Grain-size Trends Research Articles

Water ice particles detected by SELENE's Spectral Profiler at lunar shadowed regions in various local times and latitudes

Processes of water (OH and H2O) migration on the Moon remain unclear, prompting active research. Understanding lunar water migration requires investigation of the trapping and diffusion properties of water at various latitudes and local times. This study analyzed visible to near-infrared spectral data obtained by the Spectral Profiler (SP) onboard SELENE for shadowed regions at various local times and latitudes, not limited to the polar permanently shadowed regions. We assessed SP data for shadowed regions in 60 areas, each spanning a 10° × 10° latitude–longitude grid. Of the 1,061,907 analyzed shadowed-region data, 41,385 at various latitudes exhibited significant absorption in the 1.25 and 1.5 µm bands, indicating water ice particles. Data with the two absorption features suggest the presence of a water ice frost layer covering the lunar surface or suspended water ice particles above the lunar surface, at various latitude shadowed regions. Our spectral simulations have quantified the ice particles as being 0.1–1 µm in diameter, with a column density of 10–4–10–3 kg/m2. The spectral parameters for band absorption at the 1.5 µm band show symmetry between morning and evening sides, which is potentially attributed to the absence of variations in ice grain size and quantity. The 1.5 µm band absorption shows an increasing trend toward terminator regions, indicating variation in the water ice distribution and likely reflecting temperature conditions for water retention. The latitudinal trend of ice grain size and quantity remains uncertain because of the observed noise levels. Observations of water ice particles in shadowed regions at various latitudes and local times can provide new constraints on trapping and diffusion processes of lunar water migration.

Seasonal biophysical interactions in tidal marsh evolution: insights from a synchronized dataset in Jiangsu, China

IntroductionTidal marsh wetlands provide essential and valuable services to the wider interconnected marine and coastal environment, although the complex intertwined processes in morphological evolution remain insufficiently understood owing to synchronized data scarcity, limiting the development of numerical models and management strategies.MethodsThis study investigated the hydrodynamic, biological, sediment and morphological processes on the Doulong tidal wetlands, Jiangsu, China, using a one-year field dataset that captured spatial and seasonal variations.Results and discussionOur results indicate that biophysical interactions among multiple processes could result in some overlooked sedimentary behaviours and bio-morphological patterns in tidal marsh wetlands. Firstly, the dominance of alongshore currents caused a rapid alongshore expansion of saltmarsh patches, by which the marsh edge achieved seaward advancing, markedly different from the widely reported cross-shore expansion. Secondly, results showed that the particle size of sediment near the marsh edge coarsened when plants withered and then fined when plants grew, indicating that the seasonal variation trend of sediment grain size in saltmarshes was opposite to the trend of vegetation biomass. Thirdly, the interaction between vegetation and stranded marine debris formed banded debris zones within the saltmarsh, where debris bands could cause a biomass reduction of up to 58%, disrupting the commonly-observed parabolic biomass-elevation relationship. Meanwhile, the seasonal variation of vegetation and hydrodynamics could alter the debris positions and hence result in the formation of multiple parallel debris bands. Overall, this study provides a synchronized dataset and elucidates specific bio-morphological relationships and processes that have thus far not been systematically documented, enhancing the comprehensive understanding of tidal marsh wetland evolution.

Effects of Mg Substitution on the Structural with Rietveld Analysis, Magnetic and Magnetocaloric Properties of Ni-Cu-Cd Bulk Ceramics

