Silicate Systems Research Articles

An Investigation of the Protective Action of a Coating Based on Yttrium Aluminosilicate System on Silicon Carbide Material at a Temperature up to 1500°С

A coating based on a precursor of yttrium silicate and yttrium aluminosilicate systems on the ceramic composite material based on silicon carbide was obtained by the Schlicker-firing method and atmospheric plasma spraying. In addition, the regularities of effect of oxidation medium on the heat resistance of this coating at a temperature up to 1500°С inclusive were established.

Evaluation of Molar Volume of Silicate Systems Using a Structural Model

A structural based model is proposed to represent the molar volume of silicate melts in terms of both temperature and composition. The model links the molar volume to the internal structure of melts through the concentrations of non-bridging oxygen present in the slag. A previous proposed structural thermodynamic model is used to calculate the content of oxygen ions. The molar volume model requires only one or two parameters to obtain a good agreement between experimental and calculated data for the SiO2–Na2O, SiO2–CaO, SiO2–MgO, SiO2–MnO, and SiO2–PbO binary systems. The molar volume of ternary systems is calculated with the model assuming a linear function of the parameters from binary systems; however, the content of non-oxygen bridges is calculated using the thermodynamic model for ternary systems. Comparison is made between the experimental and model results for the SiO2–CaO–MnO, SiO2–Na2O–PbO and SiO2–CaO–MgO systems.

Zakarpatskiy perlit as component of mineral woven fabric material

Thanks to the peculiarities of the chemical composition and structure, perlite has received application for manufacturing building materials - thermal insulation and ceramic
 Results over of research of the silicate systems with transcarpathian perlite as raw material for making of mineral astringent material are driven. The features of the chemical-mineralogical composition, phase transformations during burning and astringent properties of material at the use of perlite from Beregovsky deposit in composition initial raw material mixtures are shown.
 To determine and optimize raw material stock at the production of mineral binder material of low-temperature roasting type of natural or romanticum, a computer program "RomanCem" was used.
 After burning with a maximum temperature of 1100°C, the test of the binder material from the investigated 3-component mixtures with Transcarpathian perlite is characterized by differences in phase composition and properties.
 When using for the manufacture of mineral binder material of low-temperature firing of a gypsum natural or romantic cement 3-component mixtures based on the limestone system - perlit - clay, the content of Transcarpathian perlite is possible from 4 to 22 mass. %.

Microwave sintering and fusion of low-fusing titanium body porcelain derived from sol–gel synthesis

ABSTRACTThe titanium body porcelain was synthesised through sol–gel using borate–silicate system. The porcelain was characterised by X-ray diffraction (XRD), scanning electron microscope and three-point flexure tests. The XRD and selected area electron diffraction (SAED) results showed that the porcelain was mainly amorphous. The SEM and TEM microphotographs showed that the shape of the porcelain particles was irregular and their sizes range from 5 to 25 μm, while there were no obvious pores on the porcelain surface. The flexure strength significantly increased from 18.9 to 70.6 MPa when the sintering temperature of the porcelain increased from 600 to 675°C and then slowly decreased to 49.1 MPa when the sintering temperature elevated to 700°C. The improvement of the strength was mainly due to the decrease of pores and increase of density. A closely bonded dense coating was fused on the Ti surface by microwave.

Decadal transition from quiescence to supereruption: petrologic investigation of the Lava Creek Tuff, Yellowstone Caldera, WY

