Preparação e caracterização de uma liga de titânio com a adição de tântalo e zircônio para aplicações biomédicas

Ligas de titânio são amplamente utilizadas na área biomédica devido à sua excelente resistência à corrosão em fluídos corpóreos, elevada razão resistência mecânica/densidade, baixo módulo de elasticidade e comprovada biocompatibilidade. As ligas mais promissoras para serem utilizadas na área biomédica possuem elementos em solução sólida que diminuem a temperatura de transformação de fase do titânio. Tais elementos são denominados beta-estabilizadores e obtêm-se como resultado a diminuição do módulo de elasticidade e uma excelente resistência à corrosão. Os elementos tântalo e zircônio, quando acrescentados ao titânio, melhoram a resistência à corrosão e diminuem o módulo de elasticidade, pois o tântalo é considerado um elemento β-estabilizador e o zircônio atua como elemento estabilizador desta fase, na presença de outro elemento β-estabilizador. Neste trabalho, a liga Ti-25Ta-5Zr foi preparada por fusão à arco, visando aplicações biomédicas. As caracterizações química, estrutural, microestrutural e mecânica foram realizadas por intermédio de medidas da composição química, análise de gases, espectrometria por dispersão de energia (EDS), difração de raios X, microscopias óptica e eletrônica de varredura, microdureza Vickers e módulo de elasticidade.  Os resultados obtidos mostraram uma boa estequiometria e homogeneidade da liga. As análises estrutural e microestrutural corroboraram entre si e indicaram que a liga possui a coexistência de duas fases, α‖ (com estrutura cristalina ortorrômbica) e β (com estrutura cristalina cúbica de corpo centrado). A microdureza elevou-se com a adição de tais elementos e o módulo de elasticidade possui valores abaixo das ligas utilizadas comercialmente, satisfatório para aplicação como implante ortopédico. Palavras-chave: Biomateriais, Ligas de titânio, Microestrutura

Effect of the substitutional elements on the microstructure of the Ti-15Mo-Zr and Ti-15Zr-Mo systems alloys

AbstractTitanium alloys have excellent biocompatibility, and combined with their low elastic modulus, become more efficient when applied in orthopedic prostheses. Samples of Ti-15Mo-Zr and Ti-15Zr-Mo system alloys were prepared using an arc-melting furnace with argon atmosphere. The chemical quantitative analysis was performed using an optical emission spectrometer with inductively coupled plasma and thermal conductivity difference. The X-ray diffractograms, allied with optical microscopy, revealed the structure and microstructure of the samples. The mechanical analysis was evaluated by Vickers microhardness measurements. The structure and microstructure of alloys were sensitive to molybdenum and zirconium concentration, presenting α′, α″ and β phases. Molybdenum proved to have greater β-stabilizer action than zirconium. Microhardness was changed with addition of molybdenum and zirconium, having Ti-15Zr-10Mo (436±2HV) and Ti-15Mo-10Zr (378±4HV) the highest values in each system

Structure, microstructure, and selected mechanical properties of Ti-Zr-Mo alloys for biomedical applications

New titanium alloys for biomedical applications have been developed primarily with the addition of Nb, Ta, Mo, and Zr, because those elements stabilize the β phase and they don’t cause cytotoxicity in the organism. The objective of this paper is to analyze the effect of molybdenum on the structure, microstructure, and selected mechanical properties of Ti-15Zr-xMo (x = 5, 10, 15, and 20 wt%) alloys. The samples were produced in an arc-melting furnace with inert argon atmosphere, and they were hot-rolled and homogenized. The samples were characterized using chemical, structural, and microstructural analysis. The mechanical analysis was made using Vickers microhardness and Young’s modulus measurements. The compositions of the alloys were sensitive to the molybdenum concentration, indicating the presence of α’+α”+β phases in the Ti-15Zr-5Mo alloy, α”+β in the Ti-15Zr-10Mo alloy, and β phase in the Ti-15Zr-15Mo and Ti-15Zr-20Mo alloys. The mechanical properties showed favorable values for biomedical application in the alloys presenting high hardness and low Young’s modulus compared with CP-Ti

Oxygen diffusion analysis in a new β Ti–25Ta–40Zr alloy using mechanical spectroscopy technique

