Impact of Modifier Oxides on Mechanical and Radiation Shielding Properties of B2O3-SrO-TeO2-RO Glasses (Where RO = TiO2, ZnO, BaO, and PbO)

The influence of modifier oxides (TiO2, ZnO, BaO, and PbO) on the mechanical and radiation shielding properties of boro-tellurate glasses is investigated. Samples with a composition of B2O3-SrO-TeO2-RO (RO represents the modifier oxides) were fabricated using the melt quench method, and their physical, mechanical, and radiation attenuation parameters were reported. For this aim, Monte Carlo simulation was employed to predict the radiation attenuation parameters, while the Makishima-Mackenzie model was adopted to determine the mechanical properties. The tightly packed structure with better cross-linkage density is possessed by the Ti-containing glass (SBT-Ti) system among the titled glass batch. The higher Poisson and micro-hardness values of the SBT-Ti glass indicate its structure’s reduced free volume and better compactness. For the glass with PbO, the linear and mass attenuation coefficients are highly increased compared to those glasses doped with TiO2, ZnO, and BaO. The thinner half-value layer was reported at 0.015 MeV, taking values 0.006, 0.005, 0.004, and 0.002 for samples with TiO2, ZnO, BaO, and PbO, respectively. SBT-Pb sample (with PbO) has a thinner HVL compared to other fabricated glass samples. The fabricated glasses’ thickness (Deq) equivalent to 1 cm of lead (Pb) was reported. The results demonstrated that Deq is high at low energy and equals 11.62, 8.81, 7.61, 4.56 cm for SBT-Ti, SBT-Zn, SBT-Ba, and SBT-Pb glass samples, respectively. According to the Deq results, the fabricated glasses have a shielding capacity between 30 and 43% compared to the pure Pb at gamma-ray energy of 1.5 MeV. At high energy (8 MeV), the transmission factor values for a thickness of 1 cm of the fabricated samples reach 88.68, 87.83, 85.95, and 83.11% for glasses SBT-Ti, SBT-Zn, SBT-Ba, and SBT-Pb, respectively.

Special Issue: “Processing and Treatment of Hexagonal Metals”

There is currently an increasing demand for metals with a hexagonal close-packed structure (HCP) [...]

Estimation of Iron Ore Pellet Softening in a Blast Furnace with Computational Thermodynamics

In blast furnaces it is desirable for the burden to hold a lumpy packed structure at as high a temperature as possible. The computational thermodynamic software FactSage (version 7.2, Thermfact/CRCT, Montreal, Canada and GTT-Technologies, Aachen, Germany) was used here to study the softening behavior of blast furnace pellets. The effects of the main slag-forming components (SiO2, MgO, CaO and Al2O3) on liquid formation were estimated by altering the chemical composition of a commercial acid pellet. The phase equilibria for five-component FeO-SiO2-CaO-MgO-Al2O3 systems with constant contents for three slag-forming components were computed case by case and the results were used to estimate the formation of liquid phases. The main findings of this work suggested several practical means for the postponement of liquid formation at higher temperatures: (1) reducing the SiO2 content; (2) increasing the MgO content; (3) reducing the Al2O3 content; and (4) choosing suitable CaO contents for the pellets. Additionally, the olivine phase (mainly the fayalitic type) and its dissolution into the slag determined the amount of the first-formed slag, which formed quickly after the onset of softening. This had an important effect on the acid pellets, in which the amount of the first-formed slag varied between 10 and 40 wt.%, depending on the pellets’ SiO2 content.

Framboid Self-Assembly and Self-Organization

The formation of framboids involves two distinct processes. First, pyrite microcrystals aggregate into spherical groups through surface free energy minimization. The self-assembly of framboid microcrystals to form framboids is consistent with estimations based on the classical Derjaguin-Landau-Verwey-Overbeek (DVLO) theory, which balances the attraction between particles due to the van der Waals forces against the interparticle electrostatic repulsive force. Second, the microcrystals rearrange themselves into ordered domains through entropy maximization. Icosahedral symmetry tends to minimize short-range attractive interactions and maximize entropy. The physical processes which facilitate this rearrangement are Brownian motion and surface interactions. Curved framboid interface enforce deviation from the cubic close packed structure. In the absence of a curved surface, weakly interacting colloidal particles preferentially self-assemble into a cubic close packed structure, and this is observed in irregular, non-framboidal aggregates of pyrite micro- and nanocrystals.

Research of the Influence of Silicate Fillers on Water Absorption and Microstructure of Styrene-Acrylic Dispersion Coatings

Permeability is important to ensure the protective properties of coatings based on styrene-acrylic dispersions. This indicator characterizes the complex of insulating properties of coatings, their ability to prevent the penetration of liquids, vapors and gases from the environment to the surface to be protected. It was studied the effect of aluminosilicate microspheres, which are characterized by the hydrophilic nature of the surface and highly dispersed silicate filler aerosil with a hydrophobised surface on the water absorption of styrene-acrylic coatings. Decreased of water absorption of styrene-acrylic coatings filled with aluminosilicate microspheres with the introduction of hydrophobised aerosil is linked to the fact that the fine aerosil with a high specific surface area provides the formation of a more densely packed structure. Thus, partially filling the interspherical space, which is formed by particles of microspheres with a diameter of 10-100 μm and reduces the surface defect of the styrene-acrylic coating. Localization on the surface of defective structures of particles of hydrophobised aerosil leads to a decrease in wetting of defective structures with water. Resulting deteriorating wetting the surface of the styrene-acrylic coating. Micrographs were taken to assess the nature of the distribution of aerosil on the surface of the styrene-acrylic coating. The analysis of the obtained micrographs confirms that the introduction of microspheres form large agglomerates, between which there are vacancies, which will negatively affect the technological and operational properties of the developed coatings. At the same time, the introduction of aerosil allows to obtain a more orderly structure, which allows to obtain a coating with lower internal stresses, increased aggregate stability and, as a consequence, with improved technological and operational properties.

Biomaterials with structural hierarchy and controlled 3D nanotopography guide endogenous bone regeneration

Biomaterials without exogenous cells or therapeutic agents often fail to achieve rapid endogenous bone regeneration with high quality. Here, we reported a class of three-dimensional (3D) nanofiber scaffolds with hierarchical structure and controlled alignment for effective endogenous cranial bone regeneration. 3D scaffolds consisting of radially aligned nanofibers guided and promoted the migration of bone marrow stem cells from the surrounding region to the center in vitro. These scaffolds showed the highest new bone volume, surface coverage, and mineral density among the tested groups in vivo. The regenerated bone exhibited a radially aligned fashion, closely recapitulating the scaffold’s architecture. The organic phase in regenerated bone showed an aligned, layered, and densely packed structure, while the inorganic mineral phase showed a uniform distribution with smaller pore size and an even distribution of stress upon the simulated compression. We expect that this study will inspire the design of next-generation biomaterials for effective endogenous bone regeneration with desired quality.