J. Appl. Cryst.の発刊に際して

It is possible to say that zeolites are the most widely used catalysts in industry They are crystalline microporous materials which have become extremely successful as catalysts for oil refining, petrochemistry, and organic synthesis in the production of fine and speciality chemicals, particularly when dealing with molecules having kinetic diameters below 10 A The reason for their success in catalysis is related to the following specific features of these materials:1 (1) They have very high surface area and adsorption capacity (2) The adsorption properties of the zeolites can be controlled, and they can be varied from hydrophobic to hydrophilic type materials (3) Active sites, such as acid sites for instance, can be generated in the framework and their strength and concentration can be tailored for a particular application (4) The sizes of their channels and cavities are in the range typical for many molecules of interest (5-12 A), and the strong electric fields2 existing in those micropores together with an electronic confinement of the guest molecules3 are responsible for a preactivation of the reactants (5) Their intricate channel structure allows the zeolites to present different types of shape selectivity, ie, product, reactant, and transition state, which can be used to direct a given catalytic reaction toward the desired product avoiding undesired side reactions (6) All of these properties of zeolites, which are of paramount importance in catalysis and make them attractive choices for the types of processes listed above, are ultimately dependent on the thermal and hydrothermal stability of these materials In the case of zeolites, they can be activated to produce very stable materials not just resistant to heat and steam but also to chemical attacks Avelino Corma Canos was born in Moncofar, Spain, in 1951 He studied chemistry at the Universidad de Valencia (1967−1973) and received his PhD at the Universidad Complutense de Madrid in 1976 He became director of the Instituto de Tecnologia Quimica (UPV-CSIC) at the Universidad Politecnica de Valencia in 1990 His current research field is zeolites as catalysts, covering aspects of synthesis, characterization and reactivity in acid−base and redox catalysis A Corma has written about 250 articles on these subjects in international journals, three books, and a number of reviews and book chapters He is a member of the Editorial Board of Zeolites, Catalysis Review Science and Engineering, Catalysis Letters, Applied Catalysis, Journal of Molecular Catalysis, Research Trends, CaTTech, and Journal of the Chemical Society, Chemical Communications A Corma is coauthor of 20 patents, five of them being for commercial applications He has been awarded with the Dupont Award on new materials (1995), and the Spanish National Award “Leonardo Torres Quevedo” on Technology Research (1996) 2373 Chem Rev 1997, 97, 2373−2419

From Microporous to Mesoporous Molecular-Sieve Materials and Their Use in Catalysis

Research Development on Sodium-Ion Batteries

The status of ambient temperature sodium ion batteries is reviewed in light of recent developments in anode, electrolyte and cathode materials. These devices, although early in their stage of development, are promising for large-scale grid storage applications due to the abundance and very low cost of sodium-containing precursors used to make the components. The engineering knowledge developed recently for highly successful Li ion batteries can be leveraged to ensure rapid progress in this area, although different electrode materials and electrolytes will be required for dual intercalation systems based on sodium. In particular, new anode materials need to be identified, since the graphite anode, commonly used in lithium systems, does not intercalate sodium to any appreciable extent. A wider array of choices is available for cathodes, including high performance layered transition metal oxides and polyanionic compounds. Recent developments in electrodes are encouraging, but a great deal of research is necessary, particularly in new electrolytes, and the understanding of the SEI films. The engineering modeling calculations of Na-ion battery energy density indicate that 210 Wh kg−1 in gravimetric energy is possible for Na-ion batteries compared to existing Li-ion technology if a cathode capacity of 200 mAh g−1 and a 500 mAh g−1 anode can be discovered with an average cell potential of 3.3 V.

Sodium‐Ion Batteries

A brief history and review of geopolymer technology is presented with the aim of introducing the technology and the vast categories of materials that may be synthesized by alkali-activation of aluminosilicates. The fundamental chemical and structural characteristics of geopolymers derived from metakaolin, fly ash and slag are explored in terms of the effects of raw material selection on the properties of geopolymer composites. It is shown that the raw materials and processing conditions are critical in determining the setting behavior, workability and chemical and physical properties of geopolymeric products. The structural and chemical characteristics that are common to all geopolymeric materials are presented, as well as those that are determined by the specific interactions occurring in different systems, providing the ability for tailored design of geopolymers to specific applications in terms of both technical and commercial requirements.

