1,720,959 research outputs found
Low temperature upcycling of vitreous byproduct of the MSW plasma processing into multifunctional porous glass-ceramics
Full text linkMixtures of glass residues, deriving from the plasma processing of municipal solid waste (‘Plasmastone’), and recycled glasses have been already converted into highly porous glass-ceramics by application of an inorganic gel casting technique (foaming, by intensive mechanical stirring, of alkali activated slurries) followed by sintering at 1000°C. The full potential of recycled glass, however, has not been disclosed yet. The present investigation, in fact, demonstrates that boro-alumino-silicate glass, from discarded pharmaceutical vials, may allow for sintering of cellular glass-ceramics at particularly low temperature, i.e. at 800°C. The full stabilisation of heavy metals from Plasmastone (already assessed for treatments at 1000°C) is not compromised, whereas the low processing temperatures favour the separation of magnetite, in turn imparting new functionalities (e.g. electromagnetic shielding) to waste-derived glass-ceramic foams
Case studies of up-cycling of partially crystallized ceramic waste in highly porous glass-ceramics
Full text linkHighly porous glass-based materials represent a solution for thermal insulation. However, the manufacturing costs still affect their extensive use. The present investigation proposes savings in the production of foams by use of discarded materials, such as polishing residue or vitrified asbestos-containing waste, minimizing additives and processing temperatures. Aqueous suspensions of powders, mixed with soda-lime glass, underwent progressive gelation due to alkali activation. An extensive foaming was determined by mechanical stirring, with the help of a surfactant. Finally, a firing step yielded foams exhibiting excellent strength-to-density ratios, due to densification and control of crystal phases, both supported by the glass addition
Waste-derived glass-ceramics fired in nitrogen: Stabilization and functionalization
Full text linkIn a circular economy perspective, waste-derived materials are attractive once the adopted manufacturing technology combines low costs, absolute stabilization of pollutants and interesting functionalities of the product. This paper deals with the enhancement of chemical stability and functionalities of highly porous glass-ceramic foams, from vitreous residues the plasma processing of municipal solid waste (‘Plasmastone’), by firing in nitrogen, at 800–1000 °C. Before firing, the processing relied on alkali activation of glass suspensions, followed by intensive mechanical stirring. Previous experiments had demonstrated that the stabilization of pollutants could be achieved only by mixing Plasmastone with 30 wt% recycled boro-alumino-silicate glass, in samples fired in air. The change in the atmosphere had a significant impact on the Fe2+/Fe3+ balance, leading to a different phase assemblage, in turn causing the stabilization of pollutants even operating with more common recycled soda-lime glass. The new phase assemblage also promoted functionalities such as electrical conductivity, relative permittivity and electromagnetic shielding effectiveness
Dense glass-ceramics by fast sinter-crystallization of mixtures of waste-derived glasses
Full text linkDense glass‐ceramics were obtained by cold pressing and sinter‐crystallization of a glass originated from the plasma gasification of municipal solid waste (“Plasmastone”) mixed with recycled soda‐lime glass and kaolin clay. The optimum mixture featured 45% Plasmastone/45% soda‐lime glass/10% kaolin clay and it was sintered according to a fast heat treatment (30 minutes at 1000°C with heating and cooling rates of approximately 40°C/min), mimicking that of industrial ceramic tiles. The fast treatment avoided extensive crystallization during heating, promoting the viscous flow. In this way, dense glass‐ceramics with a water absorption below 0.7% could be produced. The developed tiles presented mechanical properties comparable to those of commercial ceramic tiles. Finally, the environmental impact assessment performed on these materials showed that the leaching of hazardous elements was particularly limited. Microprobe analyses indicated that heavy metals were incorporated in newly formed crystals, consisting mainly of hedenbergite, wollastonite, and iron oxide‐rich “islands” surrounded by residual glass. The results show that Plasmastone, combined with recycled soda‐lime glass and kaolin clay, may be converted in building materials, with a possible commercial exploitation
Porous glass-ceramics made from microwave vitrified municipal solid waste incinerator bottom ash
No full textGlobal warming and depletion of resources have fueled research towards innovative building materials of low environmental impact and high performance engineering properties. Porous glass-ceramics were synthesized using municipal solid waste incinerator (MSWI) bottom ash (BA) as a starting material. BA was initially milled and then vitrified, as a purification step, by direct microwave heating, characterized by a high glass yield. Highly porous glass-ceramics were produced by intensive mechanical stirring of vitrified bottom ash (VBA) aqueous suspensions under weak alkali activation (1 M NaOH and 2.5 M NaOH) and sinter-crystallization at 800 °C or 900 °C. The obtained glass ceramics, with up to 70 vol% porosity, exhibited compressive strength well above 1 MPa, being comparable to lightweight construction materials, such as aerated concrete. High relative permittivity was measured for the 10 wt% soda-lime glass doped porous VBA material sintered at 800 °C, paving the way for its use as a potential semiconductor catalyst
New glass-based binders from engineered mixtures of inorganic waste
No full textAluminum is one of the most important strategic resources, but the Bayer process, typically applied for the purification of ores, leads to vast amounts of alkaline slurry waste, known as red mud. Though interesting for potential reprocessing, red mud is still predominantly stored in big slurry pools, due to high levels of toxic metals. Toxic ions can be easily immobilized by vitrification, but the high costs of this solution need to be balanced by the reuse of the obtained glass. The present paper is dedicated to the transformation of waste-derived glass into new binders for the construction industry, according to both “conventional melting” and “smelting” approaches. In the first case, red mud was included in a mixture of waste, designed to yield a reactive glass (CMG), that is, forming stable gels after activation in an alkaline aqueous solution. In the second approach, red mud was subjected to a thermal treatment in a reductive atmosphere, implying the separation of molten iron alloy. The remaining glassy slag, according to its chemical composition (CaO and Al2O3-rich) underwent gelation by simple interaction with pure water, without any alkaline activator, thus configuring a new “glass cement.”
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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