Flexural Strength Research Articles

Research on Mechanical Properties of a 3D Concrete Printing Component-Optimized Path by Multimodal Analysis

Three-dimensional concrete printing (3DCP) technology with solid wastes has significant potential for sustainable construction. However, the hardened mechanical properties of components manufactured using 3DCP technology are affected by weak interlayer interfaces, limiting the widespread application of 3DCP technology. To address the inherent limitations of 3DCP technology, conventional improvement strategies, such as external reinforcement and the optimization of material properties, lead to increased production costs, complex fabrication, and decreased automation. This study proposes an innovative spatial path optimization method to enhance the mechanical performance of 3D-printed, cement-based components. The novel S-path design introduces additional printed layers in the weak interlayer regions of the printed samples. This design improves the spatial distribution of fiber-reinforced filaments in continuous weak zones, thus enhancing the functional efficiency of fibers. This approach improves the mechanical performance of the printed samples, achieving compressive strengths close to those of cast samples and only a 20% reduction in average flexural strength. Compared to using a conventional printing path, the average compressive strength and flexural strength are improved by 30% and 55%, respectively, when the S-path layout is employed in 3DCP. Additionally, this method significantly reduces the anisotropy in compressive and flexural strengths to 26% and 28% of samples using conventional printing paths, respectively. Therefore, the proposed method can improve the mechanical properties and stability of the material, reducing the safety risks of printed structures.

Effect of Olive Waste Ash as a Partial Replacement of Cement on the Volume Stability of Cement Paste

Over the last decades, concrete has been excessively prone to cracks resulting from shrinkage. These dimensional changes can be affected by the incorporation of supplementary cementitious materials. This work used olive waste ash (OWA), which could substantially tackle this problem and achieve sustainability goals. For this issue, five cement paste mixes were prepared by replacing cement with OWA at different percentages varying from 0 to 20% by weight with a constant increment of 5%. The water-to-cement ratio was 0.45 for all mixes. Compressive strength and flexural strength were investigated at 7, 28, and 90 days. In addition, three shrinkage tests (drying, autogenous, and chemical) and expansion tests were also conducted for each mix and measured during 90 days of curing. The experimental findings indicated that there was a loss in compressive and flexural strength in the existence of OWA. Among all mixes containing OWA, the samples incorporating 10% OWA exhibited maximum strength values. Furthermore, the chemical and autogenous shrinkage decreased with the incorporation of OWA. However, the drying shrinkage decreased at lower levels of substitutions and increased at higher replacement levels. In addition, there was a growth in expansion rates for up to 10% of OWA content, followed by a decrease at higher levels (beyond 10%). Additionally, correlations between these volumetric stability tests were performed. It was shown that a positive linear correlation existed between chemical shrinkage and autogenous and drying shrinkage; however, there was a negative relationship between chemical shrinkage and expansion.

Mechanical and micro-structural characterization of biodegradable coir fiber–glass sheet–charcoal reinforced polymer composite: an experimental approach

In the present investigation, the combined influence of coir, glass fibers and charcoal content on the mechanical properties of epoxy-based hybrid composites has been explored, providing insights for the potential development of advanced materials with tailored performance characteristics. Through a systematic analysis of the mechanical properties (tensile strength, Young's modulus, flexural strength, flexural modulus, and Brinell hardness number), various composite formulations were evaluated to discern their performance characteristics. The study reveals significant variations in mechanical properties across different composite configurations, highlighting the critical role of fiber type and charcoal content in determining the materials’ performance. Notably, composites featuring alternating layers of glass and coir fibers exhibit superior tensile and flexural strengths, underscoring the synergistic effects of hybridization. Conversely, the introduction of charcoal as a reinforcement agent leads to deterioration in the mechanical properties, indicating a trade-off between the reinforcement and other desirable attributes. These findings offer valuable insights for the strategic design and engineering of advanced materials tailored to specific applications, paving the way for the development of high-performance epoxy-based hybrid composites with enhanced mechanical properties and durability.

