Bi-phase ceramic composite using an interpenetrating network

A secondary phase has been reinforced into a porous alumina (Al2O3) matrix using an interpenetrating network (IPN) method to enhance the mechanical properties of the porous matrix. To increase the addition effect of the secondary phase into the Al2O3 matrix, two types of SiO2 precursor were used: tetraethylorthosilicate (TEOS) of the silicate type and polydimethylsiloxane (PDMS) of the siloxane type. The PDMS does not undergo a sol–gel reaction, whereas the TEOS is converted into glass-phase SiO2 by a sol–gel reaction. This means that the siloxane type has a higher conversion ratio of precursor into the glass phase of SiO2 than does the silicate type. The mechanical properties of the composites prepared using TEOS and PDMS without sodium methoxide (NaOMe) have been improved, showing 12.9 ± 5.9 and 9.9 ± 6.4 MPa in fracture strength, respectively, and 17.2 ± 4.6 and 15.5 ± 6.9 GPa in elastic modulus, respectively, while the mechanical properties of the porous Al2O3 matrix were 6.0 ± 1.2 MPa and 8.0 ± 4.0 GPa in fracture strength and elastic modulus, respectively. However, the mechanical properties of the composite prepared using PDMS with NaOMe were higher than those of the composite prepared using TEOS with NaOMe, showing 25.3 ± 7.3 MPa and 26.3 ± 5.5 GPa in fracture strength and elastic modulus, respectively. The increase in mechanical properties was caused by the enhancement of glassification owing to the high conversion ratio of the SiO2 precursor, in the absence of a sol–gel reaction. Consequently, bi-phase composites with reasonable properties have been successfully prepared through the IPN method using inorganic precursors.