Fine-grained Al2O3–ZrO2 composites by optimization of the processing parameters

Sarraf, Hamid; Herbig, R.; Maryska, Martin

doi:10.1016/j.scriptamat.2008.02.050

Cited by 22 publications

(11 citation statements)

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“…The stability of the suspension is tested by sedimentation tests, by measuring the zeta potential and the particle size in the suspension and by determining rheological parameters [6,8]. The goal of the presented study was the preparation of stable Al 2 O 3 and Al 2 O 3 -ZrO 2 suspension by electrosteric stabilization suitable for slip casting.…”

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confidence: 99%

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

et al. 2019

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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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confidence: 99%

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

et al. 2019

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“…Previously, several researchers examined various water-soluble anionic polyelectrolyte dispersants such as PAA, PMAA, and Darvan for the stabilization of low concentrated oxide powder slurries (alumina, titania, zirconia, etc.) with average particle size of less than 1 µm [34][35][36]. Recently, we have reported fabrication of a new type of very dense and fine-grained alumina-toughened zirconia (Al 2O3-ZrO2) bioceramic composite by optimizing processing parameters with emphasis on improving and controlling fine grain growth, which leads to formation of homogeneous compact desirable microstructures using colloidal processing [36].…”

Section: Introductionmentioning

confidence: 99%

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Preparation and colloidal dispersion of highly concentrated biocompatible nanoparticles suspensions are vital for fabrication of dense bioceramic nanocomposites with improved mechanical and microstructural properties for biomedicine applications. This paper presents formation and rheological characterization of highly concentrated biocompatible aqueous ZrO2 nanosuspensions for such applications. The rheological properties including viscosity (η), shear rate (γ), and shear stress (τ) were investigated in relation to a wide range of solid loading (ϕ, by weight = 75-78 mass%). Maximum solid loading (ϕmax) was estimated with a constant 0.9 mass% concentration of a new type of anionic polyelectrolyte Dolapix CE64, suitable for casting of materials. A colloidal model was proposed to visualize the effect of solid loading on colloidal stability, rheological behavior and green microstructure of samples after casting. The maximum solid loading (ϕmax) was estimated to be 77 mass% based on the dependence of both viscosity (η) and yield stress (τ0) on solid loading (ϕ). For further validation, the maximum solid loading was compared and fittedby different rheological flow models with a correlation factor r = 0.998 for Herschel-Bulkley model, r = 0.999 forPower law model and r = 0.920 for Bingham model at shear rate γ (50 s-1). All concentrated ZrO2 nanosuspensions exhibited shear-thinning behaviour. The results obtained from rheological measurements, scanning electron microscopy imaging and flow models validate our proposed hypothesis for prediction of maximum solid loading and visualization of quality of green microstructures after casting. These results contribute to preparation, characterization, and processing of highly concentrated bio/nanoparticles suspensions; aiming to fabricate highly dense bio/nanocomposite materials with specific functionality.

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“…Therefore, it is crucial to obtain dense, fine grained Al 2 O 3 -ZrO 2 composites with the zirconia grain size less than the critical size for spontaneous transformation. In order to obtain a homogeneous fine-grained microstructure after sintering, nanoparticles must be used [6]. The uniform dispersion * Corresponding author.…”

Section: Introductionmentioning

confidence: 99%

“…of zirconia particles in the alumina matrix can be controlled by homogeneous powder synthesis techniques [6,7]. A series of powder processing techniques have been investigated to synthesize homogenous powder mixture.…”

Section: Introductionmentioning

confidence: 99%