technical ceramic solutions

Tag Archives: zirconia

Alumina is Harder than Zirconia, So It Must be More Wear Resistant?

Although it’s commonly accepted that hardness equates with wear resistance, it’s not always the case. In sliding wear environments, hard counter faces that do not interact with each other are an advantage. The engineering grades of Alumina are typically 25-50% harder than zirconia grade so in sliding wear environments or pure abrasive wear, where third body abrasive wear particles are present, alumina often outperforms Zirconia.

However, in erosive wear environments such as those caused by an abrasive slurry impacting a wear part such as an oilfield valve, Zirconia can be the best performer as it’s high toughness reduces the spread of impact cracks and the micro fracture of the surface which generate erosive wear debris and surface damage.

When running an engineering ceramic against a dissimilar material it’s not always the case that the softer material performs poorly. Y-TZP running against Y-TZP has been shown to be a very poor wear surface combination, whereas, Y-TZP running against cast iron provides a better overall wear performance than the harder, alumina/cast iron combination.

Although its beyond this article to delve too deep into the tribology of ceramic interfaces, in Zirconia on Zirconia contact it’s the low thermal conductivity of the Zirconia that can be a negative factor, as the frictional heat generated in like on like sliding does not dissipate from the surface and the surface hardness decreases with a follow on increase in wear related damage.

Innovnano’s 3YSZ nanopowder – an ideal material for hip and knee implants

Coimbra, 22 May 2013 – Innovnano, an expert manufacturer of high performance ceramic powder, has developed 3 mol % yttria stabilised zirconia powder (3YSZ) – an advanced technical ceramic with medical device applications. Thanks to a uniform nanostructure and formation of a high stability phase under pressure, Innovnano’s 3YSZ combines extreme component strength and fracture-resistance with enhanced biocompatibility, making it the ideal ceramic material for extended-life orthopaedic implants, particularly knee and hip replacements. With advanced mechanical and tribological performance as well as ageing resistance, Innovnano’s 3YSZ powder offers an attractive solution to medical implant manufacturers, which, through increased implant lifetime, can offer their customers reduced time, costs and morbidity through fewer repeat, invasive procedures.    

Innovnano’s 3YSZ is manufactured using the company’s patented Emulsion Detonation Synthesis (EDS) technology, producing a highly pure, nanostructured ceramic powder with desirable homogeneity and an even distribution of yttria.  Stemming from the powders’ nanostructure, the 3YSZ can be sintered at lower temperatures, to keep grain size to a minimum. The resulting high density ceramic provides excellent mechanical performance and exceptional bending strength – an essential property for orthopaedic implants which are put under constant mechanical stresses and strains. Furthermore, thanks to the small grain size, the 3YSZ ceramic shows enhanced material stability and, in turn, increased resistance to hydrothermal ageing.  

With ever-increasing life expectancy, orthopaedic implants need to be able to stand the test of time, with minimised requirements for revisional surgery. Usually, under significant or repeated stress, a crack can begin to form on the surface of the implant, which over time can cause it to fail. With Innovnano’s 3YSZ, this same stress induces the 3YSZ to undergo structural transformation which acts to compress any crack, delaying or preventing its growth, and subsequently improving the fracture resistance. It is this phase transformation which can therefore increase the lifetime of joint replacements.