Crystal Core Research Articles

Sensitive Near-Infrared Refractive Index Sensors Based on D-Shaped Photonic Crystal Fibers.

We report a numerical study of D-shaped photonic crystal fiber based plasmonic refractive index sensor with high resolution and sensitivity in the near-infrared region. D-shaped photonic crystal fiber is formed by side polishing one part of photonic crystal fiber. It has a polishing surface where plasmonic gold layer is coated to modulate the resonant wavelength and enhance the refractive index sensitivity. Several D-shaped photonic crystal fiber plasmonic sensors with various distances from the photonic crystal fiber's core to the polishing surface and gold thicknesses are designed and their characteristics are analyzed by the finite element method. The simulation results indicate that distance from the photonic crystal fiber's core to the polishing surface causes modifications in the loss intensity, the resonant wavelength, and the refractive index sensitivity of D-shaped photonic crystal fiber plasmonic sensor. Mass production of refractive index sensors were achieved using a simple fabrication process, whereby the D-shaped photonic crystal fiber is grinded where distance from the photonic crystal fiber's core to the polishing surface is less than one layer thickness and then coated with the gold layer. For the refractive index sensing applications, the maxima theoretical resolution and sensitivity of D-shaped photonic crystal fiber plasmonic sensor reach 2.98 × 10 6refractive index unit and 6,140 nm/refractive index unit in range of 1.30-1.37, respectively. We also report an initial fabrication of the D-shaped photonic crystal fiber following the standard stack-and- draw method to demonstrate the feasibility of the proposed device by using our in-house equipments. The proposed D-shaped photonic crystal fiber plasmonic sensor design in this work would be useful for the development of cheap refractive index sensors with high sensitivity and resolution.

The Ludicovian of the Raahe–Ladoga Zone of the Fennoscandian Shield (Isotope-Geochemical Composition and Geodynamic Nature)

Abstract —In the northern Ladoga area, the age of the Sortavala Group rocks in the southeast of the Raahe–Ladoga zone of junction of the epi-Archean Fenno-Karelian Craton and the Paleoproterozoic Svecofennian province, their relationship with dome granitoids, the age of the provenances, and the time of metamorphic processes were estimated. The study was focused on the Nd isotope composition of rocks, the geochemical and isotope-geochronological parameters of zircon from the granite-gneisses of the Kirjavalakhti dome, the basal graywackes of the lower unit and the trachytes of the middle unit of the Sortavala Group, and the plagio- and diorite-porphyry dikes cutting the volcanosedimentary units of this group. The new isotope-geochemical data show a Neoarchean age of the granitoids of the Kirjavalakhti dome (2695 ± 13 Ma) and their juvenile nature (εNd(T) = +1.5). The granitoids underwent tectonometamorphic transformations (rheomorphism) in the Paleoproterozoic (Sumian) (2.50–2.45 Ga), which are recorded in the U–Th–Pb isotope system of the rims of the ancient cores of zircon crystals. The volcanosedimentary complex of the Sortavala Group formed on the heterogeneous polychronous (3.10–2.46 Ga) continental crust of the epi-Archean Fenno-Karelian Craton. With regard to the errors in determination of the age of clastic zircon, the minimum concordant U–Th–Pb ages of 1940–1990 Ma of detrital zircon from volcanomictic graywackes of the Pitkyaranta Formation can be taken as the upper age bound of terrigenous rocks, which agrees with the maximum age of the Sortavala Group rocks estimated from the U–Th–Pb (SIMS) age of 1922 ± 11 Ma of the Tervaoya diorites (Matrenichev et al., 2006). According to the proposed new tectonic model, the accumulation of the volcanosedimentary complex of the Sortavala Group, its metamorphism, erosion, and overlapping by the Ladoga Group turbidites had already occurred in the pericratonic part of the epi-Archean Fenno-Karelian Craton by the time of the Svecofennian continent–island arc collision, subduction, and formation of bimodal volcanoplutonic complexes of the young Pyhäsalmi island arcs and felsic volcanics of the Savo schist belt (1920–1890 Ma).

