Effects of polyelectrolytes on the hardness of borax decahydrate crystals

Abstract

The hardness of borax decahydrate crystals was measured using cationic polyelectrolytes of FO4115, FO4400 and FO4990 with anionic polyelectrolytes of AN923, AN930 and AN999 as an additive. The measurements were carried out in the indentation load range of 10 g to 30 g. It was determined that the Vickers hardness (H_V) decreased with increasing applied load, showing that the borax decahydrate crystals exhibited an indentation size effect. Vickers microhardness measurements revealed that pure borax decahydrate crystals had a brittle structure, yet the crystals obtained in additive media were categorized as a soft material. The proportional specimen resistance model was applied to determine the load-independent microhardness. The crystal hardness of borax decahydrate was found to change depending on the type and concentration of polyelectrolyte used. In addition to the mechanical properties, the thermal and physical characteristics of borax decahydrate crystals were investigated by thermogravimetric and Fourier transform infrared spectroscopy analysis. The characterization results confirmed that the polyelectrolytes were adsorbed on the crystal’s surface.

Keywords

• Borax decahydrate,crystal hardness,polyelectrolyte,PRS model

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