Fabrication and Characterization of Porous Biochar and Si3N4 Bioceramic Toughened Natural Fibre Epoxy Composite

Abstract

This study investigates the mechanical, thermal, and wears characteristics of eco-friendly composite materials (designated as N1 to N5) with varying ratios of silicon nitride (biogenic Si₃N₄) and biochar along with jute and kenaf microfiber. The primary aim of this research study was to investigate the suitability of low cost biomass derived functional ceramic fillers in composite material instead of high cost industrial ceramics. Both the bio carbon and biogenic Si₃N₄ were synthesized from waste sorghum husk ash via pyrolysis and thermo-chemical method. Further the composites are prepared via mixed casting process and post cured at 100 °C for 5 h. According to results, the mechanical properties show a consistent improvement, attributed to the contributions of biogenic Si₃N₄. Moreover, the specific wear rate decreases progressively, with a larger biogenic Si3N4 and bio carbon filler %. The presence of biochar acts as solid lubricant and offered balanced friction coefficient. The composite N4 attained maximum mechanical properties including tensile (110 MPa), flexural (173 MPa), impact (6.1 J), hardness (82 shore-D), compressive (138 MPa) and lap shear strength (16 MPa). On contrary, the composite N5 attained least thermal conductivity of 0.235 W/mK, Sp. Wear rate of 0.00545 with COF of 0.26. Similarly, the scanning electron microscope (SEM) analysis revealed highly adhered nature of fillers with matrix, indicating their cohesive nature indicating the strong interfacial adhesion between the fillers and the matrix, attributed to the presence of biochar, which enhances mechanical interlocking and provides functional groups that promote chemical bonding with the polymer matrix, leading to improved load transfer efficiency and overall composite performance. Moreover, thermal conductivity values exhibit a marginal decline with the presence of biogenic Si3N4 and biochar. Overall, the study demonstrated that biomass-derived functional fillers are capable candidates for providing the required toughness and abrasion-free surfaces, as evidenced by the increased impact strength, improved wear resistance, and enhanced durability observed in treated specimens compared to the control samples.This approach offers both economic and environmental benefits by reducing human exposure to hazardous pollutants through the utilization of biomass-derived materials, which help divert waste from landfills, lower air pollution caused by burning conventional plastics, and minimize soil contamination from non-biodegradable waste. In addition, the developed natural fiber-reinforced composites exhibited competitive mechanical performance compared to conventional industrial ceramic-reinforced composites, demonstrating comparable strength, enhanced toughness, and improved damping properties while offering the advantages of lower density, biodegradability, and cost-effectiveness. These findings highlight the potential of biomass-derived fillers as sustainable alternatives in structural applications.