To see the other types of publications on this topic, follow the link: High-order X-FEM.
Journal articles on the topic 'High-order X-FEM'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'High-order X-FEM.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Legrain, G., N. Chevaugeon, and K. Dréau. "High order X-FEM and levelsets for complex microstructures: Uncoupling geometry and approximation." Computer Methods in Applied Mechanics and Engineering 241-244 (October 2012): 172–89. http://dx.doi.org/10.1016/j.cma.2012.06.001.
Full text
2
Sawada, Tomohiro, and Akira Tezuka. "High-order gaussian quadrature in X-FEM with the lagrange-multiplier for fluid-structure coupling." International Journal for Numerical Methods in Fluids 64, no. 10-12 (November 25, 2010): 1219–39. http://dx.doi.org/10.1002/fld.2343.
Full text
3
Wu, Shaoqi, Olivier Dazel, Gwénaël Gabard, and Grégory Legrain. "High-order X-FEM for the simulation of sound absorbing poro-elastic materials with coupling interfaces." Journal of Sound and Vibration 510 (October 2021): 116262. http://dx.doi.org/10.1016/j.jsv.2021.116262.
Full text
4
Rezikyan, Aram, Zechariah J. Jibben, Bryan A. Rock, Gongpu Zhao, Franz A. M. Koeck, Robert F. Nemanich, and Michael M. J. Treacy. "Speckle Suppression by Decoherence in Fluctuation Electron Microscopy." Microscopy and Microanalysis 21, no. 6 (September 18, 2015): 1455–74. http://dx.doi.org/10.1017/s1431927615015135.
Full textAbstract:
AbstractWe compare experimental fluctuation electron microscopy (FEM) speckle data with electron diffraction simulations for thin amorphous carbon and silicon samples. We find that the experimental speckle intensity variance is generally more than an order of magnitude lower than kinematical scattering theory predicts for spatially coherent illumination.We hypothesize that decoherence, which randomizes the phase relationship between scattered waves, is responsible for the anomaly. Specifically,displacement decoherencecan contribute strongly to speckle suppression, particularly at higher beam energies. Displacement decoherence arises when the local structure is rearranged significantly by interactions with the beam during the exposure. Such motions cause diffraction speckle to twinkle, some of it at observable time scales.We also find that the continuous random network model of amorphous silicon can explain the experimental variance data if displacement decoherence and multiple scattering is included in the modeling. This may resolve the longstanding discrepancy between X-ray and electron diffraction studies of radial distribution functions, and conclusions reached from previous FEM studies.Decoherence likely affects all quantitative electron imaging and diffraction studies. It likely contributes to the so-called Stobbs factor, where high-resolution atomic-column image intensities are anomalously lower than predicted by a similar factor to that observed here.
5
Watthewaduge, Gayan, and Berker Bilgin. "Sizing of the Motor Geometry for an Electric Aircraft Propulsion Switched Reluctance Machine Using a Reluctance Mesh-Based Magnetic Equivalent Circuit." Machines 11, no. 1 (January 4, 2023): 59. http://dx.doi.org/10.3390/machines11010059.
Full textAbstract:
The switched reluctance motor (SRM) is a promising candidate for electric propulsion systems. In the design process of an SRM, the motor geometry needs to be determined. Using the finite element method (FEM) might be time-consuming for the sizing of the motor geometry. As an alternative, electromagnetic models based on a magnetic equivalent circuit (MEC) can be utilized for the sizing of an SRM. MEC models require fewer computational resources and can help determine the electromagnetic performance with reasonable accuracy. Using the conventional MEC method for SRM sizing might be challenging since the flux pattern inside the motor should be changed for different motor dimensions. In order to address this challenge, this paper applies a reluctance mesh-based MEC technique to determine the geometry of a three-phase 12/16 SRM for a high-lift motor in the NASA Maxwell X-57 electric aircraft. A comprehensive reluctance mesh-based MEC model is developed for this purpose. Both the static and dynamic characteristics of the SRM geometry are evaluated using the reluctance mesh-based MEC method. The determined geometry is verified using the results computed from FEM.
6
Hattali, M. L., Stéphane Valette, François Ropital, N. Mesrati, and Daniel Treheux. "Fem Calculations and Experimental Determination of Residual Stresses in Alumina/Nickel Alloy Joints. Optimization of Fabrication Parameters." Advanced Materials Research 89-91 (January 2010): 238–43. http://dx.doi.org/10.4028/www.scientific.net/amr.89-91.238.
Full textAbstract:
The study relates to joints fabricated by solid state bonding between alumina and nickel alloy HAYNESTM214®, using an intermediate nickel metallic foil. Experimentally, damages and cracks often are observed close to the metal/ceramics interface. Consequently, the residual stresses distributions in the specimen were characterized experimentally using X-ray diffraction (XRD) and indentation techniques and predicted by Finite Element Analysis (FEA) calculations using an elastic-plastic-creep model. We demonstrate that a good correlation between FEA calculations and experimental results is obtained. Then, the effect of elaboration and geometrical parameters has been studied in order to minimize the residual stresses in alumina close to the metal-ceramics interface. However, the Al2O3/Ni/HAYNESTM214® system always leads to high residual stresses. To solve this problem, we show that the use of a multi-layer Cu/Ni/Cu joint, associated with the Direct Copper Bonding method (DCB), by pre-oxidation of copper, allows reducing significantly the tensile residual stresses in ceramics.
7
Kurita, Masanori, Makoto Sato, Ikuo Ihara, and Akira Saito. "Residual Stress Distribution of Ceramic-Metal Joint." Advances in X-ray Analysis 33 (1989): 353–62. http://dx.doi.org/10.1154/s0376030800019765.
Full textAbstract:
AbstractCeramics are sometimes bonded to ductile metals in order to make up for their brittle behavior for industrial use. The residual stress will be induced in ceramics bonded to metals at high temeprature, and it has a strong influence on the strength of ceramic-metal joints. A silicon nitride plate was bonded to a carbon steel plate by brazing to a copper sheet sandwiched between the two materials. The residual stress distribution of the joint specimen was determined by x-ray diffraction using the Gaussian curve method. The measured residual stress distribution almost agreed with that calculated by the three-dimensional thermoelastoplastic stress analysis using FEM, but differed remarkably from that calculated by the two-dimensional stress analysis. This is because a stress concentration occurs at the ceramic-metal interface and the stress distributes three - dimensionally. The stress σx in the axial direction on the surface of the specimen takes maximum values at the center and the edge of the interface.
8
Guo, Zixu, Ziyuan Song, Dawei Huang, and Xiaojun Yan. "A High-Temperature Digital Image Correlation Method and its Application on Strain Measurement of Film Cooling Holes." Journal of Multiscale Modelling 12, no. 02 (June 2021): 2150003. http://dx.doi.org/10.1142/s1756973721500037.
Full textAbstract:
In this paper, a digital image correlation (DIC) method is developed and applied on film cooling holes in the submillimeter scale in high temperature. Compared with the traditional DIC method, the speckle patterning method and the optical system are improved. In detail, a kind of high temperature-resistant black paint is selected as the basecoat, and the white ZrO2 particles are evenly distributed on the specimen using high-pressure splashing method. Besides, to eliminate the radiation effect of the high-temperature specimen, the blue light source is used to illuminate the specimen, and the optical bandpass filter is placed in front of the camera to allow the blue light passing. In order to verify the DIC method, the strain measurement on a specimen with single skew hole is performed. The relative error in high temperature of the maximum strain between the measurement results and the numerical simulation results given by the finite element method (FEM) is 12%. The strain concentration factor of the single skew hole is measured as 1.83. Finally, the developed method is applied to the strain measurement of the structure with multiple film cooling holes in 870°C. The X-shape strain distribution can be observed at the hole with maximum stress, which suggests that the strain field of multiple holes has coupling effect. In addition, the strain concentration factor of multiple film cooling holes increases to 2.34.
9
Britez, C., J. Gadea, M. Carvalho, and P. Helene. "Hormigón y Hormigonado de Cimentación con Hormigón Autocompactante y de Elevadas Prestaciones (70 MPa)." Revista ALCONPAT 6, no. 1 (January 30, 2016): 28–40. http://dx.doi.org/10.21041/ra.v6i1.113.
Full textAbstract:
Hormigón y Hormigonado de Cimentación con Hormigón Autocompactante y de Elevadas Prestaciones (70 MPa)RESUMENEl Edificio Comercial Brookfield Century Plaza, localizado en Alphaville, São Paulo, Brasil, fue diseñado para ser sostenido por dos grandes bloques de hormigón. Un hormigón de alta resistencia (70 MPa) y SCC auto compactante fue desarrollado para estos dos bloques masivos de fundación (cada un mide 28.4mx 18.6m por 4.5m de altura). Un modelo numérico utilizando un software FEM fue desarrollado para predecir la ganancia térmica de hidratación de diferentes capas de hormigonado con el fin de establecer el procedimiento más adecuado para cumplir con los requisitos de tiempo y de la construcción, sin que aparezcan fisuras. Fueron establecidos y supervisados procedimientos para controlar la producción de concreto en la empresa productora de concretos y aplicarlo en el sitio de construcción. Finalmente, la temperatura interna del concreto se registró para permitir una mejor calibración del modelo.Palabras clave: concreto de alta resistencia, concreto autocompactante, concreto masivo, producción de concreto refrigerado. Material and Casting Methodology for SCC and HPC (70 MPa) Concrete Foundation BlocksABSTRACTThe Brookfield Century Plaza Commercial Building, located in Alphaville District, in São Paulo, Brazil, was designed to be supported by two direct foundation concrete blocks. A high strength (70 MPa), self-compacting concrete SCC was developed for these two massive foundation blocks (each one measures 28.4m x 18.6m by 4.5m, high). A numerical model by employing a FEM software was developed to predict the thermal hydration gain of different casting procedures, in order to establish the most appropriate one to meet the construction and schedule requirements without cracks. Directions to control concrete production at mixing plant and placing at construction site were established as well as supervised. Finally, internal concrete temperatures were recorded to enable a better model calibration.Keywords: High strength concrete, self-compacting concrete, concrete modeling, refrigerated concrete production. Concreto e Concretagem de Blocos de Fundação em Concreto Autoadensável e de Alta Resistência (70 MPa)RESUMOO Edifício Comercial Brookfield Century Plaza, localizado em Alphaville, São Paulo, Brasil, foi projetado para ser apoiado em dois grandes blocos de concreto. Um concreto de alta resistência (70 MPa) e SCC auto adensável foi desenvolvido para estes dois blocos maciços de fundação (cada um medindo 28.4m x 18.6m por 4.5m de altura). Um modelo numérico empregando um software FEM foi desenvolvido para prever o ganho de hidratação térmica de diferentes camadas de concretagem, a fim de estabelecer o procedimento mais adequado para cumprir o cronograma e os requisitos de construção, sem fissurar. Diretrizes para controlar a produção do concreto na empresa de serviços de concretagem e procedimentos de como aplicá-lo no canteiro de obras foram estabelecidas e supervisionadas. Finalmente, as temperaturas internas do concreto foram registradas para permitir uma melhor calibração do modelo.Palavras-chave: Concreto de alta resistência, concreto auto adensável, modelagem de concreto massa, produção de concreto refrigerado.
