases in Zr-Nb

    International Nuclear Information System (INIS)

    Aurelio, G.; Fernandez Guillermet, Armando

    2003-01-01

    The lattice parameters of the bcc (β) and (Ω) phases occurring metastability in a series of Zr-rich Zr-Nb alloys have been determined at and above room temperature (TR) using neutron diffraction techniques. In the first place, the effect of temperature changes upon the lattice parameters of the β and Ω phases in alloys with 10 and 18 at. % Nb was monitored using neutron thermo-diffraction. A method of analysis is applied to the data, which involve a confrontation between the observed structural properties and an idealized -or 'reference'- behavior (RB) which admits a simple mathematical description. A generalized form of the law of Vegard is adopted as RB for the β phase, whereas a specific RB is proposed for the Ω structure. The experimental data are well accounted for by this interpretation scheme, leading to a picture of the isothermal reactions occurring at high temperature, which involves the transfer of Nb from the Ω to the β phase. Finally, the neutron diffraction data on the Ω phase is combined with an electron microscopy study for the alloy with 10 at. % Nb aged at 773 K, which provides information on the composition of this phase and its evolution towards thermodynamic equilibrium. (author)

  13. The structural evolution and diffusion during the chemical transformation from cobalt to cobalt phosphide nanoparticles

    KAUST Repository

    Ha, Don-Hyung

    2011-01-01

    We report the structural evolution and the diffusion processes which occur during the phase transformation of nanoparticles (NPs), ε-Co to Co 2P to CoP, from a reaction with tri-n-octylphosphine (TOP). Extended X-ray absorption fine structure (EXAFS) investigations were used to elucidate the changes in the local structure of cobalt atoms which occur as the chemical transformation progresses. The lack of long-range order, spread in interatomic distances, and overall increase in mean-square disorder compared with bulk structure reveal the decrease in the NP\\'s structural order compared with bulk structure, which contributes to their deviation from bulk-like behavior. Results from EXAFS show both the Co2P and CoP phases contain excess Co. Results from EXAFS, transmission electron microscopy, X-ray diffraction, and density functional theory calculations reveal that the inward diffusion of phosphorus is more favorable at the beginning of the transformation from ε-Co to Co2P by forming an amorphous Co-P shell, while retaining a crystalline cobalt core. When the major phase of the sample turns to Co 2P, the diffusion processes reverse and cobalt atom out-diffusion is favored, leaving a hollow void, characteristic of the nanoscale Kirkendall effect. For the transformation from Co2P to CoP theory predicts an outward diffusion of cobalt while the anion lattice remains intact. In real samples, however, the Co-rich nanoparticles continue Kirkendall hollowing. Knowledge about the transformation method and structural properties provides a means to tailor the synthesis and composition of the NPs to facilitate their use in applications. © 2011 The Royal Society of Chemistry.

  14. Phase transformation kinetics and microstructure of NiTi shape ...

    Indian Academy of Sciences (India)

    2017-07-28

    Jul 28, 2017 ... Abstract. The effect of hydrostatic pressure on the behaviour of reverse and forward transformation temperatures and physical properties of NiTi shape memory alloy has been investigated. The transformation temperatures and physical prop- erties of the alloy change with applied pressure. It has been ...

  15. Peculiarities of phase transformation in Ni3Fe powder alloy

    International Nuclear Information System (INIS)

    Nuzhdin, A.A.

    1990-01-01

    Ordering process in sintered powder alloy Ni 3 Fe by normal and high temperatures was studied. Thermal stresses connected with porosity level of material effect on transformation peculiarities. The changes of electric conductivity, thermal expansion coefficient, bulk modulus during transformation were studied. The analysis of this changes was made

  16. Phase transformation kinetics and microstructure of NiTi shape ...

    Indian Academy of Sciences (India)

    2017-07-28

    Jul 28, 2017 ... stress and temperature, as the external driving forces, on the transformation. The shape memory effect is also related to the martensitic transformation that is essential, and an alloy exhibiting thermoelastic martensitic transition is deformed or bent at a temperature below the martensite finish temperature,.

  17. 16 channel WDM regeneration in a single phase-sensitive amplifier through optical Fourier transformation

    DEFF Research Database (Denmark)

    Guan, Pengyu; Da Ros, Francesco; Lillieholm, Mads

    2016-01-01

    We demonstrate simultaneous phase regeneration of 16-WDM DPSK channels using optical Fourier transformation and a single phase-sensitive amplifier. The BERs of 16-WDM×10-Gbit/s phase noise degraded DPSK signals are improved by 0.4-1.3 orders of magnitude......We demonstrate simultaneous phase regeneration of 16-WDM DPSK channels using optical Fourier transformation and a single phase-sensitive amplifier. The BERs of 16-WDM×10-Gbit/s phase noise degraded DPSK signals are improved by 0.4-1.3 orders of magnitude...

  18. All-optical WDM Regeneration of DPSK Signals using Optical Fourier Transformation and Phase Sensitive Amplification

    DEFF Research Database (Denmark)

    Guan, Pengyu; Røge, Kasper Meldgaard; Kjøller, Niels-Kristian

    2015-01-01

    We propose a novel all-optical WDM regeneration scheme for DPSK signals based on optical Fourier transformation and phase sensitive amplification. Phase regeneration of a WDM signal consisting of 4x10-Gbit/s phase noise degraded DPSK channels is demonstrated for the first time.......We propose a novel all-optical WDM regeneration scheme for DPSK signals based on optical Fourier transformation and phase sensitive amplification. Phase regeneration of a WDM signal consisting of 4x10-Gbit/s phase noise degraded DPSK channels is demonstrated for the first time....

  19. Deployable Composite Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA is seeking innovative structure technologies that will advance expandable exploration space modules and surface based habitats. To address this need CTD has...

  20. Structure properties and relaxor characteristics of the phases transformation in BaTi{sub 0.5}(Fe{sub 0.33}Mo{sub 0.17})O{sub 3} perovskite ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Bourguiba, Fayçal, E-mail: fayssalbourguiba@gmail.com [Laboratoire de la Matière Condensée et des Nanosciences, Département de Physique, Faculté des Sciences de Monastir, Monastir, 5019 (Tunisia); Dhahri, Ah.; Tahri, Tarek [Laboratoire de Physique appliqué, Département de physique, Faculté des sciences de, Sfax, 3018 (Tunisia); Dhahri, J. [Laboratoire de la Matière Condensée et des Nanosciences, Département de Physique, Faculté des Sciences de Monastir, Monastir, 5019 (Tunisia); Abdelmoula, N. [Laboratoire des Matériaux Ferroélectriques (LMF), LR-Physique-Mathématiques et Applications, Université de Sfax, Faculté des Sciences (FSS), Route de Soukra km 3.5 B.P 1171, 3000, Sfax (Tunisia); Taibi, K. [Laboratoire de Science et Génie des Matériaux, Faculté de Génie Mécanique et Génie des Procédés, Université des Sciences et de la Technologie Houari Boumediene BP32 El Alia, Bab Ezzouar, 16111, Alger (Algeria); Hlil, E.K. [Institut Néel, CNRS-Université J. Fourier, B.P. 166, 38042, Grenoble (France)

    2016-08-05

    The effect of replacing titanium by iron and molybdenum in the B site on the structural and physical properties of BaTi{sub 0.5}(Fe{sub 0.33}Mo{sub 0.17})O{sub 3} polycrystalline sample was investigated by X-ray diffraction, scanning electron microscopy (SEM) as well as dielectric characterizations. Crystal phase, microstructure, and dielectric property of the ceramic were examined. A single hexagonal perovskite structure with space group P6{sub 3}/mmc was obtained at 1400 °C and stabilized at room temperature. The microstructural study of the sintered pellets revealed that the plate-like grains are the typical grain morphologies in this ceramic. The temperature dependence of the dielectric properties was investigated in the frequency range 1 kHz to 1 MHz. Three dielectric relaxations were observed in the present ceramic at the temperature ranges of 330–473 K, 473–550 K and 650–800 K with a maximum in the dielectric permittivity (ε{sup ’}{sub r} ∼ 3518 at 443 K at 1 KHz, ε{sup ’}{sub r} ∼4335 at 502 K at 1 KHz and ε{sup ’}{sub r} ∼11,331 at 749 K at 1 KHz) that shifted to a higher temperature with increasing frequency. Temperature dependent variation of the dielectric constant showed a diffused phase transition which can be well described by fitting the modified Curie–Weiss relation, (1/ε{sup ‘}{sub r}–1/ε{sup ‘}{sub r,max})=(T–T{sub m}){sup γ}/C. - Highlights: • The BaTi{sub 0.5}(Fe{sub 0.33}Mo{sub 0.17})O{sub 3} ceramic was prepared by solid state reaction. • The sample crystallizes in the hexagonal P6{sub 3}/mmc structure. • Temperature dependency dielectric study showed relaxor kind phase transition for different temperature Regions.

  1. An absorbing phase transition from a structured active particle phase

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, Cristobal [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain); Ramos, Francisco [Departamento de Electromagnetismo y Fisica de la Materia and Instituto de Fisica Teorica y Computacional Carlos I, Facultad de Ciencias, Universidad de Granada, 18071 Granada (Spain); Hernandez-GarcIa, Emilio [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain)

    2007-02-14

    In this work we study the absorbing state phase transition of a recently introduced model for interacting particles with neighbourhood-dependent reproduction rates. The novelty of the transition is that as soon as the active phase is reached by increasing a control parameter a periodically arranged structure of particle clusters appears. A numerical study in one and two dimensions shows that the system falls into the directed percolation universality class.

  2. Liquid-solid surface phase transformation of fluorinated fullerene on monolayer tungsten diselenide

    KAUST Repository

    Song, Zhibo

    2018-04-04

    Hybrid van der Waals heterostructures constructed by the integration of organic molecules and two-dimensional (2D) transition metal dichalcogenide (TMD) materials have useful tunable properties for flexible electronic devices. Due to the chemically inert and atomically smooth nature of the TMD surface, well-defined crystalline organic films form atomically sharp interfaces facilitating optimal device performance. Here, the surface phase transformation of the supramolecular packing structure of fluorinated fullerene (C60F48) on single-layer tungsten diselenide (WSe2) is revealed by low-temperature scanning tunneling microscopy, from thermally stable liquid to solid phases as the coverage increases. Statistical analysis of the intermolecular interaction potential reveals that the repulsive dipole-dipole interaction induced by interfacial charge transfer and substrate-mediated interactions play important roles in stabilizing the liquid C60F48 phases. Theoretical calculations further suggest that the dipole moment per C60F48 molecule varies with the surface molecule density, and the liquid-solid transformation could be understood from the perspective of the thermodynamic free energy for open systems. This study offers insights into the growth behavior at 2D organic/TMD hybrid heterointerfaces.

  3. Liquid-solid surface phase transformation of fluorinated fullerene on monolayer tungsten diselenide

    Science.gov (United States)

    Song, Zhibo; Wang, Qixing; Li, Ming-Yang; Li, Lain-Jong; Zheng, Yu Jie; Wang, Zhuo; Lin, Tingting; Chi, Dongzhi; Ding, Zijing; Huang, Yu Li; Thye Shen Wee, Andrew

    2018-04-01

    Hybrid van der Waals heterostructures constructed by the integration of organic molecules and two-dimensional (2D) transition metal dichalcogenide (TMD) materials have useful tunable properties for flexible electronic devices. Due to the chemically inert and atomically smooth nature of the TMD surface, well-defined crystalline organic films form atomically sharp interfaces facilitating optimal device performance. Here, the surface phase transformation of the supramolecular packing structure of fluorinated fullerene (C60F48 ) on single-layer tungsten diselenide (WSe2) is revealed by low-temperature scanning tunneling microscopy, from thermally stable liquid to solid phases as the coverage increases. Statistical analysis of the intermolecular interaction potential reveals that the repulsive dipole-dipole interaction induced by interfacial charge transfer and substrate-mediated interactions play important roles in stabilizing the liquid C60F48 phases. Theoretical calculations further suggest that the dipole moment per C60F48 molecule varies with the surface molecule density, and the liquid-solid transformation could be understood from the perspective of the thermodynamic free energy for open systems. This study offers insights into the growth behavior at 2D organic/TMD hybrid heterointerfaces.

  4. The effect of zinc on the microstructure and phase transformations of casting Al-Cu alloys

    Directory of Open Access Journals (Sweden)

    Manasijević Ivana I.

    2016-01-01

    Full Text Available Copper is one of the main alloying elements for aluminum casting alloys. As an alloying element, copper significantly increases the tensile strength and toughness of alloys based on aluminum. The copper content in the industrial casting aluminum alloys ranges from 3,5 to 11 wt.%. However, despite the positive effect on the mechanical properties, copper has a negative influence on the corrosion resistance of aluminum and its alloys. In order to further improve the properties of Al-Cu alloys they are additional alloyed with elements such as zinc, magnesium and others. In this work experimental and analytical examination of the impact of zinc on the microstructure and phase transformations of Al-Cu alloys was carried out. In order to determine the effect of the addition of zinc to the structure and phase transformations of Al-Cu alloys two alloys of Al-Cu-Zn system with selected compositions were prepared and then examined using scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDX. The experimental results were compared with the results of thermodynamic calculations of phase equilibria.

  5. Orientational relationships between phases in the γ→α transformations for uranium-molybdenum alloys

    International Nuclear Information System (INIS)

    Brun, G.

    1966-04-01

    A crystallographic study has been made of the γ → α + γ transformation in the alloy containing 3 per cent by weight of molybdenum using electronic micro-diffraction; it has been possible to establish the orientational relationships governing the germination of the α phase in the γ phase. One finds: (111)γ // (100) α, (112-bar)γ // (010) α, (11-bar 0)γ // (001)α. By choosing a monoclinic lattice containing the same number of atoms as the orthorhombic lattice for defining the γ mother phase, the change in structure has been explained by adding a homogeneous (112-bar)γ [111]γ shearing deformation to a heterogeneous deformation brought about by slipping of the atoms which are not situated at the nodes of this lattice. The identity of the orientation relationships γ/α and γ/α''b and the loss of coherence γ /α as a function of temperature or of time lead to the conclusion that, in the range studied, the γ → α transformation begins with a martensitic process and continues by germination and growth. (author) [fr

  6. Crystal and morphological phase transformation of Pb(II) to Pb(IV) in chlorinated water

    International Nuclear Information System (INIS)

    Lytle, Darren A.; White, Colin; Nadagouda, Mallikarjuna N.; Worrall, Adam

    2009-01-01

    Herein, we show an important transformation of Pb(II) to Pb(IV) in chlorinated water under laboratory conditions. The study results will give an insight toward understanding how corrosion by-products on lead materials found in drinking water distribution systems develop and breakdown with time. The experiments were conducted to elucidate the morphology of lead (IV) oxide mineral transformation from hydrocerussite and its relationship to color change over a period of time. Scanning electron microscopy and transmission electron microscopy were used to describe the surface morphology, shape and size of lead solids. X-ray diffraction (XRD) analysis was performed to determine the mineral structure of lead solids. Solids analysis results were compared over a 14-day period of time to define changes in the crystal structure and morphology of lead solids. XRD analysis results of freshly synthesized lead solids showed that hydrocerussite, [Pb 3 (CO 3 ) 2 (OH) 2 ], was the only lead mineral present. After 14 days, a mixture of cerussite (PbCO 3 ) and α-PbO 2 and β-PbO 2 was present. Lead precipitates, i.e. hydrocerussite changed color from white to reddish brown confirming a transformation of the lead phase with time. This was correlated to a change in morphology from flower shaped crystals to hexagonal bars and submicron particles.

  7. Characterization, Modeling, and Energy Harvesting of Phase Transformations in Ferroelectric Materials

    Science.gov (United States)

    Dong, Wenda

    Solid state phase transformations can be induced through mechanical, electrical, and thermal loading in ferroelectric materials that are compositionally close to morphotropic phase boundaries. Large changes in strain, polarization, compliance, permittivity, and coupling properties are typically observed across the phase transformation regions and are phenomena of interest for energy harvesting and transduction applications where increased coupling behavior is desired. This work characterized and modeled solid state phase transformations in ferroelectric materials and assessed the potential of phase transforming materials for energy harvesting applications. Two types of phase transformations were studied. The first type was ferroelectric rhombohedral to ferroelectric orthorhombic observed in lead indium niobate lead magnesium niobate lead titanate (PIN-PMN-PT) and driven by deviatoric stress, temperature, and electric field. The second type of phase transformation is ferroelectric to antiferroelectric observed in lead zirconate titanate (PZT) and driven by pressure, temperature, and electric field. Experimental characterizations of the phase transformations were conducted in both PIN-PMN-PT and PZT in order to understand the thermodynamic characteristics of the phase transformations and map out the phase stability of both materials. The ferroelectric materials were characterized under combinations of stress, electric field, and temperature. Material models of phase transforming materials were developed using a thermodynamic based variant switching technique and thermodynamic observations of the phase transformations. These models replicate the phase transformation behavior of PIN-PMN-PT and PZT under mechanical and electrical loading conditions. The switching model worked in conjunction with linear piezoelectric equations as ferroelectric/ferroelastic constitutive equations within a finite element framework that solved the mechanical and electrical field equations

  8. In Situ TEM Nanoindentation Studies on Stress-Induced Phase Transformations in Metallic Materials

    Science.gov (United States)

    Liu, Y.; Wang, H.; Zhang, X.

    2016-01-01

    Although abundant phase transformations are in general thermally driven processes, there are many examples wherein stresses can induce phase transformations. Numerous in situ techniques, such as in situ x-ray diffraction and neutron diffraction, have been applied to reveal phase transformations. Recently, an in situ nanoindentation technique coupled with transmission electron microscopy demonstrated the capability to directly correlating stresses with phase transformations and microstructural evolutions at a submicron length scale. Here we briefly review in situ studies on stress-induced diffusional and diffusionless phase transformations in amorphous CuZrAl alloy and NiFeGa shape memory alloy. In the amorphous CuZrAl, in situ nanoindentation studies show that the nucleation of nanocrystals (a diffusional process) occurs at ultra-low stresses manifested by a prominent stress drop. In the NiFeGa shape memory alloy, two distinctive types of martensitic (diffusionless) phase transformations accompanied by stress plateaus are observed, including a reversible gradual phase transformation at low stress levels, and an irreversible abrupt phase transition at higher stress levels.

  9. For progress in natural science: Materials international investigations of structural phase transformation and THz properties across metal–insulator transition in VO2/Al2O3 epitaxial films

    Directory of Open Access Journals (Sweden)

    Mengmeng Yang

    2015-10-01

    Full Text Available Vanadium dioxide (VO2 epitaxial thin films on (0001-oriented Al2O3 substrates were prepared using radio frequency (RF magnetron sputtering techniques. To study the metal-insulator-transition (MIT mechanism and extend the applications of VO2 epitaxial films at terahertz (THz band, temperature-dependent X-ray diffraction (XRD and THz time domain spectroscopy of the VO2 epitaxial films were performed. Both the lattice constants and THz transmission exhibited a similar and sharp transition that was similar to that observed for the electrical resistance. Consequently, the MIT of the VO2/Al2O3 epitaxial films should be co-triggered by the structural phase transition and electronic transition. Moreover, the very large resistance change (on the order of ~103 and THz response (with a transmission modulation ratio of ~87% in the VO2/Al2O3 epitaxial heterostructures are promising for electrical switch and electro-optical device applications.

  10. Length scale effects and multiscale modeling of thermally induced phase transformation kinetics in NiTi SMA

    Science.gov (United States)

    Frantziskonis, George N.; Gur, Sourav

    2017-06-01

    Thermally induced phase transformation in NiTi shape memory alloys (SMAs) shows strong size and shape, collectively termed length scale effects, at the nano to micrometer scales, and that has important implications for the design and use of devices and structures at such scales. This paper, based on a recently developed multiscale model that utilizes molecular dynamics (MDs) simulations at small scales and MD-verified phase field (PhF) simulations at larger scales, reports results on specific length scale effects, i.e. length scale effects in martensite phase fraction (MPF) evolution, transformation temperatures (martensite and austenite start and finish) and in the thermally cyclic transformation between austenitic and martensitic phase. The multiscale study identifies saturation points for length scale effects and studies, for the first time, the length scale effect on the kinetics (i.e. developed internal strains) in the B19‧ phase during phase transformation. The major part of the work addresses small scale single crystals in specific orientations. However, the multiscale method is used in a unique and novel way to indirectly study length scale and grain size effects on evolution kinetics in polycrystalline NiTi, and to compare the simulation results to experiments. The interplay of the grain size and the length scale effect on the thermally induced MPF evolution is also shown in this present study. Finally, the multiscale coupling results are employed to improve phenomenological material models for NiTi SMA.

  11. Modelling and Analysis of Phase Transformations and Stresses in Laser Welding Process / Modelowanie I Analiza Przemian Fazowych I Naprężeń W Procesie Spawania Laserowego

    Directory of Open Access Journals (Sweden)

    Piekarska W.

    2015-12-01

    Full Text Available The work concerns the numerical modelling of structural composition and stress state in steel elements welded by a laser beam. The temperature field in butt welded joint is obtained from the solution of heat transfer equation with convective term. The heat source model is developed. Latent heat of solid-liquid and liquid-gas transformations as well as latent heats of phase transformations in solid state are taken into account in the algorithm of thermal phenomena. The kinetics of phase transformations in the solid state and volume fractions of formed structures are determined using classical formulas as well as Continuous-Heating-Transformation (CHT diagram and Continuous-Cooling-Transformation (CCT diagram during welding. Models of phase transformations take into account the influence of thermal cycle parameters on the kinetics of phase transformations during welding. Temporary and residual stress is obtained on the basis of the solution of mechanical equilibrium equations in a rate form. Plastic strain is determined using non-isothermal plastic flow with isotropic reinforcement, obeying Huber-Misses plasticity condition. In addition to thermal and plastic strains, the model takes into account structural strain and transformation plasticity. Changing with temperature and structural composition thermophysical parameters are included into constitutive relations. Results of the prediction of structural composition and stress state in laser butt weld joint are presented.

  12. Symmetry structure and phase transitions

    Indian Academy of Sciences (India)

    We study chiral symmetry structure at finite density and temperature in the presence of external magnetic field and .... the case of neutron stars as a function of chemical potential µ associated with finite baryon number density we ..... work expended to create a bubble and are given by Rc = 2σ Ph(T) Pq(T) and Wc = 4πσR2.

  13. The Structural Phase Transition in Solid DCN

    DEFF Research Database (Denmark)

    Dietrich, O. W.; Mackenzie, Gordon A.; Pawley, G. S.

    1975-01-01

    Neutron scattering measurements on deuterated hydrogen cyanide have shown that the structural phase change from a tetragonal to an orthorhombic form at 160K is a first-order transition. A transverse acoustic phonon mode, which has the symmetry of the phase change, was observed at very low energies...

  14. Composition dependence of phase transformation behavior and shape memory effect of Ti(Pt, Ir)

    International Nuclear Information System (INIS)

    Yamabe-Mitarai, Y.; Hara, T.; Kitashima, T.; Miura, S.; Hosoda, H.

    2013-01-01

    Highlights: ► The partial isothemal section at 1523 K was determined in Ti–Pt–Ir. ► The high-temperature shape memory effect of Ti(Pt, Ir) was investigated. ► The shape recovery ratio was 72% in Ti–10Pt–32Ir after deformation at 1123 K. ► Ir addition to TiPt is effective to improve shape memory effect of TiPt. -- Abstract: The phase transformation and high-temperature shape memory effect of Ti(Pt, Ir) were investigated. First, the Ti-rich phase boundary of Ti(Pt, Ir) was investigated by phase composition analysis by secondary electron microscopy (SEM) using an electron probe X-ray micro analyzer (EPMA), X-ray diffraction analysis and transmission electron microscopy (TEM). Then, the three alloys Ti–35Pt–10Ir, Ti–22Pt–22Ir, and Ti–10Pt–32Ir (at%) close to the phase boundary but in the single phase of Ti(Pt, Ir) were prepared by the arc melting method. The shape memory effect and crystal structure were investigated by compression loading–unloading tests and high-temperature X-ray diffraction analysis, respectively

  15. Phase transformations and indications for acoustic mode softening in Tb-Gd orthophosphate.

    Science.gov (United States)

    Tschauner, O; Ushakov, S V; Navrotsky, A; Boatner, L A

    2016-01-27

    At ambient conditions the anhydrous rare earth orthophosphates assume either the xenotime (zircon) or the monazite structure, with the latter favored for the heavier rare earths and by increasing pressure. Tb0.5Gd0.5PO4 assumes the xenotime structure at ambient conditions but is at the border between the xenotime and monazite structures. Here we show that, at high pressure, Tb0.5Gd0.5PO4 does not transform directly to monazite but through an intermediate anhydrite-type structure. Axial deformation of the unit cell near the anhydrite- to monazite-type transition indicates softening of the (c1133  +  c1313) combined elastic moduli. Stress response of rare-earth orthophosphate ceramics can be affected by both formation of the anhydrite-type phase and the elastic softening in the vicinity of the monazite-phase. We report the first structural data for an anhydrite-type rare earth orthophosphate.

  16. Phase transformation pathways of ultrafast-laser-irradiated Ln2O3 (Ln =Er -Lu )

    Science.gov (United States)

    Rittman, Dylan R.; Tracy, Cameron L.; Chen, Chien-Hung; Solomon, Jonathan M.; Asta, Mark; Mao, Wendy L.; Yalisove, Steven M.; Ewing, Rodney C.

    2018-01-01

    Ultrafast laser irradiation causes intense electronic excitations in materials, leading to transient high temperatures and pressures. Here, we show that ultrafast laser irradiation drives an irreversible cubic-to-monoclinic phase transformation in Ln2O3 (Ln =Er -Lu ), and explore the mechanism by which the phase transformation occurs. A combination of grazing incidence x-ray diffraction and transmission electron microscopy are used to determine the magnitude and depth-dependence of the phase transformation, respectively. Although all compositions undergo the same transformation, their transformation mechanisms differ. The transformation is pressure-driven for Ln =Tm -Lu , consistent with the material's phase behavior under equilibrium conditions. However, the transformation is thermally driven for Ln =Er , revealing that the nonequilibrium conditions of ultrafast laser irradiation can lead to novel transformation pathways. Ab initio molecular-dynamics simulations are used to examine the atomic-scale effects of electronic excitation, showing the production of oxygen Frenkel pairs and the migration of interstitial oxygen to tetrahedrally coordinated constitutional vacancy sites, the first step in a defect-driven phase transformation.

  17. Self-Structured Conductive Filament Nanoheater for Chalcogenide Phase Transition.

    Science.gov (United States)

    You, Byoung Kuk; Byun, Myunghwan; Kim, Seungjun; Lee, Keon Jae

    2015-06-23

    Ge2Sb2Te5-based phase-change memories (PCMs), which undergo fast and reversible switching between amorphous and crystalline structural transformation, are being utilized for nonvolatile data storage. However, a critical obstacle is the high programming current of the PCM cell, resulting from the limited pattern size of the optical lithography-based heater. Here, we suggest a facile and scalable strategy of utilizing self-structured conductive filament (CF) nanoheaters for Joule heating of chalcogenide materials. This CF nanoheater can replace the lithographical-patterned conventional resistor-type heater. The sub-10 nm contact area between the CF and the phase-change material achieves significant reduction of the reset current. In particular, the PCM cell with a single Ni filament nanoheater can be operated at an ultralow writing current of 20 μA. Finally, phase-transition behaviors through filament-type nanoheaters were directly observed by using transmission electron microscopy.

  18. Electro-Optic Imaging Fourier Transform Spectral Polarimeter, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Boulder Nonlinear Systems, Inc. (BNS) proposes to develop an Electro-Optic Imaging Fourier Transform Spectral Polarimeter (E-O IFTSP). The polarimetric system is...

  19. Low-pH-induced transformation of bilayer membrane into bicontinuous cubic phase in dioleoylphosphatidylserine/monoolein membranes.

    Science.gov (United States)

    Okamoto, Yoshihide; Masum, Shah Md; Miyazawa, Haruna; Yamazaki, Masahito

    2008-04-01

    Cubic biomembranes, nonbilayer membranes with connections in three-dimensional space that have a cubic symmetry, have been observed in various cells. Interconversion between the bilayer liquid-crystalline (L(alpha)) phase and cubic phases attracted much attention in terms of both biological and physicochemical aspects. Herein we report the pH effect on the phase and structure of dioleoylphosphatidylserine (DOPS)/monoolein (MO) membranes under a physiological ion concentration condition, which was revealed by small-angle X-ray scattering (SAXS) measurement. At neutral pH, DOPS/MO membranes containing high concentrations of DOPS were in the L(alpha) phase. First, the pH effect on the phase and structure of the multilamellar vesicles (MLVs) of the DOPS/MO membranes preformed at neutral pH was investigated by adding various low-pH buffers into the MLV suspension. For 20%-DOPS/80%-MO MLVs, at and below pH 2.9, a transition from the L(alpha) to cubic (Q(224)) phase occurred within 1 h. This phase transition was reversible; a subsequent increase in pH to a neutral one in the membrane suspension transformed the cubic phase into the original L(alpha) phase. Second, we found that a decrease in pH transformed large unilamellar vesicles of DOPS/MO membranes into the cubic phase under similar conditions. We have proposed the mechanism of the low-pH-induced phase transition and also made a quantitative analysis on the critical pH of the phase transition. This finding is the first demonstration that a change in pH can induce a reversible phase transition between the L(alpha) and cubic phases of lipid membranes within 1 h.

  20. Pressure-induced phase transformation in ZrW2O8 - Compressibility and thermal expansion of the orthorhombic phase

    International Nuclear Information System (INIS)

    Hu, Z.; Jorgensen, J.D.; Teslic, S.; Short, S.; Argyriou, D.N.

    1997-01-01

    In situ neutron powder diffraction has been used to show that the application of hydrostatic pressure at room temperature produces a transformation of ZrW 2 O 8 from the cubic to an orthorhombic phase beginning at 2.1 kbar and completed by 3.1 kbar, with a 5% reduction in volume. After release of pressure, the orthorhombic phase is retained at room temperature. Its thermal expansion is negative below room temperature, but is positive above room temperature with a transformation back to the cubic phase at about 390 K. The WO 4 groups are found to play the dominant role in both phase transformations. The volume compressibilities of the cubic and orthorhombic phases are 1.38 x 10 -3 and 1.53 x 10 -3 kbar -1 , respectively. (orig.)

  1. Phase Transformation and Shape Memory Effect of Ti-Pd-Pt-Zr High-Temperature Shape Memory Alloys

    Science.gov (United States)

    Yamabe-Mitarai, Yoko; Takebe, Wataru; Shimojo, Masayuki

    2017-12-01

    To understand the potential of high-temperature shape memory alloys, we have investigated the phase transformation and shape memory effect of Ti-(50 - x)Pt- xPd-5Zr alloys ( x = 0, 5, and 15 at.%), which present the B2 structure in the austenite phase and B19 structure in the martensite phase. Their phase transformation temperatures are very high; A f and M f of Ti-50Pt are 1066 and 1012 °C, respectively. By adding Zr and Pd, the phase transition temperatures decrease, ranging between 804 and 994 °C for A f and 590 and 865 °C for M f. Even at the high phase transformation temperature, a maximum recovery ratio of 70% was obtained for one cycle in a thermal cyclic test. A work output of 1.2 J/cm3 was also obtained. The recovery ratio obtained by the thermal cyclic test was less than 70% because the recovery strain was < 1% and a large irrecoverable strain was obtained. The shape recovery was explained by the austenite strength. The training effect was also investigated.

  2. Heterophase fluctuation of omega phase and X-ray diffuse scattering from dual phase structure

    International Nuclear Information System (INIS)

    Farjami, Susan; Kubo, Hiroshi

    2003-01-01

    Heterophase fluctuation of athermal omega embryos has been analyzed by assuming a dual phase structure of omega embryos composed of omega and bcc matrix phase. The two-dimensional modulation of dual phase was suggested from the quantitative estimation of coherent free energy of omega embryos using microscopic theory of elasticity and the Landau anharmonic theory for phase transformation. The X-ray diffraction theory was developed in connection to the formation of omega embryos having the dual phase structure. The offset of the diffuse peak position from the ideal omega point in the X-ray diffraction pattern is attributed to the dual phase (incommensurate phase) of omega embryos. It was also shown that the ellipsoidal shape of the diffuse intensity tailing toward the fundamental spot of the matrix phase is originated from the equilibrium shape of the omega embryo. The quantitative estimation of elastic energy modulus (EEM) in the disordered bcc matrix and in the ordered bcc matrix indicates a difference in the deviation amount of the minimum point k(q m ) from the ideal omega point k(q ω ) and a difference in the elliptical shape of embryos

  3. Phase image encryption in the fractional Hartley domain using Arnold transform and singular value decomposition

    Science.gov (United States)

    Singh, Phool; Yadav, A. K.; Singh, Kehar

    2017-04-01

    A novel scheme for image encryption of phase images is proposed, using fractional Hartley transform followed by Arnold transform and singular value decomposition in the frequency domain. Since the plaintext is a phase image, the mask used in the spatial domain is a random amplitude mask. The proposed scheme has been validated for grayscale images and is sensitive to the encryption parameters such as the order of the Arnold transform and the fractional orders of the Hartley transform. We have also evaluated the scheme's resistance to the well-known noise and occlusion attacks.

  4. Phase field study on crystal orientation effects in eutectoid phase transformation

    Directory of Open Access Journals (Sweden)

    Dong-qiao Zhang

    2017-11-01

    Full Text Available In this present work, a multi-phase field model was used to simulate the eutectoid transformation process, and on the basis of the nucleation model that was previously proposed by our research team, anisotropic and orientation relationship models were introduced to study the growth mechanism of the pearlite lamellae with anisotropy. It was found that the growth direction of the pearlite lamellae is related to its orientation and spacing. In the process of lamellar growth, deflection growth of pearlite will appear along with the adjustment of lamellar spacing, and the deflection angle is equal to the orientation difference between the austenite and the pearlite. Comparison between experimental and numerical results indicates a good consistency in pearlite morphology.

  5. Giant cardiac myxoma with malignant transformed glandular structures

    Energy Technology Data Exchange (ETDEWEB)

    Eckhardt, Boris P.; Stuckmann, Gerd; Zollikofer, Christoph L. [Institute of Radiology, Cantonal Hospital, Brauerstrasse 15, 8401 Winterthur (Switzerland); Dommann-Scherrer, Corina C. [Insitute of Pathology, Cantonal Hospital, Brauerstrasse 15, 8401 Winterthur (Switzerland); Wentz, Klaus U. [Institute of Radiology, Cantonal Hospital, Brauerstrasse 15, 8401 Winterthur (Switzerland); Medical Faculty, University of Witten/Herdecke, Alfred-Herrhausen-Strasse 50, 58448 Witten (Germany)

    2003-09-01

    A case of a right-sided giant cardiac myxoma with malignant transformation of glandular structures causing systemic metastases is described. Plain chest radiography and computed tomography localized the tumor within the heart. Exact depiction of the origin of the tumor using subtracted 2D-projection MR angiography is documented. Radiologic findings and differential diagnosis of this unique tumor are discussed. (orig.)

  6. Guest driven structural transformation studies of a luminescent metal ...

    Indian Academy of Sciences (India)

    ; crystal to crystal transformation; luminescence. ... On air drying the MOF loses free DCM molecules and changed its structure in a crystal to crystal manner to produce compound 1 [{Zn(L)2(OTf)2}.XG](1). This guest-induced breathing of the ...

