International Journal of Ceramic Engineering & Science最新文献

Pure and different percentages (0.25, 0.5, 1.0, and 2.5%) of silver (Ag) doped hydroxyapatites (Hap) were synthesized employing the wet chemical precipitation method. The samples were characterized with the aid of X-ray diffraction (phase analysis, crystallographic characterization, and crystal size calculation using Scherrer equation and different models), scanning electron microscopy, and optical bandgap energy. The Hap containing 0.25% Ag showed better photocatalytic activity in various dye concentrations, catalyst doses, and pH. At a very low catalyst dose (0.375 g/L) and 20 ppm pollutant concentration, reaction rate, and rate constant were evaluated for the Congo Red dye, ciprofloxacin, amoxicillin, and levofloxacin. The maximum rate constant (0.0028 min⁻¹) and reaction rate (9.657 × 10⁻⁸ mole L⁻¹·min⁻¹) were found for Congo Red dye and ciprofloxacin, respectively, using 0.25_Ag-Hap (0.25% Ag-doped Hap). The energies of the valance band (3.14 eV) and conduction band (−0.36 eV) were lower in the case of 0.25_Ag-Hap than the other samples. Simplified reaction mechanisms were proposed for the photocatalytic degradation of Congo Red dye, ciprofloxacin, amoxicillin, and levofloxacin.

This study delves into the impact of different potassium-waterglass (K-WG) compositions on the early reaction dynamics and strength evolution in metakaolin-based geopolymers (GP). By maintaining a constant SiO₂/Al₂O₃ ratio of 4, the study explores the influence of varying H₂O/K₂O and K₂O/Al₂O₃ ratios on GP properties under both dry and saturated curing conditions. Early reaction kinetics are examined using isothermal calorimetry at room temperature (21°C), and pH measurements provide insights into alkali leaching. A strong correlation was found between total heat release and strength gain, as evidenced by ultrasonic cement analyzer (UCA) readings. The study further identifies that increased H₂O/K₂O ratios prolong setting times and delay the geopolymerization peaks, while a higher K₂O/Al₂O₃ ratio enhances the geopolymerization process. Vicat tests confirmed the results obtained by calorimetry and UCA: only the GP4 formulation (H₂O/K₂O = 8.7 and K₂O/Al₂O₃ = 1.3) hardened in less than 7 days. Additionally, it was found that saturated curing conditions decelerate strength development, with an initial notable decline in compressive strength at 24 h compared with dry curing. However, this difference diminishes to a negligible 7.6% after 3 days. Optimal ratios of H₂O/K₂O = 8.7 and K₂O/Al₂O₃ = 1.3 were determined to be critical for achieving reliable strength measurements at 1 day of curing. pH assessments indicated strong water resistance in all GP formulations, with leaching primarily governed by diffusion mechanisms. Specifically, the K-WG composition with SiO₂/K₂O = 1.53 and H₂O/K₂O = 8.69 showcased minimal leachability. These fundamental findings are crucial for the later design of GP materials that require rapid strength development, especially crucial for applications necessitating cementing under extreme conditions, such as deep-sea drilling, geothermal energy production, and high-temperature industrial processes.

Bismuth oxide and bismuth complexes with organic ligands, particularly Schiff bases, have received much attention due to their non-toxicity, antibacterial, and photocatalytic properties in removing water and environmental contaminants by oxidative degradation. This work investigates the synthesis of bismuth complexes with the salicylidine Schiff base ligand of H₂L through hydrothermal and solvothermal methods, the preparation of bismuth oxide nanoparticles from these complexes, and the synthesis of bismuth oxide nanoparticles from bismuth nitrate. To characterize the products, several techniques including infrared, UV–vis, X-ray diffraction (XRD), energy-dispersive X-ray analysis, and scanning electron microscopy (SEM) have been used. Hydrothermally and solvothermally produced bismuth(III) complexes with H₂L had particle sizes of about 46 and 15 nm, respectively, while oxide nanoparticles made from them had sizes of about 42 and 52 nm, respectively.

The study also investigates the usage of complexes and oxide nanoparticles as photocatalysts under an ultraviolet (UV) lamp (30 W) irradiation to remove contaminants such as methyl orange, acid red 14, orange acid 7, and malachite green from water. The results showed that the bismuth complexes and oxide nanoparticles effectively remove these dyes from contaminated water samples.

In this study, the local-scale structure of geopolymers shaped by extrusion or 3D printing was investigated and correlated to the reactivity of the raw materials. The reactivity of the different metakaolin mixtures was evaluated using zeta potential measurements with different alkali silicate solutions, followed by shaping via 3D printing; additionally, the different networks formed were identified via NMR spectroscopy. The results showed that in the presence of weakly reactive basic solutions, the Al(OH)₄⁻ species were released in low amounts due to an increase in the polymerized silicate species in the solution, resulting in a low zeta potential in absolute value. Conversely, for more reactive solutions, the silicate species were more depolymerized, and the siliceous and aluminous metakaolin species were more easily released in solution, resulting in increasingly low zeta potential values. Some samples were 3D printed with metakaolin mixtures using different printers and silicate solutions (K, KNa) with alkaline cation concentrations of [M] > 2.8 M in the mixtures; here, the metakaolin zeta potential values were greater than −50 mV, and the local-scale structure consisted of more than 50% geopolymer networks (Q⁴(3Al) + Q⁴(2Al)).

