Pressure Effects on Solid State Phase Transformation of Aluminium Bronze in Cooling Process
International Nuclear Information System (INIS)
Hai-Yan, Wang; Jian-Hua, Liu; Gui-Rong, Peng; Yan, Chen; Yu-Wen, Liu; Fei, Li; Wen-Kui, Wang
2009-01-01
Effects of high pressure (6 GPa) on the solid state phase transformation kinetic parameters of aluminum bronze during the cooling process are investigated, based on the measurement and calculation of its solid state phase transformation temperature, duration and activation energy and the observation of its microstructures. The results show that high pressure treatment can reduce the solid phase transformation temperature and activation energy in the cooling process and can shorten the phase transformation duration, which is favorable when forming fine-grained aluminum bronze
The quantum state vector in phase space and Gabor's windowed Fourier transform
International Nuclear Information System (INIS)
Bracken, A J; Watson, P
2010-01-01
Representations of quantum state vectors by complex phase space amplitudes, complementing the description of the density operator by the Wigner function, have been defined by applying the Weyl-Wigner transform to dyadic operators, linear in the state vector and anti-linear in a fixed 'window state vector'. Here aspects of this construction are explored, and a connection is established with Gabor's 'windowed Fourier transform'. The amplitudes that arise for simple quantum states from various choices of windows are presented as illustrations. Generalized Bargmann representations of the state vector appear as special cases, associated with Gaussian windows. For every choice of window, amplitudes lie in a corresponding linear subspace of square-integrable functions on phase space. A generalized Born interpretation of amplitudes is described, with both the Wigner function and a generalized Husimi function appearing as quantities linear in an amplitude and anti-linear in its complex conjugate. Schroedinger's time-dependent and time-independent equations are represented on phase space amplitudes, and their solutions described in simple cases.
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.
International Nuclear Information System (INIS)
Song, Shaojie; Liu, Feng
2016-01-01
Considering a spherical misfitting precipitate growing into a finite elastic-perfectly plastic supersaturated matrix, a kinetic modeling for such solid-state partitioning phase transformation is presented, where the interactions of interface migration, solute diffusion and misfit accommodation are analyzed. The linkage between interface migration and solute diffusion proceeds through interfacial composition and interface velocity; their effects on misfit accommodation are mainly manifested in an effective transformation strain, which depends on instantaneous composition field and precipitate size. Taking γ to α transformation of a binary Fe-0.5 at.% C alloy under both isothermal and continuous cooling conditions as examples, the effects of misfit accommodation on the coupling interface migration and solute diffusion are well evaluated and discussed. For the isothermal transformation, a counterbalancing influence between mechanical and chemical driving forces is found so that the mixed-mode transformation kinetics is not sensitive with respect to the elastic–plastic accommodation of the effective misfit strain. Different from the isothermal process, during the continuous cooling condition, the effects of misfit accommodation on the kinetics of solid-state partitioning phase transformation are mainly manifested in the great decrease of the transformation starting temperature and the thermodynamic equilibrium composition. The present kinetic modeling was applied to predict the experimentally measured γ/α transformation of Fe-0.47 at.% C alloy conducted with a cooling rate of 10 K min −1 and a good agreement was achieved.
International Nuclear Information System (INIS)
Chakraborty, Tanmoy; Rogal, Jutta; Drautz, Ralf
2015-01-01
A combined density functional theory and solid-state nudged elastic band study is presented to investigate the martensitic transformation between β → (α″, ω) phases in the Ti–Ta system. The minimum energy paths along the transformation are calculated and the transformation mechanisms as well as relative stabilities of the different phases are discussed for various compositions. The analysis of the transformation paths is complemented by calculations of phonon spectra to determine the dynamical stability of the β, α″, and ω phase. Our theoretical results confirm the experimental findings that with increasing Ta concentration there is a competition between the destabilisation of the α″ and ω phase and the stabilisation of the high-temperature β phase. (paper)
High pressure phase transformations revisited
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
High pressure phase transformations revisited.
Levitas, Valery I
2018-04-25
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
Multi-channel phase-equivalent transformation and supersymmetry
Shirokov, A. M.; Sidorenko, V. N.
2000-01-01
Phase-equivalent transformation of local interaction is generalized to the multi-channel case. Generally, the transformation does not change the number of the bound states in the system and their energies. However, with a special choice of the parameters, the transformation removes one of the bound states and is equivalent to the multi-channel supersymmetry transformation recently suggested by Sparenberg and Baye. Using the transformation, it is also possible to add a bound state to the discr...
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.
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
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 ...
Phase transformations in nickel sulphide: Microstructures and mechanisms
International Nuclear Information System (INIS)
Yousfi, Oussama; Donnadieu, Patricia; Brechet, Yves; Robaut, Florence; Charlot, Frederic; Kasper, Andreas; Serruys, Francis
2010-01-01
Nickel sulphide inclusions are known to be responsible for delayed fracture in tempered glasses due to phase transformation within the inclusion. Microstructural identification of the phase transformation mechanisms in the Ni-S system close to the NiS composition were carried out on a series of partially transformed states. Observations allow to investigate the morphological evolution during transformation, the phase orientation relationships and the first stages of the transformation were investigated by optical microscopy, electron backscatter diffraction, and scanning and transmission electron microscopy. The transformation mechanisms change significantly with the change in sulphur content of the α-NiS phase. Massive transformation is observed for near-stoichiometric composition. For overstoichiometric composition, the transformation is controlled by a long-range diffusion mechanism. The influence of stoichiometry and impurities (Fe) on the microstructural evolution and transformation mechanisms has also been studied.
Kinetics of phase transformations
International Nuclear Information System (INIS)
Thompson, M.O.; Aziz, M.J.; Stephenson, G.B.
1992-01-01
This volume contains papers presented at the Materials Research Society symposium on Kinetics of Phase Transformations held in Boston, Massachusetts from November 26-29, 1990. The symposium provided a forum for research results in an exceptionally broad and interdisciplinary field. Presentations covered nearly every major class of transformations including solid-solid, liquid-solid, transport phenomena and kinetics modeling. Papers involving amorphous Si, a dominant topic at the symposium, are collected in the first section followed by sections on four major areas of transformation kinetics. The symposium opened with joint sessions on ion and electron beam induced transformations in conjunction with the Surface Chemistry and Beam-Solid Interactions: symposium. Subsequent sessions focused on the areas of ordering and nonlinear diffusion kinetics, solid state reactions and amorphization, kinetics and defects of amorphous silicon, and kinetics of melting and solidification. Seven internationally recognized invited speakers reviewed many of the important problems and recent results in these areas, including defects in amorphous Si, crystal to glass transformations, ordering kinetics, solid-state amorphization, computer modeling, and liquid/solid transformations
Electric-field control of tri-state phase transformation with a selective dual-ion switch
Lu, Nianpeng; Zhang, Pengfei; Zhang, Qinghua; Qiao, Ruimin; He, Qing; Li, Hao-Bo; Wang, Yujia; Guo, Jingwen; Zhang, Ding; Duan, Zheng; Li, Zhuolu; Wang, Meng; Yang, Shuzhen; Yan, Mingzhe; Arenholz, Elke; Zhou, Shuyun; Yang, Wanli; Gu, Lin; Nan, Ce-Wen; Wu, Jian; Tokura, Yoshinori; Yu, Pu
2017-06-01
Materials can be transformed from one crystalline phase to another by using an electric field to control ion transfer, in a process that can be harnessed in applications such as batteries, smart windows and fuel cells. Increasing the number of transferrable ion species and of accessible crystalline phases could in principle greatly enrich material functionality. However, studies have so far focused mainly on the evolution and control of single ionic species (for example, oxygen, hydrogen or lithium ions). Here we describe the reversible and non-volatile electric-field control of dual-ion (oxygen and hydrogen) phase transformations, with associated electrochromic and magnetoelectric effects. We show that controlling the insertion and extraction of oxygen and hydrogen ions independently of each other can direct reversible phase transformations among three different material phases: the perovskite SrCoO3-δ (ref. 12), the brownmillerite SrCoO2.5 (ref. 13), and a hitherto-unexplored phase, HSrCoO2.5. By analysing the distinct optical absorption properties of these phases, we demonstrate selective manipulation of spectral transparency in the visible-light and infrared regions, revealing a dual-band electrochromic effect that could see application in smart windows. Moreover, the starkly different magnetic and electric properties of the three phases—HSrCoO2.5 is a weakly ferromagnetic insulator, SrCoO3-δ is a ferromagnetic metal, and SrCoO2.5 is an antiferromagnetic insulator—enable an unusual form of magnetoelectric coupling, allowing electric-field control of three different magnetic ground states. These findings open up opportunities for the electric-field control of multistate phase transformations with rich functionalities.
International Nuclear Information System (INIS)
Jiang, Y.-H.; Liu, F.; Song, S.-J.
2012-01-01
An extended analytical model is derived for non-isothermal solid-state phase transformation assuming interface-controlled growth mode, e.g. polymorphic or allotropic transformation. In the modeling, incorporation of thermodynamic factor into kinetics of nucleation and growth is performed, so that the model can be used to describe the transformation occurring either near or far from the equilibrium state. Furthermore, the effect of the initial transformation temperature is included through a special treatment for the “temperature integral”, so that the model can be used to depict the transformation during either continuous heating or continuous cooling. Numerical calculations demonstrate that the extended analytical model is accurate enough for practical use. On this basis, a general rate equation for non-isothermal (isochronal heating and cooling) transformation is derived. Applying the present model, the overall kinetic behavior of γ/α transformation in binary substitutional Fe-based alloys (e.g. Fe–Mn and Fe–Cu) upon cooling, measured by dilatometry, is described successfully. Compared with previous work, where a site saturation assumption is generally made, the prevalence of continuous nucleation deduced using the present model prediction seems more reasonable.
Phase transformations im smart materials
International Nuclear Information System (INIS)
Newnham, R.E.
1998-01-01
One of the qualities that distinguishes living systems from inanimate matter is the ability to adapt to changes in the environment. Smart materials have the ability to perform both sensing and actuating functions and are, therefore, capable of imitating this rudimentary aspect of life. Four of the most widely used smart materials are piezoelectric Pb(Zr, Ti)O 3 , electrostrictive Pb(Mg, Nb)O 3 , magnetostrictive (Tb, Dy)Fe 2 and the shape-memory alloy NiTi. All four are ferroic with active domain walls and two phase transformations, which help to tune the properties of these actuator materials. Pb(Zr, Ti)O 3 is a ferroelectric ceramic which is cubic at high temperature and becomes ferroelectric on cooling through the Curie temperature. At room temperature, it is poised on a rhombohedral-tetragonal phase boundary which enhances the piezoelectric coefficients. Terfenol, (Tb, Dy)Fe 2 , is also cubic at high temperature and then becomes magnetic on cooling through its Curie temperature. At room temperature, it too is poised on a rhombohedral-tetragonal transition which enhances its magnetostriction coefficients. Pb(Mg, Nb)O 3 and nitinol (NiTi) are also cubic at high temperatures and on annealing transform to a partially ordered state. On further cooling, Pb(Mg, Nb)O 3 passes through a diffuse phase transformation at room temperature where it exhibits very large dielectric and electrostrictive coefficients. Just below room temperature, it transforms to a ferroelectric rhombohedral phase. The partially ordered shape-memory alloy NiTi undergoes an austenitic (cubic) to martensitic (mono-clinic) phase change just above room temperature. It is easily deformed in the martensitic state but recovers its original shape when reheated to austenite
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.
Energy Technology Data Exchange (ETDEWEB)
Rao Weifeng [Department of Materials Science and Engineering, Rutgers University, 607 Taylor Road, Piscataway, NJ 08854 (United States); Khachaturyan, Armen G., E-mail: khach@jove.rutgers.edu [Department of Materials Science and Engineering, Rutgers University, 607 Taylor Road, Piscataway, NJ 08854 (United States)
2011-06-15
A phase field theory of proper displacive transformations is developed to address the microstructure evolution and its response to applied fields in decomposing and martensitic systems. The theory is based on the explicit equation for the non-equilibrium free energy function of the transformation strain obtained by a consistent separation of the total strain into transformation and elastic strains. The transformation strain is considered to be a relaxing long-range order parameter evolving in accordance with the system energetics rather than as a fixed material constant used in the conventional Eshelby theory of coherent inclusions. The elastic strain is defined as a coherency strain recovering the crystal lattice compatibility. The obtained free energy function of the transformation strain leads to the concepts of structural anisotropy and directional flexibility of low symmetry phases. The formulated vector model of displacive transformation makes apparent a similarity between proper displacive transformation and ferromagnetic/ferroelectric transformation and, in particular, a similarity between the structural anisotropy and magnetic/polar anisotropy of ferromagnetic/ferroelectric materials. It even predicts the feasibility of a glass-like structural state with unlimited directional flexibility of the transformation strain that is conceptually similar to a ferromagnetic glass. The thermodynamics of the equilibrium between low symmetry phases and the thermodynamic conditions leading to the formation of adaptive states are formulated.
Path Dependency of High Pressure Phase Transformations
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.
Energy Technology Data Exchange (ETDEWEB)
Kaur, S; Kamal, R [Punjabi Univ., Patiala (India). Dept. of Physics
1977-09-01
Study of phase diagram and accompanying solid state transformations is essential to determine the best possible composition, manufacturing techniques and physical properties of an alloy. A simple technique having wide applications in metallurgical industry is to study the temperature--time curve of the alloy undergoing cooling with an uniform rate. An experiment which uses this technique is described. It is widely applicable in the fields of materials science, applied solid state physics, physical metallurgy and physical chemistry.
Phase transformations and systems driven far from equilibrium
International Nuclear Information System (INIS)
Ma, E.; Atzmon, M.; Bellon, P.; Trivedi, R.
1998-01-01
This volume compiles invited and contributed papers that were presented at Symposium B of the 1997 Materials Research Society Fall Meeting, Phase Transformations and Systems Driven Far From Equilibrium, which was held December 1--5, in Boston, Massachusetts. While this symposium followed the tradition of previous MRS symposia on the fundamental topic of phase transformations, this year the emphasis was on materials systems driven far from equilibrium. The central theme of the majority of the work presented is the understanding of the thermodynamics and kinetics of phase transformations, with significant coverage of metastable materials and externally forced transformations driven, for example, by energy beams or mechanical deformation. The papers are arranged in seven sections: solidification theory and experiments; nucleation; solid state transformations and microstructural evolution; beam-induced transformations; amorphous solids; interfacial and thin film transformations; and nanophases and mechanical alloying. One hundred three papers have been processed separately for inclusion on the data base
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
Design and control of a three-phase four-leg inverter for solid-state transformer applications
Shri, A.; Popovic, J.; Ferreira, J.A.; Gerber, M.B.
2013-01-01
This paper proposes the use of a three-phase four-leg (3P4L) converter in combination with an LCL filter for the inverter stage of a solid state transformer (SST). This configuration gives full control over the line-to-line, as well as the line-to-neutral voltage and currents, while providing
Phase transformation and diffusion
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
Influence of pressure on the solid state phase transformation of Cu–Al–Bi alloy
International Nuclear Information System (INIS)
Gong, Li; Jian-Hua, Liu; Wen-Kui, Wang; Ri-Ping, Liu
2010-01-01
The solid state phase transformation of Cu-Al-Bi alloy under high pressure was investigated by x-ray diffraction, energy dispersive spectroscopy and transmission electron microscopy. Experimental results show that the initial crystalline phase in the Cu-Al-Bi alloy annealed at 750 °C under the pressures in the range of 0–6 GPa is α-Cu solid solution (named as α-Cu phase below), and high pressure has a great influence on the crystallisation process of the Cu-Al-Bi alloy. The grain size of the α-Cu phase decreases with increasing pressure as the pressure is below about 3 GPa, and then increases (P > 3 GPa). The mechanism for the effects of high pressure on the crystallisation process of the alloy has been discussed. (condensed matter: structure, thermal and mechanical properties)
Directory of Open Access Journals (Sweden)
Qiang Sheng
2017-10-01
Full Text Available This work aims to give a comprehensive view of magnetic state stability and transformations in PZT-film/FeGa-dot multiferroic composite systems due to the combining effects of size, shape and interfacial coupling strain. It is found that the stable magnetic state of the FeGa nanodots is not only a function of the size and shape of the nanodot but also strongly sensitive to the interfacial coupling strain modified by the polarization state of PZT film. In particular, due to the large magnetostriction of FeGa, the phase boundaries between different magnetic states (i.e., in-plane/out-of-plane polar states, and single-/multi-vortex states of FeGa nanodots can be effectively tuned by the polarization-mediated strain. Fruitful strain-mediated transformation paths of magnetic states including those between states with different orderings (i.e., one is polar and the other is vortex, as well as those between states with the same ordering (i.e., both are polar or both are vortex have been revealed in a comprehensive view. Our result sheds light on the potential of utilizing electric field to induce fruitful magnetic state transformation paths in multiferroic film-dot systems towards a development of novel magnetic random access memories.
Phase transformations of nanostructured Zr-Y-O coatings under loading
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.
International Nuclear Information System (INIS)
Lin, Bo; Zhang, Weiwen; Zhao, Yuliang; Li, Yuanyuan
2015-01-01
The Al–5.0 wt.% Cu–0.6 wt.% Mn alloys with a variable Fe content were prepared by squeeze casting. Optical microscopy (OM), Deep etching technique, scanning electron microscopy(SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to examine the solid-state transformation of Fe-rich intermetallics during the solution heat treatment. The results showed that the Chinese script-like α-Fe, Al 6 (FeMn) and needle-like Al 3 (FeMn) phases transform to a new Cu-rich β-Fe (Al 7 Cu 2 (FeMn)) phase during solution heat treatment. The possible reaction and overall transformation kinetics of the solid-state phase transformation for the Fe-rich intermetallics were investigated. - Graphical abstract: Display Omitted - Highlights: • The α-Fe, Al 6 (FeMn) and Al 3 (FeMn) phases change to the β-Fe phases. • Possible reactions of Fe phases during solution heat treatment are discussed. • The overall fractional transformation rate follows an Avrami curve
Uncovering the intrinsic size dependence of hydriding phase transformations in nanocrystals.
Bardhan, Rizia; Hedges, Lester O; Pint, Cary L; Javey, Ali; Whitelam, Stephen; Urban, Jeffrey J
2013-10-01
A quantitative understanding of nanocrystal phase transformations would enable more efficient energy conversion and catalysis, but has been hindered by difficulties in directly monitoring well-characterized nanoscale systems in reactive environments. We present a new in situ luminescence-based probe enabling direct quantification of nanocrystal phase transformations, applied here to the hydriding transformation of palladium nanocrystals. Our approach reveals the intrinsic kinetics and thermodynamics of nanocrystal phase transformations, eliminating complications of substrate strain, ligand effects and external signal transducers. Clear size-dependent trends emerge in nanocrystals long accepted to be bulk-like in behaviour. Statistical mechanical simulations show these trends to be a consequence of nanoconfinement of a thermally driven, first-order phase transition: near the phase boundary, critical nuclei of the new phase are comparable in size to the nanocrystal itself. Transformation rates are then unavoidably governed by nanocrystal dimensions. Our results provide a general framework for understanding how nanoconfinement fundamentally impacts broad classes of thermally driven solid-state phase transformations relevant to hydrogen storage, catalysis, batteries and fuel cells.
International Nuclear Information System (INIS)
Gao, Lei; Ding, Xiangdong; Sun, Jun; Lookman, Turab; Salje, E. K. H.
2016-01-01
The energy landscape of Zr at high hydrostatic pressure suggests that its transformation behavior is strongly pressure dependent. This is in contrast to the known transition mechanism in Ti, which is essentially independent of hydrostatic pressure. Generalized solid-state nudged elastic band calculations at constant pressure shows that α-Zr transforms like Ti only at the lowest pressure inside the stability field of ω-phase. Different pathways apply at higher pressures where the energy landscape contains several high barriers so that metastable states are expected, including the appearance of a transient bcc phase at ca. 23 GPa. The global driving force for the hcp-ω transition increases strongly with increasing pressure and reaches 23.7 meV/atom at 23 GPa. Much of this energy relates to the excess volume of the hcp phase compared with its ω phase.
Energy Technology Data Exchange (ETDEWEB)
Gao, Lei; Ding, Xiangdong, E-mail: dingxd@mail.xjtu.edu.cn, E-mail: ekhard@esc.cam.ac.uk; Sun, Jun [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Lookman, Turab [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Salje, E. K. H., E-mail: dingxd@mail.xjtu.edu.cn, E-mail: ekhard@esc.cam.ac.uk [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ (United Kingdom)
2016-07-18
The energy landscape of Zr at high hydrostatic pressure suggests that its transformation behavior is strongly pressure dependent. This is in contrast to the known transition mechanism in Ti, which is essentially independent of hydrostatic pressure. Generalized solid-state nudged elastic band calculations at constant pressure shows that α-Zr transforms like Ti only at the lowest pressure inside the stability field of ω-phase. Different pathways apply at higher pressures where the energy landscape contains several high barriers so that metastable states are expected, including the appearance of a transient bcc phase at ca. 23 GPa. The global driving force for the hcp-ω transition increases strongly with increasing pressure and reaches 23.7 meV/atom at 23 GPa. Much of this energy relates to the excess volume of the hcp phase compared with its ω phase.
Kinetics of solid state phase transformation UAl3 + Al -> UAl4
International Nuclear Information System (INIS)
Cunha, C.A. da.
1986-01-01
The Kinetics of phase transformation UAl 3 + Al -> UAl 4 of two Al-U alloys, with 31.4 and 33.4 wt% U respectively, was studied by quantitative microscopy. The results have shown that this transformation is a nucleation and thermally activated growth process. The nucleation occurs heterogeneously at the UAl 3 /Al (∞) interfaces and the growth is controlled by volume diffusion. The empirical activation energy of the process was determined, which mean value is about 54.8 Kcal/mol. The growth Kinetic of UAl 4 phase is a parabolic law. The UAl 4 /UAl 3 and UAl 4 /Al (∞) interfaces migrates in opposite directions, with the UAl 4 /UAl 3 interface velocity being approximately 5 times greater than that of UAl 4 /Al (∞) interface. The chemical diffusion coefficient of Al and U in the UAl 4 phase were evaluated to be of the order of 10 -9 cm 2 /s at 600 0 C. (author) [pt
Li, Xiangyu; Huang, Zhanhua; Zhu, Meng; He, Jin; Zhang, Hao
2014-12-01
Hilbert transform (HT) is widely used in temporal speckle pattern interferometry, but errors from low modulations might propagate and corrupt the calculated phase. A spatio-temporal method for phase retrieval using temporal HT and spatial phase unwrapping is presented. In time domain, the wrapped phase difference between the initial and current states is directly determined by using HT. To avoid the influence of the low modulation intensity, the phase information between the two states is ignored. As a result, the phase unwrapping is shifted from time domain to space domain. A phase unwrapping algorithm based on discrete cosine transform is adopted by taking advantage of the information in adjacent pixels. An experiment is carried out with a Michelson-type interferometer to study the out-of-plane deformation field. High quality whole-field phase distribution maps with different fringe densities are obtained. Under the experimental conditions, the maximum number of fringes resolvable in a 416×416 frame is 30, which indicates a 15λ deformation along the direction of loading.
Energy Technology Data Exchange (ETDEWEB)
Lin, Bo [School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); School of Mechanical Engineering, Gui Zhou University, Guiyang 550000 (China); Zhang, Weiwen, E-mail: mewzhang@scut.edu.cn [School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); Zhao, Yuliang; Li, Yuanyuan [School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China)
2015-06-15
The Al–5.0 wt.% Cu–0.6 wt.% Mn alloys with a variable Fe content were prepared by squeeze casting. Optical microscopy (OM), Deep etching technique, scanning electron microscopy(SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to examine the solid-state transformation of Fe-rich intermetallics during the solution heat treatment. The results showed that the Chinese script-like α-Fe, Al{sub 6}(FeMn) and needle-like Al{sub 3}(FeMn) phases transform to a new Cu-rich β-Fe (Al{sub 7}Cu{sub 2}(FeMn)) phase during solution heat treatment. The possible reaction and overall transformation kinetics of the solid-state phase transformation for the Fe-rich intermetallics were investigated. - Graphical abstract: Display Omitted - Highlights: • The α-Fe, Al{sub 6}(FeMn) and Al{sub 3}(FeMn) phases change to the β-Fe phases. • Possible reactions of Fe phases during solution heat treatment are discussed. • The overall fractional transformation rate follows an Avrami curve.
Structural-Phase Transformations of CuZn Alloy Under Thermal-Impact Cycling
Potekaev, A. I.; Chaplygina, A. A.; Kulagina, V. V.; Chaplygin, P. A.; Starostenkov, M. D.; Grinkevich, L. S.
2017-02-01
Using the Monte Carlo method, special features of structural - phase transformations in β-brass are investigated during thermal impact using thermal cycling as an example (a number of successive order - disorder and disorder - order phase transitions in the course of several heating - cooling cycles). It is shown that a unique hysteresis is observed after every heating and cooling cycle, whose presence indicates irreversibility of the processes, which suggests a difference in the structural - phase states both in the heating and cooling stages. A conclusion is drawn that the structural - phase transformations in the heating and cooling stages occur within different temperature intervals, where the thermodynamic stimuli of one or the other structural - phase state are low. This is also demonstrated both in the plots of configurational energy, long- and short-range order parameter, atomic structure variations, and structural - phase state distributions. Simultaneously, there coexist ordered and disordered phases and a certain collection of superstructure domains. This implies the presence of low - stability states in the vicinity of the order - disorder phase transition. The results of investigations demonstrate that the structural - phase transitions within two successive heating and cooling cycles at the same temperature are different in both stages. These changes, though not revolutionary, occur in every cycle and decrease with the increasing cycle number. In fact, the system undergoes training with a tendency towards a certain sequence of structural - phase states.
Atomic disorder, phase transformation, and phase restoration in Co3Sn2
di, L. M.; Zhou, G. F.; Bakker, H.
1993-03-01
The behavior of the intermetallic compound Co3Sn2 upon ball milling was studied by x-ray diffraction, high-field-magnetization measurements, and subsequently by differential scanning calorimetry. It turns out that starting from the stoichiometric-ordered compound, mechanical attrition of Co3Sn2 generates atomic disorder in the early stage of milling. The nonequilibrium phase transformation from the low-temperature phase with orthorhombic structure to the high-temperature phase with a hexagonal structure was observed in the intermediate stage of milling. It was accompanied by the creation of increasing atomic disorder. After long milling periods, the phase transformation was completed and the atomic disordering became saturated. All the physical parameters measured in the present work remained constant during this period. The above outcome was confirmed by comparison with the high-temperature phase thermally induced by quenching. The good agreement of the results obtained by different techniques proves that the ball milling generates well-defined metastable states in Co3Sn2.
International Nuclear Information System (INIS)
Hensl, Th.; Mühlich, U.; Budnitzki, M.; Kuna, M.
2015-01-01
Highlights: • Analytical model to predict phase transformation in PSZ is developed. • Analytical model to predict number of twins in monoclinic inclusions in PSZ. • Models consider inclusions size, shape, temperature, remote loading and surface energy. - Abstract: This work focuses on micromechanical modeling of the tetragonal to monoclinic phase transformation (t–m transformation) in partially stabilized zirconia (PSZ). Tetragonal particles dispersed in a cubic matrix may transform into the monoclinic phase under sufficiently high mechanical loading or if the material is cooled down below a critical temperature. This phase transformation is supposed to be responsible for the so called transformation toughening effect of PSZ. The transformation is usually accompanied by a self-accommodation process, which reduces the occurring eigenstresses in the surrounding matrix. The influences of particle size and geometry, chemical driving force, temperature, surface energy and remote loading on the t–m transformation are estimated by a thermostatic approach. We assume, that transformations occur, once the Gibbs free energy of the transformed equilibrium state is lower than that of the untransformed reference state. To obtain an analytical solution, the microstructure is modeled as an inclusion of rectangular cross section, restrained by an infinite elastic matrix, under plane strain conditions. The developed model for phase transformation captures the well-known size and temperature dependencies. Furthermore, it indicates a significant influence of the particle geometry, that large aspect ratios of the inclusion’s cross section lower the trigger stress for phase transformation
Plasticity induced phase transformation in molecular crystals
Koslowski, Marisol
2014-01-01
Solid state amorphization (SSA) can be achieved in crystalline materials including metal alloys, intermetallics, semiconductors, minerals and molecular crystals. Even though the mechanisms may differ in different materials, the crystalline to amorphous transformation occurs when the crystal reaches a metastable state in which its free energy is higher than that of the amorphous phase. SSA is observed in metal alloys because of interdiffusion of the crystalline elements during mechanical milli...
Zhang, Jianzhong; Vogel, Sven; Brown, Donald; Clausen, Bjorn; Hackenberg, Robert
2018-05-01
In-situ time-of-flight neutron diffraction experiments were conducted on the uranium-niobium alloy with 6 wt. % Nb (U-6Nb) at pressures up to 4.7 GPa and temperatures up to 1073 K. Upon static compression at room temperature, the monoclinic structure of U-6Nb (α″ U-6Nb) remains stable up to the highest experimental pressure. Based on the pressure-volume measurements at room temperature, the least-squares fit using the finite-strain equation of state (EOS) yields an isothermal bulk modulus of B0 = 127 ± 2 GPa for the α″-phase of U-6Nb. The calculated zero-pressure bulk sound speed from this EOS is 2.706 ± 0.022 km/s, which is in good agreement with the linear extrapolation of the previous Hugoniot data above 12 GPa for α″ U-6Nb, indicating that the dynamic response under those shock-loading conditions is consistent with the stabilization of the initial monoclinic phase of U-6Nb. Upon heating at ambient and high pressures, the metastable α″ U-6Nb exhibits complex transformation paths leading to the diffusional phase decomposition, which are sensitive to applied pressure, stress state, and temperature-time path. These findings provide new insight into the behavior of atypical systems such as U-Nb and suggest that the different U-Nb phases are separated by rather small energies and hence highly sensitive to compositional, thermal, and mechanical perturbations.
Understanding mechanisms of solid-state phase transformations by probing nuclear materials
Banerjee, Srikumar; Donthula, Harish
2018-04-01
In this review a few examples will be cited to illustrate that a study on a specific nuclear material sometimes lead to a better understanding of scientific phenomena of broader interests. Zirconium alloys offer some unique opportunities in addressing fundamental issues such as (i) distinctive features between displacive and diffusional transformations, (ii) characteristics of shuffle and shear dominated displacive transformations and (iii) nature of mixed-mode transformations. Whether a transformation is of first or higher order?" is often raised while classifying it. There are rare examples, such as Ni-Mo alloys, in which during early stages of ordering the system experiences tendencies for both first order and second order transitions. Studies on the order-disorder transitions under a radiation environment have established the pathway for the evolution of ordering. These studies have also identified the temperature range over which the chemically ordered state remains stable in steady state under radiation.
Stress-Induced Cubic-to-Hexagonal Phase Transformation in Perovskite Nanothin Films.
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.
Neutron scattering study of the phase transformation of LaNi3 induced by hydriding
International Nuclear Information System (INIS)
Ruan Jinghui; Zeng Xiangxin; Niu Shiwen
1994-01-01
The phase transformation of LaNi 3 induced by hydriding and de-hydriding is investigated using the neutron diffraction and the neutron inelastic scattering. The results show that the hydriding sample, LaNi 3 H x , is transformed from crystalline state of the LaNi 3 into amorphous state with a microcrystalline characteristic of LaNi 5 , and the de-hydriding sample produced by LaNi 3 H x dehydrated at 600 degree C is decomposed into new crystalline states composed by LaNi 5 -and La-hydrides. The procedure of phase transformation is that the result of the transformation of LaNi 3 induced by hydriding shows the properties of LaNi 5 -H 2 system
On Inclusion-Matrix Interfacial Stresses in Composites Containing Phase-Transforming Phases
International Nuclear Information System (INIS)
Wang, Y.-C.; Ko, C.-C.
2010-01-01
Recent development in composites containing phase-transforming particles, such as vanadium dioxide or barium titanate, reveals the overall stiffness and viscoelastic damping of the composites may be unbounded. Negative stiffness is induced from phase transformation predicted by the Landau phase transformation theory. Although this unbounded phenomenon is theoretically supported with the composite homogenization theory, detailed stress analyses of the composites are still lacking. In this work, we analyze the two-dimensional plane stress elasticity problem of a square plate containing a circular inclusion, under the assumption that the Young's modulus of the inclusion is negative. Assumption of negative stiffness is a priori in the present analysis. A static loading condition is adopted to estimate the effective modulus of the composites by the ratio of applied stress to averaged strain on the loading edges. It is found that the interfacial stresses between the circular inclusion and matrix increase dramatically when the negative stiffness is so tuned that overall stiffness is unbounded. Furthermore, it is found that stress distributions in the inclusion are not uniform, contrary to Eshelby's theorem, which states, for two-phase, infinite composites, the inclusion's stress distribution is uniform when the shape of the inclusion has higher symmetry than an ellipse. The rationale for this nonuniform stress distributions is due to nonlocal effects induced from negative stiffness.
International Nuclear Information System (INIS)
Zain-ul-abdein, Muhammad; Nelias, Daniel; Jullien, Jean-Francois; Boitout, Frederic; Dischert, Luc; Noe, Xavier
2011-01-01
Aircraft industry makes extensive use of aluminium alloy AA 6056-T4 in the fabrication of fuselage panels using laser beam welding technique. Since high temperatures are involved in the manufacturing process, the precipitation/dissolution occurrences are expected as solid state phase transformations. These transformations are likely to affect the residual distortion and stress states of the component. The present work investigates the effect of metallurgical phase transformations upon the residual stresses and distortions induced by laser beam welding in a T-joint configuration using the finite element method. Two separate models were studied using different finite element codes, where the first one describes a thermo-mechanical analysis using Abaqus; while the second one discusses a thermo-metallo-mechanical analysis using Sysweld. A comparative analysis of experimentally validated finite element models has been performed and the residual stress states with and without the metallurgical phase transformations are predicted. The results show that the inclusion of phase transformations has a negligible effect on predicted distortions, which are in agreement with the experimental data, but an effect on predicted residual stresses, although the experimentally measured residual stresses are not available to support the analyses.
Thermally induced phase transformation of pearl powder
International Nuclear Information System (INIS)
Zhang, Guoqing; Guo, Yili; Ao, Ju; Yang, Jing; Lv, Guanglie; Shih, Kaimin
2013-01-01
The polymorphic phase transformation of thermally treated pearl powder was investigated by X-ray diffraction and thermoanalytical techniques. The phase transformation was based on quantification of the calcite content at various temperatures using Rietveld refinement analysis. The results show that the phase transformation of pearl aragonite occurred within a temperature range of 360–410 °C, which is 50–100 °C lower than the range for non-biomineralized aragonite. These thermoanalytical results suggest that the phase transformation of pearl aragonite may occur immediately after the thermal decomposition of the organic matrix in the pearl powder. An important finding is that decomposition of the organic matrix may greatly facilitate such transformation by releasing additional space for an easier structural reconstruction during the phase transformation process. - Highlights: ► Providing a new method to describe the polymorphic transition of pearl powder ► The phase transition sketch was exhibited by XRD phase quantitative analysis. ► There are dozens of degrees in advance comparing to natural aragonite. ► The phase transition occurs following the thermal decomposition of organism
Total energy calculations for structural phase transformations
International Nuclear Information System (INIS)
Ye, Y.Y.; Chan, C.T.; Ho, K.M.; Harmon, B.N.
1990-01-01
The structural integrity and physical properties of crystalline solids are frequently limited or enhanced by the occurrence of phase transformations. Martensitic transformations involve the collective displacement of atoms from one ordered state to another. Modern methods to determine the microscopic electronic changes as the atoms move are now accurate enough to evaluate the very small energy differences involved. Extensive first principles calculations for the prototypical martensitic transformation from body-centered cubic (bcc) to closepacked 9R structure in sodium metal are described. The minimum energy coordinate or configuration path between the bcc and 9R structures is determined as well as paths to other competing close-packed structures. The energy barriers and important anharmonic interactions are identified and general conclusions drawn. The calculational methods used to solve the Schrodinger equation include pseudopotentials, fast Fourier transforms, efficient matrix diagnonalization, and supercells with many atoms
Directory of Open Access Journals (Sweden)
Rie Y Umetsu
2017-10-01
Full Text Available Specific heat measurements were performed at low temperatures for Ni50Mn50−xInx alloys to determine their Debye temperatures (θD and electronic specific heat coefficients (γ. For x ≤ 15, where the ground state is the martensite (M phase, θD decreases linearly and γ increases slightly with increasing In content. For x ≥ 16.2, where the ground state is the ferromagnetic parent (P phase, γ increases with decreasing In content. Extrapolations of the composition dependences of θD and γ in both the phases suggest that these values change discontinuously during the martensitic phase transformation. The value of θD in the M phase is larger than that in the P phase. The behavior is in accordance with the fact that the volume of the M phase is more compressive than that of the P phase. On the other hand, γ is slightly larger in the P phase, in good agreement with the reported density of states around the Fermi energy obtained by the first-principle calculations.
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
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......) and measurement of the solid-state form of the dissolving solid (in situ with Raman spectroscopy). The solid phase transformations were also investigated off-line with scanning electron microscopy. TP anhydrate underwent a transformation to TP monohydrate, and NF anhydrate (form beta) to NF monohydrate (form II......). Transformation of TP anhydrate to TP monohydrate resulted in a clear decrease in the dissolution rate, while the transformation of NF anhydrate (form beta) to NF monohydrate (form II) could not be linked as clearly to changes in the dissolution rate. The transformation of TP was an order of magnitude faster than...
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.
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
Phase transformations in Higher Manganese Silicides
Energy Technology Data Exchange (ETDEWEB)
Allam, A. [MADIREL, UMR 7246 CNRS - Universite Aix-Marseille, av Normandie-Niemen, 13397 Marseille Cedex 20 (France); IM2NP, UMR 7334 CNRS - Universite Aix-Marseille, av Normandie-Niemen, Case 142, 13397 Marseille Cedex 20 (France); Boulet, P. [MADIREL, UMR 7246 CNRS - Universite Aix-Marseille, av Normandie-Niemen, 13397 Marseille Cedex 20 (France); Nunes, C.A. [Departamento de Engenharia de Materiais (DEMAR), Escola de Engenharia de Lorena (EEL), Universidade de Sao Paulo - USP, Caixa Postal 116, 12600-970 Lorena, Sao Paulo (Brazil); Sopousek, J.; Broz, P. [Masaryk University, Faculty of Science, Department of Chemistry, Kolarska 2, 611 37 Brno (Czech Republic); Masaryk University, Central European Institute of Technology, CEITEC, Kamenice 753/5, 625 00 Brno (Czech Republic); Record, M.-C., E-mail: m-c.record@univ-cezanne.fr [IM2NP, UMR 7334 CNRS - Universite Aix-Marseille, av Normandie-Niemen, Case 142, 13397 Marseille Cedex 20 (France)
2013-02-25
Highlights: Black-Right-Pointing-Pointer The phase transitions of the Higher Manganese Silicides were investigated. Black-Right-Pointing-Pointer The samples were characterised by XRD, DTA and DSC. Black-Right-Pointing-Pointer Mn{sub 27}Si{sub 47} is the stable phase at room temperature and under atmospheric pressure. Black-Right-Pointing-Pointer At around 800 Degree-Sign C, Mn{sub 27}Si{sub 47} is transformed into Mn{sub 15}Si{sub 26}. Black-Right-Pointing-Pointer The phase transition is of a second order. - Abstract: This work is an investigation of the phase transformations of the Higher Manganese Silicides in the temperature range [100-1200 Degree-Sign C]. Several complementary experimental techniques were used, namely in situ X-ray Diffraction (XRD), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). The evolution of both the lattice parameters and the thermal expansion coefficients was determined from in situ XRD measurements. The stability of the samples was investigated by thermal analysis (DTA) and Cp measurements (DSC). This study shows that Mn{sub 27}Si{sub 47} which is the stable phase at room temperature and under atmospheric pressure undergoes a phase transformation at around 800 Degree-Sign C. Mn{sub 27}Si{sub 47} is transformed into Mn{sub 15}Si{sub 26}. This phase transformation seems to be of a second order one. Indeed it was not evidenced by DTA and by contrast it appears on the Cp curve.
Geometric phases for mixed states during cyclic evolutions
International Nuclear Information System (INIS)
Fu Libin; Chen Jingling
2004-01-01
The geometric phases of cyclic evolutions for mixed states are discussed in the framework of unitary evolution. A canonical 1-form is defined whose line integral gives the geometric phase, which is gauge invariant. It reduces to the Aharonov and Anandan phase in the pure state case. Our definition is consistent with the phase shift in the proposed experiment (Sjoeqvist et al 2000 Phys. Rev. Lett. 85 2845) for a cyclic evolution if the unitary transformation satisfies the parallel transport condition. A comprehensive geometric interpretation is also given. It shows that the geometric phases for mixed states share the same geometric sense with the pure states
Shear-driven phase transformation in silicon nanowires.
Vincent, L; Djomani, D; Fakfakh, M; Renard, C; Belier, B; Bouchier, D; Patriarche, G
2018-03-23
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.
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...
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
Electron-irradiation-induced phase transformation in alumina
International Nuclear Information System (INIS)
Chen, C.L.; Arakawa, K.; Lee, J.-G.; Mori, H.
2010-01-01
In this study, electron-irradiation-induced phase transformations between alumina polymorphs were investigated by high-resolution transmission electron microscopy. It was found that the electron-irradiation-induced α → κ' phase transformation occurred in the alumina under 100 keV electron irradiation. It is likely that the knock-on collision between incident electrons and Al 3+ cations is responsible for the occurrence of electron-irradiation-induced phase transformation from α-alumina to κ'-alumina.
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.
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...... phase transformation from tetragonal to monoclinic structure has been observed at about 9 GPa. From the equation of state, the zero-pressure bulk modulus and its pressure derivative have been determined as (31.5 +/- 1.4) GPa and 4.4 +/- 0.4, respectively....
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.
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)
International Nuclear Information System (INIS)
Raoelina Andriambololona; Ranaivoson, R.T.R.; Rakotoson, H.; Solofoarisina, W.C.
2015-04-01
We present a study on linear canonical transformation in the framework of a phase space representation of quantum mechanics that we have introduced in our previous work. We begin with a brief recall about the so called phase space representation. We give the definition of linear canonical transformation with the transformation law of coordinate and momentum operators. We establish successively the transformation laws of mean values, dispersions, basis state and wave functions.Then we introduce the concept of isodispersion linear canonical transformation.
Iterative-Transform Phase Retrieval Using Adaptive Diversity
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
Induced phase transformations and nature of metastable states in ZTLL ceramics
Energy Technology Data Exchange (ETDEWEB)
Ishchuk, V M; Zavadskij, Eh A
1987-12-01
Phase transitions in ZTLL ceramics with zirconium content being 65%, titanium content - 35%, are considered. Peculiarities in the ZTLL behaviour are shown to be caused by the existence of an intermediate range between ferroelectric and antiferroelectric states. The state of samples in the range is determined by their prehistory. It is emphasized that phase transitions in ZTLL can be explained in the framework of the existing models.
Analysis and simulation of phase transformation kinetics of zeolite A from amorphous phases
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)
Phase transformations and thermodynamics of aluminum-based metallic glasses
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
The transformation behaviour of the beta phase in Zr-2.5 wt% Nb pressure tubes
International Nuclear Information System (INIS)
Griffiths, M.; Winegar, J.E.
1994-12-01
A temperature-time-transformation (TTT) diagram has been developed for the β-phase in Zr-2.5 wt% Nb pressure tubes. The results show that the morphology and/or physical state of the β-phase in pressure tubes has a significant effect on the transformation behaviour compared with a bulk Zr-19 wt%Nb alloy. (author). 14 refs., 1 tab., 15 figs
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
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.
In situ Raman spectroscopy of phase transformation in CrOx-Y2O3 system at elevated temperatures
International Nuclear Information System (INIS)
Xing Liqiong; Lu Jiqing; Bi Qingyuan; Pu Zhiying; Guo Ming; Wang Yuejuan; Luo Mengfei
2010-01-01
A CrO x -Y 2 O 3 sample was prepared by a deposition-precipitation method and phase transformation of the sample under N 2 and air atmospheres was characterized by in situ Raman spectroscopy and X-ray diffraction (XRD) techniques. It was found that when the CrO x -Y 2 O 3 sample was heated, CrO 3 transformed to YCrO 4 and then to YCrO 3 and Cr 2 O 3 . Also, the transformation started from the surface region of the sample and then extended to the bulk, due to the fact that the phase transformation was detected by Raman spectroscopy at lower temperature compared to that by XRD. In addition, both atmosphere and temperature had influence on the phase transformation in the surface region, while the phase transformation in the bulk was merely dependent on the temperature. It was also found that low oxidation state Cr(III) species on the surface could be re-oxidized to high oxidation state Cr(V) or Cr(VI) species when the thermal treated sample was exposed to ambient air.
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.
Corundum-to-spinel structural phase transformation in alumina
Energy Technology Data Exchange (ETDEWEB)
Adachi, Shogo [Department of Materials Science and Engineering, Kyushu Institute of Technology, Fukuoka 804-8550 (Japan); Ishimaru, Manabu, E-mail: ishimaru@post.matsc.kyutech.ac.jp [Department of Materials Science and Engineering, Kyushu Institute of Technology, Fukuoka 804-8550 (Japan); Sina, Younes; McHargue, Carl J.; Sickafus, Kurt E. [Materials Science and Engineering Department, University of Tennessee, Knoxville, TN 37996-2200 (United States); Alves, Eduardo [Unit of Physics and Accelerators, Ion Beam Laboratory, Instituto Superior Técnico/Instituto Tecnológico e Nuclear, EN. 10 2686-953 Sacavém (Portugal)
2015-09-01
Several polymorphs exist in alumina (Al{sub 2}O{sub 3}), and they transform to a stable α-phase with a hexagonal corundum structure on thermal annealing. This structural change is irreversible as a function of temperature, and transformation of corundum to another metastable crystalline phase has never been observed by heat treatments. In this study, we irradiated single crystals of Al{sub 2}O{sub 3} with Zr ions and obtained an irradiated microstructure consisting of a buried α-Al{sub 2}O{sub 3} layer surrounded on top and bottom by layers of a defect cubic spinel Al{sub 2}O{sub 3} phase. We examined the thermal stability of this microstructure using transmission electron microscopy and X-ray diffraction. We found that the corundum phase completely transforms to the spinel phase following annealing at 1173 K for 1 h: the thermodynamically stable phase transforms to the metastable phase by heat treatments. We discuss this unusual structural change within the context of our results as well as previous observations.
