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This study discusses the feasibility of using a combined torsional-axial rheometer to indirectly measure the complex Poisson's ratio based on shear and Young's modulus. For this purpose, isothermal frequency sweeps in torsion and extension are performed sequentially on the same cylindrical specimen and under the same environmental conditions. The method is tested on two amorphous polymers, a semicrystalline polymer, a polymer blend, and a copolymer. The article includes an extensive literature review and an uncertainty assessment of the method to provide a basis for subsequent data comparison with existing research. The experimental data show a monotonic increase in the complex Poisson's ratio up to 0.5 as the temperature approaches α-relaxation for all samples, except for the amorphous polymer. The latter shows a local minimum in the complex Poisson's ratio observed near α-relaxation, which disappears after thermal annealing of the sample above the α-relaxation temperature. The real and imaginary parts of the complex Poisson's ratio are additionally determined by evaluating both phase shift angles from torsional and extensional measurements. All polymers show a certain offset between the torsional and extensional phase shift angles in the glassy state, which gradually decreases as the temperature approaches α-relaxation. The complex Poisson's ratio results are in good agreement with the literature data obtained by existing methods. This confirms that the method is applicable to polymers up to α-relaxation temperatures with significant time savings due to the nondestructive approach. This is of particular interest, given the limited availability of data in the literature. [ABSTRACT FROM AUTHOR]

We experimentally investigated the phase relations of a peralkaline phonolitic dyke rock associated with the Ilimaussaq plutonic complex (South Greenland). The extremely evolved and iron-rich composition (magnesium number = 2, alkalinity index = 1.44, Fe[O.sup.*] = 12 wt%) may represent the parental magma of the Ilimaussaq complex. This dyke rock is therefore perfectly suited for performing phase-equilibrium experiments, since in contrast to the plutonic rocks of the complex, no major cumulate formation processes complicate defining a reasonable starting composition. Experiments were carried out in hydrothermal rapid-quench cold-seal pressure vessels at P = 100 MPa and T = 950-750 °C. [H.sub.2]O contents ranging from anhydrous to [H.sub.2]O saturated (~5 wt% [H.sub.2]O) and varying f[O.sub.2] (~ΔlogFMQ -3 to +1; where FMQ represents the fayalite-magnetite-quartz oxygen buffer) were applied. Reduced and dry conditions lead to substantial crystallization of alkali feldspar, nepheline, hedenbergite-rich clinopyroxene, fayalite-rich olivine and minor amounts of ulvospinel-rich magnetite, which represent the phenocryst assemblage of the natural dyke rock. Oxidized and [H.sub.2]O-rich conditions, however, suppress the crystallization of olivine in favor of magnetite and clinopyroxene with less or no alkali feldspar and nepheline formation. Accordingly, combined low f[O.sub.2] and a[H.sub.2]O force the evolution of the residual melt toward decreasing Si[O.sub.2], increasing Fe[O.sup.*] and alkalinity index (up to 3.55). On the contrary, high f[O.sub.2] and o[H.sub.2]O produce residual melts with relatively low Fe[O.sup.*], high Si[O.sub.2] and a relatively constant alkalinity index. We show that variations of a[H.sub.2]O and f[O.sub.2] lead to contrasting trends regarding the liquid lines of descent of iron-rich silica under saturated peralkaline compositions. Moreover, the increase in Fe[O.sup.*] and alkalinity index (reduced and dry conditions) in the residual melt is an important prerequisite to stabilize late-magmatic minerals of the dyke rock, for example, aenigmatite ([Na.sub.2][Fe.sub.5]Ti[S.sub.i6][O.sub.20]), coexisting with the most evolved melts at 750 °C. Contrary to what might be expected, experiments with high a[H.sub.2]O and interlinked high f[O.sub.2] exhibit higher liquidus Ts compared with experiments performed at low a[H.sub.2]O and f[O.sub.2] for experiments where magnetite is liquidus phase. This is because ulvospinel-poor magnetite crystallizes at higher f[O.sub.2] and has a higher melting point than ulvospinel-rich magnetite, which is favored at lower f[O.sub.2]. Keywords Crystallization experiments * Phase relations * Liquid line of descent * Peralkaline * Phonolite * Ilimaussaq, Introduction The investigation of phase equilibria is a powerful method to elucidate crystallization, differentiation and fractionation processes in magmatic systems. Previous experimental work on phase relations in igneous systems covers [...]

