Amine-functionalized alumina colloidal particles were prepared using polyethyleneimine (PEI) for enhancing the infiltration process of silica based ceramic core. The surface properties of PEI-grafted alumina particles were adjusted to improve their dispersion behavior in aqueous suspension, and the surface charge was adjusted to enhance their adsorption behavior, in neutral pH atmosphere, via an electrostatic repulsion force with a fused silica matrix containing an implied strong negative charge. The characteristics of the surface-modified particles were optimized as shown by the C–H stretching vibration and N–H bending vibration from FT-IR spectra, and the surface charge alternated from −3 to 45 mV. As a result, the dispersion behavior in aqueous solvent was advanced as indicated by the decrease of the polydispersity index, decrease of the average size from 178 to 58 nm, and sharpness of the particle size distribution parabola. These improvements greatly contributed to the acceleration of the infiltration time and efficiency (up to 30 min). Consequently, the promptly infiltrated specimens improved the flexural strength from 3.2 to 10.2 MPa and reduced the linear shrinkage rate from 1.91 to 1.05% as well.