Study of mechanical properties of composite materials reinforced with aluminum fibers

This study investigates the mechanical properties of composite materials reinforced with aluminum fibers of varying lengths and concentrations. The research aims to evaluate the effects of fiber reinforcement on both flexural and compressive strengths, using fibers of three distinct lengths (2×20 mm, 2×30 mm, and 2×40 mm) and four different concentrations (0.5%, 1%, 1.5%, and 2%) by weight within the composite matrix. Mechanical tests were performed after 28 and 56 days of curing to assess the influence of fiber reinforcement over time. The results demonstrate that increasing fiber length and concentration generally improves the flexural and compressive strengths, with the most notable gains observed at moderate fiber content. However, the study also finds that excessively high fiber percentages may lead to diminishing returns in strength performance, possibly due to fiber agglomeration or stress concentration effects. These findings provide valuable insights into optimizing the design of fiber-reinforced composite materials for various structural applications, enhancing both performance and material efficiency.

Thermo‐mechanical performance of oil palm/bamboo fiber reinforced bio epoxy hybrid composites

AbstractThe aim of this work to fabricate bamboo (B)/oil palm (O) fibers based biocomposites to assess mechanical, thermal and morphological properties. Flexural strength and modulus of hybrid biocomposite (7B:3O) exhibited a higher value (71.18 MPa and 5.24GPa) respectively among all biocomposite samples. On the other hand, pure biocomposite (B) showed a higher impact strength value (6977.8 J/m2) compared to other biocomposites. The results of TGA showed that thermal stability was observed significantly for hybrid biocomposites compared to other samples. In addition, the maximum decomposition temperature values were displayed in the hybrid biocomposite (5B5O), which was 377.82°C. Through DMA, it was likely to find the storage modulus curves (E′), loss modulus (E″) and damping factor (tan δ) for the biocomposites. The E′ showed an increase in the (3736.84 MPa) contrasted to other corresponding samples which were 3121.81 MPa, and 3209.67 MPa for 3B7O MPa and 5B5O samples, respectively. Overall, the results of DMA displayed an enhancement in the storage modulus (E′) in terms of the hybrid biocomposites representing greater stiffness and lower damping factor. SEM micrographs were utilized to understand the fiber bonding and fiber adhesion with the epoxy matrix. Furthermore, it confirmed SEM results that hybrid natural fibers enhance the complete characterisations of bio‐epoxy materials. Additionally, SEM images of the tensile fracture surfaces discovered voids and cracks. Finally, it can be concluded that the selection for the developed hybrid biocomposites provides excellent and economical lightweight biomaterials for automotive, aerospace, contractions and building components.Highlights Green hybrid biocomposites by oil palm/bamboo fiber/bioepoxy resin. Mechanical, thermal, DMA of hybrid composites carried out. Hybrid biocomposite(7B:3O) exhibited higher flexural strength value (71.18 MPa). TGA showed that the biocomposites are thermally further stable. DMA displayed an enhancement in the storage modulus (E′).

Investigation of strength, durability, and microstructure properties of concrete with waste marble powder as a partial replacement of cement

