Crystallization Path Research Articles

Tridymite formation as a direct consequence of explosive volcanism – evidence preserved in tuffisite veins and concurrently erupted volcanic ash

ABSTRACT The mineralogy of volcanic rocks is usually considered as a consecutive crystallisation path related to a liquid line of decent. Tephra and pyroclastic rocks hold a special status as their formation includes the physical disruption of the magma during an explosive eruption. We describe tuffisite samples (captured veins of pyroclastic material in coherent lava bombs) and concurrently ejected volcanic ash from the ongoing eruption of Ebeko Volcano, Russia. Our samples show that tridymite (a mineral, not present in the original phase assemblage of the magma) forms as a consequence of explosive eruptive activity, volatile exsolution and fluid flow following decompression and magma fragmentation. Vapour phase crystallisation (VPC) of cristobalite is well known from highly evolved, dome-forming eruptions due to gas flux through highly permeable and porous glassy dome rocks. At Ebeko volcano, increased permeability develops in the volcanic conduit during magma fragmentation and transient tephra storage. Magmas erupted at Ebeko are less evolved than those of typical (dome-forming) andesitic – dacitic Peléan eruptions and show comparably higher eruption temperatures favouring the formation of tridymite over cristobalite during VPC.

Crystallization path and non-isothermal kinetics of the Zr59.5Cu14.4Ni11.6Al9.7Nb4.8 metallic glass under different heating rates

In this work, the crystallization path and non-isothermal kinetics upon heating of the Zr59.5Cu14.4Ni11.6Al9.7Nb4.8 metallic glass were investigated. The devitrification process consists the formation of phases in the sequence of icosahedral quasicrystal (IQ) phase, Ni-containing phases, and Cu-containing phases. Avrami exponents were calculated at various heating rates, providing insights into the non-isothermal crystallization kinetics. The IQ phase and Ni-containing phases are interface-controlled growth, while the Cu-containing phases are diffusion-controlled growth. In addition, a continuous heating transition (CHT) diagram with a heating rate range exceeding six orders of magnitude was constructed, and the crystallization mechanism under different heating rates was revealed. These findings enrich the understanding of crystallization path and kinetics of metallic glass.

Oiling‐Out in Industrial Crystallization of Organic Small Molecules: Mechanisms, Characterization, Regulation, and Applications

AbstractOiling‐out is a common phenomenon in industrial crystallization processes that not only prolongs the total operating time but also leads to undesirable crystal morphology, making it challenging to control crystallization paths. This review provides a comprehensive overview of the oiling‐out phenomenon in organic small molecule crystallization. First, the formation mechanisms of oiling‐out are summarized from both thermodynamic and dynamic perspectives, providing the theoretical foundation for understanding the phenomenon. Then, the universal characterization methods for studying the oiling‐out phenomenon of organic small molecules are introduced in detail, covering both offline and online analytical tools. Moreover, the regulation strategy for oiling‐out, including solvents, impurities, seeding, temperature, and mixing methods are discussed. This paper also focuses on the application of oiling‐out in co‐assembly and crystal shape modulation. Finally, future opportunities and challenges are presented to address the current shortcomings and application bottlenecks in the study of organic small molecule oiling‐out phenomena. This review aims to provide valuable insights and guidance for researchers working on the crystallization of organic small molecules, particularly in the pharmaceutical industry, to better understand, control, and utilize the oiling‐out phenomenon.

Vesicularity, Density, and Crystal Size Distribution of Pumice-Scoria at South-Southeast Flank of Merapi Volcano: A Window Into Explosive Volcanic Eruption

