Search Results (40)

Plasma electrolytic oxidation (PEO) is an effective method for developing protective conversion coatings on magnesium and its alloys. The efficiency of this process is governed by several factors, including electrical parameters and electrolyte composition. Typically, PEO has been performed in alkaline silicate or phosphate solutions, often enriched with simple fluoride ions (F⁻) to improve the mechanical and anticorrosive properties of the resulting layers. Recently, the positive impact of complex fluoride ions (such as ZrF₆²⁻, TiF₆²⁻, SiF₆²⁻, AlF₆³⁻ and PF₆⁻) on the properties of conversion coatings on magnesium substrates has been shown. This review analyzes how these complex precursors influence the phase composition, morphology, and corrosion resistance of coatings. Furthermore, these parameters are compared with those obtained by using electrolytes composed of a mixture of simple fluorides and additional constituents that provide the incorporation of the appropriate elements into the coating structure (phosphorus, silicon, zirconium, titanium, or aluminum). It was indicated that when using complex fluoride salts, an important aspect is the stability of the electrolyte, which depends on pH and the presence of stabilizing additives. Ensuring that the decomposition of the complex fluoride occurs during the PEO process increases the amount of fluorine incorporated into the layers formed, leading to the formation of a coating with enhanced properties. Full article

Mafic ultrapotassic volcanics (kamafugites, mafurites) are the youngest eruptives in the Bunyaruguru volcanic field, which is part of the Toro Ankole Province at the northernmost reach of the West Branch of the East African Rift Valley. We obtained new data using LA-ICP-MS on the trace element contents (rare earth, large ion lithophile, high field strength and compatible elements) in clinopyroxene phenocrysts from mafurite lava of the Bunyaruguru volcanic field. The clinopyroxenes are notable for their anomalously high zirconium contents (up to 800–1000 ppm), which is unusual in mafic silicate magmas but typical for clinopyroxenes from carbonatite lavas. This distinctive signature is not found in clinopyroxene in coeval mafic lavas from neighboring vents. Carbonate is also found in the Bunyaruguru volcanic rocks in the form of inclusions in high-Mg olivine phenocrysts, suggesting carbonated material exists in the source of kamafugite magmas. Carbonatites are widespread in the neighboring Fort Portal volcanic field, and we interpret the high-zirconium clinopyroxene as evidence for mixing of mafurite magmas with carbonatite melts. Full article

This study investigated the radiopacity, elemental composition, cytotoxicity, and cytokine responses of contemporary calcium silicate-based cements containing different radiopacifiers. Four cement materials (NeoMTA2, NeoPUTTY, TheraCal PT, and One-Fil PT) were evaluated. Radiopacity was measured using digital radiography with a 10-step aluminum wedge and expressed in mm Al in accordance with ISO 6876; among three calibration models compared, the quadratic provided the best fit. Elemental composition was analyzed by SEM/EDX. Cytotoxicity was assessed on human dental pulp cells using the MTT assay, and IL-6 and IL-10 levels were quantified by ELISA. One-Fil PT (6.61 mm Al) and NeoPUTTY (6.09 mm Al) showed the highest radiopacity, whereas TheraCal PT (1.61 mm Al) did not meet ISO standards. SEM/EDX revealed tantalum in NeoMTA2 and NeoPUTTY, and zirconium in One-Fil PT and TheraCal PT. NeoPUTTY and NeoMTA2 demonstrated superior cell viability, while One-Fil PT showed the lowest. TheraCal PT and One-Fil PT increased IL-6 expression, whereas NeoPUTTY and NeoMTA2 promoted higher IL-10 levels. Within the limitations of this 24-h in vitro assessment, NeoMTA2 and NeoPUTTY exhibited more favorable short-term cytocompatibility and inflammatory profiles together with adequate radiopacity. These findings require confirmation through long-term in vivo and clinical studies. Full article

