243 research outputs found
A calorimetric investigation of polymorphism in a layered perovskite: KAlF4
No full textPT: J; CR: BERRY LG, 1976, POWDER DIFFRACTION F BROOKER M, 1985, UNPUB BROSSET C, 1937, Z ANORG ALLG CHEM, V235, P139 BULOU A, 1982, J PHYS C SOLID STATE, V15, P183 BULOU A, 1982, MATER RES BULL, V17, P391 COUZI M, 1985, J PHYS-PARIS, V46, P435 LAUNAY JM, 1984, MATER RES SOC S P, V21, P167 LAUNAY JM, 1985, J PHYS-PARIS, V46, P771 MILLIER B, 1985, J CHEM EDUC, V62, P64 OGASAHARA K, 1979, CHEM PHYS LETT, V68, P457 SCHOONMAN J, 1976, J SOLID STATE CHEM, V16, P413 VANOORT MJM, 1985, J CHEM SOC F1, V81, P3059 WHITE MA, UNPUB WHITE MA, 1984, THERMOCHIM ACTA, V74, P55 WHITE MA, 1985, J CHEM PHYS, V83, P5844; NR: 15; TC: 2; J9: J CHEM THERMODYN; PG: 8; GA: C5290Source type: Electronic(1
Putování se Zlatou bulou sicilskou - projektová výuka
No full textZávěrečná práce Putování se Zlatou bulou sicilskou se svým tématem věnuje vzdělávací oblasti Člověk a jeho svět. Cílem práce je představit projektovou výuku k tématu vrcholného středověku v českých zemí, která je určená pro 4. ročník ZŠ. Práce je rozdělena na dvě části - teoretickou a praktickou. V teoretické části je pozornost věnována problematice projektového vyučování obecně a praktická část předkládá konkrétní podobu takového projektu. Zlatá bula sicilská se v předkládaném projektu stane průvodkyní, která žáky seznámí s dědičnými českými králi - Přemyslem Otakarem I., Václavem I., Přemyslem Otakarem II., Václavem II. a Václavem III. Vedle politických dějin spojených s vládou posledních Přemyslovců by se žáci rovněž měli seznámit s dějinami kulturními a dějinami každodennosti
XAS and XMCD of Single Molecule Magnets
No full textMolecular magnetism is here presented with emphasis concerning the single molecule magnets (SMMs). The architecture of SMMs is reviewed as well as the various ingredients promoting magnetic anisotropy and the relation between magnetic anisotropy and the dynamics of magnetization. Then it is shown how XAS and XMCD can be unique tools to unravel the magnetic properties of SMM submonolayers grafted on clean surfaces. We bring a special attention to the spectral features associated with the magnetic anisotropy and magnetization dynamics
The nature of ammonium ion disorder in ammonium tetrafluoroaluminate, NHAlF
No full textPT: J; CR: BERRY LG, 1976, POWDER DIFFRACTION F BRADE RM, 1971, J PHYS C SOLID STATE, V4, P876 BULOU A, 1982, MATER RES BULL, V17, P391 CHIHARA H, 1983, PHYS CHEM, V87, P188 COUZI M, 1983, PHYS CHEM, V87, P232 COUZI M, 1985, J PHYS-PARIS, V46, P435 DAGHORN Y, 1985, J PHYS C SOLID STATE, V18, P383 FOURQUET JL, 1979, REV CHIM MINER, V16, P490 GIRDHAR HL, 1968, J CHEM ENG DATA, V13, P239 KNOP O, 1985, CAN J CHEM, V63, P516 KOBAYASHI K, 1985, SOLID STATE COMMUN, V53, P719 LAUNAY JM, 1984, MATER RES SOC S P, V21, P167 LEBLE A, 1982, PHYS STATUS SOLIDI, V69, P249 MACKOWIAK M, 1984, MAT RES B, V19, P249 NYQUIST RA, 1971, INFRARED SPECTRA INO PARSONAGE NG, 1978, DISORDER CRYSTALS SHINN DB, 1966, INORG CHEM, V5, P1927 SIMON F, 1922, ANN PHYS-BERLIN, V68, P241 VANOORT MJM, J CHEM SOC F1 WAGNER EL, 1950, J CHEM PHYS, V18, P296 WEIR RD, 1980, J CHEM PHYS, V73, P1386 WESTRUM EF, 1969, J CHEM PHYS, V50, P5083 WHITE MA, UNPUB WHITE MA, 1981, J CHEM THERMODYN, V13, P283 WHITE MA, 1984, THERMOCHIM ACTA, V74, P55; NR: 25; TC: 9; J9: J CHEM PHYS; PG: 5; GA: AUR04Source type: Electronic(1
Three-dimensional imaging of H2O ice at high pressure by time-domain Brillouin scattering
No full textInternational audienceTime-domain Brillouin scattering (TDBS) is applied for the first time to perform the 3D imaging of polycrystalline water ice phases, VII and VI, coexisting at a pressure of 2.1 GPa in a diamond anvil cell (DAC) at room temperature.Materials and MethodsThe TDBS is a non-destructive opto-acousto-optic pump-probe technique [1] which allows the study of a variety of transparent materials [2]. In this method, an optical pump pulse from a femtosecond laser is absorbed by an optoacoustic transducer contacting the sample. As a result, a picosecond acoustic pulse is emitted into the sample. It scatters a time-delayed optical probe pulse from the same or another femtosecond laser. Thus, via detection of the changes of the transient optical reflectivity in time, the evolution of the acoustic pulse with its propagation distance can be probed when it traverses the sample. The TDBS signal contains information on the characteristics of the acoustic pulse and the parameters of the material in the current spatially localized position of the acoustic pulse. The length of this