Bulk ceramics with optimized density are highly prioritized over ferrite nanoparticles to fabricate devices for their optimal magnetic saturation, lower coercivity, and anisotropy, enhanced resistance, etc. To achieve such bulk specimen using Ni0.5-yMgyCu0.2Cd0.3Fe2O4 disc samples are sintered at 1423 K keeping the heating and cooling rate at 10 K and 5 K respectively. In due course, structural as well as theoretical Rietveld analysis, optical, and magnetic properties have been analyzed using these bulk samples. XRD has explored structural properties and after that these values have analyzed with the Rietveld refinement procedure and obtained goodness of χ2 (1–2) value and other parameters such as lattice parameters, crystal structures, cation distribution, and maximum entropy mapping. Surface morphology and grain size have examined from the as-grown surface without further polishing and annealing by electron microscopy and revealed a decreasing trend of grain size 6.1 µm to 4.2 µm. UV–Vis spectroscopy characterization ensured optical properties for bulk as well as nanopowders and the band gap has been found in the range of 1.4 to 1.6 eV and is increasing with Mg content. Magnetic hysteresis loop exhibits a less decreasing nature up to y = 0.3 of magnetic saturation along with the Law of Approach to saturation which compiles magnetic anisotropy. The temperature-dependent magnetization curves exhibit a sharp decreasing value (i.e. dM/dT maximum) at Curie point, decreasing from 630 K to 505 K with increasing Mg content. At.3 T magnetic field the changes in relative cooling power value have been found in the range 53.82Jkg-1 to 37.79Jkg-1 which could be considered as potential for magnetocaloric refrigeration.

Mapping surface sediment characteristics in enclosed shallow‐marine environments using spatially balanced designs and the random forest algorithm

AbstractMapping the sedimentary character of the seafloor in large water‐filled basins is fundamental for understanding landform dynamics to inform research, management, intervention and conservation actions. Seabed mapping methods have undergone considerable development in the last two decades, including the uptake of machine learning approaches for sediment size prediction and classification. However, predictions of surficial sediment characteristics are often hindered by the availability of ground truthing data, their arrangement in space and the modelling approach chosen. Spatially informed sampling designs provide an opportunity to significantly improve the accuracy and uncertainty of predicted sediment distributions. In this study, we apply a machine learning algorithm to predict sediment distributions across Port Phillip Bay, a large (1930 km2) structurally controlled estuary on the southeast coast of Victoria, Australia. Surface sediment samples (n = 252) were collected using a spatially balanced design, ensuring that sampling effort was spread evenly within the embayment with increased sampling intensity placed in more heterogeneous areas. Surficial textural metrics were modelled using the random forest algorithm with bathymetric and hydrodynamic predictor variables. Models highlighted trends in sediment grain size, sorting and composition consistent with predicted wave‐ and current‐induced sediment mobilisation. Model predictions were accurate (normalised‐root mean squared error [NRMSE]: 0.14–0.16); however, standard error was not homogeneous across the study area. Uncertainty maps highlighted areas where additional sampling effort may be needed, including areas where transitional bathymetry impacted surficial sediment character and areas of anthropogenic modifications to the seabed. This study shows the benefits of undertaking spatially informed sample design, block cross‐validation during model fitting and quantifying spatial uncertainty in predictive maps to accurately quantify the fundamental boundary conditions of sediment size. The results of this study are intended to inform local coastal management, including beach renourishment activities. However, approaches outlined are applicable to any study where the seafloor grain size is a fundamental variable in understanding landscape change.

Deposition and Optical Characterization of Sputter Deposited p-Type Delafossite CuGaO2 Thin Films Using Cu2O and Ga2O3 Targets.

CuGaO2 thin films were deposited using the RF magnetron sputtering technique using Cu2O and Ga2O3 targets. The films were deposited at room temperature onto a quartz slide. The sputtering power of Cu2O remained constant at 50 W, while the sputtering power of Ga2O3 was systematically varied from 150 W to 200 W. The films were subsequently subjected to annealing at temperatures of 850 °C and 900 °C in a nitrogen atmosphere for a duration of 5 h. XRD analysis on films deposited with a Ga2O3 sputtering power of 175 W annealed at 900 °C revealed the development of nearly single-phase delafossite CuGaO2 thin films. SEM images of films annealed at 900 °C showed an increasing trend in grain size with a change in sputtering power level. Optical studies performed on the film revealed a transmission of 84.97% and indicated a band gap of approximately 3.27 eV. The film exhibited a refractive index of 2.5 within the wavelength range of 300 to 450 nm.