This study aimed to prepare experimental calcium silicate repair cements (ERCs) incorporating zirconium (Ca₃ZrSi₂O₉; CZS) or strontium substitution (Sr₅(PO₄)₂SiO₄; SPS), and to compare their physicochemical properties with white MTA-Angelus (WMTA), grey MTA-Angelus (GMTA), and Biodentine (BD). After synthesizing the CZS and SPS phases, powder–liquid cements were formulated. The setting time and radiopacity were assessed according to ISO 6876/12 and ASTM C266, the volumetric solubility by micro-CT, the pH by a pH meter, and the calcium/strontium ion release by FAAS/ICP-OES. Data were analyzed using ANOVA and Tukey’s tests (5%). The initial setting time was 11 min for SPS and 6 min for CZS (p < 0.05), while the final setting was significantly longer for SPS (49 min). Both ERCs showed radiopacity above the 3.0 mm Al minimum, with higher values for CZS (4.58 mm Al). The solubility remained controlled, with CZS presenting the highest value (3.09%). Both materials exhibited an alkaline pH, peaking at 24 h (CZS: 9.70; SPS: 10.04) and decreasing until 168 h (CZS: 7.80; SPS: 8.31). Sustained ionic release was observed: CZS showed intermediate calcium release (25.96 mg/L at 3 h), whereas SPS displayed lower values (10.95 mg/L at 168 h), without significant difference from WMTA (p > 0.05). Under these conditions, the experimental ERCs demonstrated adequate physicochemical performance comparable with commercial materials. Full article

Background/Objectives: Silicone elastomers are widely used in maxillofacial prostheses, but their service life is typically limited to 6–24 months due to progressive degradation. Reinforcement with zirconium silicate (ZrSiO₄) nanoparticles has been proposed to improve durability, yet evidence on their long-term performance under storage remains limited. This study evaluated the effect of two years of dark storage on the mechanical properties of room-temperature-vulcanized (RTV) silicone reinforced with 1.5 wt% ZrSiO₄ nanoparticles. Materials and Methods: Zirconium silicate (ZrSiO₄) nanoparticles at 1.5 wt% were incorporated into A-2186 RTV silicone specimens, which were randomly divided into two equal groups: baseline specimens stored for 24 h and aged specimens stored for 24 months under dark conditions. Mechanical properties were assessed by measuring tensile strength, elongation at break, tear resistance, and Shore A hardness in accordance with standardized protocols. Fourier transform infrared (FTIR) spectroscopy was performed to verify the structural characteristics of the ZrSiO₄ nanopowder. Statistical analysis was conducted using independent-samples t-tests, with significance set at p < 0.05. Results: After 24 months of dark storage, tensile strength and elongation at break decreased significantly (p < 0.05), indicating reduced elasticity. Tear resistance and hardness showed slight but non-significant reductions. FTIR confirmed the preservation of ZrSiO₄ structural features. Conclusions: Dark storage selectively reduced reinforced silicone’s tensile and elongation properties, while tear resistance and hardness remained relatively stable. ZrSiO₄ nanoparticles provided partial reinforcement, enhancing stability but not entirely preventing RTV silicone aging. Full article

Tin slags generated during cassiterite smelting in Brazil contain significant amounts of technologically important metals such as niobium, tantalum, and zirconium. Improper disposal of these materials represents both an environmental concern and the loss of a valuable secondary source of critical elements. This study aimed to characterize a Brazilian tin slag sample to evaluate its composition, morphology, and potential for metal recovery. The material was homogenized and analyzed by laser diffraction (particle size), ICP-OES (chemical composition), X-ray diffraction (mineral phases), differential scanning calorimetry (metallic tin), and scanning electron microscopy with energy-dispersive spectroscopy (morphology). The slag exhibited a heterogeneous particle size distribution (D90 = 0.75 mm, D50 = 0.30 mm, D10 = 0.09 mm) and a complex multiphase structure composed mainly of silica, calcium silicate, and zirconia. The chemical analysis revealed 4.8 wt% Nb and 0.8 wt% Ta, along with high concentrations of Zr (11.1 wt%), confirming the material’s potential as a secondary resource. Thorium (2.7 wt%) and uranium (0.3 wt%) were also detected, indicating the presence of radioactive constituents. The detailed characterization of the slag provides essential insights into its chemical and mineralogical complexity, which directly influence the selection of suitable recovery routes. Understanding the distribution of Nb- and Ta-bearing phases within the refractory silicate–zirconia matrix is fundamental for defining pretreatment and leaching strategies. Therefore, this study establishes a necessary foundation for the design of efficient hydrometallurgical processes aimed at recovering critical metals from Brazilian tin slags. Full article