This study primarily focuses on analyzing anelastic processes due to interstitial oxygen in the Ti–25Ta–40Zr alloy. From the structural and microstructural characterization (DRX and optical microscopy), it was detected that the Ti–25Ta–40Zr alloy is a α + β type. Peaks of anelastic relaxation were visualized in the Ti–25Ta–40Zr alloy, where the peaks are thermally activated, with the shift of Qp−1 to higher temperatures in tests performed at high frequencies. The activation energy (E), relaxation time (τ0), and diffusivity (Do) of oxygen in the alloy were obtained E = (0.49 ± 0.02) eV, τ0 = (6.3 ± 0.2) x10−19 s and D0 = (5.0 ± 0.1) x10−3 m2/s

Effect of Titanium Addition on the Structure, Microstructure, and Selected Mechanical Properties of As-Cast Zr-25Ta-xTi Alloys

Ti alloys are the most used metallic materials in the biomedical field due to their excellent biocompatibility associated with good corrosion resistance in body fluids and relatively low elastic modulus. However, the alloys used in the orthopedic area have an elastic modulus that is 2 to 4 times higher than that of human cortical bone. Searching for new alloys for biomedical applications and with low elastic modulus, zirconium gained prominence due to its attractive properties, especially its biocompatibility. The purpose of this paper is to present novel as-cast alloys of the Zr-25Ta-xTi system and analyze the influence of titanium on the structure, microstructure, microhardness, and elastic modulus of the alloys. The alloys were prepared using an arc-melting furnace. X-ray diffraction measurements and microscopy techniques were used to characterize the crystalline structure and microstructure. From structural and microstructural characterizations, it was observed that titanium acted as an α-stabilizing element since its increase in the precipitation of the orthorhombic α” phase, an intermediate phase from β to α phases, in the alloys. Regarding microhardness measurements, the alloys have higher hardness than pure zirconium due to solid solution hardening that detaches the Zr-25Ta alloy, which has a high hardness value of the precipitation of the ω phase. Among the studied alloys, the Zr-25Ta-25Ti alloy is highlighted, demonstrating the lowest result of modulus of elasticity, which is approximately 2 times higher than the human cortical bone, but many alloys used in the biomedical field, such as pure titanium, have elastic modulus values almost 3 times higher than that of human bone

Characteristics of ceramic-like coatings obtained by plasma electrolyte oxidation on different Ti alloys

Plasma electrolyte oxidation was used to modify the surface of different Ti alloys: c.p. Ti (α hcp structure), Ti–15Nb (α′ + β structure) and Ti–33Nb–33Zr (stable β cubic structure) and the influence of elements and microstructure in the TiO2-based ceramic layer formed as well as the surface properties was analyzed. The XRD patterns confirmed the presence of TiO2 (anatase and rutile) in the c.p. Ti. For Ti–15Nb (wt.%) indicated the presence the same oxides also of pentoxide niobium (Nb2O5). For Ti–33Nb–33Zr (wt.%) indicated just the presence of rutile as the stable oxide one at room temperature and dioxide zirconium (ZrO2). In addition, the formation of calcium carbonate CaCO3 and calcium phosphate Ca3(PO4)2 was detected in all 3 materials. The ceramic-like layer was more homogeneous for c.p. Ti and Ti–15Nb and more irregular hole like-pores for Ti–33Nb–33Zr. Bioactive ions used were detected in all alloys and the roughness for Ti–15Nb was higher compared to c.p. Ti. and Ti–33Nb–33Zr. The contact angle for the three samples was higher than 100°. Resumen: La electro oxidación por plasma fue utilizada con el objetivo de sintetizar recubrimientos de óxidos en la superficie de diferentes aleaciones de Ti tales como: Ti c.p. (estructura α hcp), Ti-15Nb (estructura α′+β) y Ti-33Nb-33Zr (estructura cúbica β estable). Así mismo, esta técnica permitió evaluar el efecto de los elementos de la aleación; la microestructura de la capa cerámica formada, cuya base es TiO2; así como las propiedades superficiales. Los patrones de XRD confirmaron la presencia de TiO2 (anatasa y rutilo) en el Ti c.p., así como la presencia de los mismos para la aleación Ti-15Nb (% en peso) y la formación del pentóxido de niobio (Nb2O5), mientras que para la aleación Ti-33Nb-33Zr (% en peso), el análisis de DRX mostró la presencia del rutilo, como el óxido estable a la temperatura ambiente, así como del dióxido de zirconio (ZrO2). Además, en los 3 materiales se detectó la formación del carbonato de calcio CaCO3 y fosfato de calcio Ca3(PO4)2. Adicionalmente, la capa cerámica fue más homogénea para el Ti c.p. y Ti-15Nb, mientras que los microporos formados fueron más irregulares en la aleación Ti-33Nb-33Zr. Los iones bioactivos utilizados se detectaron en todas las aleaciones. Sin embargo, la rugosidad para el Ti-15Nb fue mayor en comparación con la del Ti c.p. y Ti-33Nb-33Zr, aun cuando el ángulo de contacto para las tres muestras fue superior a 100° indicando una superficie más hidrofóbica