10
Cannillo, Valeria, Tiziano Manfredini, M. Montorsi, Cristina Siligardi, and A. Sola. "Experimental Characterization and Computational Simulation of Glass-Alumina Functionally Graded Surfaces." Materials Science Forum 492-493 (August 2005): 647–52. http://dx.doi.org/10.4028/www.scientific.net/msf.492-493.647.
Full textAbstract:
Functionally graded materials are a new and attractive class of materials incorporating an engineered spatial variation in composition and/or microstructure: this idea has immediately revealed successful since it allows to reach peculiar mechanical properties such as resistance to wear and contact damage. As a matter of fact, the final behaviour of a Functionally Graded Material is mainly influenced by its graded composition and/or microstructure. Therefore a good fabrication technique should provide a high control and reproducibility of the spatial variation in composition and/or microstructure; on the other hand, a reliable model should take into account the gradient in order to accurately predict the final behaviour of a Functionally Graded Material. The present study is focused on glass-alumina FGMs: the compositional variation, which occurs along only one direction, has been realized through percolation of a molten glass into a bulk polycrystalline alumina. The resulting Functionally Graded Coatings have been carefully characterized through Scanning Electron Microscopy, X-ray diffraction, classical mechanical tests and analysis. Moreover, their behaviour has been modeled by means of a microstructure-based FEM method. A great attention has been paid to the validation of the computational model on the basis of the experimental data. Furthermore, the experimental and the computational approaches have been combined in order to define the correlation between fabrication parameters, such as time and temperature, and resulting gradients in composition and microstructure as well as related performances. Since changes in material properties can be easily evaluated, the resulting model may be useful to simulate the material response to a given thermo-mechanical loading and to tailor the gradient as a function of the specific application.
11
Köhler, Daniel, Behdad Sadeghian, Robert Kupfer, Juliane Troschitz, Maik Gude, and Alexander Brosius. "A Method for Characterization of Geometric Deviations in Clinch Points with Computed Tomography and Transient Dynamic Analysis." Key Engineering Materials 883 (April 2021): 89–96. http://dx.doi.org/10.4028/www.scientific.net/kem.883.89.
Full textAbstract:
When joining lightweight parts of various materials, clinching is a cost efficient solution. In a production line, the quality of a clinch point is primarily controlled by measurement of dimensions, which are accessible from outside. However, methods such as visual testing and measuring the bottom thickness as well as the outer diameter are not able to deliver any information about the most significant geometrical characteristic of the clinch point, neck thickness and undercut. Furthermore, ex-situ destructive methods such as microsectioning cannot detect elastic deformations and cracks that close after unloading. In order to exceed the current limits, a new non-destructive in-situ testing method for the clinching process is necessary. This work proposes a concept to characterize clinch points in-situ by combining two complementary non-destructive methods, namely, computed tomography (CT) and ultrasonic testing. Firstly, clinch points with different geometrical characteristics are analysed experimentally using ex-situ CT to get a highly spatially resolved 3D-image of the object. In this context, highly X-ray attenuating materials enhancing the visibility of the sheet-sheet interface are investigated. Secondly, the test specimens are modelled using finite element method (FEM) and a transient dynamic analysis (TDA) is conducted to study the effect of the geometrical differences on the deformation energy and to qualify the TDA as a fast in-situ non-destructive method for characterizing clinch points at high temporal resolution.
12
Muhamad, Shalina Sheik, Jaharah A. Ghani, Che Hassan Che Haron, and Hafizal Yazid. "Cryogenic milling and formation of nanostructured machined surface of AISI 4340." Nanotechnology Reviews 9, no. 1 (November 18, 2020): 1104–17. http://dx.doi.org/10.1515/ntrev-2020-0086.
Full textAbstract:
AbstractHardened layers are commonly required for automotive components after their production using a machining process in order to enhance the service life of these components. This study investigates the possibility of producing a nanostructured machined surface which can increase the hardness of the machined surface by varying the machining parameters under cryogenic conditions in end milling of AISI 4340. The end milling experiments were performed using multi-layered TiAlN- and AlCrN-coated carbide. Prior to the experiment, a finite element method (FEM) was used to simulate the cutting temperature generated and it had been found that at cutting speed of 200–300 m/min, feed rate of 0.15–0.3 mm/tooth, axial depth of cut of 0.3–0.5 mm, and radial depth of cut of 0.2–0.35 mm, the temperature generated can be sufficiently high to cause austenitic transformation. A field emission scanning electron microscope (FESEM) equipped with angle selective backscattered (AsB) detection analysis was used to investigate the microstructure and machined-affected layers of the machined surfaces. The crystallographic orientation/phase change and nano-hardness were analysed through X-ray diffraction (XRD) and a nano-hardness testing machine. The results showed that the cryogenic machining had significantly affected the surface integrity characteristics of the AISI 4340 alloy due to refined microstructure, favourable phase structure, and higher hardness near the surface layer. The results of this study may be useful in providing an insight into a potential technological shift from conventional surface case hardening processes to the present technique.
13
Novikov, S. V., A. V. Smirnov, M. G. Isayenkova, and N. S. Ermakova. "Study of residual thermal stresses in hard-alloy coatings obtained by electropulse technology." Industrial laboratory. Diagnostics of materials 84, no. 11 (December 3, 2018): 42–45. http://dx.doi.org/10.26896/1028-6861-2018-84-11-42-45.
Full textAbstract:
Qualitative and quantitative estimates of the temperature fields and level of the residual thermal stresses (RTS) in a steel substrate and hard-alloy coating obtained by electropulse technology (EPT) are presented. The estimation was carried out using the finite element method (FEM) and universal COMSOL Multiphysics® software to simulate applied problems. The results of the simulation showed that the higher the rate of mechanical loading, the smaller the depth of heat penetration into the substrate, the residual thermal stresses being localized in the zone of thermal influence near the interaction surface. At the same time, a thin layer of steel cannot cause considerable stresses in the bulk of the hard alloy. The stresses in the steel layer reach the yield point and the layer deforms without formation of large tensile stresses in the hard alloy. A criterion has been obtained that makes it possible to reveal the range of coating application parameters in which the impact of the steel substrate on the formation of residual thermal macro-stresses in the bulk of the hard-alloy coating is minimum. Electropulse equipment has been developed for application of the hard alloy coatings. Standard x-ray sin2Ψ-method (rotation method) is used for experimental evaluation of the macrostresses in the zone of the steel contact with the coating. Studies have shown that both radial and axial stresses are compressive; the maximum absolute values of the stress are observed in the radial direction in the outer layers of the coating, while the axial stresses relax near the free surface. Radial stresses in the outer layers of the coating reach a value of -210 MPa, and axial -110 MPa. The stresses in the coating layers contacting with steel are also characterized by rather high values, of the order of -160 ... -170 MPa. A high level of stress is attributed to the fact that the coating is formed under external pressure. At the same time the compressive stresses are favorable for a hard alloy, since it exhibits high values of the ultimate compression strength.
14
Pieczka, Adam, Frank C. Hawthorne, Neil Ball, Yassir Abdu, Bożena Gołębiowska, Adam Włodek, and Jan Żukrowski. "Graftonite-(Mn), ideallyM1MnM2,M3Fe2(PO4)2, and graftonite-(Ca), ideallyM1CaM2,M3Fe2(PO4)2, two new minerals of the graftonite group from Poland." Mineralogical Magazine 82, no. 6 (May 15, 2018): 1307–22. http://dx.doi.org/10.1180/minmag.2017.081.109.
