Influence of Sintering on the Development of Alumina-Toughened …
171
Fig. 3 Thermally etched scanning electron micrographs showing microstructures of the developed
ATZ composites at 1600 °C, at (i) A lower magnification a conventional sintered and b microwave
sintered and (ii) A higher magnification c conventional sintered sample and d microwave sintered
sample. (Color figure online)
Since the sintered samples were non-conductive, they were coated with a thin
gold layer prior to examination or observation in a scanning electron microscope
(SEM). From Fig. 3a, c, and b, d shows different magnifications of the SEM micrographs for the convention sintered (CS) and microwave (MW) sintered composites.
From Fig. 3b, both white and dark gray phases for the t-ZrO 2 and Al 2 O 3 were
easily observed as pointed by the arrows. The microwave (MW) sintered sample was
applied to facilitate rapid heating under pressure-less conditions. Both dispersion
and densification of the powder particles occurred rapidly and did not get enough
time for grain growth resulting in a smaller grain when compared to the conventional
sintered (CS) samples. The developed microwave (MW) sintered samples revealed
a near uniform distribution in the matrix, and the grains were closely packed in
the matrix with evidence of grain refinement and resultant dense composites. From
Fig. 3a, it is easily observed that even though a near uniform distribution of the
reinforced particles was achieved, the grain size was not as significant as that for
the microwave (MW) sintered composite samples despite using the same sintering
temperature. However, from Fig. 3a–d, it is noticed that all the samples attained full
density with homogeneously dispersed grains of Al 2 O 3 and ZrO 2 in the alumina
171
Fig. 3 Thermally etched scanning electron micrographs showing microstructures of the developed
ATZ composites at 1600 °C, at (i) A lower magnification a conventional sintered and b microwave
sintered and (ii) A higher magnification c conventional sintered sample and d microwave sintered
sample. (Color figure online)
Since the sintered samples were non-conductive, they were coated with a thin
gold layer prior to examination or observation in a scanning electron microscope
(SEM). From Fig. 3a, c, and b, d shows different magnifications of the SEM micrographs for the convention sintered (CS) and microwave (MW) sintered composites.
From Fig. 3b, both white and dark gray phases for the t-ZrO 2 and Al 2 O 3 were
easily observed as pointed by the arrows. The microwave (MW) sintered sample was
applied to facilitate rapid heating under pressure-less conditions. Both dispersion
and densification of the powder particles occurred rapidly and did not get enough
time for grain growth resulting in a smaller grain when compared to the conventional
sintered (CS) samples. The developed microwave (MW) sintered samples revealed
a near uniform distribution in the matrix, and the grains were closely packed in
the matrix with evidence of grain refinement and resultant dense composites. From
Fig. 3a, it is easily observed that even though a near uniform distribution of the
reinforced particles was achieved, the grain size was not as significant as that for
the microwave (MW) sintered composite samples despite using the same sintering
temperature. However, from Fig. 3a–d, it is noticed that all the samples attained full
density with homogeneously dispersed grains of Al 2 O 3 and ZrO 2 in the alumina