Crystal phase-selective synthesis of intermetallic palladium borides and phase-regulated (electro)catalytic properties

Three crystal phases of Pd-B intermetallics, including Pd6B, Pd5B2 and Pd2B, are synthesized, and their phase-dependent catalytic activities toward electrochemical water splitting and Suzuki coupling reaction are studied. In both...

Phonon confinement and interface lattice dynamics of ultrathin high-k rare earth sesquioxide films: the case of Eu2O3 on YSZ(001)

We demonstrate that sub-nanometer-thick layers exhibiting exotic crystal phases that might form at the interface between two materials constitute a source of novel vibrational dynamics of thin films and multilayers.

App-based Quantification of Crystal Phases and Amorphous Content in ZIFs Biocomposites

The performance of Zeolitic Imidazolate Frameworks (ZIFs) as protective hosts for proteins in drug delivery or biocatalysis strongly depends on the type of crystalline phases used for the encapsulation of the biomacromolecule (biomacromolecule@ZIF). Therefore, quantifying the different crystal phases, and the amount of amorphous content of ZIFs is becoming increasingly important for a better understanding of the structure-property relationship. Typically, crystalline ZIF phases are qualitatively identified from diffraction patterns. However, accurate phase examinations are time-consuming and require specialized expertise. Here, we propose a calibration procedure (internal standard ZrO2) for the rapid and quantitative analysis of crystalline and amorphous ZIF phases from diffraction patterns. We integrated the procedure into a user-friendly web application, named ZIF Phase Analysis, which facilitates ZIF-based data analysis. As a result, it is now possible to quantify i) the relative amount of various common crystal phases (sodalite, diamondoid, ZIF-CO3-1, ZIF-EC-1, U12 and ZIF-L) in biomacromolecule@ZIF biocomposites based on Zn2+ and 2-methylimidazole (HmlM) and ii) the crystalline-to-amorphous ratio. This new analysis tool will advance the research on ZIF biocomposites for drug delivery and biocatalysis.

Probing electric properties of GaP nanowires with Kelvin probe force microscopy

Surface electronic properties of GaP nanowires were investigated using scanning probe force microscopy. I-V curves of individual free-standing NWs with different doping types were obtained. Surface Fermi level positions in the nanowires of different crystal phases and doping types were extracted using phase-modulated Kelvin probe force microscopy. The results indicate on weak Fermi level pinning in GaP nanowires. The difference between wurtzite and zinc blende GaP work function is observed.

Simultaneous Recovery of Struvite and Irrigation Water for Agricultural Purposes Obtained from Dewatering Liquor through Electrodialysis

Wastewater contains resources, which can be recovered for secondary use if treated properly. Besides research in zero liquid discharge solutions, the aim of the study was a simultaneous recovery of products from a wastewater treatment plant’s dewatering liquor. To be specific, we investigated a simultaneous recovery of struvite and irrigation water using electrodialysis (ED) in laboratory experiments. Two products were obtained from ED—concentrate and diluate. The concentrate was precipitated to obtain struvite. On average, 11 g of wet precipitate (including 17.58% of dry solids) were obtained from 1 L of concentrate. Crystal phases were confirmed by powder X-ray diffraction (XRD), with showing 94–97% recovery of struvite, while the remaining 3–6% were identified as hazenite. The average yield of crystal struvite was 1.76 g. Both struvite and hazenite may further be used as a fertilizer. Next, we suggest using the second ED product, the diluate, as irrigation water if it meets the irrigation water requirements. Attention was paid to the concentrations of dissolved solids (DS) in diluate, which decreased by an average of 93% compared to the input values in the dewatering liquor. In line with the observed Czech or EU standards indicators, we can say that the diluate can be used in agriculture, namely as irrigation water (Category I—water suitable for irrigation).

The Oruanui Eruption: Insights into the Generation and Dynamics of the World's Youngest Supereruption