Full textAbstract:
AbstractTwo new minerals of the graftonite group, graftonite-(Mn), ideallyM(1)MnM(2),M(3)Fe2(PO4)2, and graftonite-(Ca), ideallyM(1)CaM(2),M(3)Fe2(PO4)2, were discovered in phosphate nodules of two beryl–columbite–phosphate pegmatites at Lutomia and Michałkowa, respectively, in the Góry Sowie Block, Lower Silesia, southwest Poland. Graftonite-(Mn) is pinkish brown, whereas graftonite-(Ca) shows more brownish colouration. Both minerals have a vitreous lustre, a good cleavage observed along (010) and irregular fracture; both are transparent and neither of them is fluorescent. They are brittle and have a Mohs hardness of ~5. The minerals are non-pleochroic, colourless in all orientations, biaxial (+), with mean refractive indices α = 1.710(2) and 1.690(2), β = 1.713(2) and 1.692(2), and γ = 1.725(2) and 1.710(5), respectively. With complete order of Ca at theM(1) site, the formulae of the holotype crystals areM(1)(Mn0.70Ca0.30)M(2),M(3)(Fe1.34Mn0.60Mg0.06Zn0.01)Σ3(PO4)2for graftonite-(Mn) andM(1)(Ca0.98Mn0.02)M(2),M(3)(Fe1.38Mn0.56Mg0.05)Σ3(PO4)2for graftonite-(Ca). Both crystal chemistry and crystal-structure refinement (R1= 2.34 and 1.63%, respectively) indicate that theM(1) site is occupied dominantly by Mn in graftonite-(Mn) and by Ca in graftonite-(Ca), and theM(2) andM(3) sites are occupied by Fe2+and Mn2+, with Fe2+dominant over Mn2+at the aggregateM(2) +M(3) sites. Graftonite-(Mn) and graftonite-(Ca) are isostructural with graftonite,M(1)FeM(2),M(3)Fe2(PO4)2(monoclinic system; space-group symmetryP21/c), with the unit-cell parametersa= 8.811(2) Å,b= 11.494(2) Å,c= 6.138(1) Å, β = 99.23(3)° and V = 613.5(4) Å3, anda= 8.792(2) Å,b= 11.743(2) Å,c= 6.169(1) Å, β = 99.35(3)° andV= 628.5(1) Å3, respectively. The densities calculated on the basis of molar weights and unit-cell volumes are 3.793 g/cm3for graftonite-(Mn) and 3.592 g/cm3for graftonite-(Ca). The eight strongest lines in powder X-ray diffraction patterns on the basis of single-crystal data are, respectively [d, Å,I(hkl)]: 2.874, 100, (230 + 040); 2.858, 79, (221); 3.506, 73, (130); 2.717, 79, ($\bar{3}$11); 2.952, 55, (131); 2.916, 53, ($\bar{1}$12); 2.899, 44, (300); 3.016, 35, ($\bar{1}$02); and 3.654, 100, (130); 2.979, 85, (221); 3.014, 77, (230); 3.042, 76, (040 +$\bar{1}$12); 2.834, 68, ($\bar{3}$11); 3.097, 57, (131); 3.133, 56, ($\bar{1}$02); 2.542, 30, (311). Both minerals are common primary phosphates in phosphate nodules, occurring as lamellar intergrowths with sarcopside ± triphylite/lithiophilite, products of exsolution from a (Li,Ca)-rich graftonite-like parent phase crystallized at high temperature from P-bearing hydrosaline melts.
15
Verelst, M., K. R. Kannan, G. N. Subbanna, C. N. R. Rao, Ch Laurent, and A. Rousset. "Investigations of the reduction behavior of iron-impregnated alumina gels (Fe/AlOOH) and the formation of Fe0–Al2O3 metal-ceramic composites." Journal of Materials Research 7, no. 11 (November 1992): 3072–79. http://dx.doi.org/10.1557/jmr.1992.3072.
Full textAbstract:
Fe/AlOOH gels calcined and reduced at different temperatures have been investigated by a combined use of Mössbauer spectroscopy, x-ray diffraction, and electron microscopy in order to obtain information on the nature of the iron species formed as well as the various reduction processes. Calcination at or below 1070 K mainly gives reducible Fe3+ while calcination at higher temperatures gives substitutional Fe3+ in the form of Al2−xFexO3. The Fe3+ species in the calcined samples are, by and large, present in the form of small superparamagnetic particles. Crystallization of Al2O3 from the gels is catalyzed by Fe2O3 as well as FeAl2O4. Fe (20 wt. %)/AlOOH gels calcined at or below 870 K give FeAl2O4 when reduced in hydrogen at 1070 K or lower and a ferromagnetic Fe0–Al2O3 composite (with the metallic Fe particles >100 Å) when reduced at 1270 K. Samples calcined at 1220 K or higher give the Fe0–Al2O3 composite when reduced in the 870–1270 K range, but a substantial proportion of Fe3+ remains unreduced in the form of Al2−xFexO3, showing thereby the extraordinary stability of substitutional Fe3+ to reduction even at high temperatures. Besides the ferromagnetic Fe0–Al2O3 composite, high-temperature reduction of Al2−xFexO3 yields a small proportion of superparamagnetic Fe0–Al2O3 wherein small metallic particles (<100 Å) are embedded in the ceramic matrix. In order to preferentially obtain the Fe0–Al2O3 composite on reduction, Fe/AIOOH gels should be calcined at low temperatures (∼1100 K); high-temperature calcination results in Al2−xFexO3. Several modes of formation of FeAl2O4 are found possible during reduction of the gels, but a novel one is that involving the reaction, 2Fe3+ + Fe0 → 3Fe2+.
16
McBain, Geordie Drummond. "The primitive Orr–Sommerfeld equation and its solution by finite elements." ANZIAM Journal 63 (September 20, 2022): C168—C181. http://dx.doi.org/10.21914/anziamj.v63.17159.
Full textAbstract:
The linear stability of parallel shear flows of incompressible viscous fluids is classically described by the Orr–Sommerfeld equation in the disturbance streamfunction. This fourth-order equation is obtained by eliminating the pressure from the linearized Navier–Stokes equation. Here we consider retaining the primitive velocity-pressure formulation, as is required for general multidimensional geometries for which the streamfunction is unavailable; this affords a uniform description of one-, two-, and three-dimensional flows and their perturbations. The Orr–Sommerfeld equation is here discretized using Python and scikit- fem, in classical and primitive forms with Hermite and Mini elements, respectively. The solutions for the standard test problem of plane Poiseuille flow show the primitive formulation to be simple, clear, very accurate, and better-conditioned than the classical. References L. Allen and T. J. Bridges. Numerical exterior algebra and the compound matrix method. Numer. Math. 92 (2002), pp. 197–232. doi: 10.1007/s002110100365 M. Azaïez, M. Deville, and E. H. Mund. Éléments finis pour les fluides incompressibles. Lausanne: EPFL Press, 2011. url: https://www.epflpress.org/produit/146/9782880748944/elements-finis-pour-les-fluides-incompressibles F. Charru. Instabilités hydrodynamiques. EDP Sciences, 2007. url: https://laboutique.edpsciences.fr/produit/97/9782759801107/instabilites-hydrodynamiques. W. O. Criminale, T. L. Jackson, and R. D. Joslin. Theory and Computation in Hydrodynamic Stability. Cambridge University Press, 2003. doi: 10.1017/CBO9780511550317 A. Davey. A simple numerical method for solving Orr–Sommerfeld problems. Q. J. Mech. Appl. Math. 26 (1973), pp. 401–411. doi: 10.1093/qjmam/26.4.401 J.-P. Dedieu. Condition operators, condition numbers, and condition number theorem for the generalized eigenvalue problem. Lin. Alg. Appl. 263 (1997), pp. 1–24. doi: 10.1016/S0024-3795(96)00366-7 J. J. Dongarra, B. Straughan, and D. W. Walker. Chebyshev tau-QZ algorithm methods for calculating spectra of hydrodynamic stability problems. Appl. Numer. Math. 22 (1996), pp. 399–434. doi: 10.1016/S0168-9274(96)00049-9 P. G. Drazin and W. H. Reid. Hydrodynamic Stability. Cambridge University Press, 2004. doi: 10.1017/CBO9780511616938 A. Ern. Éléments finis. Paris: Dunod, 2005. url: https://www.dunod.com/sciences-techniques/aide-memoire-elements-finis T. Gustafsson and G. D. McBain. scikit-fem: A Python package for finite element assembly. J. Open Source Softw. 5, 2369 (2020). doi: 10.21105/joss.02369 N. P. Kirchner. Computational aspects of the spectral Galerkin FEM for the Orr–Sommerfeld equation. Int. J. Numer. Meth. Fluids 32 (2000), pp. 105–121. doi: 10.1002/(SICI)1097-0363(20000115)32: 1<105::AID-FLD938>3.0.CO;2-X Y. S. Li and S. C. Kot. One-dimensional finite element method in hydrodynamic stability. Int. J. Numer. Meth. Eng. 17 (1981), pp. 853–870. doi: 10.1002/nme.1620170604 M. Mamou and M. Khalid. Finite element solution of the Orr–Sommerfeld equation using high precision Hermite elements: plane Poiseuille flow. Int. J. Numer. Meth. Fluids 44 (2004), pp. 721–735. doi: 10.1002/fld.661 M. L. Manning, B. Bamieh, and J. M. Carlson. Descriptor approach for eliminating spurious eigenvalues in hydrodynamic equations. Tech. rep. 2007. url: http://arxiv.org/abs/0705.1542 G. D. McBain, T. H. Chubb, and S. W. Armfield. Numerical solution of the Orr–Sommerfeld equation using the viscous Green function and split-Gaussian quadrature. J. Comput. Appl. Math. 224 (2009), pp. 397–404. doi: 10.1016/j.cam.2008.05.040 S. A. Orszag. Accurate solution of the Orr–Sommerfeld stability equation. J. Fluid Mech. 50 (1971), pp. 689–703. doi: 10.1017/S0022112071002842 P. Paredes, M. Hermanns, S. Le Clainche, and V. Theofilis. Order 104 speedup in global linear instability analysis using matrix formation. In: Comput. Methods Appl. Mech. Eng. 253 (2013), pp. 287–304. doi: 10.1016/j.cma.2012.09.014 V. Theofilis. Advances in global linear instability analysis of nonparallel and three-dimensional flows. Prog. Aerosp. Sci. 39 (2003), pp. 249–315. doi: 10.1016/S0376-0421(02)00030-1 J. V. Valério, M. S. Carvalho, and C. Tomei. Filtering the eigenvalues at infinite from the linear stability analysis of incompressible flows. J. Comput. Phys. 227 (2007), pp. 229 –243. doi: 10.1016/j.jcp.2007.07.017 D. Varieras, P. Brancher, and A. Giovannini. Self-sustained oscillations of a confined impinging jet. Flow Turbul. Combust. 78, 1 (2007). doi: 10.1007/s10494-006-9017-7 P. Virtanen, R. Gommers, T. E. Oliphant, et al. SciPy 1.0: Fundamental algorithms for scientific computing in Python. Nat. Meth. 17 (2020), pp. 261–272. doi: 10.1038/s41592-019-0686-2 J. A. Weideman and S. C. Reddy. A MATLAB differentiation matrix suite. ACM Trans. Math. Softw. 26 (2000), pp. 465–519. doi: 10.1145/365723.365727 S. Yiantsios and B. G. Higgins. Analysis of superposed fluids by the finite element method: Linear stability and flow development. Int. J. Numer. Meth. Fluids 7 (1987), pp. 247–261. doi: 10.1002/fld.1650070305
17
He, Dongdong, Yuming Xiong, Li Wang, Wei Sun, Runqing Liu, and Tong Yue. "Arsenic (III) Removal from a High-Concentration Arsenic (III) Solution by Forming Ferric Arsenite on Red Mud Surface." Minerals 10, no. 7 (June 28, 2020): 583. http://dx.doi.org/10.3390/min10070583.
