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Methane is an extremely stable molecule, a major component of natural gas, and also one of the most potent greenhouse gases contributing to global warming. Consequently, the capture and activation of methane is a challenging and intensively studied topic. A major research goal is to find systems that can activate methane even at low temperature. Here, combining ultrahigh vacuum catalytic experiments followed by X-ray photoemission spectra and accurate density functional theory (DFT) based calculations, we show that small Ni clusters dispersed on the (001) surface of TiC are able to capture and dissociate methane at room temperature. Our DFT calculations reveal that two-dimensional Ni clusters are responsible of this chemical transformation, evidencing that the lability of the supported clusters appears to be a critical aspect in the strong adsorption of methane. A small energy barrier of 0.18 eV is predicted for CH4 dissociation into adsorbed methyl and hydrogen atom species. In addition, the calculated reaction free energy profile at 300 K and 1 atm of CH4 shows no effective energy barriers in the system. Comparing with other reported systems which activate methane at room temperature, including oxide and zeolite-based materials, indicates that a different chemistry takes place on our metal/carbide system. The discovery of a carbide-based surface able to activate methane at low temperatures paves the road for the design of new types of catalysts towards an efficient conversion of this hydrocarbon into other added-value chemicals, with implications in climate change mitigation.

El campo de los biomateriales ha crecido sustancialmente en los últimos años desde que en 1969 se realizase la primera conferencia sobre biomateriales en la universidad de Clemson, Carolina del Sur. Se definió entonces biomaterial como cualquier material natural o artificial utilizado para crear soportes o implantes que permitan reemplazar estructuras biológicas perdidas o enfermas, restaurando así su forma y función [01]. Para entender el gran foco de atención que ha recibido el campo de los biomateriales es necesario comprender las causas que han llevado a la comunidad científica a la necesidad de desarrollar nuevos materiales para cumplir con las necesidades biológicas que este nuevo campo requiere. Así, según datos de la American Academy of Othopedics Surgeons se estima que un 90% de la población mayor de 40 años sufre enfermedades degenerativas asociadas con la perdida de funcionalidad en estructuras biológicas tales como huesos, órganos o tejidos. Si a esto se le suma que, según las previsiones de las naciones unidas [02], la población en Europa mayor de 60 años se estima duplicará su número en 2050 pasando de 962 millones en 2017 a más de 2100 millones en 2050, se espera que en los próximos años más de un 25% de la población requiera de soluciones contra los problemas degenerativos relativos al cuerpo. Así, si la atención se centra en el campo de la ortopedia, donde se ha producido un mayor impacto en el número de enfermedades y problemas degenerativos, se calcula que en 2030 el número total de reemplazos de cadera crecerá un 174%, alcanzando la alarmante cifra de 572.000 operaciones por año, mientras que la demanda en reemplazos parciales y totales de rodilla crecerá un 673%, con un total de 3,48 millones de procedimientos esperados [02]. Estas enfermedades degenerativas relativas a los huesos suelen ser debido a una carga excesiva o una ausencia del proceso biológico de regeneración y llevan, normalmente, a una degradación de las propiedades mecánicas de los mismos huesos, siendo a largo plazo la sustitución del hueso dañado por un implante, la solución más efectiva. En consecuencia, se ha incrementado la demanda de implantes en el campo de la ortopedia, así como en otros campos de la medicina como el dental o el vascular. Aun así, los implantes no están exentos de problemáticas que limiten su uso, así como su esperanza de vida dentro del cuerpo y por ello se están realizando numerosas investigaciones para intentar optimizar las propiedades de los materiales que los componen para mejorar la compatibilidad de los mismos dentro del ecosistema humano. Así, aquellos materiales que presenten propiedades mecánicas similares al hueso, excelente aceptación por parte del ambiente corporal, así como nula toxicidad o propensión a inflamación, serán candidatos idóneos para optimizar la aceptación del implante por parte del hueso y así prolongar la vida útil del mismo evitando el tan temido fallo aséptico o mecánico del mismo.