Alkali resistance is a critical factor for the long-term performance of glass fibers in cementitious composites. While zirconium oxide doping has proven effective in enhancing the durability of basalt fibers, its high cost and limited solubility motivate the search for viable alternatives. This study presents the first systematic investigation of titanium dioxide (TiO₂) doping in basalt-based glasses across a wide compositional range (0–8 mol%). X-ray fluorescence and diffraction analyses confirm complete dissolution of TiO₂ within the amorphous silicate network, with no phase segregation. At low concentrations (≤3 mol%), Ti⁴⁺ acts as a network modifier in octahedral coordination ([TiO₆]), reducing melt viscosity and lowering processing temperatures. As TiO₂ content increases, titanium in-corporates into tetrahedral sites ([TiO₄]), competing with Fe³⁺ for network-forming positions and displacing it into octahedral coordination, as revealed by Mössbauer spectroscopy. This structural redistribution promotes phase separation and triggers the crystallization of pseudobrukite (Fe₂TiO₅) at elevated temperatures. The formation of a protective Ti(OH)₄ surface layer upon alkali exposure enhances chemical resistance, with optimal performance observed at 4.6 mol% TiO₂—reducing mass loss in NaOH and seawater by 13.3% and 25%, respectively, and improving residual tensile strength. However, higher TiO₂ concentrations (≥5 mol%) lead to pseudobrukite crystallization and a narrowed fiber-forming temperature window, rendering continuous fiber drawing unfeasible. The results demonstrate that TiO₂ is a promising, cost-effective dopant for basalt fibers, but its benefits are constrained by a critical solubility threshold and structural trade-offs between durability and processability. Full article

Calcium silicate-based sealers (CSBS) vary in chemical composition, which can influence treatment outcomes. Therefore, the study aimed at comparing several commercially available CSBS regarding microstructure and elemental characterization. Four CSBS (AH Plus Bioceramic Sealer, BioRoot RCS, BioRoot Flow, TotalFill BC Sealer) and a control resin-based sealer (AH Plus) were evaluated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray powder diffraction analysis (XRD). The specimens were analyzed after setting (SEM, EDX, XRD), as well as after 7 (SEM) and 28 days (SEM, EDX) of incubation in Hank’s balanced salt solution. AH Plus exhibited a uniform matrix and small amounts of calcium (Ca), significantly decreasing after incubation. In contrast, CSBSs exhibited crystalline forms on the surface and increased Ca content, significantly increasing after 28 days of incubation. The main crystalline phase for all tested CSBS was zirconium oxide, while for ERBS it was calcium tungstate. In conclusion, the amount of calcium increased on the surface of CSBSs after incubation, which alkalinized the pH, promoting mineralization, apatite formation, and antibacterial potential. Despite this, the formation of a hydroxyapatite layer was not demonstrated, possibly due to the high dissolution potential of CSBSs. Full article

Calcium ion sensors are essential in clinical diagnosis, particularly in the management of chronic kidney disease. Multiple approaches have been developed to measure calcium ions, including flame photometry and ion chromatography. However, these devices are bulky and require specialized staff for operation and evaluation. The integration of all-solid-state ion-selective determination allows the design of miniaturized and low-cost sensing that can be used for the continuous monitoring of electrolytes. However, clinical use has been limited due to the low electrochemical stability and selectivity and high noise rate. This manuscript reports for the first time a novel miniaturized Ca²⁺ ion-selective sensor, developed by using a two-layer nanocomposite thin film (5 µm thick). The device consists of functionalized silica nanoparticles embedded in a poly(vinyl chloride) (PVC) film, which was deposited onto a nanoporous zirconium silicate nanoparticle layer that served as the sensing surface. Systematic evaluation revealed that perfluoroalkane-functionalized silica nanoparticles enhanced Ca²⁺ selectivity by minimizing K⁺ diffusion, confirmed by both potentiometric measurements and quartz microbalance studies. The final sensor demonstrated a super-Nernstian sensitivity of 37 mV/Log[Ca²⁺], a low signal drift of 28 µV/s, a limit of detection of 1 µM, and exceptional selectivity against Na⁺, K⁺, and Mg²⁺ ions. Long-term testing showed stable performance over three months of continuous operation. Clinical testing was conducted on patients with chronic kidney disease. An accurate real-time monitoring of electrolyte dynamics in dialysate samples was observed, where final concentrations matched those observed in physiological conditions. Full article

