Improving the Strength of ZTA Foams with Different Strategies: Immersion Infiltration and Recoating

Abstract

The combination of high strength and toughness, excellent wear resistance and moderate density makes zirconia-toughened alumina (ZTA) a favorable ceramic, and the foam version of it may also exhibit excellent properties. Here, ZTA foams were prepared by the polymer sponge replication method. We developed an immersion infiltration approach with simple equipment and operations to fill the hollow struts in as-prepared ZTA foams, and also adopted a multiple recoating method (up to four cycles) to strengthen them. The solid load of the slurry imposed a significant influence on the properties of the ZTA foams. Immersion infiltration gave ZTA foams an improvement of 1.5 MPa in compressive strength to 2.6 MPa at 87% porosity, only resulting in a moderate reduction of porosity (2–3%). The Weibull modulus of the infiltrated foams was in the range of 6–9. The recoating method generated an increase in compression strength to 3.3–11.4 MPa with the reduced porosity of 58–83%. The recoating cycle dependency of porosity and compression strength is nearly linear. The immersion infiltration strategy is comparable to the industrially-established recoating method and can be applied to other reticulated porous ceramics (RPCs).

Refitting of Zirconia Toughening into Open-Cellular Alumina Foams by Infiltration with Zirconyl Nitrate

“…Interestingly, the porosity-corrected strength of the ZTA foams made by the alumina hollow strut infiltration, with subsequent refitting of the ZrO 2 transformation toughening phase via ZrO(NO 3 ) 2 , is superior to ZTA foams, which were hollow strut-infiltrated with a dispersion of ZTA powder directly [26,28]. For these RPCs the normalized compressive strength is in line with pure, hollow strut-infiltrated alumina foams (Figure 12).…”

“…In the present work, the concept of the hollow strut infiltration in alumina RPCs is combined with the transformation toughening through ZrO 2 grains within the Al 2 O 3 matrix. However, in contrast to previous studies [26,28], the zirconia phase is not provided as a component in the ceramic raw material. Instead, it is loaded into the strut material via capillary force-driven infiltration of the porosity within the alumina-infiltrated ceramic strut material using a zirconia precursor solution.…”

“…This problem is circumvented for the hollow strut infiltration, where cavities inside the strut material are filled preferably without a significant impact on porosity and thickening of the ceramic struts. The infiltration can be performed with a ceramic dispersion of the same raw material as the struts are made of, as well as a different ceramic phase [14,25,26,27,28,29]. Furthermore, the infiltration process can be performed at elevated temperature, either by using a melt or a reactive infiltration technique, and has been essentially applied in the manufacturing of Si-SiC foams for high temperature applications [30,31,32].…”

Green Preparation and Dry Sliding Wear Properties of a Macro-ZTA/Fe Composite Produced by a Two-Step Method

“…In recent years, researchers investigated various iron and steel matrix composites, such as TiC-Stainless steel composite [5,6], WC/Fe composite [7,8], and ZTAp/iron composite [9]. Among these composites, ZTA particle reinforced iron matrix composite is a promising wear-resistant composite material, in which ZTA particle has a high hardness and toughness, thermal shocks resistance, and a relatively close thermal expansion coefficient with iron [10,11].…”

Tailoring of the Wetting Behavior of Alumina Dispersions on Polymer Foams by Methylcellulose Addition: A Route Toward Mechanically Stable Ceramic Replica Foams

“…The second strategy, post‐treatment of the replica foams, includes a repeated coating of the as‐received foams as well as a selective filling of the hollow strut cavities present after the template removal . These techniques can selectively mend the specific defects in ceramic replica foams resulting in a significantly improved strength at a moderate reduction of the total porosity.…”