Beryl as indicator of metasomatic processes in the California Blue Mine topaz-beryl pegmatite and associated miarolitic pockets

Beryl occurs in a wide variety of rare-element pegmatites and has provided significant insights into their evolution. The geochemical signatures of beryl can record igneous and metasomatic processes but rarely could they be studied at the same location in both, the pegmatite body and associated miarolitic pockets. Further, the link between beryl chemistry and the petrogenesis of pegmatites has not yet been established convincingly. This study focuses on the recently discovered topaz-beryl granitic pegmatite deposit at the California Blue Mine in San Bernardino County, California, USA. This pegmatite deposit provides an exceptional opportunity to study microtextural (SEM and WDS-element maps) and major EMPA and trace element LA-ICP-MS concentrations in beryl in the pegmatite body and associated miarolitic pockets. The mineralogy of the pegmatites consists of: quartz + K-feldspar + albite (i.e., cleavelandite variety) + biotite + muscovite ± spessartine ± beryl (i.e., aquamarine variety) ± topaz, with a mineralogic zoning that includes border, wall, intermediate, and core zone. The miarolitic pockets contain gem quality beryl, topaz, and quartz crystals. Two major beryl types were distinguished including a primary (Brl I) and a metasomatic beryl (Brl II). Brl I occurs in the intermediate pegmatite zone and displays a blocky concentric crystal zoning characterized by a core enriched in Al and rims enriched in Na, Rb, K, and Sc. In contrast, Brl II is found mostly in the pegmatite core zone and at the contacts to, or within miarolitic pockets, and is characterized by a distinct enrichment in Cs and Li correlating with an enrichment in Na, B, and As and a depletion in Rb, K, Sc, and Fe. Brl II occurs as two variants including as replacement of Brl I (i.e., dissolution-precipitation microtextures in the pegmatites) and as single hydrothermal crystals (i.e., precipitation in the miarolitic pockets). The contrasting trends between Brl I and Brl II are interpreted to reflect two distinct processes affecting trace element variations in beryl including fractionation from a magma with systematic crystal core to rim zoning (decreasing Li and enrichment in Na, K, Rb, Sc, and Fe), and metasomatism with enrichment in Li, Cs, Na, B and As. An extensive beryl trace element dataset was generated in this study and further compared to beryl of the NYF (Nb-Y-F) and LCT (Li-Cs-Ta) pegmatite families worldwide. A significant link was found between beryl chemistry and the petrogenetic relationships of the pegmatites, which were used to distinguish four major geochemical beryl groups: (i) a low and a high Fe–Mg — alkali group, both displaying a positive alkali vs. Fe + Mg correlation; (ii) a low Fe–Mg — high alkali group displaying a negative alkali vs. Fe + Mg correlation; (iii) a low Li–Cs group; (iv) a high Li–Cs group. The more evolved LCT-type pegmatites generally overlap with the low Fe–Mg — high alkali and high Li–Cs groups (ii and iv). In contrast, NYF pegmatites coincide better with the trends observed for the low Li–Cs group as well as the low/high Fe–Mg — alkali beryl groups displaying a positive Fe + Mg vs. alkali correlation (i and iii). The beryl signatures from the California Blue Mine coincide with the NYF pegmatite classification but a partial overlap with the LCT pegmatites indicates a possible mixed origin or crustal contamination (i.e., hybrid pegmatites). These new insights reveal that beryl signatures provide a significant tool for interpreting the evolution of pegmatites from different geologic settings and permits distinguishing between igneous and metasomatic origins.

Melt Percolation, Melt-Rock Reaction and Oxygen Fugacity in Supra-Subduction Zone Mantle and Lower Crust from the Leka Ophiolite Complex, Norway

