Abstract in English:

Abstract This study evaluates the potential partial replacement of sand by blast furnace flue dust (BFFD) in coating mortars to reduce the environmental impact caused by solid residues generated by the iron-making industry. Mortars were produced with varying rates of sand replacement by BFFD, and curing was conducted at room temperature and in lime-saturated water. Axial and radial compressive strength were evaluated at ages up to 28 days, and density, water absorption, and apparent porosity were measured after 28 days of curing. The results indicate that partial replacement of sand by BFFD is viable after curing at ambient conditions, leading to a reduction in mortar density without significantly altering compressive strength. However, the compressive strength of BFFD-added mortars decreases when curing is carried out in water-saturated lime.

Abstract in English:

Abstract Flash sintering, renowned for its rapid densification of ceramic materials, lacks comprehensive studies on the influence of electric field and current density on densification due to potential variations based on furnace type and sample geometry. This study introduces a computational modeling technique using response surface methodology to predict densification, onset temperature, and steady-state temperature in flash sintering. A mathematical model was developed to optimize densification in 8YSZ cylindrical and dog-bone samples, employing a central composite design combined with response surface methodology. Results predicted optimal electric field and current density values for densification across both geometries, elucidating their effects on onset and sample temperatures. Validation showed less than 5 % variation from experimental values, except for onset temperature and T BBR in dog-bone samples, with 11 % and 13 % variations, respectively. These findings suggest the technique could be extended to incorporate additional process boundary conditions for different sample geometries, broadening its applicability.

Abstract in English:

Abstract 45S5 bioglass microspheres are very attractive in the biomedical field, as they can stimulate and guide bone and soft tissue regeneration. One of the main factors influencing the success of these materials is their chemical composition. Therefore, knowing the effect of the microsphere synthesis method on this composition is extremely important. In this work, microspheres with a diameter distribution of 35-150 µm were prepared from a bio-glass with the composition 45S5 using the flame spheroidization method. Their bioactivity was studied in a simulated biological fluid (SBF) at 37 ºC. An important loss in the concentration of Na and P was detected in the spheroidization process, reaching 85% and 73%, respectively, in microspheres smaller than 65 µm. The P distribution was heterogeneous. These modifications affected the early stages of the hydroxyapatite formation mechanism, delaying its deposition on the surface of the microspheres concerning the parent bio-glass.

Abstract in English:

Abstract The increasing release of gases that cause the greenhouse effect brings the need to develop products that minimize the environmental impact. In the civil construction sector, clinker, the main raw material for cement, releases large amounts of carbon dioxide during production. Thus, research related to geopolymers has stood out due to the lower release of gases into the atmosphere. Geopolymers are materials developed from aluminosilicates activated in a highly alkaline medium through geopolymerization. The compositions were prepared by varying the sodium hydroxide solutions NaOH (5, 7.5, and 10, Mols/L) and the proportions of sodium silicate Na2SiO3 to NaOH (1:2, 1:1 and 2:1) to determine a composition with the best characteristics. The factorial experiments of the type 3² were planned with 2 factors and 3 levels. The materials obtained were analyzed at 7 days of curing at room temperature. With the analysis of the results, it was possible to identify that the variation of the parameters SiO2/Al2O3 and Na2O/SiO2 have a significant influence. The Na2SiO3/NaOH ratio is the most important factor in the strength gain at early age. Compressive strength varied between 4.46 and 41.14 MPa as the smallest and highest SiO2/Al2O3 ratio, respectively.

Abstract in English:

Abstract This study studied the influence of some parameters of reinforcement phase, such as the volume fraction and grain size, on the physical, mechanical, and microstructural properties of alumina matrix composite. The samples of the silica-alumina composite were prepared by powder metallurgy method, which was carried out by adding 0, 14, and 27 %vol of silica to alumina as a reinforcement phase. The particle size averages of silica were 19.37 μm and 129.4 μm. The bulk density, apparent porosity, linear shrinkage, hardness, compressive strength, SEM for microstructure, and XRD analysis for the samples were tested. The results of tests for the produced samples showed that increasing the volume fraction to a certain limit and using the fine particle size for the reinforcement phase improve the physical and mechanical properties of the alumina matrix composite outstandingly and achieve the best densification for the samples.