  7. Deconstructing the BRICs : Structural Transformation and Aggregate Productivity Growth

    NARCIS (Netherlands)

    de Vries, Gaaitzen; Erumban, A. A.; Timmer, M.P.; Voskoboynikov, I.; Wu H.X., [No Value

    2011-01-01

    This paper studies structural transformation and its implications for productivity growth in the BRIC countries based on a new database that provides trends in value added and employment at a detailed 35-sector level. We find that for China, India and Russia reallocation of labour across sectors is

  8. On the use of Stockwell transform in structural dynamic analysis

    Indian Academy of Sciences (India)

    Wavelet transform has undertaken fast theoretical and application-oriented development in the last two ... earthquake and its application is demonstrated for the nonlinear response of three-story frame structure for the .... a huge number of records in seismology along with the recent big data studies in geophysics, astronomy ...

  9. Structural transformation, biased technological change, and employment in Vietnam

    DEFF Research Database (Denmark)

    Abbott, Philip; Tarp, Finn; Wu, Ce

    Employment in Vietnam and elsewhere in Asia has grown more slowly than GDP over the last several decades. This means GDP per capita is rising. Vietnamese policymakers, however, are concerned that ongoing structural transformation is creating too few jobs. We use data for seven aggregated sectors...

  10. Structural Transformation, Biased Technological Change, and Employment in Vietnam

    DEFF Research Database (Denmark)

    Abbott, Philip; Tarp, Finn; Wu, Ce

    2015-01-01

    Employment in Vietnam and elsewhere in Asia has grown more slowly than GDP over the last several decades. This means GDP per capita is rising. Vietnamese policymakers, however, are concerned that ongoing structural transformation is creating too few jobs. We use data for seven aggregated sectors...

  11. Estimation of phase derivative from a single fringe pattern using Riesz transforms

    Science.gov (United States)

    Tounsi, Yassine; Zada, Sara; Muhire, Desire; Siari, Ahmed; Nassim, Abdelkrim

    2017-11-01

    We propose a technique to estimate the phase derivative in both x and y directions based on Riesz transform from a single speckle correlation fringes. The originality of this technique is to exploit Riesz transform for phase derivatives estimation, spatial modulation, speckle denoising, and measure of features similarity. Phase modulation process is realized by combining a digital spatial carrier and Riesz quadrature; speckle denoising is computed using Riesz wavelets transform, and the performance is evaluated by Riesz features SIMilarity. Before applying our method on real speckle correlation fringes, its performance is tested by numerical simulation.

  12. First-principles screening of structural properties of intermetallic compounds on martensitic transformation

    Science.gov (United States)

    Lee, Joohwi; Ikeda, Yuji; Tanaka, Isao

    2017-11-01

    Martensitic transformation with good structural compatibility between parent and martensitic phases are required for shape memory alloys (SMAs) in terms of functional stability. In this study, first-principles-based materials screening is systematically performed to investigate the intermetallic compounds with the martensitic phases by focusing on energetic and dynamical stabilities as well as structural compatibility with the parent phase. The B2, D03, and L21 crystal structures are considered as the parent phases, and the 2H and 6M structures are considered as the martensitic phases. In total, 3384 binary and 3243 ternary alloys with stoichiometric composition ratios are investigated. It is found that 187 alloys survive after the screening. Some of the surviving alloys are constituted by the chemical elements already widely used in SMAs, but other various metallic elements are also found in the surviving alloys. The energetic stability of the surviving alloys is further analyzed by comparison with the data in Materials Project Database (MPD) to examine the alloys whose martensitic structures may cause further phase separation or transition to the other structures.

  13. Microstructure and structural phase transitions in iron-based superconductors

    International Nuclear Information System (INIS)

    Wang Zhen; Cai Yao; Yang Huai-Xin; Tian Huan-Fang; Wang Zhi-Wei; Ma Chao; Chen Zhen; Li Jian-Qi

    2013-01-01

    Crystal structures and microstructural features, such as structural phase transitions, defect structures, and chemical and structural inhomogeneities, are known to have profound effects on the physical properties of superconducting materials. Recently, many studies on the structural properties of Fe-based high-T c superconductors have been published. This review article will mainly focus on the typical microstructural features in samples that have been well characterized by physical measurements. (i) Certain common structural features are discussed, in particular, the crystal structural features for different superconducting families, the local structural distortions in the Fe 2 Pn 2 (Pn = P As, Sb) or Fe 2 Ch 2 (Ch = S, Se, Te) blocks, and the structural transformations in the 122 system. (ii) In FeTe(Se) (11 family), the superconductivity, chemical and structural inhomogeneities are investigated and discussed in correlation with superconductivity. (iii) In the K 0.8 Fe 1.6+x Se 2 system, we focus on the typical compounds with emphasis on the Fe-vacancy order and phase separations. The microstructural features in other superconducting materials are also briefly discussed. (topical review - iron-based high temperature superconductors)

  14. Structural and Compositional Transformations of Biomass Chars during Fast Pyrolysis

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Steibel, Markus; Spliethoff, Hartmut

    In this work the physical and chemical transformations of biomass chars during fast pyrolysis, considered as a 2nd stage of combustion, has been investigated. Seven biomasses containing different amount of ash and organic components were reacted at up to 1673 K with high heating rates in a wire......-mesh reactor and the resulting chars were retrieved. In order to obtain information on the structural and compositional transformations of the biomass chars, samples were subjected to elemental analysis, scanning electron microcopy with EDX and Raman spectrometry. The results show that there are significant...

  15. Phase transformation and deformation behavior of NiTi-Nb eutectic joined NiTi wires.

    Science.gov (United States)

    Wang, Liqiang; Wang, Cong; Zhang, Lai-Chang; Chen, Liangyu; Lu, Weijie; Zhang, Di

    2016-04-06

    NiTi wires were brazed together via eutectic reaction between NiTi and Nb powder deposited at the wire contact region. Phase transformation and deformation behavior of the NiTi-Nb eutectic microstructure were investigated using transmission electron microscopy (TEM) and cyclic loading-unloading tests. Results show that R phase and B19' martensite transformation are induced by plastic deformation. R phase transformation, which significantly contributes to superelasticity, preferentially occurs at the interfaces between NiTi and eutectic region. Round-shaped Nb-rich phase with rod-like and lamellar-type eutectics are observed in eutectic regions. These phases appear to affect the deformation behavior of the brazed NiTi-Nb region via five distinct stages in stress-strain curves: (I) R phase reorientation, (II) R phase transformation from parent phase, (III) elastic deformation of reoriented martensite accompanied by the plastic deformation of Nb-rich phase and lamellar NiTi-Nb eutectic, (IV) B19' martensitic transformation, and (V) plastic deformation of the specimen.

  16. Transient analyses using symmetrical component calculus in three-phase resistive and transformer-type SFCLs

    Science.gov (United States)

    Cho, Y. S.; Choi, H. S.; Jung, B. I.

    2010-11-01

    A transformer-type superconducting fault current limiter (SFCL) can control fault current by adjusting a turn's ratio of the primary and secondary windings. In addition, by inserting a neutral line into the secondary winding, the power burden of the superconducting elements can be evenly distributed. We compared the operating and transient characteristics of the three-phase resistive and transformer-type SFCLs in the balanced and unbalanced faults that occur in power systems. In transformer-type SFCLs, where the primary and secondary windings of each phase were connected to one iron core, flux was induced to each winding of the normal phases by the fault current of the fault phase, thus causing simultaneous quench between superconducting elements. In the three-phase power systems, however, when faults occurred in more than two phases, the flux from fault current of the fault phase affected the other normal phase, thus decreasing the reduction ratio of fault current. We confirmed, however, that the fault current was reduced by 70% relative to cases without SFCLs. The results of the analysis of the transient characteristics of the three-phase transformer-type SFCL through the symmetrical component calculus showed that in the case of triple line-to-ground fault, a difference between positive and negative phase currents was large enough to cause an increase in the phase angle (δ) between the generator creating the power and the motor acting as a load. Thus, we expect that the transient stability deteriorates.

  17. In situ HVEM studies of phase transformation in Zr alloys and compounds under irradiation

    International Nuclear Information System (INIS)

    Motta, A.T.; Faldowski, J.A.; Okamoto, P.R.

    1996-01-01

    The High Voltage Electron Microscope (HVEM)/Tandem facility at Argonne National Laboratory has been used to conduct detailed studies of the phase stability and microstructural evolution in zirconium alloys and compounds under ion and electron irradiation. Detailed kinetic studies of the crystalline-to-amorphous transformation of the intermetallic compounds Zr 3 (Fe 1-x Ni x ), Zr(Fe 1-x ,Cr x ) 2 , Zr 3 Fe, and Zr 1.5 Nb 1.5 Fe, both as second phase precipitates and in bulk form, have been performed using the in-situ capabilities of the Argonne facility, under a variety of irradiation conditions (temperature, dose rate). Results include a verification of a dose rate effect on amorphization and the influence of material variables (stoichiometry x, presence of stacking faults, crystal structure) on the critical temperature and on the critical dose for amorphization. Studies were also conducted of the microstructural evolution under irradiation of specially tailored binary and ternary model alloys. The stability of the ω-phase in Zr-20%Nb under electron and Ar ion irradiation was investigated as well as the β-phase precipitation in Zr-2.5%Nb under Ar ion irradiation. The ensemble of these results is discussed in terms of theoretical models of amorphization and of irradiation-altered solubility

  18. Study of effect of chromium on titanium dioxide phase transformation

    Indian Academy of Sciences (India)

    MTi samples with different atomic chromium percentages were synthesized by sol–gel method and calcined at 400 °C under air. The effects of Cr and temperature on titanium dioxide phase transition were studied. In situ measurement showed the presence of anatase phase for all samples at temperature < 500 °C. Without ...

  19. Study of effect of chromium on titanium dioxide phase transformation

    Indian Academy of Sciences (India)

    Administrator

    Abstract. MTiX samples with different atomic chromium percentages were synthesized by sol–gel method and calcined at 400 °C under air. The effects of Cr and temperature on titanium dioxide phase transition were studied. In situ measurement showed the presence of anatase phase for all samples at temperature < 500 ...

  20. Effect of isochronal annealing on phase transformation studies of ...

    Indian Academy of Sciences (India)

    train of nanomaterials is of crucial importance both from fundamental and application points of view. ... Phase transition and magnetic properties of iron oxide. NPs have been studied by Guo et al.13 They reported ... intermediate Fe3O4 phase and the magnetic properties were found to be strongly different from those of the ...

  1. Phase transformation kinetics and microstructure of NiTi shape

    Indian Academy of Sciences (India)

    It has been clearly seen from differential scanning calorimetry that with theincrease of applied pressure, while A s , A f and M f transformation temperatures decrease, Ms value increases. Moreover, it is obvious that with the increase of applied pressure, Gibbs free energy increases by 5.2883 J, while elastic energy increases ...

  2. Phase transformation kinetics and microstructure of NiTi shape ...

    Indian Academy of Sciences (India)

    It has been clearly seen from differential scanning calorimetry that with theincrease of applied pressure, while A s , A f and M f transformation temperatures decrease, Ms value increases. Moreover, it is obvious that with the increase of applied pressure, Gibbs free energy increases by 5.2883 J, while elastic energy increases ...

  3. Salt-occluded zeolite waste forms: Crystal structures and transformability

    International Nuclear Information System (INIS)

    Richardson, J.W. Jr.

    1996-01-01

    Neutron diffraction studies of salt-occluded zeolite and zeolite/glass composite samples, simulating nuclear waste forms loaded with fission products, have revealed complex structures, with cations assuming the dual roles of charge compensation and occlusion (cluster formation). These clusters roughly fill the 6--8 angstrom diameter pores of the zeolites. Samples are prepared by equilibrating zeolite-A with complex molten Li, K, Cs, Sr, Ba, Y chloride salts, with compositions representative of anticipated waste systems. Samples prepared using zeolite 4A (which contains exclusively sodium cations) as starting material are observed to transform to sodalite, a denser aluminosilicate framework structure, while those prepared using zeolite 5A (sodium and calcium ions) more readily retain the zeolite-A structure. Because the sodalite framework pores are much smaller than those of zeolite-A, clusters are smaller and more rigorously confined, with a correspondingly lower capacity for waste containment. Details of the sodalite structures resulting from transformation of zeolite-A depend upon the precise composition of the original mixture. The enhanced resistance of salt-occluded zeolites prepared from zeolite 5A to sodalite transformation is thought to be related to differences in the complex chloride clusters present in these zeolite mixtures. Data relating processing conditions to resulting zeolite composition and structure can be used in the selection of processing parameters which lead to optimal waste forms

  4. Extensively Reversible Thermal Transformations of a Bistable, Fluorescence-Switchable Molecular Solid: Entry into Functional Molecular Phase-Change Materials.

    Science.gov (United States)

    Srujana, P; Radhakrishnan, T P

    2015-06-15

    Functional phase-change materials (PCMs) are conspicuously absent among molecular materials in which the various attributes of inorganic solids have been realized. While organic PCMs are primarily limited to thermal storage systems, the amorphous-crystalline transformation of materials like Ge-Sb-Te find use in advanced applications such as information storage. Reversible amorphous-crystalline transformations in molecular solids require a subtle balance between robust supramolecular assembly and flexible structural elements. We report novel diaminodicyanoquinodimethanes that achieve this transformation by interlinked helical assemblies coupled with conformationally flexible alkoxyalkyl chains. They exhibit highly reversible thermal transformations between bistable (crystalline/amorphous) forms, along with a prominent switching of the fluorescence emission energy and intensity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Investigations of Temperatures of Phase Transformations of Low-Alloyed Reinforcing Steel within the Heat Treatment Temperature Range

    Directory of Open Access Journals (Sweden)

    Kargul T.

    2017-06-01

    Full Text Available The paper presents the results of DSC analysis of steel B500SP produced in the process of continuous casting, which is intended for the production reinforcement rods with high ductility. Studies were carried out in the temperature range below 1000°C in a protective atmosphere of helium during samples heating program. The main objective of the study was to determine the temperature range of austenite structure formation during heating. As a result of performed experiments: Ac1s, Ac1f – temperatures of the beginning and finish of the eutectoid transformation, Ac2 – Curie temperature of the ferrite magnetic transformation and the temperature Ac3 of transformation of proeutectoid ferrite into austenite were elaborated. Experimental determination of phase transformations temperatures of steel B500SP has great importance for production technology of reinforcement rods, because good mechanical properties of rods are formed by the special thermal treatment in Tempcore process.

  6. Nonlocal transformation of the internal quantum particle structure

    Directory of Open Access Journals (Sweden)

    Alexey Yu. Samarin

    2016-09-01

    Full Text Available The analysis of the integral wave equation, having path integral kernel, has resulted, that collapse phenomenon is based on the nonlocal transformation of the internal structure of a quantum particle, considering in the form of the matter fields collection. This nonlocality allows to escape the contradiction between the reduction quantum mechanics postulate and special relativity. It is shown, that the wave function transformation, corresponding to von Neumann's reduction, has the deterministic nature and the quantum mechanics stochasticity is a consequence of a macroscopic measurer presence in the measuring process. Besides it is demonstrated, that the decogerence phenomenon has the same mechanism of the wave function transformation. EPR-type experiment is described in detail and the possibility of the faster-then light communication is proved, as well the possible rules of thumb of this communication are proposed.

  7. Structural transformation in mechanosynthesized bcc Fe-Al-Si(Ge) solid solutions during heating

    International Nuclear Information System (INIS)

    Kubalova, L.M.; Sviridov, I.A.; Vasilyeva, O.Ya.; Fadeeva, V.I.

    2007-01-01

    X-ray diffractometry and Moessbauer spectroscopy study of Fe 50 Al 25 Si 25 and Fe 50 Al 25 Ge 25 alloys obtained by mechanical alloying (MA) of elementary powders was carried out. Phase transformation during heating of synthesized products was studied using differential scanning calorimetry (DSC). After 2.5 h of MA monophase alloys containing bcc Fe(Al, Ge) solid solutions Fe(Al, Si) are formed. Fe(Al, Si) is partially ordered B2 type and Fe(Al, Ge) is completely disordered. DSC curves of synthesized alloys displayed the presence of exothermal peaks caused by phase transformation. The metastable Fe(Al, Si) solid solution transformed into FeAl 1-x Si x (B2) and FeSi 1-x Al x (B20) equilibrium phases. The Fe(Al, Ge) solid solution transformed into equilibrium phases through intermediate stage of Fe 6 Ge 3 Al 2 metastable phase formation. The Fe 6 Ge 3 Al 2 phase dissociated into three equilibrium phases: FeAl 1-x Ge x (B2), χ-Fe 6 Ge 5 and η-Fe 13 (Ge, Al) 8 (B8 2 ). The structure of Fe 6 Ge 3 Al 2 was calculated by Rietveld method, the distribution of Al and Ge in the elementary cell and its parameters were calculated. Moessbauer study showed that Fe(Al, Si) and Fe(Al, Ge) solid solutions are paramagnetic. In the equilibrium state the alloy containing Si is also paramagnetic while the alloy with Ge showed ferromagnetic properties

  8. Elucidating the origins of phase transformation hysteresis during electrochemical cycling of Li–Sb electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Donghee [Materials Department; University of California; Santa Barbara; Santa Barbara, USA; Huo, Hua [Department of Chemistry; University of Cambridge; Cambridge, UK; Harbin Institute of Technology; School of Chemical Engineering & Technology; Johnston, Karen E. [Department of Chemistry; University of Cambridge; Cambridge, UK; Ménétrier, Michel [CNRS; Universite de Bordeaux; Pessac F33600, France; ALISTORE-ERI; FR CNRS#3104; Monconduit, Laure [Institut Charles Gerhardt Montpellier-UMR 5253 CNRS; ALISTORE European Research Institute (3104 CNRS); Université Montpellier 2; Montpellier, France; ALISTORE-ERI; Grey, Clare P. [Department of Chemistry; University of Cambridge; Cambridge, UK; Van der Ven, Anton [Materials Department; University of California; Santa Barbara; Santa Barbara, USA

    2015-01-01

    In this combined computational and experimental study, we identify the origins of phase transformation hysteresis during cycling of Sb electrodes, which undergoes alloying reactions upon lithiation.

  9. Phase transformations during sintering of mechanically alloyed TiPt

    CSIR Research Space (South Africa)

    Nxumalo, S

    2010-10-01

    Full Text Available first and high temperature melting phases form last12. This behaviour is what is observed in this work with the four phases with low melting points being formed which are Ti(Pt), Ti3Pt, TiPt and Ti3Pt5. It is therefore, probable that phase formation.... 1.0 Introduction TiPt is a potential alloy for use as a high temperature shape memory alloy (SMA). Shape memory alloys are alloys that will revert to the shape they had before deformation if the deformed alloy is annealed at a certain temperature...

  10. The influence of peak shock stress on the high pressure phase transformation in zirconium

    Directory of Open Access Journals (Sweden)

    Brown D.W.

    2012-08-01

    Full Text Available At high pressures zirconium is known to undergo a phase transformation from the hexagonal close packed (HCP alpha phase to the simple hexagonal omega phase. Under conditions of shock loading, the high-pressure omega phase is retained upon release. However, the hysteresis in this transformation is not well represented by equilibrium phase diagrams and currently models that accurately represent such a solid-solid phase transformation coupled with the multi-phase plasticity likely under shock conditions do not exist. For this reason, the influence of peak shock stress on the retention of omega phase in Zr is explored in this study. In-situ VISAR measurements along with post-mortem metallographic and neutron diffraction characterization of soft recovered specimens have been utilized to quantify the volume fraction of retained omega phase, morphology of the shocked alpha and omega phases, and qualitatively understand the kinetics of this transformation. This understanding of the role of peak shock stress will be utilized to address physics to be encoded in our present macro-scale models.

  11. Critical indices for reversible gamma-alpha phase transformation in metallic cerium

    Science.gov (United States)

    Soldatova, E. D.; Tkachenko, T. B.

    1980-08-01

    Critical indices for cerium have been determined within the framework of the pseudobinary solution theory along the phase equilibrium curve, the critical isotherm, and the critical isobar. The results obtained verify the validity of relationships proposed by Rushbrook (1963), Griffiths (1965), and Coopersmith (1968). It is concluded that reversible gamma-alpha transformation in metallic cerium is a critical-type transformation, and cerium has a critical point on the phase diagram similar to the critical point of the liquid-vapor system.

  12. Multi-stage phase retrieval algorithm based upon the gyrator transform.

    Science.gov (United States)

    Rodrigo, José A; Duadi, Hamootal; Alieva, Tatiana; Zalevsky, Zeev

    2010-01-18

    The gyrator transform is a useful tool for optical information processing applications. In this work we propose a multi-stage phase retrieval approach based on this operation as well as on the well-known Gerchberg-Saxton algorithm. It results in an iterative algorithm able to retrieve the phase information using several measurements of the gyrator transform power spectrum. The viability and performance of the proposed algorithm is demonstrated by means of several numerical simulations and experimental results.

  13. Multi-stage phase retrieval algorithm based upon the gyrator transform

    OpenAIRE

    Rodrigo Martín-Romo, José Augusto; Duadi, Hamootal; Alieva, Tatiana Krasheninnikova; Zalevsky, Zeev

    2010-01-01

    The gyrator transform is a useful tool for optical information processing applications. In this work we propose a multi-stage phase retrieval approach based on this operation as well as on the well-known Gerchberg-Saxton algorithm. It results in an iterative algorithm able to retrieve the phase information using several measurements of the gyrator transform power spectrum. The viability and performance of the proposed algorithm is demonstrated by means of several numerical simulations and exp...

  14. The kinetics of phase transformations during tempering of low alloy medium carbon steel

    OpenAIRE

    J. Krawczyk; J. Pacyna; P. Bała

    2007-01-01

    Purpose: This work contains a detailed description of the kinetics of phase transformations during tempering ofhardened low alloy medium carbon steel. Moreover, the differences in hardness and microstructure of samples ofthe investigated steel in relationship to the heat treatment were evaluated.Design/methodology/approach: CHT diagram, illustrating the kinetics of phase transformations duringcontinuous heating (tempering) from as-quenched state of investigated steel, was elaborated using a D...

  15. Fundamental Studies on Phase Transformations and Mechanical Properties of Fusion Welds in Advanced Naval Steels

    Science.gov (United States)

    2017-07-31

    Steel , Phase Transformations 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 18. NUMBER a. REPORT b.ABSTRACT c. THIS PAGE ABSTRACT OF PAGES u u...Studies on Phase Transformations and Mechanical Properties of Fusion Welds in Advanced Naval Steels Sb. GRANT NUMBER N00014-12-1-0475 Sc. PROGRAM...Release; distribution is unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT NUCu-140 and 10 wt% Ni steel were developed as candidate materials for use in

  16. In-situ Monitoring of Dynamic Phenomena during Solidification and Phase Transformation Processing

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Amy J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Cooley, Jason C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Morris, Christopher [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Merrill, Frank E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hollander, Brian J [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mariam, Fesseha G [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Patterson, Brian M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Imhoff, Seth D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lee, Wah Keat [Brookhaven National Lab. (BNL), Upton, NY (United States); Fezzaa, Kamel [Argonne National Lab. (ANL), Argonne, IL (United States); Deriy, Alex [Argonne National Lab. (ANL), Argonne, IL (United States); Tucker, Tim J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Clarke, Kester D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Field, Robert D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Thoma, Dan J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Teter, David F. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Beard, Timothy V. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hudson, Richard W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Freibert, Franz J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Korzekwa, Deniece R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Farrow, Adam M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Cross, Carl E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mihaila, Bogdan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lookman, Turab [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hunter, Abigail [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Choudhury, Samrat [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karma, Alain [Northeastern Univ., Boston, MA (United States); Ott, Jr., Thomas J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Barker, Martha R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); O' Neill, Finian [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hill, Joshua [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Emigh, Megan G. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2012-07-30

    The purpose of this project is to: (1) Directly observe phase transformations and microstructure evolution using proton (and synchrotron x-ray) radiography and tomography; (2) Constrain phase-field models for microstructure evolution; (3) Experimentally control microstructure evolution during processing to enable co-design; and (4) Advance toward the MaRIE vision. Understand microstructure evolution and chemical segregation during solidification {yields} solid-state transformations in Pu-Ga.

  17. The Physics of Structural Phase Transitions

    CERN Document Server

    Fujimoto, Minoru

    2005-01-01

    Phase transitions in which crystalline solids undergo structural changes present an interesting problem in the interplay between the crystal structure and the ordering process that is typically nonlinear. Intended for readers with prior knowledge of basic condensed-matter physics, this book emphasizes the physics behind spontaneous structural changes in crystals. Starting with the relevant thermodynamic principles, the text discusses the nature of order variables in collective motion in structural phase transitions, where a singularity in such a collective mode is responsible for lattice instability as revealed by soft phonons. In this book, critical anomalies at second-order structural transitions are first analyzed with the condensate model. Discussions on the nonlinear ordering mechanism are followed with the soliton theory, thereby interpreting the role of long-range order. Relevant details for nonlinear mathematics are therefore given for minimum necessity. The text also discusses experimental methods fo...

  18. Thermodynamics and phase transformations the selected works of Mats Hillert

    CERN Document Server

    Lilensten, Jean

    2006-01-01

    This book is a compendium of Mat Hillert's publications. Mat Hillert is a world specialist in metal alloy at the origin of a universal computing code used to calculate the diagrams of phase. This work is in English.

  19. Adaptation to developmental transformations during the various phases of motherhood.

    Science.gov (United States)

    Trad, P V

    1991-01-01

    The developmental processes that surround pregnancy and motherhood exert powerful and all-encompassing effects on the lives of the women undergoing such changes. Research has recently determined that the physiological and emotional transformations that occur in pregnant women may have a significant impact on the relationship that gradually develops between mothers and their infants. The growth of this relationship with the infant is directly related to the developmental challenges confronting the expectant women and new mother. Although many women are fearful or ambivalent about expressing their emotions during such periods of developmental change because of the implications of such feelings, exploratory work that encourages the disclosure of dreams and fantasies often enables the therapist to predict the patient's future ability to cope with the challenges of motherhood. This article examines five cases in which the developmental transformations experienced by the woman during the antenatal and postnatal periods significantly influenced the evolution of an attachment relationship with the infant.

  20. Modelling laser-induced phase transformations in semiconductors

    Czech Academy of Sciences Publication Activity Database

    Gatskevich, E.; Přikryl, Petr; Ivlev, G.

    2007-01-01

    Roč. 76, č. 1 (2007), s. 65-72 ISSN 0378-4754. [MODELLING 2005. Plzeň, 04.07.2005-08.07.2005] R&D Projects: GA ČR GA201/04/1503 Institutional research plan: CEZ:AV0Z10190503 Keywords : laser-induced phase transitions * moving boundary problem * non-equilibrium phase changer Subject RIV: BA - General Mathematics Impact factor: 0.738, year: 2007

  1. Grid-Based Fourier Transform Phase Contrast Imaging

    Science.gov (United States)

    Tahir, Sajjad

    Low contrast in x-ray attenuation imaging between different materials of low electron density is a limitation of traditional x-ray radiography. Phase contrast imaging offers the potential to improve the contrast between such materials, but due to the requirements on the spatial coherence of the x-ray beam, practical implementation of such systems with tabletop (i.e. non-synchrotron) sources has been limited. One recently developed phase imaging technique employs multiple fine-pitched gratings. However, the strict manufacturing tolerances and precise alignment requirements have limited the widespread adoption of grating-based techniques. In this work, we have investigated a technique recently demonstrated by Bennett et al. that utilizes a single grid of much coarser pitch. Our system consisted of a low power 100 microm spot Mo source, a CCD with 22 microm pixel pitch, and either a focused mammography linear grid or a stainless steel woven mesh. Phase is extracted from a single image by windowing and comparing data localized about harmonics of the grid in the Fourier domain. A Matlab code was written to perform the image processing. For the first time, the effects on the diffraction phase contrast and scattering amplitude images of varying grid types and periods, and of varying the window function type used to separate the harmonics, and the window widths, were investigated. Using the wire mesh, derivatives of the phase along two orthogonal directions were obtained and new methods investigated to form improved phase contrast images.

  2. Characterizing Phase Transformations and Their Effects on Ferritic Weld Residual Stresses with X-Rays and Neutrons

    Science.gov (United States)

    Dai, H.; Francis, J. A.; Stone, H. J.; Bhadeshia, H. K. D. H.; Withers, P. J.

    2008-12-01

    Weld residual stresses often approach, or exceed, the yield strength of the material, with serious implications for the integrity of engineering structures. It is not always feasible to measure residual stresses, so integrity assessments often rely heavily on numerical models. In ferritic steels, the credibility of such models depends on their ability to account for solid-state phase transformations, which can have a controlling effect on the final residual stress state. Furthermore, a better understanding of weld transformations provides an opportunity to engineer the weld stress state and microstructure for improved life. In this article, the complementary merits of synchrotron X-ray and neutron diffraction are exploited both to verify and refine weld models and to inspire the development of weld filler metals to control weld stresses. In terms of weld filler metal design, X-ray diffraction is used to characterize phase transformations in real time during realistic weld cooling cycles, for understanding small-scale behavior and identifying features that need to be incorporated into finite-element models. Meanwhile, neutron diffraction is used to elucidate the practical consequences of solid-state phase transformations on the macroscopic scale, thereby providing crucial validatory structural integrity data.

  3. Phases of the transformation of the energy system. A holistic view of all conversion chains and consumption sectors

    International Nuclear Information System (INIS)

    Henning, Hans-Martin; Palzer, Anderas; Pape, Carsten; Borggrefe, Frieder; Jachmann, Henning; Fischedick, Manfred

    2015-01-01

    The transformation of the German energy system towards a significant reduction of energy-related CO 2 emissions can be described by a sequence of different phases. Phase transitions result from individual structural requirements in the overall system under continuous further development of renewable energy converters, in particular solar and wind power. The upcoming second phase of transformation is characterized by a comprehensive system integration of volatile renewable energy in particular in the field of electricity supply. This requires both a flexible complementary production as well as the activation of flexibility options on the consumption side. The main drives for the reconstruction of the German energy system are the climate policy goals of the Federal Government. [de

  4. In situ investigation of ordering phase transformations in FePt magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wittig, James E., E-mail: j.wittig@vanderbilt.edu [Interdisciplinary Materials Science, Vanderbilt University, PMB 351683, 2301 Vanderbilt Place, Nashville, TN 37232 (United States); Bentley, James, E-mail: bentleyj48@gmail.com [Materials Science and Technology Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6376 (United States); Allard, Lawrence F., E-mail: allardlfjr@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6376 (United States)

    2017-05-15

    In situ high-resolution electron microscopy was used to reveal information at the atomic level for the disordered-to-ordered phase transformation of equiatomic FePt nanoparticles that can exhibit outstanding magnetic properties after transforming from disordered face-centered-cubic into the tetragonal L1{sub 0} ordered structure. High-angle annular dark-field imaging in the scanning transmission electron microscope provided sufficient contrast between the Fe and Pt atoms to readily monitor the ordering of the atoms during in situ heating experiments. However, during continuous high-magnification imaging the electron beam influenced the kinetics of the transformation so annealing had to be performed with the electron beam blanked. At 500 °C where the reaction rate was relatively slow, observation of the transformation mechanisms using this sequential imaging protocol revealed that ordering proceeded from (002) surface facets but was incomplete and multiple-domain particles were formed that contained anti-phase domain boundaries and anti-site defects. At 600 and 700 °C, the limitations of sequential imaging were revealed as a consequence of increased transformation kinetics. Annealing for only 5 min at 700 °C produced complete single-domain L1{sub 0} order; such single-domain particles were more spherical in shape with (002) facets. The in situ experiments also provided information concerning nanoparticle sintering, coalescence, and consolidation. Although there was resistance to complete sintering due to the crystallography of L1{sub 0} order, the driving force from the large surface-area-to-volume ratio resulted in considerable nanoparticle coalescence, which would render such FePt nanoparticles unsuitable for use as magnetic recording media. Comparison of the in situ data acquired using the protocol described above with parallel ex situ annealing experiments showed that identical behavior resulted in all cases. - Highlights: • HAADF STEM imaging reveals the

  5. Study of the Isothermal Oxidation Process and Phase Transformations in B2-(Ni,PtAl/RENE-N5 System

    Directory of Open Access Journals (Sweden)

    Luis Alberto Cáceres-Díaz

    2016-09-01

    Full Text Available Changes in composition, crystal structure and phase transformations of B2-(Ni,PtAl coatings upon isothermal oxidation experiments (natural and scale free oxidation at 1100 °C, as a function of time beyond their martensitic transformation, are reported. Specifically, the analysis of lattice parameter and composition are performed to identify changes in the B2-(Ni,PtAl phase upon the chemically-driven L10-(Ni,PtAl and L12-(Ni,Pt3Al transformations. The B2-(Ni,PtAl phase was found to disorder and transform the martensite during the heat treatments for both oxidation experiments at approximately 36.3 and 40.9 at. % of Al, 47.7 and 42.9 at. % of Ni, 6.2 and 8.5 at. % of Pt, 4.2 and 2.9 at. % of Cr and 4.4 and 3.8 at. % of Co. The lattice constant and the long-range order parameter of the B2-(Ni,PtAl phase decreased linearly as a function of the elemental content irrespective of the nature of the oxidation experiments.

  6. Structural transformation of nickel hydroxide films during anodic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Crocker, Robert W. [Univ. of California, Berkeley, CA (United States); Muller, Rolf H. [Univ. of California, Berkeley, CA (United States)

    1992-05-01

    The transformation of anodically formed nickel hydroxide/oxy-hydroxide electrodes has been investigated. A mechanism is proposed for the anodic oxidation reaction, in which the reaction interface between the reduced and oxidized phases of the electrode evolves in a nodular topography that leads to inefficient utilization of the active electrode material. In the proposed nodular transformation model for the anodic oxidation reaction, nickel hydroxide is oxidized to nickel oxy-hydroxide in the region near the metal substrate. Since the nickel oxy-hydroxide is considerably more conductive than the surrounding nickel hydroxide, as further oxidation occurs, nodular features grow rapidly to the film/electrolyte interface. Upon emerging at the electrolyte interface, the reaction boundary between the nickel hydroxide and oxy-hydroxide phases spreads laterally across the film/electrolyte interface, creating an overlayer of nickel oxy-hydroxide and trapping uncharged regions of nickel hydroxide within the film. The nickel oxy-hydroxide overlayer surface facilitates the oxygen evolution side reaction. Scanning tunneling microscopy of the electrode in its charged state revealed evidence of 80 - 100 Angstrom nickel oxy-hydroxide nodules in the nickel hydroxide film. In situ spectroscopic ellipsometer measurements of films held at various constant potentials agree quantitatively with optical models appropriate to the nodular growth and subsequent overgrowth of the nickel oxy-hydroxide phase. A two-dimensional, numerical finite difference model was developed to simulate the current distribution along the phase boundary between the charged and uncharged material. The model was used to explore the effects of the physical parameters that govern the electrode behavior. The ratio of the conductivities of the nickel hydroxide and oxy-hydroxide phases was found to be the dominant parameter in the system.

  7. Structural transformation of nickel hydroxide films during anodic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Crocker, R.W.; Muller, R.H.

