This study provides an in-depth review of the electrical properties of composite materials, encompassing metals, ceramics, polymers, and nanocomposites reinforced with nanometric particles. It examines critical electrical characteristics, such as conductivity and dielectric properties, and their implications for diverse applications. The analysis highlights the significant enhancement of electrical conductivity through the incorporation of metallic nanoparticles, which establish conductive networks within polymer matrices. By exploring the interactions between composite constituents, the study elucidates the behavior of these materials under varying conditions, offering valuable insights into their performance. This comprehensive review serves as a foundation for targeted future research, facilitating detailed investigations into specific composite types and their potential limitations. Furthermore, it enriches the existing literature by providing a broad perspective on the electrical properties of composites, paving the way for advancements in fields such as electronics, biomedical devices, and environmental technologies. This work underscores the importance of understanding component interactions to drive innovation and develop novel applications for composite materials.

In recent years, the use of lignocellulosic natural fibers (LNFs) as reinforcements in composites has increased significantly [1,2]. This trend is driven by environmental concerns and the need to reduce dependence on petroleum reserves [3]. Consequently, there is a growing interest in environmentally friendly materials aligned with the principles of sustainable development. LNFs are considered a promising alternative due to their low cost, renewability, biodegradability, and low specific weight [4,5]. As a result, these fibers have been employed across various technological sectors, particularly in engineering applications. Hybrid composites combining natural and synthetic fibers are being investigated to enhance mechanical performance while reducing weight and cost, balancing the advantages and disadvantages of each constituent. Thus, the present study investigates the influence of different stacking configurations involving aramid fabric and jute fibers, and separately, aramid fabric and sisal fibers, as reinforcement components in composite materials. These composite systems were subjected to ballistic testing using .22 caliber ammunition. Based on the measurements of impact and residual velocities, the absorbed energy and the ballistic limit velocity of the projectile were calculated. Preliminary results indicated that the incorporation of aramid layers into the sisal-based composites enhanced the energy absorption under projectile impact, likely due to modifications in the fracture mechanisms of the composites. In contrast, the jute-based composite did not exhibit significant changes.

Recycling natural fibers plays a crucial role in promoting environmental sustainability by reducing waste, conserving resources, and lowering the environmental impact of textile production. Natural fibers such as cotton, wool, and linen are biodegradable, but when disposed of in landfills, they contribute to pollution and resource depletion. By recycling these materials, we not only extend the life cycle of valuable resources but also decrease the demand for virgin fiber production, which often involves intensive water, energy, and chemical use. Additionally, recycling natural fibers supports a circular economy, encouraging more responsible consumption and production practices while helping to reduce greenhouse gas emissions and textile waste accumulation. On the other hand, the reinforcement of polymer matrices with natural fibers is opening new avenues for enhancing both the environmental and economic sustainability of the polymer industry, while also broadening their applications in engineering. This study investigates the additive manufacturing of composite materials reinforced with short coffee waste shells. A range of characterizations—including scanning electron microscopy and tensile testing—are presented, along with a statistical analysis of the tensile results using Weibull distribution. By incorporating this organic waste into engineered composites, the useful life of coffee shells is extended, contributing to environmental sustainability, and offering potential socio-economic benefits at the local level. The results demonstrate that the produced filaments possess promising mechanical strength and suggest the viability of scaling up the manufacturing process.

A growing demand for research about ballistic armor shields follows the increase of violence around the world. Ultimately, different composite materials with polymeric matrices have already presented the minimum performance as an individual protection required with cheaper and lower density, such as those reinforced with natural lignocellulosic fiber (NLF). The Cyperus malaccensis, a type of sedge fiber, is already used in simple items like ropes, furniture, and paper, but has not yet been investigated as composite reinforcement for possible ballistic protection applications. Therefore, composite plates were prepared for the ballistic tests, one for each condition of 10, 20 and 30 vol% sedge fibers. Each plate has been subjected to 5 test-shots  using 7.62 mm commercial ammunition. The fibers were embedded under pressure in the epoxy resin matrix and cured at room temperature for 24 hours. The tested specimens were examined by scanning electron microscopy. Besides, analysis of variance was performed and the absorbed energy of all specimens were evaluated.

