Study on Metakaolin-Based Geopolymer and Its Use on Joining Alumina
Date Issued
2015
Date
2015
Author(s)
Hsu, Cheng-Yen
Abstract
The joining of ceramic materials is a challenging issue. The primary purpose of the present study explores the use of metakaolin-based geopolymers to bond alumina substrates. The geopolymer mortar is in liquid form before bonding. A strong structure is achieved after curing. In the present study, sodium hydroxide is able to activate the reactions in geopolymer. The sodium content is a critical factor for geopolymers; the sodium content in the geopolymer in the present study is varied. The resulting microstructure and mechanical properties of the Al2O3/geopolymer/Al2O3 joined specimens are measured. The results demonstrate that excess sodium ions locate in the interstices of the structure, making it difficult to form a cross-linked frame, thus reduces the degree of polymerization. Compressive strength test shows a decrease for the specimens with the sodium content of 10.7%. The FTIR analysis indicates that the degree of polymerization is decreased as more sodium is introduced. Moreover, because sodium is relatively volatile, the specimens with high sodium content suffered a severe weight loss and deformation. As the temperature is raised to 700°C, amorphous geopolymer transforms to crystalline nepheline. After examined the microstructure and composition of the trilayer specimens, a sodium oxide layer was found at the interface. This interlayer enhances the adhesion strength between geopolymer and alumina substrate. The steady-state energy release rate measured from the four-point bending test also exhibited a positive correlation with the sodium content. A low thermal conductivity was observed for the trilayer specimens.
Subjects
Geopolymer
Al2O3
Bonding
Interfacial strength
Thermal conductivity
Type
thesis
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