Abstract Samples of peridotites and pyroxenites from the mantle and lower crustal sections of the Leka Ophiolite Complex (LOC; Norway) are examined to investigate the effects of melt-rock reaction and oxygen fugacity variations in the sub-arc oceanic lithosphere. The LOC is considered to represent supra-subduction zone (SSZ) oceanic lithosphere, but also preserves evidence of pre-SSZ magmatic processes. Here we combine field and microstructural observations with mineral chemical and structural analyses of different minerals from the major lithologies of the LOC. Wehrlite and websterite bodies in both the mantle and lower crust contain clinopyroxene likely formed at a pre-SSZ stage, characterised by high Al, high Cr, low Mg crystal cores. These clinopyroxenes also exhibit low Al, low Cr, high Mg outer rims and intracrystalline dissolution surfaces, indicative of reactive melt percolation during intrusion and disruption of these lithologies by later, SSZ-related, dunite-forming magmas. Chromian-spinel compositional variations correlate with lithology; dunite-chromitite Cr-spinels are characterised by relatively uniform and high TiO2 and Al2O3, indicating formation by melt-rock reaction associated with SSZ processes. Harzburgite Cr-spinel compositions are more variable but preserve a relatively high Al2O3, low TiO2 endmember that may reflect crystallisation in a pre-SSZ oceanic spreading centre setting. An important finding of this study is that the LOC potentially preserves the petrological signature of a transition between oceanic spreading centre processes and subsequent SSZ magmatism. Single crystal Cr-spinel Fe3+/ΣFe ratios calculated on the basis of stoichiometry (from electron microprobe [EPMA] and crystal structural [X-ray diffraction; XRD] measurements) correlate variably with those calculated by point-source (single crystal) Mössbauer spectroscopy. Average sample EPMA Fe3+/ΣFe ratios overestimate or underestimate the Mössbauer-derived values for harzburgites, and always overestimate the Mössbauer Fe3+/ΣFe ratios for dunites and chromitites. The highest Fe3+/ΣFe ratios, irrespective of method of measurement, are therefore generally associated with dunites and chromitites, and yield calculated log(fO2)FMQ values of up to ~ + 1.8. While this lends support to the formation of the dunites and chromitites during SSZ-related melt percolation in the lower part of the LOC, it also suggests that these melts were not highly oxidised, compared to typical arc basalts (fO2FMQ of > + 2). This may in turn reflect the early (forearc) stage of subduction zone activity preserved by the LOC and implies that some of the arc tholeiitic and boninitic lava compositions preserved in the upper portion of the ophiolite are not genetically related to the mantle and lower crustal rocks, against which they exhibit tectonic contacts. Our new data also have implications for the use of ophiolite chromitites as recorders of mantle oxidation state through time; a global comparison suggests that the Fe3+/ΣFe signatures of ophiolite chromitites are likely to have more to do with local environmental petrogenetic conditions in sub-arc systems than large length-scale mantle chemical evolution

The novel method of synthesis of nanostructured materials for the enhancing recovery in oil displacement technologies

The work is dedicated to a research into the physicochemical aspects of carbon nanopowder production from the gas phase by the pyrolysis of the initial precursors in a cyclic adiabatic process in a flow-through chemical compression reactor (CCR). The method allows the production of carbon nanomaterials, such as the carbon nanoparticles and globular soot particles, as well, as the core-shell structures representing the 4–7 nm composite particles with a SiC crystal core covered with graphene layers. Products have controlled and reproducible properties, and output capacity of the method is sufficient for technological purposes. The nanopowders are characterized by high-resolution transmission electron (TEM) and scanning electron (SEM) microscopy, X-ray diffraction analysis and Raman spectroscopy. The nanomaterials were used to manufacture their aqueous suspensions - nanofluids, which have shown their effectiveness in enhancing oil recovery in oil displacement technologies.

Electronic States and Energy Dissipations of Vortex Core in Pure FeSe Single Crystals Investigated by Microwave Surface Impedance Measurements

In order to clarify electronic states and energy dissipations due to a motion of a vortex core in pure FeSe, which is a candidate superconductor possessing a super-clean core, we measured the microwave surface impedance of pure FeSe single crystals under finite magnetic fields. From the magnetic-field dependence of the flux-flow resistivity, we found that a barometer of electronic states inside the vortex core $\omega_{0}\tau_{\rm core}$ is $1\pm0.5$, suggesting that the vortex core of pure FeSe is in the moderately clean regime contrary to the expectation of the super-clean core. We also found that the mean-free path inside the vortex core is suppressed at the distance of the order of the core radius. Based on observed results and previous reports, we discussed possible origins of rather small $\omega_{0}\tau_{\rm core}$ value in terms of the multiple-bands nature of FeSe and additional mechanisms producing extra energy dissipations specific to the vortex core in motion.