ZnO varistors doped with $��Y_2�O_3�$, $��{\mathrm{Bi}}_2�O_3�$, and $��{\mathrm{Co}}_2�O_3�$ were analyzed for electrical performance, microstructure, phase composition, and elemental distribution using electrical performance testing, scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy tests. The best results were obtained with 0.5 mol% $��Y_2�O_3�$, 2 mol% $��{\mathrm{Bi}}_2�O_3�$, and 3 mol% $��{\mathrm{Co}}_2�O_3�$

The aim of this work is to study the influence of the palm fibers treated with soda hydroxide solution on the properties of the compressed earth bricks stabilized (CEBs) with alkali-activated binder. The improvement in their mechanical parameters is attributable with 15 wt.% of alkali-activated binder-based natural pozzolan. To achieve this objective, mortars composed of treated fibers at different levels (0.1, 0.2, 0.3, 0.4, and 0.5 wt.%) of lengths of 4 and 16 cm have been developed. These different mortars with and without fibers were subjected to mechanical (dry and wet compressive test, flexural test), physical (water absorption), mineralogical (XRD, FTIR), and microstructural (SEM/EDS) characterizations after 7 and 90 days. The results revealed that in general the incorporation of fibers improves the mechanical and physical properties of CEBs stabilized with 15 wt.% of alkali-activated binder. Furthermore, the X-ray diffraction analysis indicated that certain mineralogical phases of the raw materials dissolve during alkaline activation. The Fourier transform infrared spectra revealed the effectiveness of the fibers in sorption water molecules. Moreover, optical examination reveals that the binder utilized completely wraps the fibers. This demonstrates that the treated fibers function flawlessly as a filler in the matrix. At 90 days with the addition of 0.4 wt.% fibers, the maximum dry compressive strength and flexural strength values were 8.08$�\pm$0.40 and 5.8$�\pm$0.19 MPa, respectively. The stabilized earth bricks reinforced with 0.4 wt.% of palm fibers exhibited the mechanical properties values fitting the requirements of the materials candidate for the building construction applications especially as masonry bricks.

Handling the massive quantities of by-products from metallurgical processes has become a major concern in recent decades. Efforts to develop sustainable alternatives for these secondary resources are ongoing to achieve the transition to climate neutrality. This study has investigated the potential of employing vanadium-bearing slag as a new value-added binder in refractories, aiming to replace virgin raw materials. Two types of vanadium-bearing slags from BOF, each containing <2 wt.% vanadium were studied. Low-cement vanadium slag-based castables were prepared by gradually substituting 0, 2.5, and 5 wt.% of the commercial calcium aluminate cements (Secar71 and CMA72) by the slags. The flow values of the mixes containing 5 wt.% of slag decrease significantly from about 90% to 30% after 30 min, showing poor ability to flow and thus are not considered as self-flow castables. Castables containing 2.5 wt.% of slag present a cold crushing strength value, in the range of 71–116 MPa while values for castables containing 5 wt.% of slag fall into the range of 53–68 MPa due to the lower packing properties leading to higher porosity and reduce in strength. Similar observation was concluded for cold modulus of rupture. The micrographs of the samples containing both slag and cement show promising compatibility between the binder and aggregates after sintering at 1500°C. Overall, characteristics obtained with the samples containing slag show promising alternatives as a refractory lining.

The silver-exchanged zeolites were created using a solid-state ion exchange method with silver sulfate and silver nitrate salts. Various techniques, including X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, were employed to examine the structure, morphology, and physical-chemical properties of the samples. The antimicrobial effectiveness of the zeolites was tested against gram-negative Escherichia coli and gram-positive Staphylococcus aureus, common bacteria found in wastewater. Before the silver exchange, the original zeolite exhibited small clustered particles, but after the exchange, its shape underwent significant transformation. The original clinoptilolite did not contain any silver, whereas the silver-exchanged samples AgSSE6% and AgNSE6% had silver contents of 2.29% and 3.80%, respectively. The XRD analysis confirmed the presence of Ag and AgO within the structure of the exchanged clinoptilolite. BET analysis indicated that the incorporation of Ag ions into the zeolite structure through ion exchange led to a reduction in surface area and micropores volume. The research findings revealed that zeolites exchanged with silver were more effective in inhibiting the growth of S. aureus, compared to E. coli. Additionally, zeolites treated with AgSO₄ exhibited a wider inhibition zone against both bacteria compared to zeolites treated with AgNO₃.

The present study deals with two kaolins from Eseka and Dibamba-Cameroon to determine their potential suitability as additive of CEM I 42.5R and to optimize the properties of cement in the sense to promote low-carbon cement. X-ray diffractometry was used to establish the mineralogical composition of two kaolins. X-ray fluorescence was carried out to determine the chemical composition of kaolins and cement. Fine metakaolin powders obtained at 700°C were used as additive in CEM I 42.5R. Furthermore, consistency, setting time, water absorption, compressive and flexural test, and shrinkage test were evaluated. Scanning electron microscopy analysis was carried out to evaluate the microstructure variation. The substitution of CEM I with metakaolin resulted in a considerable increase in compressive and flexural strength from days 7 to 28 at optimum value. The compressive and flexural strengths at 28 days at optimum value of metakaolin increase to 52% and 44%, respectively, explaining the equilibrium oxides in the cement. The maximum values of strength with 20 wt.% MK1 and 30 wt.% MK2 at 7, 14, and 28 days appear in both cases when the ratio of SiO₂/Al₂O₃ is between 2.8 and 2.9. The silica modulus and alumina modulus of cement–metakaolin improved when metakaolin was added. The properties of cement were optimized with a 52% increase in compressive strength at 28 days.