Archive for September, 2008
SEM in-situ investigation on failure of nanometallic film/substrate structures under three-point bending loading
by Wang, Xi-Shu; Yan, Cheng-Kun; Li, Ying; Xue, Yibin; Meng, Xiang-Kang; Wu, Bi-Sheng
Three-point bending tests on nanocrystalline Cu or Cu/Ni-film/Cu-substrate samples were conducted in-situ with scanning electron microscopy (SEM) observations. The SEM in-situ observations show undulation deformation of the surface of thin film, as the thin film fractures easily at the concave–convex points of deformation and multi-cracks appear on the surface of the thin film in a periodic fashion. The critical wavelength of undulation is calculated based on experimental observations, which are comparable with the theoretical predictions. For the Cu/Ni multi-layered films/substrate structures, the micro-cracking pattern depends on the interfacial strength between the film and the substrate, rather than the interfacial strength between the layers of films.
DOI: 10.1007/s10704-008-9257-8
Online Date: 9/15/2008
Print publication date: 6/1/2008
View article on SpringerLink
Effects of microstructure on flexural strength of biomorphic C/SiC composites
by Park, Hee S.; Jang, Jong J.; Lee, Kyong H.; Lim, Kwang H.; Park, Sang B.; Kim, Yun C.; Hong, Soon H.
Biomorphic C/SiC composites were fabricated from different kinds of wood by liquid silicon infiltration (LSI) following a two-step process. In the first-step, the wood is converted into carbon preforms by pyrolysis in a nitrogen atmosphere. The carbon preforms are then infiltrated by silicon melt at 1,560°C under vacuum to fabricate C/SiC composites. The mechanical properties of the C/SiC composites were characterized by flexural tests at ambient temperature, 1,000, and 1,300°C, and the relationship between mechanical properties and microstructure was analyzed. The flexural strength of the biomorphic composites was strongly dependent on the properties of the carbon preforms and the degree of silicon infiltration. The flexural strength increased with increasing SiC content and bulk density of composite, and with decreasing porosity in the C/SiC composite. An analysis of fractographs of fractured C/SiC composites showed a cleavage type fracture, indicating brittle fracture behavior.
DOI: 10.1007/s10704-008-9259-6
Online Date: 9/13/2008
Print publication date: 6/1/2008
View article on SpringerLink