Cold Sintering Process (CSP) was employed to densify hydroxyapatite (HAp) using phosphoric acid (H₃PO₄) as a transient liquid phase at low temperature. HAp powders synthesized by aqueous precipitation were CSP-processed at 200 °C under 600 MPa for 30 min with H₃PO₄ contents of 5 or 10 wt% at 1 or 2 M. Apparent density (Archimedes), biaxial flexural strength (three-ball method, ABNT NBR ISO 6872), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to correlate processing, microstructure, and properties. Despite the low thermal budget, CSP achieved apparent densities of 2.44–2.55 g cm⁻³, corresponding to 77.64–84.21% of the theoretical density. The 5%–2 M condition reached the highest densification (84.21%), whereas 10%–1 M delivered the best mechanical performance (σ_f = 36.08 ± 8.88 MPa), indicating that strength is not governed by densification alone. XRD confirmed predominance of the HAp phase (ICDD 00-009-0432) for all groups; average crystallite sizes ranged from 34.35 to 56.92 nm, with specific surface area increasing as crystallite size decreased (up to 87.53 m² g⁻¹). SEM revealed a microstructural evolution consistent with dissolution–reprecipitation: from porous, weakly coalesced networks (5%–1 M) to denser, better-bridged grains (10%–1 M), while excessive acidity (10%–2 M) promoted local fragility. Overall, tailoring the chemistry of the transient liquid phase enables efficient, phase-preserving, and energy-saving densification of HAp via CSP, offering a viable route for bioceramics where low processing temperatures and controlled microstructures are required.

For composite production, commercial corn starch plasticized with 30% glycerol was used. Ubim fibers were sourced from the local market in Belém (PA) and subjected to peeling and milling processes to optimize adhesion to the polymer matrix. The composites were processed using a single-screw extruder in five TPS/fiber ratios (0, 5, 10 and 15 wt.%). Films and test specimens were molded by hot pressing under standardized parameters. The composites were characterized through density, hardness (ASTM D2240), tensile strength (ASTM D638), and impact tests, as well as microstructural analyses by scanning electron microscopy (SEM) and phase evaluation by X-ray diffraction (XRD).

The results showed that the addition of ubim fibers to the thermoplastic starch composites significantly increased tensile strength, demonstrating the effectiveness of natural reinforcement in enhancing the mechanical properties of the polymer matrix. SEM analyses revealed morphological changes, highlighting good interfacial adhesion between the ubim fibers and TPS, which is essential for efficient stress transfer. XRD indicated the presence of semi-crystalline structures influenced by fiber incorporation. These findings confirm that the use of natural fibers, such as ubim, is a promising strategy for developing biodegradable composites with improved performance. Such materials exhibit high potential for sustainable plastic packaging applications, combining mechanical performance with reduced environmental impact.

This research explores the radiological shielding performance of hybrid composites made from aramid and linen fabrics embedded in an epoxy polymer matrix, reinforced with bismuth oxide (Bi2O3), using Monte Carlo N-Particle (MCNP) simulations. The study aims to assess gamma radiation attenuation by analyzing photon flux across composite layers and energy deposition within the material. The MCNP code was utilized to simulate gamma photon interactions, investigating the effects of Bi2O3 concentration, layer thickness, and fabric arrangement. Bi2O3, known for its high atomic number and density, significantly enhances the composite’s radiation attenuation capabilities while maintaining structural integrity. The results indicate substantial reductions in photon flux and efficient energy absorption, driven by the combined properties of aramid’s mechanical strength, linen’s eco-friendliness, and Bi2O3’s superior radiation-blocking capacity. The simulations highlight how composite design influences shielding effectiveness, providing valuable insights into developing lightweight, durable materials for radiological protection in medical imaging, aerospace, and industrial applications. This work lays the groundwork for experimental validation and optimization of Bi2O3-reinforced hybrid composites, advancing the development of sustainable, high-performance solutions for radiation shielding and contributing to safer and more efficient protective technologies.

