Composition Of Grains Research Articles

Platinum Group Minerals in Sulfide Droplets of the Zhelos Intrusion, Eastern Sayn, Russia: First Data

The composition of platinum group minerals localized in sulfide droplets from peridotites of the Zhelos intrusion was studied on a scanning electron microscope and on an electron probe microanalyzer. As part of this study, also an analytical approach based on the variation in accelerating voltage, electron beam intensity and probe diameter is considered in order to estimate the X-ray generation region, when analyzing PGM microinclusions comparable in size to the radiation generation region or smaller. Estimates were made of the possibility of reducing the size of the local analysis area when the accelerating voltage was reduced. The influence of the matrix composition on the results of the local analysis of PGM microphases and accuracy of the Pd and Pt content determination was also evaluated. The findings of the experiments conducted allowed for the successful identification of elements belonging to the PGM microphases and the host matrix. This approach enabled the estimation of the precise levels of impurity elements in their composition. Using a scanning electron microscope in the automatic scanning mode for the detection of heavy elements, 10 single and composite grains of three platinum group minerals larger than 5 µm and 22 microphases ranging in size from 0.3 to 4 µm were detected in the sulfide droplets. The large phases are merenskyite, omeiite and michenerite, with merenskyite being predominant. Among the microscopic inclusions were identified Pd-Bi-Te, Os-Ru-As and Rh-As-S phases. The composition of the studied palladium bismuthotelluride samples indicates a formation temperature range of 489–700 °C.

Enzymatic hydrolysates of grain and products of its processing. A review of the subject field

The paper presents a review of scientific publications devoted to investigation of an action of enzyme preparations and their compositions on various grain substrates, production of enzymatic hydrolysates and structurally modified secondary products of grain processing. Depending on the set goals, the main of which is the industrial use of products of enzymatic modification, a method is proposed for separation of hydrolysates into two groups: (1) with isolation and purification of protein from ballast compounds with the following hydrolysis and (2) without preliminary isolation of protein. The present review is based on the results of studies by national and foreign scientists with the use of search systems and databases: eLibrary, CyberLeninka, Google Scholar, ScienceDirect, Springer open, PubMed. Analysis of the subject field shows a very wide range of publications related to characteristics of enzymatic hydrolysates produced using biopolimers of animal and plant raw materials as a substrate. Over the last ten years, the number of studies on enzymatic modification of various types of grain and leguminous crops, and composite grain mixtures has increased significantly; the possibilities of their use as enriching, functional-technological and functional components of feedstuff and food products have been studied. The revival of the microbiological branch, including production of domestic enzyme preparations, is based on experimental studies on the search for new producer strains and improvement of methods for isolation, purification and stabilization of enzymes. All studies by national and foreign authors support the topicality and good prospects of increasing a range of the use of enzymatic hydrolysates obtained from the grain raw material and secondary products of its processing in various areas of the feedstuff production, food industry and pharmacology.

Ultrasonic-assisted-infiltration of Al5083/SiC 30PPI- C4 composites and its characterization

This article describes the fabrication of interpenetrating co-continuous ceramic composite Al5083/SiC composites using the ultrasonic-assisted gas pressure infiltration technique. Composites were made using open porous foam with 30 pores per inch (PPI). According to microstructural analyses, the ultrasonic-assisted infiltration technique improves infiltration, and refines the composite's grain structure. The evaluation of mechanical properties demonstrates that the Ultrasonic Treatment (UT) enhances the 30PPI-C4 composite's hardness and compression strength. The inclusion of ultrasonic treatment raises the hardness of the 30PPI-C4 composite alloy from around 135.5 HB to about 142 HB. Compared to the untreated 30PPI-C4 composite, the ultrasonic treatment-assisted manufacturing increased the composite's compression strength by almost 7%. A conical projectile was used for ballistic testing, and the distance the projectile penetrated into the 30PPI-C4 composite was used to determine the depth of damage. Without the ultrasonic treatment, the projectile pierces the 30PPI-C4 composite 5.92 ± 0.55 mm. On the other hand, the depth of penetration is decreased to about 4.09 ± 0.13 mm following ultrasonic treatment.

