SiO2 Composites Research Articles

Preparation of La2Zr2O7 composite SiO2 aerogels and their fiber-reinforced materials for thermal insulation applications

Lanthanum zirconate (La2Zr2O7) aerogel, with its unique pyrochlore structure, is extensively utilized in thermal insulation owing to its nanopore formation. Nevertheless, the single-phase La2Zr2O7 aerogels have drawbacks of being tough to mold, having a structure that can collapse at high temperatures. This study employed the epoxide sol-gel method to prepare mesoporous aerogels with complete shapes, low densities, and high specific surface areas consisting of La2Zr2O7 composite SiO2 (LZS). Meanwhile, the formed SiO2 amorphous phase can inhibit the growth of pyrochlore crystals and improve the thermal stability of the material. When the amount of SiO2 reached 10 % (LZS10), its density was 0.094+0.006 g/cm3, and the surface area was 88.7 m2/g with 24 % pore volume retention after heat treatment at 1000 °C, showing excellent heat resistance. Quartz fiber reinforced LZS10 aerogel composites (FLZS10) with a thickness of 5 mm were also prepared to study their thermal insulation properties in practical applications. Among them, FLZS10 exhibits a thermal conductivity of 0.057±0.002 W·m−1·K−1 after heat treatment at 1000 °C. When one side of FLZS10 is exposed to a flame at 1000 °C, the temperature of the opposite side is only 284.7 °C, indicating an outstanding thermal insulation performance.

Геохимия органического вещества природных битумов в разрезе р. Кожвы (Тимано-Печорская провинция)

The objects of study are diaplectic and melt silicate glasses from vein melt impactites of the Kara astrobleme. Microscopic and spectroscopic characteristics of two glasses with fundamentally different formation mechanisms were obtained, which allowed comparing their structural features. We found that silicate diaplectic and melt impact glasses from high-pressure/high-temperature vein bodies of the Kara astrobleme were characterized by similar structural features — a high degree of polymerization, the presence of four-membered and polymembered SiO4 rings, which was characteristic of all glasses were the SiO2 composition. Diaplectic glasses are characterized by the constant presence of three-membered SiO4 rings; melt glasses were characterized by the absence of this feature, which was determined by more extreme conditions for the glass from melt.

Сравнительная характеристика диаплектовых и расплавных силикатных стёкол Карской астроблемы

The objects of study are diaplectic and melt silicate glasses from vein melt impactites of the Kara astrobleme. Microscopic and spectroscopic characteristics of two glasses with fundamentally different formation mechanisms were obtained, which allowed comparing their structural features. We found that silicate diaplectic and melt impact glasses from high-pressure/high-temperature vein bodies of the Kara astrobleme were characterized by similar structural features — a high degree of polymerization, the presence of four-membered and polymembered SiO4 rings, which was characteristic of all glasses were the SiO2 composition. Diaplectic glasses are characterized by the constant presence of three-membered SiO4 rings; melt glasses were characterized by the absence of this feature, which was determined by more extreme conditions for the glass from melt.

Evaluation of Mechanical and Wear Assessment of Al-1.2Si-0.75Fe/Mullite MMCs for Industrial Applications

The outline idea is based on saddling the high quality and wear capacities of eminent engineered fortifications, for example with the lightweight and minimal effort of preparing or squandering fiery remains. There is almost no writing which has considered the outline of Aluminium Matrix Composites (AMCs) with the utilization of fortifications of agro squander slag. The Scanning Electron Microscope (SEM) images of gleaming samples, the subsequent were examined. The distribution of strengthening flecks (Mullite (Al2O3 -SiO2 )) is recovered to be steady. Mullite specks are not confined to the grain frontiers. From the wear studies of Al4006 alloy, it was observed that there was more wear out of the surface when compared to Al4006/ Al2O3 -SiO2 composites. Wear tracks of Al4006 alloy show a tough face with extra grooves and ridges associated with wear tracks of Al4006/Al2O3 -SiO2 composites dispersion and binding of the Al2O3 -SiO2 in the composite could indeed be explained by the reduced wear rate. Also, the addition of cenospheres acts as a load-bearing material which protects the matrix from more wear out. Wear track investigation described more wear out and deep abrasive trenches in as-cast contrasted to that of composites which may be due to the lack of load-bearing reinforcing material (mullite) which worsens the material strength leading to more tear or wear out. Overall, from the current studies, it can observed that as the mullite particle reinforcement increases the matrix hardness, strength, and density increase. This study highlights the essential characteristics of the technique of liquid metallurgy and its application to Al4006 MMCs reinforced with mullite.