Evaluating the permanent deformation of soils used in pavements or final earthwork layers is essential for designing highways and railways when adopting a mechanistic approach to structural design. However, due to environmental concerns, exploiting new soil deposits for such projects has become increasingly challenging, making soil stabilization or reinforcement a viable alternative. In this context, this study sought to explore the effect of adding piassava fibers to a clayey soil commonly found in subgrade layers in Brazil. Repeated load triaxial tests were conducted to assess permanent deformation under two pairs of deviator and confining stresses: (210, 70) and (450, 100) kPa, with 100,000 loading cycles applied at a frequency of 5 Hz. Resilient modulus tests were performed following national standards, using samples of natural soil, natural soil with 1.5% piassava fiber, and natural soil with 1.5% piassava fiber and 2% cement. Results showed that natural soil exhibited high permanent deformation under the higher stress pair, while the simple addition of fibers significantly reduced deformation. With the addition of cement, total permanent deformation was minimal, indicating that piassava fiber is a promising material for reinforcing pavements or earthworks.

This work proposes for the first time to develop a nanocomposite from polymethyl methacrylate (PMMA) based microfibers and reduced graphene oxide (rGO), synthesized using the Solution Blow-Spinning (SBS) technique [1]. This technique allows the production of fibers with a small diameter using a thermoplastic polymer, being capable of producing microfibers on a large scale. The interest is related to the reduction of the diameter when compared to conventional fibers, as the diameter size of these materials directly affects their properties, which tend to improve as the contact surface increases, thereby improving wettability [2][3]. The use of graphene and graphene oxide as reinforcing materials in composites has attracted attention, as they tend to provide greater rigidity, strength and conductivity to the material [4]. Graphene oxide is obtained by functionalizing graphene through exfoliation, creating regions with sp2 and sp3 hybridized carbons [5], in addition to hydroxyl and epoxy functional groups. This structure improves the interaction with the polymer matrix, increasing the rigidity of the composite and making it conductive, with the advantage of reducing costs when using reduced graphene oxide (rGO). The results obtained from experimental tests of concentration and morphology through Scanning Electron Microscopy (SEM) during the development of the nanocomposite will indicate the feasibility of producing a pure PMMA nanocomposite (matrix) reinforced with rGO in powder form (filler) for applications such as conductive polymer composites via Solution Blow Spinning.

This study investigates the radiological protection capabilities of hybrid composites composed of aramid and linen fabrics embedded in an epoxy polymer matrix, reinforced with graphene oxide (GO), through Monte Carlo N-Particle (MCNP) simulations. The research focuses on evaluating the attenuation of gamma radiation by analyzing photon flux between composite layers and energy deposition within the material structure. The MCNP code was employed to model the interaction of gamma photons with the hybrid composite, considering variations in GO concentration, layer thickness, and fabric stacking configurations. The incorporation of GO enhances the mechanical and shielding properties of the composite, leveraging its high electron density and dispersion within the epoxy matrix. Results demonstrate significant photon flux reduction and optimized energy absorption, influenced by the synergistic effects of aramid’s high tensile strength, linen’s sustainability, and GO’s radiation interaction capabilities. The simulations reveal the impact of composite design on shielding efficiency, offering insights into lightweight, flexible materials for radiological protection in medical, aerospace, and industrial applications. This work establishes a foundation for experimental validation and further optimization of GO-reinforced hybrid composites, contributing to the development of sustainable and high-performance radiation shielding solutions.

A growing demand for research about ballistic armor shields follows the increase of violence around the world. Ultimately, different composite materials with polymeric matrices have already presented the minimum performance as an individual protection required with cheaper and lower density, such as those reinforced with natural lignocellulosic fiber (NLF). The Cyperus malaccensis, a type of sedge fiber, is already used in simple items like ropes, furniture, and paper, but has not yet been investigated as composite reinforcement for possible ballistic protection applications. Therefore, composite plates were prepared for the ballistic tests, based on the condition of 30 vol% alkali treated sedge fibers. A total of seven plates have been subjected to seven test-shots  using 7.62 mm commercial ammunition. The fibers were embedded under pressure in the epoxy resin matrix and cured at room temperature for 24 hours. The tested specimens were examined by scanning electron microscopy. Besides, analysis of variance (ANOVA) was performed and the absorbed energy of all specimens were evaluated, based on a confidence level of 95%.

