We argue that the collinear 4-point probe is unsuitable for measuring in-plane and through-plane electrical conductivity of graphite-polymer composite plates, and strongly recommend the 4-wire Kelvin measurement system with parallel block electrodes. Regarding the latter, we report the effect of applied pressure on the cell resistance and determine the offset resistance in the measurement system at 69 bar by extrapolating the cell resistance for a series of graphite monoliths of different thicknesses to zero thickness. We show that the fringe field effect increases the conductance of the cell, and ipso facto the conductance of the sample plate, when the cross-sectional area of the sample plate exceeds that of the block electrodes. An evaluation of the measurement uncertainty of the through-plane electrical conductivity, shows that the uncertainty of the through-plane resistance of the two gas diffusion layers (carbon fibre mat) and their interfacial contact resistance with the sample and electrodes whilst under compression (collectively referred to here as the 'offset resistance') is the major contributor. This article complements the US Fuel Cell Council's protocol 05-160 and the Keithley White Paper (No. 2399) in establishing an effective measurement procedure to enable a more reliable comparison of conductivity data.

The growing societal and political focus on the use of environmentally friendly technologies has led to an ever-increasing interest in electrolysis technologies in the scientific communities. This development is reflected by the plethora of candidate catalysts for the hydrogen and oxygen evolution reactions, as well as the CO2 reduction reaction, reported in the literature. However, almost none of them entered the stage of application yet. Likewise, the reports on process engineering inadequately address the utilization of these catalysts, as well as electrode and cell concepts, that might be suitable for the market. Evidently, a closer collaboration between chemists and engineers from industry and academia is desirable to speed up the development of these disruptive technologies. Herein, we elucidate the critical parameters and highlight the necessary aspects to accelerate the development of industrially relevant catalysts capable of fulfilling the forthcoming challenges related to energy conversion and storage. The aim of this Perspective, composed by industrial and academic partners, is to critically question current undertakings and to encourage researchers to strike interdisciplinary research pathways.

Cu2Mo10O30 was prepared as a monophasic material comprising dark blue platy crystals by reacting Cu with MoO 3 under argon at 550 degrees C. Single-crystal X-ray diffractometry showed that Cu2Mo10O30 is a stoichiometric compound that crystallizes with a monoclinic (C2/c) cell: a = 16.6359(6); b = 9.3112(3); c = 27.1597(9) angstrom; beta = 102.621(3)* (Z = 8). Electron paramagnetic resonance spectroscopy revealed that Cu2Mo10O30 displays mixed-valency; ((Cu2-xCuxII)-Cu-I)((Mo2+xMo8-xVI)-Mo-v)O-30 (0 << x <= 2). Differential scanning calorimetry and in situ hightemperature powder X-ray diffractometry showed that Cu2Mo10O30 decomposes greater than or similar to 550 degrees C under an inert atmosphere. Dark blue acicular crystals of CuMo9O26 were discovered as a side-product in materials prepared inside evacuated glass ampoules at 500 degrees C. Single-crystal X-ray diffractometry showed these to crystallize with an orthorhombic (Pmmn) cell: a = 3.74190(10); b = 26.4941(4); c = 9.15300(10) angstrom; (Z = 2). Rietveld refinement of the powder X-ray diffraction data for these materials revealed Cu2Mo10O30 with minor CuMo9O26 and `Cu0.1MoO3'.

Thermal gravimetric analysis and in situ high-temperature powder X-ray diffraction (HT-PXRD) revealed that MnSO4 begins to thermally decompose under air at similar to 625 degrees C, which is significantly lower than the values reported in the literature. The reaction is kinetically sluggish and yields bixbyite, Mn2O3, greater than or similar to 625 degrees C and hausmannite, Mn3O4, greater than or similar to 850 degrees C. Na6Mn2[Al6Si6O24](SO4)(2) was prepared as a novel sodalite-type phase by reacting zeolite A, Na-6[Al6Si6O24], with MnSO4 as a compacted mixed-powder monolith at 650 degrees C under air. In situ HT-PXRD indicated that this reaction commenced at about 620 degrees C. Rietveld refinement of the PXRD data recorded at 20 degrees C showed that Na(6)Ma(2)[Al6Si6O24](SO4)(2) crystallizes with a cubic cell, a = 0.89780(2) nm, and is isostructural (I (4) over bar 3m) with the mineral hauyne, Na6Ca2[Al6Si6O24](SO4)(2). The product material contained traces of Mn2O3 which imparts a purplish-brown coloration; highlighting the problem of preparing Na6Mn2[Al6Si6O24](SO4)(2) as a monophasic material within the narrow temperature 'window' available for this reaction.