Full textAbstract:
Arsenic (As) is considered one of the most serious inorganic pollutants, and the wastewater produced in some smelters contains a high concentration of arsenic. In this paper, we purified the high-concentration arsenic solution with red mud and Fe3+ synergistically. In this system, arsenite anions reacted with Fe(III) ions to form ferric arsenite, which attached on the surface of red mud particles. The generated red mud/Fe1−x(As)x(OH)3 showed a better sedimentation performance than the pure ferric arsenite, which is beneficial to the separation of arsenic from the solution. The red mud not only served as the carrier, but also as the alkaline agent and adsorbent for arsenic treatment. The effects of red mud dosage, dosing order, pH, and molar ratio of Fe/As on arsenic removal were investigated. The efficiency of arsenic removal increased from a pH of 2 to 6 and reached equilibrium at a pH of 7. At the Fe/As molar ratio of 3, the removal efficiency of arsenic ions with an initial concentration of 500 mg/L reached 98%. In addition, the crystal structure, chemical composition, and morphological properties of red mud and arsenic removal residues (red mud/Fe1−x(As)x(OH)3) were characterized by XRD, XPS, X-ray fluorescence (XRF), SEM-EDS, and Raman spectroscopy to study the mechanism of arsenic removal. The results indicated that most of the arsenic was removed from the solution by forming Fe1−x(As)x(OH)3 precipitates on the red mud surface, while the remaining arsenic was adsorbed by the red mud and ferric hydroxide.
18
Sánchez-López, Perla, Yulia Kotolevich, Evgeny Khramov, Ramesh Kumar Chowdari, Miguel Angel Estrada, Gloria Berlier, Yan Zubavichus, Sergio Fuentes, Vitalii Petranovskii, and Fernando Chávez-Rivas. "Properties of Iron-Modified-by-Silver Supported on Mordenite as Catalysts for NOx Reduction." Catalysts 10, no. 10 (October 9, 2020): 1156. http://dx.doi.org/10.3390/catal10101156.
Full textAbstract:
A series of mono and bimetallic catalysts based on a Fe-Ag mixture deposited on mordenite was prepared by ion-exchange and evaluated in the catalytic activity test of the de-NOx reaction in the presence of CO/C3H6. The activity results showed that the most active samples were the Fe-containing ones, and at high temperatures, a co-promoter effect of Ag on the activity of Fe catalysts was also observed. The influence of the order of cation deposition on catalysts formation and their physicochemical properties was studied by FTIR (Fourier Transform Infrared Spectroscopy) of adsorbed NO, XANES (X-ray Absorption Near-Edge Structure), and EXAFS (Extended X-ray Absorption Fine Structure) and discussed in terms of the state of iron. Results of Fe K-edge XANES oscillations showed that, in FeMOR catalysts, iron was present in a disordered state as Fe3+ and Fe2+. In FeAgMOR, the prevailing species was Fe3+, while in the AgFeMOR catalyst, the state of iron was intermediate or mixed between FeMOR and FeAgMOR. The Fe K-edge EXAFS results were characteristic of a disordered phase, the first coordination sphere being asymmetric with two different Fe-O distances. In FeAgMOR and AgFeMOR, coordination of Fe-O was similar to Fe2O3 with a few amount of Fe2+ species. We may conclude that, in the bimetallic FeAgMOR and AgFeMOR samples, a certain amount of tetrahedral Al3+ ions in the mordenite framework is replaced by Fe3+ ions, confirming the previous reports that these species are active sites for the de-NOx reaction. Based on the thermodynamic analysis and experimental data, also, it was confirmed that the order of deposition of the components influenced the mechanism of active sites’ formation during the two steps ion-exchange synthesis.
19
Mabuchi, Jun, and Yoichi Nishino. "Effects of Order-Disorder Transition on High-Temperature Deformation Behavior of (Fe1-xVx)3Al Alloys (x≤1/3)." Journal of the Japan Institute of Metals 69, no. 10 (2005): 880–85. http://dx.doi.org/10.2320/jinstmet.69.880.
Full text
20
Heimann, Philip, Stefan Moeller, Sergio Carbajo, Sanghoon Song, Georgi Dakovski, Dennis Nordlund, and David Fritz. "Laser power meters as an X-ray power diagnostic for LCLS-II." Journal of Synchrotron Radiation 25, no. 1 (January 1, 2018): 72–76. http://dx.doi.org/10.1107/s1600577517014096.
Full textAbstract:
For the LCLS-II X-ray instruments, laser power meters are being developed as compact X-ray power diagnostics to operate at soft and tender X-ray photon energies. These diagnostics can be installed at various locations along an X-ray free-electron laser (FEL) beamline in order to monitor the transmission of X-ray optics along the beam path. In addition, the power meters will be used to determine the absolute X-ray power at the endstations. Here, thermopile power meters, which measure average power, and have been chosen primarily for their compatibility with the high repetition rates at LCLS-II, are evaluated. A number of characteristics in the soft X-ray range are presented including linearity, calibrations conducted with a photodiode and a gas monitor detector as well as ultra-high-vacuum compatibility tests using residual gas analysis. The application of these power meters for LCLS-II and other X-ray FEL sources is discussed.
21
Evaristo, Diego S., Raí F. Jucá, João M. Soares, Rodolfo B. Silva, Gilberto D. Saraiva, Robert S. Matos, Nilson S. Ferreira, Marco Salerno, and Marcelo A. Macêdo. "Antiferromagnet–Ferromagnet Transition in Fe1−xCuxNbO4." Materials 15, no. 21 (October 22, 2022): 7424. http://dx.doi.org/10.3390/ma15217424.
Full textAbstract:
Iron niobates, pure and substituted with copper (Fe1−xCuxNbO4 with x = 0–0.15), were prepared by the solid-state method and characterized by X-ray diffraction, Raman spectroscopy, and magnetic measurements. The results of the structural characterizations revealed the high solubility of Cu ions in the structure and better structural stability compared to the pure sample. The analysis of the magnetic properties showed that the antiferromagnetic–ferromagnetic transition was caused by the insertion of Cu2+ ions into the FeNbO4 structure. The pure FeNbO4 structure presented an antiferromagnetic ordering state, with a Néel temperature of approximately 36.81K. The increase in substitution promoted a change in the magnetic ordering, with the state passing to a weak ferromagnetic order with a transition temperature (Tc) higher than the ambient temperature. The origin of the ferromagnetic ordering could be attributed to the increase in super-exchange interactions between Fe/Cu ions in the Cu2+-O-Fe3+ chains and the formation of bound magnetic polarons in the oxygen vacancies.
22
Rochette, Pierre, Natalia S. Bezaeva, Andrei Kosterov, Jérôme Gattacceca, Victor L. Masaitis, Dmitry D. Badyukov, Gabriele Giuli, Giovani Orazio Lepore, and Pierre Beck. "Magnetic Properties and Redox State of Impact Glasses: A Review and New Case Studies from Siberia." Geosciences 9, no. 5 (May 15, 2019): 225. http://dx.doi.org/10.3390/geosciences9050225.
Full textAbstract:
High velocity impacts produce melts that solidify as ejected or in-situ glasses. We provide a review of their peculiar magnetic properties, as well as a new detailed study of four glasses from Siberia: El’gygytgyn, Popigai, urengoites, and South-Ural glass (on a total of 24 different craters or strewn-fields). Two types of behavior appear: 1) purely paramagnetic with ferromagnetic impurities at most of the order of 10 ppm; this corresponds to the five tektite strewn-fields (including the new one from Belize), urengoites, and Darwin glass. Oxidation state, based in particular on X-ray spectroscopy, is mostly restricted to Fe2+; 2) variable and up to strong ferromagnetic component, up to the 1 wt % range, mostly due to substituted magnetite often in superparamagnetic state. Accordingly, bulk oxidation state is intermediate between Fe2+ and Fe3+, although metallic iron, hematite, and pyrrhotite are sometimes encountered. Various applications of these magnetic properties are reviewed in the field of paleomagnetism, magnetic anomalies, recognition of glass origin, and formation processes.
23
Chou, Loiland, and Lobo. "Reverse Water-Gas Shift Iron Catalyst Derived from Magnetite." Catalysts 9, no. 9 (September 14, 2019): 773. http://dx.doi.org/10.3390/catal9090773.
Full textAbstract:
The catalytic properties of unsupported iron oxides, specifically magnetite (Fe3O4), were investigated for the reverse water-gas shift (RWGS) reaction at temperatures between 723 K and 773 K and atmospheric pressure. This catalyst exhibited a fast catalytic CO formation rate (35.1 mmol h−1 gcat.−1), high turnover frequency (0.180 s−1), high CO selectivity (> 99%), and high stability (753 K, 45000 cm3h−1gcat.−1) under a 1:1 H2 to CO2 ratio. Reaction rates over the Fe3O4 catalyst displayed a strong dependence on H2 partial pressure (reaction order of ~0.8) and a weaker dependence on CO2 partial pressure (reaction order of 0.33) under an equimolar flow of both reactants. X-ray powder diffraction patterns and XPS spectra reveal that the bulk composition and structure of the post-reaction catalyst was formed mostly of metallic Fe and Fe3C, while the surface contained Fe2+, Fe3+, metallic Fe and Fe3C. Catalyst tests on pure Fe3C (iron carbide) suggest that Fe3C is not an effective catalyst for this reaction at the conditions investigated. Gas-switching experiments (CO2 or H2) indicated that a redox mechanism is the predominant reaction pathway.