Effect of activated fluxes on the BZC and Cr (VI) concentration in stellite hardfacing operation

Hardfacing is a surface coating method commonly used to deposit materials having high corrosion and wear resistance on a base metal. In this work, the effect of single and multicomponent fluxes on the breathing zone concentration (BZC) and Cr (VI) concentration, during a stellite hardfacing operation were studied. Flux components used were TiO2, Al2O3 and SiO2. The mixture design of the design of experiments (DoE) was used to identify the influence of each flux component on the reduction of breathing zone concentration (BZC) and Cr (VI) concentration. The findings of the study indicated that binary flux composition comprising 50% Al2O3 and 50% TiO2 offered a significant reduction in breathing zone concentration of fumes by more than 90%. This was attributed to the lower ionization potential of these flux materials and the consequent improvement in the arc stabilization reactions in the weld atmosphere SiO2 in the flux composition was found to befit the reduction of Cr (VI) concentration in fumes through the encapsulation and agglomeration of chromium fumes. The mixture design of design of experiments (DoE) was used to identify the influence of each flux component in the reduction of BZC and Cr (VI) concentration.

The Holocene silicon biogeochemistry of Yellowstone Lake, USA

Silicon (Si) is an essential macronutrient for diatoms, an important component of lacustrine primary productivity that represents a link between the carbon and silicon cycles. Reconstructions of lake silicon cycling thus provide an underexploited window onto lake and catchment biogeochemistry. Silicon isotope geochemistry has potential to provide these reconstructions, given the competing source and process controls can be deconvolved. The silica-rich volcanic and hydrothermal systems in Yellowstone National Park are a great source of dissolved silicon into Yellowstone Lake, a system with high silicon, and thus carbon, export rates and the formation of diatom–rich sediment. Yellowstone Lake sediments should be an archive of past silicon biogeochemistry, although the effect of sublacustrine hydrothermal activity or hydrothermal explosion events is unclear.Here, we analysed lake water, tributaries, and hydrothermal vent fluids from Yellowstone Lake for their dissolved Si concentrations, isotope composition (δ30Si) and Ge/Si ratios to evaluate the sources of variability in the lake's Si cycle. Bulk elemental composition and biogenic SiO2 (bSiO2) content, together with δ30Si and Ge/Si ratios from a single diatom species, Stephanodiscus yellowstonensis, were analysed in two sediment cores spanning the last 9880 cal. yr BP. We investigate these datasets to identify long term Holocene changes in hydrothermal activity and effects of large and short-term events i.e., hydrothermal and a volcanic eruption.Combinations of bSiO2, δ30Si and Ge/Si with XRF and lithology data revealed that Yellowstone Lake has a resilient biogeochemical system: hydrothermal explosions are visible in the lithology but have no identifiable impact on bSiO2 accumulation or on the δ30Si signature. Both cores show similarities that suggest a stable and homogeneous dSi source across the entire lake. A narrow range of δ30Si and Ge/Si values suggests that the productive layer of the lake was well mixed and biogeochemically stable, with consistently high hydrothermal inputs of Si throughout the Holocene to buffer against the disturbance events. Variation in bSiO2 concentration through time is weakly correlated with an increase towards younger sediment in the δ30Si fossil diatom record in both cores. This increase mirrors that seen in ocean records, and follows changes known in summer insolation, summer temperatures and lake water-column mixing since the deglaciation. This suggests that climate forcing, and soil formation ultimately govern the silicon isotope record, which we suggest is via a combination of changes in weathering stoichiometry, diatom production, and relative proportion of dSi sources.

