Silica Content Research Articles

Diatom-Based Photobiological Treatment of Reverse Osmosis Concentrate: Optimization of Light and Temperature and Biomass Analysis

As global water scarcity intensifies, the desalination of brackish groundwater and surface water plays a critical role in augmenting water supplies. However, managing reverse osmosis concentrate (ROC) from brackish water desalination remains challenging due to silica and calcium accumulation and precipitation, which cause membrane scaling and reduce freshwater recovery. This study employed the brackish diatom Gedaniella flavovirens Psetr3 in a photobiological treatment to remove dissolved silica and calcium, offering a natural, sustainable solution to improve freshwater recovery. Optimal treatment conditions were identified, with a light intensity of 200 µmol m−2 s−1 and incubation temperatures between 23 °C and 30 °C maximizing silica uptake (up to 46 ± 3 mg/L/day) while minimizing diatom mortality. This study reports, for the first time, the silica, organic, and calcite content in diatom biomass and their production rates during the photobiological treatment of ROC using G. flavovirens Psetr3. The photobiological treatment of one million gallons (3785 m3) per day of ROC would produce 174 kg of silica, 163 kg of organics, and 314 kg of calcite daily. These findings provide valuable insights into the potential for utilizing these bioresources to offset the costs of photobiological treatment and subsequent desalination processes.

Benthic Foraminifera and Diatom Relationship: Insights from RbcL Gene Sequences in Palk Bay

Understanding the symbiotic relationships between benthic foraminifera and diatoms is crucial for ecological studies, particularly in environmental changes. In this study, DNA barcoding, targeting the rbcL gene, was applied to identify diatoms and evaluate their diversity within the foraminiferal shells in Thondi, Palk Bay. Foraminifera were isolated from the sediment samples collected using grab samplers at six different locations. The separated benthic foraminifera were then used for DNA barcoding. The obtained DNA sequences were aligned and analyzed comprehensively using Geneious Pro v5.1. A higher population of Ammonia parkinsoniana was observed in March 2023 compared to May 2023, with a notable presence of algal symbionts. Seasonal temperature fluctuations exhibited a strong positive influence on the abundance of A. parkinsoniana. Changes in salinity and temperature were suggested to induce species shifts within the intertidal foraminiferal community. The symbiotic diatoms within the A. parkinsoniana shells were confirmed through rbcL gene sequencing and Scanning Electron Microscope (SEM) imaging. Phylogenetic analysis indicated a 50% similarity between the foraminifera and diatoms. SEM imagery displayed diatoms attached to the surface of A. parkinsoniana cells, while Energy Dispersive X-ray (EDX) analysis detected silica content at the diatom sites. This study highlights the potential of DNA barcoding to identify and develop novel chloroplast markers to elucidate foraminiferal symbiotic relationships.

Effects of Silicon Concentration and Synthesis Duration on Lignin Structure: A Spectroscopic and Microscopic Study.

Silicon (Si) is a highly abundant mineral in Earth's crust. It plays a vital role in plant growth, providing mechanical support, enhancing grain yield, facilitating mineral nutrition, and aiding stress response mechanisms. The intricate relationship between silicification and lignin chemistry significantly impacts cell wall structure. Yet, the precise influence of Si on lignin synthesis remains elusive. This study investigated the interaction between Si and lignin model compounds during invitro synthesis. Employing spectroscopic and microscopic analyses, we delineated how Si concentrations modulate lignin polymerization dynamics, particularly affecting molecular conformation and aggregation behavior over time. Fluctuations in the polymer structure are directly related to both the synthesis time and the concentration of silica. Our results demonstrate that lower Si concentrations promote the aggregation of lignin oligomers into larger particles, while higher concentrations increase the possibility of oligomer repulsion, thus preventing particle growth. These findings elucidate the intricate interplay between Si and lignin, which is crucial for understanding plant cell wall structure and stress resilience. Moreover, the results provide insights for developing lignin-silica materials with increasing applications in industry and medicine.