Abstract in English:

Abstract Additive manufacturing (AM) of ceramics by vat photopolymerization (VPP) is a process in which a slurry composed of a liquid photopolymer supercharged with ceramic particles is cured in layers in a vat by a light source located below (bottom-up) or above (top-down) the vat, resulting in a three-dimensional body, after organics removal and sintering resulting in a ceramic part. This work aims to carry out a developmental design and fabrication of a “top-down” VPP AM machine for ceramics. The criteria and boundaries of the project were: commercial DLP projector with high-pressure mercury lamp without a UV filter, layer deposition of 10 micrometers thick, vat with 75mm in diameter and 75 mm in height, spreading and leveling of layers by blades, Creation Workshop 1.0.0.75 software for control and operation of layers and movement of blades by stepper motors and also digital image projection. The result was accessible and reproducible equipment capable of depositing layers and controlling light exposure time, allowing the generation of complex bodies with their consolidated layers. This open-source project allows the community to gain experience, acquire resources, and build trust before investing in more advanced systems. Furthermore, it acts as a rich source of collaborative ideas and designs.

Abstract in English:

Abstract This study evaluated the microtensile bond strength between a hybrid ceramic and a composite resin under different surface treatments and aging. Hybrid ceramic blocks were divided into five groups based on surface treatment and thermocycling: HF: 5% hydrofluoric acid; HFS: hydrofluoric acid and silane; A110S: sandblasting with aluminum oxide and silicatization; A50: aluminum oxide particle blasting; R: roughening. All samples were cemented to composite resin. After 24-hour storage in distilled water at 37ºC, the blocks were cut into sticks and tested immediately or after 10,000 cycles. Microtensile bond strength was tested using a universal testing machine. Failure modes were visualized and classified as cohesive, adhesive, and predominantly adhesive. Statistical differences were found between groups for surface treatment and thermocycling (p<0.05). Hybrid ceramics showed higher bond strength when etched with hydrofluoric acid and silanized, but bond strength decreased after thermocycling in all groups.

Abstract in English:

Abstract This investigation demonstrated the effects of calcium aluminate cement’s total or partial replacement with a potassium-metakaolin-based geopolymeric binder (K-GP) in high-alumina castables. Experimental measurements were conducted to analyze the produced samples’ processing, microstructure, and properties after curing and firing (800-1400 °C). The results highlighted K-GP as a viable binder option for producing cement-free refractories. After firing at 1100-1400 °C, the improved properties of geopolymer-bonded refractories were attributed to their complex resultant microstructure, comprising alumina particles strongly adhered by a glassy phase and contained randomly distributed clusters of kaliophilite and/or leucite grains within the ceramic matrix. After firing at 1250 °C, the samples exhibited a promising set of properties: high thermal shock resistance, modulus of rupture of 17.01 MPa, Young’s modulus of 67.15 GPa, porosity of 16.85%, density of 2.87 g/cm³, and linear shrinkage of 0.33%. These properties are suitable for applications at intermediate temperatures (i.e., petrochemical and non-ferrous industries).

Abstract in English:

Abstract In this study, we report an experimental investigation of the structural, morphological, and electrical properties of the ZrO2-Ag-Graphene sheet. In particular, we use the tape casting technique to produce the flexible ZrO2 ceramic sheet and impregnation and magnetron sputtering techniques to incorporate graphene and silver. Structural and morphological analyses indicate the presence of graphene and silver in the ceramic matrix, confirming the methods efficiency. We noticed that with the deposition of graphene and silver on the ZrO2 sheet, there is a decrease in electrical resistance. This fact is associated with the crystalline structure and morphology of graphene and silver, which makes sheets attractive in electrical applications. Thus, our results become fascinating for specific technological applications.