Materials research for passive solar systems: Solid-state phase-change materials
Benson, D. K.; Webb, J. D.; Burrows, R. W.; McFadden, J. D. O.; Christensen, C.
1985-03-01
A set of solid-state phase-change materials is being evaluated for possible use in passive solar thermal energy storage systems. The most promising materials are organic solid solutions of pentaerythritol (C5H12O4), pentaglycerinve (C5H12O3), and neopentyl glycol (C5H12O2). Solid solution mixtures of these compounds can be tailored so that they exhibit solid-to-solid phase transformations at any desired temperature between 25 C and 188 C, and have latent heats of transformation etween 20 and 70 cal/g. Transformation temperatures, specific heats, and latent heats of transformation have been measured for a number of these materials. Limited cyclic experiments suggest that the solid solutions are stable. These phase-change materials exhibit large amounts of undercooling; however, the addition of certain nucleating agents as particulate dispersions in the solid phase-change material greatly reduces this effect. Computer simulations suggest that the use of an optimized solid-state phase-change material in a Trombe wall could provide better performance than a concrete Trombe wall four times thicker and nine times heavier.
Effect of Phase Transformations on Seismic Velocities
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.
Ancilla-approximable quantum state transformations
International Nuclear Information System (INIS)
Blass, Andreas; Gurevich, Yuri
2015-01-01
We consider the transformations of quantum states obtainable by a process of the following sort. Combine the given input state with a specially prepared initial state of an auxiliary system. Apply a unitary transformation to the combined system. Measure the state of the auxiliary subsystem. If (and only if) it is in a specified final state, consider the process successful, and take the resulting state of the original (principal) system as the result of the process. We review known information about exact realization of transformations by such a process. Then we present results about approximate realization of finite partial transformations. We not only consider primarily the issue of approximation to within a specified positive ε, but also address the question of arbitrarily close approximation
Ancilla-approximable quantum state transformations
Energy Technology Data Exchange (ETDEWEB)
Blass, Andreas [Department of Mathematics, University of Michigan, Ann Arbor, Michigan 48109 (United States); Gurevich, Yuri [Microsoft Research, Redmond, Washington 98052 (United States)
2015-04-15
We consider the transformations of quantum states obtainable by a process of the following sort. Combine the given input state with a specially prepared initial state of an auxiliary system. Apply a unitary transformation to the combined system. Measure the state of the auxiliary subsystem. If (and only if) it is in a specified final state, consider the process successful, and take the resulting state of the original (principal) system as the result of the process. We review known information about exact realization of transformations by such a process. Then we present results about approximate realization of finite partial transformations. We not only consider primarily the issue of approximation to within a specified positive ε, but also address the question of arbitrarily close approximation.
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
Specific features of phase transformations in germanium monotelluride
International Nuclear Information System (INIS)
Bigvava, A.D.; Gabedava, A.A.; Kunchuliya, Eh.D.; Shvangiradze, R.R.
1981-01-01
Phase transformations in germanium monotelluride are studied . using DRON-0.5 and DRON-1 plants with high-temperature chamber GPVT-1500 at Cu, Ksub(α) radiation. It is shown that in the whole homogeneity range α GeTe is a metastable phase which is formed under the conditions of fast cooling of alloy from temperatures >=Tsub(cub) (temperature of transition in cubic crystal system). An equilibrium γ-phase is obtained by annealing of dispersed powders and metal-ceramic specimens of alloys with 50.3; 50.6; 50.9 at % Te. Lattice parameters of rhombic γ-phase do not depend on tellurium content in initial α- phase. α→γ transformation is observed at any temperature less than Tsub(cub) with the change of alloy composition, namely tellurium precipitation. γ-phase transforms into β at higher temperatures than α-phase [ru
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.
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
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)
Errandonea, D; Häusermann, D; Uchida, T
2003-01-01
We studied the phase behaviour and the P - V - T equation of state of Mg by in situ energy-dispersive x-ray diffraction in a multi-anvil apparatus in the pressure-temperature range up to 18.6 GPa and 1527 K. At high temperatures, an hcp to dhcp transition was found above 9.6 GPa, which differs from the hcp to bcc transformation predicted by theoretical calculations. At room temperature, the hcp phase remains stable within the pressure range of this study with an axial ratio, c/a, close to the ideal. The melting of Mg was determined at 2.2, 10 and 12 GPa; the detected melting temperatures are in good agreement with previous diamond anvil cell results. The P - V - T equation of state determined based on the data of this study gives B sub 0 = (36.8 +- 3) GPa, B sub 0 ' = 4.3 +- 0.4, alpha sub 0 = 25 x 10 sup - sup 6 K sup - sup 1 , partial deriv alpha/partial deriv T = (2.3 +- 0.2) x 10 sup - sup 7 K sup - sup 2 and partial deriv B sub 0 sub , sub T /partial deriv T = (-2.08 +- 0.09) x 10 sup - sup 2 GPa K sup -...
Braiding transformation, entanglement swapping, and Berry phase in entanglement space
International Nuclear Information System (INIS)
Chen Jingling; Ge Molin; Xue Kang
2007-01-01
We show that braiding transformation is a natural approach to describe quantum entanglement by using the unitary braiding operators to realize entanglement swapping and generate the Greenberger-Horne-Zeilinger states as well as the linear cluster states. A Hamiltonian is constructed from the unitary R i,i+1 (θ,φ) matrix, where φ=ωt is time-dependent while θ is time-independent. This in turn allows us to investigate the Berry phase in the entanglement space
Topological defects in the second-class phase transformations
International Nuclear Information System (INIS)
Dobrowolski, T.
2002-06-01
The dynamics of systems during second-class phase transformations are presented.in a frame of quantum fields theory. It is shown that solutions of non-linear field equations generate some topological defects what result in symmetry breaking and field phase transformations
Furuya, Yasubumi; Tamoto, Shizuka; Kubota, Takeshi; Okazaki, Teiko; Hagood, Nesbitt W.; Spearing, S. Mark
2002-07-01
The possibility to detect the phase transformation with martensites by heating or cooling as well as stress-loading in ferromagnetic shape memory Fe-30at percent Pd alloy thin foil by using magnetic Markhausen noise sensor was studied. MBHN is caused by the irregular interactions between magnetic domain and thermally activated martensite twins during magnetization. In general, the envelope of the MBHN voltage versus time signals in Fe-29at percent Pd ribbon showed two peaks during magnetization, where secondary peak at intermediate state of magnetization process decreased with increasing temperature, while the MBHN envelopes in pure iron did not change with increasing temperature. The variety of MBHN due to the phase transformation was apt to arise at higher frequency part of spectrum during intermediate state of magnetization process and it decreased with disappearance of martensite twins. Besides, MBHN increased monotonically with increasing loading stress and then, it decreased with unloading, however MBHN showed large hysteresis between loading and unloading passes. Based on the experimental results from MBHN measurements for both thermoelastic and stress-induced martensite phase transformations in Fe-30at percent Pd ribbon samples, MBHN method seems a useful technique to non-destructive evaluation of martensite phase transformation of ferromagnetic shape memory alloy.
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.
Effects of phase transformation of steam-water relative permeabilities
Energy Technology Data Exchange (ETDEWEB)
Verma, A.K.
1986-03-01
A combined theoretical and experimental study of steam-water relative permeabilities (RPs) was carried out. First, an experimental study of two-phase concurrent flow of steam and water was conducted and a set of RP curves was obtained. These curves were compared with semi-empirical and experimental results obtained by other investigators for two-phase, two-component flow (oil/gas; gas/water; gas/oil). It was found that while the wetting phase RPs were in good agreement, RPs for the steam phase were considerably higher than the non-wetting phase RPs in two-component systems. This enhancement of steam RP is attributed to phase transformation effects at the pore level in flow channels. The effects of phase transformation were studied theoretically. This study indicates that there are two separate mechanisms by which phase transformation affects RP curves: (1) Phase transformation is converging-diverging flow channels can cause an enhancement of steam phase RP. In a channel dominated by steam a fraction of the flowing steam condenses upstream from the constriction, depositing its latent heat of condensation. This heat is conducted through the solid grains around the pore throat, and evaporation takes place downstream from it. Therefore, for a given bulk flow quality; a smaller fraction of steam actually flows through the throat segments. This pore-level effect manifests itself as relative permeability enhancement on a macroscopic level; and (2) phase transformation along the interface of a stagnant phase and the phase flowing around it controls the irreducible phase saturation. Therefore, the irreducible phase saturation in steam-water flow will depend, among other factors, on the boundary conditions of the flow.
Quantum operations, state transformations and probabilities
International Nuclear Information System (INIS)
Chefles, Anthony
2002-01-01
In quantum operations, probabilities characterize both the degree of the success of a state transformation and, as density operator eigenvalues, the degree of mixedness of the final state. We give a unified treatment of pure→pure state transformations, covering both probabilistic and deterministic cases. We then discuss the role of majorization in describing the dynamics of mixing in quantum operations. The conditions for mixing enhancement for all initial states are derived. We show that mixing is monotonically decreasing for deterministic pure→pure transformations, and discuss the relationship between these transformations and deterministic local operations with classical communication entanglement transformations
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.
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
Chen, H.; Van der Zwaag, S.
2010-01-01
The soft impingement effect at the later stage of partitioning phase transformations has been modeled both for the diffusion-controlled growth model and for the mixed-mode model. Instead of the linear and exponential approximations for the concentration gradient in front of the interface used in the
International Nuclear Information System (INIS)
Sen, S.; Balasubramaniam, R.; Sethuraman, R.
1996-01-01
The molar volume difference between the matrix and the precipitate phases in the case of solid state phase transformations results in the creation of stain energy in the system due to the misfit strains. A finite element model based on the initial strain approach is proposed to evaluate elasto-plastic accommodation energies during solid state transformation. The three-dimensional axisymmetric model has been used to evaluate energies as a function of transformation for α-β hydrogen transformations in the Nb-H system. The transformation has been analyzed for the cases of transformation progressing both from the center to surface and from the surface to center of the system. The effect of plastic deformation has been introduced to make the model realistic, specifically to the Nb-NbH phase transformation which involves a 4% linear misfit strain. It has been observed that plastic deformation reduces the strain energies compared to the linear elastic analysis
Generalized phase transformations of spinor fields
International Nuclear Information System (INIS)
Mikhov, S.G.
1993-09-01
In this paper some generalized four parameter phase transformations of a Dirac spinor are considered. It is shown that a corresponding compensating transformation of the electromagnetic field which restores the invariance of the Dirac-Maxwell equation might exist, provided some consistency conditions are satisfied by the parameters of the transformations. These transformations are used further to consider the Maxwell equations under the assumption that a Bosonization takes place. Only one of the considered cases proves to have a solution (the other cases show to be trivial) which although unphysical is obtained explicitly. (author). 10 refs
Phase transformations in a Cu−Cr alloy induced by high pressure torsion
International Nuclear Information System (INIS)
Korneva, Anna; Straumal, Boris; Kilmametov, Askar; Chulist, Robert; Straumal, Piotr; Zięba, Paweł
2016-01-01
Phase transformations induced by high pressure torsion (HPT) at room temperature in two samples of the Cu-0.86 at.% Cr alloy, pre-annealed at 550 °C and 1000 °C, were studied in order to obtain two different initial states for the HPT procedure. Observation of microstructure of the samples before HPT revealed that the sample annealed at 550 °C contained two types of Cr precipitates in the Cu matrix: large particles (size about 500 nm) and small ones (size about 70 nm). The sample annealed at 1000 °C showed only a little fraction of Cr precipitates (size about 2 μm). The subsequent HPT process resulted in the partial dissolution of Cr precipitates in the first sample and dissolution of Cr precipitates with simultaneous decomposition of the supersaturated solid solution in another. However, the resulting microstructure of the samples after HPT was very similar from the standpoint of grain size, phase composition, texture analysis and hardness measurements. - Highlights: • Cu−Cr alloy with two different initial states was deformed by HPT. • Phase transformations in the deformed materials were studied. • SEM, TEM and X-ray diffraction techniques were used for microstructure analysis. • HPT leads to formation the same microstructure independent of the initial state.
International Nuclear Information System (INIS)
Thiessen, R.G.; Sietsma, J.; Palmer, T.A.; Elmer, J.W.; Richardson, I.M.
2007-01-01
A thermodynamically based method to describe the phase transformations during heating and cooling of martensitic dual-phase steel has been developed, and in situ synchrotron measurements of phase transformations have been undertaken to support the model experimentally. Nucleation routines are governed by a novel implementation of the classical nucleation theory in a general phase-field code. Physically-based expressions for the temperature-dependent interface mobility and the driving forces for transformation have also been constructed. Modelling of martensite was accomplished by assuming a carbon supersaturation of the body-centred-cubic ferrite lattice. The simulations predict kinetic aspects of the austenite formation during heating and ferrite formation upon cooling. Simulations of partial austenitising thermal cycles predicted peak and retained austenite percentages of 38.2% and 6.7%, respectively, while measurements yielded peak and retained austenite percentages of 31.0% and 7.2% (±1%). Simulations of a complete austenitisation thermal cycle predicted the measured complete austenitisation and, upon cooling, a retained austenite percentage of 10.3% while 9.8% (±1%) retained austenite was measured
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
Phase transformations in TiAl based alloys
International Nuclear Information System (INIS)
Zghal, Slim; Thomas, Marc; Naka, Shigehisa; Finel, Alphonse; Couret, Alain
2005-01-01
Microstructural characteristics of a fully lamellar Ti 49 Al 47 Cr 2 Nb 2 alloy have been investigated in different annealed conditions by quantitative transmission electron microscopy. Statistical analyses have yielded clear information about the γ-γ interfaces, the respective orientation groups of the γ phase, and the distribution of orientational variants. From the results, three sequences of lamellar transformation have been identified with decreasing temperature: (1) a high-temperature heterogeneous transformation characterized by the nucleation of isolated primary γ lamellae mostly belonging to the same orientation group and having locally the same order; (2) a low-temperature homogeneous transformation in the ordered α 2 phase characterized by the formation of a fine lamellar structure with an even distribution of the orientation groups and a random ordering of γ lamellae; and (3) a coherent interfacial transformation at the α 2 /γ interfaces characterized by the nucleation of ultra-fine twin related lamellae. Finally, the driving forces for these various transformations as well as the nucleation mechanisms of γ lamellae involved in these transformations are discussed
Mechanisms of diffusional phase transformations in metals and alloys
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
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)
DEFF Research Database (Denmark)
Obinger, Herbert; Starke, Peter
2014-01-01
This paper describes welfare state transformation in OECD countries since the 1970s against the background of the post-war settlement. Relying on quantitative macro-data and qualitative information from the literature, we show that welfare states have con-verged, especially regarding various...
Phase Transformations During Cooling of Automotive Steels
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).
An optical Fourier transform coprocessor with direct phase determination.
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.
International Nuclear Information System (INIS)
Holzweissig, M.J.; Canadinc, D.; Maier, H.J.
2012-01-01
This paper elucidates the stress-induced variant selection process during the isothermal austenite-to-bainite phase transformation in a tool steel. Specifically, a thorough set of experiments combining electron backscatter diffraction and in-situ digital image correlation (DIC) was carried out to establish the role of superimposed stress level on the evolution of transformation plasticity (TP) strains. The important finding is that TP increases concomitant with the superimposed stress level, and strain localization accompanies phase transformation at all stress levels considered. Furthermore, TP strain distribution within the whole material becomes more homogeneous with increasing stress, such that fewer bainitic variants are selected to grow under higher stresses, yielding a more homogeneous strain distribution. In particular, the bainitic variants oriented along [101] and [201] directions are favored to grow parallel to the loading axis and are associated with large TP strains. Overall, this very first in-situ DIC investigation of the austenite-to-bainite phase transformation in steels evidences the clear relationship between the superimposed stress level, variant selection, and evolution of TP strains. - Highlights: ► Local variations of strain were observed by DIC throughout the phase transformation. ► The study clearly established the role of the stress-induced variant selection. ► Variant selection is a key parameter that governs distortion.
Spatiotemporal Signal Analysis via the Phase Velocity Transform
International Nuclear Information System (INIS)
Mattor, Nathan
2000-01-01
The phase velocity transform (PVT) is an integral transform that divides a function of space and time into components that propagate at uniform phase velocities without distortion. This paper examines the PVT as a method to analyze spatiotemporal fluctuation data. The transform is extended to systems with discretely sampled data on a periodic domain, and applied to data from eight azimuthally distributed probes on the Sustained Spheromak Physics Experiment (SSPX). This reveals features not shown by Fourier analysis, particularly regarding nonsinusoidal mode structure. (c) 2000 The American Physical Society
Thermodynamic and kinetics models of hydrogen absorption bound to phase transformations
International Nuclear Information System (INIS)
Gondor, G.; Lexcellent, Ch.
2007-01-01
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 2 gas pressure - H 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 (α phase). When the hydrogen concentration increases, a phase transformation appears changing the α solid solution into an hydride (β phase) (solid solution + H 2 ↔ hydride). When all the solid solution has been transformed into hydride, the absorbed hydrogen atoms are in β 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 2 gas pressure and the H 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.)
Precipitation and Phase Transformations in 2101 Lean Duplex Stainless Steel During Isothermal Aging
Maetz, Jean-Yves; Cazottes, Sophie; Verdu, Catherine; Kleber, Xavier
2016-01-01
The effect of isothermal aging at 963 K (690 °C) on the microstructure of a 2101 lean duplex stainless steel, with the composition Fe-21.5Cr-5Mn-1.6Ni-0.22N-0.3Mo, was investigated using a multi-technique and multi-scale approach. The kinetics of phase transformation and precipitation was followed from a few minutes to thousands of hours using thermoelectric power measurements; based on these results, certain aging states were selected for electron microscopy characterization. Scanning electron microscopy, electron back-scattered diffraction, and transmission electron microscopy were used to quantitatively describe the microstructural evolution through crystallographic analysis, chemical analysis, and volume fraction measurements from the macroscopic scale down to the nanometric scale. During aging, the precipitation of M23C6 carbides, Cr2N nitrides, and σ phase as well as the transformation of ferrite into austenite and austenite into martensite was observed. These complex microstructural changes are controlled by Cr volume diffusion. The precipitation and phase transformation mechanisms are described.
Energy Technology Data Exchange (ETDEWEB)
Mikailoff, H [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1959-06-15
By annealing at different temperatures, we have studied the transformations of the body centred cubic {gamma} phase for two alloys containing 6 and 10 per cent molybdenum by weight respectively. There is a return to the equilibrium state by formation of the stable {alpha} orthorhombic and {epsilon} ordered tetragonal phases, following two types of reaction: - pearlite transformation by nucleation and growth from the grain boundaries, preponderant when the annealing takes place at temperature above 400 deg. C, and identical for the two types of alloys. This reaction has already been studied by numerous authors, who have constructed the corresponding TTT curves, - transformation inside the grains of the quenched solid solution when annealing takes place at 400 deg. C or below: 6 per cent alloy - precipitation of fine a phase particles, followed by progressive ordering of the solid solution enriched in molybdenum, 10 per cent alloy - formation of small ordered regions and then a fine a phase precipitate. In the course of this work we have paid particular attention to the study of intragranular reactions after low-temperature annealing, the reactions involved in this case not having been explained up to the present. The {gamma} phase transformation has been studied by means of three techniques: micrography - microhardness tests - X-ray diffraction. (author) [French] Nous avons etudie les transformations par revenu a differentes temperatures, de la phase {gamma} cubique centree des alliages U-Mo trempes, pour deux alliages a 6 et a 10 pour cent de molybdene en poids. Il y a retour a l'etat d'equilibre par formation des phases stables {alpha} orthorhombique et quadratique ordonnee, suivant deux types de reactions: - transformation perlitique par germination et croissance a partir des joints de grains, preponderante lorsque le recuit a lieu a temperature superieure a 400 deg. C, et identique pour les deux types d'alliages. Cette reaction a deja ete etudiee par de nombreux
Phase difference estimation method based on data extension and Hilbert transform
International Nuclear Information System (INIS)
Shen, Yan-lin; Tu, Ya-qing; Chen, Lin-jun; Shen, Ting-ao
2015-01-01
To improve the precision and anti-interference performance of phase difference estimation for non-integer periods of sampling signals, a phase difference estimation method based on data extension and Hilbert transform is proposed. Estimated phase difference is obtained by means of data extension, Hilbert transform, cross-correlation, auto-correlation, and weighted phase average. Theoretical analysis shows that the proposed method suppresses the end effects of Hilbert transform effectively. The results of simulations and field experiments demonstrate that the proposed method improves the anti-interference performance of phase difference estimation and has better performance of phase difference estimation than the correlation, Hilbert transform, and data extension-based correlation methods, which contribute to improving the measurement precision of the Coriolis mass flowmeter. (paper)
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
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......, but employing zeros of the z-transform (ZZT) as a signal representation, analysis, and processing domain per se, is only scarcely researched. A notable property of this domain is the translation of time domain convolution into union of sets; thus, the ZZT domain is appropriate for convolving and deconvolving...... discrimination achieves mixed phase deconvolution and equivalates complex cepstrum based deconvolution by causality, which has lower time and space complexities as demonstrated. However, deconvolution by ZZT prevents phase wrapping. Existence and persistence of ZZT domain immiscibility of the opening and closing...
Energy Technology Data Exchange (ETDEWEB)
Holzweissig, M.J., E-mail: martinh@mail.upb.de [University of Paderborn, Lehrstuhl fuer Werkstoffkunde (Materials Science), 33095 Paderborn (Germany); Canadinc, D., E-mail: dcanadinc@ku.edu.tr [Koc University, Advanced Materials Group, Department of Mechanical Engineering, 34450 Istanbul (Turkey); Maier, H.J., E-mail: hmaier@mail.upb.de [University of Paderborn, Lehrstuhl fuer Werkstoffkunde (Materials Science), 33095 Paderborn (Germany)
2012-03-15
This paper elucidates the stress-induced variant selection process during the isothermal austenite-to-bainite phase transformation in a tool steel. Specifically, a thorough set of experiments combining electron backscatter diffraction and in-situ digital image correlation (DIC) was carried out to establish the role of superimposed stress level on the evolution of transformation plasticity (TP) strains. The important finding is that TP increases concomitant with the superimposed stress level, and strain localization accompanies phase transformation at all stress levels considered. Furthermore, TP strain distribution within the whole material becomes more homogeneous with increasing stress, such that fewer bainitic variants are selected to grow under higher stresses, yielding a more homogeneous strain distribution. In particular, the bainitic variants oriented along [101] and [201] directions are favored to grow parallel to the loading axis and are associated with large TP strains. Overall, this very first in-situ DIC investigation of the austenite-to-bainite phase transformation in steels evidences the clear relationship between the superimposed stress level, variant selection, and evolution of TP strains. - Highlights: Black-Right-Pointing-Pointer Local variations of strain were observed by DIC throughout the phase transformation. Black-Right-Pointing-Pointer The study clearly established the role of the stress-induced variant selection. Black-Right-Pointing-Pointer Variant selection is a key parameter that governs distortion.
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.
Improved modeling of new three-phase high voltage transformer with magnetic shunts
Directory of Open Access Journals (Sweden)
Chraygane M.
2015-03-01
Full Text Available This original paper deals with a new approach for the study of behavior in nonlinear regime of a new three-phase high voltage power supply for magnetrons, used for the microwave generators in industrial applications. The design of this system is composed of a new three-phase leakage flux transformer supplying by phase a cell, composed of a capacitor and a diode, which multiplies the voltage and stabilizes the current. Each cell. in turn, supplies a single magnetron. An equivalent model of this transformer is developed taking into account the saturation phenomenon and the stabilization process of each magnetron. Each inductance of the model is characterized by a non linear relation between flux and current. This model was tested by EMTP software near the nominal state. The theoretical results were compared to experimental measurements with a good agreement. Relative to the current device, the new systemprovides gains of size, volume, cost of implementation and maintenance which make it more economical.
3DXRD characterization and modeling of solid-state transformation processes
DEFF Research Database (Denmark)
Juul Jensen, Dorte; Offerman, S.E.; Sietsma, J.
2008-01-01
of metallic microstructures with much more detail than hitherto possible. Among these modeling activities are three-dimensional (3D) geometric modeling, 3D molecular dynamics modeling, 3D phase-field modeling, two-dimensional (2D) cellular automata, and 2D Monte Carlo simulations....... data valuable for validation of various models of microstructural evolution is discussed, Examples of 3DXRD measurements related to recrystallization and to solid-state phase transformations in metals are described. 3DXRD measurements have led to new modeling activity predicting the evolution...
Constitutive modeling of multiphase materials including phase transformations
Perdahcioglu, Emin Semih; Geijselaers, Hubertus J.M.; Khan, A.S.; Meredith, C; Farrokh, B
2011-01-01
A constitutive model is developed for materials involving two or more different phases in their microstructure such as DP (Dual Phase) or TRIP (TRansformation Induced Plasticity) steels. Homogenization of the response of the phases is achieved by the Mean-Field method. One of the phases in TRIP
Neutron scattering studies of pretransitional phenomena in structural phase transformations
International Nuclear Information System (INIS)
Shapiro, S.M.
1979-03-01
Materials exhibiting structural phase transformations are well known to possess pretransitional phenomena. Below the transition temperature, T/sub c/, an order parameter appears and the pretransitional effects are associated with the fluctuations of the order parameter. Neutron scattering techniques have proved invaluable in studying the temporal and spatial dependence of these fluctuations. SrTiO 3 is the prototypical example of a structural phase transformation exhibiting features observable in other transformations such as martensitic and order-disorder. The experimental evolution of the understanding of the phase transformation in SrTiO 3 will be reviewed and the features observed will be shown to typify other systems
Rehder, Sönke; Wu, Jian X; Laackmann, Julian; Moritz, Hans-Ulrich; Rantanen, Jukka; Rades, Thomas; Leopold, Claudia S
2013-01-23
The objective of this study was to monitor the amorphous-to-crystalline solid-state phase transformation kinetics of the model drug ibuprofen with spectroscopic methods during acoustic levitation. Chemical and physical information was obtained by real-time near infrared (NIRS) and Raman spectroscopy measurements. The recrystallisation kinetic parameters (overall recrystallisation rate constant β and the time needed to reach 50% of the equilibrated level t(50)), were determined using a multivariate curve resolution approach. The acoustic levitation device coupled with non-invasive spectroscopy enabled monitoring of the recrystallisation process of the difficult-to-handle (adhesive) amorphous sample. The application of multivariate curve resolution enabled isolation of the underlying pure spectra, which corresponded well with the reference spectra of amorphous and crystalline ibuprofen. The recrystallisation kinetic parameters were estimated from the recrystallisation profiles. While the empirical recrystallisation rate constant determined by NIR and Raman spectroscopy were comparable, the lag time for recrystallisation was significantly lower with Raman spectroscopy as compared to NIRS. This observation was explained by the high energy density of the Raman laser beam, which might have led to local heating effects of the sample and thus reduced the recrystallisation onset time. It was concluded that acoustic levitation with NIR and Raman spectroscopy combined with multivariate curve resolution allowed direct determination of the recrystallisation kinetics of amorphous drugs and thus is a promising technique for monitoring solid-state phase transformations of adhesive small-sized samples during the early phase of drug development. Copyright © 2012 Elsevier B.V. All rights reserved.
High-pressure phase transformations of fluorite-type dioxides
International Nuclear Information System (INIS)
Lin-Gun Liu
1980-01-01
Phase transformations in six fluorite-type dioxides ('TbO 2 ', PbO 2 , 'PrO 2 ', CeO 2 , UO 2 and ThO 2 in the order of increasing cation size, where the quotation marks indicate non-stoichiometric materials) have been investigated in the diamond-anvil press coupled with laser heating. Together with earlier work, the results show that the post-fluorite phase transformations of these dioxides fall into two groups. The smaller cation group (HfO 2 , ZrO 2 and 'TbO 2 ') transforms to a cotunnite or a distorted cotunnite-type structure at pressures in the vicinity of 100 kbar and at about 1000 0 C. The larger cation group (from PbO 2 to ThO 2 ) is believed to transform to a different type of orthorhombic modification at high pressures. It is plausible that this high-pressure phase may possess a Ni 2 Si-related structure, as was observed in ThO 2 and 'PrO 2 ' at pressures greater than 150 and 200 kbar, respectively. (orig./ME)
Temperature induced reversible polymorphic phase transformations in a bis-hydrazone compound
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.
Effect of different factors on phase transformations in Fe-Mn alloys
International Nuclear Information System (INIS)
Balychev, Yu.M.; Tkachenko, F.K.
1983-01-01
Phase transformations proceeding under Fe-Mn alloy heating are studied and the effect of previous working conditions, particularly, cooling rate on these transformations is investigated. Investigations have been conducted on pure Fe-Mn alloys with 2-15% Mn. Phase transformations are shown to proceed according to α → #betta# and epsilon → #betta# reaction in Fe-Mn alloys containing 2-15% Mn under heating. Cooling rate in the range of approximately 5-1000 deg/min in preliminary working essentially affects phase transformations under subsequent heating
Directory of Open Access Journals (Sweden)
Mihaela Poienar
2014-09-01
Full Text Available The clock hour figure mathematical model of a threephase transformer can be expressed, in the most plain form, through a 3X3 square matrix, called code matrix. The lines position reflect the modification in the high voltage windings terminal and the columns position reflect the modification in the low voltage winding terminal. The main changes on the transformer winding terminal are: the circular permutation of connection between windings; terminal supply reversal; reverse direction for the phase winding wrapping; reversal the beginning with the end for a phase winding; the connection conversion from N in Z between phase winding or inverse. The analytical form of these changes actually affect the configuration of the mathematical model expressed through a transformations diagram proposed and analyzed in two ways: bipolar version and unipolar version (fanwise. In the end of the paper are presented about the practical exploitation of the transformations diagram.
QR code-based non-linear image encryption using Shearlet transform and spiral phase transform
Kumar, Ravi; Bhaduri, Basanta; Hennelly, Bryan
2018-02-01
In this paper, we propose a new quick response (QR) code-based non-linear technique for image encryption using Shearlet transform (ST) and spiral phase transform. The input image is first converted into a QR code and then scrambled using the Arnold transform. The scrambled image is then decomposed into five coefficients using the ST and the first Shearlet coefficient, C1 is interchanged with a security key before performing the inverse ST. The output after inverse ST is then modulated with a random phase mask and further spiral phase transformed to get the final encrypted image. The first coefficient, C1 is used as a private key for decryption. The sensitivity of the security keys is analysed in terms of correlation coefficient and peak signal-to noise ratio. The robustness of the scheme is also checked against various attacks such as noise, occlusion and special attacks. Numerical simulation results are shown in support of the proposed technique and an optoelectronic set-up for encryption is also proposed.
Mathematical model of phase transformations in thermo-chemical cathodes with zirconium insertion
International Nuclear Information System (INIS)
Kavokin, A.A.; Kazmi, I.H.
2007-01-01
The mathematical model of thermo-chemical processes in the cathode of plasmatron working in the gas environment is investigated. The model describes electromagnetic, temperature and concentration fields taking into account kinetic of phase transformation and chemical reaction in accordance with a state diagram. The offered approach is simpler than the Stefan's approach of describing an analogical phase transformation. As an example the case of copper cathodes with the zirconium insertion in the environment of oxygen is considered. The influence of separate parts of process on distribution of temperature inside of the insertion is estimated. On the basis of this analysis the opportunity of use of stationary approach for electric and temperature fields is shown and analytical formulas for temperature are received. After that a numerical solution for gas concentration distribution is obtained. The calculations on the specified model show that the size of area of a phase zirconium oxides depends mainly upon coefficient of diffusion of oxygen. The calculations for various types of dependencies of gas diffusion coefficient from temperature are concluded. The results of calculations develop understanding of some features of oxidation process of a zirconium insertion. Typical example of multi phase process model is the mathematical description of a heat and mass transfer occurring in metal which is being heated by an electric arch in the gas medium (1, 2, 4). The macroscopic model of physical and chemical transformations can be described as follows (3). As a metal is heated on the surface of an electrode as a function of rising results in the border dividing solid and liquid phases moves ahead deep into the electrode. At the same time there is a diffusion of gas in electrode and formation of new chemical compounds which can noticeably differ in the physical and chemical properties from each other and metal of the electrode. Moreover we shall name a phase of substance not
Density of states model for the lattice transformation in A-15 compounds
International Nuclear Information System (INIS)
Pietrass, B.; Handstein, A.; Behr, G.
1980-01-01
The cubic-tetragonal lattice transformation in A-15 compounds is described by an empirical model in which the density of states function near the Fermi energy is characterized by a two-parametric peak in addition to the constant part. Two types of peak splitting under tetragonal deformation are considered, leading to qualitatively different results about the phase transition. Results are given for the order parameter, the phase stability, the soft elastic modulus, and the paramagnetic spin susceptibility. Comparing with measurements of the magnetic susceptibility of V 3 Si single crystals near the phase transition a better agreement is obtained for a twofold degenerate density of states peak than for a threefold degenerate one. (author)
Phase transformation in rapidly quenched Fe-Cr-Co-Mo-Ti-Si-B alloys
Zhukov, D. G.; Shubakov, V. S.; Zhukova, E. Kh; Gorshenkov, M. V.
2018-03-01
The research results of phase transformations in Fe-24Cr-16Co-3Mo-0.2Ti-1Si-B alloys (with a boron content of 1 to 3% by mass) obtained by rapid quenching are presented. The structure formation regularities during the melt spinning and during the subsequent crystallization annealing in rapidly quenched bands of the Fe-Cr-Co-Mo-Ti-Si-B system alloys were studied. The changes in the phase composition of the rapidly quenched Fe-Cr-Co-Mo-Ti- Si-B system alloys after quenching at various quench rates and at different boron concentrations in the alloys are studied. It is shown that during crystallization from an amorphous state, at temperatures above 570 °C, in addition to the α-phase, the σ-phase appears first, followed by the γ-phase. Heat treatment of rapidly quenched bands to high-coercive state was carried out. A qualitative assessment of magnetic properties in a high-coercivity state was carried out. An evaluation of the level of magnetic properties in a high-coercivity state allows us to conclude that the application of a magnetic field during crystallization from an amorphous state leads to anisotropy of the magnetic properties, that is, an anisotropic effect of thermo-magnetic treatment is detected.
International Nuclear Information System (INIS)
Cho, Y.S.; Choi, H.S.; Jung, B.I.
2011-01-01
The three-phase transformer-type SFCL with a neutral line can control the current limiting rates according to the turn's ratio between primary and secondary windings. The transformer-type SFCL with a neutral line can reliably conduct the fault current limiting operation according to the reclosing operation duty and fault types. The superconducting elements recovered their superconducting state within the opening cycle of the circuit breaker according to the reclosing operation duty. It is expected to improve the transient stability and supply reliability of the power network. In a transformer-type superconducting fault current limiter (SFCL) with a neutral line, which is connected between the superconducting elements and secondary windings, we verified that the SFCL has excellent characteristics that induce the perfect simultaneous quench of the superconducting elements in the previous study. The application of the SFCL to the power networks requires its coordination with the reclosing operation duty, which protects a circuit. In this study, the fault current limiting and recovery characteristics of superconducting elements in the three-phase transformer-type SFCL with the neutral line were analyzed. The limiting rate of the fault current in the transformer-type SFCL could increased by an iron core, which allows quenching of the superconducting elements in a sound phase as well as in a faulted phase. In addition, the simultaneous quench led to uniform burdens on superconducting elements, all of which recovered their superconducting state within an opening cycle of a circuit breaker. Thus, the transformer-type SFCL with the neutral line could reliably conduct the fault current limiting and recovery operations of superconducting elements according to the reclosing operation duty and fault types.
Catalytic transformations for bipartite pure states
International Nuclear Information System (INIS)
Turgut, S
2007-01-01
Entanglement catalysis is a phenomenon that usually enhances the conversion probability in the transformation of entangled states by the temporary involvement of another entangled state (so-called catalyst), where after the process is completed the catalyst is returned to the same state. For some pairs of bipartite pure entangled states, catalysis enables a transformation with unit probability of success, in which case the respective Schmidt coefficients of the states are said to satisfy the trumping relation, a mathematical relation which is an extension of the majorization relation. This paper provides all necessary and sufficient conditions for the trumping and two other associated relations. Using these conditions, the least upper bound of conversion probabilities using catalysis is also obtained. Moreover, best conversion ratios achievable with catalysis are found for transformations involving many copies of states
Thermodynamic Modelling of Phase Transformation in a Multi-Component System
Vala, J.
2007-09-01
Diffusion in multi-component alloys can be characterized by the vacancy mechanism for substitutional components, by the existence of sources and sinks for vacancies and by the motion of atoms of interstitial components. The description of diffusive and massive phase transformation of a multi-component system is based on the thermodynamic extremal principle by Onsager; the finite thickness of the interface between both phases is respected. The resulting system of partial differential equations of evolution with integral terms for unknown mole fractions (and additional variables in case of non-ideal sources and sinks for vacancies), can be analyzed using the method of lines and the finite difference technique (or, alternatively, the finite element one) together with the semi-analytic and numerical integration formulae and with certain iteration procedure, making use of the spectral properties of linear operators. The original software code for the numerical evaluation of solutions of such systems, written in MATLAB, offers a chance to simulate various real processes of diffusional phase transformation. Some results for the (nearly) steady-state real processes in substitutional alloys have been published yet. The aim of this paper is to demonstrate that the same approach can handle both substitutional and interstitial components even in case of a general system of evolution.
Phase transformations in ion-mixed metastable (GaSb)1/sub 1 -x/(Ge2)/sub x/ semiconducting alloys
International Nuclear Information System (INIS)
Cadien, K.C.; Muddle, B.C.; Greene, J.E.
1984-01-01
Low energy (75--175 eV) Ar + ion bombardment during film deposition has been used to produce well-mixed amorphous GaSb/Ge mixtures which, when annealed, transform first to single phase polycrystalline metastable (GaSb)/sub 1-x/(Ge 2 )/sub x/ alloys before eventually transforming to the equilibrium two-phase state. At 500 0 C, for example, the annealing time t/sub a/ required for the amorphous to crystalline metastable (ACM) transformation was approx.10 min, while t/sub a/ for the crystalline metastable to equilibrium (CME) transformation was >6 h. The exothermic enthalpy of crystallization and the onset temperature of the ACM transition were determined as a function of alloy composition using differential thermal analysis. The thermodynamic data was then used to calculate the surface energy per unit area sigma of the amorphous/metastable-crystal interface. sigma was found to exhibit a minimum between x = 0.3 and 0.4. The driving energy for the transition from the crystalline metastable state to the equilibrium two-phase state was of the order of 0.12 kJ cm -3 while the activation barrier was approx.19 kJ cm -3 . Thus, the metastable alloys, which had average grain sizes of 100--200 nm and a lattice constant which varied linearly with x, exhibited good thermal and temporal stability
Stainless austenitic steels strengthened due to reversible phase transformations and by ageing
International Nuclear Information System (INIS)
Sagaradze, V.V.; Kositsyna, I.I.; Ozhiganov, A.V.
1981-01-01
The effect of the reversible phase transformations, consisting in the conduction of the direct and reverse martensite transformations and aging, during which the intermetallide γ'-phase of the composition Ni 3 Ti is formed, on the streng-thening of alloys in the Fe-Cr-Ni-Ti system is considered. Stainless austenitic steels Kh12N12T3 and Kh12N14T3, which acquire high mechanical properties: σsub(0.2)=685-785 MPa, σsub(B)=1275 MPa, delta >= 20%, as a result of reversible phase transformations and aging, are suggested. After the reversible phase transformations and ageing the steels possess a high resistance to γ-α-transformation during cold treatment [ru
International Nuclear Information System (INIS)
Feng Yuan; Duan Runyao; Ying Mingsheng
2006-01-01
We show that in some cases, catalyst-assisted entanglement transformation cannot be implemented by multiple-copy transformation for pure states. This fact, together with the result we obtained in R. Y. Duan, Y. Feng, X. Li, and M. S. Ying, Phys. Rev. A 71, 042319 (2005), namely that the latter can be completely implemented by the former, indicates that catalyst-assisted transformation is strictly more powerful than multiple-copy transformation. For the purely probabilistic setting we find, however, these two kinds of transformations are geometrically equivalent in the sense that the sets of pure states that can be converted into a given pure state with maximal probabilities not less than a given value have the same closure, regardless of whether catalyst-assisted transformation or multiple-copy transformation is used
Chemically Induced Phase Transformation in Austenite by Focused Ion Beam
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.
Directory of Open Access Journals (Sweden)
Koji Kosai
2017-11-01
Full Text Available Single-crystal germanium is a semiconductor material which shows complicated phase transformation under high pressure. In this study, new insight into the phase transformation of diamond-cubic germanium (dc-Ge was attempted by controlled cyclic nanoindentation combined with Raman spectroscopic analysis. Phase transformation from dc-Ge to rhombohedral phase (r8-Ge was experimentally confirmed for both single and cyclic nanoindentation under high loading/unloading rates. However, compared to single indentation, double cyclic indentation with a low holding load between the cycles caused more frequent phase transformation events. Double cyclic indentation caused more stress in Ge than single indentation and increased the possibility of phase transformation. With increase in the holding load, the number of phase transformation events decreased and finally became less than that under single indentation. This phenomenon was possibly caused by defect nucleation and shear accumulation during the holding process, which were promoted by a high holding load. The defect nucleation suppressed the phase transformation from dc-Ge to r8-Ge, and shear accumulation led to another phase transformation pathway, respectively. A high holding load promoted these two phenomena, and thus decreased the possibility of phase transformation from dc-Ge to r8-Ge.
Phase Transformation in Cast Superaustenitic Stainless Steels
Energy Technology Data Exchange (ETDEWEB)
Lee Phillips, Nathaniel Steven [Iowa State Univ., Ames, IA (United States)
2006-01-01
Superaustenitic stainless steels constitute a group of Fe-based alloys that are compositionally balanced to have a purely austenitic matrix and exhibit favorable pitting and crevice corrosion resistant properties and mechanical strength. However, intermetallic precipitates such as sigma and Laves can form during casting or exposure to high-temperature processing, which degrade the corrosion and mechanical properties of the material. The goal of this study was to accurately characterize the solid-solid phase transformations seen in cast superaustenitic stainless steels. Heat treatments were performed to understand the time and temperature ranges for intermetallic phase formations in alloys CN3MN and CK3MCuN. Microstructures were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy and wavelength dispersive spectroscopy (EDS, WDS). The equilibrium microstructures, composed primarily of sigma and Laves within purely austenitic matrices, showed slow transformation kinetics. Factors that determine the extent of transformation, including diffusion, nucleation, and growth, are discussed.
Energy Technology Data Exchange (ETDEWEB)
Zuniga Segundo, A. [Instituto Politecnico Nacional, Mexico, D.F. (Mexico)
2001-10-01
In this work we introduce squeezed states with real and complex squeezing parameters directly obtained in the coherent-representation of the harmonic oscillator in quantum phase space. By means of the Fourier transform, we recover the usual coordinate states and compare these states with those obtained by another method in the coordinate representation. In addition we also describe numerically its time evolution in quantum phase space and the variances Q and P. [Spanish] En este trabajo presentamos estados comprimidos con parametros de compresion reales y complejos, obtenidos directamente en la representacion de estado coherente del oscilador armonico en el espacio fase cuantico. Por medio de una transformada de Fourier recuperamos los estados en la representacion de coordenadas y los comparamos con aquellos obtenidos por otro metodo. Ademas describimos numericamente sus evoluciones temporales en el espacio fase cuantico y calculamos las varianzas de Q y P.
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.
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
Atomistic modelling of diffusional phase transformations with elastic strain
International Nuclear Information System (INIS)
Mason, D R; Rudd, R E; Sutton, A P
2004-01-01
Phase transformations in 2xxx series aluminium alloys (Al-Cu-Mg) are investigated with an off-lattice atomistic kinetic Monte Carlo simulation incorporating the effects of strain around misfitting atoms and vacancies. Atomic interactions are modelled by Finnis-Sinclair potentials constructed for these simulations. Vacancy diffusion is modelled by comparing the energies of trial states, where the system is partially relaxed for each trial state. No special requirements are made about the description of atomic interactions, making our approach suitable for more fundamentally based models such as tight binding if sufficient computational resources are available. Only a limited precision is required for the energy of each trial state, determined by the value of k B T. Since the change in the relaxation displacement field caused by a vacancy hop decays as 1/r 3 , it is sufficient to determine the next move by relaxing only those atoms in a sphere of finite radius centred on the moving vacancy. However, once the next move has been selected, the entire system is relaxed. Simulations of the early stages of phase separation in Al-Cu with elastic relaxation show an enhanced rate of clustering compared to those performed on the same system with a rigid lattice
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.
Modelling of stresses generated in steels by phase transformations
International Nuclear Information System (INIS)
Dudek, K.; Glowacki, M.; Pietrzyk, M.
