Silicate Glass Particles Research Articles

Immobilization of simulated An4+ in radioactive sludge via microwave sintering: Mechanistic and performance

In this study, we investigate radioactive sludge containing An4+ ions via simulation. Ce4+ is employed as a surrogate isotope for An4+ ions, and silicate glass particles are incorporated as stabilizing agents. Continuous microwave sintering technology is adopted to sinter the simulated radioactive sludge with varying CeO2 contents co-doped with 60 wt.% glass particles at temperatures of 1100 °C, 1200 °C, and 1300 °C to achieve sample vitrification. The phase evolution, microstructure, morphology, chemical stability, sample density, and porosity of the sintered specimens are analyzed comprehensively. The results indicate distinct maximum solubility limits at different sintering temperatures: 5 wt.%, 6 wt.%, and 13 wt.% for 1100 °C, 1200 °C, and 1300 °C respectively. Under these conditions, Ce is immobilized within the glass network structure. Notably, the Ce3+/Ce4+ ratio in the 1300 °C-Ce10 specimen reaches 2.04, and the combined percentage of Q3 and Q4 glass structural units exceeds 50 %. Beyond the optimal solubility limit, tetragonal CeO2 crystals are formed on the glass sample surface. The normalized leaching rate of Ce from the samples remains at 5.0 × 10−6 g m−2 d−1. Additionally, the sintered samples indicate densities ranging from 2.65 to 3.01 g/cm3 and porosities from 0.18 % to 1.8 %. This study introduces a novel perspective for addressing radioactive sludge treatment.

Immobilization of simulated An3+ in radioactive sludge via microwave sintering: Mechanism and performance

This study investigates the safe disposal of simulated radioactive sludge. Microwave sintering of silicate glass (SG) particles and simulated sludge is performed to prepare amorphous glass materials and oxy-apatite (AⅠxAⅡ10-x(SiO4)6O2) glass ceramics. The phase-evolution, microstructure, nucleation-growth mechanism, and chemical stability of the solidified products are systematically investigated. The optimum vitrification degree of the solidified product containing 60 wt.% SG particles in the radioactive sludge is achieved at 1200 ℃. Elements are uniformly distributed, and the final solid-solubility of Nd in the glass structure is 32 wt.%. For higher content, the Nd remained fixed at the AⅠ and AⅡ positions of an oxyapatite crystalline structure. The glass-ceramic material exhibited a high solid-solubility of Nd up to 40 wt.%. Furthermore, the normalized leaching rate of Nd was observed at a low level of 10−6 g·m−2·d−1 after 42 d. This study suggests a new processing method for the safe disposal of radioactive sludge.

Dehydration‐driven mass loss from packs of sintering hydrous silicate glass particles

AbstractGlass sintering involves the densification of packs of particles and the expulsion of the interparticle pore gas. The pore space begins as a convolute interconnected interparticle network, and ends as distributed isolated bubbles; two configurations that are separated by the percolation threshold. Here, we perform experiments in which (i) the particles are initially saturated in H2O at 871 K, and (ii) they are then heated non‐isothermally at different rates to temperatures in excess of 871 K. In step (ii), H2O becomes supersaturated and the particles diffusively lose mass as they sinter together. We use thermogravimetry to track the loss of mass with time. We find that the mass loss is initially well predicted by solutions to Fick's second law in spherical coordinates with the appropriate material and boundary conditions. However, as the sintering pack crosses the percolation threshold at a time predicted by sintering theory, we find that the mass loss deviates from simple diffusional solutions. We interpret this to be the result of an increase in the diffusion distance from the particle‐scale to the scale of the sintering pack itself. Therefore, we conclude that the open‐ to closed‐system transition that occurs at the percolation threshold is a continuous, but rapid jump for diffusive and other transport properties. We use a capillary Peclet number Pc to parameterize for this transition, such that at low Pc diffusive equilibrium is achieved before the sintering‐induced transition to closed system, whereas at high Pcthere is a “diffusion crisis” and disequilibrium may be maintained for longer relative timescales that depend on the system size.

Radiocesium-bearing microparticles cause a large variation in 137Cs activity concentration in the aquatic insect Stenopsyche marmorata (Tricoptera: Stenopsychidae) in the Ota River, Fukushima, Japan.

