444 research outputs found
Loss of coherency at interphase α/β boundary in Ti-6Al-4V alloys during deformation at 800°C
No full textTi-6Al-4V is one of the major titanium-based alloy especially for creep purposes. The alloy is generally subjected to high temperature deformation and it is generally used at warm/high temperatures. The alloy (α+β→β)-transus temperature is 995°C, that is, for temperatures within 995°C a mixed α+β phases microstructure characterizes the alloy mechanical behavioryesBelgorod State Universit
Loss of coherency and interphase α/β angular deviation from the Burgers orientation relationship in a Ti–6Al–4V alloy compressed at 800 °C
No full textThe mutual relationship between phases in two-phase titanium alloys, alpha(HCP) and beta(BCC), is such that: {0001}(alpha)parallel to{110}(beta); (alpha)parallel to (beta), which in literature are known as Burgers orientation relationships. The coherency of the two phases is controlled by this crystallographic mutual relationship. Loss of coherency between phases during deformation can originate from a non-parallelism between the two boundary crystallographic planes. This study focuses on alpha(HCP)/beta(BCC) interface coherency evolution in a lamellar Ti-6Al-4V alloy subjected to hot compression at 800 degrees C. The strain rate was 10(-3) s(-1) and deformation was carried out to average true strains of epsilon = 0.29, 0.69, and 1.20. Loss of coherency was found at strains epsilon >= 0.50. For these strains, the lamellar alpha + beta microstructure also evolved to a spheroidized morphology. The loss of interface coherency was thus associated with the acceleration of the lamellar microstructure dynamic spheroidization
The mathematical modeling of the experiment on the determination of correlation coefficients in neutron beta-decay
No full textSurface phases in iron-based alloys
No full textМорозов Сергей Иванович – кандидат физико-математических наук, доцент, кафедра общей и теоретической физики, Южно-Уральский государственный университет. е-mail: [email protected]. Жеребцов Дмитрий Анатольевич – инженер, кандидат химических наук, кафедра физической химии, Южно-Уральский государственный университет. Грибачёв Антон Сергеевич – аспирант, кафедра общей и теоретической физики, Южно-Уральский государственный университет. Morozov Sergey Ivanovich is a Cand. Sc.(Physics and Mathematics), associate professor of the General and Theoretical Physics Department, South Ural State University. е-mail: [email protected]. Zherebtsov Dmitry Anatolievich is a Cand. Sc.(Chemistry), engineer of the Physical Chemistry Department, South Ural State University.
Gribachev Anton Sergeyevich is a postgraduate student, General and Theoretical Physics Department, South Ural State University.Рассмотрены состояния свободной поверхности трехкомпонентных сплавов Fe–C–S по изображениям, полученным с помощью растрового электронного микроскопа. Подтверждена гипотеза о формах поверхностных фаз углерода и железа при комнатных температурах, предложенная в работах по изучению термической десорбции исследуемых сплавов в твердом и жидком состояниях. This paper considers the conditions of the ternary alloys Fe–C–S free surfaces judging by the images obtained by means of a scanning electron microscope. The hypothesis on the forms of carbon and iron surface phases at room temperature suggested in works on thermal desorption of solid and liquid alloys is confirmed
New experimental limits on neutron - mirror neutron oscillations in the presence of mirror magnetic field
No full textInternational audiencePresent experimental and astrophysical limits do not exclude that the neutron (n) oscillation into mirror neutron ( ), a sterile state exactly degenerate in mass with the neutron, can be a very fast process, in fact faster than the neutron decay itself, in which case it would have very interesting implications in cosmology and astrophysics. This process is sensitive to the magnetic field. Namely, if the mirror magnetic field exists at the Earth, oscillation probability can be suppressed or resonantly amplified by the applied magnetic field , depending on its strength and on the angle between and . We present the results of ultra-cold neutron storage measurements aiming to check the anomalies observed in previous experiments which could be a signal for oscillation in the presence of mirror magnetic field G. From the analysis of the experimental data new lower limits on oscillation time as a function of were obtained, assuming that the mirror magnetic field is constant in time: s (95 % C.L.) for any between 0.08 and 0.17 G, and s (95 % C.L.) for any in the interval ( ) G
The initial distribution of alloy components in the experiment of temperature programming desorption
No full textМорозов Сергей Иванович – доцент, кандидат физико-математических наук, кафедра общей и теоретической физики, Южно-Уральский государственный университет. Е-mail: [email protected]. Morozov Sergey Ivanovich is Cand. Sc.(Physics and Mathematics), associate professor, General and Theoretical Physics Department, South Ural State University. Е-mail: [email protected]
Жеребцов Дмитрий Анатольевич – кандидат химических наук, инженер, кафедра физической химии, Южно-Уральский государственный университет.