Abstract Merapi, one of the most active volcanoes in Java Island of Sunda Arc, is a constant threat to the ten million people who live within its 10-km radius of the summit. In 2010, it experienced an explosive eruptive event, sending pumice-laden pyroclastic density currents (PDC) that extended as far as 15 km down its southeastern flank. We report field observations of PDC deposits on the south-southeast flank of the volcano and calculate the vesicularity, density and crystal size distribution of pumice–scoria fragments. The density of the pumice–scoria is measured by archimedes’ principle by weighting the sample in water. The vesicularity is determined from petrography using the point counting method. Crystal Size distribution (CSD) is determined by images from thin sections using plagioclase crystals to calculate the magma residence time. Based on their physical appearance, the pumice–scoria fragments from this area are grouped into: (1) white pumice, (2) grey pumice, and (3) dark scoria. The density of white pumice is overlapping with the grey pumice group (1.5-2 g/ml); while the dark scoria is the densest among others (>2 g/ml). The vesicularity of pumice–scoria ranges from 7-30%. CSD analysis is done in two most vesicular samples from each group. The CSD result gives both shallow and steep slopes which reflect the crystal size and population density. The slope suggests that magma residence times are (a) 11.49–249.68 years for grey pumice, (b) 5.03–194.54 years for white pumice, and (c) 3.83–273.36 years for dark scoria. This research suggests that the three types of pumice–scoria from the study area generally have similar crystallization path and time. Our CSD data shows that these pumice-scoria samples tend to have steeper slopes than lava samples, indicating a more uneven crystal-growth condition.

Anisotropic Fracture of Two-Dimensional Ta2NiSe5.

Anisotropic two-dimensional materials present a diverse range of physical characteristics, making them well-suited for applications in photonics and optoelectronics. While mechanical properties play a crucial role in determining the reliability and efficacy of 2D material-based devices, the fracture behavior of anisotropic 2D crystals remains relatively unexplored. Toward this end, we herein present the first measurement of the anisotropic fracture toughness of 2D Ta2NiSe5 by microelectromechanical system-based tensile tests. Our findings reveal a significant in-plane anisotropic ratio (∼3.0), accounting for crystal orientation-dependent crack paths. As the thickness increases, we observe an intriguing intraplanar-to-interplanar transition of fracture along the a-axis, manifesting as stepwise crack features attributed to interlayer slippage. In contrast, ruptures along the c-axis surprisingly exhibit persistent straightness and smoothness regardless of thickness, owing to the robust interlayer shear resistance. Our work affords a promising avenue for the construction of future electronics based on nanoribbons with atomically sharp edges.

Kainite crystallization from RO bittern: A novel approach using discontinuous evaporation

Addressing global water scarcity and achieving sustainable water management necessitates innovative solutions for handling reverse osmosis (RO) brine. This by-product, rich in high-value salts, poses environmental challenges due to its high salinity and chemical load. This study explores a novel approach for recovering valuable minerals from brine, focusing on Kainite, a mineral with substantial industrial applications and notorious for its nucleation difficulties. This research introduces a temperature-altering technique for Kainite crystallization, adjusting temperatures from 69 °C, 55 °C, 35 °C, and 25 °C, each subsequently reduced to 15 °C. Advanced characterization techniques were utilized to analyze the crystallized phases. The FREZCHEM model was used for a comparative analysis between isothermal evaporation and the experimental discontinuous evaporation results. Findings indicate that effective Kainite crystallization occurs only with discontinuous evaporation at specific temperature pairs: 55 °C to 15 °C and 69 °C to 15 °C. A novel application of Jänecke phase diagrams through the projection of crystallization path between 55 and 15 °C, and 69 and 15 °C, was instrumental in accurately predicting the crystallization sequence under these conditions. This study underscores discontinuous evaporation's potential for resource recovery from RO brine, contributing to sustainable water management.

Adaptive Phase or Variant Formation at the Austenite/Twinned Martensite Interface in Modulated Ni–Mn–Ga Martensite

AbstractThe crystal structure and transformation path from austenite to 10M martensite in Ni–Mn–Ga single crystal are examined employing high‐energy synchrotron radiation, scanning, and transmission electron microscopy. Using temperature gradient, an austenite/twinned martensite interface is stabilized revealing the crystal structure and microstructure of both phases and the transformation sequence across the interface. Depending on the distance from the interface, three distinct types of martensite crystal lattice, namely simple tetragonal and two monoclinic modulated ones, that is, 10M′ and 10M are confirmed. In situ measurements show that lattice mismatch formed at the habit plane is compensated by the formation of micro‐twinned and branched martensite along with an elastic change in lattice parameters. It is shown that the characteristics for periodic shuffling twin boundaries, such as modulation twins or inverted stacking faults, are installed in later stages of transformation. In other words, large microstructure elements that most efficiently accommodate the strain are installed first, and then smaller elements are operable. Overall, the experimental results show that the crystal lattice does not adapt modulated phase at the habit plane and cannot be built up from simple non‐modulated tetragonal blocks but rather a specific sequence of phase transformations using shear/shuffling deformation takes place.