After the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant accident in Japan, freshwater ecosystems near the site remained contaminated by radiocesium (RCs). Clarifying RCs concentrations in aquatic insects is crucial because fishes consume these insects that transfer RCs into freshwater ecosystems. As aquatic insects are usually measured for radioactivity in bulk samples of several tens of insects, variation in RCs concentration among individuals is not captured. In this study, we investigated the variability in 137Cs activity concentration in individual aquatic insects in detritivorous caddisfly (Stenopsyche marmorata) and carnivorous dobsonfly (Protohermes grandis) larvae from the Ota River, Fukushima. Caddisfly larvae showed sporadically higher radioactivity in 4 of the 46 caddisfly larvae, whereas no such outliers were observed in 45 dobsonfly larvae. Autoradiography and scanning electron microscopy analyses confirmed that these caddisfly larvae samples contained radiocesium-bearing microparticles (CsMPs), which are insoluble Cs-bearing silicate glass particles. CsMPs were also found in potential food sources of caddisfly larvae, such as periphyton and drifting particulate organic matter, indicating that larvae may ingest CsMPs along with food particles of similar size. Although CsMP distribution and uptake by organisms in freshwater ecosystems is relatively unknown, our study demonstrates that CsMPs can be taken up by aquatic insects.

Low-Cost Mechanically Alloyed Copper-Based Composite Reinforced with Silicate Glass Particles for Thermal Applications

A nanocrystalline copper-based composite reinforced with 40 vol.% silicate glass particles was successfully produced by mechanical alloying followed by hot pressing. The raw materials of crushed copper chips and soda-lime glass debris were processed in a planetary ball mill for up to 7 h. It was shown that silicate glass as alloying addition has a positive effect on the strengthening of copper and decreases its thermal expansion coefficient. During mechanical alloying, the microhardness of the composite powder particles increases to about 320 HV. The hot-pressed material demonstrates good thermal stability and increased compressive strength compared with consolidated milled copper.

Fabrication and characterization of poly-(ε)-caprolactone and bioactive glass composites for tissue engineering applications.

Much work has focused on developing synthetic materials that have tailored degradation profiles and physical properties that may prove useful in developing biomaterials for tissue engineering applications. In the present study, three different composite sheets consisting of biodegradable poly-ε-caprolactone (PCL) and varying types of bioactive glass were investigated. The three composites were composed of 50wt.% PCL and (1) 50wt.% 13-93 B3 borate glass particles, (2) 50wt.% 45S5 silicate glass particles, or (3) a blend of 25wt.% 13-93 B3 and 25wt.% 45S5 glass particles. Degradation profiles determined for each composite showed the composite that contained only 13-93 B3 borate glass had a higher degradation rate compared to the composite containing only 45S5 silicate glass. Uniaxial tensile tests were performed on the composites to determine the effect of adding glass to the polymer on mechanical properties. The peak stress of all of the composites was lower than that of PCL alone, but 100% PCL had a higher stiffness when pre-reacted in cell media for 6weeks, whereas composite sheets did not. Finally, to determine whether the composite sheets would maintain neuronal growth, dorsal root ganglia isolated from embryonic chicks were cultured on composite sheets, and neurite outgrowth was measured. The bioactive glass particles added to the composites showed no negative effects on neurite extension, and neurite extension increased on PCL:45S5 PCL:13-93 B3 when pre-reacted in media for 24h. This work shows that composite sheets of PCL and bioactive glass particles provide a flexible biomaterial for neural tissue engineering applications.

Temporal analysis of dissolution by-products and genotoxic potential of spherical zinc-silicate bioglass: "imageable beads" for transarterial embolization.

Embolization of vascular tumors is an important tool in minimally invasive surgical intervention. Radiopaque, non-degradable, and non-deformable spherical zinc-silicate glass particles were produced in a range of 45-500 μm. Three size ranges (45-150, 150-300, and 300-500 μm) were used in the current study. The glass microspheres were eluted in polar (saline solution) and non-polar (dimethyl sulfoxide) medium, and ion release profiles were recorded using inductively coupled plasma atomic emission spectroscopy. Approximately 80% of Gaussian distribution was achieved by simple sieving. The ions released from the microspheres were dependent upon surface area to volume ratio as well as the nature of elution media. Greater ions were released from smaller particles (45-150 μm) having largest surface area in polar medium. For the genotoxicity bacterial mutation Ames assay, the concentrations of all the ions were well below their therapeutic concentration reported in the literature. No mutagenic effect was observed in the bacterial mutation Ames test. Hence, it can be concluded that the glass microspheres produced herein are non-mutagenic further supporting the materials potential as a suitable embolic agent.