Improved Ferroelectric and Magnetic Properties of Bismuth Ferrite-Based Ceramics by Introduction of Non-Isovalent Ions and Grain Engineering.

Single-phase multiferroics exhibiting ferroelectricity and ferromagnetism are considered pivotal for advancing next-generation multistate memories, spintronic devices, sensors, and logic devices. In this study, the magnetic and electric characteristics of bismuth ferrite (BiFeO3) ceramics were enhanced through compositional design and grain engineering. BiFeO3 ceramic was co-substituted by neodymium (Nd) and niobium (Nb), two non-isovalent elements, via the spark plasma sintering process using phase-pure powder prepared via sol-gel as the precursor. The symmetry of the sintered Nd-Nb co-doped samples changed from R3c to Pnma, accompanied by a decrease in the loss tangent, grain size, and leakage current density. The reduction in the leakage current density of the co-doped samples was ~three orders of magnitude. Moreover, ferroelectric, dielectric, and magnetic properties were substantially improved. The remanent polarization and magnetization values of the optimized Nd-Nb co-doped BiFeO3 sample were 3.12 μC cm-2 and 0.15 emu g-1, respectively. The multiferroic properties were enhanced based on multiple factors such as structural distortion caused by co-doping, grain size reduction, suppression of defect charges via donor doping, space-modulated spin structure disruption, and an increase in magnetic ions. The synergistic approach of composition design and grain engineering sets a paradigm for the advancement of multiferroic materials.

PHANGS-ML: The Universal Relation between PAH Band and Optical Line Ratios across Nearby Star-forming Galaxies

Abstract The structure and chemistry of the dusty interstellar medium (ISM) are shaped by complex processes that depend on the local radiation field, gas composition, and dust grain properties. Of particular importance are polycyclic aromatic hydrocarbons (PAHs), which emit strong vibrational bands in the mid-infrared, and play a key role in the ISM energy balance. We recently identified global correlations between PAH band and optical line ratios across three nearby galaxies, suggesting a connection between PAH heating and gas ionization throughout the ISM. In this work, we perform a census of the PAH heating–gas ionization connection using ∼700,000 independent pixels that probe scales of 40–150 pc in 19 nearby star-forming galaxies from the PHANGS survey. We find a universal relation between log PAH(11.3 μm/7.7 μm) and log ([S ii]/Hα) with a slope of ∼0.2 and a scatter of ∼0.025 dex. The only exception is a group of anomalous pixels that show unusually high (11.3 μm/7.7 μm) PAH ratios in regions with old stellar populations and high starlight-to-dust emission ratios. Their mid-infrared spectra resemble those of elliptical galaxies. Active galactic nucleus hosts show modestly steeper slopes, with a ∼​​​​​​10% increase in PAH(11.3 μm/7.7 μm) in the diffuse gas on kiloparsec scales. This universal relation implies an emerging simplicity in the complex ISM, with a sequence that is driven by a single varying property: the spectral shape of the interstellar radiation field. This suggests that other properties, such as gas-phase abundances, gas ionization parameter, and grain charge distribution, are relatively uniform in all but specific cases.

Imaging Spectroscopy: Earth and Planetary Remote Sensing with the PSI Tetracorder and Expert Systems from Rovers to EMIT and Beyond

A system for rapid analysis of spectroscopy data with emphasis on planetary surfaces, both imaging and single-spectrum data, is described. The system, called Tetracorder, is commanded by an expert system developed by expert spectroscopists. The Tetracorder and the expert system apply multiple algorithms to analyze a spectrum in segments, leveraging the advantages of each spectral region’s sensitivity to detecting different compounds, whether solid, liquid, or gas. The algorithms compare measured spectra to the spectral properties of materials in spectral libraries. The libraries include pure minerals, mineral mixtures that include areal mixtures, intimate mixtures, coatings, and molecular mixtures and other compounds such as organics, vegetation, liquids, and gases. Absorption bands of a particulate surface change shape with grain size, and shape changes are used in some cases to constrain grain size of each component in the surface. The different algorithm results are compared for each spectral region, and specific material composition and average grain size (when possible) are identified. The system is operational analyzing real-time data on a new generation of rovers for future planetary missions, as well as identifying materials using an imaging spectrometer on the International Space Station. Four abundance models are presented, each with increasing sophistication, that are computationally fast on imaging spectrometer data and use Tetracorder identifications to produce maps of mineral abundances. A fifth full radiative model that includes multilayer surfaces is presented but is computationally intensive. The system is open source and available on GitHub.

