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  • 1
    Electronic Resource
    Electronic Resource
    Study of ZrO〈sub〉2〈/sub〉-TiO〈sub〉2〈/sub〉 Ceramics with SnO〈sub〉2〈/sub〉, SrO〈sub〉2〈/sub〉 and Nb〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 Additives for Dielectric Resonator Application (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 591-593 (Aug. 2008), p. 381-386 
    Details
    ISSN: 1662-9752
    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: This paper presents a systematic study about ceramics made of zirconium oxide andtitanium oxide (ZrO2-TiO2) doped with tin oxide (SnO2), strontium oxide (SrO2) and niobium oxide(Nb2O5). These ceramics can be applied as dielectric resonators in microwave systems fortelecommunications. For a good microwave performance, these ceramics must reach someparameter values as high dielectric constant and high quality factor due to the dielectric losses. Theceramics were manufactured using suitable powder mixtures of ZrO2-TiO2 with additions of 1 % ofSnO2, SrO2 and Nb2O5, resulting in four different kinds of samples for analysis. The samples werecompacted by an uniaxial (190 MPa) and an isostatic (300 MPa) pressing, sintered at 1200 °C for 3hours, characterized in the chemical compound formation using X-ray Diffraction (XRD) andscanned for microstructure densification degree and grain distribution analysis in Scanning ElectronMicroscopy (SEM). The dielectric parameters were measured using a microwave system. The maingoal of present procedure is manufacture ceramic materials for promising application as dielectricresonators
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.591-593.381.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of Nb〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 on the Electrical Properties of Porous ZrO〈sub〉2〈/sub〉-TiO〈sub〉2〈/sub〉 Ceramic Used as Soil Humidity Sensor for Environmental Monitoring (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 591-593 (Aug. 2008), p. 402-407 
    Details
    ISSN: 1662-9752
    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: The soil humidity sensor plays fundamental role in the monitoring of hazard areas withlandflows and landslides, about which in Brazil stories exist since 1671. Nowadays, it is just knownthat the majority of the mass movements in the hillsides occur in rainy periods, what makes thewater the most important deflagrator agent of these movements, decreasing the soil resistance,increasing its specific weight and increasing the internal pressures as well. In this direction, thesensing elements developed by Group SUCERA/LAS/INPE uses the advantages presented forceramics, in particular metal oxides, in terms of their mechanical strength, their resistance tochemical attack and their thermal and physical stability. In this work the results of thecharacterization analyses of sensor elements of ZrO2-TiO2 doped with 1, 5, 10, 15 e 20 % Nb2O5porous ceramic, sintered at 1200 ºC are shown and discussed
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.591-593.402.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanical Properties of Zirconia Toughened Alumina Composites with TZP Partially Nanostructured Sintered by Liquid Fase (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 591-593 (Aug. 2008), p. 436-440 
    Details
    ISSN: 1662-9752
    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: A comparative study between alumina added niobia ceramics and two alumina zirconiacomposites from nanostructured TZP (7% and 14% weight) was made. On this composites thezirconia were yttria stabilized and the alumina were submicron structured. As sintering aid amixture of magnesia, niobia and talc were used on all samples. The sintering was performed at1450 oC during 60 minutes. The characteristic grain size and shape of an alumina and zirconiapowders, aggregates and agglomerates were characterized. The sintering ceramics were evaluatedthrough hardness, fracture toughness and 4 point bending test. Weibull statistic was applied on theflexural results. Although the fracture toughness result from ZTA were lower, and seems to beaffected by the liquid fase, the hardness and Weibull modulus were higher than alumina niobia. Thegrains size and the homogeneity of its distributions on the microstructure of this ceramics wascorrelated to these higher values. The results from these alumina zirconia composites showed apotential to apply as a ballistic armor material
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.591-593.436.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Evaluation of the Performance of α-SiAlON Tool when Turning Ti–6Al–4V Alloy without Coolant (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 591-593 (Aug. 2008), p. 554-559 
    Details
    ISSN: 1662-9752
