1,720,986 research outputs found
Nucleation-and-growth process in Fe80B20amorphous alloys
No full textA nucleation-and-growth process in Fe80B20 amorphous alloy ribbons has been studied using differential scanning calorimetry using an isothermal analysis mode. Measurements have been performed in the temperature range between the glass transition and the onset of crystallization. Experimental data have been fitted using the theoretical Johnson-Mehl-Avrami equation. Kinetic parameters as well as the activation energy of crystallization have been determinated. It is shown that the mechanism, which governs the nucleation-and-growth process is independent of annealing temperature; while the nucleation frequency and growth rate are dependent on temperature value. Finally it is shown that the whole devitrification of the samples cannot be completely described using only the nucleation-and-growth process
Grain-growth process during crystallization of Fe80B20 amorphous alloys
No full textIt is shown that the full isothermal crystallization analysis of Fe80B20 amorphous alloy must include not only a crystal nucleation-and-growth process but also a grain-growth process and that these two processes are separated in time during isothermal annealing. The parameters characterizing the grain-growth process have been found by the fitting calorimetrical signal with the one expected from the normal grain-growth theory. Transmission electron microscopy and selected area electron diffraction seem to confirm our results since they show that there is a good agreement between the average grain radius of crystallization products seen in the micrograph and the one calculated from the obtained parameters
The complex DSC analysis of the first crystallization peak of Fe80Si10B10 metallic glass
No full textThe crystallization of Fe-80 Si-10 B-10 glass was studied both by linear heating and isothermal differential scanning calorimetry (DSC). Two well separated crystallization peaks were always observed. On the basis of the classical isothermal Johnson-Mehl-Avrami (JMA) procedure both transient nucleation and transient growth kinetics with the complex exponent n similar to 2.8 and mean activation energy E(JMA)* = 323 kJ mol(-1) were determined for the first crystallization peak. Because for the degree of conversion alpha > 0.55 E *(alpha) dependence was observed, the deconvolution of the isothermal peak into the subsequent JMA nucleation-and-growth and grain-growth effects was used to fit the measured data. Simple JMA kinetics could not be determined for the linear heating first crystallization peak. All these results correlate with structural analysis studies
Isothermal Fractionation by DSC : Stepwise Isothermal Segregation Technique applied to Random C3C2 copolymers
No full textMagnetic properties of Fe80B20 alloys with nanocristalline structures
No full textThe magnetic properties of devitrified amorphous Fe80B20 ribbons have been studied by Mossbauer spectroscopy and magnetization measurements. The mean magnetic hyperfine field of the interfacial structural components has been found to be higher in nanocrystalline samples than in microcrystalline ones: this effect is ascribed to the epitaxial growth of small clusters of bcc Fe, with topological disorder, on Fe3B during annealing, producing nanocrystalline structures. The interfacial components present large topological disorder with three kinds of chemical short-range order. Magnetization measurements show larger hysteresis loops after heat treatment, indicating the formation of magnetic phases with higher anisotropy
Magnetization Of Pressureless Sintered Fe-B Powders
No full textWe report a study about the effects on magnetic properties of pressureless sintering without binder addition performed on iron and boron powder mixture. The obtained self-supported samples appear highly porous or very compact depending on the maximum temperature, T(max), reached during the heating process. They maintain the soft magnetic properties of original Fe-B powder mixture if T(max) does not exceed a critical temperature; afterwards the magnetic properties change very abruptly. A decrease in the magnetization saturation per unit mass, M(s), has been observed to increase the T(max) value. Mossbauer spectroscopy has revealed the presence of Fe2B boride inside the obtained samples whose quantity increases with T(max). Considering the magnetic moment per iron atom in Fe2B as the theoretical one calculated by Ching et al., it has been possible to correlate the T(max) dependence of M(s) with the growing of Fe2B boride. The compacting process seems to be due to the growth of Fe2B boride between Fe/B interfaces
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Crystallization of amorphous Fe78Si9B13 alloy
No full textCrystallization kinetics of the amorphous Fe78Si9B13 alloy has been investigated by differential scanning calorimetry in both continuous heating and isothermal annealing modes. The morphology and the growth of different phases during the devitrification process have been studied by transmission electron microscopy and X-ray diffraction. The crystallization of this glass proceedes in two separate stages which can be observed during continous heating as well as during isothermal annealing. It is shown that the lack of complete information about the preparation conditions of the amorphous precursor makes impossible to foresee the stability of the amorphous phase, as well as the phase content, the morphology and the dimensions of the grains during the crystallization process and to compare the results obtained in different investigations
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