Natural lignocellulosic fibers (NLFs) have been widely studied as sustainable alternatives to synthetic fibers, standing out for being renewable, biodegradable, economically viable and for presenting good specific mechanical properties [1-3]. In this context, the present study aimed to evaluate the flexural strength of polyester matrix composites reinforced with short jute and piassava fibers. The fibers were used in their natural form, without surface treatment, cut to a length of 15 mm, and incorporated into the matrix by manual molding (hand lay-up) using silicone molds, without the application of pressure. The specimens were produced with randomly distributed discontinuous fibers, with mass fractions adjusted to the mold volume. The bending tests indicated that the pure polyester composite presented a bending stress of 112.12 ± 17.58 MPa, while the composites reinforced with jute and piassava fibers reached 59.16 ± 8.37 MPa and 62.48 ± 5.89 MPa, respectively, representing reductions of approximately 47% and 44% in relation to the pure matrix. Fractographic analysis of the rupture surfaces revealed that the failure of the composites was predominantly governed by fiber pull-out and low interfacial adhesion between fiber and matrix, also associated with the presence of internal voids resulting from the manual molding process. These factors contributed to the reduction of the mechanical efficiency of the composites, highlighting the need for surface treatments of the fibers and improvements in processing to optimize structural performance.

This study aims to develop a nanocomposite based on recycled polycarbonate (PC) with reduced graphene oxide (rGO), intended for applications in electromagnetic radiation absorbing materials (ERAM), with emphasis on stealth technologies applied to vessels [1]. The nanofibers were produced using the Solution Blow Spinning (SBS) process, aiming to maximize efficiency in electromagnetic radiation absorption [2-4]. The methodology involved the characterization of the individual components (PC and rGO) and the resulting nanocomposite through thermal analyses (DSC and TGA), gel permeation chromatography (GPC) to determine the molar mass of PC, and complementary techniques such as Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), and electromagnetic radiation absorption analysis using a vector network analyzer. The results demonstrated that incorporating different proportions of rGO into the PC significantly enhanced radiation absorption in the X-band, indicating the formation of a promising functional system for electromagnetic shielding applications. The combined analyses revealed a homogeneous morphological structure and suitable thermal and structural properties, confirming the potential of the developed nanocomposite as an efficient alternative for use in defense and security systems [5-6].

The growing demand for sustainable solutions in civil construction, particularly in tropical regions facing a shortage of natural aggregates, has encouraged the use of mining waste as an alternative raw material for the production of artificial aggregates (Cabral et al., 2008). This study investigates the mineralogical interactions between sandy and silty textured soils and a clayey mining sludge, subjected to calcination processes aimed at forming reactive phases.

The methodology involved the formulation of mixtures with varying proportions of clayey sludge, subjected to calcination at temperature ranges defined based on mineralogical and thermal analyses. The samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), following established practices for assessing the reactivity of calcined clays (Pinheiro et al., 2023; Monteiro et al., 2004).

Preliminary results indicated the formation of potentially pozzolanic phases, such as amorphous aluminosilicates, at temperatures above 700 °C, corroborating literature findings on the influence of firing temperature on clay activation (da Silva et al., 2015). The microstructure observed via SEM showed good integration between the constituents of the mixtures after calcination, suggesting the feasibility of combining soils and mining residues for pavement applications.        

This study investigated the consolidation of hydroxyapatite (HAp) ceramics with different graphene oxide (GO) contents (0–1.00 wt.%) via the Cold Sintering Process (CSP), aiming to evaluate their effects on densification, mechanical properties, thermal stability, and microstructure [1]. CSP was performed at 200 °C under 300 MPa using diluted phosphoric acid as a transient liquid phase. Vickers hardness, fracture toughness, flexural strength, SEM/EDS, TGA/DSC, XRD with Rietveld refinement, FTIR, and Raman spectroscopy were employed for characterization.

GO addition increased the relative density from ~84.7% (pure HAp) to ~87.3% (HAp1.00GO), with the best mechanical performance observed for HAp0.50GO, which showed a hardness of 2.81 GPa, fracture toughness of 0.77 MPa·m⁰·⁵, and flexural strength of 51.63 MPa—up to 79% higher than pure HAp. These improvements were attributed to the lamellar morphology and oxygenated functional groups of GO, which promoted chemical interactions with dissolved HAp ions, enhancing precipitation-driven densification and interparticle cohesion [2].

Morphological analysis revealed that HAp0.50GO exhibited the most homogeneous and dense microstructure with well-formed interparticle bridges, while higher GO contents (0.75–1.00 wt.%) led to agglomeration and heterogeneity, impairing mechanical performance [3].