    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: Due to their high hardness and wear resistance, Si3N4 based ceramics are one of the mostsuitable cutting tool materials for machining cast iron, nickel alloys and hardened steels. However,their high degree of brittleness usually leads to inconsistent results and sudden catastrophic failures.This necessitates a process optimization when machining superalloys with Si3N4 based ceramiccutting tools. The tools are expected to withstand the heat and pressure developed when machiningat higher cutting conditions because of their high hardness and melting point. This paper evaluatesthe performance of α-SiAlON tool in turning Ti–6Al–4V alloy at high cutting conditions, up to250 m min−1, without coolant. Tool wear, failure modes and temperature were monitored to accessthe performance of the cutting tool. Test results showed that the performance of α-SiAlON tool, interms of tool life, at the cutting conditions investigated is relatively poor due probably to rapidnotching and excessive chipping of the cutting edge. These facts are associated with adhesion anddiffusion wear rate that tends to weaken the bond strength of the cutting tool
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.591-593.554.pdf
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  • 5
    Electronic Resource
    Electronic Resource
    α-SiAlON: Development and Machining Test on Gray Cast Iron (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 591-593 (Aug. 2008), p. 565-571 
    Details
    ISSN: 1662-9752
    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: The α-SiAlON ceramic cutting tool insert is developed. Silicon nitride and additivespowders are pressed and sintered in the form of cutting tool inserts at temperature of 1900 oC. Thephysics and mechanical properties of the inserts like green density, weight loss, relative density,hardness and fracture toughness are evaluated. Machining studies are conducted on grey cast ironworkpiece to evaluate the performance of α-SiAlON ceramic cutting tool. In the paper the cuttingtool used in higher speed showed an improvement in the tribological interaction between the cuttingtools and the grey cast iron workpiece resulted in a significant reduction of flank wear androughness, because of better accommodation and the presence of the graphite in gray cast iron. Theabove results are discussed in terms of their affect at machining parameters on gray cast iron
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.591-593.565.pdf
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  • 6
    Electronic Resource
    Electronic Resource
    Comparative Study on Turning CI and CGI Using Silicon Nitride Cutting Tools (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 591-593 (Aug. 2008), p. 572-577 
    Details
    ISSN: 1662-9752
    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: There has been a great interest for improving the machining of cast iron materials in theautomotive and other industries. Comparative studies for tool used to machine grey cast iron (CI)and compacted graphite iron (CGI) on dry machining were also performed in order to find out whyin this case the tool lifetime is not significantly higher. However the machining these materialswhile considering turning with the traditional high-speed steel and carbide cutting tools present anydisadvantages. One of these disadvantages is that all the traditional machining processes involve thecooling fluid to remove the heat generated on workpiece due to friction during cutting. This paperpresent a new generation of ceramic cutting tool exhibiting improved properties and importantadvances in machining CI and CGI. The tool performance was analyzed in function of flank wear,temperature and roughness, while can be observed that main effects were found for tool wear, wereabrasion to CI and inter-diffusion of constituting elements between tool and CGI, causing crater.However the difference in tool lifetime can be explained by the formation of a MnS layer on thetool surface in the case of grey CI. This layer is missing in the case of CGI
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.591-593.572.pdf
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  • 7
    Electronic Resource
    Electronic Resource
    High and Room Temperature Mechanical Evaluation of SiC Ceramics with Alumina and Rare Earth Oxides Additions (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 591-593 (Aug. 2008), p. 593-597 
    Details
    ISSN: 1662-9752
    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: In this work, the mechanical properties of SiC samples with (5 wt%) alumina and (5wt%) rare earth oxides (REO) additions were investigated at room and high temperatures. Thepossibility of using REO instead of pure yttria could bring cost reductions to obtain sintered SiCceramics. The powders were mixed, milled, sieved and hot-pressed at 1800ºC in argon atmosphere.Hardness and fracture toughness were evaluated at room temperature. The compressive creepbehavior was carried out under stress range from 150 to 300MPa and temperatures of 1300, 1350and 1400ºC. After creep tests, the surface analysis of the samples by XRD and SEM showedindications of oxidation reactions, cavity and cracking. The possible creep mechanisms activated inthis system were diffusion, grain boundary sliding and cavitation