1999-01-01
Numerical model describing stresses arising during phase transformations in steels products is presented. The full model consists of three components. The first component uses finite element solution of Fourier equation for an evaluation of the temperature field inside the sample. The second component predicts kinetics of phase transformation occurring during cooling of steel products. Coupling of these two components allows prediction of structure and properties of final products at room temperature. The third component uses elastic-plastic finite element model for prediction of stresses caused by non-uniform temperatures and by changes of volume during transformations. Typical results of simulations performed for cooling of rails after hot rolling are presented. (author)
A balance principle approach for modeling phase transformation kinetics
International Nuclear Information System (INIS)
Lusk, M.; Krauss, G.; Jou, H.J.
1995-01-01
A balance principle is offered to model volume fraction kinetics of phase transformation kinetics at a continuum level. This microbalance provides a differential equation for transformation kinetics which is coupled to the differential equations governing the mechanical and thermal aspects of the process. Application here is restricted to diffusive transformations for the sake of clarity, although the principle is discussed for martensitic phase transitions as well. Avrami-type kinetics are shown to result from a special class of energy functions. An illustrative example using a 0.5% C Chromium steel demonstrates how TTT and CCT curves can be generated using a particularly simple effective energy function. (orig.)
Acoustic emission characterization of the tetragonal-monoclinic phase transformation in zirconia
International Nuclear Information System (INIS)
Clarke, D.R.; Arora, A.
1983-01-01
The processes accompanying the tetragonal-monoclinic phase transformation in zirconia (ZrO 2 ) have been studied using acoustic emission and electron microscopy in an attempt to characterize the different mechanisms by which the transformation can be accommodated in bulk materials. Experiments in which the acoustic emission is detected as specimens are cooled through the transformation, following densification by sintering, are described. For comparison, the acoustic emission from free, nominally unconstrained powders similarly cooled through the transformation is reported. The existence of distinct processes accompanying the phase transformation is established on the basis of postexperiment multiparametric correlation analysis of the acoustic emission
Multicopy and stochastic transformation of multipartite pure states
International Nuclear Information System (INIS)
Chen Lin; Hayashi, Masahito
2011-01-01
Characterizing the transformation and classification of multipartite entangled states is a basic problem in quantum information. We study the problem under the two most common environments, local operations and classical communications (LOCC), stochastic LOCC and two more general environments, multicopy LOCC (MCLOCC), and multicopy SLOCC (MCSLOCC). We show that two transformable multipartite states under LOCC or SLOCC are also transformable under MCLOCC and MCSLOCC. What is more, these two environments are equivalent in the sense that two transformable states under MCLOCC are also transformable under MCSLOCC, and vice versa. Based on these environments we classify the multipartite pure states into a few inequivalent sets and orbits, between which we build the partial order to decide their transformation. In particular, we investigate the structure of SLOCC-equivalent states in terms of tensor rank, which is known as the generalized Schmidt rank. Given the tensor rank, we show that Greenberger-Horne-Zeilinger states can be used to generate all states with a smaller or equivalent tensor rank under SLOCC, and all reduced separable states with a cardinality smaller than or equivalent to the tensor rank under LOCC. Using these concepts, we extended the concept of the ''maximally entangled state'' in the multipartite system.
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.
Unitary transformations in solid state physics
International Nuclear Information System (INIS)
Wagner, M.
1986-01-01
The main emphasis of this book is on the practical application of unitary transformations to problems in solid state physics. This is a method used in the field of nonadiabatic electron-phonon phenomena where the Born-Oppenheimer approximation is no longer applicable. The book is intended as a tool for those who want to apply unitary transformations quickly and on a more elementary level and also for those who want to use this method for more involved problems. The book is divided into 6 chapters. The first three chapters are concerned with presenting quick applications of unitary transformations and chapter 4 presents a more systematic procedure. The last two chapters contain the major known examples of the utilization of unitary transformations in solid state physics, including such highlights as the Froehlich and the Fulton-Gouterman transformations. The book is supplemented by extended tables of unitary transformations, whose properties and peculiarities are also listed. This tabulated material is unique and will be of great practical use to those applying the method of unitary transformations in their work. (Auth.)
International Nuclear Information System (INIS)
Iwasaki, Hiroshi; Ohshima, Ken-ichi
2011-01-01
The 11th lecture about microstructures and fluctuation in solids reports on the martensitic phase transformation of alkali metals and alloys. The martensitic transformation is a diffusionless first order phase transformation. Martensitic transformations are classified into two with respect to kinetics, one is isothermal transformation and the other is athermal transformation. The former transformation depends upon both temperature and time, but the latter solely depends on temperature. The former does not have a definite transformation start temperature but occurs after some finite incubation time during isothermal holding. The isothermal martensitic transformation is changed to the athermal one under high magnetic field, and also the reverse transformation occurs under the application of hydrostatic pressure. The former phenomena were observed in Fe-Ni-Mn alloys, Fe-Ni-Cr alloys and also the reverse transformation in Fe-3.1at%Ni-0.5at%Mn alloys. The athermal transformation was observed in Li and Na metals at 73 and 36 K, respectively. A neutron diffraction study has been performed on single crystals of metallic Na. On cooling the virgin sample, the incubation time to transform from the bcc structure to the low-temperature structure (9R structure) is formed to be more than 2h at 38 K, 2 K higher than the transformation temperature of 36 K. The full width of half maximum of the Bragg reflection suddenly increased, due to some deformation introduced by the nucleation of the low-temperature structure. In relation to the deformation, strong extra-diffuse scattering (Huang scattering) was observed around the Bragg reflection in addition to thermal diffuse scattering. The kinetics of the martensitic transformation in In-Tl alloys has been studied by x-ray and neutron diffraction methods. A characteristic incubation time appeared at fixed temperature above Ms, the normal martensitic transformation start temperature. (author)
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.
Study of the phase transformations in Ni2MnGa by capacitance dilatometry
International Nuclear Information System (INIS)
Wu, X D; Finlayson, T R
2007-01-01
High precision capacitance dilatometry has been used to study the phase transformations in a Ni 2 MnGa single crystal. The results show that capacitance dilatometry is an effective method to study the phase transformations. The thermal strain accompanying the martensitic transformation was not reproducible, but became more reproducible with the application of external stress. The first-order character of the martensitic transformation was enhanced by external stress. The intermediate transformation temperature decreased with increasing external stress with a temperature coefficient of -2.40 K MPa -1 . The coefficient of thermal expansion was 1.7 x 10 -5 K -1 for the parent phase and 1.4 x 10 -5 K -1 for the intermediate phase
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.
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
Energy Technology Data Exchange (ETDEWEB)
Wu, Zeen; Hu, Rui; Zhang, Tiebang, E-mail: tiebangzhang@nwpu.edu.cn; Zhang, Fan; Kou, Hongchao; Li, Jinshan
2017-02-15
The microstructure and solidification behavior of high Nb containing TiAl alloys with the composition of Ti-46Al-8Nb-xC (x = 0.1, 0.7, 1.4, 2.5 at.%) prepared by arc-melting method have been investigated in this work. The results give evidence that the addition of carbon changes the solidification behavior from solidification via the β phase to the peritectic solidification. And carbon in solid solution enriches in the α{sub 2} phase and increases the microhardness. As the carbon content increases to 1.4 at.%, plate-shape morphology carbides Ti{sub 2}AlC (H phase) precipitate from the TiAl matrix which leads to the refinement microstructure. By aging at 1173 K for 24 h after quenching treatment, fine needle-like and granular shape Ti{sub 3}AlC (P phase) carbides are observed in the matrix of Ti-46Al-8Nb-2.5C alloy, which distribute along the lamellar structure or around the plate-shape Ti{sub 2}AlC. Transmission electron microscope observation shows that the Ti{sub 3}AlC carbides precipitate at dislocations. The phase transformation in-situ observations indicate that the Ti{sub 2}AlC carbides partly precipitate during the solid state phase transformation process. - Highlights: •Carbon changes the solidification behavior from β phase to peritectic solidification. •Dislocations in solution treated γ phase act as nucleation sites of Ti{sub 3}AlC precipitations. •Ti{sub 3}AlC precipitates as fine needle-like or granular shape in the solution treated matrix. •Ti{sub 2}AlC carbides precipitate during the solid state phase transformation process.
The Pegg–Barnett phase operator and the discrete Fourier transform
International Nuclear Information System (INIS)
Perez-Leija, Armando; Szameit, Alexander; Andrade-Morales, Luis A; Soto-Eguibar, Francisco; Moya-Cessa, Héctor M
2016-01-01
In quantum mechanics the position and momentum operators are related to each other via the Fourier transform. In the same way, here we show that the so-called Pegg–Barnett phase operator can be obtained by the application of the discrete Fourier transform to the number operators defined in a finite-dimensional Hilbert space. Furthermore, we show that the structure of the London–Susskind–Glogower phase operator, whose natural logarithm gives rise to the Pegg–Barnett phase operator, is contained in the Hamiltonian of circular waveguide arrays. Our results may find applications in the development of new finite-dimensional photonic systems with interesting phase-dependent properties. (invited comment)
Diffuse-interface model for rapid phase transformations in nonequilibrium systems.
Galenko, Peter; Jou, David
2005-04-01
A thermodynamic approach to rapid phase transformations within a diffuse interface in a binary system is developed. Assuming an extended set of independent thermodynamic variables formed by the union of the classic set of slow variables and the space of fast variables, we introduce finiteness of the heat and solute diffusive propagation at the finite speed of the interface advancing. To describe transformations within the diffuse interface, we use the phase-field model which allows us to follow steep but smooth changes of phase within the width of the diffuse interface. Governing equations of the phase-field model are derived for the hyperbolic model, a model with memory, and a model of nonlinear evolution of transformation within the diffuse interface. The consistency of the model is proved by the verification of the validity of the condition of positive entropy production and by outcomes of the fluctuation-dissipation theorem. A comparison with existing sharp-interface and diffuse-interface versions of the model is given.
International Nuclear Information System (INIS)
Rodriguez-Aseguinolaza, J.; Ruiz-Larrea, I.; No, M.L.; Lopez-Echarri, A.; Juan, J. San
2008-01-01
A thermodynamic study, based on high-sensitivity adiabatic calorimetry, of the martensitic transformation undergone by Cu-Al-Ni shape memory alloys is presented. From the specific heat data, the thermodynamic function values, and in particular the crystal free energy, as functions of temperature, have been obtained. These results have permitted a careful estimation of the phase transformation temperatures of each β 3 ' martensite plate as a function of its stored elastic energy. Within this frame, the distribution density of the elastic energy states in the martensitic phase is directly derived from the specific heat data. It also permits a simple analysis of the nucleation processes and gives a convincing explanation of the temperature memory effects
Phase transformation changes in thermocycled nickel-titanium orthodontic wires.
Berzins, David W; Roberts, Howard W
2010-07-01
In the oral environment, orthodontic wires will be subject to thermal fluctuations. The purpose of this study was to investigate the effect of thermocycling on nickel-titanium (NiTi) wire phase transformations. Straight segments from single 27 and 35 degrees C copper NiTi (Ormco), Sentalloy (GAC), and Nitinol Heat Activated (3M Unitek) archwires were sectioned into 5mm segments (n=20). A control group consisted of five randomly selected non-thermocycled segments. The remaining segments were thermocycled between 5 and 55 degrees C with five randomly selected segments analyzed with differential scanning calorimetry (DSC; -100150 degrees C at 10 degrees C/min) after 1000, 5000, and 10,000 cycles. Thermal peaks were evaluated with results analyzed via ANOVA (alpha=0.05). Nitinol HA and Sentalloy did not demonstrate qualitative or quantitative phase transformation behavior differences. Significant differences were observed in some of the copper NiTi transformation temperatures, as well as the heating enthalpy with the 27 degrees C copper NiTi wires (p<0.05). Qualitatively, with increased thermocycling the extent of R-phase in the heating peaks decreased in the 35 degrees C copper NiTi, and an austenite to martensite peak shoulder developed during cooling in the 27 degrees C copper NiTi. Repeated temperature fluctuations may contribute to qualitative and quantitative phase transformation changes in some NiTi wires. Copyright 2010 Academy of Dental Materials. All rights reserved.
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)
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
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
Effect of isochronal annealing on phase transformation studies of ...
Indian Academy of Sciences (India)
The mixed phase sample shows higher value of magnetization because of the presence of ferromagnetic γ-Fe2O3 ... 1. Introduction. The study of particle size, phase transformation and micros- ..... The results are in qualitative agreement with ...
Amorphous-to-Cu51Zr14 phase transformation in Cu60Ti20Zr20 alloy
International Nuclear Information System (INIS)
Cao, Q P; Zhou, Y H; Horsewell, A; Jiang, J Z
2003-01-01
The kinetics of an amorphous-to-Cu 51 Zr 14 phase transformation in an as-cast Cu 60 Ti 20 Zr 20 rod have been investigated by differential scanning calorimetry. The relative volume fractions of the transferred crystalline phase as a function of annealing time, obtained at 713, 716, 723, 728, and 733 K, have been analysed in detail using 14 nucleation and growth models together with the JMA model. A time-dependent nucleation process is revealed. A steady-state nucleation rate of the order of 10 22 - 10 23 nuclei m -3 s -1 in the temperature range 713-733 K and an activation energy of the order of 550 kJmol -1 for the phase transformation in the as-cast Cu 60 Ti 20 Zr 20 rod were detected, for which some possible reasons are suggested
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.)
Electron backscatter diffraction studies of focused ion beam induced phase transformation in cobalt
Energy Technology Data Exchange (ETDEWEB)
Jones, H.G., E-mail: helen.jones@npl.co.uk [National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW (United Kingdom); Day, A.P. [Aunt Daisy Scientific Ltd, Claremont House, High St, Lydney GL15 5DX (United Kingdom); Cox, D.C. [National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW (United Kingdom); Advanced Technology Institute, University of Surrey, Guildford GU2 7XH (United Kingdom)
2016-10-15
A focused ion beam microscope was used to induce cubic to hexagonal phase transformation in a cobalt alloy, of similar composition to that of the binder phase in a hardmetal, in a controlled manner at 0°, 45° and 80° ion incident angles. The cobalt had an average grain size of ~ 20 μm, allowing multiple orientations to be studied, exposed to a range of doses between 6 × 10{sup 7} and 2 × 10{sup 10} ions/μm{sup 2}. Electron backscatter diffraction (EBSD) was used to determine the original and induced phase orientations, and area fractions, before and after the ion beam exposure. On average, less phase transformation was observed at higher incident angles and after lower ion doses. However there was an orientation effect where grains with an orientation close to (111) planes were most susceptible to phase transformation, and (101) the least, where grains partially and fully transformed at varying ion doses. - Highlights: •Ion-induced phase change in FCC cobalt was observed at multiple incidence angles. •EBSD was used to study the relationship between grain orientation and transformation. •Custom software analysed ion dose and phase change with respect to grain orientation. •A predictive capability of ion-induced phase change in cobalt was enabled.
Synthesis and phase transformation mechanism of Nb{sub 2}C carbide phases
Energy Technology Data Exchange (ETDEWEB)
Vishwanadh, B., E-mail: visubathula@gmail.com [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 094 (India); Murthy, T.S.R.Ch. [Materials Processing Division, Bhabha Atomic Research Centre, Mumbai 400 094 (India); Arya, A.; Tewari, R.; Dey, G.K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 094 (India)
2016-06-25
In the present work, Niobium carbide samples were prepared through powder metallurgy route using spark plasma sintering technique. Some of these samples were heat treated at 900 °C up to 7 days. In order to investigate the phase transformation in Nb{sub 2}C carbide, the as-prepared and heat treated samples were characterized by X-ray diffraction, scanning electron microscopy and electron back scattered diffraction (EBSD) and transmission electron microscopy techniques. EBSD could index the same area of the sample in terms of any of the three allotropes of Nb{sub 2}C carbide phases (γ-Nb{sub 2}C, β-Nb{sub 2}C and α-Nb{sub 2}C) with good confidence index. From the EBSD patterns orientation relationships (OR) among γ, β and α-Nb{sub 2}C have been determined. Based on this OR when crystals of the three allotropes were superimposed, it has revealed that the basic Nb metal atom lattice (hcp lattice) in all the Nb{sub 2}C phases is same. The only difference exists in the carbides is the ordering of carbon atoms and vacancies in the octahedral positions of the hcp Nb metal atom lattice. Crystallographic analysis showed that for the transformation of γ-Nb{sub 2}C → β-Nb{sub 2}C → α-Nb{sub 2}C, large movement of Nb atoms is not required; but only by ordering of carbon atoms ensues the phase transformation. Literature shows that in the Nb–C system formation of the α-Nb{sub 2}C is not well established. Therefore, first principle calculations were carried out on these carbides. It revealed that the formation energy for α-Nb{sub 2}C is lower than the β and γ-Nb{sub 2}C carbides which indicate that the formation of α-Nb{sub 2}C is thermodynamically feasible. - Highlights: • Nb{sub 2}C carbide was produced by Spark Plasma Sintering in a single process. • Phase transformation mechanism of different Nb{sub 2}C carbide phases is studied. • In all the three Nb{sub 2}C carbides (γ, β, α), the base Nb lattice remains same. • Among γ, β and α-Nb{sub 2}C
Coupled gamma/alpha phase transformations in low-carbon steels
Mizutani, Yasushi
Since steels have been the most prevalently utilized materials for many years, the desire for steels with low alloying components with a well-balanced combination of high strength and toughness is increasing. Low carbon steels consisting of bainitic microstructures are ideally suited to meeting such technological and economic requirements. Thus it is extremely important to fully clarify the mechanism of bainite formation in order to produce this type of engineering steel by optimized alloy and process design. This research focuses on understanding the mechanism of coupled displacive/diffusional gamma/alpha transformation in low-carbon steels including bainitic and martensitic transformation, and establishing a more comprehensive and physically rational computational model for predictive control of coupled gamma/alpha transformation phenomena. Models for coupled gamma/alpha phase transformation proposed in this study are based on a mechanistic and unified theory and the following assumptions: (1) The energy dissipation due to interface motion can be linearly combined with the energy dissipation due to carbon diffusion. (2) The carbon concentrations at the interface in both gamma and alpha phases are constrained by an interface solute trapping law. (3) Interface motion during nucleation is also governed by the carbon diffusion field velocity. (4) The response function of glissile interface motion can be expressed in the form of thermally activated dislocation glide. In contrast to the conventional semi-empirical models of the previous literature, the computational model proposed in this study is demonstrated to successfully provide a comprehensive and quantitative prediction of the effects of temperature, composition, microstructure, and the interactions among them. This includes the effects of substitutional solutes, morphology of the parent gamma phase, density of nucleation sites, temperature dependent variation of flow stress of matrix, and dynamic recovery of
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.
Anatase-rutile phase transformation of titanium dioxide bulk material: a DFT + U approach
International Nuclear Information System (INIS)
Vu, Nam H; Le, Hieu V; Cao, Thi M; Pham, Viet V; Le, Hung M; Nguyen-Manh, Duc
2012-01-01
The anatase-rutile phase transformation of TiO 2 bulk material is investigated using a density functional theory (DFT) approach in this study. According to the calculations employing the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional with the Vanderbilt ultrasoft pseudopotential, it is suggested that the anatase phase is more energetically stable than rutile, which is in variance with the experimental observations. Consequently, the DFT + U method is employed in order to predict the correct structural stability in titania from electronic-structure-based total energy calculations. The Hubbard U term is determined by examining the band structure of rutile with various values of U from 3 to 10 eV. At U = 5 eV, a theoretical bandgap for rutile is obtained as 3.12 eV, which is in very good agreement with the reported experimental bandgap. Hence, we choose the DFT + U method (with U = 5 eV) to investigate the transformation pathway using the newly-developed solid-state nudged elastic band (ss-NEB) method, and consequently obtain an intermediate transition structure that is 9.794 eV per four-TiO 2 above the anatase phase. When the Ti-O bonds in the transition state are examined using charge density analysis, seven Ti-O bonds (out of 24 bonds in the anatase unit cell) are broken, and this result is in excellent agreement with a previous experimental study (Penn and Banfield 1999 Am. Miner. 84 871-6).
Phase transformations in the B2 phase of Co-rich Co-Al binary alloys
International Nuclear Information System (INIS)
Niitsu, K.; Omori, T.; Nagasako, M.; Oikawa, K.; Kainuma, R.; Ishida, K.
2011-01-01
Research highlights: → Bainitic transformation and a martensite-like structure from B2-CoAl were observed depending on quenching rate. → The phase separation into the metastable A2 + B2 structure was found in the as-quenched B2-CoAl. → The two-phase structure of A2 and B2 was found to show some coercive force after aging under a magnetic field. - Abstract: Phase transformations in the β (B2) phase of Co-21 and -23 at.% Al alloys were examined using transmission electron microscopy, energy dispersive X-ray spectroscopy and differential scanning calorimetry. The microstructures obtained from as-quenched specimens were found to be strongly affected by the quenching condition. While relatively thick sheet-specimens with a lower quenching rate showed bainitic plate precipitates with a fcc structure, a martensite-like structure was observed by optical microscopy in relatively thin specimens with a higher quenching rate. Regardless of the quenching condition, a spinodal-like microstructure composed of A2 and B2 phases was also detected and the A2 phase changed to a metastable hcp phase during further aging.
Phase transformations in the reaction cell of TiNi-based sintered systems
Artyukhova, Nadezhda; Anikeev, Sergey; Yasenchuk, Yuriy; Chekalkin, Timofey; Gunther, Victor; Kaftaranova, Maria; Kang, Ji-Hoon; Kim, Ji-Soon
2018-05-01
The present work addresses the structural-phase state changes of porous TiNi-based compounds fabricated by reaction sintering (RS) of Ti and Ni powders with Co, Mo, and no additives introduced. The study also emphasizes the features of a reaction cell (RC) during the transition from the solid- to liquid-phase sintering. Mechanisms of phase transformations occurring in the solid phase, involving the low-melting Ti2Ni phase within the RC, have been highlighted. Also, the intermediate Ti2Ni phase had a crucial role to provide both the required RS behavior and modified phase composition of RS samples, and besides, it is found to be responsible for the near-equiatomic TiNi saturation of the melt. Both cobalt and molybdenum additives are shown to cause additional structuring of the transition zone (TZ) at the Ti2Ni‑TiNi interface and broadening of this zone. The impact of Co and Mo on the Ti2Ni phase is evident through fissuring of this phase layer, which is referred to solidified stresses increased in the layer due to post-alloying defects in the structure.
International Nuclear Information System (INIS)
Boysen, H.; Frey, F.
1991-01-01
The tetragonal (t) to monoclinic (m) transformation in pure ZrO 2 was investigated by neutron powder diffraction at temperatures between 1900 K and room temperature. The results of a Rietveld analysis are compared with a previous investigation of the m → t transformation. The t → m transformation takes place near 1200 K (implaying a hysteresis of 300 K) and in a much smaller interval (about 150 K compared with about 600 K in the m → t case). There are no indications of a two-stage process as found for the m → t transformation. The structural parameters of the m phase depend only on temperature while those of the t phase differ at the same temperatures for the forward and reverse transformation. The temperature dependence of the lattice constants suggests an orientational relationship a t parallela m * and c t parallelb m . There are no macrostrains whereas the overall microstrain behaviour is similar in both cases, viz. the large microstrains present in both phases are released within the transformation regime. An analysis of temperature factors and diffuse background suggest dynamical disorder in the t phase and static disorder in the m phase. (orig.)
Non-isothermal kinetic analysis on the phase transformations of Fe–Co–V alloy
International Nuclear Information System (INIS)
Hasani, S.; Shamanian, M.; Shafyei, A.; Behjati, P.; Szpunar, J.A.
2014-01-01
Highlights: • We investigated, occurrence of different phase transformations in a FeCo- 7.15%wt V alloy upon heating to 1200 °C. • We investigated, the determination of the activation energy for these phase transformations by using five isoconversional methods. • We investigated, the calculation of the empirical kinetic triplets by using the invariant kinetic parameters method and fitting model. - Abstract: In this study, occurrence of different phase transformations was investigated in a FeCo-7 wt% V alloy upon heating to 1200 °C by the dilatometry method at different heating rates (5, 10, and 15 °C min −1 ). It was found that four phase transformations (including B2-type atomic ordering in α phase, first stage of polymorphic transformation (α → α r + γ), ordering to disordering, and second stage of polymorphic transformation (α r → γ) occur in this alloy up to 1200 °C. Two isoconversional methods, as Starink and Friedman, were used to determine variation of the activation energy with temperature, E(T). Moreover, the empirical kinetic triplets (E, A, and g(α)) were calculated by the invariant kinetic parameters (IKP) method and fitting model
Macroscopic Quantum States and Quantum Phase Transition in the Dicke Model
International Nuclear Information System (INIS)
Lian Jin-Ling; Zhang Yuan-Wei; Liang Jiu-Qing
2012-01-01
The energy spectrum of Dicke Hamiltonians with and without the rotating wave approximation for an arbitrary atom number is obtained analytically by means of the variational method, in which the effective pseudo-spin Hamiltonian resulting from the expectation value in the boson-field coherent state is diagonalized by the spin-coherent-state transformation. In addition to the ground-state energy, an excited macroscopic quantum-state is found corresponding to the south- and north-pole gauges of the spin-coherent states, respectively. Our results of ground-state energies in exact agreement with various approaches show that these models exhibit a zero-temperature quantum phase transition of the second order for any number of atoms, which was commonly considered as a phenomenon of the thermodynamic limit with the atom number tending to infinity. The critical behavior of the geometric phase is analyzed. (general)
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 (LiAlSiO_{4}), 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
International Nuclear Information System (INIS)
Cheng, Wei-Chun; Cheng, Chih-Yao; Hsu, Chia-Wei; Laughlin, David E.
2015-01-01
Fe–C–Mn–Al steels have the potential to substitute for commercial Ni–Cr stainless steels. For the development of Fe–C–Mn–Al stainless steels, phase transformations play an important role. Our methods of studying the phase transformations of the steel include heating, cooling, and/or annealing. The results of our study show that spinodal decomposition, an atomic ordering reaction and the transformation of the L1 2 phase to kappa-carbide occur in the Fe–C–Mn–Al steel. After cooling, the austenite decomposes by the spinodal mechanism into solute-lean and solute-rich austenite phases. The solute-rich austenite phase also transforms into the L1 2 phase via the ordering reaction upon cooling to lower temperatures. After quenching and prolonged annealing, the L1 2 phase grows in the austenite and finally transforms into kappa-carbide. This L1 2 phase to kappa-carbide transformation has not been observed previously
Completion of a high efficiency ultralarge capacity three-phase transformer
International Nuclear Information System (INIS)
Maejima, Masaaki; Maruyama, Katsuya; Fukuda, Teruo.
1986-01-01
As for the boosting transformers for thermal and nuclear power stations, at present the ultralarge capacity transformers of 1000 - 1200 MVA class are the main, and particularly in nuclear power, accompanying the development of improved type BWRs and the rise of system stability, there is the tendency toward further large capacity and large size. Consequently, reflecting the recent rise of energy cost, the demand of energy conservation and the reduction of required sites heightened largely as well as the high reliability. In order to meet these demands, Hitachi Ltd. has established the technology of changing to iron machines such as ultralarge iron cores and ultralarge capacity undivided disk windings using the latest design and manufacture techniques were applied to the 525 kV, 1200 MVA transformer for No.4 plant in Fukushima No.2 Nuclear Power Station, Tokyo Electric Power Co., Inc., thus a three-phase transformer of the highest level, high efficiency and ultralarge capacity was completed. In this paper, the outline of this transformer and the test for verifying its reliability are described. The technical change of large capacity three-phase transformers, the specifications, construction, manufacture, reliability test and the effect of modification of this transformer, and the expansion of application to the next generation ultralarge capacity transformers are reported. (Kako, I.)
International Nuclear Information System (INIS)
Amram, D.; Klinger, L.; Rabkin, E.
2013-01-01
Sub-micrometer-sized particles of Au–Fe alloys were obtained by solid-state dewetting of single-crystalline Au–Fe bilayer films, deposited on c-plane sapphire (α-Al 2 O 3 ) substrates. Depending on the annealing parameters, precipitation of an Fe-rich phase occurred on the side facets of the particles in an interface-limited reaction. Based on the literature values of surface and interface energies in the system, the precipitates were expected to grow inside the Au(Fe) particles, resulting in an (Fe) core–(Au) shell morphology. However, more complex, time-dependent precipitate morphologies were observed, with faceted Fe-rich precipitates attached to the parent faceted Au-rich particles of the same height being dominant at the last stages of the transformation. Our high-resolution transmission electron microscopy observations revealed a nanometric segregation layer of Au on the surface of Fe-rich particles and at their interface with sapphire. This segregation layer modified the surface and interface energies of the Fe-rich particles. A thermodynamic transformation model based on the concept of weighted mean curvature was developed, describing the kinetics of precipitations and morphology evolution of the particles during the dewetting process. Employing the values of surface and interface energies modified by segregation resulted in a good qualitative agreement between theory and experiment
Basak, Anup; Levitas, Valery I.
2018-04-01
A thermodynamically consistent, novel multiphase phase field approach for stress- and temperature-induced martensitic phase transformations at finite strains and with interfacial stresses has been developed. The model considers a single order parameter to describe the austenite↔martensitic transformations, and another N order parameters describing N variants and constrained to a plane in an N-dimensional order parameter space. In the free energy model coexistence of three or more phases at a single material point (multiphase junction), and deviation of each variant-variant transformation path from a straight line have been penalized. Some shortcomings of the existing models are resolved. Three different kinematic models (KMs) for the transformation deformation gradient tensors are assumed: (i) In KM-I the transformation deformation gradient tensor is a linear function of the Bain tensors for the variants. (ii) In KM-II the natural logarithms of the transformation deformation gradient is taken as a linear combination of the natural logarithm of the Bain tensors multiplied with the interpolation functions. (iii) In KM-III it is derived using the twinning equation from the crystallographic theory. The instability criteria for all the phase transformations have been derived for all the kinematic models, and their comparative study is presented. A large strain finite element procedure has been developed and used for studying the evolution of some complex microstructures in nanoscale samples under various loading conditions. Also, the stresses within variant-variant boundaries, the sample size effect, effect of penalizing the triple junctions, and twinned microstructures have been studied. The present approach can be extended for studying grain growth, solidifications, para↔ferro electric transformations, and diffusive phase transformations.
Energy Technology Data Exchange (ETDEWEB)
Wang, H., E-mail: wanghm@lanl.gov [Materials Science and Technology, Los Alamos National Laboratory, Los Alamos, NM (United States); Jeong, Y. [Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD (United States); Clausen, B.; Liu, Y.; McCabe, R.J. [Materials Science and Technology, Los Alamos National Laboratory, Los Alamos, NM (United States); Barlat, F. [Graduate Institute of Ferrous Technology, POSTECH (Korea, Republic of); Tomé, C.N. [Materials Science and Technology, Los Alamos National Laboratory, Los Alamos, NM (United States)
2016-01-01
The present work integrates in-situ neutron diffraction, electron backscatter diffraction and crystal plasticity modeling to investigate the effect of martensitic phase transformation on the behavior of 304 stainless steel under uniaxial tension. The macroscopic stress strain response, evolution of the martensitic phase fraction, texture evolution of each individual phase, and internal elastic strains were measured at room temperature and at 75 °C. Because no martensitic transformation was observed at 75 °C, the experimental results at 75 °C were used as a reference to quantify the effect of formed martensitic phase on the behavior of 304 stainless steel at room temperature. A crystallographic phase transformation model was implemented into an elastic–viscoplastic self-consistent framework. The phase transformation model captured the macroscopic stress strain response, plus the texture and volume fraction evolution of austenite and martensite. The model also predicts the internal elastic strain evolution with loading in the austenite, but not in the martensite. The results of this work highlight the mechanisms that control phase transformation and the sensitivity of modeling results to them, and point out to critical elements that still need to be incorporated into crystallographic phase transformation models to accurately describe the internal strain evolution during phase transformation.
Multi-stage phase retrieval algorithm based upon the gyrator transform.
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.
Multi-stage phase retrieval algorithm based upon the gyrator transform
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...
International Nuclear Information System (INIS)
Sutrakar, Vijay Kumar; Roy Mahapatra, D.
2011-01-01
A novel size dependent FCC (face-centered-cubic) → HCP (hexagonally-closed-pack) phase transformation and stability of an initial FCC zirconium nanowire are studied. FCC zirconium nanowires with cross-sectional dimensions 20 Å, in which surface stresses are not enough to drive the phase transformation, show meta-stability. In such a case, an external kinetic energy in the form of thermal heating is required to overcome the energy barrier and achieve FCC → HCP phase transformation. The FCC-HCP transition pathway is also studied using Nudged Elastic Band (NEB) method, to further confirm the size dependent stability/metastability of Zr nanowires. We also show size dependent critical temperature, which is required for complete phase transformation of a metastable-FCC nanowire.
Neutron guide geometries for homogeneous phase space volume transformation
Energy Technology Data Exchange (ETDEWEB)
Stüßer, N., E-mail: stuesser@helmholtz-berlin.de; Bartkowiak, M.; Hofmann, T.
2014-06-01
We extend geometries for recently developed optical guide systems that perform homogeneous phase space volume transformations on neutron beams. These modules allow rotating beam directions and can simultaneously compress or expand the beam cross-section. Guide systems combining these modules offer the possibility to optimize ballistic guides with and without direct view on the source and beam splitters. All systems are designed for monochromatic beams with a given divergence. The case of multispectral beams with wavelength-dependent divergence distributions is addressed as well. - Highlights: • Form invariant volume transformation in phase space. • Geometrical approach. • Ballistic guide, beam splitter, beam bender.
Neutron guide geometries for homogeneous phase space volume transformation
International Nuclear Information System (INIS)
Stüßer, N.; Bartkowiak, M.; Hofmann, T.
2014-01-01
We extend geometries for recently developed optical guide systems that perform homogeneous phase space volume transformations on neutron beams. These modules allow rotating beam directions and can simultaneously compress or expand the beam cross-section. Guide systems combining these modules offer the possibility to optimize ballistic guides with and without direct view on the source and beam splitters. All systems are designed for monochromatic beams with a given divergence. The case of multispectral beams with wavelength-dependent divergence distributions is addressed as well. - Highlights: • Form invariant volume transformation in phase space. • Geometrical approach. • Ballistic guide, beam splitter, beam bender
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
Phase diagrams and phase transformations in 'Zirlo': Zr-1% Sn-1% Nb (0,1% Fe)
International Nuclear Information System (INIS)
Canay, Marcelo G.
1996-01-01
The transformation temperatures and the phases present in Zr-base alloys with 1% at. Nb, (0,1 and 0,8) % at. Sn, (0,2 and 0,7) % at. Fe and 600 and 6000 ppmat O were studied it the present work. α ↔ α + β and α + β ↔ β transformation temperatures were determined by means of electrical resistivity variation v. temperature measurements. Scanning Electronic Microscopy (SEM) and quantitative microanalysis techniques were used in order to study the microstructures and chemical composition of the phases appearing at three different annealing temperatures (600, 800 and 850 C degrees). Samples annealed at 600 C degrees were also analyzed by X-ray diffraction methods. Oxygen influence turned out to increase the α + β ↔ β transformation temperature, while iron produced a decrease in the α ↔ α + β one. Comparing with literature data we concluded that tin increases the α + β ↔ β and decreases the α ↔ α + β temperatures while niobium decreases both. The samples annealed at 800 and 850 C degrees, showed two different microstructures of α-phases: α-plates which correspond to the α-phases portion at the annealing temperature and α-Widmanstaetten like structure formed from the β-phase when quenching the sample. A Widmanstaetten like structure consisting in α phase plates with a supersaturated (in Nb and Fe) α phase (α s ) in between was observed at 600 C degrees. It is in this α s phase the different intermetallic phases could precipitate. We were only able to identify Zr 3 Fe in two alloys with low tin and oxygen content. (author)
On mechanism of substructure formation in SmS during isomorphic phase transformations
International Nuclear Information System (INIS)
Aptekar', I.L.; Ivanov, V.I.; Tonkov, E.Yu.; Shmyt'ko, I.M.
1986-01-01
X-ray diffraction study of substructure characteristics of SmS samples subjected to treatment at different temrerature and pressure in media with different viscosity ( graphite, silicon oil) for realization of P-M-P transformations ( p-semiconductor phase, M - high pressure phase) is performed. It is assumed that with M - phase formation P - matrix volume relaxation delays, therefore the new phase particles occupy smaller volume than the initial matrix which causes the M - phase disorientation. The difference between the phase transformation rate and deformation rate under the pressure in media with various viscosity results in arising different substructural characteristics
Unconventional transformation of spin Dirac phase across a topological quantum phase transition
Xu, Su-Yang; Neupane, Madhab; Belopolski, Ilya; Liu, Chang; Alidoust, Nasser; Bian, Guang; Jia, Shuang; Landolt, Gabriel; Slomski, Batosz; Dil, J. Hugo; Shibayev, Pavel P.; Basak, Susmita; Chang, Tay-Rong; Jeng, Horng-Tay; Cava, Robert J.; Lin, Hsin; Bansil, Arun; Hasan, M. Zahid
2015-01-01
The topology of a topological material can be encoded in its surface states. These surface states can only be removed by a bulk topological quantum phase transition into a trivial phase. Here we use photoemission spectroscopy to image the formation of protected surface states in a topological insulator as we chemically tune the system through a topological transition. Surprisingly, we discover an exotic spin-momentum locked, gapped surface state in the trivial phase that shares many important properties with the actual topological surface state in anticipation of the change of topology. Using a spin-resolved measurement, we show that apart from a surface bandgap these states develop spin textures similar to the topological surface states well before the transition. Our results offer a general paradigm for understanding how surface states in topological phases arise from a quantum phase transition and are suggestive for the future realization of Weyl arcs, condensed matter supersymmetry and other fascinating phenomena in the vicinity of a quantum criticality. PMID:25882717
Pressure-induced ferroelectric to antiferroelectric phase transformation in porous PZT95/5 ceramics
International Nuclear Information System (INIS)
Zeng, T.; Dong, X.L.; Chen, X.F.; Yao, C.H.; He, H.L.
2007-01-01
The hydrostatic pressure-induced ferroelectric to antiferroelectric (FE-AFE) phase transformation of PZT95/5 ceramics was investigated as a function of porosity, pore shape and pore size. FE-AFE phase transformations were more diffuse and occurred at lower hydrostatic pressures with increasing porosity. The porous PZT95/5 ceramics with spherical pores exhibited higher transformation pressures than those with irregular pores. Moreover, FE-AFE phase transformations of porous PZT95/5 ceramics with polydisperse irregular pores were more diffuse than those of porous PZT95/5 ceramics with monodisperse irregular pores. The relation between pore structure and hydrostatic pressure-induced FE-AFE transformation was established according to stress concentration theory. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Phase transformations in an ascending adiabatic mixed-phase cloud volume
Pinsky, M.; Khain, A.; Korolev, A.
2015-04-01
Regimes of liquid-ice coexistence that may form in an adiabatic parcel ascending at constant velocity at freezing temperatures are investigated. Four zones with different microphysical structures succeeding one another along the vertical direction have been established. On the basis of a novel balance equation, analytical expressions are derived to determine the conditions specific for each of these zones. In particular, the necessary and sufficient conditions for formation of liquid water phase within an ascending parcel containing only ice particles are determined. The results are compared to findings reported in earlier studies. The role of the Wegener-Bergeron-Findeisen mechanism in the phase transformation is analyzed. The dependence of the phase relaxation time on height in the four zones is investigated on the basis of a novel analytical expression. The results obtained in the study can be instrumental for analysis and interpretation of observed mixed-phase clouds.
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.
Directory of Open Access Journals (Sweden)
Swapnil Sourav
2016-01-01
Full Text Available Phase transform properties of Indium Selenide (In2Se3 based Random Access Memory (RAM have been explored in this paper. Phase change random access memory (PCRAM is an attractive solid-state nonvolatile memory that possesses potential to meet various current technology demands of memory design. Already reported PCRAM models are mainly based upon Germanium-Antimony-Tellurium (Ge2Sb2Te5 or GST materials as their prime constituents. However, PCRAM using GST material lacks some important memory attributes required for memory elements such as larger resistance margin between the highly resistive amorphous and highly conductive crystalline states in phase change materials. This paper investigates various electrical and compositional properties of the Indium Selenide (In2Se3 material and also draws comparison with its counterpart mainly focusing on phase transform properties. To achieve this goal, a SPICE model of In2Se3 based PCRAM model has been reported in this work. The reported model has been also validated to act as a memory cell by associating it with a read/write circuit proposed in this work. Simulation results demonstrate impressive retentivity and low power consumption by requiring a set pulse of 208 μA for a duration of 100 μs to set the PCRAM in crystalline state. Similarly, a reset pulse of 11.7 μA for a duration of 20 ns can set the PCRAM in amorphous state. Modeling of In2Se3 based PCRAM has been done in Verilog-A and simulation results have been extensively verified using SPICE simulator.
High-temperature phase transformation in Cr added TiAl base alloy
Energy Technology Data Exchange (ETDEWEB)
Abe, E.; Niinobe, K.; Nobuki, M.; Nakamura, M.; Tsujimoto, T.
1999-07-01
The authors have investigated a microstructure evolution of a Ti-48Al-3.5Cr (in at.%) alloy at high-temperatures ({gt} 1,473K). In the alloy annealed at 1673K for 1.8ks, followed by air-cooling, a characteristic microstructure with a feathery fashion was uniformly formed. From a cooling-rate-controlling study, it was found that formation of the feathery structure is accomplished during continuous cooling from 1673K to 1573K, within the {alpha} + {gamma} two-phase region. Transmission electron microscopy revealed that the feathery structure is composed of lamellar colonies (5--10{micro}m) which are crystallographically tilted slightly (a few degree) with their neighbors. A surprising fact is that lamellae in each colony are mostly the {gamma} phase with few {alpha}{sub 2} phase less than 5% in volume. This suggests that the feathery structure is a metastable product and has not resulted from the {alpha} {r{underscore}arrow} {alpha} + {gamma} transformation above 1,573 K. Instead, the feathery structure formation should be attributed to the non-equilibrium {alpha} {r{underscore}arrow} {gamma} transformation which occurs at high-temperatures with a small degree of supercooling. The authors discuss this interesting phase transformation in terms of the {alpha} {r{underscore}arrow} {gamma} massive transformation, based on the continuous-cooling-transformation (CCT) diagram constructed for the present alloy.
International Nuclear Information System (INIS)
Tay, B A
2011-01-01
We use a generalized Bogoliubov transformation to construct a set of transformed occupation number states of the harmonic oscillator in the Liouville space. General expressions for the expansion coefficients of these states in the bare number basis are obtained and the properties of these states investigated. The transformation is non-dynamical in nature and divides the transformed basis into disconnected correlation subspaces under the transformation. The basis is complete and orthonormal. Elements of the basis are in general mixed states, and the state with the lowest number indices is the thermal vacuum. Since the Kossakowski-Lindblad (KL) equation remains form invariant under the same transformation, the transformation parameter can be identified to the thermal parameter of the master equation. The transformed states then acquire thermal property through this connection. We also work out the explicit expressions of the transformation matrices between the transformed states and the eigenstates of the KL equation for different temperatures.
Zhou, Junhe; Wu, Jianjie; Hu, Qinsong
2018-02-05
In this paper, we propose a novel tunable unitary transformer, which can achieve arbitrary discrete unitary transforms. The unitary transformer is composed of multiple sections of multi-core fibers with closely aligned coupled cores. Phase shifters are inserted before and after the sections to control the phases of the waves in the cores. A simple algorithm is proposed to find the optimal phase setup for the phase shifters to realize the desired unitary transforms. The proposed device is fiber based and is particularly suitable for the mode division multiplexing systems. A tunable mode MUX/DEMUX for a three-mode fiber is designed based on the proposed structure.
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
Kinetic boundaries and phase transformations of ice i at high pressure
Wang, Yu; Zhang, Huichao; Yang, Xue; Jiang, Shuqing; Goncharov, Alexander F.
2018-01-01
Raman spectroscopy in diamond anvil cells has been employed to study phase boundaries and transformation kinetics of H2O ice at high pressures up to 16 GPa and temperatures down to 15 K. Ice i formed at nearly isobaric cooling of liquid water transforms on compression to high-density amorphous (HDA) ice at 1.1-3 GPa at 15-100 K and then crystallizes in ice vii with the frozen-in disorder (ice vii') which remains stable up to 14.1 GPa at 80 K and 15.9 GPa at 100 K. Unexpectedly, on decompression of ice vii', it transforms to ice viii in its domain of metastability, and then it relaxes into low-density amorphous (LDA) ice on a subsequent pressure release and warming up. On compression of ice i at 150-170 K, ice ix is crystallized and no HDA ice is found; further compression of ice ix results in the sequential phase transitions to stable ices vi and viii. Cooling ice i to 210 K at 0.3 GPa transforms it to a stable ice ii. Our extensive investigations provide previously missing information on the phase diagram of water, especially on the kinetic paths that result in formation of phases which otherwise are not accessible; these results are keys for understanding the phase relations including the formation of metastable phases. Our observations inform on the ice modifications that can occur naturally in planetary environments and are not accessible for direct observations.
Solid state phase change materials for thermal energy storage in passive solar heated buildings
Benson, D. K.; Christensen, C.
1983-11-01
A set of solid state phase change materials was evaluated for possible use in passive solar thermal energy storage systems. The most promising materials are organic solid solutions of pentaerythritol, pentaglycerine and neopentyl glycol. Solid solution mixtures of these compounds can be tailored so that they exhibit solid-to-solid phase transformations at any desired temperature within the range from less than 25 deg to 188 deg. Thermophysical properties such as thermal conductivity, density and volumetric expansion were measured. Computer simulations were used to predict the performance of various Trombe wall designs incorporating solid state phase change materials. Optimum performance was found to be sensitive to the choice of phase change temperatures and to the thermal conductivity of the phase change material. A molecular mechanism of the solid state phase transition is proposed and supported by infrared spectroscopic evidence.