Self-propagating high-temperature synthesis is an effective method for preparing refractory ceramic materials, especially carbides and borides as fine powders. The common perception that a pressurized stainless steel reactor is necessary for conducting the synthesis has, until now, excluded it from undergraduate laboratory courses. Our students performed this synthesis using a simple and inexpensive wooden block reactor to prepare TiC, using TiO2, C and Mg as the reactants. The product at this stage is contaminated with Mg2TiO4 which forms through a side-reaction during this highly exothermic reaction. The factors that caused this provoked a stimulating class discussion and led to a method for recovering the TiC as a monophasic powder. The crude and purified product materials were characterized by powder X-ray diffraction. All in all, these aspects make this synthesis an ideal experiment for undergraduate laboratory in chemistry or materials science courses. Moreover, the skills and methods learned through this experiment ensure that students are better equipped to tackle the self-propagating high-temperature synthesis of more complex carbides and refractory ceramic materials in conventional reactors.

Zeolite Y has an iconic crystal structure, but more importantly, the hydrogen modification zeolite H-Y is the classic example of a solid acid which is used extensively as a catalyst in the oil industry. This metastable compound cannot be synthesized directly, which creates an opportunity to discuss various preparative strategies with the students, such as the three -stage procedure described here. Stage I concerns the hydrothermal synthesis of zeolite Na Y, followed by ion -exchange with an ammonium acetate solution to form zeolite NH4-Y, and the latter is subsequently converted to zeolite H-Y by thermolysis. Stages II and III may instead be performed using commercially available zeolites, Na-Y and NH4-Y, respectively, which shifts the learning objectives to structural characterization of zeolites. The characterization of the product and intermediate materials gives the students a practical insight into the applicability and limitations of powder X-ray diffraction, solid-state nuclear magnetic resonance spectroscopy, and thermogravimetric analysis, and how these analytical tools complement each other. These aspects make its synthesis and characterization an ideal practical exercise for an upper -level undergraduate laboratory in inorganic or materials chemistry courses. Moreover, the methods and skills learned during this experiment enable the students to tackle more complex zeolites and related framework materials.

A series of copper rods were reacted with sulfur vapour in evacuated glass ampoules at similar to 445 degrees C. Product materials were characterised by powder X-ray diffraction and reflected polarised light microscopy. Copper sulfurised rapidly to digenite, gamma-Cu2-xS, under these conditions, whereas the subsequent sulfurisation to covellite, CuS, was notably slower, yielding texturally distinguishable inner (secondary) and outer (primary) CuS regions. A two-stage partial sulfurisation of gamma-Cu1.8S resulted in the external growth of two successive layers of primary CuS, which demonstrates decisively that covellite - besides being a p-type metal - is ionically conducting at 445 degrees C, although considerably less so than digenite. We infer that the growth of platy covellite crystals and their radial alignment in the primary CuS layer are a consequence of copper ion mobility being restricted to the basal plane of the covellite structure. Sulfurising a coil of copper wire at similar to 445 degrees C is an effective method for synthesising covellite. (C) 2017 Elsevier Masson SAS. All rights reserved.

Trace amounts of copper have advantageous effects when creating macroporous silicon carbide monoliths to be used for combined diesel particle filter and catalyst support systems. These structures were produced from a slurry of silicon, graphite, aluminium and copper. Mixed with water, extruded and dried, the resulting bodies were pyrolyzed, sintered, and then partially oxidized, to yield a mechanically stable porous 4H-SiC microstructure with an average pore diameter of 20 μm and average accessible porosity of 57%. The Cu alloys with the Si and Al to create the sintered body via a liquid phase, and prevents the build-up of undesirable Al-containing ternary carbide crystals in the microstructure. The Cu promotes oxidation of SiC to form a 80 nm SiO2 layer that serves as a good catalyst support. The accelerated oxidation can be intercepted by dissolving the Cu component from the monoliths with an acid solution.

Addition of 5 at.% aluminium to silicon and carbon in the process of forming SiC monoliths for use as diesel particle filters and catalyst supports, creates mechanically stable, well connected, and highly porous 4H-SiC structures. These monoliths have 65% accessible porosity with pore diameters of 17−20μm. Mixtures of silicon, graphite, aluminium and water, are extruded into honeycomb structures and heated under nitrogen and argon. The 2H-AlN crystalline assembly formed during initial heating under nitrogen at 850°C acts as a template for the subsequent reaction between silicon and graphite under argon to yield 3C-SiC. During a final high temperature step under argon at 1950°C, Al-vapour/liquid is crucial for the transformation of 3C-SiC to 4H-SiC. This final step also alters the SiC crystal morphology significantly and produces large by-product crystals of Al4C3·mSiC·nAlN. The polytypic conversion and recrystallization mechanism were found, in this case, to be independent phenomena.

