Thesis (Ph. D.)--University of California, Riverside, 2009. / Includes abstract. Includes bibliographical references. Issued in print and online. Available via ProQuest Digital Dissertations.

Thesis (Ph. D.)--University of Texas at Austin, 1997. / Vita. Includes bibliographical references (leaves 226-241). Available also in a digital version from Dissertation Abstracts.

Orientador: Rubens Caram Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T06:50:38Z (GMT). No. of bitstreams: 1 Moraes_PauloEduardoLeite_M.pdf: 3749651 bytes, checksum: 89146f069c1475908f7a217f78acae9a (MD5) Previous issue date: 2013 / Resumo: O uso de ligas de titânio do tipo ß na fabricação de dispositivos ortopédicos tem aumentado continuamente nos últimos anos. Dentre as ligas do tipo ß promissoras como biomaterial destacam as ligas Ti-Nb. Nesse sistema, a precipitação indesejada da fase 'ômega' é comum e uma maneira de evitá-la é com a adição de Sn. Assim, este trabalho teve como objetivo examinar o processo de fundição de ligas Ti-30Nb (% em peso) com adições de 2, 4, 6, 8 e 10 % em peso de Sn. O trabalho foi elaborado a partir da preparação das amostras em forno a arco voltáico, seguido de conformação por processo de fundição por centrifugação e caracterização química, microestrutural e mecânica. Os resultados obtidos permitem concluir que amostras com geometrias medianamente complexas podem ser obtidas pelo processo de fundição por centrifugação. O uso de molde de cobre evita qualquer reação entre o fundido e as paredes do molde, bem como resulta em ótimo acabamento superficial. A solidificação das ligas Ti-Nb-Sn em molde de cobre resultou em microestrutura com caráter dendrítico acentuado. Observou-se que enquanto o Sn é segregado para regiões interdendríticas e o Nb concentra-se nos ramos dendríticos. No caso do processamento da Liga Ti-30Nb, a elevada taxa de resfriamento imposta pela solidificação em molde de cobre produz microestrutura formada pela martensita ortorrômbica (a"), pela fase ß e pela fase 'ômega'. À medida que o Sn foi adicionado à liga Ti-30Nb, observou-se a supressão da fase 'ômega' e também, a diminuição da fração volumétrica da fase martensítica. A análise por difração de raios-X também permitiu examinar o efeito do Sn nos parâmetros de rede da fase ß. Ensaios de dureza, de medidas de módulo de elasticidade e de ensaios de compressão mostraram que a adição de Sn resulta em comportamento mecânico que é coerente com a variação do parâmetro de rede da fase ß. / Abstract: The use of ß-type titanium alloys in the manufacture of orthopedic devices has increased steadily in recent years. Among the promising ß-type alloys to be applied as biomaterial are the Ti-Nb alloys. In the Ti-Nb system, the unwanted precipitation of 'ômega' phase is common and a way to avoid it is with the addition of Sn. Thus, this study aimed to examine the casting process of Ti-30Nb alloy (wt.%) with additions of 2, 4, 6, 8 and 10 wt% Sn. This work was carried out by preparing samples in arc furnace, forming by using centrifuge casting process and chemical, microstructural and mechanical characterization. The results obtained allowed concluding that samples with moderately complex geometries can be obtained by centrifuge casting process. The use of copper mold prevents any reaction between the melt and the mold walls, and results in excellent surface finishing. The solidification of Ti-Nb-Sn alloys in copper mold resulted in microstructure with pronounced dendritic character. It was observed that while the Sn is segregated to interdendritic regions, the Nb is concentrated in the dendritic branches. In the case of the Ti-30Nb alloy processing, the high cooling rate imposed by cast in copper mold produced a microstructure formed by orthorhombic martensite, ß phase and 'ômega' phase. As Sn is added to the Ti-30Nb alloy, it was observed the 'ômega' phase suppression as well as the decrease of the volume fraction of martensitic phase. X-ray diffraction analyses also made possible to examine the effect of Sn addition on the ß phase lattice parameters. Hardness tests, measurements of elastic modulus and compression tests showed that the addition of Sn results in mechanical behavior that is consistent with the variation of the ß phase lattice parameters. / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Osteomyelitis or bone infections remain very difficult to treat despite advances in treatment regimens and surgical technics. The bone microenvironment and compromised vasculature in addition to infected prosthesis and implants that were put in the bone during prior surgery impedes the antibiotic partition into the bone from systemic therapy in many cases. Treatment often includes surgical debridement of the infected bone and surrounding tissue, removal of implants, systemic antibiotic therapy accompanied with antibiotic containing bone void filler, in most cases polymethylmethacylate (PMMA) based bone cement. Unfortunately, PMMA has many associated problems, including non-biodegradability, inconsistent antibiotic release, and a surface susceptible to bacterial biofilm growth, ultimately necessitating removal and causing recurrent infections. Thus, recent studies have focused on designing novel bone void filling materials to deliver antibiotics and to support bone regeneration. There are two parts to designing a successful bone void filling device/material:(1) local release antibiotic for infection treatment and (2) development of a bone graft substitute to support bone regrowth. In this study, antibiotic releasing bone void filler (ABVF) putty formulations have been designed and tested. Different formulations were examined in this dissertation to describe the three components of the putty formulation - polymer, drug, and substrate. In the first formulation, different custom-made polymers were used to control drug release; Pro Osteon, a hydroxyapatite (HA) and calcium carbonate based bone graft substitute was used to provide support for bone growth. Finally, vancomycin was used as the antibiotic as it is clinically used to treat Staphylococcus aureus, the primary cause of osteomyelitis. In second formulation, commercially available and clinically used polymers, poly(lactic-co-glycolic acid) (PLGA), polycaprolactone (PCL) and, polyethylene glycol (PEG), were used to make the ABVF putty along with Pro Osteon and vancomycin. In the subsequent formulations, delivering combination antibiotics - vancomycin and rifampicin - to treat biofilm infections and, using bioglass (BG) as the substrate for faster bone regrowth were explored; PLGA, PCL and PEG constituted the polymer matrix. The ABVF putty formulations were customizable in terms of three primary components: polymers, bone graft substitutes, antibiotics. Ultimately, these were successful in curing infection and providing bone growth support.