Overcoming inter-dataset discrepancies in the grain size distributions of fine-grained sediments by partial least squares regression: A case study of the Belgian Boom Formation

The grain size distribution is an important property of all clastic sediments: it determines their mechanical properties and is directly related to their mode of transport and origin. Therefore, the accurate measurement and comparability of grain size data are important. The former has been studied in detail in literature and has been demonstrated to be significantly instrument-dependent, while the latter has not been given the same attention. The current study examined in detail a large set of grain size data measured on a single clay formation, the Oligocene Boom Formation, from which the large influence of sample preparation on the grain size distribution can be inferred. Especially the use of sonication to disintegrate silt-sized aggregates was found to be of a particularly big influence on the measured distributions. As a way to still be able to valorize non-comparable datasets, a statistical conversion procedure was introduced based on partial least squares regression in a compositional data space. The converted distributions follow the stratigraphical trends in grain size expected in the Boom Formation, while also being well correlated to hydraulic conductivity measurements performed on Boom Clay samples of similar depths. This is a strong indication that the conversion was successful. In the future, this approach can be used as a tool to harmonize any combination of compositional datasets, not just limited to grain size data, allowing a valorization of the maximal amount of data.

Identifying and Constraining Marsh-Type Transitions in Response to Increasing Erosion over the Past Century

Marsh environments, characterized by their flora and fauna, change laterally in response to shoreline erosion, water levels and inundation, and anthropogenic activities. The Grand Bay coastal system (USA) has undergone multiple large-scale geomorphic and hydrologic changes resulting in altered sediment supply, depositional patterns, and degraded barrier islands, leaving wetland salt marshes vulnerable to increased wave activity. Two shore-perpendicular transect sites, one along a low-activity shoreline and the other in a high activity area of the same bay-marsh complex, were sampled to investigate how the marshes within 50 m of the modern shoreline have responded to different levels of increased wave activity over the past century. Surface sediments graded finer and more organic with increased distance from the shoreline while cores generally exhibited a coarsening upwards grain-size trend; all cores contained multiple large sedimentological shifts. 210Pb-based mass accumulation rates over the last two decades were greater than the long-term (centurial) average at each site with the fastest accumulation rates of 7.81 ± 1.58 and 7.79 ± 1.63 kg/m2/year at the sites nearest the shoreline. A shoreline change analysis of three time-slices (1848–2017, 1957–2017, 2016–2017) shows increased erosion at both sites since 1848 with modern rates of −0.95 and −0.88 m/year. Downcore sedimentology, mass accumulation rates, and shoreline change rates paired with foraminiferal biofacies and identification of local estuarine indicator species, Paratrochammina simplissima, aided in identifying paleo marsh types, their relative proximity to the shoreline, and sediment provenance. The high-energy marsh site transitioned from middle marsh to low marsh in the 1960s, and the low-energy marsh site transitioned later, at the end of the twentieth and early twenty-first century, due to its more protected location. Marsh type transition corresponds chronologically with the coarsening upwards grain-size trend observed and the degradation of Grand Batture Island; since its submergence, signatures of multiple storm event have been preserved downcore.

Dynamic Compressive Properties and Failure Mechanism of the Laser Powder Bed Fusion of Submicro-LaB6 Reinforced Ti-Based Composites.

