Failure of ceramic materials used in high-temperature applications is initiated by the formation of creep pores. Thus, investigating the kinetics of creep pore formation, especially the evolution of their size distribution, is of key importance in obtaining an understanding of the failure mechanisms. This investigation is concerned with recent progress in the characterization of creep pores in liquid-phase sintered alumina by means of small-angle neutron scattering (SANS) techniques. It is shown that creep pores ranging from about 40 nm to >1 μm are present even after the small amount of creep deformation at the end of primary creep. For the first time a strong correlation between the size of glass pockets and the creep pores has been determined. The results give new insights into pore formation in liquid-phase sintered ceramics.

The formation of pores during creep initiates the failure of ceramic materials used for high-temperature applications. Thus, the determination of pore sizes and their number densities is of key importance in obtaining an understanding of the failure mechanisms. In former investigations it was shown that small-angle neutron scattering (SANS) and beam broadening (BB) are powerful experimental techniques for the investigation of pore size distribution. In this paper it is noted that in addition to these methods complementary high resolution SANS experiments have to be performed in order to determine pore size distributions reliably in the size range from a few nanometers to several micrometers. The evolution of such pore size distributions have been observed during the creep of liquid-phase sintered alumina.

The creep behaviour of high-alumina refractories containing increasing amounts of a fused mullitezirconia aggregate (MZA) of eutectic composition was studied experimentally. The MZA has been added with the intention of improving the work of fracture and the thermal shock resistance through microcrack toughening. The creep resistance was found to decrease with increasing MZA content. This was attributed to the formation of an increasing fraction of a substructure composed of small grains and an amorphous binder phase situated between the large agglomerate particles. Creep deformation mainly occurred within these finegrained interagglomerate regions, but rate controlled by mullite formation kinetics as an accommodation process. This interpretation is substantiated by the measured values of the stress exponent (n = 1.2–2.7) and the activation energy for creep (Q ≈ 720 kJmol) and by the finding that the creep rate was distinctly reduced by a preceding heat treatment.

Failure of ceramic materials for high-temperature applications is initiated by the formation of creep pores. Thus, the determination of the sizes and number densities of pores induced during creep testing is one key to an understanding of their failure mechanisms. Small-angle neutron scattering (SANS) techniques are for this purpose one of the most potential tools as demonstrated by an analysis of creep pores in liquid-phase-sintered, hot isostatically pressed alumina. The exploration of creep induced pores requires the analysis of SANS intensity over an extremely extended region of scattering vectors, the scanning of which needs joint use of both conventional SANS and double crystal diffractometry (DCD), an ultra-small-angle scattering technique.

Failure of ceramic materials for high-temperature applications is initiated by the formation of creep pores. Thus, the determination of the sizes and number densities of pores induced during creep testing is one key to a understanding of their failure mechanisms and related life-time predictions. For this purpose small-angle neutron scattering (SANS) techniques are one of the most potential tools as demonstrated by an analysis of creep pores in liquid-phase-sintered, hot isostatically pressed alumina. The exploration of creep induced pores requires the analysis of SANS intensity over an extremely extended region of scattering vectors, the scanning of which needs joint use of both conventional SANS and double crystal diffractometry (DCD), an ultra small angle scattering technique.