An integrated experimental-modeling approach to study the acid leaching behavior of lead from sub-micrometer lead silicate glass particles

This work focuses on the development of a procedure to study the mechanism of leaching of lead from sub-micrometer lead glass particles using 0.3moll−1 HNO3 as a leachant. Glass particles with an effective size distribution range from 0.05 to 1.4μm were generated by laser ablation (213nm Nd:YAG laser) and collected on an inline 0.2μm syringe filter. Subsequently, the glass particles on the filter were subjected to online leaching and continuous monitoring of lead (Pb-208) in the leachate by quadrupole ICP-MS. The lead leaching profile, aided by the particle size distribution information from cascade impaction, was numerically fitted to a mathematical model based on the glass intraparticle diffusion, liquid film distribution and thermodynamic glass-leachant distribution equilibrium. The findings of the modeling show that the rate-limiting step of leaching is the migration of lead from the core to the surface of the glass particle by an ion-exchange mechanism, governed by the apparent intraparticle lead diffusivity in glass which was calculated to be 3.1×10−18m2s−1. Lead leaching is illustrated in the form of graphs and animations of intraparticle lead release (in time and intraparticle position) from particles with sizes of 0.1 and 0.3μm.

Glass–NiP–CoFeP Triplex-Shell Particles with Hollow Cores and Tunable Magnetic Properties

Low density (0.55-0.92g/mL, depending on the shell thickness and composition) glass-metal-metal triplex-shell hollow particles (TSHP) were prepared by a three-step route. First, micrometer-sized silicate glass particles with hollow cores, uniform shells, and high sphericity were prepared through spray drying and subsequent melting. NiP shell was uniformly assembled to the previously obtained glass hollow particles by silver seed induced chemical reduction of Ni(2+) by sodium hypophosphite, and glass-NiP double-shell hollow particles (DSHP) with compact and uniform shells were formed. The as-formed NiP particles further acted as the seeds for the directed formation and assembly of the CoFeP shell on the NiP shell to form the final glass-NiP-CoFeP triplex-shell hollow particles (TSHP). The influences of the component of the reaction system on the composition, structure, and magnetic properties of the hollow particles were studied. The multishell hollow particles thus obtained may have some promising applications in the fields of low-density magnetic materials, conduction, microwave absorbers, catalysis, etc. This work provides an additional strategy to fabricate multishell structured hollow particles with tailored shell composition and magnetic properties, which can be extended to the controlled preparation of multishell composite particles with the shells consisting of metal, oxides, or other compounds.

Evaluation of bone regeneration, angiogenesis, and hydroxyapatite conversion in critical‐sized rat calvarial defects implanted with bioactive glass scaffolds

Bioactive glasses are biocompatible materials that convert to hydroxyapatite in vivo, and potentially support bone formation, but have mainly been available in particulate and not scaffold form. In this study, borosilicate and borate bioactive glass scaffolds were evaluated in critical-sized rat calvarial defects. Twelve-week-old rats were implanted with 45S5 silicate glass particles and scaffolds of 1393 silicate, 1393B1 borosilicate, and 1393B3 borate glass. After 12 weeks, the defects were harvested, stained with hematoxylin and eosin to evaluate bone regeneration, Periodic Acid Schiff to quantitate blood vessel area, and von Kossa and backscatter SEM to estimate newly mineralized bone and hydroxyapatite conversion of bioactive glasses. The amount of new bone was 12.4% for 45S5, 8.5% for 1393, 9.7% for 1393B1, and 14.9% for 1393B3 (*p = 0.04; cf. 1393 and 1393B1). Blood vessel area was significantly higher (p = 0.009) with 45S5 (3.8%), with no differences among 1393 (2.0%), 1393B1 (2.4%), or 1393B3 (2.2%). Percent von Kossa-positive area was 18.7% for 45S5, 25.4% for 1393, 29.5% for 1393B1, and 30.1% for 1393B3, significantly higher (p = 0.014) in 1393B1 and 1393B3 glasses than in 45S5. 45S5 and 1393B3 converted completely to HA in vivo. The 1393B3 glass provided greater bone formation and may be more promising for bone defect repair due to its capacity to be molded into scaffolds. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A 100A:3267-3275, 2012.

