A novel inorganic phosphate-based adhesive for bonding archaeological pottery: a preliminary exploration

Abstract Damage and fracture of archaeological potteries not only jeopardize the long-term preservation but also hinder their exhibition. To repair these pottery sherds effectively, this study introduces a novel inorganic phosphate-based adhesive and evaluates its effectiveness through a series of experiments. To determine the optimal base adhesive, the paper investigates the influence of varying weight ratios of the H2O–H3PO4 system and the Al(OH)3–H3PO4 system on properties including tensile lap-shear strength, microstructure, high-temperature resistance and phase composition. However, the original black color of the traditional CuO–phosphate adhesive limits its application. The innovation of this study lies in the addition of nano-TiO2 to the adhesive, which not only improves the bonding strength but also adjusts the color of the adhesive. This study has defined the optimal formulation (i.e., base adhesive = m[Al(OH)3]:m[H3PO4] = 7:100, filler = 10wt% nano-TiO2), and the final product shows no residual acid in adhesives. Additionally, the fracture surfaces are successfully bonded with a high strength of 3.56 MPa. Various ageing tests including dry-thermal ageing, hygrothermal ageing and UV irradiation ageing are conducted to assess the ageing resistance of the inorganic phosphate-based adhesive. The results indicate strong tolerance of adhesive to high temperature and high humidity environment. Preliminary applications in archaeological pottery restoration suggest that the inorganic phosphate-based adhesive offers considerable promise for repairing shattered pottery. Graphical Abstract