The magmatic processes responsible for triggering nature’s most destructive eruptions and their associated timescales remain poorly understood. Yellowstone Caldera is a large silicic volcanic system that has had three supereruptions in its 2.1-Ma history, the most recent of which produced the Lava Creek Tuff (LCT) ca. 631 ka. Here we present a petrologic study of the phenocrysts, specifically feldspar and quartz, in LCT ash in order to investigate the timing and potential trigger leading to the LCT eruption. The LCT phenocrysts have resorbed cores, with crystal rims that record slightly elevated temperatures and enrichments in magmaphile elements, such as Ba and Sr in sanidine and Ti in quartz, compared to their crystal cores. Chemical data in conjunction with mineral thermometry, geobarometry, and rhyolite-MELTS modeling suggest the chemical signatures observed in crystal rims were most likely created by the injection of more juvenile silicic magma into the LCT sub-volcanic reservoir, followed by decompression-driven crystal growth. Geothermometry and barometry suggest post-rejuvenation, pre-eruptive temperatures and pressures of 790–815 °C and 80–150 MPa for the LCT magma source. Diffusion modeling utilizing Ba and Sr in sanidine and Ti in quartz in conjunction with crystal growth rates yield conservative estimates of decades to years between rejuvenation and eruption. Thus, we propose rejuvenation as the most likely mechanism to produce the overpressure required to trigger the LCT supereruption in less than a decade.

Repeated Rhyolite Eruption From Heterogeneous Hot Zones Embedded Within a Cool, Shallow Magma Reservoir

AbstractDespite the hazard posed by explosive silicic eruptions, the magma storage conditions and dynamics that precede these events remain controversial. The Laguna del Maule volcanic field, central Chile, is an exceptional example of postglacial (younger than ca. 20,000 years) rhyolite volcanism and sustained unrest driven by a large, shallow, active silicic magma system. New zircon petrochronologic data reveal that compositionally distinct domains developed concurrently within the Laguna del Maule magma reservoir, which produced two episodes of concentrated rhyolitic eruptions at 23–19 and 8–2 ka. Zircon crystallization ages record 160 kyr of magma emplacement resulting in a several hundreds of cubic kilometers reservoir that has been imaged geophysically. The average magma emplacement rate inferred from the zircon geochronology and tomographically defined magma volume is consistent with those required by thermal models to maintain a shallow silicic system. Ti‐in‐zircon temperatures of crystal cores and rims and hiatuses in crystal growth indicates most of this volume persisted in a near‐solidus state. However, consistent patterns of trace element zoning in crystal interiors and crystallization rates derived from a model of diffusion‐limited zircon growth suggest the erupted rhyolite magma batches originated from long‐lived hot zones of extractable mush embedded within the larger, cool reservoir of rigid mush. These contrasting, coeval magma storage conditions obviate a simple hot versus cold storage dichotomy for large silicic magma systems.

Serpentine–Hisingerite Solid Solution in Altered Ferroan Peridotite and Olivine Gabbro

We present microanalyses of secondary phyllosilicates in altered ferroan metaperidotite, containing approximately equal amounts of end-members serpentine ((Mg,Fe2+)3Si2O5(OH)4) and hisingerite (□Fe3+2Si2O5(OH)4·nH2O). These analyses suggest that all intermediate compositions can exist stably, a proposal that was heretofore impossible because phyllosilicate with the compositions reported here have not been previously observed. In samples from the Duluth Complex (Minnesota, USA) containing igneous olivine Fa36–44, a continuous range in phyllosilicate compositions is associated with hydrothermal Mg extraction from the system and consequent relative enrichments in Fe2+, Fe3+ (hisingerite), Si, and Mn. Altered ferroan–olivine-bearing samples from the Laramie Complex (Wyoming, USA) show a compositional variability of secondary FeMg–phyllosilicate (e.g., Mg–hisingerite) that is discontinuous and likely the result of differing igneous olivine compositions and local equilibration during alteration. Together, these examples demonstrate that the products of serpentinization of ferroan peridotite include phyllosilicate with iron contents proportionally larger than the reactant olivine, in contrast to the common observation of Mg-enriched serpentine in “traditional” alpine and seafloor serpentinites. To augment and contextualize our analyses, we additionally compiled greenalite and hisingerite analyses from the literature. These data show that greenalite in metamorphosed banded iron formation contains progressively more octahedral-site vacancies (larger apfu of Si) in higher XFe samples, a consequence of both increased hisingerite substitution and structure modulation (sheet inversions). Some high-Si greenalite remains ferroan and seems to be a structural analogue of the highly modulated sheet silicate caryopilite. Using a thermodynamic model of hydrothermal alteration in the Fe–silicate system, we show that the formation of secondary hydrothermal olivine and serpentine–hisingerite solid solutions after primary olivine may be attributed to appropriate values of thermodynamic parameters such as elevated a S i O 2 ( a q ) and decreased a H 2 ( a q ) at low temperatures (~200 °C). Importantly, recent observations of Martian rocks have indicated that they are evolved magmatically like the ferroan peridotites analyzed here, which, in turn, suggests that the processes and phyllosilicate assemblages recorded here are more directly relevant to those occurring on Mars than are traditional terrestrial serpentinites.