24
Petrillo, Vittoria, Alberto Bacci, Illya Drebot, Michele Opromolla, Andrea Renato Rossi, Marcello Rossetti Conti, Marcel Ruijter, Sanae Samsam, and Luca Serafini. "Synchronised TeraHertz Radiation and Soft X-rays Produced in a FEL Oscillator." Applied Sciences 12, no. 16 (August 20, 2022): 8341. http://dx.doi.org/10.3390/app12168341.
Full textAbstract:
We present a scheme to generate synchronised THz and soft X-ray radiation pulses by using a free-electron laser oscillator driven by a high repetition rate (of order 10–100 MHz) energy recovery linac. The backward THz radiation in the oscillator cavity interacts with a successive electron bunch, thus producing few 105 soft/hard X-ray photons per shot (namely 1012–1013 photons/s) via Thomson/Compton back-scattering, synchronised with the mJ-class THz pulse within the temporal jitter of electron beams accelerated in the superconducting cavities of the linac (less than 100 fs). Detailed simulations have been performed in order to assess the capability of the scheme for typical wavelengths of interest, between 10 and 50 μm for the TeraHertz radiation and 0.5–3 nm for the X-rays.
25
Sánchez-López, Perla, Yulia Kotolevich, Serguei Miridonov, Fernando Chávez-Rivas, Sergio Fuentes, and Vitalii Petranovskii. "Bimetallic AgFe Systems on Mordenite: Effect of Cation Deposition Order in the NO Reduction with C3H6/CO." Catalysts 9, no. 1 (January 8, 2019): 58. http://dx.doi.org/10.3390/catal9010058.
Full textAbstract:
Mono- and bimetallic systems of Ag, Fe, and Ag–Fe exchanged in sodium mordenite zeolite were studied in the reaction of NO reduction. The transition metal cations Ag and Fe were introduced by ion exchange method both at room temperature and 60 °C; modifying the order of component deposition in bimetallic systems. These materials were characterized by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), ultraviolet-visible spectroscopy (UV-Vis), X-Ray photoelectron Spectroscopy (XPS) and High-resolution transmission electron microscopy (HR-TEM). The XPS and UV–Vis spectra of bimetallic samples revealed that under certain preparation conditions Ag+ is reduced with the participation of the Fe2+/Fe3+ ions transition and is present in the form of a Ag reduced state in different proportions of Agm clusters and Ag0 NPs, influenced by the cation deposition order. The catalytic results in the NO reduction reaction using C3H6/CO under an oxidizing atmosphere show also that the order of exchange of Ag and Fe cations in mordenite has a strong effect on catalytic active sites for the reduction of NO.
26
Feng, Xiao Mei, Li Shun Li, Zhan Dong Liu, and Da Wei Zhang. "The Position Plane Distortion Study of 2-DOF Precision Position Table." Applied Mechanics and Materials 364 (August 2013): 267–71. http://dx.doi.org/10.4028/www.scientific.net/amm.364.267.
Full textAbstract:
A new 2-DOF precision positioning table of high speed and accuracy, directly driven by voice coil actuator, is put forward. And a novel elastic decoupling mechanism is introduced in the table. In order to study its dynamic characteristic when the table works at high speed and high acceleration, the table FEA model is built and the FEA is carried out. Based on the FEA results, the position planes displacement on X, Y and Z axis of the 2-DOF table is simulated respectively, the simulation results can provide reference for the table dynamic structural design.
27
Zhukovsky, K., and I. Potapov. "Two-frequency undulator usage in compact self-amplified spontaneous emission free electron laser in Roentgen range." Laser and Particle Beams 35, no. 2 (April 12, 2017): 326–36. http://dx.doi.org/10.1017/s0263034617000180.
Full textAbstract:
AbstractThe generation of harmonics in two-frequency undulator in a self-amplified spontaneous emission free electron laser (SASE FEL) is studied in order to produce Roentgen radiation in a relatively compact sized installation. The dynamics of SASE FEL is analyzed with the help of the phenomenological model to obtain the maximum of the X-ray high-harmonic power. The model accounts for the properties of the undulator magnetic field and of the electron beam and includes the major sources of losses, such as the electron energy spread, etc. It is compared and calibrated with the existing data on a FEL experiment. The advantages of the two-frequency undulator for Roentgen SASE FEL are demonstrated and the possibility to generate powerful mild Roentgen radiation at already ~25 m length is shown. The evolution of the bunching coefficients for high harmonics is studied together with the evolution of the FEL-induced energy spread. The linear and non-linear regimes are explored for common and for two-frequency undulators The usage of the two-frequency undulator for cascade SASE FEL with high X-ray harmonic power and high-harmonic bunching coefficients with low-induced energy spread is proposed.
28
Wang, Wei, Qiong Mao, Huanhuan He, and Minghua Zhou. "Fe3O4 nanoparticles as an efficient heterogeneous Fenton catalyst for phenol removal at relatively wide pH values." Water Science and Technology 68, no. 11 (October 24, 2013): 2367–73. http://dx.doi.org/10.2166/wst.2013.497.
Full textAbstract:
In order to promote the practical application of the heterogeneous Fenton process in wastewater treatment, Fe3O4 nanoparticles were prepared and used to degrade organic pollutants efficiently over a wide pH range, using phenol as a model. During fabrication, the effects of Fe2+/Fe3+ ratio and thermal treatment temperature were investigated and optimized. Using a transmission electron microscope and X-ray diffraction, the nanoparticles were found in the form of Fe3O4 with an average size of 15 nm. The effects of Fe3O4 nanoparticle concentration H2O2 concentration, and pH on the removal efficiency and chemical oxygen demand (COD) abatement efficiency of phenol were investigated. Under optimized conditions, the nano-Fe3O4 heterogeneous Fenton system could achieve phenol and COD removal efficiencies of 100 and 70% respectively. This nanocatalyst was observed to have a high efficiency at a wider pH range (2–9), and a possible mechanisms for this effect was proposed.
29
Schaper, Lucas, Sven Ackermann, Enrico Allaria, Philipp Amstutz, Karolin Baev, Martin Beye, Christopher Gerth, et al. "Flexible and Coherent Soft X-ray Pulses at High Repetition Rate: Current Research and Perspectives." Applied Sciences 11, no. 20 (October 18, 2021): 9729. http://dx.doi.org/10.3390/app11209729.
Full textAbstract:
The successful realization of high gain free-electron lasers has opened new possibilities to X-ray scientists for investigating matter in different states. The availability of unprecedented photon properties stimulated the development of new experimental techniques capable of taking full advantage of these options and has started a virtuous collaboration between machine experts and photon users to improve further and optimize the generated X-ray pulses. Over the recent years, this has led to the development of several advanced free-electron laser (FEL) schemes to tailor the photon properties to specific experimental demands. Presently, tunable wavelength X-ray pulses with extremely high brilliance and short pulse characteristics are a few of the many options available at FELs. Few facilities can offer options such as narrowband or extremely short pulses below one fs duration and simultaneous pulses of multiple colors enabling resonant X-ray pump—X-ray probe experiments with sub fs resolution. Fully coherent X-ray radiation (both spatial and temporal) can also be provided. This new option has stimulated the application of coherent control techniques to the X-ray world, allowing for experiments with few attoseconds resolution. FELs often operate at a relatively low repetition rate, typically on the order of tens of Hz. At FLASH and the European XFEL, however, the superconducting accelerators allow generating thousands of pulses per second. With the implementation of a new seeded FEL line and with an upgrade at FLASH linac, all the new features will become available in the soft X-ray spectral range down to the oxygen K edge with unprecedented average photon flux due to the high repetition rate of pulses.
30
Beaufort, D., and A. Meunier. "Saponite, Corrensite and Chlorite-Saponite Mixed-Layers in the Sancerre-Couy Deep Drill-Hole (France)." Clay Minerals 29, no. 1 (March 1994): 47–61. http://dx.doi.org/10.1180/claymin.1994.029.1.06.
Full textAbstract:
AbstractThe clay deposits in fractures of the metamorphic basement under the Paris Basin sedimentary formations at Sancerre-Couy (France) are composed of trioctahedral species which are exceptionally well crystallized. Three samples were chosen in order to study the chemical composition of 100% expandable saponite, 50% expandable corrensite and 10% expandable chlorite-saponite mixed-layer mineral C90–S10 Two sets of microchemical analyses were performed in order to determine the variations of the composition on large and small numbers of particles. X-ray diffraction (XRD) and Mössbauer spectrometry were performed on purified samples.The mathematical decomposition of Si, Al and Mg histograms established from microanalyses of a large number of crystals of saponite, corrensite and C90–S10 evidences bimodal populations. The total Fe content of the three species is unimodal whatever the chemical composition of the surrounding rock and the Fe2+/Fe3+ ratio. The structural formulae established from a large number of microanalyses of a few particles show that there are no parental relationships between saponite, corrensite and C90–S10. The expandable layer of corrensite is characterized by a high charge. It is proposed that the tetrahedral sheets adjacent to the brucitic sheet and the exchangeable interlayer in a 2 : 1 unit are identical in corrensite.
31
Claudel, Arnaud, Elisabeth Blanquet, Didier Chaussende, D. Pique, and Michel Pons. "Influence of the N/Al Ratio in the Gas Phase on the Growth of AlN by High Temperature Chemical Vapor Deposition (HTCVD)." Materials Science Forum 615-617 (March 2009): 987–90. http://dx.doi.org/10.4028/www.scientific.net/msf.615-617.987.
Full textAbstract:
In order to achieve AlN bulk growth, HTCVD chlorinated process is investigated. High growth rate and high crystalline quality are targeted for AlN films grown on (0001) 4H SiC at 1750°C. The precursors used are ammonia NH3 and aluminium chlorides AlClx species formed in situ by action of Cl2 on high purity Al wire. Influences of N/Al ratio in the gas phase on growth rate, crystalline state and microstructure are presented. Growth rates of up to 200 µm/h have been reached for polycrystalline layers. Thermodynamic calculations were carried out and correlated to the experimental results. As-grown AlN layers were characterized by SEM and X-ray Diffraction. Surface morphology is studied by SEM and FEG-SEM and crystallographic orientations were obtained by X-ray diffraction on θ/2θ.
