Effects of calcination temperature of boron-containing magnesium oxide raw materials on properties of magnesium phosphate cement as a biomaterial

Abstract

A new magnesium phosphate bone cement (MPBC) was prepared as a byproduct of boroncontaining magnesium oxide (B-MgO) after extracting Li2CO3 from salt lakes. We analyzed the elementary composition of the B-MgO raw materials and the effects of calcination temperature on the performance of MPBC. The phase composition and microstructure of the B-MgO raw materials and the hydration products (KMgPO4·6H2O) of MPBC were analyzed by X-ray diffraction and scanning electron microscopy. The results showed that ionic impurities and the levels of toxic elements were sufficiently low in B-MgO raw materials to meet the medical requirements for MgO (Chinese Pharmacopeia, 2010 Edition) and for hydroxyapatite surgical implants (GB23101.1-2008). The temperature of B-MgO calcination had a marked influence on the hydration and hardening of MPBC pastes. Increasing calcination temperature prolonged the time required for the MPBC slurry to set, significantly decreased the hydration temperature, and prolonged the time required to reach the highest hydration temperature. However, the compressive strength of hardened MPBC did not increase with higher calcination temperatures. In the 900-1 000 °C temperature range, the hardened MPBC had a higher compressive strength. Imaging analysis suggested that the setting time and the highest hydration temperature of MPBC pastes were dependent on the size and crystal morphology of the B-MgO materials. The production and microstructure compactness of KMgPO4·6H2O, the main hydration product, determined the compressive strength.