ZnO and TiO2 Nanocolloids: State of Mechanisms that Regulating the Motility of the Gastrointestinal Tract and the Hepatobiliary System.

Using the transmission electron microscopy (TEM)/high-resolution TEM (HRTEM) and selected area electron diffraction (SAED) methods, it was shown that the nanocolloids of ZnO contain hydrolyzed ZnO nanoparticles (NPs). Typically, the nanocrystalline ZnO/Zn(OH)2 core is covered by an amorphous shell of zinc hydroxides, preventing the encapsulated crystal core from dissolving. Similar studies were carried out with TiO2 nanocolloids. It was found that burdening of rats for 30 days with a ZnO aqueous nanocolloid (AN) was accompanied by a narrowing of the amplitude range, a decrease (increase) in the frequency of spontaneous contractions (SCs), and an inhibition of the efficiency indices for smooth muscles (SMs) of the antrum and cecum. Under longer (100 days) burdening of rats with AN of ZnO, there was a tendency toward restoring the above parameters. In terms of the value and the direction of changes in most parameters for SCs of SMs, the effects (30 days) of TiO2 AN differed from those for ZnO AN and were almost the same in the case of their long-term impact. It was found that mostly M2-cholinoreceptor-dependent mechanisms of regulating the intracellular concentration of Ca2+ were sensitive to the effect of ZnO and TiO2 ANs. The molecular docking demonstrated that ZnO and TiO2 NPs did not compete with acetylcholine for the site of binding to M3 and M2 cholinoreceptors but may impact the affinity of orthosteric ligands to M2 cholinoreceptors. The studies showed that burdening rats with ZnO and TiO2 ANs was also accompanied by changes in the activity state of both intracellular enzymes and the ion transport systems for Na+, K+, and Ca2+, related to the processes of bile secretion, via the plasma membrane of hepatocytes.

A Broadband polarization filter based on liquid crystal core and gold-coated microstructure fiber

A Broadband polarization filter based on liquid crystal core and gold-coated microstructure fiber

Using cathodoluminescence to identify oscillatory zoning of perthitic K-feldspar from the equigranular Toki granite

Abstract For the first time, cathodoluminescence (CL) was used to show oscillatory zoning in perthitic K-feldspars from the equigranular Toki granite, central Japan. Based on the CL patterns, two types of zoning are identified: single core oscillatory zoning (SCOZ) and multiple core oscillatory zoning (MCOZ). The SCOZ is defined by oscillatory zoning around a single-crystal core within the K-feldspar crystal, whereas the MCOZ depicts two or more such crystal cores. The crystal cores displayed in CL images reflect the nucleation parts of magmatic K-feldspar. The existence of MCOZ patterns in K-feldspars indicates multiple nuclei. CL patterns reveal crystal growth behavior of magmatic K-feldspar in the equigranular Toki granite. CL intensities are positively correlated with titanium and barium concentrations, indicating that the CL variations depend on two factors: (1) titanium concentration as a CL activator and (2) density of Al-O−-Al structural defects. The analysis of CL images revealed that albite-rich phases in microperthite and patchperthite with low-luminescence intensities cut across the CL bands of the oscillatory zoning, indicating that the oscillatory zoning in the orthoclase-rich host phase of K-feldspar was not perturbed by the formation of microperthite and patchperthite in the post-crystallization stage. The luminescence intensities of albite-rich phases in patchperthite are lower than those in microperthite, which is due to the differences in titanium and barium concentrations between them. In the post-crystallization stage, the mass transfer of titanium and barium occurred during the formation of microperthite and patchperthite. Therefore, the difference in the luminescence intensities between microperthite and patchperthite lamellae reflects their different formation mechanisms between exsolution coarsening and dissolution-precipitation coarsening. In summary, CL analyses can be used for the evaluation of the nucleation and growth not only of anhedral K-feldspar crystals in equigranular granite but also of K-feldspar phenocrysts/megacrysts in porphyritic granite. It can reveal the spatial extent of element partitioning between the melt and crystal, along with that of mass transfer from the melt into crystals during the magma evolution. Moreover, the CL analyses can also be used for the interpretation of K-feldspar textural development during the post-crystallization stage.