Abstract in English:

Abstract This study focuses on synthesizing gallium-containing hydroxyapatite (Ga-HA) with chlorhexidine (CLX) for potential use in bone and dental tissue restoration. The Ga-HA/CLX materials were prepared using a suspension-precipitation method and were surface-functionalized with varying CLX concentrations. X-ray diffraction analysis confirmed the hexagonal structure of Ga-HA with space group P63/m, while XPS revealed the presence of gallium and a Ca/P ratio ranging from 1.50 to 1.72. Infrared spectra exhibited characteristic bands for phosphate and CH2 groups, indicating CLX incorporation. The Ga-HA/CLX materials demonstrated 100% inhibitory efficiency against Staphylococcus aureus and Escherichia coli bacterial strains. MTT assay indicated enhanced cell viability in the presence of gallium, with the Ga-HA/CLX-0.20 material classified as non-toxic with 81.0 ± 3% cell proliferation. Density Functional Theory calculations supported favorable thermodynamics in the interaction between hydroxyapatite and chlorhexidine. Overall, Ga-HA/CLX materials exhibit promising properties for biomedical applications.

Abstract in English:

Abstract This study investigates the use of rice husk ash (RHA) as a sustainable additive in ceramic brick production. RHA from the Chaco region of Argentina was analyzed using DTA/TG and XRD, revealing a decrease in the amorphous phase and an increase in crystalline phases, mainly quartz and albite, with higher RHA content. The incorporation of RHA increased porosity from 25% to 40%, while theoretical density remained stable. Mechanical tests showed a decrease in elastic modulus (72.76 GPa for 5% RHA to 71.74 GPa for 15% RHA) and modulus of rupture (MOR) (8.5 MPa for 5% RHA to 5 MPa for 30% RHA). Several models were analyzed to predict the elastic modulus, and the DEM model provided the best predictions, with a relative error of 1.43% for 15% RHA. The analysis of mechanical properties of porosity was conducted using various theoretical models, which allowed for a better understanding of the relationship between the porous structure of the bricks and their mechanical behavior. Theoretical models, such as the DEM, proved effective in describing how porosity influences mechanical properties, particularly elastic modulus and modulus of rupture. Despite the reduction in mechanical properties, bricks with up to 15% RHA are suitable for non-structural applications, offering an eco-friendly alternative to conventional bricks. This research provides a circular economy approach by transforming agricultural waste into valuable construction materials.

Abstract in English:

Abstract The spin-phonon coupling is frequently observed in magnetic materials and can be investigated using Raman spectroscopy. Surprisingly, there are no studies using Raman spectroscopy to confirm the existence of spin-phonon coupling in the Y-type Hexaferrite Ba2Zn2Fe12O22 (Zn2Y), despite its ferrimagnetic nature. In this context, this paper aims to fill this gap. Raman spectra of Zn2Y were measured from 296 K to 438 K, and a hardening of the mode at 660 cm-¹ was observed near the Curie temperature. This behavior was associated with spin-phonon coupling.

Abstract in English:

Abstract In this research, medium crude metakaolinic clay (MK, Algeria) was used as raw material for the synthesis of geopolymers. Geopolymer synthesis involved mixing metakaolin with alkaline activators, with silica fume incorporated in some formulations to enhance mechanical properties. Samples were subjected to control curing at ambient and solar conditions, and their compressive and flexural strengths were evaluated at 28 days curing age, with a compressive strength of 35 MPa and flexural strength of 10 MPa. Additional tests assessed by XRD and FTIR revealed that new crystalline phases were formed in the geopolymer samples stored under ambient and sun exposure conditions; the curing condition had a significant effect on the change in the strengths of the investigation. The results indicate that the performance of geopolymer mortars can be considerably improved, even in extreme conditions, by optimizing curing protocols and material compositions.

