Production of Alumina Matrix Nanocomposites with Inclusions of TiC and TiB_2, via Reactive Milling

摘要

One of the most recent alternatives on development of toughness in ceramic materials is the addition of nanometric particles of a second phase into a ceramic matrix. These systems are denominated ceramic matrix nanocomposites. In this work we describe the production of alumina matrix nanocomposites with inclusions of TiC and TiB_2 using as precursors, mixtures of nanometric powders prepared by reactive milling. The reactive milling was performed in high-energy mill SPEX Mixer/Mill 8000, through the reactions: 4Al + 3C +3TiO_2 and TiO_2 + B_2O_3 + 10/3Al, producing alumina with TiC and TiB_2, respectively. The reaction products were formed as strong agglomerates of nanometric particles and conventional ball milling performed the deagglomeration. The dispersed powders were characterized by X-ray diffraction and differential scanning calorimetry. The reaction products were mixed with a commercial alumina (Sumitomo AKP-53) to produce final composites with 5-weight percent and 10-weight percent of inclusions by ball milling in ethyl alcohol. The alcohol suspensions were dried by heating at 70 deg C. The powder mixtures were pressed and sintered at 1500 deg C and 1600 deg C in high-vacuum atmosphere for 1 hour. The sintered samples reached final relative density of 95-97 percent TD and the high resolution scanning electron microscopy microstructure analysis has shown the dispersion of the inclusions with a few remaining agglomerates from the synthesis process.