Improvement of Alkali Metal Resistance for NH3-SCR Catalyst Cu/SSZ-13: Tune the Crystal Size

To improve the alkali metal resistance of commercial catalyst Cu/SSZ-13 for ammonia selective catalytic reduction (NH3-SCR) reaction, a simple method to synthesize Cu/SSZ-13 with a core–shell like structure was developed. Compared with smaller-sized counterparts, Cu/SSZ-13 with a crystal size of 2.3 μm exhibited excellent resistance to Na poisoning. To reveal the influence of the crystal size on Cu/SSZ-13, physical structure characterization (XRD, BET, SEM, NMR) and chemical acidic distribution (H2-TPR, UV-Vis, Diethylamine-TPD, pyridine-DRIFTs, EDS) were investigated. It was found that the larger the crystal size of the molecular sieve, the more Cu is distributed in the crystal core, and the less likely it was to be replaced by Na to generate CuO. Therefore, a 2.3 μm sized Cu/SSZ-13 well-controlled the reactivity of the side reaction NH3 oxidation and the generation of N2O. The result was helpful to guide the extension of the service life of Cu/SSZ-13.

Mg zonation and heterogeneity in low-Mg calcite microcrystals of a depositional chalk

ABSTRACTDiagenetic low-magnesium calcite (LMC) microcrystals constitute the framework that hosts most micropores in limestone reservoirs and therefore create the storage capacity for hydrocarbons, water, and anthropogenic CO2. Limestones dominated by LMC microcrystals are also commonly used for paleoclimate reconstructions and chemostratigraphic correlations. LMC microcrystals are well known to exhibit a range of textures (e.g., granular, fitted, clustered), but there exists uncertainty with regard to how these textures form. One hypothesis is that during crystal growth, Mg is incorporated into diagenetic overgrowths (cement), where the chemical zonation and microtexture may reflect diagenetic processes. To evaluate small-scale geochemical zonation in LMC microcrystals, this study uses scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) to measure the Mg/Ca ratio across the interiors of LMC granular microcrystals from a Late Cretaceous marine chalk from the Tor Fm. (Norwegian North Sea).Mg/Ca zonation was identified in all LMC microcrystals with a diameter > 5 μm. Generally, the cores of large crystals have lower Mg/Ca (≈ 5.9 mmol/mol) and the rims have elevated Mg/Ca (≈ 13 mmol/mol). Smaller microcrystals (< 5 μm) show no resolvable zonation, but do exhibit a wide range in Mg/Ca content from 2.9 to 32.2 mmol/mol. Measured Mg/Ca values are arbitrarily divided into three populations: low Mg (average ≈ 5.9 mmol/mol), intermediate Mg (average ≈ 13.3 mmol/mol), and high Mg (average ≈ 20 mmol/mol). The observed zonation and Mg enrichment within LMC microcrystals is interpreted to reflect depositional as well as multiple diagenetic signals, such as constructive precipitation through recrystallization and pore-filling cementation.Although chalk from the Tor Fm. is dominated by granular euhedral LMC microcrystals, using SEM-EDS to find Mg/Ca heterogeneity in other LMC microcrystal textures may provide insight into the diagenetic processes that create textural variations in micropore-dominated limestones. The Mg data also more broadly suggest that there is useful, measurable diagenetic information in material that is otherwise considered homogeneous. Distinguishing between possible primary compositions and secondary cementation has implications for studies that rely on the primary chemistry of fine-grained carbonate deposits (e.g., micrite), such as paleoclimatology, Mg paleothermometry, and chemostratigraphy.

Quartz‐Hosted Melt Inclusions as Windows Into Magma Assembly and Storage Processes in the Youngest Toba Tuff

AbstractQuartz‐hosted melt inclusions are windows into the assembly and storage of compositionally zoned magmas systems like the giant magma body responsible for the 2,800 km3 Youngest Toba Tuff (YTT), Indonesia. Feldspar‐sensitive element concentrations and interelement ratios in YTT quartz‐hosted melt inclusions are found to cluster into three discrete melt inclusion populations. Each population represents a small fraction of the overall range in YTT melt compositions and no more than ∼12% to ∼21% fractional crystallization at mostly eutectoid conditions accounts for the trace elements variations within them. Kinships between host matrix glasses and co‐hosted phases are interpreted as evidence of spatially discrete chemical domains of magma within a more broadly zoned magma system. Quartz growth in the dominant portion of the system apparently occurred after extraction of melt from mush, whereas chemically distinct crystal cores in the more crystal‐rich, low‐silica magmas may have been derived from mush during extraction or remobilized by mush rejuvenation. Collectively, the chemical zoning of the YTT appears to have developed prior to most quartz growth, likely “bottom‐up” due to mush‐derived melt heterogeneity.