[ES] El titanio es uno de los elementos metálicos más abundantes de la naturaleza, que tiene importantes propiedades y características que lo hacen único y ampliamente demandado en el sector industrial. En particular, las aleaciones de titanio son las protagonistas en el sector biomédico, ya que, al presentar un módulo bajo de elasticidad, baja conductividad térmica y eléctrica, y una alta resistencia a la corrosión, son las seleccionadas para la fabricación de implantes y prótesis biomédicas. Sin embargo, se ha de tener cuidado con su manipulación porque es altamente reactivo cuando está en presencia de oxígeno, teniendo asociados unos riesgos considerables. En este trabajo, las aleaciones de titanio de las que se estudia su biocompatibilidad han sido procesadas por vía pulvimetalúrgica. Esta técnica es la más común para obtener y diseñar composiciones que pueden ser difíciles de obtener por metalurgia convencional, disminuyendo la cantidad de residuos del material durante el procesamiento e impidiendo que los elementos de aleación sean segregados (garantizando la homogeneidad de la microestructura). Se trata pues con aleaciones formadas por la mezcla elemental y el aliado mecánico de los polvos de los elementos de aleación, cuyas propiedades mecánicas han sido determinadas por una prueba de dureza y flexión de tres puntos; mientras que la caracterización microestructural se ha analizado mediante la microscopía electrónica de barrido. La biocompatibilidad es un término relativo que cubre muchos conceptos, y que indica la capacidad de un material para realizar una función biológica sin producir una reacción a un cuerpo extraño. Entonces, las aleaciones han sido sometidas a una prueba de resistencia a la corrosión, junto con una prueba de liberación de iones con saliva artificial durante 732 horas. Luego, para ver el efecto de los resultados de las pruebas anteriores y empleando una línea celular de osteosarcoma humano (MG63), se ha hecho una determinación de la toxicidad con el reactivo MTS, y posteriormente se ha realizado un ensayo de adhesión celular y proliferación, de 5 horas y 72 horas respectivamente. Por lo tanto, los resultados del estudio de las diferentes aleaciones de titanio caracterizadas por la presencia de un elemento de aleación en cada caso permiten determinar si se comportan como verdaderos biomateriales o resultan nocivos para un medio biológico., [CA] El titani es un dels elements metàl·lics més abundants de la naturalesa, que posseeix unes importants propietats i característiques que el fan únic i àmpliament demandat en el sector industrial. Concretament, els aliatges de titani son els protagonistes en el sector biomèdic ja que al presentar un baix mòdul d’elasticitat, baixa conductivitat tèrmica i elèctrica, i una elevada resistència a la corrosió, son els seleccionats per a la fabricació d’implants i pròtesis biomèdiques. No obstant, es deu de tindre en conter amb la seua manipulació ja que és altament reactiu quan es troba en presencia d’oxigen , ocasionant uns riscos considerables. En aquest treball, els aliatges de titani dels quals s’estudia la seua biocompatibilitat, han sigut processades per via pulvimetal·lúrgica. Aquesta tècnica es la més comú per a l’obtenció i disseny de composicions que puguin ser difícils d’obtenir mitjançant la metal·lúrgia convencional, disminuint la quantitat de deixalles del material durant el processat i evitant que els elements d’aliatge es segreguen (garantint la homogeneïtat de la microestructura). Es tracta amb aliatges resultats de la mescla elemental i aliat mecànic dels pols dels elements d’aliatge, les propietats mecàniques dels quals s’han determinat per una prova de duresa i de flexió a tres punts; mentre que la caracterització microestructural ha sigut analitzada per microscòpia electrònica d’escombrat. La biocompatibilitat, es un terme relatiu que engloba molts conceptes, i que indica la capacitat d’un material de realitzar una funció biològica sense produir una reacció a cos estrany. Aleshores, per estudiar-lo, primerament, s’han sotmès els aliatges a una prova de resistència a la corrosió junt a una d’alliberament d’ions amb saliva artificial durant 732 hores. A continuació, per veure l’efecte dels resultats de les proves anteriors i fent ús d’una línia cel·lular d’osteosarcoma humà (MG-63), s’ha realitzat una determinació de la toxicitat amb el reactiu MTS, i després un assaig d’adhesió i proliferació cel·lular, de 5 hores i 72 hores respectivament. Per tant, els resultats de l’estudi dels diferents aliatges de titani caracteritzats per la presencia d’un element d’aliatge en cada cas, permeten determinar si aquests es comporten com a vertaders biomaterials o resulten perjudicials per al medi biològic., [EN] Titanium is one of the most abundant metal elements of nature, which has important properties and characteristics that make it unique and widely demanded in the industrial sector. Specifically, the titanium alloys are the protagonists in the biomedical sector as by presenting a low modulus of elasticity, low thermal and electrical conductivity, and a high resistance to corrosion, are those selected for the manufacture of implants and biomedical prostheses. However, their manipulation is complicated because it is highly reactive when it is in the presence of oxygen. In this work, the titanium alloys have been processed by powder metallurgical route. This technique is the most common to obtain and design compositions that can be difficult to obtain by conventional metallurgy, amount of material waste during processing and preventing the alloy elements from being segregated (guaranteeing the homogeneity of the microstructure). They are alloys formed by the elementary mixture and the mechanical alloy of the powders of the alloy elements, whose mechanical properties have been determined by a three-point hardness and flexural test; while the microstructural characterization has been analyzed by scanning electron microscopy. Biocompatibility is a relative term that covers many concepts, and that indicates the ability of a material to perform a biological function without producing a reaction to a foreign body. Then, the alloys have been subjected to a corrosion resistance test, and an ion release test with artificial saliva for 732 hours. Then, to see the effect of the results of the previous tests and using a human osteosarcoma cell line (MG-63), a toxicity determination was made with the MTS reagent, and subsequently a 5-hour and 72-hour cell adhesion and proliferation test was performed respectively. Therefore, the results of the study of the different titanium alloys characterized by the presence of an alloy element in each case, allow to determine whether they behave as true biomaterials or are harmful to a biological environment.

Evaluate the quality of finishing and degree of contamination before and after handling and surface treatment of titanium (Ti) orthodontic mini-implants (OMIs). A scanning electron microscope (SEM) study on ninety-six titanium OMIs was done. Energy-Dispersive X-ray Analysis (EDX) identified the present particles on manufactured OMIs surfaces. Then, OMIs were manipulated with gauze (dry sterile, soaked in chlorhexidine) and gloves (latex, nitrile) to evaluate the contamination of these handling materials. Finally, OMIs underwent surface treatments and were placed in bone to observe the contaminants they released. Roughness (Ra) and wettability with contact angle parameter (CA) were measured on these treated OMIs. Machined OMIs presented surface irregularities and were contaminated with manufacturing-process particles (carbon, plastic Polyvinyl Chloride PVC, aluminum). Hand-manipulated OMIs were also contaminated by the handling materials. OMIs surface characteristics were as follows: acid-etched (Ra 1.3 m, CA 66 ), machined (Ra 0.3 m, CA 68 ), SB (Ra 3.3 m, CA 78 ), and SBAO (Ra 3.1 m, CA 92 ). Bone was contaminated by OMIs surface defects and extra particles. Manufactured OMIs have surface contaminants that increase with clinical handling. Surface treatments (SBAO, a combination of sandblasting and anodic oxidation) increase the roughness and contact angle, which play an important role in osseointegration. Surface-treated OMIs leave titanium particles in the bone during their insertion-removal. The use of a gauze soaked in chlorhexidine is recommended when handling OMIs. Further investigations would be interesting to study more variables and confirm the present results. Spanish Government and and European Union FEDER Generalitat de Cataluña

