Researcher Nere Garmendia, based in the Basque city of Donostia-San Sebastián, has just published her PhD, a thesis which may well mean the first step to solving this problem. According to Ms Garmendia, using a ceramic material called zirconia (Zr02), carbon nanotubes and nanoparticles of zirconia, a prothesis that will last more than 150 years can be produced.
The PhD thesis is titled Development of a new nanocompound material made of zirconia with coated carbon nanotubes, for orthopaedic applications. Ms Garmendia wished to show that the ageing and cracking of protheses could be avoided. To begin with, carbon nanotubes were added to the zirconia matrix – a technique that greatly strengthens its resistance. With this composite material as a base research was initiated.
The researcher reinforced the connection between the zirconia matrix and the nanotubes, with the intention of improving the transfer/distribution of loads. The nanotubes were coated with nanoparticles of zirconia and, in order for this to be effected, the nanoparticles were heated beyond their boiling point (hydrothermal synhtesis). This coating functioned as a bridge between the zirconia matrix and the nanotubes.
Subsequently, Ms Garmendia specified the number of coated nanotubes each piece had to have in order to achieve the optimum density at the end of the process. According to the researcher, adding zirconia nanoparticles to the nanotubes facilitates the dispersion of the material and reduces its viscosity, apart from helping to increase its density for the next and last stage: the synterisation stage. Synterisation is a process, used particularly in ceramics, in order to transform the material from powder to a compact solid. Not just any quantity is useful to achieve this maximum possible density and, thus, before synterisation, it has to be decided how many nanotubes are to be introduced and, of course, synterisation has to be subsequently carried out correctly.As Ms Garmendia calculated, if the intention is to obtain the maximum possible density (98%), in order to start the composition, 1% of its volume must be of coated nanotubes. Finally, the material has to be synterised in argon for one hour at 1,300 degrees; not more nor less.
She is currently working at Inasmet-Tecnalia where she carried out her PhD. She also worked with other bodies for the research: INSA-Lyon in France (six months), the Institute of Ceramics and Glass-CSIC in Madrid (six weeks), the Donostia International Physics Center (on various simulations), the Universitat de Barcelona (microscopy) and the CINN-CSIC in Oviedo (on the development of the material).
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