    1992-05-01

    The transformation of anodically formed nickel hydroxide/oxy-hydroxide electrodes has been investigated. A mechanism is proposed for the anodic oxidation reaction, in which the reaction interface between the reduced and oxidized phases of the electrode evolves in a nodular topography that leads to inefficient utilization of the active electrode material. In the proposed nodular transformation model for the anodic oxidation reaction, nickel hydroxide is oxidized to nickel oxy-hydroxide in the region near the metal substrate. Since the nickel oxy-hydroxide is considerably more conductive than the surrounding nickel hydroxide, as further oxidation occurs, nodular features grow rapidly to the film/electrolyte interface. Upon emerging at the electrolyte interface, the reaction boundary between the nickel hydroxide and oxy-hydroxide phases spreads laterally across the film/electrolyte interface, creating an overlayer of nickel oxy-hydroxide and trapping uncharged regions of nickel hydroxide within the film. The nickel oxy-hydroxide overlayer surface facilitates the oxygen evolution side reaction. Scanning tunneling microscopy of the electrode in its charged state revealed evidence of 80 {endash} 100 Angstrom nickel oxy-hydroxide nodules in the nickel hydroxide film. In situ spectroscopic ellipsometer measurements of films held at various constant potentials agree quantitatively with optical models appropriate to the nodular growth and subsequent overgrowth of the nickel oxy-hydroxide phase. A two-dimensional, numerical finite difference model was developed to simulate the current distribution along the phase boundary between the charged and uncharged material. The model was used to explore the effects of the physical parameters that govern the electrode behavior. The ratio of the conductivities of the nickel hydroxide and oxy-hydroxide phases was found to be the dominant parameter in the system.

  8. The Influence of Mo, Cr and B Alloying on Phase Transformation and Mechanical Properties in Nb Added High Strength Dual Phase Steels

    Science.gov (United States)

    Girina, O.; Fonstein, N.; Yakubovsky, O.; Panahi, D.; Bhattacharya, D.; Jansto, S.

    The influence of Nb, Mo, Cr and B on phase transformations and mechanical properties are studied in a 0.15C-2.0Mn-0.3Si-0.020Ti dual phase steel separately and in combination. The formation and decomposition of austenite together with recrystallization of ferrite are evaluated by dilatometry and constructed CCT-diagrams in laboratory processed cold rolled material cooled after full austenitization and from intercritical temperature range. The effect of alloying elements on formation of austenite through their effect on initial hot rolled structure is taken into account. The interpretation of phase transformations during heating and cooling is supported by metallography. The effect of alloying elements on mechanical properties and structure are evaluated by annealing simulations. It has been shown that mechanical properties are strongly influenced by alloying additions such as Nb, Mo, Cr and B through their effect on ferrite formation during continuous cooling and corresponding enrichment of remaining austenite by carbon. Depending on combined effect of these alloying elements, different phase transformations can be promoted during cooling. This allows controlling of final microstructural constituents and mechanical properties.

  9. Laser induced structural transformation in chalcogenide based superlattices

    International Nuclear Information System (INIS)

    Zallo, Eugenio; Wang, Ruining; Bragaglia, Valeria; Calarco, Raffaella

    2016-01-01

    Superlattices made of alternating layers of nominal GeTe and Sb 2 Te 3 have been studied by micro-Raman spectroscopy. A structural irreversible transformation into ordered GeSbTe alloy is induced by high power laser light exposure. The intensity ratio of anti-Stokes and Stokes scattering under laser illumination gives a maximum average temperature in the sample of 177 °C. The latter is lower than the growth temperature and of 400 °C necessary by annealing to transform the structure in a GeSbTe alloy. The absence of this configuration after in situ annealing even up to 300 °C evidences an electronic excitation induced-transition which brings the system into a different and stable crystalline state.

  10. Laser induced structural transformation in chalcogenide based superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Zallo, Eugenio, E-mail: zallo@pdi-berlin.de; Wang, Ruining; Bragaglia, Valeria; Calarco, Raffaella [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2016-05-30

    Superlattices made of alternating layers of nominal GeTe and Sb{sub 2}Te{sub 3} have been studied by micro-Raman spectroscopy. A structural irreversible transformation into ordered GeSbTe alloy is induced by high power laser light exposure. The intensity ratio of anti-Stokes and Stokes scattering under laser illumination gives a maximum average temperature in the sample of 177 °C. The latter is lower than the growth temperature and of 400 °C necessary by annealing to transform the structure in a GeSbTe alloy. The absence of this configuration after in situ annealing even up to 300 °C evidences an electronic excitation induced-transition which brings the system into a different and stable crystalline state.

  11. The transformation of amorphous calcium carbonate, ACC, to crystalline phases as function of time and temperature.

    Science.gov (United States)

    Gies, Hermann; Happel, Marian; Niedermayr, Andrea; Immenhauser, Adrian

    2017-04-01

    We present results from a structural study of the transformation of freeze dried amorphous calcium carbonate, ACC, in crystalline material using pair distribution function analysis, PDF analysis, of X-ray powder diffraction data, XPD data. PDF analysis allows for the analysis of local order of structural subunit in the range between molecular unit (1. and 2. coordination sphere) and long range periodicity as in crystalline materials. ACC was precipitated from aqueous solutions at 298 K and 278 K using different amounts of Mg cations as stabilizer. The samples were immediately separated from the solution and freeze dried. For the transformation study, the samples were heated and analysed using XPD until they were crystallized. The radial distribution obtained from the XPD data were compared to simulated radial distributions of the calcium carbonate polymorphs and their hydrated phases. An ACC precipitated from a solution with Ca:Mg:CO3 = 1:5:4 at 298 K (ration in mmol, pH = 8.2) and freeze dried right after isolation from the solution revealed a close resemblance with ikaite in its local order. Another ACC with Ca:Mg:CO3 = 1:10:1.4 (T = 298, pH = 8.7) showed distinctly different local order resembling monohydrocalcite. Both ACC, however, still had considerable amounts of water dominating the Ca-coordination sphere. During the transformation to calcite, the structural changes in the sample concerned the hydrate water coordinating Ca which was removed and replaced by the carbonate oxygens. The study shows that ACC obtained from different starting solutions show specific local order. Freeze drying leads to solid ACC powder which still contain considerable amounts of hydrate water. Structural subunits are distinct in ACC and different from the crystalline phase. The study supplements recent reports presented by Konrad et al., Purgstaller et al., and Tobler et al.. F. Konrad et al., Cryst. Growth Des. 16, 6310-6317(2016) B. Purgstaller et al., Geochimica et Cosmochimica

  12. Preparation of 147Pm metal and the determination of the melting point and phase transformation temperatures

    International Nuclear Information System (INIS)

    Angelini, P.; Adair, H.L.

    1976-07-01

    The promethium metal used in the determination of the melting point and phase transformation temperatures was prepared by reduction of promethium oxide with thorium metal at 1600 0 C and distilling the promethium metal into a quartz dome. The melting point and phase transformation temperatures of promethium metal were found to be 1042 +- 5 0 C and 890 +- 5 0 C, respectively. The ratio for the heat of the high-temperature transformation to the heat of fusion was determined to be 0.415

  13. Learning an environment-actor coordination skill: visuomotor transformation and coherency of perceptual structure.

    Science.gov (United States)

    Ryu, Young U; Buchanan, John J

    2009-06-01

    The coordination dynamics of learning were examined in a visuomotor tracking task. Participants produced rhythmic elbow flexion-extension motions to learn a visually defined 90 degrees relative phase tracking pattern with an external sinusoidal signal. There were two visuomotor transformation groups, a correct feedback group and a mirrored feedback group with feedback representing the elbow's motion transformed by 180 degrees . In Experiment 1, the to-be-tracked signal and the participant's motion signal were superimposed within a single window display. In Experiment 2, the to-be-tracked signal and participant's signal were presented in separate windows. Before day 1 practice and 24 h after day 2 practice, participants attempted visually defined 0 degrees , 45 degrees , 90 degrees , 135 degrees , and 180 degrees relative phase tracking patterns either with or without visual feedback of the arm's motion. Before practice, only the 0 degrees and 180 degrees tracking patterns were stable. Practice led to a decrease in phase error toward the required 90 degrees relative phase pattern with a corresponding increase in stability in both the experiments. No effect of visual transformation on performance emerged during practice in the single window task, but did emerge in the two window task. The one window training facilitated transfer to the four unpracticed relative phase patterns, whereas the two window training display only facilitated transfer performance to a single unpracticed relative phase pattern. These findings suggest that the perceptual structure determined the degree of learning and transfer and interacted with the visuomotor transformation. The present findings are discussed with reference to how the visual display constrains the coherency of independent signals with regard to learning and transfer and the role of perceptual discrimination processes linked to transfer.

  14. Understanding metastable phase transformation during crystallization of RDX, HMX and CL-20: experimental and DFT studies.

    Science.gov (United States)

    Ghosh, Mrinal; Banerjee, Shaibal; Shafeeuulla Khan, Md Abdul; Sikder, Nirmala; Sikder, Arun Kanti

    2016-09-14

    Multiphase growth during crystallization severely affects deliverable output of explosive materials. Appearance and incomplete transformation of metastable phases are a major source of polymorphic impurities. This article presents a methodical and molecular level understanding of the metastable phase transformation mechanism during crystallization of cyclic nitramine explosives, viz. RDX, HMX and CL-20. Instantaneous reverse precipitation yielded metastable γ-HMX and β-CL-20 which undergo solution mediated transformation to the respective thermodynamic forms, β-HMX and ε-CL-20, following 'Ostwald's rule of stages'. However, no metastable phase, anticipated as β-RDX, was evidenced during precipitation of RDX, which rather directly yielded the thermodynamically stable α-phase. The γ→β-HMX and β→ε-CL-20 transformations took 20 and 60 minutes respectively, whereas formation of α-RDX was instantaneous. Density functional calculations were employed to identify the possible transition state conformations and to obtain activation barriers for transformations at wB97XD/6-311++G(d,p)(IEFPCM)//B3LYP/6-311G(d,p) level of theory. The computed activation barriers and lattice energies responsible for transformation of RDX, HMX and CL-20 metastable phases to thermodynamic ones conspicuously supported the experimentally observed order of phase stability. This precise result facilitated an understanding of the occurrence of a relatively more sensitive and less dense β-CL-20 phase in TNT based melt-cast explosive compositions, a persistent and critical problem unanswered in the literature. The crystalline material recovered from such compositions revealed a mixture of β- and ε-CL-20. However, similar compositions of RDX and HMX never showed any metastable phase. The relatively long stability with the highest activation barrier is believed to restrict complete β→ε-CL-20 transformation during processing. Therefore a method is suggested to overcome this issue.

  15. Effects of deep cryogenic treatment on the solid-state phase transformation of Cu-Al alloy in cooling process

    Science.gov (United States)

    Wang, Yuhui; Liao, Bo; Liu, Jianhua; Chen, Shuqing; Feng, Yu; Zhang, Yanyan; Zhang, Ruijun

    2012-07-01

    The solid-state phase transformation temperature and duration of deep cryogenic treated and untreated Cu-Al alloys in cooling process were measured by differential scanning calorimetry measurement. The solid-state phase transformation activation energy and Avrami exponent were calculated according to these measurements. The effects of deep cryogenic treatment on the solid-state phase transformation were investigated based on the measurement and calculation as well as the observation of alloy's microstructure. The results show that deep cryogenic treatment can increase the solid-phase transformation activation energy and shorten the phase transformation duration, which is helpful to the formation of fine grains in Cu-Al alloy.

  16. Micromechanics of transformation fields in ageing linear viscoelastic composites: effects of phase dissolution or precipitation

    Science.gov (United States)

    Honorio, Tulio

    2017-11-01

    Transformation fields, in an affine formulation characterizing mechanical behavior, describe a variety of physical phenomena regardless their origin. Different composites, notably geomaterials, present a viscoelastic behavior, which is, in some cases of industrial interest, ageing, i.e. it evolves independently with respect to time and loading time. Here, a general formulation of the micromechanics of prestressed or prestrained composites in Ageing Linear Viscoelasticity (ALV) is presented. Emphasis is put on the estimation of effective transformation fields in ALV. The result generalizes Ageing Linear Thermo- and Poro-Viscoelasticity and it can be used in approaches coping with a phase transformation. Additionally, the results are extended to the case of locally transforming materials due to non-coupled dissolution and/or precipitation of a given (elastic or viscoelastic) phase. The estimations of locally transforming composites can be made with respect to different morphologies. As an application, estimations of the coefficient of thermal expansion of a hydrating alite paste are presented.

  17. Analytical electron microscope study of the omega phase transformation in a zirconium--niobium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zaluzec, N.J.

    1979-06-01

    An in-situ study of the as-quenched omega phase transformation in Zr--15% Nb was conducted between the temperatures of 77 and 300/sup 0/K using analytical electron microscopy. The domain size of the omega regions observed in this investigation was on the order of 30 A, consistent with previous observations in this system. No alignment of omega domains along <222> directions of the bcc lattice was observed and in-situ thermal cycling experiments failed to produce a long period structure of alternating ..beta.. and ..omega.. phase regions as predicted by one theory of this transformation. Several techniques of microstructural analysis were developed, refined, and standardized. Grouped under the general classification of Analytical Electron Microscopy (AEM) they provide the experimentalist with a unique tool for the microcharacterization of solids, allowing semiquantitative to quantitative analysis of the morphology, crystallography, elemental composition, and electronic structure of regions as small as 20 A in diameter. These techniques have complications, and it was necessary to study the AEM system used in this work so that instrumental artifacts which invalidate the information produced in the microscope environment might be eliminated. Once these factors had been corrected, it was possible to obtain a wealth of information about the microvolume of material under investigation. The microanalytical techniques employed during this research include: energy dispersive x-ray spectroscopy (EDS) using both conventional and scanning transmission electron microscopy (CTEM, STEM), transmission scanning electron diffraction (TSED), the stationary diffraction pattern technique, and electron energy loss spectroscopy (ELS) using a dedicated scanning transmission electron microscope (DSTEM).

  18. Analytical electron microscope study of the omega phase transformation in a zirconium--niobium alloy

    International Nuclear Information System (INIS)

    Zaluzec, N.J.

    1979-06-01

    An in-situ study of the as-quenched omega phase transformation in Zr--15% Nb was conducted between the temperatures of 77 and 300 0 K using analytical electron microscopy. The domain size of the omega regions observed in this investigation was on the order of 30 A, consistent with previous observations in this system. No alignment of omega domains along directions of the bcc lattice was observed and in-situ thermal cycling experiments failed to produce a long period structure of alternating β and ω phase regions as predicted by one theory of this transformation. Several techniques of microstructural analysis were developed, refined, and standardized. Grouped under the general classification of Analytical Electron Microscopy (AEM) they provide the experimentalist with a unique tool for the microcharacterization of solids, allowing semiquantitative to quantitative analysis of the morphology, crystallography, elemental composition, and electronic structure of regions as small as 20 A in diameter. These techniques have complications, and it was necessary to study the AEM system used in this work so that instrumental artifacts which invalidate the information produced in the microscope environment might be eliminated. Once these factors had been corrected, it was possible to obtain a wealth of information about the microvolume of material under investigation. The microanalytical techniques employed during this research include: energy dispersive x-ray spectroscopy (EDS) using both conventional and scanning transmission electron microscopy (CTEM, STEM), transmission scanning electron diffraction (TSED), the stationary diffraction pattern technique, and electron energy loss spectroscopy (ELS) using a dedicated scanning transmission electron microscope

  19. Kinetics of solid state phase transformations: Measurement and ...

    Indian Academy of Sciences (India)

    Administrator

    This latter quan- tity that may be obtained from equilibrium phase diagram (lever rule) or may be set as an internal ref- erence value which is obtained under very slow heating or cooling conditions. A rough estimate of τ. (assumed to be β independent in the trial estimation) can be obtained from the experimental data using.

  20. Structural Phase Transition in Adipic Acid

    Science.gov (United States)

    Srinivasa Gopalan, R.; Kumaradhas, P.; Kulkarni, G. U.

    1999-11-01

    The structure of adipic acid undergoing phase transition at ∼136 K has been investigated using single-crystal x-ray diffraction. On lowering the temperature, the a parameter of the room temperature monoclinic cell decreases by ∼0.25 Å. Accompanying the transition, the b parameter nearly triples while a reverts back to the room temperature value. Two-thirds of the molecules in the structure loses center of symmetry. Packing diagrams of the high- and low-temperature phases on superposition reveal that there exist alternating domains perpendicular to the b direction, which contain molecules with and without symmetry. Unsymmetric molecules show displacements along the ac diagonal. Intermolecular hydrogen contacts involving carboxylic oxygens and the methylene hydrogens seem to increase interchain interactions in the low-temperature phase.

  1. The Structural Phase Transition in Solid DCN

    DEFF Research Database (Denmark)

    Dietrich, O. W.; Mackenzie, Gordon A.; Pawley, G. S.

    1976-01-01

    Neutron scattering measurements on deuterated hydrogen cyanide have shown that the structural phase transition from a tetragonal to an orthorhombic form at 160 K is a first order transition. A transverse acoustic phonon mode, which has the symmetry of the transition was observed at very low...

  2. In-situ studies on phase transformations under electron irradiation in ...

    Indian Academy of Sciences (India)

    High voltage electron microscopy (HVEM), using electron energies adequate for causing displacements of atoms from lattice sites, is a very effective technique for studying mechanisms of solid state phase transformations and for charting the path of phase evolution in real time. This has been demonstrated in studies on ...

  3. Building Structural Complexity in Semiconductor Nanocrystals through Chemical Transformations

    Energy Technology Data Exchange (ETDEWEB)

    Sadtler, Bryce F [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2009-05-01

    Methods are presented for synthesizing nanocrystal heterostructures comprised of two semiconductor materials epitaxially attached within individual nanostructures. The chemical transformation of cation exchange, where the cations within the lattice of an ionic nanocrystal are replaced with a different metal ion species, is used to alter the chemical composition at specific regions ofa nanocrystal. Partial cation exchange was performed in cadmium sulfide (CdS) nanorods of well-defined size and shape to examine the spatial organization of materials within the resulting nanocrystal heterostructures. The selectivity for cation exchange to take place at different facets of the nanocrystal plays an important role in determining the resulting morphology of the binary heterostructure. The exchange of copper (I) (Cu+) cations in CdS nanorods occurs preferentially at the ends of the nanorods. Theoretical modeling of epitaxial attachments between different facets of CdS and Cu2S indicate that the selectivity for cation exchange at the ends of the nanorods is a result of the low formation energy of the interfaces produced. During silver (I) (Ag+) cation exchange in CdS nanorods, non-selective nucleation of silver sulfide (Ag2S), followed by partial phase segregation leads to significant changes in the spatial arrangement of CdS and Ag2S regions at the exchange reaction proceeds through the nanocrystal. A well-ordered striped pattern of alternating CdS and Ag2S segments is found at intermediate fractions of exchange. The forces mediating this spontaneous process are a combination of Ostwald ripening to reduce the interfacial area along with a strain-induced repulsive interaction between Ag2S segments. To elucidate why Cu+ and Ag+ cation exchange with CdS nanorods produce different morphologies, models for epitaxial attachments between various facets of CdS with Cu2S or

  4. Double-Exposure Optical Sectioning Structured Illumination Microscopy Based on Hilbert Transform Reconstruction

    Science.gov (United States)

    Zhou, Xing; Lei, Ming; Dan, Dan; Yao, Baoli; Qian, Jia; Yan, Shaohui; Yang, Yanlong; Min, Junwei; Peng, Tong; Ye, Tong; Chen, Guangde

    2015-01-01

    Structured illumination microscopy (SIM) with axially optical sectioning capability has found widespread applications in three-dimensional live cell imaging in recent years, since it combines high sensitivity, short image acquisition time, and high spatial resolution. To obtain one sectioned slice, three raw images with a fixed phase-shift, normally 2π/3, are generally required. In this paper, we report a data processing algorithm based on the one-dimensional Hilbert transform, which needs only two raw images with arbitrary phase-shift for each single slice. The proposed algorithm is different from the previous two-dimensional Hilbert spiral transform algorithm in theory. The presented algorithm has the advantages of simpler data processing procedure, faster computation speed and better reconstructed image quality. The validity of the scheme is verified by imaging biological samples in our developed DMD-based LED-illumination SIM system. PMID:25799234

  5. Morphological evolution of precipitates during transformation of amorphous calcium phosphate into octacalcium phosphate in relation to role of intermediate phase

    Science.gov (United States)

    Sugiura, Yuki; Onuma, Kazuo; Kimura, Yuki; Miura, Hitoshi; Tsukamoto, Katsuo

    2011-10-01

    Nucleation of amorphous calcium phosphate (ACP) and its phase transformation with a decrease in solution pH were investigated at a constant temperature of 32 °C. A solution containing a mixture of CaCl 2 and KH 2PO 4 was prepared (initial pH=7.7), and a drop was sampled at a constant interval to observe the morphological evolution of the precipitates that formed in the solution. A gel-like solution structure formed immediately after mixing and contained a small amount of sea-urchin-like ACP spherulites (3-20 μm in size). These spherulites consisted of 1.5-10-μm-long flexible needles that formed simultaneously with numerous ACP spherical particles. They first transformed into β-tri calcium phosphate-like material (called "pseudo β-TCP") and then into single crystals of octacalcium phosphate (OCP) without dissolution. The flexible needles in the spherulites changed into blade springs, then into flexible plates, and finally into rigid plates during the transformation. The OCP structure appeared in the pseudo β-TCP plates and gradually substituted for the β-TCP structure over time. The macroscopic spherulite morphology of the initial ACP remained unchanged during the phase transformation, suggesting that OCP is a pseudomorph of ACP. This feature was observed only when the ACP spherulites formed in the initial solution. Fiber-like aggregates consisting of β-TCP single crystals nucleated around the ACP spherical particles and grew over time. They survived until the final stage of the reaction, and OCP polycrystals formed in the mixture of β-TCP and ACP spheres. The OCP polycrystals gradually substituted for the ACP spheres without phase transformation of β-TCP into OCP.

  6. Structural transformation of Nb containing glass - ceramics at thermal treatment

    International Nuclear Information System (INIS)

    Pelss, J.; Misnovs, A.; Berzina, L.; Cimdins, R.; Bossert, J.

    2004-01-01

    Full text: Niobium glass ceramics is know as biomaterial in medicine: stomatology, maxillofacial surgery. The material structure and phase amount influenced on chemical and biological activity of glass-ceramics. Samples from glass powder in system NaO: CaO: Nb 2 O 5 : P 2 O 5 treated at different temperatures (750-1050 0 C) and at different time - from 1 to 6 hours. The glass - ceramics structure investigated by DTA, X-ray and SEM methods

  7. Optical image transformation and encryption by phase-retrieval-based double random-phase encoding and compressive ghost imaging

    Science.gov (United States)

    Yuan, Sheng; Yang, Yangrui; Liu, Xuemei; Zhou, Xin; Wei, Zhenzhuo

    2018-01-01

    An optical image transformation and encryption scheme is proposed based on double random-phase encoding (DRPE) and compressive ghost imaging (CGI) techniques. In this scheme, a secret image is first transformed into a binary image with the phase-retrieval-based DRPE technique, and then encoded by a series of random amplitude patterns according to the ghost imaging (GI) principle. Compressive sensing, corrosion and expansion operations are implemented to retrieve the secret image in the decryption process. This encryption scheme takes the advantage of complementary capabilities offered by the phase-retrieval-based DRPE and GI-based encryption techniques. That is the phase-retrieval-based DRPE is used to overcome the blurring defect of the decrypted image in the GI-based encryption, and the CGI not only reduces the data amount of the ciphertext, but also enhances the security of DRPE. Computer simulation results are presented to verify the performance of the proposed encryption scheme.

  8. Raman studies of pressure and temperature induced phase transformations in calcite

    International Nuclear Information System (INIS)

    Exarhos, G.J.; Hess, N.J.

    1992-01-01

    This patent describes phase stability in the calcium carbonate system investigated as a simultaneous function of pressure and temperature up to 40 kbar and several hundred degrees Kelvin. Micro-Raman techniques were used to interrogate samples constrained within a resistively heated diamond anvil cell. Measured spectra allow unequivocal identification of crystalline phases and are used to refine the P,T phase diagram. Calcium carbonate was found to exhibit both reversible and irreversible transformation phenomena among the four known phases which exist under these conditions. Time-dependent Raman intensity variations as the material is perturbed from its equilibrium state allow real-time kinetics measurements to be performed. Evidence suggests that the order of certain observed transformations may be pressure dependent. The utility of Raman spectroscopy to follow transformation phenomena and to estimate fundamental thermophysical properties from the stress dependence of vibrational mode frequencies is demonstrated

  9. Periodic orbits and TDHF phase space structure

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, Yukio; Iwasawa, Kazuo [Tsukuba Univ., Ibaraki (Japan). Inst. of Physics; Tsukuma, Hidehiko; Sakata, Fumihiko

    1998-03-01

    The collective motion of atomic nuclei is closely coupled with the motion of nucleons, therefore, it is nonlinear, and the contents of the motion change largely with the increase of its amplitude. As the framework which describes the collective motion accompanied by the change of internal structure, time-dependent Hurtley Fock (TDHF) method is suitable. At present, the authors try to make the method for studying the large region structure in quantum system by utilizing the features of the TDHF phase space. The studies made so far are briefed. In this report, the correspondence of the large region patterns appearing in the band structure chart of three-level model with the periodic orbit group in the TDHF phase space is described. The Husimi function is made, and it possesses the information on the form of respective corresponding intrinsic state. The method of making the band structure chart is explained. There are three kinds of the tendency in the intrinsic state group. The E-T charts are made for the band structure charts to quantitatively express the large region tendency. The E-T chart and the T{sub r}-T chart are drawn for a selected characteristic orbit group. It became to be known that the large region properties of the quantum intrinsic state group of three-level model can be forecast by examining the properties of the periodic orbit group in the TDHF phase space. (K.I.)

  10. STRUCTURAL TRANSFORMATION DURING COLD DEFORMED CARBON STEEL TEMPERING

    Directory of Open Access Journals (Sweden)

    I. A. Vakulenko

    2010-06-01

    Full Text Available The influence of parameters of degree of plastic deformation for 30…80 % and subsequent temper on the structure and yielding stress in the microyield region of preimproved carbon steels has been studied. The classification of dispersed phase of ferrite into two types containing the high angle boundaries and substructure boundaries respectively in relation to steels has been discussed.

  11. Synthesis of Li-Mn-O mesocrystals with controlled crystal phases through topotactic transformation of MnCO₃.

    Science.gov (United States)

    Dang, Feng; Hoshino, Tatsuhiko; Oaki, Yuya; Hosono, Eiji; Zhou, Haoshen; Imai, Hiroaki

    2013-03-21

    Mesocrystals of Li-Mn-O compounds, such as LiMn2O4, Li2MnO3, and LiMnO2-Li2MnO3, consisting of oriented nanoscale units were selectively produced under hydrothermal conditions from biomimetically prepared MnCO3 mesocrystals. Topotactic transformation through the intermediate phase of Mn5O8 inheriting a hierarchical structure of the MnCO3 precursor was essential for the formation of the mesocrystal compounds. The crystal phases were successfully controlled by varying the conditions for the hydrothermal reactions. The Li-Mn-O mesocrystals have considerable potential as cathodes of Li-ion batteries.

  12. A flow-through hydrothermal cell for in situ neutron diffraction studies of phase transformations

    Energy Technology Data Exchange (ETDEWEB)

    O' Neill, Brian [School of Chemical Engineering, The University of Adelaide, South Australia 5005 (Australia); Tenailleau, Christophe [Department of Mineralogy, South Australian Museum, North Terrace, Adelaide, South Australia 5000 (Australia); Nogthai, Yung [School of Chemical Engineering, The University of Adelaide, South Australia 5005 (Australia); Studer, Andrew [Bragg Institute, ANSTO, PMB 1 Menai, New South Wales 2234 (Australia); Brugger, Joel [Department of Mineralogy, South Australian Museum, North Terrace, Adelaide, South Australia 5000 (Australia): Department of Geology and Geophysics, The University of Adelaide, North Terrace, Adelaide, South Australia 5005 (Australia); Pring, Allan [Department of Mineralogy, South Australian Museum, North Terrace, Adelaide, South Australia 5000 (Australia): Department of Geology and Geophysics, The University of Adelaide, North Terrace, Adelaide, South Australia 5005 (Australia)]. E-mail: pring.allan@saugov.sa.gov.au

    2006-11-15

    A flow-through hydrothermal cell for the in situ neutron diffraction study of crystallisation and phase transitions has been developed. It can be used for kinetic studies on materials that exhibit structural transformations under hydrothermal conditions. It is specifically designed for use on the medium-resolution powder diffractometer (MRPD) at ANSTO, Lucas Heights, Sydney. But it is planned to adapt the design for the Polaris beamline at ISIS and the new high-intensity powder diffractometer (Wombat) at the new Australian reactor Opal. The cell will operate in a flow-through mode over the temperature range from 25-300 deg. C and up to pressures of 100 bar. The first results of a successful transformation of pentlandite (Fe,Ni){sub 9}S{sub 8} to violarite (Fe,Ni){sub 3}S{sub 4} under mild conditions (pH{approx}4) at 120 deg. C and 3 bar using in situ neutron diffraction measurements are presented.

  13. Impact of concentration and Si doping on the properties and phase transformation behavior of nanocrystalline alumina prepared via solvothermal synthesis

    International Nuclear Information System (INIS)

    Mekasuwandumrong, Okorn; Tantichuwet, Panutin; Chaisuk, Choowong; Praserthdam, Piyasan

    2008-01-01

    Solvothermal reaction of 20 g aluminum isopropoxide (AIP) in mineral oil at 300 deg. C for 2 h gave χ-alumina showing high thermal stability while the reaction with higher amounts of starting AIP (30 and 40 g) contributed contamination of pseudoboehmite. The χ-alumina thus obtained directly transformed into α-alumina completely at approximately 1400 deg. C bypassing the other transition alumina phases whereas some part of the contaminated product transformed to γ-alumina through θ-alumina and finally α-alumina. When silicon was doped in the alumina matrix (5, 10, 20 and 50 at.%) using tetraethylorthosilicate as the silicon (Si) precursor, χ-alumina was still observed without any contaminations at low concentration doping (5-20 at.%). Amorphous structure was obtained by doping 50 at.% Si. The phase transformation temperature was shifted to the high temperature after loading the Si. The α-phase transformation did not go to completion even after calcinations at 1500 deg. C. This could be due to the incorporation of Si atom in alumina lattice forming SiO 2 -Al 2 O 3 solid solution

  14. Phases of crown-gall transformation susceptible to hydroxyurea

    Directory of Open Access Journals (Sweden)

    Aldona Rennert

    2014-01-01

    Full Text Available With the use of bacterial strains, both sensitive and resistant to hydroxyurea the action of this inhibitor on tumour formation on the leaves of Kalanchoe daigremontiana infected with Agrobacterium tumefaciens was tested for five days after inoculation. The results are in agreement with the opinion that the anti-tumour effect of hydroxyurea applied in the induction phase (between 18 and 60 h after inoculation is the result of its direct action on plant cells, whereas inhibition of tumour formation by the inhibitor in the inoculation period depends on its action on the pathogenic bacteria.

  15. Morphology and phase transformations of tin oxide nanostructures synthesized by the hydrothermal method in the presence of dicarboxylic acids

    Energy Technology Data Exchange (ETDEWEB)

    Zima, Tatyana, E-mail: zima@solid.nsc.ru [Institute of Solid State Chemistry and Mechanochemistry SB RAS, 18 Kutateladze, Novosibirsk 630128 (Russian Federation); Novosibirsk State Technical University, 20 K. Marx Prospect, Novosibirsk 630092 (Russian Federation); Bataev, Ivan [Novosibirsk State Technical University, 20 K. Marx Prospect, Novosibirsk 630092 (Russian Federation)

    2016-11-15

    A new approach to the synthesis of non-stoichiometric tin oxide structures with different morphologies and the phase compositions has been evaluated. The nanostructures were synthesized by hydrothermal treatment of the mixtures of dicarboxylic acids ― aminoterephthalic or oxalic ― with nanocrystalline SnO{sub 2} powder, which was obtained via the sol-gel technology. The products were characterized by Raman and IR spectroscopy, SEM, HRTEM, and XRD analysis. It was shown that the controlled addition of a dicarboxylic acid leads not only to a change in the morphology of the nanostructures, but also to SnO{sub 2}–SnO{sub 2}/Sn{sub 3}O{sub 4}–Sn{sub 3}O{sub 4}–SnO phase transformations. A single-phase Sn{sub 3}O{sub 4} in the form of the well-separated hexagonal nanoplates and mixed SnO{sub 2}/Sn{sub 3}O{sub 4} phases in the form of hierarchical flower-like structures were obtained in the presence of organic additives. The effects of concentration, redox activity of the acids and heat treatment on the basic characteristics of the synthesized tin oxide nanostructures and phase transformations in the synthesized materials are discussed. - Graphical abstract: The controlled addition of aminoterephthalic or oxalic acid leads not only to a change in the morphology of the nanostructures, but also to SnO{sub 2}–SnO{sub 2}/Sn{sub 3}O{sub 4}–Sn{sub 3}O{sub 4}–SnO phase transformations. - Highlights: • A new approach to the synthesis of non-stoichiometric tin oxide structures is studied. • Tin oxide structures are synthesized via hydrothermal method with dicarboxylic acids. • Morphology and phase composition are changed with redox activity and dosage of acid. • The redox activity of acid has an effect on ratio of SnO and SnO{sub 2} in crystal structure. • A pure phase Sn{sub 3}O{sub 4} nanoplates and SnO{sub 2}/Sn{sub 3}O{sub 4} hierarchical structures are formed.

  16. Influence of Rapid Thermal Ramp Rate on Phase Transformation of Titanium Silicides

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, Glenn; Hu, Yao, Zhi; Smith, Paul Martin; Tay, Sing Pin; Thakur, Randhir; Yang, Jiting

    1999-05-03

    ULSI technology requires low resistance, stable silicides formed on small geometry lines. Titanium disilicide (TiSiz), which is the most widely used silicide for ULSI applications, exists in two crystallographic phases: the high resistance, metastable C49 phase and the low resistance, stable C54 phase. The major issue with TiSiz is the increasing thermal budget required to transform the C49 phase into the low resistance C54 phase as linewiths decrease below 0.25 pm. Annealing above 900"C to obtain this transformation often results in thermal degradation, so it is desirable to reduce the transformation temperature. The transformation temperature has been shown to be a fi.mction of many factors including microstructure, grain size, and impurities. In this paper we report an investig+ion of rapid thermal silicidation of titanium films (250, 400, and 600 A) on single crystalline silicon at temperatures from 300 to 1000"C. The ramp rates for these experiments are 5, 30, 70, and 200oC/s. The transformation temperature decreases as the ramp rate increases and as the initial film thickness increases. Scanning electron microscopy (SEM) is used to analyze the resultant film microstructure. The ramp rate influence on Ti silicidation is also investigated on polycrystalline Si lines with widths ranging from 0.27 to 3.0 pm.

  17. Conflict transformation, stigma, and HIV-preventive structural change.

    Science.gov (United States)

    Miller, Robin Lin; Reed, Sarah J; Francisco, Vincent T; Ellen, Jonathan M

    2012-06-01

    Over the prior decade, structural change efforts have become an important component of community-based HIV prevention initiatives. However, these efforts may not succeed when structural change initiatives encounter political resistance or invoke conflicting values, which may be likely when changes are intended to benefit a stigmatized population. The current study sought to examine the impact of target population stigma on the ability of 13 community coalitions to achieve structural change objectives. Results indicated that coalitions working on behalf of highly stigmatized populations had to abandon objectives more often than did coalitions working for less stigmatized populations because of external opposition to coalition objectives and resultant internal conflict over goals. Those coalitions that were most successful in meeting external challenges used opposition and conflict as transformative occasions by targeting conflicts directly and attempting to neutralize oppositional groups or turn them into strategic allies; less successful coalitions working on behalf of stigmatized groups struggled to determine an appropriate response to opposition. The role of conflict transformation as a success strategy for working on behalf of stigmatized groups is discussed.

