Sol-Gel Based Extrusion of Alumina Fibers

ABSTRACT

Alumina fibers were prepared by sol-gel method using an in-house fabricated extruder. The starting material used for the preparation of alumina sol was aluminium-tri-isopropoxide. A suitable binder was added to the sol and aged at room temperature for gelation to occur. When the sol became a paste appropriate for extrusion, the fibers were drawn through the extruder and dried at room temperature and subsequently sintered at 1200°, 1400°, and 1600°C in air. It was found that regardless of sintering temperature, the XRD traces indicated that the only phase present in sintered fibers was α-Al₂O₃. Thermogravimetric analysis of the extruded fibers indicated that most of the volatile compounds were burned out at 500°C. The DTA and FTIR studies confirmed the phase transition to α-Al₂O₃ and this was in good agreement with the XRD analysis. The SEM investigation revealed that a dense microstructure formed when fibers sintered at 1600°C. In addition, the SEM micrograph revealed that an intergranular fracture was the predominant fracture mode. Mechanical tests indicated that the optimum tensile strength was achieved for fibers sintered at 1600°C.

Keywords:

• Al₂O₃
• Alumina fibers
• Extrusion
• Fracture
• Grain size
• Infrared spectroscopy
• Mechanical properties
• Microstructure
• Porosity
• SEM microscopy
• Sintering
• Sol-gel process
• Strength
• Thermal analysis
• X-ray diffraction

ACKNOWLEDGMENT

The authors are thankful to the Ministry of Human Resources and Development, Government of India for financial support to this work.