Search Results (1,188)

To investigate the biosilicification capabilities of Bacillus mucilaginosus and Bacillus polymyxa, silicon concentrations in supernatants from quartz and calcium silicate cultures were monitored over a 12-day period using inductively coupled plasma optical emission spectrometry (ICP-OES). Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to evaluate changes in the absorption intensity of Si–O–Si characteristic peaks, crystalline phase transformations in the reaction products, and the microstructural morphology of quartz and calcium silicate before and after microbial leaching. The results show that after leaching with B. mucilaginosus, the dissolved silicon concentration in the quartz supernatant reached a maximum of 73.868 mg/L on day 8. In contrast, following treatment with B. polymyxa, the silicon concentration in the calcium silicate supernatant peaked earlier, at 149.153 mg/L on day 4. After microbial leaching, both substrates exhibited marked changes in the intensity of the infrared absorption peaks at 1071 cm⁻¹ and 1083 cm⁻¹, suggesting the formation of Si–O–R type organosilicon complexes. Iron tailings (containing inert silica) and fly ash (containing active silica) were selected for experimental validation. Following treatment with B. mucilaginosus for desilication over an 8-day period, the activity index of iron tailings increased from 77.83% to 90.51%, while that of fly ash rose from 66.32% to 85.01%. ICP-OES analysis confirmed that under the action of B. mucilaginosus, the trends in silicon concentration and activity index in the supernatant of silica-containing solid wastes, such as iron tailings and fly ash, were consistent with those observed in quartz, thereby demonstrating effective biological desilication. These findings provide novel insights into the development of environmentally sound disposal methods for a wider range of solid waste types. Full article

Carbon–metal composite NiCrFeC coatings, prepared with and without controlled oxygen addition, were investigated to evaluate the influence of oxygen on the structure, mechanical response, and tribological performance. X-ray diffraction revealed that oxygen-containing films (NiCrFeC + O₂) exhibit a mixed metallic–oxide microstructure with CrNi, CrO, and NiO phases, whereas oxygen-free coatings show only CrNi crystalline peaks. The incorporation of oxygen led to a substantial increase in nano-hardness, from 0.84 GPa for NiCrFeC to 1.59 GPa for NiCrFeC + O₂. Scratch testing up to 100 N indicated improved adhesion and higher critical loads for the oxygen-rich coatings. Tribological measurements performed under dry sliding conditions using a sapphire ball showed a significant reduction in friction: NiCrFeC + O₂ stabilized at ~0.20, while NiCrFeC exhibited values between 0.25 and 0.35 at 0.5 N and 0.4–0.5 at 1 N, accompanied by non-uniform sliding due to coating failure. Wear-track analysis confirmed shallower penetration depths and narrower wear scars for NiCrFeC + O₂, despite similar initial roughness (~35 nm). These findings demonstrate that oxygen incorporation enhances hardness, adhesion, and wear resistance while substantially lowering friction, making NiCrFeC + O₂ coatings promising for low-friction dry-sliding applications. Full article

Thermally compressed fast-growing wood exhibits superior mechanical properties, presenting a sustainable and cost-effective alternative to solid wood. However, to prevent structural damage and achieve higher densification during this process, effective pretreatment is essential. This study systematically evaluates the efficacy of hydrothermal and alkaline sulfite pretreatments in modifying Chinese fir (Cunninghamia lanceolata Hook.) and poplar (Populus tomentosa Carr.). The resulting compressed wood was comprehensively characterized in terms of mass loss, mechanical strength, microstructure, chemical composition, and cellulose crystallinity. Results indicate that, under the conditions tested, alkaline sulfite pretreatment was more effective than hydrothermal pretreatment in enhancing the material properties of densified wood, with peak density, compressive strength, and hardness achieved after 5 h for fir and 3 h for poplar, respectively. The results obtained under the present experimental conditions support the fact that alkaline sulfite pretreatment is an effective approach for producing densified wood with enhanced mechanical properties, suggesting its potential suitability for higher-value applications. Full article