Zherebtsov Dmitry Anatolievich is Cand. Sc.(Chemistry), engineer, Physical Chemistry Department, South Ural State UniversityРассмотрены состояния свободной поверхности двухкомпонентных
сплавов Cu–Ag по изображениям, полученным с помощью растрового электронного микроскопа. Исследовано начальное распределение компонентов
сплавов, изученных методом температурно-программируемой десорбции.
Подтверждено расслоение поверхностного твердого раствора на две фазы,
богатые медью и серебром, отмечена их эволюция в зависимости от объемного содержания серебра. This paper considers the conditions of thebinary alloys Cu–Ag free surfaces judging by the images obtained by means of a scanning electron microscope. The initial distribution of alloy components, studied by temperature programming desorption method, were analyzed. The solid solution layering to Cu and Ag rich phases was confirmed. Their evolution depending on Ag volume content was observed
Coherent Electronic Wave Packet Motion in C-60 Controlled by the Waveform and Polarization of Few-Cycle Laser Fields
No full textCitation: Li, H., Mignolet, B., Wachter, G., Skruszewicz, S., Zherebtsov, S., Sussmann, F., . . . Kling, M. F. (2015). Coherent Electronic Wave Packet Motion in C-60 Controlled by the Waveform and Polarization of Few-Cycle Laser Fields. Physical Review Letters, 114(12), 6. doi:10.1103/PhysRevLett.114.123004Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C-60 fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization.Additional Authors: Tiggesbaumker, J.;Meiwes-Broer, K. H.;Lemell, C.;Burgdorfer, J.;Levine, R. D.;Remacle, F.;Kling, M. F
Probing the high latitude ionosphere from ground-based observations: The state of current knowledge and capabilities during IPY (2007-2009)
No full textDuring the International Polar Year (IPY), one area of great interest is co-coordinated, multi-instrument probing of the ionosphere at high latitudes. This region is important not only for the applications that rely upon our understanding of it, but also because it contains the footprints of processes that have their origin in the interplanetary space. Many different techniques are now available for probing the ionosphere, from radar measurements to the analysis of very low frequency (VLF) wave paths. Combining these methods provides the ability to study the ionosphere from high in the F-region to the bottom of the D-layer. Thus, coupling processes from the magnetosphere and to the neutral atmosphere can be considered. An additional dimension is through comparisons of the response of the two polar ionospheres to similar (or the same) geomagnetic activity. With more instruments available at the South Pole inter-hemispheric, studies have become easier to accomplish such that a fuller picture of the global response to Sun-Earth coupling can be painted. This paper presents a review of the current state of knowledge in ionospheric probing. It cannot provide a comprehensive guide of the work to date due to the scale of the topic. Rather it is intended to give an overview of the techniques and recent results from some of the instruments and facilities that are a part of the IPY cluster 63-Heliosphere Impact on Geospace. In this way it is hoped that the reader will gain a flavor of the recent research performed in this area and the potential for continuing collaboration and capabilities during the IP
Femtosecond time-resolved spectroscopy in polyatomic systems investigated by velocity-map imaging and high-order harmonic generation
No full textDans cette thèse, la dynamique de photodissociation de l'azoture de chlore (ClN3) est étudiée dans le domaine temporel par imagerie de vecteur vitesse des photofragments, spécialement du chlore et de N3. Cette imagerie résolue à l'échelle femtoseconde permet d'extraire les temps de dissociation, l'établissement temporel de la balance d'énergie de la réaction ainsi que la conservation des moments. Cette étude a permis de différencier deux domaines d'énergie: l'un menant à la formation d'un fragment N3 linéaire (étude autour de 4.5 eV d'excitation électronique) et le plus intéressant aboutissant à la formation d'un fragment N3 cyclique (autour de 6 eV).