Purpose Cement plays a significant part in concrete, and with the increasing demand for concrete, cement output varies day by day, allowing production to carbon dioxide emissions. As well as marble processing creates stone slurry and solid discards. These are often dumped irresponsibly on open land, polluting the soil. This improper disposal of marble waste is a major environmental concern. This study aims to propose a sustainable solution for reusing this waste material as a concrete additive. Design/methodology/approach A total of 135 concrete cubes of size 150 × 150 × 150 mm, 54 concrete cylinders of size 150 mm dia. and 300 mm height and 54 concrete beams of size 150 × 150 × 700 mm were cast. The replacement was 0%, 2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5% and 20% by weight of cement with marble dust to create M30 concrete with a water-cement ratio of 0.45. The test was performed to find the compressive strength (CS), flexural strength (FS) and split tensile strength. Also, durability tests like rapid chloride penetration test (RCPT), acid attack, ultrasonic pulse velocity (UPV) and water permeability test were performed. Findings After 7 and 28 days of curing, it was found that replacing 5% of cement with marble powder led to an initial strength improvement of up to 25% for both curing periods. However, further increases in marble dust resulted in an inconsistent decrease in strength for all the mixtures. Also, durability properties like acid attack test, water permeability test and RCPT, showed good performance at the optimum percentage of waste marble powder (WMP) as cement replacement. The microscopic analysis revealed a denser pore structure at lower WMP replacement levels, likely due to the powder filling in gaps. Originality/value This study reveals that by substituting 5% (optimum) of cement with WMP, there was CS improvement up to 8.4% and 17% for both 7 and 28 days of curing. WMP is typically finer than cement particles and fills the voids in the concrete more effectively, resulting best performance at optimum percentage against RCPT, UPV, acid attack and water permeability.

Influence of alkali metal formates and calcium formate on workability, hydration and basic properties of reactive powder concrete

AbstractThis work aims to study whether it would be possible to use alkali metal formates and calcium formate in order to increase the workability of reactive powder concrete (RPC) and how these additives affect hydration, mechanical properties and mineralogical composition of RPC. These substances were added together with superplasticizer. Therefore, paper deals with possibility of increase in workability which would be higher when compared to the sole addition of only the superplasticizer themself. The effect of alkali metal formates and their replacement with calcium formate on slump flow, mechanical properties and pH of RPC was studied. Furthermore, the influence of potassium formate and its replacement with calcium formate and with calcium oxide on the hydration of RPC was observed with the help of isothermal calorimetry and thermal analysis. The results showed that the addition of studied compounds allows to achieve an increase in RPC slump flow. However, it is necessary to add these substances in an optimal ratio of alkali metal formate/calcium formate because a higher content of calcium formate leads to a decrease in slump flow. For ideal ratios, the compressive strength after 90 days is still above 218 MPa and the flexural strength is still above 23 MPa. In calorimetric measurements, it was observed that the addition of potassium formate leads to a decrease in the total amount of heat developed in the induction period. According to thermal analysis, additions of the studied additives to RPC caused changes in the content of portlandite and calcite.

Study on the Effect of Jute CNFs Addition on the Water Absorption and Mechanical Properties of Geopolymer Concrete

This study investigates the influence of thermoplastic polyurethane (TPU) reinforced with jute cellulose nanofibers (CNFs) on the water absorption and mechanical properties of geopolymer concrete. The integration of TPU/jute CNF nanocomposites into geopolymer concrete is explored as a strategy to enhance both its durability and mechanical performance. Geopolymer concrete, a sustainable alternative to traditional Portland cement concrete, is known for its low carbon footprint, but it suffers from high brittleness and water absorption. The water absorption behavior of the modified concrete was assessed, revealing a significant reduction in water uptake due to the hydrophobic nature of TPU and the reinforcing effect of jute CNFs. Additionally, the mechanical properties, including compressive and flexural strengths, were evaluated to understand the impact of the nanocomposites on the structural integrity of the concrete. The addition of TPU/jute CNFs notably enhanced the splitting tensile strength (63.5%), compressive strength (59%), and water absorption (0.59%) of the composite, indicating a promising route for developing high-performance construction materials. The integration of 6 wt% of TPU/jute CNF nanocomposites was found to be optimal, resulting in a uniform matrix, reduced micro-cracks, and improved compressive strength due to enhanced adhesion between the nanocomposites and the geopolymer matrix. Furthermore, a curing temperature of 100 °C was identified as ideal, minimizing unreacted fly ash and enhancing adhesion strength, while higher temperatures (140 °C) led to material deterioration due to rapid water loss. The findings demonstrate that the addition of TPU/jute CNF nanocomposites not only improves resistance to water penetration but also enhances overall mechanical performance. This supports the development of more sustainable and resilient construction materials, contributing to global efforts to reduce the environmental impact of the construction industry. Future research should focus on the long-term durability of these composites under various environmental conditions to validate their effectiveness in real-world applications.