Multipartite entangled quantum states: Transformation, Entanglement monotones and Application
Cui, Wei
Entanglement is one of the fundamental features of quantum information science. Though bipartite entanglement has been analyzed thoroughly in theory and shown to be an important resource in quantum computation and communication protocols, the theory of entanglement shared between more than two parties, which is called multipartite entanglement, is still not complete. Specifically, the classification of multipartite entanglement and the transformation property between different multipartite states by local operators and classical communications (LOCC) are two fundamental questions in the theory of multipartite entanglement. In this thesis, we present results related to the LOCC transformation between multipartite entangled states. Firstly, we investigate the bounds on the LOCC transformation probability between multipartite states, especially the GHZ class states. By analyzing the involvement of 3-tangle and other entanglement measures under weak two-outcome measurement, we derive explicit upper and lower bound on the transformation probability between GHZ class states. After that, we also analyze the transformation between N-party W type states, which is a special class of multipartite entangled states that has an explicit unique expression and a set of analytical entanglement monotones. We present a necessary and sufficient condition for a known upper bound of transformation probability between two N-party W type states to be achieved. We also further investigate a novel entanglement transformation protocol, the random distillation, which transforms multipartite entanglement into bipartite entanglement ii shared by a non-deterministic pair of parties. We find upper bounds for the random distillation protocol for general N-party W type states and find the condition for the upper bounds to be achieved. What is surprising is that the upper bounds correspond to entanglement monotones that can be increased by Separable Operators (SEP), which gives the first set of
Energy landscape for martensitic phase transformation in shape memory NiTi
International Nuclear Information System (INIS)
Kibey, S.; Sehitoglu, H.; Johnson, D.D.
2009-01-01
First-principles calculations are presented for parent B2 phase and martensitic B19 and B19' phases in NiTi. The results indicate that both B19 and B19' are energetically more stable than the parent B2 phase. By means of ab initio density functional theory, the complete distortion-shuffle energy landscape associated with B2 → B19 transformation in NiTi is then determined. In addition to accounting for the Bain-type deformation through the Cauchy-Born rule, the study explicitly accounts for the shuffle displacements experienced by the internal ions in NiTi. The energy landscape allows the energy barrier associated with the B2 → B19 transformation pathway to be identified. The results indicate that a barrier of 0.48 mRyd atom -1 (relative to the B2 phase) must be overcome to transform the parent B2 NiTi to orthorhombic B19 martensite
Investigation of phase transformations in ductile cast iron of differential scanning calorimetry
International Nuclear Information System (INIS)
Przeliorz, R; Piatkowski, J
2011-01-01
The effect of heating rate on phase transformations to austenite range in ductile cast iron of the EN-GJS-450-10 grade was investigated. For studies of phase transformations, the technique of differential scanning calorimetry (DSC) was used. Micro structure was examined by optical microscopy. The calorimetric examinations have proved that on heating three transformations occur in this grade of ductile iron, viz. magnetic transformation at the Curie temperature, pearlite→austenite transformation and ferrite→austenite transformation. An increase in the heating rate shifts the pearlite→austenite and ferrite→austenite transformations to higher temperature range. At the heating rate of 5 and 15 deg. C min -1 , local extrema have been observed to occur: for pearlite→austenite transformation at 784 deg. C and 795 deg. C, respectively, and for ferrite+ graphite →austenite transformation at 805 deg. C and 821 deg. C, respectively. The Curie temperature of magnetic transformation was extrapolated to a value of 740 deg. C. Each transformation is related with a specific thermal effect. The highest value of enthalpy is accompanying the ferrite→austenite transformation, the lowest occurs in the case of pearlite→austenite transformation.
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.
New transformation mechanism for a zinc-blende to rocksalt phase transformation in MgS
International Nuclear Information System (INIS)
Durandurdu, Murat
2009-01-01
The stability of the zinc-blende structured MgS is studied using a constant pressure ab initio molecular dynamics technique. A phase transition into a rocksalt structure is observed through the simulation. The zinc-blende to rocksalt phase transformation proceeds via two rhombohedral intermediate phases within R3m (No:160) and R3-barm (No:166) symmetries and does not involve any bond breaking. This mechanism is different from the previously observed mechanism in molecular dynamics simulations. (fast track communication)
Energy Technology Data Exchange (ETDEWEB)
Escarela-Perez, R. [Departamento de Energia, Universidad Autonoma Metropolitana, Av. San Pablo 180, Col. Reynosa, C.P. 02200, Mexico D.F. (Mexico); Kulkarni, S.V. [Electrical Engineering Department, Indian Institute of Technology, Bombay (India); Melgoza, E. [Instituto Tecnologico de Morelia, Av. Tecnologico 1500, Morelia, Mich., C.P. 58120 (Mexico)
2008-11-15
A six-port impedance network for a three-phase transformer is obtained from a 3D time-harmonic finite-element (FE) model. The network model properly captures the eddy current effects of the transformer tank and frame. All theorems and tools of passive linear networks can be used with the multi-port model to simulate several important operating conditions without resorting anymore to computationally expensive 3D FE simulations. The results of the network model are of the same quality as those produced by the FE program. Although the passive network may seem limited by the assumption of linearity, many important transformer operating conditions imply unsaturated states. Single-phase load-loss measurements are employed to demonstrate the effectiveness of the network model and to understand phenomena that could not be explained with conventional equivalent circuits. In addition, formal deduction of novel closed-form formulae is presented for the calculation of the leakage impedance measured at the high and low voltage sides of the transformer. (author)
Energy Technology Data Exchange (ETDEWEB)
Guo, Liqiu; Yang, Binjie; Qin, Sixiao [University of Science and Technology Beijing (China). Corrosion and Protection Center
2016-02-15
This paper demonstrates the hydrogen-induced phase transformation and the associated pitting nucleation sites of 2507 duplex stainless steel using scanning Kelvin probe force microscopy and magnetic force microscopy. The low potential sites in Volta potential images, which are considered as the pitting nucleation sites, are strongly dependent on the hydrogen-induced phase transformation. They firstly initiate on the magnetic martensite laths in the austenite phase or at the ferrite/austenite boundaries, and then appear near the needle-shaped microtwins in the ferrite phase, because of the difference in physicochemical properties of hydrogen-induced phase transformation microstructures.
Effect of grinding and polishing on near-surface phase transformations in zirconia
International Nuclear Information System (INIS)
Reed, J.S.; Lejus, A.M.
1977-01-01
The transformation of near-surface material on grinding and polishing has been investigated in sintered zirconia of 1 μm grain size and 99 percent density containing 4.5 and 7.0 mole percent Y 2 O 3 . Rough wet and dry grinding transformed about 20 percent cubic phase into 18 percent tetragonal and 2 percent monoclinic in material initially 47 percent cubic and 53 percent tetragonal (4.5 mole percent Y 2 O 3 ) but no change of phase in material that was fully cubic (7.0 mole percent Y 2 O 3 ). Annealing and polishing reduced lattice strain but only polishing reduced the concentration of monoclinic and tetragonal phases. Microhardness studies indicated that lattice strain and the phase transformations increased the penetration hardness to a depth of about 4 μm
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
Metallographic Study of the Isothermal Transformation of Beta Phase in Zircaloy-2
Energy Technology Data Exchange (ETDEWEB)
Oestberg, G
1960-06-15
Observations of the structure of commercial zircaloy-2 have been made in the microscope showing that the high temperature beta phase is transformed isothermally at lower temperatures into alpha plus secondary precipitate. The alpha occurs mainly as Widmanstaetten plates developed by a shear mechanism. The secondary precipitate is formed from the beta - alpha structure at the phase boundary between these phases. This precipitation of particles of secondary phase occurs on account of a eutectoid reaction, alpha also being formed. A time-temperature transformation diagram has been constructed from the observations.
The correlation of local deformation and stress-assisted local phase transformations in MMC foams
Energy Technology Data Exchange (ETDEWEB)
Berek, H., E-mail: harry.berek@ikgb.tu-freiberg.de [TU Bergakademie Freiberg, Agricolastraße 17, D-09599 Freiberg (Germany); Ballaschk, U.; Aneziris, C.G. [TU Bergakademie Freiberg, Agricolastraße 17, D-09599 Freiberg (Germany); Losch, K.; Schladitz, K. [Fraunhofer ITWM, Fraunhoferplatz 1, D-67663 Kaiserslautern (Germany)
2015-09-15
Cellular structures are of growing interest for industry, and are of particular importance for lightweight applications. In this paper, a special case of metal matrix composite foams (MMCs) is investigated. The investigated foams are composed of austenitic steel exhibiting transformation induced plasticity (TRIP) and magnesia partially stabilized zirconia (Mg-PSZ). Both components exhibit martensitic phase transformation during deformation, thus generating the potential for improved mechanical properties such as strength, ductility, and energy absorption capability. The aim of these investigations was to show that stress-assisted phase transformations within the ceramic reinforcement correspond to strong local deformation, and to determine whether they can trigger martensitic phase transformations in the steel matrix. To this end, in situ interrupted compression experiments were performed in an X-ray computed tomography device (XCT). By using a recently developed registration algorithm, local deformation could be calculated and regions of interest could be defined. Corresponding cross sections were prepared and used to analyze the local phase composition by electron backscatter diffraction (EBSD). The results show a strong correlation between local deformation and phase transformation. - Graphical abstract: Display Omitted - Highlights: • In situ compressive deformation on MMC foams was performed in an XCT. • Local deformation fields and their gradient amplitudes were estimated. • Cross sections were manufactured containing defined regions of interest. • Local EBSD phase analysis was performed. • Local deformation and local phase transformation are correlated.
The correlation of local deformation and stress-assisted local phase transformations in MMC foams
International Nuclear Information System (INIS)
Berek, H.; Ballaschk, U.; Aneziris, C.G.; Losch, K.; Schladitz, K.
2015-01-01
Cellular structures are of growing interest for industry, and are of particular importance for lightweight applications. In this paper, a special case of metal matrix composite foams (MMCs) is investigated. The investigated foams are composed of austenitic steel exhibiting transformation induced plasticity (TRIP) and magnesia partially stabilized zirconia (Mg-PSZ). Both components exhibit martensitic phase transformation during deformation, thus generating the potential for improved mechanical properties such as strength, ductility, and energy absorption capability. The aim of these investigations was to show that stress-assisted phase transformations within the ceramic reinforcement correspond to strong local deformation, and to determine whether they can trigger martensitic phase transformations in the steel matrix. To this end, in situ interrupted compression experiments were performed in an X-ray computed tomography device (XCT). By using a recently developed registration algorithm, local deformation could be calculated and regions of interest could be defined. Corresponding cross sections were prepared and used to analyze the local phase composition by electron backscatter diffraction (EBSD). The results show a strong correlation between local deformation and phase transformation. - Graphical abstract: Display Omitted - Highlights: • In situ compressive deformation on MMC foams was performed in an XCT. • Local deformation fields and their gradient amplitudes were estimated. • Cross sections were manufactured containing defined regions of interest. • Local EBSD phase analysis was performed. • Local deformation and local phase transformation are correlated
Surface modification-induced phase transformation of hexagonal close-packed gold square sheets
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.
Surface modification-induced phase transformation of hexagonal close-packed gold square sheets
Fan, Zhanxi; Huang, Xiao; Han, Yu; Bosman, Michel; Wang, Qingxiao; Zhu, Yihan; Liu, Qing; Li, Bing; Zeng, Zhiyuan; Wu, Jumiati; Shi, Wenxiong; Li, Shuzhou; Gan, Chee Lip; Zhang, Hua
2015-01-01
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.
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
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)
Single beam Fourier transform digital holographic quantitative phase microscopy
Energy Technology Data Exchange (ETDEWEB)
Anand, A., E-mail: arun-nair-in@yahoo.com; Chhaniwal, V. K.; Mahajan, S.; Trivedi, V. [Optics Laboratory, Applied Physics Department, Faculty of Technology and Engineering, M.S. University of Baroda, Vadodara 390001 (India); Faridian, A.; Pedrini, G.; Osten, W. [Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart (Germany); Dubey, S. K. [Siemens Technology and Services Pvt. Ltd, Corporate Technology—Research and Technology Centre, Bangalore 560100 (India); Javidi, B. [Department of Electrical and Computer Engineering, U-4157, University of Connecticut, Storrs, Connecticut 06269-2157 (United States)
2014-03-10
Quantitative phase contrast microscopy reveals thickness or height information of a biological or technical micro-object under investigation. The information obtained from this process provides a means to study their dynamics. Digital holographic (DH) microscopy is one of the most used, state of the art single-shot quantitative techniques for three dimensional imaging of living cells. Conventional off axis DH microscopy directly provides phase contrast images of the objects. However, this process requires two separate beams and their ratio adjustment for high contrast interference fringes. Also the use of two separate beams may make the system more vulnerable to vibrations. Single beam techniques can overcome these hurdles while remaining compact as well. Here, we describe the development of a single beam DH microscope providing whole field imaging of micro-objects. A hologram of the magnified object projected on to a diffuser co-located with a pinhole is recorded with the use of a commercially available diode laser and an arrayed sensor. A Fourier transform of the recorded hologram directly yields the complex amplitude at the image plane. The method proposed was investigated using various phase objects. It was also used to image the dynamics of human red blood cells in which sub-micrometer level thickness variation were measurable.
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...
Misfit dislocations and phase transformations in high-T sub c superconducting films
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.
Understanding Strain-Induced Phase Transformations in BiFeO3 Thin Films.
Dixit, Hemant; Beekman, Christianne; Schlepütz, Christian M; Siemons, Wolter; Yang, Yongsoo; Senabulya, Nancy; Clarke, Roy; Chi, Miaofang; Christen, Hans M; Cooper, Valentino R
2015-08-01
Experiments demonstrate that under large epitaxial strain a coexisting striped phase emerges in BiFeO 3 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 BiFeO 3 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.
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
Antiferrodistortive phase transitions and ground state of PZT ceramics
International Nuclear Information System (INIS)
Pandey, Dhananjai
2013-01-01
The ground state of the technologically important Pb(Zr x Ti (1-x) )O 3 , commonly known as PZT, ceramics is currently under intense debate. The phase diagram of this material shows a morphotropic phase boundary (MPB) for x∼0.52 at 300K, across which a composition induced structural phase transition occurs leading to maximization of the piezoelectric properties. In search for the true ground state of the PZT in the MPB region, Beatrix Noheda and coworkers first discovered a phase transition from tetragonal (space group P4mm) to an M A type monoclinic phase (space group Cm) at low temperatures for x=0.52. Soon afterwards, we discovered yet another low temperature phase transition for the same composition in which the M A type (Cm) monoclinic phase transforms to another monoclinic phase with Cc space group. We have shown that the Cm to Cc phase transition is an antiferrodistortive (AFD) transition involving tilting of oxygen octahedra leading to unit cell doubling and causing appearance of superlattice reflections which are observable in the electron and neutron diffraction patterns only and not in the XRD patterns, as a result of which Noheda and coworkers missed the Cc phase in their synchrotron XRD studies at low temperatures. Our findings were confirmed by leading groups using neutron, TEM, Raman and high pressure diffraction studies. The first principles calculations also confirmed that the true ground state of PZT in the MPB region has Cc space group. However, in the last couple of years, the Cc space group of the ground state has become controversial with an alternative proposal of R3c as the space group of the ground state phase which is proposed to coexist with the metastable Cm phase. In order to resolve this controversy, we recently revisited the issue using pure PZT and 6% Sr 2+ substituted PZT, the latter samples show larger tilt angle on account of the reduction in the average cationic radius at the Pb 2+ site. Using high wavelength neutrons and high
A thick-interface model for diffusive and massive phase transformation in substitutional alloys
International Nuclear Information System (INIS)
Svoboda, J.; Vala, J.; Gamsjaeger, E.; Fischer, F.D.
2006-01-01
Based on the application of the thermodynamic extremal principle, a new model for the diffusive and massive phase transformation in multicomponent substitutional alloys is developed. Interfacial reactions such as the rearrangement of the lattice, solute drag and trans-interface diffusion are automatically considered by assigning a finite thickness and a finite mobility to the interface region. As an application of the steady-state solution of the derived evolution equations, the kinetics of the massive γ → α transformation in the Fe-rich Fe-Cr-Ni system is simulated. The thermodynamic properties of the interface may influence significantly the contact conditions at the interface as well as the conditions for the occurrence of the massive transformation and its kinetics. The model is also used for the simulation of the diffusion-induced grain boundary migration in the same system. By application of the model a realistic value for the Gibbs energy per unit interface area is obtained
Effect of phase transformations on laser forming of Ti-6Al-4V alloy
International Nuclear Information System (INIS)
Fan, Y.; Cheng, P.; Yao, Y.L.; Yang, Z.; Egland, K.
2005-01-01
In laser forming, phase transformations in the heat-affected zone take place under steep thermal cycles, and have a significant effect on the flow behavior of Ti-6Al-4V alloy and the laser-forming process. The flow-stress data of a material are generally provided as only dependent on strain, strain rate, and temperature, while phase transformations are determined by both temperature and temperature history. Therefore, effect of phase transformations on the flow behavior of materials in thermomechanical processing is not given necessary considerations. In the present work, both the α→β transformation during heating and the decomposition of β phase, producing martensite α ' or lamellae α dependent on cooling rate, are numerically investigated. The spatial distribution of volume fractions of phases is obtained by coupling thermal and phase transformation kinetic modeling. Consequently, the flow stress of Ti-6Al-4V alloy is calculated by the rule of mixtures based on the phase ratio and the flow stress of each single phase, which is also a function of temperature, strain, and strain rate. According to the obtained flow-stress data, the laser-forming process of Ti-6Al-4V alloy is modeled by finite element method, and the deformation is predicted. A series of carefully controlled experiments are conducted to validate the theoretically predicted results
Equivalence of quantum states under local unitary transformations
International Nuclear Information System (INIS)
Fei Shaoming; Jing Naihuan
2005-01-01
In terms of the analysis of fixed point subgroup and tensor decomposability of certain matrices, we study the equivalence of quantum bipartite mixed states under local unitary transformations. For non-degenerate case an operational criterion for the equivalence of two such mixed bipartite states under local unitary transformations is presented
Energy Technology Data Exchange (ETDEWEB)
Cheng, Wei-Chun, E-mail: weicheng@mail.ntust.edu.tw [Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei 106, Taiwan (China); Cheng, Chih-Yao; Hsu, Chia-Wei [Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei 106, Taiwan (China); Laughlin, David E. [Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA (United States)
2015-08-26
Fe–C–Mn–Al steels have the potential to substitute for commercial Ni–Cr stainless steels. For the development of Fe–C–Mn–Al stainless steels, phase transformations play an important role. Our methods of studying the phase transformations of the steel include heating, cooling, and/or annealing. The results of our study show that spinodal decomposition, an atomic ordering reaction and the transformation of the L1{sub 2} phase to kappa-carbide occur in the Fe–C–Mn–Al steel. After cooling, the austenite decomposes by the spinodal mechanism into solute-lean and solute-rich austenite phases. The solute-rich austenite phase also transforms into the L1{sub 2} phase via the ordering reaction upon cooling to lower temperatures. After quenching and prolonged annealing, the L1{sub 2} phase grows in the austenite and finally transforms into kappa-carbide. This L1{sub 2} phase to kappa-carbide transformation has not been observed previously.
International Nuclear Information System (INIS)
Lahoche, L.; Universite de Technologie de Compiegne; Lorman, V.; Roelandt, J.M.; Rochal, S.B.
1996-01-01
A model is proposed for the structural transformation and corresponding induced deformation in physical three-dimensional interface of the metal-oxide system. The thermodynamical and elastic state of the system is described by the Landau-Ginzbourg free energy. Calculated theoretical phase diagram shows several different types of isothermal growth processes. The model is applied to the case of the oxidation of the (001) Fe surface. (orig.)
International Nuclear Information System (INIS)
Lakhani, Archana; Kushwaha, Pallavi; Rawat, R; Kumar, Kranti; Banerjee, A; Chaddah, P
2010-01-01
Glass-like arrest has recently been reported in various magnetic materials. As in structural glasses, the kinetics of a first order transformation is arrested while retaining the higher entropy phase as a non-ergodic state. We show visual mesoscopic evidence of the irreversible transformation of the arrested antiferromagnetic-insulating phase in Pr 0.5 Ca 0.5 Mn 0.975 Al 0.025 O 3 to its equilibrium ferromagnetic-metallic phase with an isothermal increase of magnetic field, similar to its iso-field transformation on warming. The magnetic field dependence of the non-equilibrium to equilibrium transformation temperature is shown to be governed by Le Chatelier's principle. (fast track communication)
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.
Energy Technology Data Exchange (ETDEWEB)
Paul, Arya; Bhattacharya, Jayee; Sengupta, Surajit [S N Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Calcutta 700 098 (India); Rao, Madan [Raman Research Institute, C V Raman Avenue, Bangalore 560 080 (India)
2008-09-10
We study the nucleation dynamics of a model solid state transformation and the criterion for microstructure selection. Using a molecular dynamics (MD) simulation, we had shown that the dynamics of the solid is accompanied by the creation of transient non-affine zones (NAZ), which evolve with the rapidly moving transformation front. Guided by our MD results, we formulate a dynamical continuum theory of solid state transformation, which couples the elastic strain to the non-affine deformation. We demonstrate that our elastoplastic description recovers all qualitative features of the MD simulation. We construct a dynamical phase diagram for microstructure selection, including regimes where martensite or ferrite obtains, in addition to making several testable predictions.
International Nuclear Information System (INIS)
Firstov, G.S.; Koval, Yu.N.; Van Humbeeck, J.; Portier, R.; Vermaut, P.; Ochin, P.
2006-01-01
The present paper focuses on the phase transformations during crystallization of the melt-spun Zr-29.56 at.% Cu-19.85 at.% Ni high-temperature shape memory alloy (HTSMA). This alloy exhibits a martensitic transformation in the bulk polycrystalline state at temperatures above crystallization of the metallic glass with the same composition. The crystallization kinetics were investigated by differential scanning calorimetry. The intermediate and final products of crystallization for this HTSMA were studied by means of transmission electron microscopy. The chain of the transformations starting from crystallization and ending at martensitic transformation will be described. Perspectives of the thin film production of Zr-based HTSMA will be discussed
Energy Technology Data Exchange (ETDEWEB)
Firstov, G.S. [Institute for Metal Physics, National Academy of Sciences, 36 Vernadsky blvd., UA-03680, Kiev-142 (Ukraine)]. E-mail: gfirst@imp.kiev.ua; Koval, Yu.N. [Institute for Metal Physics, National Academy of Sciences, 36 Vernadsky blvd., UA-03680, Kiev-142 (Ukraine); Van Humbeeck, J. [Department MTM, Catholic University of Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee (Leuven) (Belgium); Portier, R. [Laboratoire de Metallurgie Structurale ENSCP, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Vermaut, P. [Laboratoire de Metallurgie Structurale ENSCP, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Ochin, P. [Centre d' Etudes de Chimie Metallurgique-CNRS UPR2801, 15 rue Georges Urbain, 94407 Vitry-sur-Seine (France)
2006-11-25
The present paper focuses on the phase transformations during crystallization of the melt-spun Zr-29.56 at.% Cu-19.85 at.% Ni high-temperature shape memory alloy (HTSMA). This alloy exhibits a martensitic transformation in the bulk polycrystalline state at temperatures above crystallization of the metallic glass with the same composition. The crystallization kinetics were investigated by differential scanning calorimetry. The intermediate and final products of crystallization for this HTSMA were studied by means of transmission electron microscopy. The chain of the transformations starting from crystallization and ending at martensitic transformation will be described. Perspectives of the thin film production of Zr-based HTSMA will be discussed.
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.
Opie, Saul
Hydrodynamic phenomena such as the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities can be described by exponential/linear growth of surface perturbations at a bimaterial interface when subjected to constant/impulsive acceleration. A challenge in designing systems to mitigate or exploit these effects is the lack of accurate material models at large dynamic strain rates and pressures. In particular, little stress-strain constitutive information at large strain rates and pressures is available for transient material phases formed at high pressures, and the continuum effect the phase transformation process has on the instability evolution. In this work, a phase-aware isotropic strength model is developed and partially validated with a novel RM-based instability experiment in addition to existing data from the literature. With the validated material model additional simulations are performed to provide insight into to the role that robust material constitutive behavior (e.g., pressure, temperature, rate dependence) has on RM instability and how RM instability experiments can be used to characterize and validated expected material behavior. For phase aware materials, particularly iron in this work, the simulations predict a strong dependence on the Atwood number that single phase materials do not have. At Atwood numbers close to unity, and pressures in the high pressure stability region, the high pressure phase dominates the RM evolution. However, at Atwood numbers close to negative one, the RM evolution is only weakly affected by the high-pressure phase even for shocks well above the phase transformation threshold. In addition to RM evolution this work looks at the closely related shock front perturbation evolution. Existing analytical models for isentropic processes in gases and liquids are modified for metal equation of states and plastic behavior for the first time. It is found that the presence of a volume collapsing phase transformation with increased
Power Transformer Operating State Prediction Method Based on an LSTM Network
Directory of Open Access Journals (Sweden)
Hui Song
2018-04-01
Full Text Available The state of transformer equipment is usually manifested through a variety of information. The characteristic information will change with different types of equipment defects/faults, location, severity, and other factors. For transformer operating state prediction and fault warning, the key influencing factors of the transformer panorama information are analyzed. The degree of relative deterioration is used to characterize the deterioration of the transformer state. The membership relationship between the relative deterioration degree of each indicator and the transformer state is obtained through fuzzy processing. Through the long short-term memory (LSTM network, the evolution of the transformer status is extracted, and a data-driven state prediction model is constructed to realize preliminary warning of a potential fault of the equipment. Through the LSTM network, the quantitative index and qualitative index are organically combined in order to perceive the corresponding relationship between the characteristic parameters and the operating state of the transformer. The results of different time-scale prediction cases show that the proposed method can effectively predict the operation status of power transformers and accurately reflect their status.
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
Critical indices for reversible gamma-alpha phase transformation in metallic cerium
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.
Phase transformation induced by swift heavy ion irradiation of pure metals
International Nuclear Information System (INIS)
Dammak, H.; Dunlop, A.; Lesueur, D.
1996-01-01
It is now unambiguously established that high electronic energy deposition (HEED), obtained by swift heavy ion irradiation, plays an important role in the damage processes of pure metallic targets: (i) annealing of the defects created by elastic collisions in Fe, Nb, Ni and Pt, and (ii) creation of additional defects in Co, Fe, Ti and Zr. For Ti, we have recently evidenced by transmission electron microscopy observations that the damage creation by HEED is very important and leads to a phase transformation. Titanium evolves from the equilibrium hcp alpha-phase to the high pressure omega-phase. We studied the influence of three parameters on this phase transformation: ion fluence, electronic stopping power and irradiation temperature. The study of Ti and the results concerning other metals (Fe, Zr, etc.) and the semi-metal Bi allow us to propose criteria to predict in which metals HEED could induce damage: those which undergo a phase transformation under high pressure. As a matter of fact, beryllium is strongly damaged when submitted to HEED and seems to behave very similarly to titanium. The fact that such phase changes from a crystalline form to another form were only observed in those metals in which high pressure phases exist in the pressure-temperature diagram, strongly supports the Coulomb explosion model in which the generation of (i) a shock wave and (ii) collective atomic movements are invoked to account for the observed damage creation. (orig.)
Numerical simulation of heterogeneous phase transformations
International Nuclear Information System (INIS)
Combeau, H.; Lacaze, J.
1993-01-01
A numerical model is presented for the simulation of diffusion controlled phase transformations in multicomponent alloys. A closed system is considered, with simple geometric shape, either planar, cylindrical or spherical. The temperature inside this microscopic volume is homogeneous, but can vary according to any specified monoteneous law. Particular care has been given to the description of the solute profiles where the concentration gradients are the steepest, i.e. near the interface between the parent and the resultant phases. Solute redistribution at the interface is described by means of an original method which ensures that the overall solute balance is satisfied. A non linear system is obtained which includes the diffusion equations in both phases and the boundary conditions. The solution of this system makes use of a special algorithm which has been devised for a quick convergence. An example is presented which deals with microsegregation build-up during solidification of a multi-component nickel base alloy. (orig.)
Conceptual Design of a Single Phase 33 MVA HTS Transformer with a Tertiary Winding
International Nuclear Information System (INIS)
Lee, S. W.; Kim, W. S.; Hahn, S. Y.; Hwang, Y. I.; Choi, K. D.
2006-01-01
We have proposed a 3 phase, 100 MVA, 154 kV class HTS transformer substituting for a 60 MVA conventional transformer. The power transformer of 154 kV class has a tertiary winding besides primary and secondary windings. So the HTS transformer should have the 3rd superconducting winding. In this paper, we designed conceptually the structure of the superconducting windings of a single phase 33 MVA transformer. The electrical characteristics of the HTS transformer such as % impedance and AC loss vary with the arrangement of the windings and gaps between windings. We analyzed the effects of the winding parameters, evaluated the cost of each design, and proposed a suitable HTS transformer model for future power distribution system.
DEFF Research Database (Denmark)
Israelsen, Niels Møller; Maria, Michael; Feuchter, Thomas
2018-01-01
-linearities lead together to an unknown chirp of the detected interferogram. One method to compensate for the chirp is to perform a pixel-wavenumber calibration versus phase that requires numerical extraction of the phase. Typically a Hilbert transform algorithm is employed to extract the optical phase versus...... wavenumber for calibration and dispersion compensation. In this work we demonstrate UHR-OCT at 1300 nm using a Super continuum source and highlight the resolution constraints in using the Hilbert transform algorithm when extracting the optical phase for calibration and dispersion compensation. We demonstrate...... that the constraints cannot be explained purely by the numerical errors in the data processing module utilizing the Hilbert transform but must be dictated by broadening mechanisms originating from the experimentally obtained interferograms....
Classification of cyclic initial states and geometric phase for the spin-j system
Energy Technology Data Exchange (ETDEWEB)
Skrynnikov, N.R.; Zhou, J.; Sanctuary, B.C. [Dept. of Chem., McGill Univ., Montreal, PQ (Canada)
1994-09-21
Quantum states which evolve cyclically in their projective Hilbert space give rise to a geometric (or Aharonov-Anandan) phase. An aspect of primary interest is stable cyclic behaviour as realized under a periodic Hamiltonian. The problem has been handled by use of time-dependent transformations treated along the lines of Floquet's theory as well as in terms of exponential operators with a goal to examine the variety of initial states exhibiting cyclic behaviour. A particular case of special cyclic initial states is described which is shown to be important for nuclear magnetic resonance experiments aimed at the study of the effects of the geometric phase. An example of arbitrary spin j in a precessing magnetic field and spin j=1 subject to both axially symmetric quadrupolar interaction and a precessing magnetic field are presented. The invariant (Kobe's) geometric phase is calculated for special cyclic states. (author)
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.
Phase unwrapping in digital holography based on non-subsampled contourlet transform
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.
Energy Technology Data Exchange (ETDEWEB)
Dong, Wen D.; Carlos Valadez, J.; Gallagher, John A.; Jo, Hwan R.; Lynch, Christopher S., E-mail: cslynch@seas.ucla.edu [Department of Mechanical and Aerospace Engineering, The University of California, Los Angeles, 420 Westwood Plaza, Los Angeles, California 90095 (United States); Sahul, Raffi; Hackenberger, Wes [TRS Technologies, 2820 East College Avenue, State College, Pennsylvania 16801 (United States)
2015-06-28
Ceramic niobium modified 95/5 lead zirconate-lead titanate (PZT) undergoes a pressure induced ferroelectric to antiferroelectric phase transformation accompanied by an elimination of polarization and a volume reduction. Electric field and temperature drive the reverse transformation from the antiferroelectric to ferroelectric phase. The phase transformation was monitored under pressure, temperature, and electric field loading. Pressures and temperatures were varied in discrete steps from 0 MPa to 500 MPa and 25 °C to 125 °C, respectively. Cyclic bipolar electric fields were applied with peak amplitudes of up to 6 MV m{sup −1} at each pressure and temperature combination. The resulting electric displacement–electric field hysteresis loops were open “D” shaped at low pressure, characteristic of soft ferroelectric PZT. Just below the phase transformation pressure, the hysteresis loops took on an “S” shape, which split into a double hysteresis loop just above the phase transformation pressure. Far above the phase transformation pressure, when the applied electric field is insufficient to drive an antiferroelectric to ferroelectric phase transformation, the hysteresis loops collapse to linear dielectric behavior. Phase stability maps were generated from the experimental data at each of the temperature steps and used to form a three dimensional pressure–temperature–electric field phase diagram.
Martensitic phase transformations in Ni–Ti-based shape memory alloys: The Landau theory
International Nuclear Information System (INIS)
Shchyglo, Oleg; Salman, Umut; Finel, Alphonse
2012-01-01
We present a simple Landau free energy functional for cubic-to-orthorhombic and cubic-to-monoclinic martensitic phase transformations. The functional is derived following group–subgroup relations between different martensitic phases – tetragonal, trigonal, orthorhombic and monoclinic – in order to fully capture the symmetry properties of the free energy of the austenite and martensite phases. The derived free energy functional is fitted to the elastic and thermodynamic properties of NiTi and NiTiCu shape memory alloys which exhibit cubic-to-monoclinic and cubic-to-orthorhombic martensitic phase transformations, respectively.
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
Transformers: the changing phases of low-dimensional vanadium oxide bronzes.
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.
Pressure-induced phase transformation of HfO2
International Nuclear Information System (INIS)
Arashi, H.
1992-01-01
This paper reports on the pressure dependence of the Raman spectra of HfO 2 that was measured by a micro-Raman technique using a single-crystal specimen in the pressure range from 0 to 10 GPa at room temperature. The symmetry assignment of Raman bands of the monoclinic phase was experimentally accomplished from the polarization measurements for the single crystal. With increased pressure, a phase transformation for the monoclinic phase took place at 4.3 ± 0.3 GPa. Nineteen Raman bands were observed for the high-pressure phase. The spectral structure of the Raman bands for the high-pressure phase was similar with those reported previously for ZrO 2 . The space group for the high pressure phase of HfO 2 was determined as Pbcm, which was the same as that of the high-pressure phase for ZrO 2 on the basis of the number and the spectral structure of the Raman bands
On the study of the solid-solid phase transformation of TlBiTe2
International Nuclear Information System (INIS)
Chrissafis, K.; Vinga, E.S.; Paraskevopoulos, K.M.; Polychroniadis, E.K.
2003-01-01
The narrow gap semiconductor TlBiTe 2 undergoes a solid-solid phase transformation from the rhombohedral (D 3d ) to the cubic (O h ) phase. The present paper deals with the study of this phase transformation combining the results of Differential Scanning Calorimetry (DSC) and Transmission Electron Microscopy (TEM). It has been found that during heating the transformation is an athermal activated process, which can be described only by a combination of more than one processes while during cooling it exhibits an expectable thermal hysteresis due to the volume difference. The results of the kinetic analysis combined with the electron microscopy findings, supported also by the Fourier Transform Infrared (FTIR) spectroscopy ones, lead to the conclusion that TlBiTe 2 undergoes a multiple-step, displacive, martensitic type transformation. (Abstract Copyright [2003], Wiley Periodicals, Inc.)
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
Three-body unitary transformations, three-body forces, and trinucleon bound state properties
International Nuclear Information System (INIS)
Haftel, M.I.
1976-01-01
A three-body unitary transformation method for the study of three-body forces is presented. Starting with a three-body Hamiltonian with two-body forces, unitary transformations are introduced to generate Hamiltonians that have both two- and three-body forces. For cases of physical interest, the two-body forces of the altered Hamiltonians are phase equivalent (for two-body scattering) to the original and the three-body force vanishes when any interparticle distance is large. Specific examples are presented. Applications for studying the possible role of three-body forces in accounting for trinucleon bound state properties are examined. Calculations of the 3 He and 3 H charge form factors and Coulomb energy difference with hyperspherical radial transformations and with conventional N-N potentials are performed. The form factor calculations demonstrate how the proposed method can help obtain improved agreement with experiment by the introduction of appropriate three-body forces. Calculations of the Coulomb energy difference confirm previous estimates concerning charge symmetry breaking in the N-N interaction
International Nuclear Information System (INIS)
Jung, V.
1982-07-01
Drawing annealed cylindric 18/8 Cr Ni steels, which are originally free of textures, produces the transformed phases - hcp and bcc - both showing major texture contributions with increasing stretching of the cylindric specimens. After stretching the original fcc-phase shows two orientations: [100]fcc vertical stroke vertical stroke cylinder axis and [111]fcc vertical stroke vertical stroke cylinder axis, i.e. direction of stress. In both cases the martensitic phase is produced by gliding and shear in the sequence fcc → hcp → bcc by Nishiyama-Wasserman (N-W) or Kurdjumov-Sachs (K-S) transformation in the (111)fcc planes, which enclose a small angle with direction of stress, i.e. cylinder axis. The calculated orientation distributions of the (110)bcc reflex are compared with the distribution measured by neutron diffraction to get information on the bulk material. The special K-S transformation with only 6 (110)bcc orientations shows relatively good agreement with the measured distribution, except at small angles ω between the cylinder axis and the scattering vector. This might be caused by the isotropic fraction of the fcc phase producing an anisotropic (110)bcc orientation distribution. (orig.) [de
Bhattacharya, T
2002-01-01
Our high-pressure Raman scattering experiments on pentaerythritol (C(CH sub 2 OH) sub 4) show that this compound undergoes at least three phase transformations up to 25 GPa. Splitting of various modes at approx 6.3, approx 8.2 and 10 GPa suggests that these phase transformations result in lowering of crystalline symmetry. A very small discontinuous change in slope of most of the Raman-active modes is observed at 0.3 GPa. However, no other signature of a phase transition was observed at this pressure. The observed correlation of the pressures for the onset of the two phase transformations with the limiting values of the distances between various non-bonded atoms in the parent phase suggests that the molecular rearrangements across the phase transformations are not very drastic. In addition, our earlier Fourier transform infrared and present Raman investigations indicate that high-pressure compression leads to increase in strength of the hydrogen bond present in this compound.
Isometric and unitary phase operators: explaining the Villain transform
International Nuclear Information System (INIS)
Hemmen, J L van; Wreszinski, Walter F
2007-01-01
The Villain transform plays a key role in spin-wave theory, a bosonization of elementary excitations in a system of extensively many Heisenberg spins. Intuitively, it is a representation of the spin operators in terms of an angle and its canonically conjugate angular momentum operator and, as such, has a few nasty boundary-condition twists. We construct an isometric phase representation of spin operators that conveys a precise mathematical meaning to the Villain transform and is related to both classical mechanics and the Pegg-Barnett-Bialynicki-Birula boson (photon) phase operators by means of suitable limits. In contrast to the photon case, unitary extensions are inadequate because they describe the wrong physics. We also discuss in some detail the application to spin-wave theory, pointing out some examples in which the isometric representation is indispensable
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)
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.)
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.
Photostress analysis of stress-induced martensite phase transformation in superelastic NiTi
Energy Technology Data Exchange (ETDEWEB)
Katanchi, B. [Mechanical Engineering Faculty, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Choupani, N., E-mail: choupani@sut.ac.ir [Mechanical Engineering Faculty, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Khalil-Allafi, J. [Research Center for Advance Materials, Faculty of Materials Engineering, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Baghani, M. [School of Mechanical Engineering, College of Engineering, University of Tehran (Iran, Islamic Republic of)
2017-03-14
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.
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)
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...
Investigation of phase transformation for ferrite–austenite structure in stainless steel thin films
Energy Technology Data Exchange (ETDEWEB)
Merakeb, Noureddine [Laboratory of Physical Metallurgy and Property of Materials (LM2PM), Metallurgy and Materials Engineering Department, Badji Mokhtar University, P.O. Box 12, Annaba 23000 (Algeria); Messai, Amel [Laboratoire d' Ingénierie et Sciences des Matériaux Avancés (ISMA), Institut des Sciences et Technologie, Abbès Laghrour University, Khenchela 40000 (Algeria); Ayesh, Ahmad I., E-mail: ayesh@qu.edu.qa [Department of Mathematics, Statistics and Physics, Qatar University, Doha (Qatar)
2016-05-01
In this work we report on phase transformation of 304 stainless steel thin films due to heat treatment. Ex-situ annealing was applied for evaporated 304 stainless steel thin films inside an ultra-high vacuum chamber with a pressure of 3 × 10{sup −7} Pa at temperatures of 500 °C and 600 °C. The structure of thin films was studied by X-ray diffraction (XRD) and conversion electron Mössbauer spectroscopy (CEMS) techniques. The results revealed a transformation from α-phase that exhibits a body-centered cubic structure (BCC) to γ-phase that exhibits a face-centered cubic (FCC) due to annealing. In addition, the percentage of γ-phase structure increased with the increase of annealing temperature. Annealing thin films increased the crystal size of both phases (α and γ), however, the increase was nonlinear. The results also showed that phase transformation was produced by recrystallization of α and γ crystals with a temporal evolution at each annealing temperature. The texture degree of thin films was investigated by XRD rocking curve method, while residual stress was evaluated using curvature method. - Highlights: • Stainless steel thin films were fabricated by thermal evaporation on quartz. • Alpha to gamma phase transformation of thin films was investigated. • Annealing of thin films reduces disruption in crystal lattice. • The stress of as-grown thin films was independent on the thin film thickness. • The stress of the thin films was reduced due to annealing.
Energy Technology Data Exchange (ETDEWEB)
Moura, G.M. [Universidade Federal do Maranhão, CCSST, Imperatriz, MA, 65900-410 (Brazil); Universidade Federal do Sul e Sudeste do Pará, ICEN, Marabá, PA 68505-080 (Brazil); Carvalho, J.O. [Universidade Federal do Maranhão, CCSST, Imperatriz, MA, 65900-410 (Brazil); Instituto Federal do Tocantins, Araguaína, TO, 77.826-170 (Brazil); Silva, M.C.D.; Façanha Filho, P.F. [Universidade Federal do Maranhão, CCSST, Imperatriz, MA, 65900-410 (Brazil); Santos, A.O. dos, E-mail: adenilson1@gmail.com [Universidade Federal do Maranhão, CCSST, Imperatriz, MA, 65900-410 (Brazil)
2015-09-01
L-Histidinium bromide monohydrate (LHBr) single crystal is a nonlinear optical material. In this work the high temperature phase transformation and the thermal stability of single crystals of LHBr was investigated by X-ray diffraction, thermogravimetric analysis, differential thermal analysis, differential scanning calorimetry and Raman spectroscopy. The results showed the LHBr phase transformation of orthorhombic (P2{sub 1}2{sub 1}2{sub 1}) to monoclinic system (P 1 2 1) at 120 °C, with the lattice parameters a = 12.162(1) Å, b = 16.821(2) Å, c = 19.477(2) Å and β = 108.56(2)°. These techniques are complementary and confirm the structural phase transformation due to loss water of crystallization. - Highlights: • -histidinium bromide single crystal was grown by slow evaporation technique. • X-ray diffraction characterize the high-temperature phase transformation. • The structural phase transformation occur due to loss of water of crystallization. • The LHBr thermal expansion coefficients exhibit an anisotropic behavior.
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.
Effect of grain boundaries on shock-induced phase transformation in iron bicrystals
Zhang, Xueyang; Wang, Kun; Zhu, Wenjun; Chen, Jun; Cai, Mengqiu; Xiao, Shifang; Deng, Huiqiu; Hu, Wangyu
2018-01-01
Non-equilibrium molecular-dynamic simulations with a modified analytic embedded-atom model potential have been performed to investigate the effect of three kinds of grain boundaries (GBs) on the martensitic transformation in iron bicrystals with three different GBs under shock loadings. Our results show that the phase transition was influenced by the GBs. All three GBs provide a nucleation site for the α → ɛ transformation in samples shock-loaded with up = 0.5 km/s, and in particular, the elastic wave can induce the phase transformation at Σ3 ⟨110⟩ twist GB, which indicates that the phase transformation can occur at Σ3 ⟨110⟩ twist GB with a much lower pressure. The effect of GBs on the stress assisted transformation (SAT) mechanisms is discussed. All variants nucleating at the vicinity of these GBs meet the maximum strain work (MSW) criterion. Moreover, all of the variants with the MSW nucleate at Σ5 ⟨001⟩ twist GB and Σ3 ⟨110⟩ tilt GB, but only part of them nucleate at Σ3 ⟨110⟩ twist GB. This is because the coincident planes between both sides of the GB would affect the slip process, which is the second stage of the martensitic transformation and influences the selection of variant. We also find that the martensitic transformation at the front end of the bicrystals would give rise to stress attenuation in samples shock-loaded with up = 0.6 km/s, which makes the GBs seem to be unfavorable to the martensitic transformation. Our findings have the potential to affect the interface engineering and material design under high pressure conditions.
A kinetic Monte Carlo method for the simulation of massive phase transformations
International Nuclear Information System (INIS)
Bos, C.; Sommer, F.; Mittemeijer, E.J.