Thermal analysis indicated that GO incorporation improved thermal stability and reduced degradation related to β-TCP formation. XRD confirmed the preservation of the crystalline HAp phase in all compositions, with no secondary phases detected. Rietveld refinement showed decreased crystallite size and increased specific surface area for intermediate GO contents (0.25 and 0.50 wt.%), suggesting higher surface reactivity and potential bioactivity [4].

FTIR confirmed the preservation of HAp’s chemical structure, while Raman spectroscopy detected D and G bands from GO in samples with ≥0.50 wt.%, confirming its incorporation and revealing variations in carbon structural order with increasing GO content. The lowest ID/IG ratio (0.57) for HAp0.75GO indicated greater graphitic order, whereas HAp1.00GO displayed the highest disorder (ID/IG = 0.92), likely due to agglomeration.

Overall, the optimal GO content was ~0.50 wt.%, balancing densification, microstructural integrity, mechanical strength, and thermal stability without compromising crystallinity. These results demonstrate the feasibility of producing HAp/GO ceramics via CSP at low temperature with enhanced properties for advanced biomedical applications, such as synthetic bone grafts with improved mechanical resistance and stability [5].

The integration of thorium into uranium dioxide (UO₂) fuel presents a promising strategy to enhance fuel cycle sustainability, reduce long-term radiotoxicity, and improve proliferation resistance in nuclear reactors. This study investigates the neutronic performance of a mixed oxide fuel composed of UO₂ and thorium dioxide (ThO₂) in the context of Small Modular Reactors (SMRs), focusing on both a single fuel rod and a complete fuel assembly configuration. The SCALE simulation suite was employed to model and analyze key neutronic parameters, including effective multiplication factor (k-eff), neutron flux distribution, and isotopic evolution over burnup. The analysis explores various UO₂/ThO₂ ratios, with special attention to the moderation properties, resonance absorption behavior, and the production of fissile ²³³U from thorium. In the single-rod model, the addition of ThO₂ slightly reduces initial reactivity but leads to favorable breeding characteristics due to the generation of ²³³U, which contributes to sustained fission over time. In the full assembly configuration, moderation effects and inter-rod neutron interactions further influence the reactivity trends and spatial flux profiles. Results demonstrate that mixed UO₂/ThO₂ fuel exhibits competitive neutronic behavior when compared to conventional UO₂ fuel, with notable advantages in terms of fissile regeneration and longer fuel cycle potential. Moreover, the thorium content contributes to flattening the power distribution across the assembly, which may reduce localized thermal stresses and improve fuel utilization. These findings highlight the feasibility of incorporating thorium into SMR fuel designs and encourage further investigation into thermo-mechanical performance and reprocessing implications. The study supports the development of advanced fuel cycles aligned with the goals of next-generation reactor technologies.

The shortage of natural aggregates in tropical regions has driven the development of alternative materials for road infrastructure applications. Among these, artificial aggregates produced through clay calcination have been investigated for their mechanical properties and pozzolanic reactivity potential (Cabral, 2008; da Silva et al., 2015; Friber et al., 2023). This study proposes the production of artificial aggregates from soil–waste mixtures, incorporating a clay-rich mining sludge, aiming to add value to mineral waste and reduce reliance on conventional materials.

The formulations were defined based on preliminary mineralogical analyses using X-ray diffraction (XRD) and scanning electron microscopy (SEM), with the objective of identifying the phases formed and microstructural changes induced by calcination (Monteiro et al., 2004; Pinheiro et al., 2023). The calcination temperature was selected to maximize the formation of amorphous cementitious phases. After calcination, the aggregates were used to mold cylindrical specimens using split molds, which were then subjected to repeated load triaxial tests to determine the permanent deformation a key parameter for assessing the mechanical performance of materials used in pavement base and subbase layers.

Initial results indicated that the artificial aggregate exhibits elastic behavior compatible with that of traditional pavement materials, reinforcing its potential as a technically and environmentally sustainable solution.