Tribological and mechanical endowments of polyoxymethylene by liquid‐phase exfoliated graphene nanofiller

AbstractIn this study, a viable route to the development of a high‐performance polyoxymethylene (POM)‐based nanocomposite is proposed to overcome tribomechanical‐related issues in high‐precision sliding parts. Prior to melt‐blending, graphene nanoplatelet (GNP) filler was processed via a series of liquid‐phase exfoliation and surface modification with 3‐aminopropyltriethoxysilane. Results indicate that GNP is successfully exfoliated with minimum defect ratio and improves interfacial bonding within the matrix. Uniform dispersion and stable load‐transfer capability of POM/GNP with 0.5 wt% loading significantly enhanced flexural, tensile and impact strength by overall 26.4%, in contrast to unfilled POM. Dry friction tests against a steel ball also showed the lowest reduction in friction coefficient and wear rate by 22% and 40.6%, respectively, at the same amount of GNP loading due to the large specific surface coverage and lubricious transfer film chelation onto the steel counterface. Furthermore, dissipated energy accumulation by friction work was calculated in the sliding interfaces based on friction force–displacement hysteresis loop where the POM/GNP 0.5 wt% wear surface consumed ca 21.7% less energy in a dry frictional shearing process compared to neat POM. However, lack or excess loading of processed GNP exhibited insufficient or poor matrix–filler adhesion and led to deterioration of the composite properties due to particle agglomeration which can cause stress concentration and serve as a failure site. The adoption of the proposed methodology would demonstrate excellent material characteristics in thin‐walled precision parts where both mechanical and tribological performances are the primary concern. © 2024 Society of Chemical Industry.

A Newly Bio-Based Material for the Construction Industry Using Gypsum Binder and Rice Straw Waste (Oryza sativa)

Construction is one of the economic sectors with the greatest influence on climate change. In addition to working procedures, the primary carbon footprint is attributed to the choice of materials and the energy required for their manufacturing. The underlying idea of this study is to minimize the effects and offer new solutions to emerging problems in the quest for materials that can be deemed as natural, such as gypsum (calcium sulphate dihydrate) and rice straw (Oryza sativa). The acquisition of these materials involves a lower carbon footprint compared to the conventional materials. It is well known since ancient times that gypsum and cereal straw can be used in construction, with numerous examples still available. Cereal straw is one of the oldest construction materials, traditionally combined with earth and occasionally with certain binders, with it continuing to be employed in construction in many countries to this day. This work showcases the feasibility of producing stable prefabricated elements from straw waste with construction gypsum, addressing a significant environmental concern posed by the alternative of having to burn such materials. In this study, for the proposed bio-based material, specific tests, such as thermal conductivity, flexural and compressive strength, and fire resistance, were carried out to evaluate the principal physical and mechanical characteristics for different compositions of water, gypsum, and straw fiber samples. The results highlighted the good performance of the proposed materials in order to spread their use in the green building industry. The addition of straw fibers improved, in different ways, some important physical characteristics of these components so as to diminish environmental pollution and to obtain better material performance. The tests highlighted the different behaviors of the proposed material with respect to the different cuts of the straw and as well as the water/gypsum ratio; this is not very well understood and probably depends on the micro structure of the straw fibers. The blocks with raw straw showed a significant improvement in the breaking mechanism (1775.42 N) compared to the blocks with cut straw (712.26 N) when subjected to bending tests, and their performance in compression tests was also acceptable. Additionally, a very interesting reduction in thermal conductivity was achieved by incorporating rice straw (0.233 W/mK), and high fire exposure times were obtained, with gypsum preventing the spread of ignition in any type of fiber.