  18. Low temperature fabrication of hexagon shaped h-MoO{sub 3} nanorods and its phase transformation

    Energy Technology Data Exchange (ETDEWEB)

    Dhage, S.R. [School of Semiconductor and Chemical Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of)], E-mail: sanjay.dhage@gmail.com; Hassan, M.S. [School of Semiconductor and Chemical Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Yang, O.-Bong [School of Semiconductor and Chemical Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of)], E-mail: obyang@chonbuk.ac.kr

    2009-04-15

    Hexagon shaped h-MoO{sub 3} nanorods have been fabricated via the probe sonication route using ammonium molybdate, urea and sodium dodecyl sulphate at 70 deg. C. Pure metastable h-MoO{sub 3} and {alpha}-MoO{sub 3} were obtained under the current synthetic conditions. The h-MoO{sub 3} phase was transformed to {alpha}-MoO{sub 3} phase at 400 deg. C, while the hexagon shape rods structures of h-MoO{sub 3} were collapsed and transformed to elongated particles of {alpha}-MoO{sub 3}. As-prepared products were characterized by thermogravimetric analysis (TG), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM)

  19. Influence Cr on Crystallization and the Phase Transformations of the Bronze BA1044

    Directory of Open Access Journals (Sweden)

    B. P. Pisarek

    2007-07-01

    Full Text Available The investigations were introduced in the paper, method of thermal and derivative analysis (TDA, the process of crystallization and phase transformation in the solid state of the aluminium bronze CuA110Fe4Ni4 (BA1044 and with the addition 0.3% Cr. Two intermetallic phase were identified in the microstructure of the bronze BA1044: κFel - rich in Fe and Cu and κFe2 - rich in Fe, and in the microstructure of the bronze BA1044+0.3 % Cr only one phase κFel - rich in Fe, Cu and Cr. The presence of chrome in the bronze BA1044 reduce size the primary crystals of the phase β, reduces the dynamics of the processes of thermal phase transformation in the solid state and lengthens the time their of duration.

  20. Analysis of hydrogen storage in metal hydride tanks introducing an induced phase transformation

    Energy Technology Data Exchange (ETDEWEB)

    Gondor, Germain; Lexcellent, Christian [Institut FEMTO-ST, Departement de Mecanique Appliquee (LMARC), Universite de Franche-Comte, UMR CNRS 6174, 24 Chemin de l' Epitaphe, 25000 Besancon (France)

    2009-07-15

    Hydrogen absorption in a metal hydride tank is generally studied based on a heat and mass transfer analysis. The originality of this investigation is that the phase transformation from a solid ({alpha} phase) to hydride ({beta} phase) solution is included in the hydrogen absorption mechanism. Toward this end, a modelling of the equilibrium pressure, composition (absorbed or desorbed hydrogen atoms per metal atoms), and isothermal curves of a LaNi{sub 5} alloy is performed. Moreover, a kinetic model is developed taking into account the steps of hydrogen absorption and desorption (i.e., physisorption, chemisorption, surface penetration, nucleation and growth of the hydride phase and diffusion). Simulations are then performed to show the impact of external conditions (hydrogen gas pressure and temperature) and parameter values (wall heat transfer, conductivities of gas and solid, viscosity, porosity, etc.) on refilling time. The physical nature of the phase transformation associated to the hydrogen storage remains an open problem. (author)

  1. Transformation: Structure/space studies in bionics and space design

    Science.gov (United States)

    Gruber, Petra; Imhof, Barbara

    2007-02-01

    This paper discusses the architectural design project "Transformation Structure Space", which was carried out at the Department of Building Construction HB2 in 2004. The goal of the study was to find innovative solutions for space system design through the application of bionic (biomimetic) approaches. Using specific research both fields as the foundation, five different architectural projects based on a scientific-technological concept were developed. The introduction of natural role models into the design process and the development of the application in space and the respective setting proved to be a difficult task within the timeframe of a design program, nonetheless all of the projects show very innovative aspects.

  2. Pressure-induced structure phase transition on Y sub 2 O sub 3

    CERN Document Server

    Ma Yan Ming; Ma Hong An; Pan Yue Wu; Cui Qi Liang; Liu Bing Bing; Cui Tian; Zou Guang Tian; LiuJing

    2002-01-01

    Diamond anvil cell (DAC) is adopted to carry out in situ high pressure measurements for Y sub 2 O sub 3 powder sample in the range from ambient to 23 GPa, by using synchrotron X-ray diffraction method. Two structural phase transitions were observed in the pressure range. At P = 12.8 GPa, Y sub 2 O sub 3 transforms from cubic to monoclinic structure. At P = 21.8 GPa, Y sub 2 O sub 3 transforms from monoclinic to another new phase. However, the crystal structure of the new phase cannot be determined, because the diffraction pattern of the sample disappears. The decompressed sample is monoclinic structure, indicating that the first pressure-induced phase transition is irreversible

  3. APPROACH TO DETERMINATION OF NO LOAD CURRENT OF THREE-PHASE POWER TRANSFORMERS WITH PLANE RODS MAGNETIC SYSTEMS

    Directory of Open Access Journals (Sweden)

    T. E. Divchuk

    2018-02-01

    Full Text Available Purpose. Development a new effective approach for determining the open-circuited transformer parameters by implementing a combination of a schematic and spatial mathematical model of nonstationary electromagnetic fields in three-phase transformers, taking into account the constructive structure of the active part, the nonlinearity of the magnetic properties of electrical steels providing high accuracy and computational efficiency. Methods. The researches were carried out using the methods of the electromagnetic field theory, the theory of electrical circuits, the theory of power transformers, mathematical physics, the finite element method, regression analysis methods. Results. Theoretical researches of electromagnetic processes based on numerical realization of a three-dimensional mathematical model of a power three-phase transformer in open-circuited operation are carried out. An approach is proposed for improving the field simulation efficiency of the open-circuited operation, which consists in reducing the dimension of the computational domain and the transition to 2D models. It allow reducing the computing resources cost more than 2.8 times, time resources more than 250 times at a weighted average discrepancy of not more than 3.6%. The regularities of the distribution of flux density and the energy of the magnetic field for the active part of the transformer in open-circuited operation are determined. Their quantitative ratio value for the rods of different phases, which determining the ratio of the currents and resistances of the forward and reverse sequences of the transformer are calculated. A new approach to determine the open-circuited parameters of three-phase transformers with flat rod magnetic systems, based on the methods of circuit and 3D modeling, harmonic analysis and symmetrical components is realized. It characterized by high efficiency of numerical realization and accuracy for transient processes in switching moment of the

  4. Methods of Weyl representation of the phase space and canonical transformations. 1

    International Nuclear Information System (INIS)

    Budanov, V.G.

    1984-01-01

    The kernel structure of canonical transformation and differential equation for the intertwining operator is found. The Weyl symbol of operators producing linear canonical transformations is associated with the Cayley transformation of classical canonical transformation. Due to the invariance of the Weyl formalism a complete study of singularity and factorization of these symbols is manageable. In particular, one can study the symbols of Green functions and elements of Lie groups and find the spectra of arbitrary stationary quadratic Hamiltonians with the help of the known classification of the spectra of classical systems

  5. Moessbauer study of the magnetic phase transformations in SnMn3N

    International Nuclear Information System (INIS)

    Nagy, D.L.; Zimmer, G.J.; Lohner, T.; Senateur, J.P.

    1975-01-01

    Moessbauer measurements were performed on SnMn 3 N with the aim of verifying the magnetic phase transformations at 175 and 230 K and the Neel transition at 475 K as well as of seeking an explanation for the anomalous peak in magnetic susceptibility about 380 K. Moessbauer spectra were taken at several temperatures between 83 and 475 K and evaluated by a least square fitting program. Abrupt changes in the hyperfine field were found at 175, 230 and 350 K indicating first-order magnetic phase transformations at these temperatures; the 350 K transformation is certainly related to the anomaly in susceptibility. About 475 only a smooth change in the hyperfine field was found suggesting the Neel transition to be of the second order. An attempt is made to explain the relatively high hyperfine field in the cubic antiferromagnetic phase. (A.K.)

  6. Photostress analysis of stress-induced martensite phase transformation in superelastic NiTi

    International Nuclear Information System (INIS)

    Katanchi, B.; Choupani, N.; Khalil-Allafi, J.; Baghani, M.

    2017-01-01

    Phase transformation in shape memory alloys is the most important factor in their unique behavior. In this paper, the formation of stress induced martensite phase transformation in a superelastic NiTi (50.8% Ni) shape memory alloy was investigated by using the photo-stress method. First, the material's fabrication procedure has been described and then the material was studied using the metallurgical tests such as differential scanning calorimetry and X-ray diffraction to characterize the material features and the mechanical tensile test to investigate the superelastic behavior. As a new method in observation of the phase transformation, photo-stress pictures showed the formation of stress induced martensite in a superelastic dog-bone specimen during loading and subsequently it's disappearing during unloading. Finally, finite element analysis was implemented using the constitutive equations derived based on the Boyd-Lagoudas phenomenological model.

  7. Flexible retrospective phase stepping in x-ray scatter correction and phase contrast imaging using structured illumination.

    Directory of Open Access Journals (Sweden)

    Han Wen

    Full Text Available The development of phase contrast methods for diagnostic x-ray imaging is inspired by the potential of seeing the internal structures of the human body without the need to deposit any harmful radiation. An efficient class of x-ray phase contrast imaging and scatter correction methods share the idea of using structured illumination in the form of a periodic fringe pattern created with gratings or grids. They measure the scatter and distortion of the x-ray wavefront through the attenuation and deformation of the fringe pattern via a phase stepping process. Phase stepping describes image acquisition at regular phase intervals by shifting a grating in uniform steps. However, in practical conditions the actual phase intervals can vary from step to step and also spatially. Particularly with the advent of electromagnetic phase stepping without physical movement of a grating, the phase intervals are dependent upon the focal plane of interest. We describe a demodulation algorithm for phase stepping at arbitrary and position-dependent (APD phase intervals without assuming a priori knowledge of the phase steps. The algorithm retrospectively determines the spatial distribution of the phase intervals by a Fourier transform method. With this ability, grating-based x-ray imaging becomes more adaptable and robust for broader applications.

  8. Management of the Structural Transformation of Regional Economy

    Directory of Open Access Journals (Sweden)

    Khamid Nurislamovich Gizatullin

    2018-03-01

    Full Text Available The article presents the research of the structural transformation of the economy. The authors have formulated the theoretical concept and the basic reasons for structural transformation of the economy in regions. According to the authors’ approach, the economy should function as a whole system. This defining principle is aimed at the systemic effect. The loss of regions’ control, and, in some cases, deviation from the national goals are the main reasons for the reduction in the Russian economic efficiency. As a result of the liberalization of the economy, the principle of selective investments has become the dominant one as a result of the liberalization of the economy. It broke the synergetic principle used for the formulation of economic strategy. The authors recommend to structure an efficient economy on the basis of the specificity of the economic situation due to its internal state and international realities. We also advise to achieve the balance between regional development and the development of country’s economic competitiveness. The article substantiates the need to overcome the growth of negative trends. These trends are due to the deformation of the most important economic principles and relationships as a result of weakness in the structural and investment policy. Thus, the high-priority task is the orientation of economic development to ensure the technical and technological independence of the economic system. This strategy contains the determining directions for the next development stages. We propose to focus the modernization of the structure of regional economy on the combination of the conceptual foundations of the federal structural policy and regional conditions for its implementation. Regional economy should balance economic initiative and independence in terms of the methods and means for its implementation. We recommend to combine the economic growth with the regional environmental management and the regulation of

  9. Phase transformations and resulting microstructures in Ti - 47 Al -2 Cr alloy

    International Nuclear Information System (INIS)

    Ghasemi-Armaki, H.; Heshmati-Manesh, S.; Jafarian, H. R.; Nili-Ahmadabadi, M.

    2008-01-01

    During the last three decades, intermetallic alloys have focused attention because of their high strength to weight ratio and good creep resistance. Titanium aluminide alloys based on γ-Ti Al are potential candidates to replace Ni-based super alloys currently used in jet engine components at high temperatures because of their low density, high melting temperature, good elevated-temperature strength and modulus retention, high resistance to oxidation and hydrogen absorption, and excellent creep properties. One of the major concerns in these alloys is their poor ductility at room and intermediate temperatures which has been improved slightly by microstructure modifications through heat treatment. Thus, modification of microstructure during cooling and CCT diagram in these alloys is of vital importance. In this study, Ti - 47 Al - 2 Cr intermetallic alloy has been prepared by remelting 4 times with a vacuum arc remelting furnace. Homogenizing treatment was done at 1125 d eg C for 72 h in a sealed vacuum quartz tube. All heat treatments on the samples were carried out in a vacuum heat treatment furnace under a pressure of 10 -1 bar. The atmosphere inside the furnace was changed to that of high purity argon for each heat treatment as an added precaution against oxidation. In this paper, phase transformations in a γ-Ti Al based intermetallic alloy containing chromium were investigated. Heat treatments on samples of this alloy at temperatures above Tα and subsequent cooling with various cooling rates resulted in variety of microstructures. The schematic CCT diagram for this alloy was drawn from microstructural studies using microscopy routs and X-ray diffraction. Then, cyclic heat treatment with grain refining purpose was conducted on a sample of this alloy having massive gamma microstructure. During cyclic heat treatment, gradual dissociation of the gamma phase resulted in the formation of a Widmanstaetten type structure. Trend of microstructure evolution and

  10. Phase-transformation and subgrain-deformation characteristics in a cobalt-based superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Benson, M.L. [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996 (United States); Reetz, B. [Institute for Materials Science and Technology, Technical University Berlin, Berlin D-10587 (Germany); Liaw, P.K., E-mail: pliaw@utk.edu [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996 (United States); Reimers, W. [Institute for Materials Science and Technology, Technical University Berlin, Berlin D-10587 (Germany); Choo, H. [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996 (United States); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Brown, D.W.; Saleh, T.A. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Klarstrom, D.L. [Haynes International, Inc., Kokomo, IN 46904 (United States)

    2011-02-25

    Research highlights: {yields} The mechanical behavior of a cobalt-based superalloy was investigated. {yields} Two diffraction techniques were used to study deformation mechanisms of materials. {yields} In-situ neutron diffraction provides the volume-averaged information. {yields} The peak-profile analysis reveals the information on a subgrain level. {yields} The material exhibited a transformation texture for the HCP phase under loading. - Abstract: A complimentary set of experiments, in situ neutron diffraction and ex situ synchrotron X-ray diffraction, were used to study the phase-transformation and subgrain-deformation characteristics of a cobalt-based superalloy. The neutron diffraction indicated a strain-induced phase transformation in the cobalt-based superalloy under uniaxial tension and compression. The synchrotron X-ray diffraction revealed stacking-fault accumulation and twinning under the same loading conditions. The extent of transformation was found to be greater under tension than under compression. Tensile plastic strains below 2% were accommodated by the stacking-fault creation, while those greater than 2% were accommodated by the phase transformation. Twinning was found to be more active under compressive loading than under tensile loading.

  11. Strain-induced phase transformation in a cobalt-based superalloy during different loading modes

    Energy Technology Data Exchange (ETDEWEB)

    Benson, Michael L. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Liaw, Peter K., E-mail: pliaw@utk.edu [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Choo, Hahn [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Brown, Donald W. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Daymond, Mark R. [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, ON K7N3L6 (Canada); Klarstrom, Dwaine L. [Hayne' s International, Inc., Kokomo, IN 46904 (United States)

    2011-07-15

    Highlights: {yields} The strain-induced FCC {yields} HCP phase transformation in a cobalt-based superalloy was investigated with neutron-diffraction experiments and with in-situ loading {yields} The transformation onset and the accumulation rate for each loading case were quantified for monotonic tension, monotonic compression, high-cycle fatigue, and low-cycle fatigue, respectively {yields} The dissipation of the hysteresis energy by microstructural changes may not always be negligible for modeling the temperature evolution during mechanical deformation - Abstract: The strain-induced face-centered cubic (FCC) {yields} hexagonal-close packed (HCP) phase transformation in a cobalt-based superalloy was investigated with four in situ loading neutron-diffraction experiments: monotonic tension, monotonic compression, high-cycle fatigue, and low-cycle fatigue. The transformation onsets for the four respective cases were 685 MPa, 698 MPa, 1 cycle, and 3 cycles, respectively. The HCP phase accumulated at rates of 0.1 wt.%-MPa{sup -1} and 0.05 wt.%-MPa{sup -1} for the tension and compression cases, respectively. For the cyclic-loading cases, the accumulation rates were found to be inversely proportional to the number of fatigue cycles. The results under the different loading modes suggest that the phase transformation occurs according to a tensile plastic-work criterion.

  12. Phase-transformation and subgrain-deformation characteristics in a cobalt-based superalloy

    International Nuclear Information System (INIS)

    Benson, M.L.; Reetz, B.; Liaw, P.K.; Reimers, W.; Choo, H.; Brown, D.W.; Saleh, T.A.; Klarstrom, D.L.

    2011-01-01

    Research highlights: → The mechanical behavior of a cobalt-based superalloy was investigated. → Two diffraction techniques were used to study deformation mechanisms of materials. → In-situ neutron diffraction provides the volume-averaged information. → The peak-profile analysis reveals the information on a subgrain level. → The material exhibited a transformation texture for the HCP phase under loading. - Abstract: A complimentary set of experiments, in situ neutron diffraction and ex situ synchrotron X-ray diffraction, were used to study the phase-transformation and subgrain-deformation characteristics of a cobalt-based superalloy. The neutron diffraction indicated a strain-induced phase transformation in the cobalt-based superalloy under uniaxial tension and compression. The synchrotron X-ray diffraction revealed stacking-fault accumulation and twinning under the same loading conditions. The extent of transformation was found to be greater under tension than under compression. Tensile plastic strains below 2% were accommodated by the stacking-fault creation, while those greater than 2% were accommodated by the phase transformation. Twinning was found to be more active under compressive loading than under tensile loading.

  13. Critical kinetic control of non-stoichiometric intermediate phase transformation for efficient perovskite solar cells

    Science.gov (United States)

    Rong, Yaoguang; Venkatesan, Swaminathan; Guo, Rui; Wang, Yanan; Bao, Jiming; Li, Wenzhi; Fan, Zhiyong; Yao, Yan

    2016-06-01

    Organometal trihalide perovskites (OTP) have attracted significant attention as a low-cost and high-efficiency solar cell material. Due to the strong coordination between lead iodide (PbI2) and dimethyl sulfoxide (DMSO) solvent, a non-stoichiometric intermediate phase of MA2Pb3I8(DMSO)2 (MA = CH3NH3+) usually forms in the one-step deposition method that plays a critical role in attaining high power conversion efficiency. However, the kinetic understanding of how the non-stoichiometric intermediate phase transforms during thermal annealing is currently absent. In this work, we investigated such a phase transformation and provided a clear picture of three phase transition pathways as a function of annealing conditions. The interdiffusion of MAI and DMSO varies strongly with the annealing temperature and time, thus determining the final film composition and morphology. A surprising finding reveals that the best performing cells contain ~18% of the non-stoichiometric intermediate phase, instead of pure phase OTP. The presence of such an intermediate phase enables smooth surface morphology and enhances the charge carrier lifetime. Our results highlight the importance of the intermediate phase growth kinetics that could lead to large-scale production of efficient solution processed perovskite solar cells.Organometal trihalide perovskites (OTP) have attracted significant attention as a low-cost and high-efficiency solar cell material. Due to the strong coordination between lead iodide (PbI2) and dimethyl sulfoxide (DMSO) solvent, a non-stoichiometric intermediate phase of MA2Pb3I8(DMSO)2 (MA = CH3NH3+) usually forms in the one-step deposition method that plays a critical role in attaining high power conversion efficiency. However, the kinetic understanding of how the non-stoichiometric intermediate phase transforms during thermal annealing is currently absent. In this work, we investigated such a phase transformation and provided a clear picture of three phase transition

  14. Stability of a laser cavity with non-parabolic phase transformation elements

    CSIR Research Space (South Africa)

    Litvin, IA

    2013-05-01

    Full Text Available aberration in high–power transversally pumped laser rods,” Opt. Commun. 259(1), 223–235 (2006). 14. A. G. Fox and T. Li, “Resonant Modes in a Maser Interferometer,” Bell Syst. Tech. J. 40, 453–488 (1961). 15. O. Svelto, Principles of Lasers, 3rd edition.... Consequently the intra-cavity implementation of any non-conventional phase transformation elements or taking into account the thermal lensing which in general has a non-parabolic phase transformation [13], leads to a solution of the complicated Fox...

  15. Phase-based motion magnification video for monitoring of vital signals using the Hermite transform

    Science.gov (United States)

    Brieva, Jorge; Moya-Albor, Ernesto

    2017-11-01

    In this paper we present a new Eulerian phase-based motion magnification technique using the Hermite Transform (HT) decomposition that is inspired in the Human Vision System (HVS). We test our method in one sequence of the breathing of a newborn baby and on a video sequence that shows the heartbeat on the wrist. We detect and magnify the heart pulse applying our technique. Our motion magnification approach is compared to the Laplacian phase based approach by means of quantitative metrics (based on the RMS error and the Fourier transform) to measure the quality of both reconstruction and magnification. In addition a noise robustness analysis is performed for the two methods.

  16. Studies of Phase Transformation in Molecular Crystals Using the Positron Annihilation Technique

    DEFF Research Database (Denmark)

    Eldrup, Morten Mostgaard; Lightbody, David; Sherwood, John N.

    1980-01-01

    An examination has been made of the brittle/plastic phase transformation in the molecular crystals cyclohexane, DL-camphene and succinonitrile using the positron annihilation technique. In each material, the transition is characterized by a distinct increase in ortho-positronium lifetime. The inf......An examination has been made of the brittle/plastic phase transformation in the molecular crystals cyclohexane, DL-camphene and succinonitrile using the positron annihilation technique. In each material, the transition is characterized by a distinct increase in ortho-positronium lifetime...

  17. Radiation-Induced Phase Transformations in Ilmenite-Group Minerals

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, J. N.

    1997-12-31

    Transmission electron microscopy (TEM) is a powerful tool for characterizing and understanding radiation-induced structural changes in materials. We have irradiated single crystals of ilmenite (FeTiO{sub 3}) and geikielite (MgTiO{sub 3}) using ions and electrons to better understand the response of complex oxides to radiation. Ion irradiation experiments of bulk single crystals at 100 K show that ilmenite amorphized at doses of less than 1x10(exp15) Ar(2+)/sq cm and at a damage level in the peak damage region of 1 displacement per atom (dpa). Transmission electron microscopy and electron diffraction of a cross-sectioned portion of this crystal confirmed the formation of a 150 am thick amorphous layer. Geikielite proved to be more radiation resistant, requiring a flux of 2x10(exp 15) Xe(2+)/sq cm to induce amorphization at 100 K. This material did not amorphize at 470 K, despite a dose of 2.5 x10(exp 16) Xe(2+)/sq cm and a damage level as high as 25 dpa. Low temperature irradiations of electron- transparent crystals with 1 MeV Kr(+) also show that ilmenite amorphized after a damage level of 2.25 dpa at 175 K.Similar experiments on geikielite show that the microstructure is partially amorphous and partially crystalline after 10 dpa at 150 K. Concurrent ion and electron irradiation of both materials with 1 MeV Kr(+) and 0.9 MeV electrons produced dislocation loops in both materials, but no amorphous regions were formed. Differences in the radiation response of these isostructural oxides suggests that in systems with Mg-Fe solid solution, the Mg-rich compositions may be more resistant to structural changes.

  18. Oxygen mobility and structural phase transformation in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} measured by anelastic spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Albuquerque de Gimenez, Juliana Maria; Grandini, Carlos Roberto; Santos, Dayse Iara dos

    2004-08-01

    One of the most studied ceramic superconductors for application has been, undoubtedly, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}. Although being a multiphasic material, it has proved to have great advantages compared to other ceramic systems. Measurements of the elastic energy loss and modulus (anelastic spectroscopy) as a function of temperature can distinguish among different atomic jumps that occur inside the various phases or at different local ordering. In this paper, mechanical loss spectra of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} bar shaped samples, made by a conventional method, have been measured between 80 and 600 K, using a torsion pendulum operating in frequencies below 50 Hz, for samples annealed in vacuum up to 600 K. Possible relaxation mechanisms are proposed to explain the origin of the mechanical-loss peaks observed 300 and 500 K.

  19. Phase Transformation of Adefovir Dipivoxil/Succinic Acid Cocrystals Regulated by Polymeric Additives

    Directory of Open Access Journals (Sweden)

    Sungyup Jung

    2013-12-01

    Full Text Available The polymorphic phase transformation in the cocrystallization of adefovir dipivoxil (AD and succinic acid (SUC was investigated. Inspired by biological and biomimetic crystallization, polymeric additives were utilized to control the phase transformation. With addition of poly(acrylic acid, the metastable phase newly identified through the analysis of X-ray diffraction was clearly isolated from the previously reported stable form. Without additives, mixed phases were obtained even at the early stage of cocrystallization. Also, infrared spectroscopy analysis verified the alteration of the hydrogen bonding that was mainly responsible for the cocrystal formation between AD and SUC. The hydrogen bonding in the metastable phase was relatively stronger than that in the stable form, which indicated the locally strong AD/SUC coupling in the initial stage of cocrystallization followed by the overall stabilization during the phase transformation. The stronger hydrogen bonding could be responsible for the faster nucleation of the initially observed metastable phase. The present study demonstrated that the polymeric additives could function as effective regulators for the polymorph-selective cocrystallization.

  20. Characteristics of the Phase-shifting Transformer Realized According to the "Polygon" Connection

    Directory of Open Access Journals (Sweden)

    Kalinin L.P.

    2017-12-01

    Full Text Available The object of the study is a two-transformer phase-shifting device with a span of adjustment of the angle of phase shift . In order to determine the energy characteristics of the investigated device, it has been put the scope to study the regime's parameters, performing adjustment of the angle of phase shift. This was made possible due to the use of the thyristor key for 10 positions and the low of it’s switching. The model was developed for a series of computational experiments for the cases of: idle, short circuit and loaded regime. A comparative analysis of the technical characteristics of the studied device, with the phase-reversing transformers investigated earlier has been carried out. The novelty of the work consists in the development of a scheme of a two-transformer phase regulating device. The additional winding of the magnetizing transformer was connected on an opposite side to the winding of the phase-shifting transformer. It has been achieved a reduction in the value of the magnetic induction in the core, as well as an increase of the stability in the process of adjusting the angle of phase shift. The analysis of the obtained characteristics of the device made it possible, by comparison with the available variants of existing circuits, to conclude that the developed one was of increased technical efficiency. The proposed technical solution decreased the installed capacity of the equipment, which in turn lead to a reduction of the weight and size indices and, as a consequence, of its cost.

  1. Synthesis of Li-Mn-O mesocrystals with controlled crystal phases through topotactic transformation of MnCO3

    Science.gov (United States)

    Dang, Feng; Hoshino, Tatsuhiko; Oaki, Yuya; Hosono, Eiji; Zhou, Haoshen; Imai, Hiroaki

    2013-02-01

    Mesocrystals of Li-Mn-O compounds, such as LiMn2O4, Li2MnO3, and LiMnO2-Li2MnO3, consisting of oriented nanoscale units were selectively produced under hydrothermal conditions from biomimetically prepared MnCO3 mesocrystals. Topotactic transformation through the intermediate phase of Mn5O8 inheriting a hierarchical structure of the MnCO3 precursor was essential for the formation of the mesocrystal compounds. The crystal phases were successfully controlled by varying the conditions for the hydrothermal reactions. The Li-Mn-O mesocrystals have considerable potential as cathodes of Li-ion batteries.Mesocrystals of Li-Mn-O compounds, such as LiMn2O4, Li2MnO3, and LiMnO2-Li2MnO3, consisting of oriented nanoscale units were selectively produced under hydrothermal conditions from biomimetically prepared MnCO3 mesocrystals. Topotactic transformation through the intermediate phase of Mn5O8 inheriting a hierarchical structure of the MnCO3 precursor was essential for the formation of the mesocrystal compounds. The crystal phases were successfully controlled by varying the conditions for the hydrothermal reactions. The Li-Mn-O mesocrystals have considerable potential as cathodes of Li-ion batteries. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr33767g

  2. Investigation of structural transformations in surface layer of phosphate glasses incorporating radiactive wastes

    International Nuclear Information System (INIS)

    Aloj, A.S.; Kolycheva, T.I.; Trofimenko, A.V.; Shashukov, E.A.

    1985-01-01

    The objective of the paper was to clarify possibilities of detection of structural transformations initial stages on the surface of phosphate glasses using the method of infrared reflection spectroscopy. Phase composition of crystalline compounds formed in surface glass layer is determined by the method of X-ray diffraction. All experiments were performed using sodium alumophosphate glass comprising the model mixture of fission product of the following compostion (mass%): Na 2 O-22.0, Al 2 O 3 -14.0, P 2 O 5 -50.0, Fe 2 O 3 -3.5, Cs 2 O-3.5, SrO-3.0, Ln 2 O 3 -4.0, where Ln 2 O 3 is a mixture of cerium, lanthanum and europium oxides. Sample preparation were carried out by molten glass deposition on platinum forms 15mm in diameter and 4mm thick. Glasses were treated within the 600-400deg.C temperature range. Fixing of processes accompanied by structural transformations was accomplished the method of rapid cooling. It has been shown that phase transformations, taking place in investigated phosphate glasses under the action of heat, result in deterioration of chemical properties. Analysis of IR spectra has revealed that emergence of structural transformations in surface layer of investigated glasses results in variation of a ratio of 1060 and 1140cm - 1 reflection band intensities. Experimental dependences of the time of beginning of variation of 1060 and 1140cm - 1 bands relative intensity on temperature are presented. Insemilogarithmic coordinates this dependence has a straight line form within the 600-400 deg C temperature range and is desc ribed by the following formular: lg r=-7.41+5.70x10 3 x1/T, where r is the time of process beginning, h. Extrapolation of established to the region of low temperature is shown. Competence of such extrapolation may be confirmed in the course of further experiments

  3. Control of the γ-alumina to α-alumina phase transformation for an optimized alumina densification

    Energy Technology Data Exchange (ETDEWEB)

    Lamouri, S.; Hamidouche, M.; Bouaouadja, N.; Belhouchet, H.; Garnier, V.; Fantozzi, G.; Trelkat, J.F.

    2017-07-01

    In this work, we studied the aptitude to sintering green bodies using γ-Al2O3 transition alumina as raw powder. We focused on the influence of the heating rate on densification and microstructural evolution. Phase transformations from transition alumina γ→δ→θ→α-Al2O3 were studied by in situ X-rays diffraction from the ambient to 1200°C. XRD patterns revealed coexistence of various phase transformations during the heating cycle. DTA and dilatometry results showed that low heating rate leads to a significant reduction of the temperature of the α-Al2O3 alumina formation. Around 1190, 1217 and 1240°C were found when using 5, 10 and 20°C/min of heating rate, respectively. The activation energy for θ-Al2O3→α-Al2O3 transformation calculated by Kissinger and JMA equations using dilatometry method were 464.29 and 488.79kJ/mol, respectively and by DTA method were 450.72 and 475.49kJ/mol, respectively. In addition, the sintering of the green bodies with low heating rate promotes the rearrangement of the grains during θ-Al2O3→α-Al2O3 transformation, enhancing the relative density to 95% and preventing the development of a vermicular structure. (Author)

  4. Phase unwrapping in digital holography based on non-subsampled contourlet transform

    Science.gov (United States)

    Zhang, Xiaolei; Zhang, Xiangchao; Xu, Min; Zhang, Hao; Jiang, Xiangqian

    2018-01-01

    In the digital holographic measurement of complex surfaces, phase unwrapping is a critical step for accurate reconstruction. The phases of the complex amplitudes calculated from interferometric holograms are disturbed by speckle noise, thus reliable unwrapping results are difficult to be obtained. Most of existing unwrapping algorithms implement denoising operations first to obtain noise-free phases and then conduct phase unwrapping pixel by pixel. This approach is sensitive to spikes and prone to unreliable results in practice. In this paper, a robust unwrapping algorithm based on the non-subsampled contourlet transform (NSCT) is developed. The multiscale and directional decomposition of NSCT enhances the boundary between adjacent phase levels and henceforth the influence of local noise can be eliminated in the transform domain. The wrapped phase map is segmented into several regions corresponding to different phase levels. Finally, an unwrapped phase map is obtained by elevating the phases of a whole segment instead of individual pixels to avoid unwrapping errors caused by local spikes. This algorithm is suitable for dealing with complex and noisy wavefronts. Its universality and superiority in the digital holographic interferometry have been demonstrated by both numerical analysis and practical experiments.

  5. Phase retrieval from a single fringe pattern by using empirical wavelet transform

    International Nuclear Information System (INIS)

    Guo, Xiaopeng; Zhao, Hong; Wang, Xin

    2015-01-01

    Phase retrieval from a single fringe pattern is one of the key tasks in optical metrology. In this paper, we present a new method for phase retrieval from a single fringe pattern based on empirical wavelet transform. In the proposed method, a fringe pattern can be effectively divided into three components: nonuniform background, fringes and random noise, which are described in different sub-pass. So the phase distribution information can be robustly extracted from fringes representing a fundamental frequency component. In simulation and a practical projection fringes test, the performance of the present method is successfully verified by comparing with the conventional wavelet transform method in terms of both image quality and phase estimation errors. (paper)

  6. Gyrator transform of Gaussian beams with phase difference and generation of hollow beam

    Science.gov (United States)

    Xiao, Zhiyu; Xia, Hui; Yu, Tao; Xie, Ding; Xie, Wenke

    2018-03-01

    The optical expression of Gaussian beams with phase difference, which is caused by gyrator transform (GT), has been obtained. The intensity and phase distribution of transform Gaussian beams are analyzed. It is found that the circular hollow vortex beam can be obtained by overlapping two GT Gaussian beams with π phase difference. The effect of parameters on the intensity and phase distributions of the hollow vortex beam are discussed. The results show that the shape of intensity distribution is significantly influenced by GT angle α and propagation distance z. The size of the hollow vortex beam can be adjusted by waist width ω 0. Compared with previously reported results, the work shows that the hollow vortex beam can be obtained without any model conversion of the light source.