Nanominerals and nanoparticles in feed coal and bottom ash: implications for human health effects

Environmental and human health risk assessments of nanoparticle effects from coal and bottom ash require thorough characterisation of nanoparticles and their aggregates. In this manuscript, we expand the study of human exposure to nanosized particles from coal combustion sources (typically <100 nm in size), characterising the complex micromineralogy of these airborne combustion-derived nanomaterials. Our study focuses on bottom ash generated in the Santa Catarina power station (Brazil) which uses coal enriched in ashes, many potential elements (e.g. Cr and Ni) and pyrite. Transmission electron microscope data reveal nanoscale C deposits juxtaposed with and overgrown by slightly larger aluminosilicate (Al-Si) glassy spheres, oxides, silicates, carbonated, phosphates and sulphates. Iron oxides (mainly hematite and magnetite) are the main bottom ash products of the oxidation of pyrite, sometimes via intermediate pyrrhotite formation. The presence of iron oxide nanocrystals mixed with silicate glass particles emphasises the complexity of coal and bottom ash micromineralogy. Given the potentially bioreactive nature of such transition metal-bearing materials, there is likely to be an increased health risk associated with their inhalation.

Sodium silicate bonded borate glass scaffolds for tissue engineering

Borate and silicate glass particles and microspheres with size distributions in the range of approximately 100–400 micron were loosely compacted and bonded by sodium silicate solution to prepare resorbable, porous glass constructs with porosity 30–50%. Conversion of the binding borate glass to hydroxyapatite was investigated by measuring the weight loss of the constructs in a solution of 0.25 M K2HPO4 with a pH value of 9.0 at 37 °C, as a function of time. Almost full conversion of the borate glass to hydroxyapatite was achieved in less than 6 days. X-ray diffraction revealed an initially amorphous product that subsequently crystallized to hydroxyapatite.

The preparation and characterization of sol–gel zinc silicate glass particles with pyramid shape and millimetre size

Geometrically shaped particles of glasses and glasses containing micro- and nano-crystalline inclusions can be used in coatings and composites for microwave or optical applications. In the present paper, the feasibility of the sol–gel fabrication of shaped particles with millimetre-size is described. Zinc silicate pyramid shaped glass particles were prepared via sol–gel processing using wax moulds for casting. Thermal treatment yielded crack-free and transparent pyramid shaped particles. Optical microscopy and scanning electron microscopy, powder X-ray diffraction and nitrogen gas adsorption measurements of the samples provide evidence for the constitution of the particles.

Minimum-size detection limit for volcanic glass particles using automated scanning electron microscopy

Ice cores contain a detailed record of fallout from large volcanic eruptions. Identification of volcanic glass particles is used to aid in dating ice cores (tephrachronology). In addition, it should be possible to relate concentrations of volcanogenically-derived species; silicate glass particles, sulfate (from oxidation of SO2), chloride and fluoride to atmospheric levels which existed shortly after eruption. This information, coupled with proxy meteorological records from the core, can be used to assess the climatic impact from major volcanic eruptions.Automated scanning electron microscopy has been used to detect volcanic glass particles &gt;1 μm in diameter in ice core meltwater samples filtered onto Nuclepore filters. It is important to be able to detect submicrometer volcanic glass particles because of their longer atmospheric residence time and the fact that they comprise a significant portion of the number of glass particles deposited in an ice core. Existing procedures for automated analysis of micrometer size particles need to be modified to efficiently analyze submicrometer particles.

Interaction of aircraft and explosive eruption clouds - A volcanologist's perspective

Eruption clouds contain a variety of solid, liquid, and gaseous materials. Silicate glass particles with melting temperatures of 800-1200°C are often the dominant solid material, and can cause significant problems in turbine aircraft engines. Plinian eruptions propel silicate glasses to altitudes of up to 60 km, and are then dispersed over large areas by prevailing winds. The basic characteristics of these clouds are described, and suggestions about how to avoid aircraft mishaps are listed.