Wollastonite-containing glass-ceramics from the CaO–Al2O3–SiO2 and CaO–MgO–SiO2 ternary systems

Glass-ceramics (GCs) are polycrystalline materials produced from parent glasses by the controlled crystallization that results in crystalline phase(s) embedded in a residual amorphous matrix. Typically, GCs are produced by a conventional glass route with subsequent crystallization for which two heat treatments are usually applied, the former to generate nuclei and the latter being a crystal growth stage. Alternatively, another technically viable route for manufacturing GCs involves sintering of glass-powder compacts followed by crystallization (sinter-crystallization).Wollastonite-containing GCs from the CaO–Al2O3–SiO2 and CaO–MgO–SiO2 systems find a wide variety of uses in different technological fields, including construction, architecture, medical and high-tech fields. For example, a special type of wollastonite-containing GC marketed under the name of Neoparies®, which is stronger and lighter than natural stone, features high resistance to weathering/chemical attack and is manufactured on a large scale for construction and architectural applications. In the biomedical field, the well-known Cerabone® products have been used in bone-contact applications for many years.The main goal of this brief review is to provide a critical analysis of the experimental trials focusing on the synthesis of wollastonite-containing GC materials and to discuss the various fields of their application. Constitution of phase diagram of CaO–Al2O3–SiO2 and CaO–MgO–SiO2 systems are comprehensively discussed with connection to melt crystallization path and crystalline phase formation. Furthermore, special emphasis will be given to the production of wollastonite-containing GCs for construction and architectural purposes from natural raw materials and wastes, as well as to the recent advancement in developing wollastonite-containing GC biomaterials for bone repair.

Petrogenesis of magnesian troctolitic granulite clasts from Chang'e -5 drilling sample: Implications for the origin of ejecta material from lunar highlands

The lunar soil collected by the Chang'e-5 (CE-5) mission contains both local materials and components of various sources. The latter could have derived from the excavation of impact craters in the highlands away from the landing site, providing valuable information on the composition of the lunar crust beyond the mare basalts sampled by the CE-5 mission. In this study, we examined the mineralogy and petrology of magnesian troctolitic granulites (or troctolites) recovered in the CE-5 soil. The troctolites exhibit a granoblastic texture but have a finer grain size compared to Apollo granulites, and almost all plagioclase remains unaltered and not converted to maskelynite. The major element composition shows a SiO2 content of 45.4 wt%, CaO of 12 wt%, TiO2 of 0.2 wt%, Th of 0.1 ppm, and an Mg# of 76, lower than those of the Mg troctolitic lunar meteorites NWA 5744 and NWA 10401. The trace element budget indicates that the magnesian troctolites are KREEP-poor, which distinguishes them from the Mg-suite rocks in Apollo samples but is similar to some troctolitic lunar meteorites (NWA 10401). Furthermore, we predict –by using MELTS modeling– a plausible genetic connection between the Mg-suite rocks, and our troctolites, suggesting that the latter may be pristine and formed during a later stage along a fractional crystallization path. This scenario challenges the hybridization model and strengthens the evidence in favour of the fractional crystallization modeling. To ascertain the potential origin crater for the magnesian granulites, a comparative analysis was conducted with NWA 10401. Based on our findings, we propose that the Pythagoras crater, situated north of the CE-5 landing site, is the most probable source of the aforementioned magnesian troctolitic granulites. The ejecta from this crater may have been deposited between the Eratosthenian-aged mare basalts and the Imbrian-aged mare basalts beneath the CE-5 landing site. The KREEP-poor troctolitic granulite in the Chang'e-5 soil could represent paleo-ejecta from Pythagoras crater, excavated by subsequent impacts on the Eratosthenian-aged basalts and delivered them to the CE-5 site. The original location of the Mg troctolitic granulites is inferred to be near-surface, buried by the uppermost crustal rocks (<10 km), which is consistent with its contact with feldspathic impact glass.