<p>This work investigates the pre- and syn-eruptive magmatic processes that culminated in the world’s youngest supereruption – the ~25.4 ka, 530 km³ Oruanui eruption from Taupo volcano, New Zealand – from the perspective of crystals contained in single parcels of frozen magma (pumice). The eruption is unusual in its variety of magmatic compositions. About 98-99 % by mass of the juvenile material is high-SiO₂ rhyolite (HSR; >74 wt% SiO₂), with lesser volumes of tholeiitic and calc-alkaline mafic magmas (total 3-5 km³; basaltic andesite to andesite: 53-63 % SiO₂), low-silica rhyolite (LSR: 0.1-0.5 km³; <74 wt% SiO₂) and a ‘foreign’ biotite-bearing rhyolite from an adjacent magma source (0.03 km³; ~74 wt% SiO₂). Detailed textural and chemical data from amphibole, plagioclase, and orthopyroxene are placed within the context of an established time-stratigraphic, volcanological and petrographic framework, of unrivalled detail globally for an eruption of this age and magnitude. Other previously published information from zircon and quartz is also incorporated. This unique contextual information is used to constrain observations and inferences regarding the processes that moved the Oruanui magma from a largely uneruptible crystal-rich progenitor at depth (where an eruption was possible), to a highly eruptible melt-rich magma at shallow crustal levels (where eruption was inevitable). A thermally and compositionally stratified crystal mush body, with an upper SiO₂-saturated and quartz bearing cap at ~3.5 km depth and quartz-free roots extended down to at least ~10 km. This inference is made on three bases. 1) That the quartz cores contain trapped melt that is more evolved than the melt component of the immediately pre-eruptive magma body, indicating their growth within mush from a more evolved interstitial melt. 2) The majority of plagioclase, amphibole, and orthopyroxene cores, in contrast to quartz have compositions that indicate growth from less evolved melts than that encountered in the final melt-dominant magma body. 3) Barometric estimates from amphibole core compositions indicate derivation from a range of depths (~3.5 to 10 km). The spatial and temporal transitions from mush to melt-dominant magma body are recorded in the textural and compositional zonations within the crystal phases. Crystals from all levels of the zoned mush body were entrained during the melt extraction process resulting in a diversity of crystal compositions being brought together in the melt-dominant magma body. Textural disequilibrium features in the cores of orthopyroxene and plagioclase crystals reflect their temporary departure from stability during the accompanying significant decompression (recorded in the amphibole model pressures). Counterpart chemical signatures, reflecting this partial orthopyroxene and plagioclase dissolution, are recorded in the amphiboles which show no textural evidence for destabilisation during ascent. Crystal chemical and textural zonation in the rim growths of the plagioclase, orthopyroxene, and amphibole record further crystallisation in the accumulating melt-dominant magma body, and reflect cooling and compositional evolution of the body towards its final pre-eruptive conditions. The timing of growth of the melt dominant magma body is constrained by Fe-Mg diffusion modelling of key boundaries in orthopyroxene crystals. Accumulation of this body began only ~1600 years and peaked at 230 years prior to the eruption, as vast volumes of melt and entrained crystals were drained from the mush body and began to accumulate at shallower levels (~3.5 to 6.0 km depth). Within the thin, sill-like melt-dominant magma body, significant heat loss drove vigorous convection. Textural and chemical zonation patterns within the rim-zones of plagioclase, orthopyroxene and amphibole, inferred to have grown solely in the melt-dominant magma body, depict a secular cooling and melt evolution trends towards final uniform thermal (~770 °C) and compositional conditions inferred for the HSR magma. Despite the rapid accumulation of a vast volume of crystal-poor HSR magma at shallow crustal levels, the apparent gas-saturated nature of that magma, and vigorous convection within the melt-dominant magma body itself, the chronologies from HSR orthopyroxene imply that the magma underwent a period of stasis of about 60 years. The presence of 3-16 wt% of ‘foreign’ biotite-bearing juvenile pumices in the early Oruanui fall deposits (phases 1 and 2) show that coincident with the onset of the Oruanui eruption, magma was transported laterally in a dike from an adjacent independent magma system 10-15 km to the NNE to intersect the active Oruanui conduit. Consideration of the tectonic stress orientations associated with this lateral transport imply that an external tectonic influence through a major rifting event was a critical factor in the initiation of the Oruanui eruption. Only the presence of the foreign magma, and linkages to detailed field-based and geochemical constraints enables the tectonic influence to be identified. During the eruption itself, minor quantities of Oruanui LSR magma were erupted , and with a crystal cargo, reflecting derivation from deeper (mostly >6 km), hotter (~820 °C) sources in the crystal mush roots to the system. Comparisons of LSR crystal compositions with cores to many HSR crystals for plagioclase, orthopyroxene and amphibole imply that the LSR magma was derived from pockets in the mush zone ruptured during escalation of the eruption vigour during phase 3. The LSR and its crystals are inferred to be closely similar in their characteristics to the feedstock magma that generated the melt-dominant body and evolved through subsequent cooling and fractionation to form the HSR. In overall terms, the evidence from the crystal phases demonstrates that a super-sized rhyolite magma body can be physically created in a geologically very short period of time. The compositional textures and data for all the mineral phases, both previously published and newly presented in this work, yield a consistent story of extraordinarily rapid extraction of LSR melt and entrained crystals into a rapidly evolving and cooling HSR body. When coupled with field constraints these data establish a central role for extensional tectonics in regulating the pre-and syn-eruptive processes and their timings in the Oruanui system.</p>

The Oruanui Eruption: Insights into the Generation and Dynamics of the World's Youngest Supereruption

