Abstract

This study investigates the role of sodium hydroxide (NaOH) and potassium hydroxide (KOH) as alkali activators 
for modifying agro-marine residue ash used as reinforcement in aluminum matrix composites (AMMCs). The core 
challenge addressed is the inconsistent surface characteristics of bio-derived ashes, which compromise interfacial 
bonding and limit industrial adoption of eco-composites. Using SEM, EDS, FTIR, and XRD analyses, the study com
pares the physicochemical changes induced by NaOH and KOH treatments. NaOH-treated particles developed 
smoother, more uniform surfaces with higher hydroxylation and crystallinity, supporting enhanced wettability 
and interfacial adhesion. In contrast, KOH-treated particles exhibited denser, rougher morphologies with greater 
microporosity, favoring mechanical interlocking and improved thermal resistance. FTIR confirmed hydroxyl function
alization in the 3200–3600  cm−1 region, and EDS revealed increased surface oxygen content in both treatments. XRD 
analysis highlighted a significant increase in crystallinity, especially for NaOH + heat-treated samples, which reached 
peak intensities of up to 76.4%. Although mechanical properties were not directly measured, the microstructural 
and chemical modifications observed are strong predictors of improved structural integrity and performance in metal 
matrix systems. Optimal processing conditions were identified at 4 M concentration, with NaOH requiring shorter 
activation times (30–60 min) compared to KOH (60–120 min). These findings establish a foundation for designing 
application-specific, functionally graded composites. By valorizing agro-marine waste and enabling surface engineer
ing through selective alkali activation, this work supports the development of cost-effective, sustainable, and high
performance composites suitable for lightweight, thermally stable, and wear-resistant industrial applications.