Innovnano, Coimbra, Portugal, has developed a ready-to-press 2mol% yttria-stabilised zirconia (2YSZ) with an outstanding fracture toughness. According to the company, Innovnano’s 2YSZ offers all the desired mechanical performance of 3YSZ, the current industry-standard powder of choice, combined with the highly desirable added benefit of high fracture toughness. Despite having a lower percentage of the stabilising yttria, Innovnano’s 2YSZ has the added benefit of ageing and stability comparable to that of 3YSZ. Innovnano’s 2YSZ, therefore, provides an excellent alternative to 3YSZ for physically demanding structural ceramic applications.
Recent testing by Innovnano and an independent laboratory has shown that the mechanical strength of 2YSZ remains above 1,000 MPa, while fracture toughness is significantly increased up to 14 MPa.m0.5. 2YSZ bars that had undergone Cold Isostatic Pressing (CIP) and conventional sintering were subjected to cyclic stress-strain ageing tests in saline solution, with all test pieces passing the ISO 13356 standard methodology of 1 million cycles at 320 MPa (maximum) and 20 Hz frequency without failure. The four-point bending strength was also determined for 2YSZ bars before and after the cyclic stress-strain experiment. After 106 cycles, the test showed only a 13% loss in flexural strength. Further cyclic stress-strain ageing experiments were also successfully performed (106 cycles at 20 Hz) using 1100 MPa as maximum pressure, highlighting the outstanding resistance of these 2YSZ powders to mechanical ageing.
The unique properties of Innovnano’s 2YSZ, combining enhanced fracture toughness with high levels of stability and ageing resistance, are attributed to the powder’s nanostructure, formed during Innovnano’s unique industrial synthesis process. All of the zirconia ceramics in the company’s range are manufactured using Innovnano’s proprietary Emulsion Detonation Synthesis (EDS) method. EDS involves a unique cycle of high temperatures, pressures and rapid quenching in a fully automated system, based on the detonation of two water-in-oil emulsions in a single step reaction. This produces nanostructured powders with guaranteed small grain sizes and high chemical homogeneity. In the case of 2YSZ, its nanostructure, as well as the EDS process itself, contributes to the increased powder stability.
2YSZ is the latest product to be added to Innovnano’s growing product portfolio. The desirable properties of 2YSZ mean that it is appropriate for hard-wearing applications, especially those that require a material with high fracture toughness. It is available from Innovnano as a ready-to-press powder for CIP and uniaxial pressing. It can also be incorporated as the zirconia phase of zirconia-toughened alumina/alumina-toughened zirconia (ZTA/ATZ), as well as other cermets.
Paul Newbatt, Sales & Marketing Director at Innovnano, commented, “Taking advantage of the energetic nature of our unique manufacturing process, we have developed a nanostructured 2YSZ powder that offers a high fracture toughness alternative to conventional micron-sized 3YSZ engineered ceramics. It provides the fracture toughness of a low-yttria containing YSZ with the stability of a higher yttria-containing YSZ, striking the balance between two key structural ceramics needs. We believe a powder with this unique combination of properties to be an exciting new development for the ceramics market.”
Innovnano told PIM International that further development of the new powder is underway to ensure its suitability for Ceramic Injection Moulding (CIM) applications. This new CIM powder is planned for later in the year (Q2 2017).