In this study, lanthanum hexaboride (LaB6) particle-reinforced titanium matrix composites (PRTMCs, TC4/LaB6) were successfully manufactured using the laser powder bed fusion (LPBF) process. Thereafter, the effect of the mass fraction of LaB6 on the microstructure and the dynamic compressive properties was investigated. The results show that the addition of LaB6 leads to significant grain refinement. Moreover, the general trend of grain size reveals a concave bend as the fraction increases from 0.2% to 1.0%. Furthermore, the texture intensity of prior β grains and α grains was found to be weakened in the composites. It was also observed that the TC4/LaB6 have higher quasi-static and dynamic compressive strengths but lower fracture strain when compared with the as-built TC4. The sample with 0.5 wt.% LaB6 was found to have the best strength-toughness synergy among the three groups of composites due to having the smallest grain size. Furthermore, the fracture mode of TC4/LaB6 was found to change from the fracture under the combined action of brittle and ductility to the cleavage fracture. This study was able to provide a theoretical basis for an in-depth understanding of the compressive properties of additive manufacturing of PRTMCs under high-speed loading conditions.

Fabrication of single-crystal Fe-Mn-Al-Cu alloys by cyclic heat treatments

In general, single crystal shape memory alloys exhibit superior shape memory effect and superelasticity when compared to their polycrystalline counterparts. However, it is challenging and costly to prepare a single crystal in traditional ways, such as the Czochralski method and directional solidification technique. Recently, cyclic heat treatment (CHT) has emerged as a facile and cost-effective method to fabricate single crystal by inducing abnormal grain growth. In the present work, we aimed to fabricate Fe-Mn-Al-Cu single crystals utilizing the CHT technique. Single crystal Fe-Mn-Al-Cu shape memory alloys were successfully prepared, and the effect of CHT parameters on abnormal grain growth was investigated. It was revealed that increasing the cooling rate resulted in a non-monotonic response in the maximum grain size, which initially increased and was followed by a subsequent decrease. This behavior was attributed to the subgrain refinement, increase in subgrain misorientation angles, and the narrowing of the low density zones (LDZs) of subgrains. Decreasing the lower temperature of CHT caused similar trends in maximum grain size, due to the increase in subgrain misorientation angle and the expansion of the LDZs. Extending the holding time at the lower temperature of CHT had minimal impact on grain size. Increasing the heating rate of CHT resulted in a reduction in the maximum grain size because of the narrowing of the LDZs. Moreover, the addition of 2 wt% Cu led to a reduction of the maximum grain size, attributing to the decreased solvus temperature of the γ phase as a result of Cu addition. Consequently, the γ phase and subgrains were refined, and the LDZs were narrowed.

Epitaxial growth and characterization of magnesium gallate (MgGa2O4) thin films by pulsed laser deposition

In this work, crystalline MgGa2O4 thin films were grown on c-plane sapphire substrates using the pulsed laser deposition (PLD) technique in a broad range of temperatures and oxygen pressures. The parameters for the crystalline growth were within the temperature range of 300 ℃ to 700 ℃ and the pressure range of 1 × 10-1 to 1 × 10-3 Torr. The acquired XRD patterns confirmed the film growth along the [111] preferential crystal orientation in the lattice and the rocking curve measurement of the prominent (222) plane showed an increasing trend of the crystallinity with growth temperature and pressure. Furthermore, the XRD phi (φ) scan demonstrated the six-fold rotational symmetry of the MgGa2O4 films and the epitaxial relationship of 30° between the film and sapphire substrate. The XPS spectra confirmed the presence of +2 and +3 oxidation state for Mg and Ga respectively, in the films and vacancies that increase with decreasing oxygen partial pressure. The direct bandgap of MgGa2O4 films was obtained to be ∼5.27 ± 0.03 eV by analyzing the UV-Vis absorbance spectra. The film surface exhibited a granular morphology with an increasing trend in grain size as the temperature increased. The refractive index and thickness of these films were in the range of ∼1.90 ± 0.02 and ∼70 ± 2.0 nm, respectively determined from the fitted spectroscopic ellipsometry data. The surface roughness was obtained from AFM images and found to be in good agreement with those obtained from the analysis of the ellipsometry data.