32
Wiedorn, Max O., Salah Awel, Andrew J. Morgan, Kartik Ayyer, Yaroslav Gevorkov, Holger Fleckenstein, Nils Roth, et al. "Rapid sample delivery for megahertz serial crystallography at X-ray FELs." IUCrJ 5, no. 5 (July 27, 2018): 574–84. http://dx.doi.org/10.1107/s2052252518008369.
Full textAbstract:
Liquid microjets are a common means of delivering protein crystals to the focus of X-ray free-electron lasers (FELs) for serial femtosecond crystallography measurements. The high X-ray intensity in the focus initiates an explosion of the microjet and sample. With the advent of X-ray FELs with megahertz rates, the typical velocities of these jets must be increased significantly in order to replenish the damaged material in time for the subsequent measurement with the next X-ray pulse. This work reports the results of a megahertz serial diffraction experiment at the FLASH FEL facility using 4.3 nm radiation. The operation of gas-dynamic nozzles that produce liquid microjets with velocities greater than 80 m s−1 was demonstrated. Furthermore, this article provides optical images of X-ray-induced explosions together with Bragg diffraction from protein microcrystals exposed to trains of X-ray pulses repeating at rates of up to 4.5 MHz. The results indicate the feasibility for megahertz serial crystallography measurements with hard X-rays and give guidance for the design of such experiments.
33
Mancuso, Adrian P., Andrew Aquila, Lewis Batchelor, Richard J. Bean, Johan Bielecki, Gannon Borchers, Katerina Doerner, et al. "The Single Particles, Clusters and Biomolecules and Serial Femtosecond Crystallography instrument of the European XFEL: initial installation." Journal of Synchrotron Radiation 26, no. 3 (April 12, 2019): 660–76. http://dx.doi.org/10.1107/s1600577519003308.
Full textAbstract:
The European X-ray Free-Electron Laser (FEL) became the first operational high-repetition-rate hard X-ray FEL with first lasing in May 2017. Biological structure determination has already benefitted from the unique properties and capabilities of X-ray FELs, predominantly through the development and application of serial crystallography. The possibility of now performing such experiments at data rates more than an order of magnitude greater than previous X-ray FELs enables not only a higher rate of discovery but also new classes of experiments previously not feasible at lower data rates. One example is time-resolved experiments requiring a higher number of time steps for interpretation, or structure determination from samples with low hit rates in conventional X-ray FEL serial crystallography. Following first lasing at the European XFEL, initial commissioning and operation occurred at two scientific instruments, one of which is the Single Particles, Clusters and Biomolecules and Serial Femtosecond Crystallography (SPB/SFX) instrument. This instrument provides a photon energy range, focal spot sizes and diagnostic tools necessary for structure determination of biological specimens. The instrumentation explicitly addresses serial crystallography and the developing single particle imaging method as well as other forward-scattering and diffraction techniques. This paper describes the major science cases of SPB/SFX and its initial instrumentation – in particular its optical systems, available sample delivery methods, 2D detectors, supporting optical laser systems and key diagnostic components. The present capabilities of the instrument will be reviewed and a brief outlook of its future capabilities is also described.
34
Siegfried, S. A., E. V. Altynbayev, N. M. Chubova, A. Heinemann, V. A. Dyadkin, E. V. Moskvin, D. Menzel, et al. "Spin chirality is flipped in transition-metal monogermanides." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1546. http://dx.doi.org/10.1107/s2053273314084538.
Full textAbstract:
Using high pressure method polycrystalline powder samples of Mn1-xFexGe and Fe1-yCoyGe have been synthesized with x/y running from 0.0 to 1.0. The crystallite size for these compounds is in the order of 10 microns. SQUID magnetization and small angle neutron scattering (using SANS-1 at the MLZ, Garching) have revealed the helical magnetic ordering of the samples within the concentration range of x = [0.0 – 1.0] and y = [0.0 – 0.8]. The values of the helical wavevector k have been taken from the SANS pattern. As it could be seen in Fig.1 a) for Mn1-xFexGe the wavevector k remains roughly constant around 2 nm^-1 for x ≤ 0.4, while going down to a minimum for (|k| -> 0) at xc ≍ 0.75 and increases again to a value of 0.09 nm^-1 for pure FeGe. For Fe1-yCoyGe the k value smoothly decreases from 0.09 nm-1 for pure FeGe to its minimum at yc ≍ 0.6 and increase again for y = 0.8 to its maximum of 0.14 nm^-1 (Fig.1 b). For x/y -> xc/yc we observe a transformation of the helical magnetic structure to a ferromagnetic-like one at the critical concentrations. The change of the magnetic structure from helimagnetic to ferromagnetic-like goes along with a different sign of the magnetic chirality for x/y < xc/yc and x/y > xc/yc [1,2].
35
Watanabe, M., D. W. Ackland, and D. B. Williams. "Practical Estimation of Analytical Sensitivity for EDS in an Intermediate Voltage FEG-STEM." Microscopy and Microanalysis 3, S2 (August 1997): 965–66. http://dx.doi.org/10.1017/s1431927600011715.
Full textAbstract:
One of the ultimate objectives for energy-dispersive X-ray spectrometry (EDS) in the analytical electron microscope (AEM) is single-atom detection in thin specimens, as well as quantitative microanalysis with high accuracy approaching ±1% relative. In order to realize the single-atom analysis, the design of the AEM has to be optimized with respect to improvements in spatial resolution and detectability limits. The detectability limit, as defined by the minimum mass fraction (MMF), is given by:where P is the peak intensity of interest, (P/B) is the peak-to-background ratio for that peak, and r is the acquisition time. To improve the sensitivity for analysis, any or all of the variables P, (P/B), and τ should be increased. Intermediate-voltage analytical electron microscopes combined with high brightness field-emission gun (FEG) are expected to improve the MMF, while maintaining high spatial resolution. Additionally, the MMF should also be improved by maximizing the solid angle of X-ray collection.
36
Tomita, T., M. Kawasaki, M. Takeguchi, T. Honda, and M. Kersker. "A 200kV Comprehensive Analytical Electron Microscope." Proceedings, annual meeting, Electron Microscopy Society of America 54 (August 11, 1996): 416–17. http://dx.doi.org/10.1017/s0424820100164544.
Full textAbstract:
With the use of a high-brightness electron source, the performance of the analytical electron microscope (AEM) has significantly improved. It features a variety of sophisticated analytical functions, such as X- ray spot analysis, area analysis, electron beam energy analysis, electron diffraction, and phase analysis using a biprism for holography. Here, we report the results of our analysis using a 200kV comprehensive AEM which has an integrated ZrO/W emitter as its optic source. The AEM (JEM- 2010F) is equipped with an X-ray energy dispersive spectrometer (EDS), scanning image observation device (ASID), parallel detection electron energy loss spectrometer (PEELS), and TV camera.(1) X-ray mapping using EDS and ASID With FEG, the probe current in a 1 nm probe is increased by two-order orders of magnitude, and the background noise generated near the sample and in the illumination system is minimized. As a result, EDS analysis features high sensitivity at a minimum detection of 1% weight fraction from an ultra-micro area of lnm diameter.
37
Mutashar, Riyam A. "Design of High Gain Slotted Circular Microstrip Antenna for X-band Applications." BASRA JOURNAL OF SCIENCE 39, no. 3 (December 1, 2021): 414–31. http://dx.doi.org/10.29072/basjs.2021306.
Full textAbstract:
In this study, new structures of circular microstrip antennas, which operating in X-band frequency using etched slots on the patch radiating, are designed and simulated. These slots are rectangular and crescent shapes in different sizes. The proposed structures are fed by a coaxial line feed. The antennas designed are simulated and studied in order to obtain the optimum performance of the proposed antenna using Ansoft High Frequency Structure Simulator. The simulated results were discussed in terms of reflection coefficient, input impedance, gain, radiation patterns and surface currents. It is found that the optimum antenna design has resonance frequency 9.346 GHz with a bandwidth of reflection coefficient of 705 MHz, which is required for X-band applications. Therefore, this optimum designed is helpful for many applications in the system of modern wireless communication.
38
Waheed, Ammara, Quanquan Shi, Nobutaka Maeda, Daniel M. Meier, Zhaoxian Qin, Gao Li, and Alfons Baiker. "Strong Activity Enhancement of the Photocatalytic Degradation of an Azo Dye on Au/TiO2 Doped with FeOx." Catalysts 10, no. 8 (August 13, 2020): 933. http://dx.doi.org/10.3390/catal10080933.
Full textAbstract:
The doping of Au/TiO2 with FeOx is shown to result in a strong enhancement of its photocatalytic activity in the degradation of the azo dye Orange II. In order to examine the source of this enhancement, Au-FeOx/TiO2 nanocomposites containing different molar ratios of Au:Fe were synthesized, and X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and high-resolution transmission electron microscope (HRTEM) analyses indicated that the TiO2-supported Au nanoparticles were partially covered with an amorphous layer of FeOx species, in which the iron was present as Fe2+ and Fe3+. The metal-semiconductor system, i.e., Au/TiO2, showed only a moderate degradation rate, whereas doping with FeOx strongly enhanced the degradation activity. The bandgap energy decreased gradually from Au/TiO2 (3.13 eV) to the catalyst with the highest FeOx loading Au-FeOx (1:2)/TiO2 (2.23 eV), and this decrease was accompanied by a steady increase in the degradation activity of the catalysts. XPS analyses revealed that compared to Au/TiO2, on Au-FeOx/TiO2 a much higher population density of chemisorbed and/or dissociated oxygen species was generated, which together with the decreased bandgap resulted in the highest photocatalytic activity observed with Au-FeOx (1:2)/TiO2. The processes occurring during reaction on the catalyst surface and in the bulk liquid phase were investigated using operando attenuated total reflection IR spectroscopy (ATR-IR) combined with modulation excitation spectroscopy (MES), which showed that the doping of Au/TiO2 with FeOx weakens the interaction of the dye with the catalyst surface and strongly enhances the cleavage of the azo bond.
