Caracterización de CP-Titanio producido mediante inyección aglutinante y pulvimetalurgia convencional

El titanio (Ti) y sus aleaciones se encuentran entre los materiales más utilizados en aplicaciones biomédicas. Además de ser biocompatibles, estos materiales tienen una baja densidad, una alta resistencia a la corrosión y unas propiedades mecánicas notables. Es muy difícil producir piezas con geometría compleja utilizando métodos convencionales de pulvimetalurgia (PM) ya que este método se basa en dar forma a polvos bajo fuerzas uniaxiales utilizando moldes. La Inyección Aglutinante (Binder Jetting) es un tipo de técnica de fabricación aditiva que no necesita moldes para dar forma a los polvos. Este estudio se centra en comparar las propiedades de las piezas porosas de CP-Ti producidas con PM e Inyección Aglutinante. Las piezas se sinterizaron durante 120 min en una atmósfera de argón a 1200 °C. Después de la sinterización, se alcanzaron valores de densidad relativa de aproximadamente el 94% y el 92% en las muestras producidas por PM y con la impresora 3D, respectivamente. También se observó que la muestra producida con una presión de compactación de 25 MPa tiene una dureza de 317 ± 10 HV0.05 y un límite elástico bajo compresión de 928 MPa, mientras que la pieza producida con la impresora 3D tiene una dureza de 238 ± 8 HV0. 05 y un límite elástico bajo compresión de 342 MPa. Aunque la dureza y resistencia de las muestras producidas con la impresora 3D fueron menores que las de PM, sus propiedades son adecuadas para producir implantes que reemplacen las estructuras óseas.

Improvement of Mechanical and Corrosion Properties of Commercially Pure Titanium Using Alumina PEO Coatings

In this study, the surface of commercially pure titanium (Cp-Ti) was covered by a 21–95 µm-thick aluminum oxide layer using plasma electrolytic oxidation. Coating characterization revealed the formation of nodular and granular α- and γ-Al2O3 phases with minor amounts of TiAl2O5 and Na2Ti4O9 which yielded a maximum 49.0 GPa hardness and 50 N adhesive critical load. The corrosion resistance behavior in 3.5 wt.% NaCl solution of all plasma electrolytic oxidation (PEO) coatings was found to be two orders of magnitude higher compared to bare Ti substrate.

Investigation of Biocompatible PEO Coating Growth on cp-Ti with In Situ Spectroscopic Methods

The problem of the optimization of properties for biocompatible coatings as functional materials requires in-depth understanding of the coating formation processes; this allows for precise manufacturing of new generation implantable devices. Plasma electrolytic oxidation (PEO) opens the possibility for the design of biomimetic surfaces for better biocompatibility of titanium materials. The pulsed bipolar PEO process of cp-Ti under voltage control was investigated using joint analysis of the surface characterization and by in situ methods of impedance spectroscopy and optical emission spectroscopy. Scanning electron microscopy, X-ray diffractometry, coating thickness, and roughness measurements were used to characterize the surface morphology evolution during the treatment for 5 min. In situ impedance spectroscopy facilitated the evaluation of the PEO process frequency response and proposed the underlying equivalent circuit where parameters were correlated with the coating layer properties. In situ optical emission spectroscopy helped to analyze the spectral line evolutions for the substrate material and electrolyte species and to justify a method to estimate the coating thickness via the relation of the spectral line intensities. As a result, the optimal treatment time was established as 2 min; this provides a 9–11 µm thick PEO coating with Ra 1 µm, 3–5% porosity, and containing 75% of anatase. The methods for in-situ spectral diagnostics of the coating thickness and roughness were justified so that the treatment time can be corrected online when the coating achieves the required properties.

Fabrication of hydrophobic surfaces on Titanium using Micro-EDM exhibiting antibacterial properties

Microbial contamination on medical assistive devices has been the major challenge for biomedical industries. The present work is focused on producing patterned surfaces on commercially pure Titanium (cp-Ti) using Micro-Electrical Discharge Machining (Micro-EDM) technique, and the feasibility of patterned surface in restricting bacterial growth. Geometrical patterning in form of micro-holes have been produced on cp-Ti biomaterials with Micro-EDM in two forms, one with 20 µm inter-distance forming a dense pattern and the other with 60 µm inter-distance forming a sparse pattern. The patterned surface establishes the degree of hydrophobicity as 130° and 106° for densely patterned and sparsely patterned surfaces respectively. Further, the effect of bacterial adhesion over the textured cp-Ti surfaces are challenged with model bacteria gram negative Escherichia coli (e.coli) in Luria broth (LB) agar media. The Colony Forming Unit (CFU) count obtained for densely patterned surface compared with that of non-patterned surface reflects 90% reduced bacterial growth. The instances of pattern formation and bacterial growth have been observed with Scanning Electron Microscopy. The enhanced material properties with micro-patterning that combat microbial activities on the biomaterial surface proves its efficacy in adoption for biomedical applications, with significant reduction in bacterial contamination on medical devices or implants, leading toward reduced healthcare risks and issues related to bacterial infections on the biomaterials.

Influence of Calcium Acetate Concentration in Electrolyte on Tribocorrosion Behaviour of MAO Treated Titanium

Ti-based materials are widely used for dental and orthopaedic implant applications due to their adequate mechanical properties, corrosion behaviour and biocompatibility. However, these materials are biologically inert and display poor wear resistance. In one of the most studied processes that aims to overcome these drawbacks, Ti surfaces are often covered by anodic oxide films with the incorporation of bioactive agents such as Ca and P. Although there are several works on the tribocorrosion behaviour of MAO-treated Ti surfaces, the influence of electrolyte composition on the corrosion kinetics under sliding is yet to be fully understood. In the present work, anodic oxide films were produced on cp-Ti surfaces with different calcium acetate concentrations in the electrolyte. Tribocorrosion behaviour was investigated by reciprocating sliding tests performed in 8 g/L NaCl solution at body temperature, under potentiostatic conditions. The results showed that higher concentrations of calcium acetate had a detrimental effect on tribocorrosion kinetics, however, they resulted in less mechanical damage due to alterations in the topography and structure of the MAO layer.

Electrochemical Behaviour of Ti and Ti-6Al-4V Alloy in Phosphate Buffered Saline Solution

The electrochemical behavior of commercially pure titanium (CP Ti) and Ti-6Al-4V (Grade 5) alloy in phosphate buffered saline solution (PBS, pH = 7.4) at 37 °C (i.e., in simulated physiological solution in the human body) was examined using open circuit potential measurements, linear and potentiodynamic polarization and electrochemical impedance spectroscopy methods. After the impedance measurements and after potentiodynamic polarizationmeasurements, the surface of the samples was investigated by scanning electron microscopy, while the elemental composition of oxide film on the surface of each sample was determined by EDS analysis. The electrochemical and corrosion behavior of CP Ti and Ti-6Al-4V alloys is due to forming a two-layer model of surface oxide film, consisting of a thin barrier-type inner layer and a porous outer layer. The inner barrier layer mainly prevents corrosion of CP Ti and Ti-6Al-4V alloy, whose thickness and resistance increase sharply in the first few days of exposure to PBS solution. With longer exposure times to the PBS solution, the structure of the barrier layer subsequently settles, and its resistance increases further. Compared to Ti-6Al-4V alloy, CP Ti shows greater corrosion stability.