Elastic properties and damping behavior of alumina–zirconia composites at room temperature

Alumina (Al2O3) and zirconia (ZrO2) have good overall properties and thus are widely used oxide technical ceramics. The biggest drawback of Al2O3 is its low fracture toughness. In contrast, ZrO2 is relatively tough, but is also much more expensive. In order to improve the alumina toughness, composite ceramics are being developed. Slip casting technology has economic advantages over the conventional hot isostatic pressure technology, but problems may arise when preparing stable highly-concentrated suspensions (slip) for filling the mold. The purpose of this study is to prepare aqueous suspensions using 70 wt. % α-Al2O3, with 0, 1, 5 and 10 wt. % of added t-ZrO2. Suspensions were electrosterically stabilized using the ammonium salt of polymethylacrylic acid, an alkali-free anionic polyelectrolyte dispersant. Also, magnesium oxide in form of magnesium aluminate spinel (MgAl2O4) was used to inhibit the abnormal alumina grain growth during the sintering process. Minimum viscosities were used as stability estimators, where an increase in ZrO2 content required adding more dispersant. After sintering, the Vickers indentation test was used to determine the hardness and the indentation fracture toughness from the measurement of the crack length. Also, the brittleness index (Bi, μm−1/2) was calculated from values of Vickers hardness and the Vickers indentation fracture toughness. It was found that with increasing ZrO2 content the fracture toughness increased, while the hardness as well as the brittleness index decreased. Zirconia loading reduces the crystallite sizes of alumina, as confirmed by the X-ray diffraction analysis. SEM/EDS analysis showed that ZrO2 grains are distributed in the Al2O3 matrix, forming some agglomerates of ZrO2 and some pores, with ZrO2 having a smaller grain size than Al2O3.

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“…%, the relative density decreased and consequently the porosity has increased. Similar results were published previously [39].…”

Section: Resultssupporting

confidence: 93%

Hardness and Indentation Fracture Toughness of Slip Cast Alumina and Alumina-Zirconia Ceramics

et al. 2019

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“…Table 2, and ϕ the porosity, i.e. the volume fraction of pores), which is known to provide one of the lowest estimates of the porosity dependence of Young's modulus (which is often a quite realistic one for moderately high porosities) [20]. Other relations, in particular the power-law relation (Gibson-Ashby relation), yield much higher values and are known to provide appropriate predictions mainly for highly cellular materials with porosities above 70% [21].…”

Section: Young's Modulus and Its Dependence On Composition And Porositymentioning

confidence: 99%

Temperature dependence of Young׳s modulus of silica refractories

Gregorová

Černý

Pabst

et al. 2015

Ceramics International

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“…Now, for porous materials with statistically isotropic microstructures relative sound velocities (additional index “ r ”) can be defined by normalizing with the sound velocities of the dense materials (additional index “0”), that is,

\begin{equation}{\;}{V_{Tr\;{\mathrm{or}}\;Lr}} = \frac{{{V_{T\;{\mathrm{or}}\;L}}}}{{{V_{T0\;{\mathrm{or}}\;L0}}}}\;\end{equation}

which is more convenient for comparison with theoretical predictions. Predictions for the porosity dependence of the sound velocity 22 can be derived from the well‐known predictive models for elastic properties, including the Maxwell–Mori–Tanaka (MMT) relation, 23,24 the differential relation 24,25 or Gibson–Ashby relation for open‐cell foams, 26,27 the (Pabst–Gregorová‐type) exponential relation 28,29 and the self‐consistent model relation, 24,29 as well as the numerical (Pabst–Uhlířová) benchmark relation for partially sintered materials with concave porosity (overlapping solid sphere model) 30 and the one‐parameter (Pabst–Gregorová) percolation relation, 31 the latter with critical porosity

{\phi _c} =

0.36 (complement to the solid volume fraction of 0.64 for random close packing or maximally random jammed structure) 24 . In the following relations the porosity is denoted by ϕ and for simplicity all predictions are given here for Poisson's ratios sufficiently close to 0.2, if not noted otherwise (the generalization to other Poisson's ratios is straightforward, however, and may be invoked if needed) 22 …”

Section: Theoreticalmentioning

confidence: 99%

“…The sound velocity prediction based on the (Pabst–Gregorová‐type) exponential relation 28 is

\begin{equation}{\;}{V_r} = \sqrt {\frac{{{\mathrm{ex}}{{\mathrm{p}}^{\left( {\frac{{ - 2\phi }}{{1 - \phi }}} \right)}}}}{{1 - \phi }}} \;.\end{equation}

…”

Section: Theoreticalmentioning

confidence: 99%

Porosity dependence of sound velocities in partially sintered alumina, zirconia, ATZ, and mullite ceramics

Šimonová,

Pabst

2023

J Am Ceram Soc.

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Young's modulus and sound velocities of partially sintered alumina, zirconia, ATZ, and mullite ceramics with a broad range of porosities determined via the impulse excitation technique (IET) and the ultrasonic wave propagation pulse‐echo technique (UPT) are found to be in good agreement and exhibit sigmoidal curves as a function of the sintering temperature. The porosity dependence of the relative values of Young's modulus and sound velocities is either close to or below (but never above) the prediction based on an exponential relation, and none of them is significantly below the prediction based on a percolation relation or a recently proposed numerical benchmark relation for overlapping monosized spheres. Values are lower when concave pores or irregular anisometric grains are dominating. The correlation of the normalized longitudinal wave velocities and relative transverse wave velocities, with VL/VT ratios ranging from 0.50 to 1.91, is well predicted by models for Poisson's ratios between 0.35 and 0.2.

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Elastic properties and damping behavior of alumina–zirconia composites at room temperature

Cited by 40 publications

References 29 publications

Hardness and Indentation Fracture Toughness of Slip Cast Alumina and Alumina-Zirconia Ceramics

Hardness and Indentation Fracture Toughness of Slip Cast Alumina and Alumina-Zirconia Ceramics

Temperature dependence of Young׳s modulus of silica refractories

Porosity dependence of sound velocities in partially sintered alumina, zirconia, ATZ, and mullite ceramics

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