A low-grade uranium-gold polymetallic ore is associated with many rare elements, such as beryllium (Be), zirconium (Zr), thorium (Th), and cerium (Ce). It has potential development and utilization value. In order to improve the development and utilization rate of a low-grade uranium-gold polymetallic ore, beryllium (Be) in low-grade uranium-gold polymetallic ore was extracted by a combined method of (NH)₂SO₄ and Al₂(SO₄)₃. The effects of different concentrations of (NH₄)₂SO₄ solution on the leaching of beryllium (Be) in low-grade uranium-gold polymetallic ore with different particle sizes after sieving were studied; microstructure and physicochemical analyses were carried out. The leaching mechanism of beryllium (Be) was revealed. The experimental results showed that when the low-grade uranium-gold polymetallic ore in (NH)₂SO₄ solution is 6 g/L and Al₂(SO₄)₃ is 3 g/L, the particle size of the ore sample is 0.01 mm, the concentration of beryllium (Be) in the leaching solution reaches 0.521 mg/L after 3 days of leaching, the concentration of beryllium (Be) in the leaching solution of the sample without Al₂(SO₄)₃ solution is 0.007 mg/L, and the leaching rate of beryllium (Be) reaches 98.6%. SEM and XRD analyses showed that the silicate composition in the sample after leaching was obviously destroyed compared with the control group when the (NH)₂SO₄ solution was 6 g/L, which increased the contact area on the surface of the ore sample and promoted the leaching of beryllium (Be) in the uranium ore sample. The research results lay a theoretical foundation for the development and extraction of beryllium (Be) associated with low-grade uranium-gold polymetallic ore. Full article

Aluminum 7075 alloys are widely utilized in aerospace, transportation, and marine industries due to their high strength and low density. However, further research is needed to understand their mechanical, thermomechanical, and vibrational behaviors when reinforced. This study focuses on the development of Al 7075 composites reinforced with zirconium silicate (ZrSiO₄), processed via sand stir casting. The mechanical properties, including tensile, compression, and impact strength, as well as thermomechanical and vibrational behaviors, were thoroughly investigated. A planetary ball mill was used to mix ZrSiO₄ with a wettability agent, and the results indicated that the addition of ZrSiO₄ with the wettability agent significantly enhanced the mechanical properties. Fourier Transform Infrared Spectroscopy (FTIR) was employed to identify the compounds formed after adding the reinforcement and wettability agent. Scanning Electron Microscope (SEM) images and Energy-dispersive X-ray (EDX) analysis revealed a uniform distribution of the particles within the matrix. The tensile, compression, and impact strengths increased by 20%, 21%, and 19%, respectively, with the addition of 8 wt% ZrSiO₄; however, strain decreased. Additionally, heat treatment further enhanced the mechanical properties of the composites. The thermomechanical properties showed improvement even at elevated temperatures, and the damping factor was enhanced with the addition of ZrSiO₄. The elemental composition of the reinforced composites was analyzed using EDX, confirming the presence of the reinforcement. This research highlights the potential of Al 7075-ZrSiO₄ composites for improved performance in various applications. Full article

