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Abstracts from the X INSTM National Conference on Materials Science and Technology
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Tuneable Permeability to H2, CO2, He, and Ar in Graphene Oxide−PDDA Self-Assembled Multilayers, Yielding Good Selectivity at High Flux
Full text linkToday, the most effective and suitable method to obtain molecular H2 is the
extraction from mixtures where it is present, using gas-sieving membranes.
To this aim, the preparation and characterization of layered nano-composites
are described, made of alternated layers of positively charged Poly(Diallyl
Dimethyl Ammonium chloride) (PDDA) and negatively charged graphene
oxide (GO) nanosheets with high and tunable selectivity for H2 purification.
The composites are assembled exploiting electrostatic interactions and the
layer-by-layer technique; this study correlates permeance tests with changes
in chemical composition and structure of the material using X-rays
Photoelectron Spectroscopy, X-rays diffraction water contact angle, and
surface zeta-potential measurements. Thanks to its layered nature, the
GO-PDDA composite shows an excellent selectivity, allowing faster
permeation of H2 as compared to CO2 and Argon. By transforming the GO to
reduced GO, the porosity of the nanosheets can be further increased, in this
way increasing the permeance of the material and its selectivity at the same
time, thus allowing to overcome the Robeson limit, the technological upper
boundary to the performance of actual membranes
Mixed Matrix Membranes based on PPO and graphene for gas separation
Full text linkNovel composite Mixed Matrix Membranes (MMM) were fabricated by dispersion of different loadings of graphene nanoparticles (from 0.3 to 15 % weight percentage) in a dense permeable glassy polymer, poly (2,6-dimethyl-1,4-phenylene oxide), PPO, by
solvent casting procedure. The permeability, selectivity and diffusivity of helium, nitrogen and carbon dioxide have been measured at two different temperatures, 35° and 65°C and the effect of graphene loading was studied. (R. Rea et al. 2018)
Graphene/Graphene Oxide stabilized polyvinylamine nanocomposite membranes for CO2 separation
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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
Permeability and Selectivity of PPO/Graphene Composites as Mixed Matrix Membranes for CO2 Capture and Gas Separation
Full text linkWe fabricated novel composite (mixed matrix) membranes based on a permeable glassy
polymer, Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), and variable loadings of few-layer graphene,
to test their potential in gas separation and CO2 capture applications. The permeability, selectivity
and diffusivity of different gases as a function of graphene loading, from 0.3 to 15 wt %, was measured
at 35 and 65 ◦C. Samples with small loadings of graphene show a higher permeability and
He/CO2 selectivity than pure PPO, due to a favorable effect of the nanofillers on the polymer
morphology. Higher amounts of graphene lower the permeability of the polymer, due to the
prevailing effect of increased tortuosity of the gas molecules in the membrane. Graphene also
allows dramatically reducing the increase of permeability with temperature, acting as a “stabilizer”
for the polymer matrix. Such effect reduces the temperature-induced loss of size-selectivity for He/N2
and CO2/N2, and enhances the temperature-induced increase of selectivity for He/CO2. The study
confirms that, as observed in the case of other graphene-based mixed matrix glassy membranes,
the optimal concentration of graphene in the polymer is below 1 wt %. Below such threshold,
the morphology of the nanoscopic filler added in solution affects positively the glassy chains packing,
enhancing permeability and selectivity, and improving the selectivity of the membrane at increasing
temperatures. These results suggest that small additions of graphene to polymers can enhance their
permselectivity and stabilize their propertie
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
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