Remote Sensing-Based Simulation of Snow Grain Size and Spatial–Temporal Variation Characteristics of Northeast China from 2001 to 2019

The size of snow grains is an important parameter in cryosphere studies. It is the main parameter affecting snow albedo and can have a feedback effect on regional climate change, the water cycle and ecological security. Larger snow grains increase the likelihood of light absorption and are important for passive microwave remote sensing, snow physics and hydrological modelling. Snow models would benefit from more observations of surface grain size. This paper uses an asymptotic radiative transfer model (ART model) based on MOD09GA ground reflectance data. A simulation of snow grain size (SGS) in northeast China from 2001 to 2019 was carried out using a two-channel algorithm. We verified the accuracy of the inversion results by using ground-based observations to obtain stratified snow grain sizes at 48 collection sites in northeastern China. Furthermore, we analysed the spatial and temporal trends of snow grain size in Northeastern China. The results show that the ART model has good accuracy in inverting snow grain size, with an RMSD of 65 μm, which showed a non-significant increasing trend from 2001 to 2019 in northeast China. The annual average SGS distribution ranged from 430.83 to 452.38 μm in northeast China, 2001–2019. The mean value was 441.78 μm, with an annual increase of 0.26 μm/a, showing a non-significant increasing trend and a coefficient of variation of 0.014. The simulations show that there is also intermonth variation in SGS, with December having the largest snow grain size with a mean value of 453.92 μm, followed by January and February with 450.77 μm and 417.78 μm, respectively. The overall spatial distribution of SGS in the northeastern region shows the characteristics of being high in the north and low in the south, with values ranging from 380.248 μm to 497.141 μm. Overall, we clarified the size and distribution of snow grains over a long time series in the northeast. The results are key to an accurate evaluation of their effect on snow–ice albedo and their radiative forcing effect.

Sediment transport trend and its influencing factors in coastal bedrock island sea areas-a case study of Chudao island, China

Coastal bedrock islands sea areas have a unique natural environment, frequent human activities, and complex sedimentary dynamic processes. In this paper, we select the Chudao Island sea area off the coast of Shandong Peninsula, China, as a typical research area to investigate the sediment transport trends and influencing factors by means of high-precision bathymetric survey, high-density sediment sampling, grain-size trend analysis and hydrodynamic numerical modeling. Results and analysis indicate that the grain size parameters including mean grain-size, sorting coefficient and skewness are zonal distributed, roughly parallel to the isobaths. While the overall sediment transport trend is from island shore to sea, with several convergence centers near the loop centers of bottom flow and at the edge of the agriculture area. The near-bottom flow velocity is primary factor that controlling the significance of sediment transport trend, while the flow decides the general patterns of sediment transport trend and sediment distribution. Submarine topography can either directly transport sediments down its slope, or indirectly affect the direction of sediment transport by constraining the near-bottom flow from shallow to deep waters. Besides the natural factors of bottom flow and submarine topography, human activities represented by aquaculture also affect the sediment transport trend in coastal bedrock island sea areas. First, the increased sedimentation rate caused by organic matters and the diffusion of scallop fragments may cause sediment coarsening. Second, the artificial aquaculture facilities can reduce flow velocity and therefore hinder the initiation, suspension and transport of sediment near the aquaculture areas. Our methods and findings provide high-resolution details to insight into the sediment transport trends to improve the understanding of the modern sediment dynamics in small-scale coastal bedrock island sea areas and provide reference for corresponding engineering and agriculture activities.