A New α + β Ti-15Nb Alloy with Low Elastic Modulus: Characterization and In Vitro Evaluation on Osteogenic Phenotype

This study aimed to produce Ti-15Nb alloy with a low elastic modulus, verify its biocompatibility, and determine whether the alloy indirectly influences cellular viability and morphology, as well as the development of the osteogenic phenotype in cells cultured for 2, 3, and 7 days derived from rat calvarias. Two heat treatments were performed to modify the mechanical properties of the alloy where the Ti-15Nb alloy was heated to 1000 °C followed by slow (−5 °C/min) (SC) and rapid cooling (RC). The results of structural and microstructural characterization (XRD and optical images) showed that the Ti-15Nb alloy was of the α + β type, with slow cooling promoting the formation of the α phase and rapid cooling the formation of the β phase, altering the values for the hardness and elastic modulus. Generally, a more significant amount of the α phase in the Ti-15Nb alloy increased the elastic modulus value but decreased the microhardness value. After the RC treatment, the results demonstrated that the Ti-15Nb alloy did not present cytotoxic effects on the osteogenic cells. In addition, we did not find variations in the cell quantity in the microscopy results that could suggest cell adhesion or proliferation modification

A detailed analysis of the structural, morphological characteristics and micro-abrasive wear behavior of nitrided layer produced in α (CP–Ti), α+β (Ti–6Al–4V), and β (TNZ33) type Ti alloys

The present work aimed to create a hard surface on a titanium surface via plasma nitriding to improve microhardness and wear properties of the as-cast (α-CP-Ti (CP–Ti), α+β-Ti6Al4V (Ti–Al–4V), and β-Ti-33Nb–33Zr (TNZ-33) samples. For the nitriding process, two temperature conditions (650 °C and 700 °C) were used. The presence of nitrides was evaluated by XRD. The microstructure and chemical composition were studied by electron microscopy and EDS. The roughness was evaluated by confocal microscopy. The microhardness and wear properties were analyzed using the Vickers microhardness and micro-abrasive wear test. Plasma nitriding led to the formation of TiN on CP-Ti, TiN, and Ti2N on Ti–6Al–4V, and TiN and ZrN on TNZ-33 samples. At 700 °C, the TiN increased on CP-Ti, while the Ti2N increased for Ti–6Al–4V and the ZrN increased for TNZ-33. The length of the nitride layer decreased when the temperature increased for CP-Ti and Ti–6Al–4V samples. However, for the TNZ33 alloy, the layer increased from 6.3 to 7.6 μm. The chemical analyses confirmed the presence of nitrogen on the substrate surfaces. After the nitriding process, all materials significantly increased the hardness. The hardness after plasma nitriding can be followed by: CP-Ti > TNZ-33> Ti–6Al–4V (at 650 °C); CP-Ti > Ti–6Al–4V > TNZ-33 (at 700 °C). The wear properties of all samples were improved after plasma nitriding treatment

Antimicrobial Cu-Doped TiO2 Coatings on the β Ti-30Nb-5Mo Alloy by Micro-Arc Oxidation

Among the different surface modification techniques, micro-arc oxidation (MAO) is explored for its ability to enhance the surface properties of Ti alloys by creating a controlled and durable oxide layer. The incorporation of Cu ions during the MAO process introduces additional functionalities to the surface, offering improved corrosion resistance and antimicrobial activity. In this study, the β-metastable Ti-30Nb-5Mo alloy was oxidated through the MAO method to create a Cu-doped TiO2 coating. The quantity of Cu ions in the electrolyte was changed (1.5, 2.5, and 3.5 mMol) to develop coatings with different Cu concentrations. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron and atomic force microscopies, contact angle, and Vickers microhardness techniques were applied to characterize the deposited coatings. Cu incorporation increased the antimicrobial activity of the coatings, inhibiting the growth of Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa bacteria strains, and Candida albicans fungus by approximately 44%, 37%, 19%, and 41%, respectively. Meanwhile, the presence of Cu did not inhibit the growth of Escherichia coli. The hardness of all the deposited coatings was between 4 and 5 GPa. All the coatings were non-cytotoxic for adipose tissue-derived mesenchymal stem cells (AMSC), promoting approximately 90% of cell growth and not affecting the AMSC differentiation into the osteogenic lineage