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 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 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.