2004-01-01
A multi-lattice kinetic Monte Carlo method has been developed for the atomistic simulation of massive phase transformations. Beside sites on the crystal lattices of the parent and product phase, randomly placed sites are incorporated as possible positions. These random sites allow the atoms to take favourable intermediate positions, essential for a realistic description of transformation interfaces. The transformation from fcc to bcc starting from a flat interface with the fcc(1 1 1)//bcc(1 1 0) and fcc[1 1 1-bar]//bcc[0 0 1-bar] orientation in a single component system has been simulated. Growth occurs in two different modes depending on the chosen values of the bond energies. For larger fcc-bcc energy differences, continuous growth is observed with a rough transformation front. For smaller energy differences, plane-by-plane growth is observed. In this growth mode two-dimensional nucleation is required in the next fcc plane after completion of the transformation of the previous fcc plane
A study of phase transformation in a TiAlNb alloy and the effect of Cr addition
Energy Technology Data Exchange (ETDEWEB)
Kesler, Michael S.; Goyel, Sonalika; Rios, Orlando [University of Florida, Materials Science and Engineering, P.O. Box 116400, Gainesville, FL 32611 (United States); Cupid, Damian M. [University of Florida, Materials Science and Engineering, P.O. Box 116400, Gainesville, FL 32611 (United States); Freiberg University of Mining and Technology, Institute of Materials Science, Freiberg (Germany); Seifert, Hans J. [Freiberg University of Mining and Technology, Institute of Materials Science, Freiberg (Germany); Ebrahimi, Fereshteh, E-mail: febra@mse.ufl.edu [University of Florida, Materials Science and Engineering, P.O. Box 116400, Gainesville, FL 32611 (United States)
2010-05-15
The phase transformation paths, transformation temperatures and phase equilibria of Ti-45Al-27Nb and Ti-45Al-22Nb-5Cr (at%) alloys were evaluated over a temperature range from 865 deg. C to 1600 deg. C. Both alloys solidified as single {beta}-phase and transformed to {gamma} + {sigma} phases upon slow cooling. The addition of Cr did not affect the {beta} {yields} {gamma} transformation temperature upon slow cooling. In contrast, the temperature, at which the {sigma}-phase formed, was reduced noticeably. Upon heating, the temperature at which the {beta}-phase evolves from the {gamma} + {sigma} microstructure was found to decrease significantly with the addition of Cr. In the ternary alloy the formation of the {gamma}-phase could not be retarded on quenching, however, the substitution of Nb with Cr allowed for the retainment of the {beta}-phase to room temperature. These results are explained by the partitioning of Cr into the {beta}-phase, which in addition to thermodynamic stability reduces the kinetics of transformations at lower temperatures.
A study of phase transformation in a TiAlNb alloy and the effect of Cr addition
Energy Technology Data Exchange (ETDEWEB)
Kesler, Michael [University of Florida, Gainesville; Goyel, Sonalika [University of Florida, Gainesville; Rios, Orlando [ORNL; Cupid, Damian M [Freiberg University of Mining and Technology; Seifert, Hans J [Freiberg University of Mining and Technology; Ebrahimi, Fereshteh [University of Florida, Gainesville
2010-01-01
The phase transformation paths, transformation temperatures and phase equilibria of Ti-45Al-27Nb and Ti-45Al-22Nb-5Cr (at%) alloys were evaluated over a temperature range from 865 C to 1600 C. Both alloys solidified as single {beta}-phase and transformed to {gamma} + {sigma} phases upon slow cooling. The addition of Cr did not affect the {beta} {yields} {gamma} transformation temperature upon slow cooling. In contrast, the temperature, at which the {sigma}-phase formed, was reduced noticeably. Upon heating, the temperature at which the {beta}-phase evolves from the {gamma} + {sigma} microstructure was found to decrease significantly with the addition of Cr. In the ternary alloy the formation of the {gamma}-phase could not be retarded on quenching, however, the substitution of Nb with Cr allowed for the retainment of the {beta}-phase to room temperature. These results are explained by the partitioning of Cr into the {beta}-phase, which in addition to thermodynamic stability reduces the kinetics of transformations at lower temperatures.
A study of phase transformation in a TiAlNb alloy and the effect of Cr addition
International Nuclear Information System (INIS)
Kesler, Michael S.; Goyel, Sonalika; Rios, Orlando; Cupid, Damian M.; Seifert, Hans J.; Ebrahimi, Fereshteh
2010-01-01
The phase transformation paths, transformation temperatures and phase equilibria of Ti-45Al-27Nb and Ti-45Al-22Nb-5Cr (at%) alloys were evaluated over a temperature range from 865 deg. C to 1600 deg. C. Both alloys solidified as single β-phase and transformed to γ + σ phases upon slow cooling. The addition of Cr did not affect the β → γ transformation temperature upon slow cooling. In contrast, the temperature, at which the σ-phase formed, was reduced noticeably. Upon heating, the temperature at which the β-phase evolves from the γ + σ microstructure was found to decrease significantly with the addition of Cr. In the ternary alloy the formation of the γ-phase could not be retarded on quenching, however, the substitution of Nb with Cr allowed for the retainment of the β-phase to room temperature. These results are explained by the partitioning of Cr into the β-phase, which in addition to thermodynamic stability reduces the kinetics of transformations at lower temperatures.
International Nuclear Information System (INIS)
Ageev, N.V.; Babarehko, A.A.
1983-01-01
Peculiarities of texture formation in metals undergoing phase transformations in the temperature range of heat treatment and hot working are investigated theoretically and experimentally. A low-temperature phase after hot working is shown to inherite a high-temperature phase texture due to definite orientation conformity during phase transformation. Strengthened heat and thermomechanical treatments, as a rule, do not destroy material texture but change it
Lectures notes on phase transformations in nuclear matter
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
Study on the immunity state of mouse exposed to mobile phone radiation during embryonic phase
International Nuclear Information System (INIS)
Pei Yinhui; Gao Hui
2008-01-01
Objective: To study the effect of mobile phone radiation on mouse which exposed to radiation during embryonic phase. Methods: Pregnant mice were exposed to mobile phone radiation. The mice's netrophile phage percentage and spleen lymphocyte transformation rate were detected respectively 2 months after birth. Results: The netrophile phage percentage of experimental mice was seemly the same as that of control group, and there was no significant difference (P>0.05), but the spleen transformation rate showed the diverse trend. Conclusion: The specific cellular immunity of mice, which ex- posed to mobile phone radiation during embryonic phase, was seen to be in a state of decreasement. (authors)
Phase-covariant quantum cloning of qudits
International Nuclear Information System (INIS)
Fan Heng; Imai, Hiroshi; Matsumoto, Keiji; Wang, Xiang-Bin
2003-01-01
We study the phase-covariant quantum cloning machine for qudits, i.e., the input states in a d-level quantum system have complex coefficients with arbitrary phase but constant module. A cloning unitary transformation is proposed. After optimizing the fidelity between input state and single qudit reduced density operator of output state, we obtain the optimal fidelity for 1 to 2 phase-covariant quantum cloning of qudits and the corresponding cloning transformation
Energy Technology Data Exchange (ETDEWEB)
Feng, Kai; Wang, Yibo [Shanghai Key laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Li, Zhuguo, E-mail: lizg@sjtu.edu.cn [Shanghai Key laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)
2015-08-15
Austenitic stainless steel 316L is ion implanted by carbon with implantation fluences of 1.2 × 10{sup 17} ions-cm{sup −} {sup 2}, 2.4 × 10{sup 17} ions-cm{sup −} {sup 2}, and 4.8 × 10{sup 17} ions-cm{sup −} {sup 2}. The ion implantation induced graded microstructure and phase transformation in stainless steel is investigated by X-ray diffraction, X-ray photoelectron spectroscopy and high resolution transmission electron microscopy. The corrosion resistance is evaluated by potentiodynamic test. It is found that the initial phase is austenite with a small amount of ferrite. After low fluence carbon ion implantation, an amorphous layer and ferrite phase enriched region underneath are formed. Nanophase particles precipitate from the amorphous layer due to energy minimization and irradiation at larger ion implantation fluence. The morphology of the precipitated nanophase particles changes from circular to dumbbell-like with increasing implantation fluence. The corrosion resistance of stainless steel is enhanced by the formation of amorphous layer and graphitic solid state carbon after carbon ion implantation. - Highlights: • Carbon implantation leads to phase transformation from austenite to ferrite. • The passive film on SS316L becomes thinner after carbon ion implantation. • An amorphous layer is formed by carbon ion implantation. • Nanophase precipitate from amorphous layer at higher ion implantation fluence. • Corrosion resistance of SS316L is improved by carbon implantation.
Grain nucleation and growth during phase transformations
DEFF Research Database (Denmark)
Offerman, S.E.; Dijk, N.H. van; Sietsma, J.
2002-01-01
of individual grains. Our measurements show that the activation energy for grain nucleation is at least two orders of magnitude smaller than that predicted by thermodynamic models. The observed growth curves of the newly formed grains confirm the parabolic growth model but also show three fundamentally...... different types of growth. Insight into the grain nucleation and growth mechanisms during phase transformations contributes to the development of materials with optimal mechanical properties....
Theory of phase transformation and reorientation in single crystalline shape memory alloys
International Nuclear Information System (INIS)
Zhu, J J; Liang, N G; Cai, M; Liew, K M; Huang, W M
2008-01-01
A constitutive model, based on an (n+1)-phase mixture of the Mori–Tanaka average theory, has been developed for stress-induced martensitic transformation and reorientation in single crystalline shape memory alloys. Volume fractions of different martensite lattice correspondence variants are chosen as internal variables to describe microstructural evolution. Macroscopic Gibbs free energy for the phase transformation is derived with thermodynamics principles and the ensemble average method of micro-mechanics. The critical condition and the evolution equation are proposed for both the phase transition and reorientation. This model can also simulate interior hysteresis loops during loading/unloading by switching the critical driving forces when an opposite transition takes place
Directory of Open Access Journals (Sweden)
Shenghan Jiang
2014-09-01
Full Text Available In topologically ordered quantum states of matter in (2+1D (spacetime dimensions, the braiding statistics of anyonic quasiparticle excitations is a fundamental characterizing property that is directly related to global transformations of the ground-state wave functions on a torus (the modular transformations. On the other hand, there are theoretical descriptions of various topologically ordered states in (3+1D, which exhibit both pointlike and looplike excitations, but systematic understanding of the fundamental physical distinctions between phases, and how these distinctions are connected to quantum statistics of excitations, is still lacking. One main result of this work is that the three-dimensional generalization of modular transformations, when applied to topologically ordered ground states, is directly related to a certain braiding process of looplike excitations. This specific braiding surprisingly involves three loops simultaneously, and can distinguish different topologically ordered states. Our second main result is the identification of the three-loop braiding as a process in which the worldsheets of the three loops have a nontrivial triple linking number, which is a topological invariant characterizing closed two-dimensional surfaces in four dimensions. In this work, we consider realizations of topological order in (3+1D using cohomological gauge theory in which the loops have Abelian statistics and explicitly demonstrate our results on examples with Z_{2}×Z_{2} topological order.
International Nuclear Information System (INIS)
Cao, Siwei; Zhao, Ji-Cheng
2015-01-01
A dual-anneal diffusion multiple (DADM) approach is developed for effective determination of intermediate-temperature phase diagrams that are critical to the establishment of reliable thermodynamic databases. A large amount of phase equilibrium data was obtained from DADMs to construct the Fe–Cr–Ni isothermal sections at 1200, 900, 800 and 700 °C. The DADM approach is also a systematic and effective way to study phase precipitation from wide ranges of compositions, thus generating rich atlases of microstructures induced by various transformations. The results from this study indicate that the body-centered cubic to sigma phase transformation in the Fe–Cr–Ni system took place initially through a massive transformation mechanism
Effect of lattice mismatch-induced strains on coupled diffusive and displacive phase transformations
Bouville, Mathieu; Ahluwalia, Rajeev
2006-01-01
Materials which can undergo slow diffusive transformations as well as fast displacive transformations are studied using the phase-field method. The model captures the essential features of the time-temperature-transformation (TTT) diagrams, continuous cooling transformation (CCT) diagrams, and microstructure formation of these alloys. In some materials systems there can exist an intrinsic volume change associated with these transformations. We show that these coherency strains can stabilize m...
International Nuclear Information System (INIS)
Soysal, A.O.; Semlyen, A.
1994-01-01
A general methodology is presented for the state equation approximation of a multiple input-output linear system from transfer matrix data. A complex transformation matrix, obtained by eigen analysis at a fixed frequency, is used for diagonalization of the transfer matrix over the whole frequency range. A scalar estimation procedure is applied for identification of the modal transfer functions. The state equations in the original coordinates are obtained by inverse transformation. An iterative Gauss-Newton refinement process is used to reduce the overall error of the approximation. The developed methodology is applied to the phase domain modeling of untransposed transmission lines. The approach makes it possible to perform EMTP calculations directly in the phase domain. This results in conceptual simplification and savings in computation time since modal transformations are not needed in the sequences of the transient analysis. The presented procedure is compared with the conventional modal approach in terms of accuracy and computation time
Directory of Open Access Journals (Sweden)
R. Przeliorz
2010-04-01
Full Text Available The effect of heating rate on phase transformations to austenite range in ductile iron of the EN-GJS-450-10 grade was investigated. For studies of phase transformations, the technique of differential scanning calorimetry (DSC was used. Microstructure was examined by optical microscopy. The calorimetric examinations have proved that on heating three transformations occur in this grade of ductile iron, viz. magnetic transformation at the Curie temperature, pearlite→austenite transformation and ferrite→austenite transformation. An increase in the heating rate shifts the pearlite→austenite and ferrite→austenite transformations to higher temperature range. At the heating rate of 5 and 15°C/min, local extrema have been observed to occur: for pearlite→austenite transformation at 784°C and 795°C, respectively, and for ferrite→austenite transformation at 805°C and 821°C, respectively. The Curie temperature of magnetic transformation was extrapolated to a value of 740°C. Each transformation is related with a specific thermal effect. The highest value of enthalpy is accompanying the ferrite→austenite transformation, the lowest occurs in the case of pearlite→austenite transformation.
Efficient selection of banks of transformers
International Nuclear Information System (INIS)
Garcia G, Grester; De Armas T, Marcos A.
2009-01-01
This paper show a procedure to select the most profitable transformer banks in an specific service or in new investments with emphasis in the reduction of the operational losses, the cost in useful life, and the increase of the system efficiency using techniques of artificial intelligence. The method constitutes a tool that can be used in field conditions without invasive test and with data of easy acquisition according to the state of the art. The program was developed to analyze any type of transformers or transformer bank connection? single phase, three phase transformers or two or three transformers in symmetric or asymmetric configuration for three phase and single phase services. The economic analysis is made by the Cost of Cycle Life (CCV) of the analyzed configuration. As a case the results obtained in the gas station La Calzada of the Cienfuegos municipality is presented.
Lakhani, Archana; Kushwaha, Pallavi; Rawat, R.; Kumar, Kranti; Banerjee, A.; Chaddah, P.
2010-01-01
Glass-like arrest has recently been reported in various magnetic materials. As in structural glasses, the kinetics of a first order transformation is arrested while retaining the higher entropy phase as a non-ergodic state. We show visual mesoscopic evidence of the irreversible transformation of the arrested antiferromagnetic-insulating phase in Pr0.5Ca0.5Mn0.975Al0.025O3 to its equilibrium ferromagnetic-metallic phase with an isothermal increase of magnetic field, similar to its iso-field transformation on warming. The magnetic field dependence of the non-equilibrium to equilibrium transformation temperature is shown to be governed by Le Chatelier's principle.
Energy Technology Data Exchange (ETDEWEB)
Hauptman, A; Kleinberger, R; Okuzumi, H; Perio, P; Tournarie, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1961-07-01
Periodic anti-phases are ordered structures in which the movable elements alternates regularly between two available sites, in one or two directions. We study in the present work two particular properties of periodic anti-phases : 1- The irrationality or the continuous variation of the periodic anti-phase. 2- The reversible transition between the anti-phase state and that of long distance order. We have calculated the distribution of the diffracted amplitudes for the 'rational statistic' model. They can easily be identified and the two types of diagram observed are presented. For the long distance anti-phase-order transformation, we propose a model in which a domain grows laterally at the expense of the other. Calculation shows that in this case certain order reflections re-appear accompanied by extra satellites whose amplitude is not proportional to that of the pure anti-phase satellites, the opposite of the case of a double diffraction. The irreversible evolution of Au{sub 3}Mn alloys is then described; in this case interactions between domains of different type occur. Finally a diagram for the alloy Au{sub 3}Mn is given; the anti-phase boundaries are made up of 130 planes. (authors) [French] Les antiphases periodiques sont des structures ordonnees dans lesquelles l'element ordonnable alterne regulierement entre deux sites disponibles, suivant une ou deux directions. Nous etudions, dans le travail presente, deux proprietes particulieres des antiphases periodiques: 1- L'irrationalite ou la variation continue de la periode d'antiphase. 2- La transition reversible entre l'etat antiphase et l'etat d'ordre a grande distance. Nous avons calcule la distribution des amplitudes diffractees pour le modele 'rationnel statistique'. Elles sont facilement identifiables et les deux types de diagrammes observes sont presentes. Pour la transformation antiphase-ordre a longue distance, nous proposons un modele de croissance laterale d'un domaine au detriment de l'autre. Le calcul
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....
Mumtaz, Fiza; Jaffari, G. Hassnain; Hassan, Qadeer ul; Shah, S. Ismat
2018-06-01
We present detailed comparative study of effect of isovalent i.e. Eu+3 substitution at A-site and tetra (Ti+4, Zr+4), penta (V+5) and hexavalent (W+6) substitutions at B-site in BiFeO3. Eu+3 substitution led to phase transformation and exhibited mixed phases i.e. rhombohedral and orthorhombic, while tetravalent substituents (Ti+4 and Zr+4) led to stabilization of cubic phase. In higher valent (i.e. V+5 and W+6) cases solubility limit was significantly reduced where orthorhombic phase was observed as in the case of parent compound. Phase transformation as a consequence of increase in microstrain and chemical pressure induced by the substituent has been discussed. Solubility limit of different B-site dopants i.e. Zr, W and V was extracted to 5%, 2% and 2%, respectively. Extra phases in various cases were Bi2Fe4O9, Bi25FeO40, Bi14W2O27, and Bi23V4O44.5 and their fractional amount have been quantified. Ti was substituted up to 15% and has been observed to be completely soluble in the parent compound. Solubility limits depends on ionic radii mismatch and valance difference of Fe+3 and dopant, in which valance difference plays more dominant role. Solubility limit and phase transformation has been explained in terms of change in bond strength and tolerance factor induced by incorporation of dopant which depend on its size and valence state. Detail optical, dielectric, ferroelectric, magnetic and transport properties of Eu and Ti co-doped samples and selected low concentration B-site doped compositions (i.e. 2%) have presented and discussed. Two d-d transitions and three charge transfer transitions were observed within UV-VIS range. Both change in cell volume for the same phase and transformation in crystal structure affects the band gap. Increase in room temperature dielectric constant and saturation polarization was also found to increase in case of Eu-Ti co-doped samples with increasing concentration of Ti. Substitution of Eu at A-site and Ti at B-site led to
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
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)
Charge density wave instabilities and incommensurate structural phase transformations
International Nuclear Information System (INIS)
Axe, J.D.
1977-10-01
Incommensurate structural phase transformations involve the appearance of modulated atomic displacements with spatial periodicity unrelated to the fundamental periodicity of the basic lattice. In the case of some quasi one- or two-dimensional metals such transformations are the result of Fermi-surface instabilities that also produce electronic charge density waves (CDW's) and soft phonon modes due to metallic electron screening singularities. Incommensurate soft mode instabilities have been found in insulators as well. Recent neutron scattering studies of both the statics and dynamics of incommensurate structural instabilities will be reviewed
Mechanically induced atomic disorder and phase transformations. Doctoral thesis
Energy Technology Data Exchange (ETDEWEB)
Limei, D
1992-11-30
The study shows the possibilities of preparing alloys in various metastable configurations by the simple technique of ball milling. Firstly, chapter 2 gives the description of experimental techniques. In chapter 3, evidence of atomic anti-site disordering in A15-structure superconducting compounds Nb3Sn and Nb3Au during an early stage of milling is demonstrated. Chapter 4 represents the experimental results on the B2-structure magnetic compounds CoGa and CoAl upon mechanical impact. These compounds are well known for their particular type of atomic disorder, namely triple-defect disorder. Various examples of experimental evidence of phase transformations induced by mechanical grinding are presented in chapter 5. Section 5.2 gives an example of amorphization induced by mechanical attrition in the intermetallic compound Ni3Sn. Section 5.3 shows the milling experiment of the intermetallic compound V3 Ga. In section 5.4, for the first time, the observation of a phase transformation to a high-temperature phase with a complex structure will be demonstrated for the intermetallic compound Co3Sn2. In the last chapter, detailed studies on the intermetallic Nb-Au binary compounds for a variety of compositions are presented.
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.
Energy Technology Data Exchange (ETDEWEB)
Nguyen, Anh-Tuan; Kang, Jeong-Ki; Kim, Woo-Sik [Department of Chemical Engineering, Kyung Hee University, Seocheon-Dong, Giheung-Gu, 446-701 Yongin-Si (Korea, Republic of); Choi, Guang Jin [Department of Pharmaceutical Engineering, Inje University, 607 Uhbang-Dong, Gimhae, 621-746 Kyungnam (Korea, Republic of)
2011-01-15
The phase transformation of Guanosine 5{sup '}-Monophousphate (GMP) in drowning-out crystallization using a batch system was experimentally monitored and mathematically modeled. The solid (amorphous and crystalline GMP hydrate) and liquid phases of the GMP products were simultaneously monitored using a video microscope, FT-IR, and UV/Vis spectroscopy during the phase transformation. For the modeling, the phase transformation was assumed to occur via the simultaneous dissolution of amorphous GMP and growth of crystalline GMP hydrate in the solution. Based on a comparison of the experimental results and model predictions, both the dissolution and growth of the GMP solids were found to contribute competitively to the phase transformation. When varying the crystallization conditions, in this case the agitation speed and feed concentration, the phase transformation was significantly promoted when increasing the agitation speed, yet independent of the feed concentration. The simple mathematical model used for the GMP phase transformation was quite successful in describing the experimental results. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Energy Technology Data Exchange (ETDEWEB)
Lai Wei, E-mail: laiwei@msu.ed [Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824 (United States); Ciucci, Francesco [Heidelberg Graduate School of Mathematical and Computational Methods for the Sciences, University of Heidelberg, INF 368 D - 69120 Heidelberg (Germany)
2010-12-15
Thermodynamics and kinetics of phase transformation in intercalation battery electrodes are investigated by phenomenological models which include a mean-field lattice-gas thermodynamic model and a generalized Poisson-Nernst-Planck equation set based on linear irreversible thermodynamics. The application of modeling to a porous intercalation electrode leads to a hierarchical equivalent circuit with elements of explicit physical meanings. The equivalent circuit corresponding to the intercalation particle of planar, cylindrical and spherical symmetry is reduced to a diffusion equation with concentration dependent diffusivity. The numerical analysis of the diffusion equation suggests the front propagation behavior during phase transformation. The present treatment is also compared with the conventional moving boundary and phase field approaches.
Finite size effects in phase transformation kinetics in thin films and surface layers
International Nuclear Information System (INIS)
Trofimov, Vladimir I.; Trofimov, Ilya V.; Kim, Jong-Il
2004-01-01
In studies of phase transformation kinetics in thin films, e.g. crystallization of amorphous films, until recent time is widely used familiar Kolmogorov-Johnson-Mehl-Avrami (KJMA) statistical model of crystallization despite it is applicable only to an infinite medium. In this paper a model of transformation kinetics in thin films based on a concept of the survival probability for randomly chosen point during transformation process is presented. Two model versions: volume induced transformation (VIT) when the second-phase grains nucleate over a whole film volume and surface induced transformation (SIT) when they form on an interface with two nucleation mode: instantaneous nucleation at transformation onset and continuous one during all the process are studied. At VIT-process due to the finite film thickness effects the transformation profile has a maximum in a film middle, whereas that of the grains population reaches a minimum inhere, the grains density is always higher than in a volume material, and the thinner film the slower it transforms. The transformation kinetics in a thin film obeys a generalized KJMA equation with parameters depending on a film thickness and in limiting cases of extremely thin and thick film it reduces to classical KJMA equation for 2D- and 3D-system, respectively
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.
Directory of Open Access Journals (Sweden)
Carter Hamilton
2018-05-01
Full Text Available Sheets of aluminum 2017A-T451 and 7075-T651 were friction stir-welded in a butt-weld configuration. An existing computational model of the welding process for temperature distribution and material flow was adapted to estimate the phase transformations that occur across the weld zone. Near the weld center, process temperatures are sufficient to fully dissolve the equilibrium η phase in 7075 and partially dissolve the equilibrium S phase in 2017A. Upon cooling, Guinier–Preston (GP and Guinier–Preston–Bagaryatsky (GPB zones re-precipitate, and hardness recovers. Due to the more complete dissolution of the equilibrium phase in 7075, the hardness recovery skews toward whichever side of the weld, i.e., the advancing or retreating side, represents the 7075 workpiece. Phase transformation maps generated by the numerical simulation align not only with the hardness profiles taken across the weld zone, but also with positron lifetimes obtained through positron annihilation lifetime spectroscopy (PALS. Boundaries between the aluminum matrix and the secondary phases provide open volumes to trap positrons; therefore, positron lifetimes across the weld correspond with the phase transformations that occur in 7075 and 2017A during processing.
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...
International Nuclear Information System (INIS)
Gaboriaud, R.J.; Paumier, F.; Lacroix, B.
2016-01-01
This work is focused on the transformation of the disordered fluorite cubic-F phase to the ordered cubic-C bixbyite phase, induced by isothermal annealing as a function of the residual stresses resulting from different concentrations of microstructural defects in the yttrium oxide, Y_2O_3. This transformation was studied using in-situ X-ray diffraction and was modelled using Kolmogorov–Johnson–Mehl–Avrami (KJMA) analysis. The degree of the disorder of the oxygen network was associated with the residual stress, which was a key parameter for the stability and the kinetics of the transition of the different phases that were present in the thin oxide film. When the degree of disorder/residual stress level is high, this transition, which occurs at a rather low temperature (300 °C), is interpreted as a transformation of phases that occurs by a complete recrystallization via the nucleation and growth of a new cubic-C structure. Using the KJMA model, we determined the activation energy of the transformation process, which indicates that this transition occurs via a one-dimensional diffusion process. Thus, we present the analysis and modelling of the stress state. When the disorder/residual stress level was low, a transition to the quasi-perfect ordered cubic-C structure of the yttrium oxide appeared at a rather high temperature (800 °C), which is interpreted as a classic recovery mechanism of the cubic-C structure. - Highlights: • Rare earth oxide thin films • XRD analysis • Phase transformation modelling • Residual stress effects • Crystallographic phase stability
Energy Technology Data Exchange (ETDEWEB)
Gaboriaud, R.J.; Paumier, F. [Institut Pprime, Department of Material Sciences, CNRS-University of Poitiers SP2MI-BP 30179, 86962 Futuroscope-Chasseneuil cedex (France); Lacroix, B. [CSIC, Institut de Ciencia de Materiales, University of Sevilla, Avenida Américo Vespucio, 49, 41092 Sevilla (Spain)
2016-02-29
This work is focused on the transformation of the disordered fluorite cubic-F phase to the ordered cubic-C bixbyite phase, induced by isothermal annealing as a function of the residual stresses resulting from different concentrations of microstructural defects in the yttrium oxide, Y{sub 2}O{sub 3}. This transformation was studied using in-situ X-ray diffraction and was modelled using Kolmogorov–Johnson–Mehl–Avrami (KJMA) analysis. The degree of the disorder of the oxygen network was associated with the residual stress, which was a key parameter for the stability and the kinetics of the transition of the different phases that were present in the thin oxide film. When the degree of disorder/residual stress level is high, this transition, which occurs at a rather low temperature (300 °C), is interpreted as a transformation of phases that occurs by a complete recrystallization via the nucleation and growth of a new cubic-C structure. Using the KJMA model, we determined the activation energy of the transformation process, which indicates that this transition occurs via a one-dimensional diffusion process. Thus, we present the analysis and modelling of the stress state. When the disorder/residual stress level was low, a transition to the quasi-perfect ordered cubic-C structure of the yttrium oxide appeared at a rather high temperature (800 °C), which is interpreted as a classic recovery mechanism of the cubic-C structure. - Highlights: • Rare earth oxide thin films • XRD analysis • Phase transformation modelling • Residual stress effects • Crystallographic phase stability.
Phase transformation kinetics and microstructure of NiTi shape
Indian Academy of Sciences (India)
Phase transformation kinetics and microstructure of NiTi shape memory alloy: ... by 1.4687 J. In addition, entropy of the alloys decreases by 0.2335 J (g ∘ C) − 1 ... is an obvious difference in the grain sizes of the unpressured sample and the ...
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 comp...
International Nuclear Information System (INIS)
Wang, Zhiyang; Hinterstein, Manuel; Daniels, John E.; Webber, Kyle G.; Hudspeth, Jessica M.
2014-01-01
An electric-field-induced paraelectric cubic to ferroelectric tetragonal phase transformation has been directly observed in prototypical polycrystalline BaTiO 3 at temperatures above the Curie point (T C ) using in situ high-energy synchrotron X-ray diffraction. The transformation persisted to a maximum temperature of 4 °C above T C . The nature of the observed field-induced transformation and the resulting development of domain texture within the induced phase were dependent on the proximity to the transition temperature, corresponding well to previous macroscopic measurements. The transition electric field increased with increasing temperature above T C , while the magnitude of the resultant tetragonal domain texture at the maximum electric field (4 kV mm −1 ) decreased at higher temperatures. These results provide insights into the phase transformation behavior of a prototypical ferroelectric and have important implications for the development of future large-strain phase-change actuator materials.
International Nuclear Information System (INIS)
Terasaki, Hidenori; Komizo, Yu-ichi; Nishino, Fumihiro; Ikeda, Masahiko
2007-01-01
Understanding and controlling solidification and phase transformation process of weld metal is essential for forming the microstructure with superior mechanical property. Recent evolution of analysis technique makes for solidification and phase transformation process to be in-situ analyzed, in direct and reciprocal lattice space. In the present work, unidirectional-solidification and phase transformation in the weld metal of commercial pure-titanium in Gas Tungsten Arc welding was in-situ observed by using Time-Resolved X-Ray Diffraction system with two-dimensional pixel detector. An undulator beam was used as a probe. Larger diffraction area could be detected in the time-resolution of 0.05 seconds, in unidirectional solidification and subsequent phase transformation process of pure-titanium weld metal. Furthermore, the microstructure formation during β-α phase transformation was in situ observed with High temperature Laser Scanning Confocal Microscopy. The crystal configurations in unidirectional solidification of weld metal and rapid change of phase ratio in reconstructive phase transformation were clearly analyzed. (author)
Energy Technology Data Exchange (ETDEWEB)
Lyra, A.; Dahl, W. (Technische Hochschule Aachen (Germany, F.R.). Inst. fuer Eisenhuettenkunde)
1990-01-01
Using tensile specimens with two different geometries (notched and unnotched) and five cooling rates the anisothermal phase transformation of a 100 Cr 6 steel has been investigated under influence of different strain distributions inside the specimens. The nonhomogeneous distribution of plastic strain has been achieved by tensile testing at high temperatures (800deg C). Measurement of the transformation temperatures was carried out by dilatometry and differential thermal analysis (DTA). The results reveal that due to hot deformation the pearlitic transformation curves in the CCT-Diagram are dislocated to shorter times and higher temperatures compared with the underformed state. The extent of the displacement is however a function of the strain distribution inside the specimens. (orig.).
Relationship between squeezing and entangled state transformations
Fan Hong Yi
2003-01-01
We show that c-number dilation transform in the Einstein-Podolsky-Rosen (EPR) entangled state, i.e. vertical bar eta sub 1 , eta sub 2) -> vertical bar eta sub 1 , eta sub 2 /mu) (or vertical bar eta sub 1 , eta sub 2) -> vertical bar eta sub 1 /mu, eta sub 2)), maps onto a kind of one-sided two-mode squeezing operator exp left brace i lambda/2(P sub 1 + P sub 2)(Q sub 1 + Q sub 2) - lambda/2 right brace, (or exp left brace i lambda/2(P sub 1 - P sub 2)(Q sub 1 - Q sub 2) - lambda/2 right brace). Using the IWOP technique, we derive their normally ordered form and construct the corresponding squeezed states. In doing so, some new relationship between squeezing and entangled state transformation is revealed. The dynamic Hamiltonian for such a kind of squeezing evolution is derived. The properties and application of the one-sided squeezed state are briefly discussed. These states can also be obtained with the use of a beam splitter.
Phase Transformation Study in Nb-Mo Microalloyed Steels Using Dilatometry and EBSD Quantification
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.
Phase transformations at continuous cooling in VT6ch and VT23 alloys
International Nuclear Information System (INIS)
Lyasotskaya, V.S.; Lyasotskij, I.V.; Meshcheryakov, V.N.; Ravdonikas, N.Yu.; Nadtochij, S.I.; Faustov, N.N.
1986-01-01
Phase transformations at continuous cooling at β-region temperatures in VT6ch and VT23 alloys are studied. Nonequilibrium phases: α', α'', (ω), βsub(e), αsub(e), are shown to be formed in these alloys depending on cooling composition and rate. It is established that at cooling at temperatures below Ar 3 in alloys studied high-temperature α-phase is formed, and at temperatures below 650 deg C - more dispersed low-temperature α-phase precipitating from β-solution volumes mostly enriched by alloying elements according to the intermediate mechanism. Diagrams of anisothermal β-phase decomposition for VT6ch and VT23 alloys are plotted in coincidence with the results of thermal, thermodifferential, metallographic and X-ray diffraction analyses; lines of martensite transformation, lines of high- and low-temperature α-phase formation are pointed on the diagrams. Besides, for VT23 alloy a line for (ω)-phase formation is pointed
The kinetics of the β→α transformation in unalloyed plutonium after partial formation of the β phase
International Nuclear Information System (INIS)
Robinson, A.C.; Stacey, R.J.
1976-01-01
The kinetics of the isothermal β→α transformation after complete and only partial formation of the β phase in unalloyed plutonium containing about 900 ppm of impurity are reported and compared with previously published and conventionally accepted β→α transformation kinetics after complete formation of the β phase in this material. In these experiments the heating was provided by constant temperature oil baths and the transformations were monitored by electrical resistance measurements on 0.63 mm diameter wire samples at temperatures ranging from -65 0 C to +75 0 C. After complete formation of the β phase in the plutonium used in these experiments the kinetics of the β→α transformation were in general agreement with previously published data, although the present transformations were slower than reported by previous workers. After only partial formation of the β phase the subsequent β→α transformations were found to be very fast and to be characterised by zero or very short incubation periods, rapid rates of transformation and a final equilibrium consisting of more than 90% β phase. (Auth.)
Benafan, Othmane
2012-01-01
The deformation and transformation mechanisms of polycrystalline Ni49.9Ti50.1 and Ni50.3Ti29.7Hf20 (in at.%) shape memory alloys were investigated by combined experimental and modeling efforts aided by an in situ neutron diffraction technique at stress and temperature. The thermomechanical response of the low temperature martensite, the high temperature austenite phases, and changes between these two states during thermomechanical cycling were probed and reported. In the cubic austenite phase, stress-induced martensite, deformation twinning and slip processes were observed which helped in constructing a deformation map that contained the limits over which each of the identified mechanisms was dominant. Deformation of the monoclinic martensitic phase was also investigated where the microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were compared to the bulk macroscopic response. When cycling between these two phases, the evolution of inelastic strains, along with the shape setting procedures were examined and used for the optimization of the transformation properties as a function of deformation levels and temperatures. Finally, this work was extended to the development of multiaxial capabilities at elevated temperatures for the in situ neutron diffraction measurements of shape memory alloys on the VULCAN Diffractometer at Oak Ridge National Laboratory.
Mechanically Induced Graphite-Nanodiamonds-Phase Transformations During High-Energy Ball Milling
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.
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
Directory of Open Access Journals (Sweden)
Maurice R. Kibler
2010-07-01
Full Text Available We propose a group-theoretical approach to the generalized oscillator algebra Aκ recently investigated in J. Phys. A: Math. Theor. 2010, 43, 115303. The case κ ≥ 0 corresponds to the noncompact group SU(1,1 (as for the harmonic oscillator and the Pöschl-Teller systems while the case κ < 0 is described by the compact group SU(2 (as for the Morse system. We construct the phase operators and the corresponding temporally stable phase eigenstates for Aκ in this group-theoretical context. The SU(2 case is exploited for deriving families of mutually unbiased bases used in quantum information. Along this vein, we examine some characteristics of a quadratic discrete Fourier transform in connection with generalized quadratic Gauss sums and generalized Hadamard matrices.
Energy Technology Data Exchange (ETDEWEB)
Rolly, Gaboriaud, E-mail: Rolly.gaboriaud@univ-poitiers.fr [Institut Pprime, CNRS-University of Poitiers, SP2MI-BP 30179, 86962 Chasseneuil-Futuroscope (France); Fabien, Paumier [Institut Pprime, CNRS-University of Poitiers, SP2MI-BP 30179, 86962 Chasseneuil-Futuroscope (France); Bertrand, Lacroix [CSIC – University of Sevilla, Avenida Américo Vespucio, 49, 41092 Sevilla (Spain)
2014-05-01
Ion-irradiation induced diffusion and the phase transformation of a bixbyite-fluorite related rare earth oxide thin films are studied. This work is focused on yttrium sesquioxide, Y{sub 2}O{sub 3}, thin films deposited on Si (1 0 0) substrates using the ion beam sputtering technique (IBS). As-deposited samples were annealed ant then irradiated at cryogenic temperature (80 K) with 260 keV Xe{sup 2+} at different fluences. The irradiated thin oxide films are characterized by X-ray diffraction. A cubic to monoclinic phase transformation was observed. Analysis of this phenomenon is done in terms of residual stresses. Stress measurements as a function of irradiation fluences were realised using the XRD-sin{sup 2}ψ method. Stress evolution and kinetic of the phase transformation are compared and leads to the role-played by the nucleation of point and extended defects.
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)
Rate-independent dissipation in phase-field modelling of displacive transformations
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.
Phase transformations of siderite ore by the thermomagnetic analysis data
Energy Technology Data Exchange (ETDEWEB)
Ponomar, V.P., E-mail: vitaliyponomar.vp@gmail.com; Dudchenko, N.O.; Brik, A.B.
2017-02-01
Thermal decomposition of Bakal siderite ore (that consists of magnesium siderite and ankerite traces) was investigated by thermomagnetic analysis. Thermomagnetic analysis was carried-out using laboratory-built facility that allows automatic registration of sample magnetization with the temperature (heating/cooling rate was 65°/min, maximum temperature 650 °C) at low- and high-oxygen content. Curie temperature gradually decreases with each next cycles of heating/cooling at low-oxygen content. Curie temperature decrease after 2nd cycle of heating/cooling at high-oxygen content and do not change with next cycles. Final Curie temperature for both modes was ~320 °C. Saturation magnetization of obtained samples increases up to 20 Am{sup 2}/kg. The final product of phase transformation at both modes was magnesioferrite. It was shown that intermediate phase of thermal decomposition of Bakal siderite ore was magnesiowustite. - Highlights: • Mg-siderite decomposition was investigated by thermomagnetic analysis. • Magnetization and Curie temperature change with each next cycle of heating/cooling. • Magnesioferrite is the final phase of Mg-siderite thermal decomposition. • Transformation exclude the hematite formation.
Phase transformation in a Ni-Mo-Cr alloy
International Nuclear Information System (INIS)
Dymek, S.; Wrobel, M.; Blicharski, M.; Dollar, M.
2001-01-01
The paper gives a characteristic of a nickel-based superalloy containing 25 wt.% Mo and 8 wt.% Cr with particular attention to the influence of a thermochemical and heat treatment on phase transformations. The applied heat treatments are comprised of soaking temperature 1100 o C followed by aging at 650 o C at three conditions: conventional aging for 72 hours, prolonged aging for 4000 hours and prolonged aging for 4000 hours followed by cold working and subsequent aging for 1000 hours. The conventional aging led to the formation of lenticular precipitates of the dispersed metastable Ni 2 (Mo,Cr) phase. The aging for 4000 hours brought about coarsening of the ordered domains without changing their crystallographic and ordering characteristics. The plastic deformation preceded the further aging for 1000 hours accelerated the decomposition of the Ni 2 (Mo,Cr) phase on the mixture of the Ni 3 Mo and Ni 4 Mo-based phases. (author)
Kuppan, Saravanan; Xu, Yahong; Liu, Yijin; Chen, Guoying
2017-02-01
Understanding the reaction pathway and kinetics of solid-state phase transformation is critical in designing advanced electrode materials with better performance and stability. Despite the first-order phase transition with a large lattice mismatch between the involved phases, spinel LiMn1.5Ni0.5O4 is capable of fast rate even at large particle size, presenting an enigma yet to be understood. The present study uses advanced two-dimensional and three-dimensional nano-tomography on a series of well-formed LixMn1.5Ni0.5O4 (0growth process instead of a shrinking-core or a particle-by-particle process. Superior kinetics of (100) facets at the vertices of truncated octahedral particles promote preferential delithiation, whereas the observation of strain-induced cracking suggests mechanical degradation in the material.
Phase transformations in lead zirconate-titanate doped with lanthanum
Energy Technology Data Exchange (ETDEWEB)
Ishchuk, V M; Morozov, E M
1979-07-01
Presented are the results of studies on the character of phase transitions of the lead-lanthanum zirconate-titanate (LLZT) system. The replacement of lead by lanthanum leads to the expansion of the region of antisegnetoelectric (ASE) states of solid solutions of lead zirconate-titanate (LZT) in the direction of PbTiO/sub 3/ concentration growth. An intermediate region is revealed between segnetoelectric (SE) and ASE states, material properties in which depend on their prehistory: annealed samples are in the ASE state, whereas the application of electric field exceeding some critical value induces the SE state. A family of phase diagrams obtained at consequent replacement of lead by lanthanum permits to identify phase states in any series of LLZT with a constant ratio of Zr:Ti, in the x/65/35 series in particular. Thermally depolarized state of materials of this series at x<6.5 is shown to be antisegnetoelectric at all the temperatures below the Curie point Tsub(c), and heating causes phase transition of ASE..-->..PE (paraelectric state) at Tsub(c). Polarized samples being heated, a successiveness of phase transitions of SE..-->..ASE takes place at T/sub 0/, and that of ASE reversible PE at Tsub(C) (Tsub(0)
Phase transformations in the titanium-niobium binary alloy system
International Nuclear Information System (INIS)
Moffat, D.L.
1985-01-01
A fundamental study of the phase transformations in the Ti-Nb binary alloy system was completed. Eight alloys in the range 20 to 70 at% Nb were investigated using transmission electron microscopy, light metallography, and x-ray diffraction. Measurements of electric resistivity and Vicker's microhardness also were performed. Emphasis was placed on the minimization of interstitial contamination in all steps of alloy fabrication and specimen preparation. In order to eliminate the effects of prior cold working, the alloys studied were recrystallized at 1000 0 C. Phase transformations were studied in alloys quenched to room temperature after recrystallization and then isothermally aged, and in those isothermally aged without a prior room temperature quench. It was found that the microstructures of the quenched 20 and 25% Nb alloys were extremely sensitive to quench rate - with a fast quench producing martensite, a slow quench, the omega phase. Microstructures of the higher niobium content alloys were much less sensitive to quench rate. The microstructures of the isothermally aged 20 and 25% Nb alloys were found to be sensitive to prior thermal history. Alloys quenched to room temperature and then aged at 400 0 C contained large omega precipitates, while those aged without an intermediate room temperature quench contained alpha precipitates
Energy Technology Data Exchange (ETDEWEB)
Platt, P., E-mail: Philip.Platt@manchester.ac.uk [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom); Frankel, P. [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom); Gass, M.; Howells, R. [AMEC, Walton House, Faraday Street, Birchwood Park, Risley, Warrington WA3 6GA (United Kingdom); Preuss, M. [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom)
2014-11-15
Corrosion is a key limiting factor in the degradation of zirconium alloys in light water reactors. Developing a mechanistic understanding of the corrosion process offers a route towards improving safety and efficiency as demand increases for higher burn-up of fuel. Oxides formed on zirconium alloys are composed of both monoclinic and meta-stable tetragonal phases, and are subject to a number of potential mechanical degradation mechanisms. The work presented investigates the link between the tetragonal to monoclinic oxide phase transformation and degradation of the protective character of the oxide layer. To achieve this, Abaqus finite element analysis of the oxide phase transformation has been carried out. Study of the change in transformation strain energy shows how relaxation of oxidation induced stress and fast fracture at the metal–oxide interface could destabilise the tetragonal phase. Central to this is the identification of the transformation variant most likely to form, and understanding why twinning of the transformed grain is likely to occur. Development of transformation strain tensors and analysis of the strain components allows some separation of dilatation and shear effects. Maximum principal stress is used as an indication of fracture in the surrounding oxide layer. Study of the stress distributions shows the way oxide fracture is likely to occur and the differing effects of dilatation and shape change. Comparison with literature provides qualitative validation of the finite element simulations.
Platt, P.; Frankel, P.; Gass, M.; Howells, R.; Preuss, M.
2014-11-01
Corrosion is a key limiting factor in the degradation of zirconium alloys in light water reactors. Developing a mechanistic understanding of the corrosion process offers a route towards improving safety and efficiency as demand increases for higher burn-up of fuel. Oxides formed on zirconium alloys are composed of both monoclinic and meta-stable tetragonal phases, and are subject to a number of potential mechanical degradation mechanisms. The work presented investigates the link between the tetragonal to monoclinic oxide phase transformation and degradation of the protective character of the oxide layer. To achieve this, Abaqus finite element analysis of the oxide phase transformation has been carried out. Study of the change in transformation strain energy shows how relaxation of oxidation induced stress and fast fracture at the metal-oxide interface could destabilise the tetragonal phase. Central to this is the identification of the transformation variant most likely to form, and understanding why twinning of the transformed grain is likely to occur. Development of transformation strain tensors and analysis of the strain components allows some separation of dilatation and shear effects. Maximum principal stress is used as an indication of fracture in the surrounding oxide layer. Study of the stress distributions shows the way oxide fracture is likely to occur and the differing effects of dilatation and shape change. Comparison with literature provides qualitative validation of the finite element simulations.
International Nuclear Information System (INIS)
Platt, P.; Frankel, P.; Gass, M.; Howells, R.; Preuss, M.