Ganoderma sichuanense is a widely studied medicinal mushroom, but the production of its antioxidant proteins has been scarcely evaluated. We assess the influence of different concentrations of culture media components under submerged fermentation, with and without agitation, on production of proteins with antioxidant activity from the mycelial biomass of G. sichuanense. Protein extracts were characterized by scanning electron microscopy, X-ray diffraction, and attenuated total reflectance Fourier-transform infrared spectroscopy. They were also analyzed for total protein and phenolic contents, antioxidant activities (ABTS^•+, DPPH^•, chelating ability, and reducing power), and electrophoretic profiles by SDS-PAGE. The most active extract was tested for cytoprotective potential under H₂O₂-induced oxidative stress in Saccharomyces cerevisiae. Growth kinetics of the best fermentation condition were also analyzed. Microstructural differences ranged from fibrillar to aggregated forms, depending on cultivation. Crystallinity was unaffected, but chemical differences and secondary structure organization were confirmed by infrared spectroscopy. The extract from the static culture with 10 g·L⁻¹ glucose, 5 g·L⁻¹ yeast extract, and 2.5 g·L⁻¹ soy peptone (referred as CM1S) showed the highest protein and phenolic contents and the strongest antioxidant activity (IC₅₀ = 4.8 and 24.0 µg of protein·mL⁻¹ for ABTS^•+ and DPPH^•, respectively). SDS-PAGE revealed higher protein band intensities in static cultures. CM1S showed potential to protect yeast cells from oxidative stress. The Gompertz model estimated a specific growth rate of 0.0068 h⁻¹ in CM1S. The findings highlight a cultivation strategy that modulates fungal metabolism and improves the recovery of antioxidant proteins from G. sichuanense biomass. Full article

The development of effective bone substitutes remains a central goal in regenerative medicine. In this study, lithium-modified bioglass-ceramics based on the 47.5S5 silicate oxide system were synthesized using the sol–gel method, followed by calcination and axial pressing to form cylindrical samples. These materials were sintered at 700 and 800 °C and subsequently examined to evaluate their structural, mechanical, and biological performance. Structural and microstructural analyses confirmed the presence of crystalline phases such as combeite (Na₆Ca₃Si₆O₁₈), NaLiSiO₄, Li₂SiO₃, and calcium silicates, indicating the successful incorporation of lithium within the glass-ceramic network. The bioceramics exhibited improved densification, deformability, and compressive strength with increasing sintering temperature. In vitro degradation in simulated body fluid revealed a consistent increase in mass loss with higher lithium content, suggesting enhanced resorbability linked to lithium oxide. Antibacterial testing indicated moderate antimicrobial activity, with slightly better results observed at higher sintering temperatures. Cell viability assays further supported the materials cytocompatibility. Taken together, these findings suggest that lithium substitution contributes positively to both mechanical robustness and biological behaviour, positioning these ceramics as promising bioresorbable bone substitutes with controlled degradation, suitable for bone tissue engineering where durability, bioactivity, and antimicrobial function are required. Full article

Excessive carbonation curing can impair later-age properties; therefore, determining an appropriate carbonation duration is critical for practical low-CO₂ utilization. In this study, cement paste and mortar specimens were subjected to accelerated carbonation curing under a diluted CO₂ atmosphere (3%) using a concentration-controlled scheme (2.5–3.0%), followed by standard hydration curing for up to 28 d. Carbonation durations of 500, 1000, 2000, and 6000 min were examined. The results show that an early carbonation duration of 1000 to 2000 min achieves an optimal balance between performance enhancement and subsequent hydration development. Compared with the reference specimens, compressive and flexural strengths, as well as durability-related indicators (including electrical flux and EIS parameters), are improved. In addition, the surface microstructure is refined, with a higher proportion of highly crystalline CaCO₃ (>70%). In contrast, prolonged carbonation (>2000 min) induces unfavorable microstructural evolution during subsequent hydration, leading to reductions in mechanical performance and durability. These findings provide a practical duration-control strategy for accelerated carbonation curing using low-concentration CO₂ streams (3–10%), which are typical of light-industry flue gases. Full article

