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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 7 (1996), S. 501-505 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Hydroxyapatite powders with reproducibly different Ca/P ratios and powders with varying amounts of co-precipitated magnesium, sodium and potassium were synthesized by a wet method. Solids composition, particle size and morphology, crystalline structure, sintering behaviour and microstructure were investigated in order to understand the effect of composition in the properties of the powders. Under the present conditions of synthesis, it was concluded that magnesium, sodium and potassium will enter the hydroxyapatite lattice in vestigial amounts. Magnesium gives rise to a co-precipitated amorphous phase which crystallizes as β-whitlockite on calcining. A relationship was found between the Ca/P ratio in hydroxyapatite and its sinterability. The sintering process of pure and alkali-containing hydroxyapatites is completed at 1300 °C and leads to dense ceramics in the case of pure and sodium-containing hydroxyapatites but not in potassium-containing material.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract In this work, a bioactive glass is used as a percusor of calcium-phosphate (Ca-P) film deposition onto several polymer-based materials. Both bioinert (high molecular weight polyethylene, HMWPE), and biodegradable (corn starch-based blends, SEVA-C) polymers, unreinforced or reinforced with hydroxylapatite (HA), were coated by the very simple proposed route. Also polyurethane (PU) foams, with an open-cell structure, were mineralized by the proposed method. In fact, it was possible to induce the growth of the Ca-P films not only at the surface, but also in the bulk of the PU foam. These cellular materials are intended for cancellous bone replacement applications. The morphology of the formed films was strongly dependent on the used substrate, its polar character, and on the presence of HA in its composition, as observed by SEM. Nevertheless, a well defined needly like structure was observed in all samples at high magnifications. The Ca:P ratios of the films were between 1.5 and 1.7, i.e. in the range of tricalcium phosphate-hydroxylapatite. Raman spectroscopy and thin-film x-ray diffraction (XRD) evidenced the formation of mostly amorphous calcium-phosphate films. After scraping the coating from the polymer surface and heat-treating the resulting powder at 1000°C for 1 h, HA and β-tricalcium phosphate (TCP) typical peaks were found on XRD patterns.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 33 (1998), S. 215-221 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Zirconia–titanium and zirconia–titanium alloy joints were made by diffusion bonding under an inert atmosphere at temperatures in the 1162–1494°C range. To inhibit the strong oxygen uptake by the titanium member a platinum insert was alternatively used. The microstructures and elemental profiles across the joints were investigated by scanning electron microscopy imaging and energy-dispersive spectroscopy or wavelength-dispersive spectroscopy microanalysis. It was found that direct ZrO2–Ti joining produces oxygen saturation in the Ti member and the formation of (Ti,Zr)2O at the interface. ZrO2/Pt/Ti joints present a complex layer sequence which at lower temperatures can be described on the basis of the Pt–Ti binary, except near the ceramic where a (Pt,Zr)-rich layer forms; at higher temperatures these joints develop an oxide layer of composition Ti2O3, this oxide probably resulting from local decomposition of the ceramic and reaction of oxygen with the incoming titanium. When Ti is replaced by the Ti–6 wt% Al–4 wt% V alloy in joints where Pt is present, the main consequences are the presence of liquid at lower joining temperatures and the earlier development of the oxide layer, now of nominal composition TiO. In all Pt-containing joints a phase of nominal composition Ti3Pt2 forms; it is advanced that this may be an equilibrium phase not predicted by the Pt–Ti diagrams available. All joints are weak, the fracture path running through the metal in the case of direct ZrO2–Ti joints and through the interface between the ceramic and the (Pt,Zr)-rich layer in joints where Pt is present.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2011-07-08
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics
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