Effect of silver oxide on hydroxy carbonated apatite formation for simulated body fluid soaked calcium phospho silicate system

Abstract In the present work, we have synthesized the 58SiO2-(38-x) CaO-xAg2O-4P2O5 glasses using sol-gel method and these glasses were treated for 7 days in simulated body fluid (SBF) solution. The structural properties of SBF treated samples were studied using characterization techniques such as X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). Dissolution studies also have been studied for SBF treated samples. The XRD pattern indicates that crystalline nature increases with increase in Ag2O for synthesizing samples. The formed Hydroxy Carbonated Apatite (HCA) particles were identified by XRD and EDX analysis. Dissolution studies confirmed that HCA formation decreased with Ag2O content. Finally, it was confirmed that Ag2O content resists the HCA formation.

Discrete Zr and REE mineralization of the Baerzhe rare-metal deposit, China

Abstract Although REE (lanthanides + Sc + Y) mineralization in alkaline silicate systems is commonly accompanied with Zr mineralization worldwide, our understanding of the relationship between Zr and REE mineralization is still incomplete. The Baerzhe deposit in Northeastern China is a reservoir of REE, Nb, Zr, and Be linked to the formation of an Early Cretaceous, silica-saturated, alkaline intrusive complex. In this study, we use in situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of zircon and monazite crystals to constrain the relationship between Zr and REE mineralization at Baerzhe. Three groups of zircon are identified and are differentiated based upon textural observations and compositional characteristics. Type Ia zircons display well-developed oscillatory zoning. Type Ib zircons are darker in cathodoluminescence images and have more irregular zoning and resorption features than type Ia zircons. In addition, type Ib zircons can locally occur as overgrowths on type Ia zircons. Type II zircons contain irregular but translucent cores and rims with oscillatory zoning that are murky brown in color and occur in aggregates. Textural features and compositional data suggest that types Ia and Ib zircon crystallized at the magmatic stage, with type Ia being least-altered and type Ib being strongly altered. Type II zircons, on the other hand, precipitated during the magmatic to magmatichydrothermal transition. Whereas the magnitude of the Eu anomaly is moderate in the barren alkaline granite, both magmatic and deuteric zircon exhibit pronounced negative anomalies. Such features are difficult to explain exclusively by feldspar fractionation and could indicate the presence of fluid induced modification of the rocks. Monazite crystals occur mostly through replacement of zircon and sodic amphibole; monazite clusters are also present. Textural and compositional evidence suggests that monazite at Baerzhe is hydrothermal. Types Ia and Ib magmatic zircon yield 207Pb-corrected 206Pb/238U ages of 127.2 ± 1.3 and 125.4 ± 0.7 Ma, respectively. Type II deuteric zircon precipitated at 124.9 ± 0.6 Ma. The chronological data suggest that the magmatic stage of the highly evolved Baerzhe alkaline granite lasted less than two million years. Hydrothermal monazite records a REE mineralization event at 122.8 ± 0.6 Ma, approximately 1 or 2 million years after Zr mineralization. We therefore propose a model in which parental magmas of the Baerzhe pluton underwent extensive magmatic differentiation while residual melts interacted with aqueous hydrothermal fluids. Deuteric zircon precipitated from a hydrosilicate liquid, and subsequent REE mineralization, exemplified by hydrothermal monazite, correlates with hydrothermal metasomatic alteration that postdated the hydrosilicate liquid event. Such interplay between magmatic and hydrothermal processes resulted in the formation of discrete Zr and REE mineralization at Baerzhe.