Impact Resistance and Flexural Strength of Concrete Containing Fly Ash and Glass Powder

Impact Resistance and Flexural Strength of Concrete Containing Fly Ash and Glass Powder

Investigations on the influence of thickness and preform structure on the mechanical performance of novel textile composites with woven Kevlar® fabric reinforcement and poly methylmethacrylate (Elium®) matrix

Abstract Elium (novel methyl methacrylate (MMA)) resin is a liquid thermoplastic resin curable at room temperature and a possible replacement for epoxies. The main objective of this work is to evaluate the mechanical characteristics of novel Kevlar fabric reinforced Elium composites with different thicknesses. The plain-woven structure Kevlar/Elium laminates were manufactured with 1.5 mm and 2.5 mm thicknesses through vacuum-assisted resin infusion moulding, where 8 and 12 layers of woven fabrics were used, respectively. The effect of laminate thickness was measured in terms of mechanical (tensile, flexural, shear, and dynamic mechanical analysis (DMA)) and physical (density and fibre volume fraction (FVF)) characteristics. The density of the laminates was found in the range of 1.18–1.31 g cm−3. FVF was 50.69 and 52.27% for 1.5 and 2.5 mm thick laminates, respectively. The composite with 1.5 mm thickness exhibited the highest tensile strength (667.9 MPa) and flexural strength of 330.7 MPa. Conversely, the highest interlaminar shear strength measured for 2.5 mm thick laminate is 16.5 MPa. The DMA analysis recorded the highest storage and loss modulus for 2.5 mm thickness laminates. The fractography analysis confirmed the quantified experimental observation of excessive interface debonding and delamination. Elium composites may be suitable for high-end structural applications, including marine and aircraft structures.

Study of structural and mechanical properties of composite ceramics of the AlMgB14–TiB2 system

AlMgB14 ceramics is known as a material characterized by increased hardness in combination with a low friction coefficient. Composite structures based on this ceramics have even higher strength characteristics. In the present work, we investigate the structural-phase states and physicomechanical properties of composite ceramics of the AlMgB14–TiB2 system with a variable TiB2 content, obtained by hot pressing the initial batch based on AlMgB14 and TiB2 ceramic powders preliminarily synthesized by the method of self-propagating high-temperature synthesis. It was found that the resulting materials are characterized by a composite structure represented by TiB2 inclusions distributed in the AlMgB14 matrix. The phase composition of the resulting composites is similar to the phase composition of the initial batch, with 5 to 9 wt. % of the MgAl2O4 spinel phase being formed. The microhardness of AlMgB14–TiB2 composites is up to 19.9 GPa (the hardness of AlMgB14 ceramics obtained by a similar method without additives is 7 GPa). The three-point bending strength of AlMgB14–TiB2 composite materials is 309 MPa.

Correlating FDM Printing Parameters with Mechanical Properties and Surface Quality of PLA Printouts

Abstract This study explores the correlation between four critical Fused Deposition Modeling (FDM) parameters—extrusion temperature, layer height, print speed, and infill density—and the mechanical properties and surface quality of PLA (Polylactic Acid) printouts. The mechanical properties, including Young’s modulus, tensile strength, and bending strength, were evaluated alongside surface roughness and dimensional accuracy. The results indicate that extrusion temperatures between 200°C and 220°C optimize mechanical performance, enhancing tensile strength and bending strength, while smaller layer heights (0.1 mm) improve surface smoothness but increase print time. Moderate print speeds (around 60 mm/s) offer the best balance between strength and efficiency, while higher infill densities (above 80%) enhance mechanical properties, increasing both tensile and bending strength by up to 25%. These findings provide key insights into optimizing FDM printing parameters to achieve improved structural integrity and aesthetic quality in PLA prints.

