1,721,037 research outputs found
New aqueous nanolime formulations for fully compatible consolidation treatments of historical mortars for hypogeum environment
No full textThe religious buildings characterizing by hypogea environments need of proper restoration interventions by using compatible materials. At now, organic and inorganic products proved to be inappropriate for this scope, in relation to the lack of chemical compatibility with the original substrate, to poor penetration depth and to the irreversibility of the treatments. Aim of this paper, is to present an innovative approach to safeguard the hypogea environment, by using new aqueous nanolime formulations, properly chemically tailored, for eco-friendly and green consolidation treatments. Phase composition, stability, and reactivity of the nanolime formulations were investigated, and chemical, petrographic and mechanical analyses of the mortar samples from the hypogeum were carried out. The treatments effectiveness was evaluated in terms of aesthetical features, superficial cohesion and mechanical improvement. The aqueous nanolime suspensions, pure and tailored, applied by airbrush, in-crease the superficial cohesion up to 95 % and improve the mechanical resistance of the surface and up to at least 1 cm in depth, without causing appreciable surface chromatic alterations
New nanolimes for eco-friendly and customized treatments to preserve the biocalcarenites of the “Valley of Temples” of Agrigento
No full textIn this paper we introduce new aqueous nanolime formulations, pure or properly chemically tailored, for innovative, compatible, and eco-friendly consolidation treatments on biocalcarenite stones, a renowned kind of stones used in ancient buildings throughout the Mediterranean region, which are however subject to severe decay. The phase composition, stability, and carbonation process of the nanolime formulations were investigated, while the treatments efficacy was evaluated in terms of aesthetical features, superficial cohesion, drilling resistance and durability. The aqueous nanolimes, applied by nebulization, increased the mechanical resistance on the surface and up to 2 cm in depth without appreciable surface variations, especially in the case of the tailored formulation, ensuring a good durability to UV/salt crystallization ageing
New sustainable, scalable and one-step synthesis of iron oxide nanoparticles by ion exchange process
Full text linkThis work introduces an innovative, sustainable, and scalable synthesis of iron oxides nanoparticles (NPs) in aqueous suspension. The method, based on ion exchange process, consists of a one-step procedure, time and energy saving, operating in water and at room temperature, by cheap and renewable reagents. The influence of both oxidation state of the initial reagent and reaction atmosphere is considered. Three kinds of iron nanostructured compounds are obtained (2-lines ferrihydrite; layered-structure iron oxyhydroxide δ-FeOOH; and cubic magnetite), in turn used as precursors to obtain hematite and maghemite NPs. All the produced NPs are characterized by a high purity, small particles dimensions (from 2 to 50 nm), and high specific surface area values up to 420 m2/g, with yields of production >90%. In particular, among the most common iron oxide NPs, we obtained cubic magnetite NPs at room temperature, characterized by particle dimensions of about 6 nm and a surface area of 170 m2/g. We also obtained hematite NPs at very low temperature conditions (that is 2 h at 200 °C), characterized by particles dimensions of about 5 nm with a surface area value of 200 m2/g. The obtained results underline the strength of the synthetic method to provide a new, sustainable, tunable, and scalable high-quality production
Nano Ca(OH)2 synthesis using a cost-effective and innovative method: Reactivity study
No full textCa(OH)2 nanoparticles in hydro-alcoholic dispersion (nanolime) are currently used for eco-compatible treatments of carbonate-based substrates in the field of Cultural Heritage conservation. Unfortunately, at present nanolime is synthesized by processes which present some drawbacks (considerable cost, multiple steps, low specific production yield), thus limiting the potential of its applications. We have developed a single-step procedure, based on an ion exchange process, making it possible to produce pure and crystalline Ca(OH)2 nanoparticles easily in water, at room temperature and ambient pressure, starting from cheap or renewable reactants. The simplicity of the process and its time- and energy-saving aspects are very promising factors for extending the production from laboratory to industrial scale. The aim of this paper is to investigate the structural and morphological features of the nanoparticles produced and to analyze the influence of crucial parameters of the synthesis process (i.e., time, water usage, reagent concentration and reaction volume) on the nanoparticles’ characteristics. The nanolime produced is investigated by XRD, FTIR, TEM, and AFM techniques. The nanoparticle reactivity in the carbonation process is also investigated, by varying the suspension concentration, the solvent and relative humidity conditions. Pure, crystalline, and very reactive Ca(OH)2 nanoparticles are obtained. The nanoparticles are constituted of thin lamellas, composed of primary hexagonal nanoparticles <10 nm, irrespective of time, water employed, reagents concentration, and reaction volume
Innovative and green nanolime treatment tailored to consolidate the original mortar of the façade of a medieval building in L'aquila (Italy)
No full textThis paper presents an original, green and compatible treatment to consolidate the pointing lime plastering of the façade of a medieval Italian palace, subjected to detachments and pulverization phenomena. The cohesion between the mortar constituents was refurbished by an aqueous nanolime suspension, synthesized by a cheap, time/energy-saving and scalable method, here originally tested on historic mortars. The suspension showed a high reactivity, assuring a complete carbonation in few hours, “restoring” the binder fraction with a new-formed network of calcite nanoparticles. The treatment efficacy was evaluated by chemico-physical, mineralogical and mechanical characterization both on untreated and treated specimens
Nano-sized Fe(III) oxide particles starting from an innovative and eco-friendly synthesis method
Full text linkThis paper introduces an original, eco-friendly and scalable method to synthesize ferrihydrite nanoparticles in aqueous suspensions, which can also be used as a precursor to produce α-hematite nanoparticles. The method, never used before to synthesize iron oxides, is based on an ion exchange process allowing to operate in one-step, with reduced times, at room temperature and ambient pressure, and using cheap or renewable reagents. The influence of reagent concentrations and time of the process on the ferrihydrite features is considered. The transformation to hematite is then analyzed and discussed in relation to different procedures: (1) A natural aging in the water at room temperature; and (2) heat treatments at different temperatures and times. Structural and morphological features of the obtained nanoparticles are investigated by means of several techniques, such as X-ray diffraction, X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, thermal analysis, nitrogen adsorption and magnetic measurements. Ferrihydrite shows the typical spherical morphology and a very high specific surface area of 420 m2 /g. Rhombohedral or plate-like hexagonal hematite nanoparticles are obtained by the two procedures, characterized by dimensions of 50 nm and 30 nm, respectively, and a specific surface area up to 57 m2 /g, which is among the highest values reported in the literature for hematite NPs
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
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