Miocene olivine leucitites in southern Tibet: Implications for the recycling of carbonates into the mantle during continental subduction

We present a comprehensive geochronological, mineralogical, and geochemical study on previously unknown olivine leucitites occurring in the Maiga area of southern Tibet to examine the possibility of carbonate recycling during continental subduction. The Miocene (∼16 Ma) Maiga olivine leucitites are characterized by low SiO2 (44.6–46.3 wt%), high MgO (14.0–15.7 wt%), and ultra-calcic (CaO/Al2O3 = 1.1–1.2) compositions, along with arc-like incompatible element patterns (e.g., enrichment in large-ion lithophile and light rare earth elements, and depletion in high-field-strength elements). These rocks also have extremely radiogenic 87Sr/86Sr(i) (0.715647–0.715844), unradiogenic εNd(i) (−11.6 to −11.2) and εHf(i) (−10.5 to −10.0), and moderately radiogenic 206Pb/204Pb(i) (18.44–18.46) isotopic compositions. The studied samples are also characterized by slightly heavy O isotope ratios (clinopyroxene δ18O = +6.7‰ to +8.7‰) and relatively low water contents (0.75–1.75 wt%). The geochemical features of the Maiga olivine leucitites are compatible with an origin from a carbonated peridotite mantle source. Additionally, based on the regional tectonic evolution and mid-ocean-ridge-basalt-like Zn isotopic compositions (δ66Zn = +0.26‰ to +0.30‰), we hypothesize these magmas formed from interactions between ambient mantle peridotite and recycled Ca-rich carbonate sediments during Indian continental subduction. The transition from the neighboring Miocene lamproite-like rocks in southern Tibet to olivine leucititic magmas in Maiga is assumed to reflect the tapping of two different mantle sources. The first was modified by silicate-rich sediments, which generated lamproite-like rocks, whereas the Maiga mantle source was modified by carbonate-rich sediments. This study and previous research on other K2O-rich subduction-related magmas indicate that non-negligible amounts of carbonates can be recycled deep into the mantle during continental subduction, which may play an important role in global carbon recycling.

The Effect of Lime Stone in the Probability of Formation Pores Structures in Glass Ceramic Based on Scoria Basalt Rocks

This paper provides a Lightweight material is the result of technological problems in increasing the efficiency of finished products, saving manufacturing costs and environmentally friendly technology by reducing the amount of material used. There are many kinds of material manufacturing technology, ranging from the use of lightweight materials from the start, combining materials into composites and modifying the structure and characteristics of the material to make it lightweight. One commonly used method is to mix glass-ceramic with a foaming agent in purpose to modify the structure of material. The purpose of this study is to utillize basalt rock as source of glass ceramic and mixed with limestone to form cellular structure with optimal composition. The samples was crushed and sieve through 100 mesh afterward all material is mixed varied between basalt and lime with a ratio of sample A (100% Basalt), sample B (3:7), sample C (5:5), and sample D (7:3), which were burned at a temperature of 1100°C and 1300°C. After all sample reach designated temperature, all sample undergo annealed cooling in the furnace. Based on the characterization results, the best glass-ceramic sample formed with pores structure formation was sample B which is 70% addition of limestone in basalt mixture and burned at a temperature of 1100°C with a total pore size of 63% and a density of 0.92 g/cm3, where the glass-ceramic structure detected pyroxene and lime phases with a SiO2 composition of 14.61%. Basalt cellular ceramic is obtained in optimal condition with low density and higher percentage porosity.