Investigation of silica crystallization kinetics in rice husk ash for sustainable construction materials

Concrete is one of the most widely used materials in the world, and its utilization is rising drastically with the increasing population. Around 5-8% of global carbon emissions are caused by cement production. On the other hand, approximately 160 million tons of rice husk, considered agrowaste, turn into ash annually. Rice husk ash (RHA) is particularly attractive due to its high silica content and great potential to be used as a cementitious material. However, impurities such as alkali metal oxides and uncontrolled combustion reduce the quality of silica and promote its crystallization. Numerous studies have focused on obtaining active silica through acid leaching to remove impurities, but the study on the reaction kinetics of functionalized rice husk ash is very limited. In this research, 0.1M hydrochloric acid (HCl) was used to leach rice husk at temperatures of 50°C, 60°C, and 70°C for 1.5 hours. The rice husk was then burned at 800°C for 2 hours. Subsequently, the ash was examined using various analytical and computational techniques to develop an in-depth understanding of the burning process, aimed at producing functionalized amorphous silica for sustainable construction. It was observed that 99.39% silica with 95.04% amorphous content was formed by treating rice husk with 0.1M HCl at 70°C for 1.5 hours, followed by combustion at 800°C for 2 hours. Furthermore, reaction kinetics parameters were identified using the Coats-Redfern kinetic model for the two different reaction zones of the burning process.

THERMODYNAMIC AND EXPERIMENTAL STUDIES ON THE INFLUENCE OF HIGH-ASH COAL IN THE PRODUCTION OF HIGH-CARBON FERROCHROME

This paper presents the results of scientific research that served as the foundation for developing a technology for producing high-carbon ferrochrome using a new reducing agent in the charge-high-ash coal from the "Saryadyr" deposit. To analyze the carbothermic reduction of chromium, a method of complete thermodynamic modeling (CTM) of metallurgical processes was employed, implemented using the HSC Chemistry 10.0 software package over a temperature range of 600-2800 K. The thermodynamic analysis demonstrated that the production of carbon ferrochrome using high-ash coal does not lead to sharp technological deviations: the process proceeds stably, ensuring complete reduction of chromium and iron. An analysis of the silica and alumina content in the coal ash indicated that it can replace quartzite in the charge mixture. Based on the thermodynamic data, experimental studies of the high-carbon ferrochrome production process using Saryadyr high-ash coal were conducted in a high-temperature Tammann laboratory furnace. The Tammann resistance furnace is a research facility designed to model metallurgical processes at high temperatures. During the laboratory tests, experimental samples of high-carbon ferrochrome corresponding to grade FeCr800 were obtained.

Superhydrophilic self-cleaning cotton fabric with enhanced antibacterial and UV protection properties

AbstractA multifunctional cotton fabric with superior photocatalytic self-cleaning, antibacterial activity and UV protection was prepared through treatment with TiO2/Pt/SiO2 colloid, clarifying the influence of coating formulation on these functionalities. The photocatalytic activity of coated fabrics under UV and white-fluorescent light was tested and synergistic effects of Pt and silica in enhancing the self-cleaning property of fabrics were demonstrated. Various molar ratios of Pt:Ti (0.01%, 0.1%, 0.5%, and 1%) and Ti:Si (50/50 and 30/70) were utilised in synthesising the colloids. The self-cleaning performance of fabrics was assessed through monitoring coffee stain removal efficiency and methylene blue (MB) dye degradation kinetics. The results demonstrated an effective photocatalytic self-cleaning property on fabrics coated with TiO2/Pt/SiO2 colloids. Increasing the concentrations of Pt and silica both contributed to enhancing the self-cleaning property. The fabric coated with ternary TiO2/Pt/SiO2 30/1/70 colloid resulted in 43.5% higher MB dye removal compared with pure TiO2 after 3h irradiation under visible light. Moreover, the fabrics containing Pt 1% dopant possessed excellent bactericidal activity against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria, regardless of the presence of silica. While the addition of silica slightly reduced the UV protection of coated fabrics, increasing the concentration of Pt to 1% increased the protection level to 45 + . Various characterisation techniques including SEM, XPS, XRD, and TEM were employed to study the Pt-doping of TiO2 nanoparticles, as well as the effect of Pt concentration, superhydrophilicity of silica, and the chemical composition of coatings on the functionalities of fabrics.