Crystal structure and hydrogen storage properties of ZrNbFeCo medium-entropy alloy

Crystal structure and hydrogen storage properties of ZrNbFeCo medium-entropy alloy

Influence of Lithology and Biota on Stream Erosivity and Drainage Density in a Semi‐Arid Landscape, Central Chile

Abstract Drainage density is a fundamental landscape feature that determines the length scale for hillslope sediment transport and results from the competition of diffusive hillslope and advective stream incision processes, whose efficiencies are known to vary with rock type but are notoriously difficult to quantify. Here, we present a comprehensive analysis of a catchment in semi‐arid Central Chile, where landscapes with different drainage densities, but equal tectonic and climatic conditions, have formed on three neighboring granitoid plutons (a monzogranite and two diorites). We combined topographic analysis of a 1‐m digital elevation model with 10Be‐derived denudation rates to estimate stream erosivity and soil diffusivity in the different landscapes. We find that the higher drainage density in the monzogranite is primarily due to higher stream erosivity, whereas soil diffusivity is similar between rock types. Remote sensing data from Landsat imagery confirm field observations of higher vegetation cover in the diorites, especially with regard to deeper‐rooted shrubs, which may result in increased infiltration. Based on geochemical and compositional analyses, we link vegetation differences to a relatively higher abundance of plant‐essential elements in the diorite bedrock. Additionally, the monzogranite's composition and crystal grain size supports more intense physical weathering and leads to a smaller observed hillslope grain size, which increases its erodibility. We conclude that subtle differences in composition and grain size can have a significant impact on stream erosivity and drainage density. Our results demonstrate the importance of taking lithology into account when interpreting fluvial networks and topographic metrics in slowly eroding landscapes.

Simulation of the Evolution of Phase Composition and Austenite Grain Size upon Multi-Pass Hot Deformationof Low-Alloy Steels

The paper presents a model for predicting the structural characteristics and phase composition of low-alloy steels upon hot rolling in the multi-pass deformation mode. The model considers recovery, dynamic, primary, dynamic and static recrystallization of grains, and the normal grain growth, as well as nucleation (including accelerated nucleation during deformation), growth or dissolution, and coarsening of carbonitride particles. The comparison between the calculated results and the experimental data available in the publications shows a satisfactory agreement.

Updimensioning strategy derived from synthetic equiaxed grain structures for approximating 3D grain size distributions from 2D visualizations with 1D parameters

We generated synthetic equiaxed grain structures using computer graphics software to explore the relationship between various grain size determination methods and true three-dimensional (3D) grain diameters. Mirroring grain measurement techniques, the synthetic 3D grain structures are imaged as 2D micrographs which are measured to yield 1D grain size parameters. Synthetic grain structures provide data at a mass scale and permit exploration of both polished and fractured surface micrographs, revealing one-to-one correspondence between exposed 2D grain cross-sections and individual 3D grains. Analysis of this correspondence yielded a procedure to approximate 3D equiaxed grain size and volume distributions based on the mode of the 2D fractograph grain size distribution. The 3D approximation procedure is shown to be less susceptible to different imaging conditions that affect small, undiscernible grains compared to the standard planimetric and linear intercept methods, which by design also tend to underestimate the 3D grain diameter. The procedure requires larger sample sizes to lower variance and a deeper analysis which could become more practical with machine learning (ML) models for grain boundary segmentation, which synthetic grain structures can help train. This work lays the foundation for analyzing other grain distributions such as columnar and composite grains in similar depth.