Influence of dirt and coating deterioration on the aging of solar reflectance of high-reflectance paint

Cool-roof coatings have received considerable attention worldwide as a solution for the “heat island” effect in urban areas. The solar reflectance of roofs coated with high-reflectance paint is reduced by dirt. We continuously measured the solar reflectance of a roof coated with high-reflectance paint with and without a self-cleaning function for more than two years. The solar reflectance of self-cleaning paint decreased by 0.5% per month over two years, due to the effect of dirt. The solar reflectance of conventional paint decreased by 4% per month over four months after coating and then reached a value similar to that for the self-cleaning paint for two years due to deterioration. With a slight decrease in solar reflectance, the self-cleaning function is effective in mitigating the heat island effect and obtaining continuous energy-savings. We applied the alkyl silicate system as self-cleaning for high-reflectance paint, the solar reflectance was measured continuously at 1 minute intervals, and the actual state of the fluctuation in reflectance over the short and long terms was analyzed with the influence of the altitude of the sun. The deterioration of the coating was also investigated by gloss retention and chalking test.

Investigation of a single-layer EBC deposited on SiC/SiC CMCs: Processing and corrosion behaviour in high-temperature steam

Two rare earth monosilicates (Yb2SiO5, and Lu2SiO5) were deposited using a low-cost coating application method to produce a single-layer coating. RE- oxides slurries were dip coated on oxidised CMC samples and subsequently heat treated at high temperature to ensure reaction between SiO2 and RE-oxides to form the RE-monosilicate. A single, continuous, homogeneous thick coating of 25 μm was obtained. X-ray diffraction (XRD) confirmed formation of, RE-monosilicates in Yb and Lu silicate systems. Coated samples were exposed to 90% H2O static steam environment at 1350 °C for 25, 50, 100, and 150 h. Scanning Electron Microscopy (SEM) indicated that both coatings adhered strongly to the substrate. Coating thickness reduced from 22 μm to 11 μm for Yb-coating and 13 to 4 μm for Lu-coating with increasing corrosion time from 25 to 150 h, however there was no significant attack of the CMC for all steam exposure times.

A sulfide perspective on iron isotope fractionation during ocean island basalt petrogenesis

Iron isotopic compositions are demonstrably powerful tracers of foundational planetary processes, including crust and core formation. In many volcanic environments, however, geochemical vestiges of these processes are obscured by the effects of magmatic differentiation on Fe isotopic compositions. Recent decades have witnessed continued refinement of observational and experimental approaches to Fe isotope fractionation during silicate differentiation. In contrast, the influence of sulfide fractionation on Fe isotopic compositions in terrestrial environments is known only from theoretical approaches and limited experimental data for relatively siliceous magmatic systems. One reason for this may be that sulfide fractionation is difficult to definitively trace using traditional major and minor element variation patterns. We utilize well-characterized lavas and cumulate xenoliths from Piton de la Fournaise and Piton des Neiges, Réunion Island, that have previously been examined for their highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) contents to investigate the effect of sulfide fractionation on Fe isotopes. The Fe isotopic compositions of the basalts range from δ56Fe values of 0.04 to 0.15‰ (average: 0.10‰) and the compositions of the cumulate xenoliths range from δ56Fe values of −0.07 to 0.08‰ (average: 0‰). In the absence of metal, HSE preferentially partition into sulfide phases, making them important tracers of sulfide segregation during magmatic differentiation. We find that commonly-observed co-variations between Fe isotopic compositions and major element oxide abundances are relatively underdeveloped for Réunion lavas. The correlation between Fe isotopic composition and MgO, for example, has a similar statistical significance to the correlation between Fe isotopic composition and Pd/Ir ratios, suggesting an important role of sulfides during Fe isotopic fractionation. After accounting for sulfide segregation, we determine that the parental magma Fe isotopic composition calculated for Piton de la Fournaise would be overestimated by 0.04‰ (within propagated error, 0.01–0.06‰) when considering silicate differentiation alone. An analogous calculation for Kilauea Iki basalts, for which there is available Fe isotopic and HSE data, yields a somewhat smaller difference of 0.02‰ (0–0.03‰). These differences may partially explain Fe isotopic compositions in other settings that could not previously be reconciled with a dominantly peridotitic and/or chondritic mantle source. This discovery may warrant discussion of the apparent decoupling between Fe and radiogenic isotopes in ocean island basalts, where the latter shows significant global variations and the former may show little or none. Our work highlights the need for additional constraints on the behavior of Fe isotopes during crustal recycling processes and reinforces the notion that consideration must be given to the effect of magmatic differentiation on Fe isotopic compositions.