High strength C/Si‒Ni‒C composites fabricated by reaction melt infiltration with Si‒Ni alloy at lower temperature

AbstractSilicon‒nickel alloy (Si‒Ni) was first used for fabricating continuous carbon fiber reinforced ceramic matrix composites by reaction melt infiltration process. Based on Si‒Ni phase diagram, 66.7 at.% Si‒Ni was chosen, which has a lower liquidus temperature of 1115°C. The C/Si‒Ni‒C composites were infiltrated at temperature of 1270°C‒1390°C, and the prepared composite consists of C, SiC, NiSi, and NiSi2 phases. The density of the composite is higher than 2.29 g/cm3 and their open porosity is below 3%, indicating the composite was infiltrated completely by the Si‒Ni alloy. The C/Si‒Ni‒C composite exhibits significantly higher flexural strength and fracture toughness compared to the C/C‒SiC composite infiltrated with pure silicon at 1500°C. Specifically, the flexural strength and fracture toughness of the C/Si‒Ni‒C composite infiltrated at 1390°C increase by 140% and 300%, respectively. The improvement of mechanical properties contributed to the low reactivity between silicon‒nickel with carbon fibers, and the lower infiltration temperature, which can reduce degradation of carbon fiber as reinforcement. Moreover, the NiSi2 and NiSi alloy phases in the C/Si‒Ni‒C composite replace the brittle silicon phase in the C/C‒SiC composite, which can obviously enhance the fracture toughness.

Interlaboratory study of flexural strength in additively manufactured alumina

AbstractWe report the results of an international interlaboratory study of the flexural strength of alumina fabricated across six laboratories using the vat photopolymerization ceramic additive manufacturing (AM) technology. The mechanical testing of all the specimens, 142 in total, was performed at the National Institute of Standards and Technology (NIST) according to the well‐established four‐point bending method standardized for traditional ceramics. Overall, the existing ASTM standard for the four‐point bend testing proved adequate for AM ceramics, with several modifications to the specimen requirements to account for the specifics of AM processes. Critical flaws that caused failure were identified in all but two cases using optical fractography augmented with the imaging of fracture surfaces in a scanning electron microscope. The flexural strength data, analyzed following the Weibull statistics, exhibited considerable variation among the specimen sets manufactured by different laboratories. This variability correlated with the presence of many distinct critical flaws. We identified seven types of flaws that accounted for the failure of 94% of specimens. The prevalent flaws depend on the printing direction relative to the specimen's geometry. We discuss the nature of these flaws and their relation to the printing and post‐processing conditions. Removal of several types of critical flaws will significantly improve mechanical properties of ceramic parts built using vat‐photopolymerization AM.

Synthesis and Characterization of an Alkali-Activated Binder from Blast Furnace Slag and Marble Waste

This study reports an alkali-activated binder including blast furnace slag (BFS) together with marble waste (MW). Cement is an industrial product that emits a significant amount of CO2 during its production and incurs high energy costs. MW is generated during the extraction, cutting, and processing of marble in production facilities, where dust mixes with water to form a settling sludge. This sludge is an environmentally harmful waste that must be disposed of in accordance with legal regulations. In this study, a substantial amount of MW, a by-product with considerable environmental and economic impacts worldwide, was utilized in the production of a binder through the alkaline activation of BFS. In doing this, different experimental parameters were tested to obtain the best binder samples according to workability and mechanical properties. Then, some experiments such as drying shrinkage determination, strength testing, and microstructure analyses were fulfilled through samples with the best values. The findings supported the improvement of the rapid-setting property of BFS by means of the addition of MW. MW reduced the time-dependent drying shrinkage values of BFS by 55%, especially in slag alkaline activation systems with a low or moderate alkali activator content. The substitution of MW (≤50%) in BFS increased flexural and compressive strengths (4.5 and 61.7 MPa), while a reference sample contained BFS only. Although the use of MW did not create a new phase, it contributed to a C-S-H bonding structure during the alkali activation of BFS in a microstructure analysis.