Preparation of ultrafine WC-V8C7-Cr3C2-co cemented carbides by spark plasma sintering in-situ synthesis of composite grain growth inhibitors

Preparation of ultrafine WC-V8C7-Cr3C2-co cemented carbides by spark plasma sintering in-situ synthesis of composite grain growth inhibitors

Achieving significant grain refinement efficiency in Mg-Al alloys via a GNP@MgO composite refiner

Achieving significant grain refinement efficiency in Mg-Al alloys via a GNP@MgO composite refiner

Modeling the Enceladus dust plume based on in situ measurements performed with theCassiniCosmic Dust Analyzer

We analyzed data recorded by the Cosmic Dust Analyzer on board theCassinispacecraft during Enceladus dust plume traversals. Our focus was on profiles of relative abundances of grains of different compositional types derived from mass spectra recorded with the Dust Analyzer subsystem during theCassiniflybys E5 and E17. The E5 profile, corresponding to a steep and fast traversal of the plume, has already been analyzed. In this paper, we included a second profile from the E17 flyby involving a nearly horizontal traversal of the south polar terrain at a significantly lower velocity. Additionally, we incorporated dust detection rates from the High Rate Detector subsystem during flybys E7 and E21. We derived grain size ranges in the different observational data sets and used these data to constrain parameters for a new dust plume model. This model was constructed using a mathematical description of dust ejection implemented in the software package DUDI. Further constraints included published velocities of gas ejection, positions of gas and dust jets, and the mass production rate of the plume. Our model employs two different types of sources: diffuse sources of dust ejected with a lower velocity and jets with a faster and more colimated emission. From our model, we derived dust mass production rates for different compositional grain types, amounting to at least 28 kg s−1. Previously, salt-rich dust was believed to dominate the plume mass based on E5 data alone. The E17 profile shows a dominance of organic-enriched grains over the south polar terrain, a region not well constrained by E5 data. By including both E5 and E17 profiles, we find the salt-rich dust contribution to be at most 1% by mass. This revision also results from an improved understanding of grain masses of various compositional types that implies smaller sizes for salt-rich grains. Our new model can predict grain numbers and masses for future mission detectors during plume traversals.

Structural Diagnosis of Solid Rocket Motors Using Neural Networks and Embedded Optical Strain Sensors

The main failures that could deteriorate the reliable operation of solid rocket motors (SRMs) and lead to catastrophic events are related to bore cracks and delamination. Current SRMs’ predictive assessment and damage identification practices include time-consuming and cost-demanding destructive inspection techniques. By considering state-of-the-art optical strain sensors based on fiber Bragg gratings, a theoretical study on the use of such sensors embedded in the circumference of the composite propellant grain for damage detection is presented. Deep neural networks were considered for the accurate prediction of the presence and extent of the defects, trained using synthetic datasets derived through finite element analysis method. The evaluation of this combined approach proved highly efficient in discriminating between the healthy and the damaged condition, with an accuracy higher than 98%, and in predicting the extent of the defect with an error of 2.3 mm for the bore crack depth and 1.6° for the delamination angle (for a typical ~406 mm diameter grain) in the worst case of coexistent defects. This work suggests the basis for complete diagnosis of solid rocket motors by overcoming certain integration and performance limitations of currently employed dual bond stress and temperature sensors via the more scalable, safe, sensitive, and robust solution of fiber optic strain sensors.

Vermicompost Supply Enhances Fragrant-Rice Yield by Improving Soil Fertility and Eukaryotic Microbial Community Composition under Environmental Stress Conditions.

