Tesis doctoral de Milena Patricia Arciniegas Angarita
Nowadays there are a considerable number of manufactured products developed for biomedical applications, in which the tini alloys play an important role as implanted materials due to their characteristic property of changing shape when subjected to heat or stress as stimulus. In these applications an essential issue is the biocompatibility, not only with respect to cellular contact, but also to mechanical relations, in order to obtain both a good cells-implant surface interaction and a satisfactory load distribution in the bone-implant coupling. However, to this purpose the use of tini alloys must be taken with severe precaution because of the possibility to cause allergy/toxic pathologies, as a consequence of the ni ions release from the implant to the surrounding tissues. moreover, employing metallic alloys as implant material presents some reservations due to the lack of mechanical compatibility with the bone, in terms of rigidity, which produces an inefficient load- transfer, so that the bone regeneration and fixation of the implant to the bone is affected, causing pain and faults. the main purpose of this doctoral thesis is the development and study of new ni free ti alloys with shape memory properties as well as low elastic modulus, for favouring both the cellular and the bone response, using alloying elements such as tantalum, zirconium and niobium. To this purpose, a theoretical design method was used which permitted to establish nine different chemical compositions of new alloys; moreover, this method proved to be a useful tool for obtaining ti alloys with a high probability to show the mentioned properties. The new alloys were produced with a quenching treatment and the microstructures were characterized. Finally, the thermal, mechanical and phase transformation responses of each alloy were evaluated. the new alloys present elastic modulus lower than other alloys frequently used as implant materials, with values in a range from 67 gpa (in the ti-41nb-6zr alloy) to 79 gpa (in the ti-48nb-1zr alloy). Moreover, two of them, the ti-14nb-1ta and ti-23nb-8zr alloys, exhibit thermoelastic phase transformation induced by temperature with ms temperatures of 126ºc and 45ºc, respectively, which are susceptible to be modified by thermo-mechanical treatments for adjusting these to body temperature, if necessary. As an additional characterization, the thermoelastic phase transformation induced by stress was evidenced by means of cyclic indentation tests in the mentioned alloys, but also in the ti-23ta-12nb and ti-29nb-7zr alloys. Finally, the ti-23nb-8zr and ti-41nb-6zr alloys were selected, according to the results above commented, for evaluating their chemical behaviour and the cell-new surface interactions. The results show a high corrosion resistance in both alloys due to the presence of the ta, zr and nb oxide layers. Moreover, the in vitro tests with mg 63 cells indicate an excellent adhesion at short time in both new surface, and also a higher grade of proliferation and differentiation cell with respect to the one obtained in a ti cp. It can be concluded that the alloys presented in this thesis, in particular the two latest mentioned, can be considered potential candidates as implant materials.
Datos académicos de la tesis doctoral «Desarrollo de nuevas aleaciones de ti libres de ni para aplicaciones biomedicas«
- Título de la tesis: Desarrollo de nuevas aleaciones de ti libres de ni para aplicaciones biomedicas
- Autor: Milena Patricia Arciniegas Angarita
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 24/10/2008
Dirección y tribunal
- Director de la tesis
- José María Manero Planella
- Tribunal
- Presidente del tribunal: Francisco javier Gil mur
- Juan Carlos Paniagua valle (vocal)
- yvan Houbaert (vocal)
- josep María Guilemany casadamon (vocal)