39
Bahr, Matthew Nathan, Dimple Modi, Sarsvatkumar Patel, Gossett Campbell, and Gregory Stockdale. "Understanding the Role of Sodium Lauryl Sulfate on the Biorelevant Solubility of a Combination of Poorly Water-Soluble Drugs Using High Throughput Experimentation and Mechanistic Absorption Modeling." Journal of Pharmacy & Pharmaceutical Sciences 22 (June 20, 2019): 221–46. http://dx.doi.org/10.18433/jpps30347.
Full textAbstract:
This study investigates the influence of surfactant sodium lauryl sulfate (SLS) on the solubility of poorly-water soluble drug substances, model Compound X and Compound Y, used in a fixed dose combination oral solid dosage form. To determine the impact of SLS concentration on the solubility of compounds X and Y, we experimentally determined the critical micelle concentration (CMC) of SLS in water, simulated gastric fluid (SGF), and fed state simulated intestinal fluid (FeSSIF) in the presence of Compound X and Compound Y using UV/Visible spectrophotometry at 25°C. The aggregation of SLS was characterized by calculating the standard Gibbs free energy of micellization in all the media investigated. To enhance the understanding of SLS aggregation, high throughput experiments and in-vivo mechanistic modelling were used to determine the effect of increasing levels of SLS on the solubility of compounds X and Y as both single agent and combination products to be formulated into a suitable oral solid dosage form. Micellar formation of SLS is a spontaneous process as shown by the negative values of the standard free energy of micellization. The CMC of SLS in the various media investigated in the presence of compounds X and Y decreases in the following order: water> FeSSIF> SGF. However, the aggregation of SLS in the various media is overall more spontaneous in the following order: SGF>FeSSIF>water. Using high throughput experimentation and in-vivo mechanistic modelling, it was determined that a combination oral solid product of compounds X and Y will have optimum solubility and in-vivo absorption if 2 mg of SLS was used in the oral solid dosage form. The results obtained from this study will help broaden the understanding of the micellization process involving SLS and poorly-water soluble drugs used in combination oral solid dosage forms.
40
Wang, Yue, Tianying Chang, Zhengchao Zhang, Kaijie Pei, Jie Fu, and Tingyi Liu. "Involute the reactivity of persulfate with zero-valent iron for enhanced removal of arsenic (V) in aspect involvement of Fe2+ or Fe3+." Water Science and Technology 80, no. 6 (September 15, 2019): 1031–41. http://dx.doi.org/10.2166/wst.2019.355.
Full textAbstract:
Abstract Being a fundamental issue regarding sewage treatment, heavy metals removal from industrial effluents has been subject to intense scrutiny in both the academic and practical worlds. The removal of pentavalent arsenic (As(V)), one of the most poisonous pollutants, was investigated using a sodium persulfate and iron powder system activated by ferrous ions (Fe2+-ZVI-PS). As(V) could be effectively removed by an Fe2+-ZVI-PS system in a timely fashion (minute scale) with high removal rates (more than 90.0%) over a wide range of pH (1–9) and concentration (20–100 mg/L). The removal of As(V) by the Fe2+-ZVI-PS system integrated favorably with the pseudo-second-order reaction kinetics. Researches on X-ray photoelectron spectroscopy (XPS) demonstrated that the Fe2+-ZVI-PS system enables the removal of As(V) through the process of co-precipitation and adsorption. Our findings thus emphasized that the Fe2+-ZVI-PS system should be an effective trigger to purifying arsenic from the environment. Our results indicated that the Fe2+-ZVI-PS system could be an effective candidate for remediation of arsenic in the environment.
41
Prat, Eduard, and Sven Reiche. "Compact coherence enhancement by subharmonic self-seeding in X-ray free-electron laser facilities." Journal of Synchrotron Radiation 25, no. 2 (February 19, 2018): 329–35. http://dx.doi.org/10.1107/s1600577518000395.
Full textAbstract:
X-ray free-electron lasers (FELs) are cutting-edge scientific tools able to generate transversely coherent radiation with very high power and ultra-short pulse durations. The self-seeding mechanism has been proven to increase the longitudinal coherence of the FEL radiation but its efficiency could be significantly improved, especially for soft X-rays. This paper proposes the enhancement of the performance of self-seeding by combining it with the harmonic generation mechanism. In particular, by starting the process with a subharmonic of the wavelength of interest, the coherence of the produced radiation is improved, the undulator beamline becomes more compact, and the monochromator realization is simplified. Numerical simulations for SwissFEL are presented showing that the method can be employed, within a given space, to increase the spectral brightness by one order of magnitude or more with respect to standard self-seeding. This coherence enhancement will be fundamental for many photon science applications and techniques such as resonant inelastic X-ray scattering.
42
Etter, Martin, Melanie Müller, Michael Hanfland, and Robert E. Dinnebier. "High-pressure phase transitions in the rare-earth orthoferrite LaFeO3." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 70, no. 3 (May 24, 2014): 452–58. http://dx.doi.org/10.1107/s2052520614007379.
Full textAbstract:
Sequential Rietveld refinements were applied on high-pressure synchrotron powder X-ray diffraction measurements of lanthanum ferrite (LaFeO3) revealing two phase transitions on the room-temperature isotherm up to a pressure of 48 GPa. The first structural phase transition of second order occurs at a pressure of 21.1 GPa, changing the space group fromPbnmtoIbmm. The second transition, involving a isostructural first-order phase transition, occurs at approximately 38 GPa, indicating a high-spin to low-spin transition of the Fe3+ion. Following the behavior of the volume up to the hydrostatic limit of methanol–ethanol it was possible to use inverted equations of state (EoS) to determine a bulk modulus ofB0= 172 GPa and a corresponding pressure derivative ofB′0= 4.3. In addition, the linearized version of the inverted EoS were used to determine the corresponding moduli and pressure derivatives for each lattice direction.
43
Stellato, Francesco, Maria Pia Anania, Antonella Balerna, Simone Botticelli, Marcello Coreno, Gemma Costa, Mario Galletti, et al. "Plasma-Generated X-ray Pulses: Betatron Radiation Opportunities at EuPRAXIA@SPARC_LAB." Condensed Matter 7, no. 1 (February 24, 2022): 23. http://dx.doi.org/10.3390/condmat7010023.
Full textAbstract:
EuPRAXIA is a leading European project aimed at the development of a dedicated, ground-breaking, ultra-compact accelerator research infrastructure based on novel plasma acceleration concepts and laser technology and on the development of their users’ communities. Within this framework, the Laboratori Nazionali di Frascati (LNF, INFN) will be equipped with a unique combination of an X-band RF LINAC generating high-brightness GeV-range electron beams, a 0.5 PW class laser system and the first fifth-generation free electron laser (FEL) source driven by a plasma-based accelerator, the EuPRAXIA@SPARC_LAB facility. Wiggler-like radiation emitted by electrons accelerated in plasma wakefields gives rise to brilliant, ultra-short X-ray pulses, called betatron radiation. Extensive studies have been performed at the FLAME laser facility at LNF, INFN, where betatron radiation was measured and characterized. The purpose of this paper is to describe the betatron spectrum emitted by particle wakefield acceleration at EuPRAXIA@SPARC_LAB and provide an overview of the foreseen applications of this specific source, thus helping to establish a future user community interested in (possibly coupled) FEL and betatron radiation experiments. In order to provide a quantitative estimate of the expected betatron spectrum and therefore to present suitable applications, we performed simple simulations to determine the spectrum of the betatron radiation emitted at EuPRAXIA@SPARC_LAB. With reference to experiments performed exploiting similar betatron sources, we highlight the opportunities offered by its brilliant femtosecond pulses for ultra-fast X-ray spectroscopy and imaging measurements, but also as an ancillary tool for designing and testing FEL instrumentation and experiments.
44
BACCI, A., C. MAROLI, V. PETRILLO, L. SERAFNI, and M. FERRARIO. "STUDY OF TRANSVERSE EFFECTS IN THE PRODUCTION OF X-RAYS WITH A FREE-ELECTRON LASER BASED ON AN OPTICAL UNDULATOR." International Journal of Modern Physics A 22, no. 23 (September 20, 2007): 4270–79. http://dx.doi.org/10.1142/s0217751x07037822.
Full textAbstract:
The interaction between high-brilliance electron beams and counter-propagating laser pulses produces X rays via Thomson back-scattering. If the laser source is long and intense enough, the electrons of the beam can bunch and a regime of collective effects can establish. In this case of dominating collective effects, the FEL instability can develop and the system behaves like a free-electron laser based on an optical undulator. Coherent X-rays can be irradiated, with a bandwidth very much thinner than that of the corresponding incoherent emission. The emittance of the electron beam and the distribution of the laser energy are the principal quantities that limit the growth of the X-ray signal. In this work we analyse with a 3-D code the transverse effects in the emission produced by a relativistic electron beam when it is under the action of an optical laser pulse and the X-ray spectra obtained. The scalings typical of the optical wiggler, characterized by very short gain lengths and overall time durations of the process make possible considerable emission also with emittance of the order of 1mm mrad.
45
Zhang, J., D. B. Williams, and J. I. Goldstein. "Practical Importance of Spatial Resolution and Analytical Sensitivity in AEM X-ray Microanalysis." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 2 (August 12, 1990): 432–33. http://dx.doi.org/10.1017/s0424820100135769.
Full textAbstract:
Analytical sensitivity and spatial resolution are important and closely related factors in x-ray microanalysis using the AEM. Analytical sensitivity is the ability to distinguish, for a given element under given conditions, between two concentrations that are nearly equal. The analytical sensitivity is directly related to the number of x-ray counts collected and, therefore, to the probe current, specimen thickness and counting time. The spatial resolution in AEM analysis is determined by the probe size and beam broadening in the specimen. A finer probe and a thinner specimen give a higher spatial resolution. However, the resulting lower beam current and smaller X-ray excitation volume degrade analytical sensitivity. A compromise must be made between high spatial resolution and an acceptable analytical sensitivity. In this paper, we show the necessity of evaluating these two parameters in order to determine the low temperature Fe-Ni phase diagram.A Phillips EM400T AEM with an EDAX/TN2000 EDS/MCA system and a VG HB501 FEG STEM with a LINK AN10 EDS/MCA system were used.