  7. TOPOLOGICAL TRANSIENT MODELS OF THREE-PHASE FIVE-LIMB TRANSFORMER

    Directory of Open Access Journals (Sweden)

    S. E. Zirka

    2018-02-01

    Full Text Available Purpose. To show capabilities of topological models of three-phase, five-limb transformer to correctly represent transformer operation in regimes with high flux densities in the core. As a practically important example, time domain response of transformer subjected to geomagnetically induced currents (GIC is analyzed and compared with results of a comprehensive field experiment.Methodology.  Transformer magnetic model, which takes into account geometry of the core and windings, is transformed in a dual electric equivalent scheme, whose transient is calculated by using EMTP-ATP. The results obtained demonstrate the importance of incorporating the positive and zero sequence impedances of power network.Findings. A simple and reliable model of five-limb transformer is proposed. It was found that the presence of the transformer tank can be effectively accounted for by linear inductances representing the paths of the off-core fluxes from yoke to yoke. The modeling of GIC events represented in the paper is the most accurate ever obtained for three-phase, five-leg transformers. The model is validated by close agreement of the predicted values and waveforms of the phase currents and reactive power with those measured in tests performed on two 400 MVA transformers connected back-to-back and to a 400 kV power network. Originality. It is shown that a simplified non-hysteresis model developed portrays the behavior of the of five-limb transformer under GIC condition with the same good accuracy as its hysteresis model. Both the transformer models are well grounded. So, the paper dispels some misconceptions about the influence of the hysteresis properties of the core material and tank in transient modeling of five-leg transformers.Practical value. The practical value and significance of the paper is caused by the fact that the model proposed is a simple and reliable tool for power system studies. The paper warns of using unnecessary complicated models whose

  8. Differential Chromatin Structure Encompassing Replication Origins in Transformed and Normal Cells

    Science.gov (United States)

    Di Paola, Domenic; Rampakakis, Emmanouil; Chan, Man Kid

    2012-01-01

    This study examines the chromatin structure encompassing replication origins in transformed and normal cells. Analysis of the global levels of histone H3 acetylated at K9&14 (open chromatin) and histone H3 trimethylated at K9 (closed chromatin) revealed a higher ratio of open to closed chromatin in the transformed cells. Also, the trithorax and polycomb group proteins, Brg-1 and Bmi-1, respectively, were overexpressed and more abundantly bound to chromatin in the transformed cells. Quantitative comparative analyses of episomal and in situ chromosomal replication origin activity as well as chromatin immunoprecipitation (ChIP) assays, using specific antibodies targeting members of the pre-replication complex (pre-RC) as well as open/closed chromatin markers encompassing both episomal and chromosomal origins, revealed that episomal origins had similar levels of in vivo activity, nascent DNA abundance, pre-RC protein association, and elevated open chromatin structure at the origin in both cell types. In contrast, the chromosomal origins corresponding to 20mer1, 20mer2, and c-myc displayed a 2- to 3-fold higher activity and pre-RC protein abundance as well as higher ratios of open to closed chromatin and of Brg-1 to Bmi-1 in the transformed cells, whereas the origin associated with the housekeeping lamin B2 gene exhibited similar levels of activity, pre-RC protein abundance, and higher ratios of open to closed chromatin and of Brg-1 to Bmi-1 in both cell types. Nucleosomal positioning analysis, using an MNase-Southern blot assay, showed that all the origin regions examined were situated within regions of inconsistently positioned nucleosomes, with the nucleosomes being spaced farther apart from each other prior to the onset of S phase in both cell types. Overall, the results indicate that cellular transformation is associated with differential epigenetic regulation, whereby chromatin structure is more open, rendering replication origins more accessible to initiator

  9. Gas phase ion/molecule reactions as studied by Fourier Transform Ion Cyclotron Resonance mass spectrometry

    International Nuclear Information System (INIS)

    Joergensen, S.I.

    1985-01-01

    The subject of this thesis is gas phase ion/molecule reactions as studied by Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry (chapter 2 contains a short description of this method). Three chapters are mainly concerned with mechanistic aspects of gas phase ion/molecule reactions. An equally important aspect of the thesis is the stability and reactivity of α-thio carbanions, dipole stabilized carbanions and homoenolate anions, dealt with in the other four chapters. (Auth.)

  10. Application of calorimetry in evaluation of phase transformations in the selected hypoeutectic silumins

    Directory of Open Access Journals (Sweden)

    J. Szymszal

    2009-04-01

    Full Text Available The investigations of phase transformations described in this study were carried out on hypoeutectic alloys from the Al-Si during heating and cooling. The determination and analysis of characteristic temperature values from the solidification range was made by the DSC method in calorimetric investigations carried out on a high-temperature multi HTC Setaram scanning calorimeter. Applying the lever rule, the phase composition of the examined slumins was calculated and compared with the results of DSC calorimetry.

  11. Optical, electrical and structural characterization of novel phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Herpers, Anja; Woda, Michael; Wuttig, Matthias [1. Physikalisches Institut IA, RWTH Aachen University, Aachen (Germany)

    2009-07-01

    Phase Change Materials (PCM) are alloys, which can be used in a variety of applications in information technology. Information is stored using the transformation of small regions of a thin film between the crystalline and amorphous state. This phase change is accompanied by a remarkable change of properties such as the electrical resistivity and the optical reflectivity. Furthermore the transition between both states is extremely fast at elevated temperatures but negligible at room temperature. This property portfolio is attractive for storage applications. The corresponding materials are already used in rewriteable optical data storage media such as DVD and Blu-Ray-Discs, and are promising candidates for novel non-volatile electronic memory devices such as Phase Change Random Access Memories. In this study the structural, optical and electrical properties of two materials, i.e. Ag{sub 4}In{sub 3}Sb{sub 67}Te{sub 26} and GeSe are investigated. X-Ray diffraction and X-Ray reflection measurements reveal changes in the crystal structure and the film density upon crystallization. DSC measurements provide the crystallization temperature. The optical properties in an energy range of 0.025-5.3 eV are determined combining ellipsometry and FTIR experiments. Sheet resistance measurements in the van-der-Pauw-geometry enable the measurement of the electrical properties between 300 and 600 K.

  12. Structure of martensitic phase and phonon instability in Cu61Zn39

    International Nuclear Information System (INIS)

    Konishi, Akio; Kuroiwa, Yoshihiro; Noda, Yukio

    1993-01-01

    In order to study the mechanism of the martensitic phase transformation in Cu 61 Zn 39 , neutron elastic and inelastic scattering experiments were performed at JRR-2 and JRR-3M of JAERI and HFIR or Oak Ridge National Laboratry. Measurements of phonon dispersion curve indicate that the entire TA 2 [110] phonon mode is extremely soft and shows further softening on decreasing temperature. However, no anomalies in dispersion relations found in other directions studied. The structure of the martensite phase was investigated by using a WAND spectrometer on (HHL) and (HKO) planes. Analysis of two-dimensional intensity data indicates that the structure of martensite phase in Cu 61 Zn 39 is slightly different from the 9R' structure reported by Tadaki et al. We propose a mixed phase of a distorted CsCl structure and a three-period lattice as the structure of martensite phase. (author)

  13. Pressure-induced phase transformation in zircon-type orthovanadate SmVO4 from experiment and theory

    International Nuclear Information System (INIS)

    Popescu, C; Garg, Alka B; Errandonea, D; Sans, J A; Rodriguez-Hernández, P; Radescu, S; Muñoz, A; Achary, S N; Tyagi, A K

    2016-01-01

    The compression behavior of zircon-type samarium orthovanadate, SmVO 4 , has been investigated using synchrotron-based powder x-ray diffraction and ab initio calculations of up to 21 GPa. The results indicate the instability of ambient zircon phase at around 6 GPa, which transforms to a high-density scheelite-type phase. The high-pressure phase remains stable up to 21 GPa, the highest pressure reached in the present investigations. On pressure release, the scheelite phase is recovered. The crystal structure of the high-pressure phase and the equations of state for the zircon- and scheelite-type phases have been determined. Various compressibilities, such as the bulk, axial and bond compressibilities, estimated from the experimental data are found to be in good agreement with the results obtained from theoretical calculations. The calculated elastic constants show that the zircon structure becomes mechanically unstable beyond the transition pressure. Overall there is good agreement between the experimental and theoretical findings. (paper)

  14. Pressure-induced phase transformation in zircon-type orthovanadate SmVO4 from experiment and theory.

    Science.gov (United States)

    Popescu, C; Garg, Alka B; Errandonea, D; Sans, J A; Rodriguez-Hernández, P; Radescu, S; Muñoz, A; Achary, S N; Tyagi, A K

    2016-01-27

    The compression behavior of zircon-type samarium orthovanadate, SmVO4, has been investigated using synchrotron-based powder x-ray diffraction and ab initio calculations of up to 21 GPa. The results indicate the instability of ambient zircon phase at around 6 GPa, which transforms to a high-density scheelite-type phase. The high-pressure phase remains stable up to 21 GPa, the highest pressure reached in the present investigations. On pressure release, the scheelite phase is recovered. The crystal structure of the high-pressure phase and the equations of state for the zircon- and scheelite-type phases have been determined. Various compressibilities, such as the bulk, axial and bond compressibilities, estimated from the experimental data are found to be in good agreement with the results obtained from theoretical calculations. The calculated elastic constants show that the zircon structure becomes mechanically unstable beyond the transition pressure. Overall there is good agreement between the experimental and theoretical findings.

  15. Thermal Behavior of an HSLA Steel and the Impact in Phase Transformation: Submerged Arc Welding (SAW) Process Approach to Pipelines

    Science.gov (United States)

    Costa, P. S.; Reyes-Valdés, F. A.; Saldaña-Garcés, R.; Delgado, E. R.; Salinas-Rodríguez, A.

    Heat input during welding metal fusion generates different transformations, such as grain growth, hydrogen cracking, and the formation of brittle structures, generally associated with the heat-affected zone (HAZ). For this reason, it is very important to know the behavior of this area before welding. This paper presents a study of the thermal behavior and its effect on phase transformations in the HAZ, depending on cooling rates (0.1-200 °C/s) to obtain continuous cooling transformation (CCT) curves for an high-strength low-alloy (HSLA) steel. In order to determine the formed phases, optical microscopy and Vickers microhardness measurement were used. The experimental CCT curve was obtained from an HSLA steel, and the results showed that, with the used cooling conditions, the steel did not provide formation of brittle structures. Therefore, it is unlikely that welds made by submerged arc welding (SAW) may lead to hydrogen embrittlement in the HAZ, which is one of the biggest problems of cracking in gas conduction pipelines. In addition, with these results, it will be possible to control the microstructure to optimize the pipe fabrication with SAW process in industrial plants.

  16. Thermodynamic and kinetics models of hydrogen absorption bound to phase transformations; Modelisation thermodynamique et cinetiques d'absorption d'hydrogene associees aux transformations de phase

    Energy Technology Data Exchange (ETDEWEB)

    Gondor, G.; Lexcellent, Ch. [Institut FEMTO-ST, Lab. de Mecanique Appliquee R. Chaleat (LMARC), 25 - Besancon (France)

    2007-07-01

    In order to design hydrogen gaseous pressure tanks, the absorption (desorption) of hydrogen has to be described and modelled. The equilibrium state can be described by the 'H{sub 2} gas pressure - H{sub 2} composition in the intermetallic compounds - isotherms' (PCI) curves. Several models of PCI curves already exist. At the beginning of the absorption, the hydrogen atoms and the intermetallic compounds form a solid solution ({alpha} phase). When the hydrogen concentration increases, a phase transformation appears changing the {alpha} solid solution into an hydride ({beta} phase) (solid solution + H{sub 2} {r_reversible} hydride). When all the solid solution has been transformed into hydride, the absorbed hydrogen atoms are in {beta} phase. A new thermodynamic model has been developed in order to take into account this transition phase. The equilibrium state is then given by a relation between the H{sub 2} gas pressure and the H{sub 2} concentration in the intermetallic compound for a fixed external temperature. Two kinetics models have been developed too; at first has been considered that the kinetics depend only of the entire concentration in the intermetallic compound and of the difference between the applied pressure and the equilibrium pressure. Then, has been considered that the hydrogen concentration changes in the metallic matrix. In this last case, for each hydrogenation process, the absorption velocity is calculated to determine the slowest local process which regulates the local evolution of the hydrogen concentration. These two models are based on the preceding thermodynamic model of the PCI curves. (O.M.)

  17. Microstructural transformation with heat-treatment of aluminum hydroxide with gibbsite structure

    International Nuclear Information System (INIS)

    Mitsui, Tomohiro; Matsui, Toshiaki; Eguchi, Koichi; Kikuchi, Ryuji

    2009-01-01

    Aluminum hydroxide with gibbsite structure was prepared, and the microstructural transformation of the sample heat-treated at various temperatures was investigated. The sample was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), thermogravimetry and differential thermal analysis (TG-DTA), and BET surface area. The shape of the grains in the prepared sample was hexagonal prism-like morphology. The prepared sample kept a metastable state of alumina phase at higher temperatures than the commercially available gibbsite powders. The prepared gibbsite grains underwent characteristic structural change depending on the calcination temperature. The transformation of the surface morphology was initiated at 400degC, leading to the formation of cracks with the direction parallel to the basal plane. After calcination at 1200degC, a large number of grooves were formed on the surface of the lateral planes. The specific structural change of gibbsite induced by the heat treatment was strongly related to the topotactic dehydration from gibbsite and subsequent phase transition to aluminum oxides. (author)

  18. In-Situ Analysis of Phase Transformations in a Supermartensitic Stainless Steel : A magnetic approach

    NARCIS (Netherlands)

    Bojack, A.

    2018-01-01

    This thesis studies in-situ the phase transformations during heat treatment of two advanced steels: a supermartensitic stainless steels (SMSS), on which the main focus of this work is, and Fe-C-Mn-Si steels. A magnetic technique, based on the analysis of saturation magnetization, is utilized as the

  19. Microstructure and phase transformation on milled and unmilled Ti induced by water quenching

    CSIR Research Space (South Africa)

    Bolokang, AS

    2014-10-01

    Full Text Available Materials Letters Vol. 132 Microstructure and phase transformation on milled and unmilled Ti induced by water quenching A.S.Bolokang a,b,n, M.J.Phasha c, D.E.Motaung b, F.R.Cummings a,d, T.F.G.Muller a, C.J.Arendse a a Department of...

  20. A thick-interface model for diffusive and massiv phase transformation in substitutional alloys

    Czech Academy of Sciences Publication Activity Database

    Svoboda, Jiří; Vala, J.; Gamsjäger, E.; Fischer, F. D.

    2006-01-01

    Roč. 54, č. 15 (2006), s. 3953-3960 ISSN 1359-6454 R&D Projects: GA AV ČR IAA200410601 Institutional research plan: CEZ:AV0Z20410507 Keywords : phase transformation * diffusion * modelling Subject RIV: JG - Metallurgy Impact factor: 3.549, year: 2006

  1. Phase retrieval from the magnitude of the Fourier transforms of nonperiodic objects

    International Nuclear Information System (INIS)

    Miao, J.; Sayre, D.; Chapman, H.N.

    1998-01-01

    It is suggested that, given the magnitude of Fourier transforms sampled at the Bragg density, the phase problem is underdetermined by a factor of 2 for 1D, 2D, and 3D objects. It is therefore unnecessary to oversample the magnitude of Fourier transforms by 2x in each dimension (i.e., oversampling by 4x for 2D and 8x for 3D) in retrieving the phase of 2D and 3D objects. Our computer phasing experiments accurately retrieved the phase from the magnitude of the Fourier transforms of 2D and 3D complex-valued objects by using positivity constraints on the imaginary part of the objects and loose supports, with the oversampling factor much less than 4 for 2D and 8 for 3D objects. Under the same conditions we also obtained reasonably good reconstructions of 2D and 3D complex-valued objects from the magnitude of their Fourier transforms with added noise and a central stop. copyright 1998 Optical Society of America

  2. In situ measurement of solvent-mediated phase transformations during dissolution testing

    DEFF Research Database (Denmark)

    Aaltonen, Jaakko; Heinänen, Paula; Peltonen, Leena

    2006-01-01

    In this study, solvent-mediated phase transformations of theophylline (TP) and nitrofurantoin (NF) were measured in a channel flow intrinsic dissolution test system. The test set-up comprised simultaneous measurement of drug concentration in the dissolution medium (with UV-Vis spectrophotometry...

  3. Voltage Management in Unbalanced Low Voltage Networks Using a Decoupled Phase-Tap-Changer Transformer

    DEFF Research Database (Denmark)

    Coppo, Massimiliano; Turri, Roberto; Marinelli, Mattia

    2014-01-01

    The paper studies a medium voltage-low voltage transformer with a decoupled on load tap changer capability on each phase. The overall objective is the evaluation of the potential benefits on a low voltage network of such possibility. A realistic Danish low voltage network is used for the analysis...

  4. Modelling of Diffusive and Massive Phase Transformations in Binary Systems – Thick Interface Parametric Model

    Czech Academy of Sciences Publication Activity Database

    Svoboda, Jiří; Gamsjäger, E.

    2011-01-01

    Roč. 102, č. 6 (2011), s. 666-673 ISSN 1862-5282 R&D Projects: GA MŠk(CZ) OC10029 Institutional research plan: CEZ:AV0Z20410507 Keywords : modelling * phase transformation * ediffusion Subject RIV: BJ - Thermodynamics Impact factor: 0.830, year: 2011

  5. Influence of Ni on martensitic phase transformations in NiTi

    Czech Academy of Sciences Publication Activity Database

    Frenzel, J.; George, E.P.; Dlouhý, Antonín; Somsen, Ch.; Wagner, M.F.-X.; Eggeler, G.

    2010-01-01

    Roč. 58, č. 9 (2010), s. 3444-3458 ISSN 1359-6454 R&D Projects: GA ČR GA106/09/1913 Institutional research plan: CEZ:AV0Z20410507 Keywords : NiTi shape memory alloys * Phase transformation temperatures * Thermodynamics * Vacuum arc melting Subject RIV: JJ - Other Materials Impact factor: 3.781, year: 2010

  6. Kinetics of diffusional phase transformation in multicomponent elastic-plastic materials

    Czech Academy of Sciences Publication Activity Database

    Fischer, F. D.; Simha, N. K.; Svoboda, Jiří

    2003-01-01

    Roč. 125, č. 3 (2003), s. 266-276 ISSN 0094-4289 R&D Projects: GA AV ČR KSK1010104 Keywords : diffusion -phase transformation * modelling Subject RIV: JG - Metallurgy Impact factor: 0.843, year: 2003

  7. Kinetics of phase transformations in Mg2Ni-H system

    Czech Academy of Sciences Publication Activity Database

    Čermák, Jiří; Král, Lubomír; David, Bohumil; Stloukal, Ivo

    2008-01-01

    Roč. 138, - (2008), s. 71-90 ISSN 1012-0394 R&D Projects: GA ČR GA106/07/0010 Institutional research plan: CEZ:AV0Z20410507 Keywords : hydrogen storage * hydrogen diffusion * phase transformations Subject RIV: BJ - Thermodynamics http://www.scientific.net/3-908451-49-3/71/

  8. Liquid phase sintered SiC. Processing and transformation controlled microstructure tailoring

    Directory of Open Access Journals (Sweden)

    V.A. Izhevskyi

    2000-10-01

    Full Text Available Microstructure development and phase formation processes during sintering of silicon carbide based materials with AlN-Y2O3, AlN-Yb2O3, and AlN-La2O3 sintering additives were investigated. Densification of the materials occurred by liquid-phase sintering mechanism. Proportion of alpha- and beta-SiC powders in the initial mixtures was a variable parameter, while the molar ratio of AlN/RE2O3, and the total amount of additives (10 vol. % were kept constant. Shrinkage behavior during sintering in interrelation with the starting composition of the material and the sintering atmosphere was investigated by high temperature dilatometry. Kinetics of b-SiC to a-SiC phase transformation during post-sintering heat treatment at temperatures 1900-1950 °C was studied, the degree of phase transformation being determined by quantitative x-ray analysis using internal standard technique. Evolution of microstructure resulting from beta-SiC to alpha-SiC transformation was followed up by scanning electron microscopy on polished and chemically etched samples. Transformation-controlled grain growth mechanism similar to the one observed for silicon nitride based ceramics was established. Possibility of in-situ platelet reinforced dense SiC-based ceramics fabrication with improved mechanical properties by means of sintering was shown.

  9. A new method to determinate phase transformation in shape memory alloys: infrared thermography

    International Nuclear Information System (INIS)

    Bubulinca, C.; Balandraud, X.; Grediac, M.; Plaiasu, G. A.; Abrudeanu, M.; Stanciu, S.

    2013-01-01

    In this article it is presented a shape memory alloy case, based on copper, namely Cu-Zn-Al, which is subjected to periodic mechanical traction. Traction is performed in conditions of normal temperature and pressure. The purpose of this article it is to study stress induced phase transformation. All tests are performed in same conditions. Transformation on which is based this effect occurs in two ways: by applying a stress or temperature variation. In this article it is studied stress induced phase transformation. The method to analyze the microstructure of an shape memory alloy (SMA) is relatively new and it is based on tracking the evolution of temperature. After thermal analysis we can decide in which state is one alloy without any other supplier measures (differential scanning calorimetric or electrical resistivity). If our specimen will producing thermal energy when specimen is tensile he is austenitic. If absorbing heat during the first deformation is in martensitic state. (authors)

  10. Hysteresis phenomena at metal-semiconductor phase transformation in vanadium oxides

    International Nuclear Information System (INIS)

    Lanskaya, T.G.; Merkulov, I.A.; Chudnovski , F.A.

    1978-01-01

    The hysteresis phenomena during the metal-semiconductor phase transformation (MSPT) in vanadium oxides are investigated. It is shown experimentally that the hysteresis effects during MSPT in vanadium oxides are associated not only with the martensite nature of the transformation, but also with activation processes. It is shown that the hysteresis phenomena during MSPT may be described by the distribution function of microregions of the crystal in the phase transformation temperature T 0 and the coercive temperature Tsub(c). An experimental method for constructing this distribution function was worked out. An analysis of the experimental data shows that finely dispersed films are characterized by a wide range of values of T 0 and Tsub(c) (55 deg C 0 <65 deg C, 6 deg C< Tsub(c)<12 deg C). The peculiarities of the optical recording of information on monocrystal and finely dispersed films are considered

  11. About the dynamics of structural phase transitions

    International Nuclear Information System (INIS)

    Medeiros, J.T.N.

    1975-01-01

    The dynamics of structural phase transitions with a fourth order interaction between the soft phonon fields is studied in the 1/n approximation, using many body methods at finite temperatures. Two limits are considered: high transition temperature T sub(c) (classical limit) and T sub(c) = 0 (quantum limit). The dynamical contribution to the critical coefficient eta of the correlation function is calculated in these limits. It is found that there is no dynamical contribution to eta in the classical limit, whereas in the quantum limit eta is non-zero only for dimensions of the system d [pt

  12. Internal friction behaviors of Ni-Mn-In magnetic shape memory alloy with two-step structural transformation

    Directory of Open Access Journals (Sweden)

    Zhen-ni Zhou

    2017-06-01

    Full Text Available The internal friction (IF behaviors of dual-phase Ni52Mn32In16 alloy with two-step structural transformation were investigated by dynamic mechanical analyzer. The IF peak for the martensite transformation (MT is an asymmetric shoulder rather than those sharp peaks for other shape memory alloys. The intermartensitic transformation (IMT peak has the maximum IF value. As the heating rate increases, the height of the IMT peak increases and its position is shifted to higher temperatures. In comparison with the IMT peak, the MT peak is independent on the heating rate. The starting temperatures of the IMT peak are strongly dependent on frequency, while the MT peak is weakly dependent. Meanwhile, the heights of both the MT and IMT peak rapidly decrease with increasing the frequency. This work also throws new light on their structural transformation mechanisms.

  13. Numerical and Experimental Study of Phase Transformations in Welding Processes / Badania Numeryczne I Doświadczalne Przemian Fazowych W Procesach Spawania

    Directory of Open Access Journals (Sweden)

    Piekarska W.

    2015-12-01

    Full Text Available The paper concerns the mathematical and numerical modeling of phase transformations in solid state occurring during welding. The analysis of the influence of heating rate, cooling rate and maximum temperatures of thermal cycles on the kinetics of phase transformations is presented. On the basis of literature data and experimental studies the evaluation of classic mathematical and numerical models of phase transformation is presented with respect to the advanced methods of welding by using a high speed and a high power heat source. The prediction of the structure composition in laser welded butt-joint made of S460 steel is performed, where phase transformations are calculated on the basis of modified numerical models. Temperature distributions are determined as well as the shape and size of fusion zone and heat affected zone (HAZ. Temperature field is obtained by the solution of transient heat transfer equation with convective term and external volumetric heat source taken into account. Latent heat of fusion, evaporation and heats generated during phase transformations in solid state are considered in the numerical algorithm due to the large temperature range present in analyzed process. Results of the numerical prediction of structure composition in HAZ are presented in this work. Obtained results of computer simulations are compared to experimental research performered on the laser welded joint.

  14. Subsurface characterization of an oxidation-induced phase transformation and twinning in nickel-based superalloy exposed to oxy-combustion environments

    International Nuclear Information System (INIS)

    Zhu Jingxi; Holcomb, Gordon R.; Jablonski, Paul D.; Wise, Adam; Li Jia; Laughlin, David E.; Sridhar, Seetharaman

    2012-01-01

    Highlights: ►Oxidation products of Ni-based superalloy were studied in oxy-fuel combustion conditions. ► An oxidation-induced phase transformation occurred in the subsurface region. ► One of the two product phases was not in the Ni database of Thermo-Calc. ► This unknown phase is an ordered derivative of FCC structure of Ni–Ti(–Ta) system. ► This phase is likely detrimental to the mechanical integrity of the alloy in use. - Abstract: In the integration of oxy-fuel combustion to turbine power generation system, turbine alloys are exposed to high temperature and an atmosphere comprised of steam, CO 2 and O 2 . While surface and internal oxidation of the alloy takes place, the microstructure in the subsurface region also changes due to oxidation. In this study, bare metal coupons of Ni-base superalloys were exposed in oxy-fuel combustion environment for up to 1000 h and the oxidation-related microstructures were examined. Phase transformation occurred in the subsurface region in Ni-based superalloy and led to twinning. The transformation product phases were analyzed through thermodynamic equilibrium calculations and various electron microscopy techniques, including scanning electron microscopy (SEM), orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). The mechanism by which the phase transformation and the formation of the microstructure occurred was also discussed. The possible effects of the product phases on the performance of the alloy in service were discussed.

  15. Determining the magnetically nonlinear characteristics of a three phase core-type power transformer

    International Nuclear Information System (INIS)

    Dolinar, Matjaz; Stumberger, Gorazd; Polajzer, Bostjan; Dolinar, Drago

    2006-01-01

    This paper presents nonlinear iron core model of a three-phase, three-limb power transformer which is given by the current-dependant characteristics of flux linkages. The magnetically nonlinear characteristics are determined by controlled magnetic excitation of all three limbs which allows to take into account the variable magnetic-cross couplings between different coils placed on limbs, caused by saturation. The corresponding partial derivatives of measured flux linkage characteristics are used in the transformer circuit model as a magnetically nonlinear iron core model in order to analyze the behaviour of a nonsymmetrically excited transformer. Numerical results using transformer model with the determined iron core model agree very well with the measured results

  16. Luminescence of defects in the structural transformation of layered tin dichalcogenides

    Science.gov (United States)

    Sutter, P.; Komsa, H.-P.; Krasheninnikov, A. V.; Huang, Y.; Sutter, E.

    2017-12-01

    Layered tin sulfide semiconductors are both of fundamental interest and attractive for energy conversion applications. Sn sulfides crystallize in several stable bulk phases with different Sn:S ratios (SnS2, Sn2S3, and SnS), which can transform into phases with a lower sulfur concentration by introduction of sulfur vacancies (VS). How this complex behavior affects the optoelectronic properties remains largely unknown but is of key importance for understanding light-matter interactions in this family of layered materials. Here, we use the capability to induce VS and drive a transformation between few-layer SnS2 and SnS by electron beam irradiation, combined with in-situ cathodoluminescence spectroscopy and ab-initio calculations to probe the role of defects in the luminescence of these materials. In addition to the characteristic band-edge emission of the endpoint structures, our results show emerging luminescence features accompanying the SnS2 to SnS transformation. Comparison with calculations indicates that the most prominent emission in SnS2 with sulfur vacancies is not due to luminescence from a defect level but involves recombination of excitons bound to neutral VS in SnS2. These findings provide insight into the intrinsic and defect-related optoelectronic properties of Sn chalcogenide semiconductors.

  17. Interface Propagation and Microstructure Evolution in Phase Field Models of Stress-Induced Martensitic Phase Transformations

    Science.gov (United States)

    2010-01-01

    on martensitic or dif- fusionless transformations ( Ahluwalia et al., 2003; Artemev et al., 2001; Curnoe and Jacobs, 2001a,b; Jacobs et al., 2003; Jin...497. Ahluwalia , R., Lookman, T., Saxena, A., Bishop, A.R., 2003. Elastic deformation of polycrystals. Phys. Rev. Lett. 91, 055501. Artemev, A., Jin, Y

  18. High transformer ratio of multi-channel dielectric wakefield structures

    Energy Technology Data Exchange (ETDEWEB)

    Shchelkunov, Sergey V., E-mail: sergey.shchelkunov@gmail.com [Omega-P R& D, Inc, CT 06511 (United States); Yale University, CT (United States); Marshall, Thomas C. [Omega-P R& D, Inc, CT 06511 (United States); Sotnikov, Gennadij V. [NSC Kharkov Institute of Physics and Technology, Kharkov (Ukraine); Hirshfield, Jay L. [Omega-P R& D, Inc, CT 06511 (United States)

    2016-09-01

    Dielectric wakefield (DWA) accelerator concepts are receiving attention on account of their promising performance, mechanical simplicity, and anticipated low cost. Interest in DWA physics directed toward an advanced high-gradient accelerator has been enhanced by a finding that some dielectrics can withstand very high fields (>1 GV/m) for the short times during the passage of charged bunches along dielectric-lined channels. In a two-channel structure, a drive bunch train propagates in a first channel, and in the second adjacent channel where a high gradient wakefield develops, a witness bunch is accelerated. Compared with single-channel DWA's, a two-beam accelerator delivers a high transformer ratio, and thereby reduces the number of drive beam sections needed to achieve a given final test beam energy. An overview of multi-channel DWA structures will be given, with an emphasis on two-channel structures, presenting their advantages and drawbacks, and potential impact on the field. Studies aimed to examine charging rate and charge distribution in a thin walled dielectric wakefield accelerator from a passing charge bunch and the physics of conductivity and discharge phenomena in dielectric materials useful for such accelerator applications are presented in a separate paper in the EAAC-2015 conference proceedings.

  19. Structural transformations in quenched Fe-Ga alloys

    International Nuclear Information System (INIS)

    Lograsso, T.A.; Ross, A.R.; Schlagel, D.L.; Clark, A.E.; Wun-Fogle, M.

    2003-01-01

    It has been speculated that the large increase in magnetostriction in Fe-Ga alloys results from local short-range ordering of the Ga atoms along specific crystallographic directions in the disordered Fe structure. The structural transitions associated with different cooling rates from the high temperature disordered state were investigated with X-ray diffraction of oriented single crystals of Fe-19 at% Ga. Results are presented for long-range ordering during slow cooling and indirect evidence of local short-range ordering of Ga atoms in the disordered state when the alloys are quenched is also presented. In the latter case, the short-range ordering of Ga atoms leads to a tetragonal distortion of the lattice. The dependence of the magnetostrictive response of Fe-Ga alloys on thermal history has been found to be directly related to these structural transformations in Fe-19 at% Ga alloys and experimental support for the proposed magnetostriction model based on Ga-Ga pairing along [100] crystallographic directions is presented

  20. Factors influencing shape memory effect and phase transformation behaviour of Fe-Mn-Si based shape memory alloys

    International Nuclear Information System (INIS)

    Li, H.; Dunne, D.; Kennon, N.

    1999-01-01

    The objective of this research work was to investigate the factors influencing the shape memory effect and phase transformation behaviour of three Fe-Mn-Si based shape memory alloys: Fe-28Mn-6Si, Fe-13Mn-5Si-10Cr-6Ni and Fe-20Mn-6Si-7Cr-1Cu. The research results show that the shape memory capacity of Fe-Mn-Si based shape memory alloys varies with annealing temperature, and this effect can be explained in terms of the effect of annealing on γ ε transformation. The nature and concentration of defects in austenite are strongly affected by annealing conditions. A high annealing temperature results in a low density of stacking faults, leading to a low nucleation rate during stress induced γ→ε transformation. The growth of ε martensite plates is favoured rather than the formation of new ε martensite plates. Coarse martensite plates produce high local transformation strains which can be accommodated by local slip deformation, leading to a reduction in the reversibility of the martensitic transformation and to a degradation of the shape memory effect. Annealing at low temperatures (≤673 K) for reasonable times does not eliminate complex defects (dislocation jogs, kinks and vacancy clusters) created by hot and cold working strains. These defects can retard the movement and rearrangement of Shockley partial dislocations, i.e. suppress γ→ε transformation, also leading to a degradation of shape memory effect. Annealing at about 873 K was found to be optimal to form the dislocation structures which are favourable for stress induced martensitic transformation, thus resulting in the best shape memory behaviour. (orig.)

  1. Numerical analysis of laser welding with consideration analytical methods of determining phase transformations and mechanical properties of welded joint

    Directory of Open Access Journals (Sweden)

    Piekarska Wiesława

    2018-01-01

    Full Text Available The numerical analysis of laser welding process with consideration analytical methods determining phase transformations and mechanical properties of welded joints are presents in this paper. The analytical CCT diagram and final structural composition of S355 steel are presented. The empirical relations presents in paper are determined by chemical compositions investigated steel and cooling rate between temperatures 800-500°C (t8/5. Phase composition and mechanical properties each of structures of steel in weld and heat affected zone (HAZ are determined on the basis of analytical methods. Laser welded flat is used in numerical simulations in ABAQUS. Mathematical modes of volumetric welding source are used in the calculations. Temperature fields, shape and size of melting zone for selected points in the cross-section of the joint are determined on the basis of thermal cycles obtained numerical.

  2. Comparison of the quench and fault current limiting characteristics of the flux-coupling type SFCL with single and three-phase transformer

    International Nuclear Information System (INIS)

    Jung, Byung Ik; Cho, Yong Sun; Park, Hyoung Min; Chung, Dong Chul; Choi, Hyo Sang

    2013-01-01

    Highlight: ► Comparison of quench and fault-current-limiting behavior of SFCLs by Tr type. -- Abstract: The South Korean power grid has a network structure for the flexible operation of the system. The continuously increasing power demand necessitated the increase of power facilities, which decreased the impedance in the power system. As a result, the size of the fault current in the event of a system fault increased. As this increased fault current size is threatening the breaking capacity of the circuit breaker, the main protective device, a solution to this problem is needed. The superconducting fault current limiter (SFCL) has been designed to address this problem. SFCL supports the stable operation of the circuit breaker through its excellent fault-current-limiting operation [1–5]. In this paper, the quench and fault current limiting characteristics of the flux-coupling-type SFCL with one three-phase transformer were compared with those of the same SFCL type but with three single-phase transformers. In the case of the three-phase transformers, both the superconducting elements of the fault and sound phases were quenched, whereas in the case of the single-phase transformer, only that of the fault phase was quenched. For the fault current limiting rate, both cases showed similar rates for the single line-to-ground fault, but for the three-wire earth fault, the fault current limiting rate of the single-phase transformer was over 90% whereas that of the three-phase transformer was about 60%. It appears that when the three-phase transformer was used, the limiting rate decreased because the fluxes by the fault current of each phase were linked in one core. When the power loads of the superconducting elements were compared by fault type, the initial (half-cycle) load was great when the single-phase transformer was applied, whereas for the three-phase transformer, its power load was slightly lower at the initial stage but became greater after the half fault cycle

  3. TRANSFORMATION

    Energy Technology Data Exchange (ETDEWEB)

    LACKS,S.A.

