ABSTRACT Introduction: Surface treatment is an important technique to increase adhesion between implants and bones, improving its mechanical characteristics and consequently the patient’s comfort. Objectives: Ni-Cr alloys were the object of study in this work, with the purpose of analyzing and evaluating the effect of thin films deposition of titanium nitride via plasma, on its surface and comparing with cathodic cage (CC) and hollow cathode (HC) methods, for dental applications. Methods: Eighteen samples were prepared and the experiment was conducted in two steps: the pre-sputtering (1h, 350 °C, gases: Ar and H) and sputtering (4h, 450 °C, gases: Ar, Ni, and H). To characterize and compare the samples with those of reference, the Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Vickers Microhardness and wettability tests were used. Results: The results presented by SEM showed that during the surface treatment using CC, voids were formed, and using HC, the samples showed a more homogenous behavior. In microhardness tests, using a 25gf load, it was possible to observe that the HC method allowed an increase of 87% when compared to the reference and treated samples. Significance: Lastly, it can be concluded that both methods are suitable for Ni-Cr alloy surface treatment, and the HC technique, a method already used by dental professionals, presents better results due to the formation of a thicker film layer.

Super duplex stainless steel (SDSS) combines corrosion resistance and mechanical properties, interesting to applications in the oil extraction industry. In this process, wear between the tools friction and rocky materials occurs with SDSS pipes. Due to the low tribological properties, plasma nitriding process is applied to provide a surface layer with excellent wear resistance and without significant losses in corrosion resistance. Here, conventional plasma nitriding (CPN) and cathodic cage plasma nitriding (CCPN) techniques were compared to modify SDSS surface. Before and after passing by these two nitriding processes, welded joints (WJ) were subjected to a microstructural and corrosion resistance evaluation. Aiming to characterize the final product obtained, it was used characterization techniques, such as scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results show that using the CPN technique, at 400°C, was responsible for providing greater resistance to corrosion, when analyzing the result of potentiodynamic polarization — jpassivation = 2.60x10-5 A.cm-2 and Epite = 0.83 V than the CCPN technique when applied to the SSDS, and this was attributed to the formed diffusion layer, which is composed of the expanded austenite and ferrite phases.

RESUMO A introdução da zircônia (ZrO2) como material odontológico representa um grande avanço quando comparado aos demais materiais tradicionalmente utilizados para esta finalidade. Este material destaca-se, devido às suas ótimas propriedades tais como resistência mecânica e biocompatibilidade. No entanto, existem limitações quanto a sua coloração branca e alta opacidade, não sendo possível mimetizar as características da dentição humana, afetando assim o conceito estético desses materiais e diminuindo o conforto do paciente. Este trabalho propõe desenvolver pós de zircônia pigmentada através do método Pechini, dopando-os com óxido de ferro em diferentes concentrações (3 %, 2 %, 1 %, 0,5 %, 0,25 % em mol) e itria, posteriormente calciná-los a temperatura de 1000 °C, com a finalidade de obter a mistura química mais efetiva, próxima da tonalidade da dentina humana. As amostras foram caracterizadas por Difração de Raios X (DRX), Microscopia Eletrônica de Varredura (MEV), Espectroscopia de Energia Dispersiva (EDS), teste de toxicidade e avaliação colorimétrica, confirmando a presença do ferro dentro da microestrutura da zircônia e suas modificações causadas no material. Os resultados indicam que os tamanhos de cristalitos dos pós sintetizados aumentaram de 35,45 nm para 48,97 nm, quando a concentração de ferro aumentou de 0 % para 3%. Os espectros de EDS indicaram a presença de ferro em todas as amostras, com variadas concentrações do pigmento. O método utilizado foi efetivo para a produção de pós de zircônia com variadas nuances de cores, possuindo um grande potencial para aplicações odontológicas.

ABSTRACT The introduction of zirconia (ZrO2) as a dental material, represents a major advance when compared to other materials traditionally used for this purpose. This material stands out due to its excellent properties such as mechanical resistance and biocompatibility. However, there are limitations regarding its white color and high opacity, and it is not possible to mimic the characteristics of human dentition, thus affecting the aesthetic concept of these materials and reducing patient comfort. This work proposes to develop pigmented zirconia powders using the Pechini method, doping them with iron oxide in different concentrations (3 %, 2 %, 1 %, 0.5 %, 0.25 mol%) and itria, later calcine them at a temperature of 1000 °C in order to obtain the most effective chemical mixture, close to the shade of human dentin. The samples were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), toxicity testing and colorimetric evaluation, confirming the presence of iron within the zirconia microstructure and its modifications caused in the material. The obtained results indicate that the crystallite sizes of the synthesized powders increased from 35,45 nm to 48,97 nm when the iron concentration increased from 0 % to 3 mol%. The EDS spectra indicated the presence of iron in all the samples, with varying concentrations of the pigmentant agent. The method used was effective for the production of zirconia powders with varied color nuances, having great potential for dental applications.