Sedimentary architecture of shallow-water fan-delta front in a lacustrine basin: Sangyuan section of Lower Cretaceous Xiguayuan Formation, Luanping Basin, northeast China

The sedimentary architecture of fan deltas, which commonly constitute reservoirs, is a primary control on distribution and recovery efficiency of oil and gas. Deep-water fan deltas have been extensively discussed in the literature, whereas the sedimentary architecture of shallow-water fan-delta fronts, especially the characterization of mouth bar, quantification of architectural elements, and factors controlling the various architectural elements, remain poorly understood. Here, based on the integration of field survey and unmanned aerial vehicle (UAV) observation, the sedimentary architecture of Sangyuan section of the Lower Cretaceous Xiguayuan Formation in the Luanping Basin to is qualitatively and quantitatively characterized. Furthermore, factors controlling the architecture of the shallow-water fan-delta front are highlighted. Five facies associations, which differ in both lithofacies and dimensions, were interpreted in gravel-sand deposits of Sangyuan section, and indicate variations in flow conditions during deposition. The width/thickness ratio of facies associations generally increases rapidly as the flow energy and flow concentration decreases from debris flow to traction currents during the evolution of shallow-water fan delta. Both distributary channels and mouth bars dominate facies associations in the shallow-water fan-delta front, accounting for 53.42% and 36.88% of gravel-sand deposits respectively in Sangyuan section. Mouth bar consists of gravel accretions and sand accretions. Grain size of sediments influences the relative strength of the inertial force and bed friction, which determine the effluent behavior in a river-mouth system and the vertical grain-size trend of mouth bar accretions. Gravel accretions are characterized by normal grading, and these are interpreted as the products of inertia-dominated effluent. Sand accretions exhibit coarsening-upward trends in the river-mouth systems where friction-dominated outflow occurred. The overall vertical grain-size trend of mouth bar depends on the stacking pattern of accretions rather than the grading of one accretion.

Doping induced tailoring of properties in polycrystalline spinel vanadate – MnV2O4

We investigate the structural, electronic and magnetic properties of Mn1-xCuxV2O4 (0 ≤ x ≤ 0.1) to study the role of Cu in spinel vanadate MnV2O4. X-ray diffraction studies show the synthesized materials are single phase. However, X-ray photoelectron spectroscopy reveals the presence of cations in more than one valence state. The higher valence states of cations together with the desired ones confirm the presence of excess oxygen in a formula unit and non-stoichiometry increases with increasing Cu content. Further, with increasing Cu content, lattice parameters, unit cell volumes as well as different atomic separations shrink, whereas magnetic transition temperature gradually decreases and the structural transition disappears for x = 0.1. Moreover, magnetic hysteresis loops at 5 K remain unsaturated up to 6 Tesla applied field, whereas coercivity gradually increases and remanent magnetization decreases with increasing Cu content, in tandem with the increasing trend of grain size.

Effect of tool rotation speed on microstructure and mechanical properties of underwater friction stir welding 6061 aluminium alloy

This work presents the experimental investigation of the effect of tool rotation speed (TRS) on the mechanical properties of the 6061-T6 aluminium alloy weld joint in the underwater friction stir welding (UFSW) process. The experiments are conducted with four different TRS, 710, 900, 1120, and 1400 rpm, and a constant welding speed (WS) of 20 mm/min, respectively. The welding is performed under the water in the butt joint configuration on the vertical milling machine (Model HMT FN2H). The experimental result shows that the average grain size decreases and tensile strength and hardness increases on increasing the TRS up to mid-range of the TRS and further increasing the TRS the trend of grain size and tensile strength and hardness are increases and decreases, respectively. The maximum tensile strength value is 190 MPa, and the minimum grain size is 5 µm at 1120 rpm. Additionally, the optimum condition of tensile strength and weld zone shape is compared with the conventional friction stir welding process, and it is found that tensile strength is increased by 20% and smaller weld zone shape are observed in underwater friction stir welding process. The brittle fracture dominance is observed at lower TRS and ductile dominance fracture in 900, 1120, and 1400 rpm of the weld joint.