A Study on The Suitability of Pumice Stone Powder As A Cementitious Material in Sustainable Green Concrete Production

This experimental considered involves on the performance properties of pumice powder as a supplementary cementitious material for ordinary Portland cement materials. The results showed that the pumice powder can be categorized as a pozzolanic constituents according to the ASTM C 618 standard, its main chemical composition SiO2 + Al2O3 + Fe2O3 must be higher than 70% and it was confirmed as suitable for its potential use as a supplemental cementitious resources in the production of concrete materials. As the amount of replacement of cement by the pumice powder increases its workability and density become decreases, it’s delayed in setting time observed, and it requires more water to achieve standard consistency. At 25%, it was a weight reduction of up to 3.83% was observed, as a weight of cement substituted with powdered pumice, and the compressive strength of the powdered pumice specimens was replaced with a cement at different levels of 5wt%, 10wt%, 15wt%, 20wt%, and 25wt% cement resulted in a decrease after 7, 28, 56 and 90 days. In addition, it was observed in this study that its strength decreased with increasing curing age; however; replacing ordinary Portland cement with 5wt% to 10wt% pumice powder achieved the specified minimum compressive strength after a curing time of 28 days. But, a concrete sample prepared with 15% partial replacement achieved the specified minimum compressive strength after 56 days. From 15% replacement, there is then a gradual drop in its compressive strength, and the specified minimum strength was not achieved even after a curing time of 56 days it was found that the maximum strain of the concrete was replaced with a powder pumice stone is lower than conventional concrete. Based onthe above property, it indicates the suitable pumice powder as a cementitious supplementary material in various concrete construction.

Effect of Er2O3 and gold nanoparticles on luminescence behavior of borosilicate glasses for gain bandwidth on telecommunication material application

Effect of Er2O3 and gold nanoparticles on luminescence behavior of borosilicate glasses have been investigated. The chemical compositions of SiO2, B2O3, Al2O3, CaO, Sb2O3, Na2O, K2O, Er2O3 and AuNPs were synthesized by traditional melting and quenching technique and the physical, optical and luminescence properties of the borosilicate glasses were measured. The results showed that the density, molar volume, and refractive index also increased with increasing Er2O3 concentration. The optical absorption spectra of glasses were measured in the range of 200–2000 nm. The surface plasmon resonance of AuNPs peaks are activated at 522 nm resonating with radiative transitions of Er2O3 ions. The intensity of absorption spectra increased with the increasing concentration of Er2O3 content in the sample while the intensity of glass samples doped with AuNPs show higher than without AuNPs. The emission spectra in visible region showed peaks at 535, 560 nm and 661 nm. These peaks correspond to the transition from 4I15/2 → 2H11/2, 4S3/2 and 4F9/2 states under 380 nm excitation. The near-infrared region also exhibited a broad peak at 1547 nm originating to 4I13/2 → 4I15/2 transition of Er3+ ions. In addition, the luminescence of Er3+ ions enhanced by addition of AuNPs observed in visible range, but it had the opposite effect in near-infrared range.

Efficient photo-assisted degradation of wastewater dyes using CdS nanoparticles confined in porous G-C3N4/SiO2 composites

Porous g-C3N4/SiO2 (CNS) nanocomposite was prepared using nanosized colloidal SiO2 by a sol/gel/condensation technique from thiourea and tetraethyl-orthosilicate (TEOS). The fabricated sample was confined with different amounts of CdS nanoparticles (NPs) through precipitation route. various characterization techniques were used to determine the structural, morphological, optical, and textural properties of the investigated photocatalysts. The band gap energies and the potential positions of the valence band (VB) and conduction band (CB) levels in the nanocomposite were determined. We have also explored the different degradation behaviors of the studied photocatalysts toward Rhodamine B (Rh.B) and Remazol Brilliant blue R (Re.B) under solar light irradiation. Amongst all the utilized photocatalysts, 8CNS demonstrated the best photocatalytic performance with degradation rate constants of 0.069 min−1 and 0.022 min−1 for Rh.B and Re.B, respectively. These values are found to be higher than the corresponding rates obtained at g-C3N4 and CdS. The higher degradation efficiency and photostability of CdS/CNS nanocomposites can be attributed to the presence of SiO2 and the synergetic effect of CdS which led to improving both their surface area and charge separation efficiency. Our investigated photocatalyst were found to retain their degradation efficiency after multiple usages demonstrating their sustainability. Based on the potential positions of the reactive species and trapping studies, the photocatalytic degradation mechanism has thus been proposed using superoxide radicals (.O2–) and photoinduced holes (h+) as the main reactive species participate in the degradation process. Our findings should pave novel routes for the elimination of the environmentally toxic dyes using affordable photocatalysts.