Enhancement of Composite Material Properties Based on Aggregate Network Modulation

ABSTRACTCompounding technology and the theory of filled polymers have progressed substantially. Valuable insight from these developments is that carbon black‐filled wet rubber greatly enhances the filler's dispersion and dispersion state in the matrix. The enhanced dispersion noticeably improves the properties of the polymer. This paper systematically investigated the effects of silanization reactions on filler dispersion, interaction force, and aggregation networks. Their potential impact on polymers' properties was also evaluated. To this end, we evaluated the effects of different ratios of Si69 and silica fillers in wet and dry rubbers. For better characterization and utilization of the filler network structure, the filler–filler, filler–rubber, and rubber–rubber interactions were analyzed using the Mooney–Rivlin curve model. The results revealed that wet blending and silanization reactions primarily regulated the aggregate size and filler network strength. Increasing silica content improved the Payne effect. Notably, incorporating an appropriate filler content could effectively enhance rubber's physical and mechanical properties. This paper effectively optimized the structure and properties of filled polymers by controlling silanization reaction and applying wet mixing. This research contributes to the theoretical and experimental foundation of studies in relevant fields.

The Structure-Mechanics Relationship of Bamboo-Epidermis and Inspired Composite Design by Artificial Intelligence.

Bamboo culm has been widely used in engineering for its high strength, lightweight, and low cost. Its outermost epidermis is a smooth and dense layer that contains cellulose, silica particles, and stomata and acts as a water and mechanical barrier. Recent experimental studies have shown that the layer has a higher mechanical strength than other inside regions. Still, the mechanism is unclear, especially for how the low silica concentration (<10%) can effectively reinforce the layer and prevent the inner fibers from splitting. Here, theoretical analysis is combined with experimental imaging and 3D printing to investigate the effect of the distribution of silica particles on composite mechanics. The anisotropic partial distribution function of silica particles in bamboo skin yields higher toughness (>10%) than randomly distributed particles. A generative artificial intelligence (AI) model inspired by bamboo epidermis is developed to generate particle-reinforced composites. Besides the visual similarity, it is found that the samples by the generative model show failure processes and fracture toughness identical to the actual bamboo epidermis. This work reveals the micromechanics of the bamboo epidermis. It illustrates that generative AI can help design bio-inspired composites of a complex structure that cannot be uniformly represented by a simple building block or optimized around local boundaries. It expands the design space of particle-reinforced composites for enhanced toughness modulus, offering advantages in industries where mechanical reliability is critical.

From Crop Residue to Corrugated Core Sandwich Panels as a Building Material.

This study explores the potential of using underutilized materials from agricultural and forestry systems, such as rice husk, wheat straw, and wood strands, in developing corrugated core sandwich panels as a structural building material. By leveraging the unique properties of these biobased materials within a corrugated geometry, the research presents a novel approach to enhancing the structural performance of such underutilized biobased materials. These biobased materials were used in different lengths to consider the manufacturing feasibility of corrugated panels and the effect of fiber length on their structural performance. The average lengths for wood strands and wheat straws were 12-15 cm and 3-7.5 cm, respectively, while rice husks were like particles, about 7 mm long. Due to the high silica content in rice husk and wheat straw, which negatively impacts the bonding performance, polymeric diphenylmethane diisocyanate (pMDI), an effective adhesive for such materials, was used for the fabrication of corrugated panels. Wood strands and phenol formaldehyde (PF) adhesive were used to fabricate flat outer layers. Flat panels were bonded to both sides of the corrugated panels using a polyurethane adhesive to develop corrugated core sandwich panels. Four-point bending tests were conducted to evaluate the panel's bending stiffness, load-carrying capacity, and failure modes. Results demonstrated that sandwich panels with wood strand corrugated cores exhibited the highest bending stiffness and load-bearing capacity, while those with wheat straw corrugated cores performed similarly. Rice husk corrugated core sandwich panels showed the lowest mechanical performance compared to other sandwich panels. Considering the applications of these sandwich panels as floor, wall, and roof sheathing, all these panels exhibited superior bending performance compared to 11.2 mm- and 17.42 mm-thick commercial OSB (oriented strand board) panels, which are commonly used as building materials. These sandwich structures supported a longer span than commercial OSB panels while satisfying the deflection limit of L/360. The findings suggest the transformative potential of converting renewable yet underutilized materials into an engineered concept, corrugated geometry, leading to the development of high-performance, carbon-negative building materials suitable for flooring and roof applications.