46
Yang, Yujie. "Two-Step Calcination-Method-Derived Al-Substituted W-Type SrYb Hexaferrites: Their Microstructural, Spectral, and Magnetic Properties." Magnetochemistry 8, no. 10 (September 30, 2022): 118. http://dx.doi.org/10.3390/magnetochemistry8100118.
Full textAbstract:
W-type hexaferrites were discovered in the 1950s and are of interest for their potential applications. In this context, many researchers have conducted studies on the partial substitution of Fe sites in order to modify their electric and magnetic properties. In this study, W-type SrYb hexaferrites using Al3+ as substitutes for Fe3+ sites with the nominal composition Sr0.85Yb0.15Zn1.5Co0.5AlxFe16-xO27 (0.00 ≤ x ≤ 1.25) were successfully synthesized via the two-step calcination method. The microstructures, spectral bands of characteristic functional groups, morphologies, and magnetic parameters of the prepared samples were characterized using XRD, FTIR, SEM, EDX, and VSM. The XRD results showed that, compared with the standard patterns for the W-type hexaferrite, the W-type SrYb hexaferrites with the Al content (x) of 0.00 ≤ x ≤ 1.25 were a single-W-type hexaferrite phase. SEM images showed the flakes and hexagonal grains of W-type hexaferrites with various Al content (x). The saturation magnetization (Ms) and magneton number (nb) decreased with Al content (x) from 0.00 to 1.25. The remanent magnetization (Mr) and coercivity (Hc) decreased with Al content (x) from 0.00 to 0.25. Additionally, when the Al content (x) ≥ 0.25, Mr and Hc increased with the increase in the Al content (x). The magnetic anisotropy field (Ha) and first anisotropy constant (K1) increased with the Al content (x) increasing from 0.00 to 1.25. Al-substituted W-type SrYb hexaferrites with soft magnetic behavior, high Ms, and lower Hc may be used as microwave-absorbing materials.
47
Lu, Mang, Yue Cheng, Jian-min Pan, Wen-jing Fan, Chuang Jiao, and Xiao-yu Liu. "Synthesis of MCM-41 stabilized NZVI and its use in removal of Cr(VI) from aqueous solution." Journal of Water Reuse and Desalination 5, no. 2 (December 12, 2014): 149–56. http://dx.doi.org/10.2166/wrd.2014.081.
Full textAbstract:
In this study, MCM-41 stabilized nano zero-valent iron (M-NZVI) is synthesized using the rheological phase reaction method. Characterization with transmission electron microscopy validates the hypothesis that the introduction of MCM-41 leads to a decrease in aggregation of iron nanoparticles. X-ray diffraction confirms the existence of Fe0 and the strong antioxidant activity of Fe0 nanoparticles. Batch Cr(VI) reduction experiments exhibit that solution pH, M-NZVI dosage, and reaction time have significant effects on Cr(VI) removal. A high removal efficiency of Cr(VI) (84.5%) is obtained within 60 min for 100 mg/L of Cr(VI) solution at an initial pH of 6.0 and M-NZVI dosage of 0.5 g/L at 35 °C. The Cr(VI) removal rates follow modified pseudo-first-order kinetic equations. The observed removal rate constant was 0.0168/min for the M-NZVI dosage of 1.0 g/L. Our study suggests that the introduction of an innocuous stabilizer such as MCM-41 can significantly improve the performance of Fe0 nanoparticles for environmental remediation applications.
48
Cardona-Vasquez, Jorge A., David A. Landínez-Téllez, and Jairo Roa-Rojas. "Tunable ferrimagnetic-antiferromagnetic response by the inclusion of Fe in the gadolinium-based manganite GdMnO3." Revista UIS Ingenierías 19, no. 3 (March 27, 2020): 69–77. http://dx.doi.org/10.18273/revuin.v19n3-2020007.
Full textAbstract:
In this work a study of the synthesis process, crystal structure and magnetic behavior of gadolinium manganite with Fe substitutions in Mn positions of GdMn1-xFexO3(x=0, 0.1, 0.2) is reported. The samples were synthetized by the conventional solid-state reaction method. Structural characterization of final compounds was analyzed by Rietveld refinement, which revealed its crystallization in an orthorhombic symmetry belonging to the Pbnm (No. 62) space group. Results reveal that aand ccell parameters and the unit cell volume increase, while the lattice parameter band the cell volume decrease with Fe substitution. The main effect in the structure is related to oxygen positions, i.e. in the octahedral distortions and rotations. DC susceptibility measurements, in the temperature regime between 4 K and 300 K on the application of an external field of 200 Oe, show a paramagnetic feature at high temperatures for all xstudied values, with magnetic transitions associated to a magnetic ordered state at low temperatures (21.8 K < T < 25.2 K). Meanwhile, a ferrimagnetic transition is detected for x=0.1close to T=30.7 K.In order to explain the appearance of ferrimagnetism for this configuration, a model is suggested where an imbalance in the magnetic structure of GdMnO3(type-Aantiferromagnetic) generated due to the introducing a Fe3+ion in each pair consecutive unit cells is proposed. Theeffective magnetic moment obtained agrees to the reported value for the material with x=0.0, confirming the ferrimagnetic behavior for this concentration of Fe3+in the structure.
49
Ysnaga, Orlando Elguera, Kelen M. F. Rossi de Aguiar, Cibele Bugno Zamboni, Wagner Luiz Polito, and Ubirajara P. Rodrigues-Filho. "Qualitative and Semiquantitative Determination of the Atomic and Molecular Tungsten Distributions in Hybrid Hydroxyurethanes–Poly(dimethylsiloxane) Films Containing Phosphotungstates ([PW12O40]3–)." Applied Spectroscopy 74, no. 12 (October 12, 2020): 1515–29. http://dx.doi.org/10.1177/0003702820945018.
Full textAbstract:
In this study, hybrid poly(dimethylsiloxane)-derived hydroxyurethanes films (PDMSUr-PWA) containing phosphotungstic acid (H3PW12O40/PWA) were characterized using field emission gun scanning electron microscopy (FEG-SEM), in attenuated total reflectance Fourier transform mid-infrared mode (ATR FT-MIR), and analyzed using synchrotron radiation micro-X-ray fluorescence (SR-μXRF), synchrotron radiation grazing incidence X-ray fluorescence (SR-GIXRF), laser-induced breakdown spectroscopy (LIBS), and instrumental neutron activation analysis (NAA) in order to correlate the distribution patterns of tungsten and properties of PDMSUr-PWA films. PDMS constitute elastomers with good mechanical, thermal, and chemical (hydrophobicity/non-hygroscopy) resistance. Currently, products based on urethanes (e.g., polyurethanes) are widely used in many applications as plastics, fiber-reinforced polymers, high-performance adhesives, corrosion-resistant coatings, photochromic films, among others. The possibility to combine inorganic and organic components can produce a hybrid material with unique properties. PWA has an important role as agent against the corrosion of steel surfaces in different media, besides exhibiting amazing catalytic and photochromic properties in these films. PWA kept its structure inside of these hybrid films through interactions between the organic matrix of PDMSUr and silanol from the inorganic part (organically modified silica), as was shown using ATR FT-MIR spectra. The FEG-SEM/SR-μXRF/wide-angle X-ray scattering (WAXS)/X-ray diffraction (XRD)/energy dispersive X-ray results proved the presence of PWA in the composition of domains of PDMSUr-PWA films. At PWA concentrations higher than 50 wt%/wt, tungsten segregation across the thickness is predominant, while that at PWA concentrations lower than 35 wt%/wt, tungsten segregation at surface is predominant. Inhomogeneities in the tungsten distribution patterns (at micrometric and millimetric level) may play an important role in the mechanical properties of these films (elastic modulus and hardness).
50
Salazar-Rodriguez, Roberto, Domingo Aliaga Guerra, Jean-Marc Greneche, Keith M. Taddei, Noemi-Raquel Checca-Huaman, Edson C. Passamani, and Juan A. Ramos-Guivar. "Presence of Induced Weak Ferromagnetism in Fe-Substituted YFexCr1−xO3 Crystalline Compounds." Nanomaterials 12, no. 19 (October 8, 2022): 3516. http://dx.doi.org/10.3390/nano12193516.
Full textAbstract:
Fe-substituted YFexCr1−xO3 crystalline compounds show promising magnetic and multiferroic properties. Here we report the synthesis and characterization of several compositions from this series. Using the autocombustion route, various compositions (x = 0.25, 0.50, 0.6, 0.75, 0.9, and 1) were synthesized as high-quality crystalline powders. In order to obtain microscopic and atomic information about their structure and magnetism, characterization was performed using room temperature X-ray diffraction and energy dispersion analysis as well as temperature-dependent neutron diffraction, magnetometry, and 57Fe Mössbauer spectrometry. Rietveld analysis of the diffraction data revealed a crystallite size of 84 (8) nm for YFeO3, while energy dispersion analysis indicated compositions close to the nominal compositions. The magnetic results suggested an enhancement of the weak ferromagnetism for the YFeO3 phase due to two contributions. First, a high magnetocrystalline anisotropy was associated with the crystalline character that favored a unique high canting angle of the antiferromagnetic phase (13°), as indicated by the neutron diffraction analysis. This was also evidenced by the high magnetic hysteresis curves up to 90 kOe by a remarkable high critical coercivity value of 46.7 kOe at room temperature. Second, the Dzyaloshinskii–Moriya interactions between homogenous and heterogeneous magnetic pairs resulted from the inhomogeneous distribution of Fe3+ and Cr3+ ions, as indicated by 57Fe Mössbauer studies. Together, these results point to new methods of controlling the magnetic properties of these materials.