Studies on the industrial applications of limestone samples from three geographical regions in Nigeria: Ashaka, Mfamosing, and Nkalagu

The chemical properties of limestone have been the subject of several studies in recent years, highlighting its importance in various industrial applications. The present study focuses on six limestone samples from three geographical regions in Nigeria (Ashaka, Mfamosing, and Nkalagu). The analyses of their chemical composition using the Loss on Ignition Test and X-Ray Fluorescence Spectrometry was successfully carried out. Results of the study show that CaO is the main component, comprising between 60.054 % and 78.632 % of the samples. Values of Loss of Ignition (LOI) ranged from 30.820 % to 33.280 % while SiO2 composition ranged between 5.095 % to 12.238 %. Other oxides detected, include Al2O3 and Fe2O3, which make up less than 1 % of the composition. Obtained values were compared to Limestone standards for various industries and findings indicate that the Ashaka, Mfamosing, and Nkalagu limestone samples are of high purity and suitable for use in various industrial fields, including the steel industry, manufacture of bleaching powder, manufacture of calcium carbide, sugar industry, textile manufacture, cement industry, agricultural practice (soil liming), and flue gas desulphurization. Thus limestone deposits from Ashaka, Mfamosing, and Nkalagu has more potential and application uses beyond cement production which they are currently used for

Modification and characterization of selected Zambian clays for potential use as photocatalysts

Natural materials such as clay are valued for their favorable physical and chemical characteristics on the surface. In this study, the selected Zambian clay materials are immobilized with TiO2 and manganese ions to determine their suitability for use as photocatalysts. SiO2 and Al2O3 oxide composition of Zambian clays was obtained in the range of 35.08-52.63/35.15-52.72 and 13.85-21.73/13.77-21.80, respectively, by inductively coupled plasma (ICP) and X-ray fluorescence (XRF); while Energy dispersive spectroscopy (EDS) of modified clays showed that they have 1.54% incorporation of Ti and 4.98% Mn for Chingola clay to act as UV-Vis absorbers. According to the powder X-ray diffraction analysis of raw clays, the primary phase of all samples is quartz and contains low concentrations of bentonite and kaolinite. The scanning electron microscope (SEM) showed fluffy morphology with agglomeration, while the particle sizes of the clay photocatalysts with the use of transmission electron microscopy (TEM) ranged between 3.0 and 4.8 nm. UV-vis spectroscopy of the samples showed bandgap energies ranging from 2.52-3.08 eV. The surface areas, pore volumes, and pore sizes of the investigated modified and unmodified clays determined by the Brunauer, Teller, Emmett/Barrett Joyner Halenda (BET/BJH) model ranged from 12.06-64.51 m2/g, 0.029-0.068 cm3/g, and 0.642-2.802 nm, respectively. To enhance the mixing of oil and clay, the adsorbents were grafted with silane and confirmed by Fourier transform infrared (FTIR) spectroscopy through CH peaks at ~1450 and ~2860 cm-1. The modified clay materials exhibited favorable properties for use as photocatalysts.

Physical and Optical Properties of Cuo Doped in Soda Lime Silicate Glasses Produced from Waste Glass Cullet

For this article, waste glass cullet obtained from the glass industry was used as a choice of SiO2 substitute in glass manufacturing. A series of soda lime silicate glasses doped with CuO, in composition (55−x) SiO2: 15Li2O: 20Na2O: 10CaO: xCuO (x = 0.00, 0.01, 0.02, 0.03, 0.04, and 0.05 mol%)) were prepared by melt-quenching technique. The parameters such as density and molar volume were measured and evaluated their oscillator strength, refractive index, ion concentration, polaron radius, and inter-nuclear distance. Optical properties such as refractive index, absorption spectra, optical band gab, and CIE L*a*b* were investigated. With increasing of CuO concentration, the density and the refractive index of glasses increased, while the molar volume decreased. The absorption spectra show board peak in the range of 550 to 950 nm. The addition of CuO generated the blue hue in glasses, corresponding to the CIE L*a*b color coordinate.