Effects of waste glass dust incorporation on the tribological performance of flax-epoxy hybrid composites

Waste glass dust, an industrial waste, generated in the glass-cutting industries, is considered carcinogenic and poses health risks as it is high in silica content. This research essentially explores the alternative use of these waste glass dust as functional fillers in fabricating wear-resistant hybrid polymer composites. It includes fabrication of the hybrid epoxy composites in hand lay-up route with varying weight fractions (0–0.2) of the waste glass dust along with the flax fiber (30 wt. %) and their dry sliding wear behavior is observed. Test sample preparation follows ASTM-G99–05 standard and experiments are conducted considering Taguchi's L25 design. Significant improvement in the wear resistance of the hybrid composites is obtained after incorporating the waste glass dust and flax fibers. Filler content is found to be the most effective factor in affecting the wear rate followed by the sliding velocity during the Taguchi analysis with respective contributions of 54.51% and 38.59% as obtained from the ANOVA analysis of the wear results. Normal load and sliding distance are found to affect marginally the wear rates of the composites. A predictive model is proposed to find the specific wear rate (SWR) using the test results through the regression analysis. The minimum wear rate is obtained for 20 wt. % of filler, 1000 m of sliding distance, 50 cm/sec of sliding velocity, and 10 N of load. The mechanisms predominantly responsible for the wear loss have also been studied using a scanning electron microscope.

Effect of Operational Parameters and Iron Ore Tailings Properties on Filter Cake Porosity

Objective: By evaluating operational filtration conditions, chemical, mineralogical, and particle size properties of the tailings, the study aimed to identify critical variables affecting porosity and provide predictive models for optimizing dewatering operations. Theoretical Framework: This research builds upon existing theories of solid-liquid separation and dewatering processes in mineral processing. Key references include classical works on filtration dynamics, particle size distribution, and cake porosity characterization. The study addresses gaps in literature regarding the relationship between tailings composition and filtration results. Method: The Leaf Test method was employed on 33 fresh slurry samples from the Brucutu plant to simulate industrial filtration conditions. Filtration cycle parameters such as cake formation and drying times were standardized. Porosity was calculated using Grace's equation and correlated with characterization data, including mineralogical composition, true density, and particle size. Statistical methods such as clustering, regression, and Random Forest modeling identified key predictors of porosity. Results and Discussion: The results indicated that porosity correlates strongly with silica content and certain mineralogical attributes, such as the presence of martitic hematite and quartz. Cluster analysis revealed two sample groups with distinct filtration characteristics. While operational parameters showed limited impact on porosity, the statistical models highlighted the significance of ore composition. Research Implications: This research provides a foundation for optimizing iron ore tailings filtration by identifying the key variables influencing porosity. The findings support more efficient dewatering techniques, contributing to sustainable tailings management. Further, the development of predictive models aids industrial operations in minimizing risks associated with tailings disposal. Originality/Value: This study is among the first to integrate statistical modeling and mineralogical characterization in exploring filter cake porosity. The results offer novel insights into the optimization of solid-liquid separation processes in the mining industry.

