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Celia Marcos

Bio: Celia Marcos is an academic researcher from University of Oviedo. The author has contributed to research in topics: Vermiculite & Adsorption. The author has an hindex of 10, co-authored 26 publications receiving 423 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the vermiculites were divided into two types: type 1 (Sta. Olalla, Piaui and Goias) and type 2 (Piaui, Goias and Olalla).

138 citations

Journal ArticleDOI
TL;DR: In this paper, structural transformations between the different hydration states of three vermiculite samples from Sta. Olalla (Huelva, Spain), Paulistana (Piaui, Brasil) and West China, have been observed by X-ray diffraction at atmospheric pressure, P = 1.4610 ˇ2 mbar and P = 2.4 mbar.
Abstract: Structural transformations between the different hydration states of three vermiculite samples from Sta. Olalla (Huelva, Spain), Paulistana (Piaui, Brasil) and West China, have been observed by X-ray diffraction at atmospheric pressure, P = 1.4610 ˇ2 mbar and P = 2.4610 ˇ4 mbar. The samples were studied in flake and powder forms. The effect of vacuum has been proven to be the same as that of temperature, i.e. it causes dehydration of vermiculite, but with a different evolution through the different hydration states. In fact, under vacuum, the process seems to be inhibited at a one-water layer hydration state (1-WLHS), without a further dehydration of samples to a zero-water layer hydration state (0-WLHS). Furthermore, the dehydration process has been shown to occur through different interstratified states in each vermiculite. This result has been related to the interlayer Mg-cation content, due to its affinity to water molecules. The interstratified states have been analysed by the direct Fourier-transform method. The vermiculite from Sta. Olalla exhibits the most complex process, with formation of three different interstratified phases: two phases characterized by an interstratification of interplanar

50 citations

Journal ArticleDOI
TL;DR: In this paper, the 3D structure of Mg-vermiculite is described as a disordered stack of two types of 2D building blocks, which are made up of one talc-type layer and one interlayer space containing hydrated Mg 2+ cations.
Abstract: AB str A ct A sample of Mg-vermiculite from Santa Olalla (Spain) was studied by X-ray powder diffraction, electron microprobe, and thermo-gravimetry. The 3D structure is described as a disordered stack of two types of 2D building blocks, which are made up of one talc-type layer and one interlayer space containing hydrated Mg 2+ cations. We have succeeded in the refinement of both the atomic positions and occupancies of exchangeable cations and water molecules in the interlayer space of this vermiculite using the program package DIFFaX+. The position of the Mg 2+ cations is the only difference between the two layers. Besides the water molecules associated to the octahedrally coordinated Mg 2+ , we also located water molecules in the interlayer space. The structural analysis confirms that vermiculite is a semi-ordered crystalline material characterized by the existence of a large density of defects due to random ~±b/3 translations along the crystalline [010] direction. In this way, this structure can no longer be described by means of a unit cell repeated in 3D space. Instead, long-range order is only recognized in the a-b plane. The 3D structure is described by means of a recursive method.

45 citations

Journal ArticleDOI
TL;DR: In this article, the inorganic particulate matter of the PM10 and PM2.5 fractions sampled in the city of Oviedo, Spain, were identified using a Rietveld refinement of powder X-ray diffraction data.
Abstract: Mineral particles could have influenced on the climate of Oviedo, a non-industrial city situated in the centre of an industrial zone of the North of Spain, increasing the temperature and the precipitations, in spite of the fact that “greenhouse gases” concentrations have diminished in this city in recent years. The directive (1999/30/EC) of the European Commission began to be applied in Oviedo in the year 2003. In agreement with this norm, our first aim was the identification of the inorganic particulate matter of the PM10 and PM2.5 fractions sampled in this city. X-ray diffraction and scanning electron microscopy coupled with X-ray dispersive energy spectrometry were used. The percentages of the different mineral phases of the PM were obtained by a Rietveld refinement of powder X-ray diffraction data. The compositions of the PM10 and PM2.5 fractions of this city are similar. Sulphates are the most abundant particles in the both fractions. Most sulphates, nitrates and sal-ammoniac would have formed by reaction between solid, liquid and/or gas particles and they could be associated with the power stations near to the city and traffic. Wustite and haematites come from the iron and steel industries of Gijon and Aviles. The main natural sources of halite and carbonates and silicates are sea spray and soil resuspension by the wind, respectively.

42 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the chemical and thermal exfoliation of vermiculites from Santa Olalla (Huelva, Spain), Libby (Montana, USA) and Goias (Brasil), Brazil.

38 citations


Cited by
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Journal ArticleDOI
01 Oct 1971-Nature
TL;DR: Lipson and Steeple as mentioned in this paper interpreted X-ray powder diffraction patterns and found that powder-diffraction patterns can be represented by a set of 3-dimensional planes.
Abstract: Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

1,867 citations

Journal ArticleDOI
TL;DR: In this article, a review highlights the rational design and fabrication strategy for floating photocatalyst immobilized on various lightweight substrates (e.g., perlite, vermiculite, glass microbead, polymer, cork, expanded graphite) or self-floating photocatalysts.
Abstract: The light-harvesting and recycle of powder photocatalyst in suspended system are bottlenecks for high-efficient solar photocatalysis. Floating photocatalyst are highly sought-after and good candidates for practical environmental application due to the satisfaction with above requirements simultaneously. Over the past decades, floating TiO2-based photocatalysts have attracted much attention, which makes great progress and it is significant to review the recent advances. This review highlights the rational design and fabrication strategy for floating photocatalyst immobilized on various lightweight substrates (e.g. perlite, vermiculite, glass microbead, polymer, cork, expanded graphite) or self-floating photocatalyst. The special characteristics and deep understanding of photocatalytic mechanism for floating photocatalyst are summarized and discussed thoroughly. Moreover, the future research and challenge will focus on designing and optimizing the high-efficient broadband response floating photocatalyst to improve solar energy utilization. From an application viewpoint, floating photocatalyst have real practical applications in natural environment and are worthy of great attention.