Petrological and geochemical evidence for a hot crystallization path and a recharge filtering bypass at Antimilos, Milos volcanic field, Greece

Antimilos volcano in the South Aegean Volcanic Arc, Greece, comprises an andesite–dacite suite that follows a distinct evolutionary path than the main edifice of the Milos volcanic field, despite their proximity. Petrographic and geochemical analyses reveal that basaltic andesite to low-Si dacite lavas have similar phenocryst assemblages that indicate crystallization from hot, relatively dry magmas in an upper crustal storage region. Rare antecrystic high-Mg# clinopyroxene cores with low Y, low Dy, and high Sr contents record the cryptic involvement of amphibole, a phase nominally absent from the erupted products, in the deeper parts of the plumbing system. Low temperature antecrysts with textures recording various degrees of disequilibrium suggest a protracted history of interaction between the upper crustal reservoir and deeper mafic melts, forming mobile hybrid magmas that consequently erupt as highly mingled, crystal-rich lava domes. Antimilos magmas seem to have escaped recharge filtering in the upper crust and prolonged stalling, which is the process that is probably responsible for the paucity of mafic eruptions in the rest of the Milos volcanic system. Large extensional structures offshore of Antimilos promote rapid ascent of mafic melts, inhibiting prolonged stalling and interaction with the arc crust. This model highlights the dominant role of the regional stress field in generating petrologically distinct suites in the marginal parts of some volcanic fields.

Thermodynamic constraints on the fate of carbon mobilized from subducted sediments in the overlying mantle wedge

In subduction zones, carbon from the surface can be transported into Earth's interior. Fluids released during subduction can mobilize carbon bound in solid minerals in the subducting plate, and transport it into the overlying mantle. While there is increasing attention on the composition and redox state of carbon-bearing, subduction-mobilized fluids, the fate of fluids as they migrate through and react with overlying mantle rocks is less well characterized. Using thermodynamic modeling, we quantify the evolution of carbon-bearing aqueous fluids mobilized from subducting sedimentary rocks, as they follow several possible pathways through the overlying mantle. The extent of carbon mineralization in the overlying mantle depends on the source (siliciclastic vs carbonate rock) and composition of the fluids as well as the fluid path (isothermal, cooling, heating). A heating path towards the hot core of the mantle wedge does not favor sequestration of carbon into solid phases. Along cooling trajectories, most of the dissolved carbon (61 to 98 %) forms in solid minerals when carbon-rich, siliciclastic-equilibrated fluids react with mantle rocks. In contrast to fluids from siliciclastic sediments, less carbon is sequestered in the mantle when relatively carbon-poor, limestone-equilibrated fluids react with mantle rocks. The formation of quartz-rich (birbirite), quartz-magnesite (listvenite), talc-magnesite (soapstone), and serpentine-rich (serpentinite) parageneses is predicted at decreasing water-rock ratios. Soapstones are less favored to form along fractional crystallization paths and/or lower temperatures. Listvenite assemblages form from migrating fluids with dissolved carbon concentration > 20,000 ppm. Graphite is favored to form along closed reaction, cooling paths. Moreover, several cooling paths form reduced fluids rich in hydrogen (H2), methane (CH4), and organic species. Overall, this work provides quantitative models that can comprehensively inform studies on the movement of carbon in subduction zones and into the deep Earth.

Evidence for liquid-liquid phase separation during the early stages of Mg-struvite formation.

The precipitation of struvite, a magnesium ammonium phosphate hexahydrate (MgNH4PO4 · 6H2O) mineral, from wastewater is a promising method for recovering phosphorous. While this process is commonly used in engineered environments, our understanding of the underlying mechanisms responsible for the formation of struvite crystals remains limited. Specifically, indirect evidence suggests the involvement of an amorphous precursor and the occurrence of multi-step processes in struvite formation, which would indicate non-classical paths of nucleation and crystallization. In this study, we use synchrotron-based in situ x-ray scattering complemented by cryogenic transmission electron microscopy to obtain new insights from the earliest stages of struvite formation. The holistic scattering data captured the structure of an entire assembly in a time-resolved manner. The structural features comprise the aqueous medium, the growing struvite crystals, and any potential heterogeneities or complex entities. By analysing the scattering data, we found that the onset of crystallization causes a perturbation in the structure of the surrounding aqueous medium. This perturbation is characterized by the occurrence and evolution of Ornstein-Zernike fluctuations on a scale of about 1nm, suggesting a non-classical nature of the system. We interpret this phenomenon as a liquid-liquid phase separation, which gives rise to the formation of the amorphous precursor phase preceding actual crystal growth of struvite. Our microscopy results confirm that the formation of Mg-struvite includes a short-lived amorphous phase, lasting >10s.