Phosphate (Pi) sequestration by a lanthanum (La) exchanged clay mineral (La-Bentonite), which is extensively used in chemical lake restoration, was investigated on the molecular level using a combination of 31P and 139La solid state NMR spectroscopy (SSNMR), extended X-ray absorption spectroscopy (EXAFS), powder X-ray diffraction (PXRD) and sorption studies. 31P SSNMR show that all Pi was immobilized as rhabdophane (LaPO4·n H2O, n ≤ 3), which was further supported by 139La SSNMR and EXAFS. However, PXRD results were ambiguous with respect to rhabdophane and monazite (LaPO4). Adsorption studies showed that at dissolved organic carbon (DOC) concentration above ca. 250 μM the binding capacity was only 50% of the theoretical value or even less. No other La or Pi phases were detected by SSNMR and EXAFS indicating the effect of DOC is kinetic. Moreover, 31P SSNMR showed that rhabdophane formed upon Pi sequestration is in close proximity to the clay matrix.

AbstractThe Cu+ solid electrolyte Cu2ScZr(PO4)3 is prepared by solid state reaction of a stoichiometric mixture of CuO, Sc2O3, Zr2O3, and NH4H2PO4 (1.

The title compound, with nominal formula Cu(2)ScZr(PO(4))(3), has a beige coloration and displays fast Cu(+) cation conduction at elevated temperatures. It adopts a NASICON-type structure in the space group R3c. The examined crystal was an obverse-reverse twin with approximately equal twin components. The [Sc(III)Zr(IV)(PO(4))(3)](2-) framework is composed of corner-sharing Sc/ZrO(6) octahedra and PO(4) tetrahedra. The Sc and Zr atoms are disordered on one atomic site on a crystallographic threefold axis. The P atom of the phosphate group lies on a crystallographic twofold axis. Nonframework Cu(+) cations occupy three positions. Two of the Cu(+) positions generate an approximately circular distribution around a site of 3 symmetry, referred to as the M1 site in the NASICON-type structure. The other Cu(+) position is situated close to the twofold symmetric M2 site, displaced into a position with a distorted square-based pyramidal coordination geometry. The structure has been determined at 100, 200 and 300 K. Changes in the refined site-occupancy factors of the Cu(+) positions suggest increased mobility of Cu(+) around the circular orbit close to the M1 site at room temperature, but no movement into or out of the M2 site. Free refinement of the Cu site-occupancy factors suggests that the formula of the crystal is Cu(1.92(1))ScZr(PO(4))(3), which is consistent with the low-level presence of Cu(2+) exclusively in the M2 site.

For many years SiC has been investigated because many of its properties render it superior to other ceramic materials in many aspects. Silicon carbide is thermally stable at high temperatures, has a high fracture strength and toughness [1-5], is chemically inert and is semiconducting, withstanding high voltage and high frequency, making it ideal for harsh environment applications [2,5,11]. SiC has been produced in more than 250 different polytypes only differing in the stacking sequence, but showing unequal properties [3,4,7,8]. The reason for the polytypic growth and the kinetics behind this has not yet been fully understood and the properties of the different polytypic structures are still being investigated. SiC exist in the cubic structure, 3C-SiC, also referred to as β-SiC and with hexagonal structure, α-SiC. The β structure has been considered to be the low-temperature polymorph of SiC, but extensive studies over the years have revealed that it is a metastable phase of SiC [3,6,7,8,9]. The α-SiC has been shown to exist in more than 250 different polytypes, though it is mainly produced as the 6H polytype under heat treatment [2,3,10,11]. As an exception, heat treatment of a mixture of Si, C and Al grains under Ar results in the 4H polytype [10, 11]. This ternary system, Al-Si-C, was studied under different circumstances to find an explanation for the polytypic recrystallization of 3C-SiC into the 4HSiC under these alloying conditions. We have heated pure silicon, carbon and 5%wt aluminum ~40 micron grains in several steps and characterized the results after each step to determine the kinetics and the role of aluminum on the production and recrystallization of SiC. The mixture was first pyrolyzed and then heated under vacuum to the temperature where β-SiC is produced at 1450°C in Argon atmosphere. For the conversion from β to α-SiC the temperature is raised to 1950°C for 2h followed by a subsequent cool down, also under Ar. The result is a porous structure of interconnected flake-like hexagonal 4H-SiC crystals and a waste product deposited on the cooler parts of the furnace, as yellow hexagonal flake-like crystals of ternary carbides. The elemental aluminum plays the role of solvent and diffusion agent under the ceramization process as a quasi-liquid phase and in the conversion process as promoter for the polytypic conversion from 3C-SiC to highly crystalline 4H-SiC by the formation of Al4SiC4. The hexagonal SiC structure shows 2D-nucleation growth in the 0001 direction and multiple twinning due to dislocation in the crystal presumably produced by impurities. The 3C polytype was favored when exchanging the atmosphere during conversion with N2. The purpose of this work is to clarify the subject of polytypic crystal growth exemplified by the above described conversion and deduced mechanisms. [1] Ortiz A, Munoz-Bernabe A, Borrero-Lopez O, Domınguez-Rodrıguez A, Guiberteau F, Padture N. J. Eur. Ceramic Soc. 24 (2004) 3245-3249 [2] Abderrazak H, Hmida E. Silicon Carbide: Synthesis and Properties, Properties and Applications of Silicon Carbide, Prof. Rosario Gerhardt (Ed.), ISBN: 978-953-307-201-2, InTech, DOI: 10.5772/15736, 2011 [3] Verma R, Krishna P. Polymorphism and Polytypism in Crystals. John Wiley. New York, USA, 1966 [4] Kippenberg W. Research Rep. 18 (1963) 161-174 [5] Park Y. SiC Materials and Devices. Academic Press. San Diego, USA, 1998 [6] Sharma M, Upadhyay R, Amritphale S, Chandra N. Materials Let. 65 (2011) 2161-2164 [7] Fissel A. J. Crystal Growth 212 (2000) 438-450 [8] Fissel A. Int. J. Inorganic Materials 3 (2001) 1273-1275 [9] Semmelroth K, Shultze N, Pensl G. J. Phys. Condense Matter 16 (2004) S1597-S1610 [10] Lundqvist D. Acta Chemica Scan. 2 (1948) 177-191 [11] Onbattuvelli V, Atre S. Materials and Manufacturing Pro. 26 (2011) 832-845

