Credit: CORE-Materials; Flickr CC BY-SA 2.0
New research suggests a simple solution to improve the wear resistance, fracture tolerance, and conductivity of alumina—the addition of graphene.
As ceramics go, alumina is already rather strong and resistant to corrosion and wear. For those very reasons, and because of its biocompatibility, alumina is often used in biomedical applications, such as hip prostheses and dental implants.
New research from an international team of scientists—including researchers from Graphenea, a tech company that sells graphene products and performs graphene R&D and commercialization—however, suggests that these useful properties of alumina can be improved even further.
To create the durable graphene–alumina composite, the team mixed alumina powder with graphene oxide and used spark plasma sintering to create a homogenous material.
Adding just a small amount of graphene—just 0.22% by weight—to the alumina could significantly reduce the composite’s wear rate and friction coefficient, despite larger grain size in the composite compared to alumina alone.
Experiments measured a 50% reduction in wear rate and 10% reduction in friction coefficient of the graphene–alumina composite compared to monolithic alumina, according to a Graphenea blog post.
The composite material was tested via sliding over a simulated distance of 10 km with a tribometer, which measures friction and wear as an alumina ball slides over the material.
Taking a closer look at the material revealed that graphene laminates from the composite are sheared off with friction on the ceramic matrix surface. These loose laminates form a lubricating film between the composite and the wear surface, reducing friction on the material at least in the initial stages of wear.
Graphenea previously reported that adding graphene to alumina also makes the composite 50% less breakable under strain, because graphene nanosheets bridge cracks that form in the alumina, making the composite more resilient to failure. That research also reported that graphene makes the composite a hundred million times more conductive.
The paper, published in Ceramics International, is “Wear behavior of graphene/alumina composite” (DOI: 10.1016/j.ceramint.2015.02.061).