The grainsize of volcanic fall deposits: Spatial trends and physical controls

Volcanic tephra fall deposits, which form during explosive eruptions, are commonly characterized in terms of their thickness and grainsize. While significant efforts have been undertaken to relate spatial trends in thickness to plume dispersion processes, comparably few studies have focused on understanding variations in grainsize. Yet, grainsize is a key parameter providing insight into eruption dynamics, from magma fragmentation to plume transport processes, and modulates the impacts of tephra. Here, we present a set of grainsize data extracted from the published record for 56 deposits that represent a range of eruption intensities and magnitudes. We systematically analyze the deposits in terms of modality (bimodal or unimodal grainsize distributions) and provide the median particle diameter with distance from source for component distribution modes. We found that bimodal fall deposits are formed by eruptions with large amounts of fine particles (<100 µm) and that all tephra-fall deposits show characteristic patterns of grainsize decay with distance from source that can be related to eruption plume height and thus intensity. The grainsize decay trends are also related to ash dispersion and deposition processes such as individual particle settling versus collective settling mechanisms. The maximum distance from source reached by particles of different sizes is controlled by a combination of source and transport processes. This data set provides insight into the preservation potential of deposits of different grainsizes at varying distances from their sources. Finally, we emphasize the importance of using grainsize trends in combination with thickness trends to interpret tephra-fall deposit records.

Vertical grain-size trend of mouth bar in lacustrine fan delta: Flume experiments

Field observational previously indicated a mouth bar of a fan delta could exhibit a fining- or coarsening-upward trend, which bring a new challenge to the identification of mouth bar in subsurface studies due to the lack of morphological descriptions. Previous studies have indicated that effluent behavior in river-mouth system can affect the vertical grain-size trend of mouth bar, but the drivers and magnitude of this phenomenon are not understood. We conducted flume experiments to investigate the mechanism and controlling factors of vertical grain-size trend of mouth bar. Experiment with a steeper slope of the substrate layer, greater discharge, higher sediment/water ratio, and coarser sediment induced a fining-upward trend of mouth bar, because the effluent was dominated by strong inertia. Mouth bar in the experiment with a gentler slope of the substrate layer, smaller discharge, lower sediment/water ratio, and finer sediment exhibited a coarsening-upward trend dominated by the friction-dominated effluent. The relationship between the vertical grain-size trend of mouth bar and the gradients of foreset bedding in small-scale flume models and the cut-off of 15°–18° are applicable in natural systems. Identifying depositional setting to infer depositional process in river-mouth system and analyzing the plane geometry of sandbodies are two steps in the interpretation of ancient fan deltaic rock record.

Cr3+ substitution influence on structural, magnetic and electrical properties of the Ni0.3Zn0.5Co0.2Fe2-xCrxO4 (0.00 ≤ x ≤ 0.20) nanosized spinel ferrites

• The sol-gel auto combustion method prepared the Cr 3+ substitution in Ni 0.3 Zn 0.5 Co 0.2 Fe 2-x Cr x O 4 (0.00 ≤ x ≤ 0.20) ferrite nanoparticles. • The measured lattice constant and crystallite size from XRD data show a single-phase cubic spinel. • FESEM images indicate the particles are of small size are confirmed. • There were two absorption peaks around 577.43 cm −1 and around 392.46 cm −1 in the FTIR spectra supporting their spinel structure, as is indicated by the XRD pattern. • The magnetic saturation decreased from 110.87 to 70.28 emu/g with the Cr 3+ ions substitution. • The BB interaction is prominent over the AB interaction, and the DC electricity measurement shows their highly resistive nature. The sol-gel auto combustion method was used for the preparation of the Cr 3+ substitution in Ni 0.3 Zn 0.5 Co 0.2 Fe 2-x Cr x O 4 (0.00 ≤ x ≤ 0.20) ferrite nanoparticles. The XRD data show a cubic spinel structure with a single phase of the samples. The crystallite size of nanoparticles was found to be in the range of 36.74–25.91 nm. Lattice parameter decreases with Cr 3+ concentration increases. SEM micrographs of the nanocrystalline ferrites show an increasing trend in average grain size. There were two absorption peaks around 577.43 cm −1 and around 392.46 cm −1 in the FTIR spectra supporting their spinel structure, as is indicated by the XRD pattern. The magnetic measurements show that the saturation magnetization and coercivity decreases as concentration increases.. The sample with x = 0.00 has a maximum saturation magnetization of 110.87 emu/g. Interlattice interactions are peculiar for tetrahedral and octahedral coordination, and dc electricity measurements reveal their highly resistant character.