This study aimed to develop a sustainable route for processing biogenic calcium carbonate from Perna perna mussel shell waste and converting it into hydroxyapatite (HA), as well as to evaluate its potential for bone and dental tissue engineering applications. Mussel shells were decarbonized (400 °C), milled, and converted to HA via wet chemical precipitation using a nominal Ca/P molar ratio of 1.67 during synthesis followed by thermal treatment (900 °C). Comprehensive characterization included SEM, FTIR, XRD, Raman spectroscopy, XRF, TGA, and BET analysis. Biological evaluation involved cytotoxicity assays (MTT), antimicrobial testing, and odontogenic differentiation studies (Alizarin Red) using SHEDs. Statistical analysis by one-way ANOVA and Tukey post hoc tests (α = 0.05). SEM revealed a microstructured morphology composed of agglomerates, favorable for biomedical applications. FTIR and XRD confirmed the conversion of CaCO₃ to hydroxyapatite, while thermal analysis demonstrated the material’s stability. The HA exhibited secondary minor phase (13%) β-TCP form of calcium phosphate (Ca_2.997H_0.006(PO₄)₂), high crystallinity (about 80%), and nanoscale crystallite size (85 nm, 2.5–5.0 m²/g), despite forming larger agglomerates in suspension. The material showed favorable physicochemical properties (neutral pH, −18.5 mV zeta potential), but no inhibition was detected in antimicrobial testing. In vitro assays showed excellent cytocompatibility (viability > 70% at 12.5 µg/mL) and significant osteogenic potential (high mineralization vs. controls, p < 0.05). Mussel shell-derived HA presents a sustainable, clinically relevant biomaterial with ideal properties for bone regeneration. The study establishes a complete waste-to-biomaterial pipeline while addressing key requirements for dental and orthopedic applications. Full article

Spinel-based glass-ceramics face challenges such as a narrow crystallization window for the target phase and the difficulty in suppressing the competitive Li_xAl_xSi_1−xO₂ crystals. This study proposes a method to regulate the phase formation in ZnO-MgO-Al₂O₃-SiO₂ glass by precisely controlling the heat treatment temperature. The microstructural evolution was analyzed by DSC, XRD, Raman spectroscopy, SEM, TEM, and XPS. The results indicate that the heat treatment at a nucleation temperature of 780 °C for 2 h and a crystallization temperature of 880 °C for 2 h effectively inhibits the precipitation of the Li_xAl_xSi_1−xO₂ secondary phase, yielding a glass-ceramic with nano-sized MgAl₂O₄, ZnAl₂O₄ spinel as the primary crystalline phase. The obtained glass-ceramic exhibits excellent mechanical properties, including a Vickers hardness of 922.6 HV, a flexural strength of 384 MPa, and an elastic modulus of 113 GPa, while maintaining a high visible light transmittance of 84.3%. This work provides a clear processing window and theoretical basis for fabricating high-performance, highly transparent spinel-based glass-ceramics through tailored heat treatment. Full article

This study compares fly-ash-based geopolymers reinforced with short glass fibers (GF) or flax fibers (FF). Four mixes were produced: reference (FA), 1 wt% GF, 1 wt% FF, and a hybrid (0.5 wt% GF + 0.5 wt% FF). These compositions were cast into prism and cube molds, cured at 75 °C for 24 h, and tested after 28 days. Mechanical testing included compressive strength and three-point bending, phase composition by XRD, and microstructure by optical and SEM microscopy. The GF composite showed the highest compressive strength (mean up to ~28–34 MPa versus ~17 MPa for the reference), while FF gave intermediate values (~11–22 MPa). During bending, the reference achieved the highest flexural strength (~5.5 MPa); fiber-reinforced mixes ranged from ~2.9 to 4.4 MPa. XRD indicated a typical amorphous aluminosilicate gel over crystalline remnants; SEM/optical observations revealed a denser, more compact matrix with fewer voids for GF systems, whereas FF and hybrid mixes exhibited localized porosity and fiber pull-out imprints affecting crack initiation/propagation. Overall, 1 wt% GF effectively enhances compressive performance and matrix densification, while fiber addition at the tested dosages does not improve flexural strength; optimizing fiber content/dispersion and interfacial treatment is recommended. Full article

