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 Chromium and molybdenum were introduced into alumina through gel synthesis. Both elements are soluble in aluminium hydroxide and low-temperature (〈1400°C) aluminium oxide. In the course of transformation from hydroxide to oxide, the evaporation-condensation of vapour phase (below 1000° C) causes shrinkage of the porous compact due to particle rearrangement and growth through capillary drag and adsorption. Subsequently, differences in agglomerate structure, grain growth, solute atmosphere and densification arise because of variations in the crystal lochemical behaviour of chromium and molybdenum. The solute atmospheres of chromia-vacancy and molybdenum metal reveal sub-grain boundaries and dislocations. In chromia-alumina solid solution these defects annihilate and contribute to densification (98%th) with increase in temperature to 1600° C. However, with further rise in temperature to 1700° C, the solid solution desinters to 85%th and creep cavities show transition from grain boundary to lattice creep. In Mo-Al2O3 composite the defects are locked by molybdenum solute, and as a result there is an insignificant increase in densification (30%th at 1600°C).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01161177