Atmospheric plasma spraying is used here to obtain titanium sub-oxide coatings on the following electrode substrates: a 316 stainless steel sheet, an aluminium alloy 2024 sheet, a carbon–polymer composite and nickel foam. It is necessary to increase the roughness of the substrate to aid the adhesion of the coating to the smooth electrodes; this is especially critical for the fragile carbon–polymer composite. High-energy conditions increase the strain caused by the mismatch between coefficients of thermal expansion when coating the thin steel and aluminium sheets, and degraded the carbon–polymer composite and nickel foam. Therefore, it is necessary to adjust the spraying parameters to lower-energy conditions in order to achieve well-bonded and homogeneous coatings on all four substrates and avoid the presence of cracks in their cross-section area. The suitability of the coated materials as battery electrodes was studied.

A highly rough titanium coating obtained by Cold Gas Spray (CGS) has been characterized by means of high-resolution 3D microtomography (micro-CT) with the aim to evaluate its open and close porosity for possible use in orthopaedic implants to promote osseointegration. Micro-CT allowed a qualitative and quantitative description of the main features, morphology of the pores and surface roughness of the coating. Several numerical values were obtained to describe size, form and distribution of the closed/inner and open/outer pores. Additionally, surface roughness and open porosity were image-analyzed to find the effective surface for osseointegration.

Commercially pure (Grade 4) titanium specimens with two types of microstructure (coarse-grained and nanostructured by means of equal channel angular pressing) were joined by linear friction welding (LFW). Microhardness measurements, tensile and compression tests as well as fracture surface inspection by scanning electron microscopy revealed similarity in tensile properties and significant discrepancy in compression behavior of two types of Ti specimens. Tensile test shows that fracture occurs in both cases in a region of heat affected zone. Fracture surface analysis displayed mostly ductile mode. In case of compression test coarse-grained titanium linear friction welded demonstrates a pronounced strain hardening region without fracture but nanostructured LFW titanium shows typical plastic behavior with mixing of brittle-ductile mode of rupture in the welding zone.

Already for fifteen years many researchers have been trying to discover metallic materials with unusual combinations of strength and ductility: with high strength and enhanced ductility . This combination may be achieved through different ways: alloying, nanostructuring, etc. This report is an attempt to analyze the influence of inhomogeneity of different types (structural, phase and space) on mechanical properties of commercially pure ti tanium (bulk and powder) subjected to high- pressure torsion. Experimental results for HPT bulk and powder titanium have demonstrated that mechanical behavior of CP titanium strongly depends on phase inhomogeneity (alpha + omega phases), structural inhomoge neity (bimodal grain size distribution) and space inhomogeneity (retained porosity) in case of cold consolidated Ti powder. High strength in HPT bulk titanium due to the formation of hard omega phase during HPT processing at room temperature was detected. The strong omega phase transforms back to nanograined alpha phase domains during short annealing at elevated temperature. HPT consolidation of titanium powder leads to the formation of brittle specimens showing high strength but almost zero plasticity

El proyecto desarrollado se basa en la comparación de las propiedades que presentan las estructuras porosas de titanio fabricadas por dos métodos de manufactura aditiva: la impresión 3D y el sinterizado laser. Además de las dos técnicas de fabricación, se han comparado dos tipos de geometrías: filamentos ortogonales y filamentos en forma de panel de abeja. El estudio se ha centrado en la fabricación de las muestras en el laboratorio mediante la extrusión de la tinta creada con polvo de titanio irregular comercialmente puro de grado 2 y copolímero Pluronic F127, elemento aglutinador que le proporciona la viscosidad necesaria a la mezcla. Posteriormente han sido sometidas a un post-procesado de sinterizado y eliminación del aglutinante proporcionando una mejora de las condiciones mecánicas de la pieza. Tras la fabricación de las muestras y la obtención de las piezas manufacturadas a láser gracias un proveedor externo, se ha procedido a la caracterización física, química y biológica de las estructura. Se han realizado ensayos mecánicos de compresión, ensayos de microdureza y metalografía para analizar las propiedades mecánicas de las muestras. Posteriormente, se ha comprobado la composición química de cada una de las variedades de estructura y se ha procedido al recubrimiento de fosfato de calcio por electrodeposición. Se han caracterizado las piezas con microscopia electrónica y se han ensayado a compresión para ver los efectos mecánicos del recubrimiento en las muestras. Seguidamente, se ha añadido nitrato de plata al recubrimiento anterior para comprobar las reacciones antibacterianas que tienen las estructuras, ya que la plata es conocida por tener propiedades bactericidas. Finalmente, se ha logrado la comparación de las propiedades analizadas de las cuatro variedades de muestras, se ha alcanzado con éxito el recubrimiento de las piezas con una capa de fosfato de calcio, óptimo para promover la osteointegración y osteoconducción del sistema implante-hueso y se ha conseguido complementarla con partículas de plata observando posteriormente su reacción antibacteriana por contacto directo en un sembrado de bacterias S. aureus.

A comprehensive analysis of the influence of the chiral auxiliary on the α-aminoxylation of titanium(iv) enolates with TEMPO indicated that (S) 4-tert-butyl-1-oxazolidine-2-thione is the most appropriate scaffold to provide a single diastereomer in high yields for a variety of substrates, which converts such a radical reaction into a highly chemo- and stereoselective oxidation.