pulse is commonly at nanometers spatial scale. Therefore, the technique is suitable for imaging of materials along the pulse propagation path with a spatial resolution better than optical. Two-dimensional (lateral and depth) TDBS imaging has been earlier applied for revealing the texture of solid H2O [3] and Ar [4], the phase transitions [5] and the reliable pressure dependences of elastic moduli [6] in water ice. We report here the extension of the TDBS technique to the 3D imaging of samples compressed in a DAC.To accelerate the data acquisition and to make 3D imaging possible in reasonable time, we applied, for the first time, to a sample at high pressure in a DAC, an ultrafast laser technique called asynchronous optical sampling (ASOPS). In ASOPS technique, the time delay between the pump and the probe is controlled electronically by an offset of the repetition rate frequency of two lasers without the use of a slow mechanical delay line.The experiments were conducted on water ice in a DAC at 2.1 GPa. The opto-acoustic generator (iron plate of approximately 40 μm thickness [5]) inside the sample chamber has the diameter of ∼110 μm. The full width at half maximum of the laser beams at the surface of the generator is 1.4 μm. When irradiated by the pump optical pulses at 515 nm wavelength from our ASOPS-based picosecond acoustic microscope (JAX-M1, NETA, France), it emits picosecond acoustic pulses in 14.5 μm layer of water ice on the top of laser irradiated Fe surface [5]. The maximum analyzable time delay (1.9 ns) of the probe laser pulses at 532 nm wavelength provided opportunity for imaging the ice layers up to ∼10 μm distances from the generator. The image in the volume of 40x40x10 μm3 is obtained with the lateral step of 2 μm in 2 hours. ResultsMaps of the Brillouin frequencies in the moving time windows of the acoustic pulse propagation in the ice are presented in Fig.1. They were obtained using a time-frequency analysis based on the synchronous detection principle [6]. The delay times between the probe and the pump laser pulses inside the time windows are marked above each of the cross sectional maps (a)-(c) and, thus, correspond to different depth layers in the sample. The red line attracts the eyes to the variations of the Brillouin frequency with time in a selected lateral region. Note that, because acoustic waves propagate at different velocities in different lateral points, the same time window corresponds to different depth windows in different lateral points. The estimates demonstrate that the highest and the lowest detected Brillouin frequencies are the fingerprints of presence of the ice VII, while the intermediate frequencies in the lower half of the frequency spectrum could be due to the presence of ice VI. Fig.1. 2D maps of the Brillouin frequencies distribution in the 40x40 μm2 cross sections of the tested ice volume at 2.1 GPa for shifting time slices. The red line highlights one of the lateral regions with important variations of the Brillouin frequency as a function of the distance from the generator.ConclusionsWe demonstrated the ASOPS-based 3D TDBS imaging of water ice in a DAC. This 3D imaging allows us to visualize shapes of the crystallites formed in the sample volume and their transformation with increasing load. In perspective, the 3D imaging of the transient processes at high pressures with nanometers depth resolution could be possible.Acknowledgement This research is supported by the grant .References1.C. Thomsen, H.T. Graham, H.J. Maris, J. Tauc, Optics Communications 60, 55 (1986); doi:10.1016/0030-4018(86)90116-12. V. E. Gusev, and P. Ruello, Applied Physics Reviews 5, 031101 (2018) doi:10.1063/1.50172413. S. M. Nikitin, N. Chigarev, V. Tournat, A. Bulou, D. Gasteau, B. Castagnede, A. Zerr, V. E. Gusev, Scientific Reports 5, 9352 (2015); doi:10.1038/srep093524. M. Kuriakose, S. Raetz, N. Chigarev, S. M. Nikitin, A. Bulou, D. Gasteau, V. Tournat, B. Castagnede, A. Zerr, V. E. Gusev, Ultrasonics, 69, 201 (2016); doi:10.1016/j.ultras.2016.03.0075. M. Kuriakose, N. Chigarev, S. Raetz, A. Bulou, V. Tournat, A. Zerr, V. E. Gusev, New Journal of Physics 19, 053026 (2017); doi:10.1088/1367-2630/aa6b3d 6. M. Kuriakose, S. Raetz, Q. M. Hu, S. M. Nikitin, N. Chigarev, V. Tournat, A. Bulou, A. Lomonosov, P. Djemia, V. E. Gusev, A. Zerr, Physical Review B 96, 134122 (2017); doi:10.1103/PhysRevB.96.13412
Time-domain Brillouin scattering for depth profiling of optically transparent materials: applications, limitations and perspectives