Pigment gallstones represent a heterogeneous group of concretions, classically divided into black and brown types, whose morphology and microstructure offer critical clues about their underlying pathogenesis. Gallstone formation (lithogenesis) is a complex process triggered when the physicochemical equilibrium of bile is disrupted. Background/Objectives: The spicules observed on the surface of certain black pigment gallstones have traditionally been attributed to the branching capacity of cross-linked bilirubin polymers. However, a growing body of experimental and spectroscopic evidence suggests that inorganic calcium salts, particularly calcium carbonate and calcium phosphate, play a central role in the formation of the distinctive spiculated or “coral-like” architecture. Materials and Methods: In our study, we examined a case series of 1350 consecutive patients with gallstone disease, identifying 81 patients who presented with solitary black pigment stones. We systematically explored the association between high calcium content, specifically calcium carbonate, and the occurrence of spiculated morphology. Our analyses demonstrated a robust correlation between an elevated concentration of calcium carbonate and the presence of well-defined spicules. Results: These results support the hypothesis that mineral elements, rather than organic bilirubin polymers, act as crucial determinants of the peculiar crystalline structure observed in a significant subset of pigment stones. Spiculated stones, due to their small size and sharp projections, have a higher likelihood of migrating, increasing the risk of potentially life-threatening complications, such as acute cholangitis and gallstone pancreatitis. Conclusions: Our findings, consistent with recent advanced crystallographic analyses, underscore the importance of considering mineral composition in the diagnosis and management of cholelithiasis. Understanding the factors that drive calcium carbonate precipitation is essential for developing new preventive and therapeutic strategies, aiming to modulate bile chemistry and reduce the risk of calcium-driven lithogenesis. Full article

Utilizing abundant volcanic rock resources as supplementary cementitious materials is a critical pathway for regional low-carbon construction. However, the high crystallinity of natural volcanic rocks limits their reactivity. This study systematically investigates the regulation mechanisms of Triethanolamine (TEA) and Triisopropanolamine (TIPA) on the hydration kinetics and microstructure of a cement system containing Volcanic Rock Powder (VRP) thermally treated at 700 °C. Dissolution kinetics reveal that both TEA and TIPA inhibit Si release but exhibit distinct structural selectivity in promoting metal ion dissolution: TEA demonstrates superior efficiency in promoting the release of Al and Ca ions due to lower steric hindrance, whereas TIPA exhibits a stronger specific activation capacity for insoluble Fe, which is likely attributed to the electron-donating inductive effect. Macroscopic tests show that TEA at 0.05% dosage significantly improved the 28-day compressive strength by 20.4%, attributed to the synergistic effect of efficient chemical activation and pore structure refinement. In contrast, the stronger surface activity of TIPA introduced substantial detrimental macropores; this deterioration in physical structure severely offset its chemical contributions, leading to slow late-age strength development. The study highlights the critical trade-off between chemical activation and microstructural evolution, confirming that TEA is a more suitable activator than TIPA for the Al/Fe-rich thermally treated VRP. Full article

Titanium-based bulk metallic glasses (BMGs) offer high strength, lower stiffness than Ti-6Al-4V, and superior corrosion resistance, but conventional Ti glass-forming systems often contain toxic Ni, Be, or Cu. This work investigates five novel Ti-based alloys free of these elements—Ti₄₂Zr₃₅Si₅Co_12.5Sn_2.5Ta₃, Ti₄₂Zr₄₀Ta₃Si₁₅, Ti₆₀Nb₁₅Zr₁₀Si₁₅, Ti₃₉Zr₃₂Si₂₉, and Ti_65.5Fe_22.5Si₁₂—synthesized by arc melting and suction casting. Single-track laser remelting using a selective laser melting (SLM) system was performed to simulate additive manufacturing and examine microstructural evolution, cracking behavior, mechanical properties, and cytocompatibility. All alloys solidified into fully crystalline α/β-Ti matrices with Ti/Zr silicides; no amorphous structures were obtained. Laser remelting refined the microstructure but did not induce glass formation, consistent with the known limited glass-forming ability of Cu/Ni/Be-free Ti systems. Cracking was observed at low laser energies but crack density decreased as laser energy increased. Cracks were eliminated above ~0.4 J/mm for most alloys. Ti₄₂Zr₃₅Si₅Co_12.5Sn_2.5Ta₃ exhibited the lowest stiffness (~125 GPa), while Ti₆₀Nb₁₅Zr₁₀Si₁₅ showed the highest due to silicide precipitation. Cytotoxicity tests (ISO 10993-5) confirmed all alloys to be non-toxic, with some extracts even enhancing fibroblast proliferation. This rapid laser-remelting approach enables cost-effective screening of Ti-based glass-forming alloys for additive manufacturing. Ti–Zr–Ta–Si systems demonstrated the most promising properties for further testing using the powder bed method. Full article