Dans une seconde étude, la dynamique de relaxation électronique du tétrathiafulvalène (C6H4S4-TTF) est étudiée autour de 4 eV par spectroscopie de masse résolue en temps ainsi que par spectroscopie de photoélectron. Les seuils d'ionisation dissociative sont extraits d'une détection en coïncidence entre les photoélectrons de seuil et les fragments ionisés réalisée sur rayonnement synchrotron.
Les deux dernières expériences sont basées sur la génération d'harmoniques d'ordre élevé dans l'XUV d'une impulsion femtoseconde à 800 nm ou à 400 nm. Dans la première expérience, les harmoniques sont couplées à un imageur de vecteur vitesse en tant que rayonnement secondaire VUV. Par imagerie de photoélectron résolue en temps, nous avons révélé ainsi les dynamiques de relaxation des états de Rydberg initiée par une impulsion femtoseconde XUV à 15.5 eV dans l'argon et à 9.3 eV dans l'acétylène. Dans la seconde expérience, couramment nommée spectroscopie attoseconde, les harmoniques constituent le signal pompe sonde. Deux types de spectroscopie attoseconde ont été réalisés pour étudier la dynamique vibrationnelle de SF6: une expérience en réseau transitoire créé par deux impulsions pompe Raman avec une impulsion sonde intense générant les harmoniques à partir du réseau d'excitation et une expérience d'interférence de deux rayonnement XUV en champ lointain créés par deux impulsions sonde intensesRevealing the underlying ultrafast dynamics in molecular reaction spectroscopy demands state-of-the-art imaging techniques to follow a molecular process step by step.
Femtosecond time-resolved velocity-map imaging is used to study the photodissociation dynamics of chlorine azide (ClN3). Here especially the co-fragments chlorine and N3 are studied on the femtosecond timescale in two excitation energy regions around 4.67 eV and 6.12 eV, leading to the formation of a linear N3 fragment and a cyclic N3 fragment, respectively. This work is the first femtosecond spectroscopy study revealing the formation of cyclic N3. Tetrathiafulvalene (TTF, C6H4S4) electronic relaxation is studied, while scanning the electronic excitation around 4 eV, by time resolved mass and photoelectron spectroscopy. As only few is known about the ion continuum about TTF the imaging photoelectron photoion coincidence (iPEPICO) technique is used in order to disentangle the complex ionic dissociation. The second part of the thesis is based on the generation and application of XUV light pulses by high-order harmonic generation with an intense femtosecond laser pulse in a molecular target. Two types of phase sensitive attosecond spectroscopy experiments were conducted to study the vibrational dynamics of SF6: one using strong field transient grating spectroscopy, where high-order harmonic generation takes place in a grating of excitation, and the second experiment using high-order harmonic interferometry using two intense XUV probe pulses. The temporal dependencies in phase and amplitude reveal the vibrational dynamics in SF6 and demonstrate that high-order harmonic generation is sensitive to the internal excitations. Last but not least, the use of high-order harmonics as a XUV photon source for the velocity-map imaging spectrometer is investigated. Using time-resolved photoelectron imaging, the relaxation dynamics initiated with 15.5 eV in argon and 9.3 eV in acetylene are reveale
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