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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 336-338 (Apr. 2007), p. 1599-1602 
    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: The aim of this study was to analyze the microstructure and to observe the surface reactivity ofa composite system composed of two kinds of zirconia/alumina (Z/A) composites and Vita alphaglass-ceramic, which would satisfy the biocompatibility and strength requirements for dental applications.Two zirconia/alumina composites defined as specimen A and B were used as the substrate of fixed partialdenture, while commercial Vita alpha glass-ceramic as the coating-glass.[removed info]From the experiment we canfind the following results. Zirconia particles migrated into grain boundaries and located at three or fourgrain junctions of alumina particles. The crack pattern is consistently transgranular for the zirconia grains,whereas it is intergranular for alumina grains. The mechanical properties of the composite with 66.6wt%zirconia was superior to that of 33.3wt% zirconia-composed composite, while the homogeneous bondbetween Vita alpha glass-ceramic and Z/A composites are distinct. Therefore, this system composed ofZ/A composites and Vita alpha glass-ceramic would satisfy matching properties of dental requirementsand it has a great future to be used as all-ceramic restoration materials
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 336-338 (Apr. 2007), p. 1361-1363 
    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: The SiC/Si multilayer composites were fabricated successfully by reaction sintering methodwith normal stacked papers as the raw materials. Paper was cut into rectangular sheets and stacked, theninfiltrated with phenolic resin to get a laminar structure. This paper /resin laminar composite wastransformed into porous carbon with laminar structure after heating at 800 oC for 2h in N2 atmosphere.Finally this porous laminar carbon was reheated with silicon powder at 1450-1650oC for 1-2h in a vacuumfurnace and SiC/Si multilayer composites can be obtained through the in-situ reaction between carbon andliquid silicon. The microstructure, reaction mechanism, phase composition and mechanical properties ofthese multilayer composites were researched. The final material shows a distingished laminar structurewith alternating arrangement of SiC thick layers and silicon thin layers. SiC layer was composed bybeta-SiC and a little of free silicon and carbon not reacted. The capillarity infiltration and in-situ reactionof liquid silicon act key roles in this process. Higher strength and non-catastrophic failure mode for thismaterial were observed
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 336-338 (Apr. 2007), p. 1144-1147 
    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: Reaction bonded silicon carbide (RB-SiC) was fabricated by phenol resin, starch, solidifiedagent and silicon powder through the following steps: first, carbonizing at high temperature for 7-9h,infiltrating silicon at 1450-1600oC for 0.5-2h, and then removing excessive silicon at 1700oC for 0.5h.Scanning electron microscopy and X-ray diffraction were employed to characterize and analyze themicrostructures and phase composition of the preforms and the final RB-SiC products. In addition, theeffect of carbonization temperature, the amount of starch and solidified agent on strength and apparentporosity of final RB-SiC were also discussed. The results showed that the carbonization process of phenolresin can be divided into three steps: at temperatures from 400oC to 600oC, the structure of polymerchanges less; at temperatures from 600oC to 1000oC, the fundamental chain of polymer is destroyed, andinverts to glass-like carbon; at temperatures from 1000oC to 1200oC, with the increasing of carbonizationtemperature, the structure of glass-like carbon changes into the structure of disorder graphite. And theincreased micro-pores could be obtained by adding starch
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 336-338 (Apr. 2007), p. 1320-1323 
    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: In this paper, the mechanical properties of porous Si3N4/SiC composite prepared by differentforming method (uniaxial pressing and gel-casting) were compared. Using gelcasting and two stepssintering technology, the porous SiC-particle/Si3N4 composites with a high strength, uniform structureand a relative high porosity were obtained by adding a little amount of nano carbon in slurry. The flexuralstrength of optimized material reaches to 100MPa and its porosity is more than 60%. But using uniaxialpressing and sintering at N2 atmosphere, because the green bodies have the high density, and the densitydistribution of a powder compact was not uniform, the flexural strength is not high, and at the same time,the microstructure is not uniform also
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 544-545 (May 2007), p. 391-394 