The Origin of Rhyolitic Magmas at Krafla Central Volcano (Iceland)

AbstractWe present a detailed petrologic study of rhyolites from seven eruptions spanning the full (∼190 ky) history of rhyolitic volcanism at Krafla volcano, northeast Iceland. The eruptions vary widely in size and style, but all rhyolites are crystal-poor (<6 modal%: plagioclase + augite ± pigeonite ± orthopyroxene ± titanomagnetite ± fayalite) and have similar evolved compositions (73.7–75.8 wt% normalized whole-rock SiO2) and trace element patterns. Macrocryst rim compositions from each eruption cluster within a narrow range and are appropriate for equilibrium with their carrier melt. Crystal cores and interiors display complex growth patterns and commonly host resorption surfaces, but compositional variations are slight (e.g. typically <10 mol% An for plagioclase, Mg# <10 for pyroxene), and consistent with an overall trend of cooling and differentiation by crystal fractionation. Although most crystal core and interior compositions are broadly appropriate for equilibrium with melts similar to their host whole-rock, variable growth histories, juxtaposition of grains with distinct trace element compositions, and scatter in melt inclusion compositions indicate mixing of antecrysts from compositionally similar evolved melts and/or assimilated felsic mush or intrusions before final rim growth. Evidence for mafic recharge (e.g. coupled increases in An and Fe in plagioclase) is absent in most crystals; rhyolite storage and fractionation thus occurred largely in isolation from the underlying mafic system. Comparison of observed matrix glass compositions with published experimental work on melting of altered (meta)basalts casts doubt on previous models favouring rhyolite generation by partial melting of hydrothermally altered basalts, instead supporting recent isotopic and modelling arguments for a crystallization-driven process [Hampton, R. L. et al. (2021). Journal of Volcanology and Geothermal Research 414, 107229]. MELTS fractional crystallization and assimilation-fractional crystallization (AFC) models at 1 kbar predict liquid major and trace element compositions similar to Krafla rhyolites after ∼60–70 vol% crystallization of a quartz tholeiite melt representative of the evolved crystal-poor basalts commonly erupted within Krafla caldera. We thus suggest that stalling and crystallization of these evolved basalts at shallow depth forms crystal mushes from which evolved (broadly dacitic to rhyolitic) melts are extracted. These melts ascend and mix with other compositionally similar melt bodies and/or assimilate felsic intrusive material in the uppermost crust. The Daly gap between ∼57 and 71 wt% SiO2 at Krafla is consistent with preferential extraction of evolved melts from quartz tholeiite mushes in the ∼50–70% crystallinity window. Residual solid (cumulate) compositions predicted by MELTS are exclusively mafic, hence efficient silicic melt extraction from quartz tholeiite mushes may also explain the apparent compositional bimodality in some Icelandic plutonic suites.

Interface Reaction between DD6 Single Crystal Superalloy and Ceramic Core

The interfacial reaction between alloys and ceramic materials is an important factor to influence the quality and service performance of the turbine blade. In this paper, three typical height sections of 120mm, 160mm and 210mm were selected, and the interface reactions between DD6 single crystal superalloy and silica based ceramic cores were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS). The results showed that the infiltration degree of the melt alloy increases with the increase of reaction time. The thickness of the reaction layer could be over 0.3mm when the reaction time increased up to 70min. The main reasons of forming the infiltration layer were the infiltration of the Al element and the interfacial reaction between the Al element and the ceramic core. There formed an aluminum deficient layer on the metal surface because of the interface reaction between the alloy and the ceramic core. The dense layer formed by interfacial reaction on the surface of the core will cause some difficulties for core leaching. Keywords: DD6 single crystal superalloy; Silica based ceramic core; Interface reaction

Studies on electrical properties of Fe doped ZnO nanostructured oxides synthesized by sol–gel method