Hydroxyapatite is a mineral composed of hydrated calcium phosphates. As it is the main mineral component of human bone, it is widely used in the fabrication of alloplasts for bone tissue regeneration treatments, known as scaffolds [1][2]. Scaffolds serve as a cellular matrix for the development of new bone tissue; therefore, they must have a porous structure, adequate mechanical strength, and be composed of biocompatible material [3]. To meet these criteria, additive manufacturing techniques, such as fused deposition modeling (FDM) 3D printing, are employed as an alternative for controlling structure and mechanical strength. However, if the printer operates by extruding thermoplastic material, it is necessary to synthesize polylactic acid (PLA) filament loaded with hydroxyapatite to incorporate the bioceramic into the scaffold [4]. Hydroxyapatite can be obtained through various synthesis routes or from synthetic or natural resources. In this study, hydroxyapatite was extracted from the byproduct of the Arapaima gigas fish and used to produce filaments for 3D printing. The scales were subjected to chemical treatment with NaOH and thermal treatment with sintering at 600 ºC in an oxygen-rich environment. The characterizations performed were TG, DTG, DSC, FTIR, and SEM. After these characterizations, the sample was subjected to a thermal treatment at 700 ºC, followed by the same analyses. The filaments were produced by extrusion and were loaded with 1% w/w of hydroxyapatite extracted from the scales of Arapaima gigas. The filaments were subjected to tensile testing according to ASTM C1557-20. Thermal analysis revealed that the sample sintered at 600 ºC did not undergo complete removal of organic volatiles, with mass losses of 3.6% in the range of 75 ºC – 100 ºC due to residual water; 1.1% in the range of 280 ºC – 700 ºC due to collagen residue; and 2.93% between 600 ºC – 742 ºC due to the loss of structural water from hydroxyapatite. The sample sintered at 700 ºC showed little mass loss, with a total loss of 1.68%, and a maximum degradation temperature at 619 ºC, related to the structural water present in hydroxyapatite. In both samples, FTIR analyses revealed the characteristic bands of PO₄³⁻ anions at 1091 cm⁻¹; 1022–1018 cm⁻¹; 602–563 cm⁻¹, and the presence of CO₃²⁻ ions at 1450 cm⁻¹, 1411 cm⁻¹, and 871 cm⁻¹. Scanning electron microscopy (SEM) micrographs showed that the samples sintered at 600 ºC presented agglomerates of inorganic particulates without a defined morphology. Sintering at 700 ºC promoted the growth of particulates with polygonal shapes, tending toward hexagonal formation.

The design and material selection for fuel rods in Small Modular Reactors (SMRs) play a critical role in ensuring both the neutronic efficiency and thermal safety of the reactor core. This study presents a detailed comparative analysis of the neutronic behavior and heat transfer performance of a standard fuel rod configuration using two distinct cladding materials: Zircaloy-4 and stainless steel. Simulations were conducted using the SCALE code package, employing modules suitable for neutron transport and heat generation modeling under steady-state conditions.The investigation focused on key parameters such as the effective multiplication factor (k-eff), neutron flux distribution, and axial power profile, as well as the impact of cladding material on heat conduction away from the fuel. Zircaloy-4, known for its low neutron absorption cross-section and favorable thermal conductivity, demonstrated higher neutronic reactivity and improved thermal performance compared to stainless steel. However, the use of stainless steel—often considered for its mechanical robustness and corrosion resistance—resulted in increased parasitic neutron absorption and a corresponding decrease in reactivity, requiring compensatory design adjustments.The comparative results underscore the trade-offs inherent in cladding material selection, particularly in advanced reactor systems like SMRs where compact core design and passive safety features are prioritized. The findings contribute to the optimization of fuel design by providing quantitative insights into how material choices affect reactor behavior at both the neutronic and thermal levels. This study supports ongoing efforts in the development of next-generation reactors by highlighting material-performance interdependencies that must be carefully considered during the early stages of reactor design and licensing.

Niobium is a strategic material for Brazil, a country that holds the largest global reserves of this element. However, its sintering presents significant challenges, mainly due to the high reactivity of the metal, which promotes oxide formation and hinders consolidation. This study aimed to investigate the feasibility of cold sintering of niobium at different temperatures, seeking to minimize oxidative effects and enable new technological applications. The material used was supplied by CBMM (Companhia Brasileira de Metalurgia e Mineração), and experiments were conducted at temperatures of 125 °C, 150 °C, and 175 °C. To promote the formation of a transient liquid phase, niobium powders were mixed with 10 wt.% of absolute ethanol. Sintering was performed under a simultaneous pressure of 300 MPa, with a holding time of 30 minutes at each specified temperature. After processing, the samples were characterized through density measurements, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses. The results indicated that cold sintering of niobium was effective even at the relatively low temperatures employed. XRD analysis revealed only minor peaks corresponding to the NbO phase, indicating a low incidence of oxidation during the process. These findings demonstrate the feasibility of cold sintering pure niobium, paving the way for the development of new components and applications, with advantages in reducing processing temperatures and preserving metallic properties. The use of cold sintering techniques thus represents a promising alternative for processing highly reactive metals such as niobium.