No full textInternational audienceTime-domain Brillouin scattering (TDBS) is an experimental technique for generation and detection of nanometers-in-length acoustic pulses using ultrafast lasers, which was originally referred to as picosecond acoustic interferometry [1]. Experimental signals collected with the TDBS technique in transparent materials contain Brillouin oscillations, caused by interference of the probe laser pulses reflected from stationary interfaces and from the propagating ultrashort acoustic pulses. Frequencies of the Brillouin oscillations depend on the local refractive index and the local longitudinal sound velocity. Therefore, accurate estimates in a TDBS signal of the Brillouin frequency with respect to time give an access to the variations of the material parameters as a function of material depth. TDBS experiments could give access to acoustical, optical and acousto-optical parameters of the materials [2], by carrying experiments at several incidence angles for instance. Some applications of the TDBS technique for depth profiling of polycrystalline materials under very high-pressures [3,4] as well as its ability for real-time imaging of phase transition [5] will be presented. Limitations of this imaging technique, as well as the perspectives of its extension in multiple research areas [6] and industrial fields, will also be discussed. References[1]C. Thomsen, H. T. Graham, H. J. Maris, J. Tauc, Optics Communications 60, 55 (1986). [2]A. M. Lomonosov, A. Ayouch, P. Ruello, G. Vaudel, M. R. Baklanov, P. Verdonck, L. Zhao, V. E. Gusev, ACS Nano 6, 1410 (2012).[3]M. Kuriakose, S. Raetz, N. Chigarev, S. M. Nikitin, A. Bulou, D. Gasteau, V. Tournat, B. Castagnede, A. Zerr, and V. E. Gusev, Ultrasonics 69, 259-267 (2016).[4]M. Kuriakose, S. Raetz, Q. M. Hu, S. M. Nikitin, N. Chigarev, V. Tournat, A. Bulou, A. Lomonosov, P. Djemia, V. E. Gusev, and A. Zerr, Phys. Rev. B 96, 134122 (2017).[5]M. Kuriakose, N. Chigarev, S. Raetz, A. Bulou, V. Tournat, A. Zerr, and V. E. Gusev, New J. Phys., 19, 053026 (2017).[6]V. E. Gusev, P. Ruello, Appl. Phys. Rev. 5, 031101 (2018)
On considering the elastic constant table as the matrix of an operator ; consequences in ferroelasticity
No full textThe consequences of the convention asociated with the contraction of the indices of the elastic constant tensor components are discussed. It is shown that, in order to be handled like the matrix of an operator, the elastic constant table must be written new conventions : if if ( and ), or ( and ), if . The are the components of a table . Using for the strains the convention if and if , the usual form for the elastic energy is preserved. It is shown that the terms of the elastic energy written in a diagonal form (where the are the symmetry-adapted strains) are the eigenvalues of the table that can be called matrix of the elastic constants : the “eigenvalues” of the elastic
constant table defined with the usual conventions do not lead to the right diagonal form in the cases of the teragonal , , 4 groups and in the cases of the trigonal groups. This result has consequences in the studies of the proper and pseudo-proper ferroelastic phase transitions since they are associated with the softening of one the . Some arguments showing the advantage of an extension of the conventions proposed in this paper to other kinds of tensors are given.Les conséquences de la convention associée à la contraction des indices des composantes du tenseur des constantes élastiques sont discutées. On montre que, pour être manipulé comme la matrice
d'un opérateur, le tableau des constantes élastiques doit être écrit avec de nouvelles conventions définies par : si si ( et ), ou ( et ) et si . Les sont les composantes d'un tableau . En adoptant pour les déformations
la convention si et si on conserve pour l'énergie la forme habituelle . On montre que les valeurs permettant
d'écrire l'énergie élastique sous une forme diagonale (où les sont des déformations symétrisées) sont les valeurs
propres du tableau qui peut ainsi être qualifié de matrice des constantes élastiques ; les “valeurs propres” du tableau des constantes élastiques défini avec les conventions usuelles ne permettent pas d'écrire la forme diagonale correcte dans le cas des groupes quadratiques 4, , 4/m et dans les groupes rhomboédriques. Ce résultat a des conséquences dans l'étude des transitions ferroélastiques propres ou pseudo-propres, ces transitions étant associées au ramollissement de l'un
des . Quelques arguments montrant l'interêt de l'utilisation, pour d'autres types de tenseurs, de la convention de contraction proposée sont présentés
