1,721,011 research outputs found
La reologia dei materiali ceramici tradizionali
No full textraccolta di contributi sulla misura delle caratteristiche reologiche di sospensioni ceramich
Developed and characterization of PZTN-CFO particulate ceramic composites
No full textThe surge of interest in multiferroic materials over the past 15 years has been driven by their fascinating physical properties and huge potential for technological applications such as sensors, microwave devices, energy harvesting, photovoltaic technologies, solid-state refrigeration, data storage recording technologies and multiferroic random access multi-state memories (MFRAM) [1]. Remarkable efforts have been done to develop laminated bi-layer and multilayer multiferroic composites as bulk or thin films. Such structures lead to remarkable magneto-electric coupling coefficients of a few Volts / cm∙Oe because in such configuration the ferroic layer is a "full dielectric" which can be completely polarized in the conventional way [2]. On the other hand in the particulate ceramic composites the requirement for "full dielectric" is no longer applicable, since the ferroic phases are fully separated within the composite. The strengths of particulate ceramic composites are low cost, simple production technology, higher strain mediated magneto-electric coupling (since electric order phase/magnetic phase interface density can be higher) and easy control of electrical and magnetic properties if the ferroelectric phase (generally a perovskite) and the ferromagnetic one (a ferrite with spinel structure) are mixed in a favourable proportion under the percolation threshold of the ferromagnetic phase. A great research effort is in progress to improve the fabrication of PZT-CoFe2O4 (PZT-CF) composites in order to avoid the unwanted reactions, which occur during densification of PZT-CF materials at 1100-1200 °C, and to achieve the electric saturation during the poling. Up to date, by setting a quite-fast sintering, full densification and prevention of unwanted reactions were achieved for the PZT:CF 74:26 composites [3], but the achieving of electric saturation is still a challenging. Further important achieved results were: the understanding that the main cause of reactions is the PbO loss [3]; the proposal of an equation to calculate the PbO loss through XRD analysis, considering the amount of ZrO2 and variation of perovskite's tetragonality [3]; and the ability to design the ceramic process to control the CF grain size distribution, which can be mono- or bi-modal, and overgrowth [3,4]. [1] M. M. Vopson. Crit. Rev. Solid State 4:40 (2015) 223-250 doi:10.1080/10408436.2014.992584 [2] P. Galizia, et al. J. Eur. Ceram. Soc. 36 (2016) 373-380. doi:10.1016/j.jeurceramsoc.2015.07.038 [3] P. Galizia, et al., PZT-cobalt ferrite particulate composites: Densification and lead loss controlled by quite-fast sintering. J. Eur. Ceram. Soc. (2016). doi:10.1016/j.jeurceramsoc.2016.08.025 [4] P. Galizia, et al., Multiple parallel twinning overgrowth in nanostructured dense cobalt ferrite. Mater. Design109 (2016) 19-26. doi:10.1016/j.matdes.2016.07.05
Investigation of new magneto-dielectric titania-cobalt ferrite composites
No full textNovel magneto-dielectric cobalt ferrite (CFO)- titania (TO) ceramic composites with composition (100-x)TO-xCFO with x ranging from 20 to 80 wt.% were prepared by conventional solid state reaction. Highly densified composites with two to three phases homogeneously distributed were obtained. The formation of a new ternary compound Fe2CoTi3O10 (FCTO) was observed only in composites having TO/CFO molar ratios equal to or larger than 2.2. The magneto-dielectric ceramic composites obtained can be classified by phases content in different classes with one of the starting CFO and /or TO always present; in the range of high CFO content the formation of CoTiO3 and Fe2O3 was detected. Magnetic permeability, dielectric permittivity (?') and losses (tan ?) were determined and correlated with the molar ratio of the dielectric and magnetic phases in the composite
Rhombohedral and Monoclinic Phases of PZT near the Antiferroelectric and the Morphotropic Boundaries
No full textAnelastic and dielectric spectroscopy measurements are presented, which, together with previous measurements [1], clarify some controversial aspects of the phase diagram of PbZr1-xTixO3 close to the border with the antiferroelectric (AFE) phase, and at the morphotropic phase boundary (MPB). No evidence is found of a border separating monoclinic (M) from rhombohedral (R) phases, supporting recent structural studies according to which the two phases coexist, with the fraction of M prevailing near the MPB. A large frequency independent softening at the MPB indicates a genuine M phase over only finely twinned R phase. A new phase transition is found in both the anelastic and dielectric spectra at x = 0.1, at a temperature T-IT between the Curie temperature T-C and the boundary T-T to the phases with tilted octahedra. Such a diffuse transition is interpreted as onset of disordered tilts, which finally become ordered below T-T. In this manner, the phase diagram of PZT is rationalised with respect to the common tendency of perovskites to undergo tilting when the mismatch between the cation sizes exceeds a threshold
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
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