Transparent nanoceramics, synthesized at extreme conditions of high pressure and temperature, are new classes of materials highly attractive for photonic applications, such as optical windows, which require additional increased hardness and toughness. In this study, mechanical properties of transparent polycrystalline nanoceramics consisting of triclinic Al2SiO5 kyanite (~91.4 vol%) and trigonal Al2O3 corundum (~8.6 vol%) fabricated at high pressure (10 GPa) and temperature (1200‐1400°C) were investigated. It is already known that the optical transparency of kyanite‐based nanoceramics increases with decreasing average grain size. The present study shows that the hardness of these ceramics increases with decreasing grain sizes down to ~70 nm according to the Hall‐Petch strengthening. This grain size seems to mark a transition range where an inverse Hall‐Petch effect is indicated due to signs of a moderate hardness decrease at a smaller grain size of ~35 nm. The observed hardness‐grain size relation can fairly be described by an existing composite model, which considers the crystals to be harder than the noncrystalline grain boundaries. Within the range of average grain sizes examined, the kyanite habit changes from more equant to more columnar. This behavior is associated with the observed strong crack deflection by the columnar kyanite grains with aspect (length to diameter) ratios ranging from ~2 to 10 and may positively affect the fracture toughness. [ABSTRACT FROM AUTHOR]

Halogens are excellent tracers of hydrothermal fluid sources in sedimentary, magmatic, metamorphic and ore-forming environments. In situ LA-ICP-MS analysis of Cl and Br in single fluid inclusions has provided fundamentally new insight into the processes leading to the formation of economic mineral deposits. Enrichment and depletion of Br relative to the dominant halogen Cl may be caused by several processes besides seawater evaporation and halite dissolution, which cannot be unequivocally resolved on the basis of Br/Cl ratios alone. Triple-halogen analysis (Cl, Br and I) would provide the required additional constraint permitting discrimination between possible alternative processes. We present the first iodine concentration data of fluid inclusions determined by LA-ICP-MS microanalysis, using the natural scapolite reference material Sca17 for external standardization. The robustness of the method is verified by LA-ICP-MS analysis of synthetic fluid inclusions, which were prepared at 600 °C, and 100 or 200 MPa in cold-seal pressure vessels from four starting solutions containing Na, Rb, Cs, Cl, Br and I. LA-ICP-MS analysis yielded average I concentrations in excellent agreement with the starting solutions. Average concentrations in inclusions synthesized from the solution with 27 μg g−1 I were 27.3 ± 3.9 μg g−1 I (14.3% RSD), and 77.6 ± 6.4 μg g−1 I (8.3% RSD) for the solution with 78 μg g−1 I. Chlorine and Br reference concentrations were reproduced to better than 10% and 20% RSD, respectively. The method was subsequently applied to a pilot study of natural fluid inclusion samples from three geological settings (Alpine metamorphic quartz veins, post-Variscan quartz-Pb–Zn veins, and calcite veins with Mn oxide and hematite mineralization). The data demonstrate significant differences between the samples, which can be interpreted in terms of Br and I enrichment due to reactions with organic matter and fluid mixing processes between evaporite brines and halite dissolution brines. This highlights the potential of triple-halogen LA-ICP-MS analysis in fluid inclusions for tracing the source of crustal fluids in a wide range of geological environments. [ABSTRACT FROM AUTHOR]

Transparent polycrystalline nanoceramics consisting of triclinic Al2SiO5 kyanite (91.4 vol%) and Al2O3 corundum (8.6 vol%) were fabricated at 10 GPa and 1200-1400°C. These materials were obtained by direct conversion from Al2O3-SiO2 glasses fabricated using the aerodynamic levitation technique. The material obtained at 10 GPa and 1200°C shows the highest optical transparency with a real in-line transmission value of 78% at a wavelength of 645 nm and a sample-thickness of 0.8 mm. This sample shows equigranular texture with an average grain size of 34 ± 13 nm. The optical transparency increases with decreasing mean grain size of the constituent phases. The relationship between real in-line transmission and grain size is well explained by a grain-boundary scattering model based on a classical theory. [ABSTRACT FROM AUTHOR]

We report the synthesis of alumina/stishovite nano-nano composite ceramics through a pressure-induced dissociation in Al2SiO5 at a pressure of 15.6 GPa and temperatures of 1300°C-1900°C. Stishovite is a high-pressure polymorph of silica and the hardest known oxide at ambient conditions. The grain size of the composites increases with synthesis temperature from ~15 to ~750 nm. The composite is harder than alumina and the hardness increases with reducing grain size down to ~80 nm following a Hall-Petch relation. The maximum hardness with grain size of 81 nm is 23 ± 1 GPa. A softening with reducing grain size was observed below this grain size down to ~15 nm, which is known as inverse Hall-Petch behavior. The grain size dependence of the hardness might be explained by a composite model with a softer grain-boundary phase. [ABSTRACT FROM AUTHOR]