UV radiation emitting Gd3+ activated Sr2SiO4 host system prepared by sol–gel procedure: structural, electron paramagnetic resonance, and luminescence studies

Trivalent gadolinium (Gd3+) activated strontium silicate (Sr2SiO4:xGd3+; 0.01 ≤ x ≤ 0.11) systems have been synthesized via sol–gel technique. The structural, morphological, luminescent, and magnetic properties have been investigated using X-ray diffraction patterns, scanning electron microscopy (SEM), photoluminescence (PL), and electron paramagnetic resonance (EPR) technique, respectively. The synthesized strontium silicate samples exhibit a mixed phase of α′ and β-Sr2SiO4. The SEM images show irregular morphologies with a random distribution of particles. The PL spectra confirm the ultraviolet emission from the synthesized samples and the optimum concentration of Gd3+ ions is observed at 0.05 mol. With low dopant concentrations, Sr2SiO4:Gd3+ sample displays EPR lines, mainly in the low field region with effective g-values 5.8, 4.5, 3.1, and 2.7. As dopant concentration increases, a broad line appears with geff ~ 2.1 along with the low field lines. A relatively strong crystal field is experienced by Gd3+ ion due to distortions in the immediate environment of the ion, which lead to low field EPR lines. These studies allow the use of gadolinium-activated strontium silicate in phototherapy lamps.

The Effect of Lithium on Crystallization and Microstructure of Glass-Ceramics in Soda-Lime Silicate System

This study investigated the crystallization of soda-lime silicate (NCS) system by re-melting soda-lime silicate glass cullet with Al2O3 CaCO3 and Li2O. The Li2O was added as a nucleating agent. The effect of the nucleating agent on crystallization was investigated in order to study the possibility for use as a parent glass for glass-ceramics. Soda-lime silicate cullet was the main raw material and its chemical composition by weight was 68% SiO2 2% Al2O3 9% Na2O 9% K2O 3.5% CaO 2.5% MgO 1.2% TiO2 3% SrO and 2% ZnO. Glass batches with composition (%wt) of (65-x) Cullet:13Al2O3:22CaCO3:x(Li2O) (x = 0, 1, 2, 4, 6 and 8) were melted at 1500°C for 3 hours and annealed at 600°C. All glasses added with Li2O were clear except x = 8. The crystallization was investigated by Differential Scanning Colorimetry technique (DSC). The results exhibited the exothermic peak of crystallization (TpI and TpII). The glasses with added Li2O exhibited decreasing crystallization temperature with increasing Li content. The glasses were heated at temperatures around the crystallization temperature (700, 750 and 800°C). After heat treatment, the crystalline phase in the glasses was determined by X-ray diffraction technique (XRD). The microstructure was investigated by optical microscope and Scanning Electron Microscope (SEM). The phases of Nepheline (Na,K)AlSiO4 and Wollastonite (CaSiO3) were found. The crystallization depended on the heat treatment temperature. The thermal expansion of the glasses was determined by the dilatometric method to indicate the characteristics of the glass-ceramics. In conclusion, Li2O had a strong effect on the crystallization in soda-lime silicate system. The result could be applied for the production of glass-ceramics from soda-lime cullet.