Enhancing concrete sustainability with spent diatomaceous earth from the wine industry: Long‐term experimental and statistical analysis

AbstractSpent diatomaceous earth, a by‐product of wine filtration, holds significant promise for use in concrete mixtures due to its pozzolanic properties, which enhance concrete performance. This research explores the application of spent calcined diatomaceous earth (SCDE), heat‐treated at 700°C to remove organic content, as a partial substitute for cement or sand in concrete. The high silica content of SCDE contributes to the formation of additional calcium silicate hydrates during the hydration process, leading to improvements in mechanical strength over time. The study includes a preliminary analysis of cement replacements ranging from 5% to 10% and sand replacements from 2.5% to 15%, assessing their effects on workability, density, water absorption, and compressive strength at 7 and 28 days. The testing program focuses on three key compositions: the reference concrete and optimal mixtures with 10% cement and 5% sand replacements. Compressive strength tests are conducted at 7, 28, 90, 180, and 360 days. The results, validated through ANOVA, demonstrate the influence of SCDE on concrete strength over time, with distinctive behavior patterns identified for different mixtures. The strength of concrete with replacements correlates with the reference strength, with a multiplicative factor that varies from 7 to 90 days and then. When SCDE replaces cement, the factor is less than one before 28 days due to the slow pozzolanic reaction, whereas for sand replacement, it always exceeds one because of the initial filler effect. After 90 days, the strength multiplicative factors are 1.13 for cement replacement and 1.30 for sand replacement, demonstrating the potential of SCDE for sustainable concrete manufacturing and its positive long‐term impact on mechanical performance.

Parametric analysis and prediction of dry adhesive wear characteristics of waste glass dust filled hemp-epoxy composites

Waste glass dust, an industrial waste, generated in the glass cutting industries, is carcinogenic and possesses health risk due to high silica content. As an attempt to gainfully utilize this, the possibility of using this waste glass dust as a functional filler in wear-resistant polymer composites is explored. It includes fabrication of epoxy composites in hand lay-up route with varying weight fractions (0–0.2) of the waste glass dust along with multiple layers of hemp fiber. The dry sliding wear behavior of these composites under different test conditions are studied. ASTM G99-05 standard is followed for preparing the test samples and experiments are conducted as per Taguchi’s L25 design. Wear resistance is significantly improved with addition of the filler. Among the control parameters, the filler content is the most effective factor influencing the wear rate and next comes the sliding velocity as obtained from the ANOVA and Taguchi analysis. A predictive model is proposed to find the specific wear rate (SWR). The minimum wear rate is obtained for 20 wt. % of filler, 250 m sliding distance, 50 cm/sec sliding velocity and 10 N load. The mechanisms predominantly responsible for the wear loss have also been studied using a scanning electron microscope.

Microstructure Analysis of Different NaOH Molarity Towards Fly Ash Geopolymer for Underwater Concreting Material

Geopolymer concrete is a new sustainable and environmentally friendly composite with great potential to replace conventional concrete that is mostly produced by ordinary Portland cement (OPC). Binders used for geopolymer concrete such as fly ash and blast furnaces are mostly industrial wastes or by -products containing high silica and aluminium content that act as stimulants for geopolymerization. Furthermore, geopolymers also exhibit better durability and corrosion resistance than OPCs. However, material subjected to underwater placement method typically exhibit a decrease in properties. While geopolymer has not been widely used as underwater concreting material, this research is purposed to identify the effect of underwater placement method towards geopolymer in terms of microstructure analysis. Using different molarities of sodium hydroxide (NaOH), the optimum compressive strength will be discussed for underwater concrete while correlating with the microstructure result. For alkaline activators, the ratio used is 2.5 and the ratio for solid to liquid is 2.5. The molarities used for alkaline activators were 8 M, 10 M and 12 M. Using the tremie method for underwater concrete, it is possible to measure the leaching loss with respect to the objective of this research. The best compressive strength result is 12 M. The SEM result support with 12 M molarity had less cavities and lowest density.