SITE-SELECTIVE ATMOSPHERIC PRESSURE PLASMA-ENHANCED CHEMICAL VAPOUR DEPOSITION PROCESS FOR MICROMETRIC DEPOSITION – SIMULATION AND EXPERIMENTAL STUDY
No full textAtmospheric Pressure Plasma has been used to enhance and/or initiate the Chemical Vapour Deposition (AP-PECVD) to deposit thin films or functional layer coatings over a large surface area on a large range of substrates. Now an ability to localise the AP-PECVD coating on an area of interest and control the deposition’s dimension showed its potential application as a viable technique to perform Additive Manufacturing (AM). Additive Manufacturing (AM) is a bottom-up approach in which 2-D patterning or 3-D structures are built using a layer-by-layer deposition. AM allowed easy design optimization and quickly provided the customized parts on demands, thus making itself a very popular technique in the mainstream manufacturing process. As such, it has a wide application in automotive, optics, electronics, aeronautics, medical and biotechnology fields. However, the existing AM printing techniques have some limitations regarding high-resolution printing deposition in a wide variety of substrates and very often get restricted to the types of precursors that could be printed. Whereas, due to the high energetic/reactive species in non-thermal plasma, the AP-PECVD deposition has been obtained using a wide range of precursors on a versatile surface. Thus, there has been a growing interest in performing an area selective localised AP-PECVD coating, mainly by adapting the design of the PECVD reactor. Hence, this thesis aims to design, optimize and study a one-step mask-free AP-PECVD plasma process that could locally deposit the material of interest with high precision to perform AM.
In the thesis, the technical approach undertaken by the home-built prototype “plasma torch” is to decouple the plasma generator annular tube and the precursor injector central capillary. This approach has allowed a way to tune the diameter of the deposited dot by changing the dimension of the precursor injector, which has been demonstrated by the deposition of the micro-dot as small as 400µm in diameter. Further, the flexibility to move the capillary tube without significant changes in the plasma torch's overall geometry has also allowed for selectively injecting the precursor (Methylmethacrylate, MMA) in the spatial plasma post-discharge region. Thanks to this setting, the deposited dot has high retention of monomer's chemistry (functional group) and unprecedented molecular weights (oligomeric chain up to 18 MMA units). Hence, initially, a novel area selective AP-PECVD plasma torch design has been demonstrated, and its performance has been defined to obtain the micro resolution coating.
During the research work, gas flow rates have been identified as a crucial parameter in obtaining the localised coating; three kinetic regimes with different coating morphology have been discovered. By performing a thorough computational fluid dynamic (CFD) simulation of the torch phenomena, it has been possible to establish a parallel between the fluid behaviour and the deposition size. The deposition was found to be confined in a zone created by the dynamical behaviour of gas, i.e., re-circulating vortices between the torch and substrate. Hence, later the gas flow rate was used to tune the diameter of the confinement zone, which in return changed the diameter of the deposited dot.
The gas flow dynamic impacts the involved species, i.e., reactive plasma species, precursor molecules, and the open-air interaction and distribution on the surface of the substrate. When organosilicon precursors with the presence or absence of vinyl bond and/or ethoxy groups are used, it results in different depositional chemical reactions and depositional patterns. The correlation between the depositional patterns and the mass fraction distribution of involved species has been obtained thanks to the performed CFD simulation done in parallel. Further, the likelihood of deposition mechanisms like "vinyl group opening by free radical" for vinyl containing precursor resulting in silicon oxycarbide-like (SiOxCyH) structural deposition, and the Reactive Oxygen Species (ROS)-induced "fragmentation and adsorption" deposition mechanism resulting in silica SiOx like structural deposition for siloxane containing precursor has been suggested and discussed. The understanding gained from this systematic case study implies the importance of reactive plasma species in the underlying deposition mechanisms; hence, it has been suggested that tuning/tailoring its distribution can alter the chemical nature of deposition and its pattens.