Geopolymer technology: the current state of the art

An XRD Study of the Effect of the SiO2/Na2O Ratio on the Alkali Activation of Fly Ash

A layered sodium manganese oxide, Na0.6MnO2, stable at temperatures above 800 °C, was synthesized by using a sol–gel method that employs Mn(acac)3
(ac = acetylacetonate), Na2CO3 and propionic acid to form the resin framework. This layered bronze possesses a hexagonal, P2-type structure, in which the distortion associated with Mn3+ is hardly perceptible. It reacts slowly, though reversibly, with atmospheric moisture, which causes the interlayer spacing in the structure to increase by ca. 2.5 A, through intercalation of water molecules into the interlayer gap occupied by Na+ ions. The anhydrous material was tested as a cathode in sodium cells. Although the electrochemical intercalation of Na+ occurs in two steps, the host retains its main structural features, with a slight tendency in the interlayer spacing to contract as the
sodium content increases. The similarity between the discharge and charge profiles of the first cycles reveals a quasi-reversible nature in the intercalation process and that the cell can deliver a constant specific capacity of ca. 140 A h kg−1 at 0.1 mA cm−2 when cycled in a voltage window of 3.8–2.0 V. However, the continuous strains and distortions resulting from the insertion and extraction of Na+ ions cause the host structure to gradually collapse and yield an amorphous material after the first eight cycles. This leads to a progressive reduction of the cell capacity, irrespective of the specific voltage window used.

http://www.biblioteca.uma.es/bbldoc/articulos/16639959.pdf

Synthesis and characterization of high-temperature hexagonal P2-Na0.6 MnO2 and its electrochemical behaviour as cathode in sodium cells

A procedure for Rietveld quantitative amorphous content analysis (RQACA) is outlined, in which the effects of systematic errors in the powder patterns are studied. The method derives the amorphous content from the small overestimation of an internal crystalline standard in a Rietveld refinement of an appropriate mixture. Of several standards studied, Al2O3 gave the best results. The statistical analysis of standard mixtures with a known amount of amorphous content indicated that this is a precise and accurate tool. It enables the measurement of the amorphous content with an accuracy close to 1%. Sample preparation and Rietveld analysis need to be optimized in order to minimize the systematic errors. The analysis of samples with phases displaying strong preferred orientation effects gives very high errors in the amorphous content. Samples with different absorption coefficients have also been studied in order to evaluate the importance of microabsorption. This plays an important role but it can be adequately corrected if the absorption coefficients of the standard and the sample are not very different. RQACA has been applied to tricalcium silicate, C3S, which is the main component of Portland cement. The average amorphous content of C3S, after microabsorption correction using two standards of higher and lower absorption coefficients, was found to be 19%.

Rietveld quantitative amorphous content analysis

The La10 − x(SiO4)6O3 − 1.5x
				(9.33 ≤ 10 − x
				≤ 9.73) apatite series has been prepared and hexagonal single phases were obtained in a narrow compositional range (9.33 ≤ 10 − x
				≤ 9.60). The room temperature crystal structure of La9.55(SiO4)6O2.32 has been determined from joint Rietveld refinement of neutron and laboratory X-ray powder diffraction data: a
				= 9.7257(1)
				A, c
				= 7.1864(1)
				A, V
				= 588.68(1)
				A3, Z
				= 1, RwpN
				= 3.2%, RwpX
				= 7.7%, RFN
				= 1.8%, RFX
				= 1.9%. An interstitial site for the extra-oxygen has been determined in the position very recently predicted in a theoretical study using atomistic simulations. The high temperature crystal structures have been obtained from neutron powder diffraction, NPD, collected at 773 and 1173 K showing the thermal evolution of this interstitial site. Previously reported neutron data for La9.60(GeO4)6O2.40 have also been re-analysed establishing the existence, and thermal evolution, of this interstitial site. The electrical results suggest that the samples are oxide ion conductors. The plots of the imaginary parts of the impedance, Z″, and the electric modulus, M″, vs. log (frequency), possess maxima for both curves separated by two decades in frequency. Bulk conductivities have been obtained from the fitting of the complex impedance spectra with the appropriate equivalent circuit. Bulk activation energies have been determined from two Arrhenius plots, one representing the bulk conductivities and the other representing the frequencies of the modulus peak maxima, fmax(M″). A comparative discussion of the two series, La10 − x(TO4)6O3 − 1.5x
				(T = Si, Ge), is given.

http://atarazanas.sci.uma.es/docs/articulos/16512595.pdf

Interstitial oxygen conduction in lanthanum oxy-apatite electrolytes

http://atarazanas.sci.uma.es/docs/tesisuma/16604325.pdf

Miguel A. G. Aranda

Papers

An XRD Study of the Effect of the SiO2/Na2O Ratio on the Alkali Activation of Fly Ash

Synthesis and characterization of high-temperature hexagonal P2-Na0.6 MnO2 and its electrochemical behaviour as cathode in sodium cells

Rietveld quantitative amorphous content analysis

Interstitial oxygen conduction in lanthanum oxy-apatite electrolytes

Quantitative determination of phases in the alkali activation of fly ash. Part I. Potential ash reactivity