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.591-593.593.pdf
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  • 8
    Electronic Resource
    Electronic Resource
    Turning of Compacted Graphite Iron Using Commercial TiN Coated Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 under Dry Machining Conditions (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 591-593 (Aug. 2008), p. 604-609 
    Details
    ISSN: 1662-9752
    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: Due to their high hardness and wear resistance Si3N4 based ceramics are one of the mostsuitable cutting tool materials for machining hardened materials. Therefore, their high degree ofbrittleness usually leads to inconsistent results and sudden catastrophic failures. Improvement of thefunctional properties these tools and reduction of the ecological threats may be accomplished byemploying the technology of putting down hard coatings on tools in the state-of-the-art PVDprocesses, mostly by improvement of the tribological contact conditions in the cutting zone and byeliminating the cutting fluids. However in this paper was used a Si3N4 based cutting toolcommercial with a layer TiN coating. In this investigation, the performance of TiN coating wasassessed on turning used to machine an automotive grade compacted graphite iron. As part of thestudy were used to characterise the performance of cutting tool, flank wear, temperature androughness. The results showed that the layer TiN coating failed to dry compacted graphite ironunder aggressive machining conditions. However, using the measurement of flank wear technique,the average tool life of was increased by Vc=160 m/min.The latter was also observed using atoolmakers microscope and scanning electron microscopy (SEM)
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.591-593.604.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    Study of Cutting Forces on Machinability Properties of Gray Cast Iron Using New Ceramics Cutting Tools (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 591-593 (Aug. 2008), p. 598-603 
    Details
    ISSN: 1662-9752
    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: During gray cast iron cutting, the great rate of mechanical energy from cutting forces isconverted into heat. Considerable heat is generated, principally in three areas: the shear zone, rakeface and at the clearance side of the cutting edge. Excessive heat will cause undesirable hightemperature in the tool which leads to softening of the tool and its accelerated wear and breakage.Nowadays the advanced ceramics are widely used in cutting tools. In this paper a compositionspecial of Si3N4 was sintering, characterized, cut and ground to make SNGN120408 and applyed inmachining gray cast iron with hardness equal 205 HB in dry cutting conditions by using digitalcontrolled computer lathe. The tool performance was analysed in function of cutting forces, flankwear, temperature and roughness. Therefore metal removing process is carried out for threedifferent cutting speeds (300 m/min, 600 m/min, and 800 m/min), while a cutting depth of 1 mmand a feed rate of 0.33 mm/rev are kept constant. As a result of the experiments, the lowest maincutting force, which depends on cutting speed, is obtained as 264 N at 600 m/min while the highestmain cutting force is recorded as 294 N at 300 m/min
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.591-593.598.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    Compaction Behaviour of Yttria-Zirconia Powders Obtained from Micro and Nanoparticles Mixtures (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 591-593 (Aug. 2008), p. 504-509 
    Details
    ISSN: 1662-9752
    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: The densification behavior of mixtures of nanocrystalline and conventionalmicrocrystalline zirconia powders undergoing uniaxial pressing was investigated. The mixtureswere obtained with ratios between 10 and 80 wt.% of nanoparticulate powder added to themicroparticulate powder. Nitrogen and Mercury porosimetry were used to measure the pore sizedistributions of the compacts. The powders and the fracture surfaces of the compacts were observedvia SEM. The results showed that compacts of the powder mixtures attain higher densities duringpressing than the unmixed powders. The powder mixture with 80 wt. % of nanoparticles showed thebetter particle packing efficiency. A comparison between density values of uniaxial and isostaticpressing also was done and indicated that the best results were obtained by the isostatic method
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.591-593.504.pdf
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