Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 86-89). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 86-89). Also available on the Internet.

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: Robert L. Opila, Dept. of Materials Science & Engineering. Includes bibliographical references.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 94-98). Also available in electronic version. Access restricted to campus users.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 78-83).

This thesis reports on the synthesis and characterization of PtNi dendrimer-encapsulated nanoparticles (DENs) containing on average 147 atoms. This is significant because PtNi DENs have not yet been reported. The DENs were prepared by first complexation of Pt²⁺ to the interior tertiary amines of a sixth-generation, hydroxyl-terminated (G6-OH) poly(amidoamine) (PAMAM) dendrimer template, followed by chemical reduction in the presence of free Ni²⁺ to yield PtNi DENs. UV-visible (UV-vis) absorbance measurements exhibit a broad, monotonically decreasing band characteristic of nanoparticle formation. Upon dialysis in both H₂ and O₂ this band is observed to decrease in absorbance. Transmission electron microscopy (TEM) studies indicate that particles have been synthesized and are 1.8 + 0.2 nm before dialysis and 1.9 + 0.2 nm after dialysis under H₂. Results obtained from X-ray photoelectron spectroscopy (XPS) show that Pt is present and the Pt(4f7/2) binding energy is observed at 72.0 eV before dialysis and 71.5 eV after dialysis under H₂. XPS shows that Ni is present and the Ni(2p3/2) binding energy is centered at 857.0 eV before dialysis and 856.6 eV after dialysis under H₂. Finally, oxidative electrochemical stripping is observed at 1.07 V (vs NHE) for PtNi DENs immobilized on glassy carbon electrodes (GCE) and is tentatively assigned to Ni. / text

Conductive and flexible nanocomposites can have wide applications in textiles, including wearable sensors, antenna, electrodes, etc. The objective of this research is to develop electrically conductive fibers and films that are flexible and deformable for use in textile structures able to accommodate the drape and movement of the human body. To achieve this objective, we evaluate the electrical properties of PEDOT:PSS/nickel nanostrand as well as nylon 6/nickel nanostrand nanocomposites. Nickel nanostrands (NiNS) were first used to reinforce an intrinsically conductive polymer, Poly(3,4-ethylenedioxythiophene) (PEDOT:PSS), in order to fabricate nanocomposite films with high electrical conductivity. The electrical properties of the films were evaluated by the Van der Pauw method. The addition of 10 wt% nanostrands in PDOT:PSS provided a two order of magnitude improvement in electrical conductivity. In addition to PDOT:PSS, nylon 6/NiNS nanocomposite fibers were produced using electrospinning and exhibited diameters in the sub-micron range. The NiNS-reinforced fibers had electrical conductivity that exceeded the ESD range, which offers the potential for use in protective textile applications. / text

Due to its excellent biocompatibility and mechanical properties, Ti-6Al-4V alloy has been extensively used in the medical field, especially as a material for hard tissue replacement. Owing to the unique shape memory and superelastic properties, NiTi shape memory alloy (SMA, with 50.8 at.% of Ni) has been investigated for load-bearing applications in orthopedics and dentistry. Since the longevity of current metal implants is approximately 10 to 15 years, many patients need to have revision surgeries in their lifetime. Therefore, there is great interest in the long-term stability, biocompatibility, bioactivity and other properties of Ti-6Al-4V and NiTi SMA implants. Implant-associated infections also pose serious threat to the success of metal implants. The goal of this project was to investigate several low-temperature surface modification techniques, including anodization and electrochemical deposition, and formulate coatings for potential clinical applications. Accordingly, several types of coatings were synthesized on Ti-6Al-4V and NiTi SMA substrates. Various aspects of the coatings, such as morphology, chemical composition, crystallinity, phase and bioactivity, were analyzed. Firstly, a systematic study on the formation of titania nanotubes on Ti-6Al-4V by anodization was performed. Anodizing voltage and time were varied for comparisons. A dense and compact titania nanotube layer was synthesized on Ti-6Al-4V by anodizing at 25 V for 20 min. The titania nanotubes formed were rutile. After annealing at 500oC for 1 h, the titania nanotubes became anatase. The anatase phase exhibited better wettability than the rutile phase. Secondly, dense and compact apatite coatings were formed on NiTi SMA samples through electrochemical deposition using mainly double-strength simulated body fluid (2SBF) as the electrolyte. The deposition conditions were varied and apatite coating characteristics studied. With the inclusion of collagen molecules (0.1 mg/ml) in the electrolyte (2SBFC), apatite/collagen composite coatings were fabricated. Collagen fibrils were not only observed on the surface of composite coatings but also were embedded inside in the coatings and at the coating-substrate interface. Results obtained from transmission electron microscopic and X-ray diffraction analyses showed that the apatite crystals in apatite coatings and apatite/collagen composite coatings were calcium-deficient carbonated hydroxyapatite. Apatite/collagen composite coatings exhibited excellent hydrophilicity, whereas apatite coatings displayed hydrophobic surfaces. Finally, gentamicin-loaded, tobramycin-loaded, and vancomycin-loaded apatite coatings and apatite/collagen composite coatings were synthesized on NiTi SMA samples through electrochemical deposition using different drug concentrations in the electrolytes. A comparative study of apatite coatings and apatite/collagen composite coatings as drug delivery vehicles were conducted. Different aspects of antibiotic-loaded coatings (surface characteristics, chemical composition, wettability, etc.) and in vitro release behaviour were investigated. The antibiotics were physically embedded in coatings during coating formation. Upon sample soaking in phosphate-buffered saline (PBS), the release profiles established for antibiotic-loaded coatings demonstrated different levels of initial burst release and subsequent steady release characteristics. Apatite coatings and apatite/collagen coatings displayed preferential incorporation of specific antibiotics. For instance, apatite/collagen coatings showed better vancomycin incorporation than apatite coatings and the incorporation of vancomycin was better than tobramycin for apatite/collagen coatings. Apatite coatings demonstrated better tobramycin incorporation than apatite/collagen composite coatings. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

M. Tech. Metallurgical Engineering / Mild steel is vulnerable to corrosion; this behaviour affects the material strength and electrochemical behaviour during industrial application. Mild steel also has poor tribological resistance; its application for the components of machines, however, requires good tribological property. The cost incurred from equipment failures, properties loss and increased production overheads makes is imperative to enhance mild steel's electrochemical and tribological properties. Electroless nickel plating has found extensive use in various industries attesting to its exceptional properties. The effect of bath parameters on the electroless plating process is of importance as this affects the adhesion, morphological behaviour, electrochemical properties and uniformity of coating. The key aim of this research is: To generally improve the understanding of the effect of electroless binary and ternary alloys on the corrosion and wear resistance of mild steel using weight loss method, potential measurement, linear polarization and tribological sliding wear tests. This work studies the effect of temperature, concentration, deposition time and the inclusion of Tin (Sn) as a third addition to the electroless bath. Corrosion and wear behaviour of the electroless plated mild steel was studied.

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