    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 SiC/h-BN ceramic composites with different h-BN size were fabricated by PlasmaActive Sintering (PAS) method. For the SiC/ nano-sized h-BN ceramic composites, when the h-BNcontent was increased, because the nano-sized h-BN crystals were homogeneously dispersed aroundthe SiC grains of the matrix, the bending strength and fracture toughness of the composites decreasedslowly, but the hardness decreased sharply, therefore the machinability and thermal shock resistancewere improved noticeable
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 569 (Jan. 2008), p. 113-116 
    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: Copper and aluminium laminates are alternately stacked and sintered by PAS at T=743Kunder different pressures. Microstructure of the cross section of the samples are characterized andanalyzed by means of Optical Microscope (OM), Scanning Electron Microscope (SEM) and EnergyDispersive Spectroscope (EDS). The results show that the initial Al layers melted and producedAl-rich liquid phase during sintering at T=743K, and the Al-rich liquid phase ultimately formedcomplicated L layer consisting of the saturated solid solution phase Al(Cu) and the two-phaseAl2Cu-Al(Cu) eutectic when the laminates was cooled to room-temperature. The interface betweenthe Cu layer the L layer consists of solid solution(α), Al2Cu3(δ)and Al2Cu(θ) layer. Voids and cracksare not found at or near the interfaces of the polished samples. The most important effect of thepressure is to change the shapes of interfaces, which almost smooth at 10MPa but flexual at 50MPa
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 569 (Jan. 2008), p. 45-48 
    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: SiC particles coated with nano-BN were synthesized and the machinable SiC/BN ceramicnano-composites were fabricated by Plasma Active Sintering (PAS) in N2 atmosphere. The existingand distribution of h-BN phase were revealed by X-ray diffraction (XRD), and SEM. For the existingof weak interface between h-BN and SiC grains, the machinability of both SiC/BN micro-compositesand nano-composites were improved obviously. Because the nano-sized h-BN crystals werehomogeneously dispersed around the SiC grains of the matrix, the fracture strength of thenano-composites was better than the SiC/h-BN micro-composite
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 569 (Jan. 2008), p. 53-56 
    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 machinable B4C/BN ceramics composites were fabricated by hot-pressing sinteringprocess at 1850oC for 1h under the pressure of 30MPa. The mechanical property, thermal shockbehavior and machinability of the B4C/BN ceramics composites were investigated in this article. Theexperimental results showed that the fracture strength and fracture toughness of the B4C/BNnanocomposites were significantly improved in comparison with the B4C/BN microcomposites. TheVickers hardness of the B4C/BN nanocomposites and B4C/BN microcomposites decreased graduallywith the increasing content of h-BN, while the machinability of the B4C/BN nanocomposites andB4C/BN microcomposites were significantly improved. The B4C/BN ceramics composites with theh-BN content more than 20wt% exhibited excellent machinability. The thermal shock resistances ofthe B4C/BN ceramics composites were better than that of the B4C monolith, and the thermal shockresistance of the B4C/BN nanocomposites was much better than that of the B4C/BN microcomposites.The thermal shock temperature difference (-Tc) of B4C monolith was about 300oC, while the -Tc ofthe B4C/BN microcomposites was about 500oC, the -Tc of the B4C/BN nanocomposites was about600oC
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 569 (Jan. 2008), p. 109-112 
    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
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 544-545 (May 2007), p. 155-158 
    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 solid-phase photocatalytic degradation of poly (vinyl chloride) (PVC) films wasinvestigated in ambient air. The photodegradation of the PVC and PVC-TiO2 was compared withthat of plasma-treated PVC and plasma-treated PVC-TiO2 [removed info]performing a weight loss monitoringand scanning electron microscopic (SEM) analysis. The SEM of the PVC-TiO2 film treated byplasma showed many cracks on the surface after photodegradation. Furthermore, the surfacewettability and surface structure of PVC after nitrogen plasma treatment was characterized bycontact angle, surface tension, and electron spin resonance (ESR). The experiment indicated thatthe surface free energy and wettability of PVC treated by plasma increased greatly. ESR revealedthat the signal of radicals on the surface of the plasma-treated PVC film was enhanced aftertreatment. The free radicals on the surface of plasma-treated PVC possibly decreased the activatingenergy of photocatalytic reaction, which belongs to the free radicals reaction, because the chemicalactivity of the free radicals was high. According to these findings, a mechanism on thephotodegradation of plasma-treated PVC-TiO2 is proposed
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