A Geo-Experimental Diagram for Garnet Amphibolite and Its Bearing on the Origin of Continents

Dehydration (fluid-absent) melting of garnetiferous amphibolite is now widely believed to have given rise to the tonalite-trondhjemite-granodiorite (TTG) suite of plutonic rocks that is the major component of all large Precambrian Shield terranes. The presence of garnet as a residual mineral of melting is implicated by geochemistry and for efficient gravitational segregation and disposal of the ultramafic residuum. The great volume of the ancient TTG rocks suggests that early large-scale continental accretion involved a conveyor belt process that delivered hydrated oceanic basalts to depths in the earth where garnet amphibolite is stable at the melting temperature. This process became active at some time during secular cooling of the earth. Experimental definition of the maximum (hence, oldest) geothermal gradients that could have sustained dehydration melting of garnet amphibolite has been hampered by the difficulty of achieving chemical equilibrium in unfluxed (fluid-absent) silicate systems at the low temperatures (∼800°C) where melting first occurs. An alternative approach, termed “geo-experimental,” attempts to define the PT stability field of garnet amphibolite on the basis of quantitative geothermometry-geobarometry of actual mafic rocks bearing the assemblage aluminous hornblende-almandine-rich garnet-plagioclase-quartz. The results show that garnet is stable to much lower pressures than previously thought. The garnet-in line has a positive dP/dT slope in both subsolidus and melt-present fields. A subduction temperature gradient as high as 36°C/km could have accompanied melting of garnet amphibolite and generation of TTG magmas in the earlier Archean. The near parallelism of the garnet-in line and geothermal curves could have acted like an on switch during cooling of the earth, resulting in a surge of felsic continent, with accumulation of nearly the present volume before the end of the Archean.

The effect of ligand-to-Eu3+ charge-transfer transitions (LMCT) on the photoluminescence intensity of M2SiO4: Eu3+ (M = Ca, Zn) type phosphors

Abstract In this study, silicate systems, M2SiO4 (M = Ca, Zn) were produced by solid state reaction and doped with 1 mol% Eu3+ rare-earth ion. Their heat treatments, which were conducted at 1200 °C and above for minimum 3 hours under an open atmosphere, were applied according to the DTA/TG results. Powder X-ray diffraction XRD analyses were performed to determine the phase properties of the phosphor systems after the sintering process. It was proved that the structures of two of the phosphor systems were well formed in except that the Zn2SiO4 had some ZnO secondary phases. The expected photoluminescence (PL) results were presented and the transitions of the Eu3+ ions were observed for both phosphors.

The plutonic crust of Kohistan and volcanic crust of Kohistan–Ladakh, north Pakistan/India: lessons learned for deep and shallow arc processes

Abstract The Kohistan–Ladakh terrane, northern Pakistan/India, offers a unique insight into whole-arc processes. This research review presents summaries of fundamental crustal genesis and evolution models. Earlier work focused on arc sequence definition. Later work focused on holistic petrogenesis. A new model emerges of an unusually thick ( c. 55 km) arc with a c. 30 km-thick batholith. Volatile-rich, hornblende ± garnet ± sediment assimilation-controlled magmatism is predominant. The thick batholith has a complementary mafic–ultramafic residue. Kohistan crustal SiO 2 contents are estimated at >56%. The new-Kohistan, silicic-crust model contrasts with previous lower SiO 2 estimates ( c. 51% SiO 2 crust) and modern arcs that imply <35 km crustal thicknesses and arc batholith thicknesses of c. 7 km. A synthetic overview of Kohistan–Ladakh volcanic rocks presents a model of an older, cleaved/deformed Cretaceous volcanic system at least 800 km across strike. The Jaglot–Chalt–Dras–Shyok volcanics exhibit predominant tholeiitic-calc-alkaline signatures, with a range of arc-related facies/tectonic settings. A younger, post-collisional, Tertiary silicic volcanic system (the Shamran–Dir–Dras-2–Khardung volcanics) lie unconformably upon Cretaceous basement, and erupted within an intra-continental tectonic setting. Kohistan–Ladakh tectonic model controversies remain. In essence, isotope-focused researchers prefer later (Tertiary) collisions, whilst structural field-geology-orientated researchers prefer an older (Cretaceous) age for the Northern/Shyok Suture.