Black sand as a cost-effective catalyst for methylene blue photo-remediation under visible light

Methylene blue (MB) is commonly a persistent and perilous pollutant in industrial wastewater effluent. While MB has a massive negative effect on human and ecology safety. The neutralization of such harmful material would save a huge clean water amount. This work proposes the natural and abundant black sand as a catalyst for MB photodegradation. The sand sample was calcined at three temperatures of 300°, 400°, and 600 °C. The properties of samples were analyzed with different micro- as well as spectroscopic techniques. The experimental data revealed the sample's main composition of SiO2, Fe2O3, and Al2O3. XRD and XPS results proved the formation of mixed oxides composites due to calcination, especially at 400 °C. The UV–vis analysis conducted showed that samples can absorb light in the visible range. The photodegradation reached a maximum of 975.3%, 82.7%, and 75.7% for BS400, BS600, and BS300 respectively; by illumination for 2.5 h in the visible range. The observed distinguishable catalytic performance was discussed via the spectroscopic analysis and oxygen availability in the catalyst lattice. When AO, t-BuOH, and BQ are used as scavengers instead of just BQ during the photodegradation of MB dye over BS400 catalyst, the photodegradation rate drops significantly. The degradation % of MB dye diminished to 60%, and 70% by using AO, t-BuOH, and BQ scavengers; respectively. This proved that rather than hydroxyl radicals, superoxide radicals or positive hole production is the main determining step in MB photo-degradation over BS400 catalyst.

Synthesis of the Diamond‒SiO2 Composites with the Properties of Photonic Crystals in the Visible Spectral Range

Synthesis of the Diamond‒SiO2 Composites with the Properties of Photonic Crystals in the Visible Spectral Range

Glass Microspheres Thermo-Deformation Sintering Processes in the Technologies of Obtaining Materials for Underwater Technical Equipment

Abstract In this work, the important scientific and technical problem of creating multifunctional composite materials for shipbuilding and ocean engineering was solved. The work aimed to study the thermal deformation processes of sintering glass microspheres to obtain lightweight glass composites with a cellular structure that provides positive buoyancy and sound insulation properties. For this purpose, glass microspheres of Na2O‒SiO2 and Na2O‒B2O3‒SiO2 composition with a dispersion of 10 to 60 μm were used as raw materials. They were sintered to form a closed, porous structure. The theoretical substantiation of technological parameters is based on the concepts of solid state and glassy state chemistry and physicochemical concepts of glass softening processes. The process of hot-pressing glass microspheres without plasticisers and additives was investigated. The author’s own laboratory equipment was used for the experiments. The sintering intensity was determined from the results of shrinkage processes; the kinetic shrinkage curves were constructed in semilogarithmic coordinates. The glass composite samples were examined by optical and electron microscopy. As a criterion, the storage of spherical microspheres under the influence of simultaneous heating to 700 °C with the application of pressure in the range of 0,5 to 1,5 MPa was chosen. It was established that the formation of a predominantly closed-porous structure of glass composites with a density of 350...600 kg/m3 occurs by the mechanisms of viscous glass phase flow through liquefaction processes in the walls of microspheres. At the same time, shrinkage processes in the linear direction reach up to 50%. The acoustic properties were investigated by measuring the differences in sound pressure levels in octave frequency bands using a Kundt pipe. The water absorption of the glass composite samples was determined at hydrostatic pressures up to 20 MPa. The research results were compared with the characteristics of analogue composites, such as syntactic foams and foam glass. The developed materials can be used in the design and manufacture of technical equipment for research and maintenance of underwater infrastructure. The prospects for further research are related to the feasibility study and marketing research on implementing the developed glass composites.