In order to cleanly and efficiently extract zirconium from zircon sand (the main component is ZrSiO₄), sodium hydroxide sub-molten salt was used to decompose ZrSiO₄ in this study. When ZrSiO₄ reacts with sodium hydroxide sub-molten salt, the formation of Na₂ZrSiO₅ (a water-insoluble product) considerably affects the separation efficiency of Zr and Si and increases production cost. Thus, it is necessary to control the formation of Na₂ZrSiO₅. The influence of NaOH content, reaction temperature, reaction time, and NaOH/ore mass ratio on the formation of Na₂ZrSiO₅ were systematically investigated. The optimum reaction parameters for the inhibition of Na₂ZrSiO₅ formation were as follows: 80% NaOH content, 245 °C reaction temperature, 4:1 NaOH/ore mass ratio, 10 h reaction time, and 400 r/min agitation speed. These results indicate that ZrSiO₄ is decomposed to Na₂ZrO₃ and Na₂SiO₃ by reacting with NaOH, realizing the separation of Zr and Si, and then the reactions between Na₂ZrO₃ and Na₂SiO₃ result in the formation of Na₂ZrSiO₅, during the decomposition of ZrSiO₄ using NaOH sub-molten salt. The sub-molten salt decomposition process can realize the clean extraction of zirconium, which is conducive to the sustainable development of zirconium resources. Full article

There is an essential clinical need to develop rapid process scaffolds to repair bone defects. The current research presented the development of calcium zirconium silicate/polycaprolactone for bone tissue engineering utilising melt extrusion-based 3D printing. Calcium zirconium silicate (CZS) nanoparticles were added to polycaprolactone (PCL) porous scaffolds to enhance their biological and mechanical properties, while the resulting properties were studied extensively. No significant difference was found in the melting point of the samples, while the crystallisation temperature points of the samples containing bioceramic increased from 36.1 to 40.2 °C. Thermal degradation commenced around 350 °C for all materials. According to our results, increasing the CZS content from 0 to 40 wt.% (PC40) in porous scaffolds (porosity about 55–62%) improved the compressive strength from 2.8 to 10.9 MPa. Furthermore, apatite formation ability in SBF solution increased significantly by enhancing the CZS percentage. According to MTT test results, the viability of MG63 cells improved remarkably (~29%) in PC40 compared to pure PCL. These findings suggest that a 3D-printed PCL/CZS composite scaffold can be fabricated successfully and shows great potential as an implantable material for bone tissue engineering applications. Full article

The relationship between exposure to inhaled inorganic particulate matter and risk for deployment-related lung disease in military personnel is unclear due in part to difficulties characterizing individual exposure to airborne hazards. We evaluated the association between self-reported deployment exposures and particulate matter (PM) contained in lung tissue from previously deployed personnel with lung disease (“deployers”). The PM in deployer tissues was compared to normal lung tissue PM using the analytical results of scanning electron microscopy and inductively coupled plasma mass spectrometry. The majority of PM phases for both the deployers and the controls were sub-micrometer in size and were compositionally classified as aluminum and zirconium oxides, carbonaceous particles, iron oxides, titanium oxides, silica, other silicates, and other metals. The proportion of silica and other silicates was significantly higher in the retained dust from military veterans with biopsy-confirmed deployment-related lung disease compared to the control subjects. Within the deployer population, those who had combat jobs had a higher total PM burden, though the difference was not statistically significant. These findings have important implications for understanding the role of inhaled inorganic dusts in the risk for lung injury in previously deployed military veterans. Full article

The aim of this experiment was to determine the effect of the addition of strontium oxide on the recrystallization of zirconium silicate when adding strontium oxide to the glaze composition. Zirconia glazes (four different contents) were prepared, to which strontium oxide was added in amounts of 0, 1, 3, 6, and 12 mass% SrO. The characteristic temperatures of the raw glazes were measured, based on which the maximum firing temperatures were determined. The fired glazes were subjected to a study of their phase compositions and an observation of their microstructures. An analysis of the characteristic temperatures showed a fluxing effect, but it was not as strong for all glazes. Differences in the amount of the crystalline phase of zirconium silicate obtained in the fired glazes, as well as the partial transition of zirconium silicate to the amorphous phase, were observed. Observations of the microstructure clearly indicated an increase in the homogeneity of the distribution of zirconium silicate. Full article