    2003-10-09

    Transformation, which alters the genetic makeup of an individual, is a concept that intrigues the human imagination. In Streptococcus pneumoniae such transformation was first demonstrated. Perhaps our fascination with genetics derived from our ancestors observing their own progeny, with its retention and assortment of parental traits, but such interest must have been accelerated after the dawn of agriculture. It was in pea plants that Gregor Mendel in the late 1800s examined inherited traits and found them to be determined by physical elements, or genes, passed from parents to progeny. In our day, the material basis of these genetic determinants was revealed to be DNA by the lowly bacteria, in particular, the pneumococcus. For this species, transformation by free DNA is a sexual process that enables cells to sport new combinations of genes and traits. Genetic transformation of the type found in S. pneumoniae occurs naturally in many species of bacteria (70), but, initially only a few other transformable species were found, namely, Haemophilus influenzae, Neisseria meningitides, Neisseria gonorrheae, and Bacillus subtilis (96). Natural transformation, which requires a set of genes evolved for the purpose, contrasts with artificial transformation, which is accomplished by shocking cells either electrically, as in electroporation, or by ionic and temperature shifts. Although such artificial treatments can introduce very small amounts of DNA into virtually any type of cell, the amounts introduced by natural transformation are a million-fold greater, and S. pneumoniae can take up as much as 10% of its cellular DNA content (40).

  4. Effect of microscale shear stresses on the martensitic phase transformation of nanocrystalline tetragonal zirconia powders

    DEFF Research Database (Denmark)

    Skovgaard, Mette; Ahniyaz, Anwar; Sørensen, Bent F.

    2010-01-01

    For the first time, the effect of microscale shear stress induced by both mechanical compression and ball-milling on the phase stability of nanocrystalline tetragonal zirconia (t-ZrO2) powders was studied in water free, inert atmosphere. It was found that nanocrystalline t-ZrO2 powders are extrem......For the first time, the effect of microscale shear stress induced by both mechanical compression and ball-milling on the phase stability of nanocrystalline tetragonal zirconia (t-ZrO2) powders was studied in water free, inert atmosphere. It was found that nanocrystalline t-ZrO2 powders...... was observed. Ball-milling induced microscale stress has a similar effect on the t → m phase transformation. Furthermore, it was found that even very mild milling condition, such as 120 rpm, 1 h (0.5 mm balls) was enough to induce phase transformation. Surfactant assisted ball-milling was found to be very...... effective in de-agglomeration of our nanocrystalline porous ZrO2 particles into discrete nanocrystals. However, the t → m phase transformation could not be avoided totally even at very mild milling condition. This suggests that the metastable t-ZrO2 is extreme sensitive to microscale shear stress induced...

  5. Phase transformations in lithium aluminates irradiated with neutrons; Transformaciones de fase en aluminatos de litio irradiados con neutrones

    Energy Technology Data Exchange (ETDEWEB)

    Carrera, L.M.; Delfin L, A.; Urena N, F.; Basurto, R. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Bosch, P. [UAM-I, 09340 Mexico D.F. (Mexico)

    2003-07-01

    The lithium aluminate like candidate to be used in the coverings producers of tritium in the fusion nuclear reactors, presents high resistance to the corrosion to the one to be stuck to structural materials as special steels. However, the crystallographic changes that take place in the cover that is continually subjected to irradiation with neutrons, can alter its resistance to the corrosion. In this work the changes of crystalline structure are shown that they present two types of nano structures of lithium aluminates, subjected to an average total dose 7.81 x 10{sup 8} Gy in the fixed irradiation system of capsules of the one TRIGA Mark lll nuclear reactor of the Nuclear Center of Mexico. The studied nano structures presented only phase transformations without formation of amorphous material. (Author)

  6. Vortex Domain Structure in Ferroelectric Nanoplatelets and Control of its Transformation by Mechanical Load

    Science.gov (United States)

    Chen, W. J.; Zheng, Yue; Wang, Biao

    2012-01-01

    Vortex domain patterns in low-dimensional ferroelectrics and multiferroics have been extensively studied with the aim of developing nanoscale functional devices. However, control of the vortex domain structure has not been investigated systematically. Taking into account effects of inhomogeneous electromechanical fields, ambient temperature, surface and size, we demonstrate significant influence of mechanical load on the vortex domain structure in ferroelectric nanoplatelets. Our analysis shows that the size and number of dipole vortices can be controlled by mechanical load, and yields rich temperature-stress (T-S) phase diagrams. Simulations also reveal that transformations between “vortex states” induced by the mechanical load are possible, which is totally different from the conventional way controlled on the vortex domain by the electric field. These results are relevant to application of vortex domain structures in ferroelectric nanodevices, and suggest a novel route to applications including memories, mechanical sensors and transducers. PMID:23150769

  7. Note: An improved calibration system with phase correction for electronic transformers with digital output.

    Science.gov (United States)

    Cheng, Han-miao; Li, Hong-bin

    2015-08-01

    The existing electronic transformer calibration systems employing data acquisition cards cannot satisfy some practical applications, because the calibration systems have phase measurement errors when they work in the mode of receiving external synchronization signals. This paper proposes an improved calibration system scheme with phase correction to improve the phase measurement accuracy. We employ NI PCI-4474 to design a calibration system, and the system has the potential to receive external synchronization signals and reach extremely high accuracy classes. Accuracy verification has been carried out in the China Electric Power Research Institute, and results demonstrate that the system surpasses the accuracy class 0.05. Furthermore, this system has been used to test the harmonics measurement accuracy of all-fiber optical current transformers. In the same process, we have used an existing calibration system, and a comparison of the test results is presented. The system after improvement is suitable for the intended applications.

  8. Numerical modelling of tools steel hardening. A thermal phenomena and phase transformations

    Directory of Open Access Journals (Sweden)

    T. Domański

    2010-01-01

    Full Text Available This paper the model hardening of tool steel takes into considerations of thermal phenomena and phase transformations in the solid state are presented. In the modelling of thermal phenomena the heat equations transfer has been solved by Finite Elements Method. The graph of continuous heating (CHT and continuous cooling (CCT considered steel are used in the model of phase transformations. Phase altered fractions during the continuous heating austenite and continuous cooling pearlite or bainite are marked in the model by formula Johnson-Mehl and Avrami. For rate of heating >100 K/s the modified equation Koistinen and Marburger is used. Modified equation Koistinen and Marburger identify the forming fraction of martensite.

  9. Grain alignment in bulk YBa2Cu3Ox superconductor by a low temperature phase transformation method

    International Nuclear Information System (INIS)

    Selvamanickam, V.; Goyal, A.; Kroeger, D.M.

    1994-01-01

    A quench and directional phase transformation process has been developed to achieve grain alignment in bulk YBa 2 Cu 3 O x superconductors at temperatures about 100 degree C below the peritectic temperature. Isothermal phase transformation of quenched precursors at 890 degree C for 3 min is found to result in the formation of more than 75% of YBa 2 Cu 3 O x phase without any formation of Y 2 BaCuO 5 . Phase transformation at higher temperatures leads to rapid formation of Y 2 BaCuO 5 in addition to YBa 2 Cu 3 O x . A well-aligned microstructure is achieved by directional phase transformation of the quenched compacts as a rate of 10 mm/h. The magnetic field dependence of the critical current density at 77 K of the directionally phase transformed material compares well with that of melt-textured YBCO and is superior to that of magnetically aligned and sintered YBCO

  10. Shape Memory Alloy-Based Periodic Cellular Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I effort will develop and demonstrate an innovative shape memory alloy (SMA) periodic cellular structural technology. Periodic cellular structures...

  11. Band Jahn-Teller structural phase transition in Y2In

    Science.gov (United States)

    Svanidze, E.; Georgen, C.; Hallas, A. M.; Huang, Q.; Santiago, J. M.; Lynn, J. W.; Morosan, E.

    2018-02-01

    The number of paramagnetic materials that undergo a structural phase transition is rather small, which can perhaps explain the limited understanding of the band Jahn-Teller mechanism responsible for this effect. Here we present a structural phase transition observed in paramagnetic Y2In at temperature T0=250 ±5 K. Below T0, the high-temperature hexagonal P 63/m m c phase transforms into the low-temperature orthorhombic P n m a phase. This transition is accompanied by an unambiguous thermal hysteresis of about 10 K, observed in both magnetic susceptibility M /H (T ) and resistivity ρ (T ) , indicating a first-order transition. Band structure calculations suggest a band Jahn-Teller mechanism, during which the degeneracy of electron bands close to the Fermi energy is broken. We establish that this structural phase transition does not have a magnetic component; however, the possibility of a charge density wave formation has not been eliminated.

  12. Kinetic analysis and polymorphic phase transformation of glycine in the presence of lauric acid

    Science.gov (United States)

    Polat, Sevgi; Sayan, Perviz

    2018-01-01

    The phase transformation of β-glycine to α-glycine in a water/ethanol media was investigated in terms of its polymorphism in pure media and in the presence of an additive. Lauric acid was used as the additive, and the experiments were conducted in three different concentrations. First, the polymorphic phase transformation was continuously monitored by in-line measuring of the ultrasonic velocity. Next, the X-ray diffraction (XRD) technique was applied for the solid phase analysis of the crystals to confirm the polymorphic transformation of β-glycine to α-glycine. Based on the combination of scanning electron microscopy (SEM) and morphology analyses, it was found that not only the shape but also the size of the crystals obtained were significantly affected by the additive. The crystals obtained were further characterized by means of thermogravimetric analyzer, elemental analyzer and Fourier-transform infrared (FTIR) spectrometer. The attained thermal data were utilized to calculate the activation energy using various kinetic models based on the isoconversional method. The kinetic results revealed that the addition of lauric acid led to an increase of around 10% in the average activation energy of the glycine crystals during decomposition process. As suggested by the elemental and FTIR analyses conducted, this increase could be related to lauric acid adsorption on the crystal surface.

  13. Phase transformation of alumina coating by plasma assisted tempering of aluminized P91 steels

    International Nuclear Information System (INIS)

    Jamnapara, N.I.; Mukherjee, S.; Khanna, A.S.

    2015-01-01

    Highlights: • A novel plasma assisted heat treatment process for aluminized P91 steels is reported. • Plasma plays a vital role in phase transformation of Al 2 O 3 from θ to α phase. • Presence of O ∗ species in plasma facilitates θ to α transformation. - Abstract: α-Al 2 O 3 coating on aluminized surfaces are considered candidate coatings for blanket applications in fusion reactor. In order to generate α-Al 2 O 3 , aluminized P91 steel samples were subjected to normalizing and tempering treatments at 980 °C and 750 °C respectively. Oxygen plasma has been used during tempering treatment of aluminized P91 steel samples at 750 °C for 1 h. The resulting alumina coating on plasma tempered samples were compared with those of thermally tempered samples. The alumina films were characterized using XRD, XPS, and SEM–EDS techniques. Results indicate that the thermally tempered samples had θ-Al 2 O 3 coating while the plasma tempered samples had α-Al 2 O 3 coating after heat treatment. Such transformation of alumina phase was not visible without plasma. A hypothesis of θ to α-Al 2 O 3 transformation in plasma is proposed. This paper emphasizes the role of plasma processing on generation of an improved insulation coating for TBM applications in fusion reactors

  14. Phase Transformation during Continuous Cooling of NM550 Wear-Resistant Steel

    Science.gov (United States)

    Zhang, Xin; Song, Renbo; Xiong, Wenming; Wen, Erding; Wang, Zhonghong; Guo, Ke

    The CCT (continuous cooling transformation) curve of the test steel was obtained on Gleeble-1500 thermal mechanical simulator based on the thermal dilation measurement. The test steels were the deformation with 40% under the temperature of 900°C and then were cooled to room temperature at different cooling rates. The phase transformation law and hardness change rule were emphatically investigated at the cooling rate from 0.05°C/s to 30°C/s by optical microscopy (OM), scanning electron microscope (SEM) and Vickers hardness tester. The regression model of phase transformation was calculated. The results show that the transformation of ferrite and pearlite are inhibited, which cause the dynamic CCT curve shift to the right. The microstructure of the test steel consists of ferrite and pearlite after phase transformation at the cooling rate of 0.05°C/s; the granular bainite appears at the cooling rate of 0.5°C/s due to the interaction of Mo and B; as the cooling rate increases to 2°C/s, the microstructure mainly consists of lath bainite; the martensite is observed at the cooling rate of 2°C/s and there would be total martensite if the cooling rate is higher than 5°C/s and the grain growth rate is faster at the same time. The hardness of test steels increases with the increase of cooling rate, and increases obviously when the cooling rate is lower than 5 °C/s. A theoretical basis is provided to obtain the best bainite/martensite composite microstructure. The martensitic transformation start temperature is 354.6°C and the critical cooling rate is 5°C/s. The test value and the regression model can fit well and reflect the test value trend, showing a high precision of regression.

  15. TRANSFORMER

    Science.gov (United States)

    Baker, W.R.

    1959-08-25

    Transformers of a type adapted for use with extreme high power vacuum tubes where current requirements may be of the order of 2,000 to 200,000 amperes are described. The transformer casing has the form of a re-entrant section being extended through an opening in one end of the cylinder to form a coaxial terminal arrangement. A toroidal multi-turn primary winding is disposed within the casing in coaxial relationship therein. In a second embodiment, means are provided for forming the casing as a multi-turn secondary. The transformer is characterized by minimized resistance heating, minimized external magnetic flux, and an economical construction.

  16. Structural Transformations in Nematic Liquid Crystals with a Hybrid Orientation

    Science.gov (United States)

    Delev, V. A.; Krekhov, A. P.

    2017-12-01

    The structural transformations in a nematic liquid crystal (NLC) layer with a hybrid orientation (planar director orientation is created on one substrate and homeotropic director orientation is created on the other) are studied. In the case of a dc voltage applied to the NLC layer, the primary instability is flexoelectric. It causes the appearance of flexoelectric domains oriented along the director on the substrate with a planar orientation. When the voltage increases further, an electroconvective instability in the form of rolls moving almost normal to flexoelectric domains develops along with these domains. Thus, the following spatially periodic structures of different natures coexist in one system: equilibrium static flexoelectric deformation of a director and dissipative moving oblique electroconvection rolls. The primary instability in the case of an ac voltage is represented by electroconvection, which leads to moving oblique or normal rolls depending on the electric field frequency. Above the electroconvection threshold, a transition to moving "abnormal" rolls is detected. The wavevector of the rolls coincides with the initial director orientation on the substrate with a planar orientation, and the projection of the director at the midplane of the NLC layer on the layer plane makes a certain angle with the wavevector. The results of numerical calculations of the threshold characteristics of the primary instabilities agree well with the obtained experimental data.

  17. Large Molecule Structures by Broadband Fourier Transform Molecular Rotational Spectroscopy

    Science.gov (United States)

    Evangelisti, Luca; Seifert, Nathan A.; Spada, Lorenzo; Pate, Brooks

    2016-06-01

    Fourier transform molecular rotational resonance spectroscopy (FT-MRR) using pulsed jet molecular beam sources is a high-resolution spectroscopy technique that can be used for chiral analysis of molecules with multiple chiral centers. The sensitivity of the molecular rotational spectrum pattern to small changes in the three dimensional structure makes it possible to identify diastereomers without prior chemical separation. For larger molecules, there is the additional challenge that different conformations of each diastereomer may be present and these need to be differentiated from the diastereomers in the spectral analysis. Broadband rotational spectra of several larger molecules have been measured using a chirped-pulse FT-MRR spectrometer. Measurements of nootkatone (C15H22O), cedrol (C15H26O), ambroxide (C16H28O) and sclareolide (C16H26O2) are presented. These spectra are measured with high sensitivity (signal-to-noise ratio near 1,000:1) and permit structure determination of the most populated isomers using isotopic analysis of the 13C and 18O isotopologues in natural abundance. The accuracy of quantum chemistry calculations to identify diastereomers and conformers and to predict the dipole moment properties needed for three wave mixing measurements is examined.

  18. Atomic resolution investigations of phase transformation from TaN to CrTaN in a steel matrix

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson; Hald, John

    2012-01-01

    strength of the steel. The Cr content promotes Z-phase precipitation, making MN strengthening of these materials unfeasible, since 12%Cr is necessary for oxidation resistance. The authors have suggested an acceleration of Z-phase precipitation to obtain a fine and stable distribution of CrMN instead of MN...... atoms diffuse from the steel matrix into TaN precipitates and physically transform them into CrTaN. The crystal structure of the precipitates changes from that of a typical MN NaCl type crystal structure to a Z-phase crystal structure with alternating double layers of Cr and TaN. Since there is a large......In development of 12%Cr high temperature steels used for fossil fired power plants, the precipitation of large Z-phase particles, CrMN, has been identified as a major problem since they replace small and finely distributed MN particles. This causes a premature breakdown in the longterm creep...

  19. Real-time monitoring and calculation of the derating of single-phase transformers under nonsinusoidal operation

    Science.gov (United States)

    Batan, Tufan

    The extensive use of power electronic devices in the last two decades have degraded the quality of the power system by introducing voltage and current harmonics as well as DC excitations. Such phenomena cause additional losses in transformers, resulting in elevated temperatures of transformers above their rated temperatures. This added heat degrades the insulating material of the windings, decreasing the rated lifetime of transformers. For this reason, transformers feeding nonlinear loads must be derated; that is. by limiting either their output apparent or real power such that rated temperatures are not exceeded. It is of advantage to measure the derating of transformers which are already in service, for given nonlinear loads and to calculate the derating of large transformers that cannot readily be tested in laboratories. It is one of the objectives of this thesis to validate the computed derating values of transformers with corroborating measurements. A 25kVA 7200V/240V single-phase pole transformer is analyzed using two dimensional field analysis based on the diffusion equation, employing either rectangular or polycentric grid structures. Such a field analysis allows us to visualize the complex vector potential and flux density distributions inside the unsaturated transformer operating under short-circuit conditions. One can calculate the eddy currents within conducting materials, such as copper and aluminum windings, from complex vector potential values. Short-circuit tests applied to low and high voltage windings allow us to calculate the eddy currents inside each winding and consequently their eddy-current losses. The frequency dependent AC winding resistance RAC as well as the per-unit eddy-current loss coefficient PEC-R are computed. These values are used to determine the derating of transformers via either the K-factor as proposed by Underwriters Laboratory, Inc., or via the harmonic loss factor FHL, as favored by IEEE and IEC. A new digital data

  20. Initial stages of ion beam-induced phase transformations in Gd2O3 and Lu2O3

    Science.gov (United States)

    Chen, Chien-Hung; Tracy, Cameron L.; Wang, Chenxu; Lang, Maik; Ewing, Rodney C.

    2018-02-01

    The atomic-scale evolution of lanthanide sesquioxides Gd2O3 and Lu2O3 irradiated with 1 MeV Kr ions at room temperature and 120 K, up to fluences of 1 × 1016 ions/cm2 (˜20 dpa), has been characterized by in situ transmission electron microscopy. At room temperature, both oxides exhibited high radiation tolerance. Irradiation did not cause any observable structural change in either material, likely due to the mobility of irradiation-induced point defects, causing efficient defect annihilation. For Gd2O3, having the larger cation ionic radius of the two materials, an irradiation-induced stacking fault structure appeared at low fluences in the low temperature irradiation. As compared with the cubic-to-monoclinic phase transformations known to result from higher energy (˜GeV) ion irradiation, Kr ions of lower energies (˜MeV) yield much lower rates of damage accumulation and thus less extensive structural modification. At a fluence of 2.5 × 1015 ions/cm2, only the initial stages of the cubic-to-monoclinic (C to B) phase transformation process, consisting of the formation and aggregation of defects, have been observed.

  1. The Temperature Measurement in a Three-Phase Power Transformer under Different Conditions

    Directory of Open Access Journals (Sweden)

    K. Karakoulidis

    2015-12-01

    Full Text Available Infrared thermography is a powerful non contact method with the ability to fast inspection of abnormal situations in many electrical systems and equipments. With the aim of a high resolution thermal camera a laboratory power transformer was checked under different scenarios. These scenarios include thermal measurements for 58%, 87% and 116% of rated load conditions, problems in primary or secondary phases and an asymmetric charge. The thermograpic system illustrate fast and reliable the changes in the windings of the power transformer.

  2. Study of structural transformations and phases formation upon ...

    Indian Academy of Sciences (India)

    The morphology of large-sized, porous and hexagonal platelike. Zn–Ni–Al hydrotalcite is affected by calcination temperature. BET specific surface area and pore volume are observed to increase with increase of the calcination temperature up to 700◦C followed by a further decrease with increasing temperature. Keywords.

  3. Electron spin transition causing structure transformations of earth's interiors under high pressure

    Science.gov (United States)

    Yamanaka, T.; Kyono, A.; Kharlamova, S.; Alp, E.; Bi, W.; Mao, H.

    2012-12-01

    To elucidate the correlation between structure transitions and spin state is one of the crucial problems for understanding the geophysical properties of earth interiors under high pressure. High-pressure studies of iron bearing spinels attract extensive attention in order to understand strong electronic correlation such as the charge transfer, electron hopping, electron high-low spin transition, Jahn-Teller distortion and charge disproponation in the lower mantle or subduction zone [1]. Experiment Structure transitions of Fe3-xSixO4, Fe3-xTixO4 Fe3-xCrxO4 spinel solid solution have been investigated at high pressure up to 60 GPa by single crystal and powder diffraction studies using synchrotron radiation with diamond anvil cell. X-ray emission experiment (XES) at high pressure proved the spin transition of Fe-Kβ from high spin (HS) to intermediate spin state (IS) or low spin state (LS). Mössbauer experiment and Raman spectra study have been also conducted for deformation analysis of Fe site and confirmation of the configuration change of Fe atoms. Jahn-Teller effect A cubic-to-tetragonal transition under pressure was induced by Jahn-Teller effect of IVFe2+ (3d6) in the tetrahedral site of Fe2TiO4 and FeCr2O4, providing the transformation from 43m (Td) to 42m (D2d). Tetragonal phase is formed by the degeneracy of e orbital of Fe2+ ion. Their c/a ratios are c/adisordered in the M2 site. At pressures above 53 GPa, Fe2TiO4 structure further transforms to Pmma. This structure change results in the order-disorder transition [2]. New structure of Fe2SiO4 The spin transition exerts an influence to Fe2SiO4 spinel structure and triggers two distinct curves of the lattice constant in the spinel phase. The reversible structure transition from cubic to pseudo-rhombohedral phase was observed at about 45 GPa. This transition is induced by the 20% shrinkage of ionic radius of VIFe2+at the low sin state. Laser heating experiment at 1500 K has confirmed the decomposition from the

  4. Transformation

    DEFF Research Database (Denmark)

    Peters, Terri

    2011-01-01

    Artiklen diskuterer ordet "transformation" med udgangspunkt i dels hvorledes ordet bruges i arkitektfaglig terminologi og dels med fokus på ordets potentielle indhold og egnethed i samme teminologi....

  5. Structural Transformation in Inverse-Perovskite REPt3B (RE = Sm and Gd-Tm) Associated with Large Volume Reduction.

    Science.gov (United States)

    Mondal, Sudipta; Mazumdar, Chandan; Ranganathan, Rajarao; Avdeev, Maxim

    2017-07-17

    In this work, we report the structural phase transformation of tetragonal inverse-perovskite REPt 3 B (RE = Sm, and Gd-Tm) compounds to cubic perovskite structure, with a large volume reduction of about 9% (reduction of the c axis, ∼17%; increase in the a axis, ∼5%). The structural stability of the cubic phase, however, could only be maintained by lowering the lattice parameter of the off-stoichiometric REPt 3 B x (x magnetic transition temperatures in the tetragonal and cubic phases. The different physical properties of these two phases demonstrate the interrelationship between the crystal chemistry and the physics of the system. The synthetic route to cubic REPt 3 B x identified in this work may be utilized to prepare new ternary rare-earth intermetallics in a cubic perovksite form, which was previously found to facilitate unconventional superconductivity.

  6. New insights into the phase transformations to isothermal ω and ω-assisted α in near β-Ti alloys

    International Nuclear Information System (INIS)

    Li, Tong; Kent, Damon; Sha, Gang; Stephenson, Leigh T.; Ceguerra, Anna V.; Ringer, Simon P.; Dargusch, Matthew S.; Cairney, Julie M.

    2016-01-01

    For multicomponent near-β alloys, we have investigated the mechanisms responsible for the β-to-ω and ω-to-α phase transformations upon isothermal ageing at 573 K. Experimental evidence from atom probe tomography and aberration-corrected high-resolution transmission electron microscopy indicates that the formation of isothermal ω involves a structural reconstruction assisted by nanoscale spinodal decomposition of the β matrix, prior to the specific chemistry change required to form ω, rather than a mixed-mode process with structure and chemistry changes occurring simultaneously as has been previously suggested. First, incommensurate embryonic ω evolve via a displacive mechanism within Mo-lean regions created by second-order coherent spinodal decomposition of the β matrix. The subtle spinodal decomposition in β and chemistry of embryonic ω are carefully analysed by an advanced atom probe data analysis algorithm. When the size of embryonic ω exceeds a critical value, commensurate isothermal ω forms through the exit of the other alloying solutes. O-rich regions present at the isothermal ω/β interface provide potent sites for the formation of α. The concurrent compositional partitioning of solutes in ω and α indicates the transformation from ω to α involves both a rapid lattice reconstruction at the ω/α interface and a slow Al diffusion at the α/β, therefore a mixed-mode displacive-diffusive process. This study provides novel experimental evidence to understand the much-disputed transformation processes and elucidate the mechanisms responsible for these important phase transformations.

  7. In-situ measurement of phase transformation kinetics in austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Meier, Leopold, E-mail: leopold.meier@utg.de [Technische Universität München, Lehrstuhl für Umformtechnik und Gießereiwesen, Walther-Meißner-Straße 4, 85748 Garching (Germany); Hofmann, Michael, E-mail: michael.hofmann@frm2.tum.de [Technische Universität München, Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Lichtenbergstraße 1, 85748 Garching (Germany); Saal, Patrick, E-mail: patrick.saal@utg.de [Technische Universität München, Lehrstuhl für Umformtechnik und Gießereiwesen, Walther-Meißner-Straße 4, 85748 Garching (Germany); Volk, Wolfram, E-mail: wolfram.volk@utg.de [Technische Universität München, Lehrstuhl für Umformtechnik und Gießereiwesen, Walther-Meißner-Straße 4, 85748 Garching (Germany); Hoffmann, Hartmut, E-mail: hartmut.hoffmann@utg.de [Technische Universität München, Lehrstuhl für Umformtechnik und Gießereiwesen, Walther-Meißner-Straße 4, 85748 Garching (Germany)

    2013-11-15

    Austempered ductile iron (ADI) alloyed with 0.42% Mn and 0.72% Cu was heat treated in a mirror furnace and the phase transitions were studied in-situ by neutron diffraction. The heat treatment consisted of austenitisation at 920 °C and isothermal austempering at 400 °C, 350 °C and 300 °C, respectively. Due to the growth of ferrite platelets, the austenite content decreases rapidly at all temperatures within the first 15–20 min and reaches a stable plateau after 35 min (400 °C) to 80 min (300 °C). The carbon content of the residual austenite, which was monitored and characterised by the change of the lattice parameter, increases up to 1.6 wt.% caused by redistribution from the newly formed ferrite. While at higher austempering temperatures this takes place almost parallel to the phase transformation, at 300 °C the redistribution of carbon to austenite lags behind considerably. Furthermore the neutron data revealed an austenite peak asymmetry during austempering which is attributed to successive phase transformation. It results temporarily in two fractions of austenite, an initial low-carbon and an enriched high-carbon modification. - Highlights: • The heat treatment of ADI was studied in detail by in-situ neutron diffraction. • The phase fractions were monitored and evaluated quantitatively. • The austenite carbon content increased up to 1.6 wt.% during austempering. • Peak asymmetries indicate two austenite fractions during highest transformation rates.

  8. Influence of Abrasive Shape on the Abrasion and Phase Transformation of Monocrystalline Silicon

    Directory of Open Access Journals (Sweden)

    Junqin Shi

    2018-01-01

    Full Text Available The effect of abrasive shape on the three-body abrasion behaviors of monocrystalline silicon was investigated via molecular dynamics. The axial ratio of abrasive particle varied from 1.00 to 0.40 to mimic abrasive shape. It has been observed that the particle’s movement became sliding instead of rolling when the axial ratio was smaller than a critical value 0.46. In the abrasion process, the friction force and normal force showed an approximately sinusoid-like fluctuation for the rolling ellipsoidal particles, while the front cutting of particle caused that friction force increased and became larger than normal force for sliding particles. The phase transformation process was tracked under different particle’ movement patterns. The Si-II and Bct5 phase producing in loading process can partially transform to Si-III/Si-XII phase, and backtrack to original crystal silicon under pressure release, which also occurred in the abrasion process. The secondary phase transformation showed difference for particles’ rolling and sliding movements after three-body abrasion. The rolling of particle induced the periodical and inhomogeneous deformation of substrates, while the sliding benefited producing high-quality surface in chemical mechanical polishing (CMP process. This study aimed to construct a more precise model to understand the wear mechanism benefits evaluating the micro-electro-mechanical systems (MEMS wear and CMP process of crystal materials.

  9. Solid-gaseous phase transformation of elemental contaminants during the gasification of biomass.

    Science.gov (United States)

    Jiang, Ying; Ameh, Abiba; Lei, Mei; Duan, Lunbo; Longhurst, Philip

    2016-09-01

    Disposal of plant biomass removed from heavy metal contaminated land via gasification achieves significant volume reduction and can recover energy. However, these biomass often contain high concentrations of heavy metals leading to hot-corrosion of gasification facilities and toxic gaseous emissions. Therefore, it is of significant interest to gain a further understanding of the solid-gas phase transition of metal(loid)s during gasification. Detailed elemental analyses (C, H, O, N and key metal/metalloid elements) were performed on five plant species collected from a contaminated site. Using multi-phase equilibria modelling software (MTDATA), the analytical data allows modelling of the solid/gas transformation of metal(loid)s during gasification. Thermodynamic modelling based on chemical equilibrium calculations was carried out in this study to predict the fate of metal(loid) elements during typical gasification conditions and to show how these are influenced by metal(loid) composition in the biomass and operational conditions. As, Cd, Zn and Pb tend to transform to their gaseous forms at relatively low temperatures (gasification temperature range of 1000-1200°C. Whereas Cr, Al, Fe and Mg remain in solid phase at higher temperatures (>1200°C). Simulation of pressurised gasification conditions shows that higher pressures increase the temperature at which solid-to-gaseous phase transformations takes place. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  10. Modularized Three-Phase Semiconductor Transformer with Bidirectional Power Flow for Medium Voltage Application

    Directory of Open Access Journals (Sweden)

    Do-Hyun Kim

    2016-08-01

    Full Text Available This paper describes a prototype of modularized three-phase semiconductor transformer that was developed in the lab for feasibility study. The developed prototype is composed of three units of single-phase semiconductor transformer coupled in Y-connection. Each single-phase unit has multiple units of high-voltage high-frequency resonant AC–DC converter, a low-voltage hybrid-switching DC–DC converter, and a low-voltage hybrid-switching DC–AC inverter. Also, each single-phase unit has two digital signal processor (DSP boards to control converter operation and to acquire monitoring data. The monitoring system was developed based on LabView by using controller area network (CAN communication between the DSP board and the personal computer (PC. Through diverse experimental analyses it was verified that the prototype operates with proper performance under normal and sag conditions. The developed prototype confirms the possibility of fabricating a commercial high-voltage high-power semiconductor transformer by increasing the number of series-connected converter modules in high-voltage side and improving the system efficiency with a new switching device such as an SiC device.

  11. Correlation between Thermal Treatment and Phase Transformation in Nanocrystalline Stabilized Zirconia

    Directory of Open Access Journals (Sweden)

    Tajudeen Oladele AHMED

    2013-06-01

    Full Text Available Stabilized zirconia produced via wet chemistry has chemically higher uniformity and purity. However, the grain size, particle shape, agglomerate size and specific surface area can be modified within certain degree by controlling the precipitation and sintering conditions. Generally, any physical or chemical difference between phases or effect occurring on the appearance or disappearance of a phase can be determined via thermal analysis and X-ray Diffractometry coupled with electron microscopy. In the last few decades, these materials have received tremendous attention globally in the field of defect solid-state devices. However, the challenge in this field of research has been to study thermal behaviour of these electrolytes during phase transformations and develop improved electrolytes with low activation temperature in the range of 600°C-800°C. In this paper, we report the wet chemistry of bismuth oxide stabilized zirconia having high experimental yield and low transformation temperature. Thus, the phase transformation from amorphous Zirconia to monoclinic is reported to begin above 600oC to an optimum temperature of 700oC. After calcination at 800oC for 4h, the powder have narrow particle size distribution in the range of 63-101µm. The average crystallite sizes of the synthesized powders range from 8-33nm.

  12. A study of ion-induced phase transformation in austenitic stainless steel

    International Nuclear Information System (INIS)

    Sakamoto, Isao

    1993-01-01

    The phase stability of austenitic stainless steel in an irradiation environment using low-nickel 17/7, 17/13 steel and commercial steel such as 304 and 316 steel as well as high-nickel 310 steel in order to investigate a mechanism of the ion-induced phase transformation were studied. The irradiation in steel was performed with steel constituent elements (Fe, Cr and Ni ions) and also with rare-gas elements such as Ar, Kr and Xe ions at room temperature. In addition, He, H, D and N 2 ions were irradiated in steel complementarily. The modification in the near surface region of the irradiated steel has been observed by means of conversion electron Moessbauer spectroscopy (CEMS), glancing angle X-ray diffraction (GXRD), Rutherford backscattering (RBS) and particle-induced X-ray emission (PIXE). It has been considered that the phase transformation in steel after irradiation of Ni ions was stress-induced due to a stress field around damages accumulated by irradiation. On the other hand, for Fe ion irradiation in steel, we have confirmed that the increase of Fe constituent atoms induced the phase transformation. For rare-gas ion irradiation in steel, it has been suggested that implanted rare-gas atoms aggregated and formed highly pressurized rare-gas inclusion. In both metal ion and rare-gas ion irradiation, the austenite stability was demonstrated to be well correlated with the phase conditions of the Schaffler diagram, and it has been established that the primary contribution to the driving force for these transformation comes from relief of high stress levels in the implanted layer. (J.P.N.) 76 refs

  13. Gas phase equilibrium structure of histamine.

    Science.gov (United States)

    Tikhonov, Denis S; Rykov, Anatolii N; Grikina, Olga E; Khaikin, Leonid S

    2016-02-17

    The first gas electron diffraction (GED) experiment for histamine was carried out. The equilibrium structure of histamine in the gas phase was determined on the basis of the data obtained. The refinement was also supported by the rotational constants obtained in previous studies [B. Vogelsanger, et al., J. Am. Chem. Soc., 1991, 113, 7864-7869; P. Godfrey, et al., J. Am. Chem. Soc., 1998, 120, 10724-10732] and quantum chemical calculations. The proposed mechanism of tautomerization by simultaneous intermolecular transfer of hydrogens in a histamine dimer helps to explain the distribution of tautomers in different experiments. The estimations of the conformational interconversion times provided the explanation for the absence of some conformers in the rotational spectroscopy experiments.

  14. Simulation investigation of thermal phase transformation and residual stress in single pulse EDM of Ti-6Al-4V

    Science.gov (United States)

    Tang, Jiajing; Yang, Xiaodong

    2018-04-01

    The thermal phase transformation and residual stress are ineluctable in the electrical discharge machining (EDM) process, and they will greatly affect the working performances of the machined surface. This paper presents a simulation study on the thermal phase transformation and residual stress in single-pulse EDM of Ti-6Al-4V, which is the most popular titanium alloy in fields such as aircraft engine and some other leading industries. A multi-physics model including thermal, hydraulic, metallography and structural mechanics was developed. Based on the proposed model, the thickness and metallographic structure of the recast layer and heat affected layer (HAZ) were investigated. The distribution and characteristics of residual stress around the discharge crater were obtained. The recast layer and HAZ at the center of crater are found to be the thinnest, and their thicknesses gradually increase approaching the periphery of the crater. The recast layer undergoes a complete α‧ (martensitic) transformation, while the HAZ is mainly composed by the α  +  β  +  α‧ three-phase microstructure. Along the depth direction of crater, the Von Mises stress increases first and then decreases, reaching its maximal value near the interface of recast layer and HAZ. In the recast layer, both compressive stress component and tensile stress component are observed. ANOVA results showed that the influence of discharge current on maximal tensile stress is more significant than that of pulse duration, while the pulse duration has more significant influence on average thickness of the recast layer and the depth location of the maximal tensile stress. The works conducted in this study will help to evaluate the quality and integrity of EDMed surface, especially when the non-destructive testing is difficult to achieve.

