Functionally Graded Al2O3–CTZ Ceramics Fabricated by Spark Plasma Sintering

Abstract

We studied the fabrication of functionally graded Al2O3–CeO2-stabilized-ZrO2 (CTZ) ceramics by spark plasma sintering. The ceramic composite exhibits a gradual change in terms of composition and porosity in the axial direction. The composition gradient was created by layering starting powders with different Al2O3 to CTZ ratios, whereas the porosity gradient was established with a large temperature difference, which was induced by an asymmetric graphite tool configuration during sintering. SEM investigations confirmed the development of a porosity gradient from the top toward the bottom side of the Al2O3–CTZ ceramic and the relative pore volume distributed in a wide range from 0.02 to 100 µm for the samples sintered in asymmetric configuration (ASY), while for the reference samples (STD), the size of pores was limited in the nanometer scale. The microhardness test exhibited a gradual change along the axis of the ASY samples, reaching 10 GPa difference between the two opposite sides of the Al2O3–CTZ ceramics without any sign of delamination or cracks between the layers. The flexural strength of the samples for both series showed an increasing tendency with higher sintering temperatures. However, the ASY samples achieved higher strength due to their lower total porosity and the newly formed elongated CeAl11O18 particles.

Preparation and Characterization of Fibrous Alumina and Zirconia Toughened Alumina Ceramics with Gradient Porosity

“…Gradient microstructures were successfully developed in the fibrous ceramic body by establishing a temperature gradient during sintering. The temperature difference is established between the top and bottom sides of the samples during the SPS sintering process applying an asymmetric graphite configuration, similar to that reported in our previous studies [ 11 , 13 ]. In Figure 3 , we show the recorded temperature at the top (T 1 ) and bottom side (T 2 ) of the sample as a function of set temperatures during the sintering process in the STD and ASY series.…”

“…In contrast, CeO 2 -stabilized ZrO 2 shows much better LTD resistance with excellent mechanical properties. CeAl 11 O 18 phases can also be formed during SPS due to solid-state reactions between Ce 2 O 3 and Al 2 O 3 , as was reported in a previous study [ 13 ]. It should be noted that composite fibre with highly homogeneous distributions of Al 2 O 3 and ZrO 2 phases, as well as the intragranular position of ZrO 2 , are promising in avoiding adverse reactions.…”

“…The bottom side of the samples had a typically higher temperature than the top side. Notably, the largest ΔT occurred always in the heating period and gradually decreased as the sintering progressed, the possible reasons for which we have discussed in our previous studies [ 11 , 13 ]. The temperature difference between the top and bottom sides also varied with sintering set temperature: it increased with the sintering temperature, reaching a max.…”

“…Gradient porosity structures have also attracted interest in medicine for tissue regeneration, as they provide porosity with proper mechanical strength. In our previous studies, we showed a simple way to prepare a ceramics body with gradient porosity, employing asymmetric graphite configuration during SPS [ 11 , 13 ].…”

Semisolid state sintering behavior of aluminum-stainless steel 316L-nickel composite materials in powder metallurgy

“…Despite these benefits, composite materials have an abrupt shift of characteristics at the interface, which can lead to components failure by (delamination) [5]under excessive operating conditions in which delamination is a failure mode in which a material cracks into layers. Delamination may occur in a number of materials, such as multilayer composites [6] and concrete. Layer separation may cause failure in metals such as steel rolling [7], [8].…”