ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 56, (2) 107 - 111 (2012)


EFFECTS OF PH ON AGGLOMERATION STATE OF Al2O3 – ZrO2 (ZTA) NANOCOMPOSITE POWDERS SYNTHESIZED BY TARTARIC GEL METHOD
 
Tuncer Mustafa, Gocme Hasan,
 
Department of Ceramic Engineering, Dumlupı

Keywords: Composite material, Sol-gel, Agglomeration, pH
 

Alumina – 20 vol% zirconia (ZTA) nanocomposites were synthesized by the tartaric acid sol-gel method. The precursors gelled from solutions at different pH were prepared and then calcined from 1000 to 1500oC. Surface area measurement (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the synthesized powders. Control of agglomeration state was carried out by changing the pH of the solution. Weakly agglomerated powders were obtained at pH=6, whereas the solution at pH=1 revealed hard agglomerated powders, (agglomeration degrees, N, were found to be 16425 at pH=1 and 102 at pH=6, respectively). The pH dependence of agglomeration was explained by the dissociation behavior of tartaric acid at various pH environments. XRD results showed that the powders have been fully tetragonal phase at 1000oC, while they exhibited tetragonal zirconia with minor monoclinic phase as well as α-Al2O3 at 1500oC. The presence of α-Al2O3 in the nanocrystalline composite contributes the wide range of temperature stability for t-ZrO2 up to 1500oC. TEM micrograph confirmed that alumina and zirconia were dispersed homogenously. Mechanical properties (hardness and indentation fracture toughness) of sintered samples were also determined.


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