ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract A nanocomposite material fabricated by hot pressing in the form of nanometre-sized Si3N4 particles dispersed in an Al2O3 matrix has been shown to exhibit enhanced mechanical properties compared with monolithic matrix material. It was observed by transmission electron microscopy (TEM) for the first time that the alumina grains were in the shape of elongated columns with aspect ratios in the range 2.5–4. The presence of liquid phase during sintering was found to be responsible for the appearance of columnar grains. Regular hexagon-shaped larger β′-Sialon grains formed during sintering were mainly situated at grain boundaries of the matrix material while irregular smaller dispersoids were trapped within the alumina grains. The improvement in the mechanical properties of the nanocomposite is attributed to the change in fracture mode from intergranular fracture to transgranular fracture, the “self-reinforcement effect” arising from the elongated columnar grains of the matrix, as well as the “pinning effect” due to the existence of intergranular β′-sialon particles. It was revealed that the trapped particles have an α-Al2O3 structure with partial sites of aluminium and oxygen atoms substituted by silicon and nitrogen atoms, which is also likely to lead to the strengthening of the composite.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1018550727099
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