Premium
Grain‐Boundary Viscosity of Polycrystalline Silicon Carbides
Author(s) -
Pezzotti Giuseppe,
Kleebe HansJoachim,
Ota Ken'ichi
Publication year - 1998
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1998.tb02770.x
Subject(s) - materials science , grain boundary , crystallite , composite material , intergranular corrosion , relaxation (psychology) , silicon carbide , grain size , microstructure , viscosity , metallurgy , psychology , social psychology
Internal friction experiments were conducted on three SiC polycrystalline materials with different microstructural characteristics. Characterizations of grain‐boundary structures were performed by high‐resolution electron microscopy (HREM). Observations revealed a common glass‐film structure at grain boundaries of two SiC materials, which contained different amounts of SiO 2 glass. Additional segregation of residual graphite and SiO 2 glass was found at triple pockets, whose size was strongly dependent on the amount of SiO 2 in the material. The grain boundaries of a third material, processed with B and C addition, were typically directly bonded without any residual glass phase. Internal friction data of the three SiC materials were collected up to similar/congruent2200°C. The damping curves as a function of temperature of the SiO 2 ‐bonded materials revealed the presence of a relaxation peak, arising from grain‐boundary sliding, superimposed on an exponential‐like background. In the directly bonded SiC material, only the exponential background could be detected. The absence of a relaxation peak was related to the glass‐free grain‐boundary structure of this polycrystal, which inhibited sliding. Frequency‐shift analysis of the internal friction peak in the SiO 2 ‐containing materials enabled the determination of the intergranular film viscosity as a function of temperature.