Na6Zn2[Al6Si6O24](SO4)2 was prepared as a stoichiometric phase by reacting zeolite A with ZnSO4 at 700°C for 8h. Powder-XRD showed that Na6Zn2[Al6Si6O24](SO4)2 crystallised with the sodalite structure, a=8.923(1)Å, Z=1; illustrating that Zn2+ can be substituted for Ca2+ in ideal haüyne, Na6Ca2[Al6Si6O24](SO4)2. Na6Zn2[Al6Si6O24](SO4)2 was shown to be largely immiscible with nosean, Na8[Al6Si6O24]SO4 in the solid-state. Na6Zn2[Al6Si6O24](SO4)2 decomposes above 700°C, yielding nosean, Na8[Al6Si6O24]SO4; willemite, Zn2SiO4; gahnite, ZnAl2O4; and presumably a glass phase, 2Na2O·9SiO2; with the loss of gaseous SO3. Na6Zn2[Al6Si6O24](SO4)2 was annealed under hydrogen at 700°C, yielding sphalerite, ZnS and a more voluminous sodalite, Na6[AlSiO4]6 (a=9.068(1)Å, Z=1). Solid-state NMR indicates that the aluminosilicate framework remains essentially unchanged (according to the 29Si and 27Al) throughout this reaction, with the largest change observed for 23Na.

The nonstoichiometric nickel-ore mineral, violarite, (Ni,Fe)3S4 was prepared as a phase-pure fine powder by a comparatively quick hydrothermal method from an aqueous solution of iron(II) acetate, nickel(II) acetate and DL-penicillamine in an autoclave at 130°C for 45h. Powder-XRD showed that the violarite crystallised with the thiospinel structure, a=9.478(3) Å, Z=8; SEM revealed platy crystals 10×10×1μm; EMPA gave a mean composition, Fe0.31Ni2.36S4. Violarite compositions with a higher Fe/Ni ratio than this were concluded to be metastable in this aqueous system. When DL-penicillamine was used in excess, nickeliferous pyrite formed in addition to violarite. This is the first successful method for preparing violarite directly from aqueous solution, and demonstrates that it is feasible for nickel-rich violarite to precipitate from aqueous media in a geochemical environment. The mechanism for the pseudomorphic replacement of pentlandite, (Fe,Ni)9S8 by violarite is discussed in the light of these new results. The Fe-free end-member, polydymite, Ni3S4 was also prepared by this method.

This chapter contains sections titled: Containers Milling Fabrication of Ceramic Monoliths Furnaces Powder X-Ray Diffractometry References

The title compound, Cu0.5Mn2.5(PO4)(2), is a copper-manganese phosphate solid solution with the graftonite-type structure, viz. (Mn,Fe,Ca,Mg)(3)(PO4)(2). The structure has three distinct metal cation sites, two of which are occupied by MnII and one of which accommodates CuII. Incorporation of CuII into the structure distorts the coordination geometry of the metal cation site from five-coordinate square-pyramidal towards four-coordinate flattened tetrahedral, and serves to contract the structure principally along the c axis.