In this study, amorphous Fe₆₀Nb₃B₁₇Si₆Cr₆Ni₄Mo₄ coatings were prepared using the high-velocity air fuel method. The microstructure, wear resistance, and corrosion resistance of the Fe₆₀Nb₃B₁₇Si₆Cr₆Ni₄Mo₄ coatings were examined for various levels of nanocrystallization. In contrast to the as-sprayed coating, the samples that were heat-treated formed partial α-Fe and crystalline Cr₂O₃. The generated nanocrystals exerted a dispersion-strengthening effect on the coatings, leading to enhanced hardness and fracture toughness. When the annealing temperature was below the initial crystallization temperature, the wear resistance improved by approximately 1.65 times, the wear rate decreased to half of that in the as-sprayed state, and the depth of the wear scar reduced. However, the resistance of the coatings to corrosion deteriorated as the degree of crystallization increased. X-ray photoelectron spectroscopy analysis revealed that heat treatment modified the composition of the passive film, thereby influencing its corrosion resistance. These results provide crucial insights into the application of Fe-based amorphous coatings in wear- and corrosion-resistant environments. Full article

Metallic implants used in orthopedics, such as titanium alloys, possess excellent mechanical strength but suffer from corrosion and poor bio-integration, often necessitating revision surgeries. Bioactive coatings, particularly hydroxyapatite, can enhance implant osteoconductivity, but high-purity synthetic hydroxyapatite is costly. This study investigates the development and characterization of a low-cost, biocompatible coating using hydroxyapatite derived from an unconventional natural source dromedary bone applied onto a titanium substrate via plasma spraying. Hydroxyapatite powder was synthesized from dromedary femurs through a thermal treatment process at 1000 °C. The resulting powder was then deposited onto a sandblasted titanium dioxide substrate using an atmospheric plasma spray technique. The physicochemical, structural, and morphological properties of both the source powder and the final coating were comprehensively analyzed using Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, X-ray Diffraction, and Fourier-Transform Infrared Spectroscopy. Characterization of the powder confirmed the successful synthesis of pure, crystalline hydroxyapatite, with Fourier-Transform Infrared Spectroscopy analysis verifying the complete removal of organic matter. The plasma-sprayed coating exhibited good adhesion and a homogenous, lamellar microstructure typical of thermal spray processes, with an average thickness of approximately 95 μm. X-ray Diffraction analysis of the coating revealed that while hydroxyapatite remained the primary phase, partial decomposition occurred during spraying, leading to the formation of secondary phases, including tricalcium phosphate and calcium oxide. Scanning Electron Microscopy imaging showed a porous surface composed of fully and partially melted particles, a feature potentially beneficial for bone integration. The findings demonstrate that dromedary bone is a viable and low-cost precursor for producing bioactive hydroxyapatite coatings for orthopedic implants. The plasma spray method successfully creates a well-adhered, porous coating, though process-induced phase changes must be considered for biomedical applications. Full article

This paper examined the effect of marble powder (MP) on air-cured cement-based materials when subjected to sulfuric acid (H₂SO₄) attack. Four MP replacement levels were tested: 0%, 5%, 10%, and 15% by weight of cement. The prepared samples were cured for 90 days prior to being exposed to H₂SO₄. Macroscopic tests for apparent density and compressive strength along with microstructural characterization using X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed to determine the effect of MP on the properties of the materials. The Rietveld method was used to analyze the amounts of different crystalline phases and amorphous calcium silicate hydrate (C-S-H). The obtained results indicate that 5% MP in air-cured cement -based materials exhibited the best behavior with acceptable resistance to acid attacks. This level of MP replacement was found to optimize the filler effect, improve the hydration process, and enhance the matrix density, which in turn reduces the permeability of the material and increases acid resistance. This is attributed to the balanced contribution of MP to phase formation, particularly calcite, which helps to counteract acid-induced dissolution, while also preserving the stability of C-S-H phases. This study provides a new perspective of the role of MP in influencing phase content (crystalline and amorphous phases) and their possible impacts on macroscopic properties such as apparent density and compressive strength. MP behaved as a filler, to improve hydration and resistance to acid attacks. Additionally, using MP as a replacement for ordinary Portland cement (OPC) offers a sustainable alternative by reducing waste and promoting the recycling of marble industry by-products, thereby contributing to environmental sustainability. It is recommended that, 5% MP is the optimal replacement content to enhance durability and mechanical properties in air-cured cement-based materials in aggressive environments, as it is both practical and achievable for infrastructure to be subjected to the aggressive environment. Full article