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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 141-143 (July 2008), p. 255-260 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: This paper presents an analysis of the effect of CO2 laser processing parameters on thesurface modification and heat treatment of steels. The CO2 laser and sample movement processparameters are presented. The controlled operation of these in conjunction with each other isrequired to obtain better surface hardness and structure. H13 tool steel samples were rotated at highspeeds to keep exposure times below 0.3s. Laser processed samples were analysed using EDXspectroscopy, optical microscopy, Vickers and Martens micro-hardness testing, and X-raydiffraction (XRD). Results show how the hardness profile through the surface is related to the lasertreatment and resultant microstructures. Increased surface hardness was noted due to a completemicrostructural transformation to an amorphous state in the glazed samples. The usefulness of suchcoatings on tool steels, in conjunction with other thermal barriers, for the forming of semi-solidsteel alloys is presented
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 396-398 (Oct. 2008), p. 659-662 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Selective laser sintering (SLS) has the potential to fabricate bioresorbable polymer / ceramic composite scaffolds with pre-designed external and internal architecture that can be used for bone tissue engineering applications. Scaffolds were fabricated using poly-ε-caprolactone as the base material. The effect of 15 and 30 wt% of hydroxyapatite (HA) addition was investigated in terms of compressive properties, accuracy, surface topology, and wettability. Fabricated dimensions of PCL microstructures showed great deviations from their nominal values. Average surface roughness was found to be Ra=25±4 µm. Increased HA content had no statistically significant effect on accuracy and surface roughness. However the addition of HA had a significant influence on compressive properties, hydrophobicity and wettability of the samples. Addition of 30 wt% HA improved initial compressive modulus of pure PCL scaffolds from 1.31±0.08 MPa to 1.58±0.18 MPa. Yield strength values increased from 0.14±0.07 MPa to 0.17±0.01 MPa by adding 15 wt% of HA, but decreased with further HA addition. Yield strain for all compositions was over ε=0.06. Increased HA content decreased hydrophobicity and increased wettability of scaffold surfaces. The study demonstrated the ability of SLS to fabricate tissue engineering scaffolds, and the positive effect of HA particle reinforcement in terms of compressive mechanical properties and surface characteristics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 396-398 (Oct. 2008), p. 663-666 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Three dimensional printing was investigated for fabricating hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) composite scaffolds using calcium phosphate based ceramics and calcium phosphate cement chemistry. Scaffolds were formed by printing an aqueous sodium phosphate solution on the powder bed consisting of a mixture of dicalcium phosphate anhydrous (DCPA) and calcium hydroxide powders. The sodium phosphate solution was functioning as a binder material and also as the initiator of the wet chemical reaction. Compressive mechanical properties of printed samples were examined as a function of saturation level that was inversely proportional to the powder to liquid ratio. To increase mechanical properties and obtain hydroxyapatite and β-TCP composites, the printed samples were sintered. The effect of sintering parameters including dwell time and sintering temperature were also examined. X-ray diffraction (XRD) was used to examine material composition at different stages of the manufacturing process and to confirm the presence of HA and β-TCP in the final stage. The effect of sintering procedure on the surface topology of the samples was examined using scanning electron microscopy (SEM)
    Type of Medium: Electronic Resource
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