Printable High-efficiency and Stable FAPbBr3 Perovskite Solar Cells for Multifunctional Building-integrated Photovoltaics.

Perovskite solar cells (PSCs) show great promise for next-generation building-integrated photovoltaic (BIPV) applications because of their abundance of raw materials, adjustable transparency, and cost-effective printable processing. Owing to the complex perovskite nucleation and growth control, the fabrication of large-area perovskite films for high-performance printed PSCs is still under active investigation. Herein, wepropose an intermediate-phase-transition-assisted one-step blade coating for an intrinsic transparent formamidinium lead bromide (FAPbBr3 ) perovskite film. The intermediate complex optimized the crystal growth path of FAPbBr3 , resulting in a large-area, homogeneous, and dense absorber film. A champion efficiency of 10.86% with high open-circuit voltage up to 1.57V wasobtained with a simplified device architecture of glass/FTO/SnO2 /FAPbBr3 /carbon. Moreover, the unencapsulated devices maintained 90% of their initial power conversion efficiency after aging at 75°C for 1000h in ambient air, and 96% after maximum power point tracking for 500h. The printed semitransparent PSCs, with average visible light transmittance over 45%, demonstrated high efficiencies for both small devices (8.6%) and 10 × 10 cm2 modules (5.55%). Finally, the ability to customize the color, transparency, and thermal insulation properties of FAPbBr3 PSCs makes them high prospects as multifunctional BIPVs. This article is protected by copyright. All rights reserved.

Investigating the vertical extent and short-wave radiative effects of the ice phase in Arctic summertime low-level clouds

Abstract. Low-level (cloud tops below 2 km) mixed-phase clouds are important in amplifying warming in the Arctic region through positive feedback in cloud fraction, water content and phase. In order to understand the cloud feedbacks in the Arctic region, good knowledge of the vertical distribution of the cloud water content, particle size and phase is required. Here we investigate the vertical extent of the cloud-phase and ice-phase optical properties in six case studies measured in the European Arctic during the ACLOUD campaign. Late spring- and summertime stratiform clouds were sampled in situ over pack ice, marginal sea ice zone and open-ocean surface, with cloud top temperatures varying between −15 and −1.5 ∘C. The results show that, although the liquid phase dominates the upper parts of the clouds, the ice phase was frequently observed in the lower parts down to cloud top temperatures as warm as −3.8 ∘C. In the studied vertical cloud profiles, the maximum of average liquid phase microphysical properties, droplet number concentration, effective radius and liquid water content, varied between 23 and 152 cm−3, 19 and 26 µm, 0.09 and 0.63 g m−3, respectively. The maximum of average ice-phase microphysical properties varied between 0.1 and 57 L−1 for the ice number concentration, 40 and 70 µm for the effective radius, and 0.005 and 0.08 g m−3 for the ice water content. The elevated ice crystal number concentrations and ice water paths observed for clouds, with cloud top temperatures between −3.8 and −8.7 ∘C can be likely attributed to secondary ice production through rime splintering. Low asymmetry parameters between 0.69 and 0.76 were measured for the mixed-phase ice crystals with a mean value of 0.72. The effect of the ice-phase optical properties on the radiative transfer calculations was investigated for the four cloud cases potentially affected by secondary ice production. Generally the choice of ice-phase optical properties only has a minor effect on the cloud transmissivity and albedo, except in a case where the ice phase dominated the upper cloud layer extinction. In this case, cloud albedo at solar wavelengths was increased by 10 % when the ice phase was given its measured optical properties instead of treating it as liquid phase. The presented results highlight the importance of accurate vertical information on cloud phase for radiative transfer and provide a suitable data set for testing microphysical parameterizations in models.