372 citations

Journal ArticleDOI
TL;DR: In this paper, a modified exfoliated vermiculite (La5EV) was fabricated, characterized, and investigated for phosphate removal in batch tests for the first time, and the effect of initial phosphate concentration, contact time, temperature, pH, and coexisting ions on the adsorption capacity of La5EV was investigated in detail.

255 citations

Journal ArticleDOI
TL;DR: Self-assembled clay-based 2D nanofluidic channels with surface charge-governed proton conductivity are reported, which should prove useful to the study of confined ionic transport, and will enable new ionic device designs.
Abstract: Exfoliated two-dimensional (2D) sheets can readily stack to form flexible, free-standing films with lamellar microstructure. The interlayer spaces in such lamellar films form a percolated network of molecularly sized, 2D nanochannels that could be used to regulate molecular transport. Here we report self-assembled clay-based 2D nanofluidic channels with surface charge-governed proton conductivity. Proton conductivity of these 2D channels exceeds that of acid solution for concentrations up to 0.1 M, and remains stable as the reservoir concentration is varied by orders of magnitude. Proton transport occurs through a Grotthuss mechanism, with activation energy and mobility of 0.19 eV and 1.2 × 10(-3) cm(2) V(-1) s(-1), respectively. Vermiculite nanochannels exhibit extraordinary thermal stability, maintaining their proton conduction functions even after annealing at 500 °C in air. The ease of constructing massive arrays of stable 2D nanochannels without lithography should prove useful to the study of confined ionic transport, and will enable new ionic device designs.

199 citations

Journal ArticleDOI
TL;DR: In this paper, 2D additives using few-layer vermiculite clay sheets as an example to comprehensively upgrade poly(ethylene oxide)-based solid polymer electrolyte are introduced.
Abstract: Lithium ion batteries are now the dominant power for electronics and will change the power supply for vehicles and help to smoothly integrate renewable energy sources such as solar and wind to grid. In lithium ion batteries with liquid electrolytes, the organic solvents are flammable and unstable at high voltage. Especially in lithium metal batteries (LMB) where lithium dendrites can grow, the solvents can be ignited once the dendrites shortcircuit with the cathodes. To meet the high energy density and safety requirement, it is desirable to develop solid state electrolytes with high stability and mechanical strength. The solid state electrolytes can be classified into two categories: inorganic electrolytes and solid polymer electrolytes (SPE). Inorganic electrolytes typically have ionic conductivity at room temperature (10−2–10−4 S cm−1) close to or even higher than liquid electrolyte. However, their stiffness and friability result in poor film processability and high interface resistance with electrodes.[1–7] SPE are composed of lithium salts dissociated in the polymer matrix in which Li+ is allowed to transport along with the segment motion of the polymer chains. As a result, SPE are stretchable and flexible, and thus compatible with the current film-based battery technology. However, the low ionic conductivity (<10−6 S cm−1) of SPE at ambient temperature and high-temperature instability restrict their wide utilization.[8–15] Great efforts have been devoted to improving the performance of SPE. Increasing the content of Li salts or decreasing the crystallinity of polymers with composite polymers or block copolymers were able to increase the ionic conductivity by orders of magnitude.[16–18] However, other properties of SPE such as the film forming property were decreased, leading to poor mechanical strength and thermal resistance. A successful strategy was rigid-flexible coupling that applied cellulose nonwoven to support the softened SPE.[11] Another widely employed approach is to add ceramic fillers which can interact with both the salt anions and the polymer segments to promote local amorphization and enhance Li+ transport.[19–24] Accordingly, the interaction can be tailored by screening fillers with Solid state electrolytes are the key components for high energy density lithium ion batteries and especially for lithium metal batteries where lithium dendrite growth is an inevitable obstacle in liquid electrolytes. Solid polymer electrolytes based on a complex of polymers and lithium salts are intrinsically advantageous over inorganic electrolytes in terms of processability and film-forming properties. But other properties such as ionic conductivity, thermal stability, mechanical modulus, and electrochemical stability need to be improved. Herein, for the first time, 2D additives using few-layer vermiculite clay sheets as an example to comprehensively upgrade poly(ethylene oxide)-based solid polymer electrolyte are introduced. With clay sheet additives, the polymer electrolyte exhibits improved thermal stability, mechanical modulus, ionic conductivity, and electrochemical stability along with reduced flammability and interface resistance. The composite polymer electrolyte can suppress the formation and growth of lithium dendrites in lithium metal batteries. It is anticipated that the clay sheets upgraded solid polymer electrolyte can be integrated to construct high performance solid state lithium ion and lithium metal batteries with higher energy and safety.

197 citations