published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

The thesis describes a study of the modifications of orthopaedic Ti-based substrates using nanomaterials, and the evaluation of their biocompatibility for further use as implant material, with the aim to develop new, biocompatible β-Ti/CNT composite materials. Traditionally, CNTs require the presence of a transition metal catalyst such as Fe, Ni, Co, for successful growth. Different aspects of a catalyst-assisted CVD MWCNTs growth on various Ti-based substrates including bulk, thin films and 3D porous scaffolds, have been investigated. Low concentrations of catalyst were deposited using spin coating on titanium substrates of various forms and shapes. A strong influence of the surface topography was observed. In contrast, no effect of the elemental composition of the substrate could be detected. To evaluate the biocompatibility of the newly created materials, cell culture studies using fetal human osteoblasts (fHobs) were performed. It was shown that β-Ti/MWCNTs samples possess good initial osteoblast attachment, but no long-term osteoblast activity. Hence the biocompatibility of isolated (i.e. without a Ti substrate) MWCNTs was studied, using MWCNT carpets and various types of MWCNTs buckypapers. All the samples revealed very low cell activity. While β-Ti/MWCNTs samples did not exhibit good biocompatibility, alternative β-Ti/TiC samples were synthesized with a simple CVD method and revealed good osteoblast response with increased mineralization. Moreover, good corrosion resistance and mechanical properties of β-Ti/TiC samples have been reported. Finally, successful method for non-catalytic CVD MWCNTs growth on Ti substrates was developed for the first time, thereby excluding potentially toxic catalysts from the implant material. CVD was performed with acetylene precursor on bulk titanium substrates etched with Piranha solution, which generated an appropriate surface to foster MWCNTs growth. A combination of the change in the surface roughness, improved hydrophilicity, and elemental composition of the surface as a result of the Piranha etching is likely to be responsible for the successful formation of MWCNTs.

M. Tech. Metallurgical Engineering / Ti6Al4V alloy is the leading material for hip replacement because of its biocompatibility, elastic modulus and good yield strength, but shows poor corrosion and wear properties in simulated body fluid. Thin coatings were fabricated on Ti6Al4V alloy using Zirconium, Niobium and Titanium reinforcements with the aid of Nd:YAG Rofin Sinar laser system. Niobium reinforcement produced the best coating that displayed the best corrosion resistance and percentage increase in wear resistance in simulated body fluid as compared to the substrate. Therefore, this coating will perform best as orthopaedic implant material.

Orientador: Rubens Caram Júnior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-23T05:01:49Z (GMT). No. of bitstreams: 1 Verissimo_NathaliaCarolina_M.pdf: 4539752 bytes, checksum: 5f6eb6507fb9a034b3aca9ed35fdea93 (MD5) Previous issue date: 2013 / Resumo: Ligas de Ti do tipo 'beta' contendo elementos biocompatíveis são potencialmente interessantes em aplicações ortopédicas e odontológicas. Enquanto as propriedades mecânicas dessas ligas podem ser controladas por meio de tratamentos térmicos, suas propriedades de superfície podem ser otimizadas por meio da formação de camada de nanotubos de TiO2 usando processos de anodização. Neste trabalho, amostras de Ti CP e das ligas Ti-35Nb e Ti-35Nb-4Sn, obtidas por fusão a arco voltaico em atmosfera inerte, foram anodizadas sob potencial constante de 20V durante 1 hora, usando uma solução aquosa de HF, a fim de obter uma camada de nanotubos de TiO2 amorfa. Tais camadas amorfas foram tratadas termicamente visando promover transformações de fase amorfo-anatase e anatase-rutilo. As amostras foram caracterizadas por meio de microscopia eletrônica de varredura. Os resultados obtidos indicam que camadas amorfas de nanotubos de TiO2 com espessura superior a 800 nm foram produzidas. Tratamentos térmicos combinados com ensaios de difração de raios-X permitiram identificar a formação de anatase em 225ºC em Ti CP, em 295ºC na liga Ti-35Nb e em 392ºC na liga Ti-35Nb-4Sn. A estrutura cristalina do rutilo foi observada no Ti CP em 398ºC e em 557ºC na liga Ti-35Nb. A formação de cristais de rutilo sobre a liga Ti-35Nb-4Sn ocorreu em 605ºC. Observou-se que o Nb combinado com Sn tem forte efeito estabilizador da fase anatase. Medidas de molhabilidade indicam que a fase anatase apresenta valores elevados de ângulo de contato, enquanto que a fase rutilo exibe valores menores e com características hidrofílicas. Os resultados obtidos sugerem que a combinação anatase-rutilo é a mais adequada para aplicações biomédicas e crescimento celular por não ser altamente hidrofílica / Abstract: 'beta' type Ti alloys containing biocompatible elements are potentially interesting for orthopedic and dental applications. While the mechanical properties of these alloys can be controlled by means of heat treatments, its surface properties can be optimized by formation of TiO2 nanotube layer using anodizing processes. In this work, samples of CP Ti and Ti-35Nb and Ti-35Nb-4Sn alloys obtained by arc melting under inert atmosphere were anodized using HF-based electrolyte for 1 hour, obtaining amorphous layers of TiO2 nanotubes. These layers were heat treated aiming to promote the amorphous structure and phases like anatase, mixture anatase-rutile and rutile. Samples were characterized by scanning electron microscopy. The results indicate that amorphous layers of TiO2 nanotubes with a thickness exceeding 800 nm were produced. Heat treatments combined with X-ray diffraction experiments allowed identifying the formation of anatase at 225ºC in CP Ti, at 295ºC in the Ti-35Nb alloy and at 392ºC in the Ti-35Nb-4Sn alloy. The crystal structure of rutile was observed in CP Ti at 398ºC and at 557ºC in the alloy Ti-35Nb. The formation of rutile crystals on the alloy Ti-35Nb-4Sn occurred at 605°C. It was observed that Nb combined with Sn shows a strong stabilizing effect of anatase. Wettability measurements indicate that the anatase phase shows high values of contact angle, while the rutile phase exhibits lower values and hydrophilic characteristics. The results suggest that the combination anatase-rutile is the most suitable for biomedical applications and cell growth because they are not highly hydrophilic / Mestrado / Materiais e Processos de Fabricação / Mestra em Engenharia Mecânica