Epoch Reality in Davit Turdospireli's Brief Fictional Narrative

Despite the strict canonical description for brief prose, Davit Turdospireli's brief fictional narrative not only give us a glimpse into the spiritual world of the writer and share his subjective feelings, but also clearly present a number of contemporary epochal problems of the writer. Davit Turdospireli was involved in active social and political life from an early age, while still studying at the seminary, he edited the literary and journalistic magazine "Our flag" and the almanac "Pirveli Talva". Gendarmerie carefully followed the socio-political steps of the young writer. Davit Turdospireli's miniature prose echoes in many ways the historical-political and cultural-social existence of Georgians at the beginning of the twentieth century. The historical and political events in the country pushed the writer to different ways of disguising what he had to say. In some cases, he tried to show the way to salvation for the country that had been disenfranchised, and in some cases, he created works with almost the same title and completely different content. The reason for the distress revealed in the miniature by covering it with "withered leaves" is undoubtedly caused by the contemporary presence of the writer. In the miniature dated 1916, "Love", seemingly a searcher of the philosophy of love, who has not heard anything about its annals since the beginning of the world, calls the reader to enjoy the charm of freedom and selfless struggle to break the shackles of slavery. The work on Davit Turdospireli's autographs has revealed a number of nuances characteristic of the writer's creative process. What is especially characteristic of his manuscripts, which are mostly black autographs and clearly show the writer's creative work process, are signed and undated by the author. We think that the writer deliberately did not date his manuscripts. As we have already mentioned, despite the fact that he tried to convey his message to the readers by various means, the undated manuscripts was probably one of the ways to protect free thought. Davit Turdospireli's miniatures, despite the persecution and harassment of free thought, interestingly reveal writer’s attitude to the historical and political existence of the country, at the same time, they also draw crystal paths for a better life of the country.

Evaluation of relative content and crystallization behavior of homogeneous crystals in poly (lactic acid) by terahertz spectroscopy

Poly (lactic acid) (PLA) is a typical polymer with homogeneous polymorphism. Its different crystal forms have their own crystallization paths, which endow it with special properties. Therefore, it is crucial to study the structure and crystallization behavior of PLA to better understand its properties. Here, we investigate PLA films obtained under different crystallization conditions by terahertz (THz) spectroscopy. The α′, α and their mixed crystal forms of PLA exhibit completely different spectral feature. Based on the frequency of THz characteristic peaks, we further determine the relative contents of α′ form and α form in PLA with mixed crystals, the validity of which is verified by comparing X-ray diffraction (XRD). Furthermore, the change of absorption intensity of different PLA films is significantly different with crystallization time, mainly manifested as the change rate of glassy PLA crystallized at 80 °C is faster than that of molten PLA. We believe that this is because the crystallization of the α form of PLA at 80 °C is at a disadvantage, which reduces the speed of conformational adjustment. The results show that THz spectroscopy can not only characterize the crystal changes of polymers, but can also be an effective method to study the kinetics of polymer crystallization.

Thermal and Morphological Analysis of Linear Low-Density Polyethylene Composites Containing d-limonene/β-cyclodextrin for Active Food Packaging.

Composites made of linear low-density polyethylene (LLDPE) and β-cyclodextrin/d-limonene inclusion complex (CD-lim) were prepared by melt extrusion to develop a novel food packaging material. Scanning electron microscopy evidenced a fairly good dispersion of the filler within the polymeric matrix. Infrared spectroscopy coupled with thermogravimetric analysis confirmed the presence of CD-lim in the composites, proving that the applied technology of including the essential oil within β-CD cages allows for preventing a sizable loss of d-limonene despite a high temperature and shear applied upon extrusion processing. Moreover, the influence of the filler on the thermal properties of PE was assessed. It was found that the cyclodextrin-based inclusion complex significantly fastens the crystallization path of the polyethylene matrix with an improved crystallization rate of the PE/CD-lim composites compared to the neat polymer.