Mechanical Properties and Microstructure of Alkali-Activated Cements with Granulated Blast Furnace Slag, Fly Ash and Desert Sand

In this study, desert sand was used as supplementary materials in alkali-activated cements (AAC) with granulated blast furnace slag (GBFS) and fly ash (FA). For the first time, a systematic investigation was conducted on the effects of various treatment methods and contents of desert sand on the strength and microstructure of AAC. This study also analyzed the X-ray diffractometer (XRD), Scanning Electron Microscopy-Energy Dispersive X-ray Microanalysis (SEM-EDX), Mercury Intrusion Porosimetry (MIP), pH values, and Fourier-transform infrared spectroscopy (FT-IR) properties of AAC pastes containing differently treated desert sand to uncover the mechanisms by which these treatments and dosages influence mechanical properties of AAC. Untreated desert sand (DS), temperature-treated desert sand (DS-T), and ground desert sand for two different durations (20 mins and 30 mins) all exhibited some pozzolanic activity but primarily acted as fillers in the AAC pastes. Among the samples, DS-T demonstrated the highest pozzolanic activity, though it was still less than that of fly ash (FA). The optimal dosage for the modified desert sands was determined to be 10%. However, The optimal dosage of different modified desert sands is 10%. The flexural strength of DS-G30-10 reaches 6.62 MPa and the compressive strength reaches 72.3 MPa, showing the best comprehensive mechanical properties.

Phase Evolution, Mechanical, and Electrical Properties of Lightweight Ceramic Prepared Using Scoria at Low Temperature

This study aimed to produce lightweight, eco-friendly ceramic materials with superior properties using natural raw materials and low processing temperatures. Five ceramic samples were fabricated using red clay and varying contents of volcanic scoria (10%, 20%, 30%, 40%, and 50%) through sintering at 950 °C for 4 h. The crystalline phases, electrical properties, porosity, and mechanical strength of all the ceramic specimens were comprehensively evaluated. It was determined that the chemical composition of the raw materials and the resulting phases significantly influenced these various attributes. The XRD analysis revealed that the ceramic samples primarily consisted of the crystalline phases gehlenite, low quartz, and anorthite, along with the minor wollastonite and hematite phases. As the scoria content was increased, the MgO and Fe2O3 concentrations also increased, leading to a reduction in dielectric constant, dielectric loss, and electric conductivity. Moreover, the porosity of samples decreases from S10 to S50 due to the increase in the percentage of scoria and this reduction in porosity led to increased bending strength. The findings of this study suggest that volcanic scoria can serve as a viable eco-friendly raw material to produce lightweight ceramics with excellent electrical and mechanical properties, presenting cost-effective and energy-efficient solutions for various applications.

Toughening Mechanism of CaAl12O19 in Red Mud–Al2O3 Composite Ceramics

The utilization of red mud in the production of ceramic products represents an efficient approach for harnessing red mud resources. Composite ceramics were prepared from Al2O3, red mud, and Cr2O3 by atmospheric pressure sintering, and the phase composition and microscopic morphology of the composite ceramics were investigated by XRD, SEM, and EDS. The flexural strength and fracture toughness of composite ceramics were measured by three-point bending and SENB methods. The results showed that the composite ceramics sintered at 1500 °C with the addition of 1.5 wt.% Cr2O3 had a flexural strength of 297.03 MPa, a hardness of 17.44 GPa, and a densification of 97.75% and fracture toughness of 6.57 MPa·m1/2. The addition of Cr2O3 helps to improve the low strength of red mud composite ceramic samples. The CaAl12O19 phase can form a similar “endo-crystalline” structure with Al2O3 grains, which changes the fracture mode of the ceramics and thus significantly improves the fracture toughness. The wettability tests conducted on Cu and RM–Al2O3 composite ceramic materials revealed that the composites exhibited non-wetting behavior towards Cu at elevated temperatures, while no interfacial reactions or elemental diffusion were observed. Composites have higher surface energy than Al2O3 ceramic at high temperatures. The present study provides a crucial foundation for enhancing the comprehensive utilization value of red mud and the application of red mud ceramics in the field of electronic packaging.