Abstract. To achieve excellent properties of polymer blends and composites, good dispersion and uniform distribution of second component or filler in the matrix are often required. However, more and more evidences reveal that uniform distribution is not always the best. To further prove this idea, in this work, we purposely designed and prepared different samples of isotactic polypropylene (iPP)/elastomer or iPP/!-nucleating agent with uniform and non-uniform distribution of the modifiers via stacking the blending sheets in different sequence. It was found that for a given amount of toughening agent, the impact strength of polymer blends with non-uniform distribution of elastomer or !-nucleating agent could be much higher than its uniformly dispersed counterpart, while the tensile strength and tensile modulus remain relatively constant. The instrumented impact test confirmed that among the samples with different layered structures, the absorbed energy during crack initiation differs little from each other. Whereas absorbed energy during crack propagation process shows the same trend as final impact strength, making it the controlling parameter during the impact process. When cracks are initiated at higher toughening agents content side, the relatively smooth fracture surfaces near the crack edge area proved that they absorb small energy and the adjacent inner part showed obviously plastic deformation, corresponding to higher energy absorption. Our work demonstrates again that design and control of the hierarchical structure of polymer articles is vital for high performance properties and non-uniform distribution of filler could be much better than the uniform distribution.

The single nano-scale and multi-phase nanocomposite ceramic materials including Al2O3/Al2O3n/SiCn and Al2O3/Ti(C0.7N0.3)n/SiCn are successfully fabricated. Their mechanical properties are better than those of the single-phase alumina material and conventional alumina matrix materials. The multi-scale and single-phase nanocomposite ceramic tool material Al2O3/SiCμ/SiCn is also successfully fabricated. Its flexural strength and fracture toughness is higher than those of single-scale materials Al2O3/SiCμ and Al2O3/SiCn. The multi-scale and multi-phase nanocomposite ceramic tool material Al2O3/TiCμ/TiNn is finally developed by incorporation and dispersion of micro-scale TiC particle and nano-scale TiN particle in alumina matrix, which can get higher flexural strength and fracture toughness than those of Al2O3/TiC ceramic tool material without nano-scale TiN particle. The coexistent function of nano-scale Al2O3 or Ti(C0.7N0.3), nano-scale SiC and TiN can reduce the sintering temperature and sintering duration time as well as the grain size, and improve the material densification and mechanical properties. The nano-scale SiC grains locating along the grain boundary and inside the micro-scale alumina can form the hybria intergranular-intragranular microstructure which can result in hybria intergranular-transgranular fracture and improve the mechanical properties of the ceramic material. Crack deflection, forking and bridging effects are the main cause for improving the fracture toughness of the materials including Al2O3/Ti(C0.7N0.3)n/SiCn and Al2O3/TiCμ/TiNn.