Heavy-metal contamination in agricultural soil, particularly of cadmium (Cd), poses serious threats to soil biodiversity, rice production, and food safety. Soil microbes improve soil fertility by regulating soil organic matter production, plant nutrient accumulation, and pollutant transformation. Addressing the impact of Cd toxicity on soil fungal community composition, soil health, and rice yield is urgently required for sustainable rice production. Vermicompost (VC) is an organic fertilizer that alleviates the toxic effects of Cd on soil microbial biodiversity and functionality and improves crop productivity sustainably. In the present study, we examined the effects of different doses of VC (i.e., 0, 3, and 6 tons ha-1) and levels of Cd stress (i.e., 0 and 25 mg Cd kg-1) on soil biochemical attributes, soil fungal community composition, and fragrant-rice grain yield. The results showed that the Cd toxicity significantly reduced soil fertility, eukaryotic microbial community composition and rice grain yield. However, the VC addition alleviated the Cd toxicity and significantly improved the soil fungal community; additionally, it enhanced the relative abundance of Ascomycota, Chlorophyta, Ciliophora, Basidiomycota, and Glomeromycta in Cd-contaminated soils. Moreover, the VC addition enhanced the soil's chemical attributes, including soil pH, soil organic carbon (SOC), available nitrogen (AN), total nitrogen (TN), and microbial biomass C and N, compared to non-VC treated soil under Cd toxicity conditions. Similarly, the VC application significantly increased rice grain yield and decreased the Cd uptake in rice. One possible explanation for the reduced Cd uptake in plants is that VC amendments influence the soil's biological properties, which ultimately reduces soil Cd bioavailability and subsequently influences the Cd uptake and accumulation in rice plants. RDA analysis determined that the leading fungal species were highly related to soil environmental attributes and microbial biomass C and N production. However, the relative abundance levels of Ascomycota, Basidiomycota, and Glomeromycta were strongly associated with soil environmental variables. Thus, the outcomes of this study reveal that the use of VC in Cd-contaminated soils could be useful for sustainable rice production and safe utilization of Cd-polluted soil.

Investigating the flux pinning dependence on grain orientation in YBa2Cu3O7−δ using neutron tomography

In this study, we report the first case of non-destructive characterization of the dependence of the flux trapping mechanism on the grain properties of a bulk type II superconductor using a combination of polarized neutron tomography and diffraction contrast tomography. The high temperature superconductor, YBa2Cu3O7−δ, has been used in this study due to its viable commercial growth processes typically resulting in the production of polycrystalline specimens. The diffraction tomography revealed the pseudo-single crystal nature of the sample i.e. a polycrystalline sample with 47 composite grains having a maximum grain misorientation angle of 1.86°. Polarized neutron tomography was used for characterization of the flux trapped in the material after field cooling to 90.5 K in a field of 0.5 mT and switching off the field. A combination of the results from these two non-destructive characterization techniques indicate a correlation between the anisotropy of the trapped flux with the orientation of the grains in the material in addition to a preference for the flux trapping in the grain boundaries.

The chromitites of the Herbeira massif (Cabo Ortegal Complex, Spain) revisited

The ultramafic rocks of the Herbeira Massif in the Cabo Ortegal Complex (NW Iberia) host chromitite bodies. The textural and compositional study of the host rocks and the chromitites classified them into: (1) Type-I chromitites, forming massive pods of intermediate-Cr chromite (Cr# = 0.60–0.66) within dunites; and (2) Type-II chromitites forming semi-massive horizons of high-Cr chromite (Cr# = 0.75–0.82) interlayered with dunites and pyroxenites. Minor and trace elements (Ga, Ti, Ni, Zn, Co, Mn, V and Sc) contents in the unaltered chromite cores from both types show patterns very similar to fore-arc chromitites, mimicked by the host dunites and pyroxenites. Calculated parental melt compositions suggest that Type-I chromitites crystallized from a melt akin to fore-arc basalt (FAB), while Type-II chromitites originated from a boninite-like parental melt. Both melts are characteristic of a fore-arc setting affected by extension during rollback subduction and have been related to the development of a Cambrian-Ordovician arc. These chromitites are extremely enriched in platinum-group elements (PGE), with bulk-rock PGE contents between 2,460 and 3,600 ppb. Also, the host dunites and pyroxenites exhibit high PGE contents (167 and 324 ppb, respectively), which are higher than those from the primitive mantle and global ophiolitic mantle peridotites. The PGE enrichment is expressed in positively-sloped chondrite-normalized PGE patterns, characterized by an enrichment in Pd-group PGE (PPGE: Rh, Pt and Pd) over the Ir-group PGE (IPGE: Os, Ir and Ru) and abundant platinum-group minerals (PGM) dominated by Rh-Pt-Pd phases (i.e. Rh-Ir-Pt-bearing arsenides and sulfarsenides, Pt-Ir-Pd-base-metal-bearing alloys, and Pt-Pd-bearing sulfides). The PGM assemblage is associated with base-metal sulfides (mostly pentlandite and chalcopyrite) and occurs at the edges of chromite or embedded within the interstitial (serpentinized) silicate groundmass. Their origin has been linked to direct crystallization from a S-As-rich melt(s), segregated by immiscibility from evolved volatile-rich small volume melts during subduction. At c. 380 Ma, retrograde amphibolite-facies metamorphism occurred during the exhumation of the HP-HT rocks of the Capelada Unit, which affected chromitites and their host rocks but preserved the primary composition of chromite cores of the chromitites. This event contributed to local remobilization of PGE as suggested by the negative slope between Pt and Pd and high Pt/Pd ratios in the studied chromitites, and host dunites and pyroxenites. In addition, it promoted the alteration of primary PGM assemblage and the formation of secondary PGM. Nanoscale observations made by focused ion beam high-resolution transmission electron microscopy (FIB/HRTEM) analysis of a composite grain of Rh-bearing arsenide with PGE-base-metal bearing alloys suggest the mobilization and accumulation of small nanoparticles of PGE and base-metals that precipitated from metamorphic fluids forming PGE-alloys. Finally, we offer a comparison of the Cabo Ortegal chromitites with other ophiolitic chromitites involved in the Variscan orogeny, from the Iberian Peninsula to the Polish Sudetes. The studied Cabo Ortegal chromitites are similar to the Variscan chromitites documented in the Bragança (northern Portugal) and Kraubath (Styria, Austria) ophiolitic massifs.