We report the results of the studies on electrical properties of Zn1–xFexO (x = 0.10, 0.15 and 0.20) nanoparticles synthesized using sol–gel method. X–ray diffraction (XRD) measurement confirms the presence of extra phase of ZnFe2O4 in all the samples which gets enhanced with increase in Fe concentration. Surface morphological studies using atomic force microscopy (AFM) suggest the reduction in grain size with increase in Fe doping level in ZnO. All the dielectric parameters show dispersion nature and dielectric constant has been found to increase with Fe content. The obtained dielectric behavior has been understood on the basis of Maxwell–Wagner (M − W) mechanism and Koop's theory. Frequency dependent electrical conductivity has been understood on the basis of Jonscher's universal power law that suggests a conduction of charge carrier through correlated barrier hopping (CBH) mechanism. Impedance spectroscopy measurements have been explained on the basis of crystal cores and crystal boundary density. Grain boundary contribution in conduction mechanism is identified by fitting equivalent circuit model on cole–cole plots. Temperature and magnetic field dependent variation in electrical properties of studied samples has been understood on the basis of structure–property correlations.

Synergistic Effect of Alkali Na and K Promoter on Fe-Co-Cu-Al Catalysts for CO2 Hydrogenation to Light Hydrocarbons

Alkali metal K- and/or Na-promoted FeCoCuAl catalysts were synthesized by precipitation and impregnation, and their physicochemical and catalytic performance for CO2 hydrogenation to light hydrocarbons was also investigated in the present work. The results indicate that Na and/or K introduction leads to the formation of active phase metallic Fe and Fe-Co crystals in the order Na < K < K-Na. The simultaneous introduction of Na and K causes a synergistic effect on increasing the basicity and electron-rich property, promoting the formation of active sites Fe@Cu and Fe-Co@Cu with Cu0 as a crystal core. These effects are advantageous to H2 dissociative adsorption and CO2 activation, giving a high CO2 conversion with hydrogenation. Moreover, electron-rich Fe@Cu (110) and Fe-Co@Cu (200) provide active centers for further H2 dissociative adsorption and O-C-Fe intermediate formation after adsorption of CO produced by RWGS. It is beneficial for carbon chain growth in C2+ hydrocarbons, including olefins and alkanes. FeCoCuAl simultaneously modified by K-Na exhibits the highest CO2 conversion and C2+ selectivity of 52.87 mol% and 89.70 mol%, respectively.

Epitaxial Growth of Single Crystal YAG for Optical Devices

We report the latest progress on fabrication of rare earth doped single crystal yttrium aluminum garnet (YAG) core/undoped YAG cladded fibers. Rare-earth doped single crystal core fibers were grown with laser heated pedestal growth methods. In a second step, epitaxial methods were used to grow a single crystalline undoped YAG cladding onto the core fiber. Hydrothermal and liquid phase epitaxy methods utilize the core doped fiber as the seed. X-ray diffraction of cladding reveals an equilibrium (110) morphology. Energy-dispersive X-ray spectroscopy analysis shows there is minimal diffusion of rare-earth dopants into the cladding structure. The use of scandium doping is shown to substitute at the Al3+ site, thereby allowing an additional tunability of refractive index of core structure material besides conventional Y3+ site dopants. The use of these epitaxial growth methods enables material compatibility, tuning of refractive index, and conformal growth of cladding structures onto core fibers for optical devices.

Determining thermo-mechanical stress sources of an integrated optical device

In this study, we analyze the thermo-mechanical behavior of a multi-functional integrated optical chip (MIOC) via the finite element method (FEM). MIOC is a kind of fiber optic component which has a high thermal sensitivity. So; during temperature changes its mechanical resistance has a considerable critical significance. To investigate the thermo-mechanical effects, a three-dimensional device structure is modeled and time-dependent Von-Mises stress analyses are carried out via the multiphysics approach in the simulation environment. The simulation results are evaluated regarding the change of the crystal structure, epoxy layers, and waveguide core region. It is demonstrated that structural configuration has a crucial impact on the mechanical stability of the integrated optical device. Because of this reason, case D is accepted as a preferable geometrical structure for mass production. Also, the most dominant stress effect arises from the epoxy layer interface between the fiber pigtail carrier and lithium niobate (LiNbO3) chip called region 1. In this context, we investigate the influence of extreme thermal conditions on the induced stress on region 1. Apart from the mechanical strength of the devices, optical transmission is another subject to consider. Two claims arise on this point: power flow through the waveguide core is temperature-dependent and it is also related to the stress-optical effect. Finally, we compare the simulation results with the experimental results and there is certainly a consistency between the two separate analyses. Furthermore; it can be said that manufacturing more than 500 devices facilitates the quantitative analysis of device performance.

