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Carbon-fiber-reinforced ultrahigh-temperature ceramic (C/UHTC) matrix composites are an attractive candidate for fabricating various hot structures. The present study aimed to establish a Si-free Zr–Ti melt-infiltration method for fabricating C/UHTC matrix composites. To achieve this, the wettability of Zr–Ti alloys on carbon and their reactivity to carbon were examined. The alloys were melted on graphite plates and infiltrated into model preforms, which were made of porous carbon and had median pore diameters of 3 μm. The results showed that the apparent contact angle between Zr–Ti and C measured from melted alloys on carbon in room temperature was ~20–42° and that the alloys infiltrated into the preforms regardless of the Zr or Ti content. However, with an increase in the Zr content in the alloys, carbon disappeared and was absorbed into the alloys since the reactivity of Zr was higher than that of Ti and the specific surface area of the porous preform was higher than that of carbon-fiber-reinforced carbon composites, which are a typical preform of C/UHTC matrix composites. These results clearly indicate that not only the capillary flow during infiltration but also the reactivity of alloys to preforms should be considered in the process design for fabricating high-density composites via Zr–Ti infiltration.

In this work we studied the main surface characteristics together with the in vivo osseointegration of three Zr-Ti alloys with hydroxyapatite-zirconia-silver (HAP-ZrO2- Ag) coating layer. The main purpose was to provide a quantitative evaluation and interpretation from micro to nano scale of the processes involved in the osseointegration of the HAP-ZrO2-Ag coated Zr-Ti specimens in a pig model. The surface characteristics were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). After the insertion of the implants into pig tibia, the osseointegration was investigated by means of biochemical analysis as well as bone histomorphometric and computed tomography measurements. The results of this in vivo study sustains that the capacity of the Zr-Ti specimens coated with HAPZrO2- Ag to promote osteogenesis is significant during the first month after implantation as compared with the control, being influenced by the interactions between bone tissue and HAP-ZrO2-Ag surfaces, but also by the chemical composition of the alloys.

Fil: Gamba, Nadia Soledad. Universidad Nacional del Litoral. Facultad de Ingeniería Química; Argentina Zirconium-based materials, both oxides and metals, have been studied for their important technological applications. Specifically the ZrO2, due to its high stability, biocompatibility and corrosion resistance. The tetragonal and cubic phases are the most interesting ones considering its properties and many researches attempt to stabilize these phases at low temperatures. The aim of this work is to contribute to the knowledge on this topic and to make progress in this area by using a synthesis method that produces particles with smaller size while also doping these materials with V and Ti. Moreover, Zr-based metal alloys are used in different applications such as aircraft, space devices, chemical and nuclear industries, among others. In this thesis, the synthesis and characterization of nanostructured materials of Zr-V and Zr-Ti oxide, as well as Zr-Ti metal alloys, were done. The oxides synthesis was performed by solgel method using alkoxide precursors, followed by a heat treatment. For the metallic systems, the formation of metal hydrides and alloys were studied by reactive mechanical milling with hydrogen, using zircaloy tunings and titanium metal. In all cases, the materials obtained presented homogeneous composition and nanostructured nature. It was possible to stabilize the ZrO2 tetragonal phase for certain V and Ti compositions. The nanostructured Zr-Ti alloys were synthesized in two stages: first the formation of individual hydrides, followed by their thermal decomposition under argon atmosphere. The employed temperatures are lower than the melting point for these metals, which is interesting for recycling zircaloy tunings. Los materiales con base circonio, tanto oxídicos como metálicos, han sido estudiados por sus importantes aplicaciones tecnológicas En particular, el ZrO2 por su elevada estabilidad, biocompatibilidad y resistencia a la corrosión. Las fases tetragonal y cúbica son de mayor interés y se busca estabilizarlas a temperaturas bajas. Este trabajo intenta contribuir al conocimiento y avanzar en esta temática empleando un método de síntesis para producir partículas con menor tamaño y dopando con V y Ti. Por otra parte, las aleaciones metálicas con base Zr son muy utilizadas en diferentes aplicaciones como la industria de aviación, espacial, química y nuclear, entre otras. En esta tesis, se realizó la síntesis y caracterización de materiales nanoestructurados oxídicos Zr-V y Zr-Ti y metálicos del sistema Zr-Ti. La síntesis de los óxidos se llevó a cabo por el método Solgel empleando precursores alcóxidos seguido de tratamientos térmicos. Para el sistema metálico, se estudió la formación de hidruros y aleaciones metálicas por molienda mecánica reactiva en hidrógeno, empleando virutas de zircaloy y titanio metálico. En todos los casos, los materiales obtenidos fueron de composición homogénea y de naturaleza nanoestructurada. Se logró estabilizar la fase tetragonal de ZrO2 para determinadas composiciones de V y Ti. Se lograron sintetizar aleaciones Zr-Ti en dos etapas: la formación de los hidruros individuales seguido de sus descomposiciones en argón. Las temperaturas empleadas son más bajas que las requeridas para la fusión de los metales, resultando interesante para el reciclado de virutas de zircaloy. Universidad Nacional del Litoral Consejo Nacional de Investigaciones Científicas y Técnicas