Overall, this thesis work provides insight into area selective AP-PECVD coating (plasma printing) and demonstrates that plasma technology is a viable option for additive manufacturing. The findings would be helpful in both designing the AP-PECVD plasma torch and selecting precursors for the desired organic/inorganic deposition. Thanks to the insight gained during the thesis work, the home-designed prototype of the plasma torch has been upgraded to implement in a commercial 3-D printer
Electromagnetic flowmeters modelization
No full textCette thèse a pour objet la modélisation et l’étude de débitmètres électromagnétiques produits par la société Siemens. Ces appareils permettent de mesurer le débit volumique d’un fluide conducteur en mouvement sous un champ magnétique par le biais d’électrodes mesurant le potentiel induit. L’objectif principal des travaux présentés est de modéliser un débitmètre électromagnétique, afin de disposer d’un modèle fiable et réaliste d’un point de vue magnétique, et de l’optimiser par la suite. La premier chapitre de cette thèse est consacrée à l’historique et au fondement de la théorie des débitmètres électromagnétiques de l’époque de Faraday à nos jours. Le chapitre II présente et décrit les débitmètres industriels conçus par Siemens à Haguenau en posant les bases, les termes et les notions nécessaires à la compréhension des travaux réalisés durant cette thèse. Le chapitre III vise à établir l’équation qui régit le fonctionnement des débitmètres électromagnétiques reliant le potentiel induit, la vitesse du fluide et le champ magnétique. On discutera également des principales hypothèses retenues dans le cadre de la théorie pour la modélisation numérique. Le chapitre IV introduit dans un premier temps la théorie sur le magnétisme et les principaux matériaux magnétiques. Dans un second temps, c’est la caractérisation magnétique des principaux composants utilisés pour la conception des débitmètres électromagnétiques qui est réalisée. Dans le chapitre V, une introduction à la modélisation numérique est effectuée, afin de justifier l’importance de la méthode des éléments finis pour la simulation électromagnétique des débitmètres sur le logiciel NX. La deuxième partie du chapitre se concentre sur le développement et la simulation du modèle numérique d’un débitmètre électromagnétique. Ensuite, la troisième partie est consacrée à la méthode expérimentale mise en place afin de mesurer le champ magnétique et comparer les résultats obtenus avec ceux issus de la simulation. La simulation numérique du champ magnétique ayant été validée par les mesures, le chapitre VI est consacré à la dynamique moléculaire des particules chargées contenues dans le fluide afin d’en déterminer la différence de potentiel. Enfin, le chapitre VII est consacré à l’étalonnage des débitmètres électromagnétiques, où l’on confrontera un modèle théorique aux valeurs expérimentales mesurées en production sur le site de Haguenau.This work concerns numerical modelling and study of electromagnetics flowmeters developed by Siemens. These devices are able to measure the flowrate of a conductive fluid in motion subject to a magnetic field. An induced potential is created and measured by two electrodes. The main purpose of this thesis is to modelize an electromagnetic flowmeter in order to get a realistic and reliable model to optimize the sensor in the futur. The first part of the work is to introduce the development theory of elec-tromagnetic flowmeter since the discovery of the induction law of Farady until today. The chapter II describes the industrial electromagnetics flowmeters manufactured by Siemens and provides the necessary knowledges for a better understanding of this work. In the chapter III, the electromagnetic flowmeter equation is derived and solved for the case of a homogenous magnetic field and point electrodes. This equation allows to get a relation between the induced potential, the velocity of the fluid and the magnetic field. We will discuss about the assumptions choose for this theory and used for the numerical model. In a first time the chapter IV focus on the theory of the magnetism and magnetics materials. In a second time, we present the magnetic characterization of the materials used in the electromagnetics flowmeters. In the chapter V, an introduction to the numerical modelling is done in order to justify the using of the finite element method for the magnetic simulation on the software NX Nastran. The second part of this chapter concerns the development and the numerical simulation of an electromagnetic flowmeter. At last, the third part is about the installation of a test bed to measure the magnetic field produced inside the electromagnetic flowmeter and to compare the results with the simulation. Numerical simulation of the magnetic field being checked by the measurements, the next chapter introduces molecular dynamics of the charged particles inside the measuring pipe in order to compute electrical potential. Finally, the last part introduces the calibration of electromagnetics flowmeters where a theoretical model was developed in order to compare them with experimentals values measured in production on Haguenau Siemens site
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