Fabrication and high-temperature strength of 2.5D SiO2f /SiO2 composites prepared by a combined vacuum impregnation and sol-gel method

A combined vacuum impregnation and sol-gel method was used to prepare 2.5D SiO2f/SiO2 ceramic composites with good mechanical properties in both warp and weft direction in this study. Phase change and weight gain during forming process of the ceramic composites were measured to explain the forming process. The mechanical properties of materials along different direction at room temperature and high temperature were systematically analyzed, and the fracture mechanism in different service environments was elucidated. Results indicated that dense SiO2f/SiO2 ceramic composites could be prepared by impregnating the 2.5D woven fabric preforms in silica sol and sintering them at 800 °C for > 5 cycles. Flexural strength of the composite was directly affected by the arrangement density and straightening degree of the fibers in warp/weft direction. The composite prepared in this study showed a higher flexural strength (∼91.21 MPa) in the weft direction. With the increase of temperature, the quartz fibers inside the composites became brittle due to crystallization, resulting in the failure mechanism of the ceramic composite material changing from ductile fracture to brittle fracture.

Distribution, source and contamination of rare earth elements in sediments from lower reaches of the Xiangjiang River, China

Rare earth elements (REEs) are emerging micropollutants in aquatic environments. In this study, concentrations of REEs and major elements, and mineralogical compositions of sediments from lower reaches of the Xiangjiang River (China) were analyzed using ICP-MS technique. The results suggested that sediments were characterized by terrigenous compositions TiO2, SiO2, Al2O3, K2O, Na2O and P2O, and contained high concentrations of REEs with mean total REE concentrations (∑REE) of 318.7 mg/kg. REEs were moderately enriched in upper river sediments, and slightly or less enriched in downriver sediments. The normalized REE distribution pattern for sediments was characterized by flat shalelike and Eu depleted V-shape REE patterns, which indicated REEs in sediments were lithologically contributed from sedimentary rocks and granites distributed in the watershed respectively. REEs in sediments were hosted mainly in Fe–Mn oxides, and sulfide and organic matters that were characterized by middle REEs (MREE) enrichments relative to light REEs (LREE) and heavy REEs (HREE), and the distribution and differentiation of REEs in sediments were controlled by clays, Fe–Mn oxides, organic matters and finer grains; and also by accessory minerals (e.g., zircon) from granite. The distribution features of REEs in sediments and BCR extraction results suggested that the sediment REE enrichment resulted from additional REE input from anthropogenic sources, including those in discharges from sulfide-ore smelting industries at Zhuzhou city and from phosphate fertilizer plants at Xiangtan city along the river. Thus, sediments were contaminated with REEs in moderate degree in upper river area, and REE contamination was then formed by superimposing anthropogenic REEs on lithological residues. Finally, concentrations of Ce > 100 mg/kg, Gd > 8.12 mg/kg, ∑REE >274.9 mg/kg, ∑LREE >252.3 mg/kg and ∑HREE >28.8 mg/kg here were recommended as the REE contamination levels that represented as REE indices for identifying and rating REE contamination in this mining impacted river.

Molecular dynamics simulation and experiment on analyzing mechanical properties of PMMA/SiO2 composites based on interfacial interaction

In this paper, we investigate the impact of modified SiO2 nanoparticles on the mechanical properties of Polymethyl methacrylate (PMMA) composites through a combination of molecular dynamics simulation and experimentation. Our investigation focuses on analyzing the elastic modulus, bulk modulus, shear modulus, and Cauchy ratio of pure PMMA, PMMA/SiO2 composites, and PMMA/modified SiO2 composites over a temperature range of 200–400 K. Our results indicate that, as the temperature increases, the elastic modulus, bulk modulus, and Cauchy ratio of all materials decrease, while the shear modulus initially increases and then decreases. Notably, at room temperature, the elastic modulus, bulk modulus, and shear modulus of the composites increase with an increase in the degree of nanoparticle modification, while the Cauchy ratio exhibits the opposite trend. Our findings suggest that modified SiO2 nanoparticles have the potential to enhance the mechanical properties of composite materials. To validate our simulation results, we also conducted experiments that demonstrated the rationality of our approach.