A photoelectrochemical investigation on anodic films of different thickness grown on sputter-deposited Zr and Zr–20 at.%Ti was carried out. The estimated optical band gap and flat band potential of thick ( U F ≥ 50 V) anodic films were related to their crystalline structure and compared with those obtained for thinner ( U F ≤ 8 V/SCE) anodic oxides having undetermined crystalline structure. The E g values obtained by photocurrent spectroscopy were also compared with the experimental band gap estimated by other optical ex situ techniques and with the available theoretical estimates of the zirconia electronic structures in an attempt to reconcile the wide range of band gap data reported in the literature. Finally, the optical band gap and flat band potential values obtained for tetragonal Zr 0.8 Ti 0.2 O 2 mixed oxide were compared with that expected on the basis of a correlation between E g and the film composition.

The aim of this work was to study a series of 11 different compositions of Ti-Zr binary alloys resistance to aggressive environment, i. e., their ability to keep their surface properties and mass when exposed to them as a way to evaluate their performance as biomaterials. The first stage was devoted to the fabrication of tablets from these alloys by Plasma-Skull casting method using a Discovery Plasma machine from EDG Equipamentos, Brazil. In a second stage, the chemical composition of each produced tablet was verified. In a third stage, the specimen were submitted to: as-cast microstructure analysis via optical and scanning electron microscopy (OM and SEM), x-ray dispersive system (EDS) chemical analysis via SEM, Vickers hardness tests for mechanical evaluation and corrosion resistence tests in a 0.9% NaCl solution to simulate exposition to human saliva monitored by open circuit potential and polarization curves. From the obtained results, it was possible to infer that specimens A1 (94,07 wt% Ti and 5,93% wt% Zr), A4 (77,81 wt % Ti and 22,19 wt % Zr) and A8 (27,83 wt% Ti and 72,17 wt% Zr), presented best performance regarding to corrosion resistance, homogeneity and hardness which are necessary issues for biomaterials to be applied as orthopedic and odontological prosthesis Este trabalho teve como finalidade estudar uma série de onze ligas metálicas binárias, titânio zircônio, quanto à capacidade de resistirem às deteriorações sem sofrerem modificações de suas propriedades iniciais de massa e superfície quando expostas a meios agressivos, como condição fundamental para que as mesmas sejam aplicadas como biomateriais. A primeira etapa tratou da confecção das amostras das ligas em forma de pastilhas, empregando-se o processo de fundição Plasma Skull realizado na máquina Discovery Plasma, produzida no Brasil pela EDG Equipamentos. Na segunda etapa, as amostras confeccionadas foram submetidas aos ensaios para a determinação da composição química resultante de cada liga da série após a fusão. E durante a terceira etapa foram feitos os procedimentos de avaliações das amostras quanto à homogeneidade e apresentação da microestrutura de cada uma das ligas no estado bruto de fusão, como resultados dos ensaios metalográficos por microscopia óptica e microscopia eletrônica de varredura acoplada a espectroscopia por energia dispersiva de raios-x; quanto à propriedade mecânica de dureza medida em escala Vickers (HV); e quanto às propriedades químicas de resistência à corrosão, quando expostas em solução de cloreto de sódio 0,9 %, para simular a saliva, empregando-se o monitoramento do potencial de circuito aberto e as curvas de polarização. A partir dos resultados obtidos foi possível identificar as pastilhas de composições químicas A1 (94,07% de Ti e 5,93% de Zr), A4 (77,81% de Ti e 22,19% de Zr) e A8 (27,83% de Ti e 72,17% de Zr) que resultaram como maiores detentoras do conjunto de propriedades de resistência à corrosão, homogeneidade e dureza, as quais são mais necessárias em biomateriais tipo próteses ortopédicas ou odontológicas