چكيده به لاتين
Bone china bodies contains 50 %wt bone ash, 25 %wt kaolin and 25 %wt feldspar. This ceramics products after sintering at 1250 °C contain β-tricalcium phosphate and Anorthite crystals in a heterogeneous glass matrix. Due to the extreme difference in the thermal expansion coefficient of β-TCP with other components, it attempts to replace it with Anorthite with a lower thermal expansion coefficient. In this research, first Anorthite was synthesized with mixtures of kaolin and calcite powders with a weight ratio of 7 to 3, at three different temperatures of 1000, 1200 and 1400 °C, and three different sintering times of 30, 180 and 300 minutes. Results proved that synthesis at 3 hours and 1200 °C was suitable for the reactions of Anorthite formation and using in bone china body’s composition. Then the synthesized Anorthite was replaced by bone ash in bone china in different amounts of 10 to 50 %wt and samples was sintered at 1260 °C and 3 hours and various experiments such as microstructural analysis, physical and mechanical properties tests, thermal expansion coefficient and whiteness index tests. The results showed that the sample containing 50 %wt Anorthite had flexural strength of 68.9 MPa, density of 2.12 g.cm-3, water absorption percent of 1.5, porosity percent of 0.79, thermal expansion coefficient of 5.278×10-6 °C-1 and a whitenss index of 64.04. Compared to the typical bone china body with flexural strength of 36.9 MPa, density of 1.625 g.cm-3, water absorption percent of 8.04, porosity percent of 5.54, thermal expansion coefficient of 8.876×10-6 °C-1 and a whiteness index of 70.16, the mentioned physical and mechanical properties have been improved and only 8.7% of the whiteness index has been diminished. Also the microstructure of samples containing Anorthite were observed without thermal crack and almost uniform distribution of Anorthite and quartz crystals in the heterogeneous glass matrix.
Keywords: Thermal expansion coefficient, Anorthite, β-tricalcium phosphate.
