การเตรียมและการวิเคราะห์สมบัติของเซรามิกซิลิคอนไนไตรด์สำหรับงานทันตวัสดุ

• Main Author: รญา วนานุรักษาวงศ์
• Other Authors: ธนากร วาสนาเพียรพงศ์
• Format: Theses and Dissertations
• Language: Thai
• Published: จุฬาลงกรณ์มหาวิทยาลัย 2009
• Subjects: Silicon nitride; Dental materialsซิลิกอนไนไตรด์; ทันตวัสดุ
• Online Access: https://digiverse.chula.ac.th/Info/item/dc:34947
• Institution: Chulalongkorn University

Silicon nitride ceramic is an excellent material that has high strength, hardness, toughness, and bio-inertness. These properties are interested to apply for dental core material preparation. In this research, white silicon nitride ceramic was prepared from a mixture of alpha silicon nitride 89 % wt with sintering aid at a weight ratio of silica : magnesia : yttria as 3:3:5, respectively. The mixture was ball milled for 24 h using ethanol as a medium and added 1 %wt of polyvinyl butyral as a binder. After drying, the mixed powder was formed by hydraulic pressing and binder burnout at 600 °C in air. Specimens were pre-sintered at 1450 °C for 2 h in nitrogen atmosphere for the suitable hardness before machining to be an artificial dental core shape. The specimens were then sintered again at 1650 °C for 2 h in nitrogen atmosphere. Firing shrinkage was 19.9% which closed to a popular commercial zirconia block for dental materials. The sintered silicon nitride specimens represented the synthetic dental core were paintbrush coated by a veneer paste composed of borosilicate glass powder (<150 micrometer, Pyrex) with 5 %wt of zirconia powder (3 %wt Y₂O₃ - partial stabilized zirconia) and 30 %wt of polyvinyl alcohol (5 %wt solution). After coating the veneer on the silicon nitride specimens, the firing was performed in electric tube furnace between 1000-1200 °C. The specimens fired at 1100 °C for 15 min consisting small amount of cristobalite which is the effect of zirconia addition. The veneered specimens show good bonding, smooth and glossy without defect and crazing. The veneer has thermal expansion coefficient as 3.98x10⁻⁶ °C⁻¹, rather white and semi opaque, the Vickers hardness as 4.0 GPa which is closely to the human teeth.