2014-01-01
Corrosion is a key limiting factor in the degradation of zirconium alloys in light water reactors. Developing a mechanistic understanding of the corrosion process offers a route towards improving safety and efficiency as demand increases for higher burn-up of fuel. Oxides formed on zirconium alloys are composed of both monoclinic and meta-stable tetragonal phases, and are subject to a number of potential mechanical degradation mechanisms. The work presented investigates the link between the tetragonal to monoclinic oxide phase transformation and degradation of the protective character of the oxide layer. To achieve this, Abaqus finite element analysis of the oxide phase transformation has been carried out. Study of the change in transformation strain energy shows how relaxation of oxidation induced stress and fast fracture at the metal–oxide interface could destabilise the tetragonal phase. Central to this is the identification of the transformation variant most likely to form, and understanding why twinning of the transformed grain is likely to occur. Development of transformation strain tensors and analysis of the strain components allows some separation of dilatation and shear effects. Maximum principal stress is used as an indication of fracture in the surrounding oxide layer. Study of the stress distributions shows the way oxide fracture is likely to occur and the differing effects of dilatation and shape change. Comparison with literature provides qualitative validation of the finite element simulations
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.)
Transformation of Socioeconomic Space: The Role of the State
Directory of Open Access Journals (Sweden)
Alexander Nikolaevich Shvetsov
2015-03-01
Full Text Available Modern Russia is traditionally characterized by a special and strong public participation in solving problems of spatial development. Thus, the state has following diverse roles: 1 the creator of the modern space configuration; 2 the mastermind and main driving force of modern spatial transformations; 3 the regulator and investor of these processes; 4 the main sponsor and beneficiary of space transformation; and, finally, the hostage of its own dominance in the processes of spatial transformation. However, stereotypes are being gradually overcome and public policy in the area of spatial transformations focuses not only on «public projects» but also on self-development of regions, combined with the interests of big business which plays an increasing role in the transformation of socioeconomic space. The article reveals the meaning and content of the problem of systemic interaction between the state and space concerning the modernization of the country. The author explores the range of fundamental research and applied issues resulting from the contradictory combination of traditional (historical stereotypes and the latest Russian circumstances. These issues determine the background, nature and consequences of state impacts on socio-economic space, as well as the composition, content and validity of the used instruments
Acoustic emission during R-phase and martensitic transformations in a Ti50.2Ni48.3Fe1.5 alloy
International Nuclear Information System (INIS)
Takashima, K.; Nishida, M.
1995-01-01
Acoustic emission (AE) signals generated during phase transformations in a Ti 50.2 Ni 48.3 Fe 1.5 shape memory alloy have been measured, and the AE parameters have been correlated with the phase transformation events. The AE count rate curve during cooling of the specimen was found to have two distinct peaks at temperatures of approximately 8 and -30 C. These peaks were confirmed by both optical microscopy and differential scanning calorimetry to correspond to the B2 to R phase transformation (at 8 C) and the R to B19' transformation (at -30 C) respectively. This is the first detection of the AE events associated with the R-phase transformation in Ti-Ni shape memory alloys. Although the amplitude distributions during both transformations were almost identical, both the duration and the rise time of AE events during the B2 to R phase transformation were larger than those during the R to B19' transformation. These observations suggest that the transformation velocity of the R-phase transformation is slower than that of the martensitic transformation, and are consistent with the nature of both these transformations. It is concluded that the AE technique can be applied to the determination of transformation temperatures of Ti-Ni alloys on cooling as well as DSC and electrical resistivity measurement. (orig.)
International Nuclear Information System (INIS)
Shimada, Yoshio
2015-01-01
open-phase when the transformer is no-load which United States Electric Power Research Institute (EPRI) developed. As the detailed analyses data from EPRI related to the detection method concerned have not been disclosed officially yet, in this paper, the quantitative and detailed verification results of the method using EMTP is reported. (author)
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...... in terms of a decrease of energy band gap with increasing pressure. ©2000 American Institute of Physics....
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)
Directory of Open Access Journals (Sweden)
Hsin-Hung Ou
2010-01-01
Full Text Available Based on the determination of X-ray powder diffraction, this study aims to investigate the thermal effect on the phase transformation of microwave-assisted titanate nanotubes (MTNTs. The phase transformation is highly dependent on the intercalating amount of Na(I within MTNTs and on the heating atmosphere. In other words, the presence of Na(I favors the transformation of TNTs phase into Na2Ti6O13 whereas anatase phase selectively formed in the case of MTNTs with less Na(I amount. Furthermore, H2 versus O2 is able to form anatase phase and establish a newly transformation pathway. The photocatalytic ability of the calcined MTNTs was also evaluated based on the observed rate constant of trichloroethylene degradation. In addition to anatase phase, the newly phase including Na2Ti6O13 and Ti2O3 with calcined MTNTs is able to photocatalyze trichloroethylene. MTNTs calcined with the presence of H2 also exhibit a superior photocatalytic performance to P25 TiO2.
Microstructure and phase transformations in laser clad CrxSy/Ni coating on H13 steel
Lei, Yiwen; Sun, Ronglu; Tang, Ying; Niu, Wei
2015-03-01
Laser cladding was carried out onto H13 steel with preplaced NiCrBSi+Ni/MoS2 powders using CO2 laser under the optimized experimental parameters of laser power 2 kW, scanning velocity 6 mm/s and laser beam diameter 3 mm. An X-ray diffractometer and scanning electron microscope with energy dispersive spectroscopy were applied to analyze the microstructure and phase compositions of the coating. Thermodynamic calculation was performed with Thermo-Calc software on the basis of a commercially available Ni-based Alloys' database. The experimental results show that MoS2 decomposed and S reacted with Cr to form nonstoichiometric CrxSy during the laser cladding process. The coating consists of spherical CrxSy particles, primary γ-Ni dendrite, interdendritic eutectic (γ-Ni+NiMo) and precipitated NiMo. The precipitated NiMo was fine and uniformly distributed in primary γ-Ni dendrite. The calculated results and experimental data indicate that the solidification process in the coating during laser cladding process was liquid→liquid+CrxSy→ liquid+CrxSy+γ-Ni→liquid+CrxSy+γ-Ni+ eutectic (γ-Ni+NiMo). A solid state phase transformation (fine and uniformly distributed NiMo precipitated from γ-Ni) occurred after the solidification process. The calculations agree well with the experimental data and it is helpful to understand the phase transformation and microstructure evolution in the coating.
Gyrator transform of Gaussian beams with phase difference and generation of hollow beam
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.
Hilbert transform and optical tomography for anisotropic edge enhancement of phase objects
International Nuclear Information System (INIS)
Montes-Perez, Areli; Meneses-Fabian, Cruz; Rodriguez-Zurita, Gustavo
2011-01-01
In phase object tomography a slice reconstruction is related to distribution of refractive index. Typically, this is obtained by applying the filtered back-projection algorithm to the set of projections (sinogram) obtained experimentally, which are sequentially obtained by calculating the phase of the wave emerging from the slice of the object at different angles. In this paper, based on optical implementation of the Hilbert-transform in a 4f Fourier operator, the Hilbert transform of the projections leaving of the object are obtained numerically. When these projection data are captured for a set of viewing angles an unconventional sinogram is eventually obtained, we have called it as an Hilbert-sinogram. The reconstruction obtained by applying the filtered back-projection algorithm is proportional to the Hilbert transform of the distribution of refractive index of the slice and the obtained image shows a typical isotropic edge enhancement. In this manuscript, the theoretical analysis and the numerical implementation of the Hilbert-transform, mathematical model of the edge enhancement reconstructed are extensively detailed.
Short- and long- term ageing effects on the phase transformation in Au-49.5 at % Cd
International Nuclear Information System (INIS)
Kelly, G.L.; Finlayson, T.R.; Ersez, T.; Smith, T.F.
1999-01-01
Full text: Gold-Cadmium alloys of approximately equiatomic composition are widely studied as model systems for the shape-memory effect and 'rubber-elasticity'. Rubber-elasticity occurs after ageing for a time in the low-temperature martensite phase. This ageing is accompanied by an increase in the martensite → austenite phase transformation temperature (A s ). The ageing dependence of the transformation is a critical problem when finding applications for the shape-memory effect in these materials. The origin of the ageing effect is controversial with proposed mechanisms including stabilisation of the martensite by a change in short range order or pinning of the martensite by defects. In the present study, a Au-49.5at%Cd alloy has been subjected to a series of ageing times and the phase transformation temperatures monitored using a push-rod dilatometer. One test series comprising a range of ageing times was completed and then the sample was aged in the martensite phase for several months before re-testing. Both test series show that ageing in the martensite phase increases the temperature of the reverse transformation (A s ) as expected. Previous work had suggested that all effects of any previous ageing treatments were obliterated by a single cycle through the martensite-austenite-martensite transformations. The present study shows that this is not the case. The A f and A s temperatures for each ageing time in the test series had increased by several degrees after a year of ageing and this increase was maintained despite repeated cycling through the phase transformations
CP violation with an unbroken CP transformation
Energy Technology Data Exchange (ETDEWEB)
Ratz, Michael [Department of Physics and Astronomy, University of California,Irvine, California 92697-4575 (United States); Trautner, Andreas [Bethe Center for Theoretical Physics und Physikalisches Institut der Universität Bonn,Nussallee 12, 53115 Bonn (Germany)
2017-02-21
A CP conserving SU(3) gauge theory is spontaneously broken to T{sub 7} by the vacuum expectation value (VEV) of a 15-plet. Even though the SU(3)-CP transformation is not broken by the VEV, the theory exhibits physical CP violation in the broken phase. This is because the SU(3)-CP transformation corresponds to the unique order-two outer automorphism of T{sub 7}, which is not a physical CP transformation for the T{sub 7} states, and there is no other possible CP transformation. We explicitly demonstrate that CP is violated by calculating a CP odd decay asymmetry in the broken phase. This scenario provides us with a natural protection for topological vacuum terms, ensuring that θ G{sub μν}G̃{sup μν} is absent even though CP is violated for the physical states of the model.
The kinetics of phase transformations of undercooled austenite of the Mn-Ni iron based model alloy
E. Rożniata; R. Dziurka; J. Pacyna
2011-01-01
Purpose: Present work corresponds to the research on the kinetics of phase transformations of undercooled austenite of Mn-Ni iron based model alloy. The kinetics of phase transformations of undercooled austenite of investigated alloy was presented on CCT diagram (continuous cooling transformation). Also the methodology of a dilatometric samples preparation and the method of the critical points determination were described.Design/methodology/approach: The austenitising temperature was defined ...
Directory of Open Access Journals (Sweden)
Bosneaga V.A
2013-08-01
Full Text Available The model is proposed for the calculation and research of steady state asymmetric modes and transients in three-phase three legs transformer devices with arbitrary diagram of windings connection, taking into account the electromagnetic coupling of the windings, located on different legs. Using as an example distribution transformer of 10/0.4 kV calculations and analysis were performed of the most characteristic steady asymmetrical modes, that occur during short circuit, phase failure, unbalanced load for the most common windings connections and, in particular, associated with the occurrence of zero sequence magnetic flow. For the considered regimes and schemes vector diagrams were constructed for currents and voltages as well as for the relative values of magnetic flow, which give a clear idea about their particular features.
International Nuclear Information System (INIS)
Catti, Michele
2001-01-01
The mechanism of the B3/B1 phase transition of SiC has been investigated by periodic LCAO-DFT least-enthalpy calculations. A new transformation pathway, based on a Pmm2 orthorhombic intermediate state with two SiC units per cell, is found to be energetically favored over the traditional R3m mechanism. The computed activation enthalpy is 0.75eV/SiC unit at the predicted transition pressure of 92GPa (B3LYP functional). Activation enthalpy and activation volume vs pressure are analyzed to characterize the kinetic aspects of the transformation
Second amorphous-to-crystalline phase transformation in Cu60Ti20Zr20 bulk metallic glass
DEFF Research Database (Denmark)
Cao, Q.P.; Li, J.F.; Zhang, P.N.
2007-01-01
The second amorphous-to-crystalline phase transformation in Cu60Ti20Zr20 bulk metallic glass was investigated by differential scanning calorimetry and x-ray diffractometry. The difference of the Gibbs free energies between the amorphous phase and the crystalline products during the transformation...
Welfare State Transformations and Inequality in OECD Countries
DEFF Research Database (Denmark)
2016-01-01
Editors: Melike Wulfgramm, Tonia Bieber & Stephan Leibfried This book analyzes how recent welfare state transformations across advanced democracies have shaped social and economic disparities. The authors observe a trend from a compensatory paradigm towards supply oriented social policy, and inve......Editors: Melike Wulfgramm, Tonia Bieber & Stephan Leibfried This book analyzes how recent welfare state transformations across advanced democracies have shaped social and economic disparities. The authors observe a trend from a compensatory paradigm towards supply oriented social policy...... supply orientation in most social policy fields has further contributed to social inequality. The authors work from sociological and political science perspectives, examining all of the main branches of the welfare state, from health, education and tax policy, to labour market, pension and migration...
Giovambattista, N.; Sciortino, F.; Starr, F. W.; Poole, P. H.
The potential energy landscape (PEL) formalism is a valuable approach within statistical mechanics for describing supercooled liquids and glasses. We use the PEL formalism and computer simulations to study the transformation between low-density (LDL) and high-density liquid (HDL) water, and between low-density (LDA) and high-density amorphous ice (HDA). We employ the ST2 water model that exhibits a LDL-HDL first-order phase transition and a sharp LDA-HDA transformation, as observed in experiments. Our results are consistent with the view that LDA and HDA configurations are associated with two distinct regions (megabasins) of the PEL that are separated by a potential energy barrier. At higher temperature, we find that LDL configurations are located in the same megabasin as LDA, and that HDL configurations are located in the same megabasin as HDA. We show that the pressure-induced LDL-HDL and LDA-HDA transformations occur along paths that interconnect these two megabasins, but that the path followed by the liquid and the amorphous ice differ. We also study the liquid-to-ice-VII first-order phase transition. The PEL properties across this transition are qualitatively similar to the changes found during the LDA-HDA transformation, supporting the interpretation that the LDA-HDA transformation is a first-order-like phase transition between out-of-equilibrium states.
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.
Energy Technology Data Exchange (ETDEWEB)
Lakhani, Archana; Kushwaha, Pallavi; Rawat, R; Kumar, Kranti; Banerjee, A; Chaddah, P, E-mail: rrawat@csr.ernet.i [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore-452017, M.P (India)
2010-01-27
Glass-like arrest has recently been reported in various magnetic materials. As in structural glasses, the kinetics of a first order transformation is arrested while retaining the higher entropy phase as a non-ergodic state. We show visual mesoscopic evidence of the irreversible transformation of the arrested antiferromagnetic-insulating phase in Pr{sub 0.5}Ca{sub 0.5}Mn{sub 0.975}Al{sub 0.025}O{sub 3} to its equilibrium ferromagnetic-metallic phase with an isothermal increase of magnetic field, similar to its iso-field transformation on warming. The magnetic field dependence of the non-equilibrium to equilibrium transformation temperature is shown to be governed by Le Chatelier's principle. (fast track communication)
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
Effect of extrapolation length on the phase transformation of epitaxial ferroelectric thin films
International Nuclear Information System (INIS)
Hu, Z.S.; Tang, M.H.; Wang, J.B.; Zheng, X.J.; Zhou, Y.C.
2008-01-01
Effects of extrapolation length on the phase transformation of epitaxial ferroelectric thin films on dissimilar cubic substrates have been studied on the basis of the mean-field Landau-Ginzburg-Devonshire (LGD) thermodynamic theory by taking an uneven distribution of the interior stress with thickness into account. It was found that the polarization of epitaxial ferroelectric thin films is strongly dependent on the extrapolation length of films. The physical origin of the extrapolation length during the phase transformation from paraelectric to ferroelectric was revealed in the case of ferroelectric thin films
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.
Second amorphous-to-crystalline phase transformation in Cu(60)Ti(20)Zr(20) bulk metallic glass.
Cao, Q P; Li, J F; Zhang, P N; Horsewell, A; Jiang, J Z; Zhou, Y H
2007-06-20
The second amorphous-to-crystalline phase transformation in Cu(60)Ti(20)Zr(20) bulk metallic glass was investigated by differential scanning calorimetry and x-ray diffractometry. The difference of the Gibbs free energies between the amorphous phase and the crystalline products during the transformation is estimated to be about 2.46 kJ mol(-1) at 753 K, much smaller than the 61 kJ mol(-1) obtained assuming that it is a polymorphic transformation. It was revealed that the phase transformation occurs through a eutectic crystallization of Cu(51)Zr(14) and Cu(2)TiZr, having an effective activation energy of the order of 400 kJ mol(-1). The average Avrami exponent n is about 2.0, indicating that the crystallization is diffusion controlled.
2017-07-31
naval and structural applications. However, prior to this research project, a fundamental understanding of the phase transformation behavior under the...prior to this research project, a fundamental understanding of the phase transformation behavior under the high heating and cooling rates associated...HAZ mechanical properties. Such a treatment is expensive, time consuming , and cannot be practically applied to large structures. However, the absence
Phase Transformation and Shape Memory Effect of Ti-Pd-Pt-Zr High-Temperature Shape Memory Alloys
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 training effect was also investigated.
Effect of Nb on phase transformations and microstructure in high Nb titanium aluminides
International Nuclear Information System (INIS)
Bean, Glenn E.; Kesler, Michael S.; Manuel, Michele V.
2014-01-01
Highlights: • Thermodynamically-guided design of heat treatment schedules. • Linking chemistry and heat treatment to phase morphology. • Strong dependence of phase transformation behavior on Nb concentration. - Abstract: Titanium aluminides are of interest due to their high specific strength and performance up to 750 °C. Research into high-Nb γ-TiAl based titanium aluminides has shown promising improvements in performance by introduction of the σ-Nb 2 Al phase. However, one current challenge is improving mechanical properties at room and elevated temperatures in order to enable their further implementation. These properties are closely tied with microstructural refinement, and thus phase evolution and microstructural development is the focus of this work. Phase transformation temperatures and stability ranges were determined experimentally through DSC analysis of arc melted alloys, then compared with predictions based upon computational models, and investigated through heat treatment of experimental alloys to develop an ultrafine γ + σ microstructure
Effect of Nb on phase transformations and microstructure in high Nb titanium aluminides
Energy Technology Data Exchange (ETDEWEB)
Bean, Glenn E.; Kesler, Michael S.; Manuel, Michele V., E-mail: mmanuel@mse.ufl.edu
2014-11-15
Highlights: • Thermodynamically-guided design of heat treatment schedules. • Linking chemistry and heat treatment to phase morphology. • Strong dependence of phase transformation behavior on Nb concentration. - Abstract: Titanium aluminides are of interest due to their high specific strength and performance up to 750 °C. Research into high-Nb γ-TiAl based titanium aluminides has shown promising improvements in performance by introduction of the σ-Nb{sub 2}Al phase. However, one current challenge is improving mechanical properties at room and elevated temperatures in order to enable their further implementation. These properties are closely tied with microstructural refinement, and thus phase evolution and microstructural development is the focus of this work. Phase transformation temperatures and stability ranges were determined experimentally through DSC analysis of arc melted alloys, then compared with predictions based upon computational models, and investigated through heat treatment of experimental alloys to develop an ultrafine γ + σ microstructure.
[Study of the phase transformation of TiO2 with in-situ XRD in different gas].
Ma, Li-Jing; Guo, Lie-Jin
2011-04-01
TiO2 sample was prepared by sol-gel method from chloride titanium. The phase transformation of the prepared TiO2 sample was studied by in-situ XRD and normal XRD in different gas. The experimental results showed that the phase transformation temperatures of TiO2 were different under in-situ or normal XRD in different kinds of gas. The transformation of amorphous TiO2 to anatase was controlled by kinetics before 500 degrees C. In-situ XRD showed that the growth of anatase was inhibited, but the transformation of anatase to rutile was accelerated under inactive nitrogen in contrast to air. Also better crystal was obtained under hydrogen than in argon. These all showed that external oxygen might accelerate the growth of TiO2, but reduced gas might partly counteract the negative influence of lack of external oxygen. The mechanism of phase transformation of TiO2 was studied by in-situ XRD in order to control the structure in situ.
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...
Polynomial Phase Estimation Based on Adaptive Short-Time Fourier Transform.
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.
International Nuclear Information System (INIS)
Alizadeh-Sh, M.; Marashi, S.P.H.; Pouranvari, M.
2014-01-01
Highlights: • Phase transformations during RSW of AISI430 are detailed. • Grain growth, martensite formation and carbide precipitation are dominant phase transformations. • Failure mode of AISI430 resistance spot welded joints are analyzed. • Larger FZ size provided improved load bearing capacity and energy absorption capability. - Abstract: The paper aims at investigating the process–microstructure–performance relationship in resistance spot welding of AISI 430 ferritic stainless steel. The phase transformations which occur during weld thermal cycle were analyzed in details, based on the physical metallurgy of welding of the ferritic stainless steels. It was found that the microstructure of the fusion zone and the heat affected zone is influenced by different phenomena including grain growth, martensite formation and carbide precipitation. The effects of welding cycle on the mechanical properties of the spot welds in terms of peak load, energy absorption and failure mode are discussed
A theoretical study of the omega-phase transformation in metals
Sanati, Mahdi
I have studied the formation of o-phase from electronic and mesoscopic (domain wall) points of view. To study the formation of domain walls, I have extended the Landau model of Cook for the o-phase transition by including a spatial gradient (Ginzburg) term of the scalar order parameter. In general, the Landau free energy is an asymmetric double-well potential. From the variational derivative of the total free energy I obtained a static equilibrium condition. By solving this equation for different physical parameters and boundary conditions, I obtained different quasi-one-dimensional soliton-like solutions. These solutions correspond to three different types of domain walls between the o-phase and the beta-matrix. These results are used to model the formation of the o-phase in bcc Ti. Canonical band model and first principles calculations confirmed the instability of the bcc-phase of group III and IV transition metals with respect to the o-phase transformation. I showed that the d-electron density is the controlling parameter for this type of the transformation. Also the possibility of formation of the o-phase for rare earth metals is discussed. First-principles full-potential linear muffin-tin orbital method (FPLMTO) calculations are performed for o-type displacement of the atoms to study the formation of the o-phase in TiAl and Ti 3Al2Nb alloys. The results of my calculations showed an instability in ordered B2 TiAl structure with respect to the o-phase when one third of the Al atoms are replaced by Nb atoms. These phenomena are explained, first by symmetry arguments; then a pair potential model is used to illustrate this instability based on interactions between different pair of atoms derived from the electronic structure. In addition, importance of the atomic arrangements on the structural stability of the Ti3Al2 Nb system is discussed.
International Nuclear Information System (INIS)
Hu, T.; Wen, C.S.; Lu, J.; Wu, S.L.; Xin, Y.C.; Zhang, W.J.; Chu, C.L.; Chung, J.C.Y.; Yeung, K.W.K.; Kwok, D.T.K.; Chu, Paul K.
2009-01-01
The phase constituents and transformation behavior of the martensite B19' NiTi shape memory alloy after undergoing surface mechanical attrition treatment (SMAT) are investigated. SMAT is found to induce the formation of a parent B2 phase from the martensite B19' in the top surface layer. By removing the surface layer-by-layer, X-ray diffraction reveals that the amount of the B2 phase decreases with depth. Differential scanning calorimetry (DSC) further indicates that the deformed martensite in the sub-surface layer up to 300 μm deep exhibits the martensite stabilization effect. The graded phase structure and transformation behavior in the SMATed NiTi specimen can be attributed to the gradient change in strain with depth.
Gusev, Aleksandr I.
2000-01-01
Data on order-disorder phase transformations in strongly nonstoichiometric carbides and nitrides MXy (X=C, N) of Group IV and V transition metals at temperatures below 1300-1400 K are reviewed. The order-parameter functional method as applied to atomic and vacancy ordering in strongly nonstoichiometric MXy compounds and to phase equilibrium calculations for M-X systems is discussed. Phase diagram calculations for the Ti-C, Zr-C, Hf-C, V-C, Nb-C, Ta-C, Ti-N, and Ti-B-C systems (with the inclusion of the ordering of nonstoichiometric carbides and nitrides) and those for pseudobinary carbide M(1)C-M(2)C systems are presented. Heat capacity, electrical resistivity and magnetic susceptibility changes at reversible order-disorder phase transformations in nonstoichiometric carbides are considered.
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
Nature of gallium focused ion beam induced phase transformation in 316L austenitic stainless steel
International Nuclear Information System (INIS)
Babu, R. Prasath; Irukuvarghula, S.; Harte, A.; Preuss, M.
2016-01-01
The microstructural evolution and chemistry of the ferrite phase (α), which transforms from the parent austenite phase (γ) of 316L stainless steel during gallium (Ga) ion beam implantation in Focused Ion Beam (FIB) instrument was systematically studied as a function of Ga"+ ion dose and γ grain orientations. The propensity for initiation of γ → α phase transformation was observed to be strongly dependent on the orientation of the γ grain with respect to the ion beam direction and correlates well with the ion channelling differences in the γ orientations studied. Several α variants formed within a single γ orientation and the sputtering rate of the material, after the γ → α transformation, is governed by the orientation of α variants. With increased ion dose, there is an evolution of orientation of the α variants towards a variant of higher Ga"+ channelling. Unique topographical features were observed within each specific γ orientation that can be attributed to the orientation of defects formed during the ion implantation. In most cases, γ and α were related by either Kurdjumov-Sachs (KS) or Nishiyama-Wassermann (NW) orientation relationship (OR) while in few, no known OR's were identified. While our results are consistent with gallium enrichment being the cause for the γ → α phase transformation, some observations also suggest that the strain associated with the presence of gallium atoms in the lattice has a far field stress effect that promotes the phase transformation ahead of gallium penetration.
Zhuang, Leimeng; Taddei, Caterina; Hoekman, Marcel; Leinse, Arne; Heideman, René; van Dijk, Paulus; Roeloffzen, Chris
2013-11-04
In this paper, we propose and experimentally demonstrate a novel wideband on-chip photonic modulation transformer for phase-modulated microwave photonic links. The proposed device is able to transform phase-modulated optical signals into intensity-modulated versions (or vice versa) with nearly zero conversion of laser phase noise to intensity noise. It is constructed using waveguide-based ring resonators, which features simple architecture, stable operation, and easy reconfigurability. Beyond the stand-alone functionality, the proposed device can also be integrated with other functional building blocks of photonic integrated circuits (PICs) to create on-chip complex microwave photonic signal processors. As an application example, a PIC consisting of two such modulation transformers and a notch filter has been designed and realized in TriPleX(TM) waveguide technology. The realized device uses a 2 × 2 splitting circuit and 3 ring resonators with a free spectral range of 25 GHz, which are all equipped with continuous tuning elements. The device can perform phase-to-intensity modulation transform and carrier suppression simultaneously, which enables high-performance phase-modulated microwave photonics links (PM-MPLs). Associated with the bias-free and low-complexity advantages of the phase modulators, a single-fiber-span PM-MPL with a RF bandwidth of 12 GHz (3 dB-suppression band 6 to 18 GHz) has been demonstrated comprising the proposed PIC, where the achieved spurious-free dynamic range performance is comparable to that of Class-AB MPLs using low-biased Mach-Zehnder modulators.
Weighted least squares phase unwrapping based on the wavelet transform
Chen, Jiafeng; Chen, Haiqin; Yang, Zhengang; Ren, Haixia
2007-01-01
The weighted least squares phase unwrapping algorithm is a robust and accurate method to solve phase unwrapping problem. This method usually leads to a large sparse linear equation system. Gauss-Seidel relaxation iterative method is usually used to solve this large linear equation. However, this method is not practical due to its extremely slow convergence. The multigrid method is an efficient algorithm to improve convergence rate. However, this method needs an additional weight restriction operator which is very complicated. For this reason, the multiresolution analysis method based on the wavelet transform is proposed. By applying the wavelet transform, the original system is decomposed into its coarse and fine resolution levels and an equivalent equation system with better convergence condition can be obtained. Fast convergence in separate coarse resolution levels speeds up the overall system convergence rate. The simulated experiment shows that the proposed method converges faster and provides better result than the multigrid method.
Modelling a single phase voltage controlled rectifier using Laplace transforms
Kraft, L. Alan; Kankam, M. David
1992-01-01
The development of a 20 kHz, AC power system by NASA for large space projects has spurred a need to develop models for the equipment which will be used on these single phase systems. To date, models for the AC source (i.e., inverters) have been developed. It is the intent of this paper to develop a method to model the single phase voltage controlled rectifiers which will be attached to the AC power grid as an interface for connected loads. A modified version of EPRI's HARMFLO program is used as the shell for these models. The results obtained from the model developed in this paper are quite adequate for the analysis of problems such as voltage resonance. The unique technique presented in this paper uses the Laplace transforms to determine the harmonic content of the load current of the rectifier rather than a curve fitting technique. Laplace transforms yield the coefficient of the differential equations which model the line current to the rectifier directly.
Phase transformation and microstructural changes during ageing process of an Ag-Pd-Cu-Au alloy
Energy Technology Data Exchange (ETDEWEB)
Yu, Chin-Ho; Park, Mi-Gyoung; Kwon, Yong Hoon; Seol, Hyo-Joung [Department of Dental Materials, School of Dentistry and Medical Research Institute, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Kim, Hyung-Il [Department of Dental Materials, School of Dentistry and Medical Research Institute, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of)], E-mail: hilkim@pusan.ac.kr
2008-07-28
Age-hardening behaviour and the related phase transformation and microstructural changes during isothermal ageing process were studied to elucidate the age-hardening mechanism of an Ag-based dental casting alloy composed of Ag-Pd-Cu-Au-Zn, Ir and In by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and energy dispersive spectroscopic microanalysis (EDS). In the hardness test at 350 and 400 deg. C, the hardness of the solution-treated specimen began to increase and reached a maximum value with increasing ageing time, and subsequently the hardness decreased gradually. By considering XRD results and SEM observations together, the solution-treated specimen consisted of three phases, the Ag-rich {alpha}{sub 1} phase as a matrix, the Cu-Pd {alpha}{sub 2} phase and the CuPd {beta} phase with a CsCl-type as particle-like structures. By ageing the solution-treated specimen, the Ag-rich {alpha}{sub 1} and Cu-Pd {alpha}{sub 2} phases were transformed into the Ag-rich {alpha}{sup '}{sub 1} and Cu{sub 3}Pd {alpha}{sup '}{sub 2} phases, respectively. The CuPd {beta} phase with a CsCl-type was not changed apparently during the ageing process. From the results of the hardness test, XRD study, SEM observations and EDS analysis, it could be derived that the hardness increased by the diffusion and precipitation of the Cu-rich phase from the Ag-rich matrix during the early stage of phase transformation of {alpha}{sub 1} into {alpha}{sup '}{sub 1} and that the progress of coarsening of the Cu-rich precipitates with an entanglement structure caused the hardness decrease during the later stage of phase transformation of {alpha}{sub 1} into {alpha}{sup '}{sub 1}. The particle-like structures composed of the Cu-Pd {alpha}{sub 2} and the CuPd {beta} phase with a CsCl-type contributed little to the hardness increase which occurred in the early stage of aging process.
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.
Directory of Open Access Journals (Sweden)
Sabarudin
2017-06-01
Full Text Available This research is aimed to trace the thoughts and actions as efforts to achieve vision and mission of state institute for Islamic studies of Purwokerto (IAIN. The study is directed to answer following questions. Firstly, why transformative Islam becomes a discourse on curriculum development. Secondly, how a discourse of transformative Islam implicates in curriculum development at state institute for Islamic studies of Purwokerto (IAIN. Then, the findings show that a discourse of Islam tranformative in curriculum development at state institute for Islamic studies of Purwokerto (IAIN emerges as a result of an incapability of traditional and modern Islam perspective to resolve people’s problem due to lack of critical understanding of the meaning and message of the Qur’an and Hadith. Then, implication of Islamic transformative discourse in curriculum development at state institute for Islamic studies of Purwokerto can be seen in its intra curricular activities, co-curricular, and extra curricular activities. Through intra-curricular activities, transformative Islam is embodied in Islamic building lectures. In co-curricular program, Islam is indigenized through activity of knowledge and practice of worship (nationally abbreviated PPI, while within extra-curricular activities transformative Islamic values come into student activities which are strongly supported by policies of university leaders.
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
International Nuclear Information System (INIS)
Leung Shingyu; Qian Jianliang
2010-01-01
We propose the backward phase flow method to implement the Fourier-Bros-Iagolnitzer (FBI)-transform-based Eulerian Gaussian beam method for solving the Schroedinger equation in the semi-classical regime. The idea of Eulerian Gaussian beams has been first proposed in . In this paper we aim at two crucial computational issues of the Eulerian Gaussian beam method: how to carry out long-time beam propagation and how to compute beam ingredients rapidly in phase space. By virtue of the FBI transform, we address the first issue by introducing the reinitialization strategy into the Eulerian Gaussian beam framework. Essentially we reinitialize beam propagation by applying the FBI transform to wavefields at intermediate time steps when the beams become too wide. To address the second issue, inspired by the original phase flow method, we propose the backward phase flow method which allows us to compute beam ingredients rapidly. Numerical examples demonstrate the efficiency and accuracy of the proposed algorithms.
Li, S. H.; Chen, Y. H.
2016-12-01
The iron sulfide nano-minerals possess advantages of high abundance, low cost, and low toxicity. These advantages make them be competitive in the magnetic, electronic, and photoelectric applications. Mackinawite can be used in soil or water remediations. Greigite is very important for paleomagnetic and geochemical environment studies and the anode materials for lithium ion batteries. Besides, greigite is also utilized for hyperthermia and biomedicine. Pyrrhotite can be applied as geothermometry. Due to the above-mentioned reasons, iron sulfide minerals have specific significances and they must be further investigated, like their phase transformations, magnetic properties, and etc. In this study, the iron sulfide minerals were synthesized by using a hydrothermal method. The ex-situ and in-situ X-ray diffraction (XRD) was used to examine the crystal structure and phase transformation of iron sulfide minerals. The Transmission electron microscopy (TEM) and superconducting quantum interference device (SQUID) were carried out to investigate their morphology and magnetic properties, respectively. The results suggested that the phase transformation sequence was followed the order: mackinawite → greigite → (smythite) → pyrrhotite. Two pure mineral phases of greigite and pyrrhotite were obtained under the hydrothermal conditions. The morphology of the pure greigite is granular aggregates with a particle size of approximately 30 nm and pyrrhotite presented a hexagonal sheet stacking with a particle size of thousands nanometers. The greigite had a ferri-magnetic behavior and pyrrhotite was weak ferro-magnetic. Both of them had a pseudo-single magnetic domain (PSD) based on the Day's plot from SQUID data. The complete phase-transformation pathways and high magnetization of iron sulfide minerals are observed in this study and these kind of iron sulfide minerals are worthy to further study.
Energy Barriers and Hysteresis in Martensitic Phase Transformations
2008-08-01
glacial acetic acid (CH3COOH) and 10-15% perchloric acid (HCLO4) by volume, the cathode was stainless steel , the anode was stainless steel or Ti, the...Submitted to Acta Materialia Energy barriers and hysteresis in martensitic phase transformations Zhiyong Zhang, Richard D. James and Stefan Müller...hysteresis based on the growth from a small scale of fully developed austenite martensite needles. In this theory the energy of the transition layer plays a
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/
Jung, Byung Ik; Cho, Yong Sun; Park, Hyoung Min; Chung, Dong Chul; Choi, Hyo Sang
2013-01-01
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.
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
Qin, Xunpeng; Gao, Kai; Zhu, Zhenhua; Chen, Xuliang; Wang, Zhou
2017-09-01
The spot continual induction hardening (SCIH) process, which is a modified induction hardening, can be assembled to a five-axis cooperating computer numerical control machine tool to strengthen more than one small area or relatively large area on complicated component surface. In this study, a response surface method was presented to optimize phase transformation region after the SCIH process. The effects of five process parameters including feed velocity, input power, gap, curvature and flow rate on temperature, microstructure, microhardness and phase transformation geometry were investigated. Central composition design, a second-order response surface design, was employed to systematically estimate the empirical models of temperature and phase transformation geometry. The analysis results indicated that feed velocity has a dominant effect on the uniformity of microstructure and microhardness, domain size, oxidized track width, phase transformation width and height in the SCIH process while curvature has the largest effect on center temperature in the design space. The optimum operating conditions with 0.817, 0.845 and 0.773 of desirability values are expected to be able to minimize ratio (tempering region) and maximize phase transformation width for concave, flat and convex surface workpieces, respectively. The verification result indicated that the process parameters obtained by the model were reliable.
International Nuclear Information System (INIS)
Hon, M.-H.; Chang, T.-C.; Wang, M.-C.
2008-01-01
The morphology and phase transformation of the intermetallic compounds (IMCs) formed at the Sn-9Zn-3.5Ag/Cu interface in a solid-state reaction have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The monoclinic η'-Cu 6 Sn 5 transforms to the hexagonal η-Cu 6 Sn 5 and the orthorhombic Cu 5 Zn 8 transforms to the body-centered cubic (bcc) γ-Cu 5 Zn 8 as aged at 180 deg. C. The scallop-shaped Cu 6 Sn 5 layer is retained after aging at 180 deg. C for 1000 h. In the solid-state reaction, Ag is repelled from η'-Cu 6 Sn 5 and reacts with Sn to form Ag 3 Sn, and the Cu 5 Zn 8 layer decomposes. Kirkendall voids are not observed at the Sn-9Zn-3.5Ag/Cu interface even after aging at 180 deg. C for 1000 h
Emoto, Akira; Fukuda, Takashi
2013-02-20
For Fourier transform holography, an effective random phase distribution with randomly displaced phase segments is proposed for obtaining a smooth finite optical intensity distribution in the Fourier transform plane. Since unitary phase segments are randomly distributed in-plane, the blanks give various spatial frequency components to an image, and thus smooth the spectrum. Moreover, by randomly changing the phase segment size, spike generation from the unitary phase segment size in the spectrum can be reduced significantly. As a result, a smooth spectrum including sidebands can be formed at a relatively narrow extent. The proposed phase distribution sustains the primary functions of a random phase mask for holographic-data recording and reconstruction. Therefore, this distribution is expected to find applications in high-density holographic memory systems, replacing conventional random phase mask patterns.
International Nuclear Information System (INIS)
Muddle, B.C.; Nie, J.F.; Hugo, G.R.
1994-01-01
It has been demonstrated that the theory of martensite crystallography is capable of accounting successfully for the form and crystallography of a range of plate- or lath-shaped transformation products, even when the formation of the product phase involves significant substitutional diffusion. These transformations include the precipitation of metastable hexagonal γ' (Ag 2 Al) plates in disordered face-centered cubic (fcc) solid-solution Al-Ag alloys, the formation of ordered AuCu II plates from disordered fcc solid solution in equiatomic Au-Cu alloys, and the formation of metastable 9R α 1 plates in ordered (B2) Cu-Zn and Ag-Cd alloys. The application of the theory to these transformations is reviewed critically and the features common to them identified. It is confirmed that, in all three transformations, the product phase produces relief at a free surface consistent with an invariant plane-strain shape change and that the transformations are thus properly described as displacive. The agreement between experimental observations and theoretical predictions of the transformation crystallography is in all cases excellent. It is proposed that successful application of the theory implies a growth mechanism in which the coherent or semicoherent, planar interface between parent and product phases maintains its structural identity during migration and that growth proceeds atom by atom in a manner consistent with the maintenance of a correspondence of lattice sites
Influence of processing-induced phase transformations on the dissolution of theophylline tablets
Debnath, Smita; Suryanarayanan, Raj
2004-01-01
The object of this investigation was to evaluate the influence of (1) processing-induced decrease in drug crystallinity and (2) phase transformations during dissolution, on the per-formance of theophylline tablet formulations. Anhydrous theophylline underwent multiple transformations (anhydrate »hydrate»anhydrate) during processing. Although the crystallinity of the anhydrate obtained finally was lower than that of the unprocessed drug, it dissolved at a slower rate. This decrease in dissolut...
State of art survey for design of medium frequency high power transformer
DEFF Research Database (Denmark)
Vaisambhayana, Sriram; Dincan, Catalin; Shuyu, Cao
2016-01-01
Medium and high frequency, high power transformers play an important role in footprint reduction along with their functions of galvanic isolation, and voltage transformation in all high power converters typically used in traction power systems, offshore wind plant power converters, and solid state...... transformer based distribution system grids. This state of art report analysis the various materials and design tradeoffs that govern the electromagnetic behavior and loss mechanisms of the medium frequency transformer applications. Typical winding and core geometries that have been reported extensively...
Directory of Open Access Journals (Sweden)
Michal Jambor
2017-06-01
Full Text Available Nickel base superalloys are hi-tech materials intended for high temperature applications. This property owns a complex microstructure formed by matrix of Ni and variety of precipitates. The type, form and the amount of these phases significantly affect the resulting properties of these alloys. At sufficiently long exposure to high temperatures, the transformation phase can occur, which can lead to degradation of properties of these alloys. A cyclic plastic deformation can accelerate these changes, and they could occur at significantly lower temperatures or in shorter time of exposure. The aim of this study is to describe phase transformation, which can occur by a cyclic plastic deformation at high temperatures in nickel base superalloy Inconel 718.
Energy Technology Data Exchange (ETDEWEB)
He, Hongxing; Fang, Hengrui [Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204 (United States); Miller, Mitchell D. [Department of BioSciences, Rice University, Houston, Texas 77005 (United States); Phillips, George N. Jr [Department of BioSciences, Rice University, Houston, Texas 77005 (United States); Department of Chemistry, Rice University, Houston, Texas 77005 (United States); Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Su, Wu-Pei, E-mail: wpsu@uh.edu [Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204 (United States)
2016-07-15
An iterative transform algorithm is proposed to improve the conventional molecular-replacement method for solving the phase problem in X-ray crystallography. Several examples of successful trial calculations carried out with real diffraction data are presented. An iterative transform method proposed previously for direct phasing of high-solvent-content protein crystals is employed for enhancing the molecular-replacement (MR) algorithm in protein crystallography. Target structures that are resistant to conventional MR due to insufficient similarity between the template and target structures might be tractable with this modified phasing method. Trial calculations involving three different structures are described to test and illustrate the methodology. The relationship of the approach to PHENIX Phaser-MR and MR-Rosetta is discussed.
A new approach to calculating the Berry phase
International Nuclear Information System (INIS)
Wu Lianao; Sun Jing; Zhong Jiyu
1993-01-01
It is proved that any time-dependent problem can be transformed into a time-independent one by a unitary transformation. The general equation satisfied by the transformation is given. For some time-dependent Hamiltonians the transformation can be found easily. More importantly, if the initial states are just eigenstates of the transformed Hamiltonians, the dynamical phase can be conveniently removed and the Berry phase can be found directly. (orig.)
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...
Phase transformations in cerium and thorium metals at ultra high pressures
International Nuclear Information System (INIS)
Vohra, Y.K.
1991-01-01
This paper reports on the role of pressure variable in phase transformation which has not been fully exploited in metallic elements and their alloys. The static compression of over 50% in volume can readily be obtained in most metals and this tremendous change in inter-atomic distances can lead to the formation of new exotic crystal structures. The pressure-induced electron transfer amongst existing electronic energy bands and the occupation of new bands are the driving forces in a rich variety of phase transformations. The modern high pressure diamond anvil cell techniques can produce calibrated static pressures of over 300 to 400 GPa range and this technology, when interfaced with the synchrotron radiation sources, can yield rapid structural information (1-3). These capabilities have given new impetus for investigation of phase transformations in metallic systems at extreme conditions of temperatures and pressures and in establishing phase boundaries at high pressures and high temperatures. Cerium (Ce) and thorium (Th) metals occupy special positions in the periodic table at the beginning of the 4-f lanthanide and 5-f, actinide series, respectively. Ce has one electron in the localized 4-f shell, apart from the three valence electrons. Th metal, on the other hand, has four valence electrons and an unoccupied 5-f band above the Fermi-energy at ambient conditions. In view of the unoccupied 5-f band, Th metal is normally regarded as a tetravalent transition metal like Ti, Zr, and Hf and its bonding and other electronic properties can be explained within the tetravalent transition metal framework. However, the application of ultra-high pressures causes the delocalization of the 4-f shell in Ce and it is believed that Ce above 0.8 GPa pressure is a 4-f band metal
International Nuclear Information System (INIS)
Kobe, D.H.
1989-01-01
The Berry phase is derived in a manifestly gauge-invariant way, without adiabatic or cyclic requirements. It is invariant under unitary transformations, contrary to recent assertions. A time-dependent generalized harmonic oscillator is taken as an example. The energy of the system is not in general the Hamiltonian. An energy, the time derivative of which is the power, is obtained from the equation of motion. When the system is quantized, the Berry phase is zero, and is invariant under unitary transformations. If the energy is chosen incorrectly to be the Hamiltonian, a nonzero Berry phase is obtained. In this case the total phase, the sun of the dynamical and Berry phases, is equal to the correct total phase through first order in perturbation theory. (author)
Structure and Phase Transformation in the Giant Magnetostriction Laves-Phase SmFe_{2}
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, SmFe_{2}, is a prototypical Laves compound that shows strong negative magnetostriction but relatively weak magnetocrystalline anisotropy. SmFe_{2} has been identified as a cubic Fd$ \\overline{3}\\ $m structure at room temperature, however, the cubic symmetry does not match the spontaneous magnetization along the [111]_{cubic} direction. Here we studied the crystal structure of SmFe_{2} by high-resolution synchrotron X-ray powder diffraction and X-ray total scattering methods. SmFe_{2} is found to adopt a centrosymmetric trigonal R$ \\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 SmFe_{2} could be useful to understand the magnetostriction and related physical properties of other RM_{2}-type pseudo-cubic Laves-phase intermetallic compounds.
Two-phase transformation of lepidocrocite to maghemite
Dekkers, M. J.; Gapeev, A. K.; Gendler, T. S.; Gribov, S. K.; Shcherbakov, V. P.