Abstract in English:

This study investigates the upset forging behavior of Aluminium 7068/SiC composite (AA 7068 with 5% vol. SiC) using the Finite Element Method (FEM). The effects of length-to-diameter ratio, friction coefficient, and initial relative density on the forging process are analyzed. FEM was applied to determine the bulge profile of the deformed billets during the upset forging process. Experiments were conducted to validate analytical models concerning the cold upset forging of solid cylindrical composite materials. Finite Element Method (FEM) simulations demonstrated strong correlation with the experimental data, exhibiting acceptable error margins for key deformation parameters. The study revealed significant dependencies of both hoop strain and axial stress on the specimen’s aspect ratio. Furthermore, an improvement in the formability stress index was observed with increasing axial strain. These findings offer valuable insights into the upset forging behavior of this class of composite materials.

Abstract in English:

Abstract Hydroxyapatite is a commonly used biomaterial in medical and dental implants. While it can be synthesized, it is often extracted from bovine bone. However, challenges persist in the extraction process, such as ensuring reproducibility in particle size and distribution, crystallinity, and cost-effective large-scale production. This study employs porcine bone drilling for the first time, complemented by mechanical milling and calcination, and aims to determine the route that allows obtaining submicrometric HA powders with high crystallinity and the smallest possible particle size. Characterization of the obtained powders was performed using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and Fourier-transform infrared analysis (FTIR). The resulting material in the sequence drilling-milling-calcination shows high crystallinity and purity, although larger particle sizes were observed compared to those reported in the literature. Additionally, highly pure HA with particle sizes ranging from 160 to 510 nm (mean: 277.3 nm) was obtained via the drilling-calcination-milling sequence. This particle size range represents a significant improvement in size reduction compared to other mechanical methods reported in the literature.

Abstract in English:

Abstract The ceramic industry continuously seeks sustainable and cost-effective raw materials to improve the product properties while minimizing environmental impact. This study investigates the utilization of heat-treated palm oil fuel ash (POFA) as a replacement for silica (SiO2) in the porcelain glaze formulation. The glaze batch prepared using SiO2, Al2O3 and Na2CO3 was modified by incorporating both raw and heat-treated POFA at varying concentrations as a substitute for SiO2. Scanning electron microscopy (SEM) images demonstrated that sample with 20 wt. % treated POFA exhibited a denser and more uniform microstructure with a hardness value of 569 MPa. X-ray diffraction (XRD) analysis revealed the presence of quartz and cristobalite in samples containing 20 wt. % POFA which are more stable phases formed from the SiO2. The results suggested that treated POFA enhanced the structural and mechanical properties of porcelain glazes, offering a sustainable alternative to traditional glaze raw materials.

Abstract in English:

Abstract Solar energy offers an eco-friendly alternative to address global energy challenges. This study develops a cost-effective dye-sensitized solar cell (DSSC) using niobium pentoxide (Nb2O5) as a photoanode and a polyaniline (PANI) composite as a counter electrode, replacing traditional titanium dioxide (TiO2) and platinum (Pt). Nb2O5 was synthesized via the Pechini method, and PANI through polymerization. The components were assembled using the Doctor Blading method in a sandwich configuration. Characterization revealed Nb2O5 with a band gap of ~3.0 eV and an orthorhombic morphology, demonstrating potential as a TiO2 substitute. DSSCs with composite electrodes outperformed those with pure PANI or niobium pentoxide electrodes. The PANI/Nb1 composite (1% Nb) achieved a Voc of 0.69 V and a current density of 0.075 mA cm−2. These findings highlight the promise of Nb2O5-enhanced PANI for efficient, low-cost solar energy conversion.

Abstract in Portuguese:

Resumo Este estudo investigou a produção de nanopartículas de hidroxiapatita a partir de escamas de peixe calcinadas em diferentes temperaturas (400, 600, 800 e 1000°C), com o objetivo de avaliar o efeito da temperatura de calcinação na cristalinidade e sua influência na liberação de fósforo para aplicações agrícolas. A análise de difração de raios X (XRD) demonstrou que temperaturas de calcinação mais altas levaram ao aumento da cristalinidade e a tamanhos maiores de cristalito. As nanopartículas calcinadas a 600°C exibiram a maior concentração de fósforo e a cinética de liberação mais favorável. Foi descoberto que as nanopartículas de hidroxiapatita fornecem uma quantidade significativa de fósforo biodisponível às plantas. No entanto, o aumento da cristalinidade nas amostras calcinadas em temperaturas mais altas mostrou-se prejudicial ao desenvolvimento da planta, possivelmente devido a efeitos citotóxicos ou disponibilidade reduzida de fósforo.