  15. High Temperature Dynamic Response of a Ti-6Al-4V Alloy: A Modified Constitutive Model for Gradual Phase Transformation

    Science.gov (United States)

    Gangireddy, S.; Mates, S. P.

    2017-12-01

    Dynamic deformation behavior of a commercial Ti-6Al-4V alloy is measured between room temperature and beyond the β-transus temperature with high thermal resolution using a rapid-heating Kolsky bar technique. The high thermal resolution allows for a thorough investigation of the dynamic thermal softening behavior of this alloy including effects related to the transformation from the initial hcp α/bcc β dual phase structure to a full β structure for improved modeling of high temperature dynamic manufacturing processes such as high-speed machining. Data are obtained at an average strain rate of 1800 s-1 from room temperature to 1177 °C, with total heating times limited to 3.5 s for all tests. Short heating times prevent thermal distortion of the Kolsky bar loading waves and can allow an investigation of non-equilibrium mechanical behavior, although no such behavior was identified in this study. Between 800 °C and 1000 °C, a progressive change in the thermal softening rate was observed that corresponded well with the equilibrium phase diagram for this alloy. The dynamic thermal softening behavior in the transformation region is incorporated via a new modification of the Johnson-Cook (J-C) viscoplastic constitutive equation. Rate sensitivity is determined at room temperature by combining Kolsky bar data with quasi-static measurements at strain rates from 7.5 × 10-5 s-1 to 0.16 s-1 and the data are fit using multi-parameter optimization to arrive at a full modified J-C model for Ti-6Al-4V to nearly 1200 °C. In its generic form, the modification factor we propose, G( T), is applicable to any material system undergoing gradual phase transformation over a range of temperatures.

  16. Second-order phase transition in PbO and SnO at high pressure: Implications for the litharge-massicot phase transformation

    Science.gov (United States)

    Adams, David M.; Christy, Andrew G.; Haines, Julian; Clark, Simon M.

    1992-11-01

    We have studied the structural behavior of PbO at high pressure by powder neturon diffraction in a McWhan cell, and by energy-dispersive powder x-ray diffraction and Raman spectroscopy in a diamond anvil cell. A phase (γ-PbO) occurs at room temperature between ~0.7 and ~2.5 GPa pressure, between the stability fields of litharge (phase is related to litharge by a reversible second-order transition. We infer that this is associated with the collapse of the eu acoustic mode. Unit-cell data at 1.6 GPa are Pm21n, a=4.027(3) Å, b=3.950(3) Å, c=4.767(4) Å, and Z=2. The pressure evolution of the spontaneous strain follows a simple Landau model. There are four distinct solid-state transformation paths between litharge and massicot that maintain the known topotactic relationship between the phases, maintain the translational symmetry common to both, and make use of continuous transitions between group-subgroup related structural intermediates. Both the γ phase and the modulated low-temperature phase of PbO are closely related to one step on one of these paths. Although there is evidence to suggest that the intermediate states do have a transient existence, several paths appear to be utilized. A transition to a γ-like phase also occurs in SnO, at 2.5 GPa, although there is no evidence of a massicotlike polymorph of this compound. The orthorhombic phase is stable to at least 7.5 GPa.

  17. Understanding processing-induced phase transformations in erythromycin-PEG 6000 solid dispersions

    DEFF Research Database (Denmark)

    Mirza, Sabiruddin; Heinämäki, Jyrki; Miroshnyk, Inna

    2006-01-01

    Since the quality and performance of a pharmaceutical solid formulation depend on solid state of the drug and excipients, a thorough investigation of potential processing-induced transformations (PITs) of the ingredients is required. In this study, the physical phenomena taking place during...... intermolecular interactions between the drug and polymer in the solid state were further studied by Fourier transform infrared (FTIR) spectroscopy. While in the absence of PEG the dehydration was the only transformation observed, hot-melt processing with the polymer caused the drug to undergo multiple phase...... formulation of erythromycin (EM) dihydrate solid dispersions with polyethylene glycol (PEG) 6000 by melting were investigated. PITs were monitored in situ using variable temperature X-ray powder diffraction (VT-XRPD), differential scanning calorimetry (DSC), and hot-stage microscopy (HSM). Possible...

  18. Effect of hydrogen on the microstructure, mechanical properties and phase transformations in austenitic steels

    International Nuclear Information System (INIS)

    Li, Y.Y.; Xing, Z.S.

    1989-01-01

    Effect of high-pressure hydrogen charging on the microstructure, mechanical properties and phase transformations in austenitic steels has been investigated and discussed. The results show that the strength and impact toughness of the steels increase slightly and that the ductility decreases after hydrogen charging. The existence of δ-ferrite deteriorates the resistance to hydrogen embrittlement (HE) of the steels. The occurrence of carbide in the steel resulted from aging reduces the ductility of the steel and makes the steel sensitive to HE. The existence of sufficient hydrogen promotes the ε-martensitic transformation and suppresses the α'-martensitic transformation. The permeabilities and diffusivities of hydrogen in the steels have also been determined. (orig.)

  19. Phase transformation and cooling curves of the mild steel influenced by previous hot rolling

    Directory of Open Access Journals (Sweden)

    S. Rusz

    2016-10-01

    Full Text Available Rods from mild steel S235JR were intensively rolled in the laboratory continuous mill. Specifically defined temperature of phase transformation Ar was determined from the free cooling curves measured by the temperature scanner. The Ar value increased from 763 to 786 °C with rolling temperature descending from 1 200 to 800 °C. The value of Ar = 730 °C was obtained at free cooling of the non-deformed rod of the same diameter 9,8 mm from heating temperature 1 000 °C. The obtained results were compared with continuous cooling transformation (CCT and deformation continuous cooling transformation (DCCT diagrams based on the dilatometric tests.

  20. Simulation of the remanence influence on the transient states in a single-phase multiwinding transformer

    Directory of Open Access Journals (Sweden)

    Wilk Andrzej

    2017-03-01

    Full Text Available This paper presents the mathematical model of a single-phase multi-winding core type transformer taking into account magnetic hysteresis phenomenon based on the feedback Preisach model (FPM. The set of loop differential equations was developed for a K-th winding transformer model where the flux linkages of each winding includes flux Φ common to all windings as a function of magneto motive force Θ of all windings. The first purpose of this paper is to implement a hysteresis nonlinearity involved in the Φ(Θ function which also accounts residual magnetic flux. The second purpose of this paper is experimental validation of the developed transformer model in a capacitor discharge test and several different values of residual magnetic flux.

  1. Orientational relationships between phases in the {gamma}{yields}{alpha} transformations for uranium-molybdenum alloys; Relations d'orientation entre phases dans les transformations {gamma}{yields}{alpha} des alliages uranium-molybdene

    Energy Technology Data Exchange (ETDEWEB)

    Brun, G. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1966-04-01

    A crystallographic study has been made of the {gamma} {yields} {alpha} + {gamma} transformation in the alloy containing 3 per cent by weight of molybdenum using electronic micro-diffraction; it has been possible to establish the orientational relationships governing the germination of the {alpha} phase in the {gamma} phase. One finds: (111){gamma} // (100) {alpha}, (112-bar){gamma} // (010) {alpha}, (11-bar 0){gamma} // (001){alpha}. By choosing a monoclinic lattice containing the same number of atoms as the orthorhombic lattice for defining the {gamma} mother phase, the change in structure has been explained by adding a homogeneous (112-bar){gamma} [111]{gamma} shearing deformation to a heterogeneous deformation brought about by slipping of the atoms which are not situated at the nodes of this lattice. The identity of the orientation relationships {gamma}/{alpha} and {gamma}/{alpha}''b and the loss of coherence {gamma} /{alpha} as a function of temperature or of time lead to the conclusion that, in the range studied, the {gamma} {yields} {alpha} transformation begins with a martensitic process and continues by germination and growth. (author) [French] Une etude cristallographique de la transformation {gamma} {yields} {alpha} + {gamma} dans l'alliage {alpha} 3 pour cent en poids de Mo, effectuee par microdiffraction electronique a permis d'etablir les relations d'orientation regissant la germination de {alpha} dans {gamma}. On a: (111){gamma} // (100){alpha}, (112-bar){gamma} // (010){alpha}, (11-bar 0){gamma} // (001){alpha}. En choisissant pour decrire la phase mere {gamma} une maille monoclinique contenant le meme nombre d'atomes que la maille orthorhombique {alpha}, le changement de structure a ete explique en superposant a une deformation homogene par cisaillement (112-bar){gamma} [111]{gamma} une deformation heterogene par glissement des atomes non situes aux noeuds de cette maille. L identite des relations d

  2. Phase transformation of a zirconia ceramic head after total hip arthroplasty.

    Science.gov (United States)

    Haraguchi, K; Sugano, N; Nishii, T; Miki, H; Oka, K; Yoshikawa, H

    2001-09-01

    We report two cases of surface deterioration of a zirconia ceramic femoral head associated with phase transformation after total hip arthroplasty. One head was retrieved at revision due to recurrent dislocation after six years and the other because of failure of the locking mechanism of the polyethylene liner after three years. The monoclinic content of the zirconia ceramics rose from 1% to about 30% on the surface of the heads. SEM revealed numerous craters indicating extraction of the zirconia ceramics at the surface. Surface roughness increased from an initial value of 0.006 microm up to 0.12 microm. This is the first report to show that phase transformation of zirconia ceramics causes deterioration of the surface roughness of the head in vivo after total hip arthroplasty.

  3. submitter Damage evolution in a stainless steel bar undergoing phase transformation under torsion at cryogenic temperatures

    CERN Document Server

    Ortwein, R; Skoczen, B

    2016-01-01

    Phase transformation driven by plastic strains is commonly observed in austenitic stainless steels. In the present paper, this phenomenon is addressed in connection with damage evolution. A three-dimensional constitutive model has been derived, and scalar variables for damage and the volume fraction of the transformed phase were used. The model was solved using Abaqus UMAT user defined procedure, as well as by means of simplified one-dimensional approach for a twisted circular bar. Large experimental campaign of tests was performed, including martensite content measurements within the cross-section and on the surface of the bar during monotonic and cyclic loading. Based on the residual angle of twist, damage variable was calculated. The global response of torque versus the angle of twist was measured as well. Comparison between the experimental results and the results obtained from the simplified one-dimensional approach and from the full three-dimensional approach are presented. It turns out that one-dimensi...

  4. Investigation of the phase equilibria and phase transformations associated with the Bi2Sr2CaCu2Oy superconductor

    International Nuclear Information System (INIS)

    Holesinger, T.

    1993-01-01

    The solid solution region and reaction kinetics of the Bi 2 Sr 2 CaCu 2 O y (2212) superconductor were examined as a function of temperature and oxygen partial pressure. Crystallization studies from the glassy and molten states were undertaken to determine the phase transformation and kinetics associated with the formation of 2212 and other competing phases. Crystallization of nominal 2212 glasses was found to proceed in two steps with the formation of Bi 2 Sr 2-x Ca x CuO y (2201) and Cu 2 O followed by Bi 2 Sr 3-x Ca x O y , CaO, and SrO. The 2212 phase converts from the 2201 phase with increasing temperatures. However, its formation below 800 C was kinetically limited. At 800 C and above, a nearly full conversion to the 2212 phase was achieved after only one minute although considerably longer anneal times were necessary for the system to reach equilibrium. In low oxygen partial pressures, the solidus is reduced to approximately 750 C. Solidification studies revealed an eutectic structure separating the incongruently melting 2212/2201 phases at high oxygen partial pressures from the congruently melting Bi 2 Sr 3-x Ca x O y (23x) and Bi 2 Sr 2-x Ca x O y (22x) phases present at low oxygen partial pressures. During solidification in various oxygen partial pressures, the separation of CaO in the melt and the initial crystallization of alkaline-earth cuprates leaves behind a Bi-rich liquid from which it is impossible to form single-phase 2212. Hence, significant amounts of 2201 were also present in these samples. These problems could be reduced by melt processing in inert atmospheres. Bulk 2212 material produced in this manner was found to possess high transition temperatures, high intergranular critical current densities below 20K, and modest critical current densities at 77K

  5. Effect of oxygen on the thermomechanical behavior of tantalum thin films during the β-α phase transformation

    International Nuclear Information System (INIS)

    Knepper, Robert; Stevens, Blake; Baker, Shefford P.

    2006-01-01

    Tantalum thin films were prepared in the metastable β phase, and their thermomechanical behaviors were investigated in situ in an ultrahigh vacuum environment. Controlled levels of oxygen were incorporated into the films either during deposition, by surface oxidation after deposition, or during thermomechanical testing. The transformation from the β phase to the stable α phase takes place in conjunction with a distinct increase in tensile stress. The thermomechanical behavior is strongly affected by the amount of oxygen to which the film is exposed and the method of exposure. Increasing oxygen content inhibits the phase transformation, requiring higher temperatures to reach completion. It is shown that the phase transformation takes place by a nucleation and growth process that is limited by growth. Changes in the activation energy for the phase transformation due to solute drag are estimated as a function of oxygen content and the mechanisms behind the stress evolution are elucidated

  6. Microstructures formation and phase transformations around the interface of welds between dissimilar steels

    Directory of Open Access Journals (Sweden)

    Mas Fanny

    2013-11-01

    Full Text Available The goal of this study is to understand the complex microstructures which form at the interface between a low-alloy steel and a stainless steel during welding and subsequent heat-treatment at 610 ∘C. A dual approach with both experimental measurements and thermodynamic and kinetic modeling has been chosen for both solidification and solid-state phase transformations. A very good agreement has been obtained for the carbon profile across the interface and the nature of phases which form.

  7. Machining and Phase Transformation Response of Room-Temperature Austenitic NiTi Shape Memory Alloy

    Science.gov (United States)

    Kaynak, Yusuf

    2014-09-01

    This experimental work reports the results of a study addressing tool wear, surface topography, and x-ray diffraction analysis for the finish cutting process of room-temperature austenitic NiTi alloy. Turning operation of NiTi alloy was conducted under dry, minimum quantity lubrication (MQL) and cryogenic cooling conditions at various cutting speeds. Findings revealed that cryogenic machining substantially reduced tool wear and improved surface topography and quality of the finished parts in comparison with the other two approaches. Phase transformation on the surface of work material was not observed after dry and MQL machining, but B19' martensite phase was found on the surface of cryogenically machined samples.

  8. Studies of gas phase ion/molecule reactions by Fourier transform ion cyclotron resonance mass spectrometry

    International Nuclear Information System (INIS)

    Kleingeld, J.C.

    1984-01-01

    An important field in which Fourier-transform ion cyclotron resonance has useful applications is that of gas phase ion chemistry, the subject of this thesis. First, the general picture of ion-molecule reactions in the gas phase is discussed. Next, some positive ion-molecule reactions are described, whereas the remaining chapters deal with negative ion-molecule reactions. Most of these studies have been performed using the FT-ICR method. Reactions involving H 3 O - and NH 4 - ions are described whereas the other chapters deal with larger organic complexes. (Auth.)

  9. Nine-Phase Induction Motor Dynamic Model Based On 3x9 Transformation Matrix

    Directory of Open Access Journals (Sweden)

    Mauridhi Heri Purnomo

    2013-07-01

    Full Text Available A dynamic model of multi-phase induction motors in term qdn is used to simplify analysis and separate armature and field of the motor. However, to generate dynamic model qdn, square matrices are always applied to all the analysis and based on two reference frames and a circuit of magnetically coupled transformer. In order to gain the qdn dynamic model of the nine-phase induction motors in easy, simple, quick and consistent way, the analysis is done through the equivalent circuit T model until it obtains the equations in matrix form. The 3x9 transformation matrix qdn is substituted into the equation form abc so that the matrix equation of qdn is obtained. Then qdn equation results a similar qd equivalent circuit, which has different methods n that is, based the circuit of magnetically coupled transformer. Simulation results show that the two-bases circuit is magnetically coupled into the transformer model and has similar angular speed and torque response to the motor though the load changes.

  10. Controllable Phase Transformation in Extracting Valuable Metals from Chinese Low-Grade Nickel Sulphide Ore

    Science.gov (United States)

    Cui, Fuhui; Mu, Wenning; Wang, Shuai; Xu, Qian; Zhai, Yuchun; Luo, Shaohua

    2017-10-01

    In this work, a two-stage sulphuric acid roasting and water leaching system was chosen to extract valuable metals from Chinese low-grade nickel sulphide ore. By optimizing the two-stage roasting process, first roasting temperature at 295°C with particle size of 80-91 μm with an acid-ore ratio of 1.1:1 for 2 h, and second roasting temperature at 620°C for 2 h, it was found that more than 98% of the nickel and 99% of the copper but less than 14.38% of Fe were leached into the water. Attempts were made via x-ray diffraction analysis, scanning electron microscopy, chemical phase analysis, and differential thermal and thermogravimetric analysis to reveal the phase transformations for Ni, Cu, and Mg, which could be expressed as mineral phases → sulphates hydrate → sulphates and for iron as mineral phases → hydrated ferrous sulphate → ferric sulphates and ferric oxide → oxide. The results of this work suggest that a controllable phase transformation by using a two-stage sulphuric acid roasting process is a feasible method for efficiently extracting valuable metals from Chinese nickel sulphide ore.

  11. Mechanically Induced Graphite-Nanodiamonds-Phase Transformations During High-Energy Ball Milling

    Science.gov (United States)

    El-Eskandarany, M. Sherif

    2017-05-01

    Due to their unusual mechanical, chemical, physical, optical, and biological properties, nearly spherical-like nanodiamonds have received much attention as desirable advanced nanomaterials for use in a wide spectrum of applications. Although, nanodiamonds can be successfully synthesized by several approaches, applications of high temperature and/or high pressure may restrict the real applications of such strategic nanomaterials. Distinct from the current preparation approaches used for nanodiamonds preparation, here we show a new process for preparing ultrafine nanodiamonds (3-5 nm) embedded in a homogeneous amorphous-carbon matrix. Our process started from high-energy ball milling of commercial graphite powders at ambient temperature under normal atmospheric helium gas pressure. The results have demonstrated graphite-single wall carbon nanotubes-amorphous-carbon-nanodiamonds phase transformations carried out through three subsequent stages of ball milling. Based on XRD and RAMAN analyses, the percentage of nanodiamond phase + C60 (crystalline phase) produced by ball milling was approximately 81%, while the amorphous phase amount was 19%. The pressure generated on the powder together the with temperature increase upon the ball-powder-ball collision is responsible for the phase transformations occurring in graphite powders.

  12. Prediction of Continuous Cooling Transformation Diagrams for Dual-Phase Steels from the Intercritical Region

    Science.gov (United States)

    Colla, V.; Desanctis, M.; Dimatteo, A.; Lovicu, G.; Valentini, R.

    2011-09-01

    The purpose of the present work is the implementation and validation of a model able to predict the microstructure changes and the mechanical properties in the modern high-strength dual-phase steels after the continuous annealing process line (CAPL) and galvanizing (Galv) process. Experimental continuous cooling transformation (CCT) diagrams for 13 differently alloying dual-phase steels were measured by dilatometry from the intercritical range and were used to tune the parameters of the microstructural prediction module of the model. Mechanical properties and microstructural features were measured for more than 400 dual-phase steels simulating the CAPL and Galv industrial process, and the results were used to construct the mechanical model that predicts mechanical properties from microstructural features, chemistry, and process parameters. The model was validated and proved its efficiency in reproducing the transformation kinetic and mechanical properties of dual-phase steels produced by typical industrial process. Although it is limited to the dual-phase grades and chemical compositions explored, this model will constitute a useful tool for the steel industry.

  13. Relationships between phase transformations, microstructure and properties in Ti and Pb-free alloys

    Energy Technology Data Exchange (ETDEWEB)

    Servant, Colette [Centre National de la Recherche Scientifique (C.N.R.S.), Laboratoire de Physico-Chimie de l' Etat Solide, ICMMO, Universite de Paris-Sud, 91405 Orsay (France)

    2010-10-15

    The mechanical or use properties of alloys are determined by their chemical composition and microstructure history. The microstructure changes during phase transformations occurring during solidification, thermomechanical processing and subsequent heat treatments. The best mechanical properties for the chosen application need optimized parameters of the microstructure. Tailored microstructures: can a dream come true. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Li doping effect on properties and phase transformations of KNbO.sub.3./sub..

    Czech Academy of Sciences Publication Activity Database

    Trepakov, Vladimír; Savinov, Maxim; Železný, Vladimír; Syrnikov, P. P.; Deyneka, Alexander; Jastrabík, Lubomír

    2007-01-01

    Roč. 27, - (2007), s. 4071-4073 ISSN 0955-2219 R&D Projects: GA MŠk(CZ) 1M06002 Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z10100522; CEZ:AV0Z10100520 Keywords : impurities * spectroscopy * phase transformations * perovskites Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.562, year: 2007

  15. Analysis of three-phase power transformer laminated magnetic core designs

    Directory of Open Access Journals (Sweden)

    M.I. Levin

    2014-03-01

    Full Text Available Analysis and research into properties and parameters of different-type laminated magnetic cores of three-phase power transformers are conducted. Most of new laminated magnetic core designs are found to have significant shortcomings resulted from design and technological features of their manufacturing. These shortcomings cause increase in ohmic loss in the magnetic core, which eliminates advantages of the new core configurations and makes them uncompetitive as compared with the classical laminated magnetic core design.

  16. Ab initio study of phase transformations in transition-metal disilicides

    Czech Academy of Sciences Publication Activity Database

    Káňa, Tomáš; Šob, Mojmír; Vitek, V.

    2011-01-01

    Roč. 19, č. 7 (2011), s. 919-926 ISSN 0966-9795 R&D Projects: GA AV ČR IAA100100920; GA MŠk(CZ) OC10008 Institutional research plan: CEZ:AV0Z20410507 Keywords : silicides various * phase transformation * plastic deformation mechanisms * defects * dislocation geometry and arrangement * ab-initio calculations * aero-engine components Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.649, year: 2011

  17. In-situ neutron diffraction studies of phase transformations in Si-Mn

    Czech Academy of Sciences Publication Activity Database

    Lukáš, Petr; Šittner, Petr; Zrník, J.; Jenčuš, Peter; Nový, Z.; Muránsky, Ondrej

    2005-01-01

    Roč. 7, - (2005), s. 275-280 ISSN 0255-5476. [International Conference on Residual Stresses /7./. Xian, 14.06.2005-17.06.2005] R&D Projects: GA AV ČR(CZ) IAA1048107; GA ČR(CZ) GA202/03/0891 Keywords : phase transformation * TRIP steel * neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.399, year: 2005

  18. Phase transformations in low-carbon manganese steel 6Mn16

    Directory of Open Access Journals (Sweden)

    J. Lis

    2009-01-01

    Full Text Available The kinetics of phase transformations of the austenite of 6Mn16 steel during continuous cooling are presented in a CCT diagram. Manganese partitioning between ferrite and austenite during intercritical annealing is enhanced by prior soft annealing. Due to the increased Mn concentration in austenite, the temperatures BS and MS have decreased, as compared to those achieved during cooling from the complete austenite region.

  19. Nucleation and Epitaxy-Mediated Phase Transformation of a Precursor Cadmium Carbonate Phase at the Calcite/Water Interface

    Energy Technology Data Exchange (ETDEWEB)

    Riechers, Shawn L.; Rosso, Kevin M.; Kerisit, Sebastien N.

    2017-02-24

    Mineral nucleation can be catalyzed by the presence of mineral substrates; however, the mechanisms of heterogeneous nucleation remain poorly understood. A combination of in situ time-sequenced measurements and nano-manipulation experiments were performed using atomic force microscopy (AFM) to probe the mechanisms of heteroepitaxial nucleation of otavite (CdCO3) on calcite (CaCO3) single crystals that exposed the (10-14) surface. Otavite and calcite are isostructural carbonates that display a 4% lattice mismatch, based on their (10-14) surface areas. AFM observations revealed a two-stage process in the nucleation of cadmium carbonate surface precipitates. As evidenced by changes in height, shape, growth behavior, and friction signal of the precipitates, a precursor phase was observed to initially form on the surface and subsequently undergo an epitaxy-mediated phase transformation to otavite, which then grew epitaxially. Nano-manipulation experiments, in which the applied force was increased progressively until precipitates were removed from the surface, showed that adhesion of the precursor phase to the substrate was distinctively weaker than that of the epitaxial phase, consistent with that of an amorphous phase. These findings demonstrate for the first time that heterogeneous mineral nucleation can follow a non-classical pathway like that found in homogenous aqueous conditions.

  20. Nickel and cobalt filled multiwalled carbon nantubes : structural transformation under heavy ion irradiation and high pressure

    International Nuclear Information System (INIS)

    Misra, D.S.; Misra, A.; Tyagi, Pawan K.; Karamakar, S.; Sharma, Surinder M.

    2006-01-01

    Full text: The nickel and cobalt nano wires of diameters ranging from 5-15 nm are formed inside the multiwalled carbon nantubes using microwave plasma chemical vapor deposition in our laboratory. The nano wires inside the tubes are found to have a perfect crystalline structure and the crystalline planes of (111) orientations are aligned for FCC nickel and cobalt in a particular fashion. We find that the cobalt can exist either in FCC or HCP phase in confinement depending upon the diameter of the tubes. The irradiation of these nanowires with high energy Au + ions alter the orientation of the crystalline planes and generate various types of domains and defects in the nanowires. The complete amorphization of the walls of the nano tubes is observed at the fluence of 5x10 13 /cm 2 and results in amorphization of nickel nano wires as well. The cobalt nano wires have FCC structure in ambient conditions and transform to HCP cobalt irreversibly when subjected to high pressure of ∼9 GPa. Multi-walled carbon nano tubes that encapsulate the cobalt nano wires do not undergo any other structural transformation with pressure except partial reversible amorphization beyond 9 GPa

  1. Preparation of α-alumina nanoparticles with various shapes via hydrothermal phase transformation under supercritical water conditions

    Science.gov (United States)

    Hakuta, Y.; Nagai, N.; Suzuki, Y.-H.; Kodaira, T.; Bando, K. K.; Takashima, H.; Mizukami, F.

    2013-12-01

    Alumina (Al2O3) fine particles are widely used as industrial materials including fillers for metal or plastics, paints, polisher, cosmetics and electric substrates, due to its high hardness, chemical stability, and high thermal conductivity. The performance of those industrial products is closely related to the particle size or shape of the alumina particles used, and thus a new synthetic method to control size, shape, and crystal structure of the aluminum oxide is desired for the improvement of the performance. Hydrothermal phase transformation using various aluminum compounds such as oxide, hydroxide, and salt as a staring material, is known as one of the synthetic methods for producing alumina fine particles; however, the influence about the size and shape of the starting aluminum compounds has been little mentioned, although they strongly affect the size and shape of the final products. In this study, we investigated the influence of the shape, size and crystal structure of the starting aluminum compounds on those of the products, and newly succeeded in the production of rod-like α-Al2O3 nanoparticles from fibrous boehmite nanoparticles using hydrothermal phase transformation under supercritical water conditions.

  2. Residual stress delaying phase transformation in Y-TZP bio-restorations

    Science.gov (United States)

    Allahkarami, Masoud; Hanan, Jay C.

    2012-01-01

    Engineering favorable residual stress for the complex geometry of bi-layer porcelain-zirconia crowns potentially prevents crack initiation and improves the mechanical performance and lifetime of the dental restoration. In addition to external load, the stress field depends on initial residual stress before loading. Residual stress is the result of factors such as the thermal expansion mismatch of layers and compliance anisotropy of zirconia grains in the process of sintering and cooling. Stress induced phase transformation in zirconia extensively relaxes the residual stress and changes the stress state. The objective of this study is to investigate the coupling between tetragonal to monoclinic phase transformations and residual stress. Residual stress, on the surface of the sectioned single load to failure crown, at 23 points starting from the pure tetragonal and ending at a fully monoclinic region were measured using the micro X-ray diffraction sin2 ψ method. An important observation is the significant range in measured residual stress from a compressive stress of -400 MPa up to tensile stress of 400 MPa and up to 100% tetragonal to monoclinic phase transformation.

  3. Phase retrieval for noisy fringe pattern by using empirical mode decomposition and Hilbert Huang transform

    Science.gov (United States)

    Wang, Chenxing; Da, Feipeng

    2012-06-01

    To address the issue of the intermittent noise in optical fringe pattern, an adaptive method of noise reduction is given based on empirical mode decomposition (EMD) and Hilbert Huang transform (HHT), and then the wrapped phase is obtained by performing the Hilbert transform on the refined pattern. Firstly, the signal of the fringe pattern is decomposed into several intrinsic mode functions (IMFs). With the instantaneous frequencies and marginal spectra of each IMF obtained by HHT, the criterion of identifying the noise IMF is determined. Then, it is judged whether a mode-mixing problem, which is the frequent problem in traditional EMD, appears in each noise IMF. If the problem appears, the ``noise,'' which is designed according to the signal adaptively, is added to the original signal, and then the obtained new signal is decomposed again. The process will be repeated until there is no mode mixing in the noise IMF. Finally, the wrapped phase is obtained by performing a Hilbert transform on the refined pattern with noise and background components removed. The proposed method can solve the mode-mixing problem effectively. It can reduce most of the noise and maintain a large amount of detailed phase information simultaneously. Simulation and compared experiments show the efficiency, robustness, and accuracy of the proposed method.

  4. Feminist Transformation in Higher Education: Discipline, Structure, and Institution.

    Science.gov (United States)

    Safarik, Lynn

    2003-01-01

    Using a feminist poststructuralist perspective, investigated academic feminism as a case of transformation in higher education. Used narrative analysis to examine the transformative role of feminist scholarship in the contexts of disciplines, departments, and the university, illustrated by the life histories of nine diverse feminists and their…

  5. On the use of Stockwell transform in structural dynamic analysis

    Indian Academy of Sciences (India)

    Time-frequency analysis of earthquake records using Fourier transform is a fundamental, reliable and useful tool in earthquake engineering and engineering seismology. It will be however no longer functional if the frequency variation is analysed in time domain. Short time Fourier transform is utilized for the same purpose ...

  6. Pressure-induced phase transformations in the Ba8Si46 clathrate

    DEFF Research Database (Denmark)

    Yang, Lirong; Ma, Y.M.; Iitaka, T.

    2006-01-01

    The nature of isostructural transformations of a type-I Ba8Si46 clathrate has been studied by in situ high-pressure angle-dispersive x-ray powder diffraction using liquid He as pressure transmitting medium. The good quality of the diffraction data permitted refinement of structural and thermal...

  7. Influence of Plastic Deformation on Martensitic Transformation During Hot Stamping of Complex Structure Auto Parts

    Science.gov (United States)

    Shen, Yuhan; Song, Yanli; Hua, Lin; Lu, Jue

    2017-04-01

    The ultra-high strength steel auto parts manufactured by hot stamping are widely applied for weight reduction and safety improvement. During the hot stamping process, hot forming and quenching are performed in one step wherein plastic deformation and phase transformation simultaneously take place and affect each other. Thereinto, the influence of deformation on martensitic transformation is of great importance. In the present paper, the influence of plastic deformation on martensitic transformation during hot stamping of complex structure auto parts was investigated. For this purpose, a B-pillar reinforced panel in B1500HS steel was manufactured by hot stamping, and the process was simulated by finite element software based on a thermo-mechanical-metallurgical coupled model. Considering various deformation degrees, the microstructures and mechanical properties at four typical locations of the hot stamped B-pillar reinforced panel were detected. The results show that the martensitic content and the microhardness increase with the increase in the deformation amount. There are two reasons causing this phenomenon: (1) the increase in mechanical driving force and (2) the increased probability of the martensitic nucleation at crystal defects. The x-ray diffraction analysis indicates the carbon enrichment in retained austenite which results from the carbon diffusion during the low-carbon martensite formation. Furthermore, the carbon content decreases with the increase in the deformation amount, because the deformation of austenite suppresses the carbon diffusion.

  8. Indirect phase transition of TiC, ZrC, and HfC crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Abavare, Eric K.K.; Dodoo, Samuel N.A. [Department of Physics, Kwame Nkrumah University of Science and Technology, Kumasi (Ghana); Uchida, Kazuyuki; Oshiyama, Atsushi [Department of Applied Physics, The University of Tokyo, Hongo, Tokyo (Japan); Nkurumah-Buandoh, George K.; Yaya, Abu [Department of Physics, University of Ghana, Legon (Ghana)

    2016-06-15

    We have performed first-principles calculations to analyze the electronic structures, static, and dynamical structural stabilities of the pressure-induced phase transformation of refractory compounds (transition-metal carbides) from NaCl-type (B1) to CsCl-type (B2) via zinc-blende phase using the plane-wave pseudopotential approach in the framework of the generalized gradient approximation (GGA) for the exchange and correlation functional. The ground-state properties, equilibrium lattice constant, bulk moduli, and band structures are determined for the stoichiometry of the compounds and compared with known experimental and theoretical values. We find that the phase-transition pressure for the indirect phase transition from B1→B2 via zinc-blende structure is about 17-fold for TiC, 12-fold for both ZrC and HfC, respectively, when compared with the direct phase transition. Calculated phonon instability exists for the CsCl-B2 phase, which can prevent the structures from forming and contrary to the zinc-blende and the NaCl-B1 phases. The band dispersion and electronic density of states for B1 and B2 crystal phases were explored and found to indicate metallic character in contrast with the zinc-blende phase, which has a pseudogap opening in the bandgap region suggesting a semiconducting property and also a frequency gap in the phonon spectrum. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Combined model of strain-induced phase transformation and orthotropic damage in ductile materials at cryogenic temperatures

    CERN Document Server

    Garion, Cedric

    2003-01-01

    Ductile materials (like stainless steel or copper) show at cryogenic temperatures three principal phenomena: serrated yielding (discontinuous in terms of dsigma/depsilon), plastic strain-induced phase transformations and evolution of ductile damage. The present paper deals exclusively with the two latter cases. Thus, it is assumed that the plastic flow is perfectly smooth. Both in the case of damage evolution and for the gamma-alpha prime phase transformation, the principal mechanism is related to the formation of plastic strain fields. In the constitutive modeling of both phenomena, a crucial role is played by the accumulated plastic strain, expressed by the Odqvist parameter p. Following the general trends, both in the literature concerning the phase transformation and the ductile damage, it is assumed that the rate of transformation and the rate of damage are proportional to the accumulated plastic strain rate. The gamma-alpha prime phase transformation converts the initially homogenous material to a two-p...

  10. Indoor transformer stations and ELF magnetic field exposure: use of transformer structural characteristics to improve exposure assessment.

