Effect of additives on the microstructure of machinable bioglass-ceramic

Xinhua ZHOU; Ying CHU; Anmin CHEN; Shuzhen SUN

ABSTRACT

BACKGROUND:

Machinable bioglass-ceramics became a new inorganic biomaterial; moreover, strength, toughness and machinability are significantly studied.

OBJECTIVE:

To observe the effect of ZnO, Fe2O3 and ZrO2 additives on the microstructure and properties of machinable bioglass-ceramic in K2O-MgO-CaO-SiO2-P2O5-F system.

DESIGN:

Observational contrast study.

SETTING:

Department of Orthopaedics, Tongji Hospital Affiliated to Tongji Medical College, Huazhong University of Science and Technology.MATERIALS The experiment was carried out in the Laboratory of Materials, Wuhan University of Technology from October 2003 to April 2004. K2O-MgO-CaO-SiO2-P2Os-F system, ZnO, Fe2O3 and ZrO2 additives, D/Max-ⅢA X-ray diffractometer (Japan), JSM-5610LV scanning electron microscope (SEM), HVS-1000 microhardnessmeter and 3257-35 magnetic testing device (Japan) were used in this study.

METHODS:

In the glass-ceramic of K2O-MgO-CaO-SiO2-P2O5-F system, three kinds of additives ZnO, ZnO-Fe2O3 and ZnO-Fe2O3-ZrO2 were added respectively. These three kinds of ceramics were prepared by being melted at 1 400 ℃ for 1 hour. After fire, crystal temperature was set based on differential thermal analysis curve. ① Physical properties Microhardness was determined with microhardnessmeter (HVS-1000). The flexural strength and fracture toughness were established measured with ceramic mechanical test system (MTS) method and single edge notched beam (SENB) method, respectively. Saturation magnetic moment and Curie temperature were determined with 3257-35 magnetism test machine made in Japan. Holing method was used to measure machinability. ② Test of crystalline phase and microstructure Crystalline phase analysis was carried out with X-ray diffraction (XRD D/Max-ⅢA) and microstructure analysis were conducted on an etched fracture surface using SEM (JSM-5610LV,Japan). MAIN OUTCOME

MEASURES:

Effects of ZnO, Fe2O3 and ZrO2 additives on physical properties, mineral composition and crystalline phase.

RESULTS:

① The addition of ZnO to the glass-ceramic in K2O-MgO-CaO-SiO2-P2O5-F system was beneficial to crystal growth, increasing aspect ratio of crystal, decreasing microhardness and improving toughness and machinability. ② The addition of ZnO-Fe2O3 to the glass-ceramic in K2O-MgO-CaO-SiO2-P2O5-F system can form minority Mg-Zn ferrite with magnetism. The main crystalline phase present in the glass- ceramic was diopside with small size and hardness was improved, which led to worse machinability. ③ Because of the addition of ZnO-Fe2O3-ZrO2, magnesia fluormica and fluorapatite became the main crystalline phases, and the minor phases including Mg-Zn ferrite, t-ZrO2 and m-ZrO2, etc.also presented in the glass-ceramic. This material possessed high strength and toughness, good machinability and magnetism, which could stimulate formation of new bone, and was good substitute of bone restorations. Bioassay and in vitro test indicated that the glass-ceramic in K2O-MgO-CaO-SiO2-P2O5-F system was bioactive and biocompatible.

CONCLUSION:

ZnO, Fe2O3 and ZrO2 additives play a significant role in changing crystalline structure, enhancing strength,toughness and machinability of machinable bioglass-ceramic and generating magnetism.