This paper presents the design and characterization of an ultrasonic vibration-assisted ball burnishing (VABB) tool on Ti-6Al-4V. This process is based on the modification of conventional ball burnishing, by means of the addition of a 40-kHz vibratory force to the burnishing preload exerted by the spring inside the tool. For the purposes of successfully executing the process, a new tool is designed through the assembly of different modules responsible for the various aspects involved in it. That design is hereby presented. Then, a methodology comprising acoustic emission and high frequency sampling is proposed to characterize the functioning of a prototype manufactured according to the previously presented design. The set of techniques deployed to measure the performance of the VABB prototype is presented as a feasible means of characterizing this sort of advanced manufacturing tools, especially like this one which is governed by ultrasonic frequencies. Last of all, the prototype is tested on a Ti-6Al-4V surface to validate it. The superior results of VABB, compared to the non-assisted version of the process, is shown in terms of average and total surface roughness, as well as surface hardness. The highest improvement is achieved by applying the VABB process with 300 N and 5 passes. The effectiveness of the designed prototype is confirmed, and places this kind of VABB tools as inexpensive systems to successfully execute an innovative finishing process for industrial components.

Three different surface treatments on a Ti6Al4V alloy have been in vitro tested for possible application in cementless joint prosthesis. All of them involve the novelty of using the Cold Spray technology for their deposition: (i) an as-sprayed highly rough titanium and, followed by the deposition of a thin hydroxyapatite layer with (ii) microcrystalline or (iii) nanocrystalline structure. Primary human osteoblasts were extracted from knee and seeded onto the three different surfaces. Cell viability was tested by MTS and LIVE/DEAD assays, cell differentiation by alkaline phosphatase (ALP) quantification and cell morphology by Phalloidin staining. All tests were carried out at 1, 7 and 14 days of cell culture. Different cell morphologies between titanium and hydroxyapatite surfaces were exhibited. At 1 day of cell culture, cells on the titanium coating were spread and flattened, expanding the filopodia actin filaments in all directions, while cells on the hydroxyapatite coatings showed round like-shape morphology due to slower attachment. Higher cell viability was detected at all times of cell culture on titanium coating due to a better attachment at 1 day. However, from 7 days of cell culture, cells on hydroxyapatite showed good attachment onto surfaces and highly increased their proliferation, mostly on nanocrystalline, achieving similar cell viability levels than titanium coatings. ALP levels were significantly higher in titanium, in part, because of greatest cell number. Overall, the best cell functional results were obtained on titanium coatings whereas microcrystalline hydroxyapatite presented the worst cellular parameters. However, results indicate that nanocrystalline hydroxyapatite coatings may achieve promising results for the faster cell proliferation once cells are attached on the surface.

Three different surface treatments on a Ti6Al4V alloy have been in vitro tested for possible application in cementless joint prosthesis; all of them involve the novelty of using the Cold Spray technology for their deposition: (i) an as-sprayed highly rough titanium and, followed by the deposition of a thin hydroxyapatite layer with (ii) microcrystalline or (iii) nanocrystalline structure. Primary human osteoblasts extracted from knee were seeded onto surfaces and cell viability using MTS and LIFE/DEAD assays, osteoblasts differentiation by alkaline phosphatase (ALP) quantification as well as cell morphology were tested at 1, 7 and 14 days of cell culture. Different cell morphologies between titanium and hydroxyapatite surfaces were exhibited; at 1 day of cell culture, cells on the titanium coating were spread and flattened, expanding the filopodia actin filaments in all directions, while cells on the hydroxyapatite coatings showed round like-shape morphology due to a slower attachment. Higher cell viability was detected at all times of cell culture on titanium coating due to a better attachment at 1 day. However, from 7 days of cell culture, cells on hydroxyapatite showed good attachment onto surfaces and highly increased their proliferation, mostly on nanocrystalline, achieving similar cell viability levels than titanium coatings. ALP levels were significantly higher in titanium, in part, because of greatest cell number. Overall, the best cell functional results were obtained on titanium coatings whereas microcrystalline hydroxyapatite presented the worst cellular parameters. However, results indicate that nanocrystalline hydroxyapatite coatings may achieve promising results for the faster cell proliferation once cells are attached on the surface.

Strategies to inhibit initial bacterial adhesion are extremely important to prevent infection on biomaterial surfaces. However, the simultaneous attraction of desired eukaryotic cells remains a challenge for successful biomaterial-host tissue integration. Here we describe a method for the development of a trifunctional coating that repels contaminating bacteria, kills those that adhere, and promotes osteoblast adhesion. To this end, titanium surfaces were functionalized by electrodeposition of an antifouling polyethylene glycol (PEG) layer and subsequent binding of a peptidic platform with cell-adhesive and bactericidal properties. The physicochemical characterization of the samples via SEM, contact angle, FTIR and XPS analysis verified the successful binding of the PEG layer and the biomolecules, without altering the morphology and topography of the samples. PEG coatings inhibited protein adsorption and osteoblast-like (SaOS-2) attachment; however, the presence of cell adhesive domains rescued osteoblast adhesion, yielding higher values of cell attachment and spreading compared to controls (p

Highly rough and porous commercially pure titanium coatings have been directly produced for first time by the cold spray technology, which is a promising technology in front of the vacuum plasma spray for oxygen sensitive materials. The wettability properties as well as the biocompatibility evaluation have been compared to a simply sand blasted Ti6Al4V alloy substrate. Surface topographies were analysed using confocal microscopy. Next, osteoblast morphology (Phalloidin staining), proliferation (MTS assay), and differentiation (alkaline phosphatase activity) were examined along 1, 7 and 14 days of cell culture on the different surfaces. Finally, mineralization by alizarin red staining was quantified at 28 days of cell culture. The contact angle values showed an increased hydrophilic behaviour on the as-sprayed surface with a good correlation to the biological response. A higher cell viability, proliferation and differentiation were obtained for highly rough commercial pure titanium coatings in comparison with sand blasted substrates. Cell morphology was similar in all coatings tested; at 14 days both samples showed extended filopodia. A higher amount of calcium-rich deposits was detected on highly rough surfaces. In summary, in-vitro results showed an increase of biological properties when surface roughness increases. The authors want to thank the Spanish MINECO for financial support through project MAT2013-46755-R and the Generalitat de Catalunya for the project 2014 SGR 1558, and University of Barcelona for the award of a scholarship that has helped the development of this research. This work was also supported by the Red Temática de Investigación Cooperativa en Envejecimiento y Fragilidad (RETICEF; RD12/0043/0022), the Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable (CIBERFES; CB16/10/00245) and FEDER funds.