Linking levee-building processes with channel avulsion: geomorphic analysis for assessing avulsion frequency and channel reoccupation

Abstract. A natural levee is a typical wedge-shaped deposit adjacent to a river channel. Given its location and distinctive features, the levee can serve as a key to revealing depositional processes of the coupled channel to floodplain system preserved in the rock record. Levee–floodplain topographic evolution is also closely linked to river avulsion processes which can cause catastrophic floods. Nonetheless, the levee geometry and its aggradation pattern on the floodplain have not been fully incorporated in the study of avulsion. Here, we present a levee-building model using advection settling of suspended sediment to reproduce the evolution of a fluvial levee over floods and to examine the effects of boundary conditions on levee geometry and the grain-size trend of the levee deposit. We further investigate river avulsion frequencies and potential channel reoccupation associated with the grain-size distribution of overbank sediment flux and the overflow velocity into the floodplain, both of which can control the levee geometry, especially the aggradation rate at the levee crest. In the modeling results, the levee develops (1) a concave-up profile, (2) an exponential decrease in grain size of the deposit away from the main channel, and (3) a relatively steeper shape for coarser sediment supply and vice versa. The subsequent scaling analysis supports that the input grain size to the floodplain and levee profile slope are positively correlated with the avulsion frequency, whereas the overflow velocity is inversely proportional to the avulsion frequency. In connection with the avulsion styles and levee geometry, we suggest that relatively steeper levee slopes tend to promote more reoccupations of preexisting floodplain channels as protecting abandoned channels from topographic healing, but relatively gentler levees are likely to create a new avulsion channel as their remnant channels are more vulnerable to the removal of topographic memory. The insights drawn from the current modeling work may thus have potential implications for reconstructing paleoenvironments in regard to river sediment transport and flood dynamics via levee deposits. Based on the roles of natural levees on the avulsion frequency and channel reoccupation, the flood hazards triggered by river avulsions as well as the alluvial architecture in sedimentary records can be better assessed.

Effect of Barium doping on structural and magnetic properties of Nickel Ferrite

The present study explores the impact of Barium (Ba) substitution on the structural, morphological, and magnetic properties of ultrafine Ni1-xBaxFe2O4 (0 ≤ x ≤ 1) nanoparticles synthesized by the cost-effective auto-combustion approach. Structural analysis of synthesized nanoparticles by X-ray diffraction pattern declares the transformation of Fd-3m symmetry to orthorhombic Bb21 m crystal structure. The increasing trend in volume due to the lattice expansion with the addition of Ba in NiFe2O4 is observed. In addition, the crystallite size is reduced from 35.07 to 30.69 nm due to the increase in Ba substitution. The morphology of nanoparticles confirmed by scanning electron microscopy (SEM) determines an increasing trend of grain size from 29 to 36 nm as a function of Ba doping. The room temperature hysteresis loops measured by a vibrating sample magnetometer (VSM) indicate that the magnetic coercivity increases as a function of Ba substitution and provides a maximum value of 3.5 kOe for BaFe2O4. However, saturation magnetization is maximum (∼40.7 emu/g) for NiFe2O4 and declines to a minimum value of ∼26.65 emu/g for BaFe2O4. Moreover, low-temperature magnetic measurements were estimated for BaFe2O4 through physical property measurement system (PPMS), where an increasing trend in coercivity (∼3.2–4.5 kOe), saturation magnetization (∼21–50 emu/g), and effective anisotropic magnetic constant (∼7.06 × 104–2.3 × 105 erg/g) was confirmed as the temperature decreases from 400 to 5 K.