Electrolytic charging of hydrogen, at room temperature and in the absence of externally applied stress, induced surface cracking in 316 stainless steel and cobalt based ZIMALOY. Hot Isostatic Pressed (H.I.P.) ZIMALOY showed less susceptibility to surface cracking than 316 stainless steel samples. The susceptibility of 316 stainless steel to surface cracking was determined with samples in the High Energy Rate Forged (HERF), the sensitized, the annealed, and the annealed and sensitized conditions. Investigations showed that surface cracking typically occurred at specific microstructural features. Hence, the relative susceptibilities of twin boundaries, slip bands, grain boundaries, and heavily sensitized regions was established. It was observed that twin boundaries crack most readily in non-sensitized samples, and that both grain boundaries and twin boundaries crack easily in sensitized structures. These observations, coupled with the similarity between hydrogen embrittlement and failure of orthopedic implants, suggest that orthopedic applications should use H.I.P. ZIMALOY in preference to 316 stainless steel whenever possible, and that when the use of 316 stainless steel is unavoidable, HERFed parts should be used. Further investigations are recommended to better assess the hydrogen compatibility of sensitized 316 stainless steel, and to determine the influence of sensitization on the suitability of 316 stainless steel for orthopedic application. / Master of Science

Thesis (Ph. D.)--Mississippi State University. Department of Agricultural and Biological Engineering. / Title from title screen. Includes bibliographical references.

<p>This study is focused on synthesizing Nitinol by additive manufacturing that can provide desirable mechanical properties for orthopedic implants and adding functionally gradient coating that can enhance both safety and biocompatibility for orthopedic implant applications.</p> <p><br></p> <p>The characteristics of additively manufactured Nitinol, by using the direct energy deposition (DED) technique, were experimentally studied. Because of a unique layer-by-layer manufacturing scheme, the microstructure and associated properties (mechanical and thermo-mechanical properties) of the DED Nitinol is different compared to conventionally produced Nitinol. Both the feasibility of manufacturing defect-free microstructure and the precise control of chemical composition were demonstrated. Effects of chemical compositions and post heat-treatment conditions on the phase transformation temperatures of the DED Nitinol were systematically analyzed and compared with those of conventional Nitinol. More precise control of phase transformation temperature from DED Nitinol was possible due to incoherent precipitate formation during aging heat treatment. In a similar way, the mechanical properties of the DED Nitinol were less sensitive to its chemical compositions and post heat-treatment conditions. The feasibility of the precise control of both mechanical and thermo-mechanical properties of the DED Nitinol was demonstrated which can broaden its applications. </p> <p><br></p> <p>The bulk polycrystalline properties of the NiTi phase were studied via molecular dynamics (MD) simulations. Thermo-mechanical properties that are highly sensitive to chemical composition were not precisely predicted from previous reports and studies. In this study, realistic boundary conditions were applied to calculate bulk polycrystalline properties. Thermally driven phase transitions of NiTi between martensite and austenite are simulated with external stresses in both normal and shear directions. It is shown that phase transformation temperatures are affected by applied external stresses, and realistic values compared to experimental data are correctly predicted only when external stresses in both normal and shear directions are similar to the experimentally observed values of 0.05 – 0.1 GPa. The experimentally observed grain orientation and grain boundary thickness were applied to simulation domains for the prediction of the elastic moduli. The elastic moduli of polycrystalline NiTi structure was calculated as 52 GPa which is close to the experimentally reported value of 20-40 GPa while other studies predicted over 85 GPa. </p> <p><br></p> <p>Lastly, pure titanium gradient layers were coated on the Nitinol surface for orthopedic implant applications to eliminate potentially toxic Ni ion release. Using the DED technique, both the core Nitinol and titanium gradient layers were manufactured with high purity and without microstructural defects. An additional biomedical coating of Hydroxyapatite (HA) was deposited on the outer surface using the cold spray technique. The resultant bonding strength was determined to be 26 MPa which exceeded the requirement of the ISO-13779 standard (15 MPa). The <em>in vitro</em> test of the Ni release rate from the entire gradient Nitinol structure was very low, which was comparable to drinking water.</p>

Thesis (Ph. D.)--University of Alabama at Birmingham, 2008. / Additional advisors: Yogesh K. Vohra, Xu Feng, Jack E. Lemons, Timothy M. Wick. Description based on contents viewed July 8, 2009; title from PDF t.p. Includes bibliographical references.

Thesis (MMed (Surgical Sciences. Orthopaedic Surgery))--University of Stellenbosch, 2010. / No abstract available

published_or_final_version / Orthopaedics and Traumatology / Master / Master of Philosophy