<p>This work investigates the pre- and syn-eruptive magmatic processes that culminated in the world’s youngest supereruption – the ~25.4 ka, 530 km³ Oruanui eruption from Taupo volcano, New Zealand – from the perspective of crystals contained in single parcels of frozen magma (pumice). The eruption is unusual in its variety of magmatic compositions. About 98-99 % by mass of the juvenile material is high-SiO₂ rhyolite (HSR; >74 wt% SiO₂), with lesser volumes of tholeiitic and calc-alkaline mafic magmas (total 3-5 km³; basaltic andesite to andesite: 53-63 % SiO₂), low-silica rhyolite (LSR: 0.1-0.5 km³; <74 wt% SiO₂) and a ‘foreign’ biotite-bearing rhyolite from an adjacent magma source (0.03 km³; ~74 wt% SiO₂). Detailed textural and chemical data from amphibole, plagioclase, and orthopyroxene are placed within the context of an established time-stratigraphic, volcanological and petrographic framework, of unrivalled detail globally for an eruption of this age and magnitude. Other previously published information from zircon and quartz is also incorporated. This unique contextual information is used to constrain observations and inferences regarding the processes that moved the Oruanui magma from a largely uneruptible crystal-rich progenitor at depth (where an eruption was possible), to a highly eruptible melt-rich magma at shallow crustal levels (where eruption was inevitable). A thermally and compositionally stratified crystal mush body, with an upper SiO₂-saturated and quartz bearing cap at ~3.5 km depth and quartz-free roots extended down to at least ~10 km. This inference is made on three bases. 1) That the quartz cores contain trapped melt that is more evolved than the melt component of the immediately pre-eruptive magma body, indicating their growth within mush from a more evolved interstitial melt. 2) The majority of plagioclase, amphibole, and orthopyroxene cores, in contrast to quartz have compositions that indicate growth from less evolved melts than that encountered in the final melt-dominant magma body. 3) Barometric estimates from amphibole core compositions indicate derivation from a range of depths (~3.5 to 10 km). The spatial and temporal transitions from mush to melt-dominant magma body are recorded in the textural and compositional zonations within the crystal phases. Crystals from all levels of the zoned mush body were entrained during the melt extraction process resulting in a diversity of crystal compositions being brought together in the melt-dominant magma body. Textural disequilibrium features in the cores of orthopyroxene and plagioclase crystals reflect their temporary departure from stability during the accompanying significant decompression (recorded in the amphibole model pressures). Counterpart chemical signatures, reflecting this partial orthopyroxene and plagioclase dissolution, are recorded in the amphiboles which show no textural evidence for destabilisation during ascent. Crystal chemical and textural zonation in the rim growths of the plagioclase, orthopyroxene, and amphibole record further crystallisation in the accumulating melt-dominant magma body, and reflect cooling and compositional evolution of the body towards its final pre-eruptive conditions. The timing of growth of the melt dominant magma body is constrained by Fe-Mg diffusion modelling of key boundaries in orthopyroxene crystals. Accumulation of this body began only ~1600 years and peaked at 230 years prior to the eruption, as vast volumes of melt and entrained crystals were drained from the mush body and began to accumulate at shallower levels (~3.5 to 6.0 km depth). Within the thin, sill-like melt-dominant magma body, significant heat loss drove vigorous convection. Textural and chemical zonation patterns within the rim-zones of plagioclase, orthopyroxene and amphibole, inferred to have grown solely in the melt-dominant magma body, depict a secular cooling and melt evolution trends towards final uniform thermal (~770 °C) and compositional conditions inferred for the HSR magma. Despite the rapid accumulation of a vast volume of crystal-poor HSR magma at shallow crustal levels, the apparent gas-saturated nature of that magma, and vigorous convection within the melt-dominant magma body itself, the chronologies from HSR orthopyroxene imply that the magma underwent a period of stasis of about 60 years. The presence of 3-16 wt% of ‘foreign’ biotite-bearing juvenile pumices in the early Oruanui fall deposits (phases 1 and 2) show that coincident with the onset of the Oruanui eruption, magma was transported laterally in a dike from an adjacent independent magma system 10-15 km to the NNE to intersect the active Oruanui conduit. Consideration of the tectonic stress orientations associated with this lateral transport imply that an external tectonic influence through a major rifting event was a critical factor in the initiation of the Oruanui eruption. Only the presence of the foreign magma, and linkages to detailed field-based and geochemical constraints enables the tectonic influence to be identified. During the eruption itself, minor quantities of Oruanui LSR magma were erupted , and with a crystal cargo, reflecting derivation from deeper (mostly >6 km), hotter (~820 °C) sources in the crystal mush roots to the system. Comparisons of LSR crystal compositions with cores to many HSR crystals for plagioclase, orthopyroxene and amphibole imply that the LSR magma was derived from pockets in the mush zone ruptured during escalation of the eruption vigour during phase 3. The LSR and its crystals are inferred to be closely similar in their characteristics to the feedstock magma that generated the melt-dominant body and evolved through subsequent cooling and fractionation to form the HSR. In overall terms, the evidence from the crystal phases demonstrates that a super-sized rhyolite magma body can be physically created in a geologically very short period of time. The compositional textures and data for all the mineral phases, both previously published and newly presented in this work, yield a consistent story of extraordinarily rapid extraction of LSR melt and entrained crystals into a rapidly evolving and cooling HSR body. When coupled with field constraints these data establish a central role for extensional tectonics in regulating the pre-and syn-eruptive processes and their timings in the Oruanui system.</p>