[ES] Las aleaciones de titanio son la mejor elección de materiales metálicos para aplicaciones médicas debido a sus excelentes propiedades mecánicas y biocompatibilidad. Sin embargo, la toxicidad de los elementos de las aleaciones de titanio convencionales, como Ti6Al4V, han impulsado el desarrollo de nuevas aleaciones compuestas por elementos que no produzcan efectos tóxicos. Las aleaciones binarias de Ti-Mn (5%, 10% y 17,5% de contenido en manganeso, Mn) fueron fabricadas por pulvimetalúrgia (PM) como un material potencial para su uso en aplicaciones biomédicas. Se evaluaron las microestructuras y propiedades mecánicas de las aleaciones obtenidas a partir de dos procesados de polvo distintos: aleado mecánico y mezcla elemental. Para las aleaciones con un 5% y 10 % de masa Mn en las muestras de mezcla elemental, la resistencia a flexión (981-858 MPa) y la dureza (244- 210 HV) de las aleaciones fabricadas por PM son comparables al titanio comercialmente puro (Ti CP) y, además, presentan un módulo elástico de 95-88 GPa. Gracias a los ensayos de caracterización química, el comportamiento frente corrosión y liberación de iones han resultado ser muy prometedores para estas dos mismas aleaciones. Los estudios realizados han permitido concluir que la vía pulvimetalurgica de mezcla elemental, compactación y sinterización convencional permite la obtención de materiales con amplias posibilidades en el sector médico, siempre que se respete el límite toxicológico marcado ya por otros autores (%wt Mn < 13%)., [CA] Els aliatges de titani són la millor elecció de materials metàl·lics per a aplicacions mèdiques a causa de les seues excel·lents propietats mecàniques i biocompatibilitat. No obstant açò, la toxicitat dels elements dels aliatges de titani convencionals, com Ti6Al4V, han impulsat el desenvolupament de nous aliatges compostos per elements que no produïsquen efectes tòxics. Els aliatges binaris de Ti-Mn (5%, 10% i 17,5% de contingut en manganés, Mn) van ser fabricades per pulverimetal·lúrgia (PM) com un material potencial per al seu ús en aplicacions biomèdiques. Es van avaluar les microestructures i propietats mecàniques dels aliatges obtinguts a partir de dos processaments de pols diferents: aliat mecànic i mescla elemental. Per als aliatges amb un 5% i 10 % de massa en Mn en les mostres de mescla elemental, la resistència a flexió (981-858 MPa) i la duresa (244- 210 HV) dels aliatges fabricats per PM són comparables al titani comercialment pur (Ti CP) i, a més, presenten un mòdul elàstic de 95-88 GPa. Gràcies als assajos de caracterització química, el comportament front corrosió i alliberament d'ions han resultat ser molt prometedors per a aquestes dos mateixos aliatges. Els estudis realitzats han permès concloure que la via pulverimetal·lúrgica de mescla elemental, compactació i sinterització convencional permet l'obtenció de materials amb àmplies possibilitats en el sector mèdic, sempre que es respecte el límit toxicológic marcat ja per altres autors (%wt Mn < 13%)., [EN] Titanium alloys are the best choice of metallic materials for medical applications due to their excellent mechanical properties and biocompatibility. However, the toxicity of the elements of conventional titanium alloys, such as Ti6Al4V, has prompted the development of new alloys composed of elements that do not produce toxic effects. Binary Ti-Mn alloys (5%, 10% and 17.5% manganese content, Mn) were manufactured by powder metallurgy (PM) as a potential material for use in biomedical applications. The microstructures and mechanical properties of the alloys obtained from two different powder processes were evaluated: mechanical alloy and elemental mixture. For alloys with 5% and 10% mass Mn in the elemental mixture samples, the bending strength (981-858 MPa) and hardness (244-210 HV) of the PM alloys manufactured are comparable to commercially pure titanium (Ti CP) and have an elastic modulus of 95-88 GPa. Thanks to the chemical characterization tests, the corrosion corrosion and ion release behaviour has been very promising for these two alloys. The studies carried out have led to the conclusion that the powder metallurgical route of elemental mixture, compaction and conventional sintering allows the obtaining of materials with wide possibilities in the medical sector, provided that the toxicological limit already established by other authors is respected (%wt Mn < 13%)

Ti-6Al-2Sn-4Zr-2Mo is one of the most common titanium alloys for aerospace industry. This alloy experiences oxidation phenomenon at elevated temperatures. In the present study, cyclic thermal treatments were performed in air at 500, 593 and 700¿°C, up to 500¿cycles, in order to determine the oxidation kinetics and to analyze the oxide scale and alpha-case formation. Moreover, results were compared to those achieved under isothermal conditions to elucidate differences between both thermal conditions. In this sense, metallographic techniques and X-ray diffraction, together with a detailed advanced characterization of the microstructure by Field Emission Scanning Electron Microscopy and Focus Ions Beam, were used to analyze surface oxidation evolution. Results pointed out that cyclic treatments induced a strong increase of the weight gain compared to isothermal treatments. The analysis of the oxide scale revealed the formation of not only rutile, as isothermal treatments, but also anatase. Thickness of the oxide scale was higher for cyclic conditions, while alpha case did not exceed values reached by isothermal treatments and even became lower at 500¿°C.