Hydroxyapatite (HA), an inorganic ceramic biomaterial, presents itself as a promising and active bone substitute in this scenario, as it presents characteristics similar to the mineral apatite, found in human bones and teeth. Thus, the aim of this work is to synthesize and characterize synthetic hydroxyapatite, using chicken eggshell residue as a source of calcium. The analysis of the egg shell was carried out using X-ray Diffraction (XRD) and Fourier Transform Spectroscopy (FTIR) techniques. The characterization of the hydroxyapatite powder was performed by X-Ray Diffraction (XRD), Fourier Transform Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The results for eggshell revealed the presence of absorption bands of hydroxyl groups and carbonates and phases corresponding to calcium hydroxide and calcium oxide. The HA sample showed vibration bands of hydroxyl, carbonate and phosphate groups, and hydroxyapatite and calcium oxide phases. SEM analysis indicated irregular morphological formations with dimensional variations. The EDS semiquantitatively revealed percentages of Oxygen, Phosphorus and Calcium. According to the results, type B hydroxyapatite was obtained using eggshell residue, which was also a good source of calcium in this study.

Recycling natural fibers is essential for advancing environmental sustainability, as it helps reduce waste, conserve resources, and minimize the ecological footprint of textile production. While fibers like cotton, wool, and linen are biodegradable, their disposal in landfills still contributes to pollution and the depletion of valuable materials. By recycling these fibers, we can extend their lifecycle, lessen reliance on virgin fiber production—which typically requires significant water, energy, and chemical inputs—and promote more sustainable industrial practices.

Moreover, recycling natural fibers aligns with the principles of a circular economy by encouraging responsible consumption and production, reducing greenhouse gas emissions, and limiting the accumulation of textile waste. In parallel, reinforcing polymer matrices with natural fibers is emerging as a promising approach to enhance both the environmental and economic sustainability of polymer-based products, while expanding their applicability in various engineering fields.

This study explores the fabrication of composite materials reinforced with rice husk, an agricultural byproduct. A comprehensive evaluation is provided, including scanning electron microscopy and tensile testing, alongside a statistical analysis of tensile data using the Weibull distribution. Utilizing rice husk in engineered composites not only extends the utility of this organic waste but also supports sustainability efforts and offers potential socio-economic advantages at the community level. The study presents several case examples involving both polymer and inorganic matrices, utilizing both traditional and additive manufacturing techniques.

Fuel cladding and encapsulation materials are fundamental to the structural integrity, thermal management, and neutronic performance of nuclear fuel assemblies. This study proposes the use of a hybrid composite material based on Zircaloy-4 reinforced with silicon carbide (SiC) for the encapsulation of UO₂ fuel pellets, aiming to enhance both the thermal and mechanical properties of the fuel system while maintaining favorable neutronic characteristics. The proposed Zircaloy-4/SiC composite is evaluated and compared with conventional metallic cladding materials, such as standard Zircaloy-4 and stainless steel, as well as ceramic encapsulants like stabilized zirconia (ZrO₂).The analysis considers key parameters including thermal conductivity, neutron absorption cross-section under normal and transient operating conditions. Simulations conducted using the SCALE code system assess the impact of the composite on reactivity, heat distribution, and fuel temperature profiles. Preliminary results indicate that the inclusion of SiC enhances the high-temperature performance of the cladding, while the Zircaloy-4 matrix preserves the low neutron absorption desirable for maintaining core reactivity. When compared to zirconia, the Zircaloy-4/SiC composite offers superior thermal conductivity and reduced swelling under irradiation, albeit with slightly higher neutron absorption. Nonetheless, the composite exhibits a balanced profile that combines the structural advantages of ceramics with the neutronic compatibility of metallic alloys. These findings support the viability of metal-matrix composite encapsulation as a promising pathway for accident-tolerant fuel (ATF) designs in advanced reactor systems, including SMRs and Generation IV concepts. Further experimental validation is recommended to confirm fabrication feasibility and in-reactor behavior.