2003-04-01
A detailed investigation of CRM acquired at different stages of the transformation lepidocrocite -> maghemite -> hematite is carried out. Apparently, at least two-stage lepidocrocite maghemite transformation was revealed from: a) the two-peak Ms(T) curve; b) the observation of constricted hysteresis loops appearing after annealing fresh lepidocrocite samples at elevated temperatures; c) continuous monitoring (for 500 hrs) of CRM acquisition at elevated temperatures. For the latter two sets of CRM acquisition experiments at 12 temperatures from 175C to 550C in the presence of 0.1 mT magnetic field were performed: 1) with fine dispersed natural lepidocrocite grains in a kaolin matrix (about 1 volume % of lepidocrocite), 2) for lepidocrocite peaces 3x3x3 mm in size. In both cases the CRM was detected already at 175C after 1 day of annealing. Note that this temperature is lower than the temperature of the TGA peak of the lepidocrocite -> maghemite transformation. Mossbauer spectra obtained from the peaces after annealing at 225C during 6 and 14 hours, respectively, revealed significantly different patterns. Unexpectadly, fine dispersed maghemite grains formed due the lepidocrocite dehydration in the first peace (6 hrs of annealing) occurred to be more ordered than those of from the second peace. The samples are subjected to the X-ray analysis in an attempt to clarify the observed difference. The observed phenomena can be explained by the two-phase conception of the transformation lepidocrocite -> maghemite. First the precipitation of small superparamagnetic particles of maghemite takes place growing with time. Second, these grains coalesce with each other resulting in appearance of the antiphase boundaries decreasing the susceptibility, slowing down the process of CRM acquisition and generating the constricted hysteresis loops. The work is supported by INTAS 99-1273.
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
International Nuclear Information System (INIS)
Ortigosa, Nuria; Fernández, Carmen; Galbis, Antonio; Cano, Óscar
2015-01-01
Patients suffering from atrial fibrillation can be classified into different subtypes, according to the temporal pattern of the arrhythmia and its recurrence. Nowadays, clinicians cannot differentiate a priori between the different subtypes, and patient classification is done afterwards, when its clinical course is available. In this paper we present a comparison of classification performances when differentiating paroxysmal and persistent atrial fibrillation episodes by means of support vector machines. We analyze short surface electrocardiogram recordings by extracting modulus and phase features from several time-frequency transforms: short-time Fourier transform, Wigner–Ville, Choi–Williams, Stockwell transform, and general Fourier-family transform. Overall, accuracy higher than 81% is obtained when classifying phase information features of real test ECGs from a heterogeneous cohort of patients (in terms of progression of the arrhythmia and antiarrhythmic treatment) recorded in a tertiary center. Therefore, phase features can facilitate the clinicians’ choice of the most appropriate treatment for each patient by means of a non-invasive technique (the surface ECG). (paper)
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.
Directory of Open Access Journals (Sweden)
Hani Albetran
2018-02-01
Full Text Available The influence of calcination time on the phase transformation and crystallization kinetics of anodized titania nanotube arrays was studied using in-situ isothermal and non-isothermal synchrotron radiation diffraction from room temperature to 900 °C. Anatase first crystallized at 400 °C, while rutile crystallized at 550 °C. Isothermal heating of the anodized titania nanotubes by an increase in the calcination time at 400, 450, 500, 550, 600, and 650 °C resulted in a slight reduction in anatase abundance, but an increase in the abundance of rutile because of an anatase-to-rutile transformation. The Avrami equation was used to model the titania crystallization mechanism and the Arrhenius equation was used to estimate the activation energies of the titania phase transformation. Activation energies of 22 (10 kJ/mol for the titanium-to-anatase transformation, and 207 (17 kJ/mol for the anatase-to-rutile transformation were estimated.
Albetran, Hani; Vega, Victor; Prida, Victor M; Low, It-Meng
2018-02-23
The influence of calcination time on the phase transformation and crystallization kinetics of anodized titania nanotube arrays was studied using in-situ isothermal and non-isothermal synchrotron radiation diffraction from room temperature to 900 °C. Anatase first crystallized at 400 °C, while rutile crystallized at 550 °C. Isothermal heating of the anodized titania nanotubes by an increase in the calcination time at 400, 450, 500, 550, 600, and 650 °C resulted in a slight reduction in anatase abundance, but an increase in the abundance of rutile because of an anatase-to-rutile transformation. The Avrami equation was used to model the titania crystallization mechanism and the Arrhenius equation was used to estimate the activation energies of the titania phase transformation. Activation energies of 22 (10) kJ/mol for the titanium-to-anatase transformation, and 207 (17) kJ/mol for the anatase-to-rutile transformation were estimated.
DEFF Research Database (Denmark)
Ostergaard, Jesper; Wu, Jian; Naelapää, Kaisa
2014-01-01
The current work reports the simultaneous use of UV imaging and Raman spectroscopy for detailed characterization of drug dissolution behavior including solid-state phase transformations during dissolution. The dissolution of drug substances from compacts of sodium naproxen in 0.1 HCl as well as t...... of UV imaging and Raman spectroscopy offers a detailed characterization of drug dissolution behavior in a time-effective and sample-sparing manner. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:1149-1156, 2014....
Phase transformation in {delta} Pu alloys at low temperature: In situ dilatometric study
Energy Technology Data Exchange (ETDEWEB)
Texier, G; Oudot, B; Platteau, C; Ravat, B; Delaunay, F, E-mail: gwenael.texier@cea.fr, E-mail: benoit.oudot@cea.fr [CEA, DAM, Valduc, Is sur Tille 21120 (France)
2010-03-15
The purpose of this work is to precisely study the martensitic transformation in a plutonium-gallium alloy. Thus, the thermodynamics and kinetics of the {delta}{yields}{alpha}'+{delta} phase transformation in a Pu-Ga alloy were studied under isochronal and isothermal conditions. The activation energy of the {delta}{yields}{alpha}'+{delta} phase transformation at a constant cooling rate (0.5 K.min{sup -1}) was determined by using Kissinger and Ozawa models. The average value of the activation energy was found to be at -56 kJ.mol{sup -1}. Dilatometry measurement was also used to trace 'in situ' the entire transformation for several temperatures. The kinetics of the {delta}{yields}{alpha}'+{delta} transformation were modelled under isothermal conditions in the theoretical frame of the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory. It is proposed that the transformation consists of three stages. The {alpha}' transformation begins with a nucleation of pre-existing embryos. Then, both nucleation and rapid growth of {alpha}' occurs simultaneously and finally, the plates width expend. Apparent activation energies for nucleation and growth transformation were determined from the temperature dependence of the constant K at respectively -34 kJ.mol{sup -1} and -60 kJ.mol{sup -1}. Adler et al. [1] investigated also the thermodynamics and the kinetics of the martensitic transformation in Pu alloys. These nucleation energies were found by modelling of heterogeneous martensitic nucleation via strain interaction with observed superdislocation-like nucleation sites in PuGa alloys. The values obtain by this model was very close to those we find. Investigations in steels alloys indicate that these energies are of the same order for nucleation near dislocation. Then, it could be indicating a strong relationship between these dislocations and martensitic nucleation sites.
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
Unitary Transformations in 3 D Vector Representation of Qutrit States
2018-03-12
ARL-TR-8330 ● MAR 2018 US Army Research Laboratory Unitary Transformations in 3- D Vector Representation of Qutrit States by...return it to the originator. ARL-TR-8330 ● MAR 2018 US Army Research Laboratory Unitary Transformations in 3- D Vector...2018 2. REPORT TYPE Technical Report 3. DATES COVERED June–December 2017 4. TITLE AND SUBTITLE Unitary Transformations in 3- D Vector
Transformation of bipartite non-maximally entangled states into a ...
Indian Academy of Sciences (India)
We present two schemes for transforming bipartite non-maximally entangled states into a W state in cavity QED system, by using highly detuned interactions and the resonant interactions between two-level atoms and a single-mode cavity field. A tri-atom W state can be generated by adjusting the interaction times between ...
Phase transformation of 316L stainless steel from wire to fiber
International Nuclear Information System (INIS)
Shyr, Tien-Wei; Shie, Jing-Wen; Huang, Shih-Ju; Yang, Shun-Tung; Hwang, Weng-Sing
2010-01-01
In this work, quantitative crystalline phase analysis of 316L stainless steel from wire to fiber using a multi-pass cold drawing process was studied using the Rietveld whole XRD profile fitting technique. The different diameters of the fibers: 179, 112, 75, 50, 34, 20, and 8 μm, were produced from an as-received wire with a diameter of 190 μm. The crystalline phases were identified using MDI Jade 5.0 software. The volume fractions of crystalline phases were estimated using a Materials Analysis Using Diffraction software. XRD analysis revealed that the crystal structure of as-received wire is essentially a γ-austenite crystalline phase. The phase transformation occurred during the 316L stainless steel from wire to fiber. Three crystalline phases such as γ-austenite, α'-martensite, and sigma phase of the fine fiber were observed. A cold drawing accelerates the sigma phase precipitates, particularly during the heat treatment of the fiber.
Atomic bonding of precipitate and phase transformation of Al-Cu-Mg alloy
International Nuclear Information System (INIS)
Gao Yingjun; Hou Xianhua; Mo Qifeng; Wei Chengyang; Qin Xiaobing
2007-01-01
Atomic bonding of the GPB zone and S'' phase of Al-Cu-Mg alloys in early aging stage are calculated using the empirical electron theory (EET) in solid. The results show that not only the covalence bond-network is very strong in GPB zone, but the whole covalence bond energy of S'' phase is also very large, and all the primary bond-net framework of these precipitates can consolidate the matrix of alloy. Phase transformation from GPB zone to S'' phase is explained reasonably based on atomic bonding and total binding capacity of Al and Cu atoms in these precipitates
Directory of Open Access Journals (Sweden)
J. Krawczyk
2010-07-01
Full Text Available Toothed wheels constitute essential part of the steel structural elements market. The most often hypereutectoid structural steels forcarburizing are used for toothed wheels. The final producers of toothed wheels are not demanding regarding a microstructure, providedthat the determined requirements will be fulfilled (e.g. metallurgical purity determined by ultrasounds. Therefore delivered forgings can be in an annealed or quenched state. This results from the situation that the final heat treatment or heat-chemical one is being done at one of the last stages of the toothed wheel production. An essential factor allowing to develop the proper heat treatment is the knowledge of the kinetics of phase transformations of undercooled austenite and its relating to technological conditions, being at the producer disposal, as well as to forging dimensions. Such investigations should be carried out on real melts used for forgings for toothed wheels production together with an analysis of microstructure changes on the forging cross-section. They should be based on calculation methods determining the distribution of cooling rates on its cross-section in dependence of an applied cooling medium.The mentioned above problems in relation to 18CrNiMo7-6 steel - are elucidated in this paper. The aim of the investigations wasthe description of the kinetics of phase transformations of undercooled austenite in this steel. The CCT diagram was constructed for the austenitizing temperature determined on the basis of phase transformations temperatures (the so-called critical points.
The β → α phase transformation in plutonium
International Nuclear Information System (INIS)
Mitchell, T.E.; Hirth, J.P.; Schwartz, D.S.; Mitchell, J.N.
2013-01-01
The β → α transformation in plutonium is discussed in terms of the crystallography of the two phases and the resulting topological modeling of the β/α interface. There has been little microscopy work on the transformation, but it is probably martensitic. β-Pu is monoclinic I2/m, while α-Pu is monoclinic P2 1 /m. α-Pu has been described as a hexagonal close-packed pseudostructure with AB stacking of the (0 2 0) α planes with pseudo-close-packing along [1 0 0] α and two other directions. β-Pu is less obvious, but X-ray diffraction suggests that the (1 0 3) β planes, which are selected as the terrace plane, have the highest structure factor and are therefore among the closest-packed planes. Other pseudo-close-packed planes, such as {222 ¯ } β and {321 ¯ } β , could also act as terrace planes for the transformation. The (1 0 3) β planes have a pseudo-hexagonal grid of Pu atoms with AB stacking and pseudo-close-packing along [301 ¯ ] β and two other directions. A selection of terrace planes as (0 2 0) α //(1 0 3) β with disconnections along [100] α //[301 ¯ ] β provides the basis for topological modeling. The model predicts a habit plane that is ∼6° from the terrace plane. The extra Pu atoms in the β structure (17 for every 16 in α) are accommodated by having 16 (1 0 3) β planes transform into 17 (0 2 0) α planes at steps in the interface. Short-range interstitial diffusion of Pu atoms from β to α is required for the transformation to proceed. Possible lattice invariant deformation systems are discussed
Energy Technology Data Exchange (ETDEWEB)
Gautam, Subodh K., E-mail: subodhkgtm@gmail.com [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India); Chettah, Abdelhak [LGMM Laboratory, Université 20 Août 1955-Skikda, BP 26, 21000 Skikda (Algeria); Singh, R.G. [Department of Physics, Bhagini Nivedita College, Delhi University, Delhi 110043 (India); Ojha, Sunil; Singh, Fouran [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India)
2016-07-15
Study reports the effect of swift heavy ion (SHI) irradiation induced phase transformation in undoped and Niobium doped anatase TiO{sub 2} composite thin films. Investigations were carried out at different densities of electronic excitations (EEs) using 120 MeV Ag and 130 MeV Ni ions irradiations. Films were initially annealed at 900 °C and results revealed that undoped films were highly stable in anatase phase, while the Nb doped films showed the composite nature with the weak presence of Niobium penta-oxide (Nb{sub 2}O{sub 5}) phase. The effect at low density of EEs in undoped film show partial anatase to rutile phase transformation; however doped film shows only further growth of Nb{sub 2}O{sub 5} phase beside the anatase to rutile phase transformation. At higher density of EEs induced by Ag ions, registered continuous ion track of ∼3 nm in lattice which leads to nano-crystallization followed by decomposition/amorphization of rutile TiO{sub 2} and Nb{sub 2}O{sub 5} phases in undoped and doped films, respectively. However, Ni ions are only induced discontinuous sequence of ion tracks with creation of damage and disorder and do not show amorphization in the lattice. The in-elastic thermal spike calculations were carried out for anatase TiO{sub 2} phase to understand the effect of EEs on anatase to rutile phase transformation followed by amorphization in NTO films in terms of continuous and discontinuous track formation by SHI irradiation.
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.
Backstepping Based Formation Control of Quadrotors with the State Transformation Technique
Directory of Open Access Journals (Sweden)
Keun Uk Lee
2017-11-01
Full Text Available In this paper, a backstepping-based formation control of quadrotors with the state transformation technique is proposed. First, the dynamics of a quadrotor is derived by using the Newton–Euler formulation. Next, a backstepping-based formation control for quadrotors using a state transformation technique is presented. In the position control, which is the basis of formation control, it is possible to derive the reference attitude angles employing a state transformation technique without the small angle assumption or the simplified dynamics usually used. Stability analysis based on the Lyapunov theorem shows that the proposed formation controller can provide a quadrotor formation error system that is asymptotically stabilized. Finally, we verify the performance of the proposed formation control method through comparison simulations.
Transformation of bipartite non-maximally entangled states into a ...
Indian Academy of Sciences (India)
We present two schemes for transforming bipartite non-maximally entangled states into a W state in cavity QED system, by using highly detuned interactions and the resonant interactions between ... Proceedings of the International Workshop/Conference on Computational Condensed Matter Physics and Materials Science
A complex guided spectral transform Lanczos method for studying quantum resonance states
International Nuclear Information System (INIS)
Yu, Hua-Gen
2014-01-01
A complex guided spectral transform Lanczos (cGSTL) algorithm is proposed to compute both bound and resonance states including energies, widths and wavefunctions. The algorithm comprises of two layers of complex-symmetric Lanczos iterations. A short inner layer iteration produces a set of complex formally orthogonal Lanczos (cFOL) polynomials. They are used to span the guided spectral transform function determined by a retarded Green operator. An outer layer iteration is then carried out with the transform function to compute the eigen-pairs of the system. The guided spectral transform function is designed to have the same wavefunctions as the eigenstates of the original Hamiltonian in the spectral range of interest. Therefore the energies and/or widths of bound or resonance states can be easily computed with their wavefunctions or by using a root-searching method from the guided spectral transform surface. The new cGSTL algorithm is applied to bound and resonance states of HO, and compared to previous calculations
Kinetics of solid state phase transformations: Measurement and ...
Indian Academy of Sciences (India)
Administrator
heating or cooling rate can also exert a crucial influence on the kinetic outcome is stressed. The kinetic ... A simple and general modelling methodology for understanding the kinetics of ... state is of interest on both basic and applied grounds.
Transformation behavior of the γU(Zr,Nb) phase under continuous cooling conditions
Komar Varela, C. L.; Gribaudo, L. M.; González, R. O.; Aricó, S. F.
2014-10-01
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.
Siddique, N A; Salehi, Amir; Wei, Zi; Liu, Dong; Sajjad, Syed D; Liu, Fuqiang
2015-08-03
The charge and discharge of lithium ion batteries are often accompanied by electrochemically driven phase-transformation processes. In this work, two in situ and operando methods, that is, micro-Raman spectroscopy and X-ray diffraction (XRD), have been combined to study the phase-transformation process in LiFePO4 at two distinct length scales, namely, particle-level scale (∼1 μm) and macroscopic scale (∼several cm). In situ Raman studies revealed a discrete mode of phase transformation at the particle level. Besides, the preferred electrochemical transport network, particularly the carbon content, was found to govern the sequence of phase transformation among particles. In contrast, at the macroscopic level, studies conducted at four different discharge rates showed a continuous but delayed phase transformation. These findings uncovered the intricate phase transformation in LiFePO4 and potentially offer valuable insights into optimizing the length-scale-dependent properties of battery materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Directory of Open Access Journals (Sweden)
Claas Hüter
2015-09-01
Full Text Available We give an excerpt of recent developments in the experimentally benchmarked modeling of bainite formation in the press hardening process. As the press hardening process poses a heavily multi-parameter dependent modeling challenge, we focus on three main branches which complement each other. We emphasise the combination of basic sharp interface and phase field models with pragmatically adapted multi phase field models and experimentally parametrized implementations of the Johnson-Mehl-Avrami model. In the basic thermodynamic modeling part, we review fundamental aspects of displacive and diffusional-displacive transformations to predict dominant transformation morphologies. These results provide a link to multi-phase-field implementations which allow to simulate isothermal bainitic transformations, supported by available material data from thermodynamic databases. Excellent agreement with experiments, e.g. scanning electron microscopy for the transformed bainite in the high-carbon steel 100Cr6 shows the value of these model implementations. The further connection to Johnson-Mehl-Avrami models offers to extend the understanding to transformation plasticity for the press hardening steel 22MnB5.
International Nuclear Information System (INIS)
Ferro, P
2012-01-01
In this work, the residual stress distribution induced by the solidification and cooling of a fusion zone in the vicinity of a sharp V-notch tip is investigated. The intensity of the residual asymptotic stress fields, quantified by the notch stress intensity factors, was studied for two different V-notch specimen geometries under generalized plane-strain conditions. In order to analyze the influence of phase transformations on the obtained results, simulations with and without the effects of phase transformation were carried out on ASTM SA 516 steel plates. Thanks to the possibilities of numerical modelling, additional analyses were performed without taking into account the transformation plasticity phenomenon. It was found that phase transformation effects (both volume change and transformation plasticity) have a great influence on the intensity and sign of the asymptotic stress fields at the sharp V-notch tips. This result is believed to be very important for the correct numerical determination (and future applications) of notch stress intensity factors resulting from asymptotic residual stress distributions induced by transient thermal loads. The analyses were performed with the finite element code SYSWELD. (paper)
Electronic basis of hardness and phase transformations (covalent crystals)
International Nuclear Information System (INIS)
Gilman, J J
2008-01-01
Several electronic parameters measure the stabilities of covalent crystals, including minimum energy band-gap densities, inverse polarizabilities, plasma frequencies, transverse vibrational frequencies and elastic shear moduli. Convenient is the band-gap density (energy/volume; called the 'bond modulus'). For a given bonding type, the indentation hardness is proportional to the bond modulus. Examples are the group IV elements, III-V compounds; and II-VI compounds. The motion of dislocation kinks requires the excitation of bonding electrons into anti-bonding states. The bond modulus measures this together with the work done by the applied stress when a kink moves. In addition to hardness, the bond modulus measures the compressive strain (pressure) needed to transform an ambient structure into a more dense structure. Activation of such transformations also requires the excitation of bonding electrons into anti-bonding states together with the work done by the compressive stress
Phase transformation in nanocrystalline α-quartz GeO2 up to 51.5 GPa
International Nuclear Information System (INIS)
Wang, H; Liu, J F; Wu, H P; He, Y; Chen, W; Wang, Y; Zeng, Y W; Wang, Y W; Luo, C J; Liu, J; Hu, T D; Stahl, K; Jiang, J Z
2006-01-01
The high-pressure behaviour of nanocrystalline α-quartz GeO 2 (q-GeO 2 ) with average crystallite sizes of 40 and 260 nm has been studied by in situ high-pressure synchrotron radiation x-ray diffraction measurements up to about 51.5 GPa at ambient temperature. Two phase transformations, q-GeO 2 to amorphous GeO 2 and amorphous GeO 2 to monoclinic GeO 2 , are detected. The onset and end of the transition pressures for the q-GeO 2 -to-amorphous GeO 2 phase transition are found to be approximately 10.8 and 14.9 GPa for the 40 nm q-GeO 2 sample, and 9.5 and 12.4 GPa for the 260 nm q-GeO 2 sample, respectively. The mixture of amorphous and monoclinic GeO 2 phases remains up to 51.5 GPa during compression and even after pressure release. This result strongly suggests that the difference of free energy between the amorphous phase and the monoclinic phase might be small. Consequently, defects in the starting material, which alter the free energies of the amorphous phase and the monoclinic phase, may play a key role for the phase transformation of q-GeO 2
To the theory of the first-type phase transformations for many variables
International Nuclear Information System (INIS)
Fateev, M.P.
2002-01-01
The multidimensional theory on the first-type phase transitions near the one-dimensional saddle point is considered. The transformations of the variables, describing the new phase nucleation, making it possible to achieve their complex separation in the Fokker-Planck equation, and thus to reduce the problem to the one-dimensional one, are proposed. The distribution function and nucleation velocity are determined both for the stationary and nonstationary nucleation stages. The problem on volatile liquid boiling is considered as an example for the case when there are two parameters, characterizing the new phase nucleation [ru
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
International Nuclear Information System (INIS)
Leist, Jeannis-Nicos
2009-01-01
In the framework of this thesis the influence of an electric field on the ferroelectric model systems potassium selenate and strontium titanate was studied. The kinetics of the field-induced phase transformations were observed with stroboscopic scattering methods on a millisecond time scale. In potassium selenate thereby with elastic neutron scattering could be detected that an intense third-order satellite is only to be observed up to 10 K above the lock-in transformation. In this temperature intervall the incommensurable phase consists of a domain structure with well defined discommensurations. At slow cooling under the influence of the electric field a field-induced intermediate phase is formed. It is assumed that charged defects agglomerate and hinder the mechanism of the phase transformation. Both with inelastic neutron scattering and with Raman spectroscopy no dependence of the lattice dynamics on an electric field could be stated. The kinetics of the lock-in transformation in K 2 SeO 4 is by an order of magnitude faster than in the isostructural Rb 2 ZnCl 4 . The time constants vary temperature-independently between 0.2 and 1.2 milliseconds. The faster transformation results possibly from a smaller decommmensuration density and a smaller interaction with defects. With highly resolving γ-diffractometry in could moreover be shown that beside the volume parts of the modulated phases also the modulation coherence changes timely. It is in the stroboscopic experiments moreover a dynamic stabilization of the intermediate phase observed, which is attributed to the generation of mechanical stresses by the fast alternating field. The studies on strontium titanate yielded a distinct dependence of the lattice dynamics on the sample history. Real-time studies with inelastic neutron scattering show that the field-induced ferroelectric phase transformation runs very fastly. The frequency of the soft mode follows directly the alteration of the electric field. From
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.
DEFF Research Database (Denmark)
Ekhtiari, Marzieh; Zsurzsan, Tiberiu-Gabriel; Andersen, Michael A. E.
2017-01-01
A new method is implemented in designing of self-oscillating loop for driving piezoelectric transformers. The implemented method is based on combining both analog and digital control systems. Digitally controlled time delay through the self-oscillating loop results in very precise frequency control...... and ensures optimum operation of the piezoelectric transformer in terms of gain and efficiency. Time delay is implemented digitally for the first time through a 16 bit digital-to-analog converter in the self-oscillating loop. The new design of the delay circuit provides 45 ps time resolution, enabling fine......-grained control of phase in the self-oscillating loop. This allows the control loop to dynamically follow frequency changes of the transformer in each resonant cycle. Ultimately, by selecting the optimum phase shift, maximum efficiency under the load and temperature condition is achievable....
Study of effect of chromium on titanium dioxide phase transformation ...
Indian Academy of Sciences (India)
Administrator
Study of effect of chromium on titanium dioxide phase transformation by A Bellifa (pp 669–677). Figure S1. Structural ... 4 × 1⋅9486; 2 × 1⋅9799. Octahedral packing. 2 × 2 shared edges. 8 free edges. 3 shared edges. 4 corners. 5 free edges. 2 parallel shared edges. 2 corners. 10 free edges. O. O. Coordination scheme.
Geometric Phases for Mixed States in Trapped Ions
International Nuclear Information System (INIS)
Lu Hongxia
2006-01-01
The generalization of geometric phase from the pure states to the mixed states may have potential applications in constructing geometric quantum gates. We here investigate the mixed state geometric phases and visibilities of the trapped ion system in both non-degenerate and degenerate cases. In the proposed quantum system, the geometric phases are determined by the evolution time, the initial states of trapped ions, and the initial states of photons. Moreover, special periods are gained under which the geometric phases do not change with the initial states changing of photon parts in both non-degenerate and degenerate cases. The high detection efficiency in the ion trap system implies that the mixed state geometric phases proposed here can be easily tested.
A reduction method for phase equilibrium calculations with cubic equations of state
Directory of Open Access Journals (Sweden)
D. V. Nichita
2006-09-01
Full Text Available In this work we propose a new reduction method for phase equilibrium calculations using a general form of cubic equations of state (CEOS. The energy term in the CEOS is a quadratic form, which is diagonalized by applying a linear transformation. The number of the reduction parameters is related to the rank of the matrix C with elements (1-Cij, where Cij denotes the binary interaction parameters (BIPs. The dimensionality of the problem depends only on the number of reduction parameters, and is independent of the number of components in the mixture.
Energy Technology Data Exchange (ETDEWEB)
Hon, M.-H. [Department of Materials Science and Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan (China); Chang, T.-C. [Department of Materials Science and Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan (China); Electronic and Optoelectronics Research Laboratories, Industrial Technology Research Institute, Bldg. 11, 195, Sec. 4, Chung-Hsing Road, Chutung, Hsinchu, 310, Taiwan (China); Wang, M.-C. [Faculty of Fragrance and Cosmetics, Kaohsiung Medical University, 100 Shi-Chuan 1st Road, Kaohsiung 807, Taiwan (China)], E-mail: mcwang@kmu.edu.tw
2008-06-30
The morphology and phase transformation of the intermetallic compounds (IMCs) formed at the Sn-9Zn-3.5Ag/Cu interface in a solid-state reaction have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The monoclinic {eta}'-Cu{sub 6}Sn{sub 5} transforms to the hexagonal {eta}-Cu{sub 6}Sn{sub 5} and the orthorhombic Cu{sub 5}Zn{sub 8} transforms to the body-centered cubic (bcc) {gamma}-Cu{sub 5}Zn{sub 8} as aged at 180 deg. C. The scallop-shaped Cu{sub 6}Sn{sub 5} layer is retained after aging at 180 deg. C for 1000 h. In the solid-state reaction, Ag is repelled from {eta}'-Cu{sub 6}Sn{sub 5} and reacts with Sn to form Ag{sub 3}Sn, and the Cu{sub 5}Zn{sub 8} layer decomposes. Kirkendall voids are not observed at the Sn-9Zn-3.5Ag/Cu interface even after aging at 180 deg. C for 1000 h.
Clifford coherent state transforms on spheres
Dang, Pei; Mourão, José; Nunes, João P.; Qian, Tao
2018-01-01
We introduce a one-parameter family of transforms, U(m)t,t > 0, from the Hilbert space of Clifford algebra valued square integrable functions on the m-dimensional sphere, L2(Sm , dσm) ⊗Cm+1, to the Hilbert spaces, ML2(R m + 1 ∖ { 0 } , dμt) , of solutions of the Euclidean Dirac equation on R m + 1 ∖ { 0 } which are square integrable with respect to appropriate measures, dμt. We prove that these transforms are unitary isomorphisms of the Hilbert spaces and are extensions of the Segal-Bargman coherent state transform, U(1) :L2(S1 , dσ1) ⟶ HL2(C ∖ { 0 } , dμ) , to higher dimensional spheres in the context of Clifford analysis. In Clifford analysis it is natural to replace the analytic continuation from Sm to SCm as in (Hall, 1994; Stenzel, 1999; Hall and Mitchell, 2002) by the Cauchy-Kowalewski extension from Sm to R m + 1 ∖ { 0 } . One then obtains a unitary isomorphism from an L2-Hilbert space to a Hilbert space of solutions of the Dirac equation, that is to a Hilbert space of monogenic functions.
International Nuclear Information System (INIS)
Larionov, L.V.; Livshits, L.D.; Peresada, G.I.; AN SSSR, Moscow. Inst. Fiziki Zemli)
1985-01-01
Using the methods of piezo- and resistometry the influence of preliminary plastic deformation, phase transformation induced strengthening and heat treatment on kinetics of γ reversible α transformation in cerium is studied. It is shown, that the used methods of preliminary treatment of sample material do not change pressure value of γ → α and α →γ transformation initiation and do not affect hysteresis value, but affect considerably its kinetics. Preliminary plastic deformation and structural strengthening increase the average formation rate of a new phase. According to the data of tensile tests, structural strengthening, apprearing as a result of one cycle of γ → α → γ transformation, increases cerium strength characteristics 6y 30-50% with simultaneous decrease in plasticity. Metallographic studies confirm martensitic character of γ → α → γ transformations in cerium
International Nuclear Information System (INIS)
Stüßer, N.; Hofmann, T.
2013-01-01
Tapered guides with supermirror coating are frequently used to focus neutron beams on specimens. The divergence distribution in the focused beam is of a great importance for the quality of neutron instrumentation. Using an analytic approach we derive the tapering which is needed to achieve a form invariant phase space transformation of a rectangular phase volume. In addition we consider the effect of beam attenuation by the finite reflectivity of supermirrors. -- Highlights: • Form invariant volume transformation in phase space. • Focusing modules for neutron beams. • Analytical approach. • Attenuation effects in linearly and nonlinearly tapered guides
Chimera States in Two Populations with Heterogeneous Phase-lag
DEFF Research Database (Denmark)
Martens, Erik Andreas; Bick, Christian; Panaggio, Mark
2016-01-01
The simplest network of coupled phase-oscillators exhibiting chimera states is given by two populations with disparate intra- and inter-population coupling strengths. We explore the effects of heterogeneous coupling phase-lags between the two populations. Such heterogeneity arises naturally......-uniform synchronization, including in-phase and anti-phase synchrony, full incoherence (splay state), chimera states with phase separation of 0 or π between populations, and states where both populations remain desynchronized. These desynchronized states exhibit stable, oscillatory, and even chaotic dynamics. Moreover......, we identify the bifurcations through which chimera and desynchronized states emerge. Stable chimera states and desynchronized solutions, which do not arise for homogeneous phase-lag parameters, emerge as a result of competition between synchronized in-phase, anti-phase equilibria, and fully...
One Core Phase Shifting Transformer for Control of the Power Flow Distribution in Electric Networks
Directory of Open Access Journals (Sweden)
Golub I.V.
2016-08-01
Full Text Available This paper presents the variant of phase shifting transformer that is made, unlike from traditional technology, on the basis of only one magnetic core. The paper describes the methodology related to the analysis of operation modes of device and its components. Additionally it presents a mathematical model of device with determines the relationship between input and output electric quantities as well as own longitudinal and transverse parameters of an equivalent circuit of phase shifting transformer (PST. Proposed configuration of PST is interesting from an economic and operational consideration; enable continuous control of power flow distribution in electric networks as a result of regulation a phase shift angle between input and output voltages of device.
Phase and structural transformations in annealed copper coatings in relation to oxide whisker growth
Energy Technology Data Exchange (ETDEWEB)
Dorogov, M.V.; Priezzheva, A.N. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Vlassov, S., E-mail: vlassovs@ut.ee [Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga (Latvia); Kink, I.; Shulga, E. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Dorogin, L.M. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); ITMO University, Kronverkskiy 49, 197101 Saint Petersburg (Russian Federation); Lõhmus, R. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Tyurkov, M.N.; Vikarchuk, A.A. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Romanov, A.E. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); ITMO University, Kronverkskiy 49, 197101 Saint Petersburg (Russian Federation); Ioffe Physical Technical Institute, RAS, Polytechnicheskaya 26, 194021 Saint Petersburg (Russian Federation)
2015-08-15
Highlights: • Coatings prepared by Cu microparticle electrodeposition. • Structural and phase transformation in Cu coatings annealed at 400 °C. • Annealing is accompanied by intensive growth of CuO whiskers. • Layered oxide phases (Cu{sub 2}O and CuO) in the coating are characterized. • Formation of volumetric defects in the coating is demonstrated. - Abstract: We describe structural and phase transformation in copper coatings made of microparticles during heating and annealing in air in the temperature range up to 400 °C. Such thermal treatment is accompanied by intensive CuO nanowhisker growth on the coating surface and the formation of the layered oxide phases (Cu{sub 2}O and CuO) in the coating interior. X-ray diffraction and focused ion beam (FIB) are employed to characterize the multilayer structure of annealed copper coatings. Formation of volumetric defects such as voids and cracks in the coating is demonstrated.
Energy Technology Data Exchange (ETDEWEB)
Dudek, K; Glowacki, M; Pietrzyk, M [Akademia Gorniczo-Hutnicza, Cracow (Poland)
1999-07-01
Numerical model describing stresses arising during phase transformations in steels products is presented. The full model consists of three components. The first component uses finite element solution of Fourier equation for an evaluation of the temperature field inside the sample. The second component predicts kinetics of phase transformation occurring during cooling of steel products. Coupling of these two components allows prediction of structure and properties of final products at room temperature. The third component uses elastic-plastic finite element model for prediction of stresses caused by non-uniform temperatures and by changes of volume during transformations. Typical results of simulations performed for cooling of rails after hot rolling are presented. (author)
Features of the kinetics of heterogeneous reactions with phase transformations on catalyst surfaces
Energy Technology Data Exchange (ETDEWEB)
Berman, A D; Krylov, O V
1978-01-01
This paper presents a review of 41 bibliographic references to experiments on the adsorption of various gases (e.g., carbon monoxide, formic acid, ammonia, and oxygen) on metals (e.g., nickel, molybdenum, and platinum) and oxides covers observations of two-dimensional phases during adsorption; the kinetics of adsorption and catalysis associated with two-dimensional phase transitions; and several approximate models for describing the kinetics of heterogeneous catalysis which account for two-dimensional phase transformations on catalyst surfaces.
International Nuclear Information System (INIS)
Chizhov, A.V.; Paris, M.G.A.
1998-01-01
Phase squeezed states of a single mode radiation field have been introduced as eigenstates of a linear combination of lowering and raising operators. The explicit expression in the Fock basis has been obtained and some relevant properties have been illustrated. (author)
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.
Stress-induced phase transformation and room temperature aging in Ti-Nb-Fe alloys
Energy Technology Data Exchange (ETDEWEB)
Cai, S.; Schaffer, J.E. [Fort Wayne Metals Research Products Corp, 9609 Ardmore Ave., Fort Wayne, IN 46809 (United States); Ren, Y. [Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439 (United States)
2017-01-05
Room temperature deformation behavior of Ti-17Nb-1Fe and Ti-17Nb-2Fe alloys was studied by synchrotron X-ray diffraction and tensile testing. It was found that, after proper heat treatment, both alloys were able to recover a deformation strain of above 3.5% due to the Stress-induced Martensite (SIM) phase transformation. Higher Fe content increased the beta phase stability and onset stress for SIM transformation. A strong {110}{sub β} texture was produced in Ti-17Nb-2Fe compared to the {210}{sub β} texture that was observed in Ti-17Nb-1Fe. Room temperature aging was observed in both alloys, where the formation of the omega phase increased the yield strength (also SIM onset stress), and decreased the ductility and strain recovery. Other metastable beta Ti alloys may show a similar aging response and this should draw the attention of materials design engineers.
DEFF Research Database (Denmark)
Zecchino, Antonio; Hu, Junjie; Coppo, Massimiliano
2016-01-01
Due to the increasing penetration of single-phase small generation units and electric vehicles connected to distribution grids, system operators are facing challenges related to local unbalanced voltage rise or drop issues, which may lead to a violation of the allowed voltage band. To address...... 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...... 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...
International Nuclear Information System (INIS)
Witczak, Z.; Goncharova, V.A.
1999-01-01
Compression tests have been carried out on cerium specimens at room temperature (0.27 T m ) under high hydrostatic pressures up to 1.2 GPa. A strong increase of the yield strength was observed for both isomorphic γ and α phases at pressures approaching the γ ↔ α isomorphic phase transformations. That increase was in good agreement with the theory of dislocations when the dependence of elastic properties and a lattice parameter of cerium on pressure was applied to calculate the effect of pressure on the yield stress controlled by the edge dislocations. An anomalous strong decrease of the yield stress was observed in both γ and α phases in the vicinity of both γ ↔ α phase transformations. That phenomenon was explained as an effect of pressure induced new phase atoms through spreading the cores of edge dislocations. A complete disappearance of work hardening in both γ and α phases was also observed in the wide range of pressures. The influence of hydrostatic pressure on the energy of grain boundaries of both phases was considered to be responsible for that property. The ratio of the grain boundary energy to the Peierls energy is suggested to be a criterion of the work hardening ability of f.c.c. polycrystals
Solid-state transformer-based new traction drive system and control
Feng, Jianghua; Shang, Jing; Zhang, Zhixue; Liu, Huadong; Huang, Zihao
2017-11-01
A new type of traction drive system consisting of solid-state traction transformer (SSTT), inverter unit, auxiliary inverter, traction motor and other key components is built in order to suit the demand of developing the next-generation electric traction system which will be efficient and lightweight, with high power density. For the purpose of reducing system volume and weight and improving efficiency and grid-side power quality, an efficient SSTT optimized topology combining high-voltage cascaded rectifiers with high-power high-frequency LLC resonant converter is proposed. On this basis, an integrated control strategy built upon synchronous rotating reference frame is presented to achieve unified control over fundamental active, reactive and harmonic components. The carrier-interleaving phase shift modulation strategy is proposed to improve the harmonic performance of cascaded rectifiers. In view of the secondary pulsating existing in a single-phase system, the mathematical model of secondary power transfer is built, and the mechanism of pulsating voltage resulting in beat frequency of LLC resonant converter is revealed, so as to design optimum matching of system parameters. Simulation and experimental results have verified that the traction system and control scheme mentioned in this paper are reasonable and superior and that they meet the future application requirements for rail transit.
Qian, Hui-Dong; Si, Ping-Zhan; Choi, Chul-Jin; Park, Jihoon; Cho, Kyung Mox
2018-05-01
The effects of elemental doping of Si and Fe on the ɛ→τ phase transformation and the magnetic properties of MnAl were studied. The magnetic powders of Si- and Fe-doped MnAl were prepared by using induction melting followed by water-quenching, annealing, and salt-assisted ball-milling. The Fe-doped MnAl powders are mainly composed of the L10-structured τ-phase, while the Si-doped MnAl are composed of τ-phase and a small fraction of γ2- and β-phases. A unique thin leaves-like morphology with thickness of several tens of nanometers and diameter size up to 500 nm were observed in the Si-doped MnAl powders. The Fe-doped MnAl powders show irregular shape with much larger dimensions in the range from several to 10 μm. The morphology difference of the samples was ascribed to the variation of the mechanical properties affected by different doping elements. The phase transformation temperatures of the ɛ-phase of the samples were measured. The doping of Fe decreases the onset temperature of the massive phase transformation in MnAl, while the Si-doping increases the massive phase transformation temperature. Both Fe and Si increase the Curie temperature of MnAl. A substantially enhanced coercivity up to 0.45 T and 0.42 T were observed in the ball-milled MnAl powders doped with Si and Fe, respectively.
Phase-based motion magnification video for monitoring of vital signals using the Hermite transform
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.
Berry phase in Heisenberg representation
Andreev, V. A.; Klimov, Andrei B.; Lerner, Peter B.
1994-01-01
We define the Berry phase for the Heisenberg operators. This definition is motivated by the calculation of the phase shifts by different techniques. These techniques are: the solution of the Heisenberg equations of motion, the solution of the Schrodinger equation in coherent-state representation, and the direct computation of the evolution operator. Our definition of the Berry phase in the Heisenberg representation is consistent with the underlying supersymmetry of the model in the following sense. The structural blocks of the Hamiltonians of supersymmetrical quantum mechanics ('superpairs') are connected by transformations which conserve the similarity in structure of the energy levels of superpairs. These transformations include transformation of phase of the creation-annihilation operators, which are generated by adiabatic cyclic evolution of the parameters of the system.
Energy Technology Data Exchange (ETDEWEB)
Platteau, C; Ravat, B; Texier, G; Oudot, B; Delaunay, F, E-mail: brice.ravat@cea.fr [CEA Valduc 21120 Is sur Tille (France)
2010-03-15
The partial martensitic {delta}{yields}{alpha}' transformation in plutonium alloys is sensitive to chemical composition, sample thermal history, as well as crystalline defects. The present work investigates the {delta}-Pu phase microstructure before and after the martensitic transformation {delta}{yields}{delta}+{alpha}'. More precisely, microstructural modifications of the host {delta}-phase, resulting from the stress induced by a cell volume difference of 19% between the {delta} and {alpha}'-phases, were analysed. Microstructural information about crystallite size and microstrain of a highly homogenized Pu-Ga alloy was extracted from x-ray diffraction patterns using a three dimension crystallite size and microstrain model. This is available in Rietveld refinement software and consists in anisotropic broadening analysis of diffraction peaks. Crystallite size doesn't significantly change with the phase transformation contrary to microstrain that is multiplied, on average, by five. Furthermore, internal normal and shear microstress are multiplied, respectively, by 2 and 13 when {alpha}'-phase appears. Last, dislocation densities, calculated from crystallite size and microstrain, are compared to TEM results available in the literature.
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
FEATURES OF INFLUENCE OF MACROECONOMIC MEASURES OF TRANSFORMATION ON THE STATE DEBT POLICY
Directory of Open Access Journals (Sweden)
Roman Rudyk
2015-11-01
Full Text Available The objective is to study the relationship between the debt policy and vector of macroeconomic measures which is reflected in the transformation of structure of budget deficiency payments. Also, the article defines and characterizes three main phases of the government debt policy: pre-stabilization, stabilization and post-stabilization. The author analyzes main aspects of the relationship between dept policy and monetary one. Methodology. The study is based on the works of domestic and foreign scientists engaged in research of the given problem. Theoretical concepts are supported by statistical data of key macroeconomic indicators of Ukraine’s economy. Results of the survey showed that the relationship between the debt policy and measures of macro-regulation during the transformation has the stable and permanent nature, and the use of certain instruments of government debt management is exclusively possible for a definite direction of macro policy on the one hand, and they are the elements in the system of measures for its implementation on the other hand. In the pre-stabilization phase of transformation the debt policy synthesizes the expansive solutions of monetary and fiscal authorities, and a direct link between them mediate the expansion of demand in the public sector and the preservation of soft budget constraints for micro-units; in the stabilization phase the relationship between fiscal, monetary and debt policy becomes more indirect, but are direct in that part of the borrowing purposes, subordinated to the creation of macro-stabilization mechanism of transformation; in the poststabilization period the role of indirect interconnection between the debt measures and fiscal and monetary decisions increases, but the lack of a deep micro-restructuring and deep systemic and structural reforms cause the deterioration in the macro-economic state of the system, due to which the vector of government borrowing again gravitates toward the field
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.
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.
DEFF Research Database (Denmark)
Jiang, Jianzhong; Saksl, K.; Saida, J.
2002-01-01
The amorphous-to-quasicrystalline phase transformation and the pressure effect on the transformation in a Zr66.7Pd33.3 metallic glass have been investigated by in situ x-ray diffraction measurements using synchrotron radiation. It is found that the transformation is a polymorphous reaction...
Structural phase transformation in K2SeO4
International Nuclear Information System (INIS)
Iizumi, M.; Axe, J.D.; Shirane, G.; Shimaoka, K.
1977-01-01
Successive phase transformations in K 2 SeO 4 at T 1 = 130 K and T/sub c/ = 93 K were studied by the neutron-scattering technique. The superlattice reflections in the intermediate phase were found to be incommensurate with the lattice periodicity. The wave vector characterizing the reflections is q/sub delta/ = (1-delta) a*/3 with delta = 0.07 at 122.5 K. The deviation delta decreases with decreasing temperature with an apparently discontinuous jump to zero at T/sub c/. Below this temperature, the crystal remains commensurate and is known to be ferroelectric. The incommensurate-commensurate transition and the simultaneous occurrence of the commensurate phase and the spontaneous polarization are discussed using a Landau-type expansion of the free energy in which a term proportional to Q 3 (q/sub delta/) P/sub z/ (q 3 /sub delta/) plays an essential role in driving the incommensurate-commensurate phase transformation and in inducing the spontaneous polarization. Here, Q (q/sub delta/) is the amplitude of the primary atomic displacements with wave vector q/sub delta/ and P/sub z/(q 3 /sub delta/) is the polarization wave with wave vector q 3 /sub delta/ = 3delta (a*/3) and becomes the macroscopic polarization below T/sub c/. Above T/sub i/, a Σ 2 optic-phonon branch along (xi,0,0) shows a striking softening and ω/sub j/(q) for q approx. (1/3,0,0) tends to zero at T/sub i/. The softening results from a temperature-dependent decrease of the interlayer forces with ranges a/2 and a (a is one unit-cell length along the a axis) in the presence of strong and persisting forces with a range 3a/2. The intensities of the soft phonon were measured about different reciprocal-lattice points and were used to determine the nature of the soft-phonon mode and suggest a coupled translation of potassium ions with rotational motion of SeO 4 groups to be the origin of the lattice instability
Towards an improved continuum theory for phase transformations
International Nuclear Information System (INIS)
Tijssens, M.G.A.; James, R.D.