In this study, highly-interconnected porous titanium implants were produced by powder sintering with different porous diameters and open interconnectivity. The actual foams were produced using high cost technologies: Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), and spark plasma sintering, and the porosity and/or interconnection was not optimized. The aim was to generate a bioactive surface on foams using two different strategies, based on inorganic thermo-chemical treatment and organic coating by peptide adsorption, to enhance osseointegration. Porosity was produced using NaCl as a space holder and polyethyleneglicol as a binder phase. Static and fatigue tests were performed in order to determine mechanical behaviors. Surface bioactivation was performed using a thermo-chemical treatment or by chemical adsorption with peptides. Osteoblast-like cells were cultured and cytotoxicity was measured. Bioactivated scaffolds and a control were implanted in the tibiae of rabbits. Histomorphometric evaluation was performed at 4 weeks after implantation. Interconnected porosity was 53% with an average diameter of 210 &micro, m and an elastic modulus of around 1 GPa with good mechanical properties. The samples presented cell survival values close to 100% of viability. Newly formed bone was observed inside macropores, through interconnected porosity, and on the implant surface. Successful bone colonization of inner structure (40%) suggested good osteoconductive capability of the implant. Bioactivated foams showed better results than non-treated ones, suggesting both bioactivation strategies induce osteointegration capability.

[ES] Las aleaciones de titanio son la elección por excelencia para la fabricación de implantes. Las aleaciones β de titanio son el foco de investigación en el ámbito biomédico, debido a su bajo módulo elástico, que mejora el problema de apantallamiento de tensiones. Elementos de aleación como el niobio, molibdeno y tantalio estabilizan la fase β, pero al ser elementos refractarios presentan muchas dificultades a la hora de trabajar con ellos. Las técnicas de pulvimetalurgia permiten obtener aleaciones con porcentajes muy concretos de cada elemento, pero presentan desventajas como la falta de difusión y la formación de poros. Pese a haber conseguido aleaciones β de titanio con módulos elásticos bajos, y con una alta resistencia a corrosión, la implantación de estas en el cuerpo humano tiene una elevada tasa de inflamación e infecciones. La plata es un elemento ampliamente utilizado en el campo de la medicina para evitar infecciones, por su conocida capacidad antibiótica. En este trabajo se propone el estudio del efecto de la adición de plata, en pequeños porcentajes en peso diferentes, en la aleación Ti-35Nb, obtenida mediante técnicas convencionales de pulvimetalurgia. El fin principal del trabajo es comprobar la viabilidad de las nuevas aleaciones como implantes. Las propiedades mecánicas se han determinado mediante ensayos de técnica de excitación por impulso, flexión a tres puntos, microtracción y flexión en voladizo. Para conocer las características microestructurales se han realizado ensayos de difracción de rayos X, y se ha utilizado la microscopía electrónica de barrido y la técnica de EBSD (Electron BackScattered Diffraction). Finalmente, la resistencia a la corrosión ha sido analizada mediante ensayos de corrosión electroquímica y ensayos de liberación de iones en saliva artificial. De los resultados obtenidos se extrae que las aleaciones Ti-35Nb-XAg son viables para su utilización como biomateriales., [CA] Els aliatges de titani són l'elecció per excel·lència per a la fabricació d'implants. Els aliatges β de titani són el focus de recerca en l'àmbit biomèdic, a causa del seu baix mòdul elàstic, que millora el problema d'apantallament de tensions. Elements d'aliatge com el niobi, molibdè i tàntal estabilitzen la fase β, però en ser elements refractaris presenten moltes dificultats a l'hora de treballar amb ells. Les tècniques de pulverimetal·lúrgia permeten obtenir aliatges amb percentatges molt concrets de cada element, però presenten desavantatges com la falta de difusió i la formació de porus. Malgrat haver aconseguit aliatges β de titani amb mòduls elàstics baixos, i amb una alta resistència a corrosió, la implantació d'aquestes en el cos humà té una elevada taxa d'inflamació i infeccions. La plata és un element àmpliament utilitzat en el camp de la medicina per a evitar infeccions, per la seua coneguda capacitat antibiòtic. En aquest treball es proposa l'estudi de l'efecte de l'addició de plata, en xicotets percentatges en pes diferents, en l'aliatge Ti-35Nb, obtinguda mitjançant tècniques convencionals de pulverimetal·lúrgia. La fi principal del treball és comprovar la viabilitat dels nous aliatges com a implants. Les propietats mecàniques s'han determinat mitjançant assajos de tècnica d'excitació per impuls, flexió a tres punts, microtracció i flexió en volada. Per a conèixer les característiques microestructurals s'han realitzat assajos de difracció de rajos X, i s'ha utilitzat la microscòpia electrònica d'escombratge i la tècnica de EBSD (Electron BackScattered Diffraction). Finalment, la resistència a la corrosió ha sigut analitzada mitjançant assajos de corrosió electroquímica i assajos d'alliberament d'ions en saliva artificial. Dels resultats obtinguts es pot extraure que els aliatges Ti-35Nb-XAg són viables per a la seua utilització com a biomaterials., [EN] Titanium alloys are the default choice for implant manufacture. Titanium β alloys are the focus of research in the biomedical field, due to their low elastic modulus, thing that improves the problem of stress shielding. Alloy elements such as niobium, molybdenum and tantalum stabilise the β phase, but as they are refractory elements they present many difficulties when working with them. Powder metallurgy techniques make it possible to obtain alloys with very specific percentages of each element, but it also has disadvantages such as lack of diffusion and formation of pores. In spite of having achieved β titanium alloys with low elastic modules, and high resistance to corrosion, the implantation of these in the human body has a high rate of inflammation and infections. Silver is a widely used element in the medical field to prevent infection, due to its known antibiotic capacity. In this work we propose the study of the effect of the addition of silver, in small different weight percentages, in the Ti-35Nb alloy, obtained by conventional powder metallurgy techniques. The main purpose of the work is to test the viability of these new alloys as implants. The mechanical properties have been determined by tests of impulse excitation technique, three-point bending, microtraction and cantilever bending. To determine the microstructural characteristics, X-ray diffraction tests have been carried out, and scanning electron microscopy and EBSD (Electron BackScattered Diffraction) techniques have been used. Finally, the corrosion resistance has been analyzed by electrochemical corrosion tests and ion release tests in artificial saliva. The results obtained show that Ti-35Nb-XAg alloys are viable for use as biomaterials.