One Part Method for Making Geopolymer Paste using Flocculated Sidoarjo Mud

Some efforts have proposed the utilization of Sidoarjo mud for geopolymer paste. However, the original dry mud in geopolymer concrete showed decreased compressive strength and increased required water. In this paper, the one-part method is proposed to reduce the water in the mixture. First, the mud was chemically flocculated. Then, the dry mud was mixed with fly ash, activated geothermal silicate, and sodium hydroxide mixture in solid form before then the distilled water was added. This reduced the required water to 50% compared to the two-part method. The flocculant sedimented heavy metal that resulted in higher compressive strength at a later age. At 28 days, dry flocculated mud showed higher compressive strength than the original dry mud, with a compressive strength of 13 MPa and 11 MPa, respectively. This is because of the increase of silica, alumina, and iron content from 70% in dry LUSI to 75% in dry flocculated mud.

Influence of CFBC Fly Ash Chemical Composition and Mechanical Activation on the Properties of Geopolymer

Circulating fluidized bed combustion (CFBC) fly ash has the potential as a precursor to making geopolymer concrete because of its rich silica and alumina content. However, there is a problem in utilizing CFBC fly ash caused by its chemical and physical properties that differ from the widely used pulverized coal combustion (PCC) fly ash. CFBC fly ash has a higher water requirement than PCC fly ash due to its angular particle shape, and higher sulfur and lime contained also caused a different reaction in the geopolymer system. Mechanical activation by milling the CFBC fly ash could decrease the water requirement in the mixture and make good quality CFBC fly sh-based geopolymer concrete. Three CFBC fly ash samples from different power plants in Indonesia with different chemical compositions were used in this research. The first had a low lime and no sulfur content, the second had high lime and no sulfur content, and the third had high lime and sulfur content. The milling process using a ball mill for two hours decreased the water requirement, as shown in the lower normal consistency of the fly ash. The reactivity also was increased, shown by the faster initial setting time. Besides its higher reactivity, lower water requirement increased the compressive strength of geopolymer mortar produced. This study also showed that the existence of calcium and sulfur content in the CFBC fly ash could cause unexpected results shown by the change of initial setting time, water requirement, and compressive strength.

U-Pb AGE AND GEOCHEMICAL TYPIFICATION OF THE SARAM MASSIF ROCKS (WESTERN TRANSBAIKALIA): EARLY JURASSIC GRANITOID MAGMATISM

The paper presents data on the geological position, age and features of the material composition of the Saram massif granitoids, located in the northwestern part of the Malkhan ridge of Western Transbaikalia. The structure of the massif involves two-phase rocks corresponding to syenite, early-phase moderate-alkali granite and late-phase leucogranite families. The silica content (wt. %) varies from 63.8 to 71.2 in the early-phase granitoids and from 73.2 to 77.1 in the late phases. The early-to-late-phase rocks of the massif are mostly ferruginous (Fe*=0.77–0.88 and 0.80–0.93, respectively). Based on a high modified alkaline lime index (MALI) (8.75–9.97) and relatively low SiO2 contents, the early-phase rocks can be referred to as alkaline rocks, and the late-phase rocks – as calc-alkaline rocks. According to the aluminum saturation index, the early-phase rocks (0.93–1.07) correspond to moderate-to-high-alumina rocks, and the late-phase rocks (1.09–1.13) – to high-alumina formations. Granitoids are geochemically and mineralogically different from typical agpaitic A-type granites and correspond to a special group of aluminous A-type rocks. The two phase magmatic zircon U-Pb dating yielded the 175–177 Ma age (Early Jurassic). The formation of granitoids in the Saram massif is temporally synchronous with intensive orogenesis in Transbaikalia, probably caused by the closure of the Mongol-Okhotsk Ocean.