Chemical Imaging of Hierarchical Porosity Formation within a Zeolite Crystal Visualized by Small‐Angle X‐Ray Scattering and In‐Situ Fluorescence Microscopy

AbstractIntroducing hierarchical porosity to zeolites is vital for providing molecular access to microporous domains. Yet, the dynamics of meso‐ and macropore formation has remained elusive and pore space ill‐characterized by a lack of (in situ) microscopic tools sensitive to nanoporosity. Here, we probe hierarchical porosity formation within a zeolite ZSM‐5 crystal in real‐time by in situ fluorescence microscopy during desilication. In addition, we introduce small‐angle X‐ray scattering microscopy as novel characterization tool to map intracrystal meso‐ and macropore properties. It is shown that hierarchical porosity formation initiates at the crystal surface and propagates to the crystal core via a pore front with decreasing rate. Also, hierarchical porosity only establishes in specific (segments of) subunits which constitute ZSM‐5. Such space‐dependent meso‐ and macroporosity implies local discrepancies in diffusion, performance and deactivation behaviors even within a zeolite crystal.

Jadeitite and Related Rocks in Serpentinite Mélanges from the Rio San Juan Complex, Dominican Republic: Evidence for Both Isochemical Replacement and Metasomatic Desilication of Igneous Protoliths with Fluid-Assisted Jadeite Growth

Abstract —This study presents an overview of the systematic petrography, mineralogy, and geochemistry of jadeitite and jadeite-rich rocks found as blocks in the serpentinite mélanges of the Rio San Juan Complex (RSJC) of the northern Dominican Republic. The RSJC is one of the remnants of the subduction/accretionary complex of the Great Caribbean Arc that once spanned the gap between North and South America, moved relatively eastward to its present position as the Lesser Antilles island arc, and left collisional fragments along the two continental margins. Our systematic collection of heterogeneous samples ranges from jadeitite s.str. (sensu stricto) with ≥90 vol.% jadeite to quartz-rich rocks with jadeite and lawsonite. Two suites of rock types can be recognized. In the matrix-quartz-free rock suite, albite is the principal vein-filling or interstitial phase. Quartz is present only as inclusions in the cores of some jadeite crystals. In the matrix-quartz-bearing rock suite, quartz is abundant and albite is relatively rare. The first-order question concerning jadeite-rich rocks is whether jadeite precipitated from a high-pressure aqueous fluid (“vein precipitation” or “P-type”) or whether the jadeite-rich rock formed through comprehensive metasomatic replacement of an igneous protolith (“R-type”). Some examples occur as discordant veins and are clearly P-type. For most, however, classification has been equivocal. The systematic data on the petrography and whole-rock chemistry of jadeite rocks from the RSJC presented in this paper leads to significant clarification. A major argument against R-type genesis is that the metasomatic mass transfer required to produce jadeitite and jadeite-rich rocks from any normal igneous protolith is prohibitively complex. Using whole-rock, major-element compositions, we show that many members of the matrix-quartz-bearing rock suite from the RSJC can be derived by isochemical HP/LT metamorphism of normal oceanic plagiogranites subducted together with oceanic crust. Isocon analysis shows, furthermore, that more jadeite-rich rock types and also members of the matrix-quartz-free suite can be derived from such plagiogranites primarily by straightforward desilication, a realistic scenario in a serpentine-rich environment. The quartz inclusions found in jadeite crystals of the matrix-quartz-free suite corroborate a genetic path in which the plagioclase in a plagiogranite protolith reacts to jadeite + quartz. Later desilication and the formation of albite in the Si-undersaturated rock matrix leave tell-tale quartz inclusions as relics in jadeite crystals.