[eng] In the present Thesis we continued a previous study of the nucleophilic character of titanium(IV) enolates. Particularly,we focused our attention on the analysis of substrate-controlled Michael additions to enones and other acceptors.Thus, the Michael addition of (S)-2-benzyloxy-3-pentanoneto enones was thoroughly evaluatedin Chapter 1. In the case of vinyl ketones, the best reaction conditions involved the use of two TiCl4 equivalents and afforded the 2,4-antiadducts as single diastereomers in excellent yields. In addition, the developed methodology was also evaluated with β- substituted enones, whose optimised conditions using TiCl4 and SnCl4 afforded the 2,4- anti-4,5-antiadducts with diastereoselectivities above 90:10 in all cases with good yields. Furthermore, the Michael addition of (S)-2-benzyloxy-3-pentanoneto α,β- unsaturated nitroalkenes was alsoanalysed inChapter 1. The use of two equivalents of TiCl4and aromatic nitroalkenes led to the 2,4-anti-4,5-syn adducts with excellent yields and diastereoselectivities. In turn, aliphatic nitroalkenes needed optimised conditions using TiCl4 and SnCl4 to afford the 2,4-anti-4,5-syn adducts in good diastereoselectivities and yields. Finally, the nitro group was converted into other useful functional groups. Another objective of the first part of this thesis wasto re-evaluate the synthesis of the tetrahydropyran ring from the C1-C9 fragment of herboxidiene/GEX1A. Thus, in Chapter 2 we analysed the initial retrosynthesis of the C1-C9 fragment and studied the oxa-Michael cyclization. Finally, we designed two parallel sequences to improve the first synthetic approach.The stereoselective synthesis of the tetrahydropyran ring was successfully accomplished following two different approaches. In approach 1, the number of steps was increased, but the sequence pursued a fully stereoselective pathway taking advantage of the great selectivity offered by a dimethylpyrrole amide under acidic conditions attaining a 54% yield (46% for the original approach). In approach 2, the original sequence of reactions was followed, but the suppression of unnecessary purification operations and a final isomerisation step increased notably the yield up to 58% (39% for the original approach). Keepingin mind the biradical character of certain titanium enolates, the second objective of this Thesis was to examine the uncommon radical reactivity of titanium enolates derived from chiral N-acyl oxazolidinones when exposed to radical reagents. In Chapter 3, the aminoxylation of chiral N-acyl oxazolidinones was improved using a chiral tert-butyl oxazolidinethionederived from tert-leucine. This chiral auxiliary provided the aminoxylated products as single diastereomers in all cases with excellent yields. Finally, the resulting adducts were transformed into synthetical useful intermediates. Furthermore, in Chapter 3 we also reported a highly stereoselective oxidation of titanium enolates from chiral N-acyl oxazolidinones with molecular oxygen. The direct hydroxylation of biradical titanium(IV) enolates derived from chiral oxazolidinones with O2 proved to be feasible. Thus, we described a novel approach for the synthesis of enantiomerically pure α-hydroxy carboxylic derivatives. We describe in Chapter 4 a comprehensive search of compounds capable of participating in radical reactions, which involved a brief exploration of photoredox catalysis. Finally, such research led to the discovery of a new and highly stereoselective alkylation with aliphatic diacyl peroxides. Decarboxylation of the diacyl peroxides from aliphatic acids promoted by the titanium enolates produced primary and secondary radicals and triggered the formation of the alkylated adducts as single diastereomers with excellent yields., [spa] En la presente Tesis continuamos un estudio previo sobre el carácter nucleófilo de los enolatos de titanio(IV) en adiciones de Michael con control por sustrato. Así, la adición de Michael de (S)-2-benciloxi-3-pentanona a enonas y nitroalquenos se evaluó a fondo en el Capítulo 1. En el caso de las vinil cetonas, las mejores condiciones de reacción implicaban el uso de dos equivalentes de TiCl4 o un equivalente de TiCl4 y otro de SnCl4 y proporcionaban los aductos 2,4-anti-4,5-anti con rendimientos excelentes y diastereoselectividades superiores a 90:10. Además, la metodología desarrollada también se empleó con nitroalquenos α,β-insaturados, conduciendo a proporcionar los aductos de 2,4-anti-4,5-syn con buenas diastereoselectividades y rendimientos. En el Capítulo 2 se reevaluó la retrosíntesis inicial del anillo tetrahidropiránico del fragmento C1-C9 del herboxidieno/GEX1A. La síntesis estereoselectiva del anillo de tetrahidropirano se logró con éxito siguiendo dos enfoques diferentes. En el primer enfoque, se aumentó el número de pasos, pero la secuencia siguió una ruta completamente estereoselectiva aprovechando la gran selectividad ofrecida por una dimetilpirrolamida en condiciones ácidas. En el segundo enfoque, se siguió la secuencia original, pero la supresión de operaciones de purificación innecesarias y la inclusión de una etapa de isomerización final aumentaron notablemente el rendimiento. El segundo objetivo de esta Tesis fue examinar la reactividad radical poco común de enolatos de titanio derivados de N-acil oxazolidinonas quirales cuando se exponen a reactivos radicalarios. Así, en el Capítulo 3, la aminoxilación de N-acil oxazolidinonas quirales se mejoró usando una tiazolidintiona de tert-butilo quiral derivada de tert-leucina que proporcionó los productos aminoxilados como únicos diastereómeros con rendimientos excelentes. Además, en el Capítulo 3 también llevamos a cabo una hidroxilación directa altamente estereoselectiva de enolatos de titanio a partir de N-acil oxazolidinonas quirales con oxígeno para la síntesis de derivados α-hidroxicarboxílicos enantioméricamente puros. En el Capítulo 4 describimos una búsqueda exhaustiva de compuestos capaces de participar en reacciones radicales, lo que implicó una breve exploración de la catálisis fotoredox. Finalmente, tal investigación llevó al descubrimiento de una nueva alquilación altamente estereoselectiva con peróxidos de diacilo alifáticos que conducía a la formación de los aductos alquilados como diastereómeros únicos con rendimientos excelentes.