Plant Growth-Promoting Yeasts (PGPYs) as a sustainable solution to mitigate salt-induced stress on zucchini plant growth

Among the long-term sustainable solutions to mitigate saline stress on plants, the use of plant growth promoting microorganisms (PGP) is considered very promising. While most of the efforts have been devoted to the selection and use of bacterial PGPs, little has been proposed with yeast PGP (PGPYs). In this study, three PGPY strains belonging to Naganishia uzbekistanensis, Papiliotrema terrestris and Solicoccozyma phenolica were employed singularly and in a consortium to mitigate salt stress of zucchini (Cucurbita pepo). The results demonstrated that these yeasts, when applied to salt-amended soil, mitigated the growth inhibition caused by NaCl. Among the three species, N. uzbekistanensis and P. terrestris showed the most significant improvements in plant performance, with N. uzbekistanensis exhibiting hormetic effects under salt stress by improving root length and dry plant biomass. In general, the root system was the most affected part of the plants due to the presence of the yeasts. The entire rhizosphere bacterial microbiota was significantly influenced by the addition of PGPYs, while the mycobiota was dominated by the introduced yeasts. Metabolomic fingerprinting using FTIR revealed modifications in hemicellulose and silica content, indicating that PGPY inoculation impacts not only the plant but also the soil and rhizosphere microorganisms.

Utilization of Silica from Palm Ash Waste as an Abrasive Material in Brake Friction Composite

The silica element in palm ash has the potential to be an alternative source of silica material to replace mineral silica, making it more environmentally friendly and reducing production costs. This research aims to utilize silica from palm ash waste as an abrasive material in brake friction composites. The silica from palm ash was isolated by a leaching process using 1 M HCl solution at a temperature of 70 °C for 90 minutes. Isolated silica was then characterized by X-ray fluorescence (XRF). The composition of silica was varied by volume fraction (0, 2, 4, and 6%). The mixing process of the powder mixture was conducted using a chopper mixer for 5 minutes, The powder mixture is then hot compressed using uniaxial hot pressing at a pressure of 47 MPa and a temperature of 165 °C for 15 minutes. Post-curing of the samples was carried out at a temperature of 165 °C for 10 hours. The samples were characterized by density, porosity, hardness R-scale, friction coefficient, and specific wear rate. The research results showed that the palm ash was successfully purified with a silica content of 27.3% to 57.2%. Increasing volume fraction of palm ash silica decreases in density and hardness, while porosity increases. The sample with 4% volume of palm ash silica exhibited better friction performance and a lower specific wear rate. Palm ash silica has the potential to replace the silica mineral for brake friction composites.

Exposing the Role of Silica Nanoparticles and Fiber Stacking in Mechanical, Water Absorption, and Bio-Degradation Behaviors of Banana-Papaya Hybrid Composites

Abstract Natural fiber composites are becoming more valuable in industries due to their eco-friendliness, high strength-to-weight ratio, and cost-effectiveness. This study aimed to develop and evaluate hybrid composites made from banana and papaya fibers, enhanced with silica nanoparticles, bonded with epoxy resin, to assess the effects of fiber layering sequence and silica content on their mechanical, water absorption, and biodegradation properties. Tri-layer composites with configurations such as BPB (Banana-Papaya-Banana) and PBP (Papaya-Banana-Papaya) were fabricated using the hand layup technique. Mechanical testing revealed that PBP composites exhibited superior tensile strength, which further improved when reinforced with silica nanoparticles (SiO2) in various concentrations. The PBP composite with 2 wt% SiO2 displayed optimal performance, showing tensile strength (83 MPa), flexural strength (104 MPa), impact strength (8.4 kJ/m²), and hardness (86 Shore-D) due to effective silica dispersion, enhancing load transfer and interfacial bonding. Thermal stability was also improved by the silica, making this composite suitable for high-temperature applications. Additionally, PBP/3 wt% SiO2 exhibited low water absorption (8% at 15 days) and minimal mass loss (14% at 60 days), highlighting its resistance to environmental degradation, which is essential for humid or marine environments. The PBP/2 wt% SiO2 composite is recommended for use in industries like automotive, manufacturing, and structural engineering, where its high mechanical properties, durability, and eco-friendliness make it a promising alternative to synthetic composites, thus supporting sustainable practices.