2003-01-01
We develop a continuum theory for martensitic phase transformations in which explicit use is made of atomistic calculations based on density functional theory. Following the work of Rabe and coworkers, branches of the phonon-dispersion relation with imaginary frequencies are selected to construct a localized basis tailored to the symmetry of the crystal lattice. This so-called Wannier basis helps to construct an effective Hamiltonian of a particularly simple form. We extend the methodology by incorporating finite deformations and passing the effective Hamiltonian fully to continuum level. The developments so far are implemented on the shape memory material NiTi
Reduced conservatism in stability robustness bounds by state transformation
Yedavalli, R. K.; Liang, Z.
1986-01-01
This note addresses the issue of 'conservatism' in the time domain stability robustness bounds obtained by the Liapunov approach. A state transformation is employed to improve the upper bounds on the linear time-varying perturbation of an asymptotically stable linear time-invariant system for robust stability. This improvement is due to the variance of the conservatism of the Liapunov approach with respect to the basis of the vector space in which the Liapunov function is constructed. Improved bounds are obtained, using a transformation, on elemental and vector norms of perturbations (i.e., structured perturbations) as well as on a matrix norm of perturbations (i.e., unstructured perturbations). For the case of a diagonal transformation, an algorithm is proposed to find the 'optimal' transformation. Several examples are presented to illustrate the proposed analysis.
Effect of V-Nd co-doping on phase transformation and grain growth process of TiO2
Khatun, Nasima; Amin, Ruhul; Anita, Sen, Somaditya
2018-05-01
The pure and V-Nd co-doped TiO2 samples are prepared by the modified sol-gel process. The phase formation is confirmed by XRD spectrum. Phase transformation is delayed in V-Nd co-doped TiO2 (TVN) samples compared to pure TiO2. The particle size is comparatively small in TVN samples at both the temperature 450 °C and 900 °C. Hence the effect of Nd doping is dominated over V doping in both phase transformation and grain growth process of TiO2.
The effect of manganese on the kinetics of phase transformations of austenite in structural steels
International Nuclear Information System (INIS)
Pacyna, J.; Jedrzejewska-Strach, A.
1995-01-01
The aim of this work was to examine the effect of Mn on the kinetics of phase transformations of supercooled austenite. It was executed the 4 CCT diagrams for alloys of a variable Mn content. The obtained results indicate that with the increase of Mn concentrations in austenite in the range 0.73-2.94% the times to the beginning of its transformation are lengthened and the temperatures of these transformations into ferrite and the bainitic transformations are lengthened slightly whole only the time to the beginning of a pearlitic transformation is lengthened more strongly. In the range of 2.0-2.94% Mn the times to the beginnings of all transformations grow very strongly. (author)
Operational geometric phase for mixed quantum states
International Nuclear Information System (INIS)
Andersson, O; Heydari, H
2013-01-01
The geometric phase has found a broad spectrum of applications in both classical and quantum physics, such as condensed matter and quantum computation. In this paper, we introduce an operational geometric phase for mixed quantum states, based on spectral weighted traces of holonomies, and we prove that it generalizes the standard definition of the geometric phase for mixed states, which is based on quantum interferometry. We also introduce higher order geometric phases, and prove that under a fairly weak, generically satisfied, requirement, there is always a well-defined geometric phase of some order. Our approach applies to general unitary evolutions of both non-degenerate and degenerate mixed states. Moreover, since we provide an explicit formula for the geometric phase that can be easily implemented, it is particularly well suited for computations in quantum physics. (paper)
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.
Transformation behavior of the γU(Zr,Nb) phase under continuous cooling conditions
International Nuclear Information System (INIS)
Komar Varela, C.L.; Gribaudo, L.M.; González, R.O.; Aricó, S.F.
2014-01-01
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
Sintering prevention and phase transformation of FePt nanoparticles
International Nuclear Information System (INIS)
Ding, Y.; Majetich, S.A.; Kim, J.; Barmak, K.; Rollins, H.; Sides, P.
2004-01-01
Two approaches attempted to overcome FePt nanoparticle sintering during the transformation to the high coercivity L1 0 phase, which currently limits the use of these nanoparticles in data storage media. High-pressure treatment of dilute nanoparticle solutions failed to prevent sintering due to surfactant decomposition above 360 deg. C. By pre-annealing nanoparticle monolayers to decompose the surfactant, and then coating with an immiscible SiO 2 matrix, sintering was prevented with annealing temperatures up to 700 deg. C
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...
International Nuclear Information System (INIS)
Yu, Terri M.; Brown, Kenneth R.; Chuang, Isaac L.
2005-01-01
The role of mixed-state entanglement in liquid-state nuclear magnetic resonance (NMR) quantum computation is not yet well understood. In particular, despite the success of quantum-information processing with NMR, recent work has shown that quantum states used in most of those experiments were not entangled. This is because these states, derived by unitary transforms from the thermal equilibrium state, were too close to the maximally mixed state. We are thus motivated to determine whether a given NMR state is entanglable - that is, does there exist a unitary transform that entangles the state? The boundary between entanglable and nonentanglable thermal states is a function of the spin system size N and its temperature T. We provide bounds on the location of this boundary using analytical and numerical methods; our tightest bound scales as N∼T, giving a lower bound requiring at least N∼22 000 proton spins to realize an entanglable thermal state at typical laboratory NMR magnetic fields. These bounds are tighter than known bounds on the entanglability of effective pure states
Analysis of solid-state transformations of pharmaceutical compounds using vibrational spectroscopy
DEFF Research Database (Denmark)
Heinz, Andrea; Strachan, Clare J; Gordon, Keith C
2009-01-01
OBJECTIVES: Solid-state transformations may occur during any stage of pharmaceutical processing and upon storage of a solid dosage form. Early detection and quantification of these transformations during the manufacture of solid dosage forms is important since the physical form of an active...... pharmaceutical ingredient can significantly influence its processing behaviour, including powder flow and compressibility, and biopharmaceutical properties such as solubility, dissolution rate and bioavailability. KEY FINDINGS: Vibrational spectroscopic techniques such as infrared, near-infrared, Raman and, most...... multivariate approaches where even overlapping spectral bands can be analysed. SUMMARY: This review discusses the applications of different vibrational spectroscopic techniques to detect and monitor solid-state transformations possible for crystalline polymorphs, hydrates and amorphous forms of pharmaceutical...
Experimental demonstration of conformal phased array antenna via transformation optics.
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.
Directory of Open Access Journals (Sweden)
Peter Finkel
2015-12-01
Full Text Available Recent advances in phase transition transduction enabled the design of a non-resonant broadband mechanical energy harvester that is capable of delivering an energy density per cycle up to two orders of magnitude larger than resonant cantilever piezoelectric type generators. This was achieved in a [011] oriented and poled domain engineered relaxor ferroelectric single crystal, mechanically biased to a state just below the ferroelectric rhombohedral (FR-ferroelectric orthorhombic (FO phase transformation. Therefore, a small variation in an input parameter, e.g., electrical, mechanical, or thermal will generate a large output due to the significant polarization change associated with the transition. This idea was extended in the present work to design a non-resonant, multi-domain magnetoelectric composite hybrid harvester comprised of highly magnetostrictive alloy, [Fe81.4Ga18.6 (Galfenol or TbxDy1-xFe2 (Terfenol-D], and lead indium niobate–lead magnesium niobate–lead titanate (PIN-PMN-PT domain engineered relaxor ferroelectric single crystal. A small magnetic field applied to the coupled device causes the magnetostrictive element to expand, and the resulting stress forces the phase change in the relaxor ferroelectric single crystal. We have demonstrated high energy conversion in this magnetoelectric device by triggering the FR-FO transition in the single crystal by a small ac magnetic field in a broad frequency range that is important for multi-domain hybrid energy harvesting devices.
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'orientation {gamma}/{alpha} et {gamma} /{alpha
Liquid-solid surface phase transformation of fluorinated fullerene on monolayer tungsten diselenide
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.
Liquid-solid surface phase transformation of fluorinated fullerene on monolayer tungsten diselenide
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.
Negative pressure driven phase transformation in Sr doped SmCoO₃.
Arshad Farhan, M; Javed Akhtar, M
2010-02-24
Atomistic computer simulation techniques based on energy minimization procedures are utilized for the structural investigation of perovskite-type SmCoO(3). A reliable potential model is derived which reproduces both cubic as well as orthorhombic phases of SmCoO(3). We observe a negative chemical pressure induced structural phase transformation from distorted perovskite (orthorhombic) to perfect perovskite (cubic) due to the substitution of Sr(2 + ) at the Sm(3 + ) sites. However, external hydrostatic pressure shows isotropic compression and no pressure-induced structural transformation is observed up to 100 GPa. To maintain the electroneutrality of the system, charge compensation is through oxygen vacancies which results in the brownmillerite-type structure. A defect model is proposed, which is consistent with experimental results. The solution energies for divalent and trivalent cations are also calculated. These results show that the cations having ionic radii less than 0.75 Å will occupy the Co sites and those with ionic radii larger than 0.75 Å will substitute at the Sm sites.
R. Dąbrowski; R. Dziurka; E. Rożniata
2012-01-01
Purpose: Present work corresponds to the research on the kinetic of phase transformation of undercooled austenite of 38MnCrNi6-4-4 hypoeutctoid steel. The kinetic of phase transformation of under cooled austenite of investigated alloy was presented on CCT diagram (continuous cooling transformation). Also the methodology of a dilatometric samples preparation and the method of the critical points determination were described.Design/methodology/approach: The austenitising temperature was defined...
International Nuclear Information System (INIS)
Hua-Jun, Sun; Li-Song, Hou; Yi-Qun, Wu; Xiao-Dong, Tang
2009-01-01
We demonstrate a reversible resistance switching effect that does not rely on amorphous-crystalline phase transformation in a nanoscale capacitor-like cell using Ge 1 Sb 4 Te 7 films as the working material. The polarity and amplitude of the applied electric voltage switches the cell resistance between low- and high-resistance states, as revealed in the current-voltage characteristics of the film by conductive atomic force microscopy (CAFM). This reversible SET/RESET switching effect is induced by voltage pulses and their polarity. The change of electrical resistance due to the switching effect is approximately two orders of magnitude
Operation characteristics of SFCLs combined with a transformer in three-phase power system
Energy Technology Data Exchange (ETDEWEB)
Jung, B. I.; Choi, H. S. [Chosun University, Gwangju (Korea, Republic of)
2013-12-15
The studies of superconducting fault current limiter (SFCL) for reduction of the fault current are actively underway in the worldwide. In this paper, we analyzed the characteristics of a new type SFCL using the conventional transformer and superconducting elements combined mutually. The secondary and third windings of this SFCL were connected the load and the superconducting element, respectively. The electric power was provided to load connected to secondary windings of the transformer in normal state of power system. On the other hand, when the fault occurred in power system, the fault current was limited by closing the line of third winding of the transformer. At this time, the ripple phenomenon of the fault was minimized by opening the fault line in secondary winding of a transformer in power system. The sensing of the fault state was performed by the CT(current transformer) and then turn-on and turn-off switching behavior of the SFCL was performed by the SCR(silicon-controlled rectifier). As a result, the proposed SFCL limited the fault current within a half-cycle efficiently. We confirmed that the fault current limitation rate was changed according to the winding ratio of a transformer.
Operation characteristics of SFCLs combined with a transformer in three-phase power system
International Nuclear Information System (INIS)
Jung, B. I.; Choi, H. S.
2013-01-01
The studies of superconducting fault current limiter (SFCL) for reduction of the fault current are actively underway in the worldwide. In this paper, we analyzed the characteristics of a new type SFCL using the conventional transformer and superconducting elements combined mutually. The secondary and third windings of this SFCL were connected the load and the superconducting element, respectively. The electric power was provided to load connected to secondary windings of the transformer in normal state of power system. On the other hand, when the fault occurred in power system, the fault current was limited by closing the line of third winding of the transformer. At this time, the ripple phenomenon of the fault was minimized by opening the fault line in secondary winding of a transformer in power system. The sensing of the fault state was performed by the CT(current transformer) and then turn-on and turn-off switching behavior of the SFCL was performed by the SCR(silicon-controlled rectifier). As a result, the proposed SFCL limited the fault current within a half-cycle efficiently. We confirmed that the fault current limitation rate was changed according to the winding ratio of a transformer.
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
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.
Energy Technology Data Exchange (ETDEWEB)
Cheng, Han-miao, E-mail: chenghanmiao@hust.edu.cn; Li, Hong-bin, E-mail: lihongbin@hust.edu.cn [CEEE of Huazhong University of Science and Technology, Wuhan 430074 (China); State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Wuhan 430074 (China)
2015-08-15
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.
Structure-phase transformations in 36NXTYu highly deformed alloy during aging
International Nuclear Information System (INIS)
Plotnikov, S.V.; Radashin, M.V.; Alontseva, D.L.
2001-01-01
The 36NXTYu alloy - containing 35.39% Ni, 12.43% Cr, 3.08% Ti, 1.22% Al, 0.93% Mn, 0.36% Si, 0.09% Cu , 0.03% C, 0.12% P, 0.09% S and the rest iron - has been examined. Under aging beginning in the alloy the Ni 3 (Al,Yi) type metastable γ'-phase release of with L12 structure is taking place, and then the stable η-phase (Ni 3 Ti, DO 24 ) is occurring. The thin foils structure and micro-diffraction analysis were observed with help of the electron microscope. Fractography has been watched on the scanning electron microscope. For study both phase content and samples texture the DRON-3 diffractometer was applied. The mechanical testing include one-axis static expansion with measurement of a strength limit, conventional fluidity limit, relational extension up to sample breakage. It is shown, that rolling deep levels in the 36NXTYu alloy, in the common case, do not change the structure-phase transformation morphology, but instead of γ'-phase the η-phase is discretely releasing
Phases of capitalism, welfare states, medical dominance, and health care in Ontario.
Coburn, D
1999-01-01
There has been a lacuna in previous studies of medicine and health care of concepts or structures relating changes in health care with their contextualizing social structures. That is, there is a need to more adequately account for health care and social structure in terms of dynamic rather than static concepts. This article reports the application of a general schema outlining the transformation of capitalism through the phases of entrepreneurial, monopoly, and global capitalism, first presented by Ross and Trachte, to help understand both the changing role of medicine in Canada and the historical trajectory of the development of health insurance. These related events are shown to be partly reflective of the transformed class dynamic involved in a changing capitalist mode of production. The recent history of challenges to medicare in Canada as well as evidence of the declining power of medicine are both related directly and indirectly to the increased power of business and the decline in the relative autonomy of the state accompanying globalization. The application of the phases of capitalism sequence does roughly fit the Canadian instance although some modifications will be required to account for the specifics of the Canadian case. The schema also helps resolve two previously competing class arguments about the rise of health insurance in Canada.
International Nuclear Information System (INIS)
Liu, D.M.; Nie, Z.H.; Wang, G.; Wang, Y.D.; Brown, D.E.; Pearson, J.; Liaw, P.K.; Ren, Y.
2010-01-01
A polymer-bonded Ni 45 Co 5 Mn 36.6 In 13.4 ferromagnetic shape-memory composite was fabricated, having magnetic-field-driven shape recovery properties. The thermo-magnetization curves of the composite suggested that the magnetic-field-induced reverse martensitic transformation occurs in the composite. The effects of temperature, stress, and magnetic-field on the phase transformation properties were systematically investigated using an in-situ high-energy X-ray diffraction technique. A temperature-induced reversible martensitic phase transformation was confirmed within the composite, showing a broad phase transformation interval. Stress-induced highly textured martensite was observed in the composite during uniaxial compressive loading, with a residual strain after unloading. The origin of the textured martensite can be explained by the grain-orientation-dependent Bain distortion energy. A recovery strain of ∼1.76% along the compression direction was evidenced in the pre-strained composite with an applied magnetic-field of 5 T. This recovery was caused by the magnetic-field-induced reverse martensitic phase transformation. The phase transformation properties of the ferromagnetic shape-memory composite, different from its bulk alloys, can be well explained by the Clausius-Clapeyron relation. The large magnetic-field-induced strain, together with good ductility and low cost, make the polymer-bonded Ni-Co-Mn-In composites potential candidates for magnetic-field-driven actuators.
International Nuclear Information System (INIS)
Song, T.; Ma, Q.; Sun, X.W.; Liu, Z.J.; Fu, Z.J.; Wei, X.P.; Wang, T.; Tian, J.H.
2016-01-01
The phase transition, electronic band structure, and equation of state (EOS) of cubic TcN are investigated by first-principles pseudopotential method based on density-functional theory. The calculated enthalpies show that TcN has a transformation between zincblende and rocksalt phases and the pressure determined by the relative enthalpy is 32 GPa. The calculated band structure indicates the metallic feature and it might make cubic TcN a better candidate for hard materials. Particular attention is paid to the predictions of volume, bulk modulus and its pressure derivative which play a central role in the formulation of approximate EOSs using the quasi-harmonic Debye model. - Highlights: • The phase transition pressure and electronic band structure for cubic TcN are determined. • Particular attention is paid to investigate the equation of state parameters for cubic TcN. • The thermodynamic properties up to 80 GPa and 3000 K are successfully predicted.
Evirgen, A.; Pons, J.; Karaman, I.; Santamarta, R.; Noebe, R. D.
2018-03-01
The distributions of H-phase precipitates in Ni50.3Ti29.7Hf20 and Ni50.3Ti29.7Zr20 alloys formed by aging treatments at 500 and 550 °C or slow furnace cooling and their effects on the thermal martensitic transformation have been investigated by TEM and calorimetry. The comparative study clearly reveals faster precipitate-coarsening kinetics in the NiTiZr alloy than in NiTiHf. For precipitates of a similar size of 10-20 nm in both alloys, the martensite plates in Ni50.3Ti29.7Zr20 have larger widths and span a higher number of precipitates compared with the Ni50.3Ti29.7Hf20 alloy. However, for large H-phase particles with hundreds of nm in length, no significant differences in the martensitic microstructures of both alloy systems have been observed. The martensitic transformation temperatures of Ni50.3Ti29.7Hf20 are 80-90 °C higher than those of Ni50.3Ti29.7Zr20 in the precipitate-free state and in the presence of large particles of hundreds on nm in length, but this difference is reduced to only 10-20 °C in samples with small H-phase precipitates. The changes in the transformation temperatures are consistent with the differences in the precipitate distributions between the two alloy systems observed by TEM.
Energy Technology Data Exchange (ETDEWEB)
Tambunan, Octolia Togibasa; Lee, Min Young; Kim, Deok Hyeon; Parwanta, Kadek Juliana; Jung, Chang Uk [Hankuk University of Foreign Studies, Yongin (Korea, Republic of)
2014-06-15
A phase transformation from insulating brownmillerite SrCoO{sub 2.5} to conducting perovskite SrCoO{sub 3} through electrochemical oxidation has been demonstrated for thin films of SrCoO{sub x} on a SrTiO{sub 3} (001) substrate. The cobalt-oxide film strongly favors the brownmillerite phase of SrCoO{sub 2.5} instead of the perovskite phase of SrCoO{sub 3} on a SrTiO{sub 3} (001) substrate due to its low lattice mismatch. Therefore, the phase transformation has its own retention. The alkaline water electrolysis occurs between the copper cathode and the SrCoO{sub 2.5} film anode. The H{sup +} ions are attracted to the cathode and generate H{sub 2} gas. The OH{sup -} ions are attracted to the film's surface and generate a rich amount of oxygen to fill the oxygen vacancy channel of brownmillerite SrCoO{sub 2.5}. The phase transformation was verified from the change in the out-of-plane lattice constant and the change in the resistivity of the electrolyzed film.
Thermal stability and phase transformations of martensitic Ti–Nb alloys
Directory of Open Access Journals (Sweden)
Matthias Bönisch, Mariana Calin, Thomas Waitz, Ajit Panigrahi, Michael Zehetbauer, Annett Gebert, Werner Skrotzki and Jürgen Eckert
2013-01-01
Full Text Available Aiming at understanding the governing microstructural phenomena during heat treatments of Ni-free Ti-based shape memory materials for biomedical applications, a series of Ti–Nb alloys with Nb concentrations up to 29 wt% was produced by cold-crucible casting, followed by homogenization treatment and water quenching. Despite the large amount of literature available concerning the thermal stability and ageing behavior of Ti–Nb alloys, only few studies were performed dealing with the isochronal transformation behavior of initially martensitic Ti–Nb alloys. In this work, the formation of martensites (α' and α'' and their stability under different thermal processing conditions were investigated by a combination of x-ray diffraction, differential scanning calorimetry, dilatometry and electron microscopy. The effect of Nb additions on the structural competition in correlation with stable and metastable phase diagrams was also studied. Alloys with 24 wt% Nb or less undergo a transformation sequence on heating from room temperature to 1155 K. In alloys containing >24 wt% Nb α'' martensitically reverts back to β0, which is highly unstable against chemical demixing by formation of isothermal ωiso. During slow cooling from the single phase β domain α precipitates and only very limited amounts of α'' martensite form.
Geometric phases for nonlinear coherent and squeezed states
International Nuclear Information System (INIS)
Yang Dabao; Chen Ying; Chen Jingling; Zhang Fulin
2011-01-01
The geometric phases for standard coherent states which are widely used in quantum optics have attracted considerable attention. Nevertheless, few physicists consider the counterparts of nonlinear coherent states, which are useful in the description of the motion of a trapped ion. In this paper, the non-unitary and non-cyclic geometric phases for two nonlinear coherent and one squeezed states are formulated, respectively. Moreover, some of their common properties are discussed, such as gauge invariance, non-locality and nonlinear effects. The nonlinear functions have dramatic impacts on the evolution of the corresponding geometric phases. They speed the evolution up or down. So this property may have an application in controlling or measuring geometric phase. For the squeezed case, when the squeezed parameter r → ∞, the limiting value of the geometric phase is also determined by a nonlinear function at a given time and angular velocity. In addition, the geometric phases for standard coherent and squeezed states are obtained under a particular condition. When the time evolution undergoes a period, their corresponding cyclic geometric phases are achieved as well. And the distinction between the geometric phases of the two coherent states may be regarded as a geometric criterion.
International Nuclear Information System (INIS)
Waitz, T.
1999-06-01
In CoFe crystals containing 0.85, 1.5, 5.75 and 6.0at.% Fe the thermally induced martensitic phase transformations between the close packed lattices face centered cubic (fcc), double hexagonal close packed (dhcp) and hexagonal close packed (hcp) were studied. Transmission electron microscopy methods were applied including in-situ experiments; both high-resolution transmission electron microscopy (HRTEM) images and lattice fringe images were used to analyze the transformations at an atomic scale. Based on the results of both the transformations in the bulk and the in-situ transformations it is concluded that the phase transitions occur by the formation of lamellae on the close packed habit planes. The lamellae have a minimum thickness of 10 to 15 close packed planes; therefore transformation models that are based on random overlap of stacking faults can be excluded. The glissile transformation fronts of the lamellae contain transformation dislocations (partials) that are correlated on an atomic scale. In the HRTEM images partials that are only about 0.2 nm apart were resolved and analyzed in detail by circuits that are similar to Burgers circuits. Two attracting partials on adjacent close packed planes are the structural units of the transformation fronts; they are dipoles and paired partials (with a total Burgers vector of a single partial) in the case of the transformations hcp dhcp and fcc dhcp, respectively. Different arrangements of the partials at the transformation fronts lead to two different modes A and B of the phase transition. These two modes seem to be competitive processes that can be favored by different parameters of the material (as chemical composition and microstructure). Partials of mode A transformations have the same Burgers vectors; therefore the partials repel each other causing long range internal stresses and large transformation shear strains that can lead to a surface relief. Whereas, partials of mode B transformations have different
Liu, Hao; Lin, Lingfang; Yu, Yang; Lin, Hanxuan; Zhu, Yinyan; Miao, Tian; Bai, Yu; Shi, Qian; Cai, Peng; Kou, Yunfang; Lan, Fanli; Wang, Wenbin; Zhou, Xiaodong; Dong, Shuai; Yin, Lifeng; Shen, Jian
2017-11-01
Electronic phase separation (EPS) is a common phenomenon in strongly correlated oxides. For colossal magnetoresistive (CMR) manganites, the EPS is so pronounced that not only does it govern the CMR behavior, but also raises a question whether EPS exists as a ground state for systems or a metastable state. While it has been well known that a magnetic field can drive the transition of the EPS state into a single-phase state in manganites, the reversibility of this transition is not well studied. In this work we use magnetic force microscopy (MFM) to directly visualize the reversibility of the field driven transition between the EPS state and the single-phase state at different temperatures. The MFM images correspond well with the global magnetic and transport property measurements, uncovering the underlying mechanism of the field driven transition between the EPS state and the single-phase state. We argue that EPS state is a consequence of system quenching whose response to an external magnetic field is governed by a local energy landscape.
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.
International Nuclear Information System (INIS)
Zhu, Y.Z.; Liang, D.M.; Li, J.C.; Xu, J.P.; Xue, Z.L.
2011-01-01
Highlights: → The order of solid solution of carbides influences phase transformation of C-Mn steel in cooling. → Evidences of early stage of solid solution of carbides were provides in the paper. → Transitional state evidences such as carbon enriched regions were observed in this study. - Abstract: The C-Mn steel strips microalloyed with Cr, Nb, Ti was produced by compact strip production process and then heat-treated under different conditions. Optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy were used to investigate phase transformations in the steel after different treatments. It was revealed that the phase transformations upon quenching were greatly affected by the austenization temperature and time. When the steel was annealed at 950 deg. C, carbides of Cr, Mn and Fe were dissolved dramatically, while carbides of Nb and Ti are relatively stable at this temperature. When the temperature increases to 1100 deg. C, the carbides of Nb were dissolved rapidly, while the carbides of Ti still show somewhat stable (partial dissolution). Annealing time influences both the amount and the shapes of carbides in the steel, which leads to different phase transformations in the following air cooling processes. Grain growth in the steel in annealing process strongly depends on the dissolution of carbides on grain boundaries. Additionally, a subsequent rolling after annealing treatment at 950 deg. C lead to obvious precipitation of carbides of Ti and Nb in the steel.
DEFF Research Database (Denmark)
Jiang, Jianzhong; Zhuang, Yanxin; Rasmussen, Helge Kildahl
2001-01-01
The effect of pressure on the formation of quasicrystals and the amorphous-to-quasicrystalline phase transformation kinetics in the supercooled liquid region for a Zr65Al7.5Ni10Cu7.5Ag10 metallic glass have been investigated by in situ high-pressure and high-temperature nonisothermal and isothermal...... of quasicrystals decrease, Atomic mobility is important for the formation of quasicrystals from the metallic glass whereas the relationship of the crystallization temperature vs pressure for the transition from the quasicrystalline state to intermetallic compounds may mainly depend on the thermodynamic potential...... energy barrier. To study the amorphous-to-quasicrystalline phase transformation kinetics in the metallic glass, relative volume fractions of the transferred quasicrystalline phase as a function of annealing time, obtained at 663, 673, 683, and 693 K, have been analyzed in details using 14 nucleation...
Investigation of the {Fe}/{Si} interface and its phase transformations
Fanciulli, M.; Degroote, S.; Weyer, G.; Langouche, G.
1997-04-01
Thin 57Fe films (3-10 Å) have been grown by molecular beam epitaxy (MBE) on (7 × 7) reconstructed Si(111) and (2 × 1) reconstructed Si(001) surfaces and by e-gun evaporation on an H-terminated Si(111) surface. Conversion electron Mössbauer spectroscopy (CEMS) with high statistical accuracy and resolution allowed a detailed microscopic investigation of the silicide formation mechanism and of the structural phase transformations upon annealing.
Directory of Open Access Journals (Sweden)
Jian Sheng-Rui
2008-01-01
Full Text Available AbstractThis work presents the molecular dynamics approach toward mechanical deformation and phase transformation mechanisms of monocrystalline Si(100 subjected to nanoindentation. We demonstrate phase distributions during loading and unloading stages of both spherical and Berkovich nanoindentations. By searching the presence of the fifth neighboring atom within a non-bonding length, Si-III and Si-XII have been successfully distinguished from Si-I. Crystallinity of this mixed-phase was further identified by radial distribution functions.
Kowalewska, A; Nowacka, M; Włodarska, M; Zgardzińska, B; Zaleski, R; Oszajca, M; Krajenta, J; Kaźmierski, S
2017-10-18
Reactive octahedral silsesquioxanes of rod-like [octakis(3-chloropropyl)octasilsesquioxane - T 8 (CH 2 CH 2 CH 2 Cl) 8 ] and spherical [octavinyloctasilsesquioxane - T 8 (CH[double bond, length as m-dash]CH 2 ) 8 ] structure can undergo reversible thermally induced phase transitions in the solid state. The phase behaviour has been studied with differential scanning calorimetry (DSC, including temperature modulated DSC), X-ray diffraction, dielectric relaxation spectroscopy (DRS), and nuclear magnetic resonance spectroscopy in the solid state (SS NMR), as well as positron annihilation lifetime spectroscopy (PALS) and polarized optical microscopy (POM). The mechanisms involving fitting the molecules into most symmetrical crystal lattices vary for species of different structure. Thermal energy can be used to expand the crystal lattice leading to thermochromism in the case of T 8 (CH[double bond, length as m-dash]CH 2 ) 8 or conversely to an unusual negative thermal expansion of crystals of T 8 (CH 2 CH 2 CH 2 Cl) 8 that results in their self-actuation. The complex behaviour is reflected in unusual changes in the capacitance and fractional free volume of the material. These phenomena can be used for molecular design of advanced well-defined hybrid materials capable of reversible thermally induced structural transformations. The findings present a new perspective for POSS-based flexible metal-organic frameworks (MOF) of cooperative structural transformability via entropy-based translational sub-net sliding.
Age-hardening and related phase transformation in an experimental Ag-Cu-Pd-Au alloy
Energy Technology Data Exchange (ETDEWEB)
Seol, Hyo-Joung [Department of Dental Materials, College of Dentistry, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Lee, Doung-Hun [Department of Dental Materials, College of Dentistry, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Lee, Hee-Kyung [Department of Dental Technology, Daegu Health College, San 7 Taejeon-dong, Buk-gu, Daegu 702-722 (Korea, Republic of); Takada, Yukyo [Division of Dental Biomaterials, Graduate School of Dentistry, Tohoku University, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-8575 (Japan); Okuno, Osamu [Division of Dental Biomaterials, Graduate School of Dentistry, Tohoku University, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-8575 (Japan); Kwon, Yong Hoon [Department of Dental Materials, College of Dentistry, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of); Kim, Hyung-Il [Department of Dental Materials, College of Dentistry, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739 (Korea, Republic of)]. E-mail: hilkim@pusan.ac.kr
2006-01-05
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 {alpha}{sub 1} phase and the Pd-containing Cu-rich {alpha}{sub 2} phase were transformed into four phases of the Ag-rich {alpha}{sub 1}{sup '} phase, the Cu-rich {alpha}{sub 2}{sup '} phase, the CsCl-type CuPd phase and the AuCu(I) ordered phase. Microstructure of the solution-treated specimen consisted of the Ag-rich {alpha}{sub 1} matrix, Cu-rich {alpha}{sub 2} particle-like structures of various sizes and the lamellar structure of the {alpha}{sub 1} and {alpha}{sub 2} phases. When the peak hardness was obtained, the very fine lamellar structure consisting of the Ag-rich {alpha}{sub 1}{sup '} and Cu-rich {alpha}{sub 2}{sup '} 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 {alpha}{sub 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.
Uniform sparse bounds for discrete quadratic phase Hilbert transforms
Kesler, Robert; Arias, Darío Mena
2017-09-01
For each α \\in T consider the discrete quadratic phase Hilbert transform acting on finitely supported functions f : Z → C according to H^{α }f(n):= \\sum _{m ≠ 0} e^{iα m^2} f(n - m)/m. We prove that, uniformly in α \\in T , there is a sparse bound for the bilinear form for every pair of finitely supported functions f,g : Z→ C . The sparse bound implies several mapping properties such as weighted inequalities in an intersection of Muckenhoupt and reverse Hölder classes.
P-phase precipitation and its effect on martensitic transformation in (Ni,Pt)Ti shape memory alloys
International Nuclear Information System (INIS)
Gao, Y.; Zhou, N.; Yang, F.; Cui, Y.; Kovarik, L.; Hatcher, N.; Noebe, R.; Mills, M.J.; Wang, Y.
2012-01-01
A new precipitate phase named P-phase has recently been identified in (Ni,Pt)Ti high temperature shape memory alloys. In order to understand the roles played by the fine coherent P-phase precipitates in determining the martensitic transformation temperature (M s ), strength of the B2 matrix phase, dimensional stability and shape memory effect of the alloys, a phase field model of P-phase precipitation is developed. Model inputs, including lattice parameters, precipitate–matrix orientation relationship, elastic constants and free energy data, are obtained from experimental characterization, ab initio calculations and thermodynamic databases. Through computer simulations, the shape and spatial distribution of the P-phase precipitates, as well as the compositional and stress fields around them, are quantitatively determined. On this basis, the elastic interaction energy between the P-phase precipitates and a martenstic nucleus is calculated. It is found that both the chemical non-uniformity and stress field associated with the P-phase precipitates are in favor of the martensitic transformation. Their relative contributions to the increase in M s temperature are quantified as a function of aging time and the result seems to agree with the experimental measurements. The shape and spatial distribution of the P-phase precipitates predicted by the simulations also agree well with experimental observations.
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
International Nuclear Information System (INIS)
Martynov, V.V.
1995-01-01
Using in-situ single crystal X-ray diffraction methods, thermally- and stress-induced crystal structure evolution was investigated in two Ni-Mn-Ga Heusler-type alloys. For the 51at.%Ni-24at.%Mn-25at.%Ga alloy it was found that application of external stress in a temperature range ∼20 C above the M s at first causes intensity changes of X-ray diffuse scattering peaks in β-phase. Further stressing results in stress-induced phase transformations and under the appropriate conditions three successive martensitic transformations (one is parent-to-martensite and two are martensite-to-martensite transformations) can be stress induced. Of these only the parent-to-martensite transformation can be thermally-induced. Two successive structural transformations (thermally-induced parent-to-martensite and stress-induced martensite-to-martensite transformations) were found in 52at.%Ni-25at.%Mn-23at.%Ga alloy. Crystal structure, lattice parameters, type of modulation, and the length of modulation period for all martensites were identified. (orig.)
EELS study of the inverse martensitic transformation of 2H and 18R Cu-Al-Zn alloys
International Nuclear Information System (INIS)
Espinosa-Magana, F.; Ochoa-Lara, M.T.; Lovey, F.; Flores-Zuniga, H.; Rios-Jara, D.
2010-01-01
Changes in 3d states occupancy associated with the inverse martensitic transformation in two samples of Cu-Al-Zn alloys with 2H and 18R martensitic structures were investigated by electron energy loss spectroscopy (EELS). The Cu L 2,3 white-lines intensities, which reflect the unoccupied density of states in 3d bands, were measured in situ, during the phase transformation in both the martensite and austenite phases. We find that the white-lines intensity decreases during the inverse transformation, when going from martensite to austenite. Even though the initial 3d occupation numbers in 2H and 18R martensitic structures are different, after the transformation, the 3d occupation numbers in the now austenitic structure have decreased in both samples, indicating that some electrons left Cu 3d bands during phase transformation. Interestingly enough, the occupation numbers in the final phases, which have the same structure, reach the same value, indicating that changes in EELS spectra are a consequence of structural changes.
EELS study of the inverse martensitic transformation of 2H and 18R Cu-Al-Zn alloys
Energy Technology Data Exchange (ETDEWEB)
Espinosa-Magana, F., E-mail: francisco.espinosa@cimav.edu.m [Centro de Investigacion en Materiales Avanzados, S.C., Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, Chih. 31109 (Mexico); Ochoa-Lara, M.T. [Centro de Investigacion en Materiales Avanzados, S.C., Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, Chih. 31109 (Mexico); Lovey, F. [Centro Atomico Bariloche, 8300 S.C. de Bariloche (Argentina); Flores-Zuniga, H. [Universidad Autonoma de Zacatecaa, Av. Lopez Velarde 801, Zacatecas, Zac. 98060 (Mexico); Rios-Jara, D. [Instituto Potosino de Investigacion Cientifica y Tecnologica, Camino a la Presa San Jose 2055, San luis Potosi, S.L.P. 78126 (Mexico)
2010-01-01
Changes in 3d states occupancy associated with the inverse martensitic transformation in two samples of Cu-Al-Zn alloys with 2H and 18R martensitic structures were investigated by electron energy loss spectroscopy (EELS). The Cu L{sub 2,3} white-lines intensities, which reflect the unoccupied density of states in 3d bands, were measured in situ, during the phase transformation in both the martensite and austenite phases. We find that the white-lines intensity decreases during the inverse transformation, when going from martensite to austenite. Even though the initial 3d occupation numbers in 2H and 18R martensitic structures are different, after the transformation, the 3d occupation numbers in the now austenitic structure have decreased in both samples, indicating that some electrons left Cu 3d bands during phase transformation. Interestingly enough, the occupation numbers in the final phases, which have the same structure, reach the same value, indicating that changes in EELS spectra are a consequence of structural changes.
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
Phase transformations in the rapidly solidified Ti{sub 40}Zr{sub 20}Hf{sub 20}Pd{sub 20} alloy
Energy Technology Data Exchange (ETDEWEB)
Chen, N. [Division of Engineering Materials, Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Yao Kefu [Division of Engineering Materials, Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)], E-mail: kfyao@tsinghua.edu.cn; Louzguine-Luzgin, D.V. [Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577 (Japan); Qiu Shengbao [Division of Engineering Materials, Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Ranganathan, S. [Department of Metallurgy, Indian Institute of Science, Bangalore 560 012 (India); Inoue, A. [Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577 (Japan)
2007-10-15
We report that an approximant phase was initially obtained in amorphous Ti{sub 40}Zr{sub 20}Hf{sub 20}Pd{sub 20} alloy. In the initial stage of the devitrification process, the approximant phase transforms into an icosahedral (I) phase with a high thermal stability while the cF96 Zr{sub 2}Ni-type (space group Fd3-bar m with a=1.25nm and 96 atoms cell{sup -1}) particles precipitate from the amorphous matrix. Eventually the I phase grows to several hundred nanometers when annealed at about 1000K and then transforms into the Zr{sub 2}Ni-type phase with an endothermic reaction.
Energy Technology Data Exchange (ETDEWEB)
Lima, Joao Cardoso de; Ferreira, Ailton da Silva, E-mail: joao.cardoso.lima@ufsc.br [Universidade Federal de Santa Catarina (UFSC), Florianopolis (Brazil); Rovani, Pablo Roberto; Pereira, Altair Soria [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre (Brazil)
2016-07-01
Full text: Alloys based on titanium and nickel with shape memory effect (SME) have been widely investigated due to potential use in different areas of science and technology, such as electronics, medicine, and space.1 Among them, the superalloys Ti-Ni-Fe show high corrosion resistance and good mechanical properties even at high temperatures that make them suitable for use in applications such as power plant components that work under aggressive conditions. At room temperature, the TiNi alloy has a monoclinic (B19'), known as the martensitic phase. With increasing temperature, the B19' phase transforms into a trigonal/hexagonal (B19) phase, known as the R- or pre martensitic phase, which, in its turn, transforms into a cubic (B2) structure, known as the austenitic phase. On cooling to room temperature, the reverse B2→B19→B19' phase transformations are observed. Since the B19↔B19' transformation occurs at a temperature low enough to inhibit diffusion-controlled processes, it belongs to a class of diffusionless phase transformations known as martensitic transformations. For this study, a Ti{sub 50}Ni{sub 25}Fe{sub 25} (B2) alloy was prepared by mechanical alloying, and the effects of high pressures up to 18 GPa will be presented. The structural changes with increasing pressure were followed by recording in situ angle-dispersive X-ray diffraction (ADXRD) diffractograms, in transmission geometry, using a long fine focus Mo X-ray tube and an imaging plate detector. The obtained results were already reported in Ref [1]. (1) A. S. Ferreira, P. R. Rovani, J. C. de Lima, A. S. Pereira, J. Appl. Phys. 117 (2015). (author)
International Nuclear Information System (INIS)
Das Gupta, A.; Horton, J.A.
1985-01-01
The sequence of disordering transformation processes in the A/sub 3/B type alloy series (Ni/sub 70/Fe/sub 30/)/sub 3/(V/sub 98-x/Al/sub x/Ti/sub 2/), currently under development for high-temperature structural applications, was studied by differential scanning calorimetry (DSC), x-ray diffraction, optical microscopy, and transmission electron microscopy (TEM). Results of DSC show that in all alloys there are two endothermic stages of phase transformation from the ordered to the disordered state. With increasing chi, the disordering transition temperature, T/sub c/, reaches a maximum --1000 0 C at chi ≅ 50 and then decreases. Interrupted heating, followed by water quenching, was used to characterize the crystal structure and the microstructure of the intermediate phases. For the x = 20 alloy, TEM observations showed ordered regions of DO/sub 22/ phase in a matrix of disordered fcc (Al) phase at intermediate temperatures. The ordered domains transformed morphologically into cuboid like regions at higher temperatures. From a combined study by all the techniques, the authors conclude that in alloy with x between 0 and 20, the sequence of phase transformations from heating is: DO/sub 2/ → DO/sub 22/ + Al → Al, whereas in alloys with x > 40, the major sequence is Ll/sub 2/ + B/sub 2/ → Ll/sub 2/ + Al → Al
Schmitt, Regina; Kuhn, Charlotte; Müller, Ralf
2017-07-01
A continuum phase field model for martensitic transformations is introduced, including crystal plasticity with different slip systems for the different phases. In a 2D setting, the transformation-induced eigenstrain is taken into account for two martensitic orientation variants. With aid of the model, the phase transition and its dependence on the volume change, crystal plastic material behavior, and the inheritance of plastic deformations from austenite to martensite are studied in detail. The numerical setup is motivated by the process of cryogenic turning. The resulting microstructure qualitatively coincides with an experimentally obtained martensite structure. For the numerical calculations, finite elements together with global and local implicit time integration scheme are employed.
Quasi-phase transformation in ferromagnetic semiconductors with two-charged donors
International Nuclear Information System (INIS)
Kovalenko, A.A.; Nagaev, Eh.L.
1978-01-01
Effect of term inversion of two-charged donors 1s2s → 1s 2 on properties of ferromagnetic semiconductors, has been investigated. Term inversion is accompanied by changes in local magnetic ordering in the donor area and takes place as spread phase transformation of the first type in the system of n 2 atoms, enveloped by donor 2s-orbit. It is a reason for creating not only heat capacity peak at Tsub(c), but another peak at inversion temperature Tsub(i) as well. At temperatures T > Tsub(i) introduction of external magnetic field can lead to a reverse term inversion 1s 2 → 1s2s, under that condition crystal magnetization should clearly increase. Term inversion tells upon electric properties of crystals: in Ti inversion point, the energy of conductivity activation of ungenerate semiconductors changes abruptly. In the case of larger concentrations of donors, term inversion can lead to metal-insulator transformation. Analysis of experimental data on magnetic susceptibility of EuO crystals with oxygen vacancies, shows that transformation in these crystals takes place according to a different mechanism
Present day state of knowledge of α/β allotropic transformation of uranium
International Nuclear Information System (INIS)
Englander, M.
1960-01-01
The technological conditions of the problem of α/β allotropic transformation of uranium are presented first. Then, the author explains the qualitative reasons why in non-allied uranium: 1) the new phase germination follows a consistent process; 2) the new phase growth, at the expense of the mother phase, proceeds either by martensitic-type shear or by thermal diffusion if the temperature and impurities amount are high enough. Reprint of a paper published in La Mettalurgia Italiana, vol. LI, no. 11, p. 497-504, 1959 [fr
International Nuclear Information System (INIS)
Chen, Xian; Tamura, Nobumichi; MacDowell, Alastair; James, Richard D.
2016-01-01
The alloy Cu_2_5Au_3_0Zn_4_5 undergoes a huge first-order phase transformation (6% strain) and shows a high reversibility under thermal cycling and an unusual martensitc microstructure in sharp contrast to its nearby compositions. This alloy was discovered by systematically tuning the composition so that its lattice parameters satisfy the cofactor conditions (i.e., the kinematic conditions of compatibility between phases). It was conjectured that satisfaction of these conditions is responsible for the enhanced reversibility as well as the observed unusual fluid-like microstructure during transformation, but so far, there has been no direct evidence confirming that these observed microstructures are those predicted by the cofactor conditions. To verify this hypothesis, we use synchrotron X-ray Laue microdiffraction to measure the orientations and structural parameters of variants and phases near the austenite/martensite interface. The areas consisting of both austenite and multi-variants of martensite are scanned by microLaue diffraction. The cofactor conditions have been examined from the kinematic relation of lattice vectors across the interface. The continuity condition of the interface is precisely verified from the correspondent lattice vectors between two phases.
Choi, Yun Seok; Alkhalifah, Tariq Ali; Saragiotis, Christos
2011-01-01
an approach based on unwrapping the