    Science.gov (United States)

    Okokon, Enembe Oku; Roivainen, Päivi; Kheifets, Leeka; Mezei, Gabor; Juutilainen, Jukka

    2014-01-01

    Previous studies have shown that populations of multiapartment buildings with indoor transformer stations may serve as a basis for improved epidemiological studies on the relationship between childhood leukaemia and extremely-low-frequency (ELF) magnetic fields (MFs). This study investigated whether classification based on structural characteristics of the transformer stations would improve ELF MF exposure assessment. The data included MF measurements in apartments directly above transformer stations ("exposed" apartments) in 30 buildings in Finland, and reference apartments in the same buildings. Transformer structural characteristics (type and location of low-voltage conductors) were used to classify exposed apartments into high-exposure (HE) and intermediate-exposure (IE) categories. An exposure gradient was observed: both the time-average MF and time above a threshold (0.4 μT) were highest in the HE apartments and lowest in the reference apartments, showing a statistically significant trend. The differences between HE and IE apartments, however, were not statistically significant. A simulation exercise showed that the three-category classification did not perform better than a two-category classification (exposed and reference apartments) in detecting the existence of an increased risk. However, data on the structural characteristics of transformers is potentially useful for evaluating exposure-response relationship.

  11. Suppression of superconductivity and structural phase transitions under pressure in tetragonal FeS.

    Science.gov (United States)

    Lai, Xiaofang; Liu, Ying; Lü, Xujie; Zhang, Sijia; Bu, Kejun; Jin, Changqing; Zhang, Hui; Lin, Jianhua; Huang, Fuqiang

    2016-08-08

    Pressure is a powerful tool to study iron-based superconductors. Here, we report systematic high-pressure transport and structural characterizations of the newly discovered superconductor FeS. It is found that superconductor FeS (tetragonal) partly transforms to a hexagonal structure at 0.4 GPa, and then completely transforms to an orthorhombic phase at 7.4 GPa and finally to a monoclinic phase above 9.0 GPa. The superconducting transition temperature of tetragonal FeS was gradually depressed by pressure, different from the case in tetragonal FeSe. With pressure increasing, the S-Fe-S angles only slightly change but the anion height deviates farther from 1.38 Å. This change of anion height, together with the structural instability under pressure, should be closely related to the suppression of superconductivity. We also observed an anomalous metal-semiconductor transition at 6.0 GPa and an unusual increased resistance with further compression above 9.6 GPa. The former can be ascribed to the tetragonal-orthorhombic structural phase transition, and the latter to the electronic structure changes of the high-pressure monoclinic phase. Finally, a phase diagram of tetragonal FeS as functions of pressure and temperature was mapped out for the first time, which will shed new light on understanding of the structure and physics of the superconducting FeS.

  12. Copper coordination polymers constructed from thiazole-5-carboxylic acid: Synthesis, crystal structures, and structural transformation

    Energy Technology Data Exchange (ETDEWEB)

    Meundaeng, Natthaya; Rujiwatra, Apinpus [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Prior, Timothy J., E-mail: t.prior@hull.ac.uk [Chemistry, University of Hull, Kingston upon Hull HU6 7RX (United Kingdom)

    2017-01-15

    We have successfully prepared crystals of thiazole-5-carboxylic acid (5-Htza) (L) and three new thiazole-5-carboxylate-based Cu{sup 2+} coordination polymers with different dimensionality, namely, 1D [Cu{sub 2}(5-tza){sub 2}(1,10-phenanthroline){sub 2}(NO{sub 3}){sub 2}] (1), 2D [Cu(5-tza){sub 2}(MeOH){sub 2}] (2), and 3D [Cu(5-tza){sub 2}]·H{sub 2}O (3). These have been characterized by single crystal X-ray diffraction and thermogravimetry. Interestingly, the 2D network structure of 2 can directly transform into the 3D framework of 3 upon removal of methanol molecules at room temperature. 2 can also undergo structural transformation to produce the same 2D network present in the known [Cu(5-tza){sub 2}]·1.5H{sub 2}O upon heat treatment for 2 h. This 2D network can adsorb water and convert to 3 upon exposure to air. - Highlights: • Rare examples of coordination polymers of thiazole-5-carboxylic acid were prepared. • Non-covalent interactions play a key role on the assembly of the complexes in solid state. • Structural transformation of a 2D framework to a 3D upon removal of methanol is observed.

  13. Hybrid CO2 laser/waterjet (CO2-LWJ) cutting of Polycrystalline Cubic Boron Nitride (PCBN) blanks with phase transformation induced fracture

    Science.gov (United States)

    Wu, Zhuoru; Melaibari, Ammar A.; Molian, Pal; Shrotriya, Pranav

    2015-07-01

    The present paper investigates a transformation induced fracture mechanism for the cutting of Polycrystalline Cubic Boron Nitride (PCBN) sample by a hybrid CO2 laser/waterjet (CO2-LWJ) manufacturing process. In CO2-LWJ machining, a laser was used for local heating followed by waterjet quenching leading to fracture propagation along the sample surface. Cutting results indicate that as line energy of the laser was increased the sample response transitioned from scribing to through cutting. Raman spectroscopy analysis of the cut surface indicates that laser heated PCBN undergoes chemical phase transformation from sp3-bonded cubic Boron Nitride (cBN) into hexagonal Boron Nitride (hBN) and other sp2-bonded phases. The sp2-bonded structure occupies more volume than sp3-bonded structure such that the transformed material has a tendency to expand the original material and leads to surface deformation around the cutting path. Surface profile of the cut samples was experimentally measured using profilometry and compared with numerical predictions in order to estimate the expansion strain and dimensions of transformation region. Based on the obtained expansion strain and transformation zone, stress fields and crack driving forces were computed for channeling cracks that result in material separation. Comparison of the crack driving forces with fracture toughness of PCBN shows that transformation induced crack propagation is the feasible mechanism for cutting during CO2-LWJ machining.

  14. Transformation behavior of the γU(Zr,Nb) phase under continuous cooling conditions

    Energy Technology Data Exchange (ETDEWEB)

    Komar Varela, C.L., E-mail: cavarela@cnea.gov.ar [Instituto Sabato, UNSAM-CNEA, Comisión Nacional de Energía Atómica, Avenida General Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); Gerencia de Ciclo del Combustible Nuclear, Comisión Nacional de Energía Atómica, Avenida General Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); Gribaudo, L.M. [Gerencia de Materiales, GAEN, Comisión Nacional de Energía Atómica, Avenida General Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); González, R.O.; Aricó, S.F. [Instituto Sabato, UNSAM-CNEA, Comisión Nacional de Energía Atómica, Avenida General Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); Gerencia de Materiales, GAEN, Comisión Nacional de Energía Atómica, Avenida General Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina)

    2014-10-15

    The selected alloy for designing a high-density monolithic-type nuclear fuel with U–Zr–Nb alloy as meat and Zry-4 as cladding, has to remain in the γU(Zr,Nb) phase during the whole fabrication process. Therefore, it is necessary to define a range of concentrations in which the γU(Zr,Nb) phase does not decompose under the process conditions. In this work, several U alloys with concentrations between 28.2–66.9 at.% Zr and 0–13.3 at.% Nb were fabricated to study the possible transformations of the γU(Zr,Nb) phase under different continuous cooling conditions. The results of the electrical resistivity vs temperature experiments are presented. For a cooling rate of 4 °C/min a linear regression was determined by fitting the starting decomposition temperature as a function of Nb concentration. Under these conditions, a concentration of 45.3 at.% Nb would be enough to avoid any transformation of the γU(Zr,Nb) phase. In experiments that involve higher cooling conditions, it has been determined that this concentration can be halved.

  15. Chemical synthesis, phase transformation and magnetic proprieties of FePt and FePd nanoparticles

    International Nuclear Information System (INIS)

    Delattre, Anastasia

    2010-01-01

    This work aims at understanding the chemical synthesis of FePt and FePd nanoparticles (NPs), and at exploring how to implement the phase transformation from the chemically disordered to the L10 phase, without coalescence. Using hexadecanenitrile instead of oleylamine, we obtain NPs with a more homogenous internal composition, instead of core-shell NPs. Through a systematic study (designed experiment relying on Taguchi tables), we developed the FePd synthesis, while evidencing the role of each ligand and of the reductor. To induce the crystalline phase transformation while avoiding coalescence, we explored two ways. In the first one, atomic vacancies are introduced in the NPs through light ion irradiation, atomic mobility being ensured by annealing at moderate temperature (300 C). As a result, the blocking temperature is multiplied by 4, due to anisotropy enhancement. However, strong chemical ordering in the L10 phase cannot be achieved. The second approach relies on the dispersion of the NPs in a salt (NaCl) matrix, prior to annealing at 700 C: high chemical ordering is achieved, and the blocking temperature is beyond 400 C. We then developed a single-step process to remove the salt by dissolution in water and to re-disperse NPs in stable aqueous or organics solutions. These high magnetic anisotropy NPs are then readily available for further chemical or manipulation steps, with applied perspectives in areas such as data storage, or biology. (author)

  16. Transient Structures and Possible Limits of Data Recording in Phase-Change Materials.

    Science.gov (United States)

    Hu, Jianbo; Vanacore, Giovanni M; Yang, Zhe; Miao, Xiangshui; Zewail, Ahmed H

    2015-07-28

    Phase-change materials (PCMs) represent the leading candidates for universal data storage devices, which exploit the large difference in the physical properties of their transitional lattice structures. On a nanoscale, it is fundamental to determine their performance, which is ultimately controlled by the speed limit of transformation among the different structures involved. Here, we report observation with atomic-scale resolution of transient structures of nanofilms of crystalline germanium telluride, a prototypical PCM, using ultrafast electron crystallography. A nonthermal transformation from the initial rhombohedral phase to the cubic structure was found to occur in 12 ps. On a much longer time scale, hundreds of picoseconds, equilibrium heating of the nanofilm is reached, driving the system toward amorphization, provided that high excitation energy is invoked. These results elucidate the elementary steps defining the structural pathway in the transformation of crystalline-to-amorphous phase transitions and describe the essential atomic motions involved when driven by an ultrafast excitation. The establishment of the time scales of the different transient structures, as reported here, permits determination of the possible limit of performance, which is crucial for high-speed recording applications of PCMs.

  17. Microstructural characterization and phase transformation of ternary alloys near at Al3Ti compound

    International Nuclear Information System (INIS)

    Angeles Ch, C.

    1999-01-01

    This research work is related with the structural characteristic and compositional values of the crystalline phases, which are found in ternary alloys of Ti-Al-Fe and TI-Al-Cu. These types of alloys were obtained using a rapid solidification technique (10 3 -10 4 K/s) and pure elements such as Al, Ti, Fe and Cu (99.99%). These cooling velocities allow the formation of stable phases and small grain sizes (approximately in range of a few micras). The obtained results indicate the presence of Al 3 Ti and others phases of L1 2 type. These phases are commonly found in a matrix rich in A1. The microalloyed elements (Cu and Fe) substitute the aluminum in both kinds of phases. Alloys with low content of Cu show transition states from the tetragonal structure DO 22 to the cubic phases L1 2 . The structural characteristics of the alloys are related with some microhardness measurement. The results show that the presence of the L1 2 phase tends to increase to hardness depending of the content of this phase

  18. Atomistic simulation of cubic and tetragonal phases of U-Mo alloy: Structure and thermodynamic properties

    Science.gov (United States)

    Starikov, S. V.; Kolotova, L. N.; Kuksin, A. Yu.; Smirnova, D. E.; Tseplyaev, V. I.

    2018-02-01

    We studied structure and thermodynamic properties of cubic and tetragonal phases of pure uranium and U-Mo alloys using atomistic simulations: molecular dynamics and density functional theory. The main attention was paid to the metastable γ0 -phase that is formed in U-Mo alloys at low temperature. Structure of γ0 -phase is similar to body-centered tetragonal (bct) lattice with displacement of a central atom in the basic cell along [ 001 ] direction. Such displacements have opposite orientations for part of the neighbouring basic cells. In this case, such ordering of the displacements can be designated as antiferro-displacement. Formation of such complex structure may be interpreted through forming of short U-U bonds. At heating, the tetragonal structure transforms into cubic γs -phase, still showing ordering of central atom displacements. With rise in temperature, γs -phase transforms to γ-phase with a quasi body-centered cubic (q-bcc) lattice. The local positions of uranium atoms in γ-phase correspond to γs -phase, however, orientations of the central atom displacements become disordered. Transition from γ0 to γ can be considered as antiferro-to paraelastic transition of order-disorder type. This approach to the structure description of uranium alloy allows to explain a number of unusual features found in the experiments: anisotropy of lattice at low temperature; remarkably high self-diffusion mobility in γ-phase; decreasing of electrical resistivity at heating for some alloys. In addition, important part of this work is the development of new interatomic potential for U-Mo system made with taking into account details of studied structures.

  19. Fourier Analysis and Structure Determination: Part I: Fourier Transforms.

    Science.gov (United States)

    Chesick, John P.

    1989-01-01

    Provides a brief introduction with some definitions and properties of Fourier transforms. Shows relations, ways of understanding the mathematics, and applications. Notes proofs are not included but references are given. First of three part series. (MVL)

  20. Controlling magnetoelectric coupling by nanoscale phase transformation instrain engineered bismuth ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y. Y. [University of Washington, Seattle; Vasudevan, Rama K [ORNL; Pan, K. [Xiangtan University, Xiangtan Hunan, China; Xie, S. H. [University of Washington, Seattle; Liang, W. -I. [National Chiao Tung University, Hsinchu, Taiwan; Kumar, Amit [ORNL; Jesse, Stephen [ORNL; Chen, Y. -C. [National Cheng Kung University, Tainan, Taiwan; Chu, Y.-H. [National Chiao Tung University, Hsinchu, Taiwan; Nagarajan, Valanoor [University of New South Wales; Kalinin, Sergei V [ORNL; Li, J. Y. [University of Washington, Seattle

    2012-01-01

    The magnetoelectric coupling in multiferroic materials is promising for a wide range of applications, yet manipulating magnetic ordering by electric field proves elusive to obtain and difficult to control. In this paper, we explore the prospect of controlling magnetic ordering in misfit strained bismuth ferrite (BiFeO3, BFO) films, combining theoretical analysis, numerical simulations, and experimental characterizations. Electric field induced transformation from a tetragonal phase to a distorted rhombohedral one in strain engineered BFO films has been identified by thermodynamic analysis, and realized by scanning probe microscopy (SPM) experiment. By breaking the rotational symmetry of a tip-induced electric field as suggested by phase field simulation, the morphology of distorted rhombohedral variants has been delicately controlled and regulated. Such capabilities enable nanoscale control of magnetoelectric coupling in strain engineered BFO films that is difficult to achieve otherwise, as demonstrated by phase field simulations.

  1. Phase transformation and conductivity in nanocrystal PbS under pressure

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Gerward, Leif; Secco, R.

    2000-01-01

    The grain-size effect on the phase transition induced by pressure in PbS was studied by in situ high-pressure electrical resistance and synchrotron radiation x-ray powder diffraction measurements. The mean transition pressure of the B1-to-B16 phase transformation was found to be 6.3±1.3 GPa in 8......±1 nm PbS while it is 3.1±0.7 GPa for 10 µm PbS. The resistivity of the B16 PbS phase decreases exponentially with pressure in both samples at ambient temperature. They follow R[proportional]exp(–CP), where C = –0.64 GPa–1 for 10 µm PbS and C = –0.34 GPa–1 for 8±1 nm PbS. These results are discussed...

  2. Structure determination at room temperature and phase transition ...

    Indian Academy of Sciences (India)

    Unknown

    displacement of Bi atoms along the 'a' axis might be responsible for ferroelectricity in these compounds. The high temperature X-ray data above Tc indicate no structural transition for A = Ba and Pb while A = Sr transforms to the tetragonal structure. Keywords. ab initio structure; powder XRD; Rietveld refinement; Aurivillius ...

  3. Improved PLL structures for single-phase grid inverters

    DEFF Research Database (Denmark)

    Ciobotaru, Mihai; Teodorescu, Remus; Blaabjerg, Frede

    2005-01-01

    of the reference signals. This paper presents two improved phase-locked-loop (PLL) methods for single-phase grid connected systems. The investigated PLL methods are based on a transport delay method and an inverse Park transformation method. The improvements in the case of using the delay-based PLL are: non......-frequency dependent and better filtering of the harmonics. For the other investigated PLL method based on inverse Park transformation the improvement consists of better filtering of the harmonics. Experimental results validate the effectiveness of the two proposed methods....

  4. Experimental Testing and Model Validation of a Decoupled-Phase On-Load Tap Changer Transformer in an Active Network

    DEFF Research Database (Denmark)

    Zecchino, Antonio; Hu, Junjie; Coppo, Massimiliano

    2016-01-01

    to reproduce the main feature of an unbalanced grid. The experimental activities are recreated in by carrying out dynamics simulation studies, aiming at validating the implemented models of both the transformer as well as the other grid components. Phase-neutral voltages’ deviations are limited, proving...... this problem, distribution transformers with on-load tapping capability are under development. This paper presents model and experimental validation of a 35 kVA three-phase power distribution transformer with independent on-load tap changer control capability on each phase. With the purpose of investigating...

  5. The impact of natural transformation on adaptation in spatially structured bacterial populations

    OpenAIRE

    Moradigaravand, Danesh; Engelstädter, Jan

    2014-01-01

    Background Recent studies have demonstrated that natural transformation and the formation of highly structured populations in bacteria are interconnected. In spite of growing evidence about this connection, little is known about the dynamics of natural transformation in spatially structured bacterial populations. Results In this work, we model the interdependency between the dynamics of the bacterial gene pool and those of environmental DNA in space to dissect the effect of transformation on ...

  6. Solid–gaseous phase transformation of elemental contaminants during the gasification of biomass

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Ying; Ameh, Abiba [Centre for Bioenergy & Resource Management, School of Energy, Environment & Agrifood, Cranfield University, Cranfield MK43 0AL (United Kingdom); Lei, Mei [Centre for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101 (China); Duan, Lunbo [Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096 (China); Longhurst, Philip, E-mail: P.J.Longhurst@cranfield.ac.uk [Centre for Bioenergy & Resource Management, School of Energy, Environment & Agrifood, Cranfield University, Cranfield MK43 0AL (United Kingdom)

    2016-09-01

    Disposal of plant biomass removed from heavy metal contaminated land via gasification achieves significant volume reduction and can recover energy. However, these biomass often contain high concentrations of heavy metals leading to hot-corrosion of gasification facilities and toxic gaseous emissions. Therefore, it is of significant interest to gain a further understanding of the solid–gas phase transition of metal(loid)s during gasification. Detailed elemental analyses (C, H, O, N and key metal/metalloid elements) were performed on five plant species collected from a contaminated site. Using multi-phase equilibria modelling software (MTDATA), the analytical data allows modelling of the solid/gas transformation of metal(loid)s during gasification. Thermodynamic modelling based on chemical equilibrium calculations was carried out in this study to predict the fate of metal(loid) elements during typical gasification conditions and to show how these are influenced by metal(loid) composition in the biomass and operational conditions. As, Cd, Zn and Pb tend to transform to their gaseous forms at relatively low temperatures (< 1000 °C). Ni, Cu, Mn and Co converts to gaseous forms within the typical gasification temperature range of 1000–1200 °C. Whereas Cr, Al, Fe and Mg remain in solid phase at higher temperatures (> 1200 °C). Simulation of pressurised gasification conditions shows that higher pressures increase the temperature at which solid-to-gaseous phase transformations takes place. - Highlights: • Disposal of plants removed from metal contaminated land raises environmental concerns • Plant samples collected from a contaminated site are shown to contain heavy metals. • Gasification is suitable for plant disposal and its emission is modelled by MTDATA. • As, Cd, Zn and Pb are found in gaseous emissions at a low process temperature. • High pressure gasification can reduce heavy metal elements in process emission.

  7. Two-Way Transformation between fcc- and Nonfcc-Structured Gold Nanoclusters.

    Science.gov (United States)

    Dong, Hongwei; Liao, Lingwen; Wu, Zhikun

    2017-11-02

    Precisely tuning the structure of nanomaterials, especially in a two-way style, is challenging but of great importance for regulating properties and for practical applications. The structural transformation from nonfcc to fcc (face center cubic) in gold nanoclusters has been recently reported; however, the reverse process, that is, the structural transformation from fcc to nonfcc, not to mention the two-way structural transformation between fcc and nonfcc, remains unknown. We developed a novel synthesis method, successfully fulfilled the two-way structure transformation, and studied the stability of gold nanoclusters with different structures. Additionally, a novel gold nanocluster was synthesized and structurally resolved by single-crystal X-ray crystallography. This work has important implications for structure and property tuning of gold nanoclusters and might open up some new potential applications for gold nanoclusters.

  8. Synthesis of iron oxide nanorods via chemical scavenging and phase transformations of intermediates at ambient conditions

    Energy Technology Data Exchange (ETDEWEB)

    Deshmukh, Ruchi; Mehra, Anurag; Thaokar, Rochish, E-mail: rochish@che.iitb.ac.in [Indian Institute of Technology-Bombay, Department of Chemical Engineering (India)

    2017-01-15

    Chemically induced shape transformations of isotropic seeds, comprised of iron oxyhydroxides and iron oxide borate into nanorods, is reported. Transient growth studies show that the nanorods are formed via phase transformation and aggregation of various metastable species. Addition of tetra-methyl-ammonium hydroxide (TMAH) to the in situ synthesized seeds ensures a typical reaction pathway that favors formation of magnetite (Fe {sub 3}O{sub 4}) via the steps of chemical etching, phase transformation of intermediates, and crystal consolidation. Whereas, with addition of sodium hydroxide (NaOH), either magnetite (Fe {sub 3}O{sub 4}) or a mixture of (γ-Fe {sub 2}O{sub 3} + α-FeOOH) is obtained. The shape with both the additives is always that of nanorods. When the seeds treated with TMAH were aged in an ultrasonication bath, rods with almost twice the length and diameter (length = 2800 nm, diameter = 345 nm) are obtained as compared to the sample aged without ultrasonication (length = 1535 nm, diameter = 172 nm). The morphology of nanostructures depending upon other experimental conditions such as, aging the sample at 60 {sup ∘}C, seeds synthesized under ultrasonication/ stirring or externally added are also examined and discussed in detail. All the samples show high coercivity and strong ferromagnetic behavior at room temperature and should be promising candidates as ferro-fluids for various applications.

  9. Polynomial Phase Estimation Based on Adaptive Short-Time Fourier Transform.

    Science.gov (United States)

    Jing, Fulong; Zhang, Chunjie; Si, Weijian; Wang, Yu; Jiao, Shuhong

    2018-02-13

    Polynomial phase signals (PPSs) have numerous applications in many fields including radar, sonar, geophysics, and radio communication systems. Therefore, estimation of PPS coefficients is very important. In this paper, a novel approach for PPS parameters estimation based on adaptive short-time Fourier transform (ASTFT), called the PPS-ASTFT estimator, is proposed. Using the PPS-ASTFT estimator, both one-dimensional and multi-dimensional searches and error propagation problems, which widely exist in PPSs field, are avoided. In the proposed algorithm, the instantaneous frequency (IF) is estimated by S-transform (ST), which can preserve information on signal phase and provide a variable resolution similar to the wavelet transform (WT). The width of the ASTFT analysis window is equal to the local stationary length, which is measured by the instantaneous frequency gradient (IFG). The IFG is calculated by the principal component analysis (PCA), which is robust to the noise. Moreover, to improve estimation accuracy, a refinement strategy is presented to estimate signal parameters. Since the PPS-ASTFT avoids parameter search, the proposed algorithm can be computed in a reasonable amount of time. The estimation performance, computational cost, and implementation of the PPS-ASTFT are also analyzed. The conducted numerical simulations support our theoretical results and demonstrate an excellent statistical performance of the proposed algorithm.

  10. Chiral Liquid Crystals: Structures, Phases, Effects

    Directory of Open Access Journals (Sweden)

    Ingo Dierking

    2014-06-01

    Full Text Available The introduction of chirality, i.e., the lack of mirror symmetry, has a profound effect on liquid crystals, not only on the molecular scale but also on the supermolecular scale and phase. I review these effects, which are related to the formation of supermolecular helicity, the occurrence of novel thermodynamic phases, as well as electro-optic effects which can only be observed in chiral liquid crystalline materials. In particular, I will discuss the formation of helical superstructures in cholesteric, Twist Grain Boundary and ferroelectric phases. As examples for the occurrence of novel phases the Blue Phases and Twist Grain Boundary phases are introduced. Chirality related effects are demonstrated through the occurrence of ferroelectricity in both thermotropic as well as lyotropic liquid crystals. Lack of mirror symmetry is also discussed briefly for some biopolymers such as cellulose and DNA, together with its influence on liquid crystalline behavior.

  11. High-energy X-ray study of short range order and phase transformations in titanium-vanadium

    International Nuclear Information System (INIS)

    Ramsteiner, I.B.

    2005-01-01

    This work presents a study of configurational correlations and phase transformations in the binary alloy Ti-V, using high-energy X-ray diffraction. The experiments have been performed at the European Synchrotron Radiation Facility (ESRF) in Grenoble. The high-energy (60-100 keV) technique developed recently allows in-situ measurements on bulk material in transmission geometry. The first part of the thesis discusses multiple scattering effects which might occur with this method. These effects are experimentally verified and discussed. Special emphasis is put on the questions, whether they affect the results obtained with this method, and how they can be avoided. Understanding alloys on the most fundamental level requires knowledge about the atomic interaction potentials. Competing with entropy, these potentials determine the configurational short range order in a disordered alloy, which generates together with static and dynamic distortions the diffuse scattering. The thesis presents measurements and calculations of the diffuse scattering patterns of Ti-V. The calculations, taking into account configurational correlations, static distortions induced by atomic size mismatch and thermal diffuse scattering, agree with the experimental data. Structural transformations in Ti-V are carefully characterized using high-energy x-ray diffraction in combination with the complementary transmission electron microscopy (TEM). While the first technique allows to study the phenomena in-situ and time-resolved, TEM yields real space images and chemical information about the phases. Ti-V near the equiatomic composition is a beta-Ti-alloy. The body centered cubic beta phase is retained at room temperature by fast quenching. Aging the material below the phase transformation temperature, however, leads to the precipitation of hexagonal alpha titanium. Another transformation process confusing earlier works is identified as TiC formation from carbon impurities in the material. In addition

  12. Cost Optimal Design of a Single-Phase Dry Power Transformer

    Directory of Open Access Journals (Sweden)

    Raju Basak

    2015-08-01

    Full Text Available The Dry type transformers are preferred to their oil-immersed counterparts for various reasons, particularly because their operation is hazardless. The application of dry transformers was limited to small ratings in the earlier days. But now these are being used for considerably higher ratings.  Therefore, their cost-optimal design has gained importance. This paper deals with the design procedure for achieving cost optimal design of a dry type single-phase power transformer of small rating, subject to usual design constraints on efficiency and voltage regulation. The selling cost for the transformer has been taken as the objective function. Only two key variables have been chosen, the turns/volt and the height: width ratio of window, which affects the cost function to high degrees. Other variables have been chosen on the basis of designers’ experience. Copper has been used as conductor material and CRGOS as core material to achieve higher efficiency, lower running cost and compact design. The electrical and magnetic loadings have been kept at their maximum values without violating the design constraints. The optimal solution has been obtained by the method of exhaustive search using nested loops.

  13. Pressure-induced transformations in PrVO4 and SmVO4 and isolation of high-pressure metastable phases.

    Science.gov (United States)

    Errandonea, Daniel; Achary, S Nagabhusan; Pellicer-Porres, Julio; Tyagi, Avesh K

    2013-05-06

    Zircon-type PrVO4 and SmVO4 have been studied by high-pressure Raman spectroscopy up to 17 GPa. The occurrence of phase transitions has been detected when compression exceeds 6 GPa. The transformations are not reversible. Raman spectra of the high-pressure phases show similarities with those expected for a monazite-type phase in PrVO4 and a scheelite-type phase in SmVO4.The high-pressure phases have been also synthesized using a large-volume press and recovered at ambient conditions. X-ray diffraction measurements of the metastable products recovered after decompression confirms the monazite (PrVO4) and scheelite (SmVO4) structures of the high-pressure phases. Based upon optical properties of the reported new polymorphs, novel applications for rare-earth vanadates are proposed, including photocatalytic hydrogen production.

  14. Numerical estimation of phase transformations in solid state during Yb:YAG laser heating of steel sheets

    International Nuclear Information System (INIS)

    Kubiak, Marcin; Piekarska, Wiesława; Domański, Tomasz; Saternus, Zbigniew; Stano, Sebastian

    2015-01-01

    This work concerns the numerical modeling of heat transfer and phase transformations in solid state occurring during the Yb:YAG laser beam heating process. The temperature field is obtained by the numerical solution into transient heat transfer equation with convective term. The laser beam heat source model is developed using the Kriging interpolation method with experimental measurements of Yb:YAG laser beam profile taken into account. Phase transformations are calculated on the basis of Johnson - Mehl - Avrami (JMA) and Koistinen - Marburger (KM) kinetics models as well as continuous heating transformation (CHT) and continuous cooling transformation (CCT) diagrams for S355 steel. On the basis of developed numerical algorithms 3D computer simulations are performed in order to predict temperature history and phase transformations in Yb:YAG laser heating process

  15. Numerical estimation of phase transformations in solid state during Yb:YAG laser heating of steel sheets

    Energy Technology Data Exchange (ETDEWEB)

    Kubiak, Marcin, E-mail: kubiak@imipkm.pcz.pl; Piekarska, Wiesława; Domański, Tomasz; Saternus, Zbigniew [Institute of Mechanics and Machine Design Foundations, Częstochowa University of Technology, Dąbrowskiego 73, 42-200 Częstochowa (Poland); Stano, Sebastian [Welding Technologies Department, Welding Institute, Błogosławionego Czesława 16-18, 44-100 Gliwice (Poland)

    2015-03-10

    This work concerns the numerical modeling of heat transfer and phase transformations in solid state occurring during the Yb:YAG laser beam heating process. The temperature field is obtained by the numerical solution into transient heat transfer equation with convective term. The laser beam heat source model is developed using the Kriging interpolation method with experimental measurements of Yb:YAG laser beam profile taken into account. Phase transformations are calculated on the basis of Johnson - Mehl - Avrami (JMA) and Koistinen - Marburger (KM) kinetics models as well as continuous heating transformation (CHT) and continuous cooling transformation (CCT) diagrams for S355 steel. On the basis of developed numerical algorithms 3D computer simulations are performed in order to predict temperature history and phase transformations in Yb:YAG laser heating process.

  16. α-Phase transformation kinetics of U – 8 wt% Mo established by in situ neutron diffraction

    International Nuclear Information System (INIS)

    Garlea, Elena; Steiner, M. A.; Calhoun, C. A.; Klein, R. W.; An, K.; Agnew, S. R.

    2016-01-01

    The α-phase transformation kinetics of as-cast U - 8 wt% Mo below the eutectoid temperature have been established by in situ neutron diffraction. α-phase weight fraction data acquired through Rietveld refinement at five different isothermal hold temperatures can be modeled accurately utilizing a simple Johnson-Mehl-Avrami-Kolmogorov impingement-based theory, and the results are validated by a corresponding evolution in the γ-phase lattice parameter during transformation that follows Vegard’s law. Neutron diffraction data is used to produce a detailed Time-Temperature-Transformation diagram that improves upon inconsistencies in the current literature, exhibiting a minimum transformation start time of 40 min at temperatures between 500 °C and 510 °C. Lastly, the transformation kinetics of U – 8 wt% Mo can vary significantly from as-cast conditions after extensive heat treatments, due to homogenization of the typical dendritic microstructure which possesses non-negligible solute segregation

  17. Analytical Determining Of The Steinmetz Equivalent Diagram Elements Of Single-Phase Transformer

    Directory of Open Access Journals (Sweden)

    T. Aly Saandy

    2015-08-01

    Full Text Available This article presents to an analytical calculation methodology of the Steinmetz Equivalent Diagram Elements applied to the prediction of Eddy current loss in a single-phase transformer. Based on the electrical circuit theory the active and reactive powers consumed by the core are expressed analytically in function of the electromagnetic parameters as resistivity permeability and the geometrical dimensions of the core. The proposed modeling approach is established with the duality parallel series. The equivalent diagram elements empirically determined by Steinmetz are analytically expressed using the expressions of the no loaded transformer consumptions. To verify the relevance of the model validations both by simulations with different powers and measurements were carried out to determine the resistance and reactance of the core. The obtained results are in good agreement with the theoretical approach and the practical results.

  18. Transformation of Selenium-Containing Phases in Copper Anode Slimes During Leaching

    Science.gov (United States)

    Li, Xue Jiao; Yang, Hong Ying; Jin, Zhe Nan; Chen, Guo Bao; Tong, Lin Lin

    2017-10-01

    The transformation of selenium-containing phases in copper anode slimes during the leaching process was investigated based on the Eh-pH diagram, leaching efficiencies of metals, and characterization of the residues produced during leaching. The leaching efficiency of selenium increases slowly to 17.7% in the first 50 min and then more rapidly to 98.3% in the next 110 min. The Eh-pH diagram indicates that elemental selenium is an intermediate product of the oxidation of selenide to selenite. The x-ray powder diffraction data and scanning electron microscopy-energy-dispersive x-ray spectroscopy data demonstrate that selenium leaching can be divided into three stages. Ag-Cu selenide first transforms into silver selenide and then converts to elemental selenium. Finally, elemental selenium is dissolved as selenite. The intermediate product, elemental selenium, is the main reason for the slow initial leaching rate of selenium.

  19. Stress-induced phase transformations studied by in-situ transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    No, M L; Ibarra, A [Dpto de Fisica Aplicada II, Facultad de Ciencia y Tecnologia, UPV/EHU. Apdo 644, 48080 Bilbao (Spain); Caillard, D [CEMES/CNRS, BP 4347, 29 rue J. Marvig, 31055 Toulouse Cedex (France); San Juan, J, E-mail: maria.no@ehu.e [Dpto de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, UPV/EHU. Apdo 644, 48080 Bilbao (Spain)

    2010-07-01

    In this work, we carry out a detailed study, by in-situ Transmission Electron Microscopy (in-situ TEM), focused on two single-crystals of Cu-Al-Ni shape memory alloys with different transformation temperatures. The first single crystal is in beta phase at Room Temperature (RT) and has been cycled under stress, by super-elastic effect, inside the TEM. Two different mechanisms for the nucleation of {beta}'{sub 3} and {gamma}'{sub 3} martensite phases were observed: a) Martensite can nucleate on dislocations during super-elastic tests and when withdrawing the stress, the reverse transformation takes place by the disappearance of the martensite plate on the dislocation. b) During mechanical cycling martensite plates nucleate in other plates. The second single crystal is in martensite phase at RT, and when the stress is applied different mechanisms are observed: a) Reorientation and interface motion of the plates under the external applied stress, b) nucleation of mobile dislocations inside the martensite. A quantitative analysis of the experimental results, having into account the images and the diffraction patterns, has been realized and different mechanisms have been proposed to explain the experimental results.

  20. Rate-independent dissipation in phase-field modelling of displacive transformations

    Science.gov (United States)

    Tůma, K.; Stupkiewicz, S.; Petryk, H.

    2018-05-01

    In this paper, rate-independent dissipation is introduced into the phase-field framework for modelling of displacive transformations, such as martensitic phase transformation and twinning. The finite-strain phase-field model developed recently by the present authors is here extended beyond the limitations of purely viscous dissipation. The variational formulation, in which the evolution problem is formulated as a constrained minimization problem for a global rate-potential, is enhanced by including a mixed-type dissipation potential that combines viscous and rate-independent contributions. Effective computational treatment of the resulting incremental problem of non-smooth optimization is developed by employing the augmented Lagrangian method. It is demonstrated that a single Lagrange multiplier field suffices to handle the dissipation potential vertex and simultaneously to enforce physical constraints on the order parameter. In this way, the initially non-smooth problem of evolution is converted into a smooth stationarity problem. The model is implemented in a finite-element code and applied to solve two- and three-dimensional boundary value problems representative for shape memory alloys.