Features of use of unlawful kaolin for the manufacture of a cement clinker

Results over of research of the silicate systems of carbonate raw material with the varieties of clay component for making of cement clinker. The features of the chemical-mineralogical composition, phase transformations during burning and astringent properties of clinker are shown when unenriched kaolin and fly ash are used as alumina-silica-containing components of the initial raw material mixture. In the chemical technology of hydraulic mineral astringents, clay raw material serves, first of all, as a source of SiO , Al O , Fe O oxides, which must form from CaO during the baking of crystalline phases of silicates, aluminates and calcium aluminferrite, with the development of which impart the properties of the product of production. In turn, the above oxides arise in the process of technology during the heat treatment of raw mixtures due to the destruction of the lattice of rock-forming minerals. Hence the obvious dependence of the number and reactivity of oxides on the chemical and mineralogical composition of clay raw material, which, according to essential differences, is classified into a number of groups. Deepening of scientific ideas about this dependence can become an additional factor for im- proving the intensification of the technology of silicate binders, which became the subject of research in the given work. The chemical and mineralogical composition of the clay component of raw materials for the production of clinker and cement based on it is an important factor in the structure of the binder material at the stages of the technological process and the determination of the properties of the final product. Taking into account the peculiarities of the composition of unbleached kaolin (high content of kaolinite, quartz, feldspar), the feasibility of its application in the production of cement for clinker production is related to the possibility of adjusting the kinetics and the direction of phase transformations during the burning of the material. From the point of view of resource conservation and technology, the complex application of aluminum and silicon-containing raw materials components of natural (unaffected kaolin) and man-made (fly ash) origin is shown. Deepening of scientific ideas about this dependence can become an additional factor for improving the intensification of the technology of silicate binders, which became the subject of research in the given work.

Near-Infrared Ratiometric Luminescent Thermometer Based on a New Lanthanide Silicate.

A new lanthanide silicate system, Na2 K[Ln3 Si6 O18 ] (Ln=Lu, Yb/ Er, Lu/Eu, or Lu/Yb/Er), comprising microcrystals embedded in an amorphous siliceous matrix, obtained by sintering at 1373 K a Na3 K[Ln2 Si6 O17 ]⋅3 H2 O nano-crystalline precursor, is reported. The crystal structure of these lanthanide silicates was solved from high-resolution synchrotron power X-ray diffraction data collected at 110 K, and further supported by 29 Si MAS NMR and Eu3+ luminescence. The materials crystallize in the Pī triclinic centrosymmetric space group, exhibiting a dense framework consisting of hexameric [Si6 O18 ]12- cyclosilicate units, and chains of two distinct {LnO6 } octahedra. Na2 K[(Lu0.75 Yb0.20 Er0.05 )3 Si6 O18 ] is the first example of a lanthanide silicate operative as a near-infrared ratiometric luminescent thermometer, with good sensitivity at cryogenic temperatures (<100 K). Upon excitation at 903 nm, the ratio between the 2 F7/2 →2 F5/2 (Yb3+ ) and 4 I13/2 →4 I15/2 (Er3+ ) emissions was used for sensing temperature in the 12-450 K range, reaching a maximum thermal sensitivity of 2.6 % K-1 at 26.8 K.

An investigation of microstructure evolution for plasma electrolytic oxidation (PEO) coated Al in an alkaline silicate electrolyte

In the current investigation, plasma electrolytic oxidation (PEO) ceramic coatings on Al are galvanostatically synthesized at various processing stages in an alkaline silicate system. The resultant coatings are systematically surveyed in terms of the following respects: the applied voltage and surface sparking evolution over the studied course of PEO are recorded by the signal acquisition system and the real time imaging, respectively; the phase constitution, the surface morphology, polished cross section of the coated specimens, the fractured cross section and coating/substrate interface of the detached coatings are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) assisted with energy-dispersive X-ray spectrometer (EDS), respectively. In particular, the coatings detached by an in-house developed electrochemical way disclose the coating microstructure in a new angle, which allows the cross section and the coating/substrate interface to come clearly into focus. The microstructure evolution of the oxide ceramic coatings and the correspondences among the characteristic microstructures of the free surface, the fractured cross section and the coating/substrate interface are presented and discussed. Further, based on the present PEO coating microstructure, a model of the coating growth that evolves over time is proposed.