Effects of variable slab components and tectonics on magma composition in the intra-oceanic Kermadec Arc-Backarc system

The Kermadec Arc-Backarc system (25–39°S) in the southwest Pacific is an important natural laboratory to examine the controls on arc magma compositions, because the physical parameters that are thought to influence subduction-related magmatism (the thickness and composition of the upper plate, mantle depletion and partial melting, and the slab components) change along the arc. Furthermore, the presence of back-arc and rear-arc volcanism allow insight into how mantle composition varies with distance to the trench. We present new major and trace element and Pb–Sr–Nd–Hf isotope data for 101 lava samples from 10 volcanoes along the Kermadec Arc, and combine these with published data for volcanic arc front, rear-arc, and back-arc lavas. The Kermadec Arc-Backarc magmas experienced similar fractional crystallization paths, and those erupted onto oceanic crust are not affected by crustal assimilation. The degree of partial melting varies along and across the arc, partly due to variations in the thickness of the lithosphere of the upper plate, but also due to variations in slab fluid input. We distinguish four different arc segments varying from 100 to 600 km wide, which erupt lavas with distinct compositions due to differences in along-arc slab input. All Kermadec arc and rear-arc lavas were derived from mantle sources to which the sediment melt and a fluid from subducted Pacific oceanic crust or the Hikurangi Seamounts had been added. Increasing sediment melt input into the mantle wedge southwards is reflected in increasing 87Sr/86Sr and Th/Nd, and decreasing 143Nd/144Nd southwards towards New Zealand. Some volcanoes from the central Kermadec Arc show with unusually radiogenic Pb isotope compositions that are probably derived from subducted alkaline rocks from seamounts built on the Hikurangi Plateau. The geochemical segmentation of the Kermadec Arc indicates that slab-derived components can be relatively homogeneous on large scales, but small features like seamounts cause complex additions to the slab component.

Crystal Structures and Conduction Paths of Sc-Doped CaTiO3 Fast Oxide-Ion Conductors with Orthorhombic Symmetry

The crystal structures and electron density distributions (EDDs) of Ca-deficient Sc-doped CaTiO3 fast oxide-ion conductors, Ca0.97(Ti0.97Sc0.03)O3-δ (CTS3) and Ca0.96(Ti0.9Sc0.1)O3-δ (CTS10), were investigated in the temperature range of 298-1173 K in N2 to analyze the effect of composition on the perovskite structure and oxide-ion transport mechanism. CTS3 and CTS10 exhibited orthorhombic Pnma symmetry in temperature ranges of 298-1173 K and 973-1173 K, respectively, with CTS10 exhibiting lower symmetry and reduction in oxide-ion conductivity below 973 K. The EDDs of CTS3 and CTS10 at 1173 K indicated unique chemical bonds and conduction paths. CTS3 and CTS10 showed covalent bonds between (Ti,Sc) and O1 (or O2) sites. CTS3, with a lower oxide-ion conductivity than that of CTS10, exhibited pseudo-one-dimensional (1D) zig-zag curved conduction paths for oxide-ions along the a-axis, unlike previously reported curved migration paths along the b-axis in CaTiO3, and chemical bonds between Ca and O1 sites, indicating oxide-ion conduction suppression. In CTS10, additional conduction paths were observed along the a-axis, forming three-dimensional (3D) zig-zag curved conduction paths in the ac-plane and along the b-axis, with the weakening of the chemical bonds between the Ca and O1 sites. The oxide-ion conductivity and mobile oxide-ion concentration of CTS10 were 3.6 and 2.0 times those of CTS3, respectively, at 1173 K; the higher oxide-ion conductivity of CTS10 could be attributed to an increase in the mobile oxide-ion concentration and mobility with a 1D to 3D change in the conduction paths and a weakening of chemical bonds between the Ca and O1 sites.

Identification of various salt crystallization and water freezing patterns induced by temperature variation from Na2SO4 – H2O system confined in porous materials

Among inorganic salts, sodium sulfate is considered as one of the most dangerous to porous building materials. The pores of building materials are usually occupied by aqueous salt solution. Hence, the phase transitions of both, water and salt should be considered simultaneously during temperature decrease. In the present paper we describe an extensive experimental study devoted to the analysis of combined salt crystallization and water freezing in the Na2SO4–H2O system confined in the pores of sandstone and red clay brick induced by temperature variation. Salt and water phase transition patterns were investigated using differential scanning calorimetry. Saturated samples were subjected to 20 cooling-heating scans, where the initial temperature was changed in each cycle. Such a procedure enabled us to define three different crystallization paths of Na2SO4 hydrates and ice depending on the initial conditions. Based on the recorded heat flow, the crystallization enthalpies of hepta- and decahydrate of sodium sulfate were estimated.