The purpose of this study is to develop new implant surfaces in which polymeric domains with antibacterial properties can alternate with titanium domains and to determine the cell behaviour on the substrates. Surface microgrooves with a separation of 60 μm between them were performed on pure titanium disks using a modified 3D printer. Shavings were removed after the process. These were then coated with an antibacterial polysaccharide (chitosan) and mouse C2C12 myoblast and MC3T3-E1 pre-osteoblast were cultured on the hybrid substrates to determine cell adhesion. Surface geometries were determined using optical microscopy. Functionalized (F) and unfuctionalized (NF) substrates were characterized using field emission scanning electron microscopy (FESEM) and water contact angle. Stability of the coating in water was also investigated. FESEM images showed surface microgrooves with a micro-topography on the ridges between them. It was observed the entire surface covered with a thin coating of chitosan which followed the surface features. MC3T3-E1 pre-osteoblasts preferentially adhered on the titanium regions whereas C2C12 myoblasts distributed uniformly throughout the whole surface., The authors are grateful for the financial support of the Spanish Ministry of Economy and Competitiveness through the MAT2013-46467-C4-1-R project (including the Feder funds). CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, “Iniciativa Ingenio 2010”, Consolider Program. CIBER actions are financed by the “Instituto de Salud Carlos III” with assistance from the European Regional Development Fund. The authors thank “Dionís” of Universitat Politècnica de València for his valuable help in the microscopy measurements. CR, SR and DMC thank the FCT, POPH/FSE for the SFRH/BPD/90870/2012, SFRH/BD/111478/2015 and SFRH/BD/82411/2011 grants, respectively., info:eu-repo/semantics/publishedVersion

Quantum chemical calculations have unveiled the unexpected biradical character of titanium(IV) enolates from N-acyl oxazolidinones and thiazolidinethiones. The electronic structure of these species therefore involves a valence tautomerism consisting of an equilibrium between a closed shell (formally Ti(IV) enolates) and an open shell, biradical, singlet (formally Ti(III) enolates) electronic states, whose origin is to be basically found in changes of the Ti−O distance. Spectroscopic studies of the intermediate species lend support to such a model, which also turns out to be crucial for a better understanding of the overall reactivity of titanium(IV) enolates. In this context, a thorough computational analysis of the radical addition of titanium(IV) enolates from N-acyl oxazolidinones to TEMPO has permitted us to suggest an entire mechanism, which accounts for the experimental details and the diastereoselectivity of the process. All together, this evidence highlights the relevance of biradical intermediates from titanium(IV) enolates and may be a useful contribution to the foundations of a more insightful comprehension of the structure and reactivity of titanium(IV) enolates.

Hierarchical structures were obtained applying two different nanotexturing surface treatments onto highly rough commercial pure titanium coatings by cold spray: (i) anodic oxidation and (ii) alkaline treatments. An extended surface characterization in terms of topography, composition, and wettability has been performed to understand how those parameters affect to cell response. Primary human osteoblasts extracted from knee were seeded onto the as-sprayed titanium surface before and after the nanotexturing treatments. Cell viability was tested by using MTS and LIVE/DEAD assays, as well as osteoblasts differentiation by alkaline phosphatase (ALP) quantification at 3 and 10 days of cell culture. The combination of micro-/nano-roughness results in a significantly increase of cell proliferation, as well as cell differentiation after 10 days of cell culture in comparison with the non-treated coatings.

Las superficies de los implantes son un foco para la colonización de bacterias, ya sean externas, o se encuentren dentro del organismo. El problema reside en que pueden provocar infecciones severas, con consecuencias devastadoras para el organismo. La dificultad reside en que los implantes son zonas muy poco vascularizadas y tanto los antibióticos, como los antígenos del sistema inmune tienen muy difícil el acceso. Por ello se está estudiando que el propio implante ya lleve consigo propiedades antibacterianas. En concreto, en este proyecto se estudia que implantes de titanio puedan ir recubiertos de un film polimérico con algún principio activo incrustado, que provoque la inhibición de proliferación bacteriana sobre la superficie del implante. Este proyecto contempla la posibilidad de que creando multicapas se pueda ralentizar el proceso de difusión y por tanto, alargar el efecto antibacteriano. Como principios activos empleados para el estudio se ha seleccionado el Carvacrol, un aceite esencial con propiedades antibacterianas y la Doxiciclina, un antibiótico perteneciente al grupo de las tetraciclinas. De esta forma se estudia como varia el proceso de difusión y la caracterización de las superficies de las diferentes muestras dependiendo de las moléculas empleadas.