Si3N4/TiC nanocomposite ceramics have been fabricated by hot pressing technique with Al2O3 and Y2O3 as additives. The results showed that well dispersed composite powder was carried out by adding dispersant and adjust...Si3N4/TiC nanocomposite ceramics have been fabricated by hot pressing technique with Al2O3 and Y2O3 as additives. The results showed that well dispersed composite powder was carried out by adding dispersant and adjusting pH values of suspensions. Remarkable increase in flexural strength at room temperatures was obtained by adding nanoparticles in Si3N4 matrix with 10% （wt pct） of nano-Si3N4 and 15% of nano-TiC. The flexural strength, fracture toughness and hardness were 1025 MPa, 7.5 MPa.m^1/2 and 15.6 GPa, respectively. The microstructures of materials were analyzed by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）, which indicated that TiC nanoparticles distribute in the matrix and at the grain boundaries. According to the fracture form, low contents of nano particles could refine matrix grains and lead to the crack deflection as well as crack pinning. The multiplex microstructure was formed by mixing nano-Si3N4 particles. The crack trajectories exhibited crack deflection, rod-like grain bridging and pull-out.展开更多
The Si3N4-based nanocomposites reinforced with micro ZrO2 and nano SiC particles were prepared by polarity dispersant and vacuum-sintering technology. The mechanical properties and microstructures were tested. The res...The Si3N4-based nanocomposites reinforced with micro ZrO2 and nano SiC particles were prepared by polarity dispersant and vacuum-sintering technology. The mechanical properties and microstructures were tested. The results show that appropriate amount of micro ZrO2 and nano SiC particles, not only enhance the microhardness, but also block the excessively growth of β-Si3N4 and β-Si3N4 grains, so they finally all grow up to uniformly pole-shaped grains. This process is similar to the strengthening and toughening mechanism of grain whiskers and makes a remarkable improvement on the toughness. Compared with Si3N4 ceramic, the toughness of Si3N4/SiC/ZrO2 nanocomposites are increased from 6.2 MPa·m1/2 to 11 MPa·m1/2.展开更多
基金supported by the National Natural Sci ence Foundation of China(No.50105011)the Foundation for the author by the National Excellent Doctoral Disserta tion of China(200231)+2 种基金the Natural Science Foundation of Shandong Province(Y2004F14)the SRF for ROCS([2002]247),MOE,Chinathe SRF for ROCS(2002[247]),SEM.
文摘Si3N4/TiC nanocomposite ceramics have been fabricated by hot pressing technique with Al2O3 and Y2O3 as additives. The results showed that well dispersed composite powder was carried out by adding dispersant and adjusting pH values of suspensions. Remarkable increase in flexural strength at room temperatures was obtained by adding nanoparticles in Si3N4 matrix with 10% （wt pct） of nano-Si3N4 and 15% of nano-TiC. The flexural strength, fracture toughness and hardness were 1025 MPa, 7.5 MPa.m^1/2 and 15.6 GPa, respectively. The microstructures of materials were analyzed by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）, which indicated that TiC nanoparticles distribute in the matrix and at the grain boundaries. According to the fracture form, low contents of nano particles could refine matrix grains and lead to the crack deflection as well as crack pinning. The multiplex microstructure was formed by mixing nano-Si3N4 particles. The crack trajectories exhibited crack deflection, rod-like grain bridging and pull-out.
文摘The Si3N4-based nanocomposites reinforced with micro ZrO2 and nano SiC particles were prepared by polarity dispersant and vacuum-sintering technology. The mechanical properties and microstructures were tested. The results show that appropriate amount of micro ZrO2 and nano SiC particles, not only enhance the microhardness, but also block the excessively growth of β-Si3N4 and β-Si3N4 grains, so they finally all grow up to uniformly pole-shaped grains. This process is similar to the strengthening and toughening mechanism of grain whiskers and makes a remarkable improvement on the toughness. Compared with Si3N4 ceramic, the toughness of Si3N4/SiC/ZrO2 nanocomposites are increased from 6.2 MPa·m1/2 to 11 MPa·m1/2.
