Physical properties of sintered alumina doped with different oxides

Abstract

Corundum (α-alumina) is a suiTab. material for usage in various industry fields owing to its chemical stability, electrical and mechanical features. It is known that properties of ceramics could be modified by addition of different oxides, as well as by changing the consolidation parameters. In this respect, alumina was doped with 1 wt.% of Cr 2 O 3 , Mn 2 O 3 and NiO, followed by 1 hour of mechanical activation in a high-energy planetary ball mill. A sensitive dilatometer was used for sintering of powder mixtures up to 1400 o C and recording the obtained dilatation. The final density varied between cca. 1.9 and 3.3 g/cm 3. Microstructural changes were detected by SEM measurements. Changes in electrical permittivity and loss tangent were associated with the preparation conditions (types of additives, duration of mechanical activation). For a given mixture, the sintering increases the relative permittivity and decreases losses, exhibiting the optimal values of 8.32 and 0.027, respectively, for the sample activated 60 minutes and sintered, with the addition of MnO 2. Mechanical measurements indicate significant differences in strength with the addition of different transition metal oxides. Samples with Mn and Ni, activated and sintered, with strength of 121 and 86 MPa, respectively, have a significantly higher tensile strength than the other tested samples, due to their more compact microstructures.

Electrochemical and structural properties of Ni(II)-alumina composites as an annealing temperature function

“…It is known that properties of alumina can be modified by addition of different metals or metal oxides, as well as by changing the consolidation parameters [8,9].…”

Numerical modeling of the porosity influence on the elastic properties of sintered materials

“…The effects of clustering and interfacial debonding of particles on the mechanical properties of sintered materials were the topic of majority of the prior studies. Number of studies confirmed the fact that less porosity in the material microstructure leads to higher material stiffness and strength, while an irregular shape of pores strongly influences the material fracture toughness and strength [3][4][5][6][7]. But sometimes porosity is quite necessary e.g.…”

“…Typical microstructure of sintered material, after sintering process, usually leads to a denser microstructure, with closed pores and parts of well sintered grains as presented at Fig. 1 (SEM micrograph of sintered alumina at 1400 o C [3]). To fully simulate such a microstructure, a three-dimensional (3D) model of a random distribution of pores shape and size is required.…”

Effect of Al(OH)3 and La2O3 on the sintering behavior of CaO granules via CaCo3 decomposition

“…The optimal additive amount of Al(OH) 3 and La 2 O 3 was 1.5 wt%, which were the same as that in the humidity chamber.It should be noticed that the hydration rate was gradually accelerated with the process of soaking days. As we know, even a small addition of oxide influences the densification, reducing the sintering temperature, suppressing or promoting the grain growth, modifying the microstructure and mechanical properties [21]. It is the general phenomenon that sintering aids could form a low-viscosity ternary liquid phase to promote densification via liquid-phase sintering, the process of sintering was accelerated by the decomposition product of Al(OH) 3 .…”