A route to fabricate low resistance joints between Eu–Ba–Cu–O bulk, single grain superconductors

The fabrication of large (RE)–Ba–Cu–O single grains [(RE)BCO], where RE = Y, Gd, Eu or Sm, with the complex geometries required for many practical applications is currently limited by the time intensive, complex nature of the grain growth process. In addition, the shapes achievable using established melt processing techniques, such as top seeded melt growth, are constrained significantly by the limited number of post-processing techniques readily available. Machining of these materials is also difficult given their ceramic-like mechanical properties, which makes them both brittle and hard. A potential alternative to the slow and inflexible melt growth processes is to join many small, single grains to form one large composite grain, connected by electrically and mechanically high-performance joints. A reliable joining technique would also greatly reduce the need for post-growth machining processes. In this work we extend our previous investigation of the use of single grain YBCO-Ag as an intermediate joining material to achieve effective and reliable superconducting joints between EuBCO-Ag bulk, single grain superconductors. The technique reported in the earlier studies requires limited specialist equipment and does not require tight process parameter control, since there is no need to re-grow the joining material at the intergrain interface. This technique is of particular interest given that the difference between the peritectic temperatures of the bulk superconductor and the intermediate joining material is large. We report the properties of seven joints engineered at different joining temperatures. The trapped field properties of the resulting joined samples were measured and the microstructure at the position of the joint examined. We demonstrate that this simple and the rapid joining technique makes it possible to manufacture composite grains in an industrially important (RE)BCO bulk superconductor with comparable superconducting properties to those of a single grain of similar dimensions.

Effect of SHS powder processing on structure formation and optical transmittance of MgO–Y2O3 composite ceramic

Effect of SHS powder processing on structure formation and optical transmittance of MgO–Y2O3 composite ceramic

Investigating nano-SiC reinforced WE43 magnesium matrix surface composites

Magnesium matrix surface composites have been garnering attention due to their superior mechanical and corrosion resistance properties. An idea of facile fabrication of surface composite composed of nano-SiC reinforced WE43 matrix through friction stir processing was explored in this study. Also, the effects of tool geometries, tool rotations, and tool feeds on resultant properties were comprehensively investigated. Uniform dispersion of SiC nanoparticles within stir zone was evident. Square tool demonstrated the most promising results. Processing at 1700 rev min−1 and 60 mm min−1 with a square tool produced finest grains in surface composites exhibited exceptional microhardness (180.8 HV), nanohardness (1.867 GPa), elastic modulus (41.69 GPa), and wear resistance (0.0254 mm3 min−1). Besides it, WE43 substrates also exhibited superior mechanical properties when processed with a square tool at 800 rev min−1 and 60 mm min−1. This research opens up new possibilities for the development of reliable magnesium matrix surface composites for multifunctional applications.