Abstract in English:

Abstract This study investigates the influence of LiF on the sintering behavior of Si3N4 ceramics with SiO2-CaO-Al2O3 at the eutectic composition. Compositions containing 90 wt. % Si3N4 were sintered at 1650-1815ºC for 1 hour. The ceramics were characterized in terms of density, microstructure, and hardness. At 1650ºC, the β/(α+β)-Si3N4 ratio rose from 28.4% (0 wt. % LiF) to 63.7% (2 wt. % LiF), exceeded 98% at 1700ºC, and reached 100% at ≥1770ºC. In LiF-free samples, higher sintering temperatures resulted in a higher relative density (95.6±0.4%) and hardness (12.99±0.42 GPa). LiF improved densification and hardness at low content and sintering temperature, yielding 89.4±0.3% relative density and 9.71±0.42 GPa hardness (1 wt. % LiF) compared to 84.1±0.5% and 6.78±0.29 GPa (0 wt. % LiF), both at 1650ºC. At higher temperatures, LiF decreased both properties, likely due to its tendency to evaporate.

Abstract in English:

Abstract The glass industry stands at a critical moment in its evolution, confronted with the urgent need for decarbonization while striving to maintain operational efficiency and product quality. This paper delves into the current scenario of the glass industry, highlighting its significant contributions to global sustainability efforts while confronting substantial challenges in reducing carbon emissions. This paper looks at different ways to reduce carbon emissions in glass production, focusing on how much energy is needed to make glass and how important melting furnaces are to this process. These include using oxy-fuel, electricity, hydrogen, and possible combinations. Emphasizing the need for innovative approaches to mitigate refractory corrosion and other operational issues resulting from changes in combustion processes, the study underscores the importance of ongoing research and development in materials science and combustion technology. The paper looks at how the different parts of the furnace, its atmosphere, flame, and the refractory behave in complex ways. This helps us understand how to improve furnace performance and make them last longer so that the glass industry can be more sustainable.

Abstract in English:

Abstract Polyvinyl alcohol (PVA) has been used in cementitious composites such as concrete, mortars, and recycled aggregates. This study compiled academic research on its use as an addition, in fiber form or surface treatment in cementitious composites. The use of PVA in mortars reduced the drying shrinkage and increased the flexural strength. Although, PVA leads to a loss of workability and compressive strength. Concrete modified with polymer exhibits similar behavior. Investigations on concrete reinforced with PVA fibers reveal an improvement in deformation capacity, and in tensile and flexural strengths. The polymer may resulting in significant long-term deformations and reduction in compressive strength. In recycled aggregates treated with PVA, it contributes to the sealing of surface cracks and improves the interfacial transition zone. It may also decreased the compressive strength. Future research on the use of PVA in cementitious composites can be used in specific engineering applications.

Abstract in English:

Abstract Nanofibers are an efficient way to enhance the catalytic activity of ceramic materials due to their large surface area, small crystallite size, and greater reactivity compared to bulk materials. In addition, the recombination of the e-/h+ pair is low in the composite nanofibers, increasing the catalytic efficiency. Interestingly, the addition of oxides and metal doping along nanofibers improves semiconductor properties, which makes their photocatalytic action and activation under visible light even stronger. This is especially true in the search for efficient photocatalytic systems that can degrade dyes in water using the principle of heterogeneous photocatalysis. Researchers have extensively studied nanofibrous composites of semiconductor oxides or decorated with metal particles due to their high reactivity, ability to absorb, and potential